Uncertainty and disturbance estimator-based model predictive control for wet flue gas desulphurization system

Wet flue gas desulphurization technology is widely used in the industrial process for its capability of efficient pollution removal.The desulphurization control system,however,is subjected to complex reaction mechanisms and severe disturbances,which make for it difficult to achieve certain practically relevant control goals including emission and economic performances as well as system robustness.To address these challenges,a new robust control scheme based on uncertainty and disturbance estimator(UDE)and model predictive control(MPC)is proposed in this paper.The UDE is used to estimate and dynamically compensate acting disturbances,whereas MPC is deployed for optimal feedback regulation of the resultant dynamics.By viewing the system nonlinearities and unknown dynamics as disturbances,the proposed control framework allows to locally treat the considered nonlinear plant as a linear one.The obtained simulation results confirm that the utilization of UDE makes the tracking error negligibly small,even in the presence of unmodeled dynamics.In the conducted comparison study,the introduced control scheme outperforms both the standard MPC and PID(proportional-integral-derivative)control strategies in terms of transient performance and robustness.Furthermore,the results reveal that a lowpass-filter time constant has a significant effect on the robustness and the convergence range of the tracking error.

Multiobjective economic model predictive control using utopia-tracking for the wet flue gas desulphurization system

Efficient control of the desulphurization system is challenging in maximizing the economic objective while reducing the SO_(2) emission concentration. The conventional optimization method is generally based on a hierarchical structure in which the upper optimization layer calculates the steady-state results and the lower control layer is responsible to drive the process to the target point. However, the conventional hierarchical structure does not take the economic performance of the dynamic tracking process into account. To this end, multi-objective economic model predictive control(MOEMPC) is introduced in this paper, which unifies the optimization and control layers in a single stage. The objective functions are formulated in terms of a dynamic horizon and to balance the stability and economic performance. In the MOEMPC scheme, economic performance and SO_(2) emission performance are guaranteed by tracking a set of utopia points during dynamic transitions. The terminal penalty function and stabilizing constraint conditions are designed to ensure the stability of the system. Finally, an optimized control method for the stable operation of the complex desulfurization system has been established. Simulation results demonstrate that MOEMPC is superior over another control strategy in terms of economic performance and emission reduction, especially when the desulphurization system suffers from frequent flue gas disturbances.

The Analysis of Using MGGH in Flue Gas Desulphurization (FGD) System in Cement Plant

The paper first introduces the background and the mechanism of secondary pollution from desulfurization in cement plant. Then, take plant A as an example, using MGGH (media gas-gas heater) to control “white smoke”. MGGH uses heat medium water to heat transfer between the original flue gas and the clean flue gas, without additional heat source, and has obvious economic benefits, which is the inevitable development direction of desulfurization reform of cement kiln system in the future.

严格的环保标准是SO_2污染治理和控制的重要依据和推动力

火电厂排放的二氧化硫形成的酸雨已严重危害人类的生存环境,国家由此重新修订了《火电厂大气污染物排放标准》,严格了火电厂SO2排放的控制要求,强制要求火电厂必须安装烟气脱硫装置。本文从我国实际情况出发,比较分析了干法、半干法和湿法脱硫技术工艺,提出了适合有色金属企业—氧化铝厂配套建设的热电厂的烟气脱硫方法。

Desulphurization of Transportation Fuels by Per-Formic Acid Oxidant Using MoOx Loaded on ZSM-5 Catalyst

Desulphurization of model and real oil samples was investigated using performic acid as oxidant assisted by air as co-oxidant. The catalysts used were Mo-oxide supported on ZSM-5 zeolite, which was synthesized in the laboratory and characterized by FT-IR, XRD, SEM and SSA analysis. In case of model oil, the optimum condition determined for complete oxidation of all the model compounds including thiophene, DBT and 4,6-DMDBT were;60?C, 60 min, ambient pressure and air flow rate of 100 mL/min. The oxidation reactivity decreased from 4,6-DMDBT to DBT and thiophene, which was found to follow pseudo first order kinetics. The real oil sample used in the study included untreated naphtha (NP), light gas oil (LGO), heavy gas oil (HGO) and Athabasca bitumen (Bit.). In case of NP and LGO the sulfur removal of above 78% was attained whereas in case of HGO and Bit. samples about 60% of desulfurization was achieved.

石灰石脱硫对循环流化床中N_2O排放浓度的影响

N_2O是循环流化床锅炉运行时主要的污染物之一,石灰石脱硫会影响循环流化床锅炉中N_2O的生成和排放。石灰石脱硫过程中由于CaO对N_2O的分解的催化作用;能促进HCN向NH_3转化,减少N2O的生成;同时石灰石脱硫生成的CaS可以直接还原N_2O,减少烟气中N_2O的排放浓度。此外,石灰石脱硫产生的床料对喷氨脱氮有催化作用,可使N_2O脱氮后的残留量降低三分之二左右。因而石灰石脱硫能同时降低循环流化床中SO_2和N_2O的排放。

球团竖炉烟气脱硫工程应用研究

论述了文氏栅洗涤器及其配套系统在球团竖炉烟气脱硫工程应用方面的研究,介绍了双碱法在文氏栅洗涤器及其配套系统中的脱硫机理和工艺过程。同时对设备的防腐和废水、废渣的处理,系统的常规检测和自动监测都作了相应的研究。对文氏栅洗涤器的脱硫除尘效率、设备及工程投资、工业运行成本作了适当的介绍。文氏栅洗涤器具有良好的组合特性,适用的烟气量范围广,是用于炉窑烟气脱硫除尘的理想设备,具有广阔的开发应用前景。

火电厂烟塔合一技术应用现状与现存问题分析

【目的】烟塔合一技术是火电厂提高能效的重要改造手段,但是实际运行对现有系统造成的不利影响也不容忽视。为此,对烟塔合一技术应用现状及其在运行中存在的问题进行分析,并提出处理对策。【方法】通过综合分析现有研究,探讨了烟塔合一技术改造后造成环境影响、冷却塔塔体腐蚀以及循环冷却水水质恶化的成因和形成机理。【结果】根据计算流体动力学(computational fluid dynamics,CFD)对烟气排放轨迹以及污染物落地浓度的模拟结果,可合理设置防护距离,并通过塔顶加装挡板预防极端天气下的烟气下洗现象;针对不同部位,可采用不同防腐涂料对冷却塔进行防腐改造,以延长其使用寿命;为控制和优化循环水质,需采用深度水处理方法优化药剂投加,并适当控制循环水排污量与补水量,以维持其运行可持续性。【结论】通过采取适当的应对措施,可以有效缓解烟塔合一技术改造所带来的负面影响,提高火电厂环境效益和经济效益。

直流钢包精炼炉电化学脱硫脱氧的理论探讨

直流钢包精炼是近年来发展起来的钢液纯净化新工艺。本文从单电弧三顶电极直流钢包精炼炉工作原理出发,系统的分析了冶金过程。运用电解原理讨论了阳极和阴极的电化学反应,揭示出了直流钢包精炼实现深度脱硫脱氧的基本原理。精炼过程中的电化学反应和渣金界面化学反应是高效冶金效果的关键。

Desulphurization Characteristic of Industry Alkaline Wastes during Coal Combustion

The desulphurization characteristics of four sorts of industry alkaline wastes and one sort of limestone were studied by means of flue gas analyzer and the high temperature tube reactor. Pore structure and desulphurization product char-acteristic were investigated respectively by mercury porosimeter and XRD diffraction technology. The reasons why wastes and limestone hold the different desulphurization capability were deeply discussed. The result shows that white clay and carbide slag could capture the release of sulfur at 800-1100℃. Salt slurry and red mud could capture the re-lease of sulfur at first stage at 800-900℃. But when the experimental temperature rises to 1000℃, the sulfur capture abilities of them depress. Pore structures of waste are higher than that of limestone. This makes the sulfation reaction goes further. To sum up, wastes have better sulfur capture ability.

Mercury Speciation of Flue Gas Desulphurization By-Products in Coal-Fired Power Plants in China

The aim of this study was to develop and examine the morphology and distribution of mercury (Hg) in flue gas desulfurization (FGD) by-product. Mercury in the coal of coal-fired power plants is concentrated in the by-products of desulfurization process, and it is widely used as an additive in cement, building materials and other industries. Due to the different stability of various forms of mercury in the environment, subsequent use of products containing desulfurization by-product additives will continue to be released into the environment, endangering human health. Therefore, it is very necessary to study the form and distribution of mercury in the by-products of desulfurization in coal-fired power plants to provide a theoretical basis for subsequent harmless treatment. For content and morphology of mercury analysis, 1 sample of dry FGD ash and 6 samples of wet FGD gypsum were analyzed. The total 7 samples were extracted using a modification of sequential chemical extractions (SCE) method, which was employed for the partitioning Hg into four fractions: water soluble, acid soluble, H2O2 soluble, and residual. The Hg analysis was done with United States Environmental Protection Agency (USEPA) method 7471B. Comparing with the wet FGD gypsums of coal-fired boilers, the total Hg content in the dry FGD by-product was as high as 1.22 mg/kg, while the total Hg content in the FGD gypsum is 0.23 - 0.74 mg/kg, which was 2 times over the wet FGD gypsum. The concentration of water soluble Hg in the dry FGD by-product was the highest amount (0.72 mg/kg), accounting for 59.02% of the total mercury. While residual Hg content was 0.16 mg/kg, only about 13.11% of the total mercury. Mercury content in FGD gypsum was expressed in the form of ρ (residual Hg) > ρ (H2O2 soluble Hg) > ρ (water soluble Hg) > ρ (acid soluble Hg). The morphology and distribution of mercury in FGD by-products is supposed to be analyzed before utilization, and the impact of mercury on the environment should be considered.

Effect of Low pH on Forming Process of Desulfurization Gypsum Composite Boards Strengthened by Melamine-formaldehyde Resin

Through exploring the effects of low pH on the composite system of desulfurization gypsum(DG)enhanced by melamine-formaldehyde resin(MF),it is found that the inducing of sulfate-ion,in contrast to chloride and oxalate ions,favors the longitudinal growth of the crystalline form of the hydration product,which was relatively simple and had the highest length to width(L/D)ratio.At the same time,MF can also improve L/D ratio of gypsum hydration products,which favors the formation of hydrated whiskers.Finally,in a composite system composed of hemihydrate gypsum,MF,and glass fibers,when dilute sulfuric acid was used to regulate pH=3-4,the tight binding formed among the components of the composite system compared to pH=5-6.The hydration product of gypsum adheres tightly to glass fiber surface and produces a good cross-linking and binding effect with MF.The flexural strength,compressive strength,elastic modulus,and water absorption of the desulphurized gypsum composite board is 22.7 MPa,39.8 MPa,5608 MPa,and 1.8%,respectively.

脱硫石膏基与磷石膏基自流平砂浆的性能差异研究

分别对比研究了水泥掺量(0、2.5%、5.0%、7.5%、10.0%)和氢氧化钙掺量(0、0.25%、0.50%、1.00%、2.00%)对脱硫石膏基自流平砂浆(S砂浆)和磷石膏基自流平砂浆(P砂浆)工作性和力学性能的影响,分析了磷酸盐和二水石膏含量对S砂浆性能的影响机理。结果表明:随着水泥掺量的增加,S、P砂浆的流动度均先增加后趋于平稳,初凝时间基本先延长后缩短,S砂浆的24 h抗压强度先升高后降低,P砂浆的24 h抗压强度先降低后升高;随着氢氧化钙掺量的增加,S、P砂浆的初凝时间均先延长后缩短再趋于平稳,S砂浆的流动度先增加后趋于平稳,P砂浆的流动度先增加后降低,24 h抗压强度变化规律与掺水泥时相同;磷酸盐的掺入降低了S砂浆的流动度降低,但在一定的水泥或氢氧化钙掺量范围内,磷酸盐能提高S砂浆的强度;二水石膏的掺入降低了S砂浆的流动度保持能力和强度。

Deep Desulphurization and DeNO_X in Circulating Fluidized Bed Boiler

With the revision of emission standards, deep desulphurization and DeNO X is needed in circulating fluidized bed (CFB) boilers. The operation of the first set of 300-MW CFB boiler plus limestone/gypsum wet flue gas desulphurization (FGD) system in the world shows that deep desulphurization and DeNO X of CFB boilers has higher SO2 removal efficiency at a lower Ca/S ratio compared with traditional inner desulphurization mode. It can meet the increasingly rigid emission standards, and is suitable for more fuels. Deep desulphurization and DeNO X can also achieve a highly-efficient high-temperature CFB boiler that can not only achieve inner desulphurization and low NO X emission, but benefits low-grade, high sulfur content fuels as well. Research of deep desulphurization and DeNO X will be a developing direction for CFB boilers.

粉煤灰资源利用:无机矿物改良剂对CFA源蛋白石/沙粒团聚体形成的影响

粉煤灰碱法提铝的副产物-蛋白石(SiO_(2)·nH_(2)O,非晶质二氧化硅)具有很强的吸附性,是土壤中的次生/黏土矿物。将蛋白石与沙粒复配形成团聚体应用于沙漠化土壤修复,是一种前景广阔的大规模生态化处置方式。然而,由于无机矿物质的缺乏,该团聚体与自然土壤团聚体仍有差距。本文通过短期土培实验,研究了石灰石(CaCO_(3))、脱硫石膏(CaSO_(4)·2H_(2)O)、磷酸钙(Ca_(3)(PO_(4))_(2))、赤铁矿(Fe_(2)O_(3))、三水铝石(Al(OH)_(3))等无机矿物改良剂对团聚体形成、稳定以及孔隙特征的影响,并阐述了其内在的吸附机理。结果表明,五种改良剂中,只有石膏可有效降低团聚体的pH,且石膏对提升团聚体的保水效果最为显著,但石膏会增大电导率。改良剂均能促进团聚体的形成,提高机械稳定性,石膏、CaCO_(3)、Fe_(2)O_(3)有利于提高团聚体的水稳性。XRD/SEM/FT-IR/XPS等分析表明,无机矿物与沙子/蛋白石发生吸附作用,团聚体表面形成了有利于团聚体生成的无机矿物界面层。与CK相比,改良后的大团聚体(>0.25 mm)以孔径<80μm的孔隙和边界孔隙为主,孔隙率增加、孔隙数量和平均孔隙直径(MPD)减少、孔隙结构更致密、孔隙间的连通性提高以及孔隙网络更复杂。特别是经脱硫石膏改良后,微团聚体(<0.25μm)的MPD和2~5 nm中孔的数量增加,总孔隙体积和0~2 nm微孔的数量降低;而Ca_(3)(PO_(4))_(2)和Al(OH)_(3)增加了>15 nm介孔的数量。总之,作为土壤“骨架”的无机矿物有效改善了蛋白石/沙粒团聚体的物理结构,加速了团聚体的形成。因此,脱硫石膏优化了大聚集体的形成和稳定性。经脱硫石膏改良的团聚体可作为类土壤基质,加速退化的沙漠化土壤的生态重建。

Study on the Mechanism of Ultrasonically Enhanced Flotation Desulphurization

The mechanism of ultrasonic action and the influence of ultrasonic treatment on the changfs or particle size, dissolved oxygen, pH and the feasibility of flotation desul phurization with ultrasonic enhancement are studied. A new means of ultrasonic treatment for slurry is put forward. The test results indicate that by employing this means and an approprlate floatation technology and pyrite-depressed method, the optimum effect of rlotation desul phurization can be achieved.

燃煤锅炉烟气石灰石湿法脱硫废水处理技术与应用

燃煤锅炉烟气石灰石-石膏湿法脱硫废水成分复杂,零排放治理难度较大。为达到资金、资源等投入与节能减排的综合效益,对于化学沉淀等梯级处理技术的实际应用需综合考量处理效率与技术成熟度并对投资与长期运行费用进行评估,从而确定合适的脱硫废水处理技术路线。基于燃煤锅炉石灰石湿法烟气脱硫废水的特性和相应的废水排放标准,对脱硫废水的梯级处理技术进行综合分析,深度讨论不同技术路线的特点及其适应性,并结合实际应用的案例以探讨脱硫废水零排放处理技术的发展方向。在讨论脱硫废水特性的基础上,介绍包括三联箱法、膜处理法、蒸发结晶技术及烟道蒸发技术在内的典型脱硫废水处理技术,通过对不同技术的特点分析,指出预处理能够去除废水中的污染物,即对水的预处理是脱硫废水零排放处理的基础;浓缩减量是降低能耗和成本的关键,其可有效降低蒸发固化阶段的处理负荷和水的回收利用;蒸发固化是实现零排放处理的核心,其可以固体的形式固化脱硫废水中的杂质和盐分。通过对不同零排放工艺的应用分析及基于分级工艺的优化选择,建议企业应根据脱硫废水水质特点和后续处理工艺对进水的要求以确定合适的零排放技术路线。未来应侧重于提高废水和矿物盐的综合利用率,强化不同工艺的优势组合是未来脱硫废水零排放的发展方向。

分子筛在催化脱硫中的研究进展

液体燃料(柴油和汽油)中存在的含硫化合物造成的空气污染,已成为当前社会各界关注的热点,绿色燃料对可持续发展和清洁环境至关重要。有效、完全地脱除燃料油中的含硫化合物是制备新型催化脱硫催化剂的技术关键。介绍分子筛在催化脱硫领域中的应用与研究,对现有主要的分子筛催化脱硫技术进行总结和分析,着重讨论分子筛在脱硫过程中的作用机制,阐述分子筛催化脱硫在石油加工领域中的应用现状,并对其发展前景进行展望。

湿法脱硫后烟气和浆液余热回收技术研究进展

低品位余热高效深度利用是促进燃煤电站进一步节能减排的关键之一,湿法脱硫后的低温饱和湿烟气蕴含大量潜热和水资源,大量脱硫浆液吸收烟气热量后温度升高。烟气与浆液具有巨大的余热利用和水资源回收的潜力,若直接排放烟气,直接排出浆液,不但造成资源浪费,还容易引发“白色烟羽”污染环境。本文以湿法脱硫后饱和湿烟气和脱硫浆液为研究对象,针对目前湿法脱硫技术余热回收效率低、利用难以匹配冷源等困境,总结了国内外针对脱硫后烟气水热回收和浆液余热回收技术及发展方向,研究中针对浆液余热利用仍待发展。其中,直接冷凝烟气和浆液技术和热泵技术成熟,应用广泛;溶液吸收技术能源利用率高,烟气腐蚀性低;烟气膜分离技术、浆液闪蒸、热泵技术清洁环保,回收质量高。直接冷凝烟气、浆液技术和膜分离技术需要进一步提高抗腐蚀性和转换效率;浆液闪蒸、热泵技术能耗较高,吸收式热泵技术仍需寻找高效安全环保无毒的吸收溶液。最后,探讨了目前脱硫浆液余热利用的主要方式及存在问题,回收余热主要用于供暖和电厂内部热利用,以期进一步推动湿法脱硫后烟气与浆液余热回收利用,实现燃煤电站的深度节能减排。

Preparation of α-High Strength Gypsum from Flue Gas Desulfurization Gypsum Pretreated by Hydrothermal-aging Method

The synthesis of α-calcium sulfate hemihydrate (α-CSH) from flue gas desulfurization (FGD)gypsum is a good way to realize the comprehensive utilization of FGD gypsum. To obtainα-CSH with the satisfactory performances, a facile hydrothermal-aging pretreatment process for FGD gypsum raw materials was proposed, where FGD gypsum was firstly hydrothermally converted to α-CSH whiskers, and α-CSH whiskers were further hydrated to synthesize CaSO4·2H2O (CSD) by aging under the regulation of N,N'-methylenebisacrylamide (MBA). The effects of aging time, MBA addition, aging temperature, and pH on the morphology of the synthesized CSD were investigated. The synthesized CSD crystals exhibit highly uniform prismatic morphology with the length of ca 100μm and the whiteness of 91.56%. The regulation mechanism of MBA was also illustrated. The synthesized CSD crystals with prismatic morphology were further used as raw materials to synthesize the short columnar α-CSH. The absolute dry compressive strength of paste prepared from the short columnar α-CSH is 40.85 MPa, which reaches α40 strength grade.