OIL FROM COAL.

Te Awamutu Courier, Volume 53, Issue 3827, 30 October 1936, Page 5

OIL FROM COAL.

(By Dr. W. T. Cooke.) A statement was recently made in the Australian press concerning the production of oil from coal, and mention was made of two processes now being tested on a commercial scale — the so-called hydrogenation and the Fischer-Tropsch processes. The announcement is informative, both as showing the general advance being made in the production of oil from coal and also as indicating a possible rivalry between the economic and other issues pertaining to both methods of production. The process operated by Imperial Chemical Industries (1.C.1.) and their Continental confreres, the hydrogenation, or berginisation process, aims eventually to start from coal itself, black or brown (tar also is being used at present), and by heating with hydrogen gas under pressure, to convert the material into petrol. Actually there are at least two stages in the process, apart, from the final step of refining the crude petrol. The process is essentially a destructive one chemically considered, a complex coal (or tar) being broken down into less complex material, petrol; and the

aim is to stop the simplifying process at the desired point.

The Fischer process operates almost entirely in tlie reverse manner. It starts with coke, elementary carbon, which, by means of superheated steam, is converted, in the main, into two gases, carbon monoxide and hydrogen, and these by appropriate means are induced to react with one another to build up petrol—a more complex material. The process is distinctly a synthetic one, and as in the former ease, the aim is to arrest the' process when once the tesired degree of complexity has been reached. The coke necessary for the process is obtained by the destructive distillation of coal, black or brown, heating it out of contact with air, as in making town. gas. The question therefore, naturally arises, why break down completely to coke and build up to a requisite com plexity when by berginisation a grad ual breaking down to the desired point can be effected? Why make a complete descent and I lien an ascent when a shorter descent suffices? How is it. that tlie FT process is likely to be able to compete against berginisation? Any manufacturing process stands or falls on its economic possibilities. The final results are presented to the shareholders in £ s. d. units, but during the working of the process the technologist as such is using two other system of units. In the case under discussion the technologist as chemist must know hom much petrol it is possible theoretically to get from a ton, say, of coal, and as engineer how much energy the actual working process will consume. The weight question happens to be comparatively simple of solution. The essential element in both coal and

petrol is carbon. Ordinary petrol contains 80-85 per cent carbon, the remainder being hydrogen only. Dry black coal (calculated to an ash free basis) contains also 80-85 per cent of carbon, but about 5 per cent only of hydrogen, the remainder being chiefly oxygen, sulphur and nitrogen. Tlie ultimate result of converting coal to petrol is to displace the three last mentioned elements and to make up the losses with hydrogen, so that one ton of coal yields about one ton of petrol. The energy question is more intricate. In the first place, petrol contains about 50 per cent more energy than coal—that is, -it gives about 50 per cent more heat in burning. To obtain this energy—energy being uitcreatable—there will be needed for 100 tons of petrol another 50 tons of coal beyond that needed on the "■eight basis- of calculation. This figure stands irrespective of the type oi process used. But the packing into 100 tons of petrol of the energy contained in 150 tons of coal, an upgrading process, can be achieved only by the expenditure of an additional supply of energy, such as can be obtained, for example, from an additional supply of coal. This extra amount cannot, obviously, be known until the process of conversion is defined and its efficiency tested in practice. All the schemes in operation at present involve both tlie production of elevated temperatures and pressures, and also the mechanical handling of initial materials and final products. Clearly then, any one particular scheme of operations might haply he shorter, quicker and more efficient than any other, and so consume less additional coal. This possibility explains the custom of camparing and evaluating schemes on a thermal or

energy basis—that is, comparing the energy in the final products with that originally in the total coal used. The 1.5.1. claim a conversion factor of about 40 per cent for I heir process, which is equivalent to tlie conversion of 31-4 tons of coal to 1 ton of petrol, it. seems likely that the F.T. process would show a similar conversion ratio, but official figures do not seem to be available. There are. however, other aspects of the general question which have to be taken into consideration. Any present. day process of converting coal into petrol is a multistage process, and at intermediate stages there .are produced, besides petrol, other and heavier oils of the type of kerosene, diesel oils aud lubricants. All of these, especially the last, vary in quality, and so in market value, and all have a ready market. Th'e different processes can be made to yield these types of oils in varying quantities; one process may, for example, be favourable to the production of good petrol, but poor lubricating oil, hence market possibilities may influence markedly the choice of process to be installed. It seems likely that, future development in the treatment of coal for obtaining oil will be a deliberate combination of three processes, namely, carbonisation, both at low and high temperatures, berginisation and the Fischer-Tropsch process of synthesis. At present this is actually the existing state of affairs, which is admittedly of the nature of a big scale research into economic and technical possibilities of the conversion of coal into oils.