2-1

2 CATEGORY 2: PETROLEUM INDUSTRY, THE PRODUCTION OF

GASEOUS AND LIQUID FUELS AS WELL AS

PETROCHEMICALS FROM CRUDE OIL, COAL, GAS OR

BIOMASS

This section covers combustion processes, handling and storage of fuel products and

industrial fuel oil recyclers that are associated with the petroleum industry or the

production of gaseous and liquid fuels from crude oil, coal, natural gas or biomass. It

does not include production of solid fuels (e.g. char from carbonization) and coal

gasification.

For processes involving:

• Carbonization and coal gasification; refer to Category 3. Note that coal

gasification may precede the processes in Category 2.

The synthetic production of liquid and gas fuels can be split into 3 main processes:

• Gas-to-liquids;

• Liquid-to-gas; and

• Solid-to-gas.

These fuels are made up of organic molecules. Gas molecules are typically short

carbon chain molecules (e.g. methane – CH4, propane – C3H8), liquids are made up of

longer molecules (e.g. hexane – C6H14, octane – C8H18) and solids consist of even longer

chain molecules (e.g. Icosane C20H42). Gas-to-liquid processes mostly go about by

combining the shorter, lighter molecules of the gas into longer, heavier molecules which

tend to have higher boiling points. These reactions typically rely on catalysts, such as

the Fischer-Tropsch reaction. The raw material feed to the Fischer-Tropsch process is a

mixture of carbon monoxide (CO) and hydrogen (H2), called “syngas”. It may contain

some methane (CH4). Depending on the source of the syngas it will require a certain

degree of conditioning, or cleaning, as it may contain impurities that could foul or react

with the catalyst (usually sulphur, in which case the Claus process can be used for

sulphur recovery).

Where natural gas is the raw material, the natural gas is mixed with steam and these

react to form a syngas.

H2O + CH4 → CO + 3 H2

(Steam + methane react to form syngas [i.e. carbon monoxide + hydrogen gas])

The syngas is then passed through the Fischer-Tropsch process to form a variety of

organic molecules some of which are liquid. Syngas may also be used directly as a fuel.

In this case it is combusted to provide heat for other processes.

2-2

Where coal, wood or other carbonaceous solids, are the raw material, the solids are first

gassified and then cleaned and passed to the Fischer-Tropsch process. To convert coal

to gas it is mixed with super-heated steam and in some cases a limited amount of

oxygen. This is commonly referred to as gasification, and may be applied to liquids as

well. The resultant gas is syngas.

H2O + C → CO + H2

(Steam + carbon react to form syngas [i.e. carbon monoxide + hydrogen gas])

Conversion of solids is sometimes (but not necessarily) undertaken by combusting the

material with a limited supply of oxygen, this results in incomplete combustion, (i.e.

generating CO instead of CO2). This is also commonly referred to as gasification.

Note that a solid-to-liquid conversion is typically made up of two steps: solid-to-gas

(gasification) followed by gas-to-liquid (typically Fischer-Tropsch process).

The APPA scheduled activities that are covered in this category are:

14. Hydrocarbon Refining Processes;

18. Benzene Processes;

25. Acid Sludge Processes; and

33. Producer Gas Processes.

2.1-1

2.1 SUB-CATEGORY 2.1: COMBUSTION INSTALLATIONS

2.1.1 APPLICABILITY

Combustion processes not used primarily for steam raising or electricity generation

All combustion installations (except test or experimental installations) including catalytic

cracking

Sub-category 2.1 deals with combustion processes associated with the production and

processing of various gaseous and liquid fuels from oil, coal (excluding coal

gasification), gas or biomass. It also deals with process fluid heaters and other material

heaters where the combustion does not fall under another sub category.

Indirect heating processes, such as process fluid heaters or distillation may have two or

more emission sources:

• The flue gasses from the combustion process; and

• Volatiles or gasses evolving from the material being heated.

The combustion flue gas is regulated by this subcategory whereas emissions from the

process it is applied to must comply with an appropriate subcategory covering that

process (for example Sub-category 2.3 in which case distillation requires heating that

may be supplied by combustion).

Testing and experimental combustion installations that fit Sub-category 2.1 descriptions

are excluded from the regulations.

It is important to note that processes for the production of gaseous and liquid fuels as

well as petrochemicals from crude oil, coal, gas or biomass may be heated by steam in

which case Category 1 applies to those processes supplying steam. For combustion

processes involved in:

• Steam and/or power generation; refer to Category 1; and

• Carbonization and coal gasification; refer to Sub-category 3.1.

2.1-2

2.1.2 PROCESS OVERVIEW

2.1.2.1 Catalyst Regeneration

Figure 2-1: Process flow diagram for catalyst regeneration in crude oil cracking

One of the most common crude oil refining methods is cracking, where long carbon

chains are broken into lighter higher value products by the use of catalysts, extreme

temperatures or steam. One of the by-products of the cracking process is the formation

of coke. This coke can deposit on and inside the pores of catalysts and needs to be

removed to ensure proper efficiencies and selectivity during the cracking process.

2.1-3

Figure 2-2: Cracking reaction including the riser, catalyst regeneration and ancillary

equipment

• The catalyst is typically in granular form and used in a fluidized bed reactor or

vertical pipes called risers to crack the heavier carbon compounds;

• The catalyst separation fluidized bed is designed to separate the catalyst using

cyclones and sent for decoking or cleaning while the gases are sent for further

processing, as it is a product, not an off-gas;

• During decoking the coke is burned off of the catalyst, sometimes with added

oxygen to ensure proper combustion, heating the catalyst;

• The heated catalyst is then entrained from the decoking reactor and separated

from the gas (this time an off-gas) using another cyclone; and

• The heated catalyst is then returned to the cracking fluidized reactor or risers.

The off-gasses will contain the fly ash and gaseous pollutants in the flue gas obtained

from the decoking reactor which can be removed using scrubbers, cyclones and

baghouses.

2.1-1

2.1.2.2 Process Fluid Heaters

Figure 2-3: Gas fired process fluid heater

2.1-2

Figure 2-4: Representation of a process fluid heating process

2.1-1

Combustion can also be used to heat process fluids or provide heat to a reaction

without the combustion gases coming into contact with the material being heated.

One such example is where a fluid can be heated in the same way that steam is

generated using a boiler, with any number of fuels (except waste oils, in which case

Category 8 should be used) combusted as the heat source. The heater can be any of

a number of designs very similar to typically seen boilers.

Emissions from the heater will contain ash (bottom and fly ashes) and gaseous

pollutants that may need treatment (such as baghouses or scrubbers) and disposal,

depending on the fuel used and operating conditions.

2.1.2.3 Biomass Gasification

Figure 2-5: Biomass gasification process

Gasification of biomass involves the conversion of the biomass material into a gaseous

fuel, commonly called a syngas, consisting mainly of CO and H2. Syngas can be used

as the starting material for many other processes including Fischer-Tropsch fuel synthesis.

Typically gasification involves the combustion of a carbonaceous solid either in the

absence of oxygen or with a controlled amount of oxygen. The process can be taken

to completion in which case the only solid removed is the ash, or partially where char is

formed (in which case Sub-category 3.3 should also be taken into account).

Industrial scale gasification can be performed by combustion of the biomass itself with

a controlled amount of oxygen to do either complete or partial gasification. The

2.1-2

resultant gas is treated to remove impurities and entrained particulate matter before

being used on site or stored as a saleable product. In the case of complete gasification

the bottoms ash will often be disposed of either in a landfill or ash dam or recovered if it

has further use/value elsewhere.

2.1.2.4 Flaring

Figure 2-6: Flaring

2.1-3

Figure 2-7: Flare schematic

2.1-4

Flaring is an open air combustion process usually on top of a stack. Flaring is used to

burn combustibles that cannot be safely processed, transported or taken off to storage

vessels. It is also sometimes added as a safety measure to burn off gasses and liquids in

a controlled manner during an emergency (i.e. fire, power failure etc.). Process upsets

and fluctuations may also result in excess gases that cannot be used in the process and

are thus flared.

Flaring presents the advantage of combusting gases (usually hydrocarbons*) which

may have toxic components to less toxic combustion products e.g. carbon dioxide and

water, but may be a source of other pollutants as well e.g.:

• Carbon monoxide from incomplete combustion;

• SO2 from combustion of compounds that contain sulphur;

• Particulate matter in the form soot from pyrolysis of organic compounds; and

• New compounds formed through de-novo synthesis.

* Not necessarily limited to hydrocarbons

2.1.5

2.1.2.5 H2S Combustion

Figure 2-8: Claus process diagram

Hydrogen sulphide (H2S) is one of the major by-products of petroleum liquid and gas fuel production and is treated

through combustion producing elemental sulphur with some SO2. In the Claus process, H2S rich flue gas is combusted to

produce elemental sulphur as a solid product and SO2.

2 H2S + O2 → S2 + 2 H2O

(hydrogen sulphide + oxygen react to produce elemental sulphur and water)

Some SO2 may be formed and thus the gasses are then catalytically processed to remove more of the sulphur (SO2 and

H2S) in the form of elemental sulphur.

2H2S + SO2 → 3S + 2H2O

(hydrogen sulphide + oxygen react to produce elemental sulphur and water)

The gasses exiting the catalytic process will be then be considered as off-gas (aka tail-gas).

2.1.6

2.1.3 ATMOSPHERIC EMISSIONS

Typical pollutants emitted to atmosphere from these processes include (but are not

limited to):

• Particulate Matter* (In the case of coal or crude oil use, particulate matter may

contain some metals);

• Sulphur Dioxide (SO2)*;

• Oxides of Nitrogen (NOx)*;

• Carbon Monoxide (CO);

• Volatile Organic Compounds (VOCs); and

• Hydrogen Sulphide (H2S).

* Regulated by the NEMAQA emission standards

The atmospheric emissions are expected to mainly be from the flue gas originating from

the combustion and are released to the atmosphere using a flue stack. Before being

released to the atmosphere the flue gas can be cleaned using a variety of processes,

depending on the target pollutant

• Scrubber: PM, SO2, NOx

• Cyclone: PM

• Baghouse: PM

Especially in the case of landfills, the improper handling of recovered particulate matter

can add to atmospheric emissions.

2.1.4 SPECIAL ARRANGEMENTS

• The NOx concentration shall be calculated as a flow-weighted average over all

combustion processes (refer to Section F: Calculations for method).

• No continuous flaring of hydrogen sulphide rich gases shall be allowed

• Allowable SO2 emissions from a refinery are calculated as the total sum of

emissions from combustion, sulphur recovery units, flares and catalytic cracking

units. For these purposes the catalytic cracking emissions will be calculated

without taking the hydro-treatment of feed into account.

2.2-1

2.2 SUB-CATEGORY 2.2: STORAGE AND HANDLING OF PETROLEUM

PRODUCTS

2.2.1 APPLICABILITY

Petroleum product storage tanks and product transfer facilities, except those used for

liquefied petroleum gas

All permanent immobile liquid storage tanks larger than 500 cubic meters cumulative

tankage capacity

Sub-category 2.2 covers the equipment specifications and air quality management

systems associated with storage and handling of liquid petroleum products with a total

cumulative storage capacity of 500 m3 or larger.

Liquid fuels are stored on producer, distributor and consumer sites which are covered in

this sub-category. The handling (loading and offloading of transport tankers) are also

covered in here as they may also release some volatiles into the atmosphere.

Liquefied petroleum gas (fuel gas that is temporarily liquefied for easier storage and

handling commonly referred to as LPG) is not covered.

2.2.2 PROCESS OVERVIEW

2.2-1

Figure 2-9: Liquid fuels storage and handling

2.2-1

2.2.2.1 Fixed Roof Storage Tank

Figure 2-10: Fixed roof storage tanks

Figure 2-11: Diagram of a fixed roof storage tank

Fixed roof storage tanks vented to the atmosphere are used for liquids with a lower

vapour pressure as the lower vapour pressure will ensure very little vapour will form

2.2-2

and escape through evaporation or pose an explosive risk. The tanks can be various

shapes and sizes though all have a rigid shape with a fixed roof.

2.2.2.2 Floating Roof Storage Tank

Figure 2-12: Diagram of external and internal floating roof storage tanks

Floating roof storage tanks are used for liquids with higher vapour pressures to

eliminate the amount of vapours formed in the headspace thereby reducing the risk

of vapour build up which may lead to fire or explosion. The floating roof can be

either the actual roof of the tank or a floating bed that is used inside of a fixed roof

tank. In either case, the roof floats on top of the stored liquid. The floating roof thus

rises or falls as the liquid level rises or falls such that there is little if no void between

the roof and the free surface of the liquid. The roof will have seals around its edges

and in the sleeves around the legs and guide posts to minimise leakage and fugitive

release of vapours.

2.2-3

2.2.2.3 Pressure Vessel Storage Tank

Figure 2-13: Pressure vessel storage tank

Figure 2-14: Diagram of a pressurized storage tank

2.2-4

Pressure vessel storage is used for liquid or gaseous mixtures at pressures above

atmospheric pressure. Storage under pressure for gasses improves the mass of gas

that can be stored as the gas density is increased under pressure. Volatile liquids

require storage under pressure to contain, and prevent the release of, vapours.

These vessels are usually reinforced and cylindrical or spherical in shape to be able

to handle elevated pressures.

2.2.3 ATMOSPHERIC EMISSIONS

The atmospheric emissions to be expected from these sites are the vapours from the

stored petroleum products and will largely be made up of various VOCs. These may

be fugitive releases from seals, couplings, and handling activities, but may also be

vapours vented during filling or to relieve pressure build-up.

VOCs can be treated either destructively, using methods like flaring, or by

absorption and or adsorption scrubbers. Vapours may also be captured, condensed

and returned to bulk storage.

The collected vapours are sometimes stored in holding tanks to be reused when

fixed volume storage is emptied or for later processing.

2.2.4 SPECIAL ARRANGEMENTS

The following transitional arrangement shall apply:

• Leak detection and repair program approved by the licensing authority

should be instituted within two years following the date of publication of the

NEMAQA Section 21 notice (i.e. before 1 April 2012).

The following special arrangements shall apply for control of TVOCs from storage,

loading and unloading of

• Raw Materials;

• Intermediate Products; and

• Final Products.

With vapour pressures above 14kPa at normal storage temperature, alternative

control measures that can achieve the same or better results may be used instead:

• Storage vessels for liquids shall be of the following types:

o Vapour pressure up to 14 kPa: Fixed roof vented to atmosphere.

o Vapour pressure above 14 kPa up to 91 kPa: External floating roof tank with

primary and secondary seals for tank diameters larger than 20m, or fixed roof

tank with internal floating deck fitted with primary seal, or fixed roof tank with

vapour recovery system.

o Vapour pressure above 91 kPa: Pressure vessel

• The roof legs, slotted pipes and/or dipping well on floating roof tanks (except

for domed floating roof tanks or internal floating roof tanks) shall have sleeves

fitted to minimize emissions.

• Relief valves on pressurized storage should undergo periodic checks for

internal leaks using a portable acoustic monitor or, if venting to atmosphere

2.2-5

with an accessible open end, tested with a hydrocarbon analyser as part of

an LDAR programme.

• Loading and unloading: All installations with a throughput of 5000m3 per

annum must be fitted with vapour recovery units. All liquid products with a

vapour pressure above 14 kPa shall be loaded/unloaded using bottom

loading, with the vent pipe connected to a gas balancing line. Vapours

expelled during loading operations must be returned to the loading tank if it is

of the fixed roof type where it can be stored prior to vapour recovery or

destruction. Where vapour balancing and/ or bottom loading is not possible,

a recovery system utilising adsorption, absorption and condensation and/or

incineration of the remaining VOC, with a collection efficiency of at least 95%

shall be fitted.

• The actual temperature in the tank should be used for vapour calculations

6

2.3 SUB-CATEGORY 2.3: INDUSTRIAL FUEL OIL RECYCLERS

2.3.1 APPLICABILITY

Installations used to recycle or recover oil from waste oils

Industrial fuel oil recyclers with a throughput > 5000 tons/month

This sub-category covers processes that convert waste oils (or oily mixtures) into oils

that have commercial use/value for example fuel oils for use in boilers and other

equipment. Used industrial oils (hydraulic oil, engine oil, etc.) can generally be

recycled into fuel oils (sometimes referred to as furnace fuels) or recycled to be

reused instead of being disposed of or destroyed (a common alternative to

recycling, covered in Category 8).

Processes that carbonize oils, are covered by Category 3.

Combustion of waste oils falls under Category 8.

2.3.2 PROCESS OVERVIEW

2.3.2.1 Waste oil processing

Figure 2-15: A centrifuge and distillation column, common process equipment

pieces in waste oil processing

7

Figure 2-16: Waste oil recovery process

The primary aims of waste oil processing are usually to remove solid impurities and

water, and then separate the oil into different valuable fractions. Solids are typically

removed by centrifuging but other solids removal processes may be employed.

Water is typically removed by allowing the material to settle and separate. The oil is

then distilled to separate various fractions based on their volatility. The products can

then be sold for combustion to produce heat and steam for process and power

generation use. The distillation process required a heat source. This heat source may

qualify as a combustion installation (Sub-category 2.1, or Category 1).

Sometimes further processing is required to remove pollutants from the oil before

combustion as the flue gas would contain dangerous compounds or have

constituents that would be more expensive to remove after combustion than before,

such as the removal of aromatics by liquid-liquid separation.

Sources of emissions to air will be from the cleaning processes involved as well as the

handling of the products. Filtered sludge and the water removed will also contain

waste materials and the handling thereof can contribute to the air emissions. Some

of the vapours removed during distillation will also contribute to emissions.

2.3.3 ATMOSPHERIC EMISSIONS

Expected atmospheric emissions will be the vapours from the distillation and pyrolysis

processes. They will include but are not limited to:

• Volatile organic compounds (VOCs)*

• Carbon dioxide (CO2)

• Carbon monoxide (CO)*

• Heavy metals

• Sulphur (SO2)* (H2S and other reduced sulphurs)

8

*Controlled by the NEMAQA standards

These can be treated using scrubbers as particulate matter will usually be low

enough for a wet bed scrubber to handle.

2.3.4 TRANSITIONAL AND SPECIAL ARRANGEMENTS

The following transitional arrangement shall apply:

• Leak detection and repair program approved by the licensing authority

should be instituted within two years following the date of publication of the

NEMAQA Section 21 notice (i.e. before 1 April 2012).

The following special arrangements shall apply for control of TVOCs from storage,

loading and unloading of

• Raw Materials;

• Intermediate Products; and

• Final Products.

With vapour pressures above 14kPa at normal storage temperature, alternative

control measures that can achieve the same or better results may be used instead:

• Storage vessels for liquids shall be of the following types:

o Vapour pressure up to 14 kPa: Fixed roof vented to atmosphere.

o Vapour pressure above 14 kPa up to 91 kPa: External floating roof tank with

primary and secondary seals for tank diameters larger than 20m, or fixed roof

tank with internal floating deck fitted with primary seal, or fixed roof tank with

vapour recovery system.

o Vapour pressure above 91 kPa: Pressure vessel

• The roof legs, slotted pipes and/or dipping well on floating roof tanks (except

for domed floating roof tanks or internal floating roof tanks) shall have sleeves

fitted to minimize emissions.

• Relief valves on pressurized storage should undergo periodic checks for

internal leaks using a portable acoustic monitor or, if venting to atmosphere

with an accessible open end, tested with a hydrocarbon analyser as part of

an LDAR programme.

• Loading and unloading: All installations with a throughput of 5000m3 per

annum must be fitted with vapour recovery units. All liquid products with a

vapour pressure above 14 kPa shall be loaded/unloaded using bottom

loading, with the vent pipe connected to a gas balancing line. Vapours

expelled during loading operations must be returned to the loading tank if it is

of the fixed roof type where it can be stored prior to vapour recovery or

destruction. Where vapour balancing and/ or bottom loading is not possible,

a recovery system utilising adsorption, absorption and condensation and/or

incineration of the remaining VOC, with a collection efficiency of at least 95%

shall be fitted.

• The actual temperature in the tank should be used for vapour calculations

Combustion of waste oil shall be subject to emission standards of Category 8.