On April 15, several MPC employees were on hand at the GPA Midstream Convention in San Antonio, Texas, to accept an Award for Environmental Excellence from the GPA Midstream Association on behalf of MPLX. The award recognizes MPLX Gathering & Processing (G&P) for demonstrating initiative and leadership in managing environmental affairs in midstream sector activities and developing successful, innovative environmental solutions.
SO WHAT EXACTLY DID MPLX DO?
“MPLX G&P Pipeline developed an innovative emissions-reducing approach to pipeline pigging,” explains Rob McHale, MPLX G&P Environmental director. “As of April 2018, G&P was required to implement flare control measures to meet environmental limits. MPLX worked with TPE Midstream to develop the Zero Emission Vacuum & Compressor (ZEVAC) Pigging Emissions Reduction System to be used for G&P pipeline pigging, which controls methane and VOC emissions by keeping them in the gathering system, rather than combusting waste gas in a flare.”
Pigging is a process of sending a specially designed cylinder (called a “pig” for its distinctive squealing sound) through a line to remove disturbances that restrict flow like excess liquids or scale build up. In the G&P gathering systems,where natural gas is collected on its way to MPLX gas plants, these lines of untreated natural gas can require frequent pigging to remove the excess condensate and water that drops out in the pipeline.
Due to the topography and composition of the raw gas stream in the Marcellus and Utica regions, pigging operations must be performed at multiple locations daily, totaling thousands of pigging events a year across the Northeast operating system. “MPLX realized that based on frequency and losses associated with these activities, a large portion of this gas could be recovered,” notes Tony Dami, Marathon Pipe Line area manager for the North East Business Unit.
The ZEVAC system thus not only reduces emissions, but also recovers valuable product that would otherwise be lost due to flaring. Dami says that MPLX has deployed this as a portable system for all pigging operations in Ohio, where significant reductions have already been achieved.
The innovative system goes beyond the legal requirements of emission reduction and can be promoted industry-wide.
G&P first worked with EPA to develop multiple ways to reduce emissions from pigging. They began with design, including shorter barrels (which equate to less emissions during isolation and depressurization), and an MPLX-patented ramp added to pig receivers (utilizing the power of gravity to push liquids back into catchers). The pipeline team continued to innovate by using the ZEVAC system in their pigging operations.
“The system can take gases in the launcher/receiver chamber at gathering line pressures and reduce the pressure of the barrel down to near-atmospheric pressure, so the gas can be directed back into the pipeline,” explains Dami.
“We are now sharing our success with this system at industry group meetings,” notes McHale. “These systems that the pigging groups are implementing are not only helping us meet environmental requirements, but they may eventually push the natural gas gathering industry to these best-in-class designs.”