LIQUID FUELS

Greymouth Evening Star, 1 June 1928, Page 4

LIQUID FUELS

HOW THEY ARE PRODUCED. ’.rhe heating of geologically’ recent coals under the exclusion of air seems to have been hitherto the simplest method for the production of liquid fuels from solid fuels, but a. new method has now been adopted by which even greater results are obtained by great pressures. Destructive distillation by; either method yields a tar in addition to certain gases and a residual coke, which contains constituents of a petroleum character. Gas coals of recent geological periods, that is, ordinary’ coal, yield up to 12 per cent, of this tar, while certain lignites, of which brown coal is one variety, and oil shades are likewise suitable materials for the manufacture of tar and petroleum by various methods of distillation. The Scottish shale-oil industry and the brown coal carbonisation works of central Germany operate along these lines. • In the Bergins process for the liquefaction of coal, which is one method adopted in Germany, hydrogen is made to react with coal at. a. pressure of more than 100 atmospheres and at a temperature of about 450 degrees. Under this process the coal is ground and kneaded with 30 per cent, of tai’ into a paste, which is continuously pressed into the high-pressure autoclave. It is understood that the coal is thus first carbonised, the temperature being sufficiently’ high for such a purpose. Reaction in a given direction has quite recently been established by experiments in which the carbonisation was obtained under ordinary’ pressure, but the hydro-genera-tion. or liquefaction, has only been obtained under exceedingly high pressure. For the process all coals arc not suitable, only those rich in volatile constituents reacting to the process. The oil of the Bergins process is said not to be equal to natural oil, but it contains an ample proportion of gasolene, though the whole product is more closely reflated to primary tars than to petroleum.

The process is exceedingly expensive owing to the extreme cost of the apparatus required, but this is a to the discovery which will probably be overcome as time passes and the utility of the process is proved to be of value to industry. There are several other methods by which similar results may be obtained, some from liquid fuels and others from hard fuels, while gaseous fuels frequently contain vapours of liquid fuels at low-boiling points. There arc benzine vapours in cokeoven gas, and low-temperature carbonisation retorts always contain vapours of this character. These vapours may be condensed by cooling or by compression, or by a combination of the two methods, both of which yield a liquid directly. Many attempts have been made since 1910 to effect the low pressure carbonisation of bituminous coal commercially, especially in Germany, where the subject has been considered one of primary importance in view of the advancement of the internal combustion engine and the need for fuel therefor. Hitherto the process has not met with a great deal of success, and the results have been more or less of a negative nature, but the cablegram indicates that a distinct move forward has been made, and that the petrol from this source will be possible in the near future, a very valuable discovery for those countries which possess coalfields but do not have any say in the distribution of the world’s oil supplies.