添加剂促进亚硫酸钙氧化的实验研究

在湿式石灰石-石膏法脱硫工艺中，副产物——亚硫酸钙的氧化是其中重要的化学过程。利用自行设计的实验室规模的反应装置，通过改变pH、亚硫酸钙浓度、空气流量、催化剂浓度和温度等条件，实验研究了多种添加剂对亚硫酸钙氧化的促进作用。实验结果可为湿法脱硫工艺的设计提供有益的参考。     

耦合回流污泥预浓缩系统的新型氧化沟工艺强化除磷

针对传统的"厌氧+氧化沟"运行模式对低碳源污水除磷能力不佳的问题,采用耦合回流污泥预浓缩系统的新型氧化沟工艺对其强化除磷进行了中试实验研究。通过采用回流污泥预浓缩系统,调试回流污泥浓缩比,提高系统的除磷能力。研究结果表明,在控制最佳回流污泥浓缩比为55%的情况下,出水TP浓度和去除率分别为0.92 mg/L和67.5%,相比于浓缩比为100%、70%、50%和30%的工况,其去除率分别增加了24.3%、27.3%、8.2%和28.6%,强化了系统的除磷效果。另外,ORP可以预示预缺氧池内无效释磷和反硝化程度,以此作为自动调整最佳回流污泥浓缩比的控制参数。     

锌、铁等离子对氧化锌烟气脱硫工艺中亚硫酸锌氧化的影响

在氧化锌法脱除烟气SO2工艺中，脱硫产物亚硫酸锌的氧化是实现锌、硫资源回收的关键环节。在pH为4～5，25℃等条件下，考察了锌、铁、镉离子对亚硫酸锌氧化过程的影响。结果发现，铁离子对亚硫酸锌氧化过程有较强的催化作用，锌离子有一定的催化作用，而低浓度的镉离子几乎不影响氧化过程。进一步的研究表明，锌、铁离子的独自催化氧化速率对各自的浓度均为0．5级响应，但在混合状态下，锌离子对铁离子的催化过程有抑制作用。     

湿式烟气脱硫系统同时脱汞研究

研究表明，湿法烟气脱硫装置(WFGD)可去除烟气中绝大部分Hg²⁺，但对单质汞的吸收效果不明显，因此研究提高湿法烟气脱硫系统中单质汞的氧化率的方法对控制汞的排放具有重要意义。综述了WFGD及在此系统中各种添加剂的脱汞性能，认为在添加剂中，气态的臭氧、液态的次氯酸和氯化钠稀溶液、 黄磷乳浊液、氢硫化钠溶液及EDTA的汞去除效果较好，且不会被SO₂大量消耗，可在WFGD系统实现同时脱硫脱汞；而气态的氯气，液态的K₂S₂O₈溶液虽然也有较好的汞去除效果，但因易被SO₂或亚硫酸盐溶液消耗，当在WFGD系统中用其氧化单质汞时，需要对脱硫塔进行分层或其他改造，使烟气中的SO₂被吸收后再控制汞，提高经济性。     

Swine wastewater treatment in a two stage sequencing batch reactor using real‐time control

Abstract

A laboratory scale two‐stage sequencing batch reactor (TSSBR) was used to study the effectiveness of pH as a real‐time control parameter in swine wastewater treatment. A Ringlace media was inserted into the A/O (Anoxic/Oxic) reactor for bacteria immobilization. The TSSBR was subjected to three levels of organic loading. The pH and ORP (Oxidation Reduction Potential) patterns obtained were consistent with distinct features, enabling the real‐time control strategy to effectively set a flexible aeration time pending on influent concentration, hence resulting in flexible cycle time and HRT (Hydraulic Retention Time) for the system. The real‐time process ensured a removal efficiency of over 99% and 95%, respectively, for ammonia and TOC (Total Organic Carbon). For NO₃ ^‐‐N and PO₄ ^‐3, the run with influent TOC = 4,000 mg/L yielded the most efficient removal of 61% and 95%, respectively. Test results suggest that pH can be a viable tool for on‐line real‐time control of a biological treatment process.     

Decolorizing of lignin wastewater using the photochemical UV/TiO2 process

Studies on applying the photochemical UV/TiO2 oxidation process to treat the lignin-containing wastewater for dissolved organic carbon (DOC), color and reducing A254 (the absorption at the wavelength of 254 nm) have been carried out. The data obtained in this study demonstrate that the UV/TiO2 process is effective in oxidizing the lignin thus reducing the color and DOC of the wastewater treated. The combined UV/TiO2 treatment can achieve better removal of DOC and color than the UV treatment alone. Color removal, based on American Dye Manufacture Index (ADMI) measurement, is greater than 99% if the pH is maintained at 3.0 with the addition of 1 g l(-1) TiO2. When 10 g l(-1) TiO2 is applied, the oxidation reduction potential (ORP) value is reached to result in an 88% removal of both DOC and color. A model was developed based on the variation of ORP during the photochemical reaction to simulate the decoloring process. The proposed model can be used to predict the color removal efficiency of the UV/TiO2 process.     

固定化氧化还原介体加速亚硝酸盐生物反硝化作用

考察了利用循环伏安法所制备的固定化氧化还原介体(AQS/PPy/ACF)加速亚硝酸盐生物反硝化的特性,及其降解过程中pH和氧化还原电位(ORP)的变化特征。结果表明,AQS/PPy/ACF可显著地加速亚硝酸盐的生物降解;在不考虑各因子间交互作用的条件下,AQS/PPy/ACF加速亚硝酸盐降解的最佳条件为温度35℃,pH=8和碳氮比为6;AQS/PPy/ACF加速亚硝酸盐生物反硝化过程中pH的变化趋势与传统的亚硝酸盐生物反硝化过程中pH的变化趋势相似;AQS/PPy/ACF的加入可使亚硝酸盐生物反硝化过程中的ORP降低约45 mV;AQS/PPy/ACF具有较好的催化稳定性。本研究可为亚硝酸盐的生物降解提供新的技术途径,并为该技术的实际应用提供理论基础。     

A real-time optimization method for economic and effective operation of electrostatic precipitators

ABSTRACT

Electrostatic precipitators (ESP) have been considered as the main particulate matter (PM) removal facility in the energy industry. This paper presents a real-time optimization method for a one-chamber industrial ESP in an ultra-low emission power plant with an intelligent optimization system (IOS). The IOS seeks to optimize the energy consumption of ESP subject to the outlet concentration requirement in real-time. A coordination control logic is designed to regulate the optimized operation set points with varying operation conditions. The operation optimized by the IOS is compared with the operations under PID (proportion-integral-derivative) and manual control. The results show that the IOS improves the emission compliance rate from 95% of manual control to 100% and the medium concentration is tuned to be 46.6% closer to the emission target. Furthermore, a good balance between emission and energy consumption is achieved, with 35.50% energy conservation for the same emission upper limit of 30 mg/m³. These results prove that the IOS significantly contributes to the efficient operation and economic PM removal by ESP for the energy industry.     

烟气脱硫过程锰催化氧化亚硫酸钙的研究

利用直径280 mm、高320 mm的间歇式搅拌槽,在MnSO4加入浓度为0～0.05 mol/L的情况下,对亚硫酸钙悬浮液进行了催化氧化实验研究.实验结果表明,锰离子的加入会改变亚硫酸钙的氧化机理及氧化过程,表现为终点氧化率和氧化速率的变化.当Mn2 浓度为0.05 mol/L时,亚硫酸钙的终点氧化率比未加入Mn2 时高30%;此外,与非催化反应过程相比,Mn2 的加入能使亚硫酸钙在一个更宽的浓度范围内(0.02～0.073 mol/L)和一个更宽的时间范围内(20～100 min)均保持较高的氧化速率水平.     

Reaction behavior of SO2 in the sintering process with flue gas recirculation

The primary goal of this paper is to reveal the reaction behavior of SO₂ in the sinter zone, combustion zone, drying–preheating zone, and over-wet zone during flue gas recirculation (FGR) technique. The results showed that SO₂ retention in the sinter zone was associated with free-CaO in the form of CaSO₃/CaSO₄, and the SO₂ adsorption reached a maximum under 900ºC. SO₂ in the flue gas came almost from the combustion zone. One reaction behavior was the oxidation of sulfur in the sintering mix when the temperature was between 800 and 1000ºC; the other behavior was the decomposition of sulfite/sulfate when the temperature was over 1000ºC. However, the SO₂ adsorption in the sintering bed mainly occurred in the drying–preheating zone, adsorbed by CaCO₃, Ca(OH)₂, and CaO. When the SO₂ adsorption reaction in the drying–preheating zone reached equilibrium, the excess SO₂ gas continued to migrate to the over-wet zone and was then absorbed by Ca(OH)₂ and H₂O. The emission rising point of SO₂ moved forward in combustion zone, and the concentration of SO₂ emissions significantly increased in the case of flue gas recirculation (FGR) technique.

Implications: Aiming for the reuse of the sensible heat and a reduction in exhaust gas emission, the FGR technique is proposed in the iron ore sintering process. When using the FGR technique, SO₂ emission in exhaust gas gets changed. In practice, the application of the FGR technique in a sinter plant should be cooperative with the flue gas desulfurization (FGD) technique. Thus, it is necessary to study the influence of the FGR technique on SO₂ emissions because it will directly influence the demand and design of the FGD system.     

湿法烟气脱硫反应过程的实验研究

在石灰石/石膏湿法烟气脱硫中试台上,系统开展了浆液pH值、飞灰浓度、液气比、入口SO2浓度、烟气速度和氧化方式等对脱硫反应过程影响的实验研究。实验表明,脱硫效率随着石膏浆液pH值、液气比的升高而增加,且入口SO2浓度越高,液气比越低,影响效应越明显;脱硫效率随着烟气速度、烟气温度和入口SO2浓度的增加而下降;石膏浆液中飞灰含量对系统脱硫效率具有一定的促进作用:pH值>5.6,飞灰浸出液中Fe3+含量相对较低,Fe3+对脱硫反应过渡态催化氧化影响程度较轻,不同工况脱硫效率差别不大。pH值<5.6,飞灰浸出液中Fe3+含量随pH值降低而增大,增效效果逐渐显著;氧化方式对脱硫反应过程有明显的影响,强制氧化工艺的脱硫效率比自然氧化的高5%左右。     

An overall risk probability-based method for quantification of synergistic and antagonistic effects in health risk assessment for mixtures: theoretical concepts

Purpose

In the assessment of health risks of environmental pollutants, the method of dose addition and the method of independent action are used to assess mixture effects when no synergistic and/or antagonistic effects are present. Currently, no method exists to quantify synergistic and/or antagonistic effects for mixtures. The purpose of this paper is to develop the theoretical concepts of an overall risk probability (ORP)-based method to quantify the synergistic and antagonistic effects in health risk assessment for mixtures.

Method

The ORP for health effects of environmental chemicals was determined from the cumulative probabilities of exposure and effects. This method was used to calculate the ORP for independent mixtures and for mixtures with synergistic and antagonistic effects.

Results

For the independent mixtures, a mixture ORP can be calculated from the product of the ORPs of individual components. For systems of interacting mixtures, a synergistic coefficient and an antagonistic coefficient were defined respectively to quantify the ORPs of each individual component in the mixture. The component ORPs with synergistic and/or antagonistic effects were then used to calculate the total ORP for the mixture.

Conclusions

An ORP-based method was developed to quantify synergistic and antagonistic effects in health risk assessment for mixtures. This represents a first method to generally quantify mixture effects of interacting toxicants.     

Application of neutral electrolyzed water spray for reducing dust levels in a layer breeding house

Reducing airborne dust is an essential process for improving hen housing environment. Dust reduction effects of neutral electrolyzed water (pH 8.2) spray were investigated in a commercial tunnel-ventilated layer breeding house during production in northern China. A multipoint sampler was used to measure airborne dust concentration to study the dust reduction effects and distribution in the house. Compared with the control treatment (without spray), airborne dust level was reduced 34% in the 3 hr after spraying 216 mL m^?2 neutral electrolyzed water in the breeding house. The dust concentration was significantly higher during the periods of feed distribution (1.13 ± 0.13 mg m^?3) and artificial insemination (0.72 ± 0.13 mg m^?3) compared with after spray (0.47 ± 0.09 mg m^?3) and during lights-off period (0.29 ± 0.08 mg m^?3) in the three consecutive testing days (P < 0.05). The experimental cage area was divided into four zones along the length of the house, with zone 1 nearest to the evaporative cooling pad and zone 4 nearest to the fans. The air temperature, relative humidity, airflow rate, and dust concentration were measured at the sampling points of the four zones in 3 consecutive days and mortality of the birds for the duration of a month were investigated. The results showed that the air temperature, airflow rate, dust concentration, and number of dead birds increase from zone 1 to zone 4 in the tunnel-ventilated layer breeding house.

Implications: It is difficult to effectively reduce hen house airborne dust levels and limited information is available on airborne dust distribution in tunnel-ventilated hen houses. This work investigates (i) the application of neutral electrolyzed water spray for reducing dust in a layer breeding houses; (ii) dust concentration variations in 24-hr house operation; as well as (iii) the effects of location on dust concentrations. It was demonstrated that neutral electrolyzed water spray can be efficiently used for dust reduction in poultry houses. Further, a better understanding of the dust concentration variations in 24-hr house operation and in different spatial zones can contribute to bird housing environment management and poultry house design so as to improve bird health.     

Efficient abatement of an iodinated X-ray contrast media iohexol by Co(II) or Cu(II) activated sulfite autoxidation process

Efficient abatement of an iodinated X-ray contrast media iohexol by an emerging sulfite autoxidation advanced oxidation process is demonstrated, which is based on transition metal ion–catalyzed autoxidation of sulfite to form active oxidizing species. The efficacy of the combination of sulfite and transition metal ions (Ag(I), Mn(II), Co(II), Fe(II), Cu(II), Fe(III), or Ce(III)) was tested for iohexol abatement. Co(II) and Cu(II) are proven to show more pronounced catalytic activity than other metals at pH 8.0. According to the quenching studies, sulfate radical (SO₄^??) is identified to be the primary species for oxidation of iohexol. Increasing dosages of metal ion or sulfite and higher pH values are favorable for iohexol abatement. Inhibition of iohexol abatement is observed in the absence of dissolved oxygen, which is vital for the production of SO₅^?? and subsequent formation of SO₄^??. Overall, activation of sulfite to produce reactive radicals with extremely low Co(II) or Cu(II) concentrations (in the range of μg L^?1) in circumneutral conditions is confirmed, which offers a potential SO₄^??-based advanced oxidation process in treatment of aquatic organic contaminants.

     

Establishment of a constructed wetland in extreme dryland

Background, aim, and scope

The project was set to construct an extensive wetland in the southernmost region of Israel at Kibbutz Neot Smadar (30°02′45″ N and 35°01′19″ E). The results of the first period of monitoring, summary, and perspectives are presented. The constructed wetland (CW) was built and the subsequent monitoring performed in the framework of the Southern Arava Sustainable Waste Management Plan, funded by the EU LIFE Fund. The specific aims were: (1) To end current sewage disposal and pollution of the ground, the aquifer, and the dry river bed (wadi) paths by biologically treating the sewage as part of the creation of a sustainable wetland ecosystem. (2) Serve as an example of CW in the Negev highlands and the Arava Valley climates for neighboring communities and as a test ground for plants and building methods appropriate to hyper arid climate. (3) Serve as an educational resource and tourist attraction for groups to learn about water reuse, recycling, local wildlife and migrating birds, including serving the heart of a planned Ecological–Educational Bird Park. This report is intended to allow others who are planning similar systems in hyper arid climates to learn from our experience.

Materials and methods

The project is located in an extreme arid desert with less than 40 mm of rain annually and temperature ranges of ?5°C to +42°C. The site receives 165–185 m³ of municipal and agricultural wastes daily, including cowshed and goat wastes and winery outflow.

Results

The CW establishment at Neot Smadar was completed in October 2006. For 8 months, clean water flowed through the system while the plants were taking root. In June 2007, the wetland was connected to the oxidation pond and full operation began. Because of seepage and evaporation, during the first several months, the water level was not high enough to allow free flow from one bed to the next. To bed A, the water was pumped periodically from the oxidation pond (Fig. 1) and from there flowed by gravitation through the rest of the system. The initial results of the monitoring are promising. In nearly all measurements, the system succeeded as expected to reduce levels of contaminants at least to the level acceptable for irrigating fruit trees and often to the level of unlimited irrigation. The introduction of the plants in the system and their physiological performance were evaluated and were found to correlate well to the quality of water in the various beds.

Discussion

It should be said at the outset that evaluation of the performance of a CW system is a long-term process. Thus, the main aim of this report is to present the problems, difficulties, preliminary results, and concepts concerned with the first stage of establishment of CW in an extremely dry region.

Conclusions

The CW system was designed to dispose of municipal and agricultural wastes in a way that not merely reduces pollution, but adds to environmental quality by creating accessible parkland for local residents and tourists. Several factors affected the performance of the system at the initial stages of operation: ecological balance between microbes and plants, big seasonal variations, seepage and evaporation reduced the flow in the initial operation of the system. Despite the initial difficulties, the quality of water coming out the system is acceptable for irrigation.

Recommendations and perspectives

The CW can function well under extreme dryland conditions. The oxidation pond was the major source of evaporation and bad odors. Therefore, alternatives to the oxidation pond are needed. Cost effectiveness of the system still has to be evaluated systematically.     

Modeling and optimization of wet flue gas desulfurization system based on a hybrid modeling method

Sulfur dioxide (SO₂) is one of the main air pollutants from many industries. Most coal-fired power plants in China use wet flue gas desulfurization (WFGD) as the main method for SO₂ removal. Presently, the operating of WFGD lacks accurate modeling method to predict outlet concentration, let alone optimization method. As a result, operating parameters and running status of WFGD are adjusted based on the experience of the experts, which brings about the possibility of material waste and excessive emissions. In this paper, a novel WFGD model combining a mathematical model and an artificial neural network (ANN) was developed to forecast SO₂ emissions. Operation data from a 1000-MW coal-fired unit was collected and divided into two separated sets for model training and validation. The hybrid model consisting a mechanism model and a 9-input ANN had the best performance on both training and validation sets in terms of RMSE (root mean square error) and MRE (mean relative error) and was chosen as the model used in optimization. A comprehensive cost model of WFGD was also constructed to estimate real-time operation cost. Based on the hybrid WFGD model and cost model, a particle swarm optimization (PSO)-based solver was designed to derive the cost-effective set points under different operation conditions. The optimization results demonstrated that the optimized operating parameters could effectively keep the SO₂ emissions within the standard, whereas the SO₂ emissions was decreased by 30.79% with less than 2% increase of total operating cost.

Implications: Sulfur dioxide (SO₂) is one of the main pollutants generated during coal combustion in power plants, and wet flue gas desulfurization (WFGD) is the main facility for SO₂ removal. A hybrid model combining SO₂ removal mathematical model with data-driven model achieves more accurate prediction of outlet concentration. Particle swarm optimization with a penalty function efficiently solves the optimization problem of WFGD subject to operation cost under multiple operation conditions. The proposed model and optimization method is able to direct the optimized operation of WFGD with enhanced emission and economic performance.     

Removal characteristics of sulfuric acid aerosols from coal-fired power plants

With increasing attention on sulfuric acid emission, investigations on the removal characteristics of sulfuric acid aerosols by the limestone gypsum wet flue gas desulfurization (WFGD) system and the wet electrostatic precipitator (WESP) were carried out in two coal-fired power plants, and the effects of the WFGD scrubber type and the flue gas characteristics were discussed. The results showed that it was necessary to install the WESP device after desulfurization, as the WFGD system was inefficient to remove sulfuric acid aerosols from the flue gas. The removal efficiency of sulfuric acid aerosols in the WFGD system with double scrubbers ranged from 50% to 65%, which was higher than that with a single scrubber, ranging from 30% to 40%. Furthermore, the removal efficiency of WESP on the sulfuric acid aerosols was from 47.9% to 52.4%. With increased concentrations of SO₃ and particles in the flue gas, the removal efficiencies of the WFGD and the WESP on the sulfuric acid aerosols were increased.

Implications: Investigations on removal of sulfuric acid aerosols by the WFGD and the WESP in the power plants were aimed at the control of sulfuric acid emission. The results showed that the improvement of the WFGD system was beneficial for the reduction of sulfuric acid emission, while the WESP system was essential to control the final sulfuric acid aerosol concentration.     

沿面放电氧化液相亚硫酸铵

为了解决湿式氨法烟气脱硫生成不稳定亚硫酸铵（（NH4）2SO3）副产物的问题,设计了以不锈钢弹簧和溶液分别作为高压和低压电极的沿面放电系统,对液相（NH4）2SO3的氧化进行了研究。空气从反应器上方进入后经放电区域形成活性物质,再由底部的曝气头鼓入溶液并与（NH4）2SO3发生反应。比较了沿面放电处理与传统曝气处理的氧化效率,考察了放电电压、载气气量和初始浓度等因素对（NH4）2SO3氧化的影响。结果表明,沿面放电对（NH4）2SO3有显著的氧化效果;优化条件下的（NH4）2SO3氧化率接近100%;溶液中（NH4）2SO4与（NH4）2SO3的浓度比小于1时有利于（NH4）2SO3的氧化。     

An Investigation of Odors and Volatile Organic Compounds Released during Composting

ABSTRACT

The emissions of odors and volatile organic compounds produced from a commercial composting operation have been studied using a laboratory-scale composting system. The composting activity of a typical commercial compost feed was followed by monitoring the composting temperature, as well as the respiratory rate. Using a controlled aeration system, the gaseous volatiles produced were tested for odors using the "dilution-to-threshold" method, as well as gas composition, as determined by gas chromatography-mass spectrometry.

The results indicated that while there may be a reasonable correlation between the release of volatile organic compounds (VOCs) and odors, care has to be taken when trying to identify offensive odors with specific chemical species. However, the data obtained suggests that offensive odors formed during commercial composting may be due to sulfurous and nitrogenous compounds, although their concentrations in the compost gases may not be very high.

The major release of VOCs occurred during the first two weeks of composting, after which the gaseous releases fell dramatically as the composting process proceeded and temperatures started to fall.     

络合铁法脱除垃圾填埋气中的H2S

建立了以EDTA和柠檬酸为铁盐络合剂的循环脱硫体系，采用络合铁法对垃圾填埋气中的H₂S进行脱硫中试实验，结果表明实验所建立的络合铁脱硫体系运行稳定，脱硫效率高，适合应用于垃圾填埋气中硫化氢脱除。