Abstract: A method for reducing NOx emissions from the combustion of carbonaceous fuels using three stages of oxidation and second stage in-situ furnace flue gas recirculation. In the first stage, a partial oxidation combustor is used to partially combust the fuel in the presence of preheated combustion air. The fuel gas produced in the partial oxidation process is passed to a second stage partial oxidation combustor while molten slag is removed and disposed of. Preheated combustion air also is introduced into the second stage of combustion to produce a slightly reducing flue gas and is injected into the furnace in such a way as to create the desired in-situ furnace flue gas recirculation. In the upper part of the furnace a third combustion air is mixed with the flue gas in a third stage of combustion to substantially complete the combustion process. Preheated steam may be added to the first or second stages of combustion.

Abstract: A method and apparatus for low-NOx combustion of a pulverized solid fuel in which combustion products from a partial oxidation combustor are mixed with a pulverized solid fuel, thereby preheating the pulverized solid fuel and resulting in devolatilization of at least a portion of the pulverized solid fuel. The preheated pulverized solid fuel and the devolatilization products are then burned in a burner firing directly into a combustion chamber.

Abstract: A method of burning plant-based fuel is involved in which the plant-based fuel is burned in a boiler designed for burning dry fuel and with the plant-based fuel being used having a moisture value which can vary in range from dry to wet. The method involves heating air with heat energy from combustion gases of the boiler to provide a source of heated air and providing heat and flow amounts of the heated air, with derived heat energy from the combustion gases, to the fuel in an amount sufficient for drying the fuel in any condition presented amongst the range between dry and wet. The flow of the heated air directed to the fuel is controlled to provide sufficient drying of the fuel before use of the fuel in the boiler and such that the heated air not needed for drying the fuel is conducted into the boiler to serve as heated combustion air.

Abstract: The firing performance of a radial, scroll, or vortex cyclone furnace can be improved when firing difficult to burn materials having a relatively low heating value or a relatively high moisture content, such as sub-bituminous and lignite coals. This can be achieved by introducing additionally heated primary air into the burner of the radial and vortex cyclone furnace or separately introducing preheated or additionally heated auxiliary air into the scroll burner. Moreover, additionally heated tertiary air can be introduced into the radial and scroll burners to further improve firing performance. Moreover, additionally heated primary air can be mixed with the coal before introducing the mixture into the scroll burner to further improve firing performance.

Abstract: A waste treatment furnace includes a first waste treatment chamber with a first burner chamber communicating therewith, and a second waste treatment chamber with a second burner chamber communicating therewith. A common bottom wall is positioned under the first and second waste treatment chambers which is inclined downwardly from the first chamber to the second chamber to facilitate transfer of waste. Each burner chamber includes a burner and a plurality of protuberances disposed across its inner surface. The protuberances effectively reflect heat from the first and second burners so that the heater air in the first and second burner chambers is homogenized.

Abstract: Combustion gas is fed to a furnace, preferably a recovery boiler for combusting black liquor from cellulose pulp processing, through a gas nozzle disposed in association with a wall of the furnace. The nozzle has a longitudinal axis of elongation, an exterior, and a hollow interior. Cooling gas is directed into contact with the nozzle exterior, and typically also the furnace wall where the nozzle engages the furnace wall. The cooling gas typically moves in a direction substantially perpendicular to the longitudinal axis of the nozzle (e.g. at a velocity of between 10-30 m/sec), and cools the nozzle. Combustion gas passes through the nozzle hollow interior and enters the furnace facilitating combustion of black liquor within the furnace. Desirably the cooling gas is redirected and enters the nozzle interior as the combustion gas. The nozzle may be further cooled by cooling fins or studs on a portion of the nozzle exterior impacted by cooling gas.

Abstract: A biomass-fueled furnace for residential or institutional space and hot water heating. Wood chips, the preferred fuel, are purchased "green and/or wet" and are stored in a dryer/storage assembly which uses waste clean exhaust gases produced by the furnace to dry them. Wood chips are fed via gravity to the primary combustion chamber where, via pyrolysis, they are burned. A thimble combustor eliminates radiant heat loss from the primary pyrolysis zone, allowing stable pyrolysis at low burning rates. A second combustion chamber fed with pre-heated air completely oxidizes pyrolysis gases. This furnace is capable of operating continuously at extremely low fuel consumption rates so that heat release can be regulated by thermostat in the same manner as conventional gas and oil fired furnaces. A combination of fuel drying plus secondary air preheating by the secondary flame allows stable operation at extremely low or "idle" fuel rates.

Abstract: An incineration plant includes a heat exchanger arranged in a flue gas flow following a reduction stage for nitrogen oxides and in front of a flue gas dust collector, and a heat transfer medium circuit for absorbing heat from the heat exchanger in the flue gas flow. The heat exchanger is connected to the heat transfer medium circuit such that the heat transfer medium conducted in the circuit is admitted to the heat exchanger. The heat transfer medium circuit has at least one additional heat exchanger for absorbing heat from the heat transfer medium. A feed water preheater is arranged in the heat transfer medium circuit.

Abstract: In an incinerator having a housing structure defining a combustion chamber provided with a pair of side walls, a stoker disposed in the combustion chamber between the side walls and an underfire air system, an overfire air system generally consisting of a first means for injecting a variable volume of air under pressure into the combustion chamber at a level above the stoker, and second means for injecting a variable volume of air under pressure into the combustion chamber at a level above the stoker, a second variable volume air injecting means including means for conveying air supplied to the combustion chamber in heat exchange relation with at least one side wall of the combustion chamber for cooling such wall.

Abstract: A high temperature fluid-to-fluid heat exchanger is described wherein heat is transferred from a higher temperature fluid flow core region to a lower temperature fluid flow annulus. The wall separating the high and low temperature fluid flow regions is comprised of a material having high thermal absorptivity, conductivity and emissivity to provide a high rate of heat transfer between the two regions. A porous ceramic foam material occupies a substantial portion of the annular lower temperature fluid flow region, and is positioned to receive radiated heat from the wall. The porosity of the ceramic foam material is sufficient to permit a predetermined relatively unrestricted flow rate of fluid through the lower temperature fluid flow region.

Abstract: This invention relates to a combustion chamber and a method for burning waste material, such as waste oil, hazardous chemicals, and municipal garbage or trash, in a manner which generates very little smoke, particulate matter, unburned hydrocarbons, or potentially hazardous fumes in the exhaust gases. The combustion chamber is enclosed within an outer wall which provides an inlet for air, fuel, and burnable waste material, and an outlet for exhaust gases. Enclosed within the outer wall is an annular wall, which divides the chamber into a central burning region inside the annular wall, and an annular space between the outer wall and the annular wall. The central burning region contains a primary burning zone, while the annulus space carries a portion of the inlet air along the length of the chamber.

Abstract: The present invention involves a regenerative thermal oxidation apparatus for purifying gases by thermal oxidation and for exchange of heat between inleting and outleting gases. The apparatus has a plurality of thermal chamber units, each such unit having a gate with at least one gate orifice movably located in a linear fashion against a base surface so as to alternatively align with various inlet and outlet openings. The improvement involves the use of a plurality of seals located between the gate and the openings with sufficient sealing capabilities between the gate and the openings to maintain each chamber at an elevated pressure, i.e. above atmospheric pressure, and so as to reduce leakage of gases from each of the chambers and reduce condensation during operation. The invention is also directed to the method utilizing this apparatus.

Abstract: The present invention is directed to an improved regenerative thermal oxidizer and a method of purifying gases by raising gases to their auto ignition temperature and by exchanging heat by inleting and outleting gases. The reactor has at least three regenerative thermal chamber units and these units have on a single surface at least three openings, a purge opening, an inlet opening and an outlet opening, which are connected to recycled outlet gases for purging, and to inlet and outlet gases respectively. Set against the purge, inlet and outlet openings is a slidable gate which has a single opening which moves through cycles so that its single opening coincides with the inlet opening of its chamber unit, or coincides with one or more spaces which are closed between the inlet and outlet opening, or with the purge opening, or coincide with the outlet opening. In other words, the gate cycles between inleting gases, no gas movement, purge position, no gas movement and outleting gases.

Abstract: To avoid high NOx emissions, the fuel is oxidized with an extremely high exhaust gas recirculation ration substantially without flames and without pulsations.

Abstract: The invention relates to a combustion device for wood or coal comprising a front wall with a fuel charging opening, two side walls, a rear wall, a bottom wall, a top wall, a door for the fuel charging opening, a control element for controlling a fresh-air inlet opening, an inner dividing wall which divides the interior of the device into a pre-combustion chamber and a post-combustion chamber, and a passage opening between the two chambers and a grating at the bottom of the pre-combustion chamber and a flue gas discharge opening; the dividing wall is horizontally disposed and a shaft pipe surrounded by an annular chamber which is in communication with the fresh-air inlet opening is inserted sealingly into its passage opening; the grating is placed on its upper end.

Abstract: Waste materials are efficiently and completely incinerated in a gasification unit with a minimum amount of fly ash while ensuring complete sterilization of residual materials. The gasification unit includes a refractory liner which is stepped to define primary, secondary, and tertiary combustion chambers where waste materials are completely incinerated. A fan is adapted to draw combustion air past the outer surface of the refractory liner to initially heat the combustion air while simultaneously cooling the refractory liner. The fan is further adapted to force combustion air under pressure into a preheating chamber in which the combustion air is preheated before passing into the primary and secondary combustion chambers. Turbulence in the combustion chambers, brought about through equalization of air pressure in the preheating chamber, is effected through the provision of tangential air inlets in the walls of the refractory liner.

Abstract: The combustion of fuel having a highly fluctuating thermal value is controlled to permit optimization of air supply and reduction of waste gas impurities. The fuel passes through a combustion chamber having a degassing and evaporation zone, a primary combustion zone, and a secondary combustion zone. Measurements are taken in the evaporation and degassification zone to determine the thermal value of the fuel. This is done by detecting the intensity of H.sub.2 O and/or CO.sub.2 spectra emanating from the fuel. The measurement results are utilized to optimize the combustion parameters. Such measurements are also made in the following zones in order to provide further control of the combustion process.

Abstract: Apparatus for carrying out a postcombustion process includes a combustion chamber (2) and a post-combustion chamber (4) provided within the vicinity of the outlet of the combustion chamber (2). A conduit (8) is fluidically connected to the post-combustion chamber (4) so as to inject fresh combustion air thereinto. A heating device (9) is disposed within the conduit (8) for pre-heating the fresh combustion air to be injected into the post-combustion chamber (4). Various sensors (11,12,14) are provided within the combustion chamber (2), post-combustion chamber (4), and conduit (8), and an electronic control circuit (13) is operatively connected to the sensors (11,12,14) as well as to the heating device (9) so as to control the heating device (9) in response to detected sensed signals from the sensors (11,12,14).

Abstract: There is provided a slagging combustion system for generating high purity working fluid suitable for driving gas turbines. The system consists of a precombustor for preheating oxidant tangentially fed to a primary slagging combustor where a solid carbonaceous material is combusted under substoichiometric slagging conditions. Slag is collected in the primary slagging combustor and products of combustion passed to a transition section where tertiary oxidant and sulfur-gettering agents are added, and then to a cyclonic secondary combustion chamber.

Abstract: The combustion of fuel having a highly fluctuating thermal value is controlled to permit optimization of air supply and reduction of waste gas impurities. The fuel passes through a combustion chamber having a degassing and evaporation zone, a primary combustion zone, and a secondary combustion zone. Measurements are taken in the evaporation and degassification zone to determine the thermal value of the fuel. This is done by detecting the intensity of H.sub.2 O and/or CO.sub.2 spectra emanating from the fuel. The measurement results are utilized to optimize the combustion parameters. Such measurements are also made in the following zones in order to provide further control of the combustion process.

Abstract: A solid fuel combustion chamber combusts the fuel utilizing underfire and overfire air. Both the underfire and overfire air derive from a common intake port, with a controllable vane determining the ratio between the two air sources. Gas flow from the solid fuel combustion chamber enters a gas combustion chamber designed to produce turbulence and thereby promote further combustion. The gas flow is then accelerated in a gas flow chamber and directed to the circulating fluid carrying tubes of a heat exchanger. The heat exchanger includes a condensation chamber which extracts sufficient heat from the gas flow to produce a condensate. An injection system superheats the condensate and injects it into the solid fuel combustion chamber to thereby reduce residue accumulation.

Abstract: In a steam generating boiler having a bottom wall supporting a char bed and sidewalls with ports through which air is admitted for combustion of combustible species in the char bed and emanating therefrom, combustion is improved by introducing an oxygen-containing gas into a lower central zone of the boiler, from at least one point remote from the sidewalls to thereby cause intimate mixing of the oxygen contained in the gas with the combustible species.

Abstract: The present invention relates to a gasification burner for heating apparatus (boiler, hot air generator or the like) which uses solid fuel. The gasification burner is placed generally at the center of the hearth of the heating apparatus to achieve gasification of the solid fuel before its transformation into charcoal or coals.

Abstract: A burner for burning, granular, pellet or similarly sized solid heating fuel includes a retort in which solid fuel is ignited and burned. A peripheral electrical igniter is included within the retort for initiating self-sustaining combustion of the solid fuel at its uppermost surface. Combustion air is supplied centrally within the retort and is emitted radially outward for burning solid fuel evenly across its uppermost surface. Thermostatic control and safety circuits are included for safely and efficiently operating the burner.

Abstract: A water-cooled air supply system for the combustion chamber of an incinerator. A longitudinal trough is formed in the lower end of the combustion chamber and a plurality of air supply tubes are spaced above the bottom of the trough. Elongated shrouds are secured in spaced relation to the upper and lower portions of each air supply tube and define cooling passages that receive a cooling medium. A plurality of outlet ports are located in each side of each air supply tube between the spaced edges of the shrouds and air is discharged from the ports into the lower end of the combustion chamber.

Abstract: An incinerator for burning waste material includes an outer steel housing having a refractory liner that defines a combustion chamber. A series of channels are secured to the inner surface of the housing and provide vertical air flow passages. The lower ends of the passages are open to the atmosphere, while the upper ends are connected to a plenum and air is drawn through the passages by a blower to thereby preheat the air and cool the outer housing. A portion of the preheated air is directed to the stack for secondary combustion purposes, while a second portion of the preheated air is returned through vertical passages in the end of the housing to a pair of lower plenums and then introduced into the lower end of the combustion chamber for primary combustion purposes. The incinerator also has an improved feed assembly for feeding waste material to the combustion chamber, which includes a hopper, a triple hydraulic cylinder and a ram movable within the hopper.

Abstract: The invention relates to a method of destroying and vaporizing refuse, primarily household waste. The material is fed into a shaft furnace, in which the material is subjected to a vaporization and combustion process in at least three zones, said zones being produced by the supply of blast air at least at three different levels in the shaft furnace which blast gas completely or partly is supplied with controlled quantities of thermal energy by means of electricity, preferably by using at least one plasma generator. The gas produced by the process is withdrawn through an annular drum, arranged about two thirds of the way up the shaft furnace. The gas leaving can be used as combustion gas e.g. for district heating plants and steam power stations with varying thermal requirements.

Abstract: A process is disclosed for inhibiting corrosion of metal surfaces and deposition of particulates in an air preheater system. In the process, a composition (preferably aqueous) comprising a corrosion inhibiting amine and a surfactant having an HLB value of from about 8 to about 20, preferably from about 10 to about 14, is supplied to the combustion gas-in side and/or to the air-in side of the air preheater for protection of the metal surfaces and minimizing such deposits. In a preferred embodiment, the process of the invention can employ an amine salt of a C.sub.12 to C.sub.24 tertiary alkyl amine an amine oxide, or an amine oxide salt, either alone or with a surfactant.

Abstract: There is disclosed an improved solid fuel combustion assembly including a combustion chamber having a high heat capacity liner and provided with primary and secondary combustion supporting fluid conduits to thereby achieve combustion temperatures in the combustion chamber of from 1000.degree. C. to 1200.degree. C.

Abstract: In a method in the operation of a firing plant of the type comprising a combustion furnace and heat exchanger means to transfer thermal energy from the flue gas of the furnace to its combustion air, wherein a vaporizable liquid, such as water, is added to the combustion air of the furnace, the combustion air pressure is reduced in the portion of the heat exchanger means where the said liquid is caused to evaporate, the necessary evaporation heat being taken from the flue gas of the furnace before the flue gas is discharged to the atmosphere. A plant for performing the method is characterized by containing a pump (11) which has a relatively small inlet opening (10) so that the pump (11) creates a negative pressure in the portion (12) of the heat exchanger (9) where the liquid, fed by means of a nozzle (13), evaporates. This allows large amounts of water to evaporate, and flue gas, which flows through the heat exchanger portion (14), is cooled to a low temperature.

Abstract: An improvement in method and apparatus of fluidized beds involving heat or combustion by pre-heating the exterior and interior of the fluidized bed in unison through the use of an exterior chamber surrounding the fluidized bed chamber. This exterior chamber also provides equalization of fluidizing gas temperature with internal fluid bed temperatures during operation of the bed and allows for a scaling down of the fluidized bed to a small size without sacrificing high efficiency.

Abstract: A burner for use in burning granulated solid fuel including a burner head having a combustion chamber and inlet and outlet openings at opposite ends thereof communicated with the combustion chamber. Means is provided to deliver granulated solid fuel to the inlet opening and means is provided for delivering primary combustion air to the inlet opening. The primary combustion air is preheated by passing along the burner head prior to entry to the inlet opening and a pilot assembly in the combustion chamber maintains a constant pilot during turndown of the burner. A retention barrier in the combustion chamber retains fuel particles larger than a predetermined size in the combustion chamber to insure complete incineration thereof.

Abstract: A heat generator comprising a fuel supply chamber (7a), having at its lower end an inwardly tapered section (12), comprising at its lower end a burner plate (14) with mixing strips (33) and a combustion pipe (20), said tapered section (12) being provided with apertures (8) for primary air in its upper part, apertures (13) for secondary air at a level just above the level of the burner plate (14) and apertures (22) for tertiary air at a level just below the level of the burner plate (14) at the level of mixing strips (33). Preferably all air supplies are preheated. The combustion pipe (20) stands in closed connection with an outlet-pipe, preferably provided with an adjustable ventilator.

Abstract: A combustion system for domestic or small industrial heating needs, utilizing biomass fuels such as wood and brush chips, sawdust, logs, nut hulls, peat, leaves and other organic waste products of forestry, agriculture and industry with essentially smokeless, clean exhaust. By preheating the combustion air, insulating the combustion process and carefully controlling the fuel to air proportions and mixing parameters, essentially complete combustion with very little excess air at high temperatures is achieved even with fuels containing over half their weight in water. This water is then condensed out of the exhaust gases in uniquely designed air and water counterflow heat exchangers that can capture over 90% of the high heat value of the fuel. This invention is capable of maintaining clean combustion at high temperatures with little excess air, at burn rates much lower than the best popular "air-tight" woodstoves and is capable of higher heat outputs than most domestic heat plants.

Abstract: A combustion heater for oil shale heats particles of spent oil shale containing unburned char by burning the char. A delayed fall is produced by flowing the shale particles down through a stack of downwardly sloped overlapping baffles alternately extending from opposite sides of a vertical column. The delayed fall and flow reversal occurring in passing from each baffle to the next increase the residence time and increase the contact of the oil shale particles with combustion supporting gas flowed across the column to heat the shale to about 650.degree.-700.degree. C. for use as a process heat source.

Abstract: Stoker type firing equipment for use with a city refuse incinerator provided with step type stokers formed by combining movable fire grates and fixed fire grates alternately and gas injectors installed in the fixed fire grates inject low temperature inert gas onto burning refuse, thus allowing free control of burning rate and burning temperature of the refuse by injecting the low temperature inert gas through the gas injectors.

Abstract: A tangentially-fired, pulverized coal burning furnace (10) having overfire air (OFA) introduced into the upper portion of the furnace. The fuel and air are introduced (36, 38) into the furnace at the burner level tangentially of an imaginary circle, so that the resultant fireball moves upwardly within the furnace with a rotational spin. The OFA is introduced (40, 42) tangentially of an imaginary circle, in the reverse rotational direction to that of the fireball, so that the exhaust gases flowing from the furnace to the rear gas pass (16) flows in a straight line, with little or no spin. The OFA is made up of a mixture of low pressure air and high pressure air of sufficient volume and pressure to nullify the spin of the fireball.

Abstract: A powered downdraft type combustion unit which substantially completely gasifies the fuel burned therein during the combustion process and produces a maximum amount of usable heat for utilization at a location remote from the combustion unit is provided. The present combustion unit includes a heavily insulated outer shroud enclosing insulated sequential combustion chambers to prevent heat loss from the combustion chambers. A primary combustion chamber is separated from a secondary combustion chamber by a plurality of refractory grates. Fuel is fed to the primary combustion chamber to be combusted therein, and the products of this stage of combustion then pass to the secondary combustion chamber where the combustion process is completed. The heat-containing combustion gases are directed from the secondary combustion chamber to a heat utilizing appliance through a conduit connected therebetween.

Abstract: A device for heating air by flue gases in steam boilers and furnaces, comprises a supply flue, sections mating therewith, and a device for protection of heat-exchange tubes against abrasive wear arranged in the flue. Each section comprises heat-exchange tubes attached to tube plates. The device for protection of the heat-exchange tubes against abrasive wear incorporates at least one screen formed by corrugated sheets facing each other and mating along the lines of contact of sheet convex portions, whereby cells are made up.

Abstract: A method and apparatus for improving the efficiency of a heat generator in which combustible fuels such as fossil fuels, refuse, or other materials are burned is described. Flue gas generated in the heat generator and combustion air are passed in heat exchange relationship in a heat exchanger. The heat exchanger is selected so that it removes a substantial amount of heat from the flue gas, whose temperature is consequently lowered to a level where a corrosive pollutant such as SO.sub.3 in the form of H.sub.2 SO.sub.4 is likely to condense out. A pollutant removing liquid is applied onto the portion of the heat exchanger where the flue gas passes through both to scrub the flue gas and protect that portion of the heat exchanger from corrosive effects from condensed pollutants.

Abstract: Apparatus and process for incinerating waste and reclaiming resources, particularly ferrous metals, galss, and aluminum, in separate output streams. The incinerator itself can use combustion draft air as a medium for separating lighter and heavier fractions of the burned material in the incinerator. The combustion zone of the incinerator is defined by a foraminated cylindrical wall which is rotated to distribute the incinerating materials and separate burned waste from the combustion zone.The incinerator can be cooled by a eutectic liquid metal coolant. The use of this coolant allows the heat exhange surfaces of the incinerator to be quite thin for greater economy, as such fluids, particularly a eutectic mixture of sodium and potassium, do not vaporize at atmospheric pressure over a wide working temperature also disclosed, as is improved means for separating aluminum rich and glass rich fractions from the heavier fraction of burned waste separated in the incinerator.

Abstract: A pulverized solid fuel is injected into a shaft furnace by being entrained in a stream of pressurized air, the resulting fuel-air mixture subsequently being further mixed with heated air being delivered to the furnace via a tuyere. The air used to entrain the pulverized fuel is diverted from the cold air supply to a mixing station, which is used to control the temperature of the hot air supplied to the furnace via the tuyere, and this diverted air is pressurized prior to the pulverized material entrainment.

Abstract: A furnace and associated heat storage assembly includes a firebox arranged within a rock storage area that incorporates a recirculating flue arrangement for returning unburned gases to below a fuel grate for mixing with fresh inlet air. The rock in the heat storage area is heated by conduction of heat from the firebox, circulating flue gases and a smoke exhaust flue. Inlet air is preheated. An open grate arrangement provides for efficient burning of solid as-producing fuel. A system for circulating air and/or liquid through the rock can be provided, as can a water storage tank.

Abstract: In order to burn a fuel of low ignition properties and low contents of volatile gases in steam generators: the combustion air is introduced in three batches at three successive places into the firebox. Preferably, the primary air is introduced at a temperature of at least about 500.degree., preferably between 500.degree. and 600.degree. C. so as to effect a pregasification of the fuel. The secondary air is then introduced at a temperature of about 350.degree. to 400.degree. C. to start the combustion of the pregasified fuel and the tertiary air is finally introduced at a temperature of only about 250.degree. to 300.degree. C. in order to complete the combustion. This temperature differentiation of heat ranges then will permit to withdraw theash as a dry discharge.

Abstract: Heat is recovered from the flue gas stream discharged from a power plant combustion zone by heat exchange of the flue gas stream against the air stream which enters the combustion zone. Each gas stream flows through two rotating air preheaters, with a first preheater rotating at a constant rate and a second preheater rotating at a variable rate. The rate of rotation of the second preheater is varied to adjust the temperature of either the heated air stream or the temperature of the flue gas stream after passage through the preheaters.

Abstract: There is always a danger of slagging on and/or corrosion of the tubes of the highest temperature superheater bank and, if present, reheater bank when burning heavy bunker fuel oil. Therefore a clean fuel burning furnace is provided which is separate from the heavy bunker fuel oil burning furnace and only the combustion gases from burning the clean fuel are used to heat the highest temperature superheater bank and, if present, reheater bank. The clean fuel is preferably provided by a gasifier in which a portion of the heavy bunker fuel oil is pre-combusted to give a clean combustible fuel gas.

Abstract: A coal fired steam generating system including an auxiliary oil fired burner combined with an air heater. The air heater provides heated air that is adapted to heat and dry the coal for combustion, while hot products of combustion exhausting from the oil fired burner supply heat to a precipitator that raises its operating temperature to increase its collecting efficiency.