Chemical Technology

TOPIC 1: CHEMICAL PROCESSING, UNIT OPERATION & UNIT PROCESS


Chemical Process Selection, Design and Operation

Adequate and flexible initial design is essential for the promotion of a chemical plant organic product or inorganic product.

In older days it was classified as inorganic chemical technology and organic chemical technology. Subsequently the oxford university made it as chemical works organization and management.

Some factors that must be considered in planning a plant are discussed in this section. The Process Engineer is an expert in the current aspects of chemical process design. Practical experience is a must if the senior design engineer is able to foresee and solve the problems of production, such as maintenance, safety and obeying the government, environmental by loss and control.

Experience consultants either individuals or professional consulting firms are able to advise, design and for erection of chemical plants.

Chemical Process Control and Instrumentation

Automatic and Instrument control chemical processes are common and essential. Instruments should not be chosen simply to record a variables, of the process. But their function is to assure consistent quality by sensing controls, recording and maintaining desired operating conditions. Instruments are the essential tool for modern processes. They are classified as

            1. Indicating Instruments          2. Recording Instruments          3. Controlling Instruments

Two types of Instruments are currently used as analogue and digital.

Analogue Instruments such as pressure spring thermometers and Bourden Gauges shows results by mechanical moments of some type of device which is directly proportional to the quantity measured.

On the other hand, digital devices are converts the quantity measured into a signal and electric circuits converts the signal to read the numerical values forward by control. Now the computers can monitor and regulate outputs from both the analogue and digital devices according to a prearranged program, also general conventional digital inputs are required. Chemical analytical control has been used in day to day factory procedures for analysis of incoming raw material or outgoing products. Thus quality chemicals are produced more in these days reliably their when human analysed control were used.

The latest advancement are the chromatography system, many spectroscopy have been automated an install of on-line basis for the process to run continuously without the problems encountered manually before.

Role of Chemical Engineers

Chemical Engineers are trained primarily to work in chemical industries. some of the vital role of the chemical engineers are as follows;

Chemical Process Economics

Engineer are totally different from Scientist by their customers of cost of production and profit generator. Therefore the objective of engineer should be to deliver safely the best product or most efficient service at lower cost to the employer and the public who consumes the product.

Material Balance

Yield and conversion are the chemical prospects from the basis for the material balances which is useful for cost determination.

Materials and their quantities from the standard practices are tabulated in the flow charts, energy given are observed for the chemical reactions and energy is frequently a major cost in chemical plants but it often possible by altering the process procedures by using modern separation technologies like “RO” and “Advanced Separation Processes” to produce high quality chemicals with low energy consumption.

Plant Location

The location of the chemical plant is decided ourselves by the availability of raw materials, transportation, market and power. Now the environmental constituents, water supply, availability of efficient labor, cost of land and waste disposal facilities form the criteria for the plant location.

Construction of Plant

For small and large companies construction engineering organizations are available that will built a plant and participate in its design. Some large chemical companies have their own civil construction department and starts their own plants.

The advancement of this is the worker who is going to operate the equipment can be more intimately corrected to the constructions and be familiar themselves for the future alternatives, expansion or modifications.

In built-in plants the top engineers are chartered engineers qualified for the development activities. They have been trained and suitably examined to guarantee technical competency and owe personal responsibility. They are now called as functional consultants and registered firm for dealing with legal aspects with proper training.

Research and Development

adequate and skilled research with patent protection is necessary for future profits. In the chemical process industries one of the outstanding tactics is rapidly changing processes, new raw materials and new markets. Research creates these changes and the factory will have a competitive progress. This research brings about development and the adoption of ideas, concepts, methodologies form the production of the industry. The results and benefits of research establishes the developing coutry on the road of progress and raise the level of life of common man.

Chemical Engineer in coming years

  1. Resources particularly energy and feed back for the Fertilizers and Heavy Chemical Industries.
  2. Infrastructure for Transportation and Telecommunications.
  3. Protection of the Environment.
  4. Development of Agro Industries where utilization of waste from Agro industries and exploitation of value added products from wastes.
  5. Transformation of Rural Economy, Industrialization and Privatization where the profits are less and consumption is more.
  6. Problems of less Technical context are,   
    • The Centre Vs. States
    • Command Economy Vs. Liberalisation & Privatisation
    • Internal Budget and External Balances
    • World Trade Globalization and relevant to India
    • Problem of Indian competitiveness   

The latest research and development have classified the following new industries;

  1. Cryogenics in Chemical Technology
  2. Chemicals from Sea
  3. Air as a Chemical Raw Material
  4. NUPLEXES ( Nuclear Power Agro Industrial Complexes )
  5. Proteins from Petroleum Fermentation and Single Cell Proteins from Animal horns.
  6. Food Industries
  7. Coal Chemicals
  8. Newer Petrochemicals
  9. Pesticides
  10. Pharmaceuticals Industries
  11. Metallurgical Industries
  12. Water treatment & Air Pollution Control

The chemical process industry had its growth from pre scientific chemical industries followed by scientific chemical industry. The growth with restrains, green challenge to chemical industry and the modern separations process involved in the indian chemical industry seen today.

We define Chemical Engineering as a synthesis of chemistry and engineering. A Chemical Engineering therefore carries out on a large scale reactions developed in the laboratory by the chemist.

The Major Areas of Work within Chemical Engineering are,

  • Research
  • Process Development
  • Process Design
  • Evaluation of Design
  • Plant Design
  • Construction
  • Production Supervision
  • Plant Technical Services
  • Sales of the Product

The Research is divided into three categories like Fundamental Research, Exploratory Research and Process Research.


S.No.

Industry

Typical Products

End User

 

 

 

 

1

Inorganic Chemicals  

H2SO4

Fertilizers, Chemicals, Petroleum Refining, Paints, Pigments, Metal Processing and Explosives

HNO3

Explosives & Fertilizers

NaOH

Rayon, Film Processing, Petroleum Refining, Pulp & Paper Industry, Lye, Cleaners, Soap & Detergents, Metal Processing

2

Organic Chemicals

Acetic Anhydride

Resins, Plastics & Nylon

Ethyl Alcohol

Antifreeze agents, Cellophane, Dynamite & Syn. Fibres

Formaldehyde

Plastics

Methanol

Mfr. Of Formaldehyde, IMS(Industrial Methylated Solvent) & Antifreeze agent

3

Petroleum& Petrochemicals

Gasoline

Motor Fuels

Kerosene

Fuel

Oil

Lubrication & Heading purposes

Ammonia

Fertilizer & Chemicals

Ethanol

Acetaldehyde solvents & other miscellaneous chemicals

Alkyl Aryl Sulfonate

Detergents

Styrene

Syn. Rubber, Polymers & Plastics

4

Pulp & Paper

Paper

Books, Records & Newspaper

Cardboard

Boxes for packing

Fiber Board

Building materials

5

Pigments & Paints

Zinc Oxide (ZnO)

Pigments for paints, inks, plastic, rubber, ceramics and linoleum

TiO2

Carbon Blade

Drying Oil

Lead Chromate

Linseed Oil

Phenolic Resins

Basic kequer warmish & enamels

Alkyl Resins

Ion exchange resins and constituents of enamel

6

Rubber

Natural Rubber(Isoprene)

Automobile tyres, moulds, sheets, footwear and insulation

Syn. Rubber (Neoprene)

Butyl Rubber

7

Plastics

Phenol Formaldehyde

Various users in all areas of everyday life

Poly Styrene

Polymethyl methacrylate

PVC

Polyethylene

Polyster

8

Synthetic Fibers

Rayon

Clothing

Nylon

Acrylics

Polyster

9

Minerals

Glass & Ceramics

Windows, containers, bricks & pipe tubes

Cement

Concrete for construction of buildings, highways, etc.

Coal

Fuels, coke and its by-products

10

Cleansing Agents

Soaps & Detergents

House hold cleaning & Industrial cleaning. Sodium alkyl aryl sulfonate is also used as wetting agent.

11

Bio Chemicals

Pharmaceuticals & Drugs

Health & Medicine applications

Fermentation product like penicillin

Medical use

Ethyl Alcohol

Solvent and Beverages

Food Products

Human sustance

12

Metals

Steel, Cu, Al & Zirconium

All the Building materials, machinery etc.

Uranium

Nuclear fuel

 

 


The largest tonnage inorganic chemicals is H2SO4. It is consumed by industry in the manufacture of other products. Thereby it reaches the public knowledge vary scarely. Large quantities are consumed by petroleum and metal industries. The important organic chemical include alcohols, dyes, dye intermediates used to produce other chemicals. Ethyl alcohol was initially produced by bio chemical fermentation before the second world war.

But now it is produced primarily from petroleum on the latest discovery of natural gas. The important petroleum products are gasoline, lubricants, petrochemicals, other fuels and miscellaneous chemicals. Since the second world war petrochemicals have assumed a commander role in the economy. The largest petrochemical ammonia is produced by reaction of H2 from natural gas or petroleum with N2 available in the Air.

This Ammonia reacts with CO2 to produce Urea in a fertilizer plant. Normally there are five different units in the fertilizer manufacture from coal based mines.

  1. Oil & Gasification plant
  2. Benfield De-sulphurization plant
  3. Ammonia plant
  4. CO2 plant
  5. Urea plant

The tendency of Urea is to form BIURETS which are used as regenerator salts in the metallurgical applications. Many plastics and synthetic detergents are produced with the help of oil refineries.


Unit Operation 

The basic physical operations of chemical engineering in a chemical process plant, that is distillation, fluid transportation, heat and mass transfer, evaporation, extraction, drying, crystallization, filtration, mixing, size separation, crushing and grinding, and conveying. In simple terms, the operation which involves physical changes are known as Unit Operation.

  1. Distillation is a unit operation is used to purify or separate alcohol in the brewery industry.

  2. The same distillation separates the hydrocarbon in a petroleum industries.

  3. Dry grapes and other food products or similar drying of filter precipitate like rayon industry where yarn is produced.

  4. Absorption of oxygen from air in a fermentation process of a sewage treatment plant and half hydrogen gas in a process fr liquid hydrogenation of oil.

  5. Evaporation of salts solutions similar to evaporation of sugar solution in the industry.

  6. Settling and sedimentation of suspend solids similar to minimizing and sewage treatment plant.

  7. Flow of liquid hydrocarbon in a petroleum refinery and flow of milk in a daily plant for the solidification in spray dryer.


Classification of Unit Operations

  1. Fluid Flow : Concerns the principle that determine the flow or transformation of fluids from one point to another. The fluid can be a liquid or a gas. This unit is entirely based on Bernoulli e's equation followed by continuity correlation.
  2. Heat Transfer : Deals with principles that govern accumulation and transfer of heat and energy from one place to another. The three concepts followed here are conduction, convection and radiation.
  3. Evaporation : A special case of heat transfer which deals with the evaporation of volatile solvent such as waste from a non-volatile solute such as salt or any other material in the solution. The evaporation of trichloro-ethylene a cleaning agent in the automobile service industry and acetone in the case of glassware in a chemical process industries follow this unit operations.
  4. Drying : An operation in which volatile liquids (usually water) are removed from solid material.
  5. Distillation : An operation where a components of the liquid mixture are separated by boiling because of their difference in vapor pressure.
  6. Absorption : A process whereby a component is removed from gas mixture by treatment with liquid.
  7. Liq-Liq Extraction : A process in which a solute in a liquid solution is removed by contact with another liquid solvent that is relatively irreversible with solution.
  8. Liq-Solid Leaching: It involves treating a finely divided solid with a liquid that dissolves and removes a solute contain in the solid.
  9. Crystallization : The removal of a solute such as a salt from solution by precipitation in the industries for large scale operations, electrostatic precipitation is operated for this concept.
  10. Mechanical physical separation: This involves separation of solids, liquids or gases by mechanical means such as filtration, settling, size reduction which are classified as separate unit operations.     
    • The outline of unit operation defines the settling tanks for sedimentation, filter press for separations, pressurized spheres for ammonia storage, pellatising for fertilizer compounds, pneumatic conveyors for cement industry, bucket wheel  elevators for thermal power stations and belt conveyors for core industries and many more in operation.



Stacks

Gases are discharged into the ambient atmosphere by stacks (referred to as chimneys in industry) of several types.
The chemical process steps involved the following;
  1. Preparing the Reactors
  2. React them
  3. Separate the Products
  4. Purify the Products
The purpose of chemical industry is to start from one and other chemical raw material arrive at a consumer product through a group of physical and chemical products. Therefore it is called as a creative industry rather than assembly industry.

This mainly fall into inorganic, natural products, organic chemicals and metallurgical industry.




Unit Processes

Processes that involve making chemical changes to materials, as a result of chemical reaction taking place. For instance, in the combustion of coal, the entering and leaving materials are differ from each other chemically. Coal and Air enters, and flue gases and residues leave the combustion chamber. Combustion is therefore a unit process. Unit processes are also referred to as chemical conversions. In simple terms, the process which involves chemical changes are known as Unit Processes.

Together with unit operations (physical conversions), unit processes (chemical conversions) form the basic building blocks of a chemical manufacturing process. Most chemical processes consist of a combination of various unit operations and unit processes.


           1. Alkylation:

             Addition of alkyl radical (CH3) with side chain final product. This alkylation process is widely used in organic  chemicals and petroleum industries. The reaction is given as,
                C=C-C-C + C-C-C
                

 

        2. Amination by Ammonolysis:               
         
          Cl-CH2CH2Cl + 4NH3 ------->
NH2CH2CH2NH2
                  EDC                                     Ethylene Diamine

    
       
This reaction is used in manufacture of dye stuffs, organic chemicals and synthetic fibres.

        3. Amination by Reduction

          CH3CHNO2CH3 + 3H2 ------> CH3CHNH2CH3
           2 Nitro Paraffin                  Iso Propylamine

            This unit process is also used in the manufacture of dye stuffs and organic chemicals.

        4. Amino Oxidation
            
          CH3CH2CH3 + NH3 + 1.5 O2 -----
> CH2:CHCN + H20
           Propylene                                 Acrylonitrile

            This reaction is used in the manufacture of plastics and synthetic fibres.

         5. Calcination
           
          CaCO3 ---Heat---
> CaO + CO2
          Limestone             Lime
            
            This reaction is used in the cement industry.

        6. Carbonylation
            
          CH3OH + CO -----
> CH3COOH            
          Methanol               Acetic Acid

            This is used in the manufacture of organic chemicals.

        7. Carboxylation



            This reaction is used in the organic chemical industry.

        8. Combustion:

            CH4 + O2 ------> CO2 + 2H2O   ( Process Heating )

        9. Condensation:

          C6H5CHO + CH3CHO ------> C6H5CH:CHCHO + H2O

             Benzaldehyde+Acetaldehyde       Cinnamaldehyde

        10.Cracking or Pyrolysis:

             C-C-C-C-C-C-C --------> C-C-C + C=C-C-C

            This reaction is used in petroleum destruction and distillation of coal.



1. Fluid - Solid Contact:

    Represented by fixed bed reaction. It is most widely used in catalytic reactor used with precious metal catalyst to minimize attrition losses. The catalyst used in the form of pellets. It can represented by the following figure.


    This is used in the packed column. The design of the column is determined by the breakthrough curve, equilibrium line for the given system of adsorbent and adsorbate's. The volume of the reactant coming from the top and the volume of which the product leaves the column, residence time, distribution decides the dimensions of the column. It is contrary to the fluid bed reactor where the bed is fluidized. Once the minimum fluidized velocity is reached the porosity of the bed is faster in a fixed bed reactor but varies from the fluidized bed where the porosity changes according to the height of the bed.
            
2. Fluid - Solid Separation: (Centrifugation)

    This operation separates very finely divided solids from liquid or mixture of liquid and liquid emulsion.


3. Wet Scrubber:

    It is an effective means of removing suspended particles from gas string by contact with liquid shower. 


    When solids are used in the place of liquid the operation is called Dry Scrubber. In the manufacture of MEK, wet scrubber is used and in other selected process industries Dry Scrubbers are used, 
    Scrubber just washes away the impurities and separate the product for further purification.

4. Filter Press:

    It is the simplest type of pressure filtration. the two important parts of the filter press are plates & frames and fabric used in between the two are made of variety of corrosion resistant materials. In the laboratory scales asbestos cloth are used for filtration at different pressures.
    The operation decides the value of specific cake resistance, filter medium resistance and compressibility of the chemical namely Kieselghur  a specific compound in the nature of diatomacceous earth which are used in the application of bio-physics and cyrstallography.



5. Fluid Storage:

    Tanks are widely used for storage of liquids of all types and atmospheric pressure when the liquid is highly volatile there is a floating roof which acts as lid for chemicals as and when the vapour pressure at which signifying the boiling point of liquid the roof changes its position and deserves the liquid from going out to the atmosphere.



6. Pressurized Spheres:

    Pressurized spheres are used for pressurized storage of liquefied gases or high vapors. The pressure permits safe storage with no vapor losses. This is seen in the fertilizer plant where ammonia is stored in spheres.



7. Gas-Liquid Contact: (Absorption)

    The best example is Absorption. It is used for taking a soluble gas in a solvent liquid and producing a solution plus an exit gas. Hydrogen Sulphide is removed from hydrocarbon by the absorption process.



8. Adsorption:

    It is classified into physiorption and chemisorption according to the process applied. The former one is almost a physical change or physical transformation while a later represents a chemical reaction which is a irreversible one. the common effluent treatment plants of varies nature lied textile effluents, sewage treatment, ETP plants in chemical industry, removal of hazardous solid wastes, etc are dealt with adsorption method and the adsorbent is regenerated over a period of time and used again and again.

9. Heat Exchangers:

    The various cooling towers of natural draft and forced draft are example of industrially applied H.Es. These are common facilities in the thermal power stations and in chemical industries the application of shell & tube heat exchangers are widely used. this is an excellent application of heat transfer from one medium to the other.

10.Membrane Separation:

    Dialysis is used to separate metals in solution having widely different molecular weight. for example caustic from sugar solution or cellulose.

11.Size Reduction:

    This involves crushing, grinding, pelletizing and prilling. Pelletizing is used in pharmaceutical industries and prilling used the manufacture of Urea. 



Modern chemical processes are offer extremely complex operations involving 100s of pieces of equipment. without a systematic approach it would be impossible to analyses an existing process or to design equipment process. The typical chemical process is analyzed with the following interdependent considerations like, 
        
    - Mass & Energy Balance
    - Thermo chemistry
    - Unit Operations
    - Plant Equipment
    - Ancillary Equipment
    - Process Plant Diagram
    - Instrumentation Control
    - Economics 
            which deals with net profit before taxation profit after taxation dividend paid to the public and share holders. Once the process as been developed and completed attention can be made to access the various liabilities, resource and assets. 

Alternatives and the remaining choices can be ranked in the order of desirability. They are as follows;

    - Effectiveness for reducing waste
    - Technical Risk
    - Extended of current views in the facility
    - Industrial Precedent
    - Capital and Operating cost incurred
    - Effect of the Quality of the product
    - Impact of Plant Operations
    - Required time for Implementation
    - Other aspects important in the particular situation according to the industrial


Conservation of Energy:
    
    dE = Q - W     This is a steady state batch process.
    dH = Q - Ws    Thia is for flow process.
           
    Q--> Heat energy transfered across system boundary.
    W-->Work energy transfered across system boundary.
    Ws->Mechanical work energy transfered across system boundary.
    E--> Internal energy of the system.
    dE, dH--> Changes in Internal Energy & Enthalpy during the process.


we are already classified the various unit operations and below is a particular basic column of mass transfer equipment.




1. Distillation:

    It is classified into Batch and Continuous Fractionation.
    a. Batch Fractionation:



        Used for intermittent operation and handling of small volume of feed and products.

    b. Continuous Fractionation:




        These are used for high volume continous seperation of complex mistures such as petroleum fractions connected to appropriate pumps, re-boilers, condensers, scrubbers, strippers and finally automatic controls.

2. Drying of Solids:

    Spray Dryer , Rotary Dryer & Tunnel Dryer are some example of these types.

3. Evaporation:

    Open pan evaporators and multiple effect evaporators as used in sugar and salt industries for example. Among these halogen family we have technology to separate chlorine and fluride but production of bromine from the 'sea brine'is almost not put into practice as the bromine chemicals is highly corrosive and necessary precaution has to be laid out for practical purpose.

4. Extraction:
  • Liquid - Liquid Extraction
  • Solid - Liquid Leaching are examples for this process

5. Fluid Handling Equipments:
  • Centrifugal pumps
  • Reciprocating pumps
  • Jet ejectors
6. Fluid - Solid Contacting:
  • Fixed Bed
  • Fluidized Bed
  • Moving Bed, etc.
7. Fluid - Solid Separation:
  • Centrifugation
  • Settling Tank / Sedimentation
  • Wet Scrubber / Dry Scrubber
  • Crystallization
  • Rotary Filter
  • Filter Press
  • Cyclone Separator
  • Electro-static Preciptator
  • Bag Filter
  • Thickeners based on Kynch Theory
8. Fluid Storage:
  • Gas Holders
  • Tanks
  • Pressurized Spheres
  • Underground Caverns which are used for the purpose of Natural Gas Storage.
9. Gas - Liquid Contact:
  • Absorption
  • Stripping
10.Heat Exchangers:
  • Fired Heaters
  • Re-boilers
  • Condensers
  • Shell & Tube Heat Exchangers
  • Jacketed Kettle
  • Quenching applied in conventional Heat Transfer and Metallurgical Operations.
11.Membrane Separation:
  • Dialysis
  • Gaseous Diffusion
12.Mixing:
  • Agitation
  • Solids Blending
13.Size Reduction & Enlargement:
  • Crushing
  • Grinding
  • Pelletizing
14.Solids Handling:
  • Pneumatic Conveying - Juices transfered to 200 km in Brazil
  • Bucket Elevators - Coal Industries
  • Screw Conveyors - Tooth Paste, Turbine Liquids
  • Belt Conveyors
15.Solid - Solid Separation:
  • Screening
  • Elutriation
  • Froth Rotation
  • Jigging
  • Magnetic Separation


CHEMICAL REACTORS

The Reactor is the heart of the chemical process. The design of an industrial chemical reactor must satisfy the requirements in four main areas.
  1. Chemical Factors
  2. Mass Transfer Factors
  3. Heat Transfer Factors
  4. Safety Factors
1. Chemical Factors:

This involve the kinetics of the reaction weather it's first order or second order and based on this chemical reaction engineering is built on the design must provide sufficient residence time to proceed the reaction for the required degree of reaction and conversion to product.

2. Mass Transfer Factors:

The reaction rate of homogeneous reaction may be controlled by the rate of diffusion of reactants rather than the chemical kinetics of Langmuir isotherm and Frendlich isotherm.

3. Heat Transfer Factors:

These describes weather the reaction is exothermic or endothermic. In Exothermic, heat is released outside and In Endothermic, heat is absorbed by reactants. The value of heat of reaction is necessary to operate the chemical reactor.

4. Safety Factors:

This involve the confinement of any hazardous reactant and products as well as the control of reaction and process conditions. 

Based on these factors the Reactor Types as follows;
    a. Mode of Operation - Batch or Continuous
    b. Phases Types - Homogeneous or Heterogeneous
    c. Reactor Geometry - Flow Pattern & Process of contacting the phases.

The five major classes of Reactor;

    i.  Batch
    ii. Stirred
    iii.Tubular
    iv.Packed Bed (Fixed)
    v. Fludised Bed

Compounds like pigments, dye stuffs, pharmaceuticals and polymers are manufactured by Batch Processes.
The Latest Heat Exchangers are Direct or Contact Exchangers In addition to Double Pipe Exchanger, Shell & Tube Exchanger and Plated Frame Exchanger.
            

Go to www.sdsenthil.com

    

TOPIC 2: CHLOR ALKALI INDUSTRY, INDUSTRIAL ACID, CEMENT, GLASS & CERAMICS AND PULP & PAPER


Sodium Chloride

Sodium chloride is the basic raw material for many chemical compounds such as NaOH, Na2CO3, Na2SO4, HCl, Na2PO4, Sodium Chlorate, Sodium Chlorite and its source of many other products through its derivatives. Practically all the chlorine products in the world is manufactured by electrolysis of Sodium Chloride (NaCl), a common salt is manufactured in three different ways;

  1. Solar evaporation of sea water
  2. Mining of rock salt
  3. From well brines

 

1. From saturated Brine by Multiple Effect Evaporator Process

Brine contains water 73.5%, sodium chloride 26.3%, calcium sulphate 0.12%, calcium chloride 0.003%, magnesium chloride 0.007%.

The flow sheet of process is given below;



Process:

  1. The Brine is first aerated to remove most of the H2S.
  2. Addition of chloride will remove H2S by displacement reaction.
  3. Brine is then pumped to settling tank where it is treated with caustic soda and soda ash to remove calcium, magnesium and ferric ions. Caustic soda and soda ash are blended in the miser to be taken to settling tank.
  4. In the Multiple Effect Evaporator (MEE) water is removed and salt crystals are removed as slurry.
  5. The slurry is sent to washer, where the salt crystals are washed with fresh brine.
  6. The washed slurry is filtered, mother liquor is return to the evaporators and salt crystals from the filter are dried and screened.
  7. Salt thus produced from the typical brine is 99.8% purity or even greater.
  8. The finest grade (some times made by grinding) is a flour salt, the next coarsest is table salt and finally the industrial salt.

The Iodine salt has the following composition;

  • Potassium Iodide (KI)    : 0.01%
  • Stabilizer Na2CO3         : 0.1%
  • Sodium Thio Sulphate    : 0.1%

 

2. From Saturated Brine by Open Pan Process

Process:

  1. Salt in the form of hopper-like crystal (grainer salt) is made by causing the salt crystal to form on the surface of brine held in an open pan.
  2. The grainer is a flat open pan 4.5 to 6.0 m width and 45 – 60 m long and about 60cm deep. Beneath the pan steam coils system provided for reciprocating the flakes for salt removal.
  3. The saturated brine mixed with circulating brine from the grinder is treated to 1200C at which temperature calcium sulphate is soluble and remove at that temperature.
  4. The precipitated calcium sulphate is removed from gravellier which consist of bed of stones.
  5. The purified brine is flash cooled to remove the remaining calcium sulphate.
  6. The slurry is then pumped to the grinders where evaporation takes place at 960C.
  7. A wet salt crystals obtain from the grinder are centrifuged, dried and screened.
  8. When the incoming brine has been treated salt of 99.98% sodium chloride can be obtained.

 

3. From Rock Salt Mining

About 35% of salt produced comes from mines of 8 different stages which are operated to produce rock salt. The salt deposits varying color from light reddish brown to half grey. The purity is 98.5%. After the rock is blasted loose they are crushed and then screened at the surface level. The remaining process is the series of grinding, screening to obtain the salft of crystal of various sizes.

 

4. From Sea Water by Solar Evaporation

Annual Evaporation exceeds precipitation, the statistics of 125mm of rain corresponding to 840mm evaporation.


By-products of Normal Salt (also called as value added products)

Manufacture of sodium sulfates from salt and sulfuric acid

2NaCl + H2SO4 ---> 2HCl + Na2SO4

Na2SO4 + 10H2O -> Na2SO4 + 2HCl

Hargreaves-Robinson Process

Sulphur Di-oxide, air, steam are passed over specially prepared porous common salt. The reaction is as follows;

2NaCl + SO2 + 1/2O2 + H2O ---> Na2SO4 + 2HCl

 

 

Bleaching Powder

Formulae:      (CaOCl2).H2O

Equation:       Ca(OH)2 + Cl2 ---> CaOCl2.H2O

The reaction is a low temperature reaction at 50OC in a counter current action by passing chorine through a rotating steel cylinder with lifting blades which slower the solid through the path of the gas. When allow to stand in air the bleaching powder absorbs CO2 liberating HOCL (Hypochlorous acid). Other organic acids also liberates same compound. The reactions are,

2CaCl (OCl) + CO2 + H2O ---> CaCl2 + CaCO3 + 3HClO

2HClO --> 2HCl + O2

After this formation bleaching powder liberates calcium chloride and oxygen. When dissolving in water the reaction gives ionized calcium chloride and hypo chloride. The reaction is,

2CaCl (OCl) ---> 2Ca2+ + 2Cl- + 2OCl-

The OCl- ion decomposes by liberating oxygen. However the acidity of the product is determined by the % of chlorine in the compound, which is defined as weight of chlorine that will exerts the same action as the chlorine compound what we choose.

In the case of Bleaching powder, average chlorine is the same as the % of chlorine in the compound. In the case of calcium hypo chloride the % of chlorine is 47.6% if the chlorine content rises to 99.2% in the compound. These values are obtained as soon as the freshly prepared compound from the process is finally taken.

 

Sulfuric Acid

  • Lead Chamber Process
  • Contact Process

Lead Chamber Process



Essentially this process consists of oxidizing a mixture of sulfur dioxide and water to sulfuric acid using nitric oxide as an oxygen carrier. The reaction is,

H2O + SO2 + NO2 ----> H2SO4 + NO

This Nitric Oxide (NO) combines with oxygen to from nitrogen dioxide which is used again in the process. The formation of NO2 is given by,

2NO + O2 ----> 2NO2

The process consists of three stages.

The first stage takes place in the Glover tower. This tower is packed with acid resistant bricks over which a constant stream of sulfuric acid made by mixing the output of lead chambers (65% Acid) and the Gay-Lusaac Tower (70% Acid) combines with oxides of Nitrogen. Then the hot mixture of SO2 and Air from the furnace is fed into the base of Glover Tower and comes into intimate contact with the descending acid of low concentration. Acid results the gases from the burners are cooled from 500 0C to about 90 0C and the oxides of nitrogen are extracted from the acid and carried over to the other chambers. In addition the acid undergoes the concentration of 70% by the time it reaches the base of the Glover Tower. Some of the spent acid after coming from the Glover Tower is also sold commercially for processed where that concentrated acid is required.

The second stage takes place in the lead chamber from which the process derives its name. Water is spread from the roof on to the mixture of gases are SO2 and NO2. They slowly react together under carefully controlled conditions of humidity and temperatures producing 65% H2SO4 which is collected on the shop floor. Lead is used in the material of construction as it is not corroded by acid. The humidity is controlled by the variations in the dry bulb temperature and wet bulb temperature observed in the psychometric chart available in the process plant.

The third stage takes place in the Gay-Lusaac Tower which is designed to recover as much as possible of the Oxides of Nitrogen from the gases leaving to the chambers after thoroughly washing with cold concentrated acid.

The main purpose of this Tower is to minimize the problem of escape of NO2 to atmosphere. But in the later stages the recovery was more important as the efficiency was high and cost very cheap. A small loss of oxide of nitrogen is inevitable. However it is made good by introducing additional nitric oxide formed by catalytic oxidation of ammonia.

This chamber process produces cheap acid of doubtful purity with concentration of 65-80% at maximum. This was used for manufacture of fertilizers, but where more concentrated acids are required the contact process is followed.

 

Contact Process

 

Today contact process is the most widely used process for the manufacture of H2SO4 throughout the world. The raw materials used to make sulfuric acid are elemental sulfur, H2SO4 and H2S.

Till 1970, Ion Pyrites and related compounds were the predominant raw materials. The large amount of sulfuric acid also produced as a by-product of non-ferrous metal smelting. i.e. roasting sulfide ores of copper, lead, molybdenum, nickel, zinc and some others. The process is dividing to the following steps;

  1. Generation of sulfur dioxide gas
  2. Catalytic Oxidation of SO2 to SO3
  3. Absorbing SO3 to form H2SO4

The reactions are as follows; 

  1. S + O2          ---> SO2
  2. SO2 + ½ O2   ---> SO3       ^H = -98KJ
  3. SO3 + H2O     ---> H2SO4    ^H = -132.5KJ (Highly Exothermic Reactions)

Properties of Sulfuric Acid

When a dilute solution of sulfuric acid is distilled a constant boiling point mixture is obtained contains 98.3% of H2SO4. This mixture boils at 338 0C and has a density of 1.84gm.cm-3 is the normal concentration acid available in the laboratory. If the little SO3 is dissolved in that acid 100% takes acid is obtained and an oily liquid which freezes to crystals of white color at 10 0C. Concentrated sulfuric acid is highly corrosive and should always be handle with care. It causes severe bores when contacted with the skin.

 

Reactions of Sulfuric Acid

It is a strong di basic acid reacting to bases to give a series of salts, like sulphates and bisulphates. It is represented by,

H2SO4 <---> H+ + HSO4- <---> 2H+ + SO4 2-

The dilute acid reacts with many metals forming sulphates and hydrogen. But it does not react with lead, copper, mercury and silver. Iron reacts to give,

Fe + H2SO4 ----> FeSO4 + H2^

When the acid highly concentrated attacks any metals forming sulphates and therefore silicon steel is used for construction of distillation column where sulfuric acid is involved. Gold or Platinum have no reaction with H2SO4 whereas copper forms copper sulfate with H2SO4 liberating SO2.

 

Uses

Manufacture of Phosphate, Ammonium Sulphate and production of these fertilizers consume about 40% of total sulfuric acid manufacture. Other large scale users are manufacture of pigments, light barium sulfate, titanium dioxides and manufacture of viscose rayon for artificial silk, detergents, dye-stuffs, drugs, explosives, plastics, for dissolving unsaturated hydrocarbon during refining of petroleum, for pickling for iron steel (removing oxide layer before galvanizing) tinning, plating & painting and finally for killing weeds for the agricultural production.


Cement

Definition

The term “Cement” refers to many different kinds of substances that are used as binders or adhesives. It refers to inorganic hydraulic cements (mostly called as Portland cement) which are hydration form relatively insoluble water bonded aggregation of high strength and dimensional stability. In the last century it has been found that iron in combination with cement has proved substantially the useful concrete for very high-rise buildings and massive constructions. Hydraulic cements also manufactured by processing and proportionate raw materials burning (clinkering) at a particular temperature and grinding the resultant product to obtain the cement.

The cement consist mainly tri-calcium silicate and di-calcium silicates. The raw material are lime stone rich in calcium and silica such as clay or shale.

Clinker Formation

Portland cements are manufactured from raw mixes including components such as calcium carbonate, clay or shale and sand. When the temperature of materials increases during the passage in the rotary kiln the following reactions occur;

  1. Evaporation of free water
  2. Release of combined water from the clay
  3. Decomposition of magnesium carbonate
  4. Decomposition of calcium carbonate
  5. Combination of lime and clay oxides

Finally cooling is done to maintain the phase equilibrium.

Manufacturing Processes

Wet process and Dry process plants produced Portland cement. It consist of quarrying and crushing the rock, including control of the clinker composition by systematic core drillings and selective quarrying.

The next process is grinding the proportioned materials to high fineness. Ball Mills are used for the both the process to grind the material although roll crushers are used for dry process.

The high temperature of operation vaporizes the alkalies, sulphur and halides (rotary kilns for Wet process, Dry process , suspension free heaters or precalciners). The grinding is done by open circuit grinding or closed circuit grinding depending on the fine powder of cement required.

Manufacturing procedures (Wet & Dry processes)

The Wet Process is the original one is being displaced by Dry Process for few factories because of saving energy, accurate control and proper mixing of the raw material. The dry process plants account for 58% of the total amount manufactured with full production capacity. It is illustrated in the following flow chart.


In the wet process the solid materials after dry crushing is reduced to fine powder in wet tube or ball mills and passes as slurry through bowl classifiers or screens. The slurry is pumped to connecting tanks where rotating arms takes the mixture homogeneous and allow the final adjustment in composition. For this purpose some of the cement plant the slurry is filtered in a continuous rotary filter and fed into the kiln.

The dry process is especially applicable to natural amount rock and to mixtures of limestone, clay, shaves as slate. In this process the materials are crushed roughly are passed through gyratory or hammer mills, dried, sized, finally grounded followed by air separation or the pneumatic process.

Before entering the rotary kiln thorough mixing and blending takes place. The rotary kiln where the powder material is fed the chemical reactions takes place. Heat is provided by burning of oil, gas or pulverized coal using preheated air obtained from cooling of the clinker from the high temperature to lower temperature. And the length of the rotary kiln is increased the thermal efficiency very high. Due to this process of heat transfer vaporization efficiency also increases because of evaporation of moisture and water in the mix. Normally the vaporization efficiency is twice the thermal efficiency for the process of conduction into material.

Dry process kilns are 150 ft long but the wet process over 500 ft kilns is quite common. The internal diameter is around 20 ft. The RPM is ½ to 2 depends on the size. The kilns are inclined so that materials fed at the upper end travel slowly to the lower firing end (by blower) and taking 3 hours to reach he bottom end.

To improve the economy of kiln heat water is removed from the wet slurry before charging into kiln. Some of the equipments are employed slurry filters and ‘Dorr Thickeners’. Efficient air pollution control equipment such as bag houses or electrostatic precipitators are required for the process. Waste heat boilers are sometimes used to conserve heat and particularly economical for dry process cement. A refractory lining is given inside wall to protect the heat form escaping outside and maintain a temperature of 800 OC. In the recent days computers are used to improve kiln control. The sketch of rotary kiln is given below;


The final product form consists of hard granular masses of ¾ of the inch in size called clinker. It is discharged form the rotating kiln into air-quenching coolers which brings the temperature to 100 0C. The cooling also preheat the combustion air pulverizing followed by grinding in the tube or ball mills and automatic packaging complete the process.

There are many types of compounds in cements according to the composition numbering 102 types of cements according to the applications. Special cements also manufactured for corrosive conditions and the various types of sulphur cements, silicate cements, adhesive cements to have a few. The industrial importance sulphur cement are resistant to solves acids, alkalis, oil, grease or other solvents. These are employed for the joining of Tiles and Cast Iron Pipes. Silicate cements with stand a temperature of 1000 0F.


Glass & Ceramics

Glass

Glass was formed naturally from common elements in the earth dust long before anyone ever thought of experimentally with this composition, moulding its shape of putting it to the myriad of used that it enjoys the world today.

Glass technology evolved around 6000 years back and sum of the today’s principles followed the old times. This includes what is today known about the structure of glass, its composition, properties, method of manufacture and uses.

The term glass follows the definition of MOREY, ‘GLASS is an inorganic substance in a condition that is continuous and analogous to the liquid state of the substance. But which as a result of a reversible change in viscosity during cooling, has obtain so high a degree of viscosity has to be for all practical rigid’.



Most glass particles are manufactured by a process in which raw material are converted at high temperature to a homogenous melt that is then formed into various articles or glass wares employed in laboratories.

The above flow diagram summarizes the details of conventional glass manufacturing. The vapor deposition of SiO2 from a flame fed with silicon chloride (SiCl4) and oxygen is basis for manufacturing high purity glass used for blanks that are redrawn into optical-wave guide fibers. Fused silica items that cannot be formed from viscous melts of SiO2 or Quartz are prepared by vapor deposition. Raw materials are selected according to purity, supply, pollution, potential, ease of melting and cost.

Sand is the most common ingredient. Limestone is the source of calcium and magnesium. The reducing agent is powdered anthracite and common colorness for glass includes Iron, chromium, cerium, cobalt and nickel.

Melting and fining depend on the batch materials interactive with each other at proper time and on the proper order. Thus the stream must be taken to obtain materials of optimum grain size, to weigh them carefully and mix intimately. The efficiency of the melting operation and the uniformity and quality of the glass product are determined in the mixing house.

Batch handling systems are widely used in the industry from manual to fully automatic small furnaces for annual production to large continuous tank for rapid machine forming. The two important equipments are screw feeder and reciprocating pusher. Control devices have advanced computer assistant operations. Radiation pyrometer with thermocouples monitor furnace temperature. Natural gas, oil, electricity are the primary source of energy and propane is used as a backup reserve for emergency. Molten glass is molded, drawn, rolled and quenched depending on the desired shape and use. Bottles, dishes, optical lenses, helix picture tubes are formed by blowing, pressing, casting and filling the glass against mould and cool it to get the desired shape.

Art glass is made manually and an glass called FRIT is obtained by powdered glass and quench between water cooled rollers, poured into water and then dried. Glass optical formed as high temperature must be cooled in order to reduce its strain and associated stress caused by temperature gradient.

The following are the types of glasses;

  1. Flint Glass
  2. Bottle Glass
  3. Pyrex Glass
  4. Photosensitive Glass
  5. Froast Glass
  6. Ground Glass
  7. Insulating Glass
  8. Vitreosil Glass (99.9% Silica)
  9. Fused Silica Glass
  10. Optical Glass
  11. Lead Glass
  12. Colored Glass
  13. Opal Glass
  14. Fiber Glass
  15. Safety Glass and
  16. Glass Wool

Ceramics

White Waxes

White wax is a generic term for ceramic products which are usually white and of fine texture. These are based on selective grades of clay bonded together with varying mount of fluxes and heated to a moderately high temperature in kiln of 1200-1500 0C. Because of the different amounts and kinds of waxes there is a variation in the degree of vitrification. Among white wax, from earthenware to vitrified china the degree of vitrification is the progressive reduction in porosity provides the basis for the useful classification of ceramic products as follows;

  1. Earthen ware – some times called as semi vitreous thinner ware is porous, non translucent with a soft glaze.
  2. China ware – a vitrified translucent ware with a medium glaze which resist abrasion to degree which is used for non-technical purposes.
  3. Porcelain – a vitrified translucent ware with a hot glaze which resist abrasion at maximum degree. It includes chemical, insulating and dental porcelain.
  4. Stone ware – one of the oldest ceramic products developed and rewarded as throughout porcelain.
  5. Sanitary ware – formed from clay is porous and preferred for vitreous application with a tri-axial composition.
  6. White ware – white ware tiles available in number of times, classified as floor tiles, resistant to abrasion and impervious to stain penetration and used as  wall tiles of a variety of colors and is formed small surface.


To represent a typical manufacturing procedure in the ceramic group, porcelain is chosen below. There are three lines of production.

Wet process porcelain – used for production of fine grained, highly glazed insulators for high voltage application and cast porcelain necessary for making pieces to large are too intricate for the other two methods.

The 3 processes are based on the same raw materials. The difference in manufacture is the drying and forming steps.


Description of Process

Raw material of proper proportions and properties to furnish porcelain of the desired quality are weighed from overhead into the weighing car. Feldspar clays and flint are mixed with water in the blender (clay-water mixture) and then passed over a magnetic separator, screen and store. Most of the water is removed by filtration. All the air is removed by the mill with the help of vacuum operation. This produces stronger or hard porcelain. The prepared clay is formed into blanks and hot pressed suitably. They are then dried, trimmed and finally completely dried all under carefully controlled conditions. The hydro separator removes the water and moisture containing impurities. The vitrification is carried out in ‘tunnel kilns’ at a particular temperature and then porcelain articles are protected by Saggers fitted in the final stage of the process. The glazing and firing are simultaneously done to obtain lustre or shiny nature of the porcelain. They are immediately tested for electrical insulation after storage for sale.   

The table-ware is manufactured by more complicated procedure then illustrated by the porcelain process. Some objects are obtained by the porcelain process. Some objects are obtained by the potter’s wheel in the conventional cottage industry employed in rural areas. For separate application, complex shapes for chemical laboratories are manufactured by different mould for the required applications.

Glazing is an important process in the manufacture of white wax. Some times a glaze is a thin coating of glass melted on the porcelain surface for porous application. The chemicals used are soda ash, potash, fluorspar, borax for this type of special application. The temperatures for glazing is around 1050-1500 0C.

 

Refractory and colorants for ceramics

It is broadly divided into two groups; one for clay based products like tiles, sanitary wares and thinner ware and the other based on silica as a major ingredient. In the manufacture of glasses continuous for laboratory conditions at normal temperature and pressure color is obtained by a suspension of the coloring medium when final stages of the product obtained.





Pulp and Paper Industry

The transmission of thought my means symbols was practiced thousands of years back, prior to Christian era. Primitive people used to stores clay, palm leaves, shells and bark of plants are which to inscribe information. Egypt is the country where origin of paper took place, now there is no production in that country of paper. On the other hand in china about 200 B.C. the paper was manufactured and now the forerunner of the industry.

Raw Materials

The raw materials employed in the pulp and paper industry are woods, rags, straws, bagasse, sulfur, limestone, alum, soda ash and clay. The only country to have all the above raw material within the country is USA.

1. Wood
    It is the outstanding source of cellulose in fact more than 90% of the paper consumed in the world is made from wood fiber. Again U.S. has the abundances of wood excepting Russia. The North American continent processes 40% of soft wood.
2. Fibrous Raw Materials
    Since 1800 where wood was first employed intensively for the manufacture of pulp no other alternative has append so for. For this purpose the reuse of waste paper become dominant and contributes 1/3 of total production.
3. Non-Fibrous Raw Materials
    The important material here is sulfur about 200,000 tones of sulfur has produced for paper production. The other materials caustic soda, soda ash, rosins and bleaching components, lime is employed for sulfite cooking process. The mineral substances such as clay, talk, chalk, barites, zinc compounds and titanium compounds are used for manufacture of paper as non-fibrous materials.

Manufacture of Pulp

  1. Wood Pulp:    The process is employed in the preparation of pulp from wood are mechanical (ground wood) and chemical (sulfite, sulfate & soda) and a combination of mechanical and chemical known as semi-chemical. The object of the formation of pulp is to separate the wood into fibers. The original wood contains 50% of non-fibrous material like lignin and inorganic matter.
  2. Mechanical Pulp:    This mechanical or ground wood process is used largely on coniferous wood (having the name from coniferous forest past). Especially with low rosin content such as spruce, balsam and hemlock, jack pine is used to produce pitchy hard wood. This mechanical pulp used for newsprint, wallpaper, wallboards and paper boards. It is sometimes mixed with chemical pulp.
  3. Chemical Pulp:    It is a material which made after treating the wood by chemical which remove the cementing material, for this pulp the wood is cleaned thoroughly from bark & knots. The logs of woods are conveyed to the chipper where they are forced at an acute angle against a disc on the surface above which heavy knives are operated on. The chipping operation produces pieces of wood of various sizes and then classified as saw dust.


Sulfite Process:

H2O + SO2 -----> H2SO3

Ca(OH)2 + 2H2SO3 -----> Ca(HSO3) + 2H2O

CaCO3 + 2H2SO3 ----> Ca(HSO3)2 + H2O + CO2

Sulfur is melted and then burned into Sulfur Di-oxide (SO2) in special rotary burners where the supply of air is regulated to prevent the formation of objectionable SO2. The gas is cooled in water immersed pipes after which it is absorbed by;
  1. Large absorbers containing milk of lime
  2. Through tall towers made of concrete packed with limestone over which water trickles down.

The sulfite pulp is used for wide application in newsprints, boards, wrapping papers and certain grades of printing papers where reasonably light color and good strength are required.

Bleach sulfite paper is used in writing, typing paper, tissues, grease proof papers and high grades of wrapping paper.


Sulfate Process:

It derives the name from fact that loss of alkali and sulfur is compensated by sodium sulfate (salt cake) or its equivalent. The term KRAFT means strong and applied to pulp prepared by this process for producing the strong pulp. The raw materials used are southern pine, spruce, jack pine, and tamarack. This is followed by cooking the chips and then washing followed by recovery of sulfate liquor. The main reaction is;

Na2SO4 + 4C ---> Na2S + 4CO

Analysis of solids in sulfate process;

Solids

Original smelt (%)

Green liquor (%)

White liquor (%)

Na2CO3

61

64

11

Na2SO4

4

5

6

Na2S

27

31

22

NaOH

-

-

61

Silica

2

-

-

Insoluble

6

-

-

Apart from the above processes there are miscellaneous processes like soda process, semi chemical pulp process and rag pulp process.

Grades of Paper

There are number of method by which paper may be classified;

  1. By the type of furnish process in the paper manufacture. Eg. Sulfite process
  2. By the property. Eg. Grease proof paper, absorbent paper.
  3. By the use to which it’s applied. Eg. Newsprint paper.
  • Tissue:           It is the lightest weight paper. Generally grade on a Yankee machine like napkins, light weight wrappings and toilet papers.
  • Wrapping:     Bags, envelopes and bread wrappers
  • Writing:         Stationary, ledger, document and type writing sheets belongs to this category
  • Printing:       Newsprint, catalogue and bible papers
  • Books:           Books & Magazines
  • Building:       Papers mixed with asbestos employed in construction work, sheathing papers, felting papers, dead ending felts for acoustic properties involves and floors the auditorium.
  • Boards:        By far the largest production of the industry falls in this class. The subdivisions are numerous like containers, binders, bottle caps, chips and wall boards.

Research

The application of science and engineering in pulp and paper manufacture are brought about to improve operation and progress in the manufacture for better products and also the reduction in prices.

Consumption

Paper products and the related chemical are important to a developing nation such as India, the per capita consumption of paper is the measure of the educational, social, cultural and industrial activities of the country as given below;

Country

Consumption (Kg/Person/Year)

USA

206

UK

167

Japan

57

USSR

16

India

1.5

The end use distribution of paper is given below;

End Use

Distribution (%)

Paper & Paper Head

65

Newsprint

20

Rayon (Chemical pulp)

15




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TOPIC 3: OIL, SOAP & DETERGENT, PETROLEUM REFINING, PETROCHEMICALS AND SUGAR

Hydrogenation of Oils

Large amount of groundnut oil, cotton seed oil, etc are hydrogenated in presence of suitable catalyst to obtain solid edible fat called vegetable ghee. The purpose of hydrogenation is to increase the melting point of oil and convert in to an edible fat. In other words, hydrogenation are hardening of oil is a process in which various unsaturated radicals are converted into completely saturated Glycerides. There fore the hydrogen plays an important role in the process with a catalyst. The process is carried out by keeping the oil at a temperature of 140-180 0C containing finely divided liquor in suspension by the subsequent absorption of Hydrogen.

Optimum conditions for the Process

  1. The Hydrogen needed can be manufactured by a number of methods but hydro carbon steam process has been widely used. The hydrogen must be very pure. Traces of gaseous sulfur compound, H2S, SO2, Arsenic and Chlorine compounds are strong catalyst poisons. These have to be removed before the hydrogenation process. 
  2. The oil must be pure as well as free from fatty acids. Fatty acids react with Nickel and its oxides to form Nickel Soap which is soluble in oil. For purification, the oil is taken in a tank fitted with steam coil are heated to 30 0C. Then caustic soda is added and mixture is agitated for about 20 minutes by compressed air. The moisture is removed by heating the oil in vacuum. The moisture may be hydrolyses the oil at high temperature and pressure to form fatty acid.
  3. In order to prevent the ‘Pyrophoric Nickel’ from catching fire the Nickel catalyst is carefully transferred to the oil out of the contact with air.
  4. In order to keep the Nickel particles in free suspension and to bring the oil in close contact with Hydrogen, the mixture of oil catalyst and Hydrogen is agitated.
  5. The catalyst is Nickel Oxide or Nickel Formate which is reduced to metal by Hydrogen gas are forms ‘Raney Nickel’. The charge is kept at maximum temperature for about one hour and then cooled. During the cooling period the Hydrogen is passed to create the product hydrogenated oil stored in the end of the process.



Recent research has shown that Palladium has been found to be more effective then Nickel. i.e. 1 part in 1,000,000 parts of oil is sufficient. And the reaction takes place at lower temperature and takes less time. The only disadvantage is Palladium is costlier than Nickel, Raney Nickel and other catalyst.

The process of Hydrogenation is exothermic reaction. There fore it is favored by low temperature. The optimum temperature is around 150 0C.

Apart from the above there are two processes of Hydrogenation of oil

1.    Dry Process

2.    Wet Process

1. Dry Process

The refined oil from the storage tank is brought into a vacuum evaporator where it is heated at about 50 0C at low pressure in order to expel air moisture. By means of the pump the oil is charged into convertor by pipe provided at the bottom of the evaporator. The convertor is a cylindrical pressure vessel provided with Hydrogen distributor. In the bottom steam coils for heating and circulating the oil. The Hydrogen gas is sent at a pressure of 5.6 atm. into the convertor. The steam is turned off to accelerate exothermic reaction and convert the oil into a hydrogenated substance for further purification process.

For the commercial value Bleaching is done for aesthetic consideration for the market value.

2. Wet Process

In wet process Nickel salt is reduced into finely divided Nickel in the oil before hydrogenation in a continuous process. There are two wet process are employed, in one process Nickel Formate is used and the reduction is carried out at 190 0C with Hydrogen.


The advantage in this first method of the wet process is removal of CO as waste removed from Deodorizer still as Co is a catalyst poison for the Nickel group.

In the second method 2% Dry Nickel Formate in powder form is mixed with 100 Kg of Oil to be hydrogenated as a current of Hydrogen is passed at a temperature of 250 0C. The pressure is 10-12atm. Introduced by nozzles to the convertor. After the reaction is completes, the temperature is brought down and ascertained the completion of hydrogenation.

There are two important advantages of this process;

More active catalyst having high surface area is obtained because the reduction of salt is carried out at low temperature.

Nickel does not come into contact with air at any stage and hence fire hazard is avoided.

Margarine

Hardened oils are consumed as such as in India, but in Europe and America they are converted to a butter called ‘Margarine’. It is prepared by emulsifying about 80% fat and 15% skimmed milk, salt, vitamin A, vitamin D, a preservative such as sodium benzoate, a yellow dye and flavoring agents.

 

Soap Making Industry

Raw Materials

1. Source of Glycerides:   The main sources of slow lathering hard oils are tallow, palm oil, whale oil, fish oil and greases, etc. Quick lathering hard oils include coconut oil, palm oil and kernel oil, etc. Soft oils are soya bean oil, cotton seed oil and inedible olive oil, etc.

2.Rosin:       A plant product contains mainly abietic acid. The colorless variety of Rosin is used in the manufacture of laundry soaps and dark variety is used in the manufacture of colored soaps. Rosin makes lather formation faster, increases the cleaning property of the soap and softens the hard soaps. Rosin requirement is about 50% and the grease is 23%.

3. Caustic Soda:       It is available in the form of flakes, blocks and sticks as well as in solution of sodium hydroxide in various concentrations. The caustic product potash is involved in the manufacture of saving creams.

4. Sodium Chloride: Sodium Chloride is used for salting out about 12.5 parts per 100 parts of oil to be saponify is used.

5. Binding Materials:         Sodium Silicate, Soda Ash, Tri Sodium Phosphate, Borax are used as Binding materials. They improve the soap texture and prevent the formation of precipitate in hard water.   

6. Fillers:      The weight of the Soap is determined by fillers such as talc, starch, glauber salt, pearl ash, etc without affecting the detergency of the washing soaps.

7. Colouring Matter:            Organic dyes and inorganic pigments are used. As a Dye the material should be inert to alkali used in making soap and should not separate when soap is blended in the process. Common coloring matters are methyl violet, Bismarck brown, safframine for red, zinc oxide for white color, chrome green for green color, cadmium for yellow color, ultra marine for blue color, eosin for pink color, vermilon for rose shade. Intermediate colors are obtained by blending the above colors.

8. Perfumes & Perfume Fixatives:          These impart fragrance for the soap. They may be natural or synthetic. Examples are sandalwood oil, lemon grass oil, clove oil, eucalyptus oil, lavender oil and cinnamon oil, etc. The synthetic perfumes are,

  • Jasmine (Benzyl Acetate)
  • Rose (Phenyl Ethyl Alcohol)
  • Lylac (Terpenol)
  • Musk (Benzoate)


Manufacture of Soap

Soap is either made by hot process or cold process. Usually laundry soaps and bath soaps are manufactured by hot process. Transparent and other special types of soaps are produced by cold process. In most of the cases soap obtained by hot process settled and separated from Glycerol solution. Subsequently Glycerol is separated out as a by-product. The hot process is divided into tow types,

  1. Batch Process
  2. Continuous Process

The Batch Process is carried out in a soap kettle made of steel plates and having large diameter. The kettle is supplied with steam with a mixture of melted fats, grease, oil in a proper amount for the mixture. The amount of caustic soda is regulated to undergo the hydrolysis reaction. The boiling is continued until the saponification is completes. A pasting mass is formed by conversion of Tri-stearin to Di-stearin. The final product contains soaps, water, glycerol, unused alkalis, sodium chloride, sodium carbonate, sodium sulfate as impurities. After this saponification is complete and the steam is cut off with the separation of salt on the surface for the batch process to stop and deliver the soap product.



In the Continuous Process the raw materials oils and fats and the catalyst usually zinc oxide are blended and fed into a hydrolyser or splitting tower fitted with steam coils through which steam is passed for heating the charge. The splitting of fat takes place continuously in a counter current manner and about 250 0C and 40 atm pressure. The fat raises again the aqueous phase which also dissolves glycerol in reaction. The fatty acids are discharged from the hydrolyser to a flash tank called decanter where excess of water is separated. They fatty acids are the passed to a heat exchanger and then to a vacuum still and distilled. The distillate is collected as overhead and bottoms are stored for recovery. Then the distillate neutralized by caustic soda in a continuous neutralizer. As the result of this soap is obtained which is with drawn hot into a agitator tank. This soap contains Water, NaOH and NaCl. This is dried in a high pressure steam exchanger by heat and pressure, finally collected in a flash tank. The pasty mass is missed with air and cooled to 65 0C. Here the soap is continuously extracted and collected into soap frames where it solidifies on cooling. Then it is cut into bars as usual. The particular process delivers the product in a day whereas the batch process operates for few more days.


Petroleum Refining

Cracking

Cracking is the process by virtue of which crude petroleum of their fractions are decomposed by heat to produce products which have lower boiling points. The main object of cracking is mainly the production of gasoline. The two types of cracking are,

  1. Thermal Cracking
  2. Catalytic Cracking

1. Thermal Cracking

The main reaction is C10H22 --Cracking-->C6H12 + C6H10

                                                        Paraffin+Olefin

The crude petroleum is heated to 1000 0F in a pipe heater. A pressure of 1000 psi is maintained and the lower molecules are further decomposed as below;

CH4 ---Decompose-->C + 2H2

Gas and Gasoline in vapor form go out as two products. The vapor phase is condensed to obtain Diesel, Petrol and then LPG in the bottling plant to serve energy requirements. The coke deposited in the process is removed periodically and the process which is a continuous one is sustaining for the various fractionation products. The various other forms of thermal cracking are as follows;

i. Viscosity Breaking
ii. Vapor Pressure Cracking
iii. Thermal Reforming

i. Viscosity Breaking:          Here various oils and residues obtained after thermal cracking are to produce various oils of different viscosity. This is called as Viscosity Breaking. The temperature is 460 0C and pressure is 500 psi.

ii. Vapor Pressure Cracking:       Here Cracking is done in such a way there is only vapor phase obtained after cracking. By doing so aromatic hydrocarbon and gaseous products are obtained.

iii. Thermal Reforming:     Here heavy gasoline of lower octane number is cracked to get higher gasoline of higher octane number. The temperature is 530 0C and pressure is 750 psi. The flow sheet of Thermal Reforming is given below;



2. Catalytic Cracking

Gasoline produced by Thermal Cracking has octane number 72. If the octane number is increased the yield decreases which can be rectified by use of catalyst to increase the rate of decomposition of the hydrocarbons in the crude petroleum. Hence gasoline produced by catalytic cracking is low in oliefic and high in paraffinic and aromatic hydrocarbon. The advantages of catalytic cracking are,

  1. No fuel from outside is required for catalytic cracking
  2. All the heat required is obtained by heating the coke deposition the catalyst
  3. The pressure is low
  4. The Gasoline has a high octane number
  5. Total yield of Gasoline is high
  6. A sulfur content of all the products is low as it is eliminated as H2S.

Types of Catalytic Cracking

The two types of Catalytic Cracking are,

  1. Fixed Bed Catalytic Cracking
  2. Moving Bed Catalytic Cracking

The first one is a catalytic cracking where fixed bed of catalyst is used. The catalyst in a form of granules or pellets and bed of the catalyst for fixed in the catalyst covers. Oil vapors which are heated to the cracking temperature through the catalyst are carbonized at which it is reactivated by burning the carbon. Oil vapors are diverted tot eh second catalyst chamber.

Second one is a catalytic cracking where moving bed of catalyst is used. The catalyst in the form of fine powder flows down through a hopper into a reactor where cracking takes place. The carbonized particles of the catalyst come down against a raising current of air to remove the carbon deposit of the catalyst as it is burnt off.

 

1. Fixed Bed Catalytic Cracking Process

The fixed bed catalytic cracking method is described in the following diagram.



The charge is passed through a heater where it is heated to cracking level then it is goes to catalyst towers. These towers have catalyst tubes and around these tubes molten salt mixtures (mixture of sodium nitrate and sodium nitrite) are circulated to distribute heat and maintain uniform temperature in the reactor. The cracked vapors form these catalyst towers of fractionators in the fractionating column to recover gases and gasoline vapors from the top and the heavy gas/oil is removed from the bottom of the column.

Gasoline vapors are cooled and condensed in the condenser and then sent to the stabilizer. In the stabilizer certain dissolved gases are removed and the desired boiling range and vapor pressure is obtained. The main catalysts used are

  1. Bauxite pellets
  2. Silicon Nitrite complex of Alumina (SiN2.Al2O3) of 6 mesh size

 

2. Moving Bed Catalytic Cracking Process

The moving bed catalytic cracking method is described in the following diagram.

Heated oil vapors go up in the reactor and catalyst comes down through the hopper which is the significance in the moving bed catalytic cracking process. After the cracking of vapors the spent catalyst is removed from the bottom. It is regenerated and sent again to the catalyst hopper through the elevators. The cracked vapors after the separation of dust separated go to the fractionator where gas oil is separated from vapors of gas and gasoline. Gas oil is with drawn from the bottom. The gas and the gasoline vapors are condensed in the condenser and are separated.

Other methods of synthesis of gasoline are by polymerization, alkylation, Fischer-Tropsch method and liquefaction of coal or hydrogenation of coal.

Normally the gases obtained from the cracking of petroleum are ethylene, propene, butene and saturated hydrocarbons like methane, ethane, propane and butane. Polymerization also classified by catalysis to obtain motor fuel.


Petrochemicals

Petroleum & Petrochemical Industries

Crude Oil Refining

Petrochemical Products

 
Composition

  1. Aliphatic Compounds are classified into n-paraffins of the formula CnH2n+2 Eg. Hexane & Heptane. The other is iso-paraffins of the formula CnH2n+2 Eg. 2-methyl hexane, a derivative of the paraffin indicated above.
  2. Cyclic Compounds of the formula CnH2n Eg. Napthene and Benzene series of the formula CnH2n-6 Eg. BTX
  3. Asphalts contain atoms of carbon, hydrogen, sulfur, oxygen and nitrogen. Various resins are used as adhesives which are semi solids in structure.

The crude is classified into paraffinic base for aliphatic compounds, naphthenic base for cyclic compounds and an intermediate base for both of the above.

 

The petroleum refinery products are classified as;

  1. Gas Fraction – Eg. Natural Gas, whose main composition is methane and the second one is LPG
  2. Light Distillates – Eg. Petroleum & Kersosene
  3. Intermediate Distillates – Eg. Diesel
  4. Heavy Distillates – Eg. Wax & Lubricating Oil
  5. Residue – Eg. Grease & Asphalt

The normal refinery processes for the manufacture of various products are done by physical changes like distillation, absorption, extraction, adsorption, crystallization, heat transfer and fluid flow to name a few. Similarly the unit processes involving chemical changes are pyrolysis, reforming, polymerization, alkylation, isomerisation, sulfur removal, hydrogenation, etc.


  • Lighter most products   –----> Methane ----> Methanol, Chloromethane
  • Naphtha ---Steam/Cracking--->  Ethylene ----> Ethyl Oxide, Acetaldehyde
                                          Propylene ---> Iso-propanol, Cumene, Polypropylene
  • C4, C5 Series    ----------->    Butane ----->  Butadiene
  • Hydrocarbons --Reforming-->     Benzene ---->  Ethyl Benzene, Maleic Anhydride
                                           Toluene -----> Nitro Toluene, Phenol
                                          Xylene ------> Phthalic Anhydride, Terephthalic Acid


Manufacture of Chloromethane

Methane on chlorination yields successfully the chloromethane by substitution of hydrogen atoms by chlorine. The flow sheet of the industrial manufacture is given below;


Reactions

CH4+Cl2 --> CH3Cl+HCl -–Cl2--> CH2Cl2+HCl -–Cl2--> CHCl3+HCl ---Cl2--> CCl4+HCl

Methane         Methyl Chloride           Methylene Chloride       Chloroform                    CTC


These compounds of the chlorination reaction are used as industrial solvents and intermediates in the manufacture of organic compounds for dye and dyestuffs manufacturing plants. Similarly we have production of ethylene oxide in a fluidized bed reactor to produce the product and used for manufacture of ethylene glycol. The reaction is exothermic and the heat generated may be used for other purposes like heat exchangers of the type of shell & tube, etc. Acetaldehyde manufactured from ethylene by exothermic reaction with palladium chloride catalyst in a series of strippers and distillation columns for the manufacture. Isopropyl alcohol is manufactured from propylene by reaction with industrial acids to form the product. Cumene is another petrochemical manufactured from benzene by packed bed staged reactor at a temperature of 250 OC in the presence of phosphoric acid. Butadiene is another compound obtained from C4H10 to produce finally styrene and rubber for the polymer industry. Phthalic anhydride and maleic anhydride are produced from tubular reactor by the production of isomers and dehydration reaction to form compound polyesters. Phenol is a very important compound obtained from Toluene by series of distillation column and used in the manufacture of phenol-formaldehyde resins, molding products, electrical applications and other various uses in the polymer industries.



Petrochemical Industry in India

It is still in a incipient state born much later than petroleum industry around 1966, the growth it made in the last two years because of technology is very much encouraging. The modest beginning of petrochemical industry started with coming of an ethylene plant of capacity 20,000 TPA by a naphtha cracker by Union Carbide in 1968. National Organic Chemicals Limited (NOCIL) soon followed the development and established 60,000 TPA naphtha cracker units at Thane in Maharashtra by 1968. Indian Petrochemical Limited (IPCL) in Baroda in the year 1971, with an investment of 1000 crores of rupees to establish a cracker unit indigenously. Subsequently ONGC which was responsible for exploration and production of Oil and Natural Gas made an active role in the aromatic ester plant by the side of Gujarat Refinery.

The development of IPCL fulfills the growth of 32 complexes all over India for the expansion of petro products. By eighth plant Rs. 5000 crores was exclusively invested by IPCL for the growth of engineering plastics. The products like alloys, poly carbonates, carbon filaments, oil blends and other polyester products where diversified by the various companies listed above.  



Sugar Industry

Today Sugar is so plentiful and so cheap that we take it granted and overlook how much science and industry accomplished in making refined sugar available to us. Primitive man had to depend on roots, fruits and saps from certain trees for any sweetness for his diet. The term sugar refers the chemical sucrose.

Sources of Sugar

  1. Sugar Cane: It was first cultivated in India from where it spread eastward to China, westward to Arabia, Egypt, Spain and finally to the new world. The sugarcane (saccharim officinaram) is a tall perennial grass having numerous bamboos like stems which grow to a height of 12 feet or more. The period of growth is normally 15-18 months, but because of the advent of the fertilizers the period shortened and a crushing season of 6 months every year is maintained for the production of sugar.
  2. Sugar Beet:  While we can guess regarding the original cultivation of sugarcane the situation is different with reference to sugar beet. The juice of the beet contains a sugar identical with that of the cane at this discovery was put into practical use.

Steps in sugar manufacture

The sugar is synthesized by the growing plant and the processing in the factory is only a succession of separations whereby the sugar is separated from the constituents of the plant.

  1. Separation of the juice from the fiber by pressure
  2. Clarification is a removal of impurities that interfere with subsequent evaporation and crystallization
  3. Removal of water by evaporation
  4. Conversion of the sugar from the dissolved condition to a solid crystal form
  5. Separation of the crystal sugar from the mother liquor followed by molasses obtained from centrifuge.
  6. Drying and packing of sugar

Clarification

The juice extract from the cane are strained to remove dirt particles, fiber or pulp after this juice is ready for clarification. The purpose of clarification is to free the juice as far as possible from all constituents except sugar without altering the sugar itself. Lime is one for the first chemical to be used are universal basis for this clarification since it is both effective and economical for the cost. The main purpose of lime is to neutralize the acidity of juice and converts many of the organic acids into insoluble calcium salt. Thus clarification remains an essential and integral part of the manufacture of sugar.

The flow process of liming is given below;


 

Analysis of typical cane molasses

 

Composition

Percentage (%)

Water

20

Sucrose

30

Raffinase

0

Invert Sugar

32

Ash

6

Organic non-sugars

12

Evaporation

The juices from the clarification must now be evaporated in order to produce crystal sugar. Today evaporation is conducted by steam-in evaporators. In the first stage of evaporation the juice is concentrated to 50%-60% sugar. This is made in MEE (Multiple Effect Evaporator) which are very effective and by efficient use of steam.

Crystallization

At this stage the evaporation is continued to the point where sugar crystals formed and separate from remaining water and impurities. There are various types of crystallizers namely horizontal, cylindrical or U shaped kerns equipped with stirring paddles. After stirring the mixture are cooled to take advantage of the lower solubility of sugar at lowest temperature.

Refining

The raw cane sugar is subjected to further refining operation before it is ready for consumption. Adsorption of impurities is followed by crystallization. The refining process takes place in the following sequence.

  1. Affination
  2. Melting
  3. Defecation
  4. Purification with Bone-char or active carbon
  5. Filtration
  6. Crystallization
  7. Centrifuging
  8. Finishing

In affination process the raw sugar is mixed with syrup which softens and dissolves the molasses without eroding the sugar crystals. In the defecation process sufficient lime is added to make the solution alkaline and the alkalinity is neutralized with calcium phosphate or phosphoric acid. The precipitate of calcium phosphate or phosphoric adsorbs most of impurities.


Bone-char Treatment

Composition

Percentage (%)

Carbon

10

Tri calcium phosphate

83

Calcium carbonate

4

Iron, Nitrogen, Silica, Calcium Sulfide

Traces

The purpose this treatment is primarily to remove color, organic and inorganic substances from the raw sugar solution. Active carbon is used for refining of sugar. It is generally employed from producing a refined, granulated sugar.

 

By-products

Molasses:     This is basically used for cattle feed. Although it has the limitation of providing only carbohydrate high protein yeast can be made from molasses and inorganic nitrogen salts, can serve as a basis for the protein content in the cattle feed. The recent development is industrial alcohol produced from molasses can be used as motor fuel. Such a development can simplify the world production of molasses.

Bagasse:       The quantity is 28,000,000 Tonnes of Bagasse per year. It is right now used in sugar factories as fuel developing co-generation plant for producing power, manufacture of plastics, paper pulp and wall boards.

Conversion of sugar to other products

Sugar represents practically a chemically pure product available at low cost and it is natural to find that serious study has given rights to development of processes to convert sugar into other products. The various conversions for molasses can be applied for sugar but extensive development can takes place parallel to the potential molasses, bagasse and press-mud whose original name is “Filter Cake”. Some undertakings compile the manufacture of sugar with the production of ethyl alcohol, butyl alcohol, acetone by fermentation.

Press-mud (Filter cake):    Press-mud or Filter cake is the solid substance obtained after juice clarification. It is almost brown color and it was used as manure for the sugar cane field itself. A sugar factory crushing 2500 TPD of sugarcane generates 75 Tonnes of Filter cake. There are about 500 sugar mills generating sugar in India with crushing capacity ranging from 2500 - 5000 TPD. The recent research on the exploitation of press-mud or filter cake shows the presence of sugar, proteins, fiber, wax and other mineral salts. Sugar is present a 0.5% in press-mud. The Protein content is 3%. The Fiber is 35%. The Wax is 12%. And the remaining is moisture or water. These components can be extracted and used for the increased use of sugar industry. The fiber part of the waste is dried and converted to carbon called as “Adsorbent Carbon” as they can substitute the role of active carbon in the adsorption operations. Though in the potential of press-mud it is estimated that we can have 750 crores of rupees provided to national exchequer annually. These constituents are downstream of multi component sugar industry by-product. They can be applied for fluoride removal to eliminate skeletal flurosis and in the Drugs & Pharma Industry for the production of anti cancer drugs, already in commercial operation in a country like Japan.


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Senthil Kumar,
Apr 28, 2009, 7:40 PM
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