High Efficiency Dust Scrubbers for Continuous Miner in Underground Mines

Based on the experimental data by a full scale test model and the relevant existing achievements, four new concepts of group dust scrubbers were designed in the paper. The new dust scrubbers consist of two to four common dust separators in series: wet fan, wet Venturi and foam filter bed. Wetting and foaming agents are used to increase the efficiency of dust separation. High efficiency is not required for each part of the group dust scrubbers, but the whole system has a high working reliability. All parts of the group dust scrubbers have the most suitable separating efficiency for different size and concentration of dust particles in airflow, according to their technical features. Four group dust scrubbers have a high efficiency from 94.4% to 99.7% for separating respirable dust at a rational cost.

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,ε,is proposed in this study to predict desulfurization efficiency of this dual-alkali FGD system.ε 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.

Self-developed Pneumatic Spraying Scrubber for Recovering NO_x from Metallurgical Exhaust

NOx is generally composed of NO,NO2,N2O,N2O4,and N2O5,which may form photochemical smoke and may lead to acid rain,greenhouse effect and destruction of the ozone layer in the atmosphere.In this paper,a new pneumatic spraying scrubber was developed for recovering NOx from metallurgical exhaust.In this device,NOx was converted into nitric acid,which was then recycled in the oxidization reactor.Compared with conventional pneumatic spraying scrubbers,the self-developed pneumatic spraying scrubber had significant advantages,such as the simple structure without liquid circulation pump,easy operation,energy conservation,and the high recovery rate.The influences of various parameters,such as the spray tube height,the spray nozzle diameter,the concentration and temperature of the absorbent,and the operating pressure,on the recovery of NOx were also investigated.The best NOx removal efficiency was 76.08%.When the spray tube height was 0.74 m,the nozzle diameter was 0.5 mm,the absorbent content was 5%at 30℃,and the operating pressure was 0.15-0.17 MPa.The invented pneumatic spraying scrubber successfully solves the problems of high-concentration NOx absorption and regeneration of nitric acid.In addition,the device can also absorb other harmful gases and provide a possible new treatment process for air pollution control.

Numerical analysis of thermal plasma scrubber for CF4 decomposition

CF4 gas emitted in the semiconductor and display manufacturing process is a very harmful greenhouse gas.It must be removed or converted safely due to its extreme toxicity.Although a CF4 decomposition system using a thermal plasma scrubber was commercialized,its removal efficiency is limited.In this work,a numerical analysis of CF4 decomposition in the thermal plasma scrubber was carried out in order to propose an efficient decomposition environment.The decomposition and recombination temperatures of CF4 were analyzed using thermodynamic equilibrium calculations.The chemical reaction of CF4 decomposition into carbon and fluorine gas was considered in this numerical analysis.The injection position and angle of the CF4 were controlled in order to enhance the decomposition rate.The vertical injection of CF4 near the torch exit improved the mixing of the CF4 with the thermal plasma flame.In addition,it was confirmed that the high temperature region expanded due to a vortex generated by strong turbulence in the bottleneck-shaped reactor.As a result,it is revealed that the CF4 injection location and the reactor configuration are the most important factors in improving the decomposition rate.

A computational fluid dynamics investigation of a novel flooded-bed dust scrubber with vibrating mesh

This work proposes a vibrating mesh screen as an alternative to the static mesh screen currently used in conventional flooded-bed dust scrubbers for removing airborne coal mine dust in the continuous mining environment.Fundamental assessments suggest that a vibrating screen may improve the dust collection efficiency of scrubber systems and mitigate the clogging issues associated with the conventional design.To evaluate this hypothesis,computational fluid dynamics(CFD)simulations were carried out to assess the effects of vibration conditions(i.e.,frequency and amplitude)on the dust particle-mesh interaction and mesh wetting conditions,which are the two decisive factors in determining the dust collection efficiency.The results suggest that the vibrating mesh screen can enhance dust particle collision opportunities on the mesh and increase mesh wetted area as compared to the static mesh screen.The effects of mesh screen aperture,coal dust concentration,and spray nozzle flow rate on the performance of the vibrating mesh are also evaluated.Finally,a simplified three-phase flow simulation including airflow,dust particles,and water droplet spray is performed,and the results reflect a significant improvement of dust collection efficiency in the liquid-coated vibrating mesh screen.

Experimental study of the dust-removal performance of a wet scrubber

A variety of dust control methods are often applied in coal mines,among which the application of wet scrubbers has proven to be an efficient technology for the removal of dust in airstreams,rather than diluting or confining the dust.In this paper,a wet scrubber design was developed.Based on a self-designed experimental test platform,the total dust concentration,respirable dust concentration,air volume,and average pressure drops of wet scrubbers with 12,16,20,and 24 blades were measured under different water intake conditions.The results show that the different water intake levels have only minimal effects on the air volume of the wet scrubbers.However,increased water intake had improved the dust removal efficiency of the wet scrubbers with the same number of blades.The wet scrubber with 16 blades was found to have the best dust removal efficiency at a water intake level of 1.35 m^(3)/h.Its total dust and respirable dust removal efficiency reached 96.81%and 95.59%,respectively.The air volume was 200.4 m^(3)/min,and the average pressure drop was determined to be 169.4 Pa.In addition,when the wet scrubber with 16 blades was applied in a coal preparation plant in China's Shanxi Province,it was observed that the total dust concentration had fallen below 8.1 mg/m^(3),and the respirable dust concentration had fallen below 5.9 mg/m^(3).Therefore,the results obtained in this research investigation provide important references for the use of wet scrubbers to improve coal production environmental conditions.

CFD modeling and laboratory studies of dust cleaning efficacy of an efficient four stage non-clogging impingement filter for flooded-bed dust scrubbers

Fibrous-type flters are used to capture dust particles in mining and other occupations where personnel are exposed for prolonged periods.Dust cleansing devices including fooded-bed dust scrubbers use these mesh-type multi-layered flters.These flters trap dust particles efciently on their surface and inside their mesh.However,their continued operation leads to dust build-up and clogging.This results in increased resistance of the flter and lowered airfow rate through the scrubber.This could potentially enhance the exposure of the miners.A non-clogging self-cleaning impingement screen type dust flter was designed by the authors for use in mining and industrial dust cleansing applications.The flter guides dirt-laden air through rapidly turning paths which forces it to shed heavier particles.The particles impact one of the impermeable solid metallic flter surfaces and are removed from the airstream.A full cone water spray installed upstream prevents any surface buildup of dust.This paper summaried the computer models generated to show the flter operations and laboratory experiments including optical particle counting to establish the cleaning efciency.

Hydrodynamics of the Pilot Scale Wet Scrubber with Restricted Outlet Absorbent Flow Rate

This paper presents the hydrodynamics of the wet scrubber coupled to a pilot CFB incineration facility. The scrubber was operated using tap water as a scrubbing liquid. The outlet liquid flow rate, Qo, and accumulation rate, Qa, strongly depend on the inlet liquid flow rate, Qin, with different profiles. At higher Qin values, Qo stabilizes, leading to higher Qa and finally flooding. The values of Qa were higher than Qo except for Qin ranging between 0.53 and 0.72 L/s (safe operating range) in which Qa ≌ Qo and Qa = Qin/2. The outlet-to-inlet liquid flow rate ratio, Qo/Qin decreased for Qin > 0.53 L/s. The increase in the accumulation-to-inlet liquid flow rate ratio, Qa/Qin, at higher Qin indicates a change in flow regime towards flooding, accompanied by an abrupt increase in the height of accumulating liquid, Ha. The difference between Qa/Qin and Qo/Qin (denoted as, ΔQao/Qin), shows a minimum close to zero in the safe operating range. The gas flow rate towards the wet scrubber had slight effect on Qo and Qa when Qin was maintained constant. The ratio Qo/Qin decreased slightly with Ha/Ht irrespective of gas velocity. Changing the liquid-to-gas ratio, L/G and Qin strongly affects the maximum and minimum values of Qo/Qin and Qa/Qin.

Assessment of NH3 Reduction and N2O Production during Treatment of Exhausted Air from Fattening Pigs Building by a Commercial Scrubber

The use of air scrubbers to reduce ammonia (NH3) emissions from buildings on pig farms is one of the most promising techniques in the GÖteborg protocol and other European regulations including the Industrial Emission Directive. In France, some air scrubbers are currently used on pig farms, mainly to reduce odours from livestock buildings. However, recent research revealed the production of N2O resulting from the treatment of air from pig buildings. In this context, a two-month study was conducted on a pig farm with 750 places for fattening pigs to check the abatement of NH3 emissions and to assess the possible production of N2O during treatment of exhausted air from buildings housing fattening pigs by a air scrubber. Concentrations of NH3 and N2O in the inlet and outlet air of the scrubber were continuously monitored using an Innova 1412 infrared analyzer. With the scrubber operating parameters (airflow, design, size), our results confirmed the production of N2O in the order of 5% of NH3-N reduced. N2O was produced by biological nitrification and/or denitrification inside the air scrubber. Statistical analysis (Pearson’s test) showed that the production of N2O was strongly influenced by the rate of airflow and the outside temperature. The abatement of NH3 emissions from the building was only 33%, i.e. much lower than the 70% - 90% usually cited in the literature.

Modeling Submicron Particles Collection in Laminar Forced Convection Gas Flow by a Rectangular Venturi Scrubber

Venturi scrubbers are usually used for large particles cleaning in turbulent gaseous flow. In this work, submicron particles scrubbing in laminar forced convection dusty air flow in a rectangular venturi scrubber have been numerically simulated. Hydrodynamics effects and scrubbing process are investigated in detail. Results are presented as flow velocity, axial pressure, streamlines pattern, particles and droplets mass fraction profile, and collect efficiency. They show that venturi scrubbers can be efficient for submicron particles scrubbing. In fact, a better collect efficiency is obtained at high particles-droplets residence time, high ratio droplets concentration/particles concentration, low venturi diameter ratioand low Reynolds numbers. There is a critical Reynolds number value for which the collect efficiency becomes very low and tends to be constant.

Impacting Factors of Elemental Mercury Re-emission across a Lab-scale Simulated Scrubber

Elemental mercury(Hg0)re-emissions from slurries and solutions were evaluated in a lab-scale simulated scrubber.Oxidized mercury(Hg2 +)standard solution was injected into the simulated scrubber at a desired rate to simulate absorbing and dissolving of Hg2 +in the flue gas across wet flue gas desulfurization(WFGD)systems. PS analytical mercury analyzer was used to continuously determine Hg0re-emission concentrations in the carrier gas from the scrubber.Sulfite ion in the slurry of CaSO3 was validated to reduce Hg 2+to Hg 0,while no Hg 0 re-emission occurred from slurries of CaSO4 and CaO.Transitional metal ions with low chemical valence such as Fe2 +,Pb 2+,Ni 2+, 2 AsO-and Cu +were used to prepare solutions with concentration levels of mmol·L-1.Reduction reaction of Hg2 +to Hg 0was observed from these solutions.Reduction capabilities for the different transitional metal ions in the solutions were:Pb2 +>Cu +>Fe 2+> 2 AsO->Ni 2+.

Numerical Simulation of Three-dimensional Heat and Mass Transfer in Spray Cooling of Converter Gas in a Venturi Scrubber

In order to predict the pressure drop,collection efficiency,velocity,temperature and mole fraction of vapor in an industrial venturi scrubber with water spraying for converter gas cooling,a three-dimensional model of heat and mass transfer with phase change is established.The gas flow and liquid droplets are treated as a continuous phase with a Eulerian approach and as a discrete phase with a Lagrangian approach,respectively.The coupled problem of heat,force,and mass transfers between gas flow and liquid droplets is solved by a commercial computational fluid dynamics(CFD) package,FLUENT.The numerical results show that the water injections have an important influence on the distributions of pressure,velocity,temperature,and mole fraction of vapor,especially for the spraying region in the throat.In the spraying region,the pressure drop is higher and the velocity is lower than in other regions due to the gas-droplet drag,while the temperature is lower because the droplet absorbs large amounts of heat from the high temperature gas and the mole fraction of vapor is higher due to the phase change of the liquid droplet.A number of cases with different water-to-gas volume flow ratios and baffle openings were simulated.The dependence of pressure drop,velocity,temperature,mole fraction of vapor,and collection efficiency on both the water-to-gas volume flow ratio and baffle opening are analyzed.The good agreements between simulation results and experiment data of pressure drop,temperature,and collection efficiency validate the model.The model should facilitate optimization of the venturi scrubber design in order to give better performance with lower pressure drops and higher collection efficiency.

Experimental study on performance of flow & desulfurisation of a gas-liquid screen scrubber for wet flue gas desulfurization

In the paper, the gas-liquid two-phase flow performance and desulfurisation performance of the gas-liquid screen scrubber were experimentally studied when limestone was used as absorbent. Experiments were carried out at varying the flue gas velocity and slurry flux in concurrent and countercurrent tower respectively. The experimental results showed that the flow resistance of absorber increased rapidly with an increase of the flue gas velocity whether in concurrent or in countercurrent tower, and the up trend of the flow resistance in the countercurrent tower was higher than those in the concurrent one. The influence of the flue gas velocity on the flow resistance of absorber was more than those of the slurry flux density. Whether in the concurrent tower or in the countercurrent one, increasing the flue gas velocity or the slurry flux density would enhance the desulphurization efficiency. The influence of the slurry flux density on the desulfurisation efficiency was greater than those of the flue gas velocity.

CFD simulation on performance of new type umbrella plate scrubber

A new type of umbrella plate scrubber was developed to address the pollution due to the dust,dioxide sulfur and other harmful gases,which were emitted from coal-burning boilers.The performance of the new device was studied through computational fluid dynamics(CFD)simulation and experiment methods.Initial work included experimental measurement of inlet-velocity,and gas phase simulation using Reynolds stress model(RSM).After gas phase was converged,particles were injected from the inlet of the new device.Discrete phase model(DPM)was used for particle trajectories determination.The pressure drop and the collection efficiency of the new device were predicted through simulation.The simulation results show that the pressure drop of the new devices is 230?250 Pa and the efficiency is 84%-86%,with the inlet velocity equal to 10.6 m/s and the dust concentration ranging from 2 to 22 g/m 3 .The CFD simulation results of the new device show good agreement with experimental data.The relative error of the pressure drop and the efficiency is approximately 4%and 10%respectively.The results obtained both from the numerical simulation and from the experiment demonstrate that CFD simulation is an effective method for this type of study.

Research on the application of the wet scrubber on the BSSF slag processing system at Baosteel

Based on the analysis results of the dust size distribution of flue gas from Baosteel's short-flow(BSSF) slag processing system and the mechanism of the wet scrubber,a wet scrubber system was designed and installed in the No.1 BSSF slag processing system at Baosteel.The results show that the dust removal efficiency of the previous system that had conventional water nozzles was only 69% with a liquid-gas ratio of 0.79 L/m3,while the dust removal efficiency reached 94% when three sets of high-efficiency dual phase spray guns were installed inside both the flue and the chimney.For the latter system,the liquid-gas ratio was 0.84 L/m3,and the dust concentration in the cleaned emissions reduced to less than 40 mg/m3.

核电厂安全壳过滤排放系统文丘里洗涤器气溶胶净化性能分析

本文通过CFD数值模拟与实验相结合的方法,探讨了气相流速、系统压力对安全壳过滤排放系统文丘里洗涤器气溶胶净化效率的影响,并对系统运行提出指导性建议。研究表明,在0~20 m/s入口气相流速于0.1~0.6 MPa系统压力范围内,气相流速与系统压力的增大均可提高文丘里洗涤器引射能力,引射量的增大对气溶胶净化效率的提高具有促进作用。研究表明流速在16 m/s(即排放量3 519 m^(3)/h)之后净化效率达到最大值,建议系统排放风量应保持在3 502 m^(3)/h以上。

Effect of ring baffle configuration in a self-priming venturi scrubber using CFD simulations

This study uses computational fluid dynamics to survey the gas‒liquid flow hydrodynamics of a self-priming venturi scrubber with and without ring baffles.Based on the simulation results,we explore how the structure and configuration parameters such as baffle height,opening-area ratio,and baffle thickness affect the injection flow rate and the homogeneity of the gas‒liquid mixture.In addition,we report the best structure and configuration parameters for the ring baffle.The best position for the ring baffle is at nearly 7/16 of the length of the diffuser above the throat.Having the baffle too near the throat causes large pressure loss,decreasing the injection flow rate.The decrease in opening-area ratio leads to a lower injection flow rate and a more homogeneous gas‒liquid mixture.The optimal value depends on the requirement of the injection flow rate.For the baffle thickness,5 mm is recommended;an overly thick baffle decreases the homogeneity of the gas‒liquid mixture near the throat.All structure parameters and configuration parameters must satisfy the requirement imposed by the injection flow rate and scrubbing efficiency.

煤气化装置洗涤系统腐蚀评估与控制研究

在煤气化过程中,原料煤中的碳、硫、氮和氯等元素会发生复杂反应生成不同种类的腐蚀性产物,在一定的条件下会表现出较强的腐蚀性,严重影响着煤气化及下游装置的安全稳定运行。文章以煤气化装置洗涤系统为研究对象,通过开展现场腐蚀监测与实验室腐蚀评价,获得了不同金属材料在洗涤系统粗合成气、黑水环境下的耐蚀性能,结合煤气化装置现场实际运行情况和工程实践经验,制定了设备及管道腐蚀控制策略。

干煤粉气化激冷流程工艺运行分析及优化措施

介绍了国能集团宁夏煤业有限责任公司400万t/a煤间接液化项目干煤粉气化激冷流程的工艺流程。针对气化炉激冷流程工艺系统运行时存在的合成气带水、带渣、带灰等问题,经分析认为主要原因是激冷室液位控制不当、合成气洗涤塔塔盘冲洗水水质差且塔盘结构设计不合理;为此,进行了相应的结构、材料、管线等方面的技改优化。运行效果表明:改造后合成气带水、带渣、带灰等问题得到了有效解决,合成气洗涤塔塔盘压差趋于平稳。

某污水处理站除臭工程设计

某制药企业产生的污水含有含硫的有机溶剂等成分,在污水处理过程中会产生硫化氢、氨气、四氢呋喃、二氯甲烷、甲基叔丁基醚等臭气污染物,设计风量为4000 m3/h,尾气处理执行《制药工业大气污染物排放标准》(GB37823-2019)表2大气污染物特别排放限值和《恶臭污染物排放标准》(GB14554-93)恶臭污染物排放标准值。