Characterization of Particulates from Power Plants

The emphasis on participate control from industrial processes has been shifted recently towards fine particulates, having diameters less than 3 microns. There exists an urgent need for more scientific information of fine particle characterization.^1,2 Coal and oil fired power plants are among the largest anthropogenic point sources of particulate matter.³ Limited knowledge is available on particle size distribution and trace metal composition in power plant emissions.^4-7 The morphological properties of particle emissions have been largely neglected. In this report we present some information on particle characteristics for an oil-fired and coal-fired power plant.     

An Integrated Program to Achieve Maximum Performance of Electrostatic Precipitators

The objective of this paper is to describe the Tennessee Valley Authority's efforts and plans in designing an operating and maintenance program that will ensure maximum performance of the electrostatic precipitators at our power generating stations. Detailed operating and maintenance manuals are being prepared for each plant for the use of plant personnel. These manuals include instructions on operation, maintenance, and testing of the precipitators. Instructions on internal and external equipment inspections to be performed during unit operation, emergency and scheduled outages, and problem diagnostic procedures are included to help the plant personnel solve problem areas. Performance curves are included in the manuals which show the effect of gas volume flow, gas temperature, gas resistivity, coal changes, and loss of transformer-rectifier sets on the precipitator performance. In addition, opacity monitors that record continuous opacity readings are being installed at all our plants to assist the plant in monitoring precipitator performance. Full-time operating and maintenance crews are being organized at the plants to monitor and maintain the precipitator and ash-removal systems. Also, a staff of technical personnel is being organized at the central office to provide technical advice and assistance in design, operation, and maintenance problems and liaison and coordination for all the plants concerning the precipitators. Periodic precipitator field inspections, performance and operating parameter optimization testing, and review of the equipment operating logs are made by the central office technical personnel. Recommendations and technical assistance are then furnished to the plant with regard to the precipitator overall performance and operating characteristics.     

Workshop on Primary Sulfate Emissions

This article is a summary report on a workshop, Measurement Technology and Characterization of Primary Sulfur Oxides Emission from Combustion Sources, sponsored by the EPA Environmental Sciences Research Laboratory at Research Triangle Park, NC, held in Southern Pines, NC. The objectives of the workshop were: to review and discuss current measurement methods and problem areas for sulfur oxides emission with attention focused on sulfuric acid, sulfates, and sulfur-bearing particulate matter; to review and discuss emission data from various combustion sources operating under different conditions, which include various pollutant controls, fuel composition, excess boiler oxygen, etc.; to delineate and recommend areas in need of research and development effort. Scientists were invited to present the results of their studies on primary sulfate emissions. The 3-day workshop devoted one day to measurement technology, a second to characterization, and a third to critical assessment of the presented papers and development of summary working group reports on each half-day session of the initial 2 days. Thirty-one papers were presented by 29 participants on measurements and characterization. Four working group reports were developed and summarized in the last day. Highlights of the papers and reports are briefly reviewed. Workshop proceedings are available as an EPA publication.     

Environmental Impact of Residential Wood Combustion Emissions and its Implications

Currently available information suggests a substantial environmental impact from residential wood combustion emissions. Air pollution from this source is widespread and increasing. Current ambient measurements, surveys, and model predictions indicate winter respirable (<2 μm) emissions from residential wood combustion can easily exceed all other sources. Both the chemical potency and deliverability of the emissions from this source are of concern. The emissions are almost entirely in the inhalable size range and contain toxic and priority pollutants, carcinogens, co-carcinogens, cilia toxic, mucus coagulating agents, and other respiratory irritants such as phenols, aldehydes, etc. This source is contributing substantially to the nonattainment of current particulate, carbon monoxide, and hydrocarbon ambient air quality standards and will almost certainly have a significant impact on potential future standards such as inhalable particulates, visibility, and other chemically specific standards. Emission from this growing source is likely to require additional expenditures by industry for air pollution control equipment in nonattainment areas.     

A Cyclone for Size-Selective Sampling of Ambient Air

A cyclone with a 47 mm after-filter has been developed for ambient air size-selective monitoring. It has been extensively evaluated with laboratory-generated aerosol. Variation of the pressure drop and 50% cut point with flow rate show that the cyclone operates in a single flow regime with a vortex in the outlet flow. The particle size cutoff curve is comparable in sharpness to a cascade impactor and is the same for solid or liquid particles. At 21.7 L/min, D ₅₀ is 2.5μm and at 15.4 L/min, D ₅₀ is 3.5 μm. Collection efficiency data for flow rates from 8 to 27 L/min fit a universal curve when plotted vs. the normalized particle diameter, (D-D ₅₀)/D ₅₀ Reentrainment of previously deposited particles is less than 1 % of the loading per day. In field tests the cyclone has proved to be a very satisfactory size-selective sampler.     

experience of the forest products industry in obtaining air quality permits for new and modified sources

A detailed study of the air quality permitting process for 65 different forest products industry projects requiring preconstruction permit approvals from EPA, state, and local air pollution control agencies was conducted. The projects included a wide array of sources including kraft recovery furnaces, lime kilns, fossil fuel and wood residue fired boilers, solid wood products manufacturing facilities, paper coaters, and printing presses. Information concerning the time involved in the permitting process, costs associated with obtaining the permits, use of air quality models and ambient monitoring data, emission control technology determinations, problem areas encountered during the permitting process, perceived benefits and drawbacks of the permitting process, and the effect of permitting requirements on project planning was obtained.

The results indicate that certain permitting requirements such as Best Available Control Technology (BACT) determinations, dispersion modeling results, and use of ambient air quality monitoring data seldom influence the emission limitations ultimately imposed in the final approved permit, with 87% of the final emission limits equivalent to the applicable New Source Performance Standard (NSPS). The 65 permitting case histories also show that obtaining permits for projects subject to Prevention of Significant Deterioration (PSD) requirements takes approximately twice as long and costs twice as much as obtaining permits for projects not subject to PSD requirements.     

Technique for Measuring the Total Concentration of Gaseous Fixed Nitrogen Species

This paper reports the development of a rapid, continuous technique for analyzing fixed nitrogen species (NH₃, HCN, CH₃NH₂, etc.). The technique uses a platinum catalyst at low pressure in combination with a conventional chemiluminescent NO _x analyzer. Previous workers observed that conventional stainless steel catalysts, and platinum catalysts operated at atmospheric pressure, do not reliably convert NH₃ to NO. The most serious problem was the variation in the efficiency of these catalysts with operating conditions. Changes in temperature, gas composition, or X_NH3 could change the conversion efficiency from 99.9% to <30%. The new conversion technique, however, is quantitative up to several thousand ppm NH₃ in either O₂/He or O₂/CO₂/N₂.     

Modeling of Carbon Monoxide Hot Spots

This paper describes the results of a measurement and modeling study of carbon monoxide (CO) concentrations In the proximity of intersections. Analysis for model performance of paired observed and predicted CO concentrations are presented. Two methodologies of pollutant prediction were used: the Intersection Midblock Model (IMM) and a statistical multiple linear regression. The results showed that both methods underpredicted frequently and dispensed results that were site specific. In addition, correlations of IMM predicted concentrations to observed concentrations were poor (typically r² values <0.25). Various explanations for this observation are proposed. The statistical approach exhibited an improved accuracy over that of IMM. However, some of the independent variables used might be difficult to obtain as a routine measurement, and use of a one or two independent parameter model yielded adjusted R² values comparable to the r² values observed with IMM. Based on these results, an Intersection model applicable under a wide range of conditions of traffic, meteorology, and geometry is not available. Research Is needed to develop one, since its use would often be called on in the development of air quality sections of Environmental Assessments or Environmental Impact Statements.