Fume treatment system and method

Abstract

A fume treatment system and method for treating a fume stream emitted from the mouth of a furnace chamber of a metal reclamation furnace system during a portion of the reclamation process includes an auxiliary hood that is smaller than the main overhead hood and is movable between an operative position over the furnace chamber mouth within the main overhead hood for collecting the fume stream emitted by the furnace chamber mouth and another position spaced from, the furnace chamber mouth. An incinerator is in fluid communication with the auxiliary hood when in the operative position. A fume stream blower causes the fume stream collected by the auxiliary hood when in the operative position to flow to the incinerator for incinerating hydrocarbons or other combustible compounds present in the fume stream during operation of the incinerator. A cyclone may be in the flow path between the auxiliary hood and the incinerator for removing particulates from the fume stream prior to entering the incinerator. Also a heat exchanger may be downstream of the incinerator for reducing the temperature of the fume stream exiting the incinerator prior to returning the fume stream to the main overhead hood for further processing.

1 . A fume treatment system for treating a fume stream emitted from the mouth of a furnace chamber of a metal reclamation furnace system during a portion of the reclamation process, the furnace system having a main overhead hood located over the furnace chamber mouth, the fume treatment system comprising an auxiliary hood that is smaller than the main overhead hood and is movable between an operative position over the furnace chamber mouth within the main overhead hood for collecting the fume stream emitted by the furnace chamber mouth and another position spaced from the furnace chamber mouth, an incinerator in fluid communication with the auxiliary hood when in the operative position, and a fume stream blower for causing the fume stream collected by the auxiliary hood when in the operative position to flow to the incinerator for incinerating hydrocarbons or other combustible compounds present in the fume stream during operation of the incinerator.  
     
     
         2 . The fume treatment system of  claim 1  wherein the furnace system is a tilting rotary furnace system, and the auxiliary hood is movable to the operative position over the furnace chamber mouth when the furnace chamber is in a tilted back position.  
     
     
         3 . The fume treatment system of  claim 1  wherein the furnace chamber includes a door that is movable between closed and open positions for substantially closing and opening the furnace chamber mouth, the door having a flue through which the fume stream is emitted from the furnace chamber for collection by the auxiliary hood when the door is closed and the auxiliary hood is in the operative position, the auxiliary hood when in the operative position permitting movement of the door between the closed and open positions.  
     
     
         4 . The fume treatment system of  claim 1  further comprising a cyclone in a flow path between the auxiliary hood and the incinerator for removing particulates from the fume stream prior to entering the incinerator.  
     
     
         5 . The fume treatment system of  claim 1  further comprising a heat exchanger downstream of the incinerator for reducing the temperature of the fume stream exiting the incinerator, the fume stream blower being either upstream or downstream of the heat exchanger.  
     
     
         6 . The fume treatment system of  claim 5  wherein the fume stream blower is downstream of the heat exchanger.  
     
     
         7 . The fume treatment system of  claim 5  wherein there is a flow path from the heat exchanger to the main overhead hood for returning the fume stream exiting the heat exchanger to the main overhead hood for further processing.  
     
     
         8 . The fume treatment system of  claim 7  wherein the returning fume stream from the heat exchanger is mixed with ambient air to further reduce the fume stream temperature.  
     
     
         9 . The fume treatment system of  claim 1  wherein there is a flow path from the incinerator to the main overhead hood for returning the fume stream exiting the incinerator to the main overhead hood for mixing with ambient air and any fugitive emissions from the furnace chamber collected by the main overhead hood.  
     
     
         10 . The fume treatment system of  claim 1  wherein the incinerator comprises a direct-fired afterburner including a burner assembly and a combustion chamber, further comprising a control unit for causing the auxiliary hood to move to the operative position over the furnace chamber mouth in response to the incinerator combustion chamber temperature reaching a first predetermined variable set point and for causing the auxiliary hood to move from the operative position to the inoperative in response to the incinerator combustion chamber temperature falling below a second predetermined variable set point that is below the first predetermined variable set point.  
     
     
         11 . The fume treatment system of  claim 1  wherein the incinerator comprises a direct-fired afterburner including a burner assembly and a combustion chamber, further comprising a timer for starting the fume stream blower a predetermined time period prior to initiating ignition of the burner assembly for purging the incinerator combustion chamber before initiating ignition of the burner assembly.  
     
     
         12 . The fume treatment system of  claim 1  further comprising means for modulating gas flow to the incinerator to maintain a predetermined temperature range in the incinerator during incineration of hydrocarbons or other combustible compounds in the fume stream.  
     
     
         13 . The fume treatment system of  claim 1  further comprising a flow control valve for modulating the fume stream to the incinerator based on fume stream temperature downstream of the incinerator.  
     
     
         14 . The fume treatment system of  claim 13  further comprising means responsive to an increase in the temperature of the fume stream downstream of the incinerator above a first predetermined set point to increase the amount of opening of the flow control valve and responsive to a decrease in the temperature of the fume stream downstream of the incinerator below a second predetermined set point which is below the first predetermined set point to decrease the amount of opening of the flow control valve.  
     
     
         15 . The fume treatment system of  claim 14  further comprising means for causing the auxiliary hood to move from the operative position to the inoperative position in response to the fume stream temperature downstream of the incinerator rising above a third predetermined set point which is higher than the first predetermined set point.  
     
     
         16 . The fume treatment system of  claim 15  further comprising means for shutting down the incinerator and the fume stream blower in response to the temperature of the fume stream downstream of the incinerator remaining above the third predetermined set point a predetermined time period.  
     
     
         17 . The fume treatment system of  claim 1  wherein the incinerator comprises a direct-fired afterburner including a burner assembly and a combustion chamber, and control means for modulating fuel flow to the burner assembly to regulate the temperature of the combustion chamber.  
     
     
         18 . The fume treatment system of  claim 17  wherein the control means includes means for reducing the amount of fuel flow to the burner assembly in response to the combustion chamber temperature rising above a predetermined first set point.  
     
     
         19 . The fume treatment system of  claim 18  further comprising a flow control valve for modulating the fume stream to the incinerator based on fume stream temperature downstream of the incinerator, means for increasing the amount of opening of the flow control valve in response to the combustion chamber temperature rising above a predetermined second set point which is higher than the predetermined first set point after the fuel flow to the burner assembly has been reduced to a minimum, and means responsive to the combustion chamber temperature remaining above the predetermined second set point a predetermined time period for causing the fume treatment system to perform an incinerator over temperature emergency shutdown comprising at least one of the following: moving the auxiliary hood from the operative position to the inoperative position, shutting down safety shut off valves for halting the supply of fuel and oxygen to the burner assembly, and shutting down the fume stream blower.  
     
     
         20 . The fume treatment system of  claim 1  further comprising a forced air heat exchanger downstream of the incinerator for reducing the temperature of the fume stream exiting the incinerator, and a control valve for modulating the flow of cooling air through the heat exchanger.  
     
     
         21 . The fume treatment system of  claim 20  further comprising means for increasing the opening of the control valve to increase the flow of cooling air through the heat exchanger in response to the temperature of the cooling air out of the heat exchanger rising above a predetermined first set point and for decreasing the opening of the control valve to decrease the flow of cooling air through the heat exchanger in response to the temperature of the cooling air out of the heat exchanger dropping below a predetermined second set point which is below the predetermined first set point.  
     
     
         22 . The fume treatment system of  claim 1  wherein the furnace system is a non-ferrous metal reclamation furnace system.  
     
     
         23 . A fume treatment system for treating a fume stream emitted from the mouth of a furnace chamber of a tilting rotary non-ferrous metal reclamation furnace system during charging and initial melting of a charge of scrap material containing the metal in the furnace chamber, the furnace system having a large main overhead hood located over the furnace chamber mouth, the fume treatment system comprising a retractable hood that is smaller than the main overhead hood, the retractable hood being movable between a first position overlying the furnace chamber mouth within the main overhead hood for collecting the fume stream emitted by the furnace chamber mouth during the charging and the initial melting of the scrap material within the furnace chamber and a second position spaced from the furnace chamber mouth, an incinerator in fluid communication with the retractable hood when in the first position, and a fume stream blower for causing the fume stream collected by the retractable hood when in the first position to flow to the incinerator where hydrocarbons or other combustible compounds present in the fume stream are incinerated during operation of the fume treatment system.  
     
     
         24 . The fume treatment system of  claim 23  wherein the furnace chamber includes a door that is movable between closed and open positions for substantially closing and opening the furnace chamber mouth, the door having a flue through which the fume stream is emitted from the furnace chamber for collection by the retractable hood when the door is in the closed position and the retractable hood is in the first position, the retractable hood when in the first position permitting movement of the door between the closed and open positions.  
     
     
         25 . A method of treating a fume stream emitted from the mouth of a furnace chamber of a metal reclamation furnace system during a portion of the reclamation process, the furnace system having a main overhead hood located over the furnace chamber mouth, comprising the steps of positioning a second hood that is smaller than the main overhead hood over the furnace chamber mouth within the main overhead hood to collect the fume stream emitted by the furnace chamber mouth, and causing the fume stream collected by the second hood to flow through an incinerator where hydrocarbons or other combustible compounds present in the fume stream are incinerated.  
     
     
         26 . The method of  claim 25  wherein the fume stream that is emitted from the furnace chamber mouth during charging and initial melting of a charge of scrap material containing the metal in the furnace chamber is collected by the second hood and caused to flow through the incinerator for incinerating hydrocarbons or other combustible compounds present in the fume stream, further comprising the step of moving the second hood to a position remote from the furnace chamber mouth during other portions of the reclamation process.  
     
     
         27 . The method of  claim 25  wherein the furnace system is a tilting rotary furnace system, and the second hood is selectively positioned over the furnace chamber mouth when the furnace chamber is in a tilted back position.  
     
     
         28 . The method of  claim 27  wherein the furnace system is a non-ferrous metal reclamation furnace system.  
     
     
         29 . The method of  claim 27  wherein the furnace chamber includes a door that is movable between closed and open positions for substantially closing and opening the furnace chamber mouth, and the door has a flue through which the fume stream is emitted from the furnace chamber for collection by the second hood when the door is in the closed position and the second hood is positioned over the furnace chamber mouth, further comprising the steps of moving the door between the closed and open positions during times when the second hood is in position over the furnace chamber mouth.  
     
     
         30 . The method of  claim 25  further comprising the step of causing the fume stream that is collected by the second hood when in position over the furnace chamber mouth to flow through a cyclone for removing particulates from the fume stream prior to flowing through the incinerator.  
     
     
         31 . The method of  claim 25  further comprising the step of cooling the fume stream after the incineration step.  
     
     
         32 . The method of  claim 31  further comprising the step of returning the fume stream to the main overhead hood after the cooling step.  
     
     
         33 . The method of  claim 32  further comprising the step of mixing the returned cooled fume stream with ambient air within the main overhead hood.  
     
     
         34 . The method of  claim 25  further comprising the steps of returning the fume stream to the main overhead hood after the incineration step, and mixing the returned fume stream with ambient air and any fugitive emissions from the furnace chamber collected by the main overhead hood.  
     
     
         35 . The method of  claim 25  wherein the incinerator includes a combustion chamber, further comprising the steps of causing the second hood to move into position over the furnace chamber mouth in response to the temperature within the combustion chamber reaching a first predetermined variable set point and for causing the second hood to move away from the furnace chamber mouth in response to the combustion chamber temperature falling below a second predetermined variable set point that is below the first predetermined variable set point.  
     
     
         36 . The method of  claim 25  wherein the incinerator comprises a direct-fired afterburner including a burner assembly and a combustion chamber, further comprising the steps of modulating gas flow to the burner assembly to maintain a predetermined temperature range in the combustion chamber during the fume stream incineration step.  
     
     
         37 . The method of  claim 25  further comprising the step of modulating the fume stream to the incinerator based on fume stream temperature downstream of the incinerator.  
     
     
         38 . The method of  claim 37  further comprising the steps of increasing the fume stream flow to the incinerator in response to an increase in the temperature of the fume stream downstream of the incinerator above a first predetermined set point, and decreasing the fume stream flow to the incinerator in response to a decrease in the temperature of the fume stream downstream of the incinerator below a second predetermined set point which is below the first predetermined set point.  
     
     
         39 . The method of  claim 38  further comprising the step of moving the second hood away from the furnace chamber mouth in response to the fume stream temperature downstream of the incinerator rising above a third predetermined set point which is higher than the first predetermined set point.  
     
     
         40 . The method of  claim 39  further comprising the step of shutting down the fume treatment in response to the temperature of the fume stream downstream of the incinerator remaining above the third predetermined set point a predetermined time period.  
     
     
         41 . The method of  claim 25  wherein the incinerator comprises a direct-fired afterburner including a burner assembly and a combustion chamber, further comprising the steps of modulating fuel flow to the burner assembly to regulate the temperature of the combustion chamber by reducing the amount of fuel flow to the burner assembly in response to the combustion chamber temperature rising above a predetermined first set point.  
     
     
         42 . The method of  claim 41  further comprising the steps of modulating the fume stream flow to the incinerator based on fume stream temperature downstream of the incinerator, increasing the fume stream flow in response to the combustion chamber temperature rising above a predetermined second set point which is higher than the predetermined first set point after the fuel flow to the burner assembly has been reduced to a minimum, and causing the fume treatment system to perform an incinerator over temperature emergency shutdown in response to the combustion chamber temperature remaining above the predetermined second set point a predetermined period of time.