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at all successful. The maximum rate of combustion that could be obtained was 2.5 pounds of coal per cubic foot of furnace volume, or a heat re- leased of 32,000 b.t.u. per hour per cubic foot of furnace, and the effi- ciency of boiler performance was only 54 per cent. The writer, who was one of the participants of these tests, could not work up’ any enthusiasm regarding these results, and became a member in good standing of “the criminal order of oil burners.” In fact, advocates of pulverized fuel for marine plants were given but little tolerance for the next few years after these tests. In the meantime, however, the man- ufacturers of pulverized fuel equip- ment were not standing still. They realized that the enormous furnaces required for satisfactory combustion were a severe handicap in their com- petition with stoker installations, and the problem of reducing furnace vol- ume became a serious consideration, so that by 1925, several devices were developed which shortened the length of flame considerably, and permitted reduction’ in the furnace volumes. New Equipment Developed This brought up the question of marine installations again, and after studying the results that had been obtained on shore plants, the fuel conservation committee was convinced that further possible progress made along these same lines would eventu- ally develop a combustion of equip- ment which would be entirely prac- tical for marine use, and would per- mit the economies in the marine plant that are today being obtained on shore. At almost the same time, further stimulus was given to the question by the numerous diesel installations which have been made in the fleets of our foreign competitors. The fuel economy possible in a diesel installation would drive steam off the seas, if it were not for the high initial cost of dieselization. This high cost has retarded dieselization considerably, but has by no means stopped it, and the steam men have been forced into developing their equipment so as to reduce the dif- ferential in the operating fuel cost between the diesel and the steam ‘plant. High pressure, high tem- perature steam has received a con- siderable impetus, and with the re- inforcement of pulverized fuel, it is’ possible to meet the challenge of the diesel, not in terms of pounds of fuel per shaft horsepower, it is true, but in the terms which decide whether a business is profitable or not; that 98 is, in the cost per shaft horsepower developed, and this with a plant whose initial cost will be materially less than that of the diesel. We must always keep in mind that there are a lot of ships afloat to- day, and the operating cost of these ships to the average shipowner is just as important, if not more so, than the operating cost of new tonnage, and it is for this class of ships that the successful solution of the pulver- ized fuel problem offers the great- est salvation. Further Tests Authorized These facts were all considered by the fuel conservation committee, and they decided that they would tackle the problem. Therefore, arrange- ments were made with the bureau of engineering of the United States navy, that a series of development tests should be made at the fuel test plant at Philadelphia, using pulverized fuel in a scotch boiler, which was fur- nished by the United States shipping board from one of the vessels of the laid-up fleet. The service given by the United States navy to the merchant marine in carrying out these tests is just another example of the service that a trained military organization can give to its country in times of peace as well as in times of war. The first type of burner selected for test was not chosen so much from its characteristics of being a practical marine type, for, as a mat- ter of fact, it had several marked disadvantages from this point of view, in its state of development as_ sub- mitted for test, but rather it was chosen to determine the combustion condi‘ions that could be obtained from a burner which was the direct anti- thesis of the stream line burner. This burner was the Fuller Lehigh Well type burner, arranged in a ver- tical plane, and consisted of four nozzles, so arranged that the stream of coal, together with the air neces- sary for combustion from each of these nozzles, would cut the stream issuing from the adjacent nozzle, set- ting up a terrific turbulence. This type of burner has all of the air necessary for combustion used as primary or carrying air, and any attempt to regulate the air supply would have a direct effect on the turbulence produced, and also, inas- much as an air swept ball type of mill was used to pulverize the coal, it would also have a direct effect on the fineness of the coal. The boiler used for these tests was not fitted with either air heaters or superheaters, while the boiler used MARINE REVIEW—April, 1927 with the stream line burner in 1921 had both of these accessories to im- prove the boiler performance; yet, these latter tests showed a remark- able advance in performance, as may be noted from the fact that combus- tion rates as high as 6.19 pounds per cubic foot of furnace volume were obtained with a release of 88,330 b.t.u. per cubic foot, and a boiler efficiency of 68.7 per cent was obtained from the boiler itself, without the aid of either air heaters or superheaters. At termination of these tests, an air heater has been installed, as it. was apparent from these tests that all measures should be taken to speed up flame propagation, and one of the means of accomplishing this end is tc have the air necessary for combustion heated to as high a temperature as possible before it enters the furnace. The use of heated air in the pulver- ized mill also reduces the variable in the fineness of the coal caused by moisture in the fuel. The question of uniform quality of coal of sufficient fineness to insure satisfactory ignition and complete combustion is of paramount impor- tance in connection with the use of pulverized fuel in marine boilers, just as it is the case in regard to the correct viscosity of fuel oil. In the shore station, a much wider latitude in degree of fineness is permissible, inasmuch as in the large volume fur- nace with the long flame travel, the coarser particles of the’ fuel may be ignited further along in the flame travel, and while in the earlier part of the flame the efficiency of com- bustion may be relatively low, this is compensated for by completion of the combustion in the latter stages. In the marine boiler, this is not permissible, the limited length of flame travel makes it imperative that complete ignition takes place as soon as possible, and that efficient com- bustion starts at the very early stages. Better Results on Latest Test The present equipment that is un- der test is the Peabody burner, which is a turbulent burner using both primary and secondary air. The primary air carries the coal to the furnace under comparatively low air pressure and it enters the furnace with the coal though an annular slot ina snail-shaped casting located at the mouth of the furnace. This arrange- ment is, in effect, an infinite number of nozzles directing a coal stream against the stream from another in- finite number of nozzles. These in- finite number of streams cutting each other produce a _ violent turbulence