7 CATEGORY 7: INORGANIC CHEMICALS INDUSTRY
The following APPA scheduled processes are covered by this category:
1. Sulphuric Acid Processes
2. Phosphate Fertilizer Processes
4. Nitric Acid Processes
5. Ammonium Sulphate and Ammonium Chloride Processes
6. Chlorine Processes
7. Hydrochloric Acid Processes
11. Arsenic Processes
21. Hydrofluoric Acid Processes
23. Lead Processes
24. Fluorine Processes
40. Beryllium Processes
41. Selenium Processes
42. Phosphorous Processes
43. Ammonia Processes
44. Hydrogen Cyanide Processes
47. Calcium Carbide Processes
50. Chromium Processes
52. Cadmium Processes
61. Antimony Processes
62. Mercury
7.1 SUB-CATEGORY 7.1: PRIMARY PRODUCTION AND USE IN
MANUFACTURING OF AMMONIA, FLOURINE, CHLORINE AND
HYDROGEN CYANIDE
7.1.1 APPLICABILITY
Production and use in manufacturing of ammonia, fluorine and chlorine gas
All installations
The APPA scheduled processes covered in this sub-category include:
5. Ammonium Sulphate and Ammonia Processes
24. Fluorine Processes
43. Ammonia Processes
44. Hydrogen Cyanide Processes
7.1.2 PROCESS OVERVIEW
7.1.2.1 Ammonia
Figure 7-1: Production of ammonia
Hydrogen is reacted with nitrogen to yield NH3 (ammonia) which is cooled and stored in
tanks.
N2 + 3H2 2NH3
(Nitrogen + Hydrogen ammonia)
Nitrogen is obtained from air separation. Hydrogen is obtained from various methods,
one of which is steam reforming as illustrated in Figure 7-1.
7.1.2.2 Fluorine
Figure 7-2: Production of fluorine
Fluorspar (CaF2) is treated with sulphuric acid to produce hydrogen fluoride
(hydrofluoric acid) which is then mixed with potassium hydroxide to form potassium bifluoride.
CaF2 + H2SO4 CaSO4 + 2 HF
HF + KOH KHF2 + H2O
The potassium bi-fluoride is electrolysed to release fluorine and hydrogen. The gas
streams are captured individually at the anodes and cathodes (separated by steel
skirts) to yield a hydrogen and a fluorine stream.
7.1.2.3 Chlorine
Figure 7-3: Production of chlorine
Salt brine (NaCl) or potassium chloride solutions can be electrolysed to produce hydrogen and chlorine gas streams, at
the anode and cathodes, respectively. These streams can be separated using a diaphragm to allow for individual
extraction of the elements. A by-product of hydroxide (Na/K - OH) is formed that remains in solution.
7.1.2.4 Hydrogen Cyanide
Figure 7-4: Production of Hydrogen Cyanide
The most important process is the Andrussow oxidation in which methane and ammonia react in the presence of Oxygen
at high temperatures (1200°C) over a Platinum catalyst. Of lesser importance is the Degussa process (BMA process) in
which no oxygen is added and the energy must be transferred indirectly through the reactor wall. In the Shawinigan
process, hydrocarbon e.g. propane, is reacted with ammonia. When heated strongly, formamide decomposes to
hydrogen cyanide and water vapour.
7.1.3 ATMOSPHERIC EMISSIONS
Typical pollutants emitted to atmosphere from this process include (but are not
necessarily limited to):
•
Sulphur Dioxide (SO2)
•
Carbon Monoxide (CO)
•
Carbon Dioxide (CO2)
•
Hydrogen Fluoride (HF)*
•
Chlorine (Cl2)*
•
Ammonia (NH3)*
•
Hydrogen Cyanide (HCN)*
* Regulated by the NEMAQA emission standards
The atmospheric emissions are expected to be primarily from by-products of the
chemical reactions. Before releasing to atmosphere the flue gas can be cleaned using
a variety of methods, depending on the target pollutant, common examples are:
•
Scrubber: PM, SO2, NOx, HF, CL2, NH3, HCN
•
Cyclone: PM
•
Baghouse: PM
•
Electrostatic Precipitator: PM
7.1.4 SPECIAL ARRANGEMENTS
None
7.2 SUB-CATEGORY 7.2: PRIMARY PRODUCTION OF ACIDS
7.2.1 APPLICABILITY
The primary production of hydrofluoric, hydrochloric, nitric and sulphuric acid (including
oleum) in concentrations exceeding 10%, also processes in which oxides of sulphur are
emitted through the manufacture of acid sulphites of alkalis or alkaline earth or through
the production of liquid sulphur dioxide or sulphurous acid and secondary production of
hydrochloric acid through regeneration
All installations with exception of those producing sulphuric acid as part of the recovery
of metals from ore
APPA scheduled processes covered in this sub-category are:
1. Sulphuric Acid Processes
4. Nitric Acid Processes
7. Hydrochloric Acid Processes
21. Hydrofluoric Acid Processes
Acids are used in wide variety of industrial process as reagents, to control chemical
reactions, as well as cleaning agents.
7.2.2 PROCESS OVERVIEW
7.2.2.1 Hydrofluoric acid
Hydrofluoric acid is used widely in oil refining as well as to produce various fluorinated
organic compounds. It may also be used as an etching agent.
Figure 7-4: Production of hydrofluoric acid
Fluorspar is treated with sulphuric acid to yield hydrogen fluoride which is separated.
Alternatively, it can be produced as a by-product from phosphoric acid which is made
from mineral apatite which contains traces of fluoro-apatite.
CaF2 + H2SO4 2HF + CaSO4
(Fluorspar + sulphuric acid hydrogen fluoride + gypsum)
7.2.2.2 Hydrochloric acid
Hydrochloric acid has wide industrial use as a pickling agent as well as for the
production of chlorinated organic compounds.
Figure 7-5: Production of hydrochloric acid
Hydrochloric acid is produced by reaction of chlorine and hydrogen gases. Sodium
chloride solution (brine) is electrolysed to produce the gases, and produces caustic
soda (NaOH) as a by-product.
•
Sodium-chloride brine is converted to hydrogen and chlorine by electrolysis;
•
These are then captured and reacted to produce hydrogen chloride gas;
•
The hydrogen chloride gas is dissolved in deionized water to produce
hydrochloric acid.
7.2.2.3 Nitric acid
Nitric acid is a significant industrial chemical. It has a wide variety of uses including
production of nitrate fertilisers and explosives.
Figure 7-6: Nitric acid production
Nitric acid can be made by simply reacting nitrogen dioxide (NO2) with water which
can be bubbled through hydrogen peroxide to improve yield. NO2 is derived from the
oxidation of ammonia to produce nitric oxide which is subsequently oxidised to
produce NO2.
4 NH3 + 5 O2 4 NO + 6 H2O
2NO + O2 2NO2
NO2 + H2O HNO3
Alternatively adding sulphuric acid to nitrate salt (NaNO3) yields nitric acid.
7.2.2.4 Sulphuric acid
Sulphuric acid (H2SO4) is one of the most abundantly produced chemicals in the world.
It has wide use as an industrial reagent, in the production of other acids, and in the
production of sulphates.
Figure 7-7: Sulphuric acid production
Sulphur is burned to form sulphur dioxide (SO2). SO2 can also be collected from various
industrial processes including:
•
Roasting of sulphide ores; and
•
Oxidation and concentration of sulphur in flue gases from fuels containing
sulphur.
SO2 is then oxidized in the presence of a vanadium oxide catalyst (V2O5) into sulphur
trioxide. The sulphur trioxide can then be processed in one of two ways:
It can be mixed with sulphuric acid and then hydrated to form oleum (H2S2O7) or
with sufficient water yield sulphuric acid.
It can be directly hydrated to give sulphuric acid, though this is an extremely
exothermic reaction and unless performed properly will create a mixed gas stream
that is very difficult to separate.
7.2.3 ATMOSPHERIC EMISSIONS
Typical pollutants emitted to atmosphere from these processes include (but are not
necessarily limited to):
•
Sulphur Dioxide (SO2)*
•
Carbon Monoxide (CO)
•
Carbon dioxide (CO2)
•
Oxides of nitrogen (NOx, measured as NO2)*
•
Fluorides (measured as HF)*
•
Hydrogen chloride (HCL)*
•
Sulphuric acid mist and sulphur trioxide (measured as SO3)*
* Regulated by the NEMAQA emission standards
The atmospheric emissions are expected to be primarily from by-products of the
chemical reactions. Before releasing to atmosphere the flue gas can be cleaned using
a variety of methods, depending on the target pollutant, common examples are:
•
Scrubber: PM, SO2, NOx, Fluorides, NOx, HCl, SO3
•
Cyclone: PM
•
Baghouse: PM
•
Electrostatic Precipitator: PM
7.2.4 SPECIAL ARRANGEMENTS
None
7.3 SUB-CATEGORY 7.3: PRIMARY PRODUCTION OF CHEMICAL
FERTILIZER
7.3.1 APPLICABILITY
The production of superphosphates, ammonium nitrate, ammonium phosphates and
ammonium sulphate and their processing into solid fertilizer mixtures (NPK mixtures)
All installations
APPA scheduled processes covered in this sub-category are:
2. Phosphate Fertilizer Processes
43. Ammonia Processes
Fertilisers are typically produced by the application of various acids with phosphates
and/or ammonia. Some of these reactions may be heated by combustion processes
to improve yield and increase production rates.
7.3.2 PROCESS OVERVIEW
7.3.2.1 Superphosphates
Figure 7-8: Superphosphate production
Various superphosphates are produced by reacting concentrated sulphuric or
phosphoric acid with finely ground phosphate containing rocks to produce
superphosphate or triple superphosphate, respectively. The main by-products are
calcium sulphate (gypsum*).
7.3.2.2 Ammonium nitrate
Figure 7-9: Ammonium nitrate production
Concentrated nitric acid and anhydrous ammonia are reacted to give aqueous
ammonia nitrate which is then concentrated and spray dried. The resulting pellets are
then dried further and coated to prevent cracking.
NH3 + HNO3 NH4NO3
(ammonia + nitric acid ammonium nitrate)
*
More specifically ‘phosphogypsum’
7.3.2.3 Ammonium phosphate
Figure 7-10: Ammonium phosphate production
Phosphoric acid and ammonia is reacted to form the ammonium phosphate salt in
powder form.
H3PO4 + NH3 (NH4)3(PO4)5
(Phosphoric acid + ammonia ammonium phosphate)
7.3.2.4 Ammonium sulphate
Figure 7-11: Ammonium sulphate production
Sulphuric acid is sprayed into a chamber containing ammonia gas to form ammonium
sulphate powder. Alternatively a mixture of ammonia gas and water vapour is
introduced into a solution of ammonium sulphate and sulphuric acid.
7.3.3 ATMOSPHERIC EMISSIONS
Typical pollutants emitted to atmosphere from this process include (but are not
necessarily limited to):
•
Acid vapours (H2SO4, HNO3)
•
Sulphur Dioxide (SO2)*
•
Carbon Monoxide (CO)
•
Carbon dioxide (CO2)
•
Total Fluorides (measured as HF)*
•
Ammonia (NH3)*
* Regulated by the NEMAQA emission standards
The atmospheric emissions are expected to be primarily from by-products of the
chemical reactions. Before releasing to atmosphere the flue gas can be cleaned using
a variety of methods, depending on the target pollutant, common examples are:
•
Scrubber: PM, SO2, NOx, Fluorides, NOx, NH3
•
Cyclone: PM
•
Baghouse: PM
•
Electrostatic Precipitators: PM
7.3.4 SPECIAL ARRANGEMENTS
None
7.4 SUB-CATEGORY 7.4: MANUFACTURING ACTIVITY INVOLVING THE
PRODUCTION, USE IN MANUFACTURING OR RECOVERY OF
ANTIMONY, ARSENIC, BERYLLION, CADMIUM, CHROMIUM, COBALT,
LEAD, MERCURY AND SELENIUM BY THE APPLICATION OF HEAT
7.4.1 APPLICABILITY
Manufacturing activity involving the production, use or recovery of antimony, arsenic,
beryllium, cadmium, chromium, cobalt, lead, mercury, selenium, thallium and their salts
not covered elsewhere by the application of heat, excluding their use as catalyst
All installations producing more than 1 ton per month
APPA scheduled processes covered in this sub-category are:
11. Arsenic Processes
23. Lead Processes
40. Beryllium Processes
41. Selenium Processes
50. Chromium Processes
52. Cadmium Processes
61. Antimony Processes
62. Mercury Processes
7.4.2 PROCESS OVERVIEW
Most of these materials are produced as a by-product of other metals, specifically from:
•
Lead
•
Tin
•
Copper
•
Nickel
The methods used include electrolysis, roasting, and chemical separation to isolate
these elements from the main products or their wastes. There are a wide variety of
applicable processes.
7.4.2.1 Mercury
Figure 7-12: Production of Mercury
•
Mercury can be produced from Cinnabar, a mercury containing mineral by
roasting it with lime (calcium oxide) or iron to reduce the mercury which fumes
off of the roast.
•
These fumes are captured and condensed to produce liquid mercury while the
rest of the gases are carried through to the abatement equipment
7.4.3 ATMOSPHERIC EMISSIONS
Typical pollutants emitted to atmosphere from this process include (but are not
necessarily limited to):
•
Particulate Matter (PM)*
•
Sulphur Dioxide (SO2)
•
Carbon Monoxide (CO)
•
Carbon dioxide (CO2)
•
Oxides of nitrogen (NOx)
* Regulated by the NEMAQA emission standards
The atmospheric emissions are expected to be primarily from by-products of the
chemical reactions. Before releasing to atmosphere the flue gas can be cleaned using
a variety of methods, depending on the target pollutant, common examples are:
•
Scrubber: PM, SO2, NOx
•
Cyclone: PM
•
Baghouse: PM
•
Electrostatic Precipitator: PM
7.4.4 SPECIAL ARRANGEMENTS
Operators shall estimate the emissions of the metals using a method set out in Section 2.
Where the estimated emissions exceed 10 tons per annum for anyone of the metals, or
25 tons per annum for a combination of the metals, an air quality impact assessment for
the emissions shall be submitted to the licensing authority annually, commencing by 1
April 2011.
7.5 SUB-CATEGORY 7.5: PRODUCTION OF CALCIUM CARBIDE
7.5.1 APPLICABILITY
Production of calcium carbide
All installations producing more than 10 tons per month
APPA scheduled process No. 47 Calcium Carbide Processes is covered by this subcategory.
Calcium carbide (CaC2) is an important raw material used in the manufacture of
acetylene and calcium hydroxide (slaked lime – Ca(OH)2.
7.5.2 PROCESS OVERVIEW
Figure 7-13: Calcium carbide production
Calcium carbide is produced industrially in electric arc furnace from a mixture of lime
(CaO) and a carbonaceous material (usually coke). The material is heated to between
1800°C and 2100°C. The reaction takes place in two steps:
CaO + C Ca + CO
Ca + 2 C CaC2
The calcium carbide is subsequently tapped off, cooled, crushed and separated.
Material is received and typically stored in silos. CaO cannot be stored outside as it will
dissolve in and react with water to form CaOH. The carbon source may be stored in the
open in which case it may need to be dried before feed to the furnace. The materials
are mixed in the required proportions and crushed before feed to the furnace.
Modern electric arc furnaces are closed and thus operate without excess air, this results
in the formation of carbon monoxide (CO). The CO can either be flared or tapped off
to be used as a fuel gas.
Tapping fumes from the furnace may be captured by tapping hoods and extracted to
abatement equipment.
7.5.3 ATMOSPHERIC EMISSIONS
Typical pollutants emitted to atmosphere from this process include (but are not
necessarily limited to):
•
Particulate Matter (PM)*
•
Sulphur Dioxide (SO2)
•
Carbon Monoxide (CO)
•
Carbon dioxide (CO2)
•
Oxides of nitrogen (NOx)
* Regulated by the NEMAQA emission standards
The atmospheric emissions are expected to be primarily from by-products of the
chemical reactions. Before releasing to atmosphere the flue gas can be cleaned using
a variety of methods, depending on the target pollutant, common examples are:
•
Scrubber: PM, SO2, NOx
•
Cyclone: PM
•
Baghouse: PM
•
Electrostatic Precipitator: PM
7.5.4 SPECIAL ARRANGEMENTS
None
7.6 SUB-CATEGORY 7.6: PRODUCTION OF PHOSPHOROUS AND
PHOSPHATE SALTS NOT MENTIONED ELSEWHERE
7.6.1 APPLICABILITY
Production of phosphorous and phosphate salts
All installations producing more than 10 ton per month
APPA scheduled process No. 42 Phosphorous Processes is covered by this sub-category.
Note that phosphate fertilisers are covered in Sub-category 7.3.
7.6.2 PROCESS OVERVIEW INORGANIC PHOSPHATES
The main applications of inorganic phosphates are in:
•
Fertilisers;
•
Animal feeds: calcium phosphates, in particular dicalcium phosphate (DCP),
and other phosphates;
•
Detergents, in particular sodium tripolyphosphate (STPP); and
•
Human food or pharmaceutical ingredients: in particular sodium
tripolyphosphate (STPP), other sodium phosphates and other non Naphosphates, based on different cations.
In general terms, all inorganic phosphates can be seen as mostly derived from
phosphate rock. The process from phosphate rock to final product may schematically
be seen to involve four major steps:
•
Dissolution of phosphate from the rock to yield phosphoric acid;
•
Purification of phosphoric acid to a varying degree of purity;
•
Neutralisation of phosphoric acid by reaction with sodium, calcium, ammonium;
and/or;
•
Other ions to produce the required inorganic phosphate followed by
dehydration or drying
7.6.3 PROCESS OVERVIEW ELEMENTAL PHOSPHOROUS
Phosphate rock (calcium phosphate) is reacted in a submerged arc furnace to
produce phosphorous which is precipitated under water to limit oxidation.
Material is received and may be stored in silos or in the open. The carbon source may
be stored in the open in which case it may need to be dried before feed to the
furnace. The materials are mixed in the required proportions and crushed before feed
to the furnace.
Figure 7-14: Phosphorous production
7.6.4 ATMOSPHERIC EMISSIONS
Typical pollutants emitted to atmosphere from this process include (but are not
necessarily limited to):
•
Particulate Matter (PM)*
•
Sulphur Dioxide (SO2)
•
Carbon Monoxide (CO)
•
Carbon dioxide (CO2)
•
Oxides of nitrogen (NOx)
* Regulated by the NEMAQA emission standards
The atmospheric emissions are expected to be primarily from by-products of the
chemical reactions. Before releasing to atmosphere the flue gas can be cleaned
using a variety of methods, depending on the target pollutant, common examples
are:
•
Scrubber: PM, SO2, NOx
•
Cyclone: PM
•
Baghouse: PM
•
Electrostatic Precipitator: PM
7.6.5 SPECIAL ARRANGEMENTS
None