RE-ENTRAINMENT DECREASE IN ELECTROSTATIC PRECIPITATOR TO THE REGENERATION UNIT SPENT SULFURIC ACID

This paper aims to improve the efficiency of uniform flow electrostatic collector. First, the principle of electrostatic dust removal technology, including electrostatic dust removal principle and an overview of uniform flow electrostatic dust collector. Then, methods to improve dust removal efficiency by analyzing the relationship between dust removal efficiency and operating parameters. These include electric field design optimization, dust removal plate optimization, and airflow distribution control. Then, the factors affecting the efficiency of dust removal are analyzed, including the particle characteristics and the gas characteristics. Finally, the electric field optimization design based on numerical simulation and the airflow distribution optimization design based on CFD simulation are presented. Through theoretical simulation and optimization design, the dust removal efficiency of uniform flow electrostatic dust collector can be improved and the dust removal effect can be further optimized.

The wet electrostatic precipitator (WESP) overcomes the shortcomings of traditional electrostatic precipitators, such as dust re-entrainment and back corona. It can effectively remove high-specific-resistivity dust, with a good removal effect on PM2.5. It is proposed to adopt chemical agglomeration and humidification agglomeration technology in the wet electrostatic precipitators to achieve ultra-low dust emissions from coal-fired power plants. The results show that the addition of chemical agglomerates, surfactants, and water vapor all affect the dust diameter of coal-fired power plants. After adding sesbania gum (SG), the D50 of dust particles increases from 28.29 μm to 48.22 μm. And the D50 of dust particles is 36.46 μm when spraying 3.6 kg/h water vapor only. With the cooperation of chemical agglomeration agents and water vapor, the dust agglomeration effect and removal efficiency can be further improved. When 10 mg/L SG is synergistically combined with 2.9 kg/h water vapor, the D50 is 64.75 μm, and the dust removal efficiency reaches 97.88%. On this basis, by adding 5 mg/L of Hexadecyltrimethylammonium bromide (CTAB), the D50 is 83.06 μm, and the dust removal efficiency increases to 98.62%. The synergistic effect of chemical agglomeration and humidification agglomeration promotes the aggregation of dust from coal-fired power plants. It can improve the removal efficiency of WESP for fine particulate matter but has little impact on the operation of existing equipment. The synergistic effects of multiple agglomeration technologies are also the direction for future research on the removal efficiency of fine particulate matter.

Almost all coal based thermal power plants (CTPP) in India use electrostatic precipitator (ESP) for reduction of particulate matter (PM) in flue gas generated due to the combustion of Indian coal. This coal is characterized by high ash content, low calorific value and low sulfur content resulting in the generation of a very large amount of highly electrically‐resistive fly‐ash; thereby requiring a very large size ESP to minimize the fly‐ash emissions. However, the flue‐gas particle size distribution analysis showed that 60% of the particles are above 15 μm size, which can be conveniently removed using a low‐cost inertial separator such as a cyclone separator. It is proposed that a cyclone be used, as a pre‐cleaner to ESP so that the large size fraction of fly‐ash can be removed in the pre‐cleaning and the remaining flue‐gas entering the ESP will then contain only small size particles with low dust loading, thereby requiring a small ESP, and improving overall efficiency of dust removal. A low efficiency (65%), high throughput cyclone is considered for pre‐cleaning flue gas and the ESP is designed for removal of the remaining 35% fly‐ ash from the flue gas. It is observed that with 100% dust load, the ESP requires six fields per pass, whereas with cyclone as a pre‐cleaner, it requires only five fields per pass. Introducing cyclone into the flue gas path results in additional head loss, which needs to be overcome by providing additional power to induced draft (ID) fan. The permissible head loss due to the cyclone is estimated by comparing the power requirement in the bag filter control unit and cyclone‐ESP combined unit. It is estimated that a head loss of 10 cm of water can be permitted across the cyclone so as to design the same for 65% efficiency.

To prevent fouling in blast furnace gas top pressure recovery turbine units, the dust content of the gas must be reduced, necessitating its deep purification. A critical challenge to be addressed is the low collection efficiency of fine particulate matter. To improve the collection efficiency of the fine particulate dust in BFG by wet electrostatic precipitators (WESPs), this study implemented measures such as optimizing nozzle atomization performance and the spatial distribution of droplets, along with adding chemical agglomeration agents and surfactants. These approaches promoted the chemical agglomeration of fine dust and enhanced dust collection efficiency. In this study, five nozzle types, six chemical agglomerating agents, and three surfactants were tested. The results show that, under overlapping spray conditions, the 1/8 solid cone nozzle produced the smallest droplet size with the most uniform spatial distribution, exhibiting a d50 of 141.17 μm. When this nozzle was used in combination with guar gum (GG) as a chemical agglomerant, the d50 of BFG dust increased from 8.46 μm to 14.75 μm. The synergistic application of 5 mg/m3 sesbania gum (SBG) and 5 mg/m3 octylphenol ethoxylate (OP-10) further increased the dust d50 to 19.08 μm. Using the 1/8 solid cone nozzle and an XTG concentration of 5 mg/m3 resulted in the highest dust collection efficiency of 96.76%, while the synergistic use of SBG/OP-10 achieved an efficiency of 97.69%. This study elucidates the influence of nozzle atomization characteristics and spray liquid type on dust agglomeration and collection efficiency, achieving an improvement in dust-removal efficiency and the capture of fine-particulate dust, and providing both theoretical and practical foundations for the deep purification of blast furnace gas.

To address the issue of excessive soil content in straw feed after harvesting by a straw feed harvester, this study designed a dust removal apparatus. Its optimal operating parameters were determined through a combination of numerical simulations and field experiments. Using dust removal efficiency as the evaluation criterion, the Box-Behnken experiment and variance analysis revealed that the factors influencing the dust removal efficiency of the apparatus, in order of significance, were the number of dust removal drums, the aperture of the dust sieve, and the rotational speed of the dust removal drums. The optimal parameter combination consisted of 5 dust removal drums, a dust sieve aperture of 5 mm, and a drum rotational speed of 370 r/min. The dust removal efficiency obtained from numerical simulation using these optimal parameters was 94.1%, while the field verification test yielded an efficiency of 93.5%, with a relative error of 0.64% between the two results, confirming the accuracy of the numerical simulation parameters. The optimized dust removal apparatus significantly improves the quality of straw fodder by reducing dust content, which not only enhances the efficiency of straw recycling but also supports sustainable agricultural practices, promoting both mechanization and green development in the industry.

Asphalt hot regeneration pavement maintenance vehicle is a type of in situ heating waste asphalt special vehicle equipment for mix and regeneration of aged asphalt. When waste asphalt mixture is heated and melted, a lot of organic fumes are typically produced, along with dust from the mixing process. Because of the complex composition of the exhaust gases produced by asphalt hot regeneration pavement maintenance vehicles, it can be difficult to purify and remove them using a single method. In order to effectively purify exhaust gas with complicated compositions, a multistage combined treatment dust removal system structure is presented that includes cyclone sections, spray sections, and adsorption sections. With an emphasis on the cyclone section structure with the dust-gas separation function, computational fluid dynamics (CFD) is used to analyze the internal flow field characteristics, turbulence intensity, tangential velocity, and velocity field vector characteristics. The results reveal that the more symmetrical the distribution of tangential velocity field and static pressure field is, the greater the cyclone dust collector’s dust removal efficiency is, the more stable the flow field is, and the lower the turbulence intensity is. Furthermore, the center cyclone’s growing speed is adversely connected with dust removal effectiveness. As a result, an antiventuri cyclone dust collector with a scrambling column was designed. When the inlet air speed is 6 m/s, the dust removal efficiency of the improved device is 97.0%, which is 5.1% higher than that of the original device, and when the inlet air speed is 8 m/s, the dust removal efficiency of the improved device is 97.3%, which is 4.16% higher than that of the original device. With the increase of the inlet air speed, the difference between them keeps decreasing.

With their advantages of high dust removal efficiency and low drag characteristics, hybrid wet-filter precipitators have great potential for dust control in coal mines, but the underlying mechanisms are not well understood. In this study, to help fill this knowledge gap, a hybrid wet-filter precipitator consisting of a 40-layer metal filter and a defogger device is designed and a prototype is constructed. Experiments are conducted to investigate its drag characteristics under wind velocities from 0.85 to 5.68 m/s and its dust removal performance under wind velocities of 2 and 4 m/s. On the basis of results with the initial design, which show that the dust removal efficiency does not meet the target value of 99%, two rounds of improvement are implemented to enhance the dust removal efficiency. Results show that the defogger device contributes ∼80% of the total drag. The drag from the metal filters is found to increase by over 80% on average after sampling, since some of dust particles are left on the filters, decreasing their porosity. The installation of two-layer air filters on the leeside of the metal filter unit is found to increase the efficiency to 99.89% and 99.80% under wind velocities of 2 and 4 m/s, respectively, although this is at the cost of increased drags. Additionally, it is found that the replacement of the defogger by a 20-layer metal filter is not desirable, since this increases the downstream air humidity to more than 100%, which can cause damage to the centrifugal blower system. Therefore, new designs for the defogger device need to be examined in future studies.

In China, the particulate matter (PM) pollution has caused serious environmental and health concerns, and it is still a huge challenge to control PM pollution. In order to alleviate the hazardous of PM pollution, the dust collector is widely used to separate PM from gas streams. However, after a period of operating, whether the removal efficiency of the dust collector still meet the requirement of the emission limit is unknown. The dust removal efficiency test device was designed and its performance was investigated in this study. The flow field simulation result showed that the test device had a good uniformity, which was consistent with previous measured result. Moreover, it found that the linear relationship between the light scattering concentration and the filtration membrane weighed concentration was y=2.285x, and when the inlet wind speed was about 0.5 m/s, the dust removal efficiency of the dust collector was more than 99.73%, the outlet dust concentration was (0.03-0.04) mg/m3, which was below the emission limit of 15 mg/m3. When the inlet dust concentration was about 200 mg/m3 and the inlet wind speed was (0.25-0.75) m/s, the dust removal efficiency was more than 99.98%. To sum up, the designed test device can be used to estimate the dust removal efficiency of various types of dust collectors.

Air pollution, especially particulate pollution, has become a serious issue with the acceleration of industrialization. Wet scrubbers are widely used in industries for air purification due to their advantages. However, most scrubber studies have predominantly focused on fillers and injection methods, neglecting the systematic investigation of the tower rotation angle and particulate physical properties on dust removal performance. In this study, the geometric model of the scrubber was established based on the actual equipment in a refinery. Computational fluid dynamics (CFD) was employed, along with the fluid volume (VOF) and discrete phase (DPM) models, to solve the relevant equations. The grid independence and model were verified. Particles with different diameters were injected into the scrubber with different angle steel tray arrangements (α = 15°, 30°, 45°), and the dust removal efficiency was calculated. The results show that the dust removal efficiency generally increases with the increase of particle diameter. When the particle diameter is 200–300 μm, the efficiency is consistent. Before 350 μm, the highest efficiency is achieved at α = 30°, and the lowest at α = 15°; above 350 μm, the highest is at α = 30°, and the lowest at α = 45°. The tray angle affects air distribution uniformity, and α = 45° shows more uniform air distribution. This research provides a scientific basis for optimizing scrubber design and operation. It systematically explores the influence of tray angle and particle diameter on dust removal efficiency, filling the research gap in this area and guiding the improvement of scrubber technology in industrial applications.

The removal of industrial dust is mainly realized by various dust removal equipment. The electrostatic dust remover can remove more than 99.5% of the dust particles of various diameters, but the dust removal effect of particulate particles is not significant. Among them, for the finer particles in the dust, the dust removal effect is poor. After measurement, the efficiency of electrostatic dust removal is 80%-85% for fine particles with a particle diameter of 10-1μm [1]. With our higher demand for particulate emissions, improving the removal of industrial fine particulates is imminent. In the process of dust generation, dust particles collide or come into contact through various paths, thereby combining to generate larger particles, and this process becomes the condensation of dust. The dust agglomeration technology is generally used as a pre-treatment of the flue gas in the field of flue gas dust removal. By enriching the fine particles, the fine particles become larger, and then the dust is removed through the dust removal device.

Unmanned probes, mainly powered by solar panels, are effective tools for exploiting space resources to expand the human habitat. However, it remains a great challenge for the unmanned probes to actively repel multiscale dust particles in space. Inspired by the synergistic antifouling mechanism of fly wings and legs, a biomimetic dynamic antifouling surface (BDAS) was prepared based on a combination of self-assembly and template inversion. BDAS consists of flexible and controllable cilia with ultrahigh aspect ratio. Under the control of an external magnetic field, BDAS can perform three modes of dust removal tasks. The synergism of these three modes ensures that BDAS provides superior dust removal against multiscale dust particles in complex environments. Compared to conventional passive dust removal surfaces, the dust removal efficiency is increased by 941%. As proof of concept, BDAS was installed on a lunar probe and achieved effective removal of simulated lunar soil (up to 1158%).

Experimental study on the atomization characteristics and dust removal efficiency of a fan-shaped nozzle for purifying working environment

The limestone quarry in PT Indocement Tunggal Prakarsa (ITP) in Cirebon is considered as a complex quarry in terms of chemical composition and material hardness. From the beginning of the plant operation up to the end of 2015, the dust removal was rely on electrostatic precipitator (EP) system. Whenever limestone from specific quarry zones were incorporated into Raw Mill (RM) feed or there was an upset condition, the dust emission increased significantly. Beside higher demand of electricity, an EP system requires lower gas inlet temperature in order to remove the dust effectively which requires larger cooling water in the previous gas conditioning tower to cool down gas from 400 °C to about 100 °C. By considering the drawbacks, the EP system was replaced by a bag filter (BF) system. The BF allows higher temperature of gas inlet and it has higher dust removal efficiency. In this study, the efficiency of the two different dust removal systems is compared. The effect of process variables i.e. RM feed, kiln feed, inlet temperature and pressure, and small size particle fraction to the dust emission are studied by multivariate linier regression analysis. It is observed that the BF system can reduce significantly the dust emission from 30 to 6 mg/m3 and in the same time reducing CO2 emission by 0.24 ton/year from the electricity consumption saving.

Dust removal efficiency of high pressure atomization in underground coal mine

Fully Mechanized Workface ZHONG Yang, WU Meng-meng*, YANG Xin-xiang, XIAO Wei Shandong University of Science and Technology, College of Mining and Safety Engineering, Shandong Qingdao 266590Abstract Cyclonic duster has become the mainstream in fully mechanized workface, better than any other kinds of dusters in dust removal efficiency, sewage discharge, disassembly and assembly, moving with the boring machine etc. This paper reveals the effect that the opening of the throttle plate significantly affects the water jet by Bernoulli equation, and the parameters related to the vibration effect by the vibration frequency formula, and also states that when the centrifugal force and the air resistance are in balance, dust particles began settling on the cavity. Wet dust removal technology has developed rapidly over the last two to three decades and become mainstream technology in coal mine production. There are lots of papers focusing on dusting efficiency influenced by changing parameters, such as nozzle types, structure parameters, wind speed and ventilation volume. This paper summarizes characteristics related to mechanisms of wet dusting and dust capturing. It also outlines the research advance of mine wet duster and analyzes the existing problems. The paper focuses on the mechanisms of three types of wet duster in fully mechanized workface. The research and application of future are also prospected.