ECONOMY OF COAL

Evening Post, Volume CX, Issue 52, 29 August 1925, Page 9

ECONOMY OF COAL

GOVERNMENT RESEARCH

LOW TEMPERATURE CARBONI- . SATION

NEW ERA FOR INDUSTRY,

(FROM OUR OWN CORRJSPONDBNT.)

LONDON, 9th July. "It is as certain as wo are standing in this House this afternoon," said the Prime Minister the other day, "that what has been proved successfully in the laboratory in regard to low temperature carbonisation of coal will be proved successful commercially, and when that day comes . • • it will give this country, probably, the greatest push forward in development that it has had since the discovery of steam."

Low temperature carbonisation was started by a private company thre«' or four years ago, but now the British Government is making further experiments at the Fuel Research Station at Greenwich. Carbonisation of coal consists in the heating of it at suitable, temperatures in airtight retorts. Admission of air would be bad for the products, which, generally speaking, may be divided up as follows: —Smokeless fuel superior in heating qualities to the best coal; liquid fuel; motor spirit;- fuel oil; lubricants ; gaseous fuel for lighting, heating, and power purposes ; - and other materials which may be used in the preparation of fertilisers, explosives, disinfectants, and dyes.- In the laboratory the whole process ia successfully carried out from beginning tp end in an apparatus of glass and siHoa, the little retort of which ia heated by a gas-fired or electricially-heated furnace.

COAL BLENDING

The indention of this apparatus vtaa a \ matter of great importance. It is now possible within a few hours to get accurate information as to the most desirable treatment for any coal or blend qf coals, and to ascertain the cluantity and quality of resulting products. There are almost as many types of qpal as of human beinga; each type has its own definite characteristic. But. generally speaking, for the purposes of carbonisation coal may be divided into two types —swelling and non-swelling. The former, when subjected to carbonisation alone, exercises great pressure upon the wqlls of the retort (which sometimes it has been known to seriously damage), holds up the discharge, a,nd yields a residue, doscribed as a light, porous mass. Bui the, aim is to get a residue which will npt crumble as ordinary coke does, but which will be strong, coherent, ancl convpniently transportable. That can' only be done as a (Consequence of scientific blending of coals. The difficulty of the problem may be appreciated from the fact that most seams consist of bands of varying fusibility, cacti of wliich if carbonised will produce smokeless residue of different structure. , There is nothing else to be done, therefore, except to break down the coals and mix the swelling with tho non-swelling kinds. But it is essential that the right proportions bo ascertained. This blending is in itself a fine art (or science). . SIX CWT QF BY-PRODUCTS PER TON At the Fuel Research Station four retorts altogether are to be employed, allowing for a through-put of twenty tons daily. A correspondent of the "Daily Chroniclo" who visited the station explains that just as the right blending of the coals put. into the retorts could only be ascertained after much experience, so the best material from which to construct the retorts themselves could only be determined after long and patient trials. Mild steel and fire-brick were rejected, aryl cast iron was eventually chosen. But here, again, the utmost care had to bo exercised. For experience has shown that unless the right kind of metal is selected it is possible, when a temperature of 650deg C. is exceeded, for a cast iron 12ft retort to grow several inches in length within .a short time. A retort that increased in size as a growing boy does would be useless. Not only for tho preservation of the retort, but for the ufflcient carbonising of tha material inside, it is essential that the temperature be kept within bounds and as uniform as possible. This, it is now claimed, •can be done.

The retort in' use a*- the station ia externally heated; hot-flue gases from tho brick heating chamber which surrounds it play upon its walls Tho coal goes in at the top of the high retort, and the transformed product, in the shape of smokeless fuel, automatically, emergeg into a cooling chamber at the bottom. During this passaga weight to the extent of 6cwt per ton of coal used has been lost; but, as compensation for that, quantities of crude oil and gas have .been obtainei and safely stored.

WHAT THE COAL YIELDS

A bubbling foam is formed; gases escape ; tar exudes; and ultimately the turbulent mass loses its plasticity and becomes rigid, the bubbles formed in the beginning from the fused substance determining the final structure of tha smokeless fuel. When this red-hot oven has wrought its magic we get products consisting of fuol that is free from smoke and equal in quality to the best Welsh steam coal; gas'which may prove to bo a source of generating cheap power; oil for the Navy, and mercantile marine ; motor spirit for tho motor industry; fertilisers to stimulate the land; disinfectarits to promote public health; dyes to bring colour to life; or explosives to destroy ouo another in time of war. Already much progress has been made> towards that standard; meanwhile, the tests carried out on a large scale fully confirm the results obtained in tho laboratory;

A LANCASHIRE COMPANY

A Lancashire firm now carrying on the procosa of carbonisation of coal pass a strea.ni of heated, inert gas and steam through their retorts ; the average temperature of the carbonisation is fairly high, approximately 1400 to 1600deg ]?., .but varied as required. The average yielil from one ton of 25 to 35 per cent, volatile coal with normal working is about 11,000 cubic feet of town's gas of per cubic foot, 25 gallons ofoils, at leiist 40 lb of amonium sulphate, and the equivalent of 70 per cent, of tho weight of the coal as free-burning smokeless fuol, with 3 to 5 per cent, of volatile matter, which has a very fine grained structure, somewhat resembling charcoal.