Research on the use of sintering flue gas desulphurization gypsum as a cement retarder

The characteristics of the desulphurized gypsum produced in the flue gas desulphurization （FGD） process of the Baosteel sintering plant are investigated in this study. According to the technical and quality requirements of gypsum in the cement industry ,the feasibility of using desulphurized gypsum as a cement retarder is also studied. The results show that desulphurized gypsum can be used as a cement retarder instead of natural gypsum.

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.

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.

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.

不同阻垢剂官能团对脱硫石膏结晶的影响

为评价不同循环水阻垢剂成分对脱硫石膏品质的作用,选用含特定官能团的6种单一成分阻垢剂进行成核试验和生长试验,研究其对石膏结晶过程的影响。成核试验中,含磺酸基阻垢剂使石膏结晶诱导时间缩短3.2%,磺酸基提高硫酸钙过饱和度,有利于石膏成核。含膦酸基和羧基阻垢剂使石膏结晶诱导时间延长6.5%~45.2%,抑制石膏成核。生长试验中,含磺酸基阻垢剂使石膏粒径减小30.3%,细碎石膏结晶增多。含膦酸基和羧基阻垢剂使石膏粒径增大21.5%~72.6%,石膏形貌发生畸变,出现片状孪晶。膦酸基和羧基主要通过吸附作用使石膏特定位置生长速率改变,使石膏发生畸变,有利于石膏生长。因此,含羧基官能团的阻垢剂对石膏品质负面影响最小,更适合作为全厂废水零排放背景下的循环水阻垢剂。

施加脱硫石膏对盐碱土改良和固碳的影响

【目的】探究脱硫石膏施用对盐碱土改良效果和固碳作用。【方法】以新疆塔里木河流域下游荒漠盐碱土为研究对象,分析脱硫石膏不同施用量(0、10、20、30、40、50 t/hm^(2))对土层厚度为0~40 cm的土壤理化性质及土壤固碳的影响。【结果】与对照组相比,施用脱硫石膏显著降低0~20 cm土层土壤pH,增加土壤盐分含量;施用脱硫石膏量为40 t/hm^(2)的土壤有机碳储量达到最高,比对照组增加0.029 kg/m^(2);与对照组相比,脱硫石膏施用量分别为10、40 t/hm^(2)时,处理土壤的无机碳储量分别增加0.21、0.18 kg/m^(2);从改良时间来看,施用脱硫石膏改良土壤固碳效应的持续时间为0~7 d,其中施用量为40 t/hm^(2)时的效果最好;土壤碳储量受土壤pH、土壤盐分、降水量和蒸散发的影响较大。【结论】从盐碱土的改良效果及固碳作用来看,脱硫石膏施用量为40 t/hm^(2)时能显著降低土壤pH,且过程中具有显著的固碳作用。

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。

火电厂粉煤灰与脱硫石膏资源化利用现状

火力发电厂主要产生的固态废弃物为粉煤灰和脱硫石膏,由于未能得到充分的运用,我家每年都会积累大量的此类废弃物。基于对粉煤灰和脱硫石膏的规范化利用,以及相关法律法规、政策文件和利用技术的详细研究和理解,深入探讨粉煤灰的现行利用状况。近年来,我国对粉煤灰的利用模式并未经历明显的变迁。主流的应用领域依然是水泥、混凝土及各类建材的深度加工产品。这些领域的应用,不仅充分利用粉煤灰的特性,而且也在一定程度上缓解环境压力。然而,尽管粉煤灰在这些领域的应用已经相当成熟,但在其他一些可能的应用方向上,如道路建设和土地回填等,开发和利用却相对较少。脱硫石膏的应用路径具有较高的多样性,其主要被应用于作为建筑材料中的石膏和水泥固化剂。此外,其也被用于生产复合凝胶材料、土壤改良、硫酸钙晶须制备,以及其他高附加值化学品的生产等领域。建议在已经有成熟应用的领域中,进一步拓宽粉煤灰和脱硫石膏在我国的利用范围。深化粉煤灰与脱硫石膏的高附加值科技探索,提升其综合运用的良性层次。

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。

SDA脱硫系统资源化利用烧结脱硫废水的应用实践

本文分析了石灰/石灰石-石膏湿法脱硫废水的主要特点,对SDA脱硫工艺的技术特点进行研究分析,提出了在SDA脱硫系统中,使用部分湿法脱硫的压滤废水代替工艺水制作脱硫浆液的思路并予以实施,分析了在SDA脱硫系统中资源化利用湿法脱硫废水的可行性,提出了一种消纳湿法脱硫废水的新方法。对同行业有一定借鉴意义。

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。

煤电企业湿法脱硫石膏处置与综合利用现状分析

以14家煤电企业为调查研究对象,全面调查各煤电企业脱硫石膏处置与综合利用现状,对比分析各煤电企业脱硫石膏品质间的差别,并根据现有技术条件提出改进建议。调查结果表明,参与调查的14家煤电企业中,有9家综合利用率为100%,占比64.29%,处置方式为外销或委托第三方综合处置;有5家综合利用率为0,占比35.71%,处置方式为自有灰场贮存或外运灰场贮存;14家煤电企业脱硫石膏总产量为1 184 927 t,综合利用405 848 t,资源化利用率为45.10%,整体资源化利用率较低;14家煤电企业脱硫石膏化验分析项目中含水率、CaSO3·1/2H2O、CaCO3、CaSO4·2H2O质量分数平均值分别为11.32%、0.34%、2.75%、85.63%,其中CaSO3·1/2H2O、CaCO3质量分数平均值分别达到≤1%、≤3%的设计值要求,含水率、CaSO4·2H2O质量分数平均值均未达到≤10%、≥90%的设计值要求。研究结果可为煤电企业技术管理工作提供数据和技术支持。

Cause Analysis and Countermeasure of Gypsum Rain in Coal-fired Power Plants

Focusing on the phenomenon of gypsum rain while wet desulphurization(WFGD) were adopted in coal fired power plant without GGH, the paper studied and put forward the solutions : (1) desulfurization facilities related equipment modification;(2) optimal operation of existing desulfurization facilities.

Utilization of Thermally Treated Flue Gas Desulfurization (FGD) Gypsum and Class-C Fly Ash (CFA) to Prepare CFA-Based Geopolymer

The feasibility of utilization of flue gas desulfurization （FGD） gypsum and Class-C fly ash （CFA） to prepare CFA-based geopolymer were studied. The results showed that geopolymer made from 90% CFA and 10% FGD gypsum （FGDG） which was thermally treated at 800 ℃ for 1 h obtained the better compressive strength of 37.0 MPa. The micro characteristics and structures of the geopolymer samples of CFA and CFA-FGDG were tested by XRD, FT-IR, and SEM-EDXA after these samples cured at 75 ℃ for 8 h followed by 23 ℃ for 28 d. Both the geopolymer samples of CFA and CFA-FGDG have significant asymmetric stretching of A1-O/Si-O bonds and Si-O-Si / Si-O-A1 bending band. In geopolymer sample of CFA-FGDG, a small quantity of lathy products probably being the ettringite wrapped over the spherical fly ash particle, and the concentration of sulfur is much more than that in geopolymer sample of CFA. It is indicated that FGD gypsum may react during alkali-activated and geopolymeric process.

Distribution and Accumulation of Major and Trace Elements in Gypsum Samples from Lignite Combustion Power Plant

Flue gas containing volatile elements, fine fly ash particulates not retained by particle control devices, and limestone are the most important sources of trace and major elements (TMEs) in wet flue gas desulphurization (WFGD) gypsum. In this study, samples of gypsum slurry were separated into fine and coarse fractions. Multi-elemental analysis of 45 elements in the different size fractions of gypsum, slurry waters and lignite were performed by k0-INAA (k0-instrumental neutron activation analyses). The study found that the volatile elements (Hg, Se and halogens) in the flue gas accumulate in the fine fractions of gypsum. Moreover, the concentrations of most TMEs are considerably higher in the fine fractions compared to the coarse fractions. The exceptions are Ca and Sr that primarily originate from the limestone. Variations of TMEs in the finer fractions are dependent on the presence of CaSO4·2H2O that is the main constituent of the coarse fraction. Consequently, the content of TMEs in the fine fraction is highly dependent on the efficiency of separating the fine fraction from the coarse fraction. Separation of the finer fraction, representing about 10% of the total gypsum, offers the possibility to remove effectively TMEs from WFGD slurry.

循环流化床锅炉脱硫技术改造实践

我公司循环流化床锅炉烟气处理设施采用双碱法脱硫,在运行过程中脱硫设施经常出现故障,且随着新环保标准的出台,现有的环保设施已满足不了使用要求。本文介绍了循环流化床锅炉在由双碱法脱硫技改为石灰-石膏法脱硫过程中,对部分利旧设备、设施的技术改造,以及石灰-石膏法脱硫法关键技术的创新,改造完成后,不仅大大节约了投资,而且达到了预期的环保效益。

施用脱硫石膏对荒漠碱土剖面土壤有机碳分布的影响

石膏类钙源物对于盐碱土改良具有显著作用。为了探究施加钙源物对荒漠碱土土壤有机碳(SOC)的影响,设置以钙源物脱硫石膏施用量0、10、20、30、40 t/hm^(2)共5个处理水平,对荒漠碱土0~20 cm土层进行改良,分析改良后SOC在0~100 cm剖面上的分布、改良土层SOC的变化趋势以及影响因素。结果表明:脱硫石膏施用量为30 t/hm^(2)时,改良土层改碱效果最好,pH下降为8.24(初始值为9.97),电导率(EC)为0.98 mS/cm。脱硫石膏土壤改良对SOC的影响深度为0~40 cm,下层SOC含量无明显变化(P>0.05)。随着改良时间的增加,在15 d后SOC含量无显著变化。随着施加量的增加,当施用量为40 t/hm^(2)时,改良土层SOC含量和土壤有机碳密度(SOCD)均减少(P<0.05)。降水量和相对湿度对改良土层SOC含量减少有促进作用,作用大小:降水量>相对湿度;太阳总辐射和温度对改良土层SOC含量减少则有抑制作用,作用大小:太阳总辐射>温度。改良土层在获得最佳的碱性改良效果的同时,并不会造成SOC含量的下降。

脱硫石膏-废水泥碳化再生砌块的力学性能及机理

本文以废水泥的再生利用为研究目标,构造了脱硫石膏-废水泥体系,评估了碳化对脱硫石膏-废水泥体系再生砌块力学性能和表观密度的影响,并通过XRD、FTIR和SEM揭示了再生砌块的成分、化学结构和形貌变化。结果表明,在石膏存在的条件下,废水泥的碳化可顺利进行。碳化过程能够有效增加脱硫石膏-废水泥样品的抗压强度。当水灰比为0.4、废水泥掺量为60%(质量分数)时,与未碳化的样品相比,碳化过程使样品的抗压强度提高了108.3%;当水灰比为0.8、废水泥掺量为65%(质量分数)时,与未碳化的样品相比,碳化过程使样品的抗压强度提高了270.0%。通过调整水灰比和废水泥掺量可控制碳化产物的化学结构和微观形貌,碳化过程对废水泥内部的水化具有一定促进作用,在促进体系力学性能增强的同时降低了块体的表观密度。研究结果将为综合利用废水泥和脱硫石膏两种固体废弃物提供新思路和可靠的再生应用方案。

脱硫石膏基材料的水泥改性研究

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