The effect of hydrocarbon impurities on the methanol steam-reforming process for fuel cell applications.

摘要

Because the methanol steam-reforming process typically utilizes a catalyst to promote reaction, contamination in fuel feedstock can have a detrimental effect on the reforming capability of a fuel processor. For this reason, an experimental investigation was conducted in an attempt to quantify and model the effects of several hydrocarbon contaminants on the methanol steam-reforming process.; An experimental methanol steam-reforming rig was designed and constructed that consisted of an integrated system of pumps, vaporizers, and a catalytic reactor. The reactor assembly was equipped with axially distributed, individually controlled electrically resistive heat bands that provided distributed heat for the endothermic steam reforming reaction, and allowed for near-isothermal reactor operation. Components were sized and integrated to allow for a range of operating conditions, which was well suited for a parametric study of the methanol steam-reforming process.; A plug-flow reactor model was developed that incorporated a reforming reaction model, basic reactor theory, and a compensation factor for the detrimental effect of any possible contaminants. Application of this model allowed for the comparison of data obtained from experimentation using contaminated and non-contaminated methanol feedstock.; Experimentation was conducted at atmospheric pressure and in a temperature range of 250°C to 300°C, which is typical for the methanol steam-reforming process. In addition to the reaction temperature, space velocity, the contaminant species, and the concentration of the contaminant in the feedstock fuel were independent variables evaluated over the course of experimentation. Three different contaminants were used, including a lightweight mineral oil, isooctane, and kerosene.; Results showed that very small quantities (less than 0.1% by weight) of mineral oil present in the feedstock methanol caused immediate and irreparable damage to the conversion catalyst. Kerosene in quantities of less than 0.5% by weight also resulted in degradation of the conversion catalyst, although the level of degradation was considerably lower and occurred over a greater time scale than in the mineral oil case. Experimentation conducted using the feedstock contaminated with isooctane in quantities up to 1.0% by weight resulted in no noticeable decrease in fuel processor performance, at least for the exposure time (∼50 hours) considered during this research.