基于NiO/Ca2Al2SiO7的沼气自热化学链重整制氢热分析动力学模拟

以水泥的主要成分Ca₂Al₂SiO₇为惰性载体,采用热分析动力学研究了NiO/Ca₂Al₂SiO₇氧载体作用下沼气的化学链重整(chemical looping reforming, CLR)制氢性能。通过自编的MATLAB^?代码计算得到430种工况下CLR模拟结果,充分考虑NiO负载率y_NiO、氧载体循环流率F_s、氧载体转化率变化ΔX_s、水蒸气浓度x_{H_{2}O}及空气反应器温度T_AR的影响。调节氧载体循环流率,可实现对(xNiO+Ca₂Al₂SiO₇)/biogas质量比的控制,进而调整系统总焓变化ΔH,实现自热化学链重整(CLRa),即ΔH=0。在CLRa状态下,T_AR和ΔX_s的升高均导致H₂产率降低,而F_s增加则有助于提高H₂产率。模拟结果表明,当NiO含量低于10%(质量)、T_AR接近1150 K、ΔX_s小于0.25、F_s大于2 kg?s^-1、x_{H_{2}O}小于54.5%（体积）时,H₂产率可达最优值1.57(m³ H₂)?(m³ biogas)^-1。对系统的热量平衡分析显示,CLRa能够在自热状态下运行,且反应器出口处气流携带热量能够满足进口处气流的预热需求。

Thermodynamics simulation of biogas fueled chemical looping reforming for H2 generation using NiO/Ca2Al2SiO7

Thermodynamics analyses were carried out in biogas fueled chemical looping reforming (CLR) process for H₂ generation, where the main component of cement Ca₂Al₂SiO₇ was used as a support for NiO/Ca₂Al₂SiO₇ oxygen carrier. Around 430 cases for CLR were studied via a home-built MATLAB^? code, considering the effects of NiO loading y_NiO, oxygen carrier circulation rate F_s, oxygen carrier conversion variation ΔX_s, steam concentration x_{H_{2}O} and air reactor temperature T_AR. The global enthalpy variation ΔH can be easily tuned to ΔH=0, i.e. CLRa state, by varying the (NiO+Ca₂Al₂SiO₇)/biogas ratio. Under CLRa state, increase of T_AR and ΔX_s can lead to the decrease of H₂ yield, while rising of F_s would result in the higher H₂ yield. The simulation suggests that the optimized H₂ yield of 1.57 (m³ H₂)?(m³ biogas)^-1 can be achieved with NiO loading lower than 10%(mass), T_AR close to 1150 K, ΔX_s lower than 0.25, F_s higher than 2 kg?s^-1 and x_{H_{2}O} lower than 54.5%(vol). Heat balance of the global FR, AR and WGS reactors showed that the CLRa can be run under auto-thermal condition, meanwhile heat at exits of reactors can be recovered to be used in the preheating of gases entering reactors.