Supported liquid catalysts for removal of high temperature fuel cell contaminants.

Weimer, A. W. ; Czerpak, P. ; Hilbert, P.

Technical Information Center Oak Ridge Tennessee

关键词: Catalysts;    Fuel cells;    Ambient temperature;    Containmants;    Fluidized beds;   

RP-ID  :  DE2001772422

学科分类：工程和技术（综合）

美国|英语

来源: National Technical Reports Library

【 摘 要 】

A novel catalytic synthesis gas oxidation process using molten carbonate salts supported on compatible fluidized iron oxide particles (supported-liquid-phase-catalyst (SLPC) fluidized bed process) was investigated. This process combines the advantages of large scale fluidized bed processing with molten salt bath oxidation. Molten salt catalysts can be supported within porous fluidized particles in order to improve mass transfer rates between the liquid catalysts and the reactant gases. Synthesis gas can be oxidized at reduced temperatures resulting in low NO(sub x) formation while trace sulfides and halides are captured in-situ. Hence, catalytic oxidation of synthesis gas can be carried out simultaneously with hot gas cleanup. Such SLPC fluidized bed processes are affected by inter-particle liquid capillary forces that may lead to agglomeration and de-fluidization of the bed. An understanding of the origin and strength of these forces is needed so that they can be overcome in practice. Process design is based on thermodynamic free energy minimization calculations that indicate the suitability of eutectic Na(sub 2)CO(sub 3)/K(sub 2)CO(sub 3) mixtures for capturing trace impurities in-situ (< 1 ppm SO(sub x) released) while minimizing the formation of NO(sub x)(< 10 ppm). Iron oxide has been identified as a preferred support material since it is non-reactive with sodium, is inexpensive, has high density (i.e. inertia), and can be obtained in various particle sizes and porosities. Force balance modeling has been used to design a surrogate ambient temperature system that is hydrodynamically similar to the real system, thus allowing complementary investigation of the governing fluidization hydrodynamics. The primary objective of this research was to understand the origin of and to quantify the liquid capillary interparticle forces affecting the molten carbonate SLPC fluidized bed process. Substantial theoretical and experimental exploratory results indicate process feasibility. The potential environmental gain from success is enormous, impacting all areas of the world where coal is burned to supply steam or direct industrial heat. Project success may lead to an integrated combustion system providing for simultaneous catalytic oxidation and hot gas cleanup of raw synthesis gas from an upstream coal gasifier.