冷压制备工业硅生产用碳质还原剂球团及成型机理研究

发布时间：2018-07-26 16:27

【摘要】：木炭因其灰分低,孔隙率高,是工业硅生产的最佳碳质还原剂。随着森林资源的日益匮乏,人类环保意识的提高,导致木炭价格升高甚至木炭厂停产,对工业硅生产造成严重影响。因此,寻找完全替代木炭的碳质还原剂已刻不容缓。工业硅生产用碳质还原剂具有以下要求：化学成分要求固定碳高、水分低、挥发分适中、灰分低(灰分含量5%,Fe含量0.2%)；具有一定的机械强度；粒度组成合适；电阻率高和化学反应能力强。本论文以云南周边地区的提供的烟煤和生产中由于运输、破碎、洗料等工艺产生的粉料(简称粉料)为原料,两者颗粒粒度小,制团后方能入炉。冷压成型后除化学成分外,其他性能通过生球抗压强度、干球抗压强度、抗碎率、热强度和孔隙率来反映。烟煤灰分含量为16.09%,需要进行预处理。粉料化学组成满足工业硅生产的要求,不需进行预处理。本论文首先研究了烟煤的预处理,并对工业硅生产用碳质还原剂球团的原料进行选择。烟煤预处理过程分为浮选和酸浸两个阶段,浮选最佳工艺参数如下：选用三粗两精闭路实验流程,起泡剂松醇油用量为120g/t；捕收剂柴油用量为600g/t；抑制剂玻璃用量为2300g/t。经浮选后,灰分含量为4.68%,Fe元素含量为0.32%,不能满足工业硅生产对碳质还原剂化学成分的要求,需对其进一步脱灰除铁。酸浸脱灰除铁过程采用4mol/L盐酸浸出,反应温度为60℃,浸出时间为60min,液固比为5：1,废酸循环使用3次后,酸浸后的精煤灰分含量为3.89%,Fe含量为0.17%,满足工业硅生产对碳质还原剂化学成分的要求。将预处理后的烟煤或粉料作为球团原料进行冷压制团,比较球团性能,选用粉料作为工业硅生产用碳质还原剂球团的原料。其次,以R为粘结剂,研究了冷压成型过程,最佳工艺参数如下：成型压力为25MPa, NaOH溶液浓度为4.8mo1/L、含量取8.0%,微硅粉加入量为8.0%,洗精煤：石油焦：木炭为9.3：8.8：1(质量一定),成型颗粒最大粒度范围为3.3mm～4.75mm、比例占60%；R粘结剂含量为3.5%。在此条件下,所制备的球团性能最佳,生球抗压强度为698.0N,干球抗压强度为6985.0N,抗碎率为93.68%,热强度为55.25%,孔隙率为14.69%。生产结果表明：此球团可以用于工业硅生产,但炉况较差,球团性能有待提高。本论文以此球团性能为参考。再次,研究了以煤沥青、NaHA(腐植酸钠)、木质素磺酸钠、水玻璃以及淀粉类粘结剂(淀粉A、淀粉B、淀粉C与淀粉D)对球团性能的影响,其中以淀粉D制备的球团性能最佳,综合考虑,其含量选用1.96%,此时,生球抗压强度为873.2N,干球抗压强度为8091.4N,抗碎率为99.21%,热强度为94.44%,孔隙率为5.86%。以上性能除孔隙率外其他性能均满足生产要求,因此,在此基础上,进一步研究了非生物质造孔剂空心微珠、氧化钙和生物质造孔剂稻壳、玉米秸秆、小麦秸秆、水稻秸秆与木屑对球团性能的影响,结果表明,除空心微珠制备的球团不能满足工业硅生产要求外,以其他物质为造孔剂制备的球团性能均较好。当选用水稻秸秆为造孔剂时,最佳含量为2.5%时,成型颗粒最大粒度为4.75mm,分布模数为0.5时球团性能最佳,在此条件下,生球抗压强度为4700.2N,干球抗压强度为9536.1N,抗碎率为99.07%,热强度为96.21%,孔隙率为30.78%,能满足工业硅生产的要求。此外,研究了冷压成型过程中含水率、润湿介质和粘结剂、造孔剂、成型压力、物料粒度组成对球团性能影响机理,得到以下结论：冷压成型过程中,以NaOH溶液为润湿介质时,NaOH与淀粉D反应产生的新化学键对颗粒的结合能力提高。颗粒与粘结剂之间的结合力是机械结合力和物理化学结合力综合作用的结果,其中,机械结合力的作用大于物理化学结合力的作用。水稻秸秆在球团中提高孔隙率的主要是由于本身其密度小,外力消失后容易发生塑性形变等特性决定的；原料粒度组成符合GGS粒度特性方程时,球团性能最佳。最后将最佳工艺参数下制备的球团投入25.5MVA半封闭旋转矿热炉中,通过工业化生产数据分析可知：该球团能够满足工业硅生产的要求,最佳替代量为80%。
[Abstract]:Due to its low ash content and high porosity, charcoal is the best carbonaceous reducing agent in industrial silicon production. With the increasing shortage of forest resources and the improvement of human environmental awareness, the price of charcoal increased even in the charcoal plant, which has a serious effect on the industrial silicon production. Therefore, it is urgent to find a carbonaceous reducing agent to replace the charcoal. The carbon reducing agent for production has the following requirements: chemical composition requires high fixed carbon, low moisture, moderate volatilization, low ash content (ash content 5%, Fe content 0.2%), a certain mechanical strength, suitable size composition, high resistivity and chemical reaction ability. This paper is provided in the coal and production of the surrounding area of Yunnan because of the high resistivity and chemical reaction ability. In addition to chemical composition, other properties are reflected by the compressive strength of the raw ball, the compressive strength of the dry ball, the crushing rate, the heat strength and the porosity. The ash content of the bituminous coal is 16.09%, which needs to be pretreated. The chemical composition meets the requirements of industrial silicon production without preprocessing. In this paper, the pretreatment of bituminous coal was first studied, and the raw materials of carbon reduction agent pellets used in industrial silicon production were selected. The pretreatment process of bituminous coal was divided into two stages of flotation and acid leaching. The optimum flotation process parameters were as follows: the three coarse two finish closed circuit experiment process was selected. The amount of the defoaming agent is 120g/t, the amount of the collector diesel oil is 600g/t, the amount of the inhibitor glass is 2300g/t. after flotation, the ash content is 4.68%, the content of the Fe element is 0.32%. It can not meet the requirement of the chemical composition of the carbon reducing agent in the industrial silicon production. It needs further deashing and removing iron. The process of acid soot deashing and removing iron is 4mol/L hydrochloric acid. The leaching time is 60 C, the leaching time is 60min, the liquid and solid ratio is 5:1, the waste acid is recycled 3 times. The ash content of the refined coal after acid leaching is 3.89%, the content of Fe is 0.17%, which meets the requirement of the chemical composition of the carbonaceous reducing agent in the industrial silicon production. The powder is used as the raw material for the production of carbon reducing agent pellets for industrial silicon. Secondly, the cold press molding process is studied with R as a binder. The optimum process parameters are as follows: the molding pressure is 25MPa, the concentration of NaOH solution is 4.8mo1/L, the content is 8%, the micro silicon powder is added to 8%, the washed coal is coke: charcoal is 9.3:8.8:1 (quality certain), The maximum grain size range of the formed particles is 3.3mm to 4.75mm, and the proportion is 60%. Under the R binder content 3.5%., the pellet has the best performance, the ball compression strength is 698.0N, the dry ball compressive strength is 6985.0N, the crushing rate is 93.68%, the heat strength is 55.25%, and the porosity of 14.69%. production shows that this pellet can be used in industrial silicon. Production, but the condition of the furnace is poor, the performance of pellet needs to be improved. This paper takes this ball as a reference. Again, the effects of coal tar pitch, NaHA (humic acid sodium), sodium lignosulfonate, water glass and starch binder (starch A, starch B, starch C and starch D) on pellet performance are studied. The performance of pellets prepared by starch D is the best and comprehensive examination The content is 1.96%. At this time, the compressive strength of the ball is 873.2N, the compressive strength of the dry ball is 8091.4N, the crushing rate is 99.21%, the heat strength is 94.44%, the porosity is above 5.86%., and the other properties except the porosity are all satisfied with the production requirements. Therefore, on this basis, the hollow microspheres, calcium oxide and biological materials of non biomass pore making agents are studied on this basis. The effect of the porous rice husk, corn straw, wheat straw, rice straw and wood chips on the pellet performance was found. The results showed that the Pelletizing Properties of the pellets prepared by other substances except the hollow microspheres could not meet the industrial silicon production requirements. When the water rice straw was selected as the pore making agent, the optimum content was 2.5%. When the maximum particle size is 4.75mm and the distribution modulus is 0.5, the ball has the best performance. Under this condition, the compressive strength of the ball is 4700.2N, the compressive strength of the dry ball is 9536.1N, the crushing rate is 99.07%, the heat strength is 96.21%, the porosity is 30.78%, which can meet the requirements of the industrial silicon production. In addition, the water content, wetting medium and bond during the cold pressing process are studied. The influence mechanism of agent, pore forming agent, molding pressure and material size composition on pellet properties is obtained. The following conclusions are obtained: in the process of cold pressing, when the NaOH solution is the wetting medium, the new chemical bonds produced by the reaction of NaOH and starch D increase the binding capacity of the particles. The binding force between the particles and the binder is the mechanical binding force and the physical and chemical binding force. As a result of the comprehensive effect, the effect of mechanical binding force is greater than that of physical chemical binding force. The main reason for the increase of the porosity of rice straw in the pellet is due to its small density and the characteristics of plastic deformation after the external force is disappearing. When the particle size composition of the raw material is in line with the GGS particle size characteristic equation, the best performance of the pellets is the best. The pellets prepared under the best technological parameters are put into the 25.5MVA semi closed rotary mine hot stove. The analysis of industrial production data shows that the pellet can meet the requirements of industrial silicon production, and the optimum replacement amount is 80%..
【学位授予单位】：昆明理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN304.12

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