Experimental study on characteristics of hydrogen production from exhaust gas-fuel reforming in a catalytic fixed-bed reactor

Since the hydrogen-rich gas can be generated on-board by the catalytic reforming of exhaust gas from the engine, reformed exhaust gas-fuel recirculation is an attractive method for waste-heat recuperation and performance enhancement for the engines fueled by natural gas (NG). In the present study, the industrial Ni/Al2O3 catalyst was selected to investigate the effects of wall temperature, feed ratio and gas hourly space velocity (GHSV) on hydrogen production from exhaust gas-fuel reforming in a catalytic fixed-bed reactor. Meanwhile, Ni/Al2O3 fresh catalyst was characterized by the X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) techniques. The simulated exhaust gas was prepared based on the exhaust gas from a marine NG engine at 75% propeller load. The experimental results show that the higher wall temperature is favored for steam reforming to deliver higher H-2 concentration in the reformate gas, which result in the increase of the H-2 volume fraction at reformer outlet, H-2 yield and CH4 conversion with the wall temperature. The maximum values of H-2 yield and H-2 volume fraction from the reformer outlet can reach up to approximately 0.96 and 22%, respectively. From the view of reforming process, that CH4/O-2 = 2 and H2O/CH4 = 2 is considered as the optimum matching feed ratio. When a GHSV is approximately 7500 h(-1), the H-2 volume fraction at reformer outlet can be maximized. Under the given conditions, a more preferable reforming energy efficiency can be achieved when H2O/CH4 = 2, CH4/O-2 = 3, GHSV = 6000 h(-1) and high wall temperature.

Automated summary

This study investigated the effects of wall temperature, feed ratio, and gas hourly space velocity (GHSV) on hydrogen production from exhaust gas-fuel reforming using Ni/Al2O3 catalyst. Higher wall temperature favored steam reforming to deliver higher H2 concentration, resulting in increased H2 yield and CH4 conversion. Optimum matching feed ratio was CH4/O2 = 2 and H2O/CH4 = 2, with maximum H2 volume fraction achieved at GHSV of approximately 7500 h^(-1).