198 THE COLLIERY GUARDIAN. ______________________________________ July 24, 1914. Colliery Consumption and Machine Economy at an Upper Silesian Colliery. By Dr. KARL SCHULTZE.* From a paper read before the Midland Institute of Mining, Civil, and Mechanical Engineers. In the year 1910, Dr. Ilgner offered to the Royal Technical School, Breslau, a prize for an investigation into the cost of power at Silesian collieries, with the view of establishing the factors by which the most economical production of power could be ascertained. The investigation was to be conducted at such Silesian collieries as either wholly or for the most part were driven with steam, so as to asecertain what surplus energy and conservation of energy from exhaust steam could be obtained from the coal consumed and the water evaporated. After careful inspection of many collieries, the Ferdinand Mine of the Kattowitz Company was at last selected, the winding engines in this case being driven by steam, while a newly equipped central elec- tric station provided power for most of the other work. The Ferdinand Colliery was originally opened in 1823, but has lately been entirely remodelled. The output of the mine is about 1,000,000 tons yearly, the power used consisting of steam, electricity, and compressed air. The winding engines, central electrical station, air compressing plant, and some other small machines are driven by steam. Compressed air serves for driving hammer drills, oscillating conveyors, some small under- ground ventilators, crabs, and pumps, and also for ventilation by means of air jets. The remainder of the mechanical appliances at the mines are driven electric- ally. There are two adjoining ranges of boilers, one of which furnishes saturated steam at a pressure of 1051b., and the other superheated steam at a pressure of 150 lb. per sq. in., which were both being hand fired at the time of the experiments. The latter plant has since been fitted with mechanical stokers, having revolving furnace grates. The firing coal consisted in part of slack and partly of screen pickings. The feed water was con- densed water from the central condensation plant, and the cooling water from the two turbo-generators and the air compressor. The cooling water was obtained from a brook 1,200 yds. distant and from cooling towers, and was then used in the turbo-generators and the air com- pressors. There were no economisers. There were 18 Lancashire boilers, each with 861 sq. ft. of heating surface and 28 sq. ft. of grate area. The winding engine at the Mauve shaft is an old engine which has been remodelled. It is of 300-horse power, with two cylinders 33| in. in diameter by 5 ft. 2 in. stroke, fitted with a Koepe .pulley, and winding from a depth of 900 ft. a useful load of 1 ton 4J cwt. The winding engine at the Benjamin shaft is of 600- horse power, with two cylinders 44 in. in diameter by 6| ft. stroke, Kraft valve gear, and parallel drum, draw- ing from a depth of 938 ft. a load of 4 tons 18 cwt. The winding engine at the Gruschka shaft is a com- pound two-cylinder engine of 1,000-horse power, the diameter of the high-pressure cylinder being 50 in., and that of the low-pressure cylinder 68 in., with a stroke of 8 ft. The drum is 29| ft. in diameter. The engine draws from a depth of 1,290 ft. a useful load of 4 tons 18 cwt. All three winding engines are connected with the central condensation plant, but during the time when the experiments were being made they were exhausting into the atmosphere. The other boiler plant, which supplies superheated steam to the turbines and engines in the central power station and to the air compressors, consists of 16 twin boilers, each with 947 sq. ft. of heating surface and 46 sq. ft. of grate area. In 1910, superheater tubes were added to raise the temperature of the steam to 632 degs. Fahr. (266-22 degs. of superheat). The central electricity station has a capacity of 4,170 kw. from six generators. It includes two vertical engines, one of 400 and the other of 600-horse power; two horizontal engines of 1,000-horse power; two AEG Curtis turbines, each of 1,500-horse power. An air compressor of 485-horse power in a separate building has a capacity of 176,600 cu. ft. of free air per hour, and compresses it to six atmospheres (90 lb. per sq. in.). The central condensation plant, built by Bal eke in 1906, is coupled to the turbines and engines generating electricity, as also to the air compressor. An oil separator is placed between the engines and the con- denser. Each condenser has an independent air pump and cold water circulating pump electrically driven. Quite a substantial part of the exhaust steam is required in winter for heating the baths, offices, work- shops, and ventilating shafts. The pumping is done electrically. On three levels the old steam pumps remain in reserve. In the screens the steam engines are also kept, in case of a breakdown of the electric motors. The generators produce three-phase current at 550 volts, 50 periods. There are 113 motors, and 33 trans- formers in connection with the station. Besides these, about 23 per cent, of the current goes to the blast fur- naces of the Kattowitz Company. All the water is pumped from the 984 ft. and 1,640 ft. levels. The pumping plant at the 984 ft. level con- sists of three 460-horse power differential Bergmann pumps, each capable of raising 1,210 galls, of water per minute. At the 1,640 ft. level there are two pairs of * Translated by Mr. G. Blake Walker and Mr. Arthur Franks, and revised by author. The paper, which appeared originally in Gliickauf (1913, vols. xliii., xliv., and xlv., pp. 757 et seq.), has been reproduced in an abbreviated form by permission of that journal. differential Bergmann pumps of 90 and 190-horse power capacity, which deliver 330 galls, and 660 galls, per minute respectively into the sump of the 984 ft. level. During the experimental year a new 875-horse power double differential pump of the same type came into operation, raising 1,320 galls, per minute direct to the surface. The pump is driven by a motor working on 2,000 volts, and supplied direct from the central station; the other pumps take their current, from a substation at the 984 ft. level. The ventilation is produced by two suction Capell fans at the Ludwig and Richard shafts. The depression at the Ludwig shaft is 1-1 in. of water gauge, and pro- duces 141,200 cu. ft. of air per minute. Its 50-horse power fan motor takes its current at 2,000 volts, whereas the 60-horse power motor at the Richard shaft runs on 500 volts. The latter fan produces a depression of 2-65 in. of water gauge at 88,250 cu. ft. of air per minute. There are also jets of compressed air connected with the compressed air ranges of pipes. These are used in drifts and similar places. The coal from the 1,640 ft. level is temporarily raised by means of a 36-horse power electric hoist in the Mauve shaft to the 1,312 ft. level. A 150-horse power electric hoist at the Richard shaft is mainly used for timber, etc. Oscillating conveyors driven by com- pressed air are used at the working places. The haulage is done by 15 electric locomotives, which bring the coal to the shafts, with the aid of a few small haulage engines. Steam Production. In order to ascertain the actual composition and heat- ing value of the coal, two shovelfuls were taken as samples from the coal tipped into the fire holes, and from the accumulation thus obtained samples were sent for testing to the Technical High School at Breslau. The average of the samples tested yielded the following results :— Shaly coal, Dust coal. Maximum heating value 11,394 B.Th.IT.... 10,908 B.Th.U. Moisture .................. 4’3 per cent. ... 5'5 per cent. Ash....................12’9 „ ...16’0 „ An analysis taken in August gave the following results . Shaly coal. Dust coal. Per cent. Per cent. Carbon ______________ 64T ... 62'7 Hydrogen ______________ 3’96 ... 3'39 Sulphur ______________ 1’14 ... 1T0 m Battery of Twin Boilers.—The results show that the monthly average output of the boilers fluctuated between 4-65 lb. of water evaporated per sq. ft. of heating surface per hour in July, and 6-55 lb. of water per sq. ft. in January. The average steam generated on week-days in January, taking into account six Sundays and holidays (on which only some 500 tons against 800 tons on ordinary week-days were evaporated), works out at 7-07 lb. of water per sq. ft. The greatest average output was 8-12 lb. of water per sq. ft. The steam production shown for January is exceed- ingly high. That the boiler plant was not strictly pro- portional to the output of steam is shown very clearly by the great fluctuations in pressure. The pressure gauge curves show that the steam pressure frequently fell from 150 to 105 lb. per sq. in., and even sometimes to 75 lb. As the electric plant required to be enlarged, and the existing condensation plant was also insuffi- cient, the management were in favour of the erection of an exhaust steam turbine, in order to relieve the battery of twin boilers, and increase the work of the Lancashire boilers where there was some margin. The reason for the unequal call upon the two boiler plants was that, in the beginning, the Lancashire boilers had to supply the entire but relatively small steam consump- tion of the colliery. The plant for electric power was erected later, in 1898, and provided with its own special boiler plant. Now, as the steam pumping plants, etc., underground were replaced by corresponding electrically driven plants, the strain on the Lancashire boilers was transferred to the battery of twin boilers. Another reason for the unsatisfactory result was the muddy feed water, which caused a formation of sediment in the boiler, and consequently loss in the transmission of heat, the boiler plates showing at frequent intervals large bulges, which had to be extensively repaired at great cost; in fact, on one occasion, a boiler plate was penetrated by chipping with a pointed hammer, the thickness of the plate being in this place little more than 0-04 in. The boiler plants were worked 74 and 61 per cent, of the possible time respectively. The amount of reserve capacity was therefore 26 and 39 per cent. In general, it may be sufficient to reserve a quarter of a group of boilers for emergencies and repairs; but, con- sidering the severe working of the twin boilers, involving continual most expensive repairs, 26 per cent, is very low. Lancashire Boilers.—The conditions of the Lancashire boiler plant were much better. The ascertained effi- ciency, equal to 0-586, is satisfactory, and corresponds with recognised practice under the same working condi- tions. The output of the boilers varied between 2-65 lb. of water per sq. ft. of heating surface in the warm, and 3-80 lb. of water per sq. ft. in the cold months. The influence of the weather conditions was important, because the heating of the buildings, workshops, and offices absorbed large quantities of steam. With a low output the number of stokers could be reduced, the repairs were less, and, above all, the pressure of steam was better maintained. The performance of the boiler plant in comparison with the heating surface was rather poor. The reserve of 39 per cent, is unnecessarily high, and more work might have been got out of these boilers. Useful Work. A good idea of the efficiency of a plant is obtained if the effective work of all engines be compared with the quantity of fuel used. Heat and work are mutually convertible, and 640 calories (2,540 British thermal units) correspond to 1-horse power hour. The practical difficulty of dealing with all the details lies not only in its extent, but also in the fact that a common factor ' is inapplicable for some engines. One must, therefore, be content to ascertain the effect of the energy pro- duced in the most important units of its working. For this purpose, the daily efficiency of all steam-driven engines has been determined continuously, as regards the electric kilowatt hours produced, the output of the mine, and the wrork of the compressors. Further investigations could only be made on a few other steam users. The calculated efficiency, therefore, includes the relation between the coal, steam, mechanical work, and the useful work of the steam engines. . The proportion of the total useful work performed to the heat energy of the coal supplied to the surface of the boilers gives the total efficiency in transforming heat into useful work. This with the twin boilers varies between 3-62 and 4-48 per cent., and with the Lanca- shire boilers between 2-39 and 5-02 per cent. Such an efficiency is a very bad one, but appears even worse when it is remembered that a quarter of the useful heat was absorbed by the heating apparatus. This latter may represent under ordinary conditions an efficiency of about 50 per cent., because here the losses in heat are not so great as in transforming heat into mechanical power. Taking into account the amount of heat sup- plied to the heating apparatus, the average efficiency of the heat generated should be, in more perfect plants (with the same proportion of power), about 21 per cent., so that really only a-fifth part was secured of what may be regarded as possible in the present state of technical science. This result indicates already that in all parts of the colliery the avoidable losses appear extraordinarily large. Steam Distribution of the Battery of Twin Boilers. The battery of twin boilers supplied steam to (1) the turbines and reciprocating engines in the central elec- trical station; (2) the compressor; and (3) a part of the steam heating plant. For the investigation of the utilisation of the quantities of steam produced, it was very advantageous that it was possible to organise a continuous supervision over the largest consumers—that is, the turbines. The method of measuring and calcu- lating by which each day of the experimental period the quantities of steam consumed were fixed depended on the observation of the steam conditions before the stop valves, as already explained. The steam consumption of the turbo-generators deter- mined in the above manner, shows during the month of July a large decrease in the average consumption. This is due to a thorough overhaul of both engines, during which operation one turbine especially showed a very advanced state of deterioration and wasting of the blades. The choking of the passages was most detri- mental to the efficiency of the turbine. With decreasing boiler pressure it often happened that the speed of the turbines decreased very considerably, and it was neces- sary to stop several large motors. In addition to this, the low vacuum and the disadvantageous overload caused a high consumption of steam. The average output of the central electrical station was only 1,700 kilowatts. With regard to the wide variations in the consumption of electricity caused by the Martha Works —a rolling mill connected with the central electrical station—it was necessary to have a reciprocating engine continuously working as well as the turbines. The peak load (only for some few minutes) was 2,300 kilowatts. The ascertained consumption of the turbines having been deducted, as mentioned, from the quantities of feed water evaporated, it was only necessary to deter- mine the distribution of the remainder to the recipro- cating engines in the central electricity station, to the air compressors, and the steam heating. The results of these determinations may be seen in the following table :— Distribution of Steam from the Battery of Compound Boilers. Particulars. Tons. Percentage of the steam- production. Blow-off losses 4,550 ... 2’2 Consumption of feed-pumps... 3,170 ... 1’5 Leakages in the piping and at a seldom-used crane 3,790 ... 1’8 Consumption of the turbines for production of 9,024,200 kilowatt-hours 117,010 ... 55’5 Consumption of the reciprocat- ing engines for production of 3,453,100 kilowatt-hours ... 58,220 ... 27’6 Consumption of the compres- sor-engines for production of 1,677,200 horse power- hours, 132,375,000 cu. ft., or (3,750,000 b.b.m.) compressed air at 84 lbs. pressure and 68 degs. Fahr 13,770 .. . 6’5 Consumption of heating-steam inclusive of the losses here shown caused by leakages... 10,040 ... 4’9 Consumption of feed-water from October 1911, to August, 1912 ........... 210,550 ... 100’0