666 THE COLLIERY GUARDIAN. September 25, 1914. Table I.—Comparison of Heating Gases. Coke-Oven Gas. Blast-Furnace Gas. Composition. Volume Per Cent. 1 Cubic Metre contains Grammes. Weight Per Cent. Calorific Value. Volume Per Cent. 1 Cubic Metre contains Grammes. Weight Per Cent. Calorific Value. H2 CH. co . . . CnHm • • • • co2 53-50 23'50 4-60 100 2'60 14-80 47'20 166 85 57 GO 12 50 50'95 185 00 9-04 31-95 1105 2-40 9-80 35'76 1,637 2,251 141 270 1 00 29-60 7'40 62 00 0-89 37020 145'70 775-50 0'007 2879 11'21 60'00 30'6 905-76 Total 100 00 520-00 100'00 4,200 lOo-oo 1,291-79 100'00 936 Table II.—Theoretical Comparison of the Waste Gas. Composition 1 Cubic Metre Coke-Oven Gas+ 25 Per Cent. Excess Air-Waste Gas at Oven Temperature. 1 Cubic Metre Furnace Gas+ 25 Per Cent. Excess Air - Waste Gas at Oven Temperature. Volume. Grammes. Volume Per Cent Weight Per Cent. Volume. Grammes. Volume Per Cent. Weight Per Cent. CO2 . . • . ^2 N? H2O CO . . . 327'00 197'40 3,860'50 1,025'00 652-70 282-20 4,825'60 820'00 6'04 3'65 71'35 18'96 9'94 4-18 73 34 12'54 370'00 38 00 1,340 90 10 00 739 50 54'20 1,676'10 8-00 21'04- 2'15 76-25 0'56 29-90 219 67 58 0-33 Total 5,409-90 6.580-50 100 00 100-00 1,758-90 2,477'90 100-00 100-00 1 Table III.—Comparison, of the Waste Gas. Composition. Coke-Oven Gas. Blast-Furnace Gas. Obtained Volume per Cent. Calculated Volume per Cent. Obtained Volume per Cent. Calculated Volume per Cent. co3 . 7'20 7 45 19-80 2110 cb' ■ ' 5 40 4 45 1-20 2 22 N, 87’40 88 10 78-00 76-68 100 00 100-00 100-00 100 00 Table IV.— Draught Measured in Millimetres Water Gauge. Draught In. Coke-Oven Gas Heating. Blast-Furnace Heating. Coke Side. Machine Side. Coke Side. ; Machine Side. Regenerator l£-2 2-21 31 4 Exit pipe 10-12 12-14 10-12 12-14 . Chimney 5 52 Table V.—Temperature in the Heating Flues. Oven No. Blast-F urnace Gas Heating. Coke-Oven Gas Heating. 51 1200 1170 52 1285 1180 53 1250 1220 54 1230 1220 55 1250 1230 56 1225 1180 57 1240 1250 58 1250 1230 59 J240 1180 60 1300 1210 61 1250 1200 62 1220 1175 63 1275 1220 64 1260 1210 Average 1253 1200 Table VI.—Tabulated Comparison of the Values of Co/ce-Oven and Blast-Furnace Gas. Coke-Oven Gas. Blast-Furnace Gas. Gross calorific value of the gas Calorific value of 1 cubic metre gas and air mixture Calorific value with 25 per cent, excess air Specific heat of the waste gas . Air taken up by one volume of gas . Air taken up with 25 per cent, excess air Volume of waste gas for 1 cubic metre gas Heating gas per 1000 calories required . Yield of waste gas per 1000 calories 4,200 calories. 880 740 1-75 376 volumes. 470 5-4 0’238 cub. met. 1’28 volumes. 936 calories. 541 .. 490 ,, 0-58 ,, 0’73 volumes. 0-91 176 ,, 1 067 cub. met. 1’88 volumes. Various opinions have been expressed with regard to the effect of the coke oven gas on the steel, but at Friedrich Wilhelmshutte no deleterious effect has been noticed. The life of the furnace, too, has been found to be increased by about one-third with coke oven gas, as compared with producer gas, and the following is Dr. Biermann’s recommendation of blastfurnace gas for heating coke ovens :— “ In addition to the great economical advantage accompanying the use of blastfurnace gas, it is also to be preferred from the practical point of view. Stoppage of the gas mains through naphthalene or tar is avoided. On account of the flameless combustion, choking of the jets, such as occurs easily with coal gas, is impossible, and therefore the troublesome regular cleaning of these is not necessary. The formation of hot local flames, and thereby the disintegration of the firebrick material, is avoided, and depositions of dust in the chambers and heating flues has not occurred.” Detailed information concerning what goes on inside the coke oven during carbonisation of the charge of coal is naturally difficult to obtain. The writer has pleasure in reproducing two temperature charts embodying results obtained on a Koppers’ coke oven plant. Pyro- meters were inserted at different points in the charge of coal, numbered 1, 2, and 3 respectively (figs. 5 and 6). Temperature measurements were taken every hour throughout the whole of the time of carbonisation, and the curves reproduced indicate the temperatures obtain- ing at different points during the period. The marked effect on the temperature of an increase of 3 per cent, in the moisture content of the coal will be noted. THE ROBEY PATENT UNIFLOW ENGINE. A type of engine that has recently come to the front is the “ unidirectional ” or “ uniflow ” engine, in which, as the name denotes, the steam is compelled to flow always in one direction. In ordinary steam engines the flow of the steam is continually changing, i.e., the steam enters at the end of the cylinder, drives the piston forward, and then during the return stroke leaves the cylinder again at the same end through which it entered. A necessity of such engines is that the inlet and outlet ports should be very 790 3B81 f II S ill Patent Robey (Tniflow Engine, Fitted with Rope Flywheel, Driving Mine Fan. close together, and with the exhaust steam returning to the same cylinder end as that by which it entered the cylinder, the clearance spaces are very much reduced in temperature. These cold surfaces extract a large amount of heat from the live steam entering at each stroke, which, of course, results in considerable con- densation in the cylinder. In a patent “ uniflow ” engine, equipped with drop valve expansion gear, which has just been put on the market by Messrs. Robey and Company Limited, of Lincoln, the inlet of the steam is at one end of the cylinder by means of a drop admission valve, the exhaust is in the centre of the cylinder, the ports being uncovered by the piston at the proper moment. Owing to this, the outgoing exhaust steam has not to pass any- where near the hot inlet surfaces; thus there is no drop in temperature when the hot steam is again admitted to the cylinder. In this way a very small cut-off can be used, thus expanding the steam in one cylinder instead of a number. The area of loss is very much less than in the case of an engine with quadruple cylinders. To this also must be added the very great saving in effi- ciency owing to the use of one cylinder only and engine details, against four in the case of a quadruple expan- sion engine, and two in the case of a simple compound. A feature of these engines is the positive valve gear. The seat in which the valve works is an entirely separate casting from the cylinder, and is held in position in the cylinder by the bonnet cover, which is also an entirely separate casting. These seats and the recess in which they fit are all accurately tooled to gauges, and the seats provided with a soft copper ring let in so that no jointing material is required, and they can be removed and replaced at any time with the greatest ease. The spindle actuating the valve is carried through to the upper part of the bonnet cylinder, where a spring is provided so that the valve is quickly closed. The valve spindle is grooved to form a labyrinth packing, which causes practically no friction, the spindle being a ground fit in the sleeve. The gear works on fixed points, there being no sliding shaft, and therefore any wear which may take place is most easily and readily adjusted. The valve lifting levers are always in contact, thus ensuring quiet working, and the length of time the valve is open is regulated by a cam on the strap of an eccentric, which is mounted on the valve shaft. This cam is under the control of the governor, the duty of -which is entirely restricted to placing the cam in the position that the load demands. The governor fitted is of the static type, which auto- matically varies the cut-off to suit the work being done, and controls the gear so that a constant speed is main- tained with varying loads. This type of engine can be supplied either to work con- densing or non-condensing, and it is especially suitable for working with steam of the highest pressures and superheat. The condenser supplied is of the jet type. Messrs. Robey also make a combination of engine with boiler and superheater, which forms a complete and compact unit, where space is restricted, and where economy in fuel is an important consideration. Some of the chief advantages claimed for the “ uniflow ” engines are :—High efficiency and economy in steam consumption; simplicity of construction with consequent low upkeep costs; high vacuum in cylinder due to large exhaust area; accessibility of piston for examination; all working parts totally enclosed and provided with forced lubrication; suitability for high steam pressures and all temperatures of superheat; less floor space than cross compound or tandem engine; small head room required. The accompanying photograph shows a “ uniflow ” engine driving a mine fan at one of the pits of the Ashington Coal Company Limited. Hull Coal Exports.—The official return of the exports of coal from Hull for the week ending Tuesday, September 15, 1914, is as follows :—Amsterdam, 500 tons; Bombay, 810; Dunkirk, 2,170; Gefle, 5,251, Harnas, 1,803: Hahnstadt, 1,508; Harlingen, 895; Kallundborg, 1,840; Kalvala, 872; Kalmar, 1,196; Landscrona, 1.017; Lulea, 6,273; Malmo, 1,154; Oporto, 1,447; Rotterdam, 1,257; Ronne, 1.240; Savona, 4.600; Palermo, 496—total, 34,329 tons. Corre- sponding period September 1913—total, 92,738 tons.