GB695339A - Improvements relating to plants for producing a supply of compressed air - Google Patents

Abstract

695,339. Gas turbine plant; centrifugal compressors. SULZER FRERES SOC. ANON. Oct. 1, 1951 [Oct. 28, 1950]. No. 22798/51. Classes 110(i) and 110(iii) A plant for supplying air to an outside consumer having a pressure air compressor driven by a turbine of a gas turbine plant including a combustion chamber and a compressor of approximately the same pressure ratio as the pressure air compressor, has an external motor connected through a clutch to the compressor of the gas turbine plant, means for connecting the inlet of this compressor to the atmosphere or to the discharge of the pressure air compressor, and means for connecting the outlet of this compressor to the combustion chamber or the outside consumer, the arrangement being such that with the gas turbine plant out of operation, the compressor of the gas turbine plant may be driven by the motor to supply air to the consumer. In the plant shown, air is compressed in a pressure air compressor 1 and discharged in part to a consumer A e.g. a blast furnace or a steel converter, and in part through an intercooler 5 to a compressor 7 of a gas turbine plant. The air after further compression in the compressor 7 is heated in an exhaust gas heat exchanger 9 before being applied to a combustion chamber 11. Combustible gas, e.g. blast furnace gas, is supplied to the combustion chamber 11 by the compressor 13. The hot combustion gases pass to a gas turbine 15 which drives the compressor 1 direct and the compressors 7, 13 through gearing 19, 20, 22. The compressor 7 may be driven through gearing 24, 25 and a releasable coupling 26 by an electric motor 23. The plant is started by the electric motor 23. If for any reason the gas turbine plant is out of use, the coupling 26 may be engaged and the compressor 7 used to supply air to the consumer A. For this purpose, the valves 32, 33 are opened, the valves 29, 30 and 31 closed and the coupling 21 disengaged. During normal operation the coupling 26 may be left engaged and the motor 23 used to make up a deficiency in driving power of the turbine 15 or take off the surplus power of this turbine. The compressor 7 may be of the axialflow type but is preferably of the multi-stage centrifugal type since this latter type of compressor has a flat delivery pressure mass flow characteristic which gives a considerable change in the air flow to the consumer A for a given change in the turbine inlet temperature. The rotor blades of the centrifugal compressor are arranged so that the angle between a plane tangential to the blade flank at the outlet and a plane tangential to the periphery of the rotor at this point and parallel to the axis of the rotor is between 70‹ and 110‹. In a modification, the turbine 15 is divided into two stages, arranged in series, the high pressure stage drives the compressor 7 and the low pressure stage the compressor 1. With this arrangement a by-pass pipe with a regulating valve may be arranged between the inlets of the turbines to increase the range of control of the air supply to the consumer A. A reheat combustion chamber may be arranged between the two turbines. The regulation may be controlled by the demands of the consumer A. The output of the plant may be determined by adjustment of the valve 30 or by means of adjustable inlet guide blades for the compressor 7.