THE COLLIERY GUARDIAN. _______________________________________________________________________________ December 20, 1918. 1301 MIDLAND INSTITUTE OF MINING, CIVIL ANO MECHANICAL ENGINEERS. (Continued from page 1242.) Economic Considerations in Coke Oven Practice. The meeting then resumed the discussion of the paper on “ Some Economic Considerations in Coke Oven Practice ” (Colliery Guardian, November 15, 1918, p. 1022), which was read at the meeting on November 9 by Mr. Colquhoun, of Sheffield. Mr. M. IV. Blythe (Thorncliffe Ironworks) wrote that one advantage of horizontal flues appealed to him very strongly, namely, that the whole of each Hue was exposed to view, and by means of an optical pyrometer the temperatures in each flue and in each part of the flue could be determined accurately. Further, in the Semet-Solvay oven the temperature in each of these flues could be adjusted and varied with ease. It was possible so to adjust the zones of heat that there was a gradual decrease from the bottom to the top of the oven. This should lead, at least theoretically, to less degradation of the by- products. In practice the results were not obviously better than with vertical flues. Mr. Colquhoun had stated that there was uniform distribution of heat, a statement that certainly required modification. He (the writer) should prefer to say that the distribu- tion of heat was sufficiently uniform. In the Semet- Solvay flue there was a distinctly hot zone in each a few feet from the point of entry of the air and gas, and there were also differences of temperature along the length of the flue walls. For example, the follow- ing observations were made on the wall of one of the fourth flues (counting from the top) : 1,085 degs., 1,100 degs., 1,130 degs., and 1,160 degs. Cent., and in the hot zone 1,220 degs. Cent. It must be remem- bered that differences of heat, within limits, were not so important as were variations, and in vertical flue ovens variations of heat were bound to be con- siderable. In the Koppers regenerator oven it was impossible to observe the wall of the vertical flues with the optical pyrometer, and all that could be seen was the top horizontal flue and the bottom air block. The following observations were made on the bottom air block, which corresponded to the hot zone in the Semet-Solvay oven: — Degs. Cent. ? At the moment of “changing over’* ... 1,500 After 10 minutes .-._________________1,410 ----- „ 20 „ - ... ... .... ... 1,370 „ 30 „ __________________1,370 In no flue, vertical or horizontal, was the distri- bution of heat perfect, and much more could be done in this direction than was the case at present, by action based on the accurate measurement of flue temperatures. The whole success of the operation of coking, whether the aim be gas or by-products, or a rapid output of coke, depended on maintaining proper flue temperatures. At present this important matter was left largely to the eye of judgment of the gas- regulator. Ovens should be so constructed that all parts of the flue walls could be optically inspected and the temperature accurately determined. Mr. Colqu- houn had also stated that one person only was neces- sary for working the feed table and conveyor. At both of the 12 ton batteries referred to in his paper two persons were employed on this work alone. It was found that the time taken to stamp a 12 ton charge was 32 minutes, and not 24 as stated by the author, and in order to do even this they had had to modify the stamping plant originally supplied. With regard to the 12 ton oven, so many factors had to be considered that personally he hesitated to express an opinion either for or against it. Briefly, the points upon which he was not satisfied were the following: (1) Does the high narrow cake lead to more broken cakes? (2) Do the ends of these cakes always have to be tapered off? (3) Is there some degradation of by-products owing to the further travel of the gases through hot coke ? (4) Is a larger coke bench required, or are special arrangements necessary for dealing with the coke in order to avoid excessive moisture? Even if these queries were answered in the least favourable way, it did not follow that the 12 ton oven, under future labour conditions, would be an unattractive proposition. Possibly Mr. Colquhoun could enlighten the members on some of these points, as the question of the future size of ovens was of the first importance. • Mr. A. C. Middleton (Sheffield) wrote that, having had charge of a horizontal flue coking plant for over twelve years, he could not be accused of being preju- diced in favour of vertical flue ovens. Although hori- zontal flue ovens had much to recommend them, there was one great advantage which the vertical flue regenerative oven possessed over the horizontal flue oven, namely, the quantity of spare gas which it pro- duced. Calculations were given in Mr. Colquhoun’s paper showing the relative values of waste heat and spare gas for power-raising purposes, but one did not notice any reference to the use of this spare gas for lighting purposes. Many coking plants were situated near large towns, and those responsible for the gas undertakings of these towns would be only too glad to obtain this gas to supplement their own supply, and pay a price much higher than its value for power- producing purposes. For public supply, a high quality gas was needed (say 500 B.Th.U.); for power pro- duction, low grade gas could be utilised. For the production of high grade gas, good gas coal or coking coals were necessary; whereas for the production of power gas, inferior fuel could be used which could not take the place of gas coal, and which was often quite unsalable. Would it not be a more profitable proposition, instead of using good gas for power pur- poses, for owners of coking plants to dispose of their spare coke oven gas for lighting purposes, and utilise only the most inferior fuel to make producer gas for generating power. This practice of supplying lighting gas had been in vogue for many years in America and Germany, and was now engaging much attention in England. During the past year or two the whole of the lighting gas used in Middlesbrough had been derived from neighbouring coke ovens. By this prac- tice a considerable national economy was effected both in reducing the amount of high-class gas coal used and in utilising otherwise unsalable inferior coal for producing power. Apart altogether from the relative merits of either horizontal flue or vertical flue ovens, the question of whether it was an advantage or otherwise to compress the coal was a thorny one. Where the coal was only a poor coking coal, great advantage was gained by compressing, but it was very doubtful whether there was much gain when using a good coking coal. It was a fact that at many coking plants compressors had been discarded and hand- charging had been reverted to. With the new charging lorries and mechanical levellers this was a very much quicker operation than stamping cakes. He had heard on excellent authority of an instance where seven ovens were charged and levelled in an hour. This was much quicker than the making of cakes. With mechanical levellers it was possible to get the charge levelled quite as well as with com- pressed charges. Doubtless the yield per oven was in- creased by compressing, and with the present-day method of trade unions regulating the output of a plant at so many ovens per shift this was an ad- vantage, but the writer was convinced that this method of regulating the output of a plant would not last long. The workmen would surely notice the tendency to increase the size of ovens, and would then insist on a smaller number of ovens per shift, or would regulate their work on a tonnage basis. Mr. Colquhoun, in reply, said he was glad that the advantages of limiting the moisture in the coal were so strongly supported and supplemented by Mr. Porteous. A lower moisture than that only too usual would increase the return on capital by shortening the coking time and improving the yields of by-products, as well as (according to Mr. Porteous) increasing the yield of coke itself. Mr. Foxwell had asked whether they were “entitled to say that the water evolved from coal on distillation is combined water?’ No, they could not say that. He (the author) had fallen into the common error of speaking of combined water when he meant the formation of water which attended the carbonisation of coal. He had no doubt that, this correction being made, Mr. Foxwell would not ques- tion the moderate amount used to illustrate his argument, namely, 4 per cent. Mr. Foxwell also doubted whether horizontal flues were coming into favour again, on the ground that in America (and perhaps also in England) a much larger number of vertical flue ovens were being built. If that were so, it was because the vertical flue oven was cheaper by 10 to 15 per cent, than the Semet-Solvay oven. But although the vertical flue oven was cheaper in first cost, he (Mr. Colquhoun) thought that the ultimate cost—the prime cost per ton of coke, including repairs, over a period of, say 10 years—was in favour of the Semet-Solvay oven. Mr. Foxwell thought an equal distribution of the heat in horizontal flues was im- possible. His conception of such a flue, with a burner at one end and a constantly decreasing temperature throughout its length, was somewhat crude. The fact was that the whole volume of burnt products, totalling over 900 cubic metres per ton of coal carbonised, in sweeping through the flue maintained a temperature practically uniform throughout its length. Mr. Blythe suggested that the words “temperature sufficiently uniform ” would be more exact than “ temperature quite uniform,” and the speaker thought he was right. Referring to the flue temperatures recently recorded by Mr. Blythe, he said there was no call for so wide a difference in the temperatures at opposite ends of the flues. Temperatures taken on December 2 in No. 4 flue at Hoyland were as follow: — Burner end. Opposite end. ... Oven Nc 1 P’130 ... U40 uveniNc. 1 ____ (1,130 ... 1,120 p,140 ___ 1,130 Oxen No. 5_____(1,150 ... 1,140 Oven No 6 - P>°40 ... 1,050 oven jno. b .... (1,030 ... 1,050 Oven No 8 11,030 ... 1,040 uven i\o. o .....(1,050 ... 1,050 It would be observed that the temperatures were frequently higher at the far end than at the burner end. The proof that the temperature was sufficiently uniform (to use Mr. Blythe’s words) in these ovens lay in that, at seven plants in Durham and Yorkshire, the standard 7 ft. ovens coked 45 tons (the lowest figure) to 48 tons (the highest figure) of coal on the dry per oven per week. This was the average capacity over a term of years. Mr. Foxwell also questioned the statement made in the paper, that the decompo- sition of the gases that were evolved was inappre- ciable below 870 to 900 degs. As a coke oven man, he (the author) was thinking of the decomposition of ammonia and benzol vapours, and not of the gases. The subsequent sentence made it plain that decompo- sition of these vapours was prevented in the state of dilution in which they occurred. With regard to the time required to stamp a compressed cake for 12 ovens (24 minutes), Mr. Blythe stated that at Thorncliffe the time taken was 32 minutes. Mr. Blythe, how- ever, would admit that up to the present time two- thirds of the coal was not washed, and was artificially wetted for compression, also it was not crushed as fine as it should be. He hoped Mr. Blythe would succeed in reducing the time. In regard to the number of men required to work the feed table and conveyor, in Durham several plants similarly laid out were operated by one youth per shift, as stated by the speaker. In respect of the 12 ton oven, Mr. Blythe would not, of course, come to a conclusion until the washery was completed at Thorncliffe, nor expect that the high narrow charge would lead to broken cakes, or necessitate undue tapering off at the ends. Mr. Blythe suspected that the longer travel of the gas in high ovens might affect the yield of by-products, but the yields obtained at Hoyland were not lower than those obtained in neighbouring ovens of smaller size. Were the yields higher from the old design of ovens, only 6 or 7 ft. high, than in the modern 8 ft. ovens? His colleague, Mr. Marr, maintained that a duplicate set of standpipes, to be put in action simultaneously during the first 12 hours of the coking period, was called for by a study of the volume of gases given off during that period. He believed Mr. Marr to be quite right, and that it would increase the yield of by-products by quick removal of the gases. All that stood in the way of the development of the idea was that coke oven contracts were settled on strictly competitive principles that frequently barred the way to improved ideas. Mr. Middleton had re- marked that “ there is one great advantage which the vertical flue regenerative oven possesses over the horizontal flue oven, namely, the quantity of spare gas which it produces.” However, Mr. Middleton was not comparing like with like, but the waste heat horizontal flue oven with the regenerative vertical flue oven. Horizontal flue regenerative ovens gave as much spare gas as any vertical. Mr. Middleton had also said “ at many coking plants compressors have been discarded and hand charging has been reverted to,” and that “it is very doubtful whether there is much gain when using a good coking coal.” That question could be decided by trying a compressed charge against an uncompressed simultaneously in the same battery. If there was no gain in compression, the matter was settled. Some who had discarded their compressing plant had been the victims of cheap and unreliable machines imported from Germany, or had not taken steps to maintain them properly. ____________________________________________________ .LAW INTELLIGENCE. JUDICIAL COMMITTEE OF THE PRIVY COUNCIL.—December 13. Present—Lord Sumner, Lord Parmoor and Lord Wrenbury. Seizure of Coaling Craft. His Majesty’s Procurator in Egypt v. Deutsche Kohlen Depot Gesellschaft.—The Judicial Committee decided in favour of the Crown in cross-appeals from the Prize Court of Alexandria, which ordered the detention only, not the condemnation, of a fleet of tugs, lighters and motor boats belonging to the Deutsche Kohlen Depot Gesellschaft. It was contended that under the Eleventh Hague Con- vention these craft were “ Bateaux exclusivement affectes a des services de petite navigation locale,” but Lord Sumner, who delivered the judgment of the board, pointed out that, while the French text made the element of size a quality of the service of the craft, in the English text it was the quality of the craft themselves which was to be considered. Their lordships found that the craft in this case were an integral and indispensable adjunct to most important ocean voyages. December 16. Present—Lord Sumner, Lord Parmoor, Lord Wrenbury, Lord Sterndale, and Sir Arthur Channell. Freedom of the Seas. A. F. Klaveness and Company v. H.M. Procurator- General.—Their lordships rejected an appeal from a judg- ment of the Prize Court dismissing the appellants’ claim to be allowed compensation for the detention of the “ Stigstad ” after the discharge of her cargo under the Order in Council of March 11, 1915. Lord Sumner, in delivering the judgment, referred to the policy of the British Government in naval warfare. He said that, while it was not proper for a Prize Court to enquire into matters of policy which led to retaliation, its function was to see whether the policy inflicted on a neutral a greater inconvenience than was reasonable. For that purpose the Court was bound to ascertain the circum- stances in which the Order was made. He added that neutrals whose principles of policy led them to refrain from punitory action of their own against the illegal action of the German Government might well be called upon to bear a passive part in the suppression of courses which were fatal to the freedom of all who used the seas. _________________________ The executive council of the Chamber of Shipping denies the Premier’s statement that a decrease in rates of freight followed the Government control of shipping, and in- stances, among other matters, that coal freight from Cardiff to the River Plate in November this year was 120s., whereas in September 1916 the freight was only 32s. 6d. Electricity from Waste Steam at Collieries.—At a meet- ing of the Yorkshire Branch of the Association of Mining Electrical Engineers at Leeds on Saturday, Mr. J. R. Haigh read a paper on “ The Electrification of Old Collieries.” He did not refer to collieries such as those in the Doncaster district, which are equipped with modern plant, but to pits of 40 or 50 years old^ a great many of which, he said, were at present working under con- ditions that were not conducive to efficiency, but at which the expenditure of a few thousand pounds would repay itself in a few years, and would afterwards yield a good dividend for the shareholders. Travelling through mining districts, one was surprised to find the amount of waste steam which passed away into the atmosphere. For years it had been argued that no means existed whereby the loss could be obviated, but it had been proved by more than one large colliery company that there was to-day on the market machinery which, if suitably installed, would turn a once inefficient concern into a highly efficient and lucra- tive one. The time had arrived when the electrical engi- neers were to come to the rescue. Prejudices which had existed for years against the use of electricity would have to be swept away. Instead of a ban being placed upon this modern and' scientific method of working collieries, they would be compelled to welcome it as their salvation, as many collieries, now hardly paying their way, would then be able to so reduce the cost of production per ton as to show a substantial profit. He went on to advocate that all the power for subsidiary purposes at a colliery should be electric. The pumping, haulage, screening, coal washing, fitting, blacksmith, joiners’ and wagon shops should be electrified, the power being generated by means of turbo alternators from the waste steam coming from the exhausts of the main winding engine, fan, and air com- pressors. Taking a colliery with an output of 1,200 tons per day, and winding engines of 1,100 horse-power, he estimated that the amount of steam wasted would give 2,390 kw. of electricity. He proceeded to show in detail how this could be utilised, and how it had been utilised at the colliery with which he is connected. The change over from steam to electric drive had proved reliable, effective, and economical. It had been found possible to save one- third of the boilers previously employed for steam raising. A discussion followed, in which the president, Mr. J. W. Harbottle, A. R. Chaytor, W. J. Hoskins and others took part. The discussion was adjourned.