Experimental and Theoretical Studies on Desulfurization Efficiency of Dual-alkali FGD System in a RST Scrubber

The effects of operating parameters on desulfurization efficiency of a dual-alkali FGD process in a rotating-stream-tray (RST) scrubber are investigated. A dimensionless factor, e, is proposed in this study to predict desulfurization efficiency of this dual-alkali FGD system. e represents the desulfurization ability of a dual alkali FGD system, determined by five main operating parameters such as sodium ion concentration, ratio of absorbent flow rate to flue gas flow rate, pH value of absorbent solution, ratio of sulfate ion to total sulfur ion in absorbent solution, and sulfur dioxide concentration of inlet flue gas. The empirical expression for predicting desulfurization efficiency at different temperatures is obtained through the experimental study and theoretical calculation. It provides useful guide for engineering design.     

Fractal Geometry of Particle Aggregates Formed in Calcium Sulfite Slurry

The solid-liquid separation is an important operation for the regenerated slurry of dual-alkali FGD system, and calcium sulfite could predominate in particle aggregates of the slurry. The settling velocity of calcium sulfite particles is a key parameter for the solid-liquid separation design. However, the settling velocity predicted by Stokes' Law could be suitable only for a spherical aggregate, but not for the irregular one. In this work, fractal geometry was introduced in order to characterize highly irregular geometric shapes. The sizes of calcium sulfite particle aggregates were analyzed using a metallographic phase microscope and image analysis. The results showed that particle aggregates had fractal features. The fractal dimensions could reveal the characteristics of the aggregates' geometry and aggregation process. An exponential relation between the fractal dimension D2 and the particle size l was determined as AμlD2. According to fractal theory, a parameter can be used to modify Stokes settling velocity close to actual settling velocity. The results could be valuable for the design of solid-liquid separation processes.     

京杭运河杭州段水污染源特征与截污措施建议

京杭运河杭州段地势低洼,一直是杭州城市和沿线郊区的污水受纳场所。经调查,在城区运河干流沿线两岸的合流管线污染源共有521处,其中生活污染源占95.2％,排入运河主河道污水量21820 m3／d。采用等标污染负荷法评价污染源,得出主要污染源80个,主要污染物为COD、BOD和NH3-N。提出了截污的基本原则和设想。     

电石渣脱硫废水中超标重金属的去除

针对电石渣脱硫废水存在重金属超标问题,采用化学沉淀法去除废水中Cd2+和Hg2+。以二硫代氨基甲酸盐(DTCR)为螯合剂,分别处理模拟含Cd2+或Hg2+废水、同时含Cd2+和Hg2+废水,以及实际电石渣脱硫废水。结果表明,投加量150 mg/L的DTCR能使模拟废水中的Cd2+和Hg2+从质量浓度10 mg/L分别降低到41μg/L和34μg/L;190 mg/L的DTCR能使实际电石渣脱硫废水Cd2+和Hg2+的质量浓度分别降低到42μg/L和2.0μg/L。DTCR去除电石渣脱硫废水中Cd2+和Hg2+的效率很高,pH升高略有利于提高Cd2+和Hg2+的去除效果,但在4~10内均能达到DL/T 997-2006排放要求。     

扑热息痛废水治理技术初步研究

通过实验,比较了处理扑热息痛废水的两种工艺流程,认为混凝加兼氧－好氧生物接触氧化法加氧化脱色工艺流程是合理可行的,确定了混凝类型和合理投加量以及操作条件,处理后出水指标ＣＯＤｃｒ、ＢＯＤ５、色度达到国家污水综合排放标准的二级标准。     

Fenton法处理低浓度含氰电镀废水的研究

含氰废水危害大,其排放要求越来越高。本文采用Fenton法处理低浓度含氰电镀废水,探讨了初始pH、n(H2O2):n(FeSO4)、H2O2投加量以及反应时间对废水中总氰去除率的影响。结果表明,当初始pH=3.5、n(H2O2):n(FeSO4)为3.5:1、H2O2投加量为5.0 g.L-1时,反应60 min后去除率可达到93%。反应过程中氧化与絮凝作用均影响了总氰去除率。该法成功应用于某电镀厂低浓度含氰废水的处理,去除率达到98%,效果稳定。     

活性污泥混合木屑制备生物质燃料及其燃烧特性的研究

以活性污泥混合木屑为原料制备生物质燃料,考察成型压力、物料含水率和活性污泥占比对生物质燃料的抗破碎强度和松弛密度的影响,并研究生物质燃料的燃烧特性。研究结果表明:生物质燃料的抗破碎强度和松弛密度均随着成型压力和活性污泥占比的增大而增大,物料含水率控制在15%～20%较为合适;成型压力和物料含水率对生物质燃料的抗破碎强度有显著影响,而成型压力和活性污泥占比对生物质燃料的松弛密度有显著影响;活性污泥的燃烧过程可分为水分析出、挥发分燃烧及无机盐分解3个阶段,木屑的燃烧过程可分为水分析出、挥发分析出及剩余挥发分和固定碳燃烧3个阶段;生物质燃料的燃烧过程因活性污泥占比的多少而有所差异。生物质燃料的综合燃烧性能随着木屑占比的增加而逐渐提高,活性污泥的加入可以改善生物质燃料的着火性能,合理的活性污泥混合木屑工艺和配方能够制备出燃烧性能较好的生物质燃料。     

Adsorption characteristics of carbon tetrachloride from aqueous solution onto polyacrylonitrile-based activated carbon fiber

The isotherm, mechanism and kinetics of carbon tetrachloride (CT) adsorption by polyacrylonitrile-based activated carbon fiber (PAN-ACF) were investigated in batch reactors and a continuous flow reactor, and the regeneration of PAN-ACF was also studied. Freundlich and Dubinin-Radushkevich (D-R) adsorption equations can well describe the adsorption isotherm. CT is mainly adsorbed on the exterior surface of PAN-ACF with low boundary layer effect and rate-controlling step of intra-particle diffusion. The adsorption dynamics in the batch reactor well fits with the pseudo-first-order model, and the breakthrough curves in the continuous flow reactor can be well described by the Yoon-Nelson model. The ACF can be recycled through thermal regeneration, whereas the adsorption capacity decreases from 7.87 to 4.98 mg/g after the fourth regeneration. 78%–94% of CT can be removed from the wastewater of a fluorine chemical plant on a pilot scale, which confirms the efficacy of ACF under industrial conditions. The results indicate that PAN-ACF is applicable to CT removal from wastewater.     

常压盐溶液脱硫石膏转化生成α-半水石膏

Direct phase transformation of flue gas desulfurization gypsum in hot salt solution at atmospheric pressure was investigated. The effects of temperature, salt species, salt concentration, solids content, pH and modifier were examined. The crystals obtained under different conditions and solubility of calcium sulfate in contact with solid gypsum were also determined, α-Calcium sulfate hemihydrate crystals of stubby columnar shape and regular pentahedral sides were obtained under the following conditions: salt concentration 20%-30%, operation temperature 95-100℃, solids mass content in the slurry 10%-30% and neutral pH. Thermodynamic analysis revealed that phase transformation of calcium sulfate dihydrate to α-calcium sulfate hemihydrate occurs because of the difference in solubilities between the two solid gypsum phases in this system.     

常压KCl溶液中α-半水石膏的脱水过程

一般认为,在盐溶液中,亚稳态的α-半水石膏(α-Hemi-hydrated gypgsum,α-Hh9脱水转变为无水石膏(calcium sulfate anhydrite,AH)是直接脱水的过程.研究常压、80～102℃条件下 KCl溶液中α-HH的脱水行为,通过热分析和物相测定阐明α-HH的脱水过程和产物.结果表明KCl溶液中α-HH的脱水过程有2个相转化途径:一个是α-半水石膏→二水石膏(calcium sulfate dihydrate,DH→无水石膏(α→DH→AH)历程;另一个是α-半水石膏→无水石膏(α-HH→AH)历程.α-HH脱水转化为无水石膏的过程伴随有钾石膏的生成.α-HH在KCl溶液中的脱水速率和脱水途径取决于KCl浓度和反应温度.