Extracting and cooling system for large flows of heavy ashes with efficiency increase

Abstract

The present invention relates to a system for extracting and recovering energy for large for large flows of heavy ashes produced by solid fuel boilers, able to decrease the final temperature of the extracted ash without increasing the air flow entering the boiler flue, usually fixed by the boiler designers at a value around 1.5% of the total combustion air. When the air flow needed to the cooling exceeds the maximum quantity allowable in the boiler, the system allows the air and the possible vapour to be sent to the air inletting duct entering the air/fume exchanger on the air side, thanks to a separation of the cooling environments made by the ash itself. The separation of the environments of the cooling system is handled automatically based upon a temperature signal of the ash to the discharge from the system. If the cooling air is not sufficient to cool down the ash, the cooling efficiency can be increased by the addition of nebulised water.

1 . A plant for extracting and cooling heavy ashes with recovery of thermal energy adapted to be used in association with a combustion chamber, in particular for large flows of heavy ashes deriving for example from solid fossil fuel in an energy-producing plant, the plant comprising:
 (a) extraction and transport means for extracting and transporting heavy ashes coming from the combustion chamber;   (b) a cooling system for cooling the heavy ashes, located at said extraction and transport means and adapted to determine a feeding of cooling air at the extraction and transport means, wherein at least part of said cooling air may be introduced into the combustion chamber from the bottom thereof;   (c) pressure insulation means, adapted to determine a separation of atmospheres between a first environment and a second environment of said extraction and transport means, said first environment being connected to the atmosphere of the combustion chamber and said second environment being able to be connected with an air inletting duct to an air/fume exchanger or to an air entrance of the air/fume exchanger;   (d) feeding means for feeding part of the cooling air into the air inletting duct to the air/fume exchanger or into the air entrance of the air/fume exchanger; and   (e) control means adapted to determine activation of said pressure insulation of environments depending upon ash temperature and/or flow.   
     
     
         2 . The plant according to  claim 1 , wherein said cooling system is a twofold, air-water cooling system, and wherein said control means is adapted to determine activation of the water cooling depending upon the ash temperature and/or flow. 
     
     
         3 . The plant according to  claim 1 , wherein, under said condition of pressure separation of environments, said cooling system is adapted to determine a feeding of cooling air in countercurrent with the flow of heavy ashes in said first environment and in equicurrent with such flow in said second environment. 
     
     
         4 . The plant according to  claim 1 , wherein said control means comprises sensors of temperature and/or flow of the heavy ashes, located at said extraction and transport means and/or at the pressure insulation area. 
     
     
         5 . The plant according to  claim 4 , wherein said sensors of temperature and/or flow of the heavy ashes are arranged at an ending tract of said extraction and transport means. 
     
     
         6 . The plant according to  claim 5 , wherein said temperature and/or flow sensors are located at the discharge of the heavy ashes. 
     
     
         7 . The plant according to  claim 1 , wherein said control means comprises load sensors arranged at the pressure insulation area. 
     
     
         8 . The plant according to  claim 1 , wherein said control means is adapted to determine said separation of environments so that cooling air flow, entering the combustion chamber from the bottom, does not exceed a predetermined amount of the total combustion air, preferably equal to about 1.0-1.5%. 
     
     
         9 . The plant according to  claim 1 , wherein said feeding means is adapted to connect the air inletting duct to said second environment, substantially downstream of the cooling process. 
     
     
         10 . The plant according to  claim 1 , wherein said feeding means outflow into the air inletting duct upstream of a fan for increasing air head. 
     
     
         11 . The plant according to  claim 10 , wherein said feeding means outflow into the air inletting duct upstream of a secondary air fan. 
     
     
         12 . The plant according to  claim 1 , further comprising regulating means for regulating flow of air introduced into the air inletting duct from said feeding means, arranged at said air feeding means. 
     
     
         13 . The plant according to  claim 1 , wherein said pressure insulation means comprises means for interdicting or enabling said feeding means, controlled by said control means in order to determine said environment separation when needed. 
     
     
         14 . The plant according to  claim 1 , wherein said control means comprises one or more temperature sensors arranged at said feeding means. 
     
     
         15 . The plant according to  claim 1 , wherein said extraction and transport means comprises a first extraction unit arranged or adapted to be arranged immediately downstream of the combustion chamber and a second transport unit arranged downstream of said first extraction unit, and wherein said pressure insulation means ( 8 ) is adapted to produce a pressure separation between said first extraction unit and second transport unit. 
     
     
         16 . The plant according to  claim 15 , wherein said control means is adapted to control velocity of at least one of said units. 
     
     
         17 . The plant according to  claim 1 , wherein said pressure insulation means comprises means adapted to create a head of heavy ashes between said two environments, adapted to determine said pressure separation thereof. 
     
     
         18 . The plant according to  claim 17 , wherein said pressure insulation means comprises a storage reservoir means adapted to receive heavy ashes creating said head. 
     
     
         19 . The plant according to  claim 18 , wherein said pressure insulation means comprises a hopper adapted to receive heavy ashes creating said head. 
     
     
         20 . The plant according to  claim 17 , wherein said control means comprises one or more level sensors arranged at said head. 
     
     
         21 . The plant according to  claim 1 , further comprising mixing means for mixing heavy ashes, arranged at the exhaust of the ashes and adapted to complete a cooling process thereof, and feeding means for feeding cooling air and possible steam from said mixing means to said feeding means. 
     
     
         22 . A method for extracting and cooling heavy ashes coming from a combustion chamber, in particular for large flows of heavy ashes deriving for example from fossil fuel in an energy-producing plant, the method comprising:
 (a) extracting the heavy ashes from the combustion chamber;   (b) cooling such heavy ashes along an extraction and transport path by feeding cooling air along the extraction and transport path, introducing, downstream of the cooling process, at least part of said cooling air into the combustion chamber from the bottom thereof;   (c) depending upon temperature and/or flow of the heavy ashes, activating selectively a pressure insulation between a first and a second environment arranged along said extraction and transport path, said first environment being arranged immediately downstream of the combustion chamber and said second environment being arranged downstream of said first environment and adapted to be connected to an air inletting duct in an air/fume exchanger or to an air entrance of the air/fume exchanger; and   (d) depending upon the temperature and/or flow of the heavy ashes, feeding part of the cooling air into the air inletting duct in the air/fume exchanger or into the air entrance of the air/fume exchanger.   
     
     
         23 . The method according to  claim 22 , wherein said cooling is of a twofold, air-water type and provides activation of water cooling depending upon the temperature and/or quantity of the heavy ashes. 
     
     
         24 . The method according to  claim 22 , wherein said phase provides activation of water cooling at said second environment. 
     
     
         25 . The method according to  claim 22 , wherein said cooling provides, under said condition of pressure separation of environments, a feeding of cooling air in countercurrent with the flow of heavy ashes in said first environment and in equicurrent with such flow in said second environment. 
     
     
         26 . The method according to  claim 22 , further comprising providing detection of the temperature and/or flow of the heavy ashes carried out at said extraction and transport path and/or at the pressure insulation area. 
     
     
         27 . The method according to  claim 26 , wherein said providing detection of temperature and/or flow of the heavy ashes is carried out at an ending tract of said extraction and transport path. 
     
     
         28 . The method according to  claim 27 , wherein said providing detection of temperature and/or flow is performed at the exhaust of the heavy ashes. 
     
     
         29 . The method according to  claim 22 , further comprising providing a load detection carried out at the pressure insulation area. 
     
     
         30 . The method according to  claim 22 , wherein said activating provides that said environment separation be carried out so that cooling air-flow cooling air entering the combustion chamber from the bottom of the combustion chamber does not exceed a predetermined amount of the total combustion air, preferably equal to about 1.0-1.5%. 
     
     
         31 . The method according to  claim 22 , wherein said feeding into the air inletting duct in the air/fume exchanger takes place starting from said second environment, substantially downstream of the cooling process. 
     
     
         32 . The method according to  claim 22 , wherein said feeding into the air inletting duct in the air/fume exchanger provides an outflow in said duct upstream of a fan for increasing air head. 
     
     
         33 . The method according to  claim 32 , wherein said feeding into the air inletting duct in the air/fume exchanger provides an outflow into said air inlettinq duct upstream of a secondary air fan. 
     
     
         34 . The method according to  claim 22  further comprising providing a regulation of the air flow fed into the air inletting duct in the air/fume exchanger or in the air entrance of the air/fume exchanger. 
     
     
         35 . The method according to  claim 22 , wherein said activating provides that said pressure insulation be obtained by means of the interdiction or enabling of said feeding of cooling air into the air inletting duct in the air/fume exchanger or in the air entrance of the air/fume exchanger. 
     
     
         36 . The method according to  claim 22 , further comprising providing a temperature detection performed at feeding means adapted to implement said feeding into the air inletting duct in the air/fume exchanger or in the air entrance of the air/fume exchanger. 
     
     
         37 . The method according to  claim 22 , wherein said extraction and transport path comprises a first extraction portion arranged immediately downstream of the combustion chamber and a second transport portion arranged downstream of said first portion and wherein said activating provides that said pressure insulation be obtained between said first extraction portion and second transport portion. 
     
     
         38 . The method according to  claim 36 , wherein said activating provides control of the extraction and/or transport velocity of the ashes along said path. 
     
     
         39 . The method according to  claim 22 , wherein said activating provides creation of a head of heavy ashes between said two environments, wherein the head is adapted to determine said pressure separation thereof. 
     
     
         40 . The method according to  claim 39 , wherein said activating provides level detection of said head. 
     
     
         41 . The method according to  claim 22 , further comprising providing a mixing of the heavy ashes, performed at their discharge and adapted to complete the cooling process thereof, and a feeding of cooling air and of possible steam employed or produced by said mixing in said air inletting duct.