Research Papers: Gas Turbines: Coal, Biomass, and Alternative Fuels

Carbon-Free Hydrogen and Electricity From Coal: Options for Syngas Cooling in Systems Using a Hydrogen Separation Membrane Reactor

[+] Author and Article Information
Luca De Lorenzo, Thomas G. Kreutz, Robert H. Williams

Princeton Environmental Institute, Princeton University, Princeton, NJ 08544

Paolo Chiesa

Dipartimento di Energetica, Politecnico di Milano, Piazza Leonardo da Vinci, 32-20133 Milan, Italy

Composition depends on the actual operating conditions of the HSMR, but it primarily consists of H2O and CO2, with some traces of unconverted CO, CH4, H2S, and unpermeated H2.

The low temperature limit could be overcome through a regenerator to increase the temperature before the reactor. This expensive solution was not investigated in this study.

Recent research by Way et al.  indicates that such values are in the reach of technological progress.

This H2 compressor design (number of trains and costs) is derived from our database on commercially available reciprocating compressors. Were large H2 production facilities such as these to become commonplace, it is likely that large scale centrifugal compressors would become commercially available, lowering compression costs significantly by reducing the number of parallel trains.

Neither plant QC nor plant QU lies exactly on the lines labeled “TIT 1250 C” and “TIT 850 C” for reasons having to do with minor parameter variations between the plants in this study and those of the previous one (Kreutz et al. (3))

In Fig. 2, this plant lies perfectly on plant SCU since it is working at the same S/C-HRF conditions.

Recalculated in 2006 U.S. dollars using implicit price deflators for the US gross domestic product. We did not take into account the recent escalation in project costs associated with engineering, labor, and materials

J. Eng. Gas Turbines Power 130(3), 031401 (Mar 28, 2008) (10 pages) doi:10.1115/1.2795763 History: Received May 10, 2006; Revised May 31, 2007; Published March 28, 2008

Conversion of coal to carbon-free energy carriers, H2 and electricity, with CO2 capture and storage may have the potential to satisfy at a comparatively low cost much of the energy requirements in a carbon-constrained world. In a set of recent studies, we have assessed the thermodynamic and economic performance of numerous coal-to-H2 plants that employ O2-blown, entrained-flow gasification and sour water-gas shift (WGS) reactors, examining the effects of system pressure, syngas cooling via quench versus heat exchangers, “conventional” H2 separation via pressure swing adsorption versus novel membrane-based approaches, and various gas turbine technologies for generating coproduct electricity. This study focuses on the synergy between H2 separation membrane reactors (HSMRs) and syngas cooling with radiant and convective heat exchangers; such “syngas coolers” invariably boost system efficiency over that obtained with quench-cooled gasification. Conventional H2 separation requires a relatively high steam-to-carbon ratio (S/C) to achieve a high level of H2 production, and thus is well matched to relatively inefficient quench cooling. In contrast, HSMRs shift the WGS equilibrium by continuously extracting reaction product H2, thereby allowing a much lower S/C ratio and consequently a higher degree of heat recovery and (potentially) system efficiency. We first present a parametric analysis illuminating the interaction between the syngas coolers, high temperature WGS reactor, and HSMR. We then compare the performance and cost of six different plant configurations, highlighting (1) the relative merits of the two syngas cooling methods in membrane-based systems, and (2) the comparative performance of conventional versus HSMR-based H2 separation in plants with syngas coolers.

Copyright © 2008 by American Society of Mechanical Engineers
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Grahic Jump Location
Figure 1

Schematic layout of a membrane-based plant. The table shows the composition if the syngas is exiting the gasifier.

Grahic Jump Location
Figure 2

Allowed operating range (light region) and principal limits. The different plant configurations analyzed have been located on this HRF-S/C framework.

Grahic Jump Location
Figure 3

CO conversion factors as a function of steam-to-carbon ratios, divided among the WGSR and HSMR

Grahic Jump Location
Figure 4

Composition of the shifted syngas entering the HSMR and average H2 flux across the membrane (HRF=85%)




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