544 THE COLLIERY GUARDIAN. March 12, 1915. CLEANINGS IN COKE OVEN PRACTICE. At a recent meeting of the Yorkshire Junior Gas Association, an address was delivered by the President, Air. J. W. Lee, who is chief chemist to the Grassmoor Company, to which he gave the title of “ Gleanings in By-Product Coke Oven Practice.” The address was illustrated by lantern slides and sketches. He said the battery of by-product, coke ovens at Grass- moor consisted of 110 ‘ ‘ Otto” ovens, 60 being of the waste heat type, and 50 of the regenerative type. The total capacity , of the ovens was about 550 tons of coal per day. The weight of stamped wet coal charged per .oven will average 8-25 and 9-1 tons in the waste heat oven, and 9-7 tons in the regenerative; and the charge will be burnt of! in 34 hours and 36 hours respectively. ..The total capacity of the ovens is about 550 tons of coal per day. The coal used for coking consists of mixtures of the holing slacks obtained from the Tup ton, Dunston (Heathcote), Deep Hard, and Blackshale seams. Average analyses of these, before washing, show . 1 1 Moisture Tupton. Ur cent. 5’52 .. Dunston. Per cent. . 8’08 .. Deep Hard. Percent. . 5’61 .. Black- shale. Percent. . 3’93 On dry basis— Ash 11’33 . .. 16’12 .. . 20’70 '.. . 8’80 Volatile matter 28’84 . .. 28’66 .. . 26’88 .. . 31’64 Fixed carbon ... 59’83 . . 55’22 .. . 52 42 .. . 59’66 Chlorides equal to . NaCl 0’112 .. .. 0’023 .. . 0’049 .. . 0’086 The slacks are washed in a Humboldt washer, and after washing the average of daily analyses over a long period gives :—Moisture, 11*31 per cent. On dry basis :—Ash, 6-08 per cent.; volatile matter, 34*06 per cent.; fixed carbon, 59*86 per cent. Chlorides equal to NaCl, 0*056 per cent. Average daily tests show 3*5 per cent, of the coal in the dirt. The coal is charged into the ovens, after stamping, by means of a Buchanan machine, and can also be charged from the top in case of a breakdown of the charging machinery. The coke is discharged from the oven by an electrically-driven ram, travelling on wheels (which also carry the stamper box) into a “ Goodall ” coke quencher. The coke is quenched by passing a “ Darby ” quenching hood, and finally on the revolving table. After draining, the table is reversed, and the coke passed, by means of a conveyor, over a screen into the railway wagons direct. Using a coal mixture of the following composition :— Per cent. Moisture .. ......................... 12*99 Ash ................................. 5*65 Volatile matter ...................... 30*53 Fixed carbon ......................... 50’83 the coke yield is made up of :— Large coke ....................... 95’2 Smail coke ...................... 2’0 Dust (below iin.) ................. 2’8 giving on analysis :— Large Small n f coke. . coke. nufet’ Percent. Percent. Percent. Moisture................. 1’80 ... 16’97 ... 21’55 Ash ................... 9’45 ... 10’33 ... 12’47 Volatile matter (on^dry)... 0’69 ... 3’27 ... 5’56 The “hydraulic” main is of the “dry” type, and the temperature of the main varies from about 110 degs. Cent, to 150 degs. Cent. By circulating tar through the main very little trouble is experienced with pitching up. Some solid deposit has been collected of the following composition :— Per cent. Ammonium chloride ........... 48’0 Tar (ether and benzol extract) . 30’8 Coal dust and free carbon ..... 21’2 The tar after circulation has a specific gravity of 1*166, and gives on distillation :— Per cent, by weight. Ammoniacal liquor.......... ....... 1*8 Light oils, up to 170 degs. Cent... 1’9 Middle oils, 170degs.to270 degs. Cent. 31’4 Heavy oils, above 270 degs. Cent..... 10’6 Pitch... .......................... 53’6 Free carb n content 13’8 per cent. The collected tar from all points had a specific .gravity of 1*164, and gives on distillation :— Percent. By , , By~^ volume, weight. Ammoniacal liquor .................... 2’1 ... 1*8 Light oils, up to 170 degs. Cent...... 2’3 ... 1’9 Middle oils, 170 degs. to 270degs Cent. .. 29’4 ... 26’5 Heavy oils, above 270 degs. Cent. .. 17’8 ... 16’6 Pitch .................................. — ... • 52:6 99’4 Free carbon content 11*2 per cent. Tests of the strength , of the ammoniacal liquor collected at each point shows :— Free NH3 Per cent. Fixed NH3 Per cent. Total NH; Per cent. Hydraulic main .... 0’102 .. .. 7’093 ... 7 195 First coolers . 0’382 . .. 0’083 ... 0’465 Second coolers 1’454 . .. 0’051 ... l’50> Third coolers.... 4’675 . .. 0’085 ... 4’760 Before sprays ,.. . 1’295 . ... 0’051 ... 1’346 After sprays 1*303 . .. 0*051 ... 1’354 No. 1 scrubber 0’741 ... 0’034 ... 0*775 No. 2 scrubber 0’398 . .. 0’017 ... 0’415 The ammoniacal liquor is converted into sulphate of ammonia in a Wilton plant. Two stills, each capable of dealing with 80 tons, and one still 150 tons per 24 hours, two saturators, each of sufficient capacity to produce about 10 tons per diem, and a centrifugal dryer, comprise the plant. Excellent sulphate of a good colour is produced, averaging :— Per cent. Sulphate of ammonia............... 96’90 Chloride .....-................... 0’03 Free acid....................... 0’48 Moisture........................... 2’50 Insoluble matter ................ 0’04 99’95 The waste liquor—six tests per day for a year— averages :— Per cent FreeNHs ......................... 0’0056 Fixed NH3 ....................... 0’0014 0’0070 The “devil” liquor averages:— Per cent. Free NH3.......................... 0 0228 Fixed NH3 ........................ 0’0062 0’0290 0*9 ton of sulphuric acid, and 2*5 cwt. of the lime are used per ton of sulphate produced. Except during a period when the acid supplied con- tained a large quantity of arsenic, no difficulty has been experienced in producing a salt of good colour. The ■acid should be as free as possible from iron content. A typical acid gave :—■ 143 degs. Twaddel. Per cent. Sulphuric acid, by titration ..... 80 64 Iron = Fe2O3 ..................... 0’059 166 degs. Cent. 14 per cent. 86 ter cent. The author showed by means of a sketch the method of extracting the benzol from the gas. A typical dis- tillation from the first rectifying still gave :— 6,382 gallons into still 3,863 ,, 90 per cent, crude benzol 601 „ 90 per cent, crude toluol 409 „ 90 per cent, solvent naphtha 1,256 ,, oil returned to circulation. The oil returned to circulation had a specific gravity of 1*015, and on distillation with the thermometer bulb in the vapour showed :— First drop ...................... Up to 200degs. Cent............. 200 to 270 degs. Cent............ The crude products are separately washed in a Lucas acid-proof agitator, the working capacity of the washer being 4,000 galls. In the second rectifying still, washed solvent naphtha is distilled with indirect and direct steam under vacuum. After washing and distillation the products obtained are pure 90 per cent, benzol, pure 90 per cent, toluol, and pure 90 per cent, solvent naphtha. Over a year’s working, for each ton of acid used, 7,544galls, of products have been washed, and for each ton of “ Kausticine ” (90 degs. Twaddel, 43*4 per cent. NaHO), 34,214 galls. The loss in washing is 5 per cent., 6 per cent., and 25 per cent, in benzol, toluol, and solvent naphtha respectively. The relative quantities of washed products recovered have been 74 per cent, benzol, 10*8 per cent, toluol, 15*2 per cent, solvent naphtha, and the average quantity 2*5 galls, per ton of dry coal. In use the wash oil thickens, and its efficiency decreases. It is then taken out of circulation, and returned to the distiller. The spent oil has a specific gravity of 1*090, and gives on distillation :— Pqp cent Up to 20) degs. Cent. ............ 11’6 200 d^s.—300 degs. Cent. .......... 69’4 Residue..........;................. 19’0 0*096 gall. rof fresh creosote was used per gallon of washed product recovered, and, the loss of creosote was 0*044 gall. Of the gas produced, from 75 to 90 per cent, is required to heat the waste heat ovens, and 50 per cent, to 60 per cent, to heat the regenerative type. The rest is used for lighting, heating, in gas engines, and for burning under boilers. Under the first three heads, about 7,000,000 cu. ft. per day are used. .The average composition of the purified gas is :—C02, 3*6 per cent.; CnHm, 2*6 per cent.; 0, 0*3 per cent.; CO, 7*6 per cent.; H, 50*2 per cent.; CH4, 30*1 per cent.; N, ■ 5*6 per cent. The unpurified gas contains cyanogen equal to l| lb. of Na4 Fe(Cn)fi 10 H2O per 10,000 cu. ft. The sulphur content was 25*48 grains per 100 cu. ft.; and the calorific value 550B.T.U. gross (500 net). '-The bulk of the.gas1 is used in three engines of the Westinghouse vertical tandem type, which are coupled to 350 kw. Westing- house alternators, generating Three-phase current at • 440'volts and 50 cycles. The total load on the con- nections is about 1,280-horse power; and the engines, at a load factor of 59 per cent., use" 46 cu. ft. of gas per unit of electricity. The cost per unit, including charges for management, running, repairs, purification (not gas) is 0*12d. . Experience has proved that a daily test of the exhaust gases for carbon dioxide, oxygen, and carbon monoxide results in an economical gas consumption. Average of good working results shows :—Carbon dioxide,-9*8 per cent.; oxygen, ,2*2 per. cent.; carbon monoxide, nil. The steam required for the whole coke oven plant is generated in three Babcock and Wilcox boilers by means of the waste gases from the waste heat battery. Hull Coal Exports.—The official return of the exports of coal from Hull -abroad for the week ending Tuesday, March 2, 1915, is as follows :—Alexandria, 1,500 tons ; Aarhus, 981; Aalesund, 553; Buenos Ayres, 4,770; Chris- tiania, 748; Calais, 5,753; Christiansund, 26; Dunkirk, 1,000; Elsinore, 822; Genoa, 5,048; Gothenburg, 1,305; Haugesund, 116; Honfleur, 533; Naples, 1,401; Nykjobing, 2,725; Reykjavik, 553; Rouen, 22,717; Treport, 454; Tuborg, 1,219—total, 52,224 tons. The above figures do not include bunker coal, shipments for the British Admiralty, nor the Allies’ Governments. Corresponding period March 1914—total, 60,774 tons. FIREDAMP: ITS DETECTION AND ESTIMATION. LECTURE BY PROF. McMILLAN. The above was the subject of a lecture delivered by Prof. W. H. McMillan, B.Sc., of University College, Notting- ham. at Holy Trinity Institute, Ashby-de-la-Zouch,. on Saturday, February 20, the occasion being the last of the winter iseries arranged by the joint committee of colliery managers, mining officials, and representatives of the Leicestershire and Derbyshire County Councils Education Committees. Mr. Walter Jones, C.C., a member of the Leicestershire and Derbyshire County Councils’ Alining Sub- Gommittee, presided. Prof. McMillan, in the course of his lecture, said that firedamp was usually taken to consist of methane or marsh gas, or as a mixture of gases, in which the chief constituent (methane) was accompanied by varying amounts of nitrogen, carbon dioxide, and air, while in a few instances sulphuretted hydrogen, hydrogen, and olefiant gas had. also been found to be present. A number of investigators had also proved that in some instances where cannel coals were being mined, and in some cases in which the coals were liable to spontaneous combustion, traces had been found of other combustible gases, consisting of higher members of the paraffin series. Carbon monoxide had also been found in very small quantities. From the purely scientific point of view, the presence in minute quantities of such other gases was highly interesting, but practically their occur- rence was so rare that the assumption that firedamp was a mixture of methane and air was . certainly justifiable. It was no doubt true that some of those gases had a lower explosive limit, that was to say, a smaller percentage when mixed with air would explode, but any danger which might arise from this source was compensated for practically at least by the fact that they also gave a better cap than methane for the same percentage on the flame of a safety lamp, and that, therefore, if estimated as methane, the danger attached to their presence in smaller percentages was none the less apparent. In the vast majority of cases, however, in which the firedamp issuing from blowers and boreholes had been analysed, it had been found to consist of from 90 to 99 per cent, of methane, with varying propor- tions of nitrogen, carbon dioxide, and oxygen. There were many questions of the greatest interest con- nected with the occurrence and properties of firedamp which had been only partially answered. Why, for example, did they occasionally find firedamp in metal mines, and also in some salt mines? Why should methane pre- dominate in a substance which, on distillation, gave such a complex series of other hydrocarbons? Why should it be present in large quantities in some seams of coal, and be practically unknown in others possessing similar conditions as to formation 'and depth, and giving very similar results on analysis? Why should anthracite coals, in general, give off relatively less methane than the so-called bituminous coals ? The main purpose of his lecture was to deal, however, with the various methods suggested, and those which were actually in operation for the detection and estimation of this highly dangerous constituent of mine air, and for that purpose the lecturer demonstrated with a fairly representa- tive collection of instruments of various kinds. But, he said, it might be safely stated that with certain possible exceptions there were only two methods of any practical value, namely, the detection and estimation by observations on the flame of some form of safety lamp, and the estimation by analysis. The analytical method, which was more deli- cate and accurate than the safety lamp method, had come greatly into prominence since the passing of the new Act, but the instruments on the market for use underground had not met with much favour. As a laboratory method, how- ever, it was fairly extensively used. The various methods suggested and in operation might, for his purpose, be classed under four main heads *. (1) Flame testers, which included safety lamps of the ordinary type, safety lamps burning special fuels, safety lamps having some special attachment to render them more delicate as testers ; (2) apparatus depending on the rate of diffusion of gases, including appa- ratus of the Ansell, McCutcheon, and Webster types; (3) apparatus depending on the slow or rapid combustion of the gas, and the resulting increase in temperature, decrease in pressure, or decrease in volume measured; (4) electrical detectors, or what might be called hot wire instruments, all of which really came under class 3, since they depended for their action on the increase of temperature produced by burning the gas, only it might be measured photometrically (as in the Liveing indicator), or by means of a pyrometer (as in the Williams), . or by the change in electrical resist- ance (as in the Ralph firedamp meter). -. Flame Testers. Judging from his experience in connection with mine . deputies’ examinations, there was one point which was still somewhat imperfectly understood. There, was still a fairly persistent tendency to estimate from the-height of the gas " cap in the safety lamp. This undoubtedly was a fairly sound method, provided the tester' fully realised the other factors, in addition to percentage of gas, which governed the height of the cap. But bearing in mind the facts that the height of the cap depended, among other things, on the height of the testing flame used, the kind of oil, -and size of the wick, it was evident that this basis of testing might be very misleading indeed, unless those points were care- fully taken into consideration. In fact, for the higher percentages, especially those above 3 or 3| per cent., it was possible to obtain a very big variation in the height of cap by a relatively small variation in the height of the testing flame. It was much more reliable to judge from the density of the cap. He found that anyone with ordinary vision had no difficulty whatever with most lamps in use at the present time in seeing as low as 1 per cent, of gas, while if one of the more modern safety lamps burning a lighter fuel be used, it was quite possible to distinguish between the fuel cap and the gas cap for percentages less than 1 per cent. With the lamp one could not be certain of the difference between a percentage slightly below and another slightly above J per cent., which would be necessary for some purposes of the Mines Act, or to estimate accu- rately down to % per cent., which was also necessary in some cases. It was very doubtful whether any method, short of the analytical method, could be found which would reach this high degree of accuracy, and still be in a suffi- ciently handy form. The Pieler, Chesneau, and Ashworth lamps were purely gas detectors, and gave no light what- ever, while their range for testing was limited to the smaller percentages. The deputy would have to carry another lamp, and this consideration, together with the fact