熔铝炉烟气循环燃烧过程数值模拟研究与装置设计

发布时间：2018-03-03 08:31

本文选题：熔铝炉　切入点：烟气循环燃烧　出处：《西南石油大学》2017年硕士论文　论文类型：学位论文

【摘要】：熔铝炉是铝加工制造中最重要的一个设备,其熔炼过程也是耗能最大的一个工艺环节。在国家倡导节能减排的政策下,降低熔铝炉的能耗是铝加工行业的一个重要任务。回收熔铝炉排出烟气的热能是节能最直接的方法,因此如何利用烟气热能对熔铝炉未来的节能发展具有重大意义。通过对现有熔铝炉回收烟气热能技术和装置的总结及现场实地的考察,提出了将熔铝炉排出的烟气与氧气混合后充当助燃气进入炉膛与燃料燃烧的方法,并且设计了相应的结构装置和控制系统。本文使用FLUENT软件,数值模拟循环烟气与氧气混合后进入炉膛燃烧的稳态场,通过分析数值模拟的结果得到的主要结论如下:(1)获得了设计工况下烟气循环燃烧数值模拟结果;与常温空气燃烧、预热空气燃烧相比,烟气循环燃烧可减小炉内局部高温,提升炉膛平均温度,炉内温度分布更均匀。(2)随着混合气内氧气质量分数的减小,使得混合管道截面上氧气质量分数最大值与最小值的差变大,温度的最大值与最小值之差也在变大,说明烟气与氧气混合的均匀性在逐渐变差;同时随着混合气内氧气质量分数的减小,炉膛内四个截面上的最高温度、平均温度、温度差也在减小,温度分布趋于均匀。(3)当混合气内氧气质量分数为16%和8%(氧气分布近似均匀)时,与氧气分布完全均匀的相比,炉膛内温度分布相差不大;当混合气内氧气质量分数为5%(氧气分布不均匀)时,与氧气分布完全均匀的相比,炉内温度分布不均匀、平均温度降低。(4)对燃料与助燃气喷嘴分开和集中两种进气方式、混合气速度、混合气和燃料速度比、助燃气预热温度、助燃气与燃料双预热温度进行了数值模拟及分析;喷嘴集中的进气方式形成更多的旋涡,促进炉内气体换热,炉温可达到1397℃C,在炉底温度分布更加均匀;混合气的速度为24m/s时,炉膛内回流剧烈,炉温较高;混合气和燃料的速度比为0.3时,炉温最高;助燃气预热温度越高,炉温越高;在循环不同烟气温度下,单预热与双预热相比,双预热在低温时更有优势,单预热在高温时更有优势。(5)对熔铝炉内进行热平衡迭代估算,与前人所做的蓄热式燃烧热平衡测试作为热平衡迭代计算方法的验证;结果表明,各项误差均在5%以内;对比分析蓄热式燃烧、传统空气燃烧、烟气循环燃烧三种不同的燃烧方式,结果表明烟气循环燃烧时,每吨铝料使用天然气量为80m~3,比蓄热式燃烧的82m~3和传统空气燃烧的110.5m~3更节能。
[Abstract]:Aluminum melting furnace is one of the most important equipment in the manufacture of aluminum, the melting process is a process of energy consumption in the country. The largest advocate energy-saving emission reduction policies, reduce the energy consumption of aluminum melting furnace is an important task of aluminum processing industry. The recovery of aluminum melting furnace and flue gas heat is the most energy saving method directly, so how to make use of flue gas heat energy is of great significance to the development of energy-saving aluminum melting furnace in the future. Through the review of the existing aluminum melting furnace flue gas heat recovery technology and device summary and field, the paper proposes the method of flue gas and oxygen melting furnace exhaust mixed as auxiliary gas into the furnace and fuel combustion, and the design of the structure and the corresponding control system. This paper use FLUENT software, numerical simulation of steady-state cycle gas mixed with oxygen into the furnace combustion, through the analysis of numerical simulation result. The main conclusions are as follows: (1) the design condition of flue gas circulating combustion numerical simulation results; combustion and normal temperature air, air preheating combustion flue gas circulating combustion can be reduced compared to the local high temperature furnace, increasing the average temperature of the boiler, more uniform temperature distribution in the furnace. (2) with the decrease of mass fraction of oxygen in the gas mixture the cross section of the pipeline, the mixed oxygen mass fraction of the maximum and minimum value difference is large, the maximum temperature and the minimum value of the difference is also larger, which means that the smoke mixed with oxygen in the uniformity becomes worse; at the same time, with the decrease of mass fraction of oxygen in the gas mixture, the highest temperature, four section furnace in the average temperature, temperature difference is reduced, the temperature distribution tends to be uniform. (3) when the mass fraction of oxygen mixture in 16% and 8% (approximately uniform distribution of oxygen), compared with the oxygen distribution uniform, the distribution of the temperature in furnace Little difference; when the mass fraction of oxygen mixture in 5% (oxygen distribution), compared with the oxygen distribution uniform, non-uniform temperature distribution in the furnace, the average temperature decreases. (4) of the fuel gas nozzle with the help of separated and concentrated two gas, mixed gas, mixed gas and fuel speed ratio, auxiliary gas preheating temperature, auxiliary gas and fuel preheating temperature are obtained by numerical simulation and analysis of air inlet nozzle; the formation of more concentrated vortex, promote the furnace gas heat, the furnace temperature can reach 1397 DEG C, the bottom temperature distribution is more uniform; the mixture velocity is 24m/s, the furnace high temperature; severe reflux, mixed gas and fuel velocity ratio is 0.3, the highest temperature; auxiliary gas preheating temperature is higher, the higher the temperature; in different flue gas temperature cycle, single preheating compared with double preheating, double preheating more at low temperature, single preheating The advantage in high temperature. (5) thermal equilibrium iteration estimation for aluminum melting furnace, and verified the previous regenerative combustion heat balance test as thermal equilibrium iteration method; the results show that the errors are within 5%; comparative analysis of regenerative combustion, traditional air combustion, flue gas circulating combustion three different combustion modes. Results show that the flue gas circulating combustion, the use of natural gas per ton aluminum material for 80m~3, saving more energy than regenerative combustion 82m~3 and conventional air combustion 110.5m~3.

【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG232

【参考文献】