Coal gas

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This is a historical article. For current information see syngas.

In the UK, coal gas specifically means gas made by the destructive distillation of coal. The term is not applied to other coal-derived gases, such as water gas, producer gas and syngas. US usage may be different.

Coal gas was introduced in the UK in the 1790s as an illuminating gas by the Scottish inventor William Murdoch and became very widely used for lighting, cooking, heating and powering gas engines.

Contents 1 Manufacture 2 Composition 3 By-products 3.1 Coke 3.2 Coal tar 3.3 Sulphur 3.4 Ammonia 4 Structure of the industry 5 See also

[edit] Manufacture

Coal was heated in a retort and the crude gas was passed through a condenser to remove tar and a scrubber to remove other impurities. The residue remaining in the retort was coke.

[edit] Composition

The composition of coal gas varied according to the type of coal and the temperature of carbonisation. Typical figures were:

• hydrogen 50%
• methane 35%
• carbon monoxide 10%
• ethylene 5%

In a plain burner, only the ethylene produced a luminous flame but the light output could be greatly increased by using a gas mantle.

[edit] By-products

The by-products of coal gas manufacture included coke, coal tar, sulphur and ammonia and these were all useful products.

[edit] Coke

Used as a smokeless fuel and for the manufacture of water gas and producer gas

[edit] Coal tar

This was subjected to fractional distillation to recover various products, including

• tar, for roads
• benzole, a motor fuel
• creosote, a wood preservative
• phenol, used in the manufacture of plastics
• cresols, disinfectants

[edit] Sulphur

Used in the manufacture of sulphuric acid

[edit] Ammonia

Used in the manufacture of fertilisers

[edit] Structure of the industry

Coal gas was initially maufactured by independent companies but many of these later became municipal services. Both the private and the municipal companies were nationalised under the The Gas Act 1948 and further re-structuring took place under The Gas Act 1972. For further details see British Gas plc.

Coal gas is no longer made in the UK. It was replaced first by gas made from oil and later by natural gas from the North Sea.

[edit] See also

• Gas lighting