How to Choose the Correct Emission Control Technology
Increasingly stringent clean air standards and heightened concerns over greenhouse gas emissions are driving technology enhancements in manufacturing and throughout industry. The air pollution control landscape is changing for these manufacturers and those that adapt are seeing the environmental and economic benefits, but many questions still remain. Which industrial processes favor the various abatement devices? What are the operating cost advantages to each technology? How have technologies changed to accommodate the new greenhouse gas standards? A new white paper from Anguil Environmental Systems takes a look at these questions.
Today, most manufacturers in the US are required to be compliant with regulations like the National Emission Standard for Hazardous Air Pollutants (NESHAP) or Maximum Achievable Control Technology (MACT) guidelines for their specific industry. Similar regulations are being adapted and enforced worldwide. Many of the exhaust gas emissions from industry include Volatile Organic Compounds (VOCs) as well as Hazardous Air Pollutants (HAPs). When left untreated, these emissions degrade in the presence of sunlight and contribute to low-lying ozone, or smog. In addition to their harmful effects on plants and trees, VOCs and HAPs are known to cause respiratory ailments, heart conditions, birth defects, nervous system damage and cancer in humans. Often times, these hydrocarbon-based pollutants are best destroyed through the use of thermal and catalytic oxidizers.
Process emissions from batch or continuous operations can vary greatly in volume and composition. This has resulted in a variety of different abatement technologies being applied on the countless industrial applications. Depending on the process conditions, destruction requirements and energy demands at a given facility; flares, vapor combustors, thermal oxidizers and catalytic systems have been applied for emission destruction.
Historically manufacturers have employed industrial catalysts to promote or provide a chemical reaction that can generate products from various reactants. For that reason, the environmental personnel at these plants felt very comfortable widely applying another type of catalyst for environmental control, namely the use of catalysts to remove the VOCs and HAPs from their process exhaust gases.
Like industrial catalysts, these environmental catalysts are used to promote a chemical reaction but in the case of air emission control equipment, the environmental catalyst promotes the oxidation or combustion of the emissions at lower temperatures resulting in less energy consumption.
From a capital equipment cost perspective, catalytic oxidizers can be quite expensive. When you take into account the higher capital cost, maintenance concerns, potential for higher operating expenses and subsequent greenhouse gas emissions, it seems clear why industry is looking for an alternative to the conventional catalytic oxidizer.
Over the years, production driven companies have focused mainly on new process technologies to streamline production and increase profits. It was not until recently that newer, more efficient technologies were designed to meet the varying process emissions found in many manufacturing facilities. The Regenerative Thermal Oxidizer (RTO) is an abatement technology widely used on industrial air pollution control applications because of its ability to reuse up to 97% of the thermal energy from combustion to preheat incoming, untreated pollutants.
Early RTO designs were established for process exhaust gases containing very low emission concentrations but current designs have evolved to handle much higher concentrations. Likewise, new features enable the RTO to handle challenging conditions such as emission spikes by incorporating a Hot Gas Bypass (HGB).
Since most RTOs do not have catalyst incorporated into the design, there is a significant savings in maintenance and replacement parts. And the VOC/HAP performance efficiency stays consistently high over the operational life since there is no catalyst present that can degrade with time. There is some routine maintenance with RTOs but replacement parts are limited to thermocouples, actuators, flame sensors and fan belts. Although valves are constantly cycling to direct airflow in the RTO, they perform consistently for a million or more cycles. Most valves will operate for numerous years without operational issues.
RTOs have a distinct advantage over catalytic systems as the auxiliary fuel usage is lower during low process exhaust concentrations. When concentrations are above 3% LEL (lower explosive limit) the RTO is generally self-sufficient, meaning no supplemental fuel is required for combustion. This has a direct correlation on greenhouse gas emissions from the auxiliary fuel combustion process, mainly CO2 and NOX are also reduced compared to older emission control designs with the higher fuel usage. For example, the high thermal efficiency of the RTO can reduce the auxiliary fuel consumption by hundreds of dollars per hour for larger scale chemical plants.
Employing the proper abatement system for a given application can mean the difference between compliance and non-compliance, which in many cases translates to full production or a plant shut down. Even under compliance, the improper application of an oxidizer technology can dramatically impact operating expenses and drive down profits.
Download the Anguil Environmental Systems’ white paper to learn about many of the typical emission control applications found at industrial manufacturing operations. It is important to note that very few processes are identical and therefore no one technology choice can be applied on all applications. To maximize return on investment, plants should consult with a professional as each application is unique.
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