微藻被认为是最有前景的生产生物燃料的原料之一,但对其水热液化进行能源转化时,存在如何制备低氮生物油和如何处理高浓度有机废水的两大难题。本文拟探究是否存在一种可以同时解决这两大难题的创新水热液化方法。为此,先归纳了微藻水热液化过程中含氮化合物的生成机理,并获知原料中的氮元素主要在油水两相水热产物间发生迁移转化,调节水热水相中有机氮或无机氮等含氮组成将影响生物油中氮含量。随后,综述了现有的基于水热水相调节微藻水热产油的连续水热液化法和水相循环水热液化法的研究进展,其中,连续水热法通过分离低温水热后水相同时脱氮脱碳,使生物油氮含量下降但油得率降低。水相循环水热法通过回用高温水热后水相同时富碳富氮,使生物油得率提升但氮含量增加。最后,提出了一种基于水相氮元素调控的水热液化方法,此方法可同时脱氮、富碳和节水,将微藻高效转化为低氮生物油。Microalgae is considered to be one of the most promising raw materials for biofuel production. By using hydrothermal liquefaction (HTL) of microalgae to produce bio-oil, there are two problems: how to obtain low-nitrogen bio-oil and how to deal with high-concentration organic wastewater. Therefore, we intend to explore whether there is an innovative HTL that can solve both problems at the same time. In this review, the formation mechanism of nitrogen-containing compounds in bio-oil from HTL of microalgae is summarized firstly. And the nitrogen element in raw biomass mainly migrates and transforms between bio-oil and water phase in the process of HTL of microalgae. As a result, the nitrogen content of the bio-oil could be influenced by regulating the nitrogen composition of organic nitrogen or inorganic nitrogen in water phase during HTL. Then, the recent researches on the sequential HTL and water phase recycling HTL of microalgae are reviewed. The bio-oil with low nitrogen content and a low yield is produced from sequential HTL, for the simultaneous removal of nitrogen and carbon elements by separating the water phase produced from the first step of sequential HTL. The bio-oil with a high yield and high nitrogen content is produced from water phase recycling HTL, for the simultaneous enrichment of nitrogen and carbon elements by reusing the water phase produced from HTL. At last, a method regulating the nitrogen element in water phase is proposed for the removal of nitrogen, the enrichment of carbon and the reduction of water consumption, which can be used for HTL of microalgae to efficiently produce low-
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