Treatment Technologies for Volatile Organic Compounds
What are volatile organic compounds?
Volatile Organic Compounds (VOCs) are a family of organic compounds with a high vapor pressure at room temperature. The family consists of natural and anthropogenic (human-made) chemicals. Different VOCs are emitted as gases from solid and liquid sources found mainly indoors. Accordingly, indoor VOC concentrations tend to be consistently higher than those measured outside. At the industrial level, VOC emissions are a risk factor that is mostly untreated. Emissions are common mainly in printing presses, laboratories, and medical, chemical and petrochemical industries.
VOCs are many and varied, not all compounds are toxic to humans and those that are, not all are acutely toxic. However, many VOCs are known to cause carcinogens in animals, and some are suspected or known to cause cancer in humans as well. One example is benzene, a substance known as a human carcinogen, found to be a by-product of tobacco smoke, stored fuel, and vehicle exhaust gas. Benzene is also widely used in the production of plastics, resins and synthetic fibers. Symptoms of short-term exposure to toxic VOCs include eyes irritation, nose and throat irritation, headaches, nausea and vomiting, dizziness, and worsening of asthma symptoms. Prolonged (chronic) exposure can cause liver and kidney damage, cancer, and damage to the nervous system. Most VOC gases are invisible to the eye, even at toxic concentrations.
There are several methods for treating VOCs at the industrial level.
Regenerative Thermal Oxidizers (RTO) are widely used as a means of preventing air pollution. These devices are versatile and highly efficient. The systems oxidize the VOCs at high temperatures. RTO is particularly useful for continuous processes where the air flow rates are high, and the input levels are relatively low. The significant disadvantage of these systems is the high energy required to reach a very high temperature (1000 ° C) to oxidize the compounds to the required level. Many plants around the world spend a lot of money every year on the energy needed to reach the high temperature at RTO facilities.
Catalytic Oxidizers utilize metal catalysts such as palladium, which reacts with VOCs to reduce the activation energy needed to oxidize organic compounds. The direct significance of using catalysts is to significantly reduce the power required to oxidize the organic matter. Therefore the required oxidation temperature is reduced substantially relative to the RTO solution. The oxidation temperature required for catalytic oxidizers depends on the pollutant type, but it can be assumed that most of the substances are oxidized in the temperature range of 300-500 ° C. Click here for further reading on catalytic oxidizers.
Scrubbers can be used to treat VOC under appropriate conditions and for certain compounds only when the VOC compounds are soluble in water, and the Henry constant of the process is of the proper value. Click for further reading on Scrubbers.
VOC adsorption in activated carbon facilities is a well-known technology. The technology can be used efficiently and economically in processes where emission concentrations are not high or non-sequential processes. This is because, for high emission concentrations, the technology will not be financially viable due to high carbon replacement costs. While designing the facility, there is the risk of creating heat pockets that can not be detected due to the high insulation capacity of the coal particles. In any design of an industrial activated carbon system, consult with professionals who are aware of the dangers of using this technology. Click for further reading on activated carbon filters.
Biological reactors (bioreactors) can be used to treat certain types of volatile organic compounds, but the process must be constant and continuous because biological agents use a platform of microorganisms whose growth takes up to many months and any process changes, emissions composition, temperature, humidity, is critical for bacteria growth and can cause microorganisms to fail. We do not recommend using this type of reactor in the industry because the current legal requirements do not allow waiting many months until a destroyed micro-organism has regenerated. Another problem is the demand for the broad area of such facilities.