Control of Diesel Gaseous and Particulate Emissions with a Tube-Type Wet Electrostatic Precipitator

Abstract

In this study, experiments were performed with a bench-scale tube-type wet electrostatic precipitator (wESPs) to investigate its effectiveness for the removal of mass- and number-based diesel particulate matter (DPM), hydrocarbons (HCs), carbon monoxide (CO), and oxides of nitrogen (NO_x) from diesel exhaust emissions. The concentration of ozone (O₃) present in the exhaust that underwent a nonthermal plasma treatment process inside the wESP was also measured. A nonroad diesel generator operating at varying load conditions was used as a stationary diesel emission source. The DPM mass analysis was conducted by means of isokinetic sampling and the DPM mass concentration was determined by a gravimetric method. An electrical low-pressure impactor (ELPI) was used to quantify the DPM number concentration. The HC compounds, n-alkanes, and polycyclic aromatic hydrocarbons (PAHs) were collected on a moisture-free quartz filter together with a PUF/XAD/PUF cartridge and extracted in dichloromethane with sonication. Gas chromatography (GC)/mass spectroscopy (MS) was used to determine HC concentrations in the extracted solution. A calibrated gas combustion analyzer (Testo 350) and an O₃ analyzer were used for quantifying the inlet and outlet concentrations of CO and NO_x (nitric oxide [NO] + nitrogen dioxide [NO₂]), and O₃ in the diesel exhaust stream. The wESP was capable of removing approximately 67–86% of mass- and number-based DPM at a 100% exhaust volumetric flow rate generated from 0- to 75-kW engine loads. At 75-kW engine load, increasing gas residence time from approximately 0.1 to 0.4 sec led to a significant increase of DPM removal efficiency from approximately 67 to more than 90%. The removal of n-alkanes, 16 PAHs, and CO in the wESP ranged from 31 to 57% and 5 to 38%, respectively. The use of the wESP did not significantly affect NO_x concentration in diesel exhaust. The O₃ concentration in diesel exhaust was measured to be less than 1 ppm. The main mechanisms responsible for the removal of these pollutants from diesel exhaust are discussed.     

Dust Reentrainment,Gas Distribution and Electrostatic Precipitator Performance

Field observations indicating that uniform gas flow at the precipitator outlet may not result in best performance led to a study of how reentrainment and changes in gas distribution within a precipitator affect performance. A computer model developed in the study predicts that an improvement over uniform flow performance is possible by using controlled nonuniform gas distributions at both the inlet and the outlet faces of the precipitator. The model was used to study how changes in precipitator side view geometry affect performance and offers explanations for the reduction in precipitation constants experienced with larger installations.     

Electrostatic Precipitator Performance from the Point of View of Gas Treatment Time

This paper describes a risk assessment methodology for preliminary assessment of municipal sludge incineration. The methodology is a valuable tool in that it can be used for determining the hazard indices of chemical contaminants that might be present in sewage sludge used in incineration. The paper examines source characteristics (i.e., facility design), atmospheric dispersion of emission, and resulting human exposure and risk from sludge incinerators. Seven of the ten organics were screened for furtherinvestigation. An example of the calculations are presented for cadmium.     

Calculation Of Electric Field Strength Distributions For New Electrostatic Precipitator Discharge Electrode Designs

New collecting and discharge electrode configurations are being used in electrostatic precipitators. In order to mathematically model preclpitators with these arrangements, it is necessary to develop reliable models of the field strength distributions of these electrodeplate geometries. This paper presents the concept of an equivalent wire diameter and attenuation functions, permitting use of the well-known wire-plate calculations. Experimental data presented in this paper shows the approximation techniques are sufficiently accurate.     

Fine Particle Removal Performance of a Two-Stage Wet Electrostatic Precipitator Using a Nonmetallic Pre-Charger

ABSTRACT

A novel two-stage wet electrostatic precipitator (ESP) has been developed using a carbon brush pre-charger and collection plates with a thin water film. The electrical and particle collection performance was evaluated for submicrometer particles smaller than 0.01～0.5 μm in diameter by varying the voltages applied to the pre-charger and collection plates as well as the polarity of the voltage. The collection efficiency was compared with that calculated by the theoretical models. The long-term performances of the ESP with and without water films were also compared in tests using Japanese Industrial Standards dust. The experimental results show that the carbon brush pre-charger of the two-stage wet ESP had approximately 10% particle capture, while producing ozone concentrations of less than 30 ppb. The produced amounts of ozone are significantly lower than the current limits set by international agencies. The ESP also achieved a high collection rate performance, averaging 90% for ultrafine particles, as based on the particle number concentration at an average velocity of 1 m/sec corresponding to a residence time of 0.17 sec. Higher particle collection efficiency for the ESP can be achieved by increasing the voltages applied to the pre-charger and the collection plates. The decreased collection efficiency that occurred during dust loading without water films was completely avoided by forming a thin water film on the collection plates at a water flow rate of 6.5 L/min/m2 Zukeran, A., Ikeda, Y., Ehara, Y., Matsuyama, M., Ito, T., Takahashi, T., Kawakami, H. and Takamatsu, T. 1999. Two-Stage-Type Electrostatic Precipitator Re-entrainment Phenomena under Diesel Flue Gases. IEEE. Trans. Ind. Appl, 35: 346–351. [Crossref], [Web of Science ®] , [Google Scholar].

IMPLICATIONS Current two-stage electrostatic precipitators (ESPs) have several technical problems such as a drop in collection efficiencies by small-particle re-entrainment during rapping and corrosion of metallic electrodes of the ESPs by corrosive gases. This paper evaluates a novel two-stage ESP that uses a nonmetallic pre-charger and water film collection plates to avoid the above mentioned problems of other ESPs. This ESP can be used not only for industrial applications but also for residential purposes because it has a high removal performance for fine particles with low ozone generation and maintains its efficiency due to the continuous cleaning of the collection plates with water film.     

Performance Audit Results for Volatile POHC Measurements

Audit materials containing principal organic hazardous constituents (POHCs) have been developed by EPA for use by federal, state, and local agencies or their contractors to assess the accuracy of measurement methods used during RCRA trial burn tests. Audit materials are currently available for 27gaseous organics in five, six, seven, and nine-component mixtures at parts-per-billion levels (7 to 10,000 ppb) in compressed gas cylinders in a balance gas of nitrogen. The criteria used for the selection of 27 gaseous organic compounds is described.

Stability studies indicate that all of the organics tested (with the exception of ethylene oxide and propylene oxide below 10 ppb levels) are stable enough to be used as reliable audit materials.

Subsequent to completion of the stability studies, 89 performance audits have been conducted with the audit materials to assess the accuracy of the Volatile Organic Sampling Train (VOST) and bag measurement methods during or prior to RCRA trial burn tests. A summary of the audits conducted for each POHC and the measurement system audited is shown in this paper. The audit results obtained with audit gases during RCRA trial burn tests are generally within ±50 percent of the audit concentrations.     

A Model to Predict the System Performance of an Electrostatic Precipitator for Collecting Polydisperse Particles

Abstract

This paper presents a model for predicting the performance of an electrostatic precipitator (ESP) for collecting polydisperse particles. The particle charge was obtained by modifying Cochet’s charge equation; the particle size distribution was approximated by a lognormal function; and then the statistic method of moments was employed to obtain a set of the first three moment equations. The continuous evolution of the particle size distribution in an ESP is easily taken into account by the first three moment equations. The performance of this model was validated by comparing its predictions with the existing data available in the literature. Effects of the particle size distribution on the ESP performance were examined, and the results indicated that both overall mass and number efficiencies are lower for inlet particles with a larger mass median diameter and a higher geometric standard deviation. The methodology introduced may be applied to develop design criteria and determine optimal operating conditions of an ESP for improving the collection efficiency of the submicron particles.     

Field Measurements of Particulate Matter Emissions,Carbon Monoxide,and Exhaust Opacity from Heavy-Duty Diesel Vehicles

ABSTRACT

Diesel particulate matter (PM) is a significant contributor to ambient air PM₁₀ and PM_2.5 particulate levels. In addition, recent literature argues that submicron diesel PM is a pulmonary health hazard. There is difficulty in attributing PM emissions to specific operating modes of a diesel engine, although it is acknowledged that PM production rises dramatically with load and that high PM emissions occur during rapid load increases on turbocharged engines. Snap-acceleration tests generally identify PM associated with rapid transient operating conditions, but not with high load. To quantify the origin of PM during transient engine operation, continuous opacity measurements have been made using a Wager 650CP full flow exhaust opacity meter. Opacity measurements were taken while the vehicles were operated over transient driving cycles on a chassis dynamometer using the West Virginia University (WVU) Transportable Heavy Duty Vehicle Emissions Testing Laboratories. Data were gathered from Detroit Diesel, Cummins, Caterpillar, and Navistar heavy-duty (HD) diesel engines. Driving cycles used were the Central Business District (CBD) cycle, the WVU 5-Peak Truck cycle, the WVU 5-Mile route, and the New York City Bus (NYCB) cycle. Continuous opacity measurements, integrated over the entire driving cycle, were compared to total integrated PM mass. In addition, the truck was subjected to repeat snap-acceleration tests, and PM was collected for a composite of these snap-acceleration tests. Additional data were obtained from a fleet of 1996 New Flyer buses in Flint, MI, equipped with electronically controlled Detroit Diesel Series 50 engines. Again, continuous opacity, regulated gaseous emissions, and PM were measured. The relationship between continuous carbon monoxide (CO) emissions and continuous opacity was noted. In identifying the level of PM emissions in transient diesel engine operation, it is suggested that CO emissions may prove to be a useful indicator and may be used to apportion total PM on a continuous basis over a transient cycle. The projected continuous PM data will prove valuable in future mobile source inventory prediction.     

Recent Electrostatic Precipitator Experience with Ammonia Conditioning of Power Boiler Flue Gases

Motivated by heightened recent interest, Koppers Co. has been experimenting with ammonia conditioning of power boiler flue gases for the purpose of improving the precipitability of the emitted fly ash. Chemical reactions resulting from ammonia injection are postulated. Measurements on three pulverized coal and two cyclone fired boilers, all of which emit acidic ash, are described. In all five cases, considerable but varying, increase in precipitator power input and collection efficiency resulted when gaseous ammonia in the amount of 1 5 ppm was injected between the economizer and air preheater. The conditioned fly ash showed decreased acidity and inconsistent change in electrical resistivity. Unless air heater temperatures were unusually high (>400°F), tendency of the air heater to plug was an additional, but unwanted, result. At one station with high air heater outlet temperature ammonia injection has been adopted as a permanent solution to community pressure for reduction of stack discharge. Ammonia injection downstream of the air heater produced no effect. Future plans are presented to continue the program beyond results described here.     

An Inventory of Particulate Emissions from Open Sources

Open sources are those stationary sources of air pollution too great in extent to be controlled through enclosure or ducting. Open sources of atmospheric particles include: wind erosion, tilling, and prescribed burning of agricultural cropland; surface mining and wind erosion of tailings piles; vehicular travel on both paved and unpaved roads; construction site activity; and forest fires. It is estimated that in 1976 the total open source emissions of particles in the U.S. amounted to over 580 × 10⁶ ton. These estimates indicate that emissions from the two largest open source classes, travel on unpaved roads and agricultural wind erosion, accounted for 86% of this total. The open source emissions in ten states (AZ, CA, KS, MN, MT, NM, ND, OH, SD, TX) contributed 6 2% of the national emissions for 1976.     

Particulate and Sulfur Dioxide Concentration Measurements in Patras,Greece

Abstract

The purpose of this study was to obtain a better assessment of the Patras, Greece, air quality, in terms of the primary pollutants total suspended particulates (TSPs) and sulfur dioxide (SO₂), because limited and short-duration measurements have been conducted in the past. Installation and operation of a mobile air monitoring station at two different locations in the Patras downtown area and one location in the outskirts of the city was undertaken and covered the periods July 1, 1994-January 30, 1995; March 18-August 23, 1995; and April 19-July 27, 1996, respectively. For both pollutants measured at each location, the monthly average concentrations and typical weekly variation of daily averages, as well as the diurnal variations and frequency concentration distributions in each month of the monitoring periods, were calculated and are presented in bar diagrams. The annual and winter period medians and the annual 98th percentile were also calculated and are compared with the limit and guide values provided by the European Economic Community Council Directive 80/779/EEC. In addition, comparison of SO₂ values is made with the limit values adopted by the more recent Directive 1999/30/EC. It was found that the TSP and SO₂ levels at all locations were very low and were lower than the levels found in Thessaloniki and Athens, Greece. An attempt to explain what had been measured is also undertaken. The data presented are considered essential for future reference and comparison purposes.     

Factors Affecting the Resistivity of a Particulate Layer in Electrostatic Precipitators

This paper develops an expression for the resistivity of a dust layer which takes into account its particulate nature, dependence of the surface resistivity component on water vapor pressure and temperature, the volume resistivity and the intrinsic properties of the particulate material. A new expression is given for the surface resistivity which, when combined with the equation for volume resistivity, enables the effective resistance of a dust layer to be characterized by five meaningful parameters. These parameters may be determined for a given fly ash sample from a standard set of resistivity curves. Calculated resistivity curves for an industrially produced fly ash are compared with measured curves.     

Statistical Errors in Beta Absorption Measurements of Particulate Mass Concentration

There are a number of new instruments which use the attenuation of beta radiation to determine the mass of particulate matter collected in various fashions, and thus to determine its mass concentration.^1–3 It has been shown that the mass concentration, c, can be obtained from the relationship     

A State of the Art Report on Industrial Precipitator Control Equipment

Informative report No. 3 has been prepared to provide background information on the origin, purpose, and general theory of operation of automatic power controls for industrial electrostatic precipitators. A comprehensive body of literature describing the process and mechanisms of dust collection in precipitators is readily available to those interested, but information on the control equipment used with the process is widely scattered. This report is intended to provide assistance toward the understanding of manufacturers’ literature describing specific control apparatus, and it may be used as a starting point for more intensive investigation of the subject. To the latter end, a history of the development of these controls and a bibliography of pertinent literature and patents has been included. It is expected that this report will be of particular interest to technical and supervisory personnel concerned with the selection, evaluation, and operation of precipitation equipment.     

Sources of Atmospheric Carbonaceous Particulate Matter in Pittsburgh,Pennsylvania

Abstract

The organic carbon (OC)/elemental carbon (EC) tracer method is applied to the Pittsburgh, PA, area to estimate the contribution of secondary organic aerosol (SOA) to the monthly average concentration of organic particu-late matter (PM) during 1995. An emissions inventory is constructed for the primary emissions of OC and EC in the area of interest. The ratio of primary emissions of OC to those of EC ranges between 2.4 in the winter months and 1.0 in the summer months. A mass balance model and ambient measurements were used to assess the accuracy of the emissions inventory. It is estimated to be accurate to within 50%. The results from this analysis show a strong monthly dependence on SOA contribution to the total organic PM concentration, varying from near zero during winter months to 50% or more of the total OC concentration in the summer.     

Predicting the Performance of Particulate Control Equipment

A new probabilistic modeling environment is described which allows the explicit and quantitative representation of the uncertainties inherent in new environmental control processes for SO₂ and NO_x removal. Stochastic analyses provide additional insights into the uncertainties in process performance and cost not possible with conventional deterministic or sensitivity analysis. Applications of the probabilistic modeling framework are illustrated via an analysis of the performance and cost of the fluidized bed copper oxide process, an advanced technology for the control of SO₂ and NO_x emissions from coal-fired power plants. An engineering model of a conceptual commercial-scale system provides the basis for the analysis. The model also captures interactions between the power plant, the SO₂/NO_x removal process, and other components of the emission control system. Results of the analysis address payoffs from process design improvements; the dependence of system cost on process design conditions and the availability of byproduct markets; and the likelihood that the advanced process will yield cost savings relative to conventional technology. The implications of case study results for research planning and comparisons with alternative systems also are briefly discussed.     

Performance of Wet Scrubbers on Liquid and Solid Particulate Matter

A general discussion of packed scrubbers for particle collection is presented. Data on liquid entrainment separation, ammonium chloride fume collection, and clay particle collection are given.     

Information Required for the Selection and Application of Electrostatic Precipitators for the Collection of Dry Particulate Material

This report is a continuation of two prior papers on the selection and application of electrostatic precipitators. The first papers submitted by the TA-5 committee of APCA were primarily concerned with the collection of fly ash from boiler gases. Three other major applications of industrial precipitators include the ferrous, pulp and paper, and cement fields. Other industries utilizing the precipitator but to a lesser degree are: chemical, petroleum, and non-ferrous metals. New application areas in the United States include municipal incinerators and high temperature-high pressure gas cleaning.

While a similarity of theory and equipment is common to all of the above applications, there are sufficient differences both in the processes and types of material collected to make the selection of the Individual precipitator subject to a comprehensive evaluation. In order properly to make this evaluation, it is necessary that a suitable means of communication be established between user and supplier. It is the purpose of this report to recommend ’? terminology, emphasize design factors, and list the information needed by the supplier to make a proper application of his equipment.     

Emissions of Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans from Various Industrial Sources

Abstract

This study characterized the emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) from the stack flue gases of 17 industrial sources, which were classified into 10 categories. The results show that the mean PCDD/PCDF concentration of secondary zinc smelter (Zn-S) and secondary copper smelter (Cu-S) is 2.44 ng international toxic equivalent (I-TEQ)/Nm³ (N represents normal conditions at 0 °C, 760 mmHg), which was found to be significantly greater than that of industrial waste incinerators (mean concentration = 0.15 ng I-TEQ/Nm³). These results imply that the controlling of secondary metallurgical melting processes is more important than industrial waste incineration for the reduction of PCDD/PCDF emissions. The mean emission factors of cement production, Zn-S and Cu-S, are 0.052, 1.99, and 1.73 μg I-TEQ/t product, respectively. For industrial waste incineration, the mean emission factors of waste rubber, waste liquor, waste sludge, industrial waste solid (IWI)-1, IWI-2, IWI-3, and IWI-4 are 0.752, 0.435, 0.760, 6.64, 1.67, 2.38, and 0.094 μg I-TEQ/t feed, respectively. Most of the PCDD/PCDF emission factors established in this study are less than those reported in previous studies, which could be because of the more stringent regulations for PCDD/PCDF emissions in recent years.