Effects of Magnesium and Ferric Ions on Crystallization of Calcium Sulfate Dihydrate Under the Simulated Conditions of Wet Flue-gas Desulfurization

The influences of magnesium and ferric ions in their different ratios on the rate of gypsum crystallization were studied under the conditions similar to those of wet flue-gas desulfurization（WFGD）. The results show that addition of both Mg^2＋ and Fe^3＋ increased induction time and decreased the growth efficiency up to 50% compared with the baseline（without impurities） depending on the concentration and the type of impurity. The effects of Mg^2＋ and Fe^3＋ on the surface energy and the rate of nucleation were estimated by employing the classical nucleation theory. The surface energy decreased by 8% and 14% with the addition of 0.02 mol/L magnesium or ferric ions, respectively, compared to the baseline. Mg^2＋ and Fe^3＋ made the growth rate of the （020）, （021） and （040） faces of gypsum crystal a much greater reduction, which leads to the formation of needle crystals compared to the baseline which favors the formation of plate or flakes. Furthermore, an edge detection program was developed to quantify the effects of impurities on the filtration rate of gypsum product. The results show that the inhibition efficiency of the presence of 0.02 mol/L Mg^2＋ and Fe^3＋ on the filtration rate of gypsum crystal ranges from 22% to 39%.

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.

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.

Comparison of deep desulfurization methods in alumina production process

Several methods of deep desulfurization in alumina production process were studied, and the costs of these methods were compared. It is found that most of the S2- in sodium aluminate solution can be removed by adding sodium nitrate or hydrogen peroxide in digestion process, and in this way the effect of S2- on alumina product quality is eliminated. However, the removal efficiency of 2?32OS in sodium aluminate solution is very low by this method. Both S2- and 2?32OS in sodium aluminate solution can be removed completely by wet oxidation method in digestion process. The cost of desulfurization by wet oxidation is lower than by adding sodium nitrate or hydrogen peroxide. The results of this research reveal that wet oxidation is an economical and feasible method for the removal of sulfur in alumina production process to improve alumina quality, and provide valuable guidelines for alumina production by high-sulfur bauxite.

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.

Gas-solid flow field numerical simulation of different feeding and returning formations of flue-gas circulating fluidized bed

3D Euler double-fluid model was applied and three different feedstocks and reverts formations were simulated. By calculating and analyzing the state of gas and solid fluxion in absorber using three different methods of the feedstocks and reverts in recirculating fluidized bed, described the behavior of gas and solid through the gas-phase velocity, turbulence intensity, gas-solid sliding velocity, and density of particles. The results show that the feedstocks and reverts enters into absorption tower through two symmetrical feedings and are mixed with flue gas. Based on the respective analysis of each model and the com- parison analysis of the three models, this paper drew conclusions. The turbulence intensity of absorption tower is high, gas-solid sliding speed is big, and granule concentration near the axis is high, which has advantages for desulfurization and im- proving the utilization rate of absorbent.

湿法脱硫“无梁网架式”喷淋系统分析及应用

本文利用有限元分析软件,对某电厂1000MW机组湿法脱硫喷淋塔“无梁网架式”喷淋系统喷淋模组进行建模,准确分析喷淋模组的应变、强度比和挠度情况。实测排放结果表明,烟尘和二氧化硫排放指标均超过了预期设计值,实现了超低排放,验证了“无梁网架式”喷淋系统的先进性和可靠性。

湿法脱硫中多硫离子分离方法的建立

多硫离子S_(x)^(2-)是湿式催化氧化脱硫技术中H2S向单质硫转化的中间产物,在脱硫环境中,析硫反应和副盐反应存在平行竞争关系,S_(x)^(2-)的存在形态及浓度是评价两个竞争反应程度的前提条件。本文通过紫外-可见分光光度法(UV-vis)、液相色谱-质谱仪(LC-MS)和高效液相色谱(HPLC)方法可实现对S_(x)^(2-)的存在形态及各形态浓度定量测定的目标。结果表明:UV-vis法可测定出S_(x)^(2-)的总浓度;甲基化法可将S_(x)^(2-)的各个形态进行捕捉,LC-MS和HPLC法可将各形态的甲基化多硫化物分离,且S_(x)^(2-)的硫原子数(2—10)越大保留时间越长;结合UV-vis建立的标准曲线和HPLC上各个形态S_(x)^(2-)出峰的相对强度,推算出溶液中各形态S_(x)^(2-)的绝对浓度;多硫化钠溶液主要以S_(4)^(2-)、S_(5)^(2-)、S_(6)^(2-)、S_(10)^(2-)为主,其中浓度和pH对S_(x)^(2-)的影响较小,而温度过高不利于S_(x)^(2-)的生成,从而不利于单质硫的生成。这一项工作为进一步从源头上研究副盐成因及加快析硫反应的研究奠定了基础。

Effect of additives on mercury partitioning in wet-limestone flue-gas desulfurization

The wet-flue-gas desulfurization(FGD)process plays an important role in removing water-soluble flue-gas components such as sulphur dioxide(SO_(2))and oxidized mercury compounds.Under the reducing environment of the FGD,there is the possibility of re-emission of the already absorbed mercury(Hg)to the gas phase,which may be diminished by the utilization of specific additives.In this study,the effect of two different additives on Hg re-emission from the aqueous phase and Hg partitioning in gypsum and filtrate of a lab-scale wet-limestone FGD is investigated.Furthermore,the behaviour of additives in the presence of different halides is studied.The studied additives are TMT 15■as a sulphidic precipitating agent,which forms non-soluble mercury compounds,and activated lignite(AL)as a carbon-based sorbent,which adsorbs Hg compounds from the aqueous phase.TMT 15■has no significant effect on SO_(2) absorption;on the other hand,addition of AL improves the SO_(2)-removal efficiency by up to 30%.Using both additives,Hg re-emission is suppressed in all the experimented cases except for AL in the absence of halides,in which Hg re-emission shows no change.Thus,the need to form nucleophilic oxidized mercury compounds in the slurry for the adsorption of oxidized mercury on AL can be concluded.Usage of both additives improves Hg retention in the slurry to different extents.It is shown that,for the additive-free slurries,the Hg-adsorption capacity of the solid fraction of the slurry is the limiting parameter.Moreover,the utilization of both additives results in a significant increase in the Hg concentration of solid fraction.The correlation between redox potential and partitioning of Hg in the slurry is presented by comparing the change in the redox potential of slurries when additives are used.

电厂脱硫产物中痕量元素形态及毒性浸出特性

燃煤电厂副产物脱硫石膏和污泥在雨水中或作为固体废弃物加工过程中,吸附的痕量元素会再次进入环境中,造成二次污染。选取安徽省3个典型燃煤电厂超低排放机组,通过欧洲共同体标准物质局(BCR)逐级提取法测定脱硫污泥和石膏中Cr、As、Cd和Pb的赋存形态,应用标准毒性浸出程序法(TCLP)对脱硫石膏的浸出毒性进行测定,分析脱硫副产物中Cr、As、Cd和Pb的潜在环境影响。结果表明:脱硫污泥中4种元素的质量浓度明显高于脱硫石膏;脱硫石膏中Cr和As稳定性高,Cd和Pb元素有效态占比大于50%,迁移能力强,对生态环境具有潜在的风险;脱硫污泥中Cr、Cd和As的迁移能力较强,环境风险较高,其中Cr在氧化环境中不稳定,Cd在酸性环境中更易浸出,As在氧化和还原环境中均不稳定;pH和固液比对石膏中重金属浸出有重要影响,不同元素之间存在较大差异;Pb、Cr和As浸出率随着pH的降低而增大,随液固比的增大而增大,并逐渐达到平衡;Cd的最大浸出率低于其他3种元素,浸出率与pH和固液比的相关性较弱,在pH为4.47时,浸出率较高。研究结果可为燃煤电厂脱硫副产物处置及再利用提供参考。

燃煤机组脱硫浆液循环泵定频运行控制策略优化及节能分析

为消纳可再生能源大规模并网发电,燃煤发电机组的调峰调频任务剧增,长时间处于深度调峰和变负荷过程,导致湿法烟气脱硫系统的性能下降、厂用电率大幅上升。为此,建立了超超临界660 MW燃煤发电机组的动态模型及基于双膜理论的湿法脱硫系统动态模型;模拟了变负荷过程中不同工况点切换浆液循环泵时脱硫系统的性能,发现变负荷过程中浆液和烟气流量的精准匹配可使脱硫系统在满足SO2排放的前提下实现最小的电能消耗;进一步,获得了变负荷过程中浆液循环流量阶跃变化时SO2出口质量浓度的预测模型,提出了浆液循环泵定频运行优化控制策略,可实现变负荷过程中浆液与烟气流量的最佳匹配;最后,分析了优化控制策略的节能潜力。研究结果表明:75%THA~50%THA降负荷过程中,变负荷速率为1.0%、1.5%和2.0%Pe/min,分别可节能20.12%、21.52%和22.82%;而在升负荷过程中,分别可节能10.04%、9.90%和8.66%,变负荷过程中烟气流速变化的差异是造成降负荷和升负荷过程中节能潜力不同的根本原因。

新型船用底部进气式脱硫塔流场分析

为改善船用脱硫塔内吸收液与烟气的交互程度从而达到提高脱硫效率的目的,将侧进气改为底部进气,加入聚气环和环状导流板,设计一种新型船用底部进气式脱硫塔。基于有限体积法和欧拉-拉格朗日法建立仿真模型。通过Fluent软件对船用脱硫塔正常工作时的内部流场进行仿真分析,以烟气流速分布均匀性和流动阻力为评价标准对比原始模型和改良模型。结果表明:改良模型的烟气流速分布均匀性比原始模型的提升了70%~85%,而流动阻力增加了约25%。

钙基脱硫灰在石灰石-石膏湿法脱硫系统中的应用

钙基脱硫灰的资源化利用一直是行业应用难题。本文为验证钙基脱硫灰替代石灰石-石膏湿法脱硫系统原用脱硫剂(石灰石粉)的脱硫效果,进行在混合脱硫剂中添加不同比例钙基脱硫灰的实验室和工业应用试验,分析脱硫效率、SO_(2)排放质量浓度、吸收塔浆液和石膏的化学成分、脱硫污泥量等主要工艺参数的变化情况,并对钙基脱硫灰添加前、后湿法脱硫系统的生产运行方式变化进行对比分析。结果表明:当钙基脱硫灰替代占比在50%以下时,吸收塔浆液的化学成分基本没有发生变化,系统脱硫效率均在95%以上;SO_(2)排放质量浓度均在10 mg/Nm 3以下,小于35 mg/Nm^(3)的国家排放标准,满足行业超低排放要求;石膏的化学成分基本没有发生变化,满足石膏的社会化应用标准;污泥产生量没有增加,吸收塔内的Cl-浓度有所上升但可通过增大废水排放量来解决;湿法脱硫系统的操作调整变化不大,运行成本没有明显增加。采用钙基脱硫灰替代石灰石粉可为干法、半干法脱硫灰的综合利用提供一种经济、环保的有效途径。

铝工业赤泥用于脱硫技术现状及展望

以铝工业赤泥作为原料制备工业脱硫剂,具有来源丰富、价格低廉、理论硫容高等优点,在低成本脱硫的同时,达到了“以废制废”的目的。本文总结了铝工业赤泥在脱硫方面的应用,全面综述了赤泥干法、湿法脱除SO_(2)和H_(2)S的技术现状,从活性组分利用效率、能量消耗、工艺复杂程度、后续环境问题等几个维度分析对比了几种研究方向各自的优劣,并展望了未来工业化应用可能遇到的问题和进一步研究方向。指出在湿法浆液脱除烟气中SO_(2)方面,仍需克服管道堵塞、低效率、高能耗、以及由此产生的大量稀盐处理等技术性难题,同时应对其含有的过渡金属的反应机理和活化手段进行研究;在干法脱除H_(2)S方面,需进一步从低成本活化氧化铁的途径、极端工况环境下的适用性、废脱硫剂的资源化、以及与其他工业固废的协同处理等方面展开研究。

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。

高炉煤气精脱硫工艺选择及设备优化

基于国内北方某高炉新增脱硫设施工程建设实例,对比分析微晶吸附、水解催化-干法脱硫以及水解催化-湿法脱硫三种工艺的技术特点。结合项目施工场地条件、建设及运行费用等因素,综合考虑选择水解催化-湿法脱硫工艺对现有煤气系统进行改造。针对煤气脱硫塔易偏流的现象,设计了三种不同煤气入塔管道连接方案,并采用流体仿真软件对脱硫塔内流场进行模拟分析,结果表明采用切向入口连接方式,可使塔体内气流分布均匀,增加煤气与吸收液接触时间,提高脱硫效率。

化工企业脱硫石膏盐溶液法制备硫酸钙晶须的工艺研究

采用湿法脱硫工艺处理化工厂的废气时,会产生一种固体废弃物即脱硫石膏。与传统石膏相比,化工厂脱硫石膏中含有大量的有机杂质,综合利用难度更大。通过实验探索以化工厂脱硫石膏为原料制备硫酸钙晶须的生产工艺,分别采用盐溶液法制备晶须,探索盐溶液法中不同种类、不同浓度的盐溶液对产品的晶型形貌的影响。结果表明,采取盐溶液法制备晶须时,共对比5种不同盐溶液的效果,发现质量分数为10%的氯化钙中制备的晶须形貌最好,长径比为20~40,满足国标要求,且转化率较高。

电石渣替代石灰石用于火电厂脱硫的优势分析

电石渣是富含Ca(OH)_(2)的工业固体废弃物,替代石灰石进行火电厂脱硫具有经济、环境、社会、生态多重效益。从脱硫原理、影响因素等方面对比电石渣炉内脱硫技术和炉外烟气脱硫技术,并指出电石渣与石灰石相比所具备的优势,同时分析电石渣用于电厂脱硫存在的问题以及解决的方案,为电石渣合理替代石灰石用于火电厂脱硫提出参考性建议和未来发展的方向。

燃煤电厂脱硫氧化风母管集中改造分析

对某电厂脱硫氧化风系统的改造进行分析,以氧化风母管集中制方式并充分利用单台氧化风机的调节余量,将氧化风机由原先“二用二备”优化为“一用三备”,实现了机组间氧化风系统设备与资源的共享;此外,通过新增浆液氧化在线分析仪对浆液氧化指数进行在线检测,实现了氧化风量的精确、合理配风,提高了系统对锅炉负荷或燃煤含硫量变化的适应性,降低了系统能耗。

CuCl_(2)协同FeCl_(3)尿素低共熔溶剂氧化吸收H_(2)S的研究

为了解决中小规模常规含硫天然气H_(2)S脱除问题,以尿素(UREA)和FeCl_(3)·6H_(2)O为原料合成了一种FeCl_(3) UREA低共熔溶剂(DES),并向其中加入CuCl_(2)得到FeCl_(3) UREA-CuCl_(2)脱硫剂。分别对该DES的结构和热稳定性进行了测定,通过脱硫试验考察了原料配比、CuCl_(2)浓度、H 2S气体流量及温度对脱硫性能的影响,并对其再生过程进行了探究。结果表明:该DES在80℃下可稳定存在,FeCl_(3) UREA摩尔比1∶1的DES具有更为优异的脱硫性能;CuCl_(2)的引入可使其脱硫性能得到大幅提升,最高硫容达9.64 g L。该脱硫剂更适用于较低气体流速时脱硫使用,且可通入O_(2)进行再生,脱硫剂经多次循环使用后性能变化不大。脱硫所得产物为高纯度斜方硫(α-硫)。该脱硫剂原料成本低廉,合成简单,可高效氧化吸收H_(2)S并将其转化为高纯度硫磺,为工业天然气脱硫提供参考。