Wet flue gas desulfurization performance of 330 MW coal-fired power unit based on computational fluid dynamics region identification of flow pattern and transfer process

Wet Flue Gas Desulfurization(WFGD)unit based upon spray scrubber has beenwidely employed to control SO_(2) emissions from flue gas in coal-fired power plant.To clarify the dependence of desulfurization performance on inter-phase transfer behaviors with non-ideal contacting patterns of flue gas and slurry droplets,three regions in spray scrubber are distinguished in terms of gas-slurry flow structures using CFD method in the Eulerian-Lagrangian framework.A comprehensive model is established by involving the transfer process between two phases and chemical reactions in aqueous phase,which is validatedwith the measured data froma WFGD scrubber of 330 MW coal-fired power unit.Numerical results show that the overall uniformity degree of flue gas in whole scrubber is largely determined by the force-balanced droplets in the middle part of scrubber,which is dominated by counter-current mode.Both momentum transfer behavior and SO_(2) chemical absorption process present the synchronicity with the evolution of gas-slurry flow pattern,whilst the heat transfer together with H_(2)O evaporation has little effect on overall absorption process.Three regions are firstly defined as Gas Inlet Region(GIR),Dominant Absorption Region(DAR)and Slurry Dispersed Region(SDR)from the bottom to top of scrubber.SO_(2) is mainly scrubbed in DAR,which provides much more intensive interaction between two phases compared to GIR or SDR.A better understanding of the desulfurization process is obtained from the fundamental relationship between transport phenomena and chemical reactions based upon the complicated hydrodynamics of gas-slurry two-phase flow,which should be useful for designing and optimizing the scrubber in coal-fired power unit.

Ternary System of Fe-based Ionic Liquid,Ethanol and Water for Wet Flue Gas Desulfurization

Fe-based ionic liquid （Fe-IL） was synthesized by mixing FeCl3·6H2O and 1-butyl-3-methylimidazolium chloride [Bmim]C1 in this paper. The phase diagram of a ternary Fe-IL, ethanol and water system was investigated to construct a ternary desulfurization solution for wet flue gas desulfurization. The effects of flow rate and concentration of SO2, reaction temperature, pH and Fe-IL fraction in aqueous desulfurization solution on the desulfiariza- tion efficiency were investigated. The results shows that the best composition of ternary desulfurization solution of Fe-IL, ethanol and water is 1 ： 1.5 ： 3 by volume ratio, and pH should be controlled at 2.0. Under such conditions, a desulfurization rate greater than 90% could be obtained. The product of sulfuric acid had inhibition effect on the wet desulfurization process. With applying this new ternary desulfurization solution, not only the catalyst Fe-IL can be recycled and reused, but also the product sulfuric acid can be separated directly from the ternary desulfurization system.

Removal of SO_2 from flue gas using Bayer red mud:Influence factors and mechanism

The absorbent composing of Bayer red mud and water was prepared and applied to removing SO2 from flue gas.Effects of the ratio of liquid to solid(L/S),the absorption temperature,the inlet SO2 concentration,the O2 concentration,SO4^2-and other different components of Bayer red mud on desulfurization were conducted.The mechanism of flue gas desulfurization was also established.The results indicated that L/S was the prominent factor,followed by the inlet SO2 concentration and the temperature was the least among them.The optimum condition was as follows:L/S,the temperature and the SO2 concentration were 20:1,25℃and 1000 mg/m^3,respectively,under the gas flow of 1.5 L/min.The desulfurization efficiency was not significantly influenced when O2 concentration was above 7%.The accumulation of SO4^2-inhibited the desulfurization efficiency.The alkali absorption and metal ions liquid catalytic oxidation were involved in the process,which accounted for 98.61%.

Investigation on the relationship between the fine particle emission and crystallization characteristics of gypsum during wet flue gas desulfurization process

The relationship between the fine particles emitted after desulfurization and gypsum crystals in the desulfurization slurry was investigated,and the crystallization characteristics varying with the operation parameters and compositions of the desulfurization slurry were discussed.The results showed that the fine particles generated during the desulfurization process were closely related to the crystal characteristics in the desulfurization slurry by comparison of their morphology and elements. With the higher proportion of fine crystals in the desulfurization slurry,the number concentration of fine particles after desulfurization was increased and their particle sizes were smaller,indicating that the optimization of gypsum crystallization was beneficial for the reduction of the fine particle emission. The lower p H value and an optimal temperature of the desulfurization slurry were beneficial to restrain the generation of fine crystals in the desulfurization slurry. In addition,the higher concentrations of the Fe3＋ions and the F- ions in the desulfurization slurry both promoted the generation of fine crystals with corresponding change of the morphology and the effect of the Fe3＋ ions was more obvious.With the application of the desulfurization synergist additive,it was beneficial for the inhibition of fine crystals while the thinner crystals were generated.

Model Free Adaptive Predictive Control of Desulfurization Slurry pH Based on CPS Framework

In order to improve the slurry pH control accuracy of the absorption tower in the wet flue gas desulfurization process,a model free adaptive predictive control algorithm for the desulfurization slurry pH which is based on a cyber physical systems framework is proposed.First,aiming to address system characteristics of non-linearity and pure hysteresis in slurry pH change process,a model free adaptive predictive control algorithm based on compact form dynamic linearization is proposed by combining model free adaptive control algorithm with model predictive control algorithm.Then,by integrating information resources with the physical resources in the absorption tower slurry pH control process,an absorption tower slurry pH optimization control system based on cyber physical systems is constructed.It is turned out that the model free adaptive predictive control algorithm under the framework of the cyber physical systems can effectively realize the high-precision tracking control of the slurry pH of the absorption tower,and it has strong robustness.

Effect of wet flue gas desulfurization(WFGD) on fine particle(PM_(2.5)) emission from coal-fired boilers

In this study, the characteristics of fine particles before and after wet flue gas desulfurization(WFGD) in three coal-fired heating boilers in northern China were investigated by using a dilution-based emission sampling experimental system. The influences of the WFGD process on the mass and number concentrations as well as the chemical composition of fine particles were analyzed. The removal efficiency of desulfurization processes on particulate matter mass was 30.06%–56.25% for the three study units. The WFGD had a great influence on the size distributions of particle mass concentration and number concentration. A significant increase in the number and mass concentration of particles in the size range of 0.094–0.946 μm was observed. The watersoluble ion content accounted for a very large proportion of PM_(2.5) mass, and its proportion in PM_(2.5) increased from 28.39%–41.08% to 48.96%–61.21% after the WFGD process for the three units. The desulfurizing process also drastically increased the proportion of cation component(Ca^(2+) for unit A, Mg^(2+) for unit B, and Na+for unit C) and the proportion of SO_4^(2-) in PM_(2.5), and it increased the CE/AE values of PM_(2.5) from 0.82–0.98 to 0.93–1.27 for the three study units.

Transformation and removal of ammonium sulfate aerosols and ammonia slip from selective catalytic reduction in wet flue gas desulfurization system

Selective catalytic reduction(SCR) denitration may increase the emission of NH4+and NH3.The removal and transformation characteristics of ammonium sulfate aerosols and ammonia slip during the wet flue gas desulfurization(WFGD) process, as well as the effect of desulfurization parameters, were investigated in an experimental system equipped with a simulated SCR flue gas generation system and a limestone-based WFGD system.The results indicate that the ammonium sulfate aerosols and ammonia slip in the flue gas from SCR can be partly removed by slurry scrubbing, while the entrainment and evaporation of desulfurization slurry with accumulated NH4+will generate new ammoniumcontaining particles and gaseous ammonia.The ammonium-containing particles formed by desulfurization are not only derived from the entrainment of slurry droplets, but also from the re-condensation of gaseous ammonia generated by slurry evaporation.Therefore,even if the concentration of NH4+in the desulfurization slurry is quite low, a high level of NH4+was still contained in the fine particles at the outlet of the scrubber.When the accumulated NH4+in the desulfurization slurry was high enough, the WFGD system promoted the conversion of NH3 to NH4+and increased the additional emission of primary NH4+aerosols.With the decline of the liquid/gas ratio and flue gas temperature, the removal efficiency of ammonia sulfate aerosols increased, and the NH4+emitted from entrainment and evaporation of the desulfurization slurry decreased.In addition, the volatile ammonia concentration after the WFGD system was reduced with the decrease of the NH4+concentration and p H values of the slurry.

基于深度AttLSTM网络的脱硫过程建模

脱硫过程是具有高度动态非线性和较大延迟时间的复杂工业过程,为了解决烟气脱硫过程的建模问题,设计了注意力机制下的深度长短期记忆(attention mechanism-based long short-term memory,AttLSTM)网络,并基于该网络设计自动编码器,完成脱硫过程异常点的检测。该文首次提出使用AttLSTM网络自编码器对脱硫过程进行离群点检测,并且该网络模型同样首次应用于脱硫过程的辨识任务中。从更深的意义上讲,该文尝试使用深度学习模型对复杂系统进行辨识,所建立的AttLSTM网络之前未出现在系统辨识领域,该网络的出现可以丰富辨识模型的选择,同时为人工智能技术在系统辨识领域和控制领域的应用与推广提供参考。实验结果表明,相比于之前文献出现的脱硫过程建模方法,所提方法在不同性能指标上均具有更好的表现,由此可以证明深度AttLSTM网络在脱硫场景下的有效性。

Low-temperature oxidation behavior and mechanism of semi-dry desulfurization ash from iron ore sintering flue gas

The low-temperature wet oxidation behavior of semi-dry desulfurization ash from iron ore sintering flue gas in ammonium citrate solution was investigated for efficiently utilizing the low-quality desulfurization ash. The effects of the ammonium citrate concentration, oxidation temperature, solid/liquid ratio, and oxidation time on the wet oxidation behavior of desulfurization ash were studied. Simultaneously, the oxidation mechanism of desulfurization ash was revealed by means of X-ray diffraction, Zeta electric resistance, and X-ray photoelectron spectroscopy (XPS) analysis. Under the optimal conditions with ammonium citrate, the oxidation ratio of CaSO_(3) was up to the maximum value (98.49%), while that of CaSO_(3) was only 8.92% without ammonium citrate. Zeta electric resistance and XPS results indicate that the dissolution process of CaSO_(3) could be significantly promoted by complexation derived from the ammonium citrate hydrolysis. As a result, the oxidation process of CaSO_(3) was transformed from particle oxidation to SO_(3)^(2−) ion oxidation, realizing the rapid transformation of desulfurization ash from CaSO_(3) to CaSO_(4) at low temperature. It provides a reference for the application of semi-dry desulfurization ash and contributes to sustainable management for semi-dry desulfurization ash.

石灰石—石膏湿法烟气脱硫自动控制研究

本文通过对石灰石—石膏湿法烟气脱硫工艺进行深入分析,梳理系统、设备、仪表运行逻辑,制定了石灰石—石膏湿法烟气脱硫自动控制策略,实现了石灰石—石膏湿法烟气脱硫自动运行,且运行后各参数均能稳定在合理区间,保证了电厂烟囱SO2排放值符合环保要求。

窑尾烟气脱硫工艺分析对比及实际应用

简述了某公司4000t/d水泥熟料生产线脱硫工程概况,就湿法和半干法脱硫工艺的特点及应用情况进行了比较,详细介绍了脱硫方案的选用原则及该工程选用石灰石-石膏脱硫系统的配置情况。系统投运后,该生产线窑尾主烟囱出口二氧化硫排放浓度降至30mg/Nm^(3),优于国家和山东省最新排放标准。生产线脱硫剂全部采用窑尾回灰,年可节约成本约53万元,副产物脱硫石膏可直接应用于水泥生产,年可造创经济效益约28万元。

火电厂湿法烟气脱硫废水处理施工技术分析

湿法烟气脱硫工作中,在对塔浆料中的水分进行再利用和吸收时,其中含有大量的重金属元素和Cl-元素,因此脱硫设备的腐蚀速率会大大加快,同时也会直接影响石膏整体质量。基于此,分析了多种火电厂湿法脱硫废水处理技术,通过沉淀、中和、絮凝等方法对废水进行排放和回收利用,以此提高火电厂湿法烟气脱硫废水处理质量,减少污水排放对环境的污染,优化环境质量。

新型急冷脱酸工艺在危废焚烧烟气净化中的应用

焚烧是危险废物处置常用的方式之一,焚烧烟气净化系统是烟气达标排放的重要保障。传统危废焚烧干法烟气净化工艺,存在脱酸效率低、设备易堵塞的问题,同时湿法脱酸工艺存在脱酸废水产生量大、处理成本高、处理难度大等缺点。针对最新危险废物焚烧设施烟气排放标准,开发了新型急冷脱酸烟气净化工艺,能够同时满足高温烟气处理的急冷和脱酸要求,实现废水近零排放,达到节能降耗、降低运行成本的效果。目前新型急冷脱酸烟气净化工艺已经在实际生产中得到应用,效果显著,烟气出口指标远低于国家最新排放标准。本文简要介绍了新型急冷脱酸工艺流程、反应机理和控制逻辑。通过在工艺流程、烟气净化效果、烟气净化成本和飞灰产生率等方面与湿法脱酸技术进行比较,突出了新型急冷脱酸工艺的应用优势。

双碱法烟气脱硫工艺的研究

以旋流板塔为脱硫塔 ,实验研究了Na2 CO3 Ca(OH) 2 双碱法脱硫工艺 .试验了不同液气比L G、Na+浓度、吸收液pH值和进气SO2 浓度等主要参数对脱硫率的影响 ,并考察了Na+的损失与操作条件的关系 .分析了双碱法脱硫过程的传质反应过程机理以及不同pH值对脱硫率的影响 .此外 。

钙法烟气脱硫技术研究进展

综述了湿法、干法与半干法 3种钙法烟气脱硫技术的主要特点、脱硫机理及主要影响因素。对

石灰石-石膏湿法烟气脱硫过程的试验研究

利用所建立的并流有序降膜式湿法脱硫装置,对石灰石-石膏湿法烟气脱硫过程进行了试验研究。试验结果表明:沿烟气行程上,脱硫率上升趋势逐步减弱,脱硫率较高时,再提高脱硫率,吸收段高度或液气比要大幅增加,火电厂机组在确定脱硫系统脱硫率时,应有适当选择;脱硫浆液pH值下降,且在吸收塔入口至0.5 m范围内,浆液pH值下降迅速,而后下降变缓;浆液中石灰石含量下降趋势逐步增强;同时浆液中Ca2+、六价硫S6+及四价硫S4+浓度均增加,Ca2+、S6+浓度增加使得石膏过饱和度有所增加。

烧结脱硫石膏的综合利用现状

近年来,烧结烟气脱硫石膏的利用正在被越来越多的人重视,本文在总结国内外烧结脱硫石膏的研究和应用现状的基础上,就其存在的一些问题和发展趋势提出几点自己的看法,并结合脱硫石膏性质提出了一些烧结脱硫石膏的资源化利用途径和建议。

一种新的湿法脱硫强制氧化技术

强制氧化是防止湿法脱硫系统结垢和堵塞以及脱硫废渣二次污染问题的关键。文中提出将射流曝气技术应用于石灰石 /石膏湿法脱硫的强制氧化工艺 ,并利用双膜理论针对射流曝气强制氧化工艺的气液相际传质特点进行了理论分析 ,结果表明 ,射流曝气器作为一种气液两相介质化学反应传质混合设备 ,充分利用强烈混合作用 ,提高了能量的综合利用率 ,对某湿法脱硫工程能耗的计算结果表明 :采用射流曝气方式能耗节省达 2 0 %以上 ,脱硫成本降低 ,有利于实现关键脱硫设备的国产化。

石灰湿法脱硫传质－反应过程机理

对以族流板塔作吸收器的石灰湿法烟气脱硫技术进行了试验研究，分析了石灰浆液吸收ＳＯ２的传质－反应过程，并提出了Ｃａ（ＯＨ）２浆液吸收ＳＯ２的传质－反应过程机理。本机理认为，总反应速度由气相中ＳＯ２的扩散（气相阻力）和液相中Ｃａ（ＯＨ）２固体的溶解（包括在液相阻力之内）及扩散控制；同时认为，反应过程可分为气相阻力控制、气液相阻力共同控制、液相阻力控制３个阶段。此外，本机理得到了实验的验证。以上结果将有助于改进石灰湿法烟气脱硫工业装置的设计和操作。

RFCC烟气脱硫除尘装置运行效果分析

广州分公司处于珠三角核心地区,是我国酸雨危害最严重地区之一。其重油催化裂化装置加工的重质原料油未经过加氢预处理,排放烟气中SO2质量浓度在2 500~3 800 mg/m3,颗粒物质量浓度200~300 mg/m3,烟气SO2和颗粒物含量均超过国家大气排放标准。为此,广州分公司采用湿法烟气净化技术新建一套RFCC烟气脱硫除尘装置。运行结果显示,该装置运行可靠、具有良好的操作弹性,净化烟气中的SO2和粉尘脱除率分别达到了99.9%和94.7%。洗涤废水处理系统实现高效连续液固分离,外排废水中的各项指标满足相关标准要求。