Showing papers on "Rotary kiln published in 2011"

Direct Reduction Behaviors of Composite Binder Magnetite Pellets in Coal-based Grate-rotary Kiln Process

Abstract: Directly reduced iron is an imperative burden for EAF (electric arc furnace) to make good quality and special steel. As an alternative of direct reduction processes, an innovative coal-based direct reduction of composite binder magnetite pellets in grate-rotary kiln has been developed at Central South University and put into operation. A study of the direct reduction behaviors of composite binder magnetite pellets was carried out in a simulating coal-based grate-rotary kiln process in this paper. Preheated pellets made of magnetite concentrate and composite binder and fired oxide pellets containing bentonite as binder were directly reduced using non-coking coal as reductant in a tube furnace, and their reduction behaviors have been demonstrated by measuring reducibility, variations of compress strength, porosity, phases changes and micro structure under XRD, SEM and optical microscopy. It is shown that preheated pellets possess much better reducibility than fired oxide pellets. Superior reducibility of preheated pellets should be ascribed to their higher effective diffusivity due to higher porosity. The compressive strength of preheated pellets climbs quickly after reducing for 30 min and achieve a high value at the end of reduction, leading to smooth and intact metallized pellets whereas the compressive strength of metalized pellets from reducing of fired pellets is much lower, more cracks and fractures being formed. The preheated pellets possess self-curing function because of the multiple functions of composite binder, eliminate cracks and fractures and keep pellets intact during reducing, depressing reduction degradation and preventing accretion in rotary kiln.

Simulation of olive pits pyrolysis in a rotary kiln plant

Abstract: This work deals with the simulation of an olive pits fed rotary kiln pyrolysis plant installed in Southern Italy. The pyrolysis process was simulated by commercial software CHEMCAD. The main component of the plant, the pyrolyzer, was modelled by a plug flow reactor in accordance to the kinetic laws. Products distribution and the temperature profile was calculated along reactor's axis. Simulation results have been found to fit well the experimental data of pyrolysis. Moreover, sensitivity analyses were executed to investigate the effect of biomass moisture on the pyrolysis process.

Meat and Bone Meal as a Renewable Energy Source in Cement Kilns: Investigation of Optimum Feeding Rate

Abstract: Meat and Bone Meal (MBM) is a CO2 neutral fuel, and hence is a good candidate for substituing fossil fuels like pulverized coal in rotary kiln burners used in cement kiln systems. MBM is used in several cement plants, but the optimum substitution rate has apparently not yet been fully investigated. The present study aims to find the maximum possible replacement of coal by MBM, without negatively affecting the product quality, emissions and overall operation of the process. A full-scale experiment was carried out in the rotary kiln burner of a cement plant by varying the MBM substitution rate from 0 to 7 t/hr. Clinker quality, emissions and other relevant operational data from the experiment were analysed. Additionally, coal and MBM were compared by laboratory experiments. The results revealed that MBM could safely replace more than 40% of the coal energy without giving negative effects. The limiting factor is the free lime content of the clinker. Possible explanations to the free lime increase are given. If 40% of the coal in the rotary kiln burner was replaced by MBM on a long-term basis, the total annual CO2 emissions of the plant could be reduced by 10%.

Experimental Apparatus for Studying Heat Transfer in Externally Heated Rotary Kilns

Abstract: Rotary kilns are widely used in several branches of the chemical industry. In order to control the temperature of the solid and the gas flowing through the kiln, it is important to understand the heat exchange phenomena that occur. The design and construction of a novel experimental device to study heat exchange in rotary kilns is described. The device, which comprises a rotary kiln equipped with an external electrical heating system, enables the study of the influence of various parameters such as the solid flow rate, the kiln inclination angle, the rotational speed, or the presence of lifters on heat exchange and in particular on the heat exchange coefficient between the solid and the wall. Preliminary experimental results concerning the influence of the solid flow rate and the rotational speed on the solid-to-wall heat exchange coefficient are presented.

Composite alkali-resistant refractory brick of pulverized fuel ash

Abstract: The invention provides a composite alkali-resistant refractory brick of pulverized fuel ash, wherein the composite brick is applied to the inner lining of an industrial kiln and is prepared by providing refractory aggregate, refractory powder, light aggregate, refractory clay, aluminate cement and silica micropowder to the pulverized fuel ash of solid wastes of a fuel electric plant and the coal cinder after burning, then adding water into the same and mixing, and then pressing and drying. The composite alkali-resistant refractory brick of pulverized fuel ash is composed of compact refractory material components and heat insulation material components. The percentages by weight of the compact refractory material components are as follows: the refractory aggregate is 55 to 65 %, the pulverized fuel ash is 5 to 8 %, the refractory powder is 10 to 15 %, the silica micropowder is 4 to 6 % and the aluminate cement is 8 to11 %; the percentages by weight of the heat insulation material components are as follows: the coal cinder is 50 to 65 %, the pulverized fuel ash is 5 to 10 %, the light aggregate is 5 to 10 %, the refractory clay is 5 to 8 %, the refractory powder is 10 to 16 %, the silica micropowder is 3 to 5 % and the aluminate cement is 7 to 10 %; and the compact refractory material components and the heat insulation material components of the composite alkali-resistant refractory brick of pulverized fuel ash provided by the invention are pressed into a tightly combined compound. Compared with common refractory brick, the composite alkali-resistant refractory brick of pulverized fuel ash provided by the invention has the advantages that a heat insulation layer is increased, the temperature for the skin of the rotary kiln can be reduced, a great quantity of energy can be saved and the service life of the kiln is prolonged.

Energetic and exergetic assessments of a cement rotary kiln system

Abstract: The cement production is one of the most energy consuming processes, typically accounting for 50 to 60% of the production costs. However, there are several ways of heat recovery opportunities to achieve better energetic and exergetic efficiencies for the whole system. In this paper, energetic and exergetic analyses of an existing rotary kiln system are presented, and first and second law efficiencies are calculated. Two distinct cogeneration systems which use the waste heat from both pre-heater and clinker cooler exhaust gases to produce either electricity and/or to preheat the raw material before entering the kiln system. The effect of these two heat recovery systems on the overall efficiency of the system is also discussed. The results showed that the energy and exergy efficiencies of the existing system are 54.9 and 28.1%, respectively. With the cogeneration, these exergy efficiencies have been obtained to be 70.6% for the use of waste heat recovery steam generator (WHRSG) and 81.5% for the use of heat to pre-heat the raw material, respectively, which dictates a remarkable improvement over the existing system. Key words: Cement process, rotary kiln system, energy and exergy audit, cogeneration.

Method for preparing high-nickel concentrate from low-grade red soil nickel ore

Abstract: The invention discloses a method for preparing a high-nickel concentrate from a low-grade red soil nickel ore, which comprises the following steps of: drying the low-grade red soil nickel ore until water content is 13 to 16 percent, crushing to ensure that the size of all particles is less than 3mm, grinding by using a high-pressure roller mill to ensure that particles with the size of less than 0.074mm account for 80 percent and specific surface area is not less than 2,000cm /g, adding 15 to 20 percent of composite binder and 1 to 5 percent of coal powder, and pelletizing by using a disc pelletizer to obtain green pellets with the size of 6 to 16mm; drying and preheating the green pellets on a chain grate for water removal and solidification to ensure that each piece of pellet entering a kiln has the compression strength of over 500N; directly adding the preheated and solidified pellets into a rotary kiln, and reducing at the temperature of between 1,100 and 1,250 DEG C for 60 to 120 minutes by using pea coal as a reducing agent in a mass ratio of the reducing coal to the pellets of 0.8-1.0; and cooling a reduction product, sieving, performing magnetic separation to obtain a magnetic product, crushing, grinding, and performing magnetic separation to obtain the high-nickel concentrate, wherein the composite additive comprises the following components: Na2CO3 and CaO, iron oxide powder, the coal powder and sodium humate in a ratio of (30-60):(20-30):(20-30):(5-10). The method is high in adaptability and nickel recovery rate and suitable for mass production.

Roasting Properties of Pellets With Iron Concentrate of Complex Mineral Composition

Abstract: Investigation was conducted on roasting properties of pellets with an iron concentrate of complex mineral composition. The results indicated that the pellets of complex mineral composition concentrate required higher preheating temperature and longer preheating time than that of single magnetite concentrate. Therefore, it is difficult for preheated pellets to withstand the mechanical collision in the roasting process in rotary kiln. It was found that after the iron concentrate being subjected to high pressure roll grinding, the specific surface area reached 2029. 1 cm2/g. Consequently, the preheating and roasting temperature of pellets were decreased by 70 and 50 °C and preheating and roasting time were decreased by 2 and 4 min, respectively. Meanwhile, the compression strength of preheated and roasted pellets were increased by 200 N for a pellet and 220 N for a pellet, respectively. The mechanism lied in that the increase of specific surface area activated thermal reaction and promoted formation of inter-grain bridge.

Method For Producing Positive Electrode Active Material For Lithium Ion Batteries And Positive Electrode Active Material For Lithium Ion Batteries

Abstract: The present invention provides a method for producing a high quality positive electrode active material for lithium ion batteries at low cost and at excellent production efficiency. The method for producing a positive electrode active material for lithium ion batteries includes a step of firing a powder of lithium-containing carbonate that is a precursor for positive electrode active material for lithium ion batteries in a rotary kiln. In the step, a temperature at a powder feed part inside of the rotary kiln is kept at 500° C. or more.

Technological method for extracting zinc by roasting blast furnace gas mud by virtue of rotary kiln

Abstract: The invention discloses a technological method for extracting zinc, in particular to a technological method for extracting zinc by roasting blast furnace gas mud by virtue of a rotary kiln, belonging to the technical field of metallurgy production. By applying the technological method provided by the invention, zinc oxide in the gas mud can be thoroughly reduced, and the production cost is low. The technological method comprises the following steps of: a) burdening, namely adding coke powder with the mass ratio of 16-20% into the gas mud and mixing to be uniform; b) checking, namely carrying out a sampling test on the calorific value of mixture of the gas mud and the coke powder which are uniformly mixed, wherein the acceptable calorific value is 1600-2000 kcal/kg; c) roasting and reducing, namely directly sending the qualified mixture of the gas mud and the coke powder into a kiln body of the rotary kiln to be roasted and reduced, thus zinc oxide particles and metallized slag are generated; and d) collecting, namely collecting the zinc oxide particles at the tail of the kiln and discharging residual metallized slag from the head of the kiln.

Comprehensive utilization method of red mud coal-base rotary kiln method

Abstract: The invention discloses a comprehensive utilization method of a red mud coal-base rotary kiln method, belonging to the field of comprehensive utilization of solid wastes The method comprises the following steps: fully mixing the red mud, calcium-containing compound which occupies 8-14% of the red mud, and a carbon material which occupies 20-50% of the red mud; carrying out carbon smelting reduction in a coal-base rotary kiln at the temperature of 1000-1550 DEG C; and reacting for 2-6 hours to obtain sponge iron or hot molten iron and a byproduct building material In the method, the red mud discarded in smelting aluminum oxide is effectively comprehensively utilized, thus the solid zero emission is realized The method provided by the invention has high utilization; and the metal reduction rate reaches 95-98%, and the metal recovery rate reaches 96-98%

Melting solidification integrated method and system for incineration of hazardous wastes and incinerated fly ash

Abstract: The invention discloses a melting solidification integrated method and a melting solidification integrated system for the incineration of hazardous wastes and incinerated fly ash. The method comprises the following steps of: incinerating and melting the hazardous wastes by using a multi-section incinerator which consists of a slag rotary kiln and a secondary combustion chamber; recovering the heat of smoke generated during incineration by using an afterheat boiler; conveying fly ash collected by a bag-type dust collector to the slag rotary kiln by using a silo pump and a fly ash return pipeline; performing compatibility on the fly ash and medical wastes, so that the fly ash is melted at a high temperature in the slag rotary kiln; and performing water quenching to form vitreous slag, and wrapping heavy metal by using the slag to realize the stable solidification of the metal. In the method, heat energy generated by combusting the hazardous wastes is utilized fully to provide energy for the melting solidification of the fly ash, the problem of high cost of stabilization treatment of the fly ash is solved while the innocent treatment of the hazardous wastes is realized, running cost is reduced, and the important effects of energy conservation, emission reduction and waste control by the wastes are achieved; and due to the adoption of an integrated design, the integrated system is reasonably and compactly connected and has a mature equipment structure and higher economy.

Method and system for monitoring rotary kiln running state and adjusting method of kiln

Abstract: The invention relates to a detection method for the operation state of rotary furnaces, a system thereof and a furnace adjusting method. The detection method comprises: correlating the rotation direction of a rotary furnace and the detected working current curve of a furnace drive motor, the rotation direction of the rotary furnace, and detected the mechanical parameter curves about force on eachsupport wheel and furnace transmission small gear base, to realize online detection for the abnormal change of the operation state of the rotary furnace; according the average value of the working current of the furnace drive motor in each rotary period of the furnace, the difference between the maximum and minimum values of the working current, the decrease of the mechanical parameters about force of each support wheel and furnace transmission small gear base, referring to the measurement results of the rotation central line of the rotary furnace and the geometric position of each support wheel, to confirm the adjustment direction and data of each support wheel, according to the average value of the working current of the furnace drive motor, the decreases of the difference between the maximum and the minimum values, and the decreases of the mechanical parameters about the force on the support wheels, judging the correctness of the direction adjustment of each support wheel, decidingthe accurate adjustment value of each support wheel. The device is simple, and has simple operation, reliability, long service life, high performance price ratio and wide application.

Lining structure of rotary kiln

Abstract: The invention discloses a lining structure of a rotary kiln. The lining of the rotary kiln comprises a rear kiln mouth, a preheating zone, a decomposing zone, an upper side transitional zone, a firing zone, a lower side transitional zone and a front kiln mouth, wherein the rear kiln mouth is formed by compounding corundum hollow sphere light castable with mullite amorphous castable; the preheating zone is made of an alkali-resistant composite brick or a clay composite brick or a high-aluminum composite brick or alkali-resistant castable; the decomposing zone is made of a clay composite brick or a high-aluminum composite brick or a silicon mullite composite brick; the upper side transitional zone is made of a periclase spinel composite brick or a silicon mullite composite brick or a magnesium composite brick; the firing zone is made of a magnesium chromium composite brick or a periclase spinel composite brick or a magnesium calcium zirconium composite brick or a magnesium iron aluminum composite brick; the lower side transitional zone is made of a silicon mullite composite brick or a spinel composite brick or a magnesium composite brick; and the front kiln mouth is formed by compounding corundum hollow sphere light castable with steel fiber reinforced mullite amorphous castable. The lining is made of a heavy/light composite fireproof material with an energy-saving function, the rotary kiln is subjected to segmented construction according to the requirement, and the firing zone is made of a heavy/light composite brick particularly, so that the barrel wall temperature is greatly reduced, the service life of the rotary kiln is prolonged, and energy saving and consumption reducing effects are achieved.

Method and apparatus for removing radioactive cesium

Abstract: PROBLEM TO BE SOLVED: To provide a method and an apparatus for removing radioactive cesium from waste containing the radioactive cesium at a low costSOLUTION: A radioactive cesium removing apparatus 1 includes: an incinerator 22 for incinerating combustible waste contaminated with radioactive cesium; a suspension preheater 23 configured by a multistage array of cyclones to generate calcium oxide and/or magnesium oxide from a calcium oxide source and/or a magnesium oxide source by using sensible heat of flue gas G5 exhausted from the incinerator 22 and incinerated ash of combustible C; a rotary kiln 21 for burning inorganic substances S contaminated with the radioactive cesium together with the calcium oxide and/or magnesium oxide and incinerated ash D3; and collectors 31, 32 for collecting cesium volatilized in the rotary kiln 21

Device technology configuration method for treating house refuses by using rotary cement kiln

Abstract: The invention provides a device technology configuration method for treating house refuses by using a rotary cement kiln, comprising a pre-treatment device technology configuration method and an incineration device technology configuration method, wherein the whole process of the crushing treatment of the house refuses is implemented by using the pre-treatment device technology configuration method, and a whole incineration process is carried out on the crushed house refuses by using the incineration device technology configuration method; the incineration device technology configuration comprises a double-layer power-driven flap valve, an L-shaped incinerator, a double-layer heavy punch flap valve, a vibrating conveyor and a bucket elevator; and partial tertiary air captured from a tertiary air tube of a rotary kiln enters into the L-shaped incinerator through an air intake tube and high temperature incineration is carried out on the house refuses in the incinerator, smoke generated when incineration passes through an air discharging tube and then is converged with the tertiary air tube, a loop formed by the air intake tube and the air discharging tube of the L-shaped incinerator is provided with a second high-temperature electric butterfly valve and a third high-temperature electric butterfly valve, and a first high-temperature electric butterfly valve is arranged on the tertiary air tube. Harmful gases such as dioxin can be inhibited by high-temperature environment which is generated by using the rotary cement kiln.

Pellet roasting production technology recycling residual heat and system thereof

Abstract: The invention relates to a production technique of pellet in the field of metallurgy, in particular to a pellet roasting production technology recycling residual heat and a system thereof. The technology comprises three stages, namely green pellet drying and pre-heating, green pellet roasting and high temperature pellet cooling, wherein the air flow discharged in a third cooling section in the high temperature pellet cooling stage is introduced into the air blast cooling section in the green pellet drying and pre-heating stage as a heat source. The system comprises a chain grate, a rotary kiln and a recirculation cooler, which are connected in sequence, wherein the recirculation cooler comprises a first cooling section, a second cooling section and the third cooling section; a smoke helmet of the third cooling section is connected with a bellows gas path of the air blast drying section through a multi-tube dust remover and an exhaust fan. By adopting the technology and the system thereof, heat energy can be made full use of, and the influence of waste gas on environment is reduced.

Rotary kiln automatic control system and method

Abstract: The invention relates to a rotary kiln automatic control system. The rotary kiln automatic control system comprises a fuel supplying device, a rotary kiln, a temperature detection device, a field control station, a temperature regulating module and a central control room operation station. The field control station compares the detected radiation temperature signals, flame temperature signals andflue temperature signals which are generated by the temperature detection device with the preset radiation temperature reference value, the flame temperature reference value and the flue temperature reference value to control the fuel supplying device to regulate the fuel supply and the temperature regulating module to control the air flow and to monitor the host machine of the rotary kiln; and the central control room operation station receives the radiation temperature value, the flame temperature value, the flue temperature value and the technical parameter value which are provided by the field control station, and stores and displays the received values. Thus, the system realizes automatic control of the production process of rotary kiln, ensures the stability of temperature in the rotary kiln, and further ensures the quality stability of forged reduction materials. The invention also provides an automatic control method of the rotary kiln.

Carbon dioxide production

Abstract: Apparatus for the production of carbon dioxide from limestone includes a nuclear energy source (32) arranged to generate electricity and a rotary kiln (10). The rotary kiln (10) has an inlet (15) for the introduction of limestone and an outlet (19) for the release of carbon dioxide. An electrical resistance heating element (21) disposed within the kiln (10) is arranged to be supplied with electricity derived from the nuclear energy source (32) to raise the temperature of the element (21) for transfer of heat to the interior of the rotary kiln (10). Limestone in the rotary kiln (10) is thereby heated to a temperature sufficient for the release of carbon dioxide.

Composite brick for active lime rotary kiln

Abstract: The utility model discloses a composite brick for an active lime rotary kiln, which belongs to a furnace lining material of the rotary kiln, and mainly overcomes defects of the existing composite brick that the junction between a heat-insulating layer and a work layer is poor and the connection between brick bodies is loose The composite brick comprises a brick body consisting of a heat-insulating layer and a work layer, and is characterized in that a junction surface between the heat-insulating layer and the work layer employs gear shape or small arc shape occlusive connection The utility model is simple in structure, the junction surface between the heat-insulating layer and the work layer employs gear shape or small arc shape occlusive connection, the junction strength of the junction surface of the composite brick can be improved, and the capability of resisting shearing force breakage of the composite brick can also be greatly enhanced Two end faces of the brick body are provided with right-angle lock catch steps, so a lock catch structure with mutual locking can be formed between the brick bodies, and the whole junction strength can be improved

Process simulation of activated carbon production using a rotary kiln

Abstract: The rotary kiln used for the activation of charcoal is simulated using mass and energy balances to obtain the temperature distributions of environmental gas and solid in the kiln. The computed results are used to find the optimal operation condition. In finding the optimal gas temperature for the reductive gas environment necessary to the charcoal activation, the outcome gives the amount of fuel required and the effects of other operational variables, such as feed and steam rates. While the fuel and feed rates give large variation of gas and solid temperatures, the activation steam and moisture and volatile contents in feed do not affect the temperatures significantly. It was found that the temperature distribution has a similar pattern to that of coal pyrolysis because of the similarity of heat transfer mechanism.

Rotary kiln lining and method

Abstract: Provided is a rotary kiln having a cylindrical shell having an inner cylindrical surface and a longitudinal axis and a kiln lining disposed on the inner cylindrical surface of the shell The kiln lining includes one or more radial portions of a first size of shaped refractory material disposed on the inner cylindrical surface of the shell along the longitudinal axis for at least a portion of the shell and one or more lifter sections comprising a second size of shaped refractory material that extend along the longitudinal axis for at least a portion of the shell and are between radial portions of the first size of shaped refractory material, wherein the second size of shaped refractory material is greater than the first size of shaped refractory material, such that the second size of shaped refractory material extends orthogonally from the inner cylindrical surface for a greater portion of the diameter of the shell than the first size of shaped refractory material, the second size of shaped refractory materials thereby forming a series of blunt faces Also included are methods of processing materials using the inventive kiln lining, and methods of assembling the inventive kiln lining

Dephosphorization and iron-increasing method of high phosphorus hematite by direct reduction

Abstract: The invention particularly relates to a dephosphorization and iron-increasing method of high phosphorus hematite by direct reduction, and the technical scheme comprises the following steps: mixing 60-83wt% of high phosphorus hematite powder, 10-15wt% of carbonaceous reducing agent, 6-15wt% of quicklime and 1-10wt% of additive uniformly, pressing the mixture into blocks, drying, reducing in a high temperature furnace under 1250-1350 DEG C, and keeping the temperature for 15-30 minutes; carrying out furnace cooling until the temperature is 600-800 DEG C, taking the reduction product out, naturally cooling, grinding and performing the magnetic separation to obtain pig iron particles. The additive is sodium carbonate, or potassium carbonate, or the mixture of the sodium carbonate and the potassium carbonate; drying is carried out under the condition of 110-120 DEG C until the weight of the mixture of raw materials is constant; and the high temperature furnace is a resistance furnace, or a rotary kiln, or a rotary hearth furnace, and the atmosphere in the high temperature furnace is neutral or weak-reductive. The invention has the advantages of short reduction time, simple process, high dephosphorization rate, high iron yield, less environmental pollution, recyclable residue and the like.