Emission Control Systems
Emission control systems are devices that monitor and diminish harmful byproducts of combustion and other processes that would otherwise be released into the atmosphere. Industrial processes regularly emit unburned hydrocarbons, carbon monoxide, and oxides of nitrogen and sulfur, among other harmful pollutants. Emission control systems can convert these contaminants into water vapor and carbon dioxide, which may be safely released into the environment or recirculated.
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Applications of Emission Control Systems
Ever since the EPS and other government agencies have reported on the adverse effects of hazardous air pollutants (HAPs) on human health, the U.S. population has embraced stricter regulations and committed to broad-scale pollutant control. Toxic pollutants released by the stationary sources can cause birth defects and cancer as well as alter the environmental adversely. To combat these effects, various types of air-pollution control measures have been adopted across a number of industries. These changes have resulted from the efforts of government agencies as well as citizens who seek out technologies to control air pollutants. Regulatory agencies, such as the EPA have placed strict limitations on acceptable emission levels or amount of pollutants that can be released into the environment. In order to comply, a wide range of industries are now using emission control systems. Automotive, pharmaceutical, medical, microelectronic, bio-safe labs, and aerospace industries are just a few who employ these systems to decrease harmful byproducts.
Types of Equipment Used in Emission Control Systems
While the EPA sets a strict standard, state law dictating acceptable emissions varies. Many facilities employ continuous emissions monitoring systems to aid in the control and monitoring of harmful discharges for easy reporting to federal and state supervisory committees. VOC abatement systems are popular control systems, as are air filtration systems. Industrial emission control often entails the installation of large equipment, though it is not necessarily complex. Wet scrubbers and air scrubbers involve the installation of pools or streams, which attract and remove particulates from the air as do many other air filtration systems. Both catalytic and thermal oxidizers are used to break down pollutants and purify the air by heating the materials to extreme temperatures. Those systems using incendiary temperatures often use heat recovery systems to help offset the cost of operations.
Contaminants caught by mist collectors and other such devices may also be recycled for reuse. In this way, the air pollution control industry benefits not only the environment and safety of workers, but often the company as well. The type and level of emission control system required in each setting depends largely on the quantity and specific composition of an air stream. Systems may be as small as an automotive catalytic converter or a massive scrubber atop a smoke stack. Early emissions control systems were simply add-on components that solved a particular emission need. While add-ons are still used today, products and factories often have built in emission control systems that have become a significant part of the combustion and manufacturing process.
The main functionality of pollution control equipment is to protect outdoor air quality, which involves controlling particulate matter, sulfur dioxide, carbon monoxide, oxides of nitrogen, along with volatile organic compounds of carbon and hydrogen. Emission control equipment categories include scrubbers, electrostatic precipitators, specialized air filters, dust collectors, recycling equipment, and oxidizers. However, each equipment type is designed for controlling specific contaminants—there is not a single solution that can control all contaminants.
For controlling particulate matter and volatile organic compounds, basically, two types of techniques are used: absorption and oxidation.
Absorption
Scrubbers are a group of air control devices that are administered when particulate matter and organic compounds need to be removed from an industrial exhaust airstream. The most common type of scrubber is the wet scrubber, which uses liquids—mainly water, though for different application specialized solvents are used—to scrub contaminants from an exhaust stream with the help of a nozzle in a chamber. The most modern scrubber designs—dry scrubbers—use dry slurry to wash off the acid gases from an exhaust stream.
These factors determine the removal efficiency of a scrubber:
Residence time of the gas stream in the scrubber.
Area of contact between the contaminant and solvent.
Oxidation
The oxidation process, in essence, is the combustion of volatile organic compounds and related hazardous compounds into water and carbon dioxide. The simplest is the thermal oxidizer, in which incompletely burned hydrocarbons and organic compounds are incinerated with the help of an afterburner. Direct-flame oxidizers work similarly; however, they do not need auxiliary fuel for oxidation, as the air stream has enough of a concentration of volatile compounds that work as a fuel, making it a self-sustaining system. More sophisticated oxidizer systems are available that not only oxidize the compounds but also reclaim heat for other purposes. Some oxidizers may need catalysts to increase the rate of reaction. This type of oxidizer is called a catalytic oxidizer.
These factors determine the removal efficiency of an oxidizer:
Residence time of the gas stream.
Turbulence.
Temperature.
Airflow rates of the stream.
To know if an oxidizer is working appropriately, these four factors are monitored by equipment. Other than absorption and oxidation, a phenomenon called adsorption is also used for controlling emissions. It is commonly used in activated carbon systems.
How to Choose an Efficient Emission Control System
In today's industrial landscape where compliance standards are getting stringent, installing an efficient and effective system for air pollution control is necessary for a wide range of industries. However, given the overwhelming options of hardware for air pollution control, selecting an efficient system can be a daunting task.
Installing custom hardware for air pollution controlling depends on many factors, including:
- The quantity of air pollutants.
- The volume of the pollutants being exhausted.
- Technology and design of an equipment.
- Type of volatile organic compounds (VOCs) and hazardous air pollutants (HAPs).
- Destruction requirements and energy demands.
This is the primary information that you need while deciding which system will be suitable from a multitude of options available, such as thermal oxidizers and catalytic systems, including regenerative thermal oxidizer and conventional catalytic oxidizer, flares, and vapor combustors.
The secondary factors that you have to consider for an efficient system are:
- The type of production process emitting the air pollutant to be controlled.
- The geographical location and its effect on the system.
- The number of hours a system will be operated.
- The number of emission points to be controlled by the air pollution control system.
- Temperatures and exhaust rates for individual emission points.
These factors will give you a clear picture of your needs and will prove to be important factors for making a decision.
Factors to Consider When Purchasing Emission Control Systems
With modern equipment incorporating air filtration systems and vacuum cleaners, installation of a new system is worth the investment. However, retrofitting can also be considered a good option, such as installing a secondary recovery unit and other modern equipment. Relatively, all air pollution control technologies are expensive; you need to contemplate thoroughly before making the decision, plan well, and invest time to get the best results.
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