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作者: 发布时间: 2021-07-12 27 次浏览


One-step Rotary Kiln Producing Reducing Iron Hot-pressing Block Project


Technical proposal


       Introduction of the Process


             Production Process of Reduced Iron Hot-pressing Block (HBI)


Rotary kiln reduction technology with natural gas or gas as heat source and passivator pressing block by hot pressing are the latest research and development of new technology for producing reduction iron hot pressing block by our company. The new technology is energy-saving and environmental protection, and has declared the national invention patent. It not only makes rotary kiln operation easy, Rotation kiln ringing rate becomes lower and the operation is more reliable. At the same time, due to the addition of passivation system for hot pressing forming, the waste heat is maximally utilized, and the energy consumption and production cost are reduced.


The process is mainly aimed at reducing iron ore powder or oxide scale. The raw materials used are iron ore powder (oxide scale), reducing agent (CO + anthracite) and desulfurizer. The main equipments include batching and ball-pressing system, drying heating system, secondary combustion chamber system, rotary kiln reduction system, hot pressing passivation system, exhaust air purification system, coal injection system and circulating water cooling system etc.


The main process is that after mixing iron powder, iron oxide scale and binder in a certain proportion, the material is conveyed to the forced mixer through belt conveyor. After forced mixing, the material is entered into the storage bin through belt conveyor. There are four storage silos with disc feeders installed below. The feeding quantity of disc feeder can be adjusted according to the output of ball press. Iron powder is added to the ball press through belt conveyor. The ball pressed by the machine enters the chain plate dryer through the belt conveyor. Iron powder pellets are heated by hot air drying from sintering rotary kiln in chain plate dryer. The high temperature tail gas from secondary combustion chamber enters sintering rotary kiln directly. The sintered pellets in sintering rotary kiln are fed to reduction rotary kiln at a temperature as high as 1100 C. The high temperature reduction pellets reduced by rotary kiln are screened at the outlet of kiln head, and the sieve material is humidified and cooled. The screw feeder discharges the coke, after treatment, the granular material can continue to use. The hot reduction pellets on the sieve were passivated by hot pressing with a compactor, and the reduced iron hot pressing block (HBI) product was finally produced.


          Equipment Process Layout



    The Features of Reduction Technology + Hot Pressing Passivation Technology for Natural Gas Rotary Kiln


 Reduction technology of rotary kiln using natural gas or gas as heat source and adding secondary combustion chamber + finished product sieving hot pressing block, the production process is quite different from the traditional rotary kiln process.

 1)、回转窑长度变短,一般在40m-60m左右,使投资减少;同时由于回转窑变短,回转窑热平衡极易建立,操作变得简单。由于物料在窑内时间变短,同时由于还原采用无烟煤颗粒,强度好,摩擦产生的粉末减少,使窑炉炉衬结圈几率降低 ,设备运行更可靠;

      1)、The length of the rotary kiln becomes shorter, generally about 40m-60m, so that the investment is reduced; at the same time, as the rotary kiln becomes shorter, the heat balance of the rotary kiln can be easily established and the operation becomes easier. As the material in the kiln becomes shorter, at the same time, anthracite particles are used for reduction., the iron powder produced by the friction is reduced, so that the kiln furnace liner lining is less likely to be ringed, and the equipment operation is more reliable.


The special coal injection method and secondary fan of rotary kiln make the temperature of the short rotary kiln uniform and the kiln tail temperature reaching 1100 ~ 1150 degrees;


Because the exhaust gas is rich in gas, setting up a secondary combustion chamber can burn off the combustible components such as CO in the exhaust gas, which can not only raise the temperature of the exhaust to 1150 C, but also ensure the safety and reliability of the exhaust.


the mixed reducing material discharged from rotary kiln is treated by special high temperature shaking screen. The pure high temperature reducing pellet is directly passivated by hot pressing machine. The density of hot pressing pellet can reach 6.5-6.8t/m.


The sifted waste coke can be treated, and particles larger than 2mm can be used continuously, which reduces the amount of reductant used and reduces the production cost.


Natural gas or gas is used as heat source and CO + coal particles are reduced, the dust content of tail gas is greatly reduced, and the tail gas can completely meet the prescribed emission standard after being treated by dust collector.


The high-temperature exhaust gas from the combustible components in the tail gas of the secondary combustion chamber first enters the sintering rotary kiln to heat and sinter the pellets, and then enters the chain-plate heater to dry the cold pellets, so as to maximize the use of heat energy, improve the utilization rate of energy and reduce costs.


The requirement of the raw material


Iron powder


    Iron powder TFe68%, particle size>80 mesh


Reducing agent


   The reducing agent of this project is anthracite. Each ton of pellets needs to 450 Kg. Anthracite particle size is 10 mm-20 mm.




    CaO content > 55%, particle size less than 5 mm


    Natural gas


    Calorific value of natural gas > 8000 calories


     Product requirement


metallization rate


The average metallization rate of products is 90%-92%, and the carbon content is 0.5-1%.

1)      产品形状

Shape of the product


The product is directly reduced iron hot pressing block (HBI). The shape of reduction iron block is a cylinder with diameter of 200-220 mm and height of 150-200 mm. Its density is 6.0-6.5 t/m


          Technological requirements of each system

          1.  配料压球系统

       Batching and Ball-pressing system


带秤将三种原料按照工艺要求比例给入混料皮带,由混料皮带机将混合料装入强制混料机中进行搅拌。搅拌混合均匀的料进入储料仓,通过圆盘给料机和皮带机将搅拌好的料送到高压压球机,用高压压球机将铁粉料压成冷固球团,形状为扁圆形,尺寸φ30*20mm, 冷固球团由皮带机送到链板烘干机进行烘干预热。

Iron powder, iron oxide scale and binder are respectively loaded into the feeding bin, and three kinds of raw materials are proportionally fed into the mixing belt according to the technological requirements by adjustable feeder and belt conveyer. The belt conveyor loads the mixture into the forced mixer for mixing. Mixing uniform material into the storage bin, through the disc feeder and belt conveyor, the mixing material is sent to the high-pressure ball presser. The iron powder is pressed into cold-solidified pellets by high-pressure ball presser. The shape of the pellets is flat circular and the size isφ30*20mm. The cold-solidified pellets are sent by belt conveyor to chain plate dryer for heating intervention.

    2.  链板式烘干机

     Chain plate dryer


     Chain plate dryer is divided into 10 bellows, which are divided into heating section of drying section, 6 air chambers of drying section and 4 air chambers of preheating section.


            drying section


In the drying section, the qualified cold-pressed balls with about 8% water content are first pumped and dried by hot air from the preheater of the dryer. In order to ensure that the cold-pressed ball with a lot of water does not burst in the drying section, the temperature of hot air is required. The first three bellows should be strictly controlled below 300 C, and the last three bellows should be controlled between 400 C and 500 C. The material layer is dried to dehydrate, dry and heat the cold-pressed pellets.


The exhaust hot gas extracted from the bellows is treated by electrostatic precipitation and desulfurization, and is discharged into the atmosphere by the main exhaust fan through the chimney. The length of drying section is 18 meters.


            preheating section



   In the preheating stage, the hot air flow from 500 ~650 passes through the material layer to keep the green balls warming up.

The main heat source in the preheating section is the hot air discharged from the sintering rotary kiln, and the return air is driven into the drying section by the regenerative fan. Thermocouples are installed at both the inlet and outlet ends of the regenerative fan. Before the thermocouples at the inlet end of the regenerative fan, the cooling air can be compensated and the air supply volume can be adjusted to ensure that the inlet air of the regenerative fan cannot exceed 550 .


    The temperature of the regenerative fan does not exceed 550 C and the air pressure is 5600Pa.


 The length of preheating section is 12 meters.


After baking, the cold-pressed pellets are heated in the sintering rotary kiln by conveying confidentially. The chute pipe is equipped with a chute, and the crushed materials less than 5 mm are screened out. The crushed materials are sent to the mixer for re-stirring. The tail gas discharged by chain plate dryer is below 220 C, which is discharged by the main exhaust fan into the chimney after dust removal by bag filter.


 Sintering rotary kiln


The hot air temperature in the secondary combustion chamber is 1150 C, and the pellets are directly heated and sintered in the sintering rotary kiln to improve the strength of the pellets. The hot air discharged from the sintering rotary kiln directly enters the preheating section of the chain dryer, and the hot pellets discharged from the sintering rotary kiln (temperature up to 1050 C) are sealed into the reduction rotary kiln.


Secondary Combustor System


The hot air discharged from the rotary kiln, with a temperature of about 1000 C, enters the secondary combustion chamber and combusts in an airtight way. The exhaust flue gas temperature is about 1150 C. The high temperature flue gas enters the sintering rotary kiln to heat and sinter the pellets. At the same time, the secondary combustion chamber has the function of precipitation and dust removal of the tail gas.


The secondary combustion chamber is equipped with a combustion-supporting fan with adjustable air flow. There are three rows of burners in the secondary combustion chamber for burning combustible gases such as CO in the tail gas of rotary kiln, so as to raise the tail temperature and avoid the hidden dangers in the subsequent operation.


The exhaust gas intake point is installed at the outlet of the secondary combustor, and the CO and O2 contents in the gas entering and leaving the secondary combustor are observed at any time, so as to better adjust the air flow of the combustion-supporting fan and ensure that all CO is burned out.


Temperature measuring points are installed at the inlet and outlet of the secondary combustion chamber. The inlet and outlet temperatures can be observed at any time in the operation room and the central control room.


The excess heat air of sintering rotary kiln is pulled into the heat exchanger by the heat exchanger fan, and the temperature of the hot air exchanged can reach 400 C. It can be used as the combustion-supporting air of reduction rotary kiln, secondary combustion chamber and sintering rotary kiln. The tail air after heat exchange has a temperature of about 500 C. It is driven into the dryer by the heat exchanger fan to dry the iron powder and maximize the use of heat energy.


Rotary kiln reduction system


The sintered cold-pressed pellets (or iron ore) enter the reduction rotary kiln through chute from the sintering rotary kiln, roll along the periphery of the rotary kiln and move along the axis of the kiln head, and return to a certain distance under the action of the return line, thus prolonging the kiln retention time. Gas is used as heat source for drying and heating of rotary kiln. Coal injection and feeding are started when the temperature in the kiln reaches 1000 C.


A specially designed natural gas burner is installed at the kiln head to heat the material in the kiln by adjusting the amount of combustion air and natural gas, adjusting and controlling the combustion and flame shape of natural gas. At the same time, the kiln head is equipped with two blue carbon spraying guns, which can be used in the normal operation of the rotary kiln.


After feeding in rotary kiln, coal with particle size of 10-20 mm was injected into the kiln head by granular coal spray gun, and the injection amount was 300 kg-400 kg/ton pellets.


In the end of the kiln, the recovered coke butadiene with particle size of 1-10 mm is added, and the dosage is 50-100 kg/ton pellets.


The pellets in the kiln are mainly subjected to heat radiation and are reduced by rolling. The reduction temperature of pellets ranges from 1060 to 1150 C. The temperature is adjusted by secondary wind and natural gas. There are 7 monitoring points for kiln temperature, which are measured by wired transmission.


There are 7 kiln blowers with air pressure of 2000 Pa. The injection air duct is cast by special heat-resistant steel. It is easy to disassemble when it is installed. The air flow rate of the secondary fan in the kiln body can be adjusted to ensure the reduction temperature in the rotary kiln.


The spray gun is interlinked with the temperature system, which can be controlled automatically or manually.


New sealing devices are used for kiln head and kiln tail cover.


Reduced pellets are discharged into the insulating box through chutes and fixed sieves in the head cover of rotary kiln.


Rotary kiln type is selected according to the output requirement. In order to reduce the weight of refractories at the feed and discharge ends, steel plate is used to close the inlet and the thickness of refractories at the closure is 350 mm. The residence time of pellets in rotary kiln is about 7 hours. The rotary kiln chooses variable frequency speed regulating motor to speed up.


Passivation System for Hot Press Forming


Reduced high temperature pellets enter the incubator through the chute in the head cover of rotary kiln. After screening by special high temperature vibration, the reduction pellets > 15mm are screened out. The angle of the sieve angle should be considered in the design to make it easy to flow. The less than 15mm tailings flow into the cooling equipment and are sent to the tailings disposal yard by the wind power conveying system.


   After hoisting and lifting the >15mm high temperature reduction ball, under the high temperature condition, the hydraulic press presses the reduction iron block into about 25kg hot pressure, which is transported by forklift truck to the finished product pressing site.


Exhaust air purification system

链板式烘干机排出的热废气,经除尘器除尘后由主抽风机打入脱硫系统,脱硫处理后经烟囱排入大气。烟气温度大于150℃,最高温度220℃,风量20万m3(工况),风压500Pa,含尘浓度100mg/ N m3。

The hot exhaust gas discharged by chain plate dryer is pumped into the desulfurization system by the main exhaust fan after dust removal by the dust collector, and then discharged into the atmosphere by the chimney after desulfurization treatment. The flue gas temperature is over 150 C, the highest temperature is 220 C, the air volume is 200,000 m3 (working condition), the air pressure is 5600 Pa, and the dust concentration is 100 mg/N M.

排出烟气灰尘浓度小于30mg/Nm3,H2S气体含量小于10mg/ Nm3,


The exhaust dust concentration is less than 30mg/Nm and the H2S content is less than 10mg/Nm., SO2 content should not exceed 800 ppm.


Temperature measuring points is designed for dust collector and fan entrance can monitor tail temperature in operation room and central control room at any time.


Soft connection is adopted between the inlet and outlet of the fan and the connecting pipes in the design. A pipe muffler is installed on the outlet pipes of the fan to control the noise of the fan, so as to meet the requirements of the Code for the Design of Noise Control in Industrial Enterprises.


Tailings processing system


After humidification and cooling, the waste orchid charcoal is sent to the tailings treatment plant by the wind conveying system. The granular material is received in the granular silo, and the fine powder is collected by the bag filter. After magnetic separation, granular material can be added to rotary kiln as reductant and recycled.


Manufacturing cost                         

                        单位:  /吨海绵铁




































UNIT:    /T Sponge Iron









Unit cost

Total cost


Iron ore powder and scale




reducing agent













Industrial water




Natural gas




Repair cost



Wages and benefits



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