Capital and Operating Costs of Selected Air Pollution Control Systems—IV

Previous articles in this series discussed the equipment costs of control devices, gas conditioning equipment, hoods, ductwork, and dampers. In this article, the discussion will concern the fans and associated components required to convey the gas stream from the initial pollutant source to the control device.     

Wet vs Dry Gas Cleaning In the Steel Industry

Deciding whether the gas should be cleaned by a “dry” system or a “wet” system requires a full consideration of all factors of which the capital cost is only one. Anticipating the various problems which might be expected and designing adequate measures for each calls for major engineering effort,but onlythen can a best choice be made. The principles which govern the above are illustrated by a typical selection of gas cleaning equipment to be used as part of a BOF steel making installation. Two entirely different gas cleaning systems are presently in BOF service in North America. Both will do an excellent job if properly designed. Either system will cost in excess of $2,000,000 and will require careful control and large amounts of electrical power. One system, the dry electrostatic precipitator, requires humidification of the gas; protection against explosions; elaborate electrical controls, insulators, etc.; and a rugged handling system for the bone dry dust collected. The other system, wet washing with water, Is easier to control but uses large quantities of water and electric power. As in the case of the “dry” system, handling the dirt collected is a difficult problem requiring careful study and choice of equipment. In either case the dust may be discarded or reused, but it must be handled with care lest it become an air or stream pollution problem all over again.     

The Removal of Particulate Matter from Fluid Bed Catalytic Cracking Unit Stack Gases

The application of a high-efficiency centrifugal type of separator to fluid bed catalytic cracking units is described in which most of the catalyst particles often lost to the atmosphere are concentrated into a small part of the stack gas (2%). A further separation can then be made on this small stream by an auxiliary separator which further concentrates the catalyst particle into 0.1% of the initia stream. Performance of the main and auxiliary separators are such as to reduce the loss of catalyst particles in the stack gas from 800 ppm to less than 60 ppm in a typical unit. Large amounts of power can be recovered by application of expander turbines to catalytic cracking plants employing this system of separation.     

小型锅炉烟气喷雾分离法脱硫的试验研究

以4t燃煤锅炉为对象，重点研究了喷雾分离法脱硫技术的工艺流程和主要设备，并给出了相应的试验结果。结果表明以清水为吸收剂，液气比≤0．1L／m^3，脱硫效率达到了60％—70％。本装置具有工艺简单、占地省、投资少、运行费用低的优点，特别适合用于中小型锅炉的改造。     

Innovative PCDD/F-containing gas stream generating system applied in catalytic decomposition of gaseous dioxins over V2O5-WO3/TiO2-based catalysts

Development of effective PCDD/F (polychlorinated dibenzo-p-dioxin and dibenzofuran) control technologies is essential for environmental engineers and researchers. In this study, a PCDD/F-containing gas stream generating system was developed to investigate the efficiency and effectiveness of innovative PCDD/F control technologies. The system designed and constructed can stably generate the gas stream with the PCDD/F concentration ranging from 1.0 to 100ng TEQ Nm(-3) while reproducibility test indicates that the PCDD/F recovery efficiencies are between 93% and 112%. This new PCDD/F-containing gas stream generating device is first applied in the investigation of the catalytic PCDD/F control technology. The catalytic decomposition of PCDD/Fs was evaluated with two types of commercial V(2)O(5)-WO(3)/TiO(2)-based catalysts (catalyst A and catalyst B) at controlled temperature, water vapor content, and space velocity. 84% and 91% PCDD/F destruction efficiencies are achieved with catalysts A and B, respectively, at 280 degrees C with the space velocity of 5000h(-1). The results also indicate that the presence of water vapor inhibits PCDD/F decomposition due to its competition with PCDD/F molecules for adsorption on the active vanadia sites for both catalysts. In addition, this study combined integral reaction and Mars-Van Krevelen model to calculate the activation energies of OCDD and OCDF decomposition. The activation energies of OCDD and OCDF decomposition via catalysis are calculated as 24.8kJmol(-1) and 25.2kJmol(-1), respectively.     

BOP Air Cleaning Experiences

The basic oxygen process of steel manufacture evolves a large volume of gas at high temperature during the oxygen blow. This gas contains finely divided oxide particles that are removed in gas-cleaning equipment. Either electrostatic precipitators or water scrubbers are commonly used for the purpose. These devices are quite efficient but breakdowns, usually in the auxiliary equipment, are frequent. Maintenance problems arise primarily from the high temperature of the gases which warps and cracks the plates in the hood that draws the gases to the cleaning device, and from erosion of piping caused by abrasive particles moving at high velocity. This paper presents a number of case histories of BOP gas-cleaning installations, details maintenance problems, and discusses corrective measures that have been adopted. It gives reasons why merely appropriating a large sum of money for cleaning devices does not always guarantee full abatement of air pollution from the basic oxygen process.     

PISCES: Tracking Trace Chemicals in Power Plants

PISCES, Power Plant Integrated Systems: Chemical Emissions Studies, is a multimedia chemical species project on plant emissions. Products generated in the PISCES project will help utilities design and operate their plants to minimize chemical species emissions. PISCES takes a holistic approach to the control of toxics by acknowledging that a chemical removed from a gas stream will appear in a liquid or solid stream.     

Recent Advances in Liquid Scrubbing for Fine Particulate Collection

Lone Star Steel has developed a family of high performance, long life, low capital, and low operating cost Hydro-Sonic* cleaners. A choice of driving mediums is available; either a compressible fluid ejector or fan may be used. The ejector models have no moving parts in the gas stream. Where available, waste heat may be used to power the cleaners. Cleaning levels are adjustable by the user by the selective input of energy. The Coalescer model employs a unique pressure recovery device for separation thereby reducing energy requirements for the cleaner. The Hydro-Sonic cleaners are operational In the steel, paper, and other industries.     

Tools For Evaluating New Process and Control Plans

The purpose of this paper on industrial plan evaluation is twofold: to present tools which can be used to evaluate quantitatively certain aspects of air pollution control devices, and to point up specifically two areas in which research is urgently needed. These research areas are in removing solid particles after wetting in scrubbers and use of surface active agents in scrubbing gaseous pollutants. Therefore, the body of information presented is directed to engineers in the field of evaluating the air pollution potential of new industrial plants, to scientists involved in determining the parameters and effectiveness of control devices, and to research and development scientists in the field of surfactants.

One tool presented is a chart for measuring the effectiveness of incinerator afterburners and vapor incinerators. The required inputs to the chart are the rate of flue gas flow in standard cubic feet per minute and the auxiliary fuel burner capacity in Btu per hour. The chart yields the flue gas temperature increase which will result, given in degrees F. The second tool presented is a new psychrometric graph for the humidifying and cooling of gases from processes as hot as 3000°F. Inputs into the graph are the temperature of the gases entering the sprays from the hot process and the temperature desired before they enter a control device such as a fabric filter or a scrubber. The chart yield is the amount of water needed in gallons per thousand cubic feet of gas. The only calculation needed is a correction of the hot gas volume to 70°F. Water needed to saturate the gases can be read directly also.     

Economic comparison of emission control systems for glass manufacturing furnaces with heat recovery

Glass manufacturing, like other process industries, is faced with air pollution compliance problems due to ever stricter emission limits. Several waste gas cleaning equipment options are available for air pollution control (APC) in glass plants, the most common arrangements being based on electrostatic precipitator (ESP) or fabric filter (FF) dust collectors and semi-wet or dry processes for acid gas removal. However, several counteracting aspects affect the choice of gas cleaning technologies, which are confirmed by the discrepancies encountered in actual suppliers' bids. In this paper, the main pollution control options are analyzed by carrying out a critical comparison under the cost-effectiveness point of view to select the lowest cost arrangement considering capital investment, operating expenses, and energy-saving revenues from heat recovery processes. The analysis is carried out with reference to a case study involving actual float glass production lines at Pilkington plants in Italy.     

Foreword

Fine particles have come to be recognized as being much more significant air pollutants than particles larger than several microns diameter. The removal of fine particles from an effluent gas stream is, unfortunately, more difficult than that of large particles. Because wet scrubbers are one of the major types of air pollution control equipment which can collect fine particles, it is important to define and exploit their potentialities.     

Closing Remarks

Abstract

The recent standards of performance for wastewater sources in the Synthetic Organic Chemical Manufacturing Industry (SOCMI), published by the U.S. Environmental Protection Agency (EPA), call for treatment of waste–water containing 500 ppmw volatile organic compounds (VOCs) and operating at flow rates greater than 1.0 liter per minute. There are a number of methods for achieving compliance with the treatment standards for wastewater. Among these is treatment to a VOC concentration of less than 50 ppmw with the removal of total VOC mass from the wastewater stream by 95%. If the wastewater treatment system uses stripping or evaporation, then the unit must be covered and vented to a control device. Emissions from the vent control system must be no greater than 20 ppmw. In this work, a treatment system is designed that would achieve compliance with the published standards. A novel unit operation—thin–film evaporation into a natural gas receiving stream—is used to treat the wastewater stream, while the vapor stream is combusted in a boiler or similar fired unit. The process employs a multimedia approach to minimize total treatment costs.     

Economic Comparison of Emission Control Systems for Glass Manufacturing Furnaces with Heat Recovery

ABSTRACT

Glass manufacturing, like other process industries, is faced with air pollution compliance problems due to ever stricter emission limits. Several waste gas cleaning equipment options are available for air pollution control (APC) in glass plants, the most common arrangements being based on electrostatic precipitator (ESP) or fabric filter (FF) dust collectors and semi-wet or dry processes for acid gas removal. However, several counteracting aspects affect the choice of gas cleaning technologies, which are confirmed by the discrepancies encountered in actual suppliers' bids. In this paper, the main pollution control options are analyzed by carrying out a critical comparison under the cost-effectiveness point of view to select the lowest cost arrangement considering capital investment, operating expenses, and energy-saving revenues from heat recovery processes. The analysis is carried out with reference to a case study involving actual float glass production lines at Pilkington plants in Italy.     

Thermal and catalytic incinerators for the control of VOCs

The emission of Volatile Organic Compounds (VOCs) is attracting increasing concern both from the public and by government agencies. Among the many available control technologies for the treatment of VOC containing waste streams, incineration offers an ultimate disposal strategy rather than a means for collecting or concentrating the offending compounds. This paper describes the major, commercially available thermal and catalytic incinerator systems that are designed to treat dilute, VOC containing gas streams. Qualitative guidelines are presented whereby the technologies can be compared. In addition, an example waste stream is used to illustrate a simplified procedure for calculating the material and energy balances for each of the incinerators. The resulting parameters will be used in a companion paper to estimate the capital and operating costs associated with each design. In this manner, a first estimate can be obtained of the costs of cleaning a waste stream containing low levels of VOCs.     

Capital and Operating Costs of Selected Air Pollution Control Systems — I

This is the first installment of a 4-part series which will present capital and operating costs of selected air pollution control systems. The objective of the Series is to identify the individual component costs so that realistic system cost estimates can be determined for any specific application. In Part I, cost estimating procedures and curves are provided to develop the equipment costs for electrostatic pre-cipitators, venturi scrubbers, fabric filters, incinerators, and adsorbers.     

Diesel engines: environmental impact and control.

The diesel engine is the most efficient prime mover commonly available today. Diesel engines move a large portion of the world's goods, power much of the world's equipment, and generate electricity more economically than any other device in their size range. But the diesel is one of the largest contributors to environmental pollution problems worldwide, and will remain so, with large increases expected in vehicle population and vehicle miles traveled (VMT) causing ever-increasing global emissions. Diesel emissions contribute to the development of cancer; cardiovascular and respiratory health effects; pollution of air, water, and soil; soiling; reductions in visibility; and global climate change. Where instituted, control programs have been effective in reducing diesel fleet emissions. Fuel changes, such as reduced sulfur and aromatics content, have resulted in immediate improvements across the entire diesel on- and off-road fleet, and promise more improvements with future control. In the United States, for example, 49-state (non-California) off-road diesel fuel sulfur content is 10 times higher than that of national on-road diesel fuel. Significantly reducing this sulfur content would reduce secondary particulate matter (PM) formation and allow the use of control technologies that have proven effective in the on-road arena. The use of essentially zero-sulfur fuels, such as natural gas, in heavy-duty applications is also expected to continue. Technology changes, such as engine modifications, exhaust gas recirculation, and catalytic aftertreatment, take longer to fully implement, due to slow fleet turnover. However, they eventually result in significant emission reductions and will be continued on an ever-widening basis in the United States and worldwide. New technologies, such as hybrids and fuel cells, show significant promise in reducing emissions from sources currently dominated by diesel use. Lastly, the turnover of trucks and especially off-road equipment is slow; pollution control agencies need to address existing emissions with in-use programs, such as exhaust trap retrofits and smoke inspections. Such a program is underway in California. These and other steps that can be continued and improved will allow the use of the diesel engine, with its superior fuel consumption, to continue to benefit society while greatly reducing its negative environmental and health impacts. The next ten years can and must become the "Decade of Clean Diesel."     

Information Required for the Selection and Performance Evaluation of Wet Scrubbers

The term “wet scrubber” or simply “scrubber,” for the purpose of this report, is intended to include any device using liquid to effect the removal of solid or liquid particles which are entrained in process air or gas streams. This guide is intended to provide information required for the selection and performance evaluation of all types of scrubbers installed for the primary purpose of removing such particulates from any process gas stream. It is not intended to cover scrubbers for the collection of gaseous and/or vapor constituents which involve gas absorption mechanisms.     

Thermal and Catalytic Incinerators for the Control of VOCs

Abstract

The emission of Volatile Organic Compounds (VOCs) is attracting increasing concern both from the public and by government agencies. Among the many available control technologies for the treatment of VOC containing waste streams, incineration offers an ultimate disposal strategy rather than a means for collecting or concentrating the offending compounds. This paper describes the major, commercially available thermal and catalytic incinerator systems that are designed to treat dilute, VOC containing gas streams. Qualitative guidelines are presented whereby the technologies can be compared. In addition, an example waste stream is used to illustrate a simplified procedure for calculating the material and energy balances for each of the incinerators. The resulting parameters will be used in a companion paper to estimate the capital and operating costs associated with each design. In this manner, a first estimate can be obtained of the costs of cleaning a waste stream containing low levels of VOCs.     

Air Pollution Equipment for Foundry Cupolas

The choice of air pollution equipment best suited for a specific foundry cupola involves the consideration of a number of factors.—They are: (1) The design of the cupola, including openings, door enclosures, height of stack, etc. These features greatly affect the size, cost, and efficiency of control systems. (2) The constituents of the effluent gas and the other properties, such as temperature and volume, are extremely important because corrosion, warpage, and low efficiency can result from these variables. (3) Four distinctly different types of air pollution control equipment are available for cupolas. They vary widely in initial cost, operating cost, and maintenance, but also vary widely in efficiency. (4) Local air pollution regulations and community considerations dictate the choice of air pollution equipment. Those regulations now in force are quite stringent in some localities, but quite lenient in others. An incremental approach to installation of systems would make one economically feasible for the small foundry.