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.

Experimental study on performance of flow & desulfurisation of a gas-liquid screen scrubber for wet flue gas desulfurization

In the paper, the gas-liquid two-phase flow performance and desulfurisation performance of the gas-liquid screen scrubber were experimentally studied when limestone was used as absorbent. Experiments were carried out at varying the flue gas velocity and slurry flux in concurrent and countercurrent tower respectively. The experimental results showed that the flow resistance of absorber increased rapidly with an increase of the flue gas velocity whether in concurrent or in countereurrent tower, and the up trend of the flow resistance in the cotmtercurrent tower was higher than those in the concurrent one. The influence of the flue gas velocity on the flow resistance of absorber was more than those of the slurry flux density. Whether in the concurrent tower or in the cotmtercurrent one, increasing the flue gas velocity or the slurry flux density would enhance the desulphurization efficiency. The influence of the slurry flux density on the desulfurisation efficiency was greater than those of the flue gas velocity.

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.

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.

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%.

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.

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.

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.

湿法烟气脱硫(WFGD)喷淋塔内烟气流场的数值模拟研究

借助商用Fluent软件,针对300MW机组湿法烟气脱硫(WFGD)系统喷淋塔内烟气流场进行了数值模拟,详细考察了几何结构尺寸和运行参数对喷淋塔内烟气流场的影响。数值模拟结果表明,喷淋塔内烟气流场总体趋势大体上一致,几何结构尺寸和运行参数对塔内烟气流场有较大影响。

蒸汽相变促进WFGD系统脱除PM_(2.5)的协同作用分析

蒸汽相变作为预处理措施能显著提高常规除尘设备对PM2.5细颗粒的脱除效率,但对于水汽含量低的原始燃煤烟气蒸汽耗量太大,限制了工程应用,而在燃煤电厂湿法烟气脱硫(WFGD)过程中,烟气降温增湿,再添加少量蒸汽就可以建立PM2.5凝结长大所需要的过饱和环境,进而实现WFGD系统对PM2.5的协同高效脱除。在分析蒸汽相变促进PM2.5脱除影响因素的基础上,结合湿法脱硫过程传热传质特性,定性分析了脱硫塔塔前、塔内和塔出口添加蒸汽对WFGD系统脱除PM2.5的促进作用,并提出具体工艺方案。

基于PCS7的WFGD石灰石浆液控制系统设计

基于SIEMENS公司的PCS7控制系统开发平台,为某电厂2×300MW燃煤机的石灰石/石膏湿法烟气脱硫系统设计石灰石浆液控制控制系统。详细介绍了控制系统的硬件配置和软件组态。

Dynamic optimization oriented modeling and nonlinear model predictive control of the wet limestone FGD system

Nonlinear model predictive control(NMPC)scheme is an effective method of multi-objective optimization control in complex industrial systems.In this paper,a NMPC scheme for the wet limestone flue gas desulphurization(WFGD)system is proposed which provides a more flexible framework of optimal control and decision-making compared with PID scheme.At first,a mathematical model of the FGD process is deduced which is suitable for NMPC structure.To equipoise the model’s accuracy and conciseness,the wet limestone FGD system is separated into several modules.Based on the conservation laws,a model with reasonable simplification is developed to describe dynamics of different modules for the purpose of controller design.Then,by addressing economic objectives directly into the NMPC scheme,the NMPC controller can minimize economic cost and track the set-point simultaneously.The accuracy of model is validated by the field data of a 1000 MW thermal power plant in Henan Province,China.The simulation results show that the NMPC strategy improves the economic performance and ensures the emission requirement at the same time.In the meantime,the control scheme satisfies the multiobjective control requirements under complex operation conditions(e.g.,boiler load fluctuation and set point variation).The mathematical model and NMPC structure provides the basic work for the future development of advanced optimized control algorithms in the wet limestone FGD systems.

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.

WFGD中喷淋塔液气比计算方法的探讨

从湿法烟气脱硫的数学模型着手,介绍了传质系数法和传质单位数法两种喷淋塔液气比计算和选择的方法,对于自主开发适合国内脱硫市场的喷淋塔液气比计算模型有参考意义。液气比的计算模型是建立在大量实验数据之上的,需要经大量实际工程数据的验证和修正才能用于指导WFGD工程喷淋塔的设计。

入口烟道喷雾对WFGD脱除微细颗粒物效率的影响

在研究石灰石―石膏湿法脱硫装置(WFGD)对微细颗粒物协同脱除效果的基础上,提出了一种基于雾化凝并原理的烟道入口水喷雾技术。该技术通过在吸收塔入口喷雾少量平均粒径为20μm的清水,促进微细水雾颗粒与微细粉尘颗粒的聚结,使微细粉尘粒径长大,从而提高WFGD系统对微细颗粒物的捕集效率。

双托盘技术对燃煤电厂重金属排放的影响探究

为解决燃煤发电带来的污染物排放问题,针对二氧化硫、氮氧化物、烟尘的超低排放不断实施。但现有的净化装置对燃煤烟气中的重金属脱除效率不稳定,脱除效率不高。针对此问题,文中将湿法烟气脱硫系统中的托盘进行改造升级,在26000 m^(3)/h烟气中试台架上探究单、双托盘技术及不同喷淋强度对烟气中砷、硒、铅重金属的脱除性能,并对比不同的重金属浓度下重金属脱除性能。结果表明,加装双托盘后,WFGD装置对烟气中As、Se、Pb的脱除率均大幅度提高,脱除率>80%。

燃煤电厂细颗粒物中微量元素排放影响研究

燃煤电厂排放颗粒物中的各种微量元素引起公众的广泛关注。为探究燃煤电厂排放颗粒物中微量元素含量及主要环保设备对元素排放的影响,通过现场试验、文献调研、理化分析等方法,对安徽省一台600 MW超低排放、超临界机组湿法脱硫装置(WFGD)和湿式电除尘装置(WESP)排放细颗粒物中Cr、As、Se、Cd、Pb、Hg元素分布及排放特征进行综合研究。结果表明:燃煤机组排放PM_1、PM_(1~2.5)和PM_(2.5~10)的细颗粒物浓度分别为0.85、0.18和0.02 mg/m~3,WFGD对PM_(2.5~10)的脱除效率达到95%以上,WESP对粒径小于2.5μm细颗粒物的去除效率优于WFGD。WFGD入口处PM_(10)中Cr、As、Se、Cd、Pb、Hg的质量浓度分别为22.8、0.2、28.9、27.7、7.3、2.4μg/m~3,各元素质量浓度在不同分级颗粒物中的分布规律均呈现随着粒径增大而降低的趋势。颗粒物在经过WFGD后,Se元素质量浓度下降70%,Cr元素质量浓度增加466%,Hg和Pb元素质量浓度增长325%和205%,Cd和As增长101%和113%,微量元素主要富集在细颗粒物中。WESP出口处PM_(10)中Cr、As、Se、Cd、Pb、Hg的质量浓度分别为8.3、0.2、8.9、8.2、3.5、1.0μg/m~3,颗粒物中有害微量元素呈下降趋势,其中Se元素质量浓度变化较小,其他5种元素质量浓度均下降约50%。

复合脱硫添加剂在湿法烟气脱硫系统中的工程应用

在某300MW脱硫机组对添加剂强化SO2吸收,实现高效SO2脱除的作用规律进行了研究.结果表明,脱硫添加剂的加入可以有效提高WFGD系统污染物的脱除效率,减少吸收塔浆液池浆液pH值的波动,提高石灰石传质,增加石灰石利用率和脱硫副产品石膏的品质;添加剂对SO2浓度变化具有良好的适应性,能够保证系统高效、长期稳定的运行;添加剂在脱硫系统的主要损失是石膏携带导致.通过添加剂实现WFGD系统的高效稳定运行是一种有效的手段.

燃煤烟气中SO_3转换吸收特性模拟实验

为揭示燃煤烟气中SO3进入湿法脱硫(WFGD)塔前后的转换吸收特性,采用臭氧氧化法产生SO3,并通过对SO3的浓度、不同吸收剂的吸收率及转化物的粒径分布测量分析,得到SO3进入湿法脱硫塔前后的形态转换吸收规律。结果表明:SO3转化为气溶胶颗粒物,粒径分布形成[0,40]、[41,70]、[71,100]等3个区间段,相应的置信水平分别为79%、17%、4%;不同吸收剂对SO3的吸收率从小到大依次为:CaCO3浆液(30%)<湿法脱硫浆液<NaOH溶液(0.25mol/L)<去离子水;湿法脱硫浆液对SO3的吸收率为64.21%,温度在50～85℃变化时,吸收率无明显变化;SO3在进入脱硫塔后全部以硫酸雾形态存在,净烟气中的酸雾含有未脱尽的硫酸雾部分。

添加剂强化钙基湿法烟气脱硫的试验研究

为了满足我国日益严格的环保标准,针对大量燃煤电厂已安装脱硫装置的脱硫效率亟待提高的难题,研究添加剂强化钙基湿法烟气脱硫(WFGD)方法.利用双搅拌反应器研究添加剂强化湿法烟气脱硫吸收速率的影响因素.研究结果表明,SO2吸收速率随着添加剂质量分数、入口SO2体积分数、反应温度、气液相搅拌速率比的增大而增加;随着反应时间的延长,SO2吸收速率逐渐变小.通过对实验结果的进一步分析可知,使用添加剂可以提高脱硫反应增强因子和传质系数,从而促进了SO2的吸收.