April 28, 1916. THE COLLIERY GUARDIAN. 805 AND TECHNOLOGY. Mr. Bond thought finally they would get down to 104. He did not intend, unless he was absolutely forced, to comply with the statutory regulations in future. Mr. Glover said these processes of washing with oil were particularly applicable to works where there was some sort of tar distilling or oil distilling plant in the first instance. Where there was no tar distilling plant, a very simple extension could be put down, and oil—■ petroleum or green oil—could be easily and readily distilled. Air. T. Berridge, Leamington, considered they would get into a great deal of trouble by working a certain process and reducing the illuminating power and making naphthalene. There ought to be an Act of Parliament, so- that they would have protecbion. Air. Geo. Stevenson, Long Eaton, submitted a short paper giving the results of eight months’ experience with the limestone process. The process was designed specially for low-grade semi-coking coals, and consisted in the admixture of a definite percentage (according to the analysis of the ash in the coal) of finely-ground lime- stone ; and for effective working the coal must be crushed and the mixing be constant and regular in quantity. It was claimed by the patentees that the action of lime- stone was entirely different from that of burnt lime, in that “ the limestone, when intimately mixed with coal rich in hydrocarbons, and with a high oxygen content, commences to decompose at a temperature lower than that of the resinous and other matters contained in the coal, and that the actions taking place slightly retard the evolution of the gases generally given off so freely with low-grade coals, and this allows of their becoming more stable.” An important point to note was that the coal must be small, and preferably densely charged, so that when mixed with the limestone a good surface con- tact may be ensured. In criticism of the process it was said that the limestone was an inert substance, and had no effect on the carbonisation. That some action did take place was proved by the following tests :— Pounds per ton Date of test. Kind of tar. _____ Toluene. Benzene. Aberthaw “ Druid ” brand Portland cement. British standard specification for Portland cement. 10,000 c c + Sept. 3, 1915 ... Untreated ........ 0 096 ... — Sept. 3, 1915 ... Washed ......... 0’50 ... — Sept. 17, 1915 ... Limestone washed ... 0’73 ... — Nov. 29, 1915 ... Washed ......... 0'48 ... 1:26 Jan. 6,1916 ... Limestone washed ... 1'24 ... 2’49 The tar was apparently completely altered in character, being more oily. One of the prime objects of the process was the improvement of the coke, which from these coals, with ordinary carbonisation, was generally soft and friable. In his experience, the coke was greatly improved, and it was being freely used for the most exacting purposes. The furnace clinker, admittedly, was harder, but-not seriously so. The practical results of the tests may be tabulated as follows :— Cost of Working. £ s. d. __________________________________________________________________________________________________________________________________________________________ CURRENT SCIENCE Coke Fuel for Steam Boilers. A paper on the above subject by Mr. E. W. L. Nicol, was recently read before the London and Southern Dis- trict Junior Gas Association. Regarding forced draught apparatus, the author points out that the immense capital sunk in steam generating plant, presumably designed and rated on a coal fuel basis, render it impera- tive that any coke burning attachment must conform to existing conditions. To commend itself readily to a. steam user, it must be inexpensive and capable of main- taining or increasing the steaming capacity of his boilers, whilst it must, if necessary, be suitable for attachment to- a boiler furnace without any, or any serious, inter- ruption to its working. That these conditions can generally be ensured has already been largely shown. But a great still remains to be accomplished in this and other directions. A modest yearly subscription of, say, Is. per 100 tons carbonised by the gas and coke oven companies interested would form the nucleus of a fund to provide the necessary means and incentive to inventors in this direction. Regarding the prospect of State control, the author observes that so far, no very definite indication has been made of the lines upon which control would be exercised; but a useful preliminary step in this direction would be the registration of the effective grate areas of all steam generating plant, together with the maximum and average hourly rates of fuel combustion. Armed with this information, the responsible authority, vested with the necessary power, would be enabled to act with some degree of precision in so allocating supplies of gaseous and solid fuels, that a state of efficient and practically smokeless combustion—at least, so far as steam plant is concerned—would eventually be brought about with a minimum of expenditure on new plant. Introduced on proper lines, with methods and apparatus which ensure the best results being obtained, coke fuel has, in the writer’s experience, only to be maintained at a price which shows a reasonable financial advantage to the user in order to secure continued favour. The mechanical stoking of gas coke offers considerably ______ more difficulty than is usually met with in stoking bitu- minous coal mechanically; but important progress has been made in this direction by a few of the leading makers who have specialised in this line, particularly __________________________ for externally-fired or water tube boilers of large capa- city. With the balanced draught system in use, the only serious interruptions to an otherwise continuous state of high efficiency, rarely approached with coal-fired boilers under the’best conditions of mechanical stoking, are the burning down and clinkering periods. The pre- sent tendency is, however, to increase grate areas and fire box heating surfaces. In selecting vehicles for use with coke fuel, gas companies, who are large potential users of this means of transport, would do well to encourage this tendency; and in the interests of national economy in fuel, it is to be hoped that the new regula- tions now being framed will take due cognisance of these factors. For railway passenger locomotives, the rein- statement of coke fuel to its former position of favour on some of the London lines would now perhaps involve what might be considered a too drastic overhauling of _______ their running schedules; but it is gratifying to note that here also there is a tendency to increase the proportion of grate area to that of total heating surface. Reliable tests have shown that 1 sq. ft. of fire box heating sur- face will evaporate about five times as much water per hour as will 1 sq. ft. of tube surface. Mr. Nicol exhi- bited at the meeting two scale models of the - forced draught coke burning apparatus referred to in his paper. These are exact miniature replicas of those now being extensively fitted to boiler furnaces of 2ft. Bin. to 4ft. diameter. As to the coke burning capacity of the apparatus, Mr. Nicol explained that this is limited by the tendency of the fuel to drift upon the grate, but, in his experience, the maximum rate necessary does not often exceed 251b. per grate foot hour. At 22-5 lb., the steam consumption of the jets has been independently ascertained to- be 3 per cent, of that generated, a figure which will bear favourable comparison with the steam consumption of engine-driven fans. Benzol and Toluol Extraction. Mr. J. Bond, Southport, delivered a short address at a recent meeting of the Commercial Gas Association on the extraction of benzol and toluol by American gas oil. He said the position to-day was most satisfactory with regard to toluol, and they would be pleased to know that about 25 per cent, of the toluol content of the gas was being extracted. He thought that in the majority of _________________________ undertakings the engineers should consider the advisa- bility of putting down dehydrating plant. He hoped that as an industry they would take much more interest in all products, and especially in tar products. At pre- sent they sold at a very low figure, but the necessities of the dye industry should first of all be met by the gas undertaldngs. In that respect it would be helpful to have some form of dehydrating plant. Mr. H. Pooley, Leicester, read a short paper on the extraction of benzol and toluol by green oil. He said he could not offer them in green oil washing any prospec- tive profits. The process was not an easy one, but he felt that in attempting to denude the gas of benzene and toluene they were taking a very patriotic step. Mr. J. Ferguson Bell, Derby, considered that a supply of gas of lower candle-power and possibly of a lower calorific value would be found to be equally to the advan- tage of the consumers. In the future they would be able to convince Parliament that candle-power was not necessary, and that a calorific value of about 500 British thermal units was all that was required. As to illumi- nating power, he thought that in the future they would be able to get down to 12 candles, and satisfy the con- sumer even then. grinding can be effectively carried out. Then, again, slag Portland cement, owing possibly, remarks Mr. Day, to its high alumina content, is naturally very quick in setting. This, however, can be readily adjusted by, known means, so that any specified time can be obtained. As showing in what way slag Portland cement is not in accordance with the British Standard Specification, and how it compares in its properties with cement pro- duced from limestone and clay, Dr. Day gives a table which we reproduce. The Portland cement chosen was made at the Aberthaw works of the Aberthaw and Bristol Channel Portland Cement Company, which were designed by Mr. Day. Slag Portland cement. Lb.sq.in. Lb.sq. in. Neat f(a) 7 days... 4501b. ... 644 . 623 1 G 4. 40’000 Tensile 1(6) 28 days < ~ a or, say, 539 ... 783 ... 729 f(c) 7 days.... 250 ... 283 ... 207 Sand ■< C 10,000 t(