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CREOSOTE

17th January 1941
Page 18
Page 18, 17th January 1941 — CREOSOTE
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Government Encouragement Will Stimulate the Use of This Coal Product Which Past Experiences Show to Have Possibilities as a Practicable Fuel for Petrol Engines •

TT is astonishing how little is 'actually known about a subject of which the name is practically an everyday word of our vocabulary, namely, creosote. All the information that most of us possess about this substance is that it is employed to prevent wooden posts which have to be sunk into the earth from gradually •rotting away.

Other important uses for creosote, however, are as an antiseptic, for the manufacture of lamp-black, as a lighting oil, and now as a fuel for motor engines.

This last use for creosote has suddentIy become topical, inasmuch as the Government is proposing to free it from the restrictions which, up to January 24 (the day of its release), will have prevented its use as a motor fuel. Although released, it will be subject to rationing, and the arrangements will be such as to permit of increased vehicle mileage, although the petrol ration will be decreased.

Also, the Order would appear to refer to Diesel 61,, as it says "imported oils," although there is a certain • doubt in some quarters as to whether both classes of oil are included. The scheme is to be given six months' trial,, so that the necessary experimental work on carburation can be carried out.

Made by High-temperature Carbonization There are two kinds of creosote, which, by the way, was 'originally spelt kreosate when it was first discovered a hundred years ago by the Chemist Reichenbach. The first kind to be produced wa's distilled from wood tar; shortly afterwards coal tar yielded a creosote which differed from the first discovery in that it was poisonous. This tar is the product of the destructive distillation of bituminous coal by the high-temperature process of carbonization, which operates between 900 and 1,200 degrees C.

Creosote contains naphthalene and anthracene, and the boiling points of its fractions range between 200 and 400' degrees C. When we compare this range with that of petrol between 50 and 200 degrees C., it will be appreciated that either atomization, or heating, or both, to a much greater degree than that necessary for petrol, will be needed to vaporize the creosote to a sufficient degree to render it combustible.

The amount of creosote available is said to be sufficient to supply about. 4 per cent. of the road-transport vehicles operating in ordinary times. Purely as a matter .of comparison, this figure is in advance of the fuel

possibilities given in the early days of producer gas, a year or more ago, and which has proved to be much higher than has been called for.

Up to the outbreak of war America took practically the whole production of creosote of this country, but under war conditions of sea transport this export ceased, and the lost market has, had the effect of diverting this product to the use of road transport. Hence, presumably, the Government's proposals about it.

In the past decade numerous attempts have been made to use creosote as motor fuel, most of which have been noticed in the columns of this journal from time to time. Manchester, Edinburgh and Belfast corporations are among those who have made extended trials Of this fuel, and certain investigations are now being carried out in several quarters with the same object.

Standard Specification for Creosote Needed In one particular series of trials of creosote fitel the variation in the analysis of the tar distilled from the coal of different collieries was so great as to spell failure. Obviously, therefore, it will be necessary to arrive at some specification of this fuel, which no doubt the Fuel Research Board has already done, in the same way that a standard has been set for producer-gas fuel. This fuel is susceptible to much closer approximation' to a standard of quality than is coal, although; like coal, there is no practical means for a purchaser to check quality.

It will, of course, be contended that it has never been necessary to check the quality of petrol, which is quite true; , and we may rely, perhaps, on the same standard of business integrity in this case.

There is, apparently, a wide variation in specification of creosotes from different sources, and it As necessary to assess the suitability for fuel purposes of these different products with a view to possible revision of manufacturing processes in order to ensure that the product is suitable for the market to which it aspires.

The heavier fractions—anthracene and particularly naphthalene—are the difficulty as far as carburation is concerned. Under low-temperature conditions they are liable to separate out and form deposits in tanks and carburetters. It is for this reason that heat is necessary for vaporization, and carburetters and induction systems must be suitably equipped.

Several carburetters were and Still are—made for using this fuel, all of which conform to the above-mentioned heating requirements, and in some cases a high degree of atomization has been aimed at as well as heating, to increase the combustibility of the vaporized creosote. It iS, of course, necessary to start up on petrol, and run until the engine has become sufficiently warm to turn over to creosote. • Thermostat Control of Fuel-mixture Proportions Attempts have been made to run on an automatically operated mixture-varying device, a thermostat regulating the control between 100 per cent. petrol for starting and idling, over to 100 per cent. creosote for power and open-road running.

In the Manchester experiments performance figures were given in comparison with petrol operation. These showed that petrol was consumed at the rate of 10.4 m.p.g. and creosote at 6.5 m.p.g. Mileages of 35,000 were run—sufficient to determine results. in actual service over a reasonable period. Power appeared to be satisfactory, although no bench-test results were quoted.

The wide range of high-temperature boiling points combined with the variation in speed and load of vehicle engines provide the possibility of depositing tar in the engine and of dilution of the lubricating oil in the sump. The extra. costs of cleaning and maintenance, resulting from these causes, eventually led to the abandonment of the investigations in the above case.

Under the new conditions, and with the knowledge that the Fuel Research Board must possess—and which it is assumed will be rendered available—investigations into the troubles of those earlier days will be greatly simplified. This will mean the overcoming of some of the old troubles and the prevention of others by the greater degree of ,standardization of the new fuels and their maintenance at the standards fixed.

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Organisations: Fuel Research Board

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