February 9, 1917. THE COLLIERY GUARDIAN. 281 reddish tinge, semi-flocculent. Coke, dark grey in colour, firm, light, and not readily broken on handling. An analysis of the ash contents gave the following results :—Moisture, nil; silica, 54-02 per cent.; alumina, 32-63; ferric oxide, 7-50; lime, 0-92; and sulphur trioxide, 0'24 per cent. Ovens.—The ovens are of the Semet-Solvay recupera- tive type, and are lined with special bricks of small size, which give much less trouble with contraction and expansion than the large blocks formerly in use; more- over, repairs are much facilitated and cheaper. Quick coking is one of the results of this construction, the actual time now occupied being 22 hours. The gas from the ovens rises through the ascension pipe, and dips into the hydraulic (water-sealed) main. Thence to the water tube condensers, where it is cooled to s-ueh a degree as to deposit most of its moisture and tar (together with the naphthalene), which is immediately taken up by the tar. About half of the ammonia is absorbed by the liquor of condensation. The benzol passes on unabsorbed, together with the remainder of the ammonia, and a certain residue of tar in the form of tar fog. This latter, after passing the exhauster, is forced through the tar extractor—of the Pelouze and Audouin type—the feature of which is that the tarry gas is divided into a large number of small jets by passing through a perforated plate, these jets being then caused to impinge on a blank plate, whereupon the tar sticks and runs down while the gas passes on. The gas next passes to the saturator, partially filled with weak sulphuric acid through which the gas bubbles, the ammonia combining with the sulphuric acid with the formation of sulphate, which as the solution becomes saturated crystallises out, and is removed with am ejector into a draining table, and thence to a centri- fugal drier, after which it is conveyed to the storehouse. The ammonia liquor having been separated by gravity form the tar, passes to stills, where the ammonia is driven off with live steam, the fixed ammonia being set free by the addition to the liquor of milk of lime. The still gas joins the rest of the gas on its way to the saturator. In this (semi-direct) process, no absorption is required of the ammonia vapours in water. Ammonia scrubbers are dispensed with, together with all their tanks, pipes, and pumps, and the effluent liquor is reduced in quantity by one half. The light oils still remain in the gas, and consist of benzene, toluene, and higher homologues in varying pro- portions. They are removed by scrubbing the gas with creosote oil, which creosote takes up about 4 per cent, of its weight of benzol, and the benzolised oil is next distilled with live steam, whereupon the light oils distil over and are purified by washing with strong sulphuric acid and water, and neutralised with caustic soda. The washed oil is then fractionated into crude fractions, which are subsequently rectified into the pure products by another distillation for each product. (To be continued.) STEAM TURBINES AND COAL CONSUMPTION. In the course of a paper on “ Steam Turbines for Land Purposes,” read at a meeting of the Manchester Association of Engineers, on the 27th ult., Mr. H. L. Guy said the broad lines of the developments which had matured during the past five years could be gauged by considering the difference in the production of the turbine department of the firm he was associated with. Confining attention to machines over 200 kilowatts, the following table was prepared:— Per cent, of No. of turbines built. Per cent, of total full load capacity. Average capacity. Kw. High pressure Mixed pressure Low pressure Back pressure . ... Reducing pressure The total output double that for 1910. 1910. 1915. 1910. 1915. 42-5.. 71-3 74 ...83-3 ...~l 38’5 13'6 20'6... 7’52... 8'5... 1'5 3-5... 018... 10-5... — 1-9... — ... — ...13-6 — ... 9 .... in kilowatts for 1915 wa 1910. 1915. 1-1,550.. .2,300 more than The reasons for these changes in the relative import- ance of the various types of machines were readily found. It had now been established that a pure high- pressure turbine was more efficient than a combination of a reciprocating engine exhausting into a low pressure or mixed-pressure turbine, with the result that iiigh- pressm-e turbines were being installed where the former- types were adopted a few years ago. That represented a distinct advance in the art of turbine construction, because it was still maintained at the earlier date, and with some justification, that the reciprocating low pressure turbine combination represented the ideal. Another factor, which in many cases operated to ensure the installation of a high-pressure rather than a mixed-pressure or low-pressure turbine, lay in the fact that it was often a doubtful expedient to couple a new turbine of the latter class to an obs >lete or more or less worn-out engine, which would, in any case, be scrapped long before the useful life of the turbine had expired. Another feature of the change in the class of turbines produced was shown in the following table:—■ Per cent, of No. of machines built. Average output of each machine. t I 3,000 1,500 3,000 1,500 r.p.m. r.p.m r.p.m. r.p.m. 1910 40 8 . .. 19-2 ... 588 .. 2,800 1915 76'0 .. 15-2 ... 1,810 . 5,300 As an illustration of the reliability of a modern steam turbine unit and of the importance of coal consumption, the author referred to a 6,000 kw. 1,500 r.p.m. set installed at the Port Dundas station of the Glasgow Corporation. Between July 24, 1914, and October 31, 1915, that set generated 52,852,500 units on 78'93 per cent, of the power which could have been generated if it had been carrying full load for the whole time. The set was started up in February 1914, and had generated 100,000,000 units by August 1916, so that with a coal consumption of, say, 1’75 lb. per kilowatt hour, the coal used would equal 78,250 tons in two and a-half years, or at the rate of just over 31.000 tons per annum, which represented a coal bill of £23,500 per annum with coal at 15s. per ton, so that each 1 lb improvement in steam consumption saved about £1,710 per annum in cost of fuel alone. If the saving in coal consumption alone was considered and capitalised at the rate of 10 per- cent., an increase in purchase price of £2,350 would be justified for each 1 per cent, improvement in steam consumption. For examples of high pressure turbines of the largest size we had to turn to the United States of America. The British market in the past had not demanded units of similar capacity, but when such sets were required British makers would be found able to cope with the demand in the fullest measure. As typical example of the type of large unit manufactured in America, he quoted an instance where three turbines of 90,000 kw. were erected, occupying the same floor space as the reciprocating sets they replaced. The purchase price of the turbine sets per kilowatt was only 22'5 per cent, of that of the engines, while the saving in coal alone on one set was estimated as being over £40,000 per annum. Since the installation of the first set the average monthly coal consumption had been reduced from 2’5 to 1'5 lb. per kilowatt hour. BOREHOLE TROUBLES.* By P. S. Warriner. The accompanying sketch illustrates churn drill borehole No. 1365, recently put down from the surface to the Red Ash Vein, a distance of 632 ft., at the Henry Colliery, Plains, Pa. The hole is used for a hoisting cable on the Red Ash Slope. Drilling was begun in January and completed September 1, 1916. From Api-il 18 to July 11 of this period a progress of only 5 ft. was made owing to difficulties from the efforts made to pass a running seam of faulted coal and slate which was encountered at a depth of 382 ft., and which was in all about 13 ft. in thickness. Drilling had been continued to a depth cf 15 ft. below the bottom of this seam when the shelly material began to run, filling the hole up to very near the top of the seam. From this time on it proved impossible for the driller to gain over 5 or 6 ft. through this loose material without precipi- tating a large amount of loose material into the hole, and then the drill could be removed only with great difficulty. In the event of complete submergence this drill might have become so firmly anchored that removal would have been impossible, and the outfit would thus be lost. In such circumstances it would be necessary, at a great expense, to drill through or around the lost drill, if possible; and, if not, the hole would have to be abandoned. Realising that it would be unwise to take chances in removing the full 20 ft. of material which had at this time been deposited in the bottom of the hole, it was considered advisable to cover this area at once with a thin grout. The hole was therefore filled with grout to a point 13 ft. above the top of the running seam, to give it sufficient head to force the cement into the seam as fal- as possible, in order to bond the shelly material together and prevent further running after drilling would be resumed through and beyond the cement. The cement was allowed to set for five days, and on attempting to drill it was discovered that not even an initial set had taken place. Not over three days should have been necessary for this cement to have set up hard. To make sure that ample time was given, it was undisturbed for three days more, but even then it was found to be still in a liquid state. This was pumped out at once to the bottom of the hole and refilled with grout bearing 2 per cent, of baking soda to render it quick setting. A sample of the new mixture was retained on the surface from each batch and it took on an initial set in 15 minutes. After two days, on attempting to drill, it was dis- covered that a quantity of the grout had stuck to the sides of the hole at a depth of over 200 ft., which occupied three days to clean off. For this work a hard wood plug, 10 in. in diameter and 2 ft. long, was dropped into the hole and rammed to the bottom with the drill. After chopping out the plug, the cement was again discovered to be in a liquid state, and was once more removed and re-grouted with fresh cement, containing, as before, 2 per cent, of baking soda, and given seven days to set. On discovering at this time that no set had taken place, the grout was removed once more. It was then decided to try to fill the hole with dry hydraulic cement, which was lowered in long paper bags, in two sections of six bags each. An inierval of one day was allowed between the dropping of each batch. In the hole the full head of water was about 200 ft. It was necessary to lower it about 15 ft. before inserting the cement, so that no separation would occur due to the cement passing through an unnecessary high head of water while being lowered to the bottom of the hole. Three days were taken to drop the hydraulic cement, The instalment was then allowed five days to set, but, as before, it was a complete failure. At this time the belief prevailed that the failure of the cement to set was probably due to the motion imparted to it by the rising water or to large feeders of gas bubbling through the liquid. This theory seemed so plausible that good results from the grouting might be expected if the motion of the water or gas through it could be * Lehigh Employees’ Magazine. stopped. Following this line of thought, the water was lowered to within 20 ft. of the bottom, and sufficient dry cement was poured into the hole to fill it about the faulted area. A wooden plug of the same diameter as the hole was forced down upon the top of the cement. On the head of this plug a stream of water was poured until it reached the full head of 200 ft. Thus the entire borehole was made practically airtight and solid. This method proved successful, as five days later, after- chopping out the plug, the cement was found to be as hard as rock. The drilling was continued through it until the solid bottom, 15 ft. below the trouble, had been reached. Five feet deeper in the solid, the knocking of the upper end of the drill, which at this time was opposite the lower and thin edge of the seam (see cut) fractured the cementing and brought in a large quantity of loose material. This loose stuff so bound in the bit that the rope was broken in attempting to pull it out. The rope was recovered and spliced and the drill finally removed. Further cementing was abandoned at this time, and an 8 in. casing pipe was inserted from the Skidmore Vein past the trouble to the bottom of the hole. This made it necessary to finish the hole to the Red Ash Vein with an 8 in. drill. In preparation for this it was necessary to open up the Skidmore Vein to the borehole shown in the illustration, where the pipe, after being lowered to the bottom from the surface, was capped with a bell-mouth sleeve to guide the drill when being lowered into the hole. This is also indicated on the HENRY COLLIERY SECTION THROUGH ffl cut. By July 11 drilling in the solid was begun, and continued without further delay to the Red Ash Vein, which was encountered September 1. A 6 in. casing pipe was finally inserted from the surface to the Red Ash Vein and the space between the outside of the pipe and the side of the borehole was finally filled with grout. The conclusion to be drawn from this whole trouble is that for good results when any cementing is done, the mixture must not be subjected to even a slight, continuous internal disturbance. Excess Mineral Rights Duty.—Mr. T. Jones, as referee, has issued his decision in the appeal by the trustees of the settled estates of the Earl of Lonsdale, against two assess- ments by the Commissioners of Inland Revenue, to excess mineral rights duty for the years 1914 and 1915, in Flimby, Cumberland. The matter in dispute, as reported in our issue of January 19, related to the rate of royalty which obtained during the joint auditing year. The referee, decided that the actual pre-war tonnage rent or royalty for 1912 and 1913, as paid to the appellants, was the proper standard in dealing with the tonnages of 1914 and 1915.