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Study on phosphate and Ammonium Removal using Magnesium Ammonium Phosphate Crystallization

磷酸镁铵结晶除磷除铵研究

基本信息

批准号：
07650929
负责人：
HIRASAWA Izumi
金额：
$ 1.15万
依托单位：
Waseda University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

Development of Ammonium and Phosphate ions removal process has been needed for removing them from wastewater exhausted in the process of sludge treatment, considering the concept of sludge treatment base in the metropolitan urban cite. In this research, basic investigation was done on the relation between crystallization characteristics and removability. Batch experiments were done to verify the crystallization characteristics of MAP (characteristics of water quality and operational conditions to crystallize MAP selectively), and selective crystallization conditions (temperature, pH,Mg/P molar ratio and NH4/P molar ratio) was obtained. Based on the results above, batch reactive crystallization experiments were performed, to investigate relation between the process of Magnesium and Phosphate removal and crystallization of MAP,and to clarify operational pH and Mg/P molar ratio for obtaining optimum removal efficiency and consider MAP crystallization based on nucleation and crystal growth phenomena, by measuring the dynamic change of crystal size and its shape through SEM.And also Alcohol addition method was investigated, to make clear the effect of alcohol on the solid-liquid equilibrium. Addition of alcohol lowered the solubility product.Process of MAP crystallization was considered to consist of reaction of ions, diffusion and surface integration stpes, and it was recognized that integration step determined the rate, when desirable product size was needed. Consequently design method on the material balance and crystallization rate was proposed, considering relation between crystallization rate and design method of the crystallizer.

考虑到大都市城市污泥处理基地的概念，需要开发去除污泥处理过程中排放废水中的铵态和磷酸态离子的工艺。本研究对结晶特性与可去除率之间的关系进行了基础研究。通过批量实验验证了MAP的结晶特性（水质特性和选择性结晶MAP的操作条件），得到了选择性结晶条件（温度、pH、Mg/P摩尔比和NH4/P摩尔比）。在此基础上，进行了间歇式反应结晶实验，研究了镁磷酸盐脱除过程与MAP结晶的关系，并通过扫描电镜（SEM）测量晶体尺寸和形状的动态变化，明确了获得最佳脱除效率的操作pH和Mg/P摩尔比，考虑了基于成核和晶体生长现象的MAP结晶。并研究了醇的加入方法，以明确醇对固液平衡的影响。酒精的加入降低了溶解度。认为MAP的结晶过程包括离子反应、扩散反应和表面集成反应三个阶段，并认识到当需要理想的产物尺寸时，集成步骤决定了速率。考虑结晶速率与结晶器设计方法的关系，提出了物料平衡与结晶速率的设计方法。