【作者】 毛晓明；

【导师】 姜涛； 黄柱成；

【作者基本信息】 中南大学 ， 冶金工程， 2014， 博士

【摘要】 摘要：我国钢铁行业中,烧结工序作为钢铁生产的重要组成部分,其能耗约占钢铁生产总能耗的10%～15%,其中,烧结点火能耗占烧结工序能耗的5%～10%。传统的煤气点火存在煤气利用率低、能源消耗量大、污染严重等问题,制约了钢铁企业的可持续发展。因此,积极开发不依赖高炉/焦炉煤气的铁矿石烧结点火新技术,是我国钢铁工业节能减排和高效环保的必然要求。本文以宝钢烧结生产现场为对象,对传统的煤气点火过程进行了系统解析,测定了不同点火条件下点火炉内.温度场的分布状态；针对现场煤气点火存在的不足,提出了微波热风点火新概念,建立了微波热风烧结点火的理论基础及点火模型；开发了微波热风点火烧结试验装置及点火新技术,查明了微波热风点火烧结矿的固结行为；在微波热风烧结点火扩大化试验的基础上,初步设计了工业型微波热风烧结点火系统。本研究的创新点及获得的主要结论如下：(1)解析了点火炉内温度场分布不均匀是造成传统煤气点火能耗利用率低(宝钢现场实际点火能耗为50.93MJ/mz,实际利用率仅为37.8%)的主要原因。通过改变点火强度、点火负压及点火区域皆无法实现点火炉内温度场分布的均匀性,需从本质上改变点火方式。(2)提出了微波热风点火烧结的新概念,建立了热风烧结点火的理论基础及点火模型。在点火气流中氧含量为21%时,得出微波热风烧结点火所需理论最低点火温度为618.32℃,最低点火能耗为23.68MJ/m2。在此点火条件下,表层混合料中的焦粉能够成功点燃,并保证烧结过程顺利进行。(3)成功开发了微波热风点火烧结新技术及装置,并在实验室及扩大试验中得到了应用,获得了良好的试验效果。a、实验室烧结杯试验研究结果表明,在实际点火风温为760℃(空气预先被加热至330℃)、点火时间为1.5min,单位面积点火风量682Nm3/(h·m2)的点火条件下,所获得烧结产质量指标优于煤气点火,而且其点火能耗仅为煤气点火能耗的21.61%,同时点火废气中的SO2和NOx含量明显降低。b、扩大化试验研究结果表明,在实际点火风温700℃,点火时间1.5min,单位面积点火风量960Nm3/(h.m2)的点火条件下,所获得的烧结产质量指标为：垂直烧结速度23.48mm/min,转鼓强度66.91%,烧结矿成品率69.62%,利用系数为1.453t/m2.h。与实验室结果相比,扩大试验获得的烧结矿质量明显改善,且点火能耗进一步降低至25.08MJ/m2。(4)微波热风点火烧结矿的固结行为研究发现,因微波热风点火气流中氧气含量接近21%,明显高于煤气点火热气流中的氧气含量(8-9%),所以微波热风点火中、上层烧结矿中的赤铁矿数量较多,铁酸钙分布广泛、晶形发育充分,这是微波热风点火烧结矿强度优于煤气点火烧结矿强度的重要原因。随着微波热风点火气流中氧气含量提高,烧结矿中赤铁矿数量增多,磁铁矿减少；点火气流中氧气含量的提高有利于焦粉的充分燃烧,使得料层中铁酸钙液相生成量增多,铁酸钙和赤铁矿相互熔蚀程度提高。铁酸钙作为烧结矿主要的粘结相,多呈针状、树枝状或长条状,充填于赤铁矿晶粒间,相互间嵌布关系密切。(5)初步设计了工业型微波热风点火系统,点火单元及辅助单元的工程造价约为4200万元,一台机年效益约为769.66万元,投资回报期需5.46年。通过对工艺技术、经济效益及社会效益的评估,证实了微波热风烧结点火技术的工业化实施是可行的。更多还原

【Abstract】 Abstract:In the domestic iron and steel industry, sintering process is one of the most important sections, which consumes10%～15%of the total energy. And the ignition energy consumption accounts for5%～10%of the sintering process. However, the traditional ignition based on coal gas is characterized by high gas consumption, low efficiency and serious pollution, which restricts the sustainable development of iron and steel industry. Therefore, developing novel ignition technologies independent of coal gas is inevitable for the requirements of energy conservation and emission reduction, high efficiency and environmental friendliness.In this paper, the traditional coal gas-based ignition (CGI) process was systematically analysed, and the temperature distribution of ignition spot in Bao Steel was measured. With respect to the drawbacks of conventional ignition method, the microwave-heated ignition (MHI) technology was firstly proposed and the theoretical basis and ignition model of MHI were established. The new technology and corresponding devices were developed and the consolidation behavior of MHI sintering was found out. Based on the large-scale experiments of MHI, the industrialized MHI system was preliminary designed. The following innovation and conclusions were obtained.(1) The analysis of the traditional ignition process revealed that the ununiform temperature distribution of ignition spot was the main reason for low utilization efficiency (the current ignition energy consumption in Bao Steel was50.93MJ/m2and the efficiency was only37.8%). In order to reduce the ignition energy consumption, the ignition method must be changed as it was infeasible by changing ignition intensity, negative pressure or ignition area.(2) The theoretical model of MHI indicated that, the minimum ignition temperature and heat was618.32℃and23.68MJ/m2, respectively. The coke breeze in the sinter bed was capable of combustion if the superficial one was ignited and then the sintering process was readily to go on smoothly under the above ignition conditions.(3) The novel MHI technology was developed and successfully applied in the laboratory and large-scale experiments:a、The laboratory investigation indicated that the optimal sintering ignition conditions were the following:ignition temperature at760℃(preheating temperature of ignition airflow at330℃), ignition time at1.5min and unit ignition airflow at682Nm3/(h·m2). The sintering indexes under the above conditions were slightly better than those under the traditional ignition condition, the ignition energy consumption was only21.61%of CGI and the emission of SO2and NOx by MHI was reduced obviously.b、The optimized conditions for large-scale experiments were obtained as ignition temperature at700℃, ignition time at1.5min, unit ignition airflow at960Nm3/(h㈨m2). The vertical sintering velocity of23.48mm/min, tumbling strength of66.91%, yield of69.62%and utilization efficiency of1.453t/m2·h were acquired under the above conditions. It can be observed that the quality of the finished sinter was improved remarkably in the large-scale experiment. The ignition energy consumption was only25.08MJ/m2.(4) The consolidation behavior of finished sinters by MHI sintering was found out. It was demonstrated that there was more hematite in the middle and upper sinter obtained from MHI, calcium ferrite was well developed and widely distributed as the ignition airflow of MHI had higher O2content (nearly21%) while8～9%of CGI. Because of it, the strength of finished sinters by MHI sintering was higher to CGI. The quantity of hematite was increased with increasing O2content of ignition airflow, while that of magnetite decreased. In addition, the combustion of coke breeze was enhanced and the liquid-phase of calcium ferrite was increased resulting in a greater corrosion of the minerals. Calcium ferrite was considered as the main binding phase exhibiting an acicular and foliated appearance, which was well combined and distributed among the hematite and magnetite grains.(5) The industrialized MHI system was designed preliminarily. And it was estimated that the construction costs of each ignition and auxiliary unit were42million and the benefit was7.69million each year. As a result, the estimated investment recovery time was about5.46years. The industrialization of this novel technology was proved to be feasible after assessing the technology, economic benefit and social benefit.更多还原