Novel Gas Cleaning/Conditioning for Integrated Gasification Combined Cycle

Abstract

Coal gasification can generate hydrocarbon gases that may be utilized for the synthesis of chemicals or liquid fuels, or for fuel cell power generation, if extensive, deep syngas cleaning is first conducted. Conventional gas cleaning technology for this duty is expensive and may limit the feasibility of coal usage for such applications. The Siemens Westinghouse Power Corporation has proposed a novel scheme for polishing sulfur, halide, and particulate from gases to meet very stringent cleaning requirements for chemical synthesis, or for fuel cell power generation. This "Ultra-Clean" gas polishing process is a dry process, injecting fine sulfur and halide sorbent particles into two stages of barrier filter-reactors, or granular bed filter-reactors, to accomplished the gas polishing by dry sorbent adsorption of the contaminants. The sorbent materials for each stage, their feed rates, and the two stage temperatures must be specified to satisfy the gas cleaning requirements of any specific application, with the process having the potential for sulfur species less than 60 ppbv, halides less than 10 ppbv, and particulate less than 0.1 ppmw.The Base Program experimental activities described in this report have been completed to identify candidate sorbents and suitable operating conditions for each of the two stages of the Ultra-Clean process. The laboratory process simulation testing has identified a set of zinc-based and sodium-based, -325 mesh sorbents for each of the two stages that yield the performance potential for meeting the most stringent gas cleaning requirements. With these selected sorbents, the Stage I temperature is 499 C (930 F) and the Stage II temperature is 288 C (550 F).Conceptual commercial process evaluation of a novel gas cleaning process that utilizes the Ultra-Clean gas polishing process has been performed to devise potentially viable process details for two applications: a general chemical or liquid fuel synthesis application, and a solid oxide fuel cell power generation application. Commercial process performance and economics have been estimated for this novel gas cleaning process. The results indicate promising performance and economic potential compared to the conventional, Rectisol-based, gas cleaning technology. Sorbent maximum acceptable consumption criteria have been extracted from the commercial process evaluations and show that relatively high, once-through sorbent feed rates can be economically viable in the Ultra-Clean gas polishing process. The process can also incorporate ammonia removal and mercury removal. The next phase of the program will conduct integrated, bench-scale testing of the Ultra-Clean syngas polishing process on a sub-scale coal gasifier.iii

The Effect of Impurities on Ignition Delay Times and Laminar Flame Speeds of Syngas Mixtures at Gas Turbine Conditions

“…These neat mixtures were then seeded with single impurities (COS, NH 3 , and H 2 S for the coal syngas and NO 2 , NH 3 , HCN, and SO 2 for the bio-syngas) at their maximum reported concentration [32]- [34] to estimate the effect of impurities on τ ign and S L on these baseline mixtures. Note that due to their possible large concentration and presumably great effects on combustion properties, NO 2 and H 2 S have also been studied at averaged concentrations that have been determined from several syngas mixture compositions ([2]- [5], [32]- [34]). For each type of syngas, a mixture containing all the aforementioned impurities at their maximum reported concentration was also investigated, to exhibit possible synergistic or antagonistic effects between impurities.…”

“…As mentioned earlier, in addition to these fuels and diluents, traces of impurities can also be found in syngas. These impurities are typically NH 3 , HCN, COS, H 2 S, SO 2 , and NOx (NO, NO 2 , N 2 O), although some traces of HCl and metals have also been reported [5], [31]. While the concentration of these impurities are typically very low (up to 1.3% and 0.3% vol.…”

Numerical Study on the Effect of Real Syngas Compositions on Ignition Delay Times and Laminar Flame Speeds at Gas Turbine Conditions

“…Several other compounds such as N2, CH4, C2H2, C2H4, C2H6, CO2, H2O, and impurities such as NH3, NO^, and SO2 have been reported as well. The same exercise has been done for a coal-derived syngas with an average composition determined from 40 real, coal-syngas mixtures [1,[3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The H2/CO mole ratio was determined to be 40/60 for this average coal-syngas.…”

Small-scale production of synthetic natural gas by allothermal biomass gasification

“…For small‐scale processes, a suitable gas cleaning process is dry adsorption in fixed beds. Halides can be removed with Na 2 CO 3 ∙NaHCO 3 ∙2H 2 O at an operation temperature around 400 °C .…”

“…For small-scale processes, a suitable gas cleaning process is dry adsorption in fixed beds. Halides can be removed with Na 2 CO 3 •NaHCO 3 •2H 2 O at an operation temperature around 400 C [39]. Small-scale production of SNG A. Tremel, M. Gaderer and H. Spliethoff Sulfur removal can be done with a ZnO-fixed bed at around 400 C and has the potential to decrease the sulfur concentration below the limit for methanation [40] (i.e., 1 ppm [41]).…”