Abstract:  The multi-influence of alkali metal on the steam gasification and chemical looping gasification of biomass was investigated in a fixed bed reactor． The experimental results show that the gas generation rate of potassiumloaded biomass in the steam gasification is improved significantly at 700 ℃． The volume fraction of H2 is up to 56% ～57%，and CO is reduced to about 13%． It indicates that the steam-tar reforming and water-gas shift reaction are promoted by alkali metal remarkably，and the effect of inherent potassium is better than potassium salt． When the gasification temperature was increased to 900 ℃，the secondary cracking reaction of oxygen-containing functional group improved the yield of CO，while the water-gas reaction catalyzed by alkali metal consumed CO， and the competition of these two processes causes the non-linear characteristics of CO yield． The gasification efficiency and volume percentage of CO and H2 achieve the best when the biomass is impregnated by potassium carbonate solution with mass concentration of about 5%． While contrasted with steam gasification of biomass，the gas generation rate of H2 is increased after adding oxygen carrier． And K-loaded oxygen carrier can enhance gas generation rate of H2，up to 0. 82 m3 /kg，and the gasification efficiency reaches 75%． Contrary to CO，the gas generation rate of H2 is decreased with the increase of temperature． Because K-loaded oxygen carrier causes the generation of silicate melts at high temperature，it can block the reaction channel of oxygen carrier and restrain the steam-tar reforming and water-gas shift reaction． 

Key words: biomass, chemical looping, gasification, alkali metal