Prior to the introduction of air quality standards, the use of air pollution control technology was to meet the requirements of good engineering practice. Currently, the purpose of applying and / or developing control technology is to comply with ambient air quality standards and other source related regulations. A control technology can only be applied to a controllable source. Therefore, it will be difficult to think about controlling the emissions of a volcano.
The cost of removing a contaminant from a source generally increases exponentially with the percentage of control. However, this relationship will change if it is possible to recover the pollutant for some economic purposes. For example, sulfur removal from gas processing plants was economically feasible in 1960 due to the high sulfur price on the world market.
Techniques without emission control devices
Process Change: This technique involves a modification of an existing process or the introduction of a new process. Since the 1990s the process change has been known as "pollution prevention". Consider the example of painting operations in the automotive industry. As a result of these operations large amounts of volatile organic compounds and hazardous air pollutants were released. Following the approval of the 1990 CAAA, many operations have replaced water-based PAH paints for oil-based paints to reduce emissions. Some operations have implemented processes such as electro-deposition, immersion tank and powder coating.
Process modification is a popular technique for controlling air pollution. Major efforts are being made in all industries to change pollution reduction processes. For example, Libbey Owens Ford develops new oxygen furnaces in Toledo to reduce ozone emissions during glassmaking.
Changes in industrial processes to reduce raw materials and fuels also lead to reduced air emissions. Promotions for using fluorescent lights and conducting energy audits by utilities are examples of lower demand for electricity. This results in less fuel use in the power plant and, therefore, less air pollutants are emitted.
The use of wind power, geothermal energy, hydropower and solar energy is increasing and is helping to reduce air pollution.
The EPA has initiated a major effort in the area of pollution prevention. The purpose is to "prevent" pollution instead of controlling it at the point of release. The goal is not to produce solid or hazardous waste.
Fuel change: This technique involves the use of less polluting fuel to reduce air pollution. The use of low sulfur fuel rather than high sulfur fuel by utilities is an example of this method. Remember that low sulfur fuel is much more expensive than high sulfur fuel. The other option for a utility can be the use of natural gas as fuel. Weather-based fuel switching or air pollution forecasts have been used to prevent air pollution problems in many areas.
The following table shows the advantages and disadvantages of a number of alternative fuels:
![[Image: altfuel.gif]](http://www.eng.utoledo.edu/~akumar/IAP1/Pollution%20Control_files/altfuel.gif)
Another example of this method is the use of low ash or natural gas oil for a dryer in an asphalt plant to reduce particulate matter. Introduction of compressed natural gas, propane, ethanol and automotive oxygenated fuels have helped reduce air pollutants in the US.
The use of natural gas in North America and Europe for winter warming brought a significant improvement in air quality in most cities.
Nuclear power plants are relatively pollution-free compared to coal-fired power plants. However, they have been controversial issues in their overall environmental impact.
Improve Dispersion: This approach is based on the concept that the dilution of air pollutants before they reach the ground will lower the concentrations at which the population is exposed. The use of this approach for industry is discouraged by the EPA. However, local and state agencies use the concept to develop air pollution control strategies for their area.
Prior to the 1970 CAAA, the broader approach to airborne problems was based on the motto Dilution is the solution to pollution. This is evident from the high stacks built by the Tennessee Valley Authority and others in the 1960s and 1970s.
Another form of this approach is in the form of intermittent control or an air quality prediction system. This approach attempts to control the rate of emission of the source during periods of high concentrations at the ground level. Production cuts, shutdown of a plant, switching of fuel or other strategies manage to reduce the emission rate of the source. Critical periods are determined from related meteorological data in the area.
Prediction systems are based on observations, predictive equations, or a combination of observations and predictions.
The first documented intermittent predictive control system was established in 1941 in the lead and zinc smelter in Trail, British Columbia (Canada). The plant is located in a valley near the border between the United States and Canada. Damage from harvests to orchards in the United States from the nocturnal emissions brought to the land during the disintegration of morning investment led to the formation of an international tribunal. The study led to the development of an intermittent control system to focus on the period from 3 AM to 3 hours after sunrise during the growing season.
TVA developed an AQPS plant for Paradise, Kentucky. Several hours before adverse weather conditions are predicted, output power is reduced to avoid NAAQS violation.
Many cities in Canada and the United States have regulations to restrict industrial and other activities during times of low air quality observed. Alberta Environment calls on the industry to reduce production during the early morning hours of poor air quality in the City of Calgary and Edmonton. Many western mountain communities in the US issue a public notice to turn off wood stoves when PM10 levels exceed a certain value.
The use of oxygenated gasoline in the winter months in many cities in the United States is an example of intermittent control at the national level for CO emissions. There are high CO emissions in many communities during the winter months.
Ozone action days are reported during the summer months to avoid NAAQS violations based on observations of weather variables (eg temperature) and ozone concentration at ground level. Figure 1 presents a procedure to identify ozone action days in Toledo.
Good Operating Practices: The release of unnecessary air pollutants could be avoided by maintaining good plant maintenance and proper maintenance. For example, liquid chemicals that spread through the soil evaporate rapidly and will cause an increase in the emission rate of that chemical.
Plant Shutdown / Relocation: This is not a pleasant solution for a community because of the economic impact. Most cities develop land use planning and industrial zoning regulations to avoid this situation. Stimulus to use the new technology through tax credits or subsidies can help a company relocate the plant within the city. In some cases to stop the plant is only viable solution.
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