Emission Control in Coking Operations By Use of Stage Charging

At the Clairton Coke Works of the United States Steel Corporation (the world’s largest coke plant), with coal charges of about 30,000 net tons per day, a system designated as “stage charging” has been developed for charging coal into the coke oven chamber without emissions to the atmosphere. The principles of the system are based on controlled sequential flow of the coal from the charging hoppers, during which the oven chamber is maintained under a very slight negative pressure condition by use of steam aspiration in the offtakes for on-the-main charging. The techniques are basic but require knowledge of the coal characteristics, adequate and properly maintained aspirating systems, including clean offtake piping, control of coal volume in the individual hoppers, and last, and probably most important, adherence by the operating crew to specific charging and leveling practices.     

Results of Field Measurements of Industrial Particulate Sources and Electrostatic Precipitator Performance

This paper presents results of source size distribution measurements over the size range from 0.1 μm to 5 μm for six classes of particulate sources and fractional efficiency measurements on five full scale electrostatic precipitators and one pilot scale precipitator. The precipitators all showed moderately high to high particulate collection efficiencies for particles having diameters larger than a few micrometers or smaller than a few hundredths of a micrometer and a minimum in collection efficiency for particles having diameters of a few tenths of a micrometer.     

Cooling Towers and the Environment

Measurements of natural draft cooling tower plume behavior, as well as meteorological variables, were obtained from aircraft flights near major power plants of the American Electric Power System. Persistence of the visible plume to great distances depends essentially on ambient humidity. Atmospheric stability at plume elevation was also important. Cooling tower-induced fog at ground-level was never observed in any of the tests, and aerodynamic downwash of the visible plume was absent also. The cooling towers did cause modification of natural clouds and they occasionally shadowed some local areas from the sun. Merging of the stack and cooling tower plumes was a common occurrence.     

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.     

A Wind Tunnel Study of Gaseous Pollutants in City Street Canyons

Steady state mean concentrations of tracer gas were measured in a 400:1 scale model of an idealized city with variable geometry placed within a wind tunnel at various orientations to the mean flow for a free stream velocity of 6.8 ft/sec. The tracer gas was released from two parallel line sources to simulate lanes of traffic in an effort to quantify the persistence of pollution as well as the mean values realized at street levels. An aerodynamically rough turbulent boundary layer of neutral thermal stratification was employed to simulate the atmosphere. Values of concentration measured in the model city were converted to prototype concentrations in ppm and compared to National Ambient Air Quality Standards. It was shown that single isolated structures may cause favorable mixing of pollution downwind but very high concentrations exist in the immediate leeward vicinity of the building. Two favorable geometries for city blocks tested were found to reduce pedestrian exposure to pollution both near heavy traffic congestion and downwind. It was concluded that the pollutant dilution was controlled by the mean flow rather than by turbulent diffusion and that the lateral spread of the plume was slight as one proceeded downwind of the line source. The combination of favorable geometry and higher dilution velocities may bring pollution levels down to existing Air Quality Standards. The body of information presented in this paper should interest city planners and air quality monitoring personnel, as well as those researchers attempting to study and model flow in city street canyons. It provides order of magnitude estimates on pedestrian and office worker exposure to pollutants under a wide range of conditions.     

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.     

Flow Patterns Upstream of Isokinetic Dust Sampling Probes

In isokinetic sampling from a gas stream it is usually assumed that the flow pattern upstream of the sampling probe is not affected by the presence of the probe. That some probes do seriously affect the gas streamlines is shown by velocity traverses taken with a hot wire anemometer under controlled flow conditions in a wind tunnel. The degree to v/hich the streamlines are affected depends on the wall thickness and taper of the nozzle, the stem diameter, as well as on the size and proximity of sampling accessories in the vicinity of the nozzle. For a probe to cause negligible disturbance under isokinetic conditions it should have a sharp-edged nozzle with little or no outside bevel, and the stem of the probe should be at least 11 stem diameters downstream from the nozzle inlet.     

Electrostatic Precipitator Applications in the Paper Industry

A survey of paper industry applications of electrostatic precipita-tors reveals problem areas and compares operators' experience on both tile shell and heated steel jacket units. In addition, items such as dew point operation, corrosion, electrode cleaning, wire breakage, etc. are discussed.     

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.