The Chemical Industry
Introduction
The chemical industry is one of the UK’s largest manufacturing industries. The
average growth rate of the chemical industry between 1995 and 2000 was nearly
5 times that of all manufacturing industries.
New products
Before a new product can be manufactured testing involving several stages
needs to be done to find best conditions for full-scale production:
1. Research
& Development
2. Laboratory
Process
3. Pilot Plant
4. Production
5. Review
Finding out about the material and how it can be made
Investigate possible processes and routes for
synthesis of the product in the laboratory
Medium-sized investigation of to assess product
quality, hazards and costs
Full-scale factory production of the product
Evaluation of operational procedures with a view
to improving efficiency, profit or safety.
The manufacturing process
Most manufacturing processes also involve a sequence of steps.
Eg. Production of sulphuric acid by the Contact Process:
1. Sulphur burning
S(s) + O2(g)  SO2(g)
2. Sulphur dioxide conversion
450oC
SO2(g) + ½O2(g)
SO3(g)
V2O5 catalyst
3. Sulphur trioxide absorption
ΔH = -297 kJ mol-1
ΔH = -94 kJ mol-1
SO3(g) + H2O(l)  H2SO4(l)
Raw materials and feedstocks
Feedstock
A reactant from which other chemicals can be extracted or
synthesised to manufacture a required product
Raw material
The original source of the feedstock
The major raw materials used in the chemical industry are: Crude oil, Metallic
ores and minerals, Air and Water
Crude oil
The naphtha fraction of crude oil is important as a feedstock for the chemical
processes of:
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Steam cracking to produce ethene and propene for plastics manufacture
Reforming to produce aromatic hydrocarbons for the manufacture of
dyes, drugs, etc.
Metallic ores and minerals
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Bauxite produces alumina, Al2O, to manufacture aluminium
Bauxite  Alumina  Aluminium

Rock salt produces NaOH, Cl2 and HCl on electrolysis of its aqueous
solution
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Provides nitrogen in ammonia production
Provides oxygen for oxidation of:
- Sulphur to sulphur oxides in sulphuric acid manufacture
- Ammonia to nitrogen oxides in nitric acid manufacture
Air
Water
Water is a raw material in the steam cracking of naphtha and ethane in the
hydration of ethene to produce ethanol
Water is a widely used solvent while both air and water can be used as coolants.
Choosing a manufacturing route
When choosing a manufacturing route several factors need to be taken into
account:
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Cost, availability and suitability of feedstocks
Yield of product
Recyclability of unreacted materials
Marketability of by-products
Difficulty and cost of waste disposal
Energy consumption
Atmospheric emissions
Batch or continuous process
Batch process
In a batch process the reactants are added to the reactor and the reaction is
started. The progress is carefully monitored and the reactor is emptied at the
end of the reaction. The product mixture then continues on to the separation
and purification stages. A batch reactor is usually a large cylindrical tank.
Examples of Batch Processes
 Making margarine

Colourants

Production of aspirin(salicyclic acid)
Continuous process
In a continuous process reactants flow into the reactor at one end and products
flow out of the other end. Reactor design varies from one process to another.
Examples of Continuous Processes
 Steam cracking

Contact Process- manufacture of sulphuric acid

Production of Nitric Acid – Ostwald Process

Production of ammonia- Haber Process
Advantages and Disadvantages of Batch/Continuous processes
Advantages
Disadvantages
Batch process
Better suited to small quantities
Plant cheaper to build
Plant more versatile
Good for multi-step reactions
Reactants in any physical state
Filling and emptying plant
increases production time
Can be hard to control if reaction
is exothermic
Continuous process
Ideal for large quantities of product
Product is cheaper if operated at capacity
Smaller workforce
Good for fast, single-step reactions
Difficult to use solid reactants unless
‘fluidised’
Can be difficult to control when starting
up, but easier to control when in operation
Economic aspects
The chemical industry is capital intensive rather than labour intensive ie. it only
employs about 1.5% of the British workforce.
Capital intensive industry
Large amounts of money needed to set up the
process.
Labour intensive industry
Large work-force needed to produce a relatively
small volume of product.
The conditions under which an industrial chemical process operates are based on
research and are chosen to maximise economic efficiency.
Manufacturing costs can be divided into three categories:
Capital costs
The large amounts of money needed to set up a process.
Eg. Buying property, constructing the plant, infrastructures
and research and development
Variable costs
Costs variable in relation to chemical process involved. These
costs are not incurred if production stops.
Eg. Raw materials, energy, distribution of product, overheads
and effluent treatment/disposal.
Fixed costs
The cost in relation to volume of production. These costs are
still incurred whether production is low or high, but the effect
on the selling price of the product lessens as scale of
production increases.
Eg. Labour costs, depreciation of plant, plant maintenance, land
rental and sales expenses.
The use of energy
Wasted energy causes pollution and contributes to global warming. Energy is a
major variable cost in the chemical industry due to the rapid price increases
that can occur with oil, therefore manufacturing plants tend to:
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Switch to processes requiring less energy
Utilise the heat energy from exothermic reactions elsewhere
Use ‘waste’ heat to generate energy
Sell excess energy to supply heating for local housing
Location of chemical industry
Major chemical manufacturing sites are positioned as a result of historical and
practical considerations.
Example
Grangemouth chemical works
This plant began in 1919 as a dyeworks then expanded to produce
pharmaceuticals, pigments and speciality chemicals.
The Grangemouth site was chosen for several practical reasons:
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Large flat area of land available
Good supply of water
Good transport links by rail and sea for import of raw materials and
export of products
Good supply of skilled labour due to presence of other chemical industry
in the area
Sea was accessible for effluent disposal
There was also a shortage of dyes in Britain after the start of World War I as
most used to be imported from Germany.
Safety
As with all industries the chemical industry must operate without causing
accidental injury or health risk to employees or the public. However, some major
incidents have occurred.
Eg.
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1974, Flixborough, Lincolnshire – cyclohexane plant had an explosion and
fire killing 28 and injuring 104
1984, Bhopal, India – toxic gas leak killing several thousand
In the 1980’s health, safety and the environmental impact of industry became a
major priority for governing bodies. The chemical industry is now regulated to
ensure that strict rules are enforced regarding any chemical exposure.