246 The colliery guardian. January 30, 1914 The Correlation of the Gas Lighting and Coke Oven Industries.* By J. E. CHRISTOPHER. recovered in both industries on very similar lines, namely, simple cooling followed by impact or washing types of tar separators for the last traces. On modern coke plant about 50 per cent, of the tar will be recovered (Concluded from page 190.) in the hydraulic main, 25 per cent, in the air condensers, 10 to 15 per cent, in the water condensers, and the Merits of Light and Heavy Charges. In comparing the quality of gas from chamber carbonising, it would be interesting to review the results obtained at gasworks by varying the weights and duration of the charges. So far as gas-retorts are concerned, the figures show an advantage in light charges of about 400 cubic feet of gas per ton, and our balance sheet would be:— Light charges s. d. Heavy charges, s. d. 400 cubic feet at 2s. 6d.... 1 0 2 gals, tar.. 0 3 5 lb. sulphate of ammonia ......... 0 6| I cwt. coke ..... 0 3| 1 0 1T In addition, we must take into account the reduction in naphthalene troubles, which Mr. Bell states is 50 per cent, with heavy charges. The tar in light charges has undergone an appreciable amount of cracking—roughly in proportion to the free space above the charges—see fig* 7. It can be taken with a fair degree of certainty that the tar in modern coke ovens does not suffer from cracking to the same extent as in gasworks. The writer is unable to give at the present moment any data as to the effect of smaller charges in coke ovens on the gas yield; but his experience as regards by-products leads him to infer that the correct method with coke ovens is to charge them as completely as possible Light charges have led to trouble in the hydraulic main through pitching, and there has been a tendency to from data in Estimates and Valuations, by J. F. Scott 1913. It is difficult, in making comparisons from published data, to ascertain what is or what is not included in certain costs; but the writer has included in his capital cost the following items on a coke plant and their equivalent in a retort plant:—Coal bunkers, elevators, disintegrating plant, charging and discharging machinery, condensing and scrubbing plant, exhausters, power house, and chimney. Coke-ovens, compressing plant extra to ovens only. Retort-house extra to retort plants only. Sulphate plants, tar and liquor tanks, coke conveyors. As regards repairs to the chambers of coke plants, the cost varies according to the quality of brick used and the nature of the coal. With a normal content of salt in the coal, and with good quality firebricks, the writer has had actual experience of ovens lasting eight years before relining—each oven thus having dealt with more than 15,000 tons of coal. On the other hand, cases can be quoted of lives of less than three years’ duration, due to corrosion from alkalies from the coal, which, of course, would affect gas retorts similarly. remainder in the tar washers or extractors, scrubbers, &c. Typical analyses of such tars are shown in Table 6. In the most recent coke plants where direct recovery systems are in vogue, the apparatus used for tar extrac- tion is much more compact. In the direct-recovery systems the tar is removed at a temperature varying with the moisture contents of the coal. In coke-oven practice, this temperature is usually in the neighbourhood of 80 degs. C. In average gasworks practice the temperature could be brought down to about 70 degs. C., or even lower. With reference to the recovery of ammonia at gasworks or cokeworks respectively,'we must not lose sight of the fact that, as a rule, washed slack containing up to 12 per cent, of moisture is used at coke ovens; while dry coal is the rule at gasworks. We thus obtain the following data, representing average conditions:— Average strength Coke ovens Moisture. Per cent. 12 of liquid. Per cent. 0 86 NH8 Gallons per ton. 64 Gasworks 3 2-04 NH3 27 Table 3. f^O^»ZONrAL^ 22 “x "k cvirr 65% Norwich CHAM&ERS % FREe — fZ cwr 32 Coke Overs 35*0* 6 tons Source. Specific gravity. Free carbon. Distillate. Pitch. Observer. Up to 170° C. Up to 270° C. Up to 350° C. Coalite 1-073 2-0 31 304 211 417 Lewes Vertical retort 1-113 4-0 13 0 240 90 500 Drury Do. 1-074 31 9-1 257 24 9 46-0 Newbigging 45 degs. retort 1-095 26 4*4 28-5 19-2 47-5 Colman Norwich chambers 1-180 11T 0-4 10-2 301 53-9 Colman Coke ovens 1-190 10-5 94 9’8 24'8 510 Hooper Do. 1160 65 3’0 18-0 22-4 57*0 Byrom Do. 1T80 72 — — — — Byrom Do 1-150 68 — — — — Byrom Horizontal retorts — 28-7 1-1 13*1 132 72-1 Colman Do. — 232 1-4 10-5 161 71’8 Colman Do. 1220 17-2 4-9 18’4 90 60-6 Drury Do. 1190 17’7 45 12 0 195 57’0 Newbigging Do. (heavy charges) — 170 80 32 0 40 56-0 Stewart Do. (light charges) — 36 0 30 140 50 780 Stewart Table 4. Fig. 7. lower the tar and ammonia yield, without any advantage as far as quality of coke is concerned, which is, after all, the prime consideration with the coke maker. Table 4 gives representative analyses of chamber- oven gases. It must be remembered that all these gases are from coals chosen mainly for their coking properties, and with the exception of the analyses from the United States, are the average analysis throughout the charge. The writer can state with confidence, that, given the same care in choosing coals as is exercised in gas- works, a satisfactory average gas could be turned out by any of our modern coke plants, and he can testify strongly to its uniformity. By diverting the gas from the earlier portion of the coking period this quality could still more easily be maintained. Financial Considerations. Turning to the financial side of the question, we will take the following as data for comparison :—Coke oven plant, 24 ovens to deal with unstamped or stamped charges, with five charges per oven per week in the first case, or seven charges per oven per week in the second ; each oven to hold 8 tons of dry coal per charge. In making the following comparison the writer is well aware that he is treading on very controversial ground. The figures as regards coke ovens are partly the result of his own experience with one particular type of oven, and partly the result of figures in his possession relating to four other types of ovens. The figures relating to horizontal retorts and vertical retorts are calculated *From a University lecture to the Manchester and District Junior Gas Association, January 10. — ch4 Ha CO coa Na Authority. Simplex 30 26’2 47 7 90 * 0-5 13 6 J. T. Lucking Chamber '. 3’0 26 1 576 66 t 30 3*5 E. A. Franks Semet Solvay (enriched) 54 344 48’8 40 •6 11 57 E. C. Witherby, U.S. „ „ (initial)... 48 34-1 48*4 41 •7 1-2 6-7 ,, „ (fuel) 24 266 567 4'0 ’6 09 8*8 Huessener 15 31*5 555 36 •1 1-2 6*6 C. Lowthian Bell Semet Solvay 38 31*0 49’3 6-8 •3 21 66 E. Bury Otto Hilgenstock 38 28’4 51’5 50 •6 18 8*9 A. Short Semet Solvay 20 28 0 55 8 35 •7 3 0 7*0 T. H. Byrom Hoppers 29 28-2 53*3 91 -4 2*6 35 G. S. Cooper * Not stated. f Trace. Table 5. 24 Coke-Ovens. i Hoiizmtal Veitical Stamped. Unstamped. Retorts. Retorts. Coal per day . Gas per day, approximate . Carbonising staff Wages per ton coal carbonised.... This staff could deal with greater output, and wages would then be... Capital cost of items stated 137 ( 1| million cubic feet. 17 7-3d. 4‘4d. £26 192 2 million cubic feet ) 16 5 0d. 3*8d. ,000 140 1| millions £36,000 140 1| millions £34,000 Table 6. A. B. C. D. E. F. Specific gravity.. . 1-16 .. . 1*15 ., .. 112 .. .. 1*08 .. ,. 1-08 ... 0-99 To;i70 degs. C... . 2 .. . 1 .. .. 1 .. . 6 .. 8 ... 25 „ 270 degs. C... . 17 .. . 15 .. . 82 .. . 36 .. . 38 ,, 360 degs. C... . 20 .. ,. 32 .. . 27 .. ,. 33 .. ,. 31 ) 07 Pitch . 61 .. . 52 .. .. 40 .. ,. 25 .< ,. 23 ... 18 A. B. C. D. E. F. Sample from final store tank. „ „ first air condenser. „ ,, last ,, ,, „ „ first water „ „ „ washer. „ „ after exhauster. These representative liquors are made up as follows:—• 100 Tons Coal, Moist. Moisture Coke ovens. Tons. ]2 Gasworks. Tons. 3 Water of formation 3 3 Added in scrubber 14 6 Total liquor 29 12 Add steam to stills 7 3 Total of effluent ... 36 15 The coke plants of this country deal with coal averaging 210 tons of coal per day for each plant, and produce rather over 60 tons of liquor daily. The great advantages of dispensing with this quantity of liquor, or even with one-half of it, will be readily apparent, and By-products Recovery. We will now direct our attention to the by-product side of gas and coke-oven plants—dealing with tar, ammonia and benzol. The tar, on the whole, is