【作者】 杨剑；

【导师】 黄镇宇； 王智化；

【作者基本信息】 浙江大学 ， 工程热物理， 2011， 硕士

【摘要】 氢能具有清洁高效、安全可储存、可再生和来源丰富等优点,是一种理想的可再生能源载体。规模化高效低成本制氢是发展氢能经济的基础。在众多候选制氢方式中,热化学水分解硫碘制氢具有热效率高,流程简单,可实现工业化和规模化等优势,是较理想的热化学循环制氢方式。本生反应是硫碘循环的起始步骤,本生反应产物HI和H2SO4的有效分离关系到整个系统的可运行性和经济性,是目前急需解决的科学难题之一。本文首先利用过量碘法对本生反应产物的两相分离特性进行了系统研究。在较感兴趣的工况范围内试验研究了两相分离的出现及过量碘的析出,过量碘量对两相密度、杂质含量、硫酸相组分以及碘化氢相中HI浓度的影响,温度对两相密度和杂质含量的影响以及过量水量对分层效果的影响,并综合分析得到了最佳的本生反应推荐工况。实验结果显示：温度的增加和水量的减少有利于碘在HI/H2O溶液中的溶解；过量碘量上、下限间的两相区范围随温度的升高逐步扩大,这有利于提高硫碘系统实际运行时的稳定性；在较宽实验工况范围内,模拟液完成两相分离的时间受工况变化影响较小,且能够在2min内进行的比较充分；过量碘量的加入能显著改善两相分离的效果；综合分析得到的本生反应两相分离优化工况范围是：压力P=1atm,物料比n(H2SO4)/n (HI)/n (H20)= 1/2/12,温度T=345～358K,过量碘量n(I2)=2.4-4。其中,T=351K, n (H2SO4)/n(HI)/n(H20)/n(I2)=1/2/12/2.5时,分层后的碘化氢相中HI浓度超共沸浓度,达到27.35%,且各相中的杂质含量均处于较低水平,为最佳两相分离工况。其次,利用化工流程模拟软件Aspen Plus对硫碘开路循环制氢系统进行了设计和热力学模拟,计算了氢气产率lmol/s的硫碘开路循环系统的质量平衡、能量平衡及热效率,并研究了主要设计参数对系统效率的影响。结果显示：硫碘开路循环系统的最高计算热效率达到66.79%；碘化氢相循环量和精馏塔回流比是影响系统效率的主要因素。实际运行中,优化本生反应操作条件,提高碘化氢相中HI浓度是降低HI浓缩、精馏段热负荷和电负荷,提高系统整体热效率的重要手段。更多还原

【Abstract】 Hydrogen energy, which is considered as an ideal regenerative energy carrier has many advantages such as clean, high efficiency, safety, advantageous storage, regeneration and various source. Large-scale and low-cost hydrogen production is the foundation of hydrogen economy. Compared with other candidate hydrogen production processes, the sulfur-iodine (SI) thermochemical cycle has a number of attractive features including high thermal efficiency, few flowsheet steps and available industrialization. It is the most promising thermochemical cycle for mass hydrogen production.The Bunsen reaction is the first step of SI cycle. The efficient separation of HI and H2SO4 which are the product of Bunsen reaction is a technical challenge needs to be solved. In this paper, the Iodine Excess Addition method is used to investigate the two-phase separation characteristics of Bunsen reaction products. The phenomenon of two-phase separation and excess iodine solidification is first studied in wide temperature range. Then, characteristics of two phase density, impurity in each phase, and component of sulfuric acid phase as well as HI concentration in HI phase influenced by excess iodine are discussed. The influences of temperature and excess water on two phase purification are also investigated. Finally, an optimal operating condition for the Bunsen reaction of SI thermochemical cycle is recommended. The results have indicated that:The solubility of iodine in HI/H2O solvents is increased by temperature while decreased by H2O molar ratio; The two-phase region of the product of Bunsen reaction is widened while the temperature increasing; The two-phase separation time is less than 2 minutes which is slightly effected by solution components; The two-phase separation characteristics are significantly improved by the excess iodine; Based on the results, the allowable window ranges 2.4-4 mol for the excess iodine and 345-358K for the temperature when the pressure is 1 atm and the molar ratio of H2SO4, HI and H2O is 1:2:12. The optimal operating point is represented by 2.5 mol of excess iodine and 12 mol of excess water at temperature of 351K. At this optimal operating point, the HI concentration in HI phase is over-azeotropic which reaches 27.35% while the impurities in two phases keep in low level.A flowsheet of open-loop sulfur-iodine thermochemical cycle for the production of hydrogen and sulfuric acid is designed and simulated by Aspen Plus. The production rate of H2 is fixed at 1 mol/s. The heat and mass balance as well as thermal efficiency of this process are calculated. Effects of several operating conditions on the thermal efficiency are also evaluated. The results have indicated that:The thermal efficiency of the total process is 66.79%; The molar flow rate of HI phase and the reflux ratio at HI distillation column are the main factors which influence the thermal efficiency; The optimization of Bunsen reaction process can increase the HI concentration in HI phase, decrease the heat and electric energy demand in HI concentration and distillation process which increase the total process thermal efficiency.更多还原