农林业固废超临界水热化学制氢进展--反应系统及应用

Review of Thermochemical Conversion of Agriculture and Forestry Waste for Hydrogen Production in Supercritical Water--Reaction Systems and Applications

超临界水热化学制氢技术能够将农林业固废中的生物质有机成分转化成氢能,是一种高效、经济和清洁的农林业固废能源化利用技术。本文主要从反应系统的角度出发,对超临界水热化学制氢技术进行了深入的分析。对不同类型反应系统的研究表明,间歇式反应器便于实现反应温度、压力以及反应时间的控制,但因难以扩大生产规模和无法实现热回收而不适合工业化推广;连续式反应系统具有反应性能好、经济效益高等优点,是农林废弃物超临界水热化学制氢技术从实验室走向工业化应用的必由之路。对于连续式系统,反应器材质以耐高温、耐高压和耐腐蚀的哈氏合金或铬镍铁合金为主;系统压力输送采用恒流泵和背压阀相结合的设计控制系统内部压力;超临界水的加热采用带嵌入式热电偶的接触式电阻加热方式可以实现系统快速和可控地升温;反应物料直接输送进热态超临界水中可以显著减少焦炭焦油的生成。对于不同的农林业固废,超临界水热化学制氢技术均能实现生物质向氢能的转化,但反应规律存在很大差异性,其中木质纤维素生物质废弃物的纤维素含量越高反应越容易进行,而禽畜粪便废弃物还要考虑重金属等污染物的转化问题。未来研究重点方向为:反应器的防腐蚀问题,反应器堵塞和盐沉积问题,系统在线排渣问题,针对工业化系统的建模设计、经济衡算以及与其他系统耦合的问题。

Supercritical hydrothermal chemical hydrogen production technology converts biomass organic components in agroforestry solid waste into hydrogen energy.It is an efficient,economical and clean way to make use of energy in agroforestry solid waste.This paper carries out an in-depth analysis on this technology mainly from the perspective of reaction systems.According to studies on various types of reaction systems,it is concluded that it is easy to implement control over reaction temperature,reaction pressure,and reaction time with batch reactor.However,considering the difficulty in scaling up the production and recovering the thermal energy,it is not practical to use this type of reactor in industrial applications.Boasting advantages of good reaction performance and high economic benefits,continuous reaction system is the only way to usher supercritical hydrothermal chemical hydrogen production with agroforestry solid waste from laboratory to industrial applications.The reactor in continuous reaction systems is mainly made of Hastelloy or Inconel alloy resistant to high temperature,high pressure and corrosion.The combi nation of constant current pumps and back pressure valve is used for internal pressure control of the system.Contact resistive heating with embedded thermocouples is adopted for heating of supercritical water to achieve a rapid and controllable temperature rise of the system.The formation of coke tar is significantly reduced as the reaction material is sent into the hot supercritical water directly.Supercritical hydrothermal chemical hydrogen production technology enables conversion of biomass in various agroforestry solid wastes into hydrogen,but with significant difference in reaction characteristics depending on the waste type.For lignocellulose biomass waste,high cellulose content is favorable to reaction process.As to livestock manure waste,the conversion of pollutants such as heavy metals must be considered.Further studies on this topic will focus on corrosion prevention of reactor,blockage and salt deposition in reactor,online slag removal of reaction system,and modeling design,economic balance and coupling to other systems in industrial architecture.