A steam supply system and a method of supplying steam

Abstract

The present disclosure relates to a steam supply system for supplying steam to a steam process, for example a paper drying system. The steam process has a high pressure condensate return and a low pressure condensate return. The steam supply system has a high pressure flash tank arranged to receive the high pressure condensate return and to generate a flash steam output for the steam process. The steam supply system also includes a low pressure flash tank arranged to receive the low pressure condensate return and generate a flash steam output. The steam supply system also includes a compressor arranged to compress the flash steam output of the low pressure flash tank and to provide the compressed flash steam to the high pressure flash tank.

1 - 31 . (canceled) 
     
     
         32 . A steam supply system for supplying steam to a steam process, for example a paper drying system, the steam process comprising a high pressure condensate return, and a low pressure condensate return, and wherein the steam supply system comprises:
 a high pressure flash tank arranged to receive the high pressure condensate return and to generate a flash steam output for the steam process,   a low pressure flash tank arranged to receive the low pressure condensate return and generate a flash steam output, and   a compressor arranged to compress the flash steam output of the low pressure flash tank and to provide the compressed flash steam to the high pressure flash tank.   
     
     
         33 . The steam supply system of  claim 32 , wherein the high pressure flash tank comprises a condensate output arranged to convey condensate from the high pressure flash tank to the low pressure flash tank. 
     
     
         34 . The steam supply system of  claim 32 , wherein the compressor comprises a plurality of sub-compressors. 
     
     
         35 . The steam supply system of  claim 32 , wherein the compressor is a first compressor, and wherein the steam supply system further comprises a second compressor arranged to compress a flash steam output of the high pressure flash tank. 
     
     
         36 . The steam supply system of  claim 35 , wherein the second compressor comprises a plurality of sub-compressors. 
     
     
         37 . The steam supply system of  claim 35 , wherein a first portion of the flash steam output from the high pressure flash tank is provided to the second compressor and then to the steam process at a first pressure, and wherein a second portion of the flash steam output from the high pressure flash tank is provided to the steam process at a second pressure lower than the first pressure. 
     
     
         38 . The steam supply system of  claim 32 , further comprising a boiler supply arranged to supply boiler steam, and wherein the boiler steam is combined with the flash steam output from the high pressure flash tank. 
     
     
         39 . The steam supply system of  claim 38 , wherein the boiler steam is combined with the flash steam output from the high pressure flash tank at a valve or at a thermo-compressor. 
     
     
         40 . The steam supply system of  claim 32 , further comprising one or more valves arranged to control a suction generated by the or each compressor acting on the low pressure condensate return and optionally also the high pressure condensate return. 
     
     
         41 . The steam supply system of  claim 32 , further comprising a heat pump arranged to recover thermal energy from a waste air stream of the steam process and to raise steam with the recovered thermal energy. 
     
     
         42 . The steam supply system of  claim 41 , wherein the heat pump receives condensate from the low pressure flash tank, boils the condensate to raise steam, and feeds the raised steam into the low pressure flash tank. 
     
     
         43 . The steam supply system of  claim 42 , wherein the heat pump comprises a condenser, an expansion valve, an evaporator, and a compressor, wherein the evaporator is arranged to recover thermal energy from the waste air stream, and wherein the condensate from the low pressure flash tank is circulated through the condenser for evaporation to raise steam. 
     
     
         44 . The steam supply system of  claim 43 , wherein the condenser comprises a welded plate heat exchanger. 
     
     
         45 . The steam supply system of  claim 43 , wherein the heat pump further comprises a water loop comprising the evaporator, a refrigerant circuit comprising the compressor, the condenser, and the expansion valve, and an intermediate heat exchanger through which the water loop passes and the refrigerant circuit pass. 
     
     
         46 . The steam supply system of  claim 32 , further comprising a sub-cooler arranged in the low pressure condensate return upstream of the low pressure flash tank, the sub-cooler being adapted to heat an air stream using heat from the low pressure condensate return. 
     
     
         47 . The steam supply system of  claim 46 , further comprising a bypass line from the low pressure condensate return upstream of the sub-cooler to the low pressure flash tank such that a portion of the low pressure condensate return can bypass the sub-cooler, and further comprising a control valve arranged to control flow of condensate through the bypass line. 
     
     
         48 . The steam supply system of  claim 32 , further comprising a heat exchanger arranged to receive a flash steam output from the high pressure flash tank and to heat air for the steam process. 
     
     
         49 . A method of supplying steam to a steam process, for example a paper drying system, wherein the steam process comprises a low pressure condensate return and a high pressure condensate return, the method comprising:
 flashing the low pressure condensate return at a low pressure flash tank,   flashing the high pressure condensate return at a high pressure flash tank,   compressing a flash steam output of the low pressure flash tank, and   feeding the compressed flash steam to the high pressure flash tank.   
     
     
         50 . The method of  claim 49 , further comprising compressing a flash steam output of the high pressure flash tank. 
     
     
         51 . The method of  claim 49 , comprising providing a first portion of flash steam output of the high pressure flash tank to the steam process as a low pressure steam supply, compressing a second portion of the flash steam output of the high pressure flash tank, and providing the compressed flash steam output to the steam process as a high pressure steam supply. 
     
     
         52 . The method of  claim 49 , further comprising feeding condensate from the high pressure flash tank to the low pressure flash tank. 
     
     
         53 . The method of  claim 49 , further comprising recovering thermal energy from a waste air stream of the steam process and raising steam with the recovered thermal energy. 
     
     
         54 . The method of  claim 53 , comprising using the recovered thermal energy to boil condensate from the low pressure flash tank, and providing the raised steam to the low pressure flash tank.