Sludge heat exchanger

Abstract

A heat exchanger for transferring heat energy from a heated liquid at a first temperature to sludge at a second temperature. The heat exchanger includes a first conduit for receiving a stream of sludge which houses a plurality of mixing elements. The mixing elements are characterized as having no edges perpendicular to the longitudinal axis of the conduit and are sized and positioned within the conduit such that at any plane passing perpendicularly to the longitudinal axis at least 75% of the circumference of the conduit being free of any mixing elements and no mixing elements are in contact with one another resulting in an open region of travel for sludge passing through the conduit.

1 . A heat exchanger for transferring heat energy from a heated liquid at a first temperature to sludge at a second temperature, said heat exchanger comprising a first conduit for receiving a stream of sludge, said first conduit having a length, substantially circular circumference, a longitudinal axis through said length and being open at both ends thereof, said first conduit housing a plurality of mixing elements, said mixing elements having no edges perpendicular to said longitudinal axis and are sized and positioned within said conduit such that at any plane passing perpendicularly to said longitudinal axis, at least 75% of the circumference of said conduit is free of any mixing elements and no mixing elements are in contact with one another resulting in an open region of travel for sludge passing through said first conduit along its longitudinal axis and a second conduit in the form of a sleeve having a longitudinal axis substantially coincident with the longitudinal axis of said first conduit and defining an annular space open at both ends for receiving and discharging said heated liquid. 
     
     
         2 . The heat exchanger of  claim 1  wherein said mixing elements are provided in said first conduit in complementary pairs, wherein adjacent mixing elements cause fluid passing within said first conduit to rotate in opposite directions. 
     
     
         3 . The heat exchanger of  claim 1  wherein each mixing element located within said first conduit is seated at an angle between approximately 30° to 45° to its longitudinal axis. 
     
     
         4 . The heat exchanger of  claim 1  wherein said mixing elements are in the form of primarily circular segments wherein each mixing element is characterized as being widest in profile at its midpoint and narrowest at its longitudinal end points. 
     
     
         5 . The heat exchanger of  claim 4  wherein each mixing element is of a height equal to approximately D/10 and a radius of approximately D/2 wherein D is the diameter of said first conduit. 
     
     
         6 . The heat exchanger of  claim 1  wherein said mixing elements are sized and positioned within said first conduit such that such first conduit is capable of passing therethrough solid matter contained within said sludge having a diameter of at least 75% of the diameter of said first conduit. 
     
     
         7 . The heat exchanger of  claim 1  wherein said heated liquid is water. 
     
     
         8 . The heat exchanger of  claim 2  wherein a plurality of mixing elements are located in said annular space. 
     
     
         9 . A heat exchanger for transferring heat energy from a heated liquid to sludge, said heat exchanger comprising a plurality of inner conduits for receiving a stream of sludge, said plurality of inner conduits each having a length, substantially circular circumference, longitudinal axis through said length and each being connected to one another to provide a continuous path for said sludge whereby an entry is provided in an upstream most first inner conduit for said sludge and an exist is provided for said sludge in a downstream most inner conduit, each such inner conduit housing a plurality of mixing elements having no edges perpendicular to said longitudinal axis and are sized and positioned within each said inner conduit such that at any plane passing perpendicularly to said longitudinal axis, at least 75% of the circumference of said inner conduit is free of any mixing element and no mixing elements are in contact with one another resulting in an open region of travel for sludge passing through each of said inner conduits along its longitudinal axis and a plurality of outer conduits in the form of interconnected sleeves each having a longitudinal axis substantially coincident with the longitudinal axis of the inner conduit to which it surrounds thus defining a continuous annular space open at both ends for receiving and discharging said heated liquid. 
     
     
         10 . The heat exchanger of  claim 9  wherein said mixing elements are provided in said first conduit in complementary pairs, wherein adjacent mixing elements cause fluid passing within said first conduit to rotate in opposite directions. 
     
     
         11 . The heat exchanger of  claim 9  wherein each mixing element located within said first conduit is seated at an angle between approximately 30° to 45° to its longitudinal axis. 
     
     
         12 . The heat exchanger of  claim 9  wherein said mixing elements are primarily in the form of circular segments wherein each mixing element is characterized as being widest in profile at its midpoint and narrowest at its longitudinal end points. 
     
     
         13 . The heat exchanger of  claim 12  wherein each mixing element is of a height equal to approximately D/10 and a radius of approximately D/2 wherein D is the diameter of said first conduit. 
     
     
         14 . The heat exchanger of  claim 12  wherein said mixing elements are sized and positioned within said first conduit such that said first conduit is capable of passing therethrough solid matter contained within said sludge having a diameter of at least 75% of the diameter of said first conduit. 
     
     
         15 . The heat exchanger of  claim 9  wherein said heated liquid is water. 
     
     
         16 . The heat exchanger of  claim 9  wherein plurality of mixing elements are located in said annular space.