valmet rotary kiln

lime kiln

Modern and proven ANDRITZ technologies for lime reburning include the LimeKiln with a LimeFlash dryer, a LimeCool cooler, and a LimeFire burner. These systems are the result of many years of experience and a high level of expertise in providing energy-efficient, reliable lime reburning for the recausticizing process.

Producing consistently high-quality burnt lime for slaking requires not only deep knowledge of the calcining process, but also effective energy conservation and emissions control. The lime kiln is a huge consumer of energy in a pulp mill, and a large potential generator of CO2 emissions. Energy and emissions need to be adequately controlled to consistently produce high-quality lime for cooking liquors.

ANDRITZs expertise in lime reburning has been thoroughly and successfully proven in more than 100 installations around the world. The fully automated ANDRITZ lime kiln package demonstrates low heat consumption, low emissions, and excellent availability. In addition to traditional fuels, the lime kiln can also burn 100% biofuels without the need for any fossil fuels with gasification or wood powder technologies.

rotary kilns

FEECO is a leading manufacturer of highly engineered, custom rotary kilns for processing solids. Our high temperature kilns have earned a reputation for their durability, efficiency, and longevity. We offer both direct- and indirect-fired units.

Rotary kilns work by processing material in a rotating drum at high temperatures for a specified retention time to cause a physical change or chemical reaction in the material being processed. The kiln is set at a slight slope to assist in moving material through the drum.

Direct-fired kilns utilize direct contact between the material and process gas to efficiently process the material. Combustion can occur in a combustion chamber to avoid direct flame radiation, or the flame can be directed down the length of the kiln.

All FEECO equipment and process systems can be outfitted with the latest in automation controls from Rockwell Automation. The unique combination of proprietary Rockwell Automation controls and software, combined with our extensive experience in process design and enhancements with hundreds of materials provides an unparalleled experience for customers seeking innovative process solutions and equipment.

Indirect-fired kilns are used for various processing applications, such as when processing must occur in an inert environment, when working with finely divided solids, or when the processing environment must be tightly controlled.

Calcination refers to the process of heating a material to a temperature that will cause chemical dissociation (chemical separation). This process is used frequently in the creation of inorganic materials, for example, the dissociation of calcium carbonate to create calcium oxide and carbon dioxide.

Thermal desorption is also a separation process. This process uses heat to drive off a volatile component, such as a pesticide, from an inorganic mineral, such as sand. The component is vaporized at the increased temperature, causing a separation without combustion. In some cases, an indirect rotary kiln would be best for this application, because the volatile chemicals may be combustible. The indirect kiln will supply the heat for desorption, without the material coming into direct contact with the flame.

Organic combustion refers to the treatment of organic wastes with the intent of reducing mass and volume. Organic waste is treated in the kiln, leaving behind an ash with considerably less mass and volume. This allows for more efficient and effective deposit of waste materials into landfills.

Sintering is the process of heating a raw material to the point just before melting. This increases the strength of the material, and is commonly used in the proppant industry, where sand or ceramic materials are made stronger.

Heat setting involves bonding a heat resistant core mineral with another, less heat resistant coating material. Unlike an unheated coating process, here, a rotary kiln heats the coating material to just below liquefaction point, allowing it to coat the heat resistant core more evenly and more securely. This process is commonly seen in the manufacture of roofing granules, where a mineral such as granite is coated with a colored pigment, producing a product that is both durable and aesthetically pleasing.

Reduction roasting is the removal of oxygen from a component of an ore usually by using carbon monoxide (CO). The CO is typically supplied by mixing a carbonaceous material such as coal or coke with the ore or by feeding it separately. Examples are the reduction roasting of a hematite containing material to produce magnetite that can be magnetically separated. In the Waelz process, zinc oxide in steel mill wastes is reduced to metallic zinc and volatilized for recovery in the off-gas system.

Thermal Desorption for Spent CatalystsRotary Kiln3D Indirect Kiln for Activated CarbonPyrolysis Kiln Seal3D FEECO Pyrolysis KilnPyrolysis KilnWorn Rotary Kiln RefractoryBatch Rotary Kiln TestingKiln Alignment SoftwareProcessing Challenges When Working with Rotary KilnsFEECO Batch Kiln BrochureIndustry Focus COVID-19 Demands Medical Waste Incineration CapacityIndirect Fired Rotary Kiln ReplacementRotary Kiln IncineratorsResource of the Week: Thermal Testing with Kilns3D Model of a FEECO Carbon Activation KilnRotary Kiln Testing ThumbnailRotary Kiln TestingIndirect Batch Rotary Kiln Testing, Batch Calciner Testing, Thermal Process DevelopmentKnowing When its Time to Replace Your Rotary Drum Seal, Leaf SealRotary Drum Drive ComponentsRotary Drum BreechingReplacement Rotary Drum BearingsBoomin Catalyst Market Drives Demand for Rotary Kiln Repair Services, Rotary KilnsReplacement Dryer (Drier) and Kiln BurnersCombustion ChambersReplacement Rotary Drum ShellRotary Drum Laser Alignment Process, Rotary Drum AlignmentWhy Post Maintenance Alignment is Critical to Rotary DrumsCauses of Tire (Tyre) and Trunnion Wear, Rotary Drum TireFEECO Tire (Tyre) Grinding Machine, Tire and Trunnion Grinding in ProgressRotary Drum Tire (Tyre) Wear Pattern from Excessive Wheel Skewing, Rotary Drum Tire in Need of Tire GrindingRotary Drum Tire (Tyre) Wear Pattern from Poor Housekeeping Practices, Rotary Drum Tire in Need of Tire GrindingRotary Drum Tire (Tyre) Wear Pattern from Misalignment, Rotary Drum Tire in Need of Tire GrindingRotary Drum Tire (Tyre) Wear Pattern from Using Improper Tire Lubricant, Rotary Drum Tire in Need of Tire GrindingTire (Tyre) and Trunnion Wheel GrindingTire (Tyre) and Trunnion GrindingIndirect Rotary Kiln (Calciner) for Plastics PyrolysisPlastic to Fuel Conversion via Pyrolysis Replacement Rotary Drum PartsRotary Drum Thrust RollersRotary Drum Trunnion Wheels (Rollers)Rotary Drum Riding Ring (Tire/Tyre)Resource of the Week: Girth Gears PageRotary Kiln System Optimization, Rotary Kiln Process AuditSpring-Mounted Replacement Rotary Drum Girth GearRotary Kiln Gains Traction as E-Waste Crisis Looms, Metal Recovery from E-WasteIndirect Batch Rotary Kiln Testing, Batch Calciner Testing, Thermal Process Development, Metal RecoveryDirect-Fired Rotary KilnRotary Kiln Chain and Sprocket Drive AssemblyRotary Kiln Gear and Pinion Drive AssemblyRotary Kiln Friction Drive AssemblyRotary Kiln Direct Drive AssemblyRotary Kiln Trunnion BaseRotary kiln end dam for increasing loading, retention time, and bed depthResource of the Week: Rotary Kiln Customization Slideshare PresentationKaolin Clay CalcinationLithium-ion Battery Recycling OpportunitiesRotary Kilns in Expanded Clay Aggregate ProductionBatch Kiln for Testing Expanded Clay AggregatesRotary Kiln Refractory Failure Illustration, Rotary Kiln Shell Hot SpotRotary Kiln Refractory InspectionDirect-Fired Rotary Kiln for SpodumeneCalciner (Indirect Kiln) for Lithium Recovery from SpodumeneRotary Kiln Complete SystemFEECO Batch Kiln for Testing CalcinationRotary Drum Drive BaseRotary Kilns for Advanced Thermal Processing in SustainabilityResource of the Week: Project Profile on a Rotary Kiln (Calciner) Resource Recovery SystemResource of the Week: Tire Grinding BrochureResource of the Week: Slideshare Presentation on Rotary Kiln Sizing and DesignResource of the Week: Unitized Drive Base BrochureDiagram Showing a Rotary Kiln with Co-current AirflowDiagram Showing a Rotary Kiln with Counter Current AirflowDiagram Showing Co-current Airflow View All >

The advantages to a FEECO rotary kiln are that it is built to the highest quality standards and is backed by over 60 years of process design experience. The FEECO Innovation Center offers batch and pilot scale kilns that can simulate conditions in continuous commercial rotary kilns, allowing our customers to test small samples of material under various process conditions, as well as part of a continuous process. With options in both co-current and counter-current flow, and direct or indirect configurations, the FEECO test kilns offer a variety of options to suit your thermal testing needs. We also offer support equipment such as a combustion chamber, afterburner, baghouse, and wet scrubber for testing.

grate kiln system - metso outotec

Grate Kiln systems consist of three major pieces of equipment. The Grate, the Kiln and the Cooler. The object of the process is to transform the pelletized concentrate into hardened pellets that can be used as blast furnace feed or direct reduction furnace feed.

The Travelling Grate is where pellets are dried and then heated up to a temperature of about 800-900 deg C. The heat used to dry and preheat the pellets is typically hot air pulled from the Kiln and cooler. The recycling of the the hot air from the different zones increases energy efficiencies.

In the Kiln, pellets are brought up to final indurating temps. Rotation of kiln exposes entire pellet bed to heat radiating from the burner resulting in uniform pellet quality. The kiln burner utilizes cooler off gas to heat material bed to nominal of 1200-1340 C completing the slag bonding and mineral bridging to form pellets.

In the Cooler, pellets are brought down to a suitable temperature for downstream material handling equipment. The gases from the cooler are recycled to the kiln and the grate, resulting in the Grate-Kiln being the most energy efficient system for producing indurated pellets.

The traveling grate is comprised of a blanket of plates connected into a chain that carries the pellets similar to a conveyor. The difference is that the plates in the grate chain have holes in them that allows air to pass through it. The grate chain travels flat and straight. The grate travels through a furnace with several zones that expose the pellets to different temperatures. Once the pellets are discharged into the kiln, the grate chain returns underneath. The grate is driven by a motor with gearbox or hydraulic drive. The grate is supported by rollers.

The final induration of the pellet is accomplished in a rotary kiln, wherein the principal heat transfer mechanism is radiation from the system's main burner.The process system is designed so that material transfer from the grate to the kiln occurs when the material on the grate is sufficiently preheated to have the requisite indurate strength for subsequent processing in the rotary kiln.A rotary kiln is a steel round shell with refractory lining that rotates. This shell is rotated by a drive gear and electric or hydraulic drive system. The shell is supported on large bearings. There is a single large burner that heats the pellets up as they travel through the kiln.

An annular cooler is a turntable that holds the hot pellets. Ambient air is blown through the hot pellets. The turntable is made of wedge shaped pans. The pellets fall out of the kiln directly onto the pans. The pellets travel all around the turntable until the pan is tipped and the pellets fall underneath. The pan is then righted to accept more material. The cooler pans are supported by rollers.

combustion equipment

A simple and elegant design that uses well established and proven changes in fuel/air mixing intensity to provide flame control. The Metso KFS designs avoid the complex mechanical adjustment mechanisms which are essential in the standard burner one-size-fits-all approach and avoids potential for local operations or maintenance to adjust incorrectly.

The primary air is split between axial air, for flame length and heat flux control, and swirl air for flame anchoring. A highly efficient aerodynamic swirler provides excellent flame stability. Each OptiMix burner is supplied with an integral pilot, including the extremely reliable natural gas or propane model.

For a wide range of gaseous fuels. Dual gas discharge locations ensure fine control on gas firing applications and turndown of over 20:1 ensuring the burner can be used in cold starts for refractory curing.

For conventional liquid fuels, such as #2 to #6 oils and including waste and re-refined oils. Using the proprietary CM atomiser offers at least 8:1 turndown using either steam or air atomisation. The PJ atomiser is specific for pressure jet applications. For alternative liquid fuels Metso KFS offer the WS Atomiser with air/steam-assist atomisation.

For pulverised coal and petcoke. Already a world leader in the pulp and paper industry where Metso KFS have burners firing natural gas, petcoke, methanol, and turpentine simultaneously. OptiMix S can also be designed to accommodate all types of solid alternative fuels such as lignin.

Developed using CFD Modelling, the DFN (direct-fired nozzle) burner has been proven across many projects to provide outstanding improvements in areas such as production, fuel consumption, NOx emissions, and ash ring formation.

Each DFN burner is custom-designed for the kiln both in terms of process performance and mechanical installation. High levels of performance are provided by careful use of bluff-body and swirl techniques to enhance fuel/air mixing combined with far greater flexibility than traditional straight-pipe.

The Metso KFS warm-up combustion system provides a safe and effective method to heat a rotary kiln from cold start through to main fuel firing. The Metso KFS system is ideal for existing rotary kiln operations based on straight pipe burner technology.

A key to a safe kiln warm-up is the ability to provide a stable flame for an effective and controlled heat release profile. The Metso KFS HeatSafe Burner (HSB) design is based on the proven Metso KFS OptiMixintegrated kiln burner design operating in over 100 rotary kilns.

The HSB can be gas or oil fired and incorporates a dependable source of ignition with a proprietary design fuel nozzle and high efficiency air swirler to provide easy light-off and a stable flame under variable kiln conditions.

Supporting the burners dependable flame stability are the associated fuel and primary air systems. Supervision of start-up, shutdown and operation of the HSB burner is provided by a Burner Managements System (BMS), which is fully compliant with the latest applicable standards.

As part of system design, Metso KFS offers a number of ancillary equipment items which enhance or complete the combustion system upgrade. Options are available for process and detailed design only, or full equipment supply:

rotary kiln for sale - sale rotary kiln by qualified manufactures

Rotary kiln refers to rotary calcination kiln (commonly known as rotary kiln) and belongs to the category of building materials equipment. Rotary kilns can be divided into cement kilns, metallurgical chemical kilns, and lime kilns according to different materials processed. Cement kilns are mainly used for calcining cement clinker, which divided into two categories: dry process cement kilns and wet process cement kilns. Metallurgical and chemical kilns are mainly used for magnetizing roasting of iron ore-depleted ore in iron and steel plants in the metallurgical industry; oxidizing roasting of chromium and nickel-iron ore; refractory plant roasting high alumina vanadium ore and aluminum plant roasting clinker and aluminum hydroxide; And chrome ore powder and other minerals. Limekiln (ie active lime kiln) is used for roasting active lime and light-burning dolomite used in iron and steel plants and ferroalloy plants.

Cement rotary kiln belongs to the category of building materials and equipment, it is a kind of lime kiln. 0.5mm tolerance cement rotary kiln means that the allowable error of rotary kiln shell is within plus or minus 0.5mm.

Lime rotary kiln is also called roller rotary kiln. To make sure its air leakage coefficient is less than 10 percent, lime rotary kiln adopts advanced structure and reliable combined scale-like seal in both ends. It also uses composite refractory to reduce the loss of heat radiation.

Shaft kiln, just as its name implies, is a kiln with erected shape. Shaft kiln with modern new technology has environmental protection function, energy-saving function, high mechanization, and high automaticity. It also has the ability to turn waste into wealth.

The rank of countries alumina bauxite storage is Australia, The Republic of Guinea, Jamaica, China, and India. Rich reserves provinces in China are Shanxi, Guizhou, Guangxi, and Henan province. Generally, alumina bauxite is used to produce alumina or aluminum.

The data survey found that the price of AGICO groups rotary kiln will be about 600-1000 cheaper than the prices offered by the merchants in other cities. The reasons for the analysis are as follows:

It is the main body of the rotary kiln (rotary kiln), usually 30 to 150 meters long, cylindrical, with 3 to 5 rolling circles in the middle. Most of the barrels are processed into 3-10 sections by the factory, and then welded by large trucks to the destination.

On the contrary, the cooler and the preheater are devices that rapidly reduce the temperature of the rotary kiln after firing. It looks like a small rotary kiln, but the diameter is smaller and shorter.

It is also called preheater, which is a device for preliminary heating of materials by the waste heat of exhaust gas discharged from the rotary kiln before the materials enter the rotary kiln. Most of them are vertical structures.

rotary kiln - an overview | sciencedirect topics

Rotary kilns are synonymous with cement making, being the workhorses of this industry. There are many types of rotary kiln arrangements for producing cement clinker with each incremental design goal aimed at improving energy efficiency, ease of operation, and product quality and minimizing environmental pollutants. Rotary cement kilns can be classified into wet-process kilns, semidry kilns, dry kilns, preheater kilns, and precalciner kilns. All of these are described in the book by Peray (1986) and many others, hence we will not dwell upon them here. Rather, we will briefly show the pertinent process chemistry and the heat requirements that drive them, so as to be consistent with the transport phenomena theme.

Rotary kilns have been used in various industrial applications (e.g., oil shale retorting, tar sands coking, incineration, cement production, etc.). The rotation of a cylinder-shaped vessel positioned longitudinally approximately 30 of the horizontal position ensures a continuous motion of catalyst between the entrance and exit of the kiln. With regard to the spent catalyst regeneration, the description of rotary kilns was given by Ellingham and Garrett [451]. There are two types of rotary kilns, i.e., direct fire and indirect fire.

The direct fire is a single shell vessel with rings added inside to slow the catalyst as it tumbles from the inlet (elevated part) towards outlet (lower part). The oxidation medium flows countercurrent to catalyst movement. The O2 concentration in the medium will decrease in the same direction because of its consumption. Therefore, the zone in the vessel located near the inlet may function as a stripper of volatile components of coke. The kiln is fired by gas burners directly against the outer shell of the vessel. The temperature inside the kiln is controlled by adjusting the burner heat, varying concentration of O2 in the oxidizing medium and its flow. The indirect fire kiln comprises a double-shell cylinder vessel. The inner shell is similar as that of the direct fire kiln. The space between the shells is heated either by combustion gas or steam. In some cases, the inner cylinder shell is ebullated allowing hot gases or steam to enter and contact the tumbled catalyst. The catalyst temperatures are controlled by monitoring the temperatures of the inlet and outlet gases. It is believed that Eurocat process evolved from a rotary kiln process by be improving the control of operating parameters such as temperature, gas flow, speed of rotation, etc.

The rotary kiln is used to process the lead-containing components resulting from the breaking and separation of waste batteries. The main components of a rotary kiln are an inclined cylindrical, refractory-lined reaction shaft equipped to rotate over rollers and a burner. Process heat is generated by burning fine coke or coal contained in the charge and by the exothermic heat of the PbO reduction by CO. This process produces molten lead and a slag with 35% Pb. A drawback of this technology is the short life of refractory liners.

The rotary kiln is a long tube that is positioned at an angle near horizontal and is rotated. The angle and the rotation allow solid reactants to work their way down the tube. Speed and angle dictate the retention time in the kiln. Gas is passed through the tube countercurrent to the solid reactant. The kiln is operated at high temperatures with three or four heating zones depending on whether a wet or dry feed is used. These zones are drying, heating, reaction, and soaking. Bed depth is controlled at any location in the tube with the use of a ring dam.

The most common reactor of this type is the lime kiln. This is a noncatalytic reaction where gas reacts with calcium carbonate moving down the kiln. Other reactions performed in the rotary kiln include calcination, oxidation, and chloridization.

Use of rotary kilns for hazardous waste incineration is becoming more common for disposal of chlorinated hydrocarbons such as polychlorinated biphenyls (PCBs). Flow in these kilns is cocurrent. Major advantages include high temperature, long residence time, and flexibility to process gas, liquid, solid, or drummed wastes.

The rotary kilns used in the first half of the twentieth century were wet process kilns which were fed with raw mix in the form of a slurry. Moisture contents were typically 40% by mass and although the wet process enabled the raw mix to be homogenized easily, it carried a very heavy fuel penalty as the water present had to be driven off in the kiln.

In the second half of the twentieth century significant advances were made which have culminated in the development of the precalciner dry process kiln. In this type of kiln, the energy-consuming stage of decarbonating the limestone present in the raw mix is completed before the feed enters the rotary kiln. The precalcination of the feed brings many advantages, the most important of which is high kiln output from a relatively short and small-diameter rotary kiln. Almost all new kilns installed since 1980 have been of this type. Figure1.4 illustrates the main features of a precalciner kiln.

The raw materials are ground to a fineness, which will enable satisfactory combination to be achieved under normal operating conditions. The required fineness depends on the nature of the raw materials but is typically in the range 1030% retained on a 90 micron sieve. The homogenized raw meal is introduced into the top of the preheater tower and passes downwards through a series of cyclones to the precalciner vessel. The raw meal is suspended in the gas stream and heat exchange is rapid. In the precalciner vessel the meal is flash heated to ~900C and although the material residence time in the vessel is only a few seconds, approximately 90% of the limestone in the meal is decarbonated before entering the rotary kiln. In the rotary kiln the feed is heated to ~ 1500C and as a result of the tumbling action and the partial melting it is converted into the granular material known as clinker. Material residence time in the rotary kiln of a precalciner process is typically 30 minutes. The clinker exits the rotary kiln at ~ 1200C and is cooled to ~60C in the cooler before going to storage and then being ground with gypsum (calcium sulfate) to produce cement. The air which cools the clinker is used as preheated combustion air thus improving the thermal efficiency of the process. As will be discussed in section1.5, the calcium sulfate is added to control the initial hydration reactions of the cement and prevent rapid, or flash, setting.

If coal is the sole fuel in use then a modem kiln will consume approximately 12 tonnes of coal for every 100 tonnes of clinker produced. Approximately 60% of the fuel input will be burned in the precalciner vessel. The high fuel loading in the static precalciner vessel reduces the size of rotary kiln required for a given output and also reduces the consumption of refractories. A wider range of fuel types (for example, tyre chips) can be burnt in the precalciner vessel than is possible in the rotary kiln.

Although kilns with daily clinker outputs of ~9000tonnes are in production in Asia most modem precalciner kilns in operation in Europe have a production capability of between 3000 and 5000 tonnes per day.

A rotary kiln is a physically large process unit used in cement production where limestone is decomposed into calcium oxide which forms the basis of cement clinker particles under high temperatures. The modelling of rotary kilns are well documented in literature. Mujumdar et al. 2007 developed an iteration based rotary kiln simulator (RoCKS), which integrates models for a pre-heater, calciner, kiln and clinker cooling that agreed well with observations in industry. The model takes complexities in reactions and heat transfers with different sections into account by coupling multiple models with common boundaries regarding heat and mass communications. Other work (Ngadi and Lahlaouti, 2017) neatly demonstrates an experimentally proven kiln model being applied for screening of combustion fuel used for kilns, and how it may impact the production. This contribution coupled modelling of reactions and heat transfer in the bed region and another model for combustion and heat transfer in the freeboard region.

While modelling of these processes with varying degree of complexity has been performed, proper uncertainty and sensitivity analysis of these models have not been given due importance/consideration. As the use of computer aided process engineering tools increases, the need for robust uncertainty and sensitivity analysis frameworks becomes more important. There are several frameworks of uncertainty and sensitivity analysis applied for different problems, from good modelling practice (Sin et al., 2009) to process design and product design (Frutiger et al. 2016). These frameworks typically include the following steps (0) problem statement, (i) identification of input sources of uncertainties, (ii) sampling (iii) Monte Carlo simulations and (vi) sensitivity analysis. The purpose of this work is to perform a systematic uncertainty and sensitivity analysis of rotary kiln process design in order to address the following: (1) Given a certain base case design, what is the impact of uncertainties in the model and measurements on the key process design metrics (minimum required reactor length and degree of conversion), and, (2) given a certain source of uncertainties, what is the robust design to ensure process performance with 95 % confidence.

The rotary kiln is often used in solid/liquid waste incineration because of its versatility in processing solid, liquid, and containerized wastes. The kiln is refractory lined. The shell is mounted at a 5 degree incline from the horizontal plane to facilitate mixing the waste materials. A conveyor system or a ram usually feeds solid wastes and drummed wastes. Liquid hazardous wastes are injected through a nozzle(s). Non-combustible metal and other residues are discharged as ash at the end of the kiln. Rotary kilns are also frequently used to burn hazardous wastes.

Rotary kiln incinerators are cylindrical, refractory-lined steel shells supported by two or more steel trundles that ride on rollers, allowing the kiln to rotate on its horizontal axis. The refractory lining is resistant to corrosion from the acid gases generated during the incineration process. Rotary kiln incinerators usually have a length-to-diameter (L/D) ratio between 2 and 8. Rotational speeds range between 0.5 and 2.5 cm/s, depending on the kiln periphery. High L/D ratios and slower rotational speeds are used for wastes requiring longer residence times. The kilns range from 2 to 5 meters in diameter and 8 to 40 meters in length. Rotation rate of the kiln and residence time for solids are inversely related; as the rotation rate increases, residence time for solids decreases. Residence time for the waste feeds varied from 30 to 80 minutes, and the kiln rotation rate ranges from 30 to 120 revolutions per hour. Another factor that has an effect on residence time is the orientation of the kiln. Kilns are oriented on a slight incline, a position referred to as the rake. The rake typically is inclined 5 from the horizontal.

Hazardous or non-hazardous wastes are fed directly into the rotary kiln, either continuously or semi-continuously through arm feeders, auger screw feeders, or belt feeders to feed solid wastes. Hazardous liquid wastes can also be injected by a waste lance or mixed with solid wastes. Rotary kiln systems typically include secondary combustion chambers of afterburners to ensure complete destruction of the hazardous waste. Operating kiln temperatures range from 800C to 1,300C in the secondary combustion chamber or afterburner depending on the type of wastes. Liquid wastes are often injected into the kiln combustion chamber.

The advantages of the rotary kiln include the ability to handle a variety of wastes, high operating temperature, and continuous mixing of incoming wastes. The disadvantages are high capital and operating costs and the need for trained personnel. Maintenance costs can also be high because of the abrasive characteristics of the waste and exposure of moving parts to high incineration temperatures.

A cement kiln incinerator is an option that can be used to incinerate most hazardous and non-hazardous wastes. The rotary kiln type is the typical furnace used in all cement factories. Rotary kilns used in the cement industry are much larger in diameter and longer in length than the previously discussed incinerator.

The manufacture of cement from limestone requires high kiln temperatures (1,400C) and long residence times, creating an excellent opportunity for hazardous waste destruction. Further, the lime can neutralize the hydrogen chloride generated from chlorinated wastes without adversely affecting the properties of the cement. Liquid hazardous wastes with high heat contents are an ideal supplemental fuel for cement kilns and promote the concept of recycling and recovery. As much as 40% of the fuel requirement of a well-operated cement kiln can be supplied by hazardous wastes such as solvents, paint thinners, and dry cleaning fluids. The selection of hazardous wastes to be used in cement kiln incinerators is very important not only to treat the hazardous wastes but also to reap some benefits as alternative fuel and alternative raw material without affecting both the product properties and gas emissions. However, if hazardous waste is burned in a cement kiln, attention has to be given to the compounds that may be released as air emissions because of the combustion of the hazardous waste. The savings in fuel cost due to use of hazardous waste as a fuel may offset the cost of additional air emission control systems in a cement kiln. Therefore with proper emission control systems, cement kilns may be an economical option for incineration of hazardous waste.

The rotary kiln gasifier is used in several applications, varying from industrial waste to cement production and the reactor accomplishes two objectives simultaneously: (1) moving solids into and out of a high temperature reaction zone and (2) assuring thorough mixing of the solids during reaction. The kiln is typically comprised of a steel cylindrical shell lined with abrasion-resistant refractory to prevent overheating of the metal and is usually inclined slightly toward the discharge port. The movement of the solids being processed is controlled by the speed of rotation of the kiln.

The moving grate gasifier is based on the system used for waste combustion in a waste-to-energy process. The constant-flow grate feeds the waste feedstock continuously to the incinerator furnace and provides movement of the waste bed and ash residue toward the discharge end of the grate. During the operation stoking and mixing of the burning material enhances distribution of the feedstocks and, hence, equalization of the feedstock composition in the gasifier. The thermal conversion takes place in two stages: (1) the primary chamber for gasification of the waste (typically at an equivalence ratio of 0.5) and (2) the secondary chamber for high temperature oxidation of the synthesis gas produced in the primary chamber (Grimshaw and Lago, 2010; Hankalin et al., 2011).

The rotary kiln ICM/Phoenix Bioenergy demonstration gasifier was operated at a transfer station in Newton, Kansas from 2009 to 2012 for more than 3200h, testing various types of biomass, RDF, tire-derived fuel or automobile shredded residue mixed with RDF. The 150-t-per-day facility reported to have tested more than 16 types of feedstock listed in Table 3.2 [13].

The gasification process consists of a horizontal cylinder with an internal auger which slowly rotates [15] allowing feedstock to move through the reactor, whereas air is injected at multiple points. Only small portion of the syngas was used to produce steam, whereas the rest was flared (Fig. 3.2).

Unfortunately, ICM had to take down the demonstration gasifier at the transfer station, upon completion of the project and financing grant, declaring that the facility did not prove to be a viable solution for the county. Some of the problems that ICM mention [16] were related to the availability of feedstock of only 90t per day, whereas the prototype was designed for 150t per day, but also insufficient investment from financial partners due to the lower projected returns. ICM announced that through a contract with the City of San Jose, CA they will have the ICM demonstration gasifier at the San Jos-Santa Clara Regional Wastewater Facility [17]. The facility will process 10 short tons per day of woody biomass, yard waste or construction and demolition materials mixed with biosolids from the WWT.

keeping kiln shell temperatures under control

Figure 1: KIMA Es water cooling system KilnCooler (TM) for kiln shells installed between the conventional air coolers on a rotary kiln in South Africa.Figure 2: Cooling power due to air blower capacity at kiln shell.Figure 3: Cooling power by evaporation of water.Figure 4: Not cooling the entire circumference makes it possible to avoid shrinking of the segment and reduce stress in the refractory. The right hand side image shows the precise treatment of only the hot area with the KilnCooler. Shrinking is limited only to the required area.Figure 5: Fundamental advantage of the KilnCooler is the controlled cooling of hot regions by a maximum of 2C/min. This avoids shock cooling and ensures slow coating development.Figure 6: Practical report from HeidelbergCement installation at Ennigerloh, Germany.Figure 7: The Whler Curve shows, in principle, the fatigue behaviour of steel under stress, induced by an alternating load.Figure 8: Leube Cement gained two months of full additional production by using the KilnCooler in the winter of 2015 2016. Figure 9: The KilnCooler at the Holcim plant Hoever, Hannover, Germany.Figure 10: The KilnCooler system in operation at the Afrisam Dudfield plant in South Africa.

Increasing requirements relating to energy consumption, productivity, emissions and operational costs have led to a range of ways to optimise cement production. Here KIMA Echtzeitsysteme describes its KilnCooler system, which uses water to reduce the impact of hot spots on cement rotary kilns. When we speak about putting water on an, admittedly hot, rotary kiln, many people have concerns. These should be thrown overboard. A rainstorm will bring far more water onto the kiln than the system described below.

As the margins of cement producers become more squeezed, especially in developed markets, there is increased pressure on cement plant kilns. The dark side of this drive towards operational optimisation is an increased need for maintenance. Over the year maintenance teams have to keep the kiln running from one planned stoppage to the next, without unplanned halts.

In this context one parameter is becoming particularly difficult: keeping the kiln shell temperature under control and avoiding uneven temperature profiles / hot spots when looking at the entire circumference of a kiln section. In part due to the introduction of alternative fuels, kiln temperatures now vary more rapidly and with less predictability than in the past. Formerly less critical areas of the kiln shell can also heat up unexpectedly.

To help create even and predictable kiln shell temperature profiles, KIMA Echtzeitsysteme has developed the KilnCooler, a water evaporation-based system for kiln shells. This idea often meets with the reaction that water should never be put on the kiln. This article will show that this assertion is incorrect. The system does not provide a miracle but it is very effective at cooling the kiln under certain conditions.

As with so much else in the cement sector, the exact reasons for a critical temperature increase differ from kiln to kiln, plant to plant and country to country. However, the main possible effects are the same everywhere: Increasing shell temperatures can lead to hot spots and, often, the need to stop the kiln. This can take a kiln line down for a week or more.

When calculating the costs of the resulting production losses even under conservative assumptions, one can easily see the big commercial potential underlying the prevention of an unplanned emergency stop. Table 1 shows an example calculation for a 4000t/day kiln. The example does not take into account the additional costs that occur, for example the salaries of the people who have to take care of the unplanned kiln maintenance works, the costs of additional fuel needed for heating up the kiln again and other smaller costs.

Above - Table 1: Example calculation of the costs of production loss due to an unplanned kiln stop, assuming two days for stop/cool down, two days to work on the refractories, one day for drying and one day for start-up.

This simple calculation already shows the steep increase in the cost of production loss when simply replacing the 4000t/day by higher production rates like 10,000t/day or more. If plants were able to save all of these costs by keeping the kiln in operation until the next planned shutdown, the savings could be used for other important optimisation projects.

To avoid such unnecessary production losses, it is critical to cool down the kiln shell, bring the temperatures back into balance and keep them within the desired range. The key to success in this case is controlled, punctual and efficient cooling. Due to it being a liquid, the cooling efficiency of water is several orders of magnitude higher than that of air. The following example calculation (under the assumption provided in Table 2) shows this big difference in cooling efficiency. Under the assumption that the air blown to the complete kiln can be heated up by 40C, one can dissipate roughly 2MW of thermal power by using 150,000m3/hr of air(Figure 2). The same amount of thermal power can be dissipated with 0.9L/s of water, just 3.2m3/hr water for a complete 60m kiln (Figure 3).

When spraying water to a hot metal surface one needs to take care to use the correct amount. Too much water means the cooling rate might be too high. Mechanical tensions might also occur leading to a risk of damage within the metal structures. Too little water, and the temperatures might come down too slowly or, in the worst case, continue to increase. When using the right amount of water, one can cool down temperatures as fast as necessary and stabilise them at the desired set point. To do this a water cooling system needs four main features:

A basic KIMA KilnCooler unit has four nozzles, each combined with an infrared (IR) pyrometer (range of 120 - 1000C (248 - 1832F)) and operated by a high level control. The total cooling length for one of these portable units is 2.6m. For larger areas the same systems can be daisy-chained.

The big advantage of a water cooling system is, besides its efficiency, the possibility of punctual cooling. The water flow can be switched off and on within milliseconds, which is not possible with air blowers. This is important to reduce the temperature of a hot spot, or even a warm area, back into balance with the lower temperature of the surrounding areas, which reduces the mechanical tension arising due to the difference.

While this is very effective, one also has to be aware of the risks of excessive cooling. As the water-based system cools a smaller area, there is a risk for high tension in the steel if areas are cooled to much, possibly causing damage to the refractory lining. A blower, by comparison, will cool not only the hotter areas, but also the complete circumference. While this reduces the circumferential differences, it can lead to shrinking of an entire kiln section, leading to enhanced stress for the refractory.

From evaluation, calculation and on-site experience, it was found that a cooling rate of 2C per minute (Figure 5) is a good rate at which to quickly quench hot spots while keeping mechanical tensions low. This rate also leaves enough space for adjustments by the high level control if necessary. As long as the metal temperature does not reach 600C (1112F), spraying water onto the hot metal does not harm the micro-structure of the steel. The KilnCooler controller itself is adjusted from KIMA Es site to an upper limit temperature of 500C, as above this temperature the kiln should be stopped in any case.

The practical proof of a safe and highly efficient cooling of the kiln shell was particularly provided with the development partner HeidelbergCement at Ennigerloh Factory in Germany. Accompanied by the Association of the German Cement Industry (VDZ), the thermal scan taken and illustrated in Figure 6 shows a 24-hour plot observation.

The use of the system is shown on a kiln shell section being irregularly heated by more than 50C. Starting with the commissioning of the system at about 14:00 hours, cooling down by about 50C was achieved within two hours in this real situation. As the set point of 350C is approached, the amount of water spray is automatically reduced significantly. Only 10 hours after start-up, the cooling system using water evaporation was switched off. The only slight increase in temperature and the stabilised status after switching off observed at that time, suggests that some coating has been newly formed in the kiln, so that further forced cooling is no longer necessary. Further case-studies in this article confirm that the treatment of a hot spot by means of the system avoids unexpected kiln stops.

Considering that the resistance of steel against alternating stress depends on many parameters, the use of the KilnCooler can be seen under another important light. Steel alters its strength depending on: Temperature; Surface finish; Metallurgical microstructure; Presence of oxidising or inert chemicals and; Residual stresses.

However, the steel is most affected by the number of cycles it undergoes. As the number of cycles is determined by the kilns rotation, the other parameters, especially the temperature, should be observed carefully and kept under control. To avoid fatigue of the shell, it is recommended that the temperature of the shell is kept below 400C (752F).

The Whler-Curve (Figure 7) shows, in principle, the fatigue behaviour of steel under stress, induced by an alternating load. It shows the magnitude of a cyclic stress against the logarithmic scale of cycles to failure. The number of cycles to failure is significantly reduced if the steel has an enhanced temperature. Therefore, if the steel temperature is controlled and harmonised at the entire circumference by the KilnCooler, the system can be an important tool for extending kiln life. Indeed, it makes sense to bring the KilnCooler into operation even at temperatures of 250-300C and not just after hot spots are formed.

It is important to state at this point that when KIMA Echtzeitsysteme describes hot spots we mean temperatures below 500C and not red spots at all. If the kiln shell reaches 480C the refractory might already be heavily damaged or totally removed. In this case the KilnCooler cannot help and the kiln should be stopped. The system should not be used to circumvent problems arising from poor maintenance or the choice of wrong or low performance refractories.

Answer: There is a theoretical critical thickness at which the heat conduction from the inside of the kiln through the shell to the outside would be disrupted. However, experience has shown that this thickness is never attained due to the very dry conditions on the shell and the movement of the kiln itself. The layer breaks off the kiln well before it reaches the critical thickness.

Answer: Of course the lime content in the water can lead to blockages. To avoid this, the system continuously monitors the water pressure and flow rate. In any case, blockages have not been reported so far, even with systems that have been in operation for several months. If a blockage is detected, the system will send an error message to inform operators. Removing a blockage and exchanging / cleaning the dirt trap, the nozzles or valves can be carried out within minutes.

We have used the system since August 2015. During its first winter, the system gave us more than two months of full additional production time due to quelling the first hot spots arising from the use of new alternative fuels and thinner than expected refractories. Just in front of the burning zone we have had serious problems creating a coating and balls were created for the first time ever inour production.

The system enabled us to create a stable coating in that locality once more and we reached the scheduled maintenance stop in January under full production. Previously, with air cooling fans we were not able to solve the problem. Today the system is in daily use when it comes to managing coating drops andhot spots.

When we bought the system in November 2015 we were extremely lucky, said Matthias Heuer, Production Manager. Only a few weeks later and just before the Christmas holidays we had fundamental problems with hot spots.

A massive hot spot as a result of very thin refractory lining and permanent coating drops were treated with the water spray kiln cooler. Within hours we developed a new coating and stabilised the temperature profile of the kiln surface.

Without the system we would have had to stop the kiln over the two week holiday as our maintenance team was limited during this period. This meant that we were able to operate until our scheduled kiln stop in January 2016.

Theo Conradie, Process Engineer, said, At 12.0m we had some hotter areas in which the KilnCooler reduced the temperature from 350C to 250C within a short time. Only a few hours later we saw a second spot at 9.0m with a temperature of 390C. We moved the system and the temperature dropped from 390C to 330C in around four hours.

The past two years of operation have shown that cement plants that suffer from temperature problems on the kiln shell were able to prolong kiln runtimes for weeks or months by using the KIMA KilnCooler. The system can take care of hot areas and keep the temperature within those areas at the desired set point temperatures. Also it has shown that, where possible, new coatings have been built up in the cooling area to provide a more even internal coating.

The system supports maintenance teams by giving them enough time to plan the necessary maintenance works and talking to the refractory suppliers. Due to the very low energy consumption, the operational costs are very low. It has been shown that the amount of water sprayed onto kiln is very low compared to the amount that drops from a rainstorm. It does not have any negative influence on the kiln steel as the system is intended for operation below 500C only.

The cooling efficiency of water combined with the possibility of controlled punctual spraying leads to a game-changing technology when it comes to increasing temperatures on kilns at the end of a production campaign. The earlier it is used in lower temperature regions, the more effective it is at increasing the lifetime of steel and refractory.

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cement rotary kiln, rotary kiln | cement kiln | agico cement

Cement Rotary kiln, is one kind of lime kiln, belongs to building material equipment. The rotary kiln has wide applications, such as metallurgy, chemical industry, cement, refractory materials, lime, environmental protection and other industries.

Cement rotary kiln, also called clinker kiln, can be divided into dry-process cement kiln and wet-process cement kiln according to the cement production technology. Dry-process cement rotary kiln is mainly used to calcine cement clinker. As the core equipment of NSP cement production line, cement rotary kiln is consist of shell, supporting device, transmission device, lubrication device, moving kiln head, sealing device for kiln tail, burning device and etc. dry-process cement rotary kiln has advantages of simple structure, reliable operation and easy to automatic control in the cement production line.

AGICO Cement is one of leading cement plant manufacturers offers cement kiln and other cement equipment, our cement rotary kiln has been widely applied to many cement plant. Based on 60+ years experience and advanced production equipment, we can provide EPC project and custom-designed solution to cement manufacturing.

Cement rotary kiln is a piece of cement equipment with strong durability, also plays a vital role in the cement plant. If you find any problem in the operation, solve it immediately. In general, the maintenance of rotary kiln is a complex process, here are some tips will be helpful.

First of all, check the fire hole of the rotary kiln is closed or not, ensure the close state to avoid too much cold air. Then, check the windshield of the burner at the kiln door is close to the kiln door. If the air leakage is not closed, it should be pushed to the position of close contact with the kiln door. Third, check the door cover of rotary kiln, if there is the phenomenon of positive pressure ash, should inform the central control to adjust properly. Finally, remember to check air leakage or wear out the phenomenon of resistant material, when you find the above problems, promptly inform the relevant leadership to deal with them.

Check the fish scales sealed in the kiln head, and then check the fitting condition of the fish scales in the rotary kiln and friction ring. If there is any bad condition such as non-fitting, the weight should be adjusted by tightening the device to make it fit. If there is too much aggregate in the reliable rotary kiln, the discharging pipe should be adjusted timely. After that, check the wear condition of the friction ring of rotary kiln. If the friction ring is found to be badly worn or worn out, replace it.

Check the cooling air at the kiln head, and then check the friction between kiln head and the kiln door cover. In order to ensure safety, check the oil film contact of the supporting wheel shaft and thrust plate one by one. Check oil level, oil scoop and oil distribution of rotary kiln. Next, check whether there are impurities, water droplets, oil leakage, collision, loosening and other abnormal conditions, if necessary, the temperature can be measured and control.

The service life of rotary kiln is affected by many factors, such as quality, regular maintenance, etc. AGICO CEMENT ensures the quality of the rotary kiln by strict quality control and advanced technology. Besides, regular maintenance can prolong the useful life of your rotary kiln.

Yes, in order to prevent cold air from entering the rotary kiln and smoke dust from spilling out of the cylinder, the rotary kiln is equipped with a reliable sealing device for the inlet end (tail) and an outlet end (head) of the cylinder, ensuring the sealing performance of the rotary kiln.

The cement rotary kiln produced by AGICO has been optimized and added with e dust filter products for environment protection, which is a new type of environmental protection equipment to reduce the environmental pollution caused by industrial production.

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