449 / 2018-09-04 13:09:12

Experimental Study on Sawdust Pyrolysis and In-line Catalytic Steam Reforming for Hydrogen Production

steam reforming; in-situ & ex-situ; Ni-based catalysts; hydrogen; service life

全体主题 > 生物质燃气

Sawdust pyrolysis and in-line catalytic steam reforming using Ni-based catalysts are carried out in a two-stage fixed bed reactor. The gas yield (Yg) and distribution, liquid distribution and carbon conversion efficiency (XC) are investigated under different steam flow rates (SFR) and pyrolysis temperatures (PT). Differences between steam fed into the first stage (in-situ SF) and the second stage (ex-situ SF) are compared. The Ni-based catalysts with and without K modification are characterized by XRD and TPR. The results indicate that both in-situ and ex-situ SF are beneficial to decreasing liquid products and increasing Yg and XC compared to tests without steam. The increase of SFR has no significant influence on Yg for ex-situ SF but increases the Yg, XC and H2 concentration for in-situ SF. For both in-situ and ex-situ SF, Yg increases with PT but the gas distribution is less sensitive. During the 20 min of each test, gasification of bio-char for in-situ SF has little contribution to Yg in the first 10 min but increases the CO2 and H2 yield significantly in the last 10 min compared to ex-situ SF and the effect is stronger under higher SFR or PT. In the first 10 min, ex-situ SF has higher Yg and XC than in-situ SF under lower SFR but the result is opposite under higher SFR, which indicates that SFR has a great influence on the pyrolysis process. The in-situ SF (PT=700 oC, SFR=0.12 g/min) obtains a total Yg of 1.13 g/g-bio, a H2 yield of 83.3 mg/g-bio and a H2 concentration of 57.4% with an increase of 24.3%, 35.9% and 7.3%, respectively, compared to ex-situ SF. Additionally, both steam and 0.5%K are beneficial to decreasing the coke deposition on Ni-based catalysts and the 0.5% K-Ni/Al has a longer service life.