가스유동 해석을 이용한 선박용 전기집진기의 전극판 및 집진판 형상에 따른 집진효율 예측

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.

The dust collected in the polar plates can be washed out by a spraying system in the wet electrostatic precipitator. It is important to keep the spraying system having a high efficiency lest the dust returns to the gas again. The performance of the spraying system in the electrostatic precipitation and its influence on the dust collection efficiency are presented in the paper. The atomization characteristic of the spraying nozzle is measured by changing the water pressure and operating voltage. The results show that: Collection efficiency of the electrostatic precipitation is over 99.5 % when the water pressure is 0.4 MPa.When the spraying mists diameter is 100 μm, the collection efficiency is 92 % for the dust diameter under 10 μm. It will provide a basis for the design of spraying system in wet electrostatic precipitation by this analysis.

The objectives of this study are to (a) evaluate the exergy and energy demand for constructing a hydrofractured shale gas well and determine its typical exergy and energy returns on investment (ExROI and EROI), and (b) compute the gas flow and intrinsic exergy analysis in the shale gas matrix and created fractures. An exergy system analysis of construction of a typical U.S. shale gas well, which includes the processes and materials exergies (embodied exergy) for drilling, casing and cementing, and hydrofracturing (“fracking”), was conducted. A gas flow and intrinsic exergy numerical simulation and analysis in a gas-containing hydrofractured shale reservoir with its formed fractures was then performed, resulting in the time- and two-dimensional (2D) space-dependent pressure, velocity, and exergy loss fields in the matrix and fractures. The key results of the system analysis show that the total exergy consumption for constructing the typical hydrofractured shale gas well is 35.8 TJ, 49% of which is used for all the drilling needed for the well and casings and further 48% are used for the hydrofracturing. The embodied exergy of all construction materials is about 9.8% of the total exergy consumption. The ExROI for the typical range of shale gas wells in the U.S. was found to be 7.3–87.8. The embodied energy of manufactured materials is significantly larger than their exergy, so the total energy consumption is about 8% higher than the exergy consumption. The intrinsic exergy analysis showed, as expected, very slow (order of 10−9 m/s) gas flow velocities through the matrix, and consequently very small flow exergy losses. It clearly points to the desirability of exploring fracking methods that increase the number and length of effective fractures, and they increase well productivity with a relatively small flow exergy penalty.

In order to reduce the environmental smog caused by coal combustion, air pollution control devices have been widely used in coal-fired power plants, especially of wet flue gas desulfurization (WFGD) and wet electrostatic precipitator (WESP). In this work, particulate matter with aerodynamic diameter less than 10 μm (PM10) and sulfur oxides (SOx) have been studied in a coal-fired power plant. The plant is equipped with selective catalytic reduction, electrostatic precipitator, WFGD, WESP. The results show that the PM10 removal efficiencies in WFGD and WESP are 54.34% and 50.39%, respectively, and the overall removal efficiency is 77.35%. WFGD and WESP have effects on the particle size distribution. After WFGD, the peak of particles shifts from 1.62 to 0.95 μm, and the mass concentration of fine particles with aerodynamic diameter less than 0.61 μm increases. After WESP, the peak of particle size shifts from 0.95 to 1.61 μm. The differences are due to the agglomeration and growth of small particles. The SO3 mass concentration increases after SCR, but WFGD has a great influence on SOx with the efficiency of 96.56%. WESP can remove SOx, but the efficiency is 20.91%. The final emission factors of SO2, SO3, PM1, PM2.5 and PM10 are 0.1597, 0.0450, 0.0154, 0.0267 and 0.0215 (kg · t−1), respectively. Compared with the research results without ultra-low emission retrofit, the emission factors are reduced by 1~2 orders of magnitude, and the emission control level of air pollutants is greatly improved.

A review on mercury in coal combustion process: Content and occurrence forms in coal, transformation, sampling methods, emission and control technologies

Recently, with the increasing public interest in fine dust, many compact air purifiers have been developed to provide clean air at all times. Although electrostatic precipitators are widely used as air pollution prevention facilities because of their low differential pressure and high dust collection efficiency, ozone generated during discharge can be harmful to the human body. In this study, we developed a compact electrostatic precipitator that combines a DC corona discharge module that generates an extremely small amount of ozone using a dielectric barrier effect and a particle collection module with large specific surface area. As a fundamental experiment, when the polypropylene film was coated on the ground electrode of the discharging device, the ozone concentration was reduced by up to 75%. This dielectric barrier effect suppressed the ozone concentration of the electrostatic precipitator introduced in this study to less than 10 ppb. In addition, the present device removes all dusts of more than 1 μm from fine dust, which is very harmful to human body. Therefore, the present research is expected to apply portable or wearable air cleaning devices that generate very little ozone and easily remove fine dust.

Improving nanoscale thin film deposition techniques such as atomic layer deposition (ALD) to permit operation at ambient pressure is important for high-throughput roll-to-roll processing of emerging flexible substrates, including polymer sheets and textiles. We present and investigate a novel reactor design for inorganic materials growth by ALD at atmospheric pressure. The reactor uses a custom "pressure boost" approach for delivery of low vapor pressure ALD precursors that controls precursor dose independent of reactor pressure. Analysis of continuum gas flow in the reactor shows key relations among reactor pressure, inert gas flow rate, and species diffusion that define conditions needed to efficiently remove product and adsorbed reactive species from the substrate surface during the inert gas purge cycle. Experimental results, including in situ quartz crystal microbalance (QCM) characterization and film thickness measurements for deposition of ZnO and Al(2)O(3) are presented and analyzed as a function of pressure and gas flow rates at 100 °C. At atmospheric pressure and high gas flow, ZnO deposition can proceed at the same mass uptake and growth rate as observed during more typical low pressure ALD. However, under the same high pressure and flow conditions the mass uptake and growth rate for Al(2)O(3) is a factor of ∼1.5-2 larger than at low pressure. Under these conditions, Al(2)O(3) growth at atmospheric pressure in a "flow-through" geometry on complex high surface area textile materials is sufficiently uniform to yield functional uniform coatings.

In order to design a diesel engine system and to predict its performance, it is necessary to analyze the gas flow of the intake and exhaust system. Gas flow analysis in a three-dimensional (3D) format needs a high-resolution workstation and an enormous amount of time for analysis. Calculation using the method of characteristics (MOC), which is a gas flow analysis in a one-dimensional (1D) format, has a fast calculation time and can be analyzed with a low-resolution workstation. However, there is a problem with poor accuracy in certain areas. It was assumed that the reason was that 1D could not implement the shape. The error that occurs in the shape of the bent pipe used in the intake and exhaust ports of the diesel engine was analyzed and to find a solution to the low accuracy, the results of the experiment and 1D analysis were compared. The discharge coefficient was calculated using the average mass flow rate, and as a result of applying it, the accuracy was improved for the maximum negative pressure by 0.56–1.93% and the maximum pressure by 3.11–7.86% among the intake pipe pressure results. The difference in phase of the exhaust pipe pressure did not improve. It is considered as a limitation of 1D analysis that does not improve even by applying the discharge coefficient. In the future, we intend to implement a bent pipe that cannot be realized in 1D using a 3D format and to prepare a method to supplement the reliability by using 1D–3D coupling.

Flue gases are routinely purged of their suspended fly ash burden by passing through (1) an electrostatic precipitator, (2) a scrubber, or (3) a fabric filter. These devices remove the coarser particles more efficiently than they do the finer. If the dusty gas were first pretreated by passing it through a sonic agglomerator, so that nearly all the finer particles were agglomerated into coarser ones before entering any of the above collector types, the overall collection efficiency would be improved. This report investigates the economic feasibility of such an approach. The investigation has been of a theoretical nature, supplemented by experiments on a laboratory scale, in order to evaluate sonic agglomeration constants with polystyrene latex particles, dioctyl phthalate particles, Fe/sub 2/O/sub 3/ particles, and others. The investigation indicates that intense acoustic fields cause the finer suspended particles to collide with the coarser ones in a process called orthokinetic interaction. To maintain the essential supply of coarse particles, the use of a spray to inject droplets into the sonic field appears to be helpful. The results clearly indicate that the sonic agglomerator, when viewed as a prospective auxiliary to present day electrostatic precipitators, is not an economically attractive option due to the high power requirements. In a typical modern pulverized-coal-firing utility station with a gas flow rate of 1 million ft/sup 3//min, the agglomerator would require about 1000 hp. This is certainly more power than used by current fabric-filter technology, which meets all proposed emission and opacity standards. Moreover, with the required intense sound levels of 150 decibels, sound muffling problems become serious. Assuming that a sonic agglomerator in tandem with an electrostatic precipitator would meet emissions standards at a power station, there would be sound-level code violations unless elaborate and expensive sound-deadening measures were used.

ABSTRACTThe fine particles are considered a significant pollution problem. The wet electrostatic precipitators (ESPs) have advantages of efficient collection of the fine particles with lower pressure drop and eliminating reentrainment. The wetting properties of the collector surfaces have significantly important effect on wet ESPs’ stable and secure operation. The modified rigid collector (MRC) was modified by coating specific vinyl ester resin composites and loose glass fiber cloth over the conventional carbon steel in a certain way. The rigid collector surfaces before and after modification had been characterized by scanning electron microscopy (SEM) and interface tensiometer. The effect of operating temperatures on the wetting properties of the rigid collector surfaces before and after modification was investigated. The temperature range was 40~90 °C, and the wetting properties contained liquid holdup, surface flow rate, film rate, average film thickness, and critical saturation time. The modified rigid collector surface exhibited excellent wetting properties at the operating temperatures. The fine particles collection performance compared among the MRC, the conventional rigid collector (CRC), and the flexible collector (FC) in the wet ESPs was investigated. The effects of the applied voltage, the water film, corona power, and the specific collecting area on the fine particles collection were evaluated. The modified rigid collector provided high fine particles collection effect with lower energy and water consumption.Implications: To improve the submicron particles collection efficiency and decrease energy and water consumption, the formation of uniform water film over the collector surfaces has been widely studied. The modified rigid collector was modified by coating specific vinyl ester resin composites and loose glass fiber cloth (ERGF) over the conventional carbon steel (CCS) in a certain way. The modified rigid collector surface exhibited excellent wetting properties. The wet ESPs by the modified rigid collector exhibited significantly higher particles collection efficiency than by the conventional rigid collector.

<div class="section abstract"><div class="htmlview paragraph">The Diesel engine combustion process results in harmful exhaust emissions, mainly composed of Particulate Matter (PM), Hydro Carbon (HC), Carbon monoxide (CO) and Nitrogen Oxides (NO<sub>x</sub>). Several technologies have been developed in the past decades to control these diesel emissions. One of the promising and well matured technology of reducing NO<sub>x</sub> is to implement Selective Catalytic Reduction (SCR) using ammonia (NH<sub>3</sub>) as the reducing agent. For an effective SCR system, the aqueous urea solutions should be fully decomposed into ammonia and it should be well distributed across the SCR. In the catalyst, all the ammonia is utilized for NO<sub>x</sub> reduction process. In the design stage, it is more viable to implement Computational Fluid Dynamics (CFD) for design iterations to determine an optimized SCR system based on SCR flow distribution. And in later stage, experimental test is required to predict the after-treatment system performance based on NO<sub>x</sub> reduction.</div><div class="htmlview paragraph">The SCR model predicts the NH<sub>3</sub> formation from urea decomposition and it is quantified at the SCR inlet, whereas experimental data involves the NO<sub>x</sub> reduction process. In order to validate the numerical predictions, the modeling needs to include surface reactions happening in the SCR catalyst bed. There are many factors that affect NO<sub>x</sub> conversion process, such as exhaust temperature, NO<sub>2</sub>/NO<sub>x</sub> ratio, catalyst coating, oxidation, etc. To model SCR Kinetics, various input parameters are required and also the reaction process needs to be well defined. The objective of this work is to conduct urea SCR spray modeling studies to focus on these input parameters and to observe its influence over NO<sub>x</sub> reduction process.</div></div>

The increasing interdependence between electric power and natural‐gas systems requires integrated simulation tools applicable to the coupled system. Therefore, this study proposes steady‐state and transient simulation tools for electricity‐gas integrated energy systems (IESs) by using convex optimisation. Steady‐state IES simulation is designed for long‐term planning studies while transient IES simulation, which includes line‐pack storage, is designed for real‐time operational research. The proposed convex steady‐state gas flow model introduces binary variables to represent gas flow directions, and employs the second‐order cone (SOC) to relax non‐convex pipeline gas flow equations. As a result, steady‐state gas flow analysis is formulated as a mixed integer SOC programming problem. The proposed transient gas flow model employs the implicit finite difference method to transform partial differential equations into algebraic difference equations. Moreover, the short‐term gas flow directions are specified and SOC relaxations are used. Simulation results on an integrated IEEE 24‐node system and Belgian 20‐node gas system verify the effectiveness of the proposed SOC models. The impacts of wind power forecast errors on multi‐period gas network operations are also investigated.

The formation of sulfur trioxide (SO(3)) in coal-fired utility boilers can have negative effects on boiler performance and operation, such as fouling and corrosion of equipment, efficiency loss in the air preheater (APH), increase in stack opacity, and the formation of PM(2.5). Sulfur trioxide can also compete with mercury when bonding with injected activated carbons. Tests in a lab-scale reactor confirmed there are major interferences between fly ash and SO(3) during SO(3) sampling. A modified SO(3) procedure to maximize the elimination of measurement biases, based on the inertial-filter-sampling and the selective-condensation-collecting of SO(3), was applied in SO(3) tests in three full-scale utility boilers. For the two units burning bituminous coal, SO(3) levels starting at 20 to 25 ppmv at the inlet to the selective catalytic reduction (SCR), increased slightly across the SCR, owing to catalytic conversion of SO(2) to SO(3,) and then declined in other air pollutant control device (APCD) modules downstream to approximately 5 ppmv and 15 ppmv at the two sites, respectively. In the unit burning sub-bituminous coal, the much lower initial concentration of SO(3) estimated to be approximately 1.5 ppmv at the inlet to the SCR was reduced to about 0.8 ppmv across the SCR and to about 0.3 ppmv at the exit of the wet flue gas desulfurization (WFGD). The SO(3) removal efficiency across the WFGD scrubbers at the three sites was generally 35% or less. Reductions in SO(3) across either the APH or the dry electrostatic precipitator (ESP) in units burning high-sulfur bituminous coal were attributed to operating temperatures being below the dew point of SO(3).

This article presents the results of experimental research on the purification of high-temperature aspiration emissions using a cyclone-type dust collector equipped with a disk liquid atomizer. The focus is placed on studying the influence of structural parameters of the atomizer, the physicochemical properties of the working liquid, and flow conditions on the geometric characteristics of the spray plume, droplet dispersion, and dust removal efficiency. The formation of a stable and uniform spray cone is a key factor in enhancing gas-liquid interaction and increasing the capture probability of fine and coarse dust particles. Measurements were carried out on a laboratory setup using a coordinate grid and absorbent surface to visualize droplet trajectories and spray shapes under various operating modes. The analysis included determining the plume height and cross-sectional expansion at different distances from the disk edge. The influence of variables such as disk diameter, number and shape of nozzle holes, rotational speed, gas temperature, humidity, and the presence of solid impurities in the recirculated liquid was evaluated. The study revealed that using contaminated water containing solid particles (e.g., quartz) significantly enhances the fineness of the atomized spray due to the reduction in droplet size, resulting in greater interfacial surface area. Mathematical models were developed to describe the relationship between operational parameters and the efficiency of the dust collection process. Optimization experiments demonstrated that a capture efficiency of up to 96–98% can be achieved while maintaining hydraulic resistance below 100 Pa, indicating the potential for efficient application of such systems in industrial high-temperature environments. The findings contribute to the development of resource-efficient, adaptable wet cleaning technologies for air pollution control in modern manufacturing facilities.

The fine particles are considered a significant environmental pollution problem. The wet electrostatic precipitators (ESPs) are now used most widely among the advanced fine particle removal technologies. The rigid glass fiber reinforced plastics (FRP) collectors modified with hole-slotted structures were used to enhance the water film distribution over their surfaces. This paper experimentally investigated the effects of the hole-slot patterns and the operating parameters on the particle removal performance in wet ESPs using the hole-slot-structured collector. The voltage-current characteristics and the energy consumption among the different pattern collectors were discussed. Besides, the effects of the water film on the particle number concentration classification and the effects of the applied voltage and the specific collecting electrode areas (SCA) on the relative collection efficiency (RCE) were investigated and discussed. The experiment results show that the corona current of three hole-slot structured FRP collectors was higher than that of the conventional rigid collectors (CRC) at the same voltage. Using the FRP collectors with circular holes and horizontal slots could decrease the energy consumption and using the FRP collectors with vertical slots increases the energy consumption compared with the CRC when the collection efficiency was lower than 92.5%. The water film could increase the collection efficiency of the fine particles and prevent the fine particles cross through the holes and the slots. The hole-slot-structured FRP collectors were appropriate for the working conditions of high SCA and long residence time. When the water film in the hole and slotted structures was incomplete, the fine particles could pass through the collector plate to form secondary back-mixing. Implications: The wet ESPs are used most widely among the advanced treatment technologies of the fine particles’ removal. The rigid glass fiber reinforced plastics (FRP) collectors modified with hole-slotted structures were used to enhance the water film distribution over their surfaces. The hole-slot-structured FRP collectors were appropriate for the working conditions of high SCA and long residence time. When the water film in the hole and slotted structures was incomplete, the fine particles could pass through the collector plate to form secondary back-mixing.