Typical Flow Scheme

A Typical IGCC Block Flow Diagram
One of the major uses of coal-derived syngas is to generate power in an integrated gasification combine cycle (IGCC) plant. While there are many coal gasification plants in the world co-producing electricity, chemicals and/or steam, the following are four notable, commercial-size IGCC plants currently in operation solely for producing electricity from coal and/or coke.

All of the plants began operation prior to 2000 and employ high temperature entrained-flow gasification technology. GE (formerly Texaco-Chevron) and ConocoPhillips (CoP) are slurry feed gasifiers, while Shell and Prenflo are dry feed gasifiers. None of these plants currently capture carbon dioxide (CO2). A simplified process flow diagram of the 250-MW Tampa Electric IGCC plant is shown in Figure 1 to illustrate the overall arrangement of an operating commercial scale IGCC plant. The Tampa Electric plant is equipped with both radiant and convective coolers for heat recovery as high pressure (HP) saturated steam. Figure 1 shows a simplified block flow diagram (BFD) illustrating the major process sub-systems included in an IGCC plant. The BFD shows an elevated-pressure (EP) Air Separation Unit (ASU) integrated to the gas turbine (GT) operation by extracting some of the GT air compressor discharge as feed to reduce the air separation unit (ASU) air compressor size and power consumption. The four operating IGCC plants cited, with the exception of the Wabash plant, all have EP ASU integration with the GT. The Buggenum and the Puertollano IGCC plants were designed with EP ASU/GT integration while the Tampa IGCC was modified in 2005 for EP ASU/GT integration. Oxygen-depleted nitrogen from the EP ASU is compressed back to the GT as diluents for nitrogen oxide (NOX) control, and to maintain mass flow through the GT.	CLICK ON GRAPHIC TO ENLARGE   Figure 1: Tampa Electric IGCC Process Flow
	CLICK ON GRAPHIC TO ENLARGE   Figure 2: IGCC Block Flow Diagram

Improved IGCC Efficiency

• Advanced “F” Frame Gas Turbine – The flow scheme of Figure 2 represents an improvement in efficiency over the current operating IGCC plants. This is achieved by replacing the current GE-7FA GT (used in Tampa Electric and Wabash) with an advance “F” frame GT designed for syngas firing. Compared to the 7FA GT, the advance “F” frame GT has greater throughput, higher pressure ratio, and higher firing temperature. These advances lead to more power output from the GT as well as higher heat recovery steam generation (HRSG) steam flow and temperature, which results in higher steam turbine power output. The net overall efficiency improvement for GE-based IGCC is estimated to be 2.5 percentage points for replacing the 7FA GT with the advance “F” frame GT.¹ Continued advance syngas turbine (AST) development by year 2015 is expected to further improve the net efficiency advantage for IGCC by up to 5.1 percentage points over the current 7FA GT design.
• Warm Gas Cleanup – Development in warm gas Transport Desulfurizer (WGTD) and Direct Sulfur Reduction process (DSRP) to replace the current low temperature AGR and Claus SRU/TGTU processes is expect to improve the current GE-based IGCC overall efficiency by 2 to 2.8 percentage points.¹ Part of this efficiency advantage comes from the addition of a convective cooler after the GE radiant cooler to cool the syngas down to about 427-510 °C (800-900 °F) for feed to the WGTD/DSRP. Since the CoP and Shell-based IGCC design already included a convective cooler to cool the syngas below 370 °C (700 °F), the efficiency advantage for CoP and Shell-based IGCC is expected to be less than those for the GE-based IGCC.
• Solid Coal Feed Pump – Successful development of the solid coal feed pump (e.g., Stamet Posimetric Pump) could convert the slurry-fed GE gasification into a dry-feed design, which would improve the current GE-based IGCC overall efficiency by about 1.9 percentage points.¹ Slurry feed CoP-based IGCC's is expected to have similar efficiency advantages as the GE-based IGCC. Dry feed Shell-based IGCC net efficiency is expected to be less affected by commercialization of the solid coal feed pump. The major impact to the Shell-based IGCC would be the possibility to operate at pressures higher than the current maximum set by feed lock-hopper mechanical limitations.
• ITM Oxygen Separation – Successful development of Ion Transport Membrane (ITM) oxygen generation to replace cryogenic ASU is estimated to improve the GE-based IGCC overall efficiency by about 0.5 percentage point.¹
• Coal Based Solid Oxide (SOFC) Power Plant –Integrating HP solid oxide fuel cell (SOFCs) into power plants have the potential to increase the IGCC overall efficiency to nearly 60%.¹

Effect of CO₂ Capture
The flow scheme of Figure 2 represents a typical process arrangement of a near-term commercial IGCC design without CO₂ capture. CO₂ capture and sequestration (CCS) significantly impacts the overall IGCC efficiency, and the effects are addressed in the section on Designs for CO₂ Capture.

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