Mechanisms of granular activated carbon anaerobic fluidized-bed process for treating phenols wastewater

Granular activated carbon (GAC) anaerobic fluidized bed reactor was applied to treating phenols wastewater. When influent phenol concentration was 1000 mg/L, volume loadings of phenol and COD Cr were 0 39 kg/(m 3·d) and 0 98 kg/(m 3·d), their removal rates were 99 9% and 96 4% respectively. From analyzing above results, the main mechanisms of the process are that through fluidizing GAC, its adsorption is combined with biodegradation, both activities are brought into full play, and phenol in wastewater is effectively decomposed. Meanwhile problems concerning gas liquid separation and medium plugging are well solved.

Removal of CO2 in a multistage fluidized bed reactor by amine impregnated activated carbon: optimization using response surface methodology

Carbon dioxide (CO2) is the major component of greenhouse gas. Increase in concentration of CO2 in the atmosphere leads to global warming. To remove the CO2 from waste flue gas a four-stage counter-current multistage fluidized bed adsorber was developed and operated in continuous bubbling fluidization regime for the two丒phase system. This paper describes the optimum condition for CO2 removal efficiency in a multistage fluidized bed reactor using amine impregnated activated carbon. Response surface methodology with central composite design was used to determine the effect of three variables on the response. The variables are inlet concentration of CO2 in ppm (ranging from 3000 to 20,000), impregnation ratio of monoethanol amine (ranging from 0.2 to 0.6) and weir height in mm (20-60). The response was CO2 removal efficiency. The factor which was most influential has been identified from the analysis of variance. The optimum CO2 removal efficiency for the amine impregnated activated carbon (MEA-AC) was found to be 95.17%, at initial concentration of CO2 7312.85 ppm, chemical impregnation ratio of 0.31, and weir height 48.65 mm. From the experiment, the CO2 removal efficiency was found to be 95.97% at the same operating conditions. The predicted response was found to relevance with experimental data.

The Carbonation Behaviors of Limestone Particle in Oxygen-Fuel Circulating Fluidized Bed O₂/CO₂Flue Gas

Limestone powder is still applied as SO2 sorbent in emerging oxygen-fuel circulating fluidized bed boiler, but its carbonation in O2/CO2 flue gas is an unclear problem. For a better understanding of carbonation behaviors, the tube furnace heating system was built for simulating circulating fluidized bed boiler flue gas by regulating the supply of O, CO2, N2, SO2 and H2O, and Carbonation reaction was tested. Thermal gravimetric analysis and scanning electron microscopy were used. It was found that carbonation is closely related to temperature, CO2 concentration, impurities, water vapor, and cycle times;high temperature can promote carbonation process;high concentration of CO2 can inhibit the chemical reaction stage speed of carbonation process, but it has little effect on the final conversion rate;water vapor can increase the final conversion rate of carbonation;the cycle times will reduce the activity of carbonation. The presence of carbonation turns the traditional boiler flue gas indirect desulfurization model into indirect desulfurization mechanism which does not have a negative impact on SO2 removal efficiency.

Numerical simulations and comparative analysis of two- and three-dimensional circulating fluidized bed reactors for CO2 capture

Carbon dioxide(CO2),the main gas emitted from fossil burning,is the primary contributor to global warming.Circulating fluidized bed reactor(CFBR)is proved as an energy-efficient method for post-combustion CO2 capture.The numerical simulation by computational fluid dynamics(CFD)is believed as a promising tool to study CO2 adsorption process in CFBR.Although three-dimensional(3D)simulations were proved to have better predicting performance with the experimental results,two-dimensional(2D)simulations have been widely reported for qualitative and quantitative studies on gas-solid behavior in CFBR for its higher computational efficiency recently.However,the discrepancies between 2D and 3D simulations have rarely been evaluated by detailed study.Considering that the differences between the 2D and 3D simulations will vary substantially with the changes of independent operating conditions,it is beneficial to lower computational costs to clarify the effects of dimensionality on the numerical CO2 adsorption runs under various operating conditions.In this work,the comparative analysis for CO2 adsorption in 2D and 3D simulations was conducted to enlighten the effects of dimensionality on the hydrodynamics and reaction behaviors,in which the separation rate,species distribution and hydrodynamic characteristics were comparatively studied for both model frames.With both accuracy and computational costs considered,the viable suggestions were provided in selecting appropriate model frame for the studies on optimization of operating conditions,which directly affect the capture and energy efficiencies of cyclic CO2 capture process in CFBR.

Study on Treatment of the Pesticide Wastewater by the Composite Process of Biological Active Carbon Filter-Fluid Bed

[ Objectlve] The research aimed to study treatment effect of the pesticide wastewater by the composite process of biological active car- bon filter-fluid bed. [Method] The composite process of biological active carbon filter- fluid bed was applied to treat the mixed pesticide wastewater. The removal efficiencies of CODcr, BODs, NH3-N, SS and the influence factors were investigated. [ Result] The composite process had good treatment efficiency for pesticide wastewater. After running stably, the average removal rates of CODc,, BODs, NH3-N and SS were re- spectively 91.6%, 96.2%, 90.2% and 87.5%. All indices reached the third level cdteda specified in Comprehensive Standard of the Sewage Dis- charge （DB12/356-2008）. [ Conclusionl The whole system operates reliably and simply, and provides a stable, convenient and economical solu- tion for deep treatment of the mixed pesticide wastewater.

Anaerobic tapered fluidized bed reactor for starch wastewater treatment and modeling using multilayer perceptron neural network

treatability of synthetic sago wastewater was investigated in a laboratory anaerobic tapered fluidized bed reactor （ATFBR） with a mesoporous granular activated carbon （GAC） as a support material. The experimental protocol was defined to examine the effect of the maximum organic loading rate （OLR）, hydraulic retention time （HRT）, the efficiency of the reactor and to report on its steady- state performance. The reactor was subjected to a steady-state operation over a range of OLR up to 85.44 kg COD/（m^3·d）. The COD removal efficiency was found to be 92% in the reactor while the biogas produced in the digester reached 25.38 m^3/（m^3·d） of the reactor. With the increase of OLR from 83.7 kg COD/（m^3·d）, the COD removal efficiency decreased. Also an artificial neural network （ANN） model using multilayer perceptron （MLP） has been developed for a system of two input variable and five output dependent variables. For the training of the input-output data, the experimental values obtained have been used. The output parameters predicted have been found to be much closer to the corresponding experimental ones and the model was validated for 30% of the untrained data. The mean square error （MSE） was found to be only 0.0146.

Removal of disinfection by-products formation potential by biologically intensified process

The removal of disinfection by-products formation potential(DBPFP) in artificially intensified biological activated carbon(IBAC) process which is developed on the basis of traditional ozone granular activated carbon was evaluated. By IBAC removals of 31% and 68% for THMFP and HAAFP were obtained respectively. Under identical conditions, the removals of the same substances were 4% and 32% respectively only by the granular activated carbon(GAC) process. Compared with GAC, the high removal rates of the two formed potential substances were due to the increasing of bioactivity of the media and the synergistic capabilities of biological degradation cooperating with activated carbon adsorption of organic compounds. A clear linear correlation(R 2=0.9562 and R 2=0.9007) between DOC HAAFP removal rate and Empty Bed Contact Time(EBCT) of IBAC process was observed, while that between THMFP removal rate and EBCT of GAC was R 2=0.9782. In addition certain linear correlations between THMFP, HAAFP and UV 254 (R 2=0.855 and R 2=0.7702) were found for the treated water. For IBAC process there are also more advantages such as long backwashing cycle time, low backwashing intensity and prolonging activated carbon lifetime and so on.

Effect of Operating Parameters on Carbon Dioxide Depressurized Regeneration in Circulating Fluidized Bed Downer using Computational Fluid Dynamics

Typically,heating or high-temperature treatment has been used to regenerate solid sorbent.In this study,the depressurized regeneration using a circulating fluidized bed downer was proposed and the significance of its operating parameters was identified.Two-dimensional computational fluid dynamics were employed to systematically investigate the effects of operating parameters on carbon dioxide depressurized regeneration with potassium carbonate solid sorbent particles.The simulated model was based on a laboratory scale circulating fluidized bed downer.The chemical equilibrium model for predicting the highest outlet carbon dioxide mass fraction was then used.A central composite design was employed to identify the main,quadratic,and interaction effects of operating parameters to the regeneration process.The operating parameters consisted of the outlet system pressure,inlet gas velocity,and inlet solid circulation rate,while the response variable was the released outlet carbon dioxide mass fraction.Among the multiple operating parameters,there were two main operating parameters and their combinations,namely the inlet gas velocity,outlet system pressure,square of inlet gas velocity,and interaction between inlet gas velocity and outlet system pressure,which had great impacts on the regeneration.All the main,quadratic,and interaction effects were explained.Then,the optimal operating conditions were obtained through the response surface method.

Removal of disinfection by-product formation potentials by biologically assisted GAC treatment

The object of this paper is to evaluate the removal of disinfection by-products formation potential by artificially intensified biological activated carbon（BAC） process which is developed on the basis of traditional ozone granular activated carbon （GAC）. The results show that 23.1% of trihalomethane formation potential （THMFP） and 68% of haloacetic acid formation potential （HAAFP） can be removed by BAC, respectively. Under the same conditions, the removal rates of the same substances were 12.2% and 13-25% respectively only by GAC process. Compared with GAC, the high removal rates of the two formed potential substances were due to the increasing of bioactivity of the media and the synergistic capabilities of biological degradation cooperating with activated carbon adsorption of organic compounds. BAC process has some advantages such as long backwashing cycle time, low backwashing intensity and prolonged activated carbon lifetime, etc.

中心脉冲气-液-固循环流化床微生物燃料电池产电特性

为进一步提升微生物燃料电池(MFC)的电化学性能,设计并搭建了一个中心脉冲气-液-固循环流化床微生物燃料电池(CPCFB-MFC),通过设计多组实验工况研究了脉冲液流频率和幅值、颗粒循环速率及气体流量对CPCFB-MFC产电及污水处理特性的影响。在中心液流脉冲频率为0.25 Hz、脉冲幅值为0.08 m/s、颗粒循环速率为3.3 kg/(m^(2)·s)、气体流量为2 L/min条件下,CPCFB-MFC的输出电压达到最高(为649.2 mV),此时污水处理时间最短(为77 h)。通过对比不同工况的污水处理效率和综合能耗,证明了在反应器内采用脉冲液流和气-液-固循环运行方式能进一步提升MFC的综合性能。这项工作对推动微生物燃料电池技术的产业化具有重要意义。

面向双碳目标的多元燃料循环流化床燃烧技术展望

双碳目标让煤电机组的低碳化受到广泛关注。低碳燃料替代是循环流化床(circulating fluidized bed,CFB)燃烧发电技术的重要方向之一。零碳、低碳燃料特性与煤显著不同,这对CFB燃烧技术的燃料适应性提出了新的挑战。该文从燃料的着火与燃尽、低成本污染物控制和受热面安全3个角度,剖析CFB燃烧技术燃料适应性广的理论基础,提出丰富的床料蓄热和高效物料循环是支撑其适应低碳灵活燃料燃烧的两大基础条件。可以通过构建合理流态和炉内气氛,进一步提升CFB燃烧技术在多元低碳燃料上的适应性。对于生物质燃料,利用循环物料冲刷减少高温受热面沾污、减轻腐蚀,能够提高生物质发电的蒸汽参数,进而提高生物质发电的经济性;对于氨燃料,利用炉内高温床料蓄热解决稳燃问题,利用炉内气氛调控解决低成本脱硝问题,有望攻克氨燃料的高效低成本燃烧技术;对于化工冶金过程中广泛存在的超低热值废气,可利用CFB燃烧技术无害化处理同时回收废气中热能,显著提升废气处理的经济性,减少系统能耗和碳排放。面向双碳目标,CFB燃烧技术将进一步发挥和拓展其燃料适应性广的优势,具有较好前景。

活性添加剂对生物质循环流化床燃烧特性影响研究进展

循环流化床(circulating fluidized bed,CFB)燃烧被认为是未来大规模开发利用生物质能源最有潜力的技术之一。该文概述生物质直燃CFB锅炉在运行实践中面临的受热面沾污腐蚀、床料烧结团聚、燃烧不均匀、NO_(x)原始排放高等诸多问题和对应的活性添加剂解决方案。如采用硅铝基、硫基、钙基、磷基等添加剂形成高熔点盐或降低Cl含量,可有效缓解炉内受热面沾污腐蚀等现象;借助载氧体辅助燃烧技术,有望通过替代床料的氧化还原循环反应改善炉内气氛分布均匀性并提高燃烧效率;在燃烧过程中投入适量的铁基或还原类添加剂,可抑制含氮前驱体向NO_(x)转化,亦或还原已生成的NO_(x),从而降低NO_(x)原始排放。未来,对添加剂的研究应重点关注机理分析、标准化、工程放大、固废资源化利用等方向,以期实现对生物质的清洁高效利用。

碳化条件下循环流化床粉煤灰的水化性能

以固废——循环流化床粉煤灰和脱硫石膏为矿物掺合料制备砂浆,通过碳化试验、强度试验以及X射线衍射仪、扫描电镜-能谱等微观测试手段,探究了砂浆在碳化条件下的固碳能力、力学性能和反应机理.结果表明:固废的掺入增加了浆体孔隙,提高了钙源含量,使砂浆的CO_(2)吸收量显著提高;碳化养护后砂浆的力学性能显著提高,消除了高硫带来的膨胀问题;应用该工艺可将内蒙古地区工业固废利用率提高至36.5%.

循环流化床炉生物质掺烧降碳技术研究

火电行业的降碳工作直接关系到“双碳”目标的实现,而循环流化床炉具有燃料适用性广的优势,能够大比例掺烧可再生“零碳”能源-生物质燃料,大幅降低火电厂碳排放。在役循环流化床炉和燃煤条件,进行生物质混合掺烧试验,并对燃烧稳定性、污染物排放及热效率进行了综合评估。掺烧试验结果表明:生产单位蒸汽煤耗量随掺烧比增大显著降低,燃烧工况稳定;掺烧条件下单位石灰石耗量降至4.5 kg/t蒸汽左右,SO_(2)排放量达标;掺烧后炉内温度升高,排烟温度升高,而飞灰量增大,使热损失有所增大;通过调控风量配比、料层差压及过量空气系数,总体热效率接近设计值;长期运行条件下,生物质掺烧比达到约30%,SO_(2)和NOx排放量合格,尾部受热面未受明显腐蚀,1 t蒸汽减排CO_(2)量约480 kg。

基于颗粒示踪的循环流化床锅炉煤燃烧残碳量预测

锅炉燃烧残碳量是反映锅炉燃烧效率的重要指标,预测其数值对锅炉运行调整及设计有着重要意义。依据试验测量的煤颗粒在炉内的运动路径及停留时间开展炉膛出口含碳量预测计算,探究停留时间、炉膛温度、煤种、过量空气系数对煤颗粒残碳量的影响。结果表明,停留时间越长的煤颗粒残碳量越低;床温从800℃升高到900℃,残碳量降低约40%~50%;过量空气系数从1.05增大到1.3,残碳量降低10%~30%;煤种的特性是影响残碳量的关键因素,煤的挥发分含量、固定碳含量、反应活性决定了煤的燃尽。通过与循环流化床锅炉设计方法计算含碳量对比以及实炉试验数据验证,证明煤颗粒残碳量基于运动轨迹方法预测结果的合理性。

Experimental study on the activation of coal gasification fly ash from industrial CFB gasifiers

Coal gasification fly ash(CGFA)is an industrial solid waste from the coal circulating fluidized bed(CFB)gasification process,and it needs to be effectively disposed to achieve sustainable development of the environment.To realize the application of CGFA as a precursor of porous carbon materials,the physicochemical properties of three kinds of CGFA from industrial CFB gasifiers are analyzed.Then,the activation potential of CGFA is acquired via steam activation experiments in a tube furnace reactor.Finally,the fluidization activation technology of CGFA is practiced in a bench-scale CFB test rig,and its advantages are highlighted.The results show that CGFA is characterized by a high carbon content in the range of 54.06%–74.09%,an ultrafine particle size(d50:16.3–26.1 μm),and a relatively developed pore structure(specific surface area SSA:139.29–551.97 m^(2)·g^(-1)).The proportion of micropores in CGFA increases gradually with the coal rank.Steam activation experiments show that the pore development of CGFA mainly includes three stages:initial pore development,dynamic equilibrium between micropores and mesopores and pore collapse.The SSA of lignite fly ash(LFA),subbituminous fly ash(SBFA)and anthracite fly ash(AFA)is maximally increased by 105%,13%and 72%after steam activation;the order of the largest carbon reaction rate and decomposition ratio of steam among the three kinds of CGFA is SBFA>LFA>AFA.As the ratio of oxygen to carbon during the fluidization activation of LFA is from 0.09 to 0.19,the carbon conversion ratio increases from 14.4%to 26.8%and the cold gas efficiency increases from 6.8%to 10.2%.The SSA of LFA increases by up to 53.9%during the fluidization activation process,which is mainly due to the mesoporous development.Relative to steam activation in a tube furnace reactor,fluidization activation takes an extremely short time(seconds)to achieve the same activation effect.It is expected to further improve the activation effect of LFA by regulating the carbon conversion ratio range of 27%–35%to create pores in the initial development stage.

Physicochemical Properties of Coal Gasification Fly Ash from Circulating Fluidized Bed Gasifier

The coal gasification fly ash(CGFA) is an industrial solid waste from coal gasification process and needs to be effectively disposed for environmental protection and resource utilization.To further clarify the feasibility of CGFA to prepare porous carbon materials,the physicochemical properties of ten kinds of CGFA from circulating fluidized bed(CFB) gasifiers were analyzed in detail.The results of proximate and ultimate analysis show that the CGFA is characterized with the features of near zero moisture content,low volatile content as low as 0.90%-9.76%,high carbon content in the range of 37.89%-81.62%,and ultrafine particle size(d50=15.8-46.2 μm).The automatic specific surface area(SSA) and pore size analyzer were used to detect the pore structure,it is found that the pore structure of CGFA is relatively developed,and part of the CGFA has the basic conditions to be used directly as porous carbon materials.From SEM images,the microscopic morphology of the CGFA is significantly different,and they basically have the characteristics of loose and porous structure.XRD and Roman spectroscopy were used to characterize the carbon structure.The result shows that the CGFA contains abundant amorphous carbon structure,and thus the CGFA has a good reactivity and a potential to improve pore structure through further activation.Through thermal gravimetric analysis,it can be concluded that the order of reactivity of the CGFA under CO_(2) atmosphere has a good correlation with the degree of metamorphism of the raw coal.The gasification reactivity of the CGFA is generally consistent with the change trend of micropores combined with the pore structure.According to the physicochemical properties,the CGFA has a good application prospect in the preparation of porous carbon materials.

某电子工业园区污水处理厂工程设计

针对某电子工业园区污水处理厂进水水质特性,采用粗格栅及进水泵房-细格栅及沉砂池-调节池(含事故池)-混凝初沉池-水解酸化池-厌氧-多级好氧缺氧生物池-二沉池-高效沉淀池-反硝化深床滤池-活性炭(焦)吸附流化床-氧化铝吸附滤池-接触消毒工艺,并针对难降解COD、氟化物等问题,设计了保证率高且切换灵活的运行模式,介绍了工艺流程、主要设计参数及运行效果。污水处理厂出水可以稳定达到《地表水环境质量标准》(GB3838-2002)Ⅲ类标准。

丁烷脱氢制丁烯微球催化剂制备工艺的选择以及铝溶胶加入量的影响

采用喷雾成型工艺制备了用于循环流化床丁烷脱氢制丁烯的2种微球催化剂(负载金属成型、铝球负载),并进行了催化活性评价,考察了铝溶胶黏结剂的加入量(以Al_(2)O_(3)质量分数计)对铝球负载微球催化剂相关性能的影响,以及优化配方工艺下制得该催化剂的再生性能。结果表明:铝球负载微球催化剂的综合催化性能较好,丁烯收率高达64.1%;铝溶胶含量是铝球负载微球催化剂制备过程的关键因素,必须平衡控制铝溶胶加入量为0~3.0%及优化制备工艺,才能保证铝球负载微球催化剂的孔容、磨损指数、粒径分布中的中位粒径(D50)满足循环流化床使用的相应指标要求;积炭后的铝球负载微球催化剂的10次再生循环使用性能良好,丁烯选择性可持续维持在94.0%左右,再生后的每个反应过程均能高效稳定运行50 min,丁烯收率保持在61.0%~62.0%。

A review on treatment of disinfection byproduct precursors by biological activated carbon process

Disinfection by-products(DBPs)in water systems have attracted increasing attention due to their toxic effects.Removal of precursors(mainly natural organic matter(NOM))prior to the disinfection process has been recognized as the ideal strategy to control the DBP levels.Currently,biological activated carbon(BAC)process is a highly recommended and prevalent process for treatment of DBP precursors in advanced water treatment.This paper first introduces the fundamental knowledge of BAC process,including the history,basic principles,typical process flow,and basic operational parameters.Then,the selection of BAC process for treatment of DBP precursors is explained in detail based on the comparative analysis of dominant water treatment technologies from the aspects of mechanisms for NOM removal as well as the treatability of different groups of DBP precursors.Next,a thorough overview is presented to summarize the recent developments and breakthroughs in the removal of DBP precursors using BAC process,and the contents involved include effect of pre-BAC ozonation,removal performance of various DBP precursors,toxicity risk reduction,fractional analysis of NOM,effect of empty bed contact time(EBCT)and engineered biofiltration.Finally,some recommendations are made to strengthen current research and address the knowledge gaps,including the issues of microbial mechanisms,toxicity evaluation,degradation kinetics and microbial products.