Showing papers on "Rotary kiln published in 1991"

Rotary kiln transport processes

Abstract: Slow rotation of a cylindrical kiln, partially filled with powder or granular solid, produces a planar interface between the bulk of the solid and the gas phase, tilted at the angle of repose. Particles cascade downward on this plane, moving relatively freely and randomly, providing the principal mechanism for particulate diffusion and mixing in the kiln. The plane is also the most favorable location for chemical reactions that require efficient gas–solid heat and mass transfer. Conservation equations are constructed for planar and bulk regions, coupled by the particulate exchange produced by rotation. Sample problems of mixing and heat exchange illustrate problem formulation and useful simplifications. A penetration model predicts wall-to-bed heat transfer coefficients, leading to better agreement with experiment than is obtained when planar processes are omitted.

Preparation of activated carbon from coconut shell in a small scale cocurrent flow rotary kiln

Abstract: Activated carbons were prepared at 800°C in a small scale rotary kiln fed either with fresh or precarbonized coconut shell, employing a mixture of steam and air, flowing cocurrently. Typical product rates obtained were 0.2 and 0.6g/min for fresh and precarbonized shell respectively. Product surface area increased with increasing water input concentration from about 0.5 to 5 g H2O/g feed, resulting in values up to about l,400m2/g. The use of N2 instead of air during activation did not significantly change product surface area. It was demonstrated that both carbonization and activation of the coconut shell can be carried out together in a single heating step, resulting in a higher overall yield than if carried out with the usual two steps procedure. The morphology of the carbons produced consisted of micropores <10 A width which afforded most surface area, and of macropores, some of them resembling the skeletal structure of the raw material.

Manufacture of cement clinker in long rotary kilns by the addition of volatile fuel elements directly into the calcining zone of the rotary kiln

Abstract: Methods are disclosed for the use of inexpensive volatile fuels in the calcining zone of a cement kiln during the manufacture of cement clinker in a rotary vessel.

Detoxification of aluminum spent potliner by thermal treatment, lime slurry quench and post-kiln treatment

Abstract: A method is disclosed for detoxification of aluminum spent potliner by thermal treatment in a rotary kiln while blended with limestone and metal silicates to destroy cyanides and convert the soluble fluoride salts to relatively insoluble calcium fluoride and fluoride-bearing minerals, quenching the hot kiln discharge with an aqueous lime slurry to convert residual soluble fluoride salts on the particle surfaces to an insoluble form, and treating aqueous landfill runoff and capture with lime or limestone and recycling the treated water to the process. The treated material is suitable for landfilling in a non-hazardous waste landfill or marketing as a raw material. Air emissions are innocuous and there is no aqueous discharge.

Limestone calcination in a rotary kiln

Abstract: An experimental study of the calcination of limestone has been carried out in a highly instrumented pilot-scale rotary kiln. Local gas, solids, and wall temperatures and pct calcination have been measured under a range of operating conditions to determine the influence of limestone type, feed rate, rotational speed, inclination angle, and particle size on calcination and heat flow in the kiln. Thus, it has been found that the local calcination is dependent primarily on the solids temperature and hence on heat transfer. Of the variables studied, the limestone feed rate has the strongest effect on the temperature and calcination fields, whereas inclination angle and rotational speed are relatively less important. The different limestones studied exhibited significant differences in heat-absorption capacity and calcination temperature which may be related to their radiative properties. Increasing particle size over a range of 0.75 to 3.5 mm resulted in an increase in both heat transfer to the bed and calcination.

Opposed fired rotary kiln

Abstract: A rotary kiln system wherein oxidant injection means are positioned at each stationary end and inject oxidant toward each other creating gas recirculation within the rotary kiln for improved mixing, combustion efficiency and temperature uniformity.

Rotary Kiln incineration. Comparison and scaling of field-scale and pilot-scale contaminant evolution rates from sorbent beds

Abstract: A comparison is made, for the first time, between the evolution of hydrocarbons from clay sorbent beds in a field-scale rotary kiln incinerator and in a pilot-scale rotary kiln simulator. To relate the data from the different sized units, due allowance is made for bed dynamical similitude, bed geometrical factors, and bed heat-up. To minimize the effects of disturbances caused by foreign matter in the field-scale bed and differences in loading techniques, the rate of evolution is characterized by an evolution interval defined as the time required for the middle 80% of the ultimate contaminant evolution to occur. A comparison of evolution intervals with reciprocal bed temperature reveals that the data are consistent with an analysis that assumes a uniform bed temperature (at any instant of time) and a desorption-controlled evolution rate. Furthermore, the evolution intervals scale inversely with a modified Froude number, which characterizes bed dynamics. The success in comparing field and simulator results indicates that pilot-scale rotary kilns may be used to simulate certain features of industrial-scale units if dynamical, geometrical, and thermal parameters are matched appropriately.

Incineration of xylene/sorbent packs. A study of conditions at the exit of a full-scale industrial incinerator

Abstract: The dynamic response at the exit of an industrial incinerator to the batch loading of single plastic packs containing a xylene/sorbent mixture is presented from two locations on a vertical cross section near the exit of the kiln. Data are compared for several operating modes including standard operation (without injection of turbulent air) and operation with tangentially oriented turbulent air injected at the closed end of the kiln. During each operating mode, data are also compared for two kiln rotation rates. Details accompanying the decomposition of a single pack, comparing the temporal responses of selected parameters with video images obtained from a viewport near the exit of the kiln, are reported. The data provide a much clearer picture, than heretofore possible, of conditions that exist in an industrial rotary kiln incinerator during treatment of periodically fed plastic packs. Considerable stratification is observed at the kiln exit during the treatment of the plastic packs for all operating conditions of the study. Significant bursts of xylene evolution, associated with pack dissolution and bed slumping, are inferred from continuous measurements of stable species and temperature, and also visual observation. Even during the most vigorous bursts, the incinerator stack emissions remained well within regulatorymore » limits.« less

Processed wastes as supplemental fuel for modified cement films

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.

Burner for solid and liquid or gaseous fuel

Abstract: A burner (1) for feeding solid and liquid or gaseous fuel into a burning zone (8) of a kiln, for instance a rotary kiln, and comprising central duct (2) for liquid or gaseous fuel, a surrounding annular duct (3) for primary air and a further surrounding annular duct (4) for solid fuel is provided with an outer duct system (5) for feeding yet an amount of primary air into the burning zone (8), the duct system (5) being in the form of a heat exchanger for transferring heat from the inner kiln compartment surrounding the burner (1) to the primary air transported in the duct system (5) and thereby increasing the velocity of the air passing through the system without any corresponding increase of the fan power or the energy consumption of the kiln plant, but with a substantial decrease in the amount of primary air fed to the burning zone. The duct system (5) is separated from the remainder parts of the burner (1) by an insulating layer (7).

Method of producing cement clinker

Abstract: A rotary cement kiln is operated with predried paper sludge in a secondary combustion period. The predrying of the paper sludge from a moisture content of about 50% by weight to a moisture content of about 30% by weight is effected with flue ga from the inlet end of the rotary kiln.

Mounting method for prepared-unshaped-refractory charging framework

Abstract: PURPOSE:To shorten curing time of refractories and to reduce a construction cost by providing a heat generator in a prepared-unshaped-refractory charging framework in the captioned method of an industrial furnace facility such as a rotary kiln or the like, and setting the framework of a mold. CONSTITUTION:After a framework 3 of steel plates is secured to an iron sheath 1 of a rotary kiln 7 with a plurality of framework fixing woods 5, prepared- unshaped-refractories 2 are charged, a heat generator 4 is energized to heat the heater of the generator 4. The framework 3 is heated by the generator 4, the heat is, since the framework 3 is made of metal, rapidly transmitted, the refractories 2 are externally heated, and accelerated to be dried and cured. The heating temperature of the framework by the generator is measured by a thermometer 6 mounted between the surfaces of the refractories 2. Thus, the curing time of the refractories can be shortened, the entire repairing step can be shortened, and its construction cost can be reduced.

Method and apparatus for incinerating different kinds of solid and possibly liquid waste material

Abstract: Solid and possibly liquid waste material is incinerated by a) partial combustion on the stepped grates (9, 10, 11) of the solid waste material, the latter being delivered to the rotary kiln (2) at such a high temperature, that a liquid slag is formed at the inlet of the rotary kiln, b) possibly adding liquid waste material to the solid waste material being incinerated on the stepped grates (9, 10, 11), and c) collecting the ash products from the combustion process, such as grate screenings, boiler ash, fly ash, and residual products from flue-gas cleaning, and returning these products to the input end (12) of the rotary kiln (2), at which input end these products are introduced into the liquid slag. In this manner, it is achieved that the slag, fly ash and other harmful residual products from the combustion process are fused into a glass-like mass, from which salts and heavy metal cannot be leached out.

Method and apparatus for producing burnt material and for generating electrical energy

Abstract: The invention relates to a method and apparatus for producing burnt material and for generating electrical energy, in which the material is burnt using lower-grade fuel in a rotary kiln by means of hot kiln exhaust gases and at least a proportion of the quantity of heat contained in the exhaust gases from the rotary kiln is converted into electrical energy, the temperature of these kiln exhaust gases being between 700° and 1200° C., preferably between 800° and 900° C.

Rotary Kiln Incineration of Dichloromethane and Xylene: A Comparison of Incinerability Characteristics Under Various Operating Conditions

Abstract: Comparisons are made, for the first time, between the combustion characteristics of dichloromethane and xylene in an industrial rotary kiln incinerator. The comparisons are made under different operating conditions, including variable kiln rotation rate and operation both with and without turbulence air. Continuous gas composition and temperature measurements and batch gas composition measurements were obtained from two vertical locations hear the exit region of the rotary kiln. The measurements show that there is significant vertical stratification at the exit of the kiln. Addition of turbulence air enhanced combustion conditions throughout the kiln during xylene processing. During dichloromethane processing, however, the addition of turbulence air had minimal effect and only promoted greater bulk mixing; chlorinated compounds transported from the lower kiln during operation with turbulence air were not efficiently processed in the upper kiln. Evolution of test liquids from the bed was not constant but r...

A comparison of in situ vitrification and rotary kiln incineration for soils treatment.

Abstract: In the hazardous waste community, the term “thermal destruction” is a catchallphrase that broadly refers to high temperature destruction of hazardous contaminants. Included in the thermal destruction category are treatment technologies such as rotary kiln incineration, fiuidized bed incineration, infrared thermal treatment, wet air oxidation, pyrolytic incineration, and vitrification. Among them, conventional rotary kiln incineration, a disposal method for many years, is the most well established, and often serves as a barometer to gauge the relative success of similar technologies. Public sentiment on environmental issues and increasingly stringent environmental regulations has, over time, spurred design and development of innovative thermal treatment processes directed toward reducing harmful emissions and residuals that may require further treatment or disposal. In situ vitrification (ISV), a technology that combines heat and immobiliztion, is one such innovative and relatively new technology. This pap...

Waste disposal method and device

Abstract: PURPOSE:To attempt to reduce the volume of wastes and the cost of their disposal by gasifying the volatile matters in raw material wastes with dry-distilling them to reduce their volume, then incinerating gases in the volatile matters, and utilizing the incineration heat in the incineration effectively and at the same time cleaning the incineration gases and then releasing them to the atmosphere and, on the other hand, finally diposing the carbides after the dry distilling. CONSTITUTION:Wastes are charged into one or two dry distilling gas furnaces 2 and 2' through a charging device 4 in their upper section to fill them. When dry distilling is started with air supply controlled to a specified supply, effective combustible components in the wastes are gasified as volatile components by heating and they are stored in the upper sections of the furnaces. The volatile component gases stored in the upper section are supplied to a burner furnace 13 through ducts 12 and 12. The gases are provided with a pilot flame by the air supplied by an air supply fan 15 and burned by an incinerator 14 in the upper section. The combustion gases from the incinerator 14 are supplied to a rotary kiln 16 and, on the other hand, cooled by a cooling tower 20, and at the same time sent to an electrostatic precipitator 21 to have the dusts in them caught. Further, harmful gases in chlorine series, etc., are eliminated in a gas reactor tower 22' by the slaked lime from a slaked lime silo 22. Furthermore, the gases are deodorized and released out of a chimney 19 to the atmosphere through a suction fan 18.

Scrap recovery apparatus

Abstract: Apparatus for sorting and recovery of scrap material, particularly aluminum beverage can scrap, includes a rotary kiln (10) in which the raw scrap is heat processed to leave a furnace chamber (12) of the kiln as a mix of large particles of a first composition (e.g. larger pieces of soft aluminium alloy can body) and substantially smaller particles of a second and different composition (e.g. aluminium/manganese alloy can top fines). The output end of the kiln is provided with an axially extending screen section (30) to separate the larger particles from the small immediately adjacent to the chamber so that they cn be passed immediately without substantial loss of heat to a melting furnace (38).

Production of ferronickel

Abstract: PURPOSE:To obtain a ferronickel with high reduction and recovery rates by treating an Ni ore with a specified wet process, mixing the obtained Ni oxide with a reducing material, pelleting or briquetting the mixture and reducing the pellet at a specified temp. in a rotary kiln. CONSTITUTION:An Ni ore is crushed and leached with hydrochloric acid, and the insolubles are filtered off. The leachate is dried, roasted, leached with water and filtered, and the water leaching residue is roasted to obtain a beneficiated Ni ore. The beneficiated Ni ore is mixed with a carbonaceous material, the mixture is pelletized or briquetted, and the pellet is charged into a rotary kiln and reduced at 400-1300 deg.C or at 900-1300 deg.C for 60 min. The Ni reduction rate is low at 1300 deg.C, and the operation is made difficult.

Coal desulfurization in a rotary kiln combustor

Abstract: Several issues that could have an impact on the capability to burn anthracite culm in a rotary bed boiler were identified; specifically, questions were raised concerning the specifications of the anthracite culm itself and some relating to the equipment The anthracite culm delivered was wet, (with more than 10 percent moisture), and coarser than feed material for fluidized boilers It was felt that using finer fuel, ensuring that it is largely dry, would aid the combustion of anthracite culm It also appeared that if provisions were made for more efficient internal and external recycle of ash, this would also enhance the combustion of this fuel Accordingly, the decision was made to conduct an additional campaign of tests that would incorporate these changes The tests, conducted on July 15 and 16, 1991, involved an anthracite culm that was, in fact, obtained from a fluidized bed a heating value of 3,000 Btu/lb and came with a top size of 1/4-inch Despite these changes, sustained combustion could not be achieved without the use of large quantities of supplemental fuel Based on these tests, we tend to conclude that the rotary kiln is ill suited for the combustion of hard-to-burn, low-grade solid fuels likemore » anthracite culm« less

Process and installation for the production of burned material and the generation of electrical energy

Abstract: Die Erfindung betrifft ein Verfahren und eine Anlage zur Herstellung von gebranntem Gut sowie zur Erzeugung von elektrischer Energie, wobei das Gut unter Verwendung von minderwertigem Brennstoff in einem Drehrohrofen mittels heiser Ofengase gebrannt wird und zumindest ein Teil der in den Abgasen des Drehrohrofens enthaltenen Warmemenge in elektrische Energie umgewandelt wird, wobei die Temperatur dieser Ofenabgase zwischen 700 und 1200°C, vorzugsweise zwischen 800 und 900°C, betragt The invention relates to a method and a plant for the production of burnt material and the generation of electrical energy, the material is burned using low-grade fuel in a rotary kiln by hot furnace gases and at least a portion of the heat contained in the exhaust gases of the rotary kiln into electrical energy is converted, wherein the temperature of the kiln exhaust gases 700-1200 ° C, preferably between 800 and 900 ° C

Developing incineration process designs and remediation projects from treatability studies

Abstract: The Bog Creek Farm CERCLA (Superfund) site in Howell Township, New Jersey, was extensively contaminated, allegedly with wastes from paint manufacturing. The site contained two types of incinerable wastes: contaminated soils and sediments. A remedial investigation and feasibility study (RI/FS) was conducted, leading to a recommendation to treat the most contaminated areas by incineration. This recommendation was converted into the selected approach through the Record of Decision (ROD) mechanism. Contaminants at the Bog Creek Farm site included a wide range of volatiles, semivolatiles, and heavy metals. The incineration approach chosen, therefore, had to remove the organics from the soil without creating additional problems associated with heavy metals emissions. In order to evaluate the incineration problem and develop an advisory conceptual design for its solution, Ebasco Services Incorporated performed extensive characterizations of the material. Such characterizations included performing proximate and ultimate analyses and determining other key physical, chemical, and thermodynamic properties of the soils and sludges. Energy and Environmental Research Corporation (EER) then performed treatability studies in its rotary kiln test incinerator. These treatability studies focused upon the rotary kiln, and the environment required for cleaning the soil. They assumed that contaminants in the vapor phase could be destroyed in the afterburner. Tests were conducted at bed temperatures of 1,000°F, 1,460°F, and 1,800°F. Samples were drawn from the kiln at intermediate times. Combustion regimes were therefore constructed for the treatment of Bog Creek Farm wastes, maximizing organic removal while managing the heavy metals problem. Ebasco then converted the results of the incinerability or treatability studies into an advisory conceptual design. This advisory conceptual design called for a kiln temperature of 1,600°F (bed temperature of 1,200°F) and a solids residence time in the kiln of 40 minutes. Additional data indicated that the afterburner could operate at 1,800°F in order to ensure destruction of the POHCs. Combustion chemistry fundamentals demonstrated that the minimum afterburner temperature required was 1,650°F. Ebasco converted this conceptual design into a performance specification to be used in the bid process, under the management of the U.S. Army Corps of Engineers. The remediation was then put out to bid. Chemical Waste Management was the successful bidder. The incineration was successfully completed by August 1990; the system was then demobilized, as the site was remediated.

Refractory lining of furnaces

Abstract: So that the refractory elements (22) in the shell (18) of a rotary kiln or cooler can be sintered before use, the retaining means comprise a plurality of, preferably symmetrically paired or bifurcated metal clamping members (26) each adapted for location in a slot (24) in a refractory element (22) such that, as a nut (32) is tightened on a bolt or stud (28) the or each inwardly extending arm of the member (26) is deformed by tapering walls of the slot (24).

Scaling Down of the Calcination Process for Industrial Catalyst Manufacturing

Abstract: Summary A computer model for the calculation of the temperature/time profile and the composition of the gas atmosphere in rotary kilns is described The model is applied for scaling down the continuous commercial calcination of catalyst materials to batch calcination in laboratory rotary kilns as used in catalyst development work The results of the model are compared with measurements carried out in the rotary kiln of the catalyst plant at Ghent, which produces γ-alumina extrudates used as carrier for heterogeneous catalysts The plug flow transport model assumed for the solids is confirmed by residence time distribution measurements The measured temperature profiles are in agreement with the calculated profiles after adjustment of the kinetic rate constants