Energy Efficient GO-PEEK Hybrid Membrane Process for Post-combustion Carbon Dioxide Capture Under Technical Topic: Carbon Capture and Utilization

摘要

The Department of Energy (DOE), through its Carbon Capture Program, is investigating transformational, low-cost CO_2 separation and capture technologies that can be installed in new or retrofitted into existing pulverized coal power plants to separate and capture > 90% of the CO_2 with 95% CO_2 purity at a cost of electricity (COE) 30% less than the baseline CO_2 capture approaches.~1 The COEs for DOE Case 11 (no CO_2 capture) and Case 12 (benchmark technology amine absorption) are about 68.29 mills/kWh and 123.61 mills/kWh respectively, all in 2012$.~1 To meet DOE's cost target, the COE should be less than 86.53 mills/kWh.Supported by DOE, GTI and Air Liquide have been developing a singular polyether ether ketone (PEEK) hollow fiber membrane contactor (HFMC) process for CO_2 capture, in which C02-containing flue gas passes through one side of the PEEK HFMC, while a CO_2 selective solvent flows on the other side. CO_2 permeates through the hollow fiber membrane pores and is chemically absorbed into the solvent. The CO_2 rich solvent is regenerated and sent back to the membrane absorber. This technology is currently at pilot-scale development stage (DE-FE-0012829).Also supported by DOE, we are developing an energy efficient graphite oxide (GO)-PEEK hybrid membrane process for post-combustion CO_2 capture. The GO-PEEK hybrid membrane process builds on the PEEK HFMC process for post-combustion CO_2 capture. This new process uses a conventional gas separation membrane unit (Unit 1) to capture the bulk of the CO_2 from coal-fired flue gas followed by a PEEK HFMC unit (Unit 2) to further capture CO_2 to achieve DOE's target of 90% CO_2 capture rate with 95% CO_2 purity. The Unit 1, conventional gas membrane process, has been proven to be very efficient at partial CO_2 capture (40-60%). In the current study, the Unit 1 is based on advanced ultrathin graphene oxide (GO) membranes that we recently published in Science. The integration of the advanced GO conventional gas separation process with the PEEK HFMC process takes advantages of the "Pros" of these two processes while overcoming their "Cons", which offers a new opportunity to explore further reductions in the cost of CO_2 capture.The GO membranes developed recently showed CO_2 permeance as high as approximately 1,020 GPU with CO_2/N_2 selectivity of 680. The CO_2 permeance and selectivity performances are superior to GO-based membranes reported in the literature. The CO_2/N_2 selectivity obtained to-date is 1 -2 orders of magnitude higher than other CO_2/N_2 separation membranes including those developed under DOE NETL's programs. At the same time, we have fabricated new PEEK fibers (the third generation PEEK fibers) through optimization of the hydrophobic coating layer. Two-inch-diameter modules consisting of these new PEEK hollow fibers showed an intrinsic CO_2 permeance as high as 3,300 GPU at 60 ℃.