Air Pollution Control Technology (Research Paper Sample)

Air Pollution Control Technology
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Water impact may emerge because of thermal loading when cooling water is discharged in large volumes (Greunen 2006). To counteract thermal impact, the project focuses on using forced-air cooling, lagooning, and heat exchange of exiting hot gases in order to preheat raw materials, which are entering the plant. Ammonia, which is present in the dilute aqueous streams, is recovered through steam stripping.
Since gasification process involves chemical conversion of feedstock, temperature conditions need to have an effective control. This is necessary, so that chemical conversion process does not result in production of pollutants (The Blue Ridge Environmental Defense League 2009). Biomass, which is a renewable energy, is a raw material for this project. This raw material is associated with production of CO2 gas, which is an environmental pollutant. This occurs since CO2 gas is one of the factors, which contributes to global warming when the gas is availed to the atmosphere. This indicates that the control of the temperature conditions during the chemical conversion process is significant, so that valuable and clean energy is obtained, and environmental pollution does not occur. To attain this, the project focuses on having a temperature regulator and indicator such that when temperatures are beyond the desired limits the operator is notified. This will glad the operator an opportunity to recheck, as well as adjust temperatures to the desired operation limits.
Noise is anticipated in the overall project. The main sources of the noise are the operating compressors and the movement of gas volumes. This indicates that the project deserves to attain a certain local noise criteria in order to ensure that the personnel involved in the running of the project have the capacity to do so successfully. This will ensure that the project attains its desired success. One of the effective means of controlling this noise in the project will be noise dampening. Such a system will ensure that is possible locate and localize noise sources, which have the potential of producing sound levels that exceeds 90 dBA (Hocking 2005).
Gasification process is associated with dissemination of ash, which is approximately 8 to 15 percent in terms of volume (The Blue Ridge Environmental Defense League 2009). This ash is toxic; its ability to contain low pH or acidic properties makes it introduce negative impacts on landfills. Furthermore, leaching of toxic metals mercury, lead, and cadmium occurs rapidly at low pH. Therefore, the ash needs to be cleaned, and all metal properties separated in order to ensure that the disposal of this ash does not have negative impacts on the environment, as well as contaminating the groundwater. This may be done by adopting an effective means of recycling the gasification waste. Such a means is the installation of a biomass digester, which would generate energy from this waste.
Nitrogen dioxide discharges emerge because of atmospheric nitrogen oxidation, which occurs during the process of combustion of reformer fuel (Greunen 2006). To minimize the discharges of nitrogen dioxide, the content of ammonia gas in purge gases need an effective reduction. Further, excess air should not be used in the reformer combustion. This results in a reduction of the NOx emissions, as well as improvement in the energy efficiency. NOx is an environmental pollutant since it causes harmful effects to the environment. Global warming is one of these harmful effects of NOx. Therefore, the project proposes several air pollution control technologies, which would aid in curbing the impacts of NOx and other gases.
With respect to the anticipated pollutants in this project, the proposed pollution control technology is wet scrubbers. Wet scrubbers find a wide application in particulates control. They rely on irreversible and direct contact of a liquid (bubbles, foam, or droplets) with the particulates. The design configurations for scrubbers are many. This grants scrubbers to be used in different fields of application. In order to classify wet scrubbers, the method, which is employed to induce contact between particulates and the liquid, is used. Energy, which may be expressed in terms of pressure drop on the scrubber, may also be used to classify scrubbers. This indicates that scrubbers can be classified as high, medium, or low energy.
Fabric filters is an air pollution control technology, which the project proposes to be used in the removal of dry particles from the attained gas stream (Greunen 2006). This technology involves the flow of dusty gas through and into several filter bags, which are arranged parallel to each other, and enabling retention of the dust by the fabric. This fabric acts as supporting medium of the dust layer, which accumulates on it, as well as contributes to minor particle filtering. The attained dust layer enables effective filtering of several small particles that are responsible for baghouses. Although fabric filters are effective in both low and high particles concentrations, their suitability levels are for free-flowing and dry particles only.
Types of fabric filter medium, which the project may adopt, include plastic, needled felt, woven fabric, metal, and ceramic among others. Operation temperature is the key parameter, which influences the choice of the fabric filters. Some of the benefits of using fabric filters as air control technology, which the project will enjoy, include operation of fabric filters in several dust types, higher efficiencies of collection, demand of low-pressure drops, operation in several volumetric flow rates ranges, and modular design. However, fabric filters have inherent limitations, which include threat to explosion, requirement of wide floor areas, limitation of operation within moist environments, and destruction of fabrics by corrosive chemicals or high temperatures. Needled felt is the selected fabric for this project since it is easily accessible and easier to use.
Wet scrubbers have the ability of handling mists, handling explosive and flammable dust at a minimum risk, enabling cooling of gases that are hot, provide dust collection and gas absorption in a single unit, and creating room for neutralizing corrosive dusts and gases (The Blue Ridge Environmental Defense League 2009). However, wet scrubbers are associated with corrosion problems, expensive disposal of waste sludge, unrecyclable contaminated particulates, and water pollution as a result of liquid effluent. The proposed scrubber design for the project is the one, which involves liquid droplets introduction to a spray chamber. This enables effective mixing of the gas stream and liquid in order to have contact with particulates.
Electrostatic precipitation is also an air control technology, which the project proposes to use (Yan 2007). The process involves ionization of air, which is contaminated and flowing through electrodes, charging of air particles, migration of air particles, and collection of air particles (contaminants) on opposite plates that have different charges, and removal of these particles from the associated plates (Hocking 2005). These particles can be in the form of either liquid droplets or dry dust. As such, an electrostatic precipitator involves the flow of air via a unit and the contaminant particles remain behind the plates. Hence, the particles may be washed off or knocked off (rapped) the plates, and then collected on the lower side of the electrostatic precipitator. Electrostatic precipitators have the potential of attaining higher efficiencies of collection, which occurs at low-pressure drops of the air. This air pollution control technology is unique since the collection forces of the particles do not act on the whole stream of the air but on the particles only.
Attainment of higher efficiencies, lower costs of operation, wet collection of mists and fumes, and handling large volumes of gas at low-pressure drops is the key focus of this air control technology. As such, the project focuses on leveraging on this benefit in order to attain success in its operational procedure. Nevertheless, electrostatic precipitators have a limitation in that they demand large spaces, they cannot control the emission of gases, have higher capital costs, and they cannot work effectively on particulates that have a characteristic of high electrical sensitivity.
Fuel gas treatment (FGT) enables reduction of NOx emissions. This technique has a wide classification as either wet or dry techniques (Greunen 2006). Wet technique involves absorption, which occurs via caustic scrubbing solution while dry techniques encompass non-catalytic reduction, catalytic reduction, and adsorption.
Absorption process has the ability to eliminate NOx and SOx. This process is also regarded as the wet scrubbing process. The process has a limitation of having low NO solubility, as well as absorption of NOx. In most cases, NO needs oxidation to NO2 while in the flue gas prior to any further absorption of the same occurs in water.
In non-catalytic reduction, ammonia has the potential of reducing NOx to nitrogen without a need of a catalyst in the temperature range of 900-1000oC. As such, molar ratios of 1:1 to 2:1 for NH3: NOx have the potential of attaining approximately 40-60% reduction of NOx. Unfortunately, this process has limitations of incomplete mixing of flue gas with ammonia and difficulties in temperature control. Therefore, instances of low temperatures results in the emission of unreacted ammonia while instances of high temperatures results in the oxidization of ammonia to NO.
One of the widely adopted FGT technologies is the selective catalytic reduction (SCR) (Sloss 1992). The process of SCR involves the conversion of NOx to nitrogen while using ammonia as the reducing agent. A catalyst is necessary for this pr...