SCR法烟气脱硝系统数值模拟研究
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摘要
随着新的污染物排放标准的颁布,烟气脱硝技术面临着前所未有的压力和挑战。如何经济、有效地提高脱硝效率,降低NO_x的排放量,成为大气环境污染控制工作者研究的热点问题。随着数值计算技术的发展,利用高效、便捷的计算流体力学软件对SCR法脱硝系统进行仿真为混合器和气流分布板的设计、改造提供了重要参数。其缩短了工程周期,减少了试验的盲目性,对提高SCR法脱硝系统的环境效益、社会效益和经济效益均具有重要的意义。
根据本试验室现有设备条件和发展方向,本课题采用数值模拟的方法进行SCR法烟气脱硝系统内NH_3的掺混和气流流场情况试验研究。最终以计算流体动力学理论为指导探索出了适合于SCR法脱硝系统数值模拟的方法和规律。
本文得出的主要结论如下:
(1)使用计算流体动力学软件—FLUENT软件,采用标准κ-ε模型、物质输运模型和多孔介质模型对SCR法烟气脱硝系统中的流场、物质掺混和压力场进行数值模拟计算,计算方法可靠,计算结果合理。
(2)原模型设计混合器时共设计了八片连续混合器全长一米,其压力损失过大增加了引风机负荷并且制造费用较高。现数值模拟结果表明采用两组四片间隔250mm布置方案的混合器布置方式完全可以达到掺混要求并减少了压力损失降低了制造成本。
(3)在经过几十组的模型调整后最终确定了多向组合导流片的布置方式。对其模拟结果分析表明流场均布情况满足工况要求,其断面流速均方根值达到美国RMS标准合格要求并且接近良好。
With the promulgation of the new emission standard of air pollutants, the flue gas denitration faces great pressure and challenges. How to improve the denitrated efficiency economically and effectively, and reduce the quantity of NO_x emission become research focuses. With the development of numerical calculation techniques, the numerical simulation becomes a means to solve these problems gradually. Effective CFD software is used to simulate the SCR De-NO_x system, which offers important parameters for the design and alteration of the mixing device and airflow distribution. It shortens engineering period and reduces blindness in experiment in SCR DE-NO_x system, which is beneficial to our environment, society, and economy.
Under the equipmental conditions and development directions of our laboratory, numerical simulation methods is utilized to study mass transfer and airflow distribution in SCR De-NO_x system in this subject. Finally, this subject also explores the suitable methods and rules of numerical simulation of SCR DE-NO_x system.
In this paper, the main conclusions are as follows:
(1) The computational fluid dynamics software - FLUENT software, standardκ-εmodel, and multi-holes medium model are used to simulate the flow field, material transport, and pressure field of SCR DE-NO_x system, which shows reliable and rational simulation results.
(2) The original model of mixer layout consisting of eight consecutive pieces causes too much pressure loss, increased fan load and higher manufacturing cost. Simulation results show that mixer layout consisting of four pieces with spacing of 250mm can achieve mixing effect and reduce pressure loss and manufacturing cost.
(3) The satisfying layout model is the combination of multi-diversion. Simulation results of the model show that the flow conditions meet the requirements of operating mode. The velocity mean square root meets requirements and is close to the United States RMS standard.
根据本试验室现有设备条件和发展方向,本课题采用数值模拟的方法进行SCR法烟气脱硝系统内NH_3的掺混和气流流场情况试验研究。最终以计算流体动力学理论为指导探索出了适合于SCR法脱硝系统数值模拟的方法和规律。
本文得出的主要结论如下:
(1)使用计算流体动力学软件—FLUENT软件,采用标准κ-ε模型、物质输运模型和多孔介质模型对SCR法烟气脱硝系统中的流场、物质掺混和压力场进行数值模拟计算,计算方法可靠,计算结果合理。
(2)原模型设计混合器时共设计了八片连续混合器全长一米,其压力损失过大增加了引风机负荷并且制造费用较高。现数值模拟结果表明采用两组四片间隔250mm布置方案的混合器布置方式完全可以达到掺混要求并减少了压力损失降低了制造成本。
(3)在经过几十组的模型调整后最终确定了多向组合导流片的布置方式。对其模拟结果分析表明流场均布情况满足工况要求,其断面流速均方根值达到美国RMS标准合格要求并且接近良好。
With the promulgation of the new emission standard of air pollutants, the flue gas denitration faces great pressure and challenges. How to improve the denitrated efficiency economically and effectively, and reduce the quantity of NO_x emission become research focuses. With the development of numerical calculation techniques, the numerical simulation becomes a means to solve these problems gradually. Effective CFD software is used to simulate the SCR De-NO_x system, which offers important parameters for the design and alteration of the mixing device and airflow distribution. It shortens engineering period and reduces blindness in experiment in SCR DE-NO_x system, which is beneficial to our environment, society, and economy.
Under the equipmental conditions and development directions of our laboratory, numerical simulation methods is utilized to study mass transfer and airflow distribution in SCR De-NO_x system in this subject. Finally, this subject also explores the suitable methods and rules of numerical simulation of SCR DE-NO_x system.
In this paper, the main conclusions are as follows:
(1) The computational fluid dynamics software - FLUENT software, standardκ-εmodel, and multi-holes medium model are used to simulate the flow field, material transport, and pressure field of SCR DE-NO_x system, which shows reliable and rational simulation results.
(2) The original model of mixer layout consisting of eight consecutive pieces causes too much pressure loss, increased fan load and higher manufacturing cost. Simulation results show that mixer layout consisting of four pieces with spacing of 250mm can achieve mixing effect and reduce pressure loss and manufacturing cost.
(3) The satisfying layout model is the combination of multi-diversion. Simulation results of the model show that the flow conditions meet the requirements of operating mode. The velocity mean square root meets requirements and is close to the United States RMS standard.
引文
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[21]李晓芸,赵毅,王修彦.火电厂有害气体控制技术[M].北京:中国水利水电出版社,2005:144-182.
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[26]Sarna.Supported VPO catalysts for selective oxidation of butane[J].Catal Today.2004,43:101-110
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[28]Baltensperger U,Markus A.Use of Positron-Emitting N for Studies of the Selective Reduction of NO by NH_3 over Vanadia/Titania Catalyst at Very Low Reactant Concentrations[J].Electric Power.2003,97:123-125.
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[30]涂建华,袁伟峰,朱培军.气流分布的等效阻力法模拟计算[J].环境工程,2004,22(5):37-39.
[31]杨文生,赵心夏.改进气流分布板提高电收尘器收尘效率的有效途径[J].西南民族大学学报,2003,29(3):347-351.
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