System for self-sustaining combustion of iron particles and method thereof

Abstract

There is provided a continuous combustion system for iron particles. The system comprising a multi-annular combustion tube defining in cross-section at least three distinct passages from its inlet to its outlet. A first tube that is innermost, defines a first passage providing a primary air flow with suspended iron particles. A second tube, defines an inner annular space providing a secondary air flow, a pilot combustible flow, and an ignition point of a spark generator. A third tube defines a third passage comprises a swirl generator and provides a tertiary air flow. The tubes are nested in position within the multi-annular combustion tube. The system comprises a divergent nozzle at the outlet of the multi-annular combustion tube: a combustion reactor in fluid communication with the divergent nozzle, for the generation and stabilization of a turbulent iron flame that burns the iron particles and produces oxidized iron particles; and a cyclone.

1 . A continuous combustion system for iron particles comprising
 a multi-annular combustion tube having an inlet and an outlet, the multi-annular combustion tube defining in cross-section at least three distinct passages from the inlet to the outlet; the multi-annular tube comprising:
 a first tube that is innermost, the first tube defining a first passage providing a primary air flow wherein the iron particles are suspended in the primary air flow; 
 a second tube, outside the first tube defining a second passage that is an inner annular space defined between the first tube and the second tube, wherein the inner annular space provides a secondary air flow and a pilot combustible flow, the inner annular space further comprises an ignition point of a spark generator, and 
 a third tube, the third tube positioned outside the second tube defining a third passage that is an outer annular space defined between the second tube and the third tube, wherein the outer annular space comprises a swirl generator and provides a tertiary air flow; 
 the first tube, the second tube and the third tube nested in position within the multi-annular combustion tube; 
   a divergent nozzle at the outlet of the multi-annular combustion tube;   a combustion reactor, comprising a reactor outlet opposite a reactor inlet, in fluid communication and hydraulically connected with the divergent nozzle at the reactor inlet, for the generation and stabilization of a turbulent iron flame that burns the iron particles and produces oxidized iron particles; and   a cyclone having a cyclonic inlet, a gas outlet and a particle outlet, wherein the cyclonic inlet is in fluid communication with the reactor outlet.   
     
     
         2 . The system according to  claim 1 , wherein an air gap that provides a quaternary air flow into the cyclonic inlet is defined between the cyclonic inlet and the reactor outlet. 
     
     
         3 . The system according to  claim 1 , further comprising a quaternary flow provided in the combustion reactor by a pressurized air flow through injection ports in the combustion reactor. 
     
     
         4 . The system according to  claim 1 , wherein the multi-annular combustion tube is a triple concentric tube. 
     
     
         5 . The system according to  claim 1 , further comprising a filter downstream of the cyclonic separator to capture the oxidized iron particles that escape the cyclonic separator. 
     
     
         6 . The system according to  claim 1 , further comprising a magnetic separator downstream of or incorporated in the cyclonic separator. 
     
     
         7 . The system according to  claim 1 , further comprising a temperature controlling system coupled to the cyclonic separator. 
     
     
         8 . The system according to  claim 1 , further comprising an energy generator. 
     
     
         9 . The system according to  claim 8 , wherein the energy generator is selected from a heat engine, a Stirling engine or a steam engine. 
     
     
         10 . The system according to  claim 1 , wherein the inner annular space further comprises flame arrestor beads. 
     
     
         11 . The system according to  claim 1 , further comprising pressure valves in the inner annular space to relieve the pressure in case of pressure build-up. 
     
     
         12 . The system according to  claim 1 , further comprising a metal-fuel storage compartment comprising a metal-fuel powder silo and a compressed air system coupled to the metal-fuel powder silo providing the primary air flow with the iron particles suspended. 
     
     
         13 . The system according to  claim 1 , further comprising a combustible shut-off valve. 
     
     
         14 . The system according to  claim 1 , further comprising an enclosure that reflects radiation, the enclosure housing the combustion reactor. 
     
     
         15 . A method of burning iron particles, the method comprising:
 providing multi-annular flow to a combustion reactor through a divergent nozzle, the multi-annular flow comprising:
 a primary air flow wherein the iron particles are suspended in the primary air flow, 
 a secondary air flow physically separated from the primary air flow, wherein the primary air flow is enveloped by the secondary air flow, and 
 a tertiary air flow physically separated from the secondary air, wherein the secondary air flow is enveloped by the tertiary air flow, and wherein the tertiary air flow is a turbulent swirling flow; 
   providing a pilot combustible flow with the secondary air flow and a spark igniting a pilot flame;   igniting a turbulent iron flame with the pilot flame;   allowing the turbulent iron flame to stabilize and the iron particles to burn in a reaction zone of the combustion reactor producing an air flow comprising oxidized iron particles, wherein the combustion reactor has a recirculation zone surrounding the reaction zone generated and sustained by the tertiary air flow;   stopping the pilot combustible flow;   stabilizing the turbulent iron flame; and   recovering the oxidized iron particles from the air flow with a cyclone.   
     
     
         16 . The method according to  claim 15 , further comprising providing a quaternary air flow upstream of the cyclone to control the temperature and further oxidize the iron particles. 
     
     
         17 . The method according to  claim 15 , wherein the pilot combustible flow is provided for less than 1 minute. 
     
     
         18 . The method according to  claim 15 , wherein the step of recovering the oxidized iron particles includes controlling the temperature of the walls of the cyclone. 
     
     
         19 . The method according to  claim 15 , wherein the iron particles have a size of between 1 and 100 μm. 
     
     
         20 . The method according to  claim 15 , wherein the oxidized iron particles are at least 60% by weight magnetite (Fe 3 O 4 ). 
     
     
         21 . The method according to  claim 15 , wherein the oxidized iron particles comprise less than 1% of particles having a size of less than 8 μm.