Report / Committee on Air Pollution.

  • Great Britain. Committee on Air Pollution.
Date:
1954
Catalogue details

Licence: Public Domain Mark

Credit: Report / Committee on Air Pollution. Source: Wellcome Collection.

    20/84 (page 18)
    54. The standard practice in modern power stations at present is to discharge the gases unwashed through tall chimneys 300 feet or more high. It is claimed that the hot gases have a buoyancy which carries them high into the atmosphere, where they are diluted and dispersed sufficiently to render them relatively innocuous by the time any portion diffuses to ground level. It has been strongly urged as an objection to gas-washing that it lowers the temperature of the flue gases and thereby reduces their buoyancy. The un- washed gas contains more sulphur dioxide but, being hot, it tends to disperse widely. A washed gas contains much less sulphur dioxide but, being cool, it reaches ground level more quickly ; occasionally part of the steamy cloud of flue gas is carried down by wind eddies. 55. Nevertheless, we have reached the conclusion that gas washing is desirable provided that the washing process removes not less than 90 per cent. of the sulphur dioxide in the flue gases. A lower efficiency than this would not suffice, but if 90 per cent. or more of the sulphur dioxide is removed it is most unlikely that pollution in the immediate vicinity would be aggra- vated by cooling the gas, while it is certain that over a much wider area it would be virtually eliminated. In our view the cost of gas-washing, even if it amounts to ‘06d. to -07d. a unit of electricity supplied may well be justified by the advantages of a cleaner atmosphere and the human and material benefits which would follow, until research produces more efficient and less expensive methods. Sulphur dioxide is one of the most harmful of all the polluting agents. ‘The heaviest concentrations are produced by very large fuel burning installations and it is only at such installations that the removal of sulphur dioxide is practicable at present. We therefore consider that the most efficient methods of removing sulphur dioxide from flue gases should be adopted at power stations in future, except when they are so sited as to avoid polluting densely populated areas. Gas-washing should not, how- ever, be taken as a justification for lowering the height of chimneys. 56. Although much attention has been devoted to removing sulphur dioxide from power station gases, it must not be overlooked that complete success would still leave more than three-quarters of the sulphur problem unsolved. In general industry the scale of operations is so much less than in the electricity industry that no system of gas washing likely to operate at a reasonable cost is yet in sight. No known methods exist whereby the greater part of the sulphur from industrial and domestic chimneys can be prevented from being poured into the atmosphere in the form of corrosive gases. The increasing use of town gas, a fuel virtually sulphur-free, will assist in reducing sulphur pollution, and the use of electricity will have the same effect when the sulphur problem at power stations has been solved. There will still remain many uses of fuel, such as steam-raising, for which the more expensive refined sources of energy will be too costly. There is thus no present prospect of substanti- ally reducing the emission of sulphur oxide from general industry or domestic fires. This is an important issue which requires further attention and it is one of the matters which we recommend for intensive research. 57. We would point out that sulphur is an important raw material for industry, and that world supplies of sulphur for the future are by no means sure. There are possibilities (to put it no higher) that significant amounts of sulphur and saleable sulphur compounds could be recovered from coal- cleaning plants, from coke oven gas, from oil refinery gases, from producer gas and from the flue gases of very large fuel-burning installations. It would seem to us that expenditure on the removal of sulphur from the atmosphere, which would at the same time yield sulphur and saleable sulphur compounds from indigenous raw material might well be a profitable national investment, and that Government assistance towards the development of processes would be worth considering.