Aug., 1913
T H E J O U R N A L OF I J V D U S T R l i l L Ai\TD
Norway saltpeter, while the 1913 consumption is estimated to be 3,000 to 4,000 tons. The production of calcium cyanamide by the Societa Anomima Per La Utalisazione Delle Forze Idrauliche Della Dalmazia in Sebenico has so far amounted to about 6,000 tons; it is thought, however, t h a t this output will be considerably increased when the works a t Almissa are completed. I n 1912, Austria consumed 5,000 tons of calcium cyanamide; the results obtained from its employment were not altogether unfavorable and no complaints were made concerning the difficulties which were encountered upon its introduction. The question for the future of the calcium cyanamide industry seems t o be whether it will be possible to ensure the demand when the price of Chili saltpeter falls. There is no doubt, however, that, for a number of years, either Nonvay saltpeter or calcium cyanamide will determine the price of Chili saltpeter and ammonium sulfate.
ENGILI7EERING C H E M I S T R Y
699
The consumption of gas per capita of population per annum is now over 8,000 cubic feet, and it is calculated t h a t only I O per cent of this is used for illumination in flat flame burners. Compare also the value of the residuals with that of 50 years ago. The yield of tar per ton of English coal is about 13 gallons, and of ammoniacal liquor about 40 gallons of 8 ounces strength. I n addition to this, some works now recover cyanogen, which was formerly lost in the iron mass used for purification.
THE PURIFICATION OF COAL GAS I n an address delivered before the Institution of Gas Engineers, June, 1913, W. B. Davidson dealt with the removal of the impurities present in crude coal gas from a commercial 5 2 , 679). and practical standpoint (Chem. Trade I., The valuable and complex product, tar, worth from $0.84 t o $I , 6 8 per ton of coal carbonized, contained many different comzoo of which had already been identified. pounds-nearly THE GAS INDUSTRY OF ENGLAND Vertical retort installations had not hitherto been designed t o Elliott (Ant. Gas Light I.,98, No. 26, 420) states that about reduce as successfully to a minimum the cost of tar handling as 1850 there were some 13 gas companies in England, operating the old installations of horizontal and inclined retorts, though works within a radius of 4 miles from Charing Cross and having he was of the opinion that the working could be made just as a total capital of about $aj,ooo,ooo. These works contained easy as with the horizontal systems by circulating hot watcr retorts, with about 10,000 mouthpieces, and used about 800,000 through the hydraulic main and providing agitators for mixing tons of coal to produce 8 thousand million cubic feet of gas per the contents of the same before running off. When the hyyear. The price of gas was 6 to 7 shillings ($I j o t o $I 75) per draulic main was very hot, as with coke ovens and some vertical 1,000 cubic feet A11 the companies were competing for busiretorts, ammonium chloride showed itself in the form of small ness, and were not very happy in the matter of paying divi- crystals which rendered the t a r less fluid and gave rise t o stopdends. It was estimated that a t least one-ninth of the gas made pages in the t a r pipes. A remedy for this was the introduction did not reach the consumers, the leakage from the mains being of water or liquor in the hydraulic main a t definite intervals, so high. The residuals (principally coke and some tar) brought preferably before agitating and drawing off the contents. There a return of about $3,000,000 per annum. About 13 gallons of were two ways in which losses might be sustained by the gas ammoniacal liquor of 4O Twaddle (8 ounces) was the average manufacturer if he did not look carefully after t a r removal. yield per ton of coal carbonized. This liquor was sold for about One was in the large amount of benzine which might be extracted z shillings j pence (40 cents per butt: = about 130gallons). by t a r by too drastic condensation or prolonged contact with The average yield of t a r was about 11 gallons per ton of coal the gas, and the other was the degree of freedom of the gas from carbonized. Comparing these figures with the results of recent the last traces of tar before entering the ammonia washers. times, the value of the t a r has become much more important, The presence of even a few grains of t a r per IOO cubic feet was because, a t that time, there was no aniline color industry. sufficient to render ammonia washers liable t o get blocked up. The principal uses of t a r were as a wood preservative, for Naphthaline wTould be a valuable ingredient as regards both covering iron, and for some sorts of wooden work, especially candle power and calorific value were it not that it is prone t o fence posts and rails. Some naphthas were obtained by dis- condense out in &hesolid state in awkward situations, or were it tillation, for making varnishes, and for burning in lamps, and not volatile a t high temperatures. As it was, it could be rcthe green oil, which distilled off last, was used for axle grease. garded only as a n impurity. It was most prevalent in gas made This material was afterward (1870) found to yield anthracene in horizontal or inclined retorts a t high temperature or with t h a t gave the beautiful turkey-red dye, and revolutionized the light charges. It was not so much the quantity of naphthaDutch madder industry. line present that determined the necessity of purification as The various London companies were in keen competition for the proportion of vapor of heavy oils which condensed o u t business when another competitor entered the field with a chal- along with the naphthaline and kept it in solution. This impurity offered comparatively little difficulty when suitable lenge of four shilling gas, and a promise of further reduction. This new company was the Great Central Gas Consumers’ Com- preventive measures were employed. pany, engineered by Alexander Angus Croll, and the president The content of hydrocyanic acid in crude coal gas amounted of the company was Jlr. Dakin, the tea merchant The works as a rule to only 0 , 2 2 per cent by volume, which, converted into were calculated t o produce 800 million cubic feet per annum, crystals of prussiate of soda, was equivalent to 4% Ibs. per I O , and cost A2 10,000 ($I ,ojo,ooo) with 4 gasholders of a capacity ooo cubic feet, or 5 . 4 lbs. per ton of coal. The elimination of of 1,000,ocm cubic feet. The company laid 7 0 miles of mains hydrocyanic acid from coal gas was optional, but in any case and the output was about IOO,OOO cubic feet per day, produced the great bulk of it would be removed by the iron oxide in the from I O or I I tons of coal. Wr. Croll was interested in an alum ordinary purifier with formation of Prussian blue; but for the works, in which he, no doubt, used the ammoniacal liquor of sake of improved purity, and the prevention of corrosion and the gas works. He was also the inventor of improvements in stoppages, it was very desirable that it should be removed as gas meters, and had a meter manufactured in London. Like all completely as possible. enterprises of this character, the Great Central Gas Consumers’ During past years, until just recently, there had been small Company was ultimately absorbed (1870) into the Gas Light incentive to extract cyanogen for sale, owing to the low price and Coke Company. By may of contrast, compare the English of prussiate of soda. Recently prices had shown an upward gas industry of to-day, with its output of over ~oo,ooo,ooo,oootendency, and i t was possible on a large plant to make a n e t cubic feet per annum. Of this, the great Beckton works can pro- profit of about $0.02 per lb. of prussiate of soda recovered per duce 60,000,000 cubic feet per day, and uses I,OOO,OOO tons of ton of coal. coal per annum. The South Metropolitan works and the ComDavidson believed t h a t a great deal of laxity prevailed genmercial Company’s plant will probably produce as much more. erally in the estimation of sulfuretted hydrogen. Concern as
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T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
Vol. 5 , No. 8
It has been found necessary to have a powerful filtering apparatus of large output, and for this purpose Abt & Bayer have constructed the continuous filtering machine, illustrated in the figures shown herewith, which are taken from a paper on the subject read by Leonce Fabre, before the Soci6t6 Technique de 1’Industrie du Gaz en France. The machine consists of a cylin-
t o the quantity present was lessened by the fact that purification with oxide of iron was a very simple process, and, moreover, exact methods of determination were rather troublesome. With proper precautions the ordinary absorption method of gas analysis could be applied with success, especially for purposes of comparison. Midland coals yielded on an average I .4per cent of sulfuretted hydrogen in the crude gas, which was equivalent to 14 lbs. of sulfur per ton of coal. Davidson discussed the utility of ammonia as a purifying agent. To members of the Birmingham gas engineering staff it became clear some years ago that Young, Hills, Claus, Holgate, and others in the sixties and subsequent years had not discovered the true science and art of distilling gas liquor. The large scale experiments on the Claus process carried out a t Belfast failed very badly; not only was the elimination of sulfuretted hydrogen and carbonic acid very incomplete (about 50 per cent), but the losses of ammonia were so great as to be fatal to any process of the kind. During the past few years Davidson had carried o u t a large number of experiments both in distilling and in gas washing in the works and in the laboratory, with results sufficiently promising to convince the Birmingham Gas Committee t h a t something could be done on similar lines to those of the Claw process, but with important improvements in the methods of distilling the liquor and washing the gas. About two years ago the erection of a liquid purification plant was started on the coal-test plant for the treatment of the gas made by the test installation of 18 Dessau retorts carbonizing 14 to 16 tons of coal daily. The plant included a still, condensers, sulfur kiln, and depositing chambers, with the necessary tanks for storage of liquor. With the object of carrying out preliminary tests an additional gas washer of the vertical centrifugal type, together with a simple tower scrubber, had been provided a year previously, and after twelve months’ trial-not quite continuous-the process of extracting sulfuretted hydrogen and carbonic acid from the gas by means of purified ammonia solution had been pronounced successful, and the plant was now being enlarged and improved so as t o deal with twice the amount of gas.
drical drum, the surface of which is formed of long filter cells parallel to the axis, the cells being so arranged that they dip into the tank or chamber containing the sewage mud. On the inside they are connected to a centrally situated chamber, common to all, in which a vacuum is produced, as described below. The hollow shaft supporting the system of cells forming the drum is arranged to permit the rotating of the machine. One end of the shaft carries a pipe to the inside of the chamber, turning down into the central chamber, and immersed in the filtered liquid in its lowest portion. The pipe which is connected to a suction pump assists the action of the filtering cells, and extracts a large amount of moisture from the filtered material as the drum revolves. In the other end of the shaft there is another tube, which carries compressed air to the inner surface
THE MANUFACTURE OF GAS FROM SEWAGE SLUDGE According to the Ameracan Gas Lzght Journal, 98,N o . 2 3 , 367, a process has been adopted by the IIunicipality of Brunn, in Austria, by which the solid matter in sewage is transformed
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into gas, economically and successfully. The apparatus to be used effects the drying of the sewage matter, and this dried material is afterwards distilled in retorts in precisely the way t h a t coal is treated.
of each cell in rotation, the point at which it is brought under the action of the compressed air being shown in the transverse section. The drum is rotated slowly, and each cell filled with the dried material comes in turn to the point where the vacuum
