Development and application of a novel swirl cyclone scrubber—(1) Experimental

Conventional cyclones have a lower collection efficiency for smaller particles and conventional wet scrubbers have significant clogging and fouling problems by salt formation at the tip, the inside and outside of the nozzles, the tubes and the walls of scrubbers. Also, many companies and manufacturing sites have been in trouble for collecting their adhesive particulates. The novel swirl scrubber that we have developed consists mainly of a cyclone and a swirl scrubber with an impact cone and plates. This study reports the collection efficiency of particulates and the application of the novel swirl scrubber. The particle collection efficiency as a function of particle size was investigated with changes of plate angles, nozzle size and pressure, and volumetric flow rate of scrubbing medium. The particle collection efficiency increased with a decrease in plate angle, an increase in pressure of scrubbing medium at the nozzle tip, and an increase in volumetric flow rate of the scrubbing medium. The collection efficiency of PM₁₀ by scrubbing effect was much higher than that by cyclonic effect. In particular, the total increase in particle collection efficiency by scrubbing effect was significant (around 2.5 μm) in particle aerodynamic diameter. The developed novel swirl scrubber can be used for significantly increasing the collection efficiency of TSP, PM₁₀, and PM_2.5, in particular, which have adhesive characteristics. The costs for installation, operation and maintenance of the scrubber system are much cheaper than those of cyclones and scrubbers or other particulate collecting devices.     

TiO2光催化降解气态污染物的影响因素研究进展

TiO2光催化技术作为处理气态污染物的一种手段,具有高效、稳定、无二次污染等优点。光催化反应效率的高低受到TiO2自身性质、光催化反应工艺条件等因素的影响。本文分别从TiO2晶型、晶粒尺寸、TiO2的存在形态、TiO2的负载、掺杂改性、贵金属沉积等与TiO2材料性质相关的因素以及废气初始浓度与流速、废气中的含氧量、湿度、光源和光照强度、反应温度等光催化反应的工艺条件两方面,概述了目前关于TiO2光催化净化废气影响因素的研究进展,介绍了TiO2在气相光催化过程中的失活与再生,并从可见光催化剂的制备应用、多组分污染物气相光催化降解机理及影响因素等方面对未来TiO2光催化研究方向提出建议。     

Computational modeling of a utility boiler tangentially-fired furnace retrofitted with swirl burners

The paper presents 3D numerical investigation of OP-380 boiler tangentially-fired furnace utilizing bituminous coal. The boiler was retrofitted by replacing traditional jet burners with RI-JET2 (Rapid Ignition — JET) swirl burners. This kind of solution is unique in power generation systems. The purpose of this work is to show how the flow, combustion performance and heat exchange in the furnace are affected by introducing rapid ignition phenomena in RI-JET2 burners instead of delayed ignition associated with the traditional jet burners. Results were compared to simulations of similarly designed boiler equipped with traditional jet burners. Furnace simulation was preceded with a single RI-JET2 burner simulation at the inlet to a virtual combustion chamber. The results have shown that pulverized coal (PC) concentrator separates the PC into two streams: concentric with fine particles and axial with coarse particles. Stable flame operation was noticed even without secondary and tertiary air swirl. 3D simulations of combustion chamber have shown that in a burner zone a visibly isolated, concentrated flame exists in the furnace axis. This kind of flame shape reduces corrosion risk and furnace walls slagging as a result of RI-JET2 burner's long range.     

Assembled alginate/chitosan micro-shells for removal of organic pollutants

Natural polyelectrolyte micro-shells were constructed through layer-by-layer (LbL) assembling of alginate sodium (ALG) and chitosan (CHI) onto weakly cross-linked melamine formaldehyde (MF) colloidal particles and subsequent removal of core. The assembled materials presented good film formation ability. It was found that under moderate conditions (room temperature, pure water solution) the ALG/CHI micro-shells can effectively load organic pollutants such as 2,4-dichlorophenol (DCP) and salicylic acid (SA). SEM and AFM images confirmed that the loading behavior of pollutants in the shells occurred and displayed that the feature of shell architecture changes before and after loading. The loading amount of pollutants into shell system was calculated and characterized through HPLC. The loading kinetics analysis showed that the loading process can reach an equilibrium state after approximately 4 h. Compared to the conventional polyelectrolyte (PSS/PAH)₅ shells, the (ALG/CHI)₅ shells had stronger adsorption capacity and faster adsorption rate for pollutant loading. The adsorption isotherm result of organics in the ALG/CHI micro-shells can be well described by Langmuir equation. Advantages of the assembled natural micro-shells composed of ALG/CHI i.e. efficient loading ability to pollutants in aqueous ecosystem, good stability responded to external stimuli as well as fast loading process render them potentially applicable as environmental-friendly micro-container for the treatment of organic pollutants from aqueous solution.     

Prediction of gaseous pollutants and heavy metals during fluidized bed incineration of dye sludge

This research provides an equilibrium model for predicting both the emission of gaseous pollutants and the fate of heavy metals during incineration of biologically treated dye sludge in a bench-scale fluidized bed incinerator. Major gaseous pollutants and hazardous trace heavy metals have been also measured under various operating conditions. The predicted values, which were derived by using a thermodynamic equilibrium model, can be used to determine the optimum operating parameters and the risk associated with hazardous waste incineration by means of verifying experimental data. However, prediction of NO_x emission using a thermodynamic equilibrium model during incineration of waste was not simple. The reason is that the variation of NO_x emission during incineration of waste was affected by the various operating parameters, such as air-fuel ratio(λ _T ), primary air factor(λ ₁ /λ _T ), combustor geometry, method of heat release, and preheating of combustion air. According to the distributions of Cr and Pb simulated by the equilibrium model, all of the Cr in the feed was retained in the ash as the solid phase of Cr₂CO₃. However, most Pb was retained in the ash during incineration as the solid phase of PbSO₄, or heterogeneously deposited onto the fly ash as PbO(g) when the combustion gas becomes cool. Presented at the Int’/Sym. on Chem. Eng. (Cheju, Feb. 8–10, 2001), dedicated to Prof. H. S. Chun on the occasion of his retirement from Korea University.     

Numerical modelling of swirl flow induced by a three-lobed helical pipe

Increasingly in the process industries, the introduction of swirl flow upstream of bends is being used in particle-laden flow to reduce wear. This paper describes a computational fluid dynamics model of the swirl flow that is induced in an airflow passing through a horizontally mounted three-lobed helical pipe. It then goes on to discuss the results of the model verification and validation studies performed. The numerical model was used to further investigate the flows observed within and downstream of both a straight circular pipe and a three-lobed helical pipe that were previously studied during experiments conducted on a laboratory rig for a range of Reynolds numbers. A comparative analysis of the experimental and model predicted data concluded that the simulation results replicated well the experimental results for the control pipe. For the helical pipe, axial velocities were in reasonable agreement with experimental measurements across the range of Reynolds numbers studied. However, tangential velocities were under-predicted by an average of 35% in comparison to the experimental results. As a result, swirl intensity values were also under-predicted, but the values of the computed swirl decay rates were in agreement with those observed during the experiments.     

Novel MBRs for the removal of organic priority pollutants from industrial wastewaters: a review

Organic pollutants which are commonly discharged by the 21 industrial groups identified by the US EPA are regulated under the toxic and priority pollutants list. Novel membrane bioreactor (MBR) systems developed in the last two decades, such as the high‐retention MBRs (HR‐MBRs) and extractive MBRs (EMBRs), could be applied in the retention/extraction of targeted organics from point‐source industrial wastewater to meet stringent regulatory requirements. This paper combines previous reviews and studies conducted on the individual novel MBRs to discuss the potential in applying these technologies in the removal of targeted organic pollutants from industrial wastewater by providing a summary of the technologies and discussing the research gaps that currently hamper their commercialization. Future research should focus on long‐term operation with real industrial wastewaters to identify membrane, operational and biodegradation limitations for further optimization. This includes advances in microbiology and the application of novel membranes to boost the biodegradation and removal capabilities of these novel MBR systems. Energy and economic analyses of the MBRs operated at the pilot/demo scale are required to compare their benefits with conventional treatment systems. © 2015 Society of Chemical Industry     

金属-有机骨架材料用于水中痕量药物污染物的吸附脱除

由于其结构复杂、多态性和多个电离位点等特点,水中的药物污染物很难达到完全脱除。因此,寻找一种高效的吸附剂,对降低此类污染物对人体和环境的影响是至关重要的。金属-有机骨架材料（metal-organic frameworks,MOFs）具有超高比表面积/孔隙率、高度化学/结构可调性以及可设计性等优点,在液相吸附分离中表现出优异的性能。本文简述了近年来MOFs材料、功能化MOFs材料以及MOFs衍生碳材料用于水中痕量抗生素和其他类药物污染物脱除的研究进展。针对特定的药物分子,通过引入特定的官能团及其他物质（如多壁碳纳米管、磁性Fe₃O₄等）可以有效提高吸附能力。此外,通过分析MOFs与药物分子之间的相互作用力,包括静电作用、氢键、π-π相互作用等,并结合本文作者课题组的研究内容,认为今后的研究重点是利用先进的理论计算方法定向筛选或设计高效吸附材料,并充分考虑动力学吸附,以实现水中痕量药物污染物的高效脱除。     

再生水中微量有机污染物去除的研究进展

随着饮用水和非饮用水再生利用计划的不断发展,市政再生水利用过程中潜在的微量有机污染物对水生态和人类健康形成威胁。国内外研究者就微量有机污染物的来源、种类、检测方法、去除技术开展了一系列的研究。在传统的生化工艺基础上进行了改进和创新,同时研发了包括膜技术、吸附技术和高级氧化技术在内的新技术。分析和介绍了目前国内外在污水及再生水中微量有机污染物去除方面的研究,并对今后的研究方向进行了展望。     

Simultaneous removal of SO2, NO and particulate by pilot-scale scrubber system

SO _x and NO _x have both previously been identified as primary precursors of acid rain, and thus the abatement of SO _x and NO _x emissions constitutes a major target in the field of air pollution control. In this study, the efficacy of a pilot-scale scrubber was evaluated with regard to the simultaneous removal of SO₂, NO and particulate with wet catalysts. The removal efficiencies of particulate were measured to be 83, 92 and 97% with catalyst flux of 0.5, 0.8 and 1.5 L/min, respectively. The average removal efficiencies of particulate with different nozzles were approximately 94 and 90% with FF6.5 (5/8 in.) and 14 W (1.0 in.) nozzles, respectively. At least 96–98% of particulate and SO₂ were removed, regardless of the stage number of reactor. In a one-stage scrubber, 83.3% removal efficiency of NO was achieved after 48 hours; however, the two-stage scrubber achieved an NO removal efficiency of 95.7%. Regardless of the liquid-gas ratio, SO₂ and particulate were removed effectively, whereas NO was removed about 84% and 74% under liquid-gas ratio conditions of 39.32 L/m³ and 27.52 L/m³, respectively. In experiments using STS and P.P. pall ring as packing material, particulate and SO₂ removal efficiency values in excess of 98% were achieved; however, NO removal was correlated with the different packing materials tested in this study. With the above optimum operation conditions, even after 20 hours, the removal efficiency for NO stayed at 95% or higher, the removal efficiency for SO₂ stayed at 97% or higher, and the removal efficiency for particulate stayed at 92% or higher. In accordance, then, with the above results, it appears that this process might be utilized in scrubber systems, as well as systems designed to simultaneously remove particulate, SO₂ and NO from flue gas.     

Simulation of turbulent combustion and NO formation in a swirl combustor

A presumed probability density function (PDF) model for temperature fluctuation is proposed and formulated in this paper. It incorporates a two-step reaction mechanism for propane combustion and the thermal and prompt NO formation mechanisms. The present model, together with a new algebraic Reynolds stress model (ASM), is employed to simulate the turbulent combustion and NO formation in a swirl combustor. The calculated propane, carbon monoxide, and carbon dioxide concentrations agree with the measurement. The calculated gas temperature and oxygen and NO concentrations are in general agreement with the measured data. The simulated results show that NO forms mainly in the upstream region of the combustor. The flue gas recirculation effectively abates the nitrogen oxides (NO_x) emission in the combustor.     

Carbon materials and catalytic wet air oxidation of organic pollutants in wastewater

The use of carbon materials as catalytic support or direct catalyst in catalytic wet air oxidation (WAO) of organic pollutants is reviewed. The discussion covers important engineering aspects including the characterisation, activity and stability of carbon catalysts, process performance, reaction kinetics and reactor modelling. Recommendations for further research in catalytic WAO are outlined.     

Mass transfer and reaction process of the wet desulfurization reactor with falling film by cross-flow scrubbing

In the present study, a series of wet flue gas desulfurization experiments have been carried out in comparison with different slurry feeding ways, i.e., by series connection and by parallel connection, by means of cross-flow scrubbing with falling film. The experiment results show that there is optimal desulfurization performance for the slurry feeding way by series connection. A liquid side mass transfer-reaction model and desulfurization mass transfer by cross-flow scrubbing model have been developed. The pH values of the outlet slurry inside the reactor and the ion concentration distributions of H₂SO₃, HSO₃⁻ and SO₃²⁻ along the axial direction of the tubes were obtained by analyzing and calculating the models. The calculation values agree well with the experimental values. It shows that the models can predict well the ion concentration distributions along the axial direction of the tubes. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Simulation of gas-particle turbulent combustion in a pulverized coal-fired swirl combustor

A particle stochastic trajectory model for turbulence-particle reaction interactions is proposed and formulated in the present paper. This model provides the basis for a comprehensive model of pulverized coal combustion. It is applied to the simulation of gas-particle turbulent flow and combustion in a pulverized coal-fired swirl combustor. The results are compared with the measured test data and those obtained by the particle stochastic trajectory model without considering turbulence-particle reaction interactions. The predicted gas temperature and species concentrations in the upstream region of the combustor are improved by utilizing the model with turbulence-particle reaction interactions.     

Tar removal from the producer gas of a small scale downdraft gasifier using a fatty acid based,wet packed-bed scrubber

Small scale gasification combined heat and power (CHP) systems offer an alternative to diesel fuelled generators for power generation in remote communities and industrial sites. Tar and particulates in the producer-gas can damage the internal combustion engine generator and increase operation and maintenance costs. In this work, we present a novel trickle-bed scrubber using filtered waste cooking oil as a cost effective and easy-to-operate gas clean-up method for a small CHP system. The performance of the trickle-bed scrubber was compared against a packed-bed filter utilizing woodchips in a 20 kW_th downdraft gasifier. Used-cooking oil was selected as the solvent and woodchips as the bed-material as these are readily available, inexpensive, and can be recycled in the gasifier as fuel. A woodchip packed-bed filter reduced the tar and particulate matter (PM) in the producer gas from gasification of spruce chips (11% moisture) from 1.6 to 1.4 g/Nm³ and from 0.16 to 0.087 g/Nm³ respectively. The trickle-bed scrubber was able to reduce the tar and PM in the producer gas from gasification of pinewood (8% moisture) from 1.38 to 0.28 g/Nm³, and 0.209 to 0.082 g/Nm³, respectively. Tar and PM removal efficiency improved by 60% and 29% respectively. Components such as benzene, toluene, naphthalene, and biphenylene were the major tar components. After passing the trickle-bed, most tar was removed, with a preference for removal of multi-ringed aromatics and gravimetric tars. Parameters such as the tar and particulate concentration, feedstock moisture content, and feedstock source affect the performance of the gas clean-up system.     

Polymer supports for the removal and degradation of hazardous organic pollutants: an overview

Over the last decades, the presence of highly organic pollutants has increased and become an environmental problem that affects all forms of life. To solve or reduce this problem, multiple strategies have been proposed for the elimination and degradation of organic compounds in aqueous media. This review aims to revise and critically discuss the most recent advances in polymer supports to be used for the adsorption and degradation of organic pollutants. However, the greatest challenge with respect to this issue is the industrial scale‐up of bioremediation processes that allow the removal and degradation of compounds in a continuous and large‐scale manner. © 2019 Society of Chemical Industry     

Numerical prediction of dust capture efficiency of a centrifugal wet scrubber

The gas, liquid, and dust particle behavior inside a centrifugal wet scrubber was simulated and a submodel for predicting its collection efficiency was developed that also takes in account the reduction in collection efficiency due to droplet carryover. Centrifugal wet scrubbers are used in many industries and deliver a high scrubbing efficiency at relatively low capital and operational costs. However, they often experience problems such as droplet carryover at high gas flows and reduced collection efficiency at low gas flows. An improved understanding of flow processes inside the scrubbers is needed to develop a better scrubber design. An experimental test facility was setup for this purpose which also served to validate the CFD modeling results. Ideal operating parameters for maximum scrubbing efficiency and minimum droplet carryover were identified. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1001–1012, 2018     

附加电场超滤膜去除水中有机污染物的研究

研究了附加电场超滤膜工艺去除水中有机污染物的性能,结果表明:原水中的腐殖酸在电场中发生电泳迁移,减少了向膜表面的移动,同时发生凝聚现象,沉积在膜表面形成疏松的滤饼层,有效减缓了膜污染。附加电场后对腐殖酸和4-MBC的去除率均有很大提高。同时发现,吸附是大孔径低压膜去除小分子4-MBC的主要作用,水中腐殖酸的存在对超滤去除4-MBC有很大的促进作用。     

Enrichment of inorganic trace pollutants in re-circulated water streams from a wet limestone flue gas desulphurisation system in two coal power plants

The enrichment of inorganic trace pollutants in re-circulated water streams was studied at two power plants equipped with wet limestone Flue Gas Desulphurisation (FGD) system from the first re-circulation cycle of water up to the start of sampling campaigns. To elucidate the enrichment of inorganic trace pollutants as result of water re-circulation, a partial and total mass balances were undertaken. A t-Student analysis was performed to ascertain whether the mean contribution of filtered water affected the balance of elements and the enrichment of this water stream. The t-Student revealed the mean contribution of filtered water to total mass balance was statistically significant (p < 0.05) for Na, Mg, Cl, B, Mn, Se, Cd, Mo, and U at first plant, and Na, Cl, K, Mg, Hg, Li, B, F, Ni, Zn, Mn, Co Sc, Ge, Se, at the second one. High levels of inorganic trace pollutants in filtered water could be affected by limestone purity, electrostatic precipitator gas temperature, use of additives, fluoride and/or sulphate complexes, and the S/F and S/Cl ratios in the scrubber, which may reduce the gaseous retention efficiencies in FGD and increase the emission of metals by entraining and/or evaporation of droplets as particulate matter from gypsum slurry.     

湿干比对组合填料人工渗滤带除污性能的影响

湿干比作为人工渗滤系统的重要控制参数,影响系统的处理效果。采用模拟人工渗滤系统装置,研究不同湿干比对人工渗滤系统除污能力的影响,试验过程中测定了CODC4、NH3-N、N02-N、NO3--N、TN、TP等指标的变化。结果表明,湿干比为3：4时,人工渗滤系统的除污能力较湿干比为1：6时略好,且能更快形成脱氮环境。对于人工渗滤系统而言,不是湿干比越小就越利于污染物去除,只有选择合适的湿干比,才既能保证系统内充分复氧,又能维持系统内的微生物群落对营养的需求。