氯化铝对脱水污泥超临界水气化产氢的影响

如何选择或开发合适的催化剂以提高产氢量成为污泥超临界水气化技术,是实现实际应用的关键。选取氯化铝(AlCl_3)作为催化剂,以污水厂脱水污泥为对象,采用间歇式高温高压反应釜,在400℃、24 MPa、30 min的条件下进行超临界水催化气化实验。分析AlCl_3对脱水污泥超临界水气化产氢以及关键产物的影响,探讨AlCl_3的催化机理。结果表明,AlCl_3能够显著促进脱水污泥超临界水气化产氢,在6wt%添加量下氢气产率达到11.52 mol/kg OM,比不添加提高了近43倍。AlCl_3的添加会促进小分子有机物聚合生成酚类物质,抑制小分子聚合生成焦炭。AlCl_3催化机理是水解生成HCl和A_l2(OH)_3。HCl作为酸性水解剂,促进污泥中碳水化合物在亚临界条件下水热解转化成小分子物质,并进一步在超临界条件下气化产生氢气;Al_2(OH)_3作为碱性化合物催化剂,促进水气转化反应促进产氢,二者共同作用促进脱水污泥超临界水气化产氢。

Effect of aluminum chloride on hydrogen production from supercritical water gasification of dewatered sewage sludge

How to choose or develop a suitable catalyst to promote hydrogen production from supercritical water gasification of dewatered sewage sludge has become a essential technology to realize of technology resource utilization. To study the catalytic effect and mechanism of aluminium chloride (AlCl3), in the present study, AlCl3 was selected as catalyst, sewage sludge was selected as an object, intermittent high temperature and high pressure reactor was adopted. Supercritical water catalytic gasification experiment is accomplished under the conditions of 400 °C, 24 Mpa and 30 min. The influence of AlCl3 on hydrogen production and key product from supercritical water gasification of dewatered sewage sludge was analysed , and the catalytic mechanism was discussed. Results show that hydrogen production from supercritical water gasification of sewage sludge was significantly promoted by adding AlCl3. The hydrogen yield reached 11.52 mol/kg OM with 6 wt% AlCl3 added nearly 43 times higher than that of no AlCl3 added. Phenols polymerised from micromolecules was encouraged and the coke was inhibited when AlCl3 was added. The catalytic mechanism is the hydrolysis reaction of AlCl3, which can forming HCl and Al2(OH)3. HCl acted as an acid hydrolysis agent that facilitate carbohydrate hydrolysis to micromolecules under subcritical condition further gasificate to produce hydrogen under supercritical condition. Al2(OH)3 acted as an alkaline compound catalyzer that promote the water-gas shift reaction and improve the hydrogen yield. The above principles work together to promote supercritical water gasification of dewatered sewage sludge to produce hydrogen.