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To Use Pulverized Coal System Will Convert S.S. Mercer to Burn Powdered Coal—Tests Here and Abroad Successful—Fuel Costs Reduced—Less Fire Room Labor URNING pulverized coal in ma- B rine boilers of either the’ water tube or scotch type is already en- tirely practical. It has been success- tully done in test installations for some time. During the operation of these tests many experiments have been made naturally to determine the best and most efficient way to burn pulverized coal. It is because the directors, of such stations as the one at the League Island navy yard, Philadelphia, and the experimental installations of pri- vate companies, are determined to de- velop the greatest efficiency and the best manner of burning pulverized coal that this system is not yet gen- erally offered as a commercial propo- sition for installation on board ship. The test at present being carried out at the fuel testing station at the League Island navy yard is with a standard scotch marine type of boiler. The entire test unit is self-contained. That is, the coal is brought there in its natural state and is pulverized, and blown into the furnaces in the amount required for combustion. The system used is similar in many respects to that used in burning fuel oil. High Degree of Fineness Necessary Ordinary soft bunker coal is crushed by iron balls in a revolving drum. The finely powdered coal which is so fine that it has the feel of taleum powder when rubbed in the hand passes under air pressure through pipes of approxi- mately 5 inches in diameter to each furnace. In the system used at the navy yard the fine particles of coal are given a whirling motion as they enter the furnace. Lighting off the boiler is done by using fuel oil for a brief period and then shifting to the powd- ered coal. Complete combustion takes place and the flame practically fills the furnace space. Only a light resi- due of ash remains which can readily be removed as necessary, probably not more frequently than once in every twenty-four hours. Experiments are being continued to determine the pro- per mixture of air and fuel and the necessary quantity of fuel covering the entire range of possible boiler ratings. When this is established the question of maneuvering with pulver- ized coal will be largely settled. A By A. H. Jansson continuous night and day run _ will also be carried out in order to find out in a practical way what effect this will have on the operation of the system. ' It is generally conceded that the ap- plication of pulverized coal to marine water tube boilers is far simpler than to the fire tube or scotch marine type. The writer had the opportunity of seeing powdered coal burned in a ma- ‘rine water tube boiler with complete success. It was really remarkable how simple the whole installation seemed. There was no pulsation or drumming and combustion was entirely complete. The flames had much the appearance of that obtained when burning oil. In this case fires can be lighted di- rectly with the powdered coal without the preliminary use of oil. A ball mill of cylindrical type was used for pul- verizing the coal and as in the case of the scotch boiler types the coal was taken in its natural state, ground to prover fineness and then blown into the furnace as required for the particular rating under which the boiler was operating. From a practical point of view com- ing to an actual installation on board ship the problem is no longer the suc- cessful burning of the coal but it is rather in working out convenient and economical means of handling the com- paratively large quantities of coal in the bunkers so that as needed the coal may be readily moved to the mill or mills for crushing. Also the de- finite development of mills capable of giving the proper fineness of coal in sufficient quantities without sacrificing an undue amount in weight and space. Another point is that the process of crushing the coal should be made as nearly noiseless as is mechanically possible. With these important auxil- iary features thoroughly solved the burning of pulverized coal on board ship should prove entirely successful. Powdered Coal System Practical In the tests briefly reviewed above it was stated that efficiencies were cb- tained comparable with those when using oil as fuel. It is quiet evident, if efficiencies over 80 per cent can be obtained in using powdered coal, that this system will prove very econom- ical. MARINE REVIEW—August, 1927 Spot price for bunker coal in New York alongside ship on July 19 was $5.65 per ton. Fuel oil was quoted at its lowest price for over a year an the same day at $1.65 a barrel. Taking coal at 14,000 b.t.u. per pound and oil at 18,600 b.t.u., one pound of oil is equivalent to 1.3825 pounds of coal. If the quantity of oil in one barrel weighs 336 pounds then one barrel of fuel oil will be equivalent in heat value to 445 pounds of coal. At the rate of $5.65 a ton for coal this would mean that an amount of coal costing $1.12 will do the same amount of work as one barrel of oil at $1.65. Which means that even for the present low price of oil the cost of producing steam using pulverized coal will be 32 per cent less than that using oil. It is easily conceivable that under conditions of high priced oil and low priced coal that this difference could be increased greatly in favor of coal. Another factor of great importance is the possibility of burning lower grade coal. By removing the human element from the stoking of boilers it will be possible to maintain indefinite periods of steady steaming. There will be no possibilities of difficulties with the black gang and the last man killing labor will then have been removed from ship operations. It will, of course, also reduce the expense of the fire room crew which needs to be no larger than for oil burning. What the British are Doing Interest in the practical application of pulverized coal for marine purposes is world wide and it is particularly keen in Great Britain. A complete and interesting lengthy paper with many diagrams and tables was read by Engineer Captain J. C. Brand at the summer meetings of the sixty- eighth session of the Institution of Naval Architects on July 12 at Cam- bridge, England. The paper indicates the types of fuel suitable for pulver- ization and discusses the effect of grinding, preheating, turburlence and moisture on combustion in confined spaces. The author’s definition of powdered fuel as used in his paper includes any carbonaceous fuel which is in a sufficiently finely divided state to be impelled by or borne in air and burned while in a state of suspension. 21