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1、高炉炼铁Jan Terpar, Imrich KostialDepartment of Informatics and Process ControlFaculty of BERGTechnical University of Koice B.Nemavej304200 KosiceSlovak Republic高炉是一个巨大的内部为耐火材料的刚炉，铁矿石，焦炭和石灰石倾入炉顶，预热空气在底部吹入。经过物理化学反应后转换成的铁水，既一种液态铁的氧化物。原材料在炉内经6至8小时降低到炉底部，得到的最终产品是液态渣铁，炎热的空气在炉底被吹上行在6至8秒到顶端后，将进行各种化学反应。高炉一旦启动，最
2、少将连续运行4到10年后，才将高炉熄火，进行维护。1 高炉炼铁反应过程在原料矿、球团 、烧结矿在高炉内反应后得到铁矿石。原矿石来自于地表，其块状的大小为0.5至1.5英寸。一些矿石铁的含量的大约为 50到70，这些矿石要么是赤铁矿（氧化铁）要么是磁铁矿（Fe3O4）。这些矿石可以直接送入高炉而不需任何进一步的处理。此外，一些矿石铁的含量较低必须进行处理使其铁含量增加。球团矿是含有60至65铁，它是一些低铁含量的矿石，在被碾碎、磨成粉末，将所谓的废料煤矸石剔除后，其余富含铁的粉球和高炉内的燃煤产生强烈的反应形成的颗粒。烧结矿是从原料矿，焦炭，石灰石和其他许多钢铁厂含有一些铁废料按一定的比例烧结后
3、获得所需的产品化学，然后将其混合在一起。这些混合的原料，然后放置在一起形成一种类似钢铁传送带烧结链，它是在燃气炉和原矿在经过焦炭热融合形成成面积较大，尺寸从0.5顷到2.0英寸的矿石。铁矿石，球团矿，烧结矿在高炉内反应后形成为液态铁在和含有其他剩余杂质液态渣。焦炭是一种烟煤混合物。将煤炭粉碎，磨成粉末，然后送入炼焦炉内。经过18至24小时的反应时间，由于高温使煤炭中熟焦油等杂质被剔除，在被冷却后并形成大小从1英寸到4英寸不等的焦炭。焦炭内含有90至93的碳，但一些灰分和硫原煤相比，是十分强劲的。焦炭能够产生热量与气体，具有很高的能源价值 ，热量与气体在高炉内与铁矿石，球团，烧结反应，形成液态铁
4、。最后，是原材料石灰石炼制过程。石灰石是从地球上由使用炸药爆破得来的。它经过粉碎，筛选，然后得到一个大小范围从0.5英寸到1.5英寸的石灰石。这可以是高钙石灰石，含有镁的石灰石石或混合类型的石灰石。由于熔化后石灰石中的硫和其他杂质被去除，高炉操作者可以混合不同的石头产生所需的化学矿渣和各种特性，如熔点低和高流动性的材料。所有的原料都存储在一个矿田，一旦这些材料被送到到炉顶，将在高炉内经过多次化学，物理反应后下降到高炉的底部。铁矿石，球团和烧结是在高炉内的料位的降低意味着在铁氧化物氧是由一系列化学反应形成的。这些反应发生情况如下：1) 3 Fe2O3 + CO = CO2 + 2 Fe3O42)
5、 Fe3O4 + CO = CO2 + 3 FeO 3) FeO + CO = CO2 + Fe or FeO + C = CO + Fe在同一时间通过这些铁氧化物的净化反应后，他们也开始软化，然后融化为液态铁，最后缓慢地流向高炉的底部。焦炭料位下降到炉底的时候，预热空气或热风进入高炉，在热风的作用下，焦炭立即发生反应，同时产生热量。C + O2 = CO2 + Heat 由于反应发生在存在过剩的碳的情况下，焦炭在高温下与产生的二氧化碳反应，生成一氧化碳。反应过程如下：CO2+ C = 2CO这种反应生成的一氧化碳，是用来与铁矿石中的氧化铁反应生成铁的。 高炉内石灰石料位下降的同时，产生的化学
6、反应如下：CaCO3 = CaO + CO2这种反应需要的大量的能量，并且只有在炉内温度达到约1600 F时才开始开始。从这个反应所形成的氧化钙是用来去除铁所含有的硫。这种硫化反应是：FeS + CaO + C = CaS + FeO + CO反应后，硫化钙（CaS）成为矿渣的一部分，矿渣也包括剩余的二氧化硅（SiO2），氧化铝（Al2O3），氧化镁（MgO）为或氧化钙（CaO），随着铁矿石，球团，烧结或焦炭进入。最后液体渣下降到高炉的底部，同时，因为它密度较低，漂浮在液态铁的上部。另一个炼铁过程的产物，除了铁水和炉渣，是热高温的有毒气体。这些气体经高炉炉顶流出后进入烟气处理设备，并通过设备中
7、去除其中可吸入颗粒和对气体进行冷却。这种气体还可以通过“热风灶”进行预热，并进入高炉成为“热风”燃料。其他气体中的任何一种可送到锅炉房，用于产生蒸汽涡轮风扇转生成的压缩空气并作为“冷风”送到炉灶。高炉是一个逆流容器，固体料位下降的同时气体上，在这一过程中伴有大量的化学和物理反应，产生我们所需要的最终产品液态铁。2 高炉炼铁的工艺过程通过上面的描述，我们以知道高炉内部反应过程，现在让我们回顾一下炼铁工艺过程。原料可以在矿石堆场，也可在矿石码头和驳船的地方用来卸货。在矿石堆场存储的原料原矿，球团，烧结，石灰石或几种混合矿石或可能是焦炭。这些材料被转移到储存室可通过输送皮带配矿。材料也可以通过矿石转
8、运车转移到储存室。每个矿，球团，烧结，焦炭，石灰石类型倒入单独的储料槽内。在称量斗内对各种原料进行称量，各种原料按一定比例进行配比，配料的目的是获得较高的生产率和性能稳定的优质铁水，符合高炉冶炼生产的要求。称量好的矿石再经过主皮带机运至料坑矿石汇总称量斗。碎矿皮带机设在料坑两侧的筛下，筛下的碎矿由皮带机转运至返矿仓。在炉顶, 通过布料设备双钟和旋转布料器装入炉喉。一些现代高炉在自动化技术的控制下完成同样的动作。在炉顶的材料，当炉内不缺料时，一些原料（矿，球团或烧结型组成的），焦煤和石灰石积累在炉顶。 高炉操作人员小心通过控制炉顶的布料顺序来控制控制气体流量和炉内化学反应。该原材料的通过大小钟进
9、入高炉内部， 而炉内密封的气体，围绕炉内均匀分布的原料。现代一些高炉没有大小钟，而是有2个或3个密封舱式料斗旋转槽，可以改变其角度，让更多在炉料灵活的精确的布置在炉内。在高炉炉顶四个泄压装置，炉气从这里离开高炉。 两个泄压装置合并成一个放散管。这两个放散管然后在炉顶合并成煤气管道。在高炉的顶部有泄放阀，可释放气体，保护炉内气体的压力，以防止炉内气体压力突然激增。放出气体通过煤气管道进入除尘器里，其中过滤的粗颗粒矿渣，积累到一定量后有卡车或其他设备运出倾倒 。过滤后气体流经一个文氏管洗涤器，使气体不在含有其它的细小颗粒，最后气体经过气雾分离器，不仅能降低气体的温度，而且能够获得较纯净的煤气。一些
10、现代高炉配备有混合洗涤冷却装置，用来准备清洗和冷却的气体。被过滤后煤气经过管道，进入蓄热室。这里紧挨着高炉的地方通常有3或4个圆柱形火炉 。气体在燃烧炉中的底部被加热并通过炉内的耐火材料上升。连续经过几个燃烧炉中的耐火材料后，形成热量储存在蓄热室内。大量的空气，从80,000 ft3/min到230,000 ft3/min，经涡轮鼓风机吹入并流过的空气脱湿机到燃烧炉。冷风然后进入先前已在加热和炉耐火砖内储存的热量的蓄热室内，形成“热风”。热风温度可从1600 F到2300 F，取决于炉的燃烧炉设计和生产条件。这被加热的空气，然后流出燃烧炉，并被吹入到高炉内。同时连接到主冷装置的热风主要是与用于
11、控制热风温度并保持恒定的温度。热风主要进入一个园圈形状的管道围炉，所谓的“热风管”。通过热风管后，热风直接入炉是通过一个名为“风口”喷嘴直接入炉。这些风口同样间隔围绕高炉周围。高炉规模较小可能有14对风口，而规模较大的高炉有40对风口，组成这些风口所用的材料是铜，是因为直接冷却水冷却后的温度依然也可能达到3600 F到4200 F。原油，焦油，天然气，煤和氧粉也可通过风口与高炉内焦炭结合，释放更多的能量，可以提高高炉的生产量。与此同时，在在出铁口与出渣口分别开始流出铁水和矿渣水。3 结论高炉是钢铁生产的第一步，把铁矿石还原成生铁的连续生产过程。世界上第一座高炉出现在14世纪，每一天能生产生铁1
12、吨。随着技术的发展，高炉设备在不断的改进的，现代的巨大高炉，每天能实现生产13000吨的生铁。即使设备进行了改进和生产速率的提高，但在高炉内的进程是基本保持不变的。高炉将进入下一个千年的生存，而面积较大，高效率的熔炉在铁水的生产过程中将获得在其成本与其炼铁技术的竞争优势。Working of a Blast Furnace Jan Terpar, Imrich KostialDepartment of Informatics and Process ControlFaculty of BERGTechnical University of Koice B.Nemavej304200 Kosic
13、eSlovak Republic The purpose of a blast furnace is to chemically reduce and physically convert iron oxides into liquid iron called hot metal. The blast furnace is a huge, steel stack lined with refractory brick, where iron ore, coke and limestone are dumped into the top, and preheated air is blown i
14、nto the bottom. The raw materials require 6 to 8 hours to descend to the bottom of the furnace where they become the final product of liquid slag and liquid iron. These liquid products are drained from the furnace at regular intervals. The hot air that was blown into the bottom of the furnace ascend
15、s to the top in 6 to 8 seconds after going through numerous chemical reactions. Once a blast furnace is started it will continuously run for four to ten years with only short stops to perform planned maintenance.1 The Process Iron oxides can come to the blast furnace plant in the form of raw ore, pe
16、llets or sinter. The raw ore is removed from the earth and sized into pieces that range from 0.5 to 1.5 inches. This ore is either Hematite (Fe2O3) or Magnetite (Fe3O4) and the iron content ranges from 50% to 70%. This iron rich ore can be charged directly into a blast furnace without any further pr
17、ocessing. Iron ore that contains a lower iron content must be processed or beneficiated to increase its iron content. Pellets are produced from this lower iron content ore. This ore is crushed and ground into a powder so the waste material called gangue can be removed. The remaining iron-rich powder
18、 is rolled into balls and fired in a furnace to produce strong, marble-sized pellets that contain 60% to 65% iron. Sinter is produced from fine raw ore, small coke, sand-sized limestone and numerous other steel plant waste materials that contain some iron. These fine materials are proportioned to ob
19、tain a desired product chemistry then mixed together. This raw material mix is then placed on a sintering strand, which is similar to a steel conveyor belt, where it is ignited by gas fired furnace and fused by the heat from the coke fines into larger size pieces that are from 0.5 to 2.0 inches. The
20、 iron ore, pellets and sinter then become the iquid iron produced in the blast furnace with any of their remaining impurities going to the liquid slag. The coke is produced from a mixture of coals. The coal is crushed and ground into a powder and then charged into an oven. As the oven is heated the
21、coal is cooked so most of the volatile matter such as oil and tar are removed. The cooked coal, called coke, is removed from the oven after 18 to 24 hours of reaction time. The coke is cooled and screened into pieces ranging from one inch to four inches. The coke contains 90 to 93% carbon, some ash
22、and sulfur but compared to raw coal is very strong. The strong pieces of coke with a high energy value provide permeability, heat and gases which are equired to reduce and melt the iron ore, pellets and sinter.The final raw material in the ironmaking process in limestone. The limestone is removed fr
23、om the earth by blasting with explosives. It is then crushed and screened to a size that ranges from 0.5 inch to 1.5 inch to become blast furnace flux . This flux can be pure high calcium limestone, dolomitic imestone containing magnesia or a blend of the two types of limestone. Since the limestone
24、is melted to become the slag which removes sulfur and other impurities, the blast furnace operator may blend the different stones to produce the desired slag chemistry and create ptimum slag properties such as a low melting point and a high fluidity. All of the raw materials are stored in an ore fie
25、ld and transferred to the stockhouse before charging. Once these materials are charged into the furnace top, they go through numerous chemical and hysical reactions while descending to the bottom of the furnace.The iron ore, pellets and sinter are reduced which simply means the oxygen in the iron ox
26、ides is emoved by a series of chemical reactions. These reactions occur as follows:1) 3 Fe2O3 + CO = CO2 + 2 Fe3O4 2) Fe3O4 + CO = CO2 + 3 FeO 3) FeO + CO = CO2 + Fe or FeO + C = CO + Fe At the same time the iron oxides are going through these purifying reactions, they are also beginning to soften t
27、hen melt and finally trickle as liquid iron through the coke to the bottom of the furnace. The coke descends to the bottom of the furnace to the level where the preheated air or hot blast enters the blast furnace. The coke is ignited by this hot blast and immediately reacts to generate heat s follow
28、s: C + O2 = CO2 + Heat Since the reaction takes place in the presence of excess carbon at a high temperature the carbon dioxide is reduced to carbon monoxide as follows:CO2+ C = 2CO The product of this reaction, carbon monoxide, is necessary to reduce the iron ore as seen in the previous iron oxide
29、reactions. The limestone descends in the blast furnace and remains a solid while going through its first reaction s follows:CaCO3 = CaO + CO2 This reaction requires energy and starts at about 1600F. The CaO formed from this reaction is used to remove sulfur from the iron which is necessary before th
30、e hot metal becomes steel. This sulfur emoving reaction is: FeS + CaO + C = CaS + FeO + CO The CaS becomes part of the slag. The slag is also formed from any remaining Silica (SiO2), Alumina (Al2O3), Magnesia (MgO) or Calcia (CaO) that entered with the iron ore, pellets, sinter or coke. The liquid s
31、lag then trickles through the coke bed to the bottom of the furnace where it floats on top of the iquid iron since it is less dense.Another product of the ironmaking process, in addition to molten iron and slag, is hot dirty gases. These gases exit the top of the blast furnace and proceed through ga
32、s cleaning equipment where particulate matter is removed from the gas and the gas is cooled. This gas has a considerable energy value so it is burned as a fuel in the hot blast stoves which are used to preheat the air entering the blast furnace to become hot blast. Any of the gas not burned in the s
33、toves is sent to the boiler house and is used to generate steam which turns a turbo blower that generates the compressed air known as cold blast that comes to the stoves. The blast furnace is a counter-current realtor where solids descend and gases ascend. In this reactor there are numerous chemical
34、 and physical reactions that produce the desired final product which is hot metal.2 The Blast Furnace Plant Now that we have completed a description of the ironmaking process, let s review the physical quipment comprising the blast furnace plant. There is an ore storage yard that can also be an ore
35、dock where boats and barges are unloaded. The raw materials stored in the ore yard are raw ore, several types of pellets, sinter, limestone or flux blend and possibly coke. These materials are transferred to the stockhouse/hiline complex by ore bridges equipped with grab buckets or by conveyor belts
36、. Materials can also be brought to the stockhouse/hiline in rail hoppers or transferred from ore bridges to self-propelled rail cars called ore transfer cars. Each type of ore, pellet, sinter, coke and limestone is dumped into separate storage bins . The various raw materials are weighed according t
37、o a certain recipe designed to yield the desired hot metal and slag chemistry. This material weighing is done under the storage bins by a rail mounted scale car or computer controlled weigh hoppers that feed a conveyor belt. The weighed materials are then dumped into a skip car which rides on rails
38、up the inclined skip bridge to the receiving hopper at the top of the furnace. The cables lifting the skip cars are powered from large winches located in the hoist house . Some modern blast furnace accomplish the same job ith an automated conveyor stretching from the stockhouse to the furnace top. A
39、t the top of the furnace the materials are held until a charge usually consisting of some type of metallic (ore, pellets or sinter), coke and flux (limestone) have accumulated. The precise filling order is developed by the blast furnace operators to carefully control gas flow and chemical reactions
40、inside the furnace. The materials are charged into the blast furnace through two stages of conical bells which seal in the gases and distribute the raw materials evenly around the circumference of the furnace throat. Some modern furnaces do not have bells but instead have 2 or 3 airlock type hoppers
41、 that discharge raw materials onto a rotating chute which can change angles allowing more flexibility in precise material placement inside the furnace.Also at the top of the blast furnace are four uptakes where the hot, dirty gas exits the furnace dome. The gas flows up to where two uptakes merge in
42、to an offtake . The two offtakes then merge into the downcomer . At the extreme top of the uptakes there are bleeder valves which may release gas and protect the top of the furnace from sudden gas pressure surges. The gas descends in the downcomer to the dustcatcher, where coarse particles settle ou
43、t, accumulate and are dumped into a railroad car or truck for disposal. The gas then flows through a Venturi Scrubber which removes the finer particles and finally into a gas cooler where water sprays reduce the temperature of the hot but clean gas. Some modern furnaces are equipped with a combined
44、scrubber nd cooling unit. The cleaned and cooled gas is now ready for burning. The clean gas pipeline is directed to the hot blast stove . There are usually 3 or 4 cylindrical shaped stoves in a line adjacent to the blast furnace. The gas is burned in the bottom of a stove and the heat rises and tra
45、nsfers to refractory brick inside the stove. The products of combustion flow through passages in these bricks, out of the stove into a high stack which is shared by all of the stoves.Large volumes of air, from 80,000 ft3/min to 230,000 ft3/min, are generated from a turbo blower and flow through the
46、cold blast main up to the stoves. This cold blast then enters the stove that has been previously heated and the heat stored in the refractory brick inside the stove is transferred to the cold blast to form hot blast. The hot blast temperature can be from 1600F to 2300F depending on the stove design
47、and condition. This heated air then exits the stove into the hot blast main which runs up to the furnace. There is a mixer line connecting the cold blast main to the hot blast main that is equipped with a valve used to control the blast temperature and keep it constant. The hot blast main enters int
48、o a doughnut shaped pipe that encircles the furnace, called the bustle pipe . From the bustle pipe, the hot blast is directed into the furnace through nozzles called tuyeres (pronounced tweers). These tuyeres are equally spaced around the circumference of the furnace. There may be fourteen tuyeres on a small blast furnace and forty tuyeres on a large blast furnace. These tuyeres are made of copper and are water cooled since the temperature directly in front of the them may be 3600F to 4200F. Oil, tar, natural gas, powdered coal and oxygen can also be injected into the furnace at tuyere level