Abstract: A process for treating toxic fly ash from an incinerator which comprises heating the fly ash held in suspension in a combustible or combusted gas at least to a temperature at which sintering of the fly ash takes place.

Abstract: A method of operating a combustion unit of a coal-fired power plant operating according to a slag tap furnace firing method, which includes supplying a titanium-containing material in addition to coal to a melting chamber for accelerating coal burn-up, burning the titanium-containing material together with the coal in the melting chamber at a temperature above 1500.degree. C., and generating fly ash and molten ash as a result of combustion in the melting chamber. Additionally, a combustion unit for a coal-fired power plant, including a melting chamber that has a combustion zone for receiving coal. The combustion zone produces fly ash.

Abstract: The method consists in causing the flue gases to pass through a filter placed inside the recovery boiler so that the fly ash contained in said flue gases can be hot filtered out. An additional flow (B) of a material is superposed on the flow of fly ash to be filtered, which material has characteristics such that it increases the melting point of the fly ash by forming high melting point eutectics so as to facilitate unclogging by preventing viscous bridges from forming between the particles of fly ash. Application to hot scrubbing of flue gases generated by burning household refuse.

Abstract: At least one main combustion chamber contains at least one pulverized coal burner. Each pulverized coal burner is operatively arranged for minimizing NO.sub.X production and for maintaining a predetermined operating temperature to liquefy ash within the combustion chamber. The combustion chamber includes a slag drain for removing slag from the combustion chamber. A slag screen is positioned in a generally U-shaped furnace flow pattern. The slag screen is positioned between the combustion chamber and a radiant furnace. The radiant furnace includes a reburning zone for in-furnace No.sub.X reduction. The reburning zone extends between a reburning fuel injection source and at least one overfire air injection port for injecting air.

Abstract: A method for reducing the carbon content of a combustion ash containing siliceous ash particles and carbon particles includes subjecting the combustion ash to comminution to reduce the particle size of the siliceous ash particles and the carbon particles followed by separating a portion of the carbon particles from the siliceous ash particles by subjecting the comminuted ash to a flow of gas which separates the carbon particles from the siliceous ash particles. The method preferably is performed in a unitary housing by employing autogenous grinding to effect the comminution of the particles and employing a classifying rotor to separate the comminuted portion of the carbon particles based on the density differential between the siliceous ash particles and the carbon particles. A method of making a concrete mixture employing the obtained combustion ash with reduced carbon content is also provided. An apparatus for reducing the carbon content of the combustion ash is also provided.

Abstract: Bottom ash and flyash having high LOI is reburned in a pulverized coal furnace. The bottom ash is added to the coal supply before the coal is pulverized. Flyash is added to the pulverized coal stream for injection with the pulverized coal or is separately injected into the furnace at or slightly above the level of the coal burners in the furnace. The bottom ash and flyash is added to the coal in direct proportion of 1% to 3.5% of the coal.

Abstract: A method of separating unburned Carbon, as particulate matter, from the flyash produced as a result of the combustion process occurring in a pulverized-coal fired steam generating power plant is disclosed. More particularly the invention separates the flyash into a coarse product group and a fine product group by utilizing the differences in specific gravity between the Carbon particles and remaining flyash as well as utilization of the dynamic classification characteristics of a rotary classifier to effect the separation whereby at least one of the two product groups comprises a relatively low weight percentage of unburned Carbon while yet comprising a relatively high percentage of the total mass of product recovered after separation.

Abstract: Apparatus for cooling ash exiting from circulating fluidized bed equipment includes an enclosure having a floor, a plurality of walls disposed around the floor and a ceiling. The enclosure also has an inlet and an outlet. The outlet is disposed in one of the walls near to the floor and the apparatus also includes tubing disposed within the enclosure for heat exchange relationship with ash entering the inlet of the ash cooler. In some forms of the invention the floor is planar and is disposed in oblique relationship to a horizontal plane. The outlet may be disposed proximate to the floor at the lowest elevational part thereof. The enclosure may be generally rectangular and may have first and second opposed sides and opposed third and fourth sides. The first and second sides are longer than the third and fourth sides. In some cases the ratio of the length of each of the first and second sides to the length of the third and fourth sides is two or three to one.

Abstract: In the process for burning combustibles, in particular garbage and refuse, on a furnace grate, the combustion regulation on the furnace grate is carried out in such a way that the ash developing at the end of the furnace grate has a temperature lying just below the melting point of the ash. The combustion regulation is preferably monitored by an infrared camera and influenced appropriately. In order to achieve the desired temperature, the combustion air is advantageously mixed with oxygen and/or preheated.

Abstract: A process and apparatus for combustion in which a combustible material is introduced into a combustion chamber and oxidant is supplied to the combustion chamber. The combustible material is burned, and forming a primary combustion zone. A mixture of flue gases and flyash having an organic content is injected into the combustion chamber downstream of the primary combustion zone to create an oxygen-deficient reburn zone, thereby lowering the temperature of combustion, reducing the NO.sub.x content of the flue gases, and reducing the potential for NO.sub.x formation in a tertiary oxidizing combustion zone disposed downstream of the oxygen-deficient reburn zone.

Abstract: In a method for processing solid residues from refuse incineration plants the slag is melted and heavy metals from the melt (16) are separated for reutilization. The slag is directly transferred from the refuse incineration plant into a first heating chamber (2) and melted there under oxidizing conditions. The melt (16) produced therefrom is transferred to a second heating chamber (3), in which the heavy metal compounds are reduced to their metallic form. Furthermore, additional finely divided residues, such as fly ash, boiler ash and filter dust, are introduced into the second heating chamber (3) via a hollow graphite electrode (19). The melt (16) is then passed on to a third heating chamber (4), in which the residual readily volatile metals are vaporized and the residual non-volatile metals are sedimented. The essentially heavy-metal-free melt is then cooled to form vitreous granules.

Abstract: A new apparatus and process for efficient removal of carbon from fly ash has been developed, whereby carbon removal occurs through oxidation as combustion. The ignition of the carbon is accomplished by bulk heating and molecular impingement of a suspended layer of fly ash by a heated oxidizing gas strewn, and the desired level of carbon burnout is accomplished by maintenance of combustion conditions.

Abstract: The present invention describes a process for the disposal of residual substances from waste incineration plants as well as activated coke and/or activated carbon. For this purpose the residual substance as well as activated coke and/or activated carbon is introduced into the annular shaft (3) of the primary chamber (2) of the furnace (1). In the primary chamber (2) a temperature of 1250.degree. C. to 1500.degree. C. is set. The molten material flowing off leaves the primary chamber (2) together with the flue gases through the central outlet (4). The molten material is passed through the secondary chamber (5) and is discharged as slag.

Abstract: A process for the treatment of solid residue from a refuse incineration plant, involving:melting the solid residue in a first heating chamber under oxidizing conditions to provide a melt;reducing any heavy metal compounds present in the melt to elemental metal in a second heating chamber; andtransferring the resulting melt to a third heating chamber;wherein any elemental metal is sedimented in each heating chamber and the sedimented elemental metal is continuously returned from two of the heating chambers to the remaining heating chamber, wherein the elemental metal is collected in at least one of the first or second heating chambers and discharged therefrom, and an apparatus for performing the process.

Abstract: A new apparatus and process for efficient removal of carbon from fly ash has been developed, whereby carbon removal occurs through oxidation as combustion. The ignition of the carbon is accomplished by bulk heating and molecular impingement of a suspended layer of fly ash by a heated oxidizing gas stream, and the desired level of carbon burnout is accomplished by maintenance of combustion conditions.

Abstract: The invention relates to a method and a device for melting down solid combustion residues such as slags, ashes and fine dusts from waste combustion installations (11) with solid, liquid and/or gaseous fossil fuels in a melting device. In order to reduce the necessary energy by combusting fossil fuels, the supply of the combustion residues (12) from the waste combustion installation (11) takes place directly into the filling opening (13) of the melting device. The melting device is designed as a shaft furnace (10) with a furnace space (14, 15) with a refractory lining, the combustion residues (12) being melted down by means of a fuel/oxygen mixture or by means of a fuel/oxygen-air mixture which is introduced into the shaft furnace below the combustion residue fill (21).

Abstract: Bottom ash is taken out of an incinerator after undergoing a moistening process and is subjected to a drying process to reduce its water content to less than 10 weight % or it is taken out of the incinerator with water content less than 10 weight %. Fly ash is taken out of the discharge gas processing system of the incinerator without going through a moistening process. The bottom ash and fly ash, thus taken out, are separately weighed and discharged to a same transporting device and are transported to a melting furnace while being mixed together.

Abstract: Glass and metal are recovered separately by melting from the solid residues produced in a refuse incineration plant, particularly from slag. The melting is effected in two zones. In the first, top melting zone the oxidic constituents of the residues are converted into a glass melt. In the second, bottom melting zone the metallic constituents of the residues are converted at a higher temperature into a metal melt. The two melts are recovered separately.

Abstract: Dustlike and/or finely divided solids which arise in the purification of flue gases, in particular from refuse incineration plants, are subjected to a thermal treatment. In this case, the said solids are fed to a filter device along a predetermined transport path by a gas stream having at least the thermal treatment temperature. After the filtration, the solids can be subjected to a thermal post-treatment. The thermal treatment can serve to destroy halogenated, in particular aromatic, hydrocarbons, to remove ammonia or other volatile constituents.

Abstract: A method of collecting and conditioning either or both of a fluid bed combustion cyclone or bed ash, from a sulfur-containing petroleum coke combustion, by transferring dry combustion ash, containing anhydrous calcium sulfate and resultant lime to a pneumatic tanker, transferring the tanker with the ash to a storage site, and discharging the dry ash through a mixing pump onto the storage site while adding sufficient water to hydrate anhydrous calcium sulfate and resultant lime in the ash and provide about 7-25 percent by weight excess water in the ash.

Abstract: Fly ash is thermally processed in electrically heated, closed pre-heat and combustion chambers. In the combustion chamber, the fly ash is tumble mixed to produce maximum combustion of carbon in the fly ash. Further, the tumble mixing is done while injecting air and oxygen into the tumbling heated fly ash. The tumble mixing is accomplished by feed screws. The screw shafts are hollow with air orifices at regular intervals. As a result, an oxygenated air mixture may be injected into the tumbling fly ash to aid the combustion of the carbon in the fly ash. The flow rates for air and oxygen, the temperature of the pre-heat chamber and the combustion chamber, and the ash flow rate (speed of feed screws) may be adjusted to obtain the proper combustion to get the desired Loss On Ignition (LOI) value for the fly ash. Spectrometers monitoring the color of the output of the fly ash may be calibrated to adjust one or more of the above variables.

Abstract: Urban waste is dried and burned in a mechanical grate furnace in a reducing atmosphere to reduce the formation of NO.sub.x. Consumption of the clinker is completed in a well at the base of which a device such as a plasma torch is provided for vitrifying the clinker. The combustion gases are burned in the presence of secondary air in a circulating fluidized bed furnace. Most of the fly ash is removed from the flue gases in a filter before the gases are passed through a boiler in which they are cooled. The flue gases then pass through a conventional cleansing area from which they are evacuated by a stack. There are very low concentrations of harmful products in the flue gases and in the clinker. The fly ash collected on the exit side of the fluidized bed is recycled with the clinker to be vitrified. Heavy metals evaporated in the furnaces are recovered via a purge.

Abstract: A hydrated granular fly ash composition is disclosed. The granular fly ash may be transported with minimal dust problems while maintaining its capacity to act as a solidifying agent at a remote destination. The process for producing the fly ash involves evenly dispersing a pre-determined amount of water into the fly ash so that it is transformed into a granular form substantially eliminating dust production. An apparatus for processing the fly ash includes a hopper for receiving the fly ash, a conveyor and a modified conditioner in which the fly ash is hydrated.

Abstract: A waste material combustion apparatus for disposing of an assortment of waste material like garbage, sludge and burnable trash in which the ash produced as a result of combustion of that assorted material is collected and transported to a bag house where the ash solids are separated, the air is released to atmosphere, and the separated ash residue is collected as a product of the combustion.

Abstract: For the incineration of waste materials, a process is described, in which the waste materials are reduced in size as far as necessary and are subsequently optionally mixed with fuel and are incinerated at temperatures from 1000.degree. to 1700.degree. C. to form liquid ash, a major part of which is removed as liquid slag from the combustion chamber, and the pollutants are removed from the exhaust gases produced by the incineration. The process is characterized in that the pollutant-containing droplets of liquid ash which are suspended in the exhaust gas are separated at a temperature, which is close to the incineration temperature by at least one mass force separator and are subsequently either solidified alone or are combined with the liquid slag and solidified together with said slag.

Abstract: The present invention provides a system and method for conducting a coal combustion process. The method includes and a step of combusting pulverized coal to form flyash, including a fume component formed from organically associated inorganics in the pulverized coal, and combustion off-gases, and a step of injecting a substantially noncombustible, preformed, coarse particulate material into the combustion process.

Abstract: Waste is incinerated in a rotary furnace which discharges slag and exhaust gas connected to an afterburning chamber. The slag is discharged from the afterburning chamber directly into a glass melting furnace while the exhaust gas is removed to scrubbers which remove residues which are then fed to the glass melting furnace. Cullet and other glass forming materials are also added to the furnace in order to form a vitrified product.

Abstract: In a process to limit the production of flyash by dry bottom boilers, flyash is collected from flue gas using a collector such as an electrostatic precipitator. The collected flyash is carried in a carrier gas stream to which a fuel is added. The stream is introduced into the boiler in a manner to cause the flyash to soften, agglomerate and fall into the bottom ash pit.

Abstract: Fluidized bed reactor method and apparatus for removal of coarse material from the reactor. The apparatus comprises a discharge device including a substantially vertical pipe portion connected at one end with an outlet opening in the reactor grid, and at another end to an aeration chamber containing a discharge opening located below the level of the grid outlet opening; and a device for supplying pressurized air in short blasts of 30 to 100 milliseconds, preferably at pressures of from 2.5 to 7.0 bar, into the aeration chamber in the direction of the discharge opening to remove the coarse material from the reactor. Low pressure fluidizing air may be supplied to the vertical pipe portion as well as the aeration chamber to return small particles in the discharge device to the fluidization zone of the reactor.

Abstract: Incineration flyash is treated by reducing the organic chlorine compounds contained in the flyash. A cylindrical body equipped with a rotating shaft having a screw conveyor and agitating blades for conveying and agitating the flyash is filled to at least a 75 vol % charge so that contact of the flyash with oxygen is made as small as possible. The flyash is subjected to agitation and heat-treatment at 300.degree. C. or higher. The cylindrical body has a feeding port for the waste incineration flyash and a discharging port for the discharge of the treated flyash. The screw conveyor is at the introducing part and has a pitch that is successively reduced toward the agitating part for charging the flyash in the agitating part at a greater vol. % than that which occurs in the introducing part.

Abstract: A hearth for use in a thermal processor or incinerator includes a substantially planar grate which is inclined upwardly and which is vibrated in such a way that material deposited on the input end of the grate moves upwardly toward the output end thereof. A dam in the form of a raised wall at the beginning of the grate prevents liquids and other materials from spilling off. A plurality of openings passing through the grate allow combustion air to pass therethrough from below. Located beneath the hearth is an ash bin in the form of a plenum which catches and accumulates ashes that fall through the air openings in the grate. Air forced into the plenum is used to clean out the ash by opening an outlet port at the end thereof.

Abstract: An apparatus and method for dewatering combined ash or other combustion related products. The apparatus aspects of the invention consist of a quench bath having a curved portion containing a plunger adapted to push combustion materials contained in the quench bath up an inclined trough. A vibrator is mounted below a portion of the inclined trough located above the waterline in the quench bath. As a result, material moved up the inclined portion is subject to vibration and compaction resulting in a substantial dewatering of the combustion material. The method of the present invention provides for the steps of quenching, moving and vibrating combustion by-products to obtain a dewatered material having reduced free water run-off.

Abstract: An incinerating-fusing system for city refuse is disclosed. The system includes an incinerating furnace for incinerating city refuse, a fusing furnace for fusing ash from the incinerating furnace at a high-temperature hearth formed of carbon type combustible material, a communicating passage directly communicating an ash chute of the incinerating furnace with the fusing furnace, the communicating passage acting for dropping ash from the incinerating furnace and also for upwardly exhausting exhaust gas from the fusing furnace. The system further includes a dust collector disposed in an exhaust gas passage extending from the incinerating furnace and a dust conveying passage extending from inside of a high-temperature hearth of the fusing furnace so as to introduce dust from the dust collector.

Abstract: A method is shown for producing a lightweight aggregate by treating flyash and sewage sludge. The flyash and sewage sludge are mixed together and then agglomerated into pellets, with or without the use of a binder. The pellets may be coated and then are dried. The dried pellets are introduced into a rotary kiln in a direction that is co-current with the flow of fuel and air through the kiln. The pellets in the kiln witll be indurated and will experience complete calcination as well as varying degrees of pyrolizing and sintering. The product of the kiln is a nodular material having a low density but with a hard and porous structure. The product of the kiln is feed to a cooler. The flyash sewage sludge mixture has a significant fuel value that is usable in the kiln. Furthermore, the fuel value available in the kiln off-gases may be used for drying the materials.

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: A combustion chamber for combusting a substance includes a burner and at least three successively disposed parts including a primary chamber, a secondary chamber and an ash discharge chamber. The burner is associated with and conducts a first air flow to the primary chamber. The primary chamber has an inlet for conducting a second air flow for substoichiometric combustion of a substance to be combusted at a temperature below an ash softening point and without clinker flow. The secondary chamber has an inlet for conducting a third air flow for brief, intensive, complete combustion of the substance discharged from the primary chamber with clinker flow, and the secondary chamber has walls and a material lining the walls being resistant to fluid clinker.

Abstract: A method of recycling fly ash as slag in a wet bottom furnace is described. The furnace may have a cyclone furnace, a pulverized coal furnace, or any other type of furnace producing wet slag. All or part of the collected fly ash is collected and returned to the furnace and combined with enough fuel to melt the ash. Melted ash directed against a wall, floor or side of the cyclone or furnace will flow to the bottom of the furnace so as to facilitate the liquid slag. The fly ash may be collected by an electrostatic precipitator, baghouse, cyclone (multiclone) or other device. The fly ash may be returned to the furnace or the cyclone using air, flue gas, steam, fuel, or other gas as a carrier.

Abstract: The slag occurring in the waste burning plant (1) is conducted from the slag exit (6) of the oven, directly into a separator (7) for coarse material and iron. There is no chilling in water. After the coarse cleaning, the slag is heated again by means of hot flue gases from the waste burning oven (1) in a preheating device (8), and then, with the feeding of additional heat, melted in a melting oven (10). Flyash is mixed with the stream of slag before the preheating device (8). The harmful substances vaporizing in the preheating and melting are condensed out of the exhaust gases and recovered. Parallel with the preheating device (8) is arranged a pyrolysis oven (9) which is also heated with a partial stream of hot flue gas from the exhaust channel (3). The pyrolysis gas is used as fuel for producing additional heat in the melting oven (10). All the remaining harmful substances not vaporized enter into harmless compounds in the molten slag or are bound, insoluble by water, in the resultant fused slag.

Abstract: The present invention pertains to a process and apparatus for the refinement of exhaust particulate matter from a boiler or other device burning an organic fuel such as coal. More specifically the present invention is a process or apparatus that utilizes successive size and density classifications to achieve the desired result of carbon and sorbent removal, from the exhaust particulate, for disposal and recycling purposes.

Abstract: A process for the partial combustion of finely divided coal at high temperature and pressures to make synthesis gas having entrained particles of fly ash which are separated from the gas at high pressure. The fly ash and a minor amount of entrained gas are handled in a batchwise manner to isolate a batch in a lock hopper, depressurize the batch, strip the synthesis gas from the fly ash and cool the fly ash prior to disposal. During the depressurizing steps, the kinetic energy represented by fluids flowing from the pressurized lock hopper is utilized to provide power to a pressure recovery means and do additional work. The additional work is used to aid in the pressurization of a second lock hopper. In an alternate embodiment the additional work may be used to aid in fluidizing the particulate coal flow to the burners of the gasifier.

Abstract: A process and apparatus for the vitrification of fly ash produced from an incineration system for solid waste materials, including the combining of fly ash extracted from the pollution control device in the incineration system with fusible material, particularly glass, and preferably recycled glass extracted from the solid waste material before it is incinerated, and subsequently melting the combined glass and fly ash in a vitrification furnace in order to vitrify the fly ash and its toxic contaminants, including lead, mercury, cadmium and other heavy metals, to produce an inert vitrified ash product. The flue gas from the vitrification furnace is returned to the flue gas stream from the incinerator for introduction into the pollution control device.

Abstract: Direct coal-fired gas turbine systems and methods for their operation are provided by this invention. The gas turbine system includes a primary zone for burning coal in the presence of compressed air to produce hot combustion gases and debris, such as molten slag. The turbine system further includes a secondary combustion zone for the lean combustion of the hot combustion gases. The operation of the system is improved by the addition of a cyclone separator for removing debris from the hot combustion gases. The cyclone separator is disposed between the primary and secondary combustion zones and is in pressurized communication with these zones. In a novel aspect of the invention, the cyclone separator includes an integrally disposed impact separator for at least separating a portion of the molten slag from the hot combustion gases.

Abstract: A process for heat-treating refuse comprising the steps of decomposing in a combustion furnace a quantity of refuse into slag, emitted gas and fly dust. The fly dust is separated into a fine dust fraction and a coarse dust fraction. The coarse dust fraction is fed back to the combustion chamber, and the fine dust fraction is treated for removal of desired constituents.

Abstract: A process for the partial combustion of finely-divided coal at high temperatures and pressures to make synthesis gas having entrained particles of fly ash which are separated from the gas at high pressure. The fly ash and a minor amount of entrained gas are handled in a batchwise manner to isolate a batch in a lock hopper, depressurize the batch, strip the synthesis gas from the fly ash and cool the fly ash prior to disposal.

Abstract: A method of treating ash and dust from incineration plants. The ash and dush are coprocessed by mixing one or more hazardous wastes and/or metallic scraps therewith. The mixture is supplied to a smelting furnace together with a reducing agent.

Abstract: An apparatus for treating a combustion exhaust gas is here provided which comprises a fire furnace, a denitrating reactor for denitrating the combustion exhaust gas discharged from the fire furnace, a dust collector for collecting solids in the exhaust gas passed through the reactor, and a transport pipe for circulating the solids collected by the dust collector through the fire furnace, the apparatus being characterized in that the transport pipe is provided with an arsenic removal means for removing arsenic from the solids. The arsenic removal means may be a heating device or a washing device. The dust collector may be provided with a means for discarding the solids having a particle diameter of 10 .mu.m or less.

Abstract: The invention is a dry ash handling system that allows ash to fall into a refractory lined ash car riding on rails in a sealed tunnel. The ash falls through a chute coupled to a negative pressure rotary combustor. Any unburned waste is allowed to continue burning in a burn-out chamber while, after removal from the chute because air is allowed to be pulled through the ash from the bottom by the negative pressure. When burn-out is complete, the ash is sprayed to quench any remaining smoldering embers. After removal from the tunnel, the car is sealed with a lid and allowed to cool further. During this period, samples can be removed from the car through sample ports. The car is transported to a landfill by a tilt bed truck and a hinged door on the car allows the ash to be dumped.

Abstract: Apparatus is provided for withdrawing a stream of relatively static bed material from an operating fluidized bed reactor and gravity feeding it through a conduit to an exterior classifying chamber into which a downward flow of air is introduced. The airflow is turned in the classifier to move in an upward direction countercurrent to the flow of bed material. The velocity of the air is such that coarse bed material passes downwardly through the airflow and accumulates in the classifying chamber, while the fines are entrained in the upwardly moving airflow and both air and fines are introduced into the fluidized bed reactor.

Abstract: Method and system for recovering useful constituents from the bottom ash residue resulting from burning process refuse fuel as well as non-hazardous disposal of fly ash generated during the burning.

Abstract: A method is shown for producing a lightweight aggregate by treating flyash and sewage sludge. The flyash and sewage sludge are mixed together and then agglomerated into pellets, with or without the use of a binder. The pellets may be coated and then are dried. The dried pellets are introduced into a rotary kiln in a direction that is co-current with the flow of fuel and air through the kiln. The pellets in the kiln will be indurated and will experience complete calcination as well as varying degrees of pyrolizing and sintering. The product of the kiln is a nodular material having a low density but with a hard and porous structure. The product of the kiln is feed to a cooler. The flyash sewage sludge mixture has a significant fuel value that is usable in the kiln. Furthermore, the fuel valve available in the kiln off-gases may be used for drying the materials.