Method and system for cleaning of and heat recovery from hot gases

Abstract

Exhaust gas, produced in a thermal reactor ( 1 ) that is fed with solid fuel can be cooled and in a gas cooler ( 4 ) which produce a condensate that is further cooled in a condensate cooler ( 7 ) which produce energy. By using air moisturizing and particle separation technology the exhaust gas and the excess condensate can be clean and the energy efficiency of the plant can be increased. The method can be used for a broad spectrum of fuels and conversion technologies.

1 . A thermal plant comprising
 a thermal reactor in which a chemical process takes place during which process solid fuels reacts with oxygen to produce an exhaust gas comprising hot flue gas and/or a burnable gas
 a gas cooler cooling the exhaust gas to a temperature below the dew point of the water present in the exhaust gas thereby producing a condensate; 
 an exhaust gas heat exchanger arranged upstream of the gas cooler for extracting heat from the exhaust gas, 
 a condensate cooler cooling the condensate to extract energy from the condensate 
 wherein the thermal plant further comprises a particle separation system for separating particles from a stream of particles, said particles being produced in a thermal reactor, the stream of particles is the water condensate produced from the exhaust gas from the thermal reactor, the particle separation system being adapted to produce 
 a first stream of water having a first content of particles, the first stream is produced continuously or batch-wise, 
 a second stream of water having a second content of particles, wherein 
 the ratio between the second stream of water and the first stream of water when measured in m3/h is larger than 5, 
 the content (kg/m3) of particles in the first stream is larger than the content (kg/m3) of particles in the second stream of water, 
 the condensate cooler being arranged to cool the condensate of the second stream of water 
   and, wherein the plant further comprises:
 a feeding means provided for feeding at least fraction of the first stream of water to ash produced in a thermal reactor, to a fuel for a thermal reactor, to a filter and/or to a disposal output. 
   
     
     
         2 - 23 . (canceled) 
     
     
         24 . The thermal plant according to  claim 1 , wherein the stream of particles is a water condensate produced from the exhaust gas from a thermal reactor and wherein the separation system comprises a hydro cyclone. 
     
     
         25 . The thermal plant according to  claim 1 , further comprising a connection leading at least a fraction of the second stream of water to a moisturizing system moisturizing air used in the thermal reactor of the thermal plant. 
     
     
         26 . The thermal plant according to  claim 1 , wherein 10% or more of the first stream of water is fed to the fuel. 
     
     
         27 . The thermal plant according to  claim 1 , wherein 10% or more of the first stream of water is fed to the ash. 
     
     
         28 . The thermal plant according to  claim 1 , wherein the first stream of water is divided into two streams one being fed to ash and one being fed to fuel. 
     
     
         29 . The thermal plant according to  claim 1 , further comprising a recirculation loop for recirculating the second stream of water produced by the particle separation system back to the particle separation system. 
     
     
         30 . The thermal plant according to  claim 29 , wherein the recirculation loop comprises a filter for filtering out from the second stream of water a third stream of water having a smaller content of particles (kg/m3) than the second stream of water. 
     
     
         31 . The thermal plant according to  claim 29 , wherein the recirculation loop comprises a heat exchanger for cooling the second stream of water. 
     
     
         32 . The thermal plant according to  claim 29 , wherein the recirculation loop comprises a connection for feeding a fraction of the second stream of water to a air moisturizing system for moisturizing air to be used in a thermal reactor. 
     
     
         33 . The thermal plant according to  claim 32 , wherein the connection for feeding a fraction of the second stream of water to an air moisturizing system is arranged downstream of the heat exchanger. 
     
     
         34 . The thermal plant according to  claim 32 , wherein the connection for feeding a fraction of the second stream of water to an air moisturizing system is arranged upstream of the heat exchanger. 
     
     
         35 . A thermal plant comprising:
 a thermal reactor in which a chemical process takes place during which process solid fuels reacts with oxygen to produce an exhaust gas comprising hot flue gas and/or a burnable gas   a gas cooler cooling the exhaust gas to a temperature below the dew point of the water present in the exhaust gas thereby producing a condensate;   a condensate cooler cooling the condensate to extract energy from the condensate   an air moisturizer being adapted to produce a first and a second stream of moisturized air, wherein
 the first stream of moisturised air has a higher absolute water content, measured in kg H2O per m3 dry air, than the water content of the second stream of moisturised air, and 
 the first stream of moisturised air is introduced into a thermal reactor and used in the chemical reactions in the fuel, and 
 the second stream of moisturised air is introduced into a thermal reactor and used in chemical reactions in gasses produced by heating a fuel. 
   
     
     
         36 . The thermal plant according to  claim 35 , wherein the water content in the first stream of moisturized air is at least larger than 50% than the water content in the second stream of moisturized air. 
     
     
         37 . The thermal plant according to  claim 35 , wherein the amount (kg dry air) of the first stream of moisturized air is smaller than the amount (kg dry air) of second stream of moisturized air. 
     
     
         38 . The thermal plant according to  claim 35 , wherein the air moisturizer comprises two air scrubbers. 
     
     
         39 . The thermal plant according to  claim 38 , wherein two air scrubbers are arranged in series; the first stream of moisturized air is a fraction of moisturized air leaving a first air scrubber and the remaining fraction of the moisturized air is feed into a second air scrubber for further moisturization so as to provide the second stream of moisturized air. 
     
     
         40 . The thermal plant according to  claim 38 , wherein two air scrubbers are arranged in parallel receiving air to be moisturized from the same air source and, wherein the first and second streams of moisturized air each are produced by one air scrubber only. 
     
     
         41 . The thermal plant according to  claim 35 , wherein the air moisturizer is arranged to cool gas produced in a thermal reactor by utilizing at least the second stream of moisturized air. 
     
     
         42 . The thermal plant according  claim 35 , wherein the thermal plant comprises:
 a thermal reactor in which a chemical process takes place during which process solid fuels reacts with oxygen to produce an exhaust gas comprising hot flue gas and/or a burnable gas   a gas cooler cooling the exhaust gas to a temperature below the dew point of the water present in the exhaust gas thereby producing a condensate;   an exhaust gas heat exchanger arranged upstream of the gas cooler for extracting heat from the exhaust gas,   a condensate cooler cooling the condensate to extract energy from the condensate   wherein the thermal plant further comprises a particle separation system for separating particles from a stream of particles, said particles being produced in a thermal reactor, the stream of particles is the water condensate produced from the exhaust gas from the thermal reactor, the particle separation system being adapted to produce   a first stream of water having a first content of particles, the first stream is produced continuously or batch-wise,   a second stream of water having a second content of particles, wherein   the ratio between the second stream of water and the first stream of water when measured in m3/h is larger than 5,   the content (kg/m3) of particles in the first stream is larger than the content (kg/m3) of particles in the second stream of water,   the condensate cooler being arranged to cool the condensate of the second stream of water   
       and, wherein the plant further comprises:
 a feeding means provided for feeding at least fraction of the first stream of water to ash produced in a thermal reactor, to a fuel for a thermal reactor, to a filter and/or to a disposal output. 
 
     
     
         43 . A thermal plant comprising:
 a thermal reactor in which a chemical process takes place during which process solid fuels reacts with oxygen to produce an exhaust gas comprising a burnable gas   a gasification system for gasification of fuels, the gasification system comprising
 a thermal reactor producing a burnable gas, 
 a gas cooler cooling the produced burnable gas to a temperature below the dew point of the water present in the gas thereby producing a water condensate by condensing water vapor present in the produced burnable gas, 
 a condensate cooler cooling the condensate to extract energy from the condensate, 
 a moisturizing system adapted to 
 moisturize air to be used in the thermal reactor during conversion of fuel into a burnable gas, 
 feeding the moisturized air into the thermal reactor, and, preferably, for cooling the condensate further in relation to the cooling performed by the condensate cooler, 
 and feeding the cooled condensate to the gas cooler. 
   
     
     
         44 . A thermal plant according to  claim 43 , wherein the thermal plant comprises:
 a thermal reactor in which a chemical process takes place during which process solid fuels reacts with oxygen to produce an exhaust gas comprising hot flue gas and/or a burnable gas
 a gas cooler cooling the exhaust gas to a temperature below the dew point of the water present in the exhaust gas thereby producing a condensate; 
 an exhaust gas heat exchanger arranged upstream of the gas cooler for extracting heat from the exhaust gas, 
 a condensate cooler cooling the condensate to extract energy from the condensate 
 wherein the thermal plant further comprises a particle separation system for separating particles from a stream of particles, said particles being produced in a thermal reactor, the stream of particles is the water condensate produced from the exhaust gas from the thermal reactor, the particle separation system being adapted to produce
 a first stream of water having a first content of particles, the first stream is produced continuously or batch-wise, 
 a second stream of water having a second content of particles, wherein 
 the ratio between the second stream of water and the first stream of water when measured in m3/h is larger than 5, 
 the content (kg/m3) of particles in the first stream is larger than the content (kg/m3) of particles in the second stream of water, 
 the condensate cooler being arranged to cool the condensate of the second stream of water 
 
 and, wherein the plant further comprises:
 a feeding means provided for feeding at least fraction of the first stream of water to ash produced in a thermal reactor, to a fuel for a thermal reactor, to a filter and/or to a disposal output, such as a sewer, a chemical treatment facility and/or to the thermal reactor. 
 
   
     
     
         45 . A method for cooling produced gas from a solid fuel gasifier and for moisturizing the air for the gasifier, the gasifier being of a thermal plant comprising:
 a thermal reactor in which a chemical process takes place during which process solid fuels reacts with oxygen to produce an exhaust gas comprising hot flue gas and/or a burnable gas   a gas cooler cooling the exhaust gas to a temperature below the dew point of the water present in the exhaust gas thereby producing a condensate;   an exhaust gas heat exchanger arranged upstream of the gas cooler for extracting heat from the exhaust gas,   a condensate cooler cooling the condensate to extract energy from the condensate   wherein the thermal plant further comprises a particle separation system for separating particles from a stream of particles, said particles being produced in a thermal reactor, the stream of particles is the water condensate produced from the exhaust gas from the thermal reactor, the particle separation system being adapted to produce
 a first stream of water having a first content of particles, the first stream is produced continuously or batch-wise, 
 a second stream of water having a second content of particles, wherein 
 the ratio between the second stream of water and the first stream of water when measured in m3/h is larger than 5, 
 the content (kg/m3) of particles in the first stream is larger than the content (kg/m3) of particles in the second stream of water, 
 the condensate cooler being arranged to cool the condensate of the second stream of water 
   and, wherein the plant further comprises:
 feeding means provided for feeding at least fraction of the first stream of water to ash produced in a thermal reactor, to a fuel for a thermal reactor, to a filter and/or to a disposal output, such as a sewer, a chemical treatment facility and/or to the thermal reactor. 
   
       the method comprising
 feeding gas from the gasifier through a gas cooling system supplied with cold water from the air moisturiser, and 
 feeding the gasification air through an air moisturiser supplied with warm water from a gas cooling system.