Fig. 20.—Blass’ Gas Plant.

Figs. 14 and 15 show Liegel’s producer, the special object of which is to deal with any fuel (coal or coke) giving a tough, pasty slag on combustion. Such slags act very prejudicially by impeding the up-draught of the air and the sinking of the fuel; nor can they be removed by falling through a grate, like ordinary coal-ashes. To obviate these drawbacks the producer A is kept at a greater heat than is otherwise usual, the air required for feeding the producer being pre-heated in the channels e, e. The inside shape of the producer is such that the upper, less hot portion cannot get stopped, as it widens out towards the bottom; the lower, hotter portion, where the ashes are already fluxed, is contracted to a slit a, through which the air ascends. The grate b retains any small pieces of fuel, but allows the liquid cinder to pass through. The lateral flues c, c prevent the brickwork from being melted.

One of the best-known gas-producers for working with compressed air from below is Taylor’s, shown in fig. 16. A is the feeding-hopper, on the same principle as is used in blast-furnaces. L is the producer-shaft, with an iron casing B and peep-holes B1 to B4, passing through the brick lining M. F is the contracted part, leading to the closed ash-pit, accessible through the doors D. An injector I, worked by means of the steam-pipe J, forces air through K into F. The circular grate G can be turned round K by means of the crank E from the outside. This is done, without interfering with the blast, in order to keep the fuel at the proper level in L, according to the indications of the burning zone, as shown through the peep-holes B1 to B4. The ashes collecting at the bottom are from time to time removed by the doors D. As the steam, introduced by J, is decomposed in the producer, we here obtain a “semi-water gas,” with about 27% CO and 12% H2.

Fig. 17 shows the Dowson gas-producer, together with the arrangements for purifying the gas for the purpose of working a gas engine. a is a vertical steam boiler, heated by a central shaft filled with coke, with superheating tubes b passing through the central shaft. c is the steam-pipe, carrying the dry steam into the air-injector d. This mixture of steam and air enters into the gas-producer e below the fire-grate f. g is the feeding-hopper for the anthracite which is usually employed in this kind of producer. h, h are cooling-pipes for the gas where most of the undecomposed steam (say 10% of the whole employed in d) is condensed. i is a hydraulic box with water seal; j, a coke-scrubber; k, a filter; l, a sawdust-scrubber; m, inlet of gas-holder; n, gas-holder; o, outlet of same; p, a valve with weighted lever to regulate the admission of steam to the gas-producer; q, the weight which actuates the lever automatically by the rise or fall of the bell of the gas-holder. In practical work about ¾ ℔ of steam is decomposed for each pound of anthracite consumed, and no more than 5% of carbon dioxide is found in the resulting gas. The latter has an average calorific power of 1732 calories per cubic metre, or 161 B.T.U. per cubic foot, at 0° and 760 mm.

The Mond plant is shown in figs. 18 and 19. The gases produced in the generators G are passed through pipes r into washers W, in which water is kept in violent motion by means of paddle-wheels. The spray of water removes the dust and part of the tar and ammonia from the gases, much steam being produced at the same time. This water is withdrawn from time to time and worked for the ammonia it contains. The gases, escaping from W at a temperature of about 100° C., and containing much steam, pass though g and a into a tower, fed with an acid-absorbing liquid, coming from the tank s, which is spread into many drops by the brick filling of the tower. This liquid is a strong solution of ammonium sulphate, containing about 2.5% free sulphuric acid which absorbs nearly all the ammonia from the gases, without dissolving much of the tarry substances. Most of the liquor arriving at the bottom, after mechanically separating the tar, is pumped back into s, but a portion is always withdrawn and worked for ammonium sulphate. When escaping from the acid tower, the gas contains about 0.013% NH3, and has a temperature of about 80° C. and is saturated with aqueous vapour. It is passed through c into a second tower B, filled with blocks of wood, where it meets with a stream of comparatively cold water. At the bottom of this the water runs away, its temperature being 78° C.; at the top the gas passes away through d into the distributing main. The hot water from B, freed from tar, is pumped into a third tower C, through which cold air is forced by means of a Root’s blower by the pipe w. This air, after being heated to 76° C., and saturated with steam in the tower C, passes through l into the generator G. The water in C leaves this tower cold enough to be used in the scrubber B. Thus two-thirds of the steam originally employed in the generator is reintroduced into it, leaving only one-third to be supplied by the exhaust steam of the steam-engine. The gas-generators G have a rectangular section, 6 × 12 ft., several of them being erected in series. The introduction of the air and the removal of the ashes takes place at the narrower ends. The bottom is formed by a water-tank and the ashes are quenched here. The air enters just above the water-level, at a pressure of 4 in. The Mond gas in the dry state contains 15% carbon dioxide, 10% monoxide, 23% hydrogen, 3% hydrocarbons, 49% nitrogen. The yield of ammonium sulphate is 75 ℔ from a ton of coal (slack with 11.5% ashes and 55% fixed carbon).

Fig. 21.—Dellwik-Fleischer Producer.

One of the best plants for the generation of water-gas is that constructed by E. Blass (fig. 20). Steam enters through the valve V at D into the generator, filled with coke, and passes away at the bottom through A. The pressure of the gas should not be such that it could get into the pipe conveying the air-blast, by which an explosive mixture would be formed. This is prevented by the water-cooled damper S, which always closes the air-blast when the gas-pipe is open and vice versa. Below the entry W of the air-blast there is a throttle valve d which is closed as soon as the damper S opens the gas canal; thus a second security against the production of a mixture of air and gas is afforded. The water-cooled ring channel K protects the bottom outlet of the generator and causes the cinders to solidify, so that they can be easily removed. But sometimes no such cooling is effected, in which case the cinders run away in the liquid form. Below K the fuel is lying in a conical heap, leaving the ring channel A free. During the period of hot-blowing (heating-up) S is turned so that the air-blast communicates with the generator; d and G are open; g (the damper connected with the scrubber) and V are closed. During the period of gas-making G and d are closed, S now closes the air-blast and connects the generator with the scrubber; V is opened, and the gas passes from the scrubber into the gas-holder, the inlet w being under a pressure of 4 in. All these various changes in the opening of the valves and dampers are automatically performed in the proper order by means of a hand-wheel H, the shaft m resting on the standards t and shaft v. This hand-wheel has merely to be turned one way for starting the hot-blowing, and the opposite way for gas-making, to open and shut all the connexions, without any mistake being possible on the part of the attendant. The feeding-hopper E is so arranged that, when the cone e2 opens, e1 is shut, and vice versa, thus no more gas can escape, on feeding fresh coke into the generator, than that which is contained in E. G is the pipe through which the blowing-up gas (Siemens gas) is carried away, either into the open air (where it is at once burned) or into a pre-heater for the blast, or into some place where it can be utilized as fuel. This gas, which is made for 10 or 11 minutes, contains from 23 to 32% carbon monoxide, 7 to 1.5% carbon dioxide, 2 to 3% hydrogen, a little methane, 64 to 66% nitrogen, and has a heating value of 950 calories per cub. metre. The water-gas itself is made for 7 minutes, and has an average composition of 3.3% carbon dioxide, 44% carbon monoxide, 0.4% methane, 48.6% hydrogen, 3.7% nitrogen, and a heating value of 2970 calories per cub. metre. 1 kilogram coke yields 1.13 cub. metre water-gas and 3.13 Siemens gas. 100 parts coke (of 7000 calories) furnish 42% of their heat value as water-gas and 42% as Siemens gas.

Lastly we give a section of the Dellwik-Fleischer gas-producer (fig. 21). The feeding-hoppers A are alternately charged every half-hour, so that the layer of fuel in the generator always remains 4 ft. deep. B is the chimney-damper, C the grate, D the door for removing the slags, E the ash-door, F the inlet of the air-blast, G the upper, G1 the lower outlet for the water-gas which is removed alternately at top and bottom by means of an outside valve, steam being always admitted at the opposite end. The blowing-up generally lasts 1¾ minutes, the gas-making 8 or 10 minutes. The air-blast works under a pressure of 8 or 9 in. below the grate, or 4 to 4½ in. above the coke. The blowing-up gas contains 17 or 18% carbon dioxide and 1.5% oxygen, with mere traces of carbon monoxide. The water-gas shows 4 to 5% carbon dioxide, 40% carbon monoxide, 0.8% methane, 48 to 51% hydrogen, 4 or 5% nitrogen. About 2.5 cub. metres is obtained per kilogram of best coke.

See Mills and Rowan, Fuel and its Application (London, 1889); Samuel S. Wyer, Producer-Gas and Gas-Producers, published by the Engineering and Mining Journal (New York); F. Fischer, Chemische Technologie der Brennstoffe (1897-1901); Gasförmige Heizstoffe, in Stohmann and Kerl’s Handbuch der technischen Chemie, 4th edition, iii. 642 et seq.

(G. L.)