| Hydrogen is recognized as the ideal energy in the 21 st century.Taking all the spects into consideration,steam gasification is one of the most resonable methods for the production of hydrogen-rich gas.However,there are a few defects existing in the process of biomass gasification,mainly low content of H2 fuel gas,high tar content and low calorific value,but biomass catalytic gasification can improve hydrogen yield and reduce tar content.In this study,Steam gasification experiments of sawdust for production of hydrogen-rich gas were carried out in the high-temperature fixed bed reactor.Main contents and results are summarized as follows:1.Steam gasification of sawdust for production of hydrogen-rich gas.The effects of temperature(750~1 000 ?)and steam flow rate(0.1~0.47g/(min·g))on gasification characteristics were investigated.The results showed that: temperature and steam flow rates have great influences on the gas volume fraction.Increasing reactor temperature and introducing appropriate steam are beneficial to the production of hydrogen;however,heating value of product was decreased with the increasing amount of steam at high temperature.Taking influence of various aspects into consideration,the optimal flow rate of steam was0.34g/(min·g)at 900?.In this condition,the hydrogen content was 45.74%,the LHV of the gas was 11.63MJ/m3,the dry gas yield was 1.48m3/kg.The results showed that high temperature steam gasification had prominent advantage for production of hydrogen-rich gas from biomass,and it will have a very bright application prospect.2.Influence of CaO on hydrogen-rich gas production from steam gasification of sawdust.The effects of the amount of substance ratio of CaO and carbon element of sawdust(n(Ca)/n(C))?temperature and steam flow rate on gasification characteristics were investigated.The results showed that: increasing n(Ca)/n(C)from 0 to 1.0,the hydrogen content was increased from 45.58% to 58.62%.Using CaO as catalyst,the most optimized conditions were the flowed: n(Ca)/n(C)was 1,the gasification temperature was 750 ? and the steamflow rate was 0.34g/(min·g).Under the optimized conditions,the hydrogen content was62.55%,the hydrogen yield was 85.08m3/kg,the low heating value was 11.41 MJ/m3.3.Influence of Ni-CaO on hydrogen-rich gas production from steam gasification of sawdust.The influence of catalytic:sawdust ratio?gasification temperature and steam flow rate on gasification characteristics were investigated.The results showed: increasing catalytic:sawdust ratio from 0 to 1.5(g/g),the hydrogen content was increased from 45.58% to60.23%.Using Ni-CaO as catalyst,the most optimized conditions were the flowed:gasification temperature was 750?,catalyst:sawdust ratio was 1.5(g/g)and the steam flow rate was 0.34 g/(min·g),the hydrogen content was 60.23%,the dry gas yield was 93.75g/kg,the low heating value was 12.13 MJ/m3.4.Temperature has a great effect on the pyrolysis of tar during biomass gasification,with the increase of the gasification temperature,the tar components of fuel gas was reduced;biomass tar catalytic cracking is an effective method to convert the tar into small molecules.In this study,CaO and Ni-CaO were used as catalysts,the results showed that the tar obtained under the catalysis of Ni-CaO was less than that of CaO catalyzed,which indicated that the catalytic cracking effect of Ni-CaO on tar was better than that of CaO.In this study,hydrogen-rich gas was produced by high temperature gasification,the influence of catalyst?gasification temperature and steam flow rates were investigated.The hydrogen content of the fuel gas was more than 60%,especially using the Ni-CaO as the catalyst,and LHV was above 10 MJ/m3.This study provides the basis reference data for the biomass catalytic gasification and steam reforming to produce the hydrogen-rich gas. |
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