斯特拉塔公司Premus工艺—发展与优势.pdf

the development and advantages of xstratas premus process 斯特拉塔公司斯特拉塔公司 premus 工艺发展与优势工艺发展与优势 o. naiker xstrata alloys 斯特拉塔合金 carrington drive, ohrigstad road, lydenburg, 1120, south africa e-mail: infoxstrata.co.za abstract 摘要摘要 xstrata has modified and improved on the solid state reduction of chromite (src) process that was pioneered by showa denko in japan and previously used at xstratas lydenburg plant. the history of pre-reduction is a long one, with the src process being the first and only commercially successful one prior to premus. krupp developed the chromite direct reduction and the rotary hearth for the pre-reduction of chromite. however, these processes have not been successfully commercialised. 斯特拉塔改进了由日本昭和公司倡导，曾用于斯特拉塔斯特拉塔改进了由日本昭和公司倡导，曾用于斯特拉塔 lydenburg 厂（南非）的铬铁固态还 原工艺。虽然预还原工艺历史悠久，固态还原工艺是唯一一个商业化比 厂（南非）的铬铁固态还 原工艺。虽然预还原工艺历史悠久，固态还原工艺是唯一一个商业化比 premus 早的工艺， 克虏伯公司发展了直接还原工艺、 回转窑预还原工艺。 但是， 这些工艺的工业化都不成功。 早的工艺， 克虏伯公司发展了直接还原工艺、 回转窑预还原工艺。 但是， 这些工艺的工业化都不成功。 the are a number of significant differences between xstratas patented premus and the original consolidated metallurgical industries (cmi) process. these include, the use of lower cost anthracite fines as the reductant source together with the use of unactivated bentonite as the binding agent. in addition the use of oxygen as an energy source is used in premus but not in the original cmi process. there was a fundamental change in the operational philosophy of the process in that while the original cmi process aimed to maximize metallization of the pellets, the premus process seeks to maximize the energy output from the kiln while still achieving the required efficiencies and hence increasing furnace output. premus is designed to reduce electrical energy consumption, provide high recoveries of metallic oxides, and utilizes low cost reductant and energy sources such as anthracite and oxygen respectively. 斯特拉塔拥有专利的斯特拉塔拥有专利的 premus 工艺与经典联合冶金工艺有很多不同， 包括用廉价无烟煤作还 原剂， 用惰性膨润土作粘结剂。 另外， 工艺与经典联合冶金工艺有很多不同， 包括用廉价无烟煤作还 原剂， 用惰性膨润土作粘结剂。 另外， premus 工艺用氧气作能源， 而工艺用氧气作能源， 而 cmi 工艺则不是。工艺则不是。 premus 工艺在理念上有很大变化：工艺在理念上有很大变化：cmi 工艺立足于把球团内金属熔融最大化，工艺立足于把球团内金属熔融最大化，premus 工艺则是在 保证效率的基础上，把回转窑的能量输出最大化，因而提高电炉产量。 工艺则是在 保证效率的基础上，把回转窑的能量输出最大化，因而提高电炉产量。premus 工艺考虑降 低电耗、提高金属氧化物回收率、使用廉价还原剂和能源（例如无烟煤和氧气） 。 工艺考虑降 低电耗、提高金属氧化物回收率、使用廉价还原剂和能源（例如无烟煤和氧气） 。 due to the fact that premus is one of the most technologically advanced and competitive processes used today in the production of ferrochrome it was the process selected for xstratas new ferrochrome facility, project lion, that is due to be commissioned in the third quarter of 2006 in the steelpoort valley in mpumulanga, south africa. premus 工艺是世界上最先进和有竞争力的技术之一，斯特拉塔新铬铁厂就是采用这项技术 （南非 工艺是世界上最先进和有竞争力的技术之一，斯特拉塔新铬铁厂就是采用这项技术 （南非 lion 项目，位于项目，位于 mpumulanga steelpoort 谷地，计划谷地，计划 2006 年三季度试车） 。年三季度试车） 。 1.introduction 简介简介 the history of pre-reduction is a long one, with the pre-reduction of iron ore being a more common process. the pre-reduction of chromite ore however has not been widely used commercially. various experimental test-work has been documented and papers written on the solid state reduction of chromite ore using various reductant sources including hydrogen, methane, carbon monoxide and coke. there are only two commercial plant facilities where the solid state reduction of chrome ore had previously proved successful, the shunan denko plant in japan and the cmi plant in mpumulanga south africa. both of these plants had employed the showa denko solid-state-reduction of chromite ore (src) process and proved to be the most energy efficient plants in the world. upon xstratas acquisition of cmi from the johannesburg consolidated industries (jci) group it sought to bring down the cost structures at the lydenburg plant. between 1998 and 2001 the premus process was developed largely by in-plant trials. the patent was filed in 2002 and finally granted in february 2006. 预还原技术历史悠久， 对铁矿进行预还原尤其普遍， 对铬矿的预还原还没有大规模工业化。 有关铬矿固态还原的各类实验性工作，已有文献记载，与此相关的论文也有发表。这些论 文探讨用不同还原剂（包括氧气、甲烷、一氧化碳和焦粉）进行固态还原产生的效果。但 是，仅有两个工厂采用铬矿固态还原工艺获得成功 预还原技术历史悠久， 对铁矿进行预还原尤其普遍， 对铬矿的预还原还没有大规模工业化。 有关铬矿固态还原的各类实验性工作，已有文献记载，与此相关的论文也有发表。这些论 文探讨用不同还原剂（包括氧气、甲烷、一氧化碳和焦粉）进行固态还原产生的效果。但 是，仅有两个工厂采用铬矿固态还原工艺获得成功- shunan denko 公司和南非公司和南非 mpumulanga cmi 厂，这两个工厂采用昭和公司的固态还原工艺。实践证明，这是世界上效率最高的。 斯特拉塔公司从 厂，这两个工厂采用昭和公司的固态还原工艺。实践证明，这是世界上效率最高的。 斯特拉塔公司从 johannesburg 联合产业集团 （联合产业集团 （jci） 获得） 获得 cmi 技术以后， 致力于在技术以后， 致力于在 lydenburg 厂缩减成本。厂缩减成本。98 年到年到 01 年，年，premus 工艺在工厂试验阶段取得重大进展，工艺在工厂试验阶段取得重大进展，2002 年编入专利 批次， 年编入专利 批次，2006 年年 2 月最终获得此项专利。月最终获得此项专利。 2. the development of premus premus 工艺发展工艺发展 2.1 rationale behind the change 改进原因改进原因 the primary factors that influenced the decision to modify the original cmi process that was operational at the lydenburg works were: 改进改进 cmi 工艺，使其适合工艺，使其适合 lydenburg 厂实际需要，主要动因如下：厂实际需要，主要动因如下： increasing cost of coke breeze 焦粉价格上涨焦粉价格上涨 reduced availability of coke and char breeze 焦粉和炭粉实用性降低焦粉和炭粉实用性降低 the increase in furnace capacity warranted a higher kiln capacity 熔炉产量增加需要回转窑增容熔炉产量增加需要回转窑增容 change in operating philosophy from that of maximizing metallization levels to that of maximizing energy output from the kiln 操作理念改进从金属熔融最大化到回转窑能量输出最大化操作理念改进从金属熔融最大化到回转窑能量输出最大化 2.2 choice of reducing agent 选择还原剂选择还原剂 previously coke breeze served as the primary reductant source in the pre-reduction process. later char breeze was also introduced as a reductant source due to its lower cost. however, the fixed carbon content of char breeze is significantly lower than that of coke, having fixed carbon levels of between 70 - 75%. this resulted in a higher reductant requirement and reduced the chrome output from the kiln, effectively reducing kiln capacity at a time when all effort was placed on maximizing the kiln capacity. raw anthracite breeze which has a fixed carbon content of 82% was then identified as a potential reductant source. initially lab-scale tests where conducted, whereby pellets were produced using increasing percentages of anthracite breeze as a re-placement for coke and char breeze. the main difference in the chemical analysis between coke breeze and anthracite breeze was in the volatiles content as illustrated in table 1. as a result, the greatest risk that was foreseen was that the pellets would burst in the preheating process as the combustion of the volatiles would cause the temperature to rise uncontrollably before the pellets are dried. lab as well as small scale plant trials indicated that the pellets would not burst in the kiln. however, as a precautionary measure, the first full scale plant trials were conducting using calcined anthracite. raw anthracite was then introduced as a blend with coke breeze. 以前，预还原工艺中的主要还原剂是焦粉，后来改用廉价炭粉。但是，炭粉固定碳含量在以前，预还原工艺中的主要还原剂是焦粉，后来改用廉价炭粉。但是，炭粉固定碳含量在 70-75%之间，远远低于焦炭中固定碳含量。这就需要更多还原剂，回转窑铬输出和产量也 会降低，无烟煤固定碳含量大于 之间，远远低于焦炭中固定碳含量。这就需要更多还原剂，回转窑铬输出和产量也 会降低，无烟煤固定碳含量大于 82%，是理想的还原剂。最初实验室做法是不断提高无烟 煤比例来替代焦炭和炭块生产球团。炭块和无烟煤化学成分上的主要区别在于挥发分含量 （见表 ，是理想的还原剂。最初实验室做法是不断提高无烟 煤比例来替代焦炭和炭块生产球团。炭块和无烟煤化学成分上的主要区别在于挥发分含量 （见表 1） 。那种情况下，球团在预热阶段由于挥发分燃烧，温度不稳定上升，球团有破裂 的危险。尽管实验室和小规模生产实践表明，球团在窑炉里不会破裂，但安全起见，首次 工厂生产试验采用煅烧无烟煤，然后再把无烟煤和焦粉混合加入。 ） 。那种情况下，球团在预热阶段由于挥发分燃烧，温度不稳定上升，球团有破裂 的危险。尽管实验室和小规模生产实践表明，球团在窑炉里不会破裂，但安全起见，首次 工厂生产试验采用煅烧无烟煤，然后再把无烟煤和焦粉混合加入。 table 1: chemical analysis of various reductant sources used 表表 1 可用还原剂化学性质分析可用还原剂化学性质分析 reductant %fixed carbon 固定碳固定碳 %ash 灰分灰分 %volatiles 挥发分挥发分 source 还原剂还原剂 coke breeze 焦粉焦粉 81.8 15.4 2.8 char breeze 炭粉炭粉 76 19.3 4.7 calcined anthracite 煅烧无烟煤煅烧无烟煤 84.3 13.8 1.9 raw anthra cite 普通无烟煤普通无烟煤 81.8 13.5 4.7 2.3 initial plant trials 早期工厂试验早期工厂试验 the percentage of anthracite as a reductant source was progressively increased. the pellets produced by the pan pelletisers prior to drying and preheating are termed green pellets. the main parameters that were monitored during the plant trials were green pellet strength, green pellet appearance, uniformity in green pellet sizing and level if any of pellet bursting in the grate kiln. green pellet strength was measured via drop tests and compression strength tests. pellet strength is vital due to the fact that after drying and preheating in the grate kiln, the pellets are fed directly into the rotary kiln where pre-reduction takes place. the rotary action can result in the disintegration of weak pellets resulting in fines formation, increase in kiln build-up and operational difficulties. on-line moisture analyzers were used to gauge the moisture content of the pellets and the tendency for the pellets to burst in the grate kiln, before actual moisture results are obtained from the laboratory. green pellet sizing was monitored by taking a representative sample and measuring the diameter of the pellets. small pellets can result in over-roasting and too large pellets will lead to lower metallization levels. previous experimental test-work had indicated that the ideal pellet diameter in terms of reaction efficiency and pellet strength is about 20mm. practically the diameter should be controlled from 10 to 30mm. variability in pellet size can reduce gas permeability through the grate kiln affecting the initial drying process and resulting in pellets bursting and is therefore a key parameter to be monitored. 用作还原剂无烟煤比例逐渐提高。干燥和预热之前由盘式造球机生产出的球团称为生球团。 主要监测生球团的强度、形状、粒度和料层分布，来判断球团在链篦机里会不会破裂。生 球团强度通过坠落试验和压力测试获得。由于生球团干燥和预热之后会直接到回转窑进行 预还原，生球团强度很重要。回转窑的旋转会使低强度球团破碎，会造成回转窑内碎颗粒 堆积，增加操作难度。实验室得到实际水分含量之前，在线水分析仪会监测球团水分含量 和球团在链篦机上破裂的趋势。通过取样和测量直径来监测生球粒度。过小球团会过烧， 过大球团会降低出铁量。 试验表明， 反应率和球团强度足够的情况下， 理想球团粒度是 用作还原剂无烟煤比例逐渐提高。干燥和预热之前由盘式造球机生产出的球团称为生球团。 主要监测生球团的强度、形状、粒度和料层分布，来判断球团在链篦机里会不会破裂。生 球团强度通过坠落试验和压力测试获得。由于生球团干燥和预热之后会直接到回转窑进行 预还原，生球团强度很重要。回转窑的旋转会使低强度球团破碎，会造成回转窑内碎颗粒 堆积，增加操作难度。实验室得到实际水分含量之前，在线水分析仪会监测球团水分含量 和球团在链篦机上破裂的趋势。通过取样和测量直径来监测生球粒度。过小球团会过烧， 过大球团会降低出铁量。 试验表明， 反应率和球团强度足够的情况下， 理想球团粒度是 20mm， 实际可以控制在 ， 实际可以控制在 10-30mm 之间。球团粒度多样化会影响球团通过链篦机时的透气性，影响 干燥，引起球团破裂，这个参数是监测的重点。 之间。球团粒度多样化会影响球团通过链篦机时的透气性，影响 干燥，引起球团破裂，这个参数是监测的重点。 as the anthracite trials progressed increasing steadily from 0% to 100%, it became clear that the pellet quality deteriorated as the anthracite contribution increased to 60% and above. there was a large degree of variability in terms of pellet sizing with the diameter varying from 5mm to 35mm without any adjustments to the pan pelletizer. the surface appearance of the pellets was also poor. during this stage of the trial 4% soda ash (na2co3) activated bentonite was used as the binding agent. 随着无烟煤比例逐渐增加，超过随着无烟煤比例逐渐增加，超过 60%时球团质量开始下降。不调整盘式造球机，球团直径 在 时球团质量开始下降。不调整盘式造球机，球团直径 在 5mm 到到 30mm 之间变化时，球团粒度变化很大，球团形状也不好看。这个阶段，用之间变化时，球团粒度变化很大，球团形状也不好看。这个阶段，用 4% 的钠基膨润土作粘结剂。的钠基膨润土作粘结剂。 adjustments to the pan angle, pelletizer depth and water addition did not yield significant improvements in pellet quality at contributions of greater than 60% raw anthracite. the main factors influencing the pelletizing process such as particle size and shape, the influence of the binder used and the pre-wetting effect was then considered. 无烟煤加入超过无烟煤加入超过 60%时， 调整造球盘角度、 造球机高度和加水量对提高生球质量作用不大。 这时主要注意影响工艺的主要因素，如原料粒度、形状、粘结剂和预加湿的影响。 时， 调整造球盘角度、 造球机高度和加水量对提高生球质量作用不大。 这时主要注意影响工艺的主要因素，如原料粒度、形状、粘结剂和预加湿的影响。 the particle sizing was measured and found to be within the normal range. raw anthracite is less porous and less crystalline in comparison to coke and char which could have an influence on the pre-wetting process. further research and test-work was then done on the binder used and bentonite at different activation levels was tested. it was found that the use of 0 - 1% soda ash bentonite produced the best quality pellets at high anthracite levels. the use of 100% raw anthracite together with unactivated bentonite produced excellent quality pellets and became the standard pellet mix. 粒度应监测并控制在合理范围。无烟煤的孔隙和晶体结构比焦炭和木炭少，这对预加湿产 生影响。对粘结剂和不同基质的膨润土作进一步研究和试验发现，无烟煤含量高时，钠基 膨润土保持在 粒度应监测并控制在合理范围。无烟煤的孔隙和晶体结构比焦炭和木炭少，这对预加湿产 生影响。对粘结剂和不同基质的膨润土作进一步研究和试验发现，无烟煤含量高时，钠基 膨润土保持在 0-1%时，可得高质量球团。完全用无烟煤作还原剂时，时，可得高质量球团。完全用无烟煤作还原剂时， 加上惰性膨润土可得 到质量更好的球团。这就是合理的球团原料混合比。 加上惰性膨润土可得 到质量更好的球团。这就是合理的球团原料混合比。 trials conducted later indicated that attapulgite could also be successfully used as a binding agent in the production of pellets containing chromite and anthracite fines. 后续试验发现，可以用硅镁土作粘结剂，获得含铬铁和无烟煤粉的球团。后续试验发现，可以用硅镁土作粘结剂，获得含铬铁和无烟煤粉的球团。 during processing through the grate and rotary kiln it became apparent that the maximum volatile content that was acceptable which did not result in pellets bursting was 7%. this process change has been patented by xstrata and has been termed premus (meaning first in greek). 链篦机回转窑工艺中，的挥发分含量最多达链篦机回转窑工艺中，的挥发分含量最多达 7%时，不会引起球团裂开。这种工艺改进由斯 特拉塔公司获得专利，命名 时，不会引起球团裂开。这种工艺改进由斯 特拉塔公司获得专利，命名 premus。 2.4 theoretical explanation of results 结果理论分析结果理论分析 bentonite is a widely used binder in the pelletizing process. the main constituent of bentonite which is a determining factor in the clays properties is the clay mineral montmorillonite. bentonite presents strong col-loidal properties and its volume increases several times when coming into contact with water, creating a gelatinous and viscous fluid. in the pelletizing process a high swelling type of bentonite is desirable, a property associated with sodium-type bentonites, whilst calcium-type bentonites are characterised by low swelling. calcium bentonites are converted to sodium bentonites by the addition of suitable sodium salts corresponding to the base exchange capacity. 膨润土是造球常用粘结剂，膨润土主要成分是蒙脱石膨润土是造球常用粘结剂，膨润土主要成分是蒙脱石,蒙脱石对粘土性质有决定作用。膨润 土有很强粘性，遇水体积膨胀几倍，形成胶状粘稠流体。造球时需要具有高膨胀性的膨润 土，而钙基和钠基膨润土膨胀性都不强。根据盐基交换能力加入适量钠盐，钙基膨润土转 化成钠基膨润土。 蒙脱石对粘土性质有决定作用。膨润 土有很强粘性，遇水体积膨胀几倍，形成胶状粘稠流体。造球时需要具有高膨胀性的膨润 土，而钙基和钠基膨润土膨胀性都不强。根据盐基交换能力加入适量钠盐，钙基膨润土转 化成钠基膨润土。 ca montmorillonite + na2co3 na montmorillonite + caco3 the addition of soda ash (na2co3) to the bentonite results in what is termed activated bentonite. traditionally the use of activated bentonite in the pelletizing of ores has resulted in good quality pellets while the use of unactivated bentonite resulted in poor quality pellets. 在膨润土中加入苏打粉之后，得到活性膨润土。一般来讲用活性膨润土造球质量好，惰性 膨润土造球质量差。 在膨润土中加入苏打粉之后，得到活性膨润土。一般来讲用活性膨润土造球质量好，惰性 膨润土造球质量差。 the results obtained from the plant trials with anthracite were in contradiction to this theory and therefore warranted further investigation. the use of unactivated bentonite with coke or char resulted in poor quality pellets while the use of unactivated bentonite with carbonaceous material such as anthracite, coal and the like resulted in good quality pellets. the conclusion that was reached was that, owing to the shape of the anthra-cite particles as well as its wettability properties, lower quality calcium bentonite produced the best quality pellets. good quality pellets at 100% anthracite usage could not be produced using activated bentonite except when the level of activation was very low. calcium type bentonite is more readily available and cheaper to produce. as a result the project reduced costs both in terms of reductant usage as well as binder usage. 工厂试验得到的结果与此理论相悖， 需要进一步验证。 惰性膨润土和焦炭或木炭一同使用， 成球质量差，而和碳质材料（如无烟煤、煤）一起 工厂试验得到的结果与此理论相悖， 需要进一步验证。 惰性膨润土和焦炭或木炭一同使用， 成球质量差，而和碳质材料（如无烟煤、煤）一起 用，成球质量好。可得结论：由于无烟 煤颗粒形状和湿润性，低品质钙基膨润土成球质量最好。 用，成球质量好。可得结论：由于无烟 煤颗粒形状和湿润性，低品质钙基膨润土成球质量最好。100%无烟煤加活性膨润土造球的 话，球团品质不好，除非膨润土活性非常低。钙基膨润土获得方便，价格便宜。因此，此 项目从还原剂和粘结剂两方面节约成本。 无烟煤加活性膨润土造球的 话，球团品质不好，除非膨润土活性非常低。钙基膨润土获得方便，价格便宜。因此，此 项目从还原剂和粘结剂两方面节约成本。 the use of reductant with a high volatile in pellets would require a redesign of the drying process so as to ensure the correct energy balance. this was not seen to be critical as anthracite with a volatile content of 7% was readily available and no further test-work on increasing the volatility of the reductant used was performed. 使用高挥发分还原剂需重新设计干燥工艺，以保证能量平衡。由于挥发分含量小于使用高挥发分还原剂需重新设计干燥工艺，以保证能量平衡。由于挥发分含量小于 7%的无 烟煤容易获取，这个问题倒不重要，提高还原剂挥发分含量的深入试验也未进行。 的无 烟煤容易获取，这个问题倒不重要，提高还原剂挥发分含量的深入试验也未进行。 2.5 change in operation philosophy 工艺思路转变工艺思路转变 the energy content of the pellets produced from the rotary kiln has an intrinsic energy value derived from the metallization level of the pellet and the temperature of the pellet. therefore the higher the metallization levels, the higher the energy content of each individual pellet produced. the higher the pellet output, the higher the total energy produced by the kiln. there is a direct relationship between metallization levels in the pellets and pellet output, whereby metallization levels increase as the pellet out decreases and vice versa up to a minimum throughput level below which carbon burn-off from the kilns increases resulting in oxidation of the pellets. 回转窑里生产出的球团有一部分能量来自球团本身金属化和球团温度。因此金属化越充分， 每个球团产生的能量就越多；球团释放能量越多，整个回转窑能量输出也高。球团内金属 化程度和球团产量有直接关系，金属化程度提高，球团产量下降，反之亦然。达到低于回 转窑碳燃烧增长的最小值，球团氧化。 回转窑里生产出的球团有一部分能量来自球团本身金属化和球团温度。因此金属化越充分， 每个球团产生的能量就越多；球团释放能量越多，整个回转窑能量输出也高。球团内金属 化程度和球团产量有直接关系，金属化程度提高，球团产量下降，反之亦然。达到低于回 转窑碳燃烧增长的最小值，球团氧化。 traditionally in the cmi process, the aim has been to maximize the metallization levels in the pellets produced. the rotary kilns at the lydenburg plant were each designed to produce 20 tons per hour (tph) of roasted pellets. the aim was to increase pellet throughput at the kilns and ensure that the net energy output from the kilns increased. the rationale behind this was that the higher the energy produced from the kilns, the lower would be the specific energy requirements during the smelting process. as such the operating philosophy at the plant was changed and although metallization levels were still monitored, the total energy produced by each kiln was monitored and controlled on a daily basis. 传统的传统的 cmi 工艺目的是最大化球团金属量。工艺目的是最大化球团金属量。lydenburg 厂设计产能厂设计产能 20t /h 焙烧球团，是为了 提高球团产量和回转窑净能量输出。原理是回转窑产生的能量越高，冶炼过程中所需比能 量越低。虽然工厂操作理念变化，也对金属量进行监测，每天还会对每个回转窑总能量生 产进行监测和控制。 焙烧球团，是为了 提高球团产量和回转窑净能量输出。原理是回转窑产生的能量越高，冶炼过程中所需比能 量越低。虽然工厂操作理念变化，也对金属量进行监测，每天还会对每个回转窑总能量生 产进行监测和控制。 the output from the kiln was increased to 30 tph and although the reduction rate dropped the total energy produced by the kiln increased by 17.5%. thereafter pellet output was increased