Abstract: The invention relates to multi-stage cement calcining plant suspension preheater of the kind mentioned in the introduction, wherein the preheater comprises a top separator comprising a central tube entering the top separator in a lowermost part of the separator housing whereas the central tubes of the bottom separators enters the separator housing in an upper part of the separator housing.

Abstract: A system for air purification using cyclone separators mounted with wall structures is disclosed. Air entering a building is filtered by passage through a coupled array of cyclone separators mounted within concrete blocks. Each cyclone separator is composed of two components, a cyclone chamber and a coupler. The coupler contains the air inlet, air outlet, as well as baffles to induce cyclonic flow within the chambers. The cyclone chambers can be fashioned as cavities within solid concrete blocks or added as separate components to the couplers. Both the couplers and chambers can be employed within hollow construction blocks, and the couplers can be further incorporated within gaskets that fit between rows of construction blocks.

Abstract: In a device for restricting hot, dust-laden gas flows and, in particular, dust-laden hot cooling air from clinker coolers (4) in a tertiary air duct (5) of a clinker kiln, the restrictor (6) is formed by segments (8) which are displaceable transversely to the direction of flow in a duct (5) and which are connectable with one another.

Abstract: A method for removing sulfur containing dust particles from particulate material exiting a material preheater in which the particulate material is heated by kiln off gases may include a number of steps. Off gases from the kiln are directed through a gas conduit to the preheater to preheat particulate material traveling through the preheater in a direction countercurrent to the direction of off gas flow through the preheater. Material exiting the preheater is directed to a material bypass conduit that is separated from the gas conduit and is flow connected to a material inlet to the kiln. A stripping gas is directed through the conduit to entrain dust particles in the preheated material and to carry said dust particles away from the preheated material.

Abstract: Method and device for removing volatile organic components (VOC) from waste gases of a cement clinker kiln installation. Cooled waste gases are subjected to post-combustion carried out to an extent ensuring a concentration reduction of the VOC below admissible values. Post-combustion is carried out for production of vapor, dimensioned for a gas volume to be post-combusted, ensuring that a partial quantity of the waste gas corresponding to the gas volume allows for the reduction of emitted VOC per unit time in the waste gas below admissible concentration values by rarefaction. The partial quantity of the waste gas is simultaneously dimensioned for production of an amount of vapor sufficient for economical operation of a steam turbine. The device includes a branch line connected to a waste gas line between a pre-calciner and a waste gas suction fan, and a combustion chamber and a turbine connected to the branch line.

Abstract: The invention relates to a method of determining bed velocity and solids circulation rate in a standpipe experiencing a moving packed bed flow, such as the in the standpipe section of a circulating bed fluidized reactor The method utilizes in-situ measurement of differential pressure over known axial lengths of the standpipe in conjunction with in-situ gas velocity measurement for a novel application of Ergun equations allowing determination of standpipe void fraction and moving packed bed velocity. The method takes advantage of the moving packed bed property of constant void fraction in order to integrate measured parameters into simultaneous solution of Ergun-based equations and conservation of mass equations across multiple sections of the standpipe.

Abstract: The present invention relates to a method for the conveyance of fine-grained solids in a fluidized bed reactor and also to a corresponding plant. It is proposed to introduce a first gas or gas mixture from below through a central tube (3) into a mixing chamber (7) of the reactor (1), the central tube (3) being at least partly surrounded by a stationary annular fluidized bed (10) which is fluidized by supplying fluidizing gas. The gas velocities of the first gas or gas mixture as well as of the fluidizing gas for the annular fluidized bed (10) are adjusted such that the particle Froude numbers in the central tube (3) are between 1 and 100, in the annular fluidizied bed (10) between 0.02 and 2 in the mixing chamber (7) between 0.3 and 30.

Abstract: The present invention relates to a method for the heat treatment of fine-grained solids, in particular gypsum, in which the solids are heated to a temperature of 50 to 1000° C. in a fluidized bed reactor (1), and to a corresponding plant. To improve the energy utilization, it is proposed to introduce a first gas or gas mixture from below through a preferably central gas supply tube (3) into a mixing chamber (21) of the reactor (1), the gas supply tube (3) being at least partly surrounded by a stationary annular fluidized bed (2) which is fluidized by supplying fluidizing gas, and to adjust the gas velocities of the first gas or gas mixture as well as of the fluidizing gas for the annular fluidized bed (2) such that the particle Froude numbers in the gas supply tube (3) are between 1 and 100, in the annular fluidized bed (2) between 0.02 and 2 and in the mixing chamber (21) between 0.3 and 30.

Abstract: Methods for heating a solid material comprising a granular material are provided. Dust is removed from the granular material before it is heated. The dust is injected into the exhaust gas from the heater. The heated dust is recovered and combined with the heated granular material.

Abstract: The present invention relates to a process for producing metal oxide from metal compounds, in particular metal hydroxide or metal carbonate, in which the metal compound is conveyed into a reactor (25) with fluidized bed, heated there to a temperature of 650 15 to 1150° C. by combustion of fuel, and metal oxide is generated, as well as to a corresponding plant. To improve the utilization of energy, it is proposed to introduce a first gas or gas mixture from below through a gas supply tube (26) into a mixing chamber (20) of the reactor (25), the gas supply tube (26) being at least partly surrounded by a stationary annular fluidized bed (27) which is fluidized by supplying fluidizing gas, and 20 to adjust the gas velocities of the first gas or gas mixture and of the fluidizing gas for the annular fluidized bed (27) such that the Particle-Froude numbers in the gas supply tube (26) lie between 1 and 100, in the annular fluidized bed (27) between 0.02 and 2, and in the mixing chamber (20) between 0.3 and 30.

Abstract: A method for regulating the quantity of circulating solids in a circulating fluidized bed reactor system, whereby a solid flow/gas flow mixture leaving the fluidized bed reactor is fed tangentially into at least one cyclone separator for separation of the solid from the gas flow. The gas flow that is exhausted via a gas outflow opening of the cyclone separator. The solid that has been separated in the cyclone separator is reintroduced into the fluidized bed reactor via a recirculation line. A partial quantity of the solid flow quantity is diverted from the wall of the cyclone separator by means of a jet blast of at least one gaseous free jet formed by the nozzle into the gas outflow opening. The remaining residual quantity is fed into the recirculation line, whereby the particle spectrum of the circulating solid flow quantity in the circulating fluidized bed reactor system is largely maintained after separation into the two partial solid flow quantities as well as an installation for implementing the method.

Abstract: The aim of the invention is to create a bypass system for a cement clinker production line, which is characterized by particularly low investment costs and operating costs, thus being economically favorable. Said aim is achieved by installing the bypass system in such a way that the capacity of pre-existing system filters such as the main exhaust gas filter and/or the cooler exhaust filter can also be used for treating the bypass gas flow.

Abstract: A device for emptying hot particle material from a chamber into a transport container. The container is provided with a first pipe that can be inserted into the particle material in the chamber, and a second pipe that is connected to a vacuum source via a precipitator. The first and second pipes communicate with the upper part of the container and are spaced from each other to permit rejection of particle material in the container. The container has an outlet in its lower, downwardly narrowing part. The outlet is provided with a valve. A vertical chute surrounds the outlet, extends downwardly therefrom, and has an evacuation pipe for withdrawal of powder mixed with air that is generated inside the shaft, while particle material is being emptied through the outlet and outlet valve. The container includes a heat exchanger to cool the powder material deposited in the container. An air flow into the container.

Abstract: An apparatus for calcining gypsum including a housing having a bottom wall, open top, and a plurality of side walls extending therebetween. A fixture is located adjacent the open top for receiving gypsum from a source and transferring the gypsum into the housing. At least one burner is connected to the housing and operable for combusting an air-fuel mixture to heat the gypsum. At least one serpentine burner conduit extends from the burner through the housing and terminates through a support floor of the apparatus. The exhaust flow is then directed through a fluidization pad and into the gypsum to further heat the gypsum product. An agitation mechanism is operable to mix the gypsum adjacent the fluidization pad to prevent pockets of gypsum from coagulating and preventing fluidization of the gypsum.

Abstract: A method for operating manufacturing equipment including a heating furnace is provided. The method comprises the step of spraying a blowdown water that has been in the manufacturing equipment into effluent gas discharged from the heating furnace so as to vaporize the blowdown water and remove solid dust contained in the effluent gas. In a plant implementing this method, the amount of the effluent water can be reduced to substantially zero, no purification equipment is required, and solid sludge which has been produced in the purification equipment is thus completely reduced. Moreover, in this method, iron and zinc can be recycled as fly ash which can be easily treated and recycled.

Abstract: A dual-train or multi-train installation for the production of cement clinker from raw meal includes several cyclone suspension heat exchanger trains which provide substantially equal gas and meal loads of the following gas-solid suspensions through use of a vortex homogenization chamber (29), having an inlet opening (30) for the gas-solid suspension and having at least two outlets to a pair of pipes (28, 31) for the discharge of the thoroughly blended homogenized gas-solid suspension substreams. The vortex homogenization chamber (29) is positioned in a calcination stage (17), upstream of its branching and splitting between the several heat exchanger trains (A, B).

Abstract: The invention relates to an apparatus for treatment of material, especially for thermal and/or chemical treatment, having an ascending pipeline branch, a diversion chamber and at least one descending pipeline branch. In the diversion chamber there is provided a deflecting wall that is oriented substantially transversely to the direction of flow of the material entering the diversion chamber via the ascending pipeline branch.

Abstract: A method of producing a calcined raw meal and of producing additional steam in an existing steam generator comprises the following steps: pulverized raw meal, hydrocarbon, primary air and secondary air are fed to a calciner system (60), wherein the raw meal is calcined in a temperature range between 850 ° C. and 950 ° C., the calcined raw meal is separated from the calciner flue gases at the exit of the calciner system, the calcined raw meal is directed through a cooler (70), in which it exchanges its heat with the secondary air, the calciner exhaust gases are directed in the gas path of the backpass of the steam generator (1) at an appropriate temperature window and are used for steam production. The raw meal consists mainly of limestone (CaCO3) and the calcined material is mainly lime (CaO). The fuel feed (4) to the steam generator (1) is reduced during introduction of the exhaust gases into its backpass.

Abstract: When carrying workpieces from a loading area in which the workpieces are handled into a heat treatment furnace to make the workpieces subjected to a heat treatment process using a predetermined process gas, the loading area is evacuated and controlled at a predetermined low negative pressure. An exhaust for evacuating the loading area is connected to the loading area, and a controller controls the exhaust so that the loading area is maintained at the predetermined low negative pressure. A specific gas and particles contained in a gas discharged from the loading area are removed by filters.

Abstract: A method is provided for manufacturing, the method including processing a workpiece in a plurality of processing steps and measuring characteristics of the processing performed on the workpiece in at least two of the plurality of processing steps. The method also includes displaying the characteristics measured by overlaying the characteristics measured at each of the at least two of the plurality of processing steps to display a final resulting workpiece.

Abstract: In the method according to the invention for reducing volatile pollutants in the exhaust gases of a heat exchanger system for heating of cement raw meal or the like, partially preheated raw meal is heated to a temperature for release of the pollutants contained therein. In order to be able to achieve this with a reliable mode of operation and with relatively low investment costs, partially preheated raw meal is drawn off from an upper preheater stage and is mixed together in a mixing zone with a fraction of raw meal which is already highly heated and of such a size that the raw meal mixture which is obtained is set to a mixing temperature which releases the pollutants and as a result at least volatile sulphur oxides are incorporated into the raw meal mixture, whilst carbon monoxide formed in the course of this is led off by means of a carrier gas.

Abstract: A method of disposing of undesirable chemical compounds in waste dust generated in a first kiln in the manufacture of cement clinker by using the dust and slag as the feedstock material to a second kiln, heating the feedstock material in an oxidizing atmosphere, and raising the heat sufficient to diffuse the waste dust and the slag to form a hydraulic product such as cement clinker and lime but insufficient to volatilize previously precipitated chemical compounds in the feedstock material.

Abstract: A combustion apparatus for use as a boiler wherein RDF is burned as the fuel, or as an incinerator for burning municipal waste. The apparatus is diminished in the quantities of NOx produced, permits a dust collector to achieve an improved efficiency in separating off a free-flowing medium and assures a fluidized-bed furnace of effective fluidization of a medium. The apparatus comprises a fluidized-bed furnace (1), a cyclone (2) disposed downstream from the furnace (1) for separating a free-flowing medium and a combustion residue discharged from the furnace (1) from combustion gases and collecting these solids, and a medium-residue return channel (3) provided between the cyclone (2) and the furnace (1) for returning the free-flowing medium and the combustion residue collected by the cyclone (2 )to the furnace (1) therethrough.

Abstract: A method of disposing of undesirable chemical compounds in waste dust generated in a first kiln in the manufacture of cement clinker by using the dust and slag as the feedstock material to a second kiln, heating the feedstock material in an oxidizing atmosphere, and raising the heat sufficient to diffuse the waste dust and the slag to form a hydraulic product such as cement clinker and lime but insufficient to volatilize previously precipitated chemical compounds in the feedstock material.

Abstract: In a process for reprocessing slag and/or ash from the thermal treatment of refuse, the refuse (1) is pyrolyzed, gasified or partially combusted in a first process step, heavy-metal-containing slag and/or ash (8) having a comparatively high carbon content being formed. Said slag and/or ash (8) is then heated in a rotary kiln (6) to a temperature below the melting temperature of the slag and/or ash (8) in a second process step, the slag and/or ash (8), prior to its discharge from the rotary kiln (6), dwelling sufficiently long in the rotary kiln (6), that the heavy metals present therein are converted into their metallic form by reduction at the carbon endogenous to the slag and the readily volatile heavy metals are transferred to the gas phase and are discharged from the rotary kiln (6) together with the flue gas (9), and finally a slag (15) depleted in heavy metals being discharged from the rotary kiln (6).

Abstract: A process of treating dust from a cement manufacturing operation. The process comprises adding carbon bearing material to the dust catch from a cement manufacturing operation to form a mixture, which is formed into nodules and sizing the nodules to obtain a feed material having a selected size range. The nodules are directed as feed material to a fluidized bed which is maintained by passing air for combustion upwardly through a bed of material. The material is thermal processed within the fluidized bed in a reducing atmosphere by supplying fuel for combustion in the fluidized bed to maintain temperatures sufficient to volatilize alkali and sulfur compounds in the feed material and produce a product having an increased concentration of cement forming compounds and reduced alkali and sulfur compounds as compared to the feed material. The reduced clinker is then re-oxidized to minimize/reverse adverse color and mineralogy.

Abstract: A method and apparatus for glass manufacture is described having batch preheating and reduced pollution emission. The apparatus includes two modules containing pelletized glass and/or cullet. One module functions as a pelletized glass preheater, and the other as a filter for removing pollution emissions from furnace exhaust gases. The modules are switchable, such that the preheating module can be converted to a filter module, and the filter module converted to a preheating module, thus allowing periodic cleaning and routine maintenance.

Abstract: A method and apparatus for glass manufacture is described having batch preheating and reduced pollution emission. The apparatus includes two modules containing pelletized glass and/or cullet. One module functions as a pelletized glass preheater, and the other as a filter for removing pollution emissions from furnace exhaust gases. The modules are switchable, such that the preheating module can be converted to a filter module, and the filter module converted to a preheating module, thus allowing periodic cleaning and routine maintenance.

Abstract: An apparatus and method to recover spent lime from various manufacturing processes, such as sugar manufacturing from sugar beets and sugar cane, for use as a nutritional flowing agent for poultry and animal feeds, comprises a first holding bin for receiving expended lime cake from a lime lagoon, a second holding bin for receiving expended lime cake from dewatering stockpiles, a rotary kiln dryer, a cyclone dust collector, a negative-air-pressure dust collector, and a product storage bin. As the lime cake is processed through the rotary kiln dryer, the lime cake is dried at a temperature having an upper limit such that the nutritive value of the lime cake is not destroyed. In the kiln, a substantial portion of the lime cake is converted to dust particles suspended in air, which air is directed through one or both of the collectors to collect and remove the suspended particles therefrom.

Abstract: A heat exchanger in the form of a vessel for heat exchange of a pulverulent solid material and a gas, e.g.

Abstract: A process is disclosed for reducing the evolution of fine particles during the removal of a solvent from a mass of solid particles containing the fines or which solid particles are attritable to produce the fines in the prior treating steps and/or the solvent removal step. The process employs the addition of 1 to 20 percent by weight of water to the solid particles/solvent prior to or during the solvent removal operation.

Abstract: An improved method for cooling particulate solids in an expanded bed by successively charging the particulate solids to a plurality of expanded beds with the exhaust gas from each of the plurality of expanded beds being discarded.

Abstract: A fluidized bed combustor is adapted to deprive a combustion gas issuing therefrom of dust by bringing the combustion gas into contact with a filter medium which is a fluidizing solid discharged in conjunction with slagging ash out of the combustor.

Abstract: Oil shale, coal, inert heat transfer material and other carbon-containing solids of varying sizes are preheated with a gas in a transfer line by first separating the solids into a plurality of size fractions and then separately introducing the size fractions into the transfer line at predetermined distances from the transfer line inlet. The predetermined distances are inversely related to the size of the particles comprising each fraction of solids so that the fraction of solids containing the largest particles is introduced nearest to the gas inlet and the fraction of solids containing the smallest particles is introduced at a point furthest away from the transfer line inlet. Normally, solids withdrawn from the transfer line will have been heated to a temperature below which any liquids or gases evolve and are ready for further processing in downstream conversion units such as oil shale retorts, coal gasifiers and the like.

Abstract: A method and mechanism for heat treating a pulverulent comminuted raw material in the process of making cement including preheating the material, passing the material through a first reaction zone, supplying a first fuel supply to the first zone for supplying thermal energy for carrying out the calcination reaction, separating the material from the hot gases received from the first reaction zone and delivering the material to a second reaction zone to which is supplied a second fuel supply for supplying thermal energy for the calcination reaction in the second zone and separating the material from the hot gases from the second zone and delivering the material to a sintering kiln and then passing it to a cooler with the air from the cooler supplied to support combustion in the first zone, and with the arrangement preferably arranged in two parallel flows with each flow path containing the preheater, and the reaction zones and separators with the material flows combining just as they enter the sintering zone.

Abstract: The invention comprises a sinter belt and a collector, vacuum chambers, a gas cleaning device, an air purifying device, and an exhauster mounted adjacent the belt. Above the sinter belt are mounted assemblies for loading a bed and a charge, and an ignition hearth. Downstream from the sinter belt are mounted a sinter breaker and an inclined chute wherein are mounted vibrating screens communicating with a cooler for a sinter return and for the bed, and an air classifier. The air classifier comprises a fan, a diffuser, a movable grid for varying the speed of the air produced by the fan, and a partition member forming a settling chamber together with the chute. Within the settling chamber is mounted a device for settling coarse fines, said device communicating with the collector through the air purifying device, and with the cooler for the sinter return.

Abstract: A process for the removal of volatile liquid from particulate material employing indirect heating of the particulate material by means of combustion gases resulting from the combustion of sulfur-containing fuel, and further employing purging of the thus heated particulate material by means of combustion gases produced by the combustion of low sulfur fuel to remove vaporized volatile liquid from the particulate material. Also disclosed is a system for performing such removal of volatile liquid from particulate material.

Abstract: Coal is pretreated for a coking plant so that it is passed in two stages through two throughflow driers successively connected with one another, the driers are supplied with a heat carrier formed by a steam overheated to a temperature between 400.degree. and 600.degree. C., dust is removed from the steam after passing the throughflow driers, and the steam is heated after the dust removal in a heat exchange with a circulating gas of a coke dry cooler.

Abstract: A method and apparatus for drying coal in which the coal is dried by a hot gas and then quickly cooled with ambient air to reduce the oxidation rate and in which the air heated in the cooler is supplied to support the combustion that generates the hot gas. The drying gas exhausted from the dryer is utilized to extract coal product, to produce the fuel necessary to generate the hot drying gas and to provide a tempering gas to help maintain the combustor within a desired temperature range. Condensation of the exhaust drying gas is prevented by utilizing the hot gas discharged from the combustor, bypassing the dryer, and supplying it to the exhaust gas at a plurality of different points.

Abstract: Method and apparatus for calcining fine-grained material such as in the manufacture of cement in which the raw material is subjected to the sequential steps of pre-heating, calcining and sintering. At least one of the stages is fueled by coal dust which has been ground and dried with a drying exhaust gas derived from one of the stages. In accordance with the invention, an exhaust gas fraction is withdrawn from one of the stages, and has a relatively high concentration of injurious substances such as alkalis and sulfur. This withdrawn exhaust gas fraction is then cooled by one of a variety of methods, and then treated for the removal of the injurious substances. Finally, the cooled gas fraction is used to dry the coal dust fuel by conserving energy which would otherwise be lost in the process.

Abstract: This invention relates to a kiln of a compact upright configuration which is constructed so as to successively preheat, heat, and then cool aggregate in a continuous operation while avoiding wasteful loss of heat from the walls of the kiln or in the effluent gases. In the apparatus of this invention there is provided an upright hollow housing having an air inlet opening in a lower portion thereof and an air outlet opening in an upper portion thereof. A fan is communicatively connected to the housing for causing outside air to enter the air inlet opening and flow upwardly through the housing. A fuel burner is provided in the housing for combusting a fuel and thereby heating the air flowing upwardly within the housing.

Abstract: Relatively coarse aggregate is preheated to a relatively high temperature prior to introduction into a rotary kiln by directing the aggregate downwardly along a predetermined path of travel while maintaining the aggregate in the form of a relatively thin layer and while directing the waste heated gases from the kiln upwardly along a predetermined sinuous path of travel repeatedly passing laterally back and forth through the downwardly moving layer of aggregate from opposite sides thereof to thus provide highly effective contact of the gas with the aggregate, and while supplementally heating the waste heated gases so as to preheat the aggregate to a higher degree.

Abstract: Preheat gas is recycled to a booster heater that communicates with the preheat chamber with excess gas being directed to a quench chamber. From the quench chamber gas passes to a dust separator with the cleansed gas being utilized in low- and high-temperature drying chambers. The system is modified so as to have a mixing vessel ahead of the quench chamber in which lime dust is introduced to scrub the gas passing through prior to the gas being quenched. The gas is cleansed and utilized in a drying chamber.

Abstract: The invention concerns a process and a device for roasting an agro-food product in the form of grains.The process consists of fluidizing an auxiliary body in the form of fine solid particles in an enclosure 1, and putting the grains of the product to be roasted in flotation in the fluidized bed of particles of which the temperature is adapted to roasting, to generate the roasting by the effect of the shocks of the fine particles of the auxiliary body with the grains of the product.The invention can be applied particularly for the roasting of grains of a product such as coffee, cocoa, etc.

Abstract: Coal is passed in a two-stage process through a drying and heating zone. The coal coming from the drying zone is separated from the heat carrier gas which is then passed into the atmosphere after going through an electrodust separator. The dried coal is delivered into the heating zone. The hot gas for the heating zone is furnished by a combustion device. The exhaust gas from the heating zone is separated from the heated coal which is recovered while the exhaust gas is passed back into the drying zone. Part of the hot combustion gas coming from the combustion chamber is branched off and passed into the exhaust gas coming out of the drying zone either directly behind the drying zone or behind the separator for separating the dried coal from the exhaust gas. The temperature of the exhaust gas from the drying zone is thus prevented from sinking below the sulfuric acid dewpoint or water vapor dewpoint which might result in corrosive damage to the apparatus, particularly to the electrodust separator.

Abstract: This invention relates to a new and novel method and apparatus for reacting nongaseous material with a gaseous reactant comprising introducing a first stream containing a nongaseous material into a reaction zone; simultaneously introducing a second stream containing a gaseous reactant into the reaction zone such that the gaseous reactant immediately contacts and reacts with the first stream thereby producing a gaseous product; forming a spiralling vortex within the reaction zone to cause substantial separation of gases, including the gaseous product, from the nongaseous material; forming and removing a third stream from the reaction zone containing the gaseous product which is substantially free of the nongaseous material before a major portion of the gaseous product can react with the nongaseous material; and forming and removing a fourth stream containing the nongaseous material from the reaction zone.

Abstract: A method and an apparatus is disclosed for producing such as Portland cement from pulverant raw material in a system having at least a preheater and a rotary kiln. The preheater may be of the type having a series of stages each provided by a cyclone dust separator for successively preheating the raw material in a counterflow of kiln waste gases and in which an identified one of the stages discharges a gas flow containing more thermal energy than can be used to advantage in preheating material in the remaining stages through which such gases must pass before dispersing in the surrounding atmosphere. A portion of the gases passing from the identified stage is diverted to a heat exchanger which utilizes the heat energy in such kiln waste gases to heat a clean stream of air.

Abstract: An apparatus is disclosed for producing such as Portland cement from pulverant raw material having a preheater, an auxiliary furnace 22, a rotary kiln 2, a cooler, and a single blower connected to the top of the preheater to draw air and combustion gases through the kiln, auxiliary furnace and preheater. Preheater receives waste gas from the rotary kiln for flow through first, second, third and fourth level cyclones, with the first level cyclone(s) C.sub.1 being at an elevation higher than the kiln and the second, third and fourth level cyclones (C.sub.2, C.sub.3 and C.sub.4) each being at successively higher elevations. The auxiliary furnace 22 is preferably at the approximate level of the second level cyclone C.sub.2. The auxiliary furnace 22 is fed pulverant material from third level cyclone C.sub.3 and discharges pulverant material to a flue leading from the kiln to first level cyclones C.sub.

Abstract: Variable dual orifices in the restricted portion of the flue between the kiln and the preheater provides a controlled bypass of 0 to 100% of the kiln gases around the preheater and prevents short circuiting of process materials from the precalciner and mixing chamber to the kiln and provides a means for adjusting the orifice and system pressures to thereby provide stability of operation and control over the entire range of bypass; positive isolation of kiln gases from preheater gases during 100 percent bypass operation is ensured.