John Zink^® Flare Gas Recovery Unit

John Zink Company sets the standard in combustion technology and the design of flare systems. Our recovery process is incorporated with your flare system to safeguard company personnel and the environment. The following process diagram demonstrates the integration and function of a John Zink flare gas recovery system with an operating flare process.

A flare system consists of a vapor header that collects the flare gases from various sources, a knockout vessel, a liquid seal vessel, and the flare itself. The flare gas recovery unit connection is typically located between the knockout vessel and the liquid seal. Any liquids in the flare gas should be removed before introduction into the flare gas recovery unit. The primary control variable of the John Zink flare gas recovery unit is flare system pressure.

As the flare header pressure reaches the predetermined pressure control set point, a liquid ring compressor starts up and begins to compress the flare gas. The compressor uses an operating liquid, usually water, to perform the work of compression on the recovered gas. The operating liquid is cooled in a shell-and-tube heat exchanger, evaporative cooler or air-cooled heat exchanger to control compressor discharge temperature.

The compressor discharges the gas into a three-phase separator that separates the operating liquid from the flare gas and then the condensed hydrocarbons from the operating liquid. Instead of venting process vent streams into the flare system, the compressed gases are made available to the operating plant's fuel gas supply or possibly as a process feedstock.

Integration and control of a flare gas recovery unit is of critical importance. For example, care must be exercised in the design of the recovery system to prevent application of a vacuum to the vapor header that might draw in air and create a flammable mixture in either the flare header or the fuel gas system.

When all compressors are operating at full capacity and if the process vent flow rate continues to increase, flare gas will begin to pass through the liquid seal and flow to the flare stack. Therefore, the safety function of the flare system is maintained in the event of process upset conditions.

Contact a John Zink engineer to discuss the Flare Gas Recovery options for your application.

Contact the Flare Gas Recovery group at jzfgr@kochind.com.

John Zink Company, LLC
11920 East Apache
Tulsa, OK 74116
United States of America
+1-918-234-1800
800-421-9242 (U.S. and Canada)
email: info@johnzink.com