Continuously-Fed Non-Densified Biomass Combustion System

Abstract

A combustion system for extracting thermal energy from biomass or other formable fuels that does not require densification or other processing of the biomass prior to combustion. This system continuously feeds the biomass fuel from an auger or other conveyance system while simultaneously causing the biomass fuel to be formed with a hollow core. The biomass fuel is ignited from within the hollow core and burns primarily radially outward due to negative pressure surrounding combustion chamber thus facilitating and containing the combustion process. This system also utilizes pre-heating the fuel, primary and secondary air pre-heating, insulated combustion chambers, and carefully control combustion air to ensure substantial combustion is achieved even with fuels having high moisture content. In the preferred embodiment, a heat exchanger is utilized to capture thermal energy of combustion products for use as an energy source for additional processes.

1 . A continuously-fed formable fuel combustion system capable of combusting unprocessed or processed biomass material or other suitably formable fuels and extracting thermal energy comprising:
 A fuel storage container capable of storing processed or unprocessed fuel and means of interfacing with fuel conveying system by flange or other method.   A conveyance system interfacing with fuel storage container capable of transporting unprocessed or processed fuel from storage container to the primary combustion chamber.   A primary combustion chamber to receive primary air and fuel capable of burning of the fuel and supporting further transport of burned and partially burned combustion ash products to collection chamber   A secondary combustion chamber fluidly connected to primary combustion chamber and process wise downstream of primary combustion chamber to receive secondary air and the initial combustion effluent stream capable of further oxidizing the initial combustion effluent stream.   A heat containment chamber surrounding combustion chambers with means of interfacing with filter, ash collection, and conveying system.   A filter system to extract and collect pneumatically conveyed combustion ash products in the effluent stream from combustion chamber.   A means of collecting or recirculating conveyed combustion ash products at terminus of the primary combustion chamber.   A means of extracting thermal energy from combustion product streams such as a heat exchanger, water jacket, or membrane walls for use as heat source for an additional served process or for direct heating and further for directing exhaust stream of system.   A control system utilizing inputs from intermediate process steps to control at a minimum fuel feed rate, combustion air, and vacuum.   
   
   
       2 . The combustion system of  claim 1 , wherein the fuel storage container is of a size suitable to contain enough fuel for continuous operation of combustion system of  claim 1  until storage container can be replenished at maximum feed rate. 
   
   
       3 . The combustion system of  claim 1 , wherein the conveyance system is capable of simultaneously forming fuel material into hollow cylinder or other hollow section while conveying fuel to combustion chamber. 
   
   
       4 . The combustion system of  claim 1 , wherein the conveyance system is capable of substantially sealing conveyance system path from introducing combustion air into combustion chamber. 
   
   
       5 . The combustion system of  claim 1 , wherein the conveyance system is capable of preheating fuel prior to combustion by utilizing exhaust stream of combustion process contained within heat containment chamber. 
   
   
       6 . The combustion system of  claim 1 , wherein the primary combustion chamber is capable of directing the primary air into the hollow cavity formed in the fuel whereby centrally induced combustion air radially distributes through the fuel toward the outside perimeter of the primary combustion chamber and facilitate the combustion process. 
   
   
       7 . The combustion system of  claim 1 , wherein the primary combustion chamber possesses a plurality of longitudinal variable depth grooves on the inside perimeter that fluidly connects primary combustion chamber to secondary combustion chamber of  claim 1  whereby transport of the initial combustion effluent stream is supported. 
   
   
       8 . The combustion system of  claim 1 , wherein the secondary combustion chamber further burns fuel utilizing the initial combustion effluent stream generated in the primary combustion chamber. 
   
   
       9 . The combustion system of  claim 1 , wherein the secondary combustion chamber utilizes turning vanes or other means to mix incoming effluent of primary combustion chamber of  claim 1  and secondary combustion air whereby producing a substantially more efficient combustion. 
   
   
       10 . The combustion system of  claim 1 , wherein the collection system at terminus of combustion chamber includes of restricting free conveyance of burned and partially burned combustion ash products such as a grate, and a collection chamber for ash. 
   
   
       11 . The combustion system of  claim 1 , wherein the heat containment chamber is fluidly connected to secondary combustion chamber forming plenum for filtering system of  claim 1 . 
   
   
       12 . The combustion system of  claim 1 , wherein the heat containment chamber includes means of transferring thermal energy of combustion process contained within chamber to combustion air for both combustion chambers whereby increasing combustion efficiency. 
   
   
       13 . The combustion system of  claim 1 , wherein the filter system is fluidly connected to the heat containment chamber to separate non gaseous combustion products from gaseous combustion products and depositing them in collection container or to re-circulate them into fuel stream or combustion air stream. 
   
   
       14 . The combustion system of  claim 1 , wherein the control system comprises a programmable control unit, air modulating valves, flow meters, and vacuum blower controlling primary and secondary combustion air and vacuum maintained in heat containment chamber. 
   
   
       15 . A method for combusting unprocessed or processed fuel of variable water content, extracting thermal energy from the effluent stream, and collecting the solid portion of the combustion products comprising:
 The step of storing fuel material in a manner that allows it to be conveyed at variable feed rates by interfacing with conveyance system.   The step of conveying fuel material at variable speed rates as commanded by control system including programmable control unit.   The step of forming fuel material into a hollow section or cylinder such that combustion air can be introduced and progress from the center of the section outward.   The step of preheating fuel material in conveying system and both primary and secondary combustion air utilizing heat from the combustion gases contained within heat containment chamber.   The step of burning the fuel in the primary combustion chamber by controlling combustion air and vacuum pressure in heat containment chamber.   The step of further burning initial combustion products in secondary combustion chamber by controlling secondary combustion air and vacuum pressure within heat containment chamber.   The step of collecting burned and partially burned combustion ash products at the terminus of the primary combustion chamber.   The step of filtering and collecting particulates from exhaust stream.   The step of extracting thermal energy from combustion product streams by controlling primary and secondary combustion air, heat containment chamber vacuum, and flow rate of heat transfer fluid that heat is being transferred to.   
   
   
       16 . The method of  claim 15 , wherein further sealing of the conveyance path of the fuel material such that it substantially limits the leakage of air along the conveyance path so that commanded primary and secondary combustion air is accurately controlled. 
   
   
       17 . The method of  claim 15 , wherein vacuum pressure is maintained in heat containment chamber such that air introduced to the inside diameter perimeter of the hollow fuel section is drawn through the fuel to aid in further combustion. 
   
   
       18 . The method of  claim 15 , wherein the primary and secondary combustion chamber are fluidly connected by means of longitudinal grooves of increasing depth in the direction of effluent flow, and where the secondary combustion chamber has flow interrupting structures on the inlet to mix the initial combustion effluent stream from the primary combustion chamber with incoming secondary combustion air.