5235. Naef, P. March 12. Gas-producers; chemical and metallurgical fur. naces.-Relates to the treatment of bituminous fuel with the object of obtaining a gas free from tar with the simultaneous production of ammonia in a small volume of the gas. The invention may be adapted to furnaces for calcining and smelting, the fuel and other material being mixed. The gasproducing operation is divided into two stages, in the first of which gas is simply distilled from bituminous fuel, the fuel or the gas being heated in a variety of ways to fix the gas without destroying the ammonia, during which process water, in a liquid or gaseous state, may be introduced, while in the second stage the fuel is entirely consumed, and the gas liberated, which is practically free from ammonia, is led off separately. The plant is one of large capacity. Various forms of apparatus may be employed. In Fig. 1 is shown one form of the upper part of a shaft furnace, into which fuel is introduced by the conveyer 9 and tube 8. The gas generated in the lower part of the producer is mostly led off separately, but a portion of it may be carried by a tube 5 to a tubular heater 1; or the latter may be heated by gas from a firebox 6. The tar vapour present in the gases in the upper part of the shaft is decomposed by the heat, and a permanent gas passes away through the outlet 4. In the apparatus shown in Fig. 14, the fuel is first distilled in a rotary inclined cylinder o<9>, and then passes through a pipe o<8> to a generator o<1> The latter is provided with mechanically-moved bars o<2>, a blast inlet o<4>, steam or water inlet o<5>, discharge rollers o<6>, and a gas outlet o<7>. Some of the hot gases pass up the tube o<8> to the cylinder to distil the fuel. Water or other liquid may be sprayed into the cylinder at o<12>. Gas containing ammonia and other bye-products leaves through the outlet o<11>. Among the other modifications described are the following :-The fuel in the first stage may be agitated by rods or the like, gas from the second stage may be led to the first by internal or external pipes, the gas may pass downwards, upwards, or both downwards and upwards in the upper portion of the shaft towards the outlet, oil may be admitted to enrich the gas, the internal gas tubes may be cooled by a water jacket or by a coil, the shaft may be built in sections each having a smaller diameter than the one below, and the small quantity of gas containing the ammonia given off in the first stage may be heated outside the apparatus to convert the tar vapour into a permanent gas. Reference is made to the Specifications of the following patents, which contain descriptions of apparatus also suitable for this process :-Nos. 2888, 2888A, 2888B, 2888c, 2888D, 2888E, 2888F, 2917, 2917A, 2917B, 2917C, 2917D, and 6563, A.D. 1900.