grate-kiln system for iron ore pelletizing - metso automation - pdf catalogs | technical documentation | brochure

grate-kiln system for iron ore pelletizing - metso automation - pdf catalogs | technical documentation | brochure

Plant overview Grate-KilnTM iron ore pelletizing system The first Grate-KilnTM system pellet plant was installed in 1960. The plant took iron ore concentrate and produced superior iron ore pellets (which are spheres of high iron content and uniform quality) for blast furnace and direct reduced iron feed. Since then, Grate-Kiln systems have been used for over 50 plants, on both magnetite and hematite ores, with an installed capacity of over 115 million tpy. Downdraft drying Downdraft drying Green balls Tempered preheat Preheat zone Zone 1 Zone 2 Rotary kiln Travelling grate Annular cooler...

Process flexibility Pelletization process There are two main processes for producing iron ore pellets: The Grate-Kiln system and the straight grate system. In the straight grate system, a continuous parade of grate cars moves at the same speed though the drying, induration and cooling zones. Any change in one section effects the residence time in another. Pelletization is comprised of two main stages: (1) agglomeration and (2) induration. During agglomeration, finely ground particulates (usually 80% passing 44 micron) of ore concentrate (with a moisture content of approximately 9%) are...

Installation of conveyor chain Blanket into travelling grate Energy efficiency The Grate-Kiln induration machine is composed of three separate process pieces of equipment. The traveling grate is used primarily to dry and preheat green balls for feeding into the rotary kiln, where they are indurated. Once the green balls are made they are spread out evenly across the grate. The traveling grate provides the means for heat transfer with high, medium and low temperature gases. It utilizes the heat coming from the kiln and cooler to perform this heat recovery. These gases transfer heat by...

Traveling grate CFD Model Baffle walls Preheat zone Common windbox, sloped floor Feautures and benefits Pellet quality Ported kiln operation Predictive control systems Because the induration of the pellets occur in the rotary kiln, the pellets produced in a Grate-Kiln system are consistently of higher quality than those produced in a straight grate. The rotary kiln provides constant mixing of the pellets, bringing all the pellets to the same temperature. In a straight grate, the pellets at the top of the bed are over cooked and those at the bottom are under cooked. Higher quality means...

Kiln drive components Equipment description Grate The traveling grate is a conveyor that transports balled iron ore concentrate through cross-flow processing zones. The conveying element is a continuous loop assembly of slotted ferrous stainless steel grate plates, chain castings, and side plates to carry a bed of agglomerates. The upper, active, carrying portion of the conveying element is supported level and flat over a head shaft, intermediate upper supporting shaft/roller assemblies and a tail shaft. The grate is driven by a bull gear drive assembly and a variable frequency drive and...

Kiln The kiln is a refractory lined cylinder rotating about its axis. The kiln slopes slightly downward from feed to discharge end. The slope and rotation of the kiln move the material through it. Kiln speed is variable to vary pellet retention time. The kiln is a single chamber with an open feed end connected by housing to the grates preheat furnace Through this connection is the inflow of material to the kiln and outflow of kiln gas to the preheat furnace. The kilns discharge end is open and connected to the cooler by a firing hood. Through the firing hood, pellets flow from the kiln to...

Metso Minerals Industries Inc. 350 Railroad Street, Danville, PA 17821-2046, USA, Phone: +1 570 275 3050, Fax: +1 570 275 6789 Metso Minerals Industries, Inc. 2715 Pleasent Valley Road, York, PA 17402, USA, Phone: +1 717 843 8671 etso Minerals (South Africa) (Pty) Ltd. M Private Bag X2006, Isando, Johannesburg,1600, South Africa, Phone: +27 11 961 4000, Fax: +27 11 397 2050 Metso Minerals (Australia) Ltd. Level 2, 1110 Hay Street, West Perth, WA 6005, Australia, Phone: +61 8 9420 5555, Fax: +61 8 9320 2500 Metso Minerals (India) Pvt Ltd 1th floor, DLF Building No. 10, Tower A, DLF...

grate kiln system - metso outotec

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.

grate kiln system

grate kiln system

The economics of pellet plant operation, in terms of fuel and power consumption, flexibility in the selection of the cheapest fuel source, system availability, maintenance costs, and the simplicity of process design, contribute to the determination of building and profitably operating a pellet plant. Design innovations, supported by actual field data, have been initiated into the GRATE-KILN System design to positively address these factors.

The GRATE-KILN System has changed significantly in design concept since the first systems were commissioned for Cleveland Cliffs Iron Company in the early 1960s through the most recent startup of the LKAB KP-79 plant in Kiruna, Sweden in 1981.

Initial GRATE-KILN plants were designed with no heat recuperation systems and typically consisted of a two pass, downdraft drying and downdraft preheat grate cycle. A preheat bypass system was installed to complement the preheat off-gas supply so that these two streams delivered the required downdraft drying heat supply.

The first GRATE-KILN System with heat recuperation was supplied to Sydvaranger AB in Kirkenes, Norway. This facility was commissioned in 1972. The heat recuperation design consisted of a duct from the annular cooler which was introduced into each preheat fan via the outlet chamber of the preheat cyclone dust collectors. The intent of this design was to replace the process gas normally bypassed from the preheat furnace which, when combined with the preheat off-gas streams, comprised the drying requirement.

Analysis of both the induced and dedicated fan approaches to heat recuperation revealed deviations between design conditions and actual field data. Paramount among the deviations was the temperature of the heat recuperation gas. Calculation technique at the time of the aforementioned designs predicted a nominal 400C recoup gas temperature.

One must bear in mind that a variety of factors can affect fuel consumption from plant to plant even though the ore type is similar. In addition to the intrinsic value of the heat recuperation system, such factors as:

a. to control the transverse movement and the gapping of the chain components, b. to improve sealing to minimize ambient air in leakage, and c. to improve machine availability and the ease of maintenance.

Control of the transverse and axial gapping was gained by close control of tolerances on the various grate plate and chain link castings which comprise a pitch assembly. Control of the gapping is important because minimum gapping minimizes material fall through between adjacent grate plates and between chain castings and grate plates. By eliminating significant fall through of material, weight recovery in the process is improved and less dust and chips are handled in the recycle system.

Another important advantage of minimizing material fall through on the grate is that minimum gaps promote uniform heating of the pellet bed and a more even temperature gradient through the conveyor chain. Any gaps which form on the chain allow channeling of nominal 1000C process gases which can overheat specific areas and necessitate frequent parts replacement and reduce plant availability.

Ambient air in leakage into the process gas stream is undesirable because ambient air depresses the system temperatures. Lower process gas temperatures reduce heat transfer effectiveness which can promote higher fuel rates and higher process fan power due to the larger quantity of denser process gas to be handled.

The important features which contribute to transverse gapping control have been described above. As previously mentioned, the increase in the through rod diameter coupled with induction hardening of the through rod chain link interface will be the prime factors for a longer chain life. The life is now projected to be in the range of 44 to 52 months. This projection is based on data obtained from operating plants with similar design improvements.

Grate plates supplied on the traveling grate are one piece, cast, high grade stainless steel units. These units are extremely heat resistant and replacement is usually dictated only if one should break or become exposed to a direct flow of hot preheat zone on-gas.

The sand seal between the rotating and stationary wall has been replaced by a water seal. The water tank is attached to the rotating wall with the seal plate being part of the stationary assembly above the rotating structure. Designing a seal with minimum maintenance and operating longevity is imperative from the standpoint of process efficiency. The water seal allows the primary and final cooling fans to deliver the required gas flow to the process without any detrimental effects to the equipment. The nature of the cooling process imparts a slightly positive pressure slightly positive pressure above the pellet bed near the area of the seal. The seal design intent is to prevent the flow of ambient air into the process, which dilutes process gas temperatures and restricts the flow of cooling air through the pellet bed.

The GRATE-KILN System significantly reduces pellet production costs by utilizing coal in place of more expensive liquid or gaseous fuels. Coal is directly fired in the GRATE-KILN System, eliminating need for external combustion chambers, slag tapholes, auxiliary burners or special high priced refractories.

The relationships are expressed in terms of correlation coefficients that describe the statistical significance of a given variable relative to the deposition rate obtained at a particular temperature. The closer the correlation coefficient is to one, the better the fit of data to a straight line plot.

The most significant variables are coal heating value, and fixed carbon and ash contents. It should be noted that each of these variables is interrelated to the other. Basically, as ash content rises the fixed carbon content and heating value decrease. Coal heating value increases directly with increase in fixed carbon content. Correlation coefficients for ash to heating value and fixed carbon to heating value were found to be in the 0.73 to 0.77 range. Basic ash deposition behavior, therefore, is dependent on these interrelated coal characteristics. The term Coal Characterization Value, or CCV, has, therefore, been developed to express this relationship relative to deposition rates. It is defined as;

There have been cases where coals with ash initial deformation temperatures of 1150C have lower deposition rates than coals with greater than 1480C ash initial deformation temperatures. Coals with ash fluid temperatures in excess of 1480C have had four times the deposition rates of coals with ash fluid temperatures less than 1370C.

The drum interior is lined with a series of parallel, longitudinal, rubber belts which are anchored to the shell along the belt edging with metal strips. Flexing or droop of the belt during drum rotation purges concentrate from accumulation on the lining.

iron ore pelletisation plant, using the grate kiln process goodrich magma industrial technologies limited

iron ore pelletisation plant, using the grate kiln process goodrich magma industrial technologies limited

There are two major processes for the production of iron ore pellets straight grate & grate kiln. Straight grate plants are expensive & suited for large scale production. Grate kiln plants are economical and suited for medium scale production.

GoodRich offers iron ore pelletisation plants from a reputed manufacturer in China, based on the grate kiln technology. The plants are available in capacities from 100,000 tons to 1,200,000 tons per annum. The Chinese company has already supplied 8 pellet plants in India.

In the grate kiln process, a chain grate system is used for drying & pre-heating the green balls to be fed into the rotary kiln, where they are indurated. The pellets are finally cooled in a circular cooler.

Iron ore pellets are being increasingly favoured in modern blast furnaces. The proportion of pellets in iron making is increasing due to their properties such as higher density, uniform granularity, good reductability, etc.

Pellet is a good material for sponge iron making also. When used in the rotary kiln, pellets reduce the iron ore requirement to 1.45 tons per ton of sponge; reduce the travelling time & increase the sponge output by 20-25%. They also reduce the coal consumption by 15-20% & improve the metallization rate to 86-88%. Hence, they are sold at a premium price in the domestic market.

rotary kilns - metso outotec

rotary kilns - metso outotec

There are two main processes for producing iron ore pellets: The Grate-Kiln system and the straight grate system. In the straight grate system, a continuous parade of grate cars moves at the same speed though the drying, induration and cooling zones. Any change in one section effects the residence time in another.In the Grate-Kiln system, independent speed control of the grate, kiln and cooler are available to the operator. This provides process flexibility to adjust to changes in concentrate feed.

The use of control systems employing expert system designs increases the opportunity to optimize plant performance on a continual basis. By being able to correlate changes continually, the plant can anticipate operational changes and make corrections. Metsos implementation of this type of control technology for Grate-KilnTM pellet plant will make it possible for operators to increase capacity, reduce fuel and power consumption, and reduce maintenance costs.

Because the induration of the pellets occur in the rotary kiln, the pellets produced in a Grate-KilnTM system are consistently of higher quality than those produced in a straight grate.The rotary kiln provides constant mixing of the pellets, bringing all the pellets to the same temperature. In a straight grate, the pellets at the top of the bed are over cooked and those at the bottom are under cooked. Higher quality means fewer fines, better reducibility and less variation in compression strength.

By injecting air under the bed of pellets in the rotary kiln, complete oxidation can occur in magnetite pellets prior to the annualar cooler. This patented development by Metso, in addition to lowering fuel consumption, significantly improves pellet quality. Full oxidation at induration temperatures produces stronger pellets, while maintaining reducibility. This capability is unique to the Grate-Kiln system.

grate-kiln system operation

grate-kiln system operation

The Humboldt and its Grate-Kiln System Operation on crude ore is a mixture of cherty specular hematite and magnetite, with minor amounts of martite and sericite. Mineralization varies from coarse to extremely fine grained. The overburden varies from zero to 50 ft. The ore body is approximately 1300 ft. long and varies in thickness from 250-400.

Crushing is accomplished in three stages of open pit circuit crushing to a rod mill feed size of . One 48 Primary, one 7 std Cone Crusher as a Secondary, and two 5-84 Tertiary Crushers are used to obtain this nominal crushed product.

The crude ore is reduced to 8 mesh in a 450 HP rod mill in open circuit. A ball mill (450 HP) in closed circuit with an hydroscillator does the final grinding for liberation. The hydroscillator overflows at about 65% passing 200 mesh. This will vary somewhat, dependent upon ore hardness and mill feed rates.

The cyclone underflow discharges into conditioners at about 68% solids. Reagents are added to this series of conditioners to prepare the slurry for flotation. About 1.5 of Tall Oil is added per ton of feed. Other reagents are Aerosal OT 75 and a frother.

Two, 1000 tons per day units, are installed in the pelletizing section. Plant design is pointed towards the production of 646,000 LT per year on a 323 operating day level. The plant actually runs 365 days per year with one of the units down for repairs about once a month. There are no scheduled-down shifts on a weekly basis.

Reground concentrate is fed from 450 LT storage bins into each of the balling circuits by 86 table feeders. These feeders are driven by D.C. motors controlled by belt scales to give a uniform tonnage per unit time. One half of one percent bentonite is added to the raw concentrate prior to its being mixed and fluffed in reel type mixers.

The refractory kiln blocks are 9 deep in this photo while in the feed end of the Kiln they are 6 deep. The Kiln burner has a capacity of 500. gph of No. 6 oil, heated to 230 at a pressure of 350 psig.Each kiln is driven by a 100 HP D.C. motor which results in a variable speed of up to 120 revolutions/hour.

Primary cooling air enters below the pallets in the annular cooler and passes updraft through the hot bed of pellets. During passage through the 30 deep bed, the air temperature rises to about 1700 F. This hot air is directed into the Kiln, through the firing hood for use as secondary combustion air within the Kiln.

The kiln exit gas is directed up into the preheat furnace where it is, pulled downdraft through the 7 bed of pellets by the No. 1 Fan. The temperature of the gases over the bed varies from 1700-1900 F. After passage through the bed, the gas temperature drops to an average of 600 F.

The Kiln operator has direct control over the gas flows, system temperatures and tonnage. He has a variety of sensing, indicating, and recording instruments to aid him in evaluating the performance of the system at any given instant. The balling drum operator, while under the Kiln operators directives, can control and gauge tonnage thru any one drum, the ratio of bentonite, and the amount of water, if any, added to the incoming concentrate.

A tumble test on the pellets reports an average of 4.7% passing 28 mesh after 200 revolutions in an ASTM coke tumbling drum. The crushing strength of a nominal pellet is in the range of 750-850 lbs.

grate cooler - page 1 of 1

grate cooler - page 1 of 1

DEAR ENGINEERS....WE HAVE A PROLEM IN OUR COOLER (CLAUDIUS PETERS). WE ARE FREQUENTLY FACING THAT PROBLEM, THE PROBLEM IS , AT THE KILN DISCHARGE END OF GRATE COOLER MORE RED HOT CLINKER IS LEAKING TO THE HOPPER. DURIING SHUT DOWN WE ARE CHECKING THE CONDITION OF GRATE PLATES, AND IN THESE AREAS WE CAN SEE MORE GRATE PLATES AND SIDE SEALING PLATES ARE BURNING. THIS PROBLEM IS FREQUENTLY HAPPENING AND UPTO NOW WE COULDNT DETECT THE ACTUAL PROBLEM. THE CLINKER LEAKAGEISSAMELIKEWATER FALL. DUE TO THIS WE HAVE TO STOPOUR KILN ONCEIN A MONTH.SO IF YOU HAVE AN IDEA ABOUT THIS PROBLEM PLEASE LET ME KNOW..THANKING YOUAFSAL KANNIYANDOHA- QATAR

WE HAVE A PROLEM IN OUR COOLER (CLAUDIUS PETERS). WE ARE FREQUENTLY FACING THAT PROBLEM, THE PROBLEM IS , AT THE KILN DISCHARGE END OF GRATE COOLER MORE RED HOT CLINKER IS LEAKING TO THE HOPPER. DURIING SHUT DOWN WE ARE CHECKING THE CONDITION OF GRATE PLATES, AND IN THESE AREAS WE CAN SEE MORE GRATE PLATES AND SIDE SEALING PLATES ARE BURNING. THIS PROBLEM IS FREQUENTLY HAPPENING AND UPTO NOW WE COULDNT DETECT THE ACTUAL PROBLEM. THE CLINKER LEAKAGEISSAMELIKEWATER FALL. DUE TO THIS WE HAVE TO STOPOUR KILN ONCEIN A MONTH.

Hello Afsal,What you are describing is a common problem in clinker coolers and is generally called a "Red River".I found this passage in a book called "Clinker Coolers" by Hans E. Steuch (Chapter 3.8, p494-495), which may be helpful to you;-"The fact that especially large diameter type kilns tend to discharge fine clinker on the kilns load side and coarse clinker on the opposite side can make it difficult to get good clinker distribution. Due to the high air resistance of a fine clinker bed, red rivers often are inevitable. Studies show that red rivers can cause a variation in air distribution of 1:6 between the fine and coarse clinker side and can even cause clogging of the bed. This is why grate plates sometimes become red hot in places. Red rivers also cause an increase in clinker discharge temperature. Measures for improving the clinker distribution should start at the cooler inlet. Where snowmen cause poor clinker distribution, the cooler back and sidewalls can be kept clean with the help of compressed air cannons. Some improvements are possible by slowing down the movement of the fine clinker bed and diverting more fine clinker to the coarse cooler side, thus increasing the overall clinker bed resistance which pushes more air through the fine clinker bed. This diversion can be done by using wedge-type grates with 125-mm or 200-mm high faces. The grates are arranged in a checkerboard pattern as shown in Figure 3.8.17. An often successful way to improve the situation is to narrow the cooler grate area on the fine clinker side. By doing so, the clinker bed becomes narrower and often eliminates a severe segregation of fine and coarse clinker. It is recommended that the cooler inlet grate width not exceed 2.5 m for kiln capacities up to 2,500 metric tons per day of clinker. Figure 3.8.17 shows that some air holes in corner grates are blanked off. Corner areas often have a low clinker load which results in heavy air channeling and bypassing the clinker load. Blanked off air holes ensure that cooling air is diverted into the clinker load. When severe red river conditions exist and loss of cooler grates are experienced, Ondufin grates can be applied. The grates have cooling fins on the underside which increase the cooling surface. The grates stay cooler and last longer. In addition, if a grate is burned through, the fins prevent large clinker spillages for a considerable time. When red river conditions in a pre-1990s style cooler are extremely severe, compartments can be divided into two sections. Two cooling fans, one on each cooler side, assure that both grate areas, the fine and the coarse side, receive the proper amount of air. Or, the design can be upgraded to one with airbeams or mechanical air flow regulators for small groups of grates. Some suppliers, borrowing from the airbeam technology, offer a grate plate design for pre-1990s coolers where the air has to travel through a labyrinth in the grate first up, then down before exiting into the clinker bed. This provides an effective clinker seal that reduces the amount of clinker falling through the grate plates to the undergrate compartment. Increasing the clinker bed thickness generally improves the overall clinker distribution and heat transfer. Good results have been experienced with clinker beds up to 1 meter deep. In addition, lower grate speed has had a positive effect upon grate wear rates. High undergrate pressures and airflows adversely affect the conveying action of a reciprocating grate. High air pressures can reduce the friction between the clinker and the grate, which in turn can speed up the movement of the clinker toward the cooler discharge. The air, which expands as it rises in the bed, causes the clinker at the surface to be fluidized. The result might be that clinker flows down the slope if the grate area is inclined or that the clinker can only be moved with extremely high reciprocating speed on horizontal type coolers. To prevent clinker from flowing forward, the single grate surface should be at least horizontal. Experience has shown that the best results can be attained with a maximum of 4.7 to 5.5 kPa undergrate pressures in horizontal and 3 degree inclined coolers.AIR DISTRIBUTION VERSUS OVERALL COOLER EFFICIENCYOptimized air distribution also improves the overall thermal cooler efficiency and prevents damage to grates due to overheating. To achieve this goal, predefined amounts of cooling air need to be established for every cooler compartment. Coolers with airbeams or mechanical air flow regulators can refine the air distribution even more to sections of grate plates or to individual plates. The optimization of airflow is especially important for the heat recuperating zone. Too high amounts of air do not give maximum secondary air temperature. Too low amounts of air elevate the clinker discharge temperature. Too high amounts of air also promote fluidization of the clinker. As the finer clinker particles are likely to be entrained in the locally intensified air flow, high amounts of dust cycles between kiln and cooler are likely. Dust particles might also be picked up from highly fluidized areas and concentrate in others, thereby intensifying any red rivers. Extremely high airflows also promote heavy air channeling, giving a poor heat exchange for a grate cooler of 1970s to mid-1990s vintage. It is recommended that maximum airflow not exceed approximately 140 normal cubic meters per minute per square meter of cooler grate area. Figure 3.8.18 shows a chart of optimized cooling air distribution for a typical eight-compartment reciprocating grate cooler. The first five compartments (including quench compartment) supply secondary air and tertiary air if applicable; compartments #5 through #8 cool the clinker to a final temperature of approximately 100C. Lowering the clinker discharge temperature further with more air increases the electrical power consumption considerably. Depending upon the total amount of cooling air used, the power consumption for the cooling fans can run between 3 and 8 kWh/ton of clinker, plus up to 4 kilowatt-hours for venting.coolers, and 2.0 to 2.5 kPa in old 10 degree inclined coolers."Regards,Ted.

"The fact that especially large diameter type kilns tend to discharge fine clinker on the kilns load side and coarse clinker on the opposite side can make it difficult to get good clinker distribution. Due to the high air resistance of a fine clinker bed, red rivers often are inevitable. Studies show that red rivers can cause a variation in air distribution of 1:6 between the fine and coarse clinker side and can even cause clogging of the bed. This is why grate plates sometimes become red hot in places. Red rivers also cause an increase in clinker discharge temperature. Measures for improving the clinker distribution should start at the cooler inlet. Where snowmen cause poor clinker distribution, the cooler back and sidewalls can be kept clean with the help of compressed air cannons. Some improvements are possible by slowing down the movement of the fine clinker bed and diverting more fine clinker to the coarse cooler side, thus increasing the overall clinker bed resistance which pushes more air through the fine clinker bed. This diversion can be done by using wedge-type grates with 125-mm or 200-mm high faces. The grates are arranged in a checkerboard pattern as shown in Figure 3.8.17. An often successful way to improve the situation is to narrow the cooler grate area on the fine clinker side. By doing so, the clinker bed becomes narrower and often eliminates a severe segregation of fine and coarse clinker. It is recommended that the cooler inlet grate width not exceed 2.5 m for kiln capacities up to 2,500 metric tons per day of clinker. Figure 3.8.17 shows that some air holes in corner grates are blanked off. Corner areas often have a low clinker load which results in heavy air channeling and bypassing the clinker load. Blanked off air holes ensure that cooling air is diverted into the clinker load. When severe red river conditions exist and loss of cooler grates are experienced, Ondufin grates can be applied. The grates have cooling fins on the underside which increase the cooling surface. The grates stay cooler and last longer. In addition, if a grate is burned through, the fins prevent large clinker spillages for a considerable time. When red river conditions in a pre-1990s style cooler are extremely severe, compartments can be divided into two sections. Two cooling fans, one on each cooler side, assure that both grate areas, the fine and the coarse side, receive the proper amount of air. Or, the design can be upgraded to one with airbeams or mechanical air flow regulators for small groups of grates. Some suppliers, borrowing from the airbeam technology, offer a grate plate design for pre-1990s coolers where the air has to travel through a labyrinth in the grate first up, then down before exiting into the clinker bed. This provides an effective clinker seal that reduces the amount of clinker falling through the grate plates to the undergrate compartment. Increasing the clinker bed thickness generally improves the overall clinker distribution and heat transfer. Good results have been experienced with clinker beds up to 1 meter deep. In addition, lower grate speed has had a positive effect upon grate wear rates. High undergrate pressures and airflows adversely affect the conveying action of a reciprocating grate. High air pressures can reduce the friction between the clinker and the grate, which in turn can speed up the movement of the clinker toward the cooler discharge. The air, which expands as it rises in the bed, causes the clinker at the surface to be fluidized. The result might be that clinker flows down the slope if the grate area is inclined or that the clinker can only be moved with extremely high reciprocating speed on horizontal type coolers. To prevent clinker from flowing forward, the single grate surface should be at least horizontal. Experience has shown that the best results can be attained with a maximum of 4.7 to 5.5 kPa undergrate pressures in horizontal and 3 degree inclined coolers.

Optimized air distribution also improves the overall thermal cooler efficiency and prevents damage to grates due to overheating. To achieve this goal, predefined amounts of cooling air need to be established for every cooler compartment. Coolers with airbeams or mechanical air flow regulators can refine the air distribution even more to sections of grate plates or to individual plates. The optimization of airflow is especially important for the heat recuperating zone. Too high amounts of air do not give maximum secondary air temperature. Too low amounts of air elevate the clinker discharge temperature. Too high amounts of air also promote fluidization of the clinker. As the finer clinker particles are likely to be entrained in the locally intensified air flow, high amounts of dust cycles between kiln and cooler are likely. Dust particles might also be picked up from highly fluidized areas and concentrate in others, thereby intensifying any red rivers. Extremely high airflows also promote heavy air channeling, giving a poor heat exchange for a grate cooler of 1970s to mid-1990s vintage. It is recommended that maximum airflow not exceed approximately 140 normal cubic meters per minute per square meter of cooler grate area. Figure 3.8.18 shows a chart of optimized cooling air distribution for a typical eight-compartment reciprocating grate cooler. The first five compartments (including quench compartment) supply secondary air and tertiary air if applicable; compartments #5 through #8 cool the clinker to a final temperature of approximately 100C. Lowering the clinker discharge temperature further with more air increases the electrical power consumption considerably. Depending upon the total amount of cooling air used, the power consumption for the cooling fans can run between 3 and 8 kWh/ton of clinker, plus up to 4 kilowatt-hours for venting.coolers, and 2.0 to 2.5 kPa in old 10 degree inclined coolers."

Dear Mr.Kanniyan,The followings are may be the reason for your problem:1) In your plant are you encountering frequent snow man problem? If yes, Try to adjust the Kiln feed chemical composition,so that you canavoid snow man formation.2) Please check and confirm the cooler fans air flow displayed in CCR are matching with actual readigs. Secondary air temperature is the best indicator.3) Is there any alignment problem in the first grate? If yes, repair it immediately.4) Analyse the grate plates quality. Are they matcing with the recommendations of OEM? Try to purchase from other supplier.Regards,G.S.M.Subramanian

Hi Afsal, This is not a surpirse to hear material spillage in the 2nd generation grate coolers.When the grate plates are installed/ commissioned the minimum gap between plates are measured and the correction is done accordingly. As days movethe gap between the plates and side seals starts to increase and after some time they open up so badly to allow red hot material spillage into the bottom hoppers (loss in thermal energy when the red hot clinkeris not shredding the heat in the recuperation region). Nowin our modern 4th generation clinkercoolers fromFons Technology International, weare offering moving lanes of grate plates along the length. These coolers come in modular type so the same module with with different cooler sizes shall support 300 TPD - 13000 TPDwith less downtime for upgrade, providing 75 -80% recuperation efficiency.Hydraulicdrive increases the availability and also the lane technology allows mixing of fine and coarse clinkerby varying the stroke length of the individuallanesacross the width of the coolers. Apart from thisIso Kinetic Inlet( static inlet) is offered to avoid snowman and minimise compressed air consumption in the inlet. With the snowman free inlet the secondary and tertiary air temperatures are acheived to the best level. If you need mor information, please contact us [email protected] refer www.fonstechnology.com/ Regards, Ram

This is not a surpirse to hear material spillage in the 2nd generation grate coolers.When the grate plates are installed/ commissioned the minimum gap between plates are measured and the correction is done accordingly. As days movethe gap between the plates and side seals starts to increase and after some time they open up so badly to allow red hot material spillage into the bottom hoppers (loss in thermal energy when the red hot clinkeris not shredding the heat in the recuperation region).

Nowin our modern 4th generation clinkercoolers fromFons Technology International, weare offering moving lanes of grate plates along the length. These coolers come in modular type so the same module with with different cooler sizes shall support 300 TPD - 13000 TPDwith less downtime for upgrade, providing 75 -80% recuperation efficiency.Hydraulicdrive increases the availability and also the lane technology allows mixing of fine and coarse clinkerby varying the stroke length of the individuallanesacross the width of the coolers.

Apart from thisIso Kinetic Inlet( static inlet) is offered to avoid snowman and minimise compressed air consumption in the inlet. With the snowman free inlet the secondary and tertiary air temperatures are acheived to the best level.

iron ore pellatisation application in steel industry grate kiln process | thermax

iron ore pellatisation application in steel industry grate kiln process | thermax

Vale S.A. is a Brazilian multinational diversified metals and mining corporation. In addition to being the second-largest mining company in the world, Vale is also the largest producer of iron ore pellets. Vale S.A opened a 9 MTPA (2 x 4.5) Iron ore pellatisation plant in Sohar, Sultanate of Oman., on March 3rd, 2011. High grade iron ore for the plant is imported from Brazil & finished product is sold to Steel plants globally as a raw material feed for Blast furnace or Electric arc furnace.

Pellatisation process turns fine grained iron ore into hardened balls of approx. 8 to 16 mm diameter, which are used as feed in Blast Furnace, Electric arc furnace or DRI plant. Fine grained high quality Iron ore is mixed uniformly with Lime stone, Coke Breeze along with Bentonite & moistened with water & taken to a balling drum were in centrifugal force reduce the moistened raw material to Green Pellets of required size as specified by customer. The Green pellet thus obtained is taken to an indurating furnace having heat resistant perforated cast irontraveling grate bars arranged on two rotating drum to make an end less belt. Green Pellet is evenly placed at the feed end & burners are arranged opposite each other on longitudinal sides of the preheating & firing zone. As the belt progress a series of heavy duty fan draw air through the pellet bed & coke breeze in the Green pellet catches fire. The speed of the belt is arranged in such way that the pellets harden uniformly & emerge as red hot pellet at discharge end. The dust laden gases are treated in Pollution control equipment before letting out through stack. Unlike in Straight Grate process a Grate Kiln process employ only one burner situated at the discharge end of the Rotary Kiln. Forced Annular coolers are located at discharge end to uniformly cool pellet by an updraft of ambient air before transporting to storage silo.

Grate Kiln process is unique process designed to evenly indurate pellets to increase its mechanical properties. This process employ a conventional Straight Grate followed by a Rotary Kiln designed to churn the pellets & thus increase even heating as well to avoid fragmentation in transportation. As against a conventional burner the hot gases from the Rotary kiln are reused to preheat the green pellets so that the moisture in the Green pellet is gradually released & avoid steam formation inside pellet which would otherwise rupture the pellets. Technology for the Project was offered by KOBELCO, Japan. who has recommended Grate Kiln Technology of Metso Minerals. Grate Kiln process was then a first- of- a-kind application for Thermax, despite having supplied numerous Air pollution control equipment on Straight Grate Pellet plant. The challenge in this case was the high dust load generated due to churning of pellet inside the Kiln as well space constrain in Location of ESPs.

Process engineers at Thermax carried out extensive study & based on performance data of straight grate Pellatisation Process derived optimum design of ESP for Grate Kiln Process & accommodated in the given floor space without compromising on technical parameters .

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