To comply with EPA requirements, an oil producer uses a condenser coil in its system that controls benzene, toluene, ethylbenzene and xylene emissions.

The coil is used to first condense and then to sensibly cool the steam/hydrocarbon moisture from 212oF (100oC) to 110oF (43oC).

The process of natural gas dehydration yields a mixture of steam and off-gases including benzene, toluene, ethylbenzene and xylene (BTEX). Virtually every state has a department of environmental quality that protects the environment by requiring that onshore oil and gas producers have a system for controlling BTEX emissions.

In order to comply with state regulations, a customer of Super Radiator Coils, Chaska, Minn., designed a system for controlling BTEX emissions at its natural-gas-producing site, which required a custom-engineered condenser. A fintube air-cooled condenser is a natural fit for a remote onshore condensing application where water is not economically available, which was the case with the oil producer.

The production off-gas, having just enough pressure to move through the coil, reaches the condenser at approximately 212oF (100oC). A Super Radiator engineer designed the coil to first condense and then to sensibly cool the steam/hydrocarbon moisture from 212oF to 110oF (43oC). Ambient air was used on the condenser’s fin-side as the principal cooling agent. Because no electricity was available in the producer’s remote area, a fan could not be used to force the air over the coil. Therefore, the coil was designed to utilize the natural convection of the air as it heats up, moving through the coil. The design uses 100oF (38oC) as the worst-case estimate for the ambient air temperature during the summer months.

The resulting coil for the application has a capacity of more than 40,000 BTU/hr and a face area of 42 x 80". The stainless steel tube circuiting was specially designed to facilitate the flow of the very low-pressure vapor and has aluminum fins spaced far enough apart (four fins per inch) so it does not inhibit the natural airflow.



On the condenser's fin side, ambient air is used as the principal cooling agent. The coil was designed to utilize the natural convection of the air as it heats up while moving through the coil.

Results

Since the system was installed, the condenser coil has reliably kept the average exhaust stream temperature below 110oF (43oC). The gases that are not condensed are exhausted to the atmosphere or incinerated. The Super Radiator condenser has successfully controlled hydrocarbons previously emitted to the atmosphere, which has helped preserve air quality and protect the end user from fines for violating department of quality environmental regulations.

 

Environmental Protection Agency regulations such as the National Emissions Standards for Hazardous Air Pollutants often are strictly enforced and even tightened, requiring oil- and gas-production sites to routinely submit efficiency data from condensers. As oil and gas producers work to stay ahead of changing and rising operating costs, custom-engineered, air-cooled condensers such as this one likely will be in higher demand.



For more information from Super Radiator Coils, Minneapolis, a manufacturer of coils and heat exchangers for the process industries, call (800) 394-2645 or visit www.srcoils.com.

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