Final Report: Novel Membrane Process to Utilize Dilute Methane Streams

EPA Contract Number: EPD11071
Title: Novel Membrane Process to Utilize Dilute Methane Streams
Investigators: Lin, Haiqing
Small Business: Membrane Technology and Research Inc.
EPA Contact: Manager, SBIR Program
Phase: II
Project Period: May 1, 2011 through April 30, 2013
Project Amount: $225,000
RFA: Small Business Innovation Research (SBIR) - Phase II (2011) Recipients Lists
Research Category: SBIR - Greenhouse Gases , Small Business Innovation Research (SBIR)

Description:

Methane is the second largest contributor to global warming, after carbon dioxide. Due to increasing public awareness during the last 2 decades, various technologies and process improvements have been developed to curb methane emissions in the United States. However, there is still no economically viable technology to utilize dilute methane streams containing 1040 percent methane by volume. Such streams often are contaminated, mainly by carbon dioxide. These streams cannot be burned or flared due to their low Btu values. As a result, they are vented, contributing to the global warming effects of greenhouse gases.
 
Membrane Technology and Research, Inc. (MTR) estimates the current uneconomic, unrecovered methane emissions from these sources at 1.0 Tg (million metric tons) or 50 billion scf (standard cubic feet) per year, with an annual fuel value of $200300  million, assuming $4-6/1,000 scf natural gas. With almost 21 times the global warming effect of an equivalent weight of carbon dioxide (CO 2 ), methane emissions of 1.0 Tg per year are equivalent to emissions of 21 Tg CO 2 , equivalent to that from five 600 MWe coal-fired power plants. The utilization of this methane on or near the recovery site can help meet demands for heat and electricity, and will provide product credits to offset the costs associated with the more environmentally responsible management of dilute methane vent streams  proposed here.
 
The goal of this Phase I/II proposal was to develop a novel membrane selective contactor to recover methane from dilute methane/carbon dioxide vent gas streams. More specifically, the Phase II program focused on a pilot-scale field demonstration of the process converting waste dilute methane streams into useful fuel, to bring the proposed membrane technology to the commercial market.

Summary/Accomplishments (Outputs/Outcomes):

Two membranes with high CO2 permeance and sufficient CO2/CH4 selectivity were developed and/or evaluated for biogas/landfill gas purification.
  1. PolarisTM membranes, which selectively remove CO2, H2S and siloxanes from CH4.
  2. PegasusTM membranes, which selectively remove CO2, N2 and O2 from CH4.
 
Both PolarisTM and PegasusTM membranes were produced using the MTR commercial coater and fabricated into spiral-wound modules, which were evaluated in bench-scale and pilot-scale membrane units. Parametric tests on CO2 and N2 removal from the mixtures with CH4 were performed in these membranes and modules. The CO2 permeances of these two membranes are 10 times that of currently available commercial polymeric membranes, and when coupled with a novel selective membrane contactor, provide a low-cost way of increasing the effective methane concentration of the gas for use as fuel.
 
Several opportunities have been identified for use of these two membranes in biogas/landfill gas purification, such as siloxanes and H2S removal; they also can be used to upgrade other low, medium and high Btu gas streams. The technical and economic analyses have demonstrated the feasibility of using membrane systems based on PolarisTM or PegasusTM membranes to upgrade dilute methane streams (such as biogas/landfill gas) to fuel. Both PolarisTM and PegasusTM membranes are at early commercialization stages.

Conclusions:

MTR has been developing two membranes (PolarisTM and PegasusTM) that selectively permeate carbon dioxide and retain methane. In this project, commercial-scale membranes and modules were produced, which showed separation properties meeting the project target performance, with good stability over the time period tested. The project demonstrated the technical and economic feasibility of using these two membranes for various applications in landfill gas and biogas purification. Both PolarisTM and PegasusTM membranes are at early commercialization stages, and the MTR sales group has begun marketing the membrane products and processes for various applications involving dilute methane recovery.

Supplemental Keywords:

dilute methane streams, biogas, landfill gas, CO2 removal, membrane, separation


SBIR Phase I:

Novel Membrane Process to Utilize Dilute Methane Streams  | Final Report