超临界水氧化体系中固体颗粒在管道内沉积及输运特性研究

Study on the deposition and transport property of solid particles in supercritical water oxidation system

针对污泥超临界水氧化系统中存在的固体颗粒沉积及堵塞问题,以印染污泥为研究对象进行了其中固体颗粒在系统管线中沉积及输运特性的研究。首先,对污泥中可溶性无机盐在超临界水中析出的固体颗粒及不溶性固体的粒径分布进行了分析。然后,通过流体高速流动方法来解决固体颗粒在系统管线中的堵塞问题,分析了Davies公式计算超临界水中固体颗粒临界流速的可行性;并以此为依据获得了3741kg/h的印染污泥在25MPa、50℃~550℃条件下的临界流速和临界管径。最后,对不同管径管道内的不溶性固体颗粒在550℃超临界水中的流动特性进行了数值模拟;结合临界管径及流体压降的分析得出,本印染污泥系统的超临界水氧化管式反应器的最优内径是55mm,进一步表明临界管径对超临界水系统管径选择的指导意义。

With respect to the solid particles deposition and blocking issues during the supercritical water oxidation treatment of sludge,the precipitation and transport behaviors of solid particles in textile sludge during supercritical water are investigated.At first,the property and particle size distribution of both insoluble solid and soluble inorganic salt precipitated from supercritical water are examined.The high-speed flow method is proposed to solve the blocking problem of system pipelines.The feasibility of Davies equation to calculate the critical velocity in supercritical water is analyzed,which is employed in the treatment system of 3741 kg/h textile sludge,obtaining critical velocities and critical diameters at 25 MPa,50℃~550℃.Finally,simulation for the flow of insoluble solid particles in supercritical water with different pipe diameters at 550℃is conducted.Combing with the critical diameter and pressure drop,it is found that the optimal pipe inner diameter of the supercritical water oxidation reactor of this textile sludge system is 55 mm,further verifying the significance of critical diameter to guide the pipeline design of supercritical water system.