Basic Principles of Unit Processes and Unit Operations in Organic Chemical Industries (Part - 1) Chemical Engineering Notes | EduRev

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Chemical Engineering : Basic Principles of Unit Processes and Unit Operations in Organic Chemical Industries (Part - 1) Chemical Engineering Notes | EduRev

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Basic Principles Chemical processes, Unit Processes And Unit Operations In Organic Chemical Industries

Chemical processes usually have three interrelated elementary processes

  • Transfer of reactants to the reaction zone
  • Chemical reactions involving various unit processes
  • Separation of the products from the reaction zone using various unit operations

Processes may involve homogeneous system or heterogeneous systems. In homogeneous system, reactants are in same phase-liquid, gases or solids while heterogeneous system include two or more phases; gas liquid, gas–solid, gas-gas, liquid–liquid, liquid solid etc. Various type reactions involve maybe reversible or irreversible, endothermic or exothermic, catalytic or non-catalytic. Various variables affecting chemical reactions are temperature pressure, composition, catalyst activity, catalyst selectivity, catalyst stability, catalyst life, the rate of heat and mass transfer. The reaction may be carried out in batch, semi batch or continuous. Reactors may be batch, plug flow, CSTR. It may be isothermal or adiabatic. Catalytic reactors may be packed bed, moving bed or fluidised bed Along with knowledge of various unit processes and unit operation following information are very important for the development of a process and its commercialization [Austin,1984] Basic Chemical data: Yield conversion, kinetics

  • Material and energy balance, raw material and energy consumption per tone of product, energy changes  
  • Batch vs Continuous, process flow diagram
  • Chemical process selection: design and operation, pilot plant data, Equipment required, material of construction
  • Chemical Process Control and Instrumentation
  • Chemical Process Economics: Competing processes, Material and, Energy cost, Labour, Overall Cost of production
  • Market evaluation: Purity of product and uniformity of product for further processing 
  • Plant Location
  • Environment, Health, Safety and Hazard
  • Construction, Erection and Commissioning
  • Management for Productivity and creativity: Training of plant personals and motivation at all levels
  • Research, Development and patent
  • Process Intensification Inorder to improve productivity and make the process cost effective and for improving overall economy, compact , safe, energy efficient and environmentally sustainable plant, process intensification has become very important and  industry is looking beyond the traditional chemical engineering.

Unit Processes and Unit Operations in Chemical 

Process Industries 

Chemical process is combination of unit processes and Unit operation. Unit process involves principle chemical conversions leading to synthesis of various useful product and provide basic information regarding the reaction temperature and pressure, extent of chemical conversions and yield of product of reaction nature of reaction whether endothermic or exothermic, type of catalyst used. Unit operations involve the physical separation of the products obtained during various unit processes. Various unit processes in chemical industries are given in Table M-I 3.1. Various chemical reactions and its application in process industries are given in Table M-I 3.2.

Nitration 

Nitration involves the introduction of one or more nitro groups into reacting molecules using various nitrating agents like fuming, concentrated, aqueous nitric acid mixture of nitric acid and sulphuric acid in batch or continuous process. Nitration products find wide application in chemical industry as solvent, dyestuff, pharmaceuticals, explosive, chemical intermediates. Typical products: TNT, Nitrobenzene, m-dinitrobenzene, nitroacetanilide, alpha nitronaphthalene, nitroparaffins  

Table M-I 3.1: Unit Processes in Chemical Process Industries  

Alkylation and Hydro delkylation

Decomposition

Acylation

Fermentation

Ammonoxidation

Halogenation

Amination by reduction

Hydsogenation

Amination

Hydrohenatlysis

Aromatisation

Hydroformyl ati on

Amination by ammonalysis

Hydro lysis

Calcination

Hydration

Carbonation

Hydroammonalysis

Causticisation

Isomerisation

Chlorination and Oxy chlorination

Neutralistion

Condensation

Nitration

B i omethhanati on

Methanation

Carbinisation

 

Disproportination

Oxidation and partial oxidation

Cracking; Thermal, steam cracking, catalytic

cracking

Pyrolysis

Dehydration

Polymeristion: Addition and condensation

Chain growth and step growth,Bulk, Emulsion, suspension, solution, Radical and coordination polymeristion

Dehydrogenation

Reduction

Ditozitation and coupling

Reforming: Steam reforming

Catalytic reforming

Gasification of coal and biomass

Sulphidation

Desulphurisation and hydro desulphurisation

Sulphonatiomn

Electrolysis

Sulphation

Etherification

Xanthation

Estertification and Trans Estrerificartion

 

    
Table M-I 3.2: Important Chemical Reaction and their Application in Chemical Process Industries  

 

Reaction

 

 

Description

Fisher-Tropsch (FT) Process

The Fisher-Tropsch process produce a variety of hydrocarbons (alkanes: CnH(2n+2)) by involves a series of chemical reaction.

(2n+1) H2 + nCO→ CnH(2n+2)+ nH2O

FT process is used for synthesis of alkanes.

Friedel-Crafts

reactions

In this reaction attach substituent’s to an aromatic ring. Two main types of Friedel-Crafts reaction are acylations reaction and alkylation reactions, both proceeding by electrophilic aromatic substitution.

Basic Principles of Unit Processes and Unit Operations in Organic Chemical Industries (Part - 1) Chemical Engineering Notes | EduRev           

Friedel-Crafts process used in alkelation reactions.

Oxosynthesis

Reactions

In this process Isomeric mixture of normal- and iso-aldehydes get produces by utilizing syngas (CO and H2) and olefinic hydrocarbons as reactants. It is exothermic process, this process thermodynamically favorable at ambient pressure and temperatures. This reaction also called as hydroformylation reaction.

RCH=CH2+CO+H2→RCH2CH2CHO + R(CH3)CHCHO

Oxosynthesis used for production of alcohols.

Hofman Process

In this process, organic reaction of primary amide converts into a primary amine with one fewer carbon atom.

Basic Principles of Unit Processes and Unit Operations in Organic Chemical Industries (Part - 1) Chemical Engineering Notes | EduRev

Hofman process typical examples are conversion of aliphatic amides to aliphatic amines and aromatic amides to aromatic amines.

Free-Radical

Reaction

Any chemical reaction involving free radicals, generally radical generated

from radical initiators such as peroxide or azo bis compounds. Radical reactions are chain reactions with chain initiation, propagation and termination steps. Free radical reactions are used many organic synthesis and polymerization reactions

Beckmann

rearrangement

Beckmann rearrangement is acid catalyzed rearrangement of an oxime to an amide, which developed by German chemist Ernst Otto. A typical example of Beckmann rearrangement is synthesis of caprolactam from cyclohexanone. Caprolactam is monomer for nylon 6.

Basic Principles of Unit Processes and Unit Operations in Organic Chemical Industries (Part - 1) Chemical Engineering Notes | EduRev

Wackers Process

Wacker process is similar to hydroformylation and used for aldehyde compounds. A typical example of wacker process is oxidation of ethylene to acetaldehyde in the presence of Pd catalyst.

 [PdCl4]--+C2H4+H2O→CH3CHO+Pd+2HCl+2Cl-

Pd++ CuCl2+2Cl-→[PdCl4]--+2CuCl

2CuCl+ 0.5 O2+2HCl→2CuCl2+H2

 
 Example Preparation of TNT (trinitrotoluene) 

TNT is produce in a three-step process: First, toluene is nitrated with a mixture of sulfuric acid and nitric acid to produce mono-nitrotoluene or MNT. The MNT is separated and then renitrated to dinitrotoluene or DNT. In the final step, the DNT is nitrated to trinitrotoluene or TNT using an anhydrous mixture of nitric acid and oleum.

Basic Principles of Unit Processes and Unit Operations in Organic Chemical Industries (Part - 1) Chemical Engineering Notes | EduRevBasic Principles of Unit Processes and Unit Operations in Organic Chemical Industries (Part - 1) Chemical Engineering Notes | EduRev   


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