486 THE COLLIERY GUARDIAN. March 8, 1918. ventilation, and man way. The haulage shaft has reached 2,240 ft., of 6ft. by 10ft. cross section; the drainage and ventilation are taken care of by one inclined shaft, reaching 2,352 ft., of 6 ft. by 10 ft. cross section ; and the manway, reaching 3,042 ft. from the surface, is 6 ft. by 8 ft. in cross section. There are nine levels in this No. 1 pit, 268 ft. apart. Coal is stored at the sixth and ninth levels, where it is loaded on cars, hauled by an endless rope driven by a cross- compound endless-rope engine having a steam pressure of 701b., with 14 in. cylinder, 150 horse-power, speed 120 revolutions per minute. The No. 2 pit was started in October 1907, about 200 ft. below the Chou-tuan seam, along the second seam, which, with the first seam, constitutes about 12 ft. of coal. It was shut down for a year or so, but resumed working in March 1909. It has two main inclined shafts, namely—haulage, which is 7| ft. by 12 ft. cross section and 2,336 ft. long at present; and manway, 6| ft. by 8 ft. cross section and 2,964 ft. long. Beside this, No. 2 pit has two upcasts for pumping water, and one shaft for sand flushing. The two upcasts of 8J ft. by 11 ft. cross section, are 140 ft. and 306 ft. long, and the flushing shaft is 36 ft. deep. There are six levels in this pit, and the coal is accumu- lated from No. 2 to No. 6 level. The haulage system is the same as in No. 1 pit, except that it is electric driven, 150 horse-power, 150 revolutions per minute, by a 60-cycle, 2,100-volt, 720 horse-power motor. In the No. 3 pit there are eight levels. All coal is dumped from the third to the eighth level. The three inclined shafts, the haulage, drainage and ventilation, and manway, have 3,000 ft., 3,180 ft., and 2,130 ft. respectively. This pit was driven in October 1909, to facilitate transportation when the No. 1 pit’s produc- tion declined on account of the long distance. It is in the Pao-cha seam, which is the uppermost seam, and has a thickness of 7 ft. Later it joins the No. 1 pit with a winze at about 580 ft. from the surface. In per cent. The analyses in Table 4, direct from the mine, show two extreme cases. Table 4.—Analysis of Crude and Washed Coal. No. Water. Ash. Sulphur. Cal. 1 ... 0*10 ... 17*72 ... 70*88 ... 11*30 ... 0*709 ... 8,442* 6 ... 0-10 ... 21*02 ... 47*74 ... 31*04 ... 0*996 ... 6,612* 1 ... 0 49 ... 14*94 ... 79*50 ... 8*56 ... 1*16 ... 8,200f 6 ... 0*42 ... 16*68 ... 76*00 ... 7*32 ... 1*63 ... 7,670f * Before washing. f After washing. However, most of the coals are of No 1 type, as shown in analyses Nos. 1, 2, 3, and 4, given in Table 3. The coal from the mine is dumped through tipples to a moving screen which separates the size above and under 50 mm.; the oversize passes to a travelling metal belt, which distributes the coal to a shaking table perpendicular to it. Men standing at both sides of the table sort out the rock, and the clean coal goes to the bin, to be loaded on the outgoing train. This oversize constitutes about 19 per cent, of the total coal, of which 14 per cent, represents the coal proper, the rest rock and sulphur balls. About -J per cent, of this oversize coal, which is crushed to fine dust on the table, is sent to the fine coal bin without any further wash- ing. The sizes up to 50 mm. are elevated by means of bucket elevators to the top floor of the washery, and from there they pass through a series of shaking screens which separates four sizes: egg, walnut, pea, and fine dust. These sizes are then passed through sets of jigs; the egg, walnut, and pea sizes are sent to a 6 mm. screen jig, while the fine dust is further divided into two grades, 10 to 6 mm., 6 to 0 mm., with 12 mm. and 8 mm. screen jigs respectively. Twelve jigs are used, distributed as follows: Two jigs for egg and nut, two jigs for pea size, two jigs for 10 to 6 mm. size, four jigs for 6 to 0 mm. size, and two jigs for re-washing purposes. Feldspar is used fol* the secondary screen. The sizes are: 30mm. size for 6 to 10mm. coal.; 30 to 25mm. size for 6 to 0 mm. coal. be built. It requires about 30 men for a 12 hours shift to build one oven. The coking is all done by contract. A general idea of the number of labourers required for each process is as follows:—Loading coal to oven, 10; getting stones, 5; covering and unloading coke, 20; water quenching, 1—total, 36 men; production, 70 tons. The average working cost per ton of coke is 54c. (silver) or 27c. (gold). In 1916 the average working cost was 45c. (silver). The gases are, of course, not utilised, but this is the most economical way to make coke under the existing circumstances. A modern by-product plant of 60 ovens will probably be erected this year. The coke is of good quality, greyish-white, not so silvery-white as some cokes, and hard and strong. Its only disadvantage is its high ash content, which is the more objectionable because it contains so much alumina. The net cost of coke per ton at present, including the cost of coal mining, washing, and overhead, is 7-80 dols. (silver) or 3*90 dols. (gold) per ton. cross section, the haulage and manway shafts are 6 ft. by 10 ft. and 6 ft. by 8 ft. respectively. All inclined shafts are wooden timbered. The upcasts in the No. 2 pit were begun in May 1913, with red bricks, with the aim to pump out all the water from the mine, and provide ventilation. It was designed to put in two electric fans of 11 ft. diameter, with a capacity of 160,000 cu. ft. of air per minute, 6 in. gauge pressure from 150 horse-power motor. It connects No. 2 and No. 4 pits. Some exploring work has been done at Pao-cha- wa-tse by means of a Harked and Allcocks steam- driven diamond core drill, including one steel angle derrick and one steel “ Hopwood ” boiler (water tube type); total cost, 16,480 yen (8240 dols. gold); with a total weight of about 15 tons; capacity, 1,800ft. depth with 2 in. core. It is expected that the Pao-cha seam will be found at about 1,100 to 1,200 ft. The boring speed varies according to the nature and hard- ness of the rocks. One speed is from 4 ft. to 10 ft. per 12 hours. The new work at S-yen-kou will be started as soon as transportation facilities are completed. Mining Method.—The method of mining employed is both longwall and bord-and-pillar systems. At present the latter is more generally used, but in the case of the first and second seams, which are close together and both thick, the longwall system has proved a failure. The use of the bord-and-pillar system, with sand fill- ing flushed in as a support, was begun in 1916. The first recovery by this system is only 18 per cent., but the second working yields over 40 per cent. The cross galleries are driven in the direction of the end (to the dip) and the working galleries along the face, at right angles to the dip. Whenever there is a change in the dip, the working gallery makes a corresponding depar- ture from its straight course. For flushing, sand, broken stone, or blast furnace slag is conveyed through tubes with water under sufficient pressure to fill up the robbed space from the third or fourth seam upward. Two crushers of 18 horse-power and 50 horse-power motor, and a 3 horse-power pump are located at the surface. Pines or winter evergreen of 6 in. to 8 in. diameter and 6 ft. to 7 ft. long are extensively used for timbering purposes. They are bought at 2|c. to 3Jc. (silver) per ft. Arthur Koppel roller-bearing coal cars of 25 cu. ft. capacity are used, each car holding about half a ton of coal. A good deal of water is standing in the mine. The present drainage is about 200 cu. ft. per minute. Twenty-six pumps of various capacities are used in the coal mining. All mining is done by hand, no dynamite being used except for cross- cuts. Gas is present, so safety lamps have to be used. Mining is done by contract according to the produc- tion. The shift is 12 hours, from 4 a.m. to 4 p.m. There are about 1,500 miners in the coal mine alone. The coal cars from the mine are sent directly to the washing plant by endless rope haulage. The output of the mine has increased from 126,086 tons (2,2401b.) in 1911 to 373,927 tons in 1916, and the daily output for 1917 was about 1,200 tons. The total cost of mining the coal amounts to 3*762 dols. (silver) per ton, made up as follows : Office expenses, 0*406 dol. ; cost of levels, driving cross-cuts, etc., 0-628 dol.; boring, 0*012 dol. ; mining, 1-284 dols. ; washing, 0-178 dol. ; machinery, 0-600 dol. ; depreciation, 0*048 dol.; taxes, 0*207 dol.; general expenses, 0-398 dol. Table 5.—Jigs. Screen. Size. Mm. Screen. Feldspars Head R.p.m. No. jigs. Mm. Mm. Mm. Egg . 30-50 ... 6 . .. — ... 200 . .. 56 .. 2 Nut 18-30 ... 6 . — — — — Pea 10-18 ... 6 . 160 .’ ..' 56 2 Fine 10-6 ... 12 . 30 ... 20 . .. 146 ... 2 Dust 16-0 ... 8 . .. 25-30 ... 16 . .. 146 ... . 4 Re washing.. — ... 8 . .. 25-30 ... 16 . .. 146 ... . 2 The washing plant is worked only in the day time. It can handle 85 tons per hour. There are 20 men in each shift, and the washing cost, not including the repairing of machinery, amounts to about 5c. (silver) or 2^c. (gold) per ton. The picking cost is 20c. (gold) per ton. The sizes above pea are sold, while only the fine coal is used for coking purposes. About 21 per cent, of the coal from the jigs is ash, with about 5 per cent, in the oversize (above 50 mm.) forming a total of about 26 per cent. Most of the ash is in the dust coal, which is reserved for selling and for coke of poor, grade. There is no crushing of the coal in the process, though recently the walnut size is crushed for experi- mental purposes, and gives a much better coke. The coal washing plant is a complete concrete building which cost 270,000 dols. (silver). * It has two sets of motors: — For washing coal... For pumping water H.p. Volt. Cycle. R.p.m. 182 .. . 2,100 ... 60 .. . 1,700 18 .. . 2,100 ... 60 .. . 1.750 120 . 2,100 ... 60 .. 720 7*5 .. . 2,100 ... 60 .. 720 All water used is from the mine, and is first pumped to a reservoir. Coking Plant. Pen-hsi-hu coal is of good coking quality. The washed coal from the washer has the analysis shown in Table 6. Table 6.—Analysis of Washed Coal. xtzx tt n Volatile Fixed JN°. li2O. carbon< cai'bon. Ash. Sulphur. Cal. 1 ... 0*10 ... 17*72 ... 70*88 ... 11*20 ... 0*707 .. . 8,442 2 ... 0’10 ... 21*56 ... 67*04 11*80 ... 1*333 .. . 9,012 3 ... 0*20 ... 18*16 ... 72*92 ... 8*72 ... 2*093 .. . 9,042 Owing to lack of capital, coking is still carried on in the native method. The coking heaps consist of two frustums having the two large ends joined at the ground surface. . The diameter of the large end is from 24 ft. to 30 ft., and the small end 16 ft. to 20 ft., varying from 70 to 85 tons capacity, and can produce 45 to 54 tons of coke; the yield averages about 60 to 65 per cent. This indicates that about 15 per cent, of the coal, beside the volatile carbon, is consumed in coking. The coke runs from 16 to 25 per cent, ash, the coke ash having the composition shown in Table 7. Table 7.—Analysis of Coke Ash. SiO2. A12O3. CaO. MgO. Alkali. Fe2O3. Lump coke... 50*50 ... 39*30 ... 2*20 ... 0*80 ... 2*9 ... 4*30 Coke dust ... 53*75 ... 35*46 ... 2*05 ... 0*98 ... 2*65 ... 5*14 Table 3.—Analysis of Coal at Pen-hsi-hu. Name of JNo- coal. a cd £ c8 fl ce fl ; 02. a 1 2 3 4 5 6 Per c. 8 Per c. Per c. Pao-cha ... 0*10...17*72...70’88 Siang-tuan Chou-cha... I-cbieh.... Erh-Chieh. San-Chieh . Ssu-Chieh.. Wu-Chieh. Per c. Per c. Ft. in. 11’30. ..0*707. ..8,442. ..6 0’10...15*96 . 71*74..12*20. .1*375...8,742...4 0*00 21*56...67-04 ..11*30...1*333...9,042...3 0’20...18’16...72*92... 8*72...2-093...9,042 . 5 0*10...17*00...51*40...31*50...1*399...7,842 ..8 0*10..21*02...47*74...31*04...0*996..,6.642,..3 0*10...20*74...60*52...18*64...1*758...8,442...3 0 10...18*60...52*71...28*59...0 905 ..7,242...4 7 2 7 5 8 0 8 0 Coal Washing Plant. The coal from the mines contains a good deal of shale and pyrites. It amounts to about a total of 26 Construction of Pit.—The pit is cleaned first, and the draught passage cleared of water. Fine coal is then laid around a chimney of about 10 in. diameter, which is built up by means of lump coal to about the surface level. Then the coal is levelled; 16 or 18 hori- zontal draught channels radiating from the central chimney are laid with stones of 9 in. by 6 in. cross section. Some burning wood is put into the chimney, and the lid closed at the top; then more coal is dumped on top, making an inverted cone over the bottom one. This is left until fire is seen to be coming out; the pit is then covered with stones and ashes to prevent its burning away. When a blue flame is seen, the pit is finally fully covered up with ash. Coke when ready is quenched with water poured over the oven. It takes about two to three days for building up such an oven, 10 to 104 days for coking, depending upon the •weather, one day cooling with water, and one more day for unloading the coke—total, about 14 to 16 days. Each oven can produce 96 to 105 tons of coke every month. At present there are over 80 ovens, which product about 250 tons per day. When the second blast furnace is built, over 100 more ovens will have to COALING PLANT AT A SOUTH AFRICAN CEMENT WORKS * In the course of a description of the works of White's South African Cement Company Limited, Mr. H. Campbell gives the following particulars of the coal plant employed : — The coal, as fed to the kiln for burning, is in a fine state of division, and is so prepared that 97 per cent, passes through a 100-mesh screen. To obtain coal in this state it is necessary first to dry the material; the drying agent is the waste heat from the kiln, which is allowed to circulate round a revolving drying drum, which is enclosed within a chamber built of brick work. Duff coal is used, and as received is delivered to the elevator, which discharges into the hopper, which in turn feeds the dryer, and the amount added is con- trolled by the table feed. From the dryer the coal is elevated to the hopper placed over a kominor, which is similar to those in the wet mill, but is one size smaller. The kominor here varies from that in the wet mill, in that the screening plant is attached to the mill, and is not separate, as in the case of the wet plant. This screening plant consists of four sets of double sieves made from perforated plates having mm. slots, but the principle is identical with that of wet kominors, namely—there is only one outlet and one inlet, and the material that fails to pass through the screens must travel the full length of the mill, and be subjected to re-grinding before it can reach the screens again. Crushed coal passing from the kominor is fed direct to the tube mill, where it is finally reduced to the fineness required. The tube mill is the same size as those in the wet mill, and carries the same load of pebbles. The coal from the tube mill passes to the circulating plant and the storage silos. Coal, as is well known, is subject to ignition if stored for any length of time, and, further, coal dust, when mixed with air in correct proportions, is liable to cause explosions. These peculiarities are overcome at the works by means of keeping the coal always in motion, and providing all points where leakage is likely to occur with connections to the feed fans for the kiln; this ensures the dust being collected and blown into the kiln, where use is made of it. Two coal silos are provided which are capable of holding 150 tons of ground coa]. The*bottoms of these are sloped to form an inlet to the screw conveyor, and the coal can be drawn at will from any silo into the common conveyor, which carries it from the silos or from the tube mill to the elevator which carries the coal to the top floor of the building. The conveyor then takes the coal to No. 2 kiln hopper, and from that to No. 1 kiln hopper, and again back to the silos. The whole of this circulating plant is designed to carry twice the total consumption of the plant, so that the feed hoppers to the kilns are kept full and surplus coal is always on the move. The coal is extracted from the feed hoppers by means of two screws, which can be worked separately, and the speed of these is regulated by friction discs. The coal is carried to the end of the screws, and falls down into a pipe placed 6 in. lower, w'here it meets a blast of air thrown forward by the fan, which carries the coal direct through the feed pipe into the kiln, where combustion takes place at once, and gives the temper- ature necessary for the production of clinker. It should be noted that in this building all the elevators handling coal have their casings made of reinforced concrete. Coal, when heated up, as happens in the case of drying, contains all the constituents for vigorous rusting of iron work, and it is found by experience that the life of iron or steel casing under these circumstances is very short, while concrete is not affected in the slightest degree, but forms an efficient casing in the circumstances. * Journal of the South African Institution of Engineers. A New Motor Fuel.—The Auto (Paris) announces the discovery of a new motor fuel, of which a trial has been made with most favourable results, a motor-car carrying six persons climbing the steepest hills in Paris without the least mishap. The Auto explains that this new fuel is pro- duced by the distillation of heavy oils obtained from coal. All the by-products will be available for the preparation of explosives. The new fuel, the newspaper adds, does not foul the cylinders, nor does it leave a residue of carbon. Coal for Italy.—In the Italian Senate on Tuesday, Signor Crespi, Commissioner of Supplies, said his proposal as to the supply of coal was being carried into effect. It placed at the disposal of Italy 240,000 tons of French coal and 560,000 tons of English coal per month. Negotiations were proceeding to make up the full minimum amount required by Italy, namely—690,000 tons of coal per month. A fresh conference on sea transport would meet in London within a few days. The life of the Italian nation and the conduct of the war would depend on the assignments made to Italy.