Figure 1 is a simplified block flow diagram for co-producing hydrogen (H2) in a current technology integrated gasification combined cycle (IGCC) power plant without carbon sequestration. Syngas from the slagging gasifier is cooled by generating high pressure (HP) steam in the high temperature gas cooling (HTGC) system before it is water quenched and scrubbed to remove fine particulates. The scrubbed syngas then goes through a sour shift process to further generate H2 by reacting carbon monoxide (CO) with steam. Depending on the desired amount of H2 to be produced, supplemental steam injection into the sour shift feed may be necessary. The syngas from sour shift is then cooled in low temperature gas cooling (LTGC) before mercury removal, and followed by hydrogen sulfide (H2S) removal in a single-stage acid gas removal (AGR) unit. Only a small portion of the carbon dioxide (CO2) that is co-absorbed with the H2S is removed in the AGR. Part of the sweet syngas from the AGR is routed through the pressure swing absorption (PSA) unit to recover a 99.9% purity H2 product. The remaining sweet syngas from AGR is bypassed to the gas turbine (GT) combustor as fuel for power production. After H2 removal, the residuals from the PSA unit consist of low pressure (LP) purge gas containing all of the CO and CO2, and 10 to 30% of the H2 in the original PSA feed. This LP purge is subsequently compressed and added to the GT combustor inlet fuel to increase turbine power output. Acid gas from the AGR unit is sent to the sulfur recovery unit (SRU) to recover sulfur as a byproduct. Sulfuric acid production can be used as an alternative to the SRU.
Table 1 lists the published overall performance and efficiency of this type of IGCC/H2 co-production plant. The plant design is based on advanced dry feed entrained flow gasification technology, using Illinois No. 6 coal as feed, and with conventional acid gas removal (AGR) and PSA H2 separation technology. Performance and efficiency shown are for maximum power co-production.
|Table 1: Typical IGCC/H2 Co-Production Plant Performance & Efficiency 1|
|1.||Capital and Operating Cost of Hydrogen Production from Coal Gasification (Apr 2003)
Final Report by Parsons for NETL