Abstract: A pollutant removal/heat exchange apparatus is mounted to a wood burning stove to receive the emission products from the stove. The apparatus comprises a plurality of vertically aligned tubular electrodes which define vertical through passageways. Negatively charged disc-like electrodes are positioned within the tubular electrodes. Partially burned hydrocarbons and moisture in the emission products become negatively charged as they pass through the tubular electrodes to become deposited on the inner surfaces of the tubular electrodes. Ambient air is directed through the passageways between the tubular electrodes to extract heat from the emission products, with the heated air being discharged from the apparatus. The electrostatic precipitation of the material on the tubular electrodes not only removes undesired material from the emission products, but also enhances heat exchange with the ambient air passing through the apparatus.

Abstract: A cyclone arrangement for cleaning gas from a gas generator for gasifying coal which is exhausted at high pressures. The invention proposes that the cyclone arrangement for the cleaning of crude gas includes at least two cyclones connected in parallel on their input sides, which cyclones can be turned on and off individually. Thereby a dry cleaning of the crude gas can be performed with only a slight temperature loss. The quantity of gas corresponding to the optimum cleaning efficiency can be adjusted to the quantity of gas either discharged from the gas generator or actually required for the pressurization of the steam generator by adjusting the number of cyclones put into operation, without the need for the inclusion of buffer capacities. The gas generator comprises a pressurized fixed bed reactor.

Abstract: A coal gasifier has a fluidized bed reactor. The gasifier has a series of cyclones connected to an outlet of the gasifier to clean the gas generated by the fluidized bed reactor to isolate particulate matter. The cyclones are turned on and off individually to compensate for the variations in the gas output of the fluidized bed reactor.

Abstract: A PFBC plant which includes a gas cleaner located inside an air-filled pressure vessel is provided with means to detect erosion damage in the gas cleaner. Portions of the wall of the gas cleaner which are exposed to erosion damage are surrounded by a space defined by a gas-tight mantle. The mantle has an opening which provides a connection between the defined space and the air in the pressure vessel. Adjacent the opening is a device for indicating when air flows through the opening into the defined space.

Abstract: A rubbish treating apparatus in which the rubbish is gathered, separated, and crushed, after that the crushed rubbish is transferred to a magnetic conveyor, such that ferro-metallic rubbish and non ferro-metallic rubbish are separated. The non ferro-metallic rubbish is then transferred to a pressing device in which the rubbish is pressed, and finally the rubbish is further crumbled and burned in a burner. The gas produced while burning is purified, therefore such procedure can be used to solve the problem of pollution due to rubbish.

Abstract: A furnace system connected to a burner including a furnace for burning a fuel and air ejected from the burner into the furnace to produce a flame therein, and a combustion condition determining device for determining the conditions of combustion of the fuel in a zone of the flame extending along different strata thereof by collecting light in the flame at one point in the flame by moving such point. Signals outputted by the combustion condition determining device are utilized for monitoring or controlling the flame and controlling exhaust emission control devices for controlling exhaust emissions produced by the combustion of the fuel. Control of the conditions of combustion of the flame can be effected quickly with a high degree of precision by monitoring the flame.

Abstract: Dissolving salt encrustations which are deposited by exceeding the saturation limit from a gas saturated with water vapor on the heat exchanging surfaces of a heat exchanger, by passing the gas through a heat exchanger subdivided into several sections. The predominant part of the sections is subjected to a hot fluid heating the gas saturated with water vapor and the smaller part of the sections to a cold fluid for cooling the gas below the dew point. The salt crust is dissolved in the cooled sections by the separated condensation water and the salt solution is drained from the heat exchanger. After the salt crust is removed, the cooled sections are subjected to the hot fluid and parts of the heated sections to the cold fluid.

Abstract: A circulating fluidized bed furnace (10) is disclosed wherein a non-cyclonic particulate separator (18) is integrally disposed in the flue gas flow path between the furnace gas outlet (14) and the flue gas duct (16). The separator (18) comprises an arcuate duct (20 ) having a curvilinear inner wall (24), the portion thereof which is disposed across the inlet to the flue gas duct (16) having a plurality of openings (28) therein which provide a flow area through which a portion of the flue gas pass into the flue gas duct (16). Gas/solids separation is accomplished as the flue gas turns sharply from its arcuate path to pass through the openings (28) in the inner wall (24). The momentum of the particulate solids and the centrifugal forces acting thereon prevent the solids from sharply turning and cause the solids to continue on their arcuate flow path through the duct (20) in the remaining flue gas to a solids collection means (40) opening to the solids outlet (26) of the arcuate duct (20).

Abstract: The invention comprises a coal-fired burner system for use in a drum mix asphalt plant or drum dryer used for producing asphalt paving composition. Coal to fire the burner is ground to a -200 mesh size by an air-swept rotary impact mill, and a classifier at the exit from the mill controls the size of the particles leaving the mill. The pulverized coal particles are recovered from the exhaust airflow exiting the mill by a fiber filter collector and temporarily stored in a small surge bin. Coal is metered from the surge bin into a primary air conduit leading to the burner. The availability of a small but ready supply of coal in the surge bin provides quick response to a need for increased coal while avoiding the dangerous storage of large quantities of pulverized coal dust. As the weight of coal dust in the surge bin decreases, control circuitry provides for the processing of additional coal to maintain a ready supply of processed coal in the surge bin.

Abstract: A process for the purification of flue gas generated during the combustion of waste materials has a first embodiment wherein soluble heavy metals are precipitated and recovered in a compact form and wherein the soluble heavy metal-free extraction residue is returned to the combustion system where noxious organic substances are pyrolyzed. In another embodiment, substantially all of the heavy metals from the flue gas are collected in a single solid residue, which residue may be thermally treated to recover mercury and the treated residues subsequently returned to the combustion system wherein noxious organic substances are pyrolyzed or combined in a hazardous waste stabilizing substance.

Abstract: A steam generator in which a plurality of vertically spaced fluidized beds are provided in a single enclosure, with one boundary wall of the enclosure having openings therein for permitting the discharge of effluent gases from the fluidized beds. A heat recovery enclosure is defined adjacent the beds for receiving their effluent gases and a fluidized bed is disposed in the heat recovery enclosure. A separator system is disposed adjacent the heat recovery enclosure and receives the effluent gases from the heat recovery enclosure and separates the entrained solid particles therefrom. The separated particles are reinjected into the fluidized bed in the heat recovery enclosure.

Abstract: A compact incinerator for biomass has an upright combustion chamber coaxially surrounded by a passage through which the biomass is fed from a separator in which the primary air is separated from the biomass, to the combustion chamber. An afterburner chamber surrounds this shaft so that flue gases from the combustion chamber can pass through the shaft and be filtered by the biomass while heating the biomass before afterburning is effected in the afterburner chamber. The primary air from the separator is preheated in a preheater in indirect heating exchange by the flue gas in the same coaxial apparatus which also includes, coaxially with the combustion chamber, a flue gas/solids separator for removing solids from the flue gas before it enters the preheater.

Abstract: A method and apparatus for the heat treatment of fine-grained material wherein the degree of efficiency of the last cyclone of a multi-cyclone preheater preceding a filter is reduced in the finest grain size range and at least a proportion of the filter dust deposited in the filter is passed directly to the calciner. In this way material is prevented from caking and flowing in batches in the apparatus.

Abstract: A waste disposal system for the combustion of waste materials, that may include toxic chemical waste, wherein the wastes are combusted in a combustion unit with combustion gases directly discharged into a refractory lined housing having a plurality of ceramic filters disposed in the gas outlet wall thereof. The combustion gases are maintained in the refractory lined housing for a period of time sufficient to effect combustion of the major portion of residual vaporous waste constituents therein and then passed through the ceramic filters to remove the remainder of said vaporous waste constituents and the residual solid waste constituents. The waste-free, hot combustion gases, after passage through the filters, are directed to a heat exchanger for recovery of heat values therefrom.

Abstract: The flue gases, which are generated in a combustion chamber through combustion of solid fuels, particularly under increased pressure, are cleared of dust in a dust removal device which consists of a plurality of tubular ceramic filter elements open at one side. These filter elements are suspended in a plate, which represents the ceiling of the combustion chamber.

Abstract: Methods of and apparatus for removing contaminants from heated gases by impact separation. The contaminants are collected by adhering them to a moving surface, and they are thereafter removed from that surface.

Abstract: A garbage to hydrocarbon fuel conversion system is provided which generates electricity and hydrocarbon gases from combustible garbage. The garbage is pulverized and then burned in a destructive distillation process. The heat produced is used to generate electrical power. Dust precipitated by an electrostatic cottrell precipitator is mixed with light oil and burned in an oil burner. The heat obtained is used to maintain the destructive distillation. The gases which rise to the top of the precipitator are passed through a hydroxide solution which leaves a layer of tar and oil floating on top of the solution and a volume of hydrocarbon gases on top of this layer.

Abstract: In a coal-fired combined plant, finely powdered coal is burned at high temperature in a pressurized coal-melting combustion furnace to obtain combustion gas substantially free of dust to drive a gas turbine in order to generate electric power. Waste gas from the gas turbine is used to produce steam which drives a steam turbine for additional electric power generation. Primary dust removal from the combustion gas is carried out by removing most of the resulting coal ash in a molten state. In a secondary dust removal, the dust is removed from the combustion gas by a cyclone disposed in the combustion furnace. In a tertiary dust removal, the dust is removed from the combustion gas which is discharged through an outlet at the combustion furnace by a precision dust-removing device.

Abstract: A fluidized bed combustion apparatus in which in the free-board above the bed at least one system of plates or baffles inclined with respect to the vertical is arranged so that at least one upwardly directed channel having internally at least one group of two opposed arrays of superimposed inclined plates is formed, which plates at least alternately extend obliquely downwardly from the outside to the inside and are closely connected with the outer boundary of the channel. Preferably all plates of each array extend obliquely downwardly at an angle with the vertical within 20.degree.-50.degree. from the outside to the inside from a vertical wall defining said channel whereas the plates of the one array are off-set over a distance "s" in the vertical direction with respect to the plates of the other array.

Abstract: A steam generator for burning a normally-solid fuel which produces non-combustible solid residues, including, an elongated combustion chamber, a fuel introduction means to introduce fuel adjacent the axis of the combustion chamber as a centrally-disposed stream moving in a downstream direction, a combustion-supporting gas introduction means for introducing the gas as an annular, rotating stream about the fuel stream and which, together with the fuel introduction means forms a rotating, toroidal vortex of the fuel and the combustion-supporting gas moving in a downstream direction. The combustion chamber has a volume sufficient to burn all of the fuel and, together with the fuel introduction means and the combustion-supporting gas introduction means, cause the vortex to collapse and form plug flow thereafter. Water introduction means introduces water into the flue gas at the downstream end of the combustion chamber as a plurality of peripherally-arranged jets.

Abstract: A reaction chamber with a fluidized bed encloses two superposed cyclone separators connected in series. In order to prevent combustion gases from entering the lowermost separator by way of its particulate matter outlet, this is formed as a downwardly extended pipe, which is enclosed by a sleeve through which secondary air passes. The sleeve projects somewhat below the mouth of the pipe, and the issuing air causes an ejector action, which prevents gas from entering the pipe. The particulate matter return flow pipe from the upper cyclone is also extended downwards and terminates within the ejector. A storage vessel is located below the reaction chamber. An open conduit extends from the storage vessel to a location above the fluidized bed. Also, there is a return conduit for returning material from the storage vessel to an area above the fluidized bed. An equalizing conduit connects the vessel with an ejector supplying air to the fluidized bed.

Abstract: The volume of low-level radioactive wastes containing free water is reduced by introducing the waste as a finely atomized spray into a zone heated by means of a hot gas. Contact of the spray particles with the hot gas results in the production of a dry, flowable radioactive solid product and a gaseous non-radioactive product which contains substantially no NO.sub.x or SO.sub.x and no volatile radionuclides, which are retained in the solid product.

Abstract: A combustion gas cleaning system includes a transferring portion, a treating portion, an impurity collecting portion, an exhaust portion and a liquid purifying portion. The transferring portion includes a substantially horizontal first duct member having one end communicating with a smokestack. A first sprayer is located around the inside periphery of the first duct member. The treating portion includes an elongated substantially vertical chamber, the top of which communicates with the first duct member. The chamber has a plurality of spaced fan members disposed within the chamber transversely along the length thereof. A second sprayer is disposed adjacent each fan member. The impurity collecting portion includes a second horizontal duct member extending from the lower end of the chamber. A liquid reservoir communicates therewith through a plurality of openings in the bottom of the second duct member. The liquid level in the second duct member reduces the cross-sectional area thereof.

Abstract: A gas-permeable thermal insulator comprising a porous ceramic body of a three-dimensional reticulate structure having interconnected open cells is adapted to be installed in a heating oven or radiant tube so that exhaust gas passes through the insulator to exit the oven or tube while the waste heat of the gas is effectively recovered for reuse. The porous ceramic body is characterized by a bulk specific gravity of 0.25-0.6, an average pore diameter of 0.2-10 mm, a porosity of 75-95%, and an air pressure drop of 0.1-40 mm in water column when air passes through the body over a thickness of 1 cm at a velocity of 1 m/sec.

Abstract: Exhaust gas treatment method and apparatus extract heat from an exhaust gas by operating in a water-condensing mode which allows more heat to be recovered, removes particulate matter and condensed acid from the exhaust gas, and washes heat exchange surfaces to keep them clean and wet to improve heat transfer. Systems for heating water, air and both water and air are disclosed. Methods of constructing and assembling improved heat exchangers are disclosed.

Abstract: A furnace for burning a particulate fuel compacted into a plug which includes a force feed of particulate fuel through a compacting means and into a tubular furnace in which burning is expected within the compact fuel plug by injecting air through the furnace wall.

Abstract: A two part heat recovery unit receives a high temperature gas mixture (2) in the lower, refractory-lined dwell furnace (4) wherein the gas is cooled to condense out liquid inert ash material. The cooled gas mixture exits the dwell furnace (4) vertically upward through a transistion duct (18) which includes a restricted throat (28). Additional ash and potassium seed compounds condensed from the gas mixture in the convective furnace (20) either form a loose flyash which exits the convective furnace (20) with the gas mixture via the backpass (24), or collect on the walls and heat transfer surfaces (22) of the furnace (20) as a liquid which runs downward toward the throat (28) and is there reentrained by the high velocity gas stream.

Abstract: A process and apparatus for removing sulfur oxide from combustion gas to form Na.sub.2 SO.sub.4 and for reducing the harmful effects of Na.sub.2 SO.sub.4 on auxiliary heat exchangers in which a sodium compound is injected into the hot combustion gas forming liquid Na.sub.2 SO.sub.4 in a gas-gas reaction and the resultant gas containing Na.sub.2 SO.sub.4 is cooled to below about 1150.degree. K. to form particles of Na.sub.2 SO.sub.4 prior to contact with at least one heat exchanger with the cooling being provided by the recycling of combustion gas from a cooled zone downstream from the introduction of the cooling gas.

Abstract: A reaction chamber with a fluidized bed encloses two superposed cyclone separators connected in series. In order to prevent combustion gases from entering the lowermost separator by way of its particulate matter outlet, this is formed as a downwardly extended pipe, which is enclosed by a sleeve through which secondary air passes. The sleeve projects somewhat below the mouth of the pipe, and the issuing air causes an ejector action, which prevents gas from entering the pipe. The particulate matter return flow pipe from the upper cyclone is also extended downwards and terminates within the ejector.

Abstract: Apparatus and method for incinerating toxic and non-toxic waste using a modified preheater-type lime kiln is disclosed wherein the kiln is modified to incinerate waste and the preheater section is modified to provide an incineration processing aid such as limestone and also to more efficiently utilize and conserve heat values.

Abstract: A domestic forced-air furnace provided with a condensate collector downstream of air moving structure for flowing the products of combustion through the furnace. The furnace includes a secondary heat exchanger. Condensate produced therein is transferred therefrom through the air moving structure to the condensate separator. The secondary heat exchanger and air moving structure are inclined slightly to the horizontal so as to cause continuous flow of condensate therethrough not only during operation of the furnace but also subsequent thereto to assure removal of condensate from the furnace components and thereby avoid corrosive damage thereto from the condensate. The secondary heat exchanger provides the primary pressure drop in the combustion product flow path, permitting control of the furnace capacity by simple modification thereof without the need for changing other components, such as the air moving structure.

Abstract: A fluidized bed combustion apparatus in which in the free-board above the bed at least one system of plates or baffles inclined with respect to the vertical is arranged so that at least one upwardly directed channel having internally at least one group of two opposed arrays of superimposed inclined plates is formed, which plates at least alternately extend obliquely downwardly from the outside to the inside and are closely connected with the outer boundary of the channel. Preferably all plates of each array extend obliquely downwardly at an angle with the vertical within 20.degree.-50.degree. from the outside to the inside from a vertical wall defining said channel whereas the plates of the one array are off-set over a distance "s" in the vertical direction with respect to the plates of the other array.

Abstract: A heat generating system using solid fuel in a water jacketed combustion chamber for supplying hot water to units for space heaters and hot water storage units, and in which control means is provided for operating the fuel combustion mode to obtain recovery of the products of combustion during low rates of combustion, and to greatly reduce emissions during increased rates of combustion, the control means including thermostatic units having selected points of active and inactive responses.

Abstract: Exhaust gas treatment method and apparatus extract heat from an exhaust gas by operating in a water-condensing mode which allows more heat to be recovered, removes particulate matter and condensed acid from the exhaust gas, and washes heat exchange surfaces to keep them clean and wet to improve heat transfer. Systems for heating water, air, and both water and air are disclosed. Methods of constructing and assembling improved heat exchangers are disclosed.

Abstract: An installation for the thermal treatment of a pulverulent mineral product by gases has a support frame at a first level, a furnace for the thermal treatment of the pulverulent mineral product in suspension in hot gases generated by the combustion of air and a fuel, two groups of series-connected cyclones connected to the furnace, one of the groups of cyclones being arranged upstream of the furnace and the other group of cyclones being arranged downstream of the furnace, and conduits connecting the cyclones to each other and to the furnace so that exhaust gases from the furnace pass successively through all the cyclones of the one group while a current of air passes through all the cyclones of the other group before entering the furnace to serve as the combustion air, the exhaust gases heating the product before it enters the furnace and the air current cooling the treated product.

Abstract: A method for generating steam by a high pressure, high intensity, or high heat release method of combustion in an elongated combustion zone having upstream and downstream ends and an intermediate location and utilizing a normally-solid fuel which produces non-combustible solid residues in which the fuel is introduced axially and a volume of air, at least equal to the stoichiometric amount, is introduced as an annular, rotating stream to produce a rotating vortex of fuel and air, such introduction and flow through the combustion zone being carried out in a manner to collapse the vortex and create plug flow at the intermediate location, burning the fuel and air to produce flue gas at a heat release rate of at least 7 MM Btu/hr, abruptly terminating combustion by the introduction of water, vaporizing the water to produce a mixture of flue gas and steam, and separating solid residues therefrom.

Abstract: A city refuse incinerator provided with stoker type firing equipment for combustion of city refuse has gas injectors installed low on the inside of a furnace body to inject low temperature inert combustion exhaust gas, purified in a dust collector, so that a gas curtain is formed on the inner surface of side walls of the furnace by the low temperature inert gas, thus preventing the formation of clinkers.

Abstract: In the process for cleaning of flue gases of a power plant boiler, the flue gases are dust filtered at first and then wet desulfurized. By the wet desulfurization the flue gases are cooled down and have to be reheated before they are fed to the stack of the power plant. In known processes the flue gases to be reheated are reheated by a flame burning oil or gas. This reheating is expensive and leads to the handling and storage of a further fuel in the power plant. In order to avoid this disadvantages, according to the invention the flue gases are reheated by means of reheating energy of at least one reheating flame burning coal dust. Coal dust is a fuel which is available in a power plant, the power burners of which coal dust.

Abstract: Flue gas from a coal-fired combustion to which a dry sulfur-binding additive is supplied, after cooling is subjected to filtration to remove additive ash therefrom. According to the invention, cooled additive ash is fed to at least a portion of the flue gas to reduce the temperature thereof approximately to the water dewpoint, thereby promoting the sulfur-binding reaction.

Abstract: A waste material incineration system (10) and method of combusting waste material is provided wherein system (10) includes a longitudinally directed furnace (14) having a first combustion zone (42) and a second combustion zone (44). Waste material or other fuel is inserted into furnace (14) through a furnace inlet (26) and passes by gravity assist into a vortexing pattern dependent upon the geometrical contouring of the internal walls of furnace (14) in combination with preheating air conduits (86, 88 and 90). Subsequent to vortexing in the first combustion zone (42), the substantially fully combusted gases are transported through second combustion zone (44) for insert into a heat exchanger unit (12) and then passes to a scrubber unit (34) where the exhausted gases are further cleansed to expulsion of the cleansed exhaust gases through an exhaust stack (16) to the ambient atmosphere.

Abstract: Exhaust gas treatment method and apparatus extract heat from an exhaust gas by operating in a water-condensing mode which allows more heat to be recovered, removes particulate matter and condensed acid from the exhaust gas, and washes heat exchange surfaces to keep them clean and wet to improve heat transfer. Systems for heating water, air, and both water and air are disclosed. Methods of constructing and assembling improved heat exchangers are disclosed.

Abstract: A fluidized bed combustion system for burning fuel particles, such as coal. The system includes a housing defining a first combustion region. An endless, flexible, perforate belt is shiftably mounted in the housing for supporting coal particles of relatively large size. A blower below the belt creates fluidized air which entrains smaller coal particles in a fluidized bed above the larger coal particles. The combustion gases arising due to combustion of the coal particles passes through a secondary combustion region in which coal fines are burned. The combustion gases continue upwardly through a scrubber in which limestone particles are entrained in the combustion gases to strip sulfides therefrom. The limestone particles are regenerated by a cyclone separator while the combustion gases travel through a passage containing boilers or other heat exchangers, whereby the heat from the combustion gases is transferred to fluids in the boilers.

Abstract: The products of a molten salt combustion of hazardous wastes are converted into a cooled gas, which can be filtered to remove hazardous particulate material, and a dry flowable mixture of salts, which can be recycled for use in the molten salt combustion, by means of gas/liquid contact between the gaseous products of combustion of the hazardous waste and a solution produced by quenching the spent melt from such molten salt combustion.The process results in maximizing the proportion of useful materials recovered from the molten salt combustion and minimizing the volume of material which must be discarded. In a preferred embodiment a spray dryer treatment is used to achieve the desired gas/liquid contact.

Abstract: A method of treating reaction products which result from the combustion of fuels containing contaminants such as sulfur, chlorine, and fluorine compounds, and ash. Additives are reacted in the combustion chamber with gaseous contaminants of the reaction products of the combustion. Subsequently, the remaining reactive additives, the reactive ash constituents, and possibly supplementary additives are reacted externally of the combustion chamber with the still uncombined gaseous contaminants of the reaction products.

Abstract: A melting apparatus has a low temperature melting portion (29), an exhaust gas cooling portion (26), and a dust collecting portion (B27) which are arranged, in succession, in an exhaust gas duct (54) of a melting furnace (B22). A low boiling point dust collected in the dust collecting portion (B27) is returned to the low temperature melting portion (29) for melting by retention heat of an exhaust gas flowing into the exhaust gas duct (54).

Abstract: Burning a waste fuel blend at very high temperatures (typically greater than 4000 deg. F.) for a very short period of time (typically a matter of milliseconds) in a primary combustion zone to break the complex hazardous/toxic hydrocarbons into less complex chemicals (such as CO, CO.sub.2, H.sub.2, OH, HCl, and Cl.sub.2), passing the products of the primary zone into a secondary zone in which the products are maintained for a longer time (typically about 2 secs.) in turbulent conditions with excess air at lower combustion temperatures (typically 2000 to 2600 deg. F.) to reduce the primary zone products to a mixture of H.sub.2 O, CO.sub.2 and acids such as HCl, and quenching the products of the secondary zone.

Abstract: A method of treating reaction products which result from the flame combustion of fuels containing contaminants such as sulfur, chlorine, and fluorine compounds, and ash. Additives are added to the combustion chamber by means of a gaseous and/or liquid carrier flow accompanied by the formation of a veil which surrounds the burner flame. Subsequently, the remaining reactive additives, the reactive ash constituents, and possibly supplementary additives are reacted externally of the combustion chamber with the still uncombined gaseous contaminants of the reaction products.

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: A method of drying wet coal fines smaller than 28 mesh in size employs both a vibrating fluidized bed type dryer and a coal fired burner for supplying hot drying gases to the dryer. A regenerative separator is interposed between the coal fired burner and the fluidized bed type dryer to satisfactorily remove particle matter from the gases without unacceptable pressure losses. Hot gases exhausted from the fluidized bed type dryer are also cleansed to remove particulate coal particles which are used as fuel for the coal fired burner.