++++ Introduction

Condensates are a mixture of hydrocarbons and other components

in the above table. These are normally gaseous from the well but

condense out as liquid during the production process (see previous

chapter). This is a refinery and petrochemical feedstock.

Raw gas is processed into various products or fractions:

o Natural gas in its marketable form has been processed for a

specific composition of hydrocarbons, sour and acid components,

etc., and energy content. Content is typically 90% methane, with

10% other light alkenes.

o Natural gas liquids (NGL) is a processed purified product

consisting of ethane, propane, butane or some higher alkenes

separately, or in a blend. It is primarily a raw material for

petrochemical industry and is often processed from the condensate.

o Liquefied petroleum gas (LPG) refers to propane or butane or a

mixture of these that has been compressed to liquid at room

temperature (200 to 900 kPa depending on composition). LPG is

filled in bottles for consumer domestic use as fuel, and is also used

as aerosol propellant (in spray cans) and refrigerant (e.g., in air

conditioners). Energy to volume ratio is 74% of gasoline.

o Liquefied natural gas (LNG) is natural gas that is refrigerated and

liquefied at below -162 °C, for storage and transport. It is stored at

close to atmospheric pressure, typically less than 125 kPa. As a

liquid, LNG takes up 1/600 of the volume of the gas at room

temperature. Energy to volume ratio is 66% of gasoline. After

transport and storage it is reheated/vaporized and compressed for

pipeline transport.

o Compressed natural gas (CNG) is natural gas that is compressed

at 2-2,2 MPa to less than 1% of volume at atmospheric pressure.

Unlike higher alkenes, methane cannot be kept liquid by high

pressure at normal ambient temperatures because of a low critical

temperature. CNG is used as a less costly alternative to LNG for

lower capacity and medium distance transport. Methane for vehicle

fuel is also stored as CNG. Energy to volume ratio is typically 25% of

gasoline.

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5.3 Gas processing

Raw natural gas must be processed to meet the trading specifications of

pipeline and gas distribution companies. As part of the purification other

components such as NGL is produced, and pollutants extracted.

The diagram shows an overview of a typical gas plant. Marketable products

are listed in blue and the production process is shown in grey as it is not

considered part of the gas plant.