以原生生物质稻壳作为生物质原料,考察反应温度（350~500 ℃）、浓度（1%~4%）和碱金属催化剂K2CO3对稻壳超临界水气化制氢性能的影响。实验结果表明,升高反应温度、降低反应物浓度能有效提高稻壳的碳气化率,降低结焦率。非催化条件下,500 ℃和1%为该实验中稻壳超临界水气化的最佳工况,碳气化率达到37.6%,H2选择性达到48.3%。虽然超临界水环境可有效促进生物质的溶解与水解,且可提供过量的水促进蒸汽重整反应、水气变换反应等产气反应的进行,但稻壳的气化仍无法避免结焦问题,会阻碍原料中的有机物完全气化。碱催化剂K2CO3的添加,使其在最佳工况下,稻壳的碳气化率达到49.2%,总产气量达58.70 mol/kg。热重分析仪分析残余固体中几乎不含有碳,这可能源于碱金属催化剂可加强稻壳的水解反应,促进原料中的碳转移至气相和液相,从而极大降低焦炭的产生。此外,K2CO3对稻壳气化产物具有良好的H2选择性,H2占比达到71.0%。H2产量达到41.66 mol/kg,较非催化条件增长3.5倍。实验结果证明,稻壳在K2CO3催化超临界水气化制取富氢气体具有潜力。
Abstract
This study employed rice husk as the native biomass and investigated the effects of reaction temperatures （350- 500 ℃）, concentrations （1%-4%）, and an alkali metal catalyst （K2CO3） on the performance of supercritical water gasification for hydrogen production. Experimental results indicated that increasing reaction temperature and decreasing reactant concentration could effectively enhance the carbon gasification efficiency （CGE） and reduce the coking rate of rice husk. Under non-catalytic conditions, the optimal conditions for supercritical water gasification of rice husk were identified as 500 ℃ and 1%, achieving a CGE of 37.6% and an H2 selectivity of 48.3%. Although the supercritical water environment facilitates the dissolution and hydrolysis of biomass, providing ample water to strengthen gas production reactions such as steam reforming and water-gas shift reaction, coking during gasification of rice husk remains an intractable issue that impedes its further gasification. The addition of K2CO3, however, significantly diminished the formation of coke. Under the optimal conditions, the CGE of rice husk achieved 49.2%, with total gas yield reaching 58.70 mol/kg. The residual solid, as analyzed by Thermogravimetric Analysis, was virtually carbon-free, indicating that the alkali metal catalyst may intensify the hydrolysis of rice husk, thereby promoting the transference of carbon from the feedstock to the gaseous and liquid phases. In addition, K2CO3 exhibited excellent H2 selectivity for gasification of rice husk, with an H2 selectivity of 71.0%. And the yield of H2 also reached 41.66 mol/kg, which was 3.5 timses higher than that under the non-catalytic conditions. The experimental results demonstrated the potential for producing hydrogen-rich gas through K2CO3 which catalyzed supercritical water gasification of rice husk.
关键词
生物质 /
气化 /
制氢 /
稻壳 /
超临界水 /
K2CO3催化剂
Key words
biomass /
gasification /
hydrogen production /
rice husk /
supercritical water /
K2CO3 catalyst
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基金
河北省自然科学基金（E2023203210）
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