IGCC (Integrated Gasification Combined-Cycle) with Carbon Capture and Storage (CCS) technology allows coal to be used to generate power as cleanly as natural gas. TEC will be among the first coal-fed facilities anywhere to meet this standard.
IGCC technology has three basic components. In the gasification phase (fig. 1), heat, pressure, pure oxygen and water are used to break coal down into its component parts and convert it into a clean synthetic gas (syngas).
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The syngas is cleaned before it can be converted into substitute natural gas (SNG) which eventually fuels the power turbines. Remaining particulates are removed from the syngas in the particulate scrubber (fig. 2). Carbon monoxide is converted to carbon dioxide (CO2) by adding steam in shift vessel (fig. 3). The gasification process makes it possible to capture most of the mercury (silver), sulfur (yellow) and carbon dioxide (CO2) in the syngas (fig. 4). The captured CO2 will be transported via pipeline for use in enhanced oil recovery or storage in a saline geologic reservoir (fig. 5).
The IGCC plant then converts the syngas into substitute natural gas (SNG or methane), through a process called methanation (fig. 6). The SNG, which is relatively high in energy content, powers two gas turbines. Excess heat contained in the exhaust from those turbines then heats water to power a steam turbine (fig. 7). This high-efficiency approach is known as combined-cycle. The higher energy content of the SNG (as compared with syngas) improves the efficiency of the power production.
Because the SNG is a clean fuel, nitrogen oxide (NOx) also can be reduced considerably during and after combustion. The results are substantially lower emissions compared to conventional pulverized coal plants.