K/Ca催化木屑水蒸气气化制取富氢合成气

K/Ca Catalytic Steam Gasification of Sawdust for Production of Hydrogen-rich Syngas

研制KOH/白云石复合催化剂,以松木屑为原料,在固定床气化炉中进行水蒸气气化实验,考察催化剂制备条件、反应温度、水蒸气流量、催化剂用量对气化合成气气体组分、产气率、产氢率及碳转化率等气化特性评价指标的影响,并对所研制的K/Ca复合催化剂进行SEM、XRD和孔隙结构分析。研究表明:K元素很好地负载在白云石上。由KOH质量分数6%、K/Ca物质的量比2∶1和煅烧温度900℃制备的K/Ca复合催化剂的催化性能最好。气化温度从600℃增加到750℃,H_(2)体积分数由40.70%增加至59.09%,产氢率由16.38 g/kg增加至90.64 g/kg,但继续升高温度会造成催化剂活性下降使得H_(2)体积分数和产氢率均有所下降。水蒸气流量由0.4 mL/min增加至1.0 mL/min时,H_(2)体积分数由52.75%增加至59.09%,产氢率由68.14 g/kg增加至90.64 g/kg,进一步增加水蒸气流量则会造成系统热量损失,使得H_(2)体积分数和产氢率均有不同程度的下降。催化剂与松木屑质量比值为0.3 g/g时,H_(2)的体积分数为59.09%,产氢率为90.64 g/kg;当质量比值增加到0.6 g/g时,H_(2)的体积分数降低至58.50%,产氢率提高到103.18 g/kg,继续增加质量比,二者变化趋势明显缓慢,即催化反应基本达到平衡。综合考虑各方面影响,K/Ca复合催化剂催化松木屑水蒸气气化的最佳条件为反应温度750℃、水蒸气流量为1.0 mL/min,催化剂与原料质量比值为0.6 g/g,此时产物气中H_(2)体积分数为58.50%,产氢率为103.18 g/kg,低位热值为10.94 MJ/m^(3),碳转化率为83.25%。

KOH/dolomite composite catalyst was used to catalyze steam gasification in a fixed-bed gasifier with pine sawdust as raw material.The effects of catalyst preparation conditions,reaction temperature,steam flow rate and catalyst dosage on the evaluation indexes of gasification characteristics such as gasification synthesis hydrogen content,gas yield,hydrogen yield and carbon conversion rate were investigated.SEM,XRD and pore structure analysis of the K/Ca composite catalyst were carried out.The results showed that K element was well loaded on dolomite.The K/Ca composite catalyst prepared by KOH mass fraction of 6%,K/Ca molar ratio of 2∶1 and calcination at 900℃had the best catalytic performance.When the gasification temperature increased from 600 to 750℃,the H_(2)volume fraction increased from 40.70%to 59.09%,and the hydrogen yield rate increased from 16.38 to 90.64 g/kg.However,the catalyst activity decreased owing to the continuous increase of temperature,and the H_(2)volume fraction and hydrogen yield decreased as well.When the steam flow rate increased from 0.4 to 1.0 mL/min,the H_(2)volume fraction increased from 52.75%to 59.09%,and the hydrogen yield increased from 68.14 to 90.64 g/kg.Further increase of steam flow would lead to heat loss in the system,which would reduce the H_(2)volume fraction and hydrogen production rate.When the mass ratio of catalyst to raw material was 0.3 g/g,the volume fraction of H_(2)was 59.09%and the yield rate of hydrogen was 90.64 g/kg.When the mass ratio increased to 0.6 g/g,the volume fraction of H_(2)decreased to 58.50%,and the hydrogen production rate increased to 103.18 g/kg.When the mass ratio of biomass continuously increased,above growth became significantly slow,that was,the catalytic reaction basically reached equilibrium.With the consideration of the various aspects,the optimal conditions of K/Ca composite catalyst for pine sawdust steam gasification were as follows:reaction temperature of 750℃,water vapor flow rate of 1.0 mL/min,and mass ratio of catalyst to raw material of 0.6 g/g.At this time,volume fraction of H_(2)in product gas was 58.50%,hydrogen production rate was 103.18 g/kg,the low calorific value was 10.94 MJ/m~3,and carbon conversion was 83.25%.