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Co-production of hydrogen, electricity andCO2 from coal with
commercially ready technology.PartA:Performanceandemissions

Paolo Chiesa , Stefano Consonni , Thomas Kreutz , RobertWilliams

Abstract

This two-part paper investigates performances, costs and prospects of using commercially ready technology to convert coal to H2 and electricity, with CO2 capture and storage. Part A focuses on plant configuration and the evaluation of performances and CO2 emissions. Part B focuses on economics, establishing benchmarks for the assessment of novel technologies and guidelines for technological development.

In the co-production plants considered in the paper, coal is gasified to synthesis gas in an entrained flow gasifier. The syngasis cooled, cleaned of particulate matter, and shifted (to primarily H2 and CO2) in sour water–gas shift reactors. After further
cooling, H2S is removed from the syngas using a physical solvent (Selexol); CO2 is then removed from the syngas, again using Selexol; after being stripped from the solvent, the CO2 is dried and compressed to 150 bar for pipeline transport and underground storage. High purity H2 (99.999%) is extracted from the H2-rich syngas via a pressure swing adsorption (PSA) unit and delivered at 60 bar. The PSA purge gas is compressed and burned in a conventional gas turbine combined cycle, generating co-product electricity. The H2/electricity ratio can be varied by lowering the steam-to-carbon ratio in the syngas or by letting part of the de-carbonized syngas by-pass the PSA unit.

Performances and emissions of H2/electricity co-production with CO2 capture are compared with those of a system that vents the CO2. We examine different methods of syngas heat recovery (quench versus radiant cooling) and explore the effects of changing the electricity/H2 ratio, gasifier pressure and hydrogen purity.

Results show that state-of-the-art commercial technology allows transferring to de-carbonized hydrogen 57–58% of coal LHV, while exporting to the grid decarbonized electricity amounting to 2–6% of coal LHV. In contrast to decarbonizing coal IGCC electricity, which entails a loss of 6–8 percentage points of electricity conversion when capturing CO2 as an alternative to venting it, CO2 capture for H2 production gives a minor energy penalty (∼ 2 percentage points of export electricity). For H2 production, the efficiency gain achievable by hot syngas cooling vs. quench is a modest 2 percentage point increase in electricity for export, compared to 2–4 percentage points in the electricity case. Reducing H2 purity or increasing gasification pressure has minor effects on performance.

 

Download presentation of this paper at :

http://www.carbonsq.com/pdf/3D3.pdf

 download this paper at www.sciencedirect.com

International Journal of Hydrogen Energy 30 (2005) 747 – 767

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