火电SCR脱硝系统混合与均流CFD仿真

火电烟气脱硝系统能否达到高脱硝率与低氨气逃逸率,很大程度上取决于进入脱硝反应器之前烟气中的氮氧化物与还原剂氨气混合均匀程度和烟气速度分布。为此,需在脱硝反应器之前的烟道内安装烟气-氨混合器、导流板均流装置。采用计算流体力学仿真软件对烟道中的流态进行了仿真,结果表明,格栅型混合器的使用能够增强气体径向混合,改善烟气与氨气混合的均匀程度;在烟道转弯处加入导流板可以明显减少出口速度分布偏差。所用计算流体力学仿真软件可以给出烟道内任意位置的速度和浓度可视化输出,在经过流态模型实验的验证后,这些信息可以成为烟道内混合与均流装置优化设计的依据。     

烟气脱硝喷氨量SA-RBF神经网络最优控制

对于选择性催化还原(SCR)烟气脱硝装置喷氨量的精确控制,传统PID控制器的参数是基于设计负荷预先整定,在变工况下系统呈现出强非线性和滞后性,难以确保最佳控制量.通过引入动态结构的RBF神经网络,利用敏感度法来增加和删除神经元,解决RBF神经网络结构过大或过小的问题,保证预测网络结构的精度.该网络综合学习SCR脱硝装置主要相关参数,以NOx排放量与设定值之间误差最小作为训练信号,实现喷氨量的最优控制.实验结果表明,在变工况下,此方案与传统PID相比,能满足SCR出口NOx排放量,有效减少了氨气逃逸量,具有良好的变工况适应能力.     

基于CPSO-RBF神经网络喷氨量的最优控制

火力发电厂选择性催化还原脱硝控制方法中,由于PID控制算法具有较大的惯性和延迟,喷氨量的控制精度导致烟气出口NOx含量过高,不符合国家环保标准。因此,在分析脱硝喷氨控制影响因素基础上,建立选择性催化还原系统出口NOx的径向基函数神经网络预测模型,采用混沌局部搜索算法确定最大迭代步数,并利用混沌粒子群优化算法（CPSO）求取最优解,以实现喷氨量的最优控制。仿真实验结果表明：与传统的PID控制算法相比,提高了喷氨量的控制精确和脱硫效率,同时降低了氨气的逃逸率。     

烟气脱硝冷模气体供应管道仿真及验证

介绍了火力电站烟气脱硝冷态模型实验（FMT）装置的模拟气体供应管道计算流体力学（CFD）仿真方法,并建设了实际的冷模气体供应管道对仿真结果的验证,可用于指导火力电站脱硝工程中。在建设火力电站烟气脱硝冷态模型的项目中,氨气模拟气供应管道的建设质量是保证氨气在喷射进入烟气通道后均匀分布,从而达到提高脱硝效率的重要保障之一。因此,采用先进的计算流体力学（CFD）方法及软件,进行模拟气供应管道的仿真相当有必要。实际工程中,采用CFD软件FLUENT对供气管道进行网格化仿真,在取得满意仿真结果的基础上,进行实际的冷模供气管道建设和验证实验,获得了与仿真一致的结果。     

变论域模糊控制器单元机组SCR烟气脱硝控制研究

SCR烟气脱硝系统的脱硝率由喷氨量来控制,而喷氨流量控制系统控制喷氨量,因此,优化喷氨流量控制系统能有效提高脱硝率;设计了一种基于变论域的模糊控制器来实现喷氨量的优化控制,并采用 MATLAB 仿真软件对此控制方案进行仿真,并与传统的控制方案的结果进行对比分析;结果表明,基于变论域的模糊控制喷氨流量系统相对于传统的PID控制,其超调小,且鲁棒性较强,有效地提高了控制品质。     

600MW机组SCR系统环保指标及其经济性分析

在SCR脱硝系统运行中,氨气的喷入量应根据SCR反应器出口NOx浓度及保证的脱硝效率通过喷氨调节门进行调节。本文就某电厂2×600MW机组SCR系统实际运行情况进行分析计算,结合实际运行经验,探讨不同的负荷阶段不同的燃烧调整方案,供氨单耗实际情况。说明降低脱硝系统喷氨量要通过日常燃烧调整、设备定期维护等方法以降低脱硝入口NOx含量、氨气逃逸率等来实现,提高系统运行的经济性。     

SCR烟气脱硝系统鲁棒抗干扰控制研究

选择性催化还原(Selective Catalytic Reduction,SCR)技术是目前火电厂广泛采用的烟气脱硝方法,SCR脱硝系统反应过程复杂,具有大惯性、大迟延、强扰动和不确定性等特点,传统的PID控制无法实现喷氨量的精确控制。因此提出了一种SCR脱硝系统的鲁棒抗扰动控制方法,在设计鲁棒PID控制器的基础上,利用鲁棒时滞滤波器来达到抑制系统强干扰的目的。仿真实验表明,鲁棒时滞滤波器的加入改善了系统的动态性能,同时使得系统具有突出的抗干扰能力。该方法结构简单、整定方便、鲁棒性好,值得在工程应用中推广。     

贵州火电厂SCR脱硝运行情况分析

贵州火电目前主要燃用高硫份、高灰份煤,主要采用SCR脱硝技术,少部分电厂采用SCR+SNCR脱硝技术,在实际运行过程中出现了烟风系统积灰、空气预热器堵塞、脱硝催化剂损坏等问题,给正常生产运行带来很多安全隐患,影响机组安全、经济运行。为解决贵州省最近几年SCR脱硝技术运行中出现的问题,从原理上分析在高硫分、高灰分烟气环境下,因烟气系统各段堵灰,容易造成逃逸氨量大,硫酸氢氨堵塞的原因。通过总结近几年贵州各火力发电厂脱硝系统的治理经验,提出解决火电厂脱硝问题的关键,是通过调整烟气流场均匀性和喷氨均匀性来降低脱硝氨耗量,提出脱硝催化剂管理,热控元件维护的方法,锅炉长周期运行时可采用提高冷端综合温度,空预器冲洗、热分解等措施。     

SNCR在循环流化床DENOX技术探讨与应用

通过介绍循环流化床锅炉采用喷氨水SNCR技术脱硝系统的设计要点,细致分析了影响SNCR系统脱硝效率的因素,比如停留时间对NOx排放量的影响,反应温度范围、过剩空气系数、反应温度对氨逃逸量的影响等。这可帮助循环流化床锅炉控制以上影响因素,从而保证SNCR系统的烟气脱硝效率达到或超过50%以上。循环流化床锅炉自身具备的低氮燃烧特性,配以SNCR技术脱硝,可以将锅炉NOx排放浓度控制在100 ppm以下。     

组态王在烟气脱硝中的应用

随着国内经济发展,火电厂锅炉烟气排放指标控制越加严格,火电厂烟气污染物的排放越来越受到国家和社会的广泛关注。锅炉烟气脱硫技术已经在国内全面普及,作为脱硝还原剂液氨的运用由于受到安全、地域等因素的限制,尿素热解制氨技术逐渐受到青睐。本文重点介绍介绍组态王6.53在尿素烟气脱硝监控系统中的应用。     

Estimation and adaptive nonlinear model predictive control of selective catalytic reduction systems in automotive applications

The demands of high NO_x conversion efficiency and low tailpipe ammonia slip for urea-based selective catalytic reduction (SCR) systems have been substantially increased in the past decade, as NO_x emission legislations for Diesel engines are becoming more stringent than ever before. Since catalyst aging has a significant impact on SCR performance, robust and adaptive SCR control has been preferred for degraded SCR systems to realize emission control objectives. The purpose of this paper is twofold. Firstly, a robust ammonia coverage ratio observer was designed for estimating the ammonia coverage ratio reference for catalysts with different aging levels. An ammonia storage capacity observer was developed for estimating the actual ammonia storage capacity which can be reduced due to catalyst aging. An adaptive ammonia coverage ratio reference design was then developed to estimate the desired ammonia coverage ratio ranges at each instantaneous engine operating point for both single-cell and two-cell SCR systems at different aging levels based on a singular perturbation method. Secondly, to ensure the estimated ammonia coverage ratio falls in the desired ranges for most of engine operating conditions, robust nonlinear model predictive control (NMPC) algorithms were designed for both single-cell and two-cell SCR systems. Experimental data over US06 cycle were collected from a Diesel engine and aftertreatment system platform for controller verification. Simulation results under US06 test cycle demonstrate that the proposed NMPC algorithms were capable of consistently achieving high NO_x conversion efficiency (>95.6%) and constrained tailpipe ammonia slip (<10 ppm on average and <12 ppm on the peak) for both fresh catalyst and aged catalyst with 30% loss of ammonia storage capacity.     

Monolithic sensor array based on a quartz microbalance transducer with enhanced sensitivity for monitoring agricultural emissions

A low-cost sensor array system for agricultural applications is presented. The sensor array is based on a quartz crystal microbalance (QMB) transducer with a novel heating structure. Selective host molecules are used as gas-sensitive layers. The gas-sensitive layers were optimized for the selective detection of ammonia at varying humidity concentrations. A mode of operation is presented which allows on-line monitoring of ammonia without a reference gas (RG). In addition, this temperature modulation (TM) mode improves the signal-to-noise ratio of the sensors compared to the usually applied RG mode. Multivariate regression models are applied on the sensor array data to selectively predict the ammonia concentration in agricultural emissions.     

Cold start modelling of spark ignition engines

The ability of mean value models to replicate the key characteristics of automotive powertrains has been well established over the past four decades. There has been considerable success in the application of these models to controller design, with improved emissions and performance of the primary benefits. However, these low order models typically must make certain assumptions about the engine—with constant temperature operation a standard approximation. As economy and emissions at every point in the drive cycle become scrutinised, the cold start operation of the engine becomes more critical and the constant temperature assumption is limiting. This paper seeks to develop a model framework for capturing the temperature transients and gaseous concentrations throughout the engine. A methodology for calibrating the model is also presented, and uses a combination of steady state and transient testing. Finally, certain states in the full model are eliminated to produce a family of reduced order models, with the intention of outlining the minimum complexity required for control and optimisation studies with differing objectives.     

Field experiments on greenhouse gas emissions and nitrogen and phosphorus losses from rice paddy with efficient irrigation and drainage management

Greenhouse gas emissions,nitrogen and phosphorous losses through ammonia volatilization,leaching and surface drainage from rice paddy under efficient irrigation and drainage were analyzed based on field experimental data in order to reveal the eco-environmental impacts of efficient irrigation and drainage on rice paddy.The results showed that total methane emission from rice paddy under the controlled irrigation was reduced by more than 80% and total nitrous oxide emission increased by 15.9% compared with f...     

LPV gain-scheduled control of SCR aftertreatment systems

Hydrocarbons, carbon monoxide and some of other polluting emissions produced by diesel engines are usually lower than those produced by gasoline engines. While great strides have been made in the exhaust aftertreatment of vehicular pollutants, the elimination of nitrogen oxide (NO _x ) from diesel vehicles is still a challenge. The primary reason is that diesel combustion is a fuel-lean process, and hence there is significant unreacted oxygen in the exhaust. Selective catalytic reduction (SCR) is a well-developed technology for power plants and has been recently employed for reducing NO _x emissions from automotive sources and in particular, heavy-duty diesel engines. In this article, we develop a linear parameter-varying (LPV) feedforward/feedback control design method for the SCR aftertreatment system to decrease NO _x emissions while keeping ammonia slippage to a desired low level downstream the catalyst. The performance of the closed-loop system obtained from the interconnection of the SCR system and the output feedback LPV control strategy is then compared with other control design methods including sliding mode, and observer-based static state-feedback parameter-varying control. To reduce the computational complexity involved in the control design process, the number of LPV parameters in the developed quasi-LPV (qLPV) model is reduced by applying the principal component analysis technique. An LPV feedback/feedforward controller is then designed for the qLPV model with reduced number of scheduling parameters. The designed full-order controller is further simplified to a first-order transfer function with a parameter-varying gain and pole. Finally, simulation results using both a low-order model and a high-fidelity and high-order model of SCR reactions in GT-POWER interfaced with MATLAB/SIMULINK illustrate the high NO _x conversion efficiency of the closed-loop SCR system using the proposed parameter-varying control law.     

面向NOx脱除率优化的烟气脱硝CFD仿真研究

烟气脱硝的技术关键是还原剂与烟气混合要尽可能均匀,混合气体通过催化剂层时速度分布要尽可能均匀.以600 MW超临界燃煤火力电站烟气脱硝(DeNOx)系统为对象,对还原剂氨和烟气的混合过程进行了计算流体力学仿真,研究了关键导流板对喷氨格栅前烟气速度分布和催化剂入口处烟气速度分布的影响,并确定其尺寸及安装位置.为提高催化剂入口氨浓度分布的均匀性,根据喷氨格栅处烟道截面速度分布特点,通过仿真寻优,得到了非均匀喷氨流量设定值.     

The Potential Gains from Carbon Emissions Trading in China’s Industrial Sectors

The command and control mechanism and the market trading mechanism have been adopted by Chinese government to reduce the industrial carbon emissions. Concerns have arisen over which policy is more effective and what are the potential gains from carbon emissions trading for industrial sectors. A Data Envelopment Analysis based linear programming technology is used to compare the industrial potential gains including both the economic potential gains and the environmental potential gains from the command and control and carbon emissions trading mechanisms. An empirical study containing the data set of 38 sub-industries in China from 2006–2014 is conducted. The empirical results show that the carbon emissions trading mechanism can produce more potential gains compared with the command and control mechanism, with an average of 69.6 and 92.0% economic potential gains and 49.1 and 21.0% environmental potential gains in terms of the overall level and industrial level, respectively. Additionally, the environmental potential gains of each sub-industry can provide theoretical support for the emission quotas allocation. Finally, several policy implications based on the empirical results are proposed.     

考虑排污权交易的有限理性企业博弈模型研究

在有限理性基础上建立寡头垄断博弈模型,将其引入到排污权市场中,同时考虑了生产成本、污染治理成本、排污权交易价格的影响,使该模型更符合实际。将不同理性层次,不同结构的非线性成本函数,不完全信息等因素引入到博弈模型中,对改进后的模型的演化过程进行分析,找出博弈均衡点,并分析其稳定性。由于具有有限理性的双寡头Cournot博弈模型会产生丰富的动力学行为,因此对其进行数据模拟后并对混沌现象进行分析。在此基础上,运用延迟反馈控制法对寡头垄断博弈模型的混沌控制进行了解析分析,结果表明选择合适的控制因子可使模型稳定在Nash均衡。