CAPE Chemistry Module 3: Industrial Plants

Factors Influencing Location of an Industrial Plant

• Suitability of terrain

• Vulnerability of an area to weather/natural disaster events

• Availability and Proximity of building materials • Availability of safe disposal systems

• Availability of commodities like water

• Access to sufficient electrical power

• Proximity of skilled workers

• Effect on nearby community- providing employment versus using up productive farmland.

Health and Safety requirements

• Choosing processes and tools which are inherently safe

• Identifying hazards which cannot be eliminated, and instituting training on how to cope with it

• Having plans for coping with large-scale emergencies like hurricanes and ensuring staff has had chance for training and practice

• Ensuring that emergency exits are clearly marked

• Training staff in proper procedures including use of personal protective equipment (PPE)

• Having some staff qualified in first aid

Name the proces of Aluminium Ore Purification

Bayer Process

Main constituent of bauxite

Aluminium Oxide

Name impurities of Bauxite

Iron(iii) Oxide, Silicon Dioxide, Titanium Oxide

State steps of Bayer Process

Digestion, Filtration, Precipitation, Filtration, Calcination

Digestion process in Bayer process

ground bauxite mixed with hot sodium hydroxide.

Al2O3(s) + 2NaOH(aq) → 2NaAlO2(aq) + H2O(l)

Al2O3(s) + 2NaOH(aq) + 3H2O(l) → 2NaAl(OH)4(aq)



SiO2(s) + 2NaOH(aq) → Na2SiO3(aq) + H2O(l)

First filtration of Bayer process

The insoluble impurities like the iron oxide are filtered out as red mud, and only the soluble products remain

Precipitation of Bayer process

The heated filtrate is stirred and cooled, causing the precipitation of aluminium hydroxide crystals.

NaAlO2(aq) + 2H2O(l) → NaOH(aq) + Al(OH)3(s)

A crystal of aluminium hydroxide is usually used to seed the mixture and jumpstart precipitation.

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Carbon dioxide is pumped to trigger precipitation

2\[Al(OH)4\]-(aq) + CO2(g) → 2Al(OH)3(s) + CO32-(aq) + H2O(l) \n

Second Filtration of Bayer process

The silicates remain in solution, leaving aluminium hydroxide crystals

Calcination in Bayer process

The filter residue is heated in a rotary kiln at 1100-1300 degrees Celsius

\- drives off water

\- leaving near pure aluminium oxide (alumina)

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\- 2Al(OH)3(s) → Al2O3(s) + 3H2O(l) \n

Process of Production of Aluminium

Hall-Heroult Process

Explain Hall-Heroult Process. give equations

hydrolysis of molten alumina

alumina melts at 2050C (much energy required)

melting point decreased to 960C, molten cryolite (NaAlF6) also increases conductivity. \n

At the cathode (carbon lining), the half \n equation is: O2-(l) + C(s) → CO(g) + 2e-

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At the anode (carbon rods): Al3+(l) + 3e- → Al(l)

List uses of Aluminium and why?

cans & food packaging; non-toxic

kitchen utensils; resistant to corrosion

pots & pans; thermal conductivity

alloys in spacecraft; ligtweight

List environmental effects of Aluminium Industry

caustic red mud from extraction seep into ground water; increase pH

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fluoride gases from Hall-Heroult process escape affecting plans.

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global warming by gases: PFCs, SO2, CO2, CO

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mining destroys green areas; reduce aesthetic appeal

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disposals of used Carbon cell linings containing alkaline solutions.

separation of crude oil process called ___________

fractional distillation

Quick overview of Fractional Distillation of Crude oil

heat oil with long carbon chains in fractional column to 300C

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unboiled liquid (heaviest fraction) piped off as residues

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vapor rises through the fractionating column, where there is a temperature gradient with the coolest part at the top.

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When a hydrocarbon compound reaches a part of the column that is cooler than its boiling point, it will condense, be collected, and piped off.

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vapours which don’t condense are piped off at the top as refinery gases. This is the lightest fraction.

define reforming in crude oil industry

straight-chain hydrocarbons are broken up and then reassembled into aromatic and highly branched-chain hydrocarbons

why does the industry do reforming?

These ‘higher octane ratings’ (meaning more highly branched compounds) are more resistant to knocking, or the premature combustion of fuels in an engine implicated in engine damage and overheating.

List environmental impacts of crude oil pollution

*Exploration:*

Seismic surveys are used to determine underground oil deposits. These surveys require shock waves which are usually generated using explosions in the ocean or \n underground; destroy ecosystem and wildlife.

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*Extraction*

The surrounding land is cleared and leveled; destroys flora, fauna and habitats.

Well drilling expels brine and oil into surrounding soil and water; damages plant and aquatic life.

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*Transportation*

Oil tanker spills kill marine life and contribute to reduce air quality if they catch ablaze; affecting birds, coral reefs, polar bears.

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*Refining*

releases toxic and hazardous air pollutants (many of which are greenhouse gases) CO, oxides of Nitrogen etc

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*Use*

fuels releases compounds like carbon dioxide and nitrogen oxides into the environment.

Name to process of Ammonia production

Haber process

State the major equation for the Haber process. (include conditions)

N2(g) + 3H2(g) → 2NH3(g) H = -92kJ/mol

CONDITIONS: iron catalyst, 400C, 150-250atm

Where is Hydrogen obtained in the Haber process?(state equation and conditions)

steam reforming; reaction of methane with steam

Equation: CH4(g) + H2O(g) →CO(g) + 3H2(g)

Conditions: Ni catalyst, 700-1100C, 20atm

Quickly explain the water gas shift reaction. Include equation and conditions

Additional hydrogen is recovered from the steam through the water gas shift reaction. \n

EQUATION: CO(g) + H2O(g) → CO2 + H2(g)

CONDITIONS: Nickel Oxide catalyst, 130C

How is Nitrogen procured in Haber process?

fractional distillation of liquefied air

List uses of Ammonia

*Agriculture*

production of nirtogen-based fertilizers

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*Chemical Industry*

manufacture nitric acid, plastics, pharmaceuticals

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*Food*

nitrogen source for yeast

refrigerant gas

State impacts of Ammonia industry of environment

CO2 from the steam-reforming process is emitted

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Excess fertilizers entering natural waters results in eutrophication; death of aquatic organisms \n

Fertilizer runoff can enter domestic water supply, polluting drinking water.

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Soil acidification results when ammonium ions in the soil are nitrified by bacteria, releasing hydrogen ions; acidity can affect plant growth.

Procces of ethanol production?

fermentation

define fermentation

process where sugars are oxidized by living organisms in the absence of oxygen to release energy

why is fractional distillation important in ethanol production

When ethanol concentration reaches 12-15% however, the activity of the yeast stops as the enzymes are denatured by the toxic ethanol.

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To increase the concentration of alcohol in the solution to the wonderfully deleterious levels found in spirits (even up to 40% alcohol by volume), fractional distillation must be carried out.

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Close boiling points

Uses of ethanol

*Fuel*

Ethanol has a very clean (non-smoky) and exothermic combustion. As such, it is used as a fuel additive.

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*Beverage*

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*Solvents*

disinfectants

organic solvent

Social/Economic Impact of Alcohol Consumption

depressant on nervous system, euphoria, relaxant

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slurred speech, memory loss, liver cirrhosis, cardiovascular diseases etc.

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death

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fetal alcohol disorder

Name the process of chlorine production

electrolysis of brine in diaphragm cell

Explain the chemical process at anode and cathode of diaphragm cell in Chlorine production

*At the anode*

2Cl-(aq) →Cl2(g) + 2e- (preferably discharged)

4OH-(aq) →2H2O + O2(g) +4e-

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*At cathode*

2H+(aq) + 2e- → H2(g) (preferably discharged)

Why is separation of gases important in Chlorine production

This separation of gases is necessary because a mixture of hydrogen and chlorine gas can react explosively to form hydrogen chloride in the presence of sunlight or UV radiation.

State economic advantage of using diaphragm cell

Operates at a lower voltage than mercury cell.

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Brine can be low purity.

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Asbestos is chemically stable, relatively inexpensive and abundant.

Industrial importance of Chlorine

bleaches

PVC

organic solvent

aerosols and refrigerants(CFCs)

anesthetics like halothane

impact of chlorine industry on environment

release of asbestos; lung cancer

PVC is non-biodegradable; burning PVC releases toxins

name the process of sulphuric acid production

Contact Process

State the main stages of Contact Process

***Production*** of Sulphur Dioxide

***Oxidation*** of Sulphur Dioxide to Trioxide

***Hydration*** of trioxide to oleum

***Dilution*** of oleum to H2SO4

State two ways to product Sulphur Dioxide. Include equation and condition

*Burning Sulphur in excess air*

S(s) + O2(g) → SO2(g)

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*Combustion of Sulphur Ores*

4FeS2(s) + 11O2(g) → 2Fe2O3(s) + 8SO2(g)

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CONDITIONS: 1000C

Quickly explain Oxidation of Sulphur Dioxide to Sulphur Trioxide in Contact Process

2SO2(g) + O2(g) ⇌ 2SO3(g) H =-197kJ/mol

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CONDITIONS: vanadium (V) oxide in silica gel catalyst, 450C

Explain Hydration of Sulphur Trioxide in Contact Process

The uncontrollable hydration of sulphur trioxide produces sulphuric acid (as SO3, its acid anhydride)

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formation of intermediate oleum (fuming H2SO4)

The SO3 gas is dissolved in a concentrated sulphuric acid solution to form oleum.

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H2SO4(l) + SO3(g) → H2S2O7(l)

Explain the dilution of Oleum

The oleum is slowly diluted with water with continuous cooling to form concentrated sulfuric acid.

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H2S2O7(l) + H2O(l) → 2H2SO4(l)

industrial importance of Sulphur

SO2 as bleaching agent & preservative

H2SO4 in fertilizers, dyes, explosices, car batteries

Sulphate salts: magnesium suplhate as laxative, sodium sulphate as drying agent

Impact of Sulphuric Acid Industry

SO2 emission contribute to acid rain

H2SO4 spills on metal to explosively produce Hydrogen class

used as recyclable catalyst