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.

    16/84 (page 14)
    GRIT AND DUST 36. Grit and dust are emitted from furnaces, whether or not there is visible smoke, and from many other industrial processes. The methods of control are different from those required for the prevention of smoke. To some extent the escape of grit and dust from boiler plant can be reduced by the use of suitably prepared fuels and by careful attention to firing, but their discharge from chimneys or at low level from dusty processes can be effectively arrested only by the use of special plant provided for the purpose. Different appliances are needed for the various types of duty, and they vary in efficiency and cost. Thus, whereas well-designed mechanical arrestors, which are relatively cheap, are suitable for coarse grits from many types of industrial boiler plants, costly electrostatic precipitators, some- times preceded by mechanical arrestors, are necessary with pulverized fuel boilers ; and for many industrial processes involving fine dusts it is necessary to use Other equipment such as fabric filters. Even so, it is not possible to prevent all emissions of fine dust, and with small plants it would not be realistic to expect 100 per cent. collection of grit. The important factors are the weight of the dust discharged, the size of the particles, and whether the chimney is of sufficient height to disperse the residual dust adequately. (See Appendix VI.) 37. It is, in fact, difficult to lay down maximum tolerable limits for grit and dust emissions and they must be related to the size of the plant. Nevertheless, we consider it essential that the most up-to-date and efficient grit and dust arrestors should be used with all furnaces which burn pulverised fuels, or which burn solid fuel in any form in large quantities. Our proposals for legislation to secure this are contained in paragraph 98. This equipment should qualify for the financial assistance which we have already indicated in paragraph 29 for equipment installed to reduce air pollution. Power Stations 38. Although much thought and money have been applied to the preven- tion of pollution and to increased efficiency in burning coal, power stations remain potential sources of serious pollution by grit and dust because of the great quantities of coal used, much of which is pulverised. Furnaces fired with pulverised fuel inevitably produce large quantities of grit and dust. No plant at present known will prevent all emission of dust, and the most efficient method now in general use, electrostatic precipitation, may even when in perfect working order allow 2 per cent. of the dust to escape. There are large installations from which, even under such conditions the escape of dust may amount to 10 tons daily. The problem in regard to power stations is accentuated by the enormous size of modern power stations. The need for these must be accepted but that must not disguise the fact that they are a concentrated source of heavy pollution. Not only their equipment but also their siting are therefore of major importance. 39. Electrostatic precipitators are expensive, and for a large boiler plant may add as much as 10 per cent. to the cost of a complete boiler unit. There is, therefore, scope for different and less dusty methods of combustion. We understand that new methods which result in a much smaller discharge of dust are in the course of development, and if successful these will in time greatly mitigate the nuisance. 40. For over 20 years every statutory consent for the construction of a new power station has included a condition that the most efficient and up-to-date method of arresting grit shall be used. Many of the complaints are directed at the older boiler plants which are equipped only with