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The Challenge
The largest U.S.-based independent oil and gas producer and one of the largest independent processors of natural gas and natural gas liquids in North America was in search of new technologies to maintain the pollution control efficiency at their natural gas treatment facility.
In typical gas plants, the wellhead natural gas needs to be treated to remove water, CO2, any sulfur compounds and heavy hydrocarbons before it is sent to the pipeline. The acid gases formed by CO2 and H2S are normally removed by amine adsorption. The amine must then be stripped of these acid gases in order to be reused. The amine stripper off gas (tail gas) needs to be treated before discharge to atmosphere to remove residual hydrocarbons and meet EPA regulations.
The Solution
Gas and oil plants have historically used direct-fired thermal oxidizers with no heat recovery for tail gas treatment. The existing thermal oxidizer at this facility was using a considerable amount of auxiliary fuel to maintain temperatures of 1,500°F, ensuring all the organics were combusted but costing them a significant amount of money in operating costs. Dedicated to finding a less expensive means of regulatory compliance, the oil and gas producer challenged several air pollution control manufacturers to provide a system that was not only effective, but also energy efficient.
When Anguil was approached to address the air pollution control needs at this facility, careful measures were taken to assure the proper equipment selection.
The Result
After much consideration, Anguil offered their Model 75 (7,500 SCFM, 12,037.5 Nm3/hr) Regenerative Thermal Oxidizer (RTO) with heat recovery for efficient and effective operation. Anguil was selected because of their unique approach toward air pollution control and energy conservation.
With the Anguil two-bed RTO, the contaminated process gas is pre-heated as it passes through beds of ceramic media located in the energy recovery chambers. The process gas moves from the pre-heat chamber toward the combustion chamber, where the Volatile Organic Compounds (VOCs) are oxidized, releasing energy into the second energy recovery chamber before going to atmosphere. A diverter valve switches the process gas direction so both energy recovery beds are fully utilized, thereby reducing any auxiliary fuel requirement. This system is designed for heat recovery of 85% and is self-sustaining, requiring little auxiliary fuel use. This energy-efficient design offers significantly lower operating costs in comparison to other emission treatment methods.
The RTO is designed to prevent corrosion by the acid gases and to handle the high organic loading with low oxygen levels. The gas at this facility is “sweet” and does not contain any H2S but precautions were taken to prevent carbonic acid attack due to the CO2. In addition, Anguil provided a Class 1, Division 2, Group D control package. Heated, fresh air was also introduced into the system, providing supplemental oxygen without condensing moisture in the process stream. Anguil’s application specific engineering was an important factor in the success of this project.
The Anguil RTO is achieving 99% DRE (Destruction Rate Efficiency) and is saving the customer more than $500,000 per year in natural gas costs. Anguil’s equipment, detailed system design, installation and startup has exceeded the customer’s expectations of efficiency and affordability.