The following text may have been generated by Optical Character Recognition, with varying degrees of accuracy. Reader beware!

In regard to suitable fuels he recom- mends slack or breeze rather than larger pieces since it is more econom- ical to grind. Also small fuel is of less value on the market. For marine work Captain Brand points out that a pulverizer for grind- ing the coal should be economical in weight and space and it should be es- pecially designed to make easy re- placement and repairs. Also that its parts should be small enough to be moved through small hatchways. It is most important that all parts from the coal feed of the hopper to the spindle accesses to the beaters and fans should be dust-proof. The power required to grind coal varies with moisture content and fineness of the product. Due to the limited combustion space in a marine boiler of either water tube or scotch type it is nec- essary that the coal be reduced to a high degree of fineness. It is important to avoid moisture in fuel as it has a detrimental effect on the freedom of flow without which certainty and evenness of operation are impossible. Captain Brand goes on to say in connection with preheated air, that in order to have the coal particle, its gas envelope and _ sur- reunding air, all near the ignition point on entering the furnace, it is desirable to heat both primary and secondary air. Preheating to a tem- perature of 446 degrees Fahr. by using a heater placed in the path of the funnel gases is recommended. Turbu- lence is also considered necessary just as it is in the combustion of oil in a diesel engine. Particularly is this so for a short flame powdered fuel burner. Installation on British Ship A portion of the paper is devoted to an explanation of the author’s system of pulverized coal burning for marine installation.: Plates are also published showing drawings of an _ installation with a scotch marine boiler in a mer- chant vessel. Clarke Chapman & Co. Ltd. has also gone deeply into the question of pulverized coal and the use “ef such fuel in boilers at sea. A num- “per of trials’ with different types of burners and ‘arrangement of furnace fronts have beén carried out. Drawings show the first, second and third at-~ tempts along this line and test figures of the trials with the Clarke Chapman system are also given. In one of these trials 6.65 pounds of water was evap- erated per pound of fuel. The fuel fired per hour was 585 pounds. Water evaporated per hour was 3890 pounds. One of the interesting results was in finding that the residue from low tem- perature distillation burns with as 22 much facility as coal containing a high percentage of volatile hydrocarbons. Unit pulverizers are also discussed. The author stating that there are some excellent types on the market though their weight is somewhat excessive for the output, which is probably due to the fact that they have all prac- tically been designed for shore use where weight and space are of little moment. He recommends that if a unit machine is carried on board it be placed in a small well ventilated com- partment of its own and that it de- liver through a separator to the ready- use bin in the boiler room. The coal should be fed mechanically or pneu- matically with hot funnel gas intro- duced at the inlet though the tem- perature at the inlet should not ex- ceed 300 degrees Fahr. More funnel’ gas may be introduced at the delivery end at a temperature of 390 degrees Fahr. Advantages of the Brand System Captain Brand in his pulverized fuel system for marine installation, in order to secure freedom from risk of spontaneous combustion or explosion observes the following precautions: The fuel is dried and ground on shore. The grinding station may be on the foreshore or half a mile away. No difficulty is experienced in forcing the material through pipes. The pro- pelling agent is inert flue gas from the drier which has been cooled and compressed to a pressure of 40 pounds per square inch. Five cubic feet of gas at 40 pounds pressure is required per ton of fuel. The ship end of the hose is connected to a gas relief sep- arator fastened to the bunker lid. Before bunkering a quantity of gas is blown into the bunker through the hose, displacing any air present. It was found that one ton of dust per minute may be forced through 500 feet of 4-inch piping by a pressure of 40 pounds per square foot. Each particle of coal is sealed by inert gas with which all the interstices are filled, to the exclusion of oxygen, leaving no vehicle for the propagation of flame. Since CO, is heavier than air it takes the place of air which flows away through the separator. After completing bunkering the bunker lid joint is made and the bunker sealed to prevent admission of air and its diffusion into the CO, No moisture can gather as the compartment is air tight except what was in it when empty and that contained in the fuel dust and gas content. Where the coal is already pulver- ized as it is taken on the vessel there is fitted a ready-use bin which provides storage for sufficient fuel for MARINE REVIEW—August, 1927 a limited period of steaming. This bin is dust proof. One may be used for the whole boiler room or there may be separate ones for each large boiler. A machine cut screw feeder rotating in a casing feeds the dust forward to the down pipe. This screw is manipulated by a variable speed. gear, motor driven, and has a range of coal of from 60 pounds per hour up to a maximum for a large furnace of 700 pounds per hour. The author finally describes the ac- tual operation of the boiler with this system of pulverized coal. With suf- ficient coal in the ready-used bin the fan is started at low speed and air is admitted to the primary pipe. A lighted torch made of oily waste is passed through the spectacle hole to the front of the burner. The latter is drawn back to the inner edge of the cone brick work. The feeder serew is then started at lowest speed. At the end of five minutes the torch can be withdrawn. In fifteen minutes the cone bricks will be sufficiently warm to support combustion and the feeder pipe can be advanced farther toward the furnace. A feed rate of 60 pounds per hour should not be exceeded until the refractory in the furnace extension reaches a tempera- ture of about 930 degrees Fahr. Un- til an input of 100 pounds of dust an hour is reached the primary air sup- ply will be sufficient after which sec- ondary air should be admitted. As soon as the brick work is incandescent the primary air can be opened out and the secondary air regulated to suit the input of dust and power required. Results Are Summarized Captain Brand then calls attention to the following features of the sys- tem: 1. Finely divided fuel dust is pro- vided. 2. Preheated air is supplied. 3. Provision is made for lighting up, low and high rates of steaming. 4, Turbulence is attained with a very short flame. Change of direction of the gases deposits the slag, if any, near the ash door. 6. Expansion of the gases after pass- ing the bridge allows the heavier particles of ash to deposit in the furnace bottom, from whence they can be withdrawn. ‘ 7. Absolute control is maintained over the speed of the fuel feeder and the secondary air admission; these are interlocked for all fur- naces; so that the attendant can control all furnaces in one stoke- hold by means of one lever. 8. Sufheient refractory surface is present to permit of restarting the fires instantaneously, even after a stop of about 20 minutes. The author states that no more ov “ce eae See mr Se ey ea ee