天然气锅炉烟气余热深度回收凝结换热方法研究

发布时间：2018-10-19 10:22

【摘要】：在天然气锅炉中,排烟温度较高,排烟热损失相对较大,过热状态的水蒸气随排烟到大气中,会造成水蒸气潜热的巨大浪费。因此,天然气锅炉排烟温度较高,回收过热状态下水蒸气的潜热难是急待解决的问题。由于翅片管换热器拥有良好的传热性能,同时,其结构的紧密性和易清理性等诸多优点,在降低排烟温度,回收烟气余热的众多方式方法中占有一席之地,故本文针对天然气锅炉排烟温度较高,回收过热状态下水蒸气的潜热难的问题,结合工程热力学和计算传热学相关理论的基础上,在天然气锅炉系统尾部加装翅片管换热器深度回收排烟过程中烟气的显热和水蒸气凝结时释放的潜热,以达到降低排烟温度,深度回收烟气热量的目的。在本文中,通过实物模型分析建立其物理模型,利用仿真模拟的方法还原实际情况。利用前人的实验数据对比翅片管换热器仿真模拟计算结果的准确,验证了方法的可操作性。得出其烟气侧入口速度、翅片间距、翅片厚度和翅片高度等参数变化下的烟气凝结换热特性规律。具体包括:1.在四参数变量中,即烟气入口速度、翅片间距、翅片厚度、翅片高度中,烟气入口速度对传热规律的作用最大;翅片间距和厚度对传热的作用相继分列二三位,而翅片高度对传热规律作用效果最小。2.当改变烟气侧入口速度时,随着入口烟气速度的增大,平均换热系数增大,流动阻力增大,换热性能增强。翅片间距和厚度变小时,其换热器的传热系数的平均值和传热量均增大。当改变翅片高度时,随着翅片高度降低,其换热器的传热系数的平均值及传热量均降低。最后,采用静态投资回收期法,对翅片管换热器进行经济性评价,得出最短经济性回收周期。
[Abstract]:In the natural gas boiler, the temperature of exhaust gas is higher, the heat loss of exhaust smoke is relatively large, and the superheated water vapor will cause a huge waste of latent heat of water vapor with exhaust smoke into the atmosphere. Therefore, the gas exhaust temperature of natural gas boiler is high, and it is difficult to recover the latent heat of water vapor under superheated condition. Because finned tube heat exchanger has good heat transfer performance and its structure is compact and easy to clean, it occupies a place in many ways and methods of reducing smoke exhaust temperature and recovering flue gas waste heat. Therefore, in view of the problem of high exhaust gas temperature of natural gas boiler and difficulty in recovering latent heat of water vapor under superheated state, combined with engineering thermodynamics and calculation heat transfer theory, this paper combines the theory of engineering thermodynamics and calculation heat transfer. The finned tube heat exchanger is added to the tail of the natural gas boiler system to recover the sensible heat of flue gas and the latent heat released when the steam condenses in order to reduce the exhaust gas temperature and to recover the flue gas heat deeply. In this paper, the physical model is established through the physical model analysis, and the simulation method is used to restore the actual situation. The simulation results of finned tube heat exchanger are compared with the experimental data, and the maneuverability of the method is verified. The characteristics of flue gas condensation heat transfer are obtained under the change of inlet velocity, fin spacing, fin thickness and fin height. Specific include: 1. In the four parameter variables, that is, flue gas inlet velocity, fin spacing, fin thickness, fin height, flue gas inlet velocity has the greatest effect on heat transfer law, the effect of fin spacing and thickness on heat transfer is two or three, The finned height has the least effect on heat transfer. 2. When the inlet velocity of the flue gas side is changed, the average heat transfer coefficient increases, the flow resistance increases and the heat transfer performance increases with the increase of the inlet flue gas velocity. The average heat transfer coefficient and heat transfer quantity of the heat exchanger increase with the increase of fin spacing and thickness. When the fin height is changed, the average heat transfer coefficient and heat transfer rate of the heat exchanger decrease with the decrease of the fin height. Finally, the economic evaluation of finned tube heat exchanger is carried out by using the static investment recovery period method, and the shortest economic recovery period is obtained.
【学位授予单位】：哈尔滨理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK229

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