中文摘要：

对沼液中氨氮进行脱除,有助于降低沼液对环境的潜在危害和在农业生态应用时对植物的生理毒性,但现有沼液氨氮脱除技术存在氨氮分离反应动力学常数较小和耗时较长等问题。基于此,在扩大沼液中氨氮利用价值的目标下,该文在旋转蒸发仪上对沼液进行了减压蒸馏分离研究并探索了温度、压力和Na OH添加量对氨氮分离效果的影响,同时进行了三因素四水平的正交试验,对操作参数进行优化。研究中,采用氨氮分离一级反应动力学常数评价反应速率,用氨氮分离因子评价氨氮分离性能。单因素试验结果表明,Na OH添加量增加有利于同时提升一级反应动力学常数和分离因子。同时,降低操作压力和增加反应温度有助于提升一级反应动力学常数,但却会带来分离因子值的下降。正交试验结果表明,3个操作参数对氨氮分离效果的主次顺序依次为：p H值,压力,温度。筛选出的优方案为Na OH添加量15 g/L（p H值为13.04）、压力15 k Pa、温度35℃,此时氨氮分离一级反应动力学常数为0.97 h-1,达到90%氨氮去除率时分离因子值为395.96。这意味着对p H值提升后的沼液进行减压蒸馏,不仅可对沼液中氨氮达到较好的分离效果,理论上还能回收较高浓度的氨水用于沼气净化提纯。相比于热吹脱和气体吹脱技术,在同等p H条件下,减压蒸馏技术可在较低温度下获得更高的一级反应动力学常数,且极易通过温度和压力的改变进行提升,说明减压蒸馏法分离氨氮在反应动力学上具有优势。研究结果可为以回收高浓度氨水为目标的沼液高效低耗氨氮分离提供参考。

英文摘要：

Due to high ammonia nitrogen concentration, biogas slurry can contribute to air and water pollution through volatilization of free ammonia. Additionally, high ammonia nitrogen concentration may result in high phytotoxicity to plant germination and growth when biogas slurry is put into agricultural or horticultural applications. So ammonia nitrogen in biogas slurry should be removed. Conventional methods for removing ammonia nitrogen are based on gas or thermal stripping. However, these methods have low ammonia nitrogen removal rate and are time-consumed. Due to the higher ammonia mass transfer driving force ascribed to the lower ammonia partial pressure in gas phase, vacuum distillation has the advantages of high ammonia nitrogen removal kinetics constant and short time required. Furthermore, ammonia can also be recovered and enriched to act as the valuable carbon dioxide（CO2） absorbent to upgrade biogas. Therefore, in this study, ammonia nitrogen separation from biogas slurry by using vacuum distillation method was conducted in a rotary evaporator. And the key operating parameters including sodium hydroxide（NaO H） dosage, temperature and pressure were investigated and optimized. The first-order rate constant（k）, ammonia nitrogen removal time constant（τ）, ammonia nitrogen removal efficiency（η） and ammonia nitrogen separation factor（St） were adopted to evaluate the ammonia nitrogen removal performance. Results showed that when raw biogas slurry without p H adjustment was vacuumed, CO2 loading of biogas slurry reduced from 0.15 to 0.08 mol CO2/L under the conditions of 45 °C and 5 k Pa. But the first-order rate constant and ammonia nitrogen separation factor were low and ammonia nitrogen removal time constant was very high. Increasing NaO H dosage to elevate the initial p H value of biogas slurry was positive for enhancing the first-order rate constant and ammonia nitrogen separation factor. Additionally, if high first-order rate constant value was targeted, high removal temperature and l