Steam generation system

Abstract

There is provided an efficient steam generation system capable of reducing a temperature difference in heat to be drawn by a heat pump. A first heat pump ( 2 ) includes a first evaporator ( 7 ) and a second evaporator ( 8 ). A second heat pump ( 3 ) is connected to the first heat pump ( 2 ) via an uppermost condenser ( 10 ) serving as the first evaporator ( 7 ). A heat source fluid is passed through a second evaporator ( 8 ) of the first heat pump ( 2 ) and an evaporator ( 12 ) of the second heat pump ( 3 ) in sequence. Then, steam is generated by application of heat to water in a condenser ( 5 ) of the first heat pump ( 2 ).

1 . A steam generation system comprising:
 a single-stage or multiple-stage first heat pump in which at least the lowermost heat pump includes a first evaporator and a second evaporator; and   a single-stage or multiple-stage second heat pump connected to the first heat pump via a condenser of the uppermost heat pump, the condenser serving as the first evaporator of the lowermost heat pump, wherein   a heat source fluid is passed through the second evaporator of the first heat pump and an evaporator of the lowermost heat pump in the second heat pump in sequence, and   steam is generated by application of heat to water in a condenser of the uppermost heat pump in the first heat pump.   
     
     
         2 . The steam generation system of  claim 1 , wherein
 the second heat pump is a single-stage heat pump,   heat is drawn from the heat source fluid passed through the second evaporator of the first heat pump and the evaporator of the lowermost heat pump in the second heat pump in sequence, and   steam is generated by application of the heat to water in the condenser of the uppermost heat pump in the first heat pump.   
     
     
         3 . The steam generation system of  claim 1 , wherein
 the first heat pump is a multiple-stage heat pump in which some of or all of the heat pumps each include the first evaporator and the second evaporator as an evaporator,   each of the first evaporators connects between the vertically adjoining heat pumps, and   the heat source fluid is passed through the respective second evaporators in sequence from the upper heat pump toward the tower heat pump.   
     
     
         4 . The steam generation system of  claim 3 , wherein
 the heat pumps in the multiple-stage first heat pump each include the first evaporator and the second evaporator as an evaporator.   
     
     
         5 . The steam generation system of  claim 1 , wherein
 in the heat pump including the first and second evaporators in the single-stage or multiple-stage first heat pump, the first evaporator and the second evaporator are provided in series or in parallel on a refrigerant channel from an expansion valve to a compressor, or a first expansion valve and the first evaporator are provided in parallel with a second expansion valve and the second evaporator on a refrigerant channel from a condenser to a compressor.   
     
     
         6 . The steam generation system of  claim 1 , wherein
 the first heat pump and the second heat pump are connected in accordance with one of the following relations (a) to (c):   (a) an indirect heat exchanger is provided for receiving a refrigerant from a compressor of the second heat pump and a refrigerant from an expansion valve of the first heat pump to perform heat exchange without mixing both the refrigerants, and serves as the condenser of the second heat pump and the first evaporator of the first heat pump;   (b) an intermediate cooler is provided for receiving a refrigerant from a compressor of the second heat pump and a refrigerant from an expansion valve of the first heat pump to perform heat exchange by bringing both the refrigerants into direct contact with each other, and serves as the condenser of the second heat pump and the first evaporator of the first heat pump; and   (c) an intermediate cooler is provided for receiving a refrigerant from a compressor of the second heat pump and a refrigerant from an expansion valve of the first heat pump to perform heat exchange by bringing both the refrigerants into direct contact with each other and also to perform heat exchange without mixing both the refrigerants with a refrigerant to be supplied from the condenser of the first heat pump to the expansion valve of the second heat pump without being passed through the expansion valve, and serves as the condenser of the second heat pump and the first evaporator of the first heat pump.   
     
     
         7 . The steam generation system of  claim 1 , wherein
 when the first heat pump and/or the second heat pump are/is a multiple-stage heat pump, the adjoining heat pumps are connected in accordance with one of the following relations (a) to (c):   (a) an indirect heat exchanger is provided for receiving a refrigerant from a compressor of the lower heat pump and a refrigerant from an expansion valve of the upper heat pump to perform heat exchange without mixing both the refrigerants, and serves as a condenser of the lower heat pump and an evaporator of the upper heat pump;   (b) an intermediate cooler is provided for receiving a refrigerant from a compressor of the lower heat pump and a refrigerant from an expansion valve of the upper heat pump to perform heat exchange by bringing both the refrigerants into direct contact with each other, and serves as the condenser of the lower heat pump and the evaporator of the upper heat pump; and   (c) an intermediate cooler is provided for receiving a refrigerant from a compressor of the lower heat pump and a refrigerant from an expansion valve of the upper heat pump to perform heat exchange by bringing both the refrigerants into direct contact with each other and also to perform heat exchange without mixing both the refrigerants with a refrigerant to be supplied from the condenser of the upper heat pump to the expansion valve of the lower heat pump without being passed through the expansion valve, and serves as the condenser of the lower heat pump and the evaporator of the upper heat pump.   
     
     
         8 . The steam generation system of  claim 6 , wherein
 when the first heat pump and the second heat pump are connected in accordance with the relation (b) in  claim 6 , the refrigerant from the compressor of the second heat pump is supplied to a refrigerant channel from the intermediate cooler to the compressor, in place of or in addition to the supply to the intermediate cooler.   
     
     
         9 . The steam generation system of  claim 6 , wherein
 when the first heat pump and the second heat pump are connected in accordance with the relation (c) in  claim 6 , the refrigerant from the compressor of the second heat pump is supplied to a refrigerant channel from the intermediate cooler to the compressor in the first heat pump, or a refrigerant channel from the expansion valve to the intermediate cooler or compressor, in place of or in addition to the supply to the intermediate cooler.   
     
     
         10 . The steam generation system of  claim 6 , further comprising:
 a separator for separating the refrigerant from the expansion valve of the first heat pump into a vapor phase and a liquid phase when the first heat pump and the second heat pump are connected in accordance with the relation (c) in  claim 6 , wherein   the vapor-phase refrigerant separated by the separator is supplied to a refrigerant channel from the second evaporator to the compressor.   
     
     
         11 . The steam generation system of  claim 1 , further comprising at least one of:
 (a) a first sub-heat exchanger for performing heat exchange between the water and the refrigerant from the condenser to the expansion valve in the uppermost heat pump of the first heat pump;   (b) a second sub-heat exchanger for performing heat exchange between the heat source fluid and the refrigerant from the evaporator to the compressor in the lowermost heat pump of the second heat pump;   (c) a third sub-heat exchanger for performing heat exchange between the refrigerant from the expansion valve to the compressor in the lowermost heat pump of the first heat pump and the refrigerant from the compressor to the first evaporator in the second heat pump, in a case where the first evaporator is an indirect heat exchanger; and   (d) a fourth sub-heat exchanger for performing heat exchange between the heat source fluid and the refrigerant from the expansion valve to the compressor in the lowermost heat pump of the first heat pump, wherein   with regard to order of distribution of the water and steam to the condenser of the uppermost heat pump in the first heat pump, and the first sub-heat exchanger in the case where the first sub-heat exchanger is provided, the first sub-heat exchanger is provided on the upstream side in the case where the first sub-heat exchanger is provided,   with regard to order of distribution of the heat source fluid to the second evaporator of the first heat pump, the fourth sub-heat exchanger in the case where the fourth sub-heat exchanger is provided, the evaporator of the lowermost heat pump in the second heat pump, and the second sub-heat exchanger in the case where the second sub-heat exchanger is provided, the evaporator of the lowermost heat pump in the second heat pump is provided on the downstream side, and   with regard to order of distribution of the refrigerant to the first evaporator of the first heat pump, the third sub-heat exchanger in the case where the third sub-heat exchanger is provided, the second evaporator of the first heat pump, and the fourth sub-heat exchanger in the case where the fourth sub-heat exchanger is provided, the first evaporator and the second evaporator are provided on the upstream side of the third sub-heat exchanger and the fourth sub-heat exchanger.   
     
     
         12 . The steam generation system of  claim 1 , wherein
 the heat source fluid is a drain from a steam-utilizing facility.