Provide process troubleshooting and evaluation of a natural gas blanketing system for a fracking wastewater treatment system.
FRACKING WASTEWATER SYSTEM GAS BLANKETING TROUBLESHOOTING AND EVALUATION
The client operates a fracking wastewater treatment plant (WWTP) in the US. The facility is currently in commissioning/start-up and is slated to treat wastewater produced in local fracking operations of Marcellus and Utica Shale. The WWTP is basically designed to treat fracking wastewater for salts and naturally occurring radioactive metals. The treatment facility is generally comprised of several treatment tanks, such as equalization tanks, clarifiers, and reaction vessels, designed and arranged to produce high-quality treated water suitable for surface discharge. Tank vapor heads consist of a blanket of pipeline natural gas. A Vapor Recovery Unit (VRU) is included in the design to recover blanket gas from out-breathing tanks and limit natural gas usage. Un-recovered gas is incinerated in either a Thermal Oxidizer (TO) or an elevated flare.
Recently, the facility has experienced problematic operational issues including excessive vapor-space pressure swings, frequent and excessive bursts of blanket gas flaring, and an inability to recover vapor with the VRU. Process Engineering Associates, LLC (PROCESS) was contacted by the client to evaluate facility process design and plant operations, identify and discuss potential causes of poor plant equipment and process operations, and recommend actions to mitigate plant performance.
PROCESS visited the plant site to observe wastewater treating operations, gather process data and drawings, and interview production managers and operators. PROCESS also performed a site walk-down, observed wastewater deliveries and unloading operations, and reviewed current and historical operating conditions with site representatives.
PROCESS found that the facility was designed for regular truck deliveries. Irregular truck deliveries (caused by a combination of issues) resulted in some process tanks becoming near empty. When truck delivery was reinitiated, it created pressure imbalances that could not be accommodated by undersized gas blanketing valves. Pressure imbalances resulted in large amounts of blanket gas surging through the system, ultimately flowing into the VRU, TO, and flare systems. These unit operations are overwhelmed, resulting in a large amount of blanket gas flaring.
PROCESS developed a list of recommendations to curtail pressure swings and mitigate problems associated with irregular tuck deliveries. These recommendations focused on adding valves not in the original design, as well as resizing valves, controls, and instrumentation around the TO and VRU. At the time of this writing, the client is considering a plan of action to correct plant operations.
- Natural Gas Fracking Operations
- Process troubleshooting and evaluation