煅烧炉冷却水套三维传热特性的数值模拟与结构优化研究

发布时间：2018-01-13 07:02

本文关键词：煅烧炉冷却水套三维传热特性的数值模拟与结构优化研究　出处：《山东大学》2017年硕士论文　论文类型：学位论文

【摘要】：炭素行业中高温煅后焦在冷却水套内的冷却过程是石油焦煅烧工艺中很关键的一个环节,然而现今行业内普遍使用的夹套式冷却水套对高温煅后焦的冷却效果较差。一方面高温物料内部热量不易及时导出,冷却后焦料温度依然较高,易发生氧化,对石油焦颗粒的质量及后续工艺产生较大不利影响;另一方面中空夹套内的冷却水流速过小且分布不均,存在漩涡区,易发生汽化,影响水套的传热,因此研究水套内的传热特性以改善其换热性能迫在眉睫。本文首先使用GAMBIT软件建立了罐式煅烧炉冷却水套的几何模型,并对建立的模型划分网格,采用FLUENT软件,分别选用Mixture模型和多孔介质模型对高温焦料侧进行模拟计算,通过数值计算与实验结果的对比验证了模型的准确性,验证结果表明这两种模型可准确地对物料侧的温度场进行数值计算。其次,对单罐产量为80kg/h的煅烧炉冷却水套进行了传热特性分析,得到了冷却水侧的速度场、温度场、物料侧的温度场以及冷却水、焦料的出套温度等重要参数的演变规律,以焦料出口温度和冷却效率为评价指标,分析了夹套式水套的换热弊端。在此基础上,改变冷却水流量并进行计算,由结果可知,冷却水流量增大为原来的2倍时,焦料出口平均温度仅降低1.33K,说明增加冷却水入口流量并不能提高水套冷却效率。同时分析了焦料流量和空隙率对水套换热性能的影响,结果表明:在焦料流量从40kg/h增大到130kg/h时,焦料出口平均温度及最高温度出现单调增加的趋势,且增长斜率逐渐变小,焦料出口平均温度由552K增加到777.89K;随着焦料空隙率的增加,焦料出口平均温度及最高温度有所减小,但变化幅度不大。最后,基于水侧和焦料侧的传热分析,提出了水套的结构优化方案,并进行了优化后传热性能的数值计算研究。在冷却水侧分别布置了螺旋导流板和竖直导流板,研究结果表明:在相同的入口流量下,优化后冷却水流速大幅提高,水套内水流流动顺畅,尤其是螺旋导流板方案不存在漩涡区和局部高温区,流场和温度场分布更加均匀,不易发生汽化,即使在入口水速较小的情况下发生汽化,产生的水蒸气也能顺着流道及时排出,但水侧结构优化后中心区域焦料温度基本没有变化。因此本文提出了在焦料侧采用布置内换热管束的优化措施,首先计算分析了焦料内部布置单根换热管时的传热性能,结果表明,加入单根换热管后,水套传热性能得到了极大改善,与优化前相比焦料出口平均温度降低了 103.59K,水套冷却效率提高了 19.58%;而且随着换热管高度的增加,焦料出口平均温度单调降低且降低的斜率基本保持不变;基于内置单根换热管水套,研究了内换热管入口水速在0.08～0.4m/s之间变化时水套传热的变化,在计算流速范围内,出口焦料的平均温度仅降低0.77K,表明水速的增加并未显著提高水套的冷却能力。最后通过焦料的温度场和温度分布曲线确定了内换热管束的优化布置方案,与优化前相比,按照优化布置方案布置七根换热管束,焦料出口平均温度由721.95K降低至428.06K,出口温度不均匀系数由0.24降低至0.135,水套冷却效率由55.51%提高至 86.35%。本文结论为煅烧炉冷却水套的结构优化指明了方向,为下一步的工程应用奠定了理论基础。
[Abstract]:Carbon industry in high temperature calcined coke in the cooling water jacket in the cooling process is calcined petroleum coke is a key link in the process, however, the widespread use of the current industry jacket cooling water on the cooling effect of poor high temperature calcined coke. A heat of high-temperature material inside can not be easily timely export, after cooling coke the material temperature is still high, prone to oxidation, have a greater adverse effect on the quality and the subsequent process of petroleum coke particles; on the other hand, the cooling water jacket of the hollow speed is too small and uneven distribution, existence of vortex, easy vaporization, heat transfer effect of the water jacket, the heat transfer characteristics of water jacket in order to improve its the heat transfer performance is imminent. This thesis firstly uses the GAMBIT software to establish the geometric model of tank type calcining furnace cooling water jacket, and the establishment of the model grid, using FLUENT software, we select Mixture model and porous media Quality model is used to simulate the high temperature coke material side, by comparing the numerical and experimental results verify the accuracy of the model, the results show that the two models can be calculated accurately on the material side of the temperature field. Secondly, on the analysis of heat transfer characteristics of single tank production furnace cooling water jacket 80kg/h. The velocity field, the cooling water side temperature field, temperature field and material side of the cooling water, coke material out important parameters of temperature evolution in coke outlet temperature and the cooling efficiency as the evaluation index, analyzes the drawbacks in the jacketed hot water jacket. On this basis, the change of cooling water the flow is calculated, the result shows that the cooling water flow rate increases to 2 times of the original, coke outlet average temperature decreases only 1.33K, indicating that the increase of cooling water flow entrance does not improve efficiency. At the same time the analysis of jacket cooling coke material The flow and the influence of porosity on the heat transfer performance of the water jacket, the results showed that: in the coke material flow increased from 40kg/h to 130kg/h, the coke outlet average temperature and maximum temperature monotonically increasing trend, and the growth of the slope becomes smaller, the coke outlet average temperature increased from 552K to 777.89K with increasing porosity of coke materials; the coke outlet average temperature and maximum temperature decreased, but little change. Finally, the water side heat transfer analysis and coke material side based on the proposed structure optimization scheme of water jacket, and the numerical heat transfer performance optimization calculation. The spiral plate and vertical plates are respectively arranged in the cooling the side of the water, the results show that: in the entrance flow under the same water flow rate increase after optimization of cooling water jacket, smooth flow, especially there is no vortex and local high temperature zone spiral plate, flow field and temperature Temperature field distribution is more uniform, not easy to vaporize, vaporization occurs even at the entrance velocity of water is small, water vapor generated along the channel can be discharged, but the water side after the optimization of the structure of regional center focal material temperature changes a little. So this paper put forward the optimization measures were adopted in the focal material side arrangement of heat exchanger the bundle, first calculate the heat transfer performance of coke, material arranged inside the single heat exchange tube when the analysis results show that the addition of single tube heat exchanger, the heat transfer performance of the water jacket has been greatly improved, compared with before the optimization of coke outlet average temperature decreased 103.59K, water cooling efficiency is improved by 19.58%; and with the heat pipe height the increase of the slope material coke average exit temperature decreases monotonically with the decreasing basically unchanged; the built-in single heat exchange tube jacket based on the heat exchanger in the entrance velocity of water between 0.08 ~ 0.4m/s change when water jacket The change of heat transfer, in the calculation of velocity range, the average temperature of coke export material only decreased 0.77K, shows that with the increase of water velocity did not significantly increase the cooling capacity of water jacket. The coke material temperature field and temperature distribution curve was determined in the heat exchanger optimization layout scheme optimization, compared with before, in accordance with the layout optimization the arrangement of seven heat transfer tubes, coke outlet average temperature is decreased from 721.95K to 428.06K, the non-uniform exit temperature coefficient decreased from 0.24 to 0.135, water cooling efficiency increased from 55.51% to 86.35%. the conclusion of this paper for cooling water jacket calciner structure optimization direction, laid the theoretical foundation for the engineering application of the next step.

【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE626.87

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