'THE FACTS ABOUT SMOKE PREVENTION

-13V DAVID BROWNLIE, B.Sc. Hons. (Lond.), F.C.S., M.I.Chem.E., A.M.I.Min., dr.e.

BLACK smoke can be completely wiped out of existence by technical methods that arc now available and perfectly familiar to many chemists and engineers. These methods can be divided into two main divisions, first that in connexion with the burning of raw coal and, secondly, the preliminary treatment of coal so as to give an entirely smokeless fuel.

We can take it for the purpose of the argument, based on the average of a number of years, that Great Britain raises 250 million tons of coal per annum and consumes at home 75 per cent. of this, 187,500,000 tons, divided into, say, 40 million tons for the high temperature carbonization processes of the gas works and the coke - oven, and 147,500,000 tons burnt as raw coal liable to smoke formation. Of the latter figure I have esti- mated that 90 million tons are burnt in stationary land boiler plant alone, quite apart from locomotive and marine .boilers, for the one operation of generating steam. Further, if we assume that very roughly 50 per cent. of the smoke of the country is due to house- hold fires, then we can take it that about 30 per cent. of smoke comes from the factory chimney, almost entirely used to operate steam boilers. Now, all this smoke can be eliminated with relatively little difficulty. In the - first place about 25 per cent. of factory chimneys already give little or no smoke. I have published at various times the results of detailed scientific investigations carried out during twelve years of the working of 400 different steam boiler . plants in the United Kingdom, representing 1,513 boilers in 41 different industries and a total coal consumption of 3,250,000 tons per annum. The actual figures for black smoke were as follows, 76 per cent. of the plants being hand fired and 24 per cent. mechanically fired (1) Good .. ..

(2) Fairly good ..

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26.0 24.8 (3) Medium ..

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30.0 (4) Bad .. .. 00 17.2 (5) Very bad .. 00 00 2.0 100 . 0 The facts are, therefore, in the first place, that on present knowledge one quarter of the steam boiler plants of Great Britain, representing a consumption of over 20,000,000 tons of coal per annum, are already almost smokeless.

Obviously, therefore, on elementary first principles there is no reason why all the rest should not be equally efficient. Black smoke in boiler plants is only one indi- cation of the grossly unscientific methods adopted in this and every other country for the generation of steam. The four hundred tests mentioned showed an average net working efficiency of 58 per cent. instead of 75 per cent. That is to say, the industries of Great Britain are burning 90 million tons when 70 million tons would do the work if up-to-date principles were adopted, representing a loss to the country of £30,000,000 per annum. The methods necessary are obvious and well known to thousands of people, but the manufacturers of the country simply will not adopt them, either because of ignorance or apathy.

So far as black smoke is concerned, for example, one of the chief causes is lack of efficient draught so that the fires are not high enough in temperature to burn smokelessly with the maximum emission of radiant heat. Far too much reliance is placed on the anti- quated and out-of-date natural chimney draught, whilst in most cases the brickwork is leaky and often the flues are ridiculously inadequate in area and badly designed- Mechanical draught is not used nearly enough and when installed is often operated on the crudest lines, a common practice being, for example, a cheap installation without sufficient power reserve.

Another common cause of black smoke is inadequate methods of firing, and little or no attempt has ever been made to apply scientific methods in the hand firing of boilers. For nearly a century a fireman has been regarded as an ignorant coal shoveller following a degraded occupation and remunerated in a scandalous fashion. Thus in 1914, before the War, it was quite a common practice to pay a fireman 25s. a week or less for the exhausting work of shovelling into a boiler say 30 tons of coal a week, together with the cleaning out and handling of about 4-5 tons of red-hot ash and clinker. It never seems to enter into the head of the average manufacturer that the coal represented about £2,009 a year expenditure and proper methods of firing would save alone £2004300 per annum quite apart front preventing black smoke.

Mechanical stoking, especially on the coking principle, will almost entirely eliminate black smoke on cylindrical boilers, if operated and controlled on reasonable lines. and no water tube boiler plant ought to smoke at all.

Again, puh-erized-fuel firing, which has made enormous advances in the last four years, eliminates smoke alto- gether, whether according to the so-called " central " system or on the unit principle, and probably at least 4,000,000 tons of pulverized coal per annum are now being burnt smokelessly in the world under steam boilers.

There is, therefore, ample plant and equipment available. mechanical and forced draught, mechanical stoking, and pulverized fuel to prevent factory chimney black smoke altogether, in addition to a whole host of scientific instru- ments to aid in the process, steam meters, feed water meters, automatic flue gas analysing machines, pyro- meters, and draught gauges, which it may be stated the average manufacturer will not use on intelligent lines.

Incidentally, there are a few processes in the metaL lurgical industries as to which we are assured that the whole iron and steel industry would be ruined unless black smoke was allowed to foul the atmosphere and injure the community. This kind of tale has been heard very often during the last 125 years whenever any measure of reform or efficiency had to be introduced.. The smoke could be washed out of the gases or separated by electrostatic precipitation.

As regards the most serious cause of black smoke— household fires—this could be reduced at least 50 per cent. (that is, 25 per cent, of the total smoke of the country) even when retaining the use of raw coal. All large and medium-sized houses of the suburban villa types ought to be fitted with central heating, and the closed stove forming part of this installation is not only highly efficient but almost entirely smokeless. But one of the most important remedies is to push on as fast as possible with universal electric lighting and the use of electricity in the home for cooking and operating all kind of domestic appliances, such as, for example, vacuum cleaners and mincing machines. Gas in my opinion is no real remedy because it is extremely expensive for. continued use, 11.0 pence per therm instead of 2.0 pence for coal either as central heating or in the open fire, whilst it is far inferior to electricity for lighting, besides being both dangerous and poisonous. In this latter connexion a detailed scientific investigation into the subject of carbon monoxide poisoning in all its ramifications is long overdue.

The main solution, of course, of the black smoke (problem is the low7temperature carbonization of raw coal, so as to remove from it all the smoke-forming elements, giving a residual smokeless and free-burning fuel, quite different in this respect from gas works or metallurgical coke, whilst recovering all the valuable by- products, rich gas for use in gas engines, motor spirit, Diesel oil, fuel oil, lubricating oil, and sulphate of ammonia. It is impossible to elaborate this subject in an ordinary article, but I may say there are over fifty different low-temperature processes in the world, and in Great Britain the following are of great importance :- " Coalite," " Fusion Retort," " Maclaurin," " Merz and Maclellan," " Neilsen," Power Gas Corporation, " Pure Coal Briquette," " Richards Pringle," and " Tozer."

Once, of course, a commercial smokeless fuel is obtained the problem is at an end, and we arc very near success to-day after years of detailed work. It can only be cmphasiz,ed again that as soon as the general public are sufficiently determined on the matter, then black smoke can be wiped out in a very short time.