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Pulverized Coal for Marine Use Makes Real Progress HY should the use of pulver- W ize fuel on shipboard be de- veloped? What are the dif- ferences between a power plant at sea and one on the shore that re- quires this development work? These two questions in brief, cover the problem that was put up to the fuel conservation committee of the ship- ping board about a year ago. Why should pulverized fuel be made seagoing? Because when it has learned seagoing ways and_ learns how to behave itself in a marine plant, it will then effect economies in the operating costs of our exist- ing vessels of such a magnitude that an auditor’s statement can be a real pleasure instead of simply “a study in scarlet.” Oil fuel is ideal in many ways for steam generation, but it is absolute- ly criminal to use it for that pur- pose when the same results can be obtained from a much cheaper, and more plentiful type of fuel. All engineers have known this for years; it is no new teaching; but when they calculated the difference in efficiency which the average plant would at- tain oil as compared with coal, and when they tried to sign on _ satis- factory fire-room crews and _ found that year after year it has become increasingly difficult to obtain men with sufficient intestinal fortitude to swing on a slice bar and at the same time have enough sense to care about saving b.t.u’s, then they were in- clined to let their engineering in- stinct and scruples go by the board and join the criminal band of oil burners. Hand Firing Too Hard Those of you who have fought for steam pressure, when rolling some 30 degrees or more with the wheel kicking out, and hell in general broke loose down below, know what it means to drive men when the heat of the fires is burning up the human part of their minds, and” you, too, agree that the man who substitutes fuel oil for coal should be blessed. The author, C. J. Jefferson, is head of the fuel conservation section of the Merchant Fleet Corp., United States shipping board. This article represents the revision to March 3, 1927 of a paper presented before the tech- nical committee and members of the American Steamship Owners association, Nov. 19, 1926. 96 By C. J. Jefferson But, if the boiler efficiencies ob- tained with oil can be duplicated, and if this duplication can be ac- complished in such a way that the operating problem is no greater than that on the oil burner, and if all of this can be done with a fuel that has a b.t.u. cost approximately one- half of that of fuel oil, then it be- hooves the marine engineering frater- nity to bestir itself and find out whether or not this type of power cannot be put to work on_ ship- board. : That is the reason why the fuel conservation committtee decided to tackle the problem, for pulverized fuel has on numerous shore plants met the condition just cited. But, if this has been worked out on shore, why should there be any marine in- stallation problem? The answer to this is, simply furnace design. In the average pulverized fuel plant, where the rata of combustion has been less than a pound of fuel per cubic foot of furnace volume, deep or long furnaces have been used, which. allowed flame travel of 20 feet or more, which permitted comparatively slow flame propagation, or ignition of the individual particles of coal. Combustion Space Limited This type of furnace design is not practical on shipboard, and in the ease of the scotch marine boiler, it is not only impractical but impossible. The furnace of a scotch boiler may be made smaller, by installation of refractory lining, by accumulation of ashes and dirt, or by the collapse of the furnace, but it just cannot be made larger, and when you con- sider the present existing vessels of the merchant marine, you have got to consider scotch boilers, because the large majority of them are fitted with this old-time reliable, but inflexible type of steam generator. The furnace of the ordinary scotch boiler is approximately 8 feet long up to the combustion chamber, which is about 3 feet deep, giving a total maximum length of flame travel of 11 feet. In fact, this should be reduced to about 10 feet, as impingement of the flame against rear sheet of com- MARINE REVIEW—April, 1927 bustion chamber must be avoided. This gives you one phase of the prob- lem. You are required to cut the length of your flame in half, as compared to the ordinary shore plant. The combustion space in a three furnace separaté combustion chamber type of scotch boiler of 2500 square feet heating surface, which is the typical type of ‘boiler found on the average cargo carrier, will be some- what less than 500 cubic feet. In order to burn 2000 pounds of coal per hour in these furnaces, you must burn four pounds of coal per cubic foot, or approximately twice as much as the maximum. rate, or eight times as much as the average rate at- tempted in the shore plant, and all must be done in a completely water- cooled furnace without the benefit of stored up heat found in the refrac- tories of the large furnaces of the job on shore. Therefore, the develop- ment work that was necessary to produce satisfactory land installations must be carried on to a much greater degree of refinement before pulver- ized fuel can don its sea togs. Experiments Started in 1921 Back in 1921, the idea of pulverized fuel for marine purposes, especially for use in scotch boilers, was advo- eated, and an attempt was made at the Fleet corporation test plant at Chester, to adopt one of the typical stream line type of burner in- stallations, such as were then and are now used with satisfactory re- sults in shore plants. A_ stream line burner is simply a nozzle, with round or elongated opening, through which the pulverized coal is dis- charged into the furnace by low air pressure, the balance of the air re quired for combustion being admitted through shutter fitted slots in the furnace front. This is the simplest type of pulverized fuel burner, and if the furnace is sufficiently large, and it is possible to have from 20 to 25 feet flame travel, this type of burner is fairly successful with com- paratively coarse coal. However, the scotch boiler does not have the large combustion space, nor is 20 feet flame travel possible, and therefore, these initial tests made with the stream line burner were not