Practical Hand Book of Gas, Oil and Steam Engines / Stationary, Marine, Traction; Gas Burners, Oil Burners, Etc.; Farm, Traction, Automobile, Locomotive; A simple, practical and comprehensive book on the construction, operation and repair of all kinds of engines. Dealing with the various parts in detail and the various types of engines and also the use of different kinds of fuel.

by John B. Rathbun

(15) Operation of Producers.

A good producer operator is simply a good fireman, he must know how to keep a uniform bed of coal and how to draw the fire. While there are many thousands of men running producer plants without previous mechanical training, there are now but few steam engineers running steam engines of the same capacity but what have had at least two years’ training and sufficient mechanical knowledge to pass an examination and obtain a license. While a considerable amount of skill is necessary to obtain the best efficiency from a producer, it is a knack that is easily acquired in a short time by “sticking around” the plant. Skill in operating a producer consists chiefly in keeping the right sort of a fire without damage to the lining by poking down ashes and clinkers. When a new plant is installed, the manufacturer generally sends an instructor to operate the plant for a short time so that with a few days running in his hands any man with ordinary intelligence can overcome the difficulties which arise from time to time.

While there are many types of producers, the main difference will be found in the character of the draft, that is whether it is up, down, or crossways. Down draft producers are generally used with bituminous coals, as the tars and oils that emanate from the coal are drawn through the fire which converts them into a permanent gas, and avoids the difficulty of removing great quantities of the tar from the producer. An up draft producer will not do this as the gas is drawn directly into the mains without coming into contact with the fire. This would result in considerable expense due to the frequent cleaning. Anthracite coal which does not contain much tar can be used successfully in an up draft producer.

A compromise between the up draft and down draft producer is had in the DOUBLE ZONE producer, which “burns the candle at both ends” as it were, a fire being at both the top and bottom of the producer. Nearly any class of fuel may be used with this type.

It should be remembered that a hot fire and fuel are required for the manufacture of gas, and that the ash pit and grate must be kept clear of the ashes and clinkers that not only reduce the temperature of the fire, but also reduce the gas available at the cylinder by increasing the friction. Shaking down and cleaning out will in nearly every instance start a bucking producer into operation.

When operating under full load a much hotter fire is required than when operating under a reduced load, or the producer will not furnish the necessary gas. According to the size of the producer, the depth of the incandescent fuel will run from 30 inches in the large sizes to 15 inches in the smaller. After being charged up, suction producers will continue to give gas in sufficient quantities with the bed at half this depth. This is only possible with a hot producer, and when no fuel is being fed, as the feeding of a cold charge will reduce the output. A steady depth of fire should be kept to maintain a uniform quality of gas.

In suction producers careful watch should be kept for leaks, as the gas being below atmospheric pressure gives no outward signs of dilution. If water seals are used in the system they should be given careful attention. When using coals that are rich in tar or hydrocarbons, or with fuels that have much fine dust, considerable trouble is had with some types of producers due to “caking” or to the adhesion of the coal particles to the walls of the producers or to their adhesion to one another. In the latter case the “stickiness” of the fuel prevent the proper feed. This difficulty may often be overcome by a change in the rate of feeding or by regulating the depth of the incandescent bed.

Porosity of the fuel, and the rate at which the air is supplied to the producer determines the depth of the incandescent bed. Particular care should be taken that the blast or draft occurs evenly over the fire surface, and that no holes occur in the fire which will cause more rapid combustion in one spot than in another. Neglect of this precaution not only causes a waste of fuel but often results in the fuel “arching” and preventing further feed. The producer should be so proportioned that at full load, the rate of combustion does not exceed 24 pounds of fuel per square foot of producer area per hour.

In his researches, Professor Bone (Iron and Steel Institute, May, 1907) has shown that up to 0.32 lbs. of steam per lb. of coal can be completely decomposed in a producer, but that, from 0.45 lbs. to 0.55 lbs. should be used, approximately 80% more.

Now, in considering the question of the proper proportion of steam for the production of gas for power purposes we must bear in mind that as much heat as possible should be utilized in the producer itself. Some manufacturers of plant go so far as to state that as much as 1 lb. of steam per lb. of coal should be used, but we are safe in saying that 0.5 lb. to 0.7 lb. should be the figure for a power plant. The common practice is to use a blast saturation of 55% whenever the clinkering character of the coal renders it possible. This figure corresponds to about .57 of steam per lb. of coal gasified.

It is of the utmost importance that the proportion of steam and air should be constant, and the best figure being determined, it should not be varied to any degree. It is equally important that the fuel depth should be left constant. By this I mean that not only should the coal in the producer be kept at a specific level, but the position of the fire on the ash bed should be kept as near as possible a fixed point. Ashes should be drawn at regular intervals, or, if desired, continuously by mechanical means.

Further, the supply of air and steam should be regularly distributed, so that the velocity of the gases through the fuel shall be as nearly as possible regular across its whole area.

In some cases the by-products of a producer, such as ammonia, tar, etc., have a commercial value, and if a large amount of gas is generated it will sometimes pay to select a fuel that is rich in these particular substances.