Showing papers on "Rotary kiln published in 1993"

Lightweight aggregate from flyash and sewage sludge

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.

Method for direct gasification of solid waste materials

Abstract: Direct gasification of a high BTU content fuel gas from a hydrocarbon content solid waste material W which may include some glass content is effected by preheating heat carrier solids HCS in a flash calciner to a temperature capable of thermally cracking the hydrocarbon content of the solid waste material W directly into the high BTU content fuel gas. The HCS are separated from the products of combustion and fed into a gas sealed refractory lined horizontal axis rotary kiln retort concurrently with the solid waste W. Momentary contact and mixing of the solid waste W with the HCS in the rotary kiln in the absence of oxygen is sufficient to directly thermally crack the solid waste material into the high BTU gas product. Separated HCS are returned to the flash calciner for reheating. A trommel, coupled directly to the output of the rotary kiln retort and having a trommel screen with mesh openings smaller than glass agglomerates, but sized larger than the HCS, permits separation of the HCS and discharging of glass agglomerates from the downstream end of the trommel screen to prevent shut down of the direct gasification unit. Direct gasification of steel industry waste water treatment plant sludge, automobile shredded refuse ASR, municipal solid waste MSW and refuse derived fuel RDF and oil mill scale is effectively achieved, irrespective of glass content contaminant.

Application of pulse combustion to solid and hazardous-waste incineration

Abstract: A bench-scale Rotary Kiln Incinerator Simulator was retrofitted with a frequency-tunable pulse combustor in order to enhance the efficiency of combustion. The pulse combustor excites pulsations in the kiln and increases the completeness of combustion by promoting better mixing within the system. One phenomenon that is unique to batch-fed incineration systems, and rotary kilns in particular, is the formation of transient “puffs,” or plugs of unburned material that are formed when the instantaneous bed waste release rate is greater than the available local stoichiometric oxygen supplied from the primary burner. It is hypothesized that the additional mixing induced by the pulse combustor can reduce gas-phase stratification and enhance transport of available oxygen into the local fuel-rich zones of the puff. Tests were performed using toluene (C7H8) sorted onto a ground corn cob sorbent and placed in cardboard containers. The burner was operated in a non-pulse mode as a baseline condition, and then i...

A three-dimensional detailed numerical model of a field-scale rotary kiln incinerator

Abstract: A detailed three-dimensional numerical model of baseline (support burners only) operation in a rotary kiln incinerator is presented. The focus of this model is on gas-phase fluid mechanics, neglecting solid waste combustion and radiative heat transfer. The model is compared to experimental data, and although relatively crude, it demonstrates remarkably good qualitative and quantitative predictive capability. The model demonstrates that thermal buoyancy is the cause of observed vertical stratification near the exit of the modeled kiln. The model also suggests that the addition of turbulence mixing air actually increases the degree of stratification rather than augmenting mixing, as had been previously suggested. Elucidating the mechanism by which this occurs has resulted in a reinterpretation of the experimental data. The model also suggests that there is probably a zone of recirculation across the kiln exit plane. A parametric study using the model shows that the location and quantity of leak air into the kiln have a major influence on the flow inside the kiln. The study suggests that preheating turbulence air may have little effect on gas-phase mixing. Overall, this modeling study has demonstrated that a relatively simple numerical model of a rotary kiln incinerator can provide valuable insight into the more » process, especially when used in conjunction with experimental data. 21 refs., 17 figs., 3 tabs. « less

Method for improved manufacture of cement in long kilns

Abstract: The present invention is directed to a method and apparatus for controlling the kiln gas stream (90, 138) in a conventional long wet or dry process cement kiln (10). A portion of the kiln gas stream (90) can be withdrawn from the rotary kiln vessel (17) at a point upstream, relative to kiln gas flow of the chain system in the mineral drying zone (24). Alternatively, or in conjuction with bypass formation, the apparatus (256) can be used to add tertiary air to the kiln gas stream (90) to promote combustion efficiency downstream of the clinkering zone (28). Use of the present apparatus (56, 156) to form a kiln gas bypass stream (64) enhances operating efficiencies of long kilns by reducing dust loss, by facilitating isolation of high alkali by-product streams, by reducing alkali content of collected kiln dust, by increasing energy efficiency of long kiln operation, and by allowing greater overall control in the cement manufacturing process.

Process for making cement using low-grade fuels

Abstract: A process for producing cement, including preheating a mixture of ground raw materials (raw meal) in a preheating cyclone to form a preheated raw meal, calcining the preheated raw meal in a calciner to form a calcined raw meal, burning the calcined raw meal in a rotary kiln with the aid of a high-grade fuel to form a cement clinker, cooling the cement clinker in a rotary kiln and grinding the cooled cement clinker. The process is characterized by replacing 50 to 70% of the high-grade fuel with a low-grade fuel, gasifying the low-grade fuel in a fluidized bed to form a resulting fuel gas, supplying a first portion of the resulting fuel gas to a main burner of the rotary kiln, a second portion of the resulting fuel gas to the exhaust gas stream from the rotary kiln and a third portion of the resulting fuel gas to the calciner.

Solid waste incineration in rotary kilns

Abstract: Rotary kilns are used to dispose of many solid wastes and sludges and to thermally treat contaminated soils. In this communication the fates of hydrocarbon and metal species are examined with a view toward optimization of new kiln designs and maximizing existing unit throughout while minimizing pollutant emissions. Initially, process fundamentals are considered to characterize the controlling phenomena. Pilot- and large-scale data are then examined to define practical system complexities. Finally, techniques for data scale-up and performance prediction are summarized. Temperature is clearly the most important parameter with respect to the fate of both metal and hydrocarbon species; hence, heat transfer is often rate limiting. High temperatures favor hydrocarbon evolution, but can also enhance the formation of toxic metal fumes. Both the solid composition and the moisture content can significantly influence the time at temperature required for hydrocarbon destruction and metal vaporization. Improv...

Numerical modeling of a rotary kiln incinerator

Abstract: A computational modelling study is performed for a full-scale rotary kiln incinerator, using the commercial fluid mechanics code FLUENT. The coordinate system is three-dimensional, and turbulence and buoyancy are also modelled. A global one-step reaction is used for methane combustion. Heat transfer modelling is limited to conduction and convection. The leak air locations and flowrates, as well as the heat flux at the kiln walls are varied to study their effects on the kiln operation. A comparison is made with full-scale kiln data [1-3], and good qualitative agreement is reached. The issue of grid dependence is addressed but not resolved.

Thermal treatment of hazardous wastes: a comparison of fluidized bed and rotary kiln incineration

Abstract: Large volumes of sludge are produced by a wide variety of industrial processes and by municipal waste water treatment. Interest in incinerating these sludges, either alone or co-fired with other fuels, is increasing. The issues surrounding sludge incineration in rotary kilns and fluidized beds were identified through a series of pilot-scale tests using two slightly different paper mill sludges. The specific issues examined include hydrocarbon emissions, NO x emissions, and bottom and fly ash properties. A 61-cm i.d. × 61-cm long, 130-kW pilot-scale rotary kiln simulator (RKS) and a 23-cm i.d., 300-kW circulating fluidized bed combustor (CFB) were maintained at a nominal temperature of 1100 K and a stoichiometric ratio of 1.5

Method and apparatus for incinerating waste in a cement kiln plant

Abstract: In a generally known cement kiln plant which incorporates a preheater (1), a calciner (2) having a separation cyclone (3), a rotary kiln (4) and a clinker cooler (5), a decomposition chamber (10) is additionally installed for incineration of waste. Waste is introduced into the chamber at a location (12) and decomposed in the chamber by the heat from calcined raw meal which is conveyed to the chamber from the separation cyclone (3) of the calciner via a splitting gate (13) and a pipeline (14). Gaseous products are conveyed to the calciner (2) and burned there, whereas noncombustible by-products are discharged via an outlet (15) of the chamber (10). By utilizing the heat from preheated or calcined raw meal instead of, for example, hot exhaust gases to incinerate waste, any disturbance of the draught conditions of the cement kiln plant can be avoided, and the overall control of the calcining process is improved.

Bed mixing and heat transfer in a batch loaded rotary kiln

Abstract: A pilot-scale rotary kiln simulator has been used to make experimental measurements of the thermal response of solids charged onto a preexisting bed of hot solids material. The measurements clearly show that the bed is not thermally uniform. Time constants for bulk heating and mixing were extracted from the measurements. A simple model is developed that correlates the time constant for mixing to bed turnover rate, allowing the thermal history of a charge of solids to be predicted based on measurable parameters of the kiln and bed. The measured and predicted thermal histories show that mixture greatly augments the initial rate of heal transfer to the fresh charge of solids.

Burning of blended waste-derived supplemental fuel for improved manufacture of cement

Abstract: A method is described for environmentally sound usage of combustible hazardous waste in an operating rotary kiln. The method is particularly adapted for disposal of solid hazardous wastes, optionally in the form of a blended waste homogenate, packaged in sealable containers. The containers are used as fuel modules and charged into a rotary kiln cylinder where kiln gas temperatures range from about 950° to about 1200° C. to achieve high destruction and removal efficiencies.

Method of incinerating waste in a cement kiln plant

Abstract: In a generally known cement kiln plant, which comprises a preheater (1) with calciner (2) and separation cyclone (3), a rotary kiln (4) and a clinker cooler (5), a decomposition chamber (10) is additionally installed for incineration of waste. Waste is introduced into the chamber at (12) and decomposed in the chamber by means of the heat from calcined raw meal which is conveyed to the chamber from the separation cyclone (3) of the calciner via a splitting gate (13) and a pipeline (14). Gaseous products are conveyed to the calciner (2) and burned there, whereas non-decomposable by-products are discharged via an outlet (15) in the chamber (10). By utilizing heat from calcined raw meal for incineration of waste instead of for example hot exhaust gases, any disturbance of the draught conditions of the plant can be avoided, and the overall control of the calcining process is improved.

Simulation of steady-state heat and mass transfer in a rotary kiln incinerator

Abstract: Simulation is presented for steady-state heat and mass transfer in the combustion chamber of a rotary kiln. The gas-phase region in the chamber is divided into 3×8×4 computational volumes in r-, θ−, and z-coordinates, respectively. Conservations of mass and energy are formulated in each volume, in which convection and radiation transfers coupled with energy balance and volatilization of waste bed are considered with plug flow model. The volatilization rate of wastes is considered by using the volatilization model for a mixture of cellulose and toluene. The governing equations for all computation cells together with the boundary and auxiliary conditions constitute a nonlinear system of equations and are solved numerically. Effects of percentage excess air, rotation speed and inclination angle of the kiln at a fixed waste loading level are examined and discussed. Comparisons between two waste volatilization models are also made.

Rotary kiln arrangements

Abstract: A rotary kiln in which reaction is to occur between counterflowing reactants and an injector for a reactant extends into a reaction zone in the kiln. The injector is provided with means for adjusting the temperature of the injected reactant to a temperature in the desired range for that zone. Further means are provided for maintaining a temperature in the desired range throughout the zone. The arrangement be used in the production of uranium oxides from uranium hexafluoride.

Process and apparatus for the thermal treatment of pulverulent raw materials

Abstract: In order, in the thermal treatment of pulverulent (flour-like) raw materials, particularly for the production of cement clinker, to find a way of being able, by means of the clinker firing plant, to conveniently dispose of waste materials/residues (47) or lean gas (48) produced therefrom by thermal treatment, even when the clinker firing plant is shut down, e.g. as a result of a fault, without in the case of such a fault having to turn off the thermal disposal plant for the waste materials/residues and/or having to flare the lean gas produced, it is proposed according to the invention that lean gas (48) produced in the reactor (46) outside the clinker firing plant from the waste materials/residues (47) by gasification/carbonisation be fed to the calciner (17) and/or the rotary kiln (20) when the clinker firing plant is running and to burn it there for the purpose of saving normal fuel, and when the clinker firing plant is not running to burn the waste materials/residues (47) in the reactor (46) with an excess of oxygen and to introduce the reactor waste gases (48), for the purpose of dust removal, via line (49 or 50) into the bypass gas extraction line (30) of the clinker firing plant and/or into the cyclone suspension gas heat exchanger waste gas line (23), in each case before its dust removal device (34, 26).

Method for operating rotary kiln for reduction of iron and steel

Abstract: PURPOSE:To lower the consumption unit of carbonaceous materials by improving the recovery rate of Zn and Pb from iron and steel dust in operation of a rotary kiln for reduction of the iron and steel dust. CONSTITUTION:Powdery coke of 100 meshes is added and mixed to and with the iron and steel dust and the mixture is pelletized. The powdery coke of <=1mm average grain size is added to the pellets formed in such a manner. The amt. of the total carbon reducing agent is so adjusted as to attain 1 to 1.5equiv. by defining the stoichiometric quantity to completely metallize Fe2O3 and ZnO in the iron and steel dust as 1equiv.

Device for removing zinc in zinc-containing dust

Abstract: PURPOSE:To economically and efficiently remove zinc by recovering zinc and lead fume in a waste gas from a kiln tail chamber as zinc oxide and lead oxide and recovering a reduction product from the chamber CONSTITUTION:Coal A is pulverized by a crusher 3 and stored in a pulverized coal storage tank 7,a rotary kiln 22 is installed, and a pulverized coal burner 19 is furnished to the kiln A mixture of zinc-contg dust B and pulverized coal is air-floated to the burner 19 through a mixer 13, a conveyor fan 16, an ejector 17, etc A fuel gas C feed pipe and a feed pipe for the air from a combustion air fan 20 are connected to the burner 19 The zinc and lead fume in a waste gas from a kiln tail chamber 24 connected to the delivery side of the kiln 22 are recovered as zinc oxide and lead oxide by a bag filter 32, etc The reduction products D and E are recovered from the chamber 24 through a bucket conveyor 26, a water-cooled cooler, etc Consequently, the zinc and lead in the dust are economically recovered, and the iron component is reduced

Rotatable cooler for a rotary kiln plant

Abstract: A cooler (6) for cooling of particulate material which is subjected to heat treatment in the rotary kiln is mounted at the material outlet end (1) of a rotary kiln The cooler is provided with annular chambers (7, 8, 9) disposed around each other, and which are successively passed by the material from the outlet (5) of the kiln to a material outlet (20) in the stationary housing (15) of the cooler in countercurrent with the cooling air which flows from an air inlet (18) and through the annular chambers to the kiln in which the air thus heated is utilized as combustion air

Treating system and treating device for waste household electrical appliances and office automatic equipment

Abstract: PURPOSE: To enhance the recovery efficiency of useful materials by thermally decomposing the synthetic resins in waste constituting members in a thermal decomposition furnace, separating these synthetic resins to thermal decomposition gases and mixtures composed of melting residues and metals, treating the dry distillation gases in a petrochemical cycle and subjecting the other mixture to a fractionation treatment by crushing and screening stages. CONSTITUTION: Waste household electrical appliances 1 from which parts, such as motors and compressors, reutilizable in their original shapes are removed, are supplied by a conveyor 2 to a rotary kiln 3 where these appliances are rotated under heating and the synthetic resins in the constituting members are thermally decomposed. The dry distillation gases generated at this time are withdrawn through a line 40 and are treated in the petrochemical process including a cooler 41, an oil-water separator 42, etc. The melt is extracted from a slit in mid-way and the molten residues are discharged from a discharge port to a recovering conveyor 4 or a water sealing pit 5. The waste is then supplied to a crushing machine 6 and the iron and metals are recovered by a magnetic separator 9 in the process of transporting the crushed matter by a belt conveyor 7. The others are fractionated by an eddy current screening machine 10 to aluminum and copper which are recovered. COPYRIGHT: (C)1994,JPO&Japio

Method of incinerating waste in a rotary kiln plant, and plant therefor

Abstract: Solid combustible waste (7) is introduced into and incinerated in the outlet casing (9) of a rotary kiln (11) when brought into contact with the hot airstream flowing through the kiln.

Method for dezincificating scrap galvanized steel sheet

Abstract: PURPOSE:To evaporate and liberate deposited Zn and to use scrap galvanized steel sheet as an iron source by heating the scrap in a gaseous atmosphere of specified composition. CONSTITUTION:Solid carbon such as coke or gaseous hydrocarbons are introduced from a feeder 9 into an externally heated rotary kiln 1 provided with a burner 3 as the external heating means 2, and an oxidizing gas such as air and CO2 is simultaneously introduced from its feeder 10 and heated by the means 2 to form a reducing gas atmosphere satisfying 0.01

Glowing cement clinker reduction system - has a jaw crusher to apply pressure with a coolant prior to redn. to final grain size

Abstract: To reduce hot granular loose material, esp. cement clinker from a rotary kiln which is still glowing, the glowing material with a wide range of grain sizes is subjected to pressure in a loose pile, and then reduced to the final grain size pref. by cutting. Pref. the pressure is applied in the presence of a coolant. The reduction system operates on the jaw crusher principle, with at least one movable crushing jaw (2,3) and an expanded outlet gap (4). A roller is at the outlet gap, to form an adjustable outlet (7) with the extended end of one crushing jaw (2,3). The outlet (7) can be formed by two rollers, rotating at different speeds. The surfaces of the crushing jaws (2,3) and roller (5) are protected by a material, such as ceramic, to resist heat and wear. Connections for a coolant are above the roller (5) and within the entry zone (6) of the crusher. ADVANTAGE - The coolant air at the reduction process has a low dust content and most can be used in the kiln firing operation.

Gas scrubber for wet process rotary kilns

Abstract: In the initial part of a wet-process rotary kiln, means to decrease the amount of product dust entrained in the escaping combustion gases. Pipes running lengthwise of the kiln, in the region where the feed slurry is wet enough to flow, fill with slurry as they rotate through the slurry pool at the bottom of the kiln, and discharge their contents through exit ports so placed on each pipe as to emit streams of slurry when the pipe is carried by kiln rotation to a position near the top of the kiln. In conjunction with the forest of chains commonly used in such kilns, the transverse-flowing combustion gases are scrubbed of some of their entrained product dust content by its being entrapped in wet slurry and recycled.

Mg-al-cr spinel sand and its preparation method

Abstract: The product of this invention is constituted by bauxite (or commercial alumina), lightly roasted magnesium and chrome ore (chrome concentrate ore). Its preparation process is: the above three raw materials are formulated according to a definite ratio, crushed into a size less than 3 mm, put into a ball mill and ground, and then put into a pelletizer to form granules by dry process and finally, put into a rotary kiln for calcination. After cooling, spinel sand of magnesium, aluminium and chromium is produced. Its advantages are: raw material is widely available, production is easy, hot-shock stability is higher than that of conventional refractory. It can be applied widely as refractory lining of various industrial kiln and furnace.