16,699. Westinghouse, G., [Knox, W. J.]. Aug. 20. Gas - producers; furnaces for carbonic acid.-Water gas, illuminating- gas, carbonic - acid gas or the like, is obtained by heating a portion of the gas evolved, in a regenerative stove to a high temperature, passing the hot gas through a producer, cooling the hot gas so obtained in a heat absorber, withdrawing the excess of gas, re-heating the balance, and circulating it again through the apparatus. The direction of the circulation is periodically reversed, so that the heat given up by the hot gas to the absorber is utilized to heat the incoming gas, the heat absorber thus becoming the heating stove while the previous heating stove becomes the heat absorber. Fig. 3 is a diagram illustrating one arrangement of plant. A producer 41 is connected by a pipe 42 with a combined scrubber and steam generator 43. The latter is connected by a pipe 44 with a scrubber and condenser 45, preferably kept at a temperature below 100‹ C., from which gas is withdrawn from the circuit through the pipe 46. The scrubber 45 receives cold water from the pipe 47, and the hot water obtained is forced by the pump 48 to the scrubber 43, wherein it is mostly converted into steam, which is passed, together with the gas to be circulated, by a fan 51 into one of the heating stoves 53. While one heating stove is being thus used, the other is being heated up, preferably by gas withdrawn through the tube 55. From the stove 53, the hot mixture passes to the bottom of the producer 41. At the commencement of operations, the gas employed for heating the stoves is obtained from an outside source. When the stove has become cooled down too much, the valves are reversed, so that the stoves are intercharged. The gases from the producer pass to the steam generator and scrubber, part being withdrawn, the rest being sent again into the circulation. In another form, two gas-producers and four regenerators are used. The first producer contains coke which is gradually consumed, the other fresh coal which is gradually coked and which liberates gas. The gas is led through a heat regenerator, before passing to the steam generator, whereby the regenerator is heated, and the gas is fixed. The circulation of the gas is reversed as before. Fig. 4 shows a further modification, in which there are four heat regenerators 60, 61, 62, 63, four gas-producers 64, 65, 66, 67, two economizers or steam generators 69, 70, a fan 71 for circulating the gases, valve chambers 75, 76 for directing the gases as required, and suitable connecting pipes and valves. The regenerators are first heated, which may be effected by means of some of the gas from the producers. Two regenerators, for example 60 and 61, are connected with one pair of producers 64, 65. The butterfly valve 68 is then set so that the circulating gas passes through the economizer 70 to the stove 61, where it becomes heated. The heated gas is mixed with steam, and the mixture passes to the top of the producer 65, containing coke. Water gas is generated, and passes through a bottom connection 93 to the producer 64, containing fresh coal. Gas is distilled from the coal, and passes off with the other gas by the pipe 83 to the valve 75, and thence by the tube 79 to the regenerator 60, where the gas is fixed. From this stove, the gas passes to the economizer 69, generating steam therein and becoming itself cooled. The gas is then drawn through the fan 71, some of it being withdrawn from circulation through the tube 92, while the remainder is sent on to the economizer 70. When the stove 61 has become too cool, the stove 60 is cut out and the stove 63 is introduced, the circulation being then through the tube 90, stove 63, pipe 82, valve 75, producer 64 (which has now become full of coke), producer 65 (which is now being fed with fresh coal), stove 61, economizer 70, and valve 68. When the stove 63 has cooled down, the stove 61 is cut out, and the stove 62 is brought into the circuit, and so on. The producers are fed with fuel by the device shown in Fig. 14, consisting of a hopper 116, having a lid 117 closed with clamps 118, 119. The hopper is mounted so as to slide over a table 125 by means of levers 72. When it is desired to feed fuel, the hopper is forced over the opening 120, which is arranged above the opening 121 in the dome of the producer. When making bituminous gas, carbonic acid from limestone, or water gas from materials, such as garbage, containing sufficient moisture, the introduction of water is unnecessary, the apparatus being correspondingly simplified.