On fuel economy. 281 



Society of Chemical Industry (Jouni. Soc. C'/iem. hid., Vol. xli., 

 p. 196 T.). 



4. The Report on Low Temperature Carbonisation recently issued by the 

 Fuel Research Board (H.JNI. Stationery Office, 1922). 



Taken together, these publications give a fairly comprehensive view of the 

 present position of affairs in regard to the low-temperature carbonisation in 

 this country. The Committee is in general agreement with the view recently 

 expressed by the Fuel Research Board that, although we have not yet reached 

 the stage when a final answer can be given to the question whether or not it 

 will be possible to establish on sound industrial lines a new industry based 

 on the carbonisation of the tens of millions of tons of coal per annum which 

 are at present being consumed in the raw state in this country, yet as the 

 result of the pioneering work which has been done during recent years by 

 various organisations such knowledge and experience has been gained as affords 

 some ground for the expectation that we are approaching a conditional solution 

 of the matter 



There still seems to be some difference of opinion as to whether from 

 the commercial point of view it will be better to carbonise at temperatures 

 round about 600° C. or at somewhat higher temperatures (say, 700° C. to 

 750" C), but this may be regarded as a minor issue. It seems now to be 

 established, as the result of fairly large scale trials, that the average yields 

 of the various products now obtainable by carbonising suitable British 

 bituminous coals at a temperature of 600° C. will amount (on the weight of 

 the dry coal carbonised) to about 7.5 per cent, of tars, and about 2.5 gallons 

 per ton of motor spirit, besides about 3,500 cubic feet per ton of a rich gas 

 of a gross calorific value (say) of about 800 B.Th.Us.,^ and a 70 to 80 per cent, 

 residue of smokeless semi-coke. 



Seeing that the cash value of the semi-coke residue far exceeds that 

 of all the other products put together, and also that the price of fuel oil 

 in this country will probably alao be determined by circumstances beyond 

 our control, it seems as though the ultimate prospects of a low-temperature 

 carbonisation industry will depend upon the price which the public will be 

 willing to pay for a smokeless domestic fuel. There can be little doubt but 

 that such a fuel, properly manufactured, is a very suitable one for domestic 

 consumption ; it burns freely and smokelessly, and also, according to Dr. 

 Fishenden's recent experiments (vide Fuel Research Board Special Report 

 No. 3), it has a greater radiant efficiency than either coal or high-temperature 

 coke. Its general adoption, however, will probably depend upon two other 

 conditions being fulfilled. Firstly, it must be prepared and distributed 

 in a form which will allow of its being freely handled without undue dis- 

 integration. Secondly, if its ash content could be cheaply reduced to a 

 low figure by subjecting the coal to some washing process such as froth 

 flotation or the like before it is carbonised, its attractiveness as a domestic 

 fuel would be undoubtedly greatly increased. Indeed, it seems possible that 

 public opinion might soon be educated to regard with favour well-manufactured 

 smokeless semi-coke of better combustibility and of smaller ash content than 

 raw coal. 



From this point of view, the recent work of Sutcliffe and Evans upon the 

 influence of porosity on the combustibility of solid fuels (loc. cit.) is of 

 interest, inasmuch as it draws attention to a factor whose significance is not 

 always sufficiently recognised in fuel technology. These authors consider the 

 porosity of the cell walls of a carbonised fuel to be extremely important in 

 determining its combustibility. Their suggestion that, before the coal is 

 carbonised for the production of a free-burning smokeless domestic fuel, it 

 should be finely pulverised and briquetted by pressure without the use of a 

 binder, in order that the thermal availability of the resulting semi-coke may 

 be raised to a higher level, deserves further investigation from both the technical 

 and commercial standpoints, especially if it could be found practicable to 



2 The Fuel Research Board's Report gave figures which would average 

 about 1,000 B.Th.Us., but the Committee has thought it better to adopt the 

 more conservative estimate of 800 B.Th.Us. here. 



