Pre-Combustion CO2 Control

Pre-combustion capture is applicable to IGCC power plants and refers to removal of the CO2 from the syngas prior to its combustion for power production. A simplified process schematic for pre-combustion CO2 capture is shown below.

Process Schematic of Pre-Combustion Capture
Process Schematic of Pre-combustion Capture (click to enlarge)

Unlike a combustor, a gasifier carefully controls the amount of air or oxygen available inside it so only a small portion of the fuel burns completely. This "partial oxidation" process provides heat to drive gasification reactions. Rather than burning, most of the coal is chemically broken apart by the heat and pressure in the gasifier, setting into motion chemical reactions that produce syngas. Syngas is primarily H2 and carbon monoxie (CO) but can include other gaseous constituents whose compositions vary depending on coal characteristics and the conditions in the gasifier. After the syngas is produced, it is further processed in a WGS reactor to prepare it for pre-combustion capture. A WGS reactor is typically a fixed-bed reactor containing shift catalysts to convert CO and water into additional H2 and CO2. Following WGS, sulfur compounds and CO2 are separated from the H2 in an AGR system. Acid gases in a gasification process typically consist of hydrogen sulfide (H2S), carbonyl sulfide (COS), and CO2. Sulfur compounds and CO2 can be removed either simultaneously or selectively, depending on the shifted syngas composition and conditions, as well as the end fuel gas specifications. After CO2 removal, the H2 is used as a fuel in a combustion turbine combined cycle to generate electricity. Another application, currently being developed under DOE's Fuel Cell Program, utilizes the H2 to power solid oxide fuel cells (SOFCs) to significantly increase the overall plant efficiency.

The current state-of-the-art pre-combustion CO2 capture technologies that could be applied to IGCC systems (the glycol-based Selexol™ process and the methanol-based Rectisol® process) employ physical solvents that preferentially absorb CO2 from the syngas mixture. Several Selexol and Rectisol systems are in use at commercial scale, though not at IGCC power plants. For example, the Rectisol system is used for CO2 capture at the Dakota Gasification Company's substitute natural gas (SNG) plant in North Dakota, which is designed to remove approximately 1.5 million tons of CO2 per year from the syngas. The CO2 is purified, transported via a 320-kilometer pipeline, and injected into the Weyburn oilfield in Saskatchewan, Canada. 

NETL's pre-combustion CO2 control technology R&D includes external research projects directed at the use of physical solvents, solid sorbents, and membranes. Each of the sections below lists on-going and completed projects and provides a link for more information on each project.

Solvents

Physical Solvents
Active and completed projects researching physical solvents for pre-combustion CO2 control.

Active Physical Solvent Projects
Carbon Dioxide Capture from Integrated Gasification Combined Cycle Gas Streams Using the Ammonium Carbonate-Ammonium Bicarbonate Process SRI International
DE-FE0000896
Pilot scale
Solvents for CO2 Capture
University of Pittsburgh
R&D 048
Laboratory/ bench scale
Completed Physical Solvent Projects 
Pressure Swing Absorption Device and Process for Separating CO2from Shifted Syngas and its Capture for Subsequent Storage
New Jersey Institute of Technology
DE-FE0001323
Laboratory/ bench scale

Sorbents

Solid Sorbents
Active and completed projects researching solid sorbents for pre-combustion CO2 control.

 Active Solid Sorbent Projects
Pilot Testing of a Highly Effective Pre-Combustion Sorbent-Based Carbon Capture System  TDA Research
DE-FE0013105
Pilot scale
Completed Solid Sorbent Projects
Evaluation of Dry Sorbent Technology for Pre-Combustion CO2 Capture URS Group
DE-FE0000465
Laboratory/ bench scale
A Low-Cost, High-Capacity Regenerable Sorbent for Pre-combustion CO2 Capture
TDA Research 
DE-FE0000469
Laboratory/ bench scale

Membranes

Membranes Active and completed projects researching membranes for pre-combustion CO2 control.

Active Membrane Projects
Robust and Energy Efficient Dual-Stage Membrane-Based Process for Enhanced Carbon Dioxide Recovery  Media and Process Technology Inc.
DE-FE0013064
Laboratory/ bench scale
Development of a Precombustion Carbon Dioxide Capture Process Using High Temperature Polybenzimidazole Hollow-Fiber Membrane  SRI International
DE-FE0012965
Laboratory/ bench scale
Polymer-Based Carbon Dioxide Capture Membrane Systems  Los Alamos National Laboratory
FWP-308-13
Laboratory/ bench scale
 Efficient Regeneration of Physical and Chemical Solvents for CO2Capture
 University of North Dakota
DE-FE0002196
 Laboratory/ bench scale
Designing and Validating Ternay Pd Alloys for Optimum Sulfur/Carbon Resistance
Pall Corporation 
DE-FE0001181 
Laboratory/ bench scale
Novel Polymer Membrane Process for Pre-combustion CO2 Capture from Coal-Fired Syngas  Membrane Technology Research 
DE-FE0001124 
Laboratory/ bench scale
Hydrogen Selective Exfoliated Zeolite Membranes
University of Minnesota
DE-FE0001322
Laboratory/ bench scale
Pre-combustion Carbon Dioxide Capture by a New Dual-Phase Ceramic Carbonate Membrane Reactor Arizona State University
DE-FE0000470
Laboratory/ bench scale
Novel Membranes for CO2 Removal University of Pittsburgh / University of Notre Dame
R&D 047
Laboratory/ bench scale
Completed Membrane Projects
Fabrication and Scale-Up of Polybenzimidazole-Based Membrane System for Pre-combustion Capture of Carbon Dioxide
SRI International
FC26-07NT43090
Prototype
Pre-combustion Carbon Capture by a Nanoporous, Superhydrophobic Membrane Contactor Process
Gas Technology Institute
DE-FE0000646
Laboratory/ bench scale

 

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