烧结烟气在高炉内的清洁化及资源化行为

It is of significance to protect environment by cleaning the flue gas from sintering process. However, the desulfurization ratio and denitration ratio are not very well in conventional flue gas disposing processes. A new technology of injecting sintering flue gas into blast furnace tuyere was presented. With this technology, not only SOx and NOx could transform cleanly to harmless CaS and N2 at a high temperature and in a high reductive gaseous condition, and the desulfurization ratio and denitration ratio are expected to exceed 95%, but also CO, CO2 and O2 could be recycled and reused as available resources. In this program, high temperature experiment is designed to study the cleaning behavior of the sintering flue gas in the blast furnace; blast furnace mathematical model is programed to study the recycling behavior of the sintering flue gas. The research content of this program includes: 1) isothermal kinetic mechanism of SO2 reduced by CO/coke, and the catalyzing behavior of α-Al2O3, SiO2, Fe or metallic pellet involved in the reaction of SO2 reduced by CO; 2) isothermal kinetic mechanism of NO reduced by CO/coke, and the catalyzing behavior of CaO, SiO2, α-Al2O3, Fe2O3, Fe3O4, FeO or Fe involved in the reaction of NO reduced by CO; 3) In case of sintering flue gas injection, the variation of coke rate, fuel rate, flame temperature and thermal balance, etc.; distribution and transition of mass flow, energy flow and exergy flow of the new blast furnace or oxygen blast furnace system, and variation of the ironmaking cost.

烧结烟气的治理对保护生态环境具有重要的意义，但是传统烟气治理工艺的脱硫率和脱硝率均不理想。烧结烟气从高炉风口喷吹不仅可将SOx和NOx在高温、强还原性气氛下清洁转化为无害的CaS和N2，脱硫率和脱硝率有望突破95%，而且能回收CO、CO2和O2，使其得到资源化利用。本项目通过设计高温实验研究烧结烟气在高炉内的清洁化行为，通过高炉数学模型研究烧结烟气在高炉内的资源化行为。研究内容有：1）CO/焦炭还原SO2的等温动力学机理及α-Al2O3、SiO2、Fe和金属化球团对CO还原SO2的催化行为；2）CO/焦炭还原NO的等温动力学机理及CaO、SiO2、α-Al2O3、Fe2O3、Fe3O4、FeO、Fe等物质对CO还原NO的催化行为；3）烧结烟气喷吹后，高炉焦比、燃料比、理论燃烧温度、热平衡等的变化规律，新的高炉或氧气高炉工艺系统的能量流、物质流、㶲流的分布、传递规律，以及炼铁成本的变化规律。

将烧结烟气从高炉风口喷吹可以达到净化烟气中的SO2和NO的目的。本项目以此为背景，研究了高炉内的主要还原气相CO还原NO和SO2的动力学机理，以及探索了高炉原料对两种还原过程的催化作用。同时，建立了烧结烟气喷吹进入高炉系统的数学模型，研究了喷吹烧结烟气后高炉的各项冶炼参数的演变规律。结果表明：（1）在700-1000℃之间，用CO单独还原SO2时，反应产物主要为COS，随着温度的升高，CO浓度的增大，SO2的还原率也逐渐增大，950℃时SO2的还原率达到峰值13.5%；（2）α-Al2O3对CO-SO2反应不起催化作用，活性还原铁粉催化CO-SO2时，950℃时SO2的还原率达到峰值45.1%。在650-850℃之间，使用焦炭还原SO2时，温度为750℃时SO2的还原率最大为22.6%；金属化球团催化CO-SO2的还原规律类似于活性还原铁粉，950℃时SO2的还原率基本达到最大值为46.7%。（3）在CO还原NO的均相反应中，得出了实际最高温度1454 K、1554 K、1655 K以及1754 K时的速率常数分别为0.157、0.380、0.822和1.511 m3/(mol·s)，CO-NO还原反应的活化能为160.58 kJ/mol。（4）焦炭、烧结矿、球团矿、铁氧化物、CaO对 NO-CO 反应都具有一定的催化作用；SiO2和α-Al2O3对CO-NO反应无催化作用；焦炭催化CO-NO还原反应的活化能为84.1 kJ/mol，比均相反应的活化能降低了76.48 kJ/mol；铁及其氧化物对CO-NO反应催化性能的排序为FeO＞还原Fe粉＞Fe3O4>Fe2O3。（5）全氧高炉喷吹烧结烟气后会降低理论燃烧温度，提高直接还原度，降低CO利用率，增加燃料比。随着烧结烟气喷吹量增加，燃料比会逐渐增大；减少循环煤气量或者脱除烧结烟气中的部分N2可以提高烧结烟气喷吹量。炉身与炉缸不循环煤气时，烧结烟气喷吹温度为1250 °C，最大烧结烟气喷吹量为1132 m3·t-1；脱除烟气中95% N2时，全氧高炉的烧结烟气实际处理量可以达到3272 m³/t，炉顶煤气中的NO2浓度可以降低至50 mg·Nm-3以下，达到钢铁行业超低排放标准，而SO2浓度可降低至214.28 mg·Nm-3左右，与普通高炉的SO2浓度相当。