THE COLLIERY GUARDIAN. 1253 June 5, 1914. _____________________________________________________________________________________________________________________________ _________________________________________________________________________ Development of the Internai=Combustion Engine for Power Generation at Collieries. By JOHN DAVIDSON. From a paper read before the Institution of Mining Engineers, London, June 1914. Until recent years economy in fuel at collieries does not appear to have been considered of any importance. This no doubt was quite a natural state of affairs, as the cost of coal at the pit mouth was extremely low, and an inferior quality of fuel was often used for steam raising- purposes. Even at the present day economy in fuel does not seem to receive at many pits the consideration that it deserves, and wasteful engines for pumping, ventilating, haulage, etc., are used, the consequence being that millions of heat units are blown away into the atmosphere every hour in the form of exhaust steam. It must also have been noticed by engineers, particu- larly those who are not familiar with colliery wbrk, that condensation losses due to exposed steam ranges alone have been entirely neglected. Wherever one goes, ranges of pipes, bare and exposed to the weather, may be found. The over-all efficiency of some of these plants •—particularly where small wasteful engines are used— must be extremely low. In more modern installations greater care has been, exercised, and the losses just mentioned have been minimised to a great extent. In many recent cases where economy in fuel has received serious consideration exhaust steam turbines have been installed to make efficient use of the exhaust steam from the already existing steam engines, etc., and thus provide an econo- mical means of developing electrical power for distribu- tion throughout the colliery. Economical as this system may appear at first sight, it can only be looked upon as a kind of makeshift, with the view of improving the economy of an already exceed- ingly wasteful system: and, without going into detail at the moment, the fact that the most economical prime mover of the present day is the internal combustion engine must not be lost sight of. Whenever a steam .plant is now installed for power generating purposes at a colliery, the same can only be looked upon as a tem- porary arrangement if the colliery in the future has to compete with pits equipped with modern power plant. In the early days steam engines were practically the only prime movers possible, but since the advent of electrical transmission the author thinks that it is gener- ally recognised that the most efficient and best scheme to adopt is to put down one large generating station, and to operate the various auxiliaries electrically. In the end this minimises the amount of attention required, and gives a flexibility which is impossible under any other system in vogue at the present day. The writer includes several tables to show the running costs for :—■ (а) A steam turbine plant with coal-fired boilers. (б) A steam generating plant as above, but with the boilers fired by recovery producer-gas. (c) A plant driven by a gas engine with recovery producer. (d) Coke oven gas burnt under steam boilers with a 2,000-brake horse power turbine plant. (c) Coke oven gas used in a gas engine. Table I. Steam Turbine Plant with Coal-fired Boilers. Capital Costs (Buildings not included}. £ 2,000 brake-horse-power of steam turbines 8,000 2,000 brake-horse-power of steam boilers ... 3,500 Total capital cost.............. 11,500 Running Costs (7,200 hours per annum}. £ 10,700 tons of coal at 12s. per ton ........ 6,420 Oil and stores ........................... 700 Labour .................................. 1,040 Maintenance at 2 per cent................. 230 Interest and depreciation at 10 per cent. ... 1,150 Total running cost per annum ... 9,540 Cost per brake-horse-power = 0T59d. Equivalent cost per unit generated = 0’238d. Table II. Steam Generating Plant with Boilers Fired by Recovery Producer-Gas. Capital Costs {Buildings not included}. £ Recovery gas plant and boilers___-.....___ 23,250 2,000 brake-horse-power of steam turbines... -8,000 ______ Total capital cost______________ 31,250 Running Costs (7,200 hours per annum}. £ 20,600 tons of coal at 12s. per ton ........ 12,360 Sulphuric acid for sulphate plant ........ 1,200 Oil and stores ........................... 875 Bags and packing sulphate .............. 270 Labour ................................. 1,950 Maintenance at 2 per cent................. 615 Interest and depreciation at 10 per cent. ... 3,125 Total running cost per annum ... 20,395 Credit £ Sulphate ........................ 10,000 Tar ............................. 600 ______ ------ 10,600 ______ Net running cost per annum.... 9,795 Cost per brake-horse-power = 0T63d. Equivalent cost per unit generated = 0’244d. Table III. Plant Driven by a Gas Engine with Recovery- Producer. Capital Costs (Buildings not included}. £ Gas engine generator complete .......... 11,880 Recovery gas plant..................... 8,100 ______ Total capital cost................ 19,980 Running Costs (7,200 hours per annum}. £ 8,840 tons of coal at 12s. per ton .......... 5,304 Sulphuric acid for sulphate plant ........ 522 Oil and stores ........................... 645 Bags and packing sulphate .............. 116 Labour ................................. 1,276 Maintenance at 2 per cent................ 398 Interest and depreciation at 10 per cent. ... 1,998 Total running costs per annum... 10,259 Credit. £ Sulphate ....................... 4,350 Tar ............................ 261 ______ 4,611 _______ Net running cost per annum.... 5,648 Cost per brake-horse-power hour = 0*094d. Equivalent cost per unit generated = 0’141d. Table IV. Coke Oven Gas Burnt under Steam Boilers with a 2,000-Brake Horse Power Turbine Plant. Capital Costs (Buildings n