Regenerative Thermal Oxidizer for Flare Gas Treatment
Flare Gas as a Key Source of VOCs in the Chemical Industry
In the chemical industry, flares are a key source of VOC emissions. They primarily handle combustible organic compounds contained in process exhaust gas, excess fuel gas, and purge gas generated during both normal and abnormal production. These emissions often originate from internal leaks of equipment such as safety valves, bypass valves, and automatic control valves, or from overpressure discharge during the production process, purge gas release during unit startup and shutdown, and emergency venting during accidents. When these combustible organic compounds are not completely combusted, varying levels of VOC emissions occur.
“First-of-its-Kind” Demonstration Project for Flare Gas Environmental Protection and Energy Conservation
1. Challenges in Flare Gas Treatment
The combustible organic compounds contained in process exhaust, excess fuel gas, and purge gas are generated during normal chemical production. These emissions often come from internal leaks of safety valves, bypass valves, automatic control valves, or overpressure discharge during production. Flare gas composition, flow rate, pressure, and temperature all fluctuate cyclically within 24 hours. Some production units intermittently release part of the tail gas into the flare network over a period of two days or longer, according to process requirements, causing unstable flare gas emissions.
2. Innovative Flare Gas Treatment Process
Based on the characteristics of flare gas emissions, Yurcent has creatively adopted a Gas Holder + Thermal Oxidiser (TO) + Waste Heat Boiler + Desulfurization Tower process route for comprehensive flare gas treatment:
1) Using historical data of maximum, minimum, and stable flare gas flow, the gas holder volume, stable release amount, and height control logic of the gas holder are determined to buffer and balance the flare gas flow, providing a stable input flow to the TO.
2) Based on variations in the calorific value and oxygen content of the flare gas, the input of fuel gas and combustion air is controlled in a coordinated manner to ensure smooth operation of the boiler and SCR system.
3. Results of Flare Gas Treatment
The Flare Gas Environmental Protection and Energy Conservation Project undertaken by Xi’an Yurcent Environmental Technology Co., Ltd. has been officially put into operation.
The project includes:
A newly constructed 5,000 m³ wet-type gas holder to collect low-pressure flare gas;
A newly constructed direct-fired TO with a flare gas treatment capacity of 2,000 Nm³/h, equipped with a waste heat boiler producing 15 t/h of saturated steam at 2.5 MPa(g);
Supporting systems, including a tail gas desulfurization tower and chimney.
The unit operates at a load range of 30%–120% with an annual operating time of 8,000 hours.
