Pollution control technologies
The spraying booths need to be equipped with necessary control technologies to control pollution in the spray booths. These control technologies must be able to handle exhaust gases and vapours, aerosol particles and noise levels of 90 dB at 1000 Hz.
Acidic gases such as sulphur dioxide, need to be prevented from reaching the atmosphere and causing pollution. Therefore appropriate pollution control facilities need to be installed in the spray booths. The most efficient way of controlling gas emissions is through installation of scrubbers. These are flue gas desulfurization technology for the case of sulphur dioxide. Scrubbers are installed in the exhaust facilities of spray booths and once the pollutant mixture from the paint is emitted into the spraying booth air space, this exhaust air is collected in a chimney containing scrubbers. It thus works by spraying a wet slurry of limestone into a chamber where the calcium content of limestone reacts with the acidic gas. This ensures that the hazardous gases don’t reach the atmosphere. This mixture reduces into a non-reactive compound that collects in the chamber. This means that the chambers need to be cleaned from time to time.
Aerosols exposure, can lead to breathing problems for people working in the facility and these particles may also cause accidental fires (Goyer, 1995). Dry filters may be used to control this. The shops need to be equipped with supply air fans that move the air containing the aerosols through a heat exchanger and through filters. To efficiently do this the booths need to be operated at 1750 F. This leads to the design of three types of spray booths. Cross draft Spray Booths in this type, air enters through filters in the front of the spray booths and is exhausted through filters at the back of the booth (Heitbrink, 1995). The second type is a downdraft booth, this one is designed to let in air through filters that are installed on the roof of the booth and leave a metal grate in the floor. The exiting air contains solvent fumes (aerosols) and paint over spray. Semi downdraft is another technology utilised in this case, air enters through the roof of the booth and is exhausted through filters at the back of the booth. This control method ensures efficient control of air pollutants and emissions in the form of aerosols.
Sound levels in the spray booths need also to be taken care of. These acoustic problems may be as a result of sound produced by discharge lines and ports such as nozzles and air jets. Technologically these sound problems may be controlled using quiet design nozzles or pneumatics that are installed at air nozzles so that they can control sound levels to below 2dB which the human hear may tolerate and thus avoid damage its damage.
REFERENCES
– Texas Administrative Code on Environmental Quality, Texas Commission on Environmental Quality.(TCEQ)
– The Michigan Department of Environmental Quality (MDEQ) report on VOC and ES emissions
– TCEQ Regulatory Guidance – surface coating facilities – February 2011.
– Guidance on Emission to Atmosphere Guidance note of 2004.
