综合利用高灰分废弃焦粉制备碳质还原剂的研究

【作者】 宁哲；

【导师】 马文会； 谢克强；

【作者基本信息】 昆明理工大学 ， 冶金物理化学， 2013， 博士

【摘要】 本论文对高灰分废弃焦粉采用湿法工艺脱灰制备碳质还原剂的工艺和理论进行了系统的研究。论文中首先对工业硅和电石行业用碳质还原剂进行概述,指出目前云南省工业硅和电石产业快速发展与碳质还原剂供应不足的现状之问存在的矛盾。同时归纳了焦炭作为还原剂的悠久历史,高灰分焦粉的来源和利用现状。总结了国内外现有脱灰技术的研究成果和工业应用状况,提出高灰分焦粉脱灰制备工业硅还原剂的研究方向,从而明确提出了本论文的研究意义和主要研究内容。本论文以云南地区焦化企业生产过程中产生的焦粉为研究对象,研究了焦粉中灰分杂质的存在形态及焦粉湿法脱灰热力学,据此提出了高压碱浸-常压酸浸联合浸出的焦粉脱灰技术路线,并对脱灰过程的有关的基础问题和相关机理进行了研究。(1)利用现代分析检测技术,研究了焦粉中灰分杂质元素的种类及含量、物相组成和分布特征。焦粉中主要的灰分杂质元素为Si、Al、Fe、Ca、Ti, S,通常以氧化物的形式存在于焦粉中。灰分矿物质的主要物相为石英(Quartz)、方石英(Cristobalite)、莫来石(Mullite)、赤铁矿(Hematite)、石膏(Anhydride)。焦粉中灰分矿物质大部分呈颗粒状与碳颗粒夹杂分布,少部分镶嵌于炭基体中。由于焦粉的物理性质与煤不同,利用物理方法很难使焦粉中的灰分颗粒与碳分离,化学浸出更适于去除焦粉灰分。(2)分析焦粉湿法浸出脱灰过程中的热力学规律,分别绘制了主要灰分元素Si、Al、Fe、Ca、Ti和Mg水溶物种的Igα-pH图,不同温度条件下Al-Si-H2O系的(p-pH图和Si-H2O系、Al-H2O系和Al-Si-H2O系的lg(c)-pH图。(3)从工艺角度研究了浸出剂种类及其浓度、焦粉粒度、反应温度、反应时间、液固比等多种因素对焦粉脱灰的影响。确定了合理的工艺参数为：碱浸：粒度<75μm,温度180～200℃, NaOH溶液浓度15wt.%,保温时间30min,液固比4：1～8：1,自蒸汽压；酸浸：温度90℃；H2SO4溶液浓度12wt.%；保温时间30min;液固比6：1。在此浸出条件下,进行了扩大试验,结果证明本工艺具有良好的放大效果和适用性。焦粉灰分去除率超过84%,灰分含量低于4.5%,焦粉中Si、Al、Mg去除率>85%,Ca去除率>97%,Fe去除率>70%。(4)在确定的条件下,对焦粉脱灰过程动力学进行了研究,利用“有固态产物层的固-液反应模型”建立了碱浸温度对焦粉灰分中含硅矿物和含铝矿物脱除率的动力学方程,研究Si和Al去除过程中的限制性环节。研究结果表明：Si和Al脱除反应的表观活化能分别为27.635kJ/mol和36.041kJ/mol,都属于内扩散控制。温度对含硅矿物和含铝矿物溶出率影响的动力学方程如下：Ink’si=0.51792+3.3239×103×T/1Ink’al=-1.13402+4.33495×103×T/1(5)研究了焦粉脱灰前后物理化学性质的变化,与现有工业硅和电石生产用碳质还原剂进行比较,提出脱灰焦粉在工业硅和电石生产中的应用方式。通过脱灰焦粉物理化学性质分析和还原实验证明了脱灰焦粉作为工业硅和电石生产碳质还原剂的可行性。(6)对工艺的经济性和环境影响进行了评价。经济性分析表明脱灰焦粉制备碳质还原剂生产成本为1855.25元/t,低于目前工业硅和电石生产用碳质还原剂的价格,具有比较可观的经济效益,在经济上是可行的。环境分析表明本项目产生的废水、废渣可得到很好的二次利用,对环境影响小,从环保角度考虑是可行的。(7)利用高灰分焦粉脱灰制备碳质还原剂,提高了高灰分焦粉的附加值,解决焦炭废弃堆存带来的环境问题,为工业硅和电石生产提供一种新的碳质还原剂,实现了焦煤资源的综合回收利用。更多还原

【Abstract】 In the dissertation, the technology and fundamentals of the demineralization processing to prepare carbon reductants from high-ash waste coke breeze by pressure-leaching method are systematically studied.This dissertation firstly introduces the situations of silicon metal and calcium carbide industries and the carbon reductants used in silicon metal and calcium carbide production, and points out the contradiction between the rapid development of silicon metal and calcium carbide industries and the shortage of carbon reductants. Meanwhile, the history of coke using as a reductant and the source and usage status quo of high-ash coke breeze are also be introduced. On the basis of the over view of the domestic and international research results about demineralization techniques and the application status of these techniques, the direction in studies of the demineralization processing for carbon reductants from high-ash waste coke breeze are proposed. Thereby, significance and main contents of this resreach are put forward explicitly.The research chooses coke breeze from the coking plant in Yunnan as study object. According to the existing form of ash minerals in coke breeze and the thermodynamics analysis results of demineralization by pressure-leaching method, the technical route of pressure alkali leaching followed by acid leaching at atmospheric on coke breeze demineralization is put forward, and the theory foundation on demineralization are inveatigated.(1) The element categories and contents, the phase composition and distribution characteristics of ash in coke breeze are analysed with modern analysis and testing technology. The main ash elements in coke breeze are Si, Al, Fe, Ca, Ti and S, which exist generally as the oxidate. The main phase compositions of ash minerals are quartz, cristobalite, mullite, hematite, and anhydride. The mostly mineral particles are mixed with coke particles, and a few fine minerals particles are intimately associated with the coke matrix. It is difficult to separate minerals particles from coke particles by the physical method. The chemical leaching is more suitable for demineralization of coke breeze.(2) The thermodynamics laws of pressure leaching of coke breeze are analysed. The Igα-pH diagrams of Si, Al, Fe, Ca, Ti and Mg, the (p-pH diagram of Al-Si-H2O system at different temperature, the Ig(c)-pH diagrams of Si-H2O system, AI-H2O system and Al-Si-H2O system are construted respectively.(3) The effects of leaching agents, initial concentration, particle size, temperature, leaching duration, liquid-to-solid ratio, ect. on the degree of demineralization are examined from the technological angle. The reasonable technological conditions obtained by factor experiments are that alkali leaching; particle size<75μm, temperature180～200℃, NaOH solution concentration15wt.%, leaching duration30min, liquid-to-solid ratio4:1～8:1, self-pressure; acid leaching:temperature90℃, H2SO4solution concentration12wt.%, leaching duration30min, liquid-to-solid ratio6:1. The results of the extensive experiment conducted under the reasonable conditions prove the feasibility and applicability of the proposed demineralization method. The degree of demineralization is more than85%, the content of ash is less than4.5%, the degrees of the removal of Si, Al and Mg is more than85%, the degree of Ca removal is more than97%, and the degree of Fe removal is more than70%.(4)Under the determind conditions, the kinetics of coke breeze demineralization are studied. The original "kinetic model of Crank-Ginstling-Brounshtein" for liquid-solid reaction is used to obtain the kinetic equation for the removal of Si and Al in ash and investigate the controlled step of Si and Al removal. The results show that the Si and Al minerals removal reaction activation energy is27.635kJ/mol and36.041kJ/mol respectively, and the process of the Si and Al removal are both controlled by the interior diffusion. The kinetic equationfor the effect of alkali leaching temperature on the degree of Si and Al minerals removal are: In k’si=0.51792+3.3239×103×T/1In k’al=-1.13402+4.33495×103×T/1(5) The physical and chemical properties of coke breeze are studied before and after demineralization. Through the comparison with the reductant used in silicon metal and calcium carbide production, and the application mode of the de-ash coke breeze is put forward. The possibility of using de-ash coke breeze as reductant for silicon metal and calcium carbide production is proved by the analysis of physical and chemical property of de-ash coke breeze and the reduction experiments.(6) The environmental and economical evaluation of the process are made. The cost of the reductant from de-ash coke breeze is￥1855.25/t, lower than the price of carbon reductant for silicon metal and calcium carbide, which has considerable economic benefit. The results of environmental evaluation show that wastewater and dregs produced by the reductant production can be recycled, the productive process has low effect of environment. The results of the environmental and economical evaluation indicate that the process is feasible.(7) The reductant production from de-ash coke breeze increases the added value of high-ash coke breeze, which can solve the environmental treathens from waste piling, and it provides a new reductant resourse for silicon metal and calcium carbide production, and then to realize the comprehensive utilization of the coking coal.更多还原