PHILIPPINE COALS AS FUEL. 343 



exit of the gases of the flame stream until combustion of the volatile 

 combustible matter is completed in the combustion chamber, contains 

 the possibilit}^ of greatly increasing the efficiency of Philippine coals. 

 Satisfactory baffle walls would probably be of as much value as a con- 

 siderable increase in the length of the fire box. A boiler with the same 

 setting as those of this Bureau, but arranged with different baffling 

 forming a tile-roof furnace, has been used on Illinois coals and is said 

 to run at capacities of from 50 to 100 per cent without smoke.^° 



Various grates other than the ordinary bar have been suggested and 

 tried on coals of the sub-bituminous variety. It was hoped that the per- 

 forated grate would be more economical of coal. However, in the tests 

 of Mr. Betts' coal there was a slight incipient clinker which could not 

 be dislodged from the holes and the steam pressure fell at the end of 

 the test because of lack of draft. It was not possible to experiment 

 much with this coal beforehand and but little information regarding it 

 could be obtained. The grate worked well with Australian coal. With 

 more experience and slight modifications this may still be more satis- 

 factory than the ordinary grates. Mr. Betts has tried a herring-bone 

 grate which he reports to be very successful. The advantage of a grate 

 of this type over the ordinary gridiron is that shorter, thinner and more 

 bars may be used without danger of their melting down and in this way 

 the air spaces increased in number, but diminished in size without 

 changing the ratio between air space and grate surface. It has also 

 been suggested that the loss of combustible matter in the ash could be 

 prevented by burning these coals on a rocking grate. It is hoped that 

 the study of the behavior of Philippine coal and coals of this class will 

 soon result in the discovery of a more satisfactory grate and a method 

 of combustion that will be more economical of the coal. 



Eeconstruction of the present boiler settings in the Archipelago is 

 out of the question. Greater efficiency, therefore, can be obtained only 

 by building additional baffle walls, using a more satisfactory grate, 

 elongating the fire box or heating the air before entering the grate, and 

 these improvements from an economic standpoint can best be tried 

 in the order of enumeration. 



" Breckenridge, L. P.: Univ. of III. Bull. (1906), 4, No. 31, 22. M. Ernest 

 Schmidt, Bull. soe. ind. d' Amiens, 2-3, 102; C. A. (1908), 2, 174, has called 

 attention to the fact that it is difEcult to destroy smoke after it is once formed, 

 but believes in preventing its formation by gradual introduction of coal into 

 the fire box, if possible under the burning combustible, and finally, by the use 

 of a mass of fire brick kept at a high temperature. He also considers the 

 heating of the air before entering the grate necessary. In the combustion of 

 Philippine coal where high chimney temperatures are obtained this might be 

 accomplished by a down-draft pipe through the stack. 



