Combustion systems and associated methods are disclosed herein. In some embodiments, a combustion system comprises a first combustion zone, a second combustion zone downstream of the first combustion zone, and a heat module thermally coupled to the first combustion zone and/or second combustion zone. The first combustion zone is configured to (i) receive and combust preheated air and a first fuel and (ii) generate a first exhaust gas, and the second combustion zone is configured to (i) receive and combust the first exhaust gas and a second fuel and (ii) generate a second exhaust gas. The first exhaust gas can have a first excess air and the second exhaust gas can have a second excess air less than the first excess air. The heat module can comprise a thermionic converter or another heat-to-electricity converter able to generate a power output.

A burner and methods of using the burner. The burner produces a flame from combustion air and fuel gas. Flue gas, also produced, can be withdrawn and recycled to the burner. A cooling or condition gas, such as ambient air, may be mixed with the flue gas to reduce its temperature. The burner may also utilize a stage injection so that a portion of the produced flue gas is recycled internally.

Emissions of NO.sub.X and/or CO are reduced at the stack by systems and methods wherein a primary fuel is thoroughly mixed with a specific range of excess combustion air. The primary fuel-air mixture is then discharged and anchored within a combustion chamber of a burner. Further, the systems and methods provide for dynamically controlling NO.sub.X content in emissions from a furnace by adjusting the flow of primary fuel and of a secondary stage fuel, and in some cases controlling the amount or placement of combustion air into the furnace.

A method for burning primary fuel (F1), wherein the primary fuel (F1) comprises at least a first compound containing nitrogen and a second compound comprising sulfur. The method comprises producing primary combustion gas (G1) having a temperature of at least 450° C. and comprising oxygen; feeding the primary fuel (F1) and the primary combustion gas (G1) to a primary process zone (Z1) of a furnace (200); feeding tertiary combustion gas (G3) to a secondary process zone (Z2) of the furnace (200); letting the primary fuel (F1), the primary combustion gas (G1), and/or their reaction products to move from the primary process zone (Z1) via the secondary process zone (Z2) to a tertiary process zone (Z3) of the furnace (200); and feeding quaternary combustion gas (G4) comprising oxygen to the tertiary process zone (Z3) of the furnace (200). An embodiment comprises collecting the primary fuel (F1) from a pulp process. A corresponding system.

The present invention relates to a combustion heater (100) for providing controlled heat (H) to an endothermic reaction process. The combustion heater comprises an integrated burner (20) to yield a hot burner exhaust gas (35) flow from burning a first fuel. The burner exhaust gas mixed with oxidant flows to a flue gas outlet along a flue gas flow path (FGP). Provided to the combustion chamber at a position outside a direct reach of flames from the burner is a secondary fuel conduit (30) with a plurality of nozzles (31) from which a second fuel (32) is transferred into a flow along the said flue gas flow path (FGP). The resulting combustion of the second fuel can be used to provide controlled heat to the to endothermic reaction operated in a reaction conduit (40) that is in thermal heat exchange with the combustion chamber.

A method for operating a combustion chamber is provided. The method includes introducing a fuel into the combustion chamber via a plurality of nozzles, each nozzle having an associated stoichiometry for an output end of the nozzle. The method further includes measuring the stoichiometry of each nozzle via one or more sensors to obtain stoichiometric data, and determining that at least one of a frequency and an amplitude of spectral line fluctuations derived from the stoichiometric data has exceeded a threshold. The method further includes adjusting the stoichiometry of at least one of the nozzles based at least in part on the stoichiometric data so as to maintain a flame stability of the combustion chamber.

Emissions of NO.sub.X and/or CO are reduced at the stack by systems and methods wherein a primary fuel is thoroughly mixed with a specific range of excess combustion air. The primary fuel-air mixture is then discharged and anchored within a combustion chamber of a burner. Further, the systems and methods provide for dynamically controlling NO.sub.X content in emissions from a furnace by adjusting the flow of primary fuel and of a secondary stage fuel, and in some cases controlling the amount or placement of combustion air into the furnace.

Clean combustion and equilibration equipment and methods are provided to progressively deliver, combust and equilibrate mixture of fuel, oxidant and aqueous diluent in a plurality of combustion regions and in one or more equilibration regions to further progress oxidation of products of incomplete combustion, in a manner that sustains combustion while controlling temperatures and residence times sufficiently to reduce CO and NOx emissions to below 25 ppmvd, and preferably to below 3 ppmvd at 15% O.sub.2.

A dry low NO.sub.X staged combustion system includes a fuel nozzle and a combustion compartment. The fuel nozzle includes a purge gas tube, a diffusion combustion fuel tube, an isolation gas tube, a premixed combustion fuel tube, a premixed combustion air tube. The purge gas tube is configured to feed a purge gas. The diffusion combustion fuel tube is fitted over the purge gas tube, and having an end provided with a diffusion combustion fuel swirler. The isolation gas tube is fitted over the diffusion combustion fuel tube. The premixed combustion fuel tube is fitted over the isolation gas tube. The premixed combustion air tube is fitted over the premixed combustion fuel tube. The combustion compartment is located downstream of the fuel nozzle.

The invention relates to a method of making a mineral melt, the method comprising providing a circulating combustion chamber which comprises an upper zone, a lower zone and a base zone, injecting primary particulate fuel and particulate mineral material and primary combustion gas into the upper zone of the circulating combustion chamber, thereby at least partially combusting the primary particulate fuel and thereby melting the particulate mineral material to form a mineral melt and generating exhaust gases, injecting into the lower zone of the circulating combustion chamber, through at least one first burner, secondary combustion gas and gaseous fuel and secondary particulate fuel, wherein the secondary combustion gas and gaseous fuel and secondary particulate fuel are injected via a single first burner, wherein the amount of secondary combustion gas injected via each first burner is insufficient for stoichiometric combustion of the total amount of gaseous fuel and secondary particulate fuel injected via that first burner, and injecting tertiary combustion gas into the lower zone of the circulating combustion chamber, through at least one tertiary combustion gas injector, whereby the tertiary combustion gas enables completion of the combustion of the gaseous fuel and the secondary particulate fuel, separating the mineral melt from the hot exhaust gases so that the hot exhaust gases pass through an outlet in the circulating combustion chamber and the mineral melt collects in the base zone. The invention also relates to apparatus suitable for use in the method.