Method and circuit arrangement for recovering heat from wastewaters

Abstract

The invention relates to a method and circuit arrangement for recovering heat from wastewaters, comprising—a wastewater circuit having a sewage intake shaft ( 4 ) connected to a common sewer ( 1 ) through a raw sewage line ( 2 ), and at least one heat exchanger ( 7 ) connected to the sewage intake shaft ( 4, —a primary circuit having at least one heat pump ( 8 ), and—a secondary circuit comprising at least one storage tank ( 9 ) and at least one heat utiliser, where the wastewater circuit, the primary circuit, and the secondary circuit are arranged to be in heat-transfer connection, and,—where the sewage is fed to one side of the wastewater circuit heat exchanger ( 2 ) and the working medium of the heat pump ( 9 ) of the primary circuit is fed to the other side of the same heat exchanger ( 9 ), with the working medium of the heat pump ( 8 ) being fed in a storage tank ( 9 ) and the storage tank ( 9 ) is connected to a heat utiliser. The invention is essentially characterised by that the wastewater circuit is spatially separated from the primary circuit and the secondary circuit, and that a screening case ( 5 ) is arranged in the sewage intake shaft ( 4 ) of the wastewater circuit, where a raw sewage line ( 2 ) connecting the common sewer ( 1 ) with the sewage intake shaft ( 4 ) is terminated in the screening case ( 5 ), and where one end of a coarse material remover ( 6 ) extends into the screening case ( 5 ), with the other end of the coarse material remover ( 6 ) being connected to a utilised sewage return line ( 3 ) that connects the sewage intake shaft ( 4 ) and the common sewer ( 1 ), and also that screened sewage is fed from the sewage intake shaft ( 4 ) to one side of the heat exchanger ( 7 ), with utilised sewage leaving the heat exchanger ( 7 ) being fed in the utilised sewage return line ( 3 ) such that it washes the coarse material removed by the coarse material remover ( 6 ) back to the utilised sewage return line ( 3 ).

1 . A method for recovering heat from wastewaters in a wastewater circuit, primary circuit and secondary circuit arranged in heat transfer connection, comprising the steps of
 in the wastewater circuit, feeding through a raw sewage line at least a portion of raw sewage transported in a common sewer to a screening case disposed in a sewage intake shaft, with a portion of the solids content of the sewage being captured and removed in the screening case, feeding the screened sewage to a first side of a heat exchanger, and subsequently, after heat is recovered from it, feeding the utilised sewage to a utilised sewage. return line such that it washes back the previously removed coarse material to the common sewer,   in the primary circuit, feeding the working medium circulated in the other side of the heat exchanger to the evaporator or the compressor of a heat pump, depending on whether a cooling or heating operating mode is chosen, and   feeding the heat-carrying working medium circulated in the heat pump to the storage tank of the secondary circuit, and subsequently from the storage tank to at least one heat utiliser.   
     
     
         2 . The method according to  claim 1 , wherein the utilised sewage is reintroduced to the common sewer downstream of the raw sewage intake at such a distance that the utilised sewage does not substantially alter the temperature of the raw sewage. 
     
     
         3 . A circuit arrangement for recovering heat from wastewaters, comprising
 a wastewater circuit having a sewage intake shaft connected to a common sewer through a raw sewage line, and at least one heat exchanger connected to the sewage intake shaft,   a primary circuit having at least one heat pump, and   a secondary circuit comprising at least one storage tank and at least one heat utiliser, where the wastewater circuit, the primary circuit, and the secondary circuit are arranged to be in heat-transfer connection, and   where the sewage is fed to one side of the wastewater circuit heat exchanger and the working medium of the heat pump of the primary circuit is fed to the other side of the same heat exchanger, and   the heat-carrying working medium of the heat pump is fed to the storage tank of the secondary circuit with the storage tank being connected to at least one heat utiliser,   
       wherein
 the wastewater circuit is spatially separated from the primary circuit and the secondary circuit, and 
 a screening case is arranged in the sewage intake shaft of the wastewater circuit, where a raw sewage line connecting the common sewer with the sewage intake shaft is terminated in the screening case, and where one end of a coarse material remover extends into the screening case, with the other end of the coarse material remover being connected to a utilised sewage return line that connects the sewage intake shaft and the common sewer, and 
 screened sewage is fed from the sewage intake shaft to one side of the heat exchanger, with utilised sewage leaving the heat exchanger being fed in the utilised sewage return line such that it washes the coarse material removed by the coarse material remover back to the utilised sewage return line. 
 
     
     
         4 . The circuit arrangement according to  claim 3 , wherein the screening case is implemented as a basket having perforated walls and bottom, with one end of the coarse material remover implemented as a vertical-axis screw extending in the basket. 
     
     
         5 . The circuit arrangement according to  claim 3 , wherein three heat exchangers are arranged in parallel connection in the wastewater circuit. 
     
     
         6 . The circuit arrangement according to  claim 5 , wherein the heat exchangers are shell-and-tube heat exchangers. 
     
     
         7 . The circuit arrangement according to  claim 3 , wherein two heat pumps are arranged in series connection in the primary circuit. 
     
     
         8 . The circuit arrangement according to  claim 3 , wherein two storage tanks are arranged in the secondary circuit such that they are connected through divider-collector means to a heating and cooling circuit functioning as heat utiliser.