Combustion furnace and method of operation

Abstract

A combustion furnace and a method of its operation are described. The furnace comprises a chamber defining a combustion volume having at least one primary inlet for fuel and combustion supporting gases and at least one primary outlet for combustion product gases, which chamber is provided with one or more additional ports, for example in fluid communication with a supply of gas for secondary gas flow, allowing for secondary gas flow into and/or out of the combustion volume.

1 . A combustion furnace comprises a chamber defining a combustion volume having at least one primary inlet for fuel and combustion supporting gases and at least one primary outlet for combustion product gases, which chamber is provided with one or more additional ports allowing for secondary gas flow into and/or out of the combustion volume. 
     
     
         2 . A combustion furnace in accordance with  claim 1  wherein the one or more additional ports are provided in fluid communication with a supply of gas for secondary gas flow. 
     
     
         3 . A combustion furnace in accordance with  claim 2  wherein the furnace is adapted for air firing and the additional ports are provided in fluid communication with ambient air. 
     
     
         4 . A combustion furnace in accordance with  claim 2  wherein the furnace is adapted for oxyfuel firing and the additional ports are provided in fluid communication with a CO2 rich gas source. 
     
     
         5 . A combustion furnace in accordance with  claim 2  wherein the furnace is provided with at least two sets of additional ports and wherein a first set of ports is connected to an air source and a second set is connected to rich in CO2 gas source. 
     
     
         6 . A combustion furnace in accordance with  claim 1  comprising control means adapted to control the secondary flow of gas through the one or more ports. 
     
     
         7 . A combustion furnace in accordance with  claim 6  wherein the control means are adapted to control the secondary flow of gas through the one or more ports by way of dynamic response in real time to provide variation in mass flow to the furnace as required. 
     
     
         8 . A combustion furnace in accordance with  claim 7  wherein the furnace is adapted for firing in air and oxyfuel firing modes and the control means are adapted to control the secondary flow of gas through the one or more ports at least to provide variation in mass flow to the furnace during transition between air and oxyfuel modes. 
     
     
         9 . A method of control of furnace pressure in a combustion furnace comprising a chamber defining a combustion volume having at least one primary inlet for fuel and combustion supporting gases and at least one primary outlet for combustion product gases, comprising the step of allowing secondary gas flow into and/or out of the combustion volume via one or more additional ports in the chamber. 
     
     
         10 . The method of  claim 9  comprising the step of controlled admission of secondary gas into the combustion volume as a method of secondary control of furnace pressure. 
     
     
         11 . The method of  claim 9  comprising the controlled admission of secondary gas from a secondary supply of gas. 
     
     
         12 . The method of  claim 9  wherein the furnace is adapted for air firing and the secondary gas is ambient air. 
     
     
         13 . The method of  claim 9  wherein the furnace is adapted for oxyfuel firing and the secondary gas is a CO2 rich gas source. 
     
     
         14 . The method of  claim 9  wherein the furnace is adapted for oxyfuel firing and the secondary gas is a source of nitrogen rich gas having a nitrogen content in excess of that of atmospheric air. 
     
     
         15 . The method of  claim 9  wherein the furnace is adapted for oxyfuel firing and the secondary gas is sourced from CO2 compressors vent gas. 
     
     
         16 . The method of  claim 9  wherein the furnace is adapted for oxyfuel firing and the secondary gas is sourced from the CO2 transportation pipeline. 
     
     
         17 . The method of  claim 9  comprising the supply by way of dynamic response in real time of a quantity of secondary gas to provide additional control of furnace pressure for an event selected from one or more of: mill start-up, shut-down, partial or full loss of ignition etc, and in the case of a furnace adapted for transition between air firing and oxyfuel firing during transition between air and oxyfuel modes. 
     
     
         18 . The method of  claim 9  wherein a step of controlling primary mass flow of gases out of the combustion volume via the primary outlet in conjunction with controlling of secondary gas flow into the combustion volume is used as a method of control of furnace pressure. 
     
     
         19 . The method of  claim 18  wherein a step of controlling primary mass flow of gases out of the combustion volume via the primary outlet in conjunction with controlling of secondary gas flow into the combustion volume is used as a process control step to vary gas in-leakage in a coherent and stable fashion to produce fast, accurate responses to changes in operating conditions in response to changes in load demand.