Figure 1 depicts the overall process configuration of a notable IGCC power generation unit located in the United States, the TECO Polk Power Plant Unit 1. This unit is quite representative of IGCC plants in general; further information is provided on the dedicated page for the Tampa Electric IGCC project.
Figure 2 shows a simplified block flow diagram (BFD) illustrating the major process sub-systems included in a typical 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 ASU air compressor size and power consumption. Many IGCC plants including Polk Power Unit 1 have EP ASU integration with the GT as depicted in both Figures 1 and 2. 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.
A more detailed process description of each of the processing units within an IGCC complex is presented in the discussion on IGCC process system sections.
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 discussion Pre-Combustion CO2 Capture for Gasification Application.
NETL’s Support in Advancement of IGCC Technology
DOE’s R&D program has helped develop multiple technologies to improve and increase efficiency of conventional IGCC technology discussed above. Cumulatively, the technology advances targeted both more efficient production of electric power with significant reduction in the cost of electricity (COE). An IGCC cycle including carbon capture that incorporates these advanced technologies is depicted in Figure 3. The impact of each technology on both process performance and cost were evaluated, and by way of summary the following technological advances and their benefits are expected1:
Successful implementation and integration of all these advanced technologies allows for an estimated increase of 7.0 percentage points in efficiency, as shown in Figure 4. Coupled with increased availability and improved financing structure, a reduction of 28% in COE relative to the state-of-the-art carbon capture IGCC plant has also been estimated.