GB618231A - Improvements in hot air power plant - Google Patents

Abstract

618,231. Elastic-fluid turbines. NETTEL, F., and KREITNER, J. July 8, 1945, No. 14610. '[Class 110 (iii)] [Also in Group XXVII] In a hot-air plant a continuous stream of air is compressed, preheated in a heat exchanger by surface heat transfer of waste heat in the same stream after its expansion, heated further by surface heat transfer of heat released in an external fuel combustion effected at substantially atmospheric pressure, expanded in an engine to substantially atmospheric pressure and cooled while carrying out the preheating, and a portion of the expanded and cooled air is ejected to the atmosphere while another portion of the expanded and cooled air is branched off at a point where by cooling it has reached a predetermined temperature and utilized as compressed air for the external fuel combustion the resultant combustion gases being cooled by transferring heat from them to the stream of compressed air while carrying out the heat transfer of heat released in the external fuel combustion. Fuel mav be injected into the air and burned, the resulting mixture of air and combustion products being supplied to the turbine. The expanded air from the turbine can be supplied to the heater as combustion air either before or after it has passed through the heat exchanger or it may be supplied from part of the way along the heat exchanger. As shown, a compressor 12, 14 with intercooler, compresses air in two stages and supplies it through a heat exchanger 15, to a heater 17 from which it passes to a turbine 20 which drives the compressor and an electric generator 21. Exhaust from the turbine passes back to the heat supply section of the heat exchanger. Combustion air for the furnace of the heater is drawn from this air. Hot air direct from the turbine 20 is branched off to a pulverised fuel nozzle 63 and to ducts 61 in the furnace, the supply being controlled by butterfly valves 61<1>, 62<1>. Cooler air branched off from part of the way along the heat exchanger can be supplied to the bottom of the furnace through valves 54, 56 or alternatively still cooler air from the outlet of the heat exchanger can be used. By means of valves 57<1>, 59<1> either this cooler air or hot air direct from the turbine can be used to transfer the pulverised fuel from a pulverised fuel mill 58 to the nozzle. Combustion products from the heater 17 are also passed through the heat exchanger which is divided into two portions by a partition 15a. The products are exhausted to atmosphere by a forced draught fan 29. It is not essential that the hotter air shall be supplied to the heater as all the air can be drawn from the outlet of the heat exchanger. The air not used for supply to the heater is either exhausted to atmosphere or utilised for room heating, fuel drying, water distillation or other purposes. Arrangements of plant are described in which the exhaust from the turbine is reheated and supplied to a further turbine before passing to the heat exchanger. A byepass may be provided to enable this turbine to be cut out of action. In Fig. 5 (not shown), air is supplied direct from the turbine to a point beneath the front of a travelling grate of the furnace and cooler air supplied at two further points beneath the grate at the centre of the furnace. A fan may be used to draw air from the heat exchanger and supply it to the grate. The temperature at which the air is supplied to the heaters is selected according to the type of furnace used and the condition of the fuel &c.