流化床造粒法回收猪场废水中氮磷:鸟粪石颗粒的形貌与组成

Phosphorus recovery from swine wastewater by struvite granulation in fluidized bed: morphology and composition of granules

针对现有流化床鸟粪石造粒法回收废水中氮磷时缺乏有效的方法定量描述颗粒的形貌及对应的组分含量,综合图像法、FTIR、XRD、元素组成分析和物料衡算等方法,分析了分段式流化床不同区域的颗粒形貌及对应的组分情况。研究结果表明,流化床不同区域内上升流速分别为15.0、30.6和60.0mm/s,对应鸟粪石颗粒平均粒度分别为703、963和1747μm,相应的颗粒形貌为絮团、团聚式颗粒和包层式颗粒。颗粒的主要成分为鸟粪石（MgNH_4PO_4·6H_2O,MAP）、钾型鸟粪石（MgKPO_4·6H_2O,MKP）、无定型磷酸钙（Ca_3（PO_4）_2·xH_2O,ACP）其中MAP含量均大于92%,ACP1.26%～1.75%,MKP含量为3.75%～3.91%,有机物含量低于0.4%。回收的颗粒中Cr、As、Cd和Pb等重金属含量低于现行的化肥重金属控制标准（GB/T23349-2009）限值,有效降低了重金属污染的风险,提高了回收颗粒的品质。

Image analysis,in combination with Fourier transform infrared spectroscopy（ FTIR）,X-ray diffraction（ XRD）,and material balance,was adopted to clarify the morphological and compositional changes in struvite pellets during struvite recovery from swine wastewater in a three-section fluidized-bed reactor. The results revealed that under upflow velocities of 15. 0,30. 6,and 60. 0 mm / s,condensed flocs,agglomerates,and coated granules with mean particle sizes of 703,963,and 1 747 μm,respectively were detected in the reactor.Struvite（ Mg NH_4PO_4·6H_2O,MAP） was the dominant component of the granules（ weight ratio〉 92%）,and was mixed with K-struvite（ MgKPO_4·6H_2O,MKP）（ 3. 75% to 3. 91%）,amorphous calcium phosphate（ Ca_3（PO_4）_2·xH_2O）（ 1. 26% to 1. 75%） and organic matter（ less than 0. 4%）. It was noted that the contents of heavy metals in the collected granules were below the legal limits prescribed by the Chinese National Fertilizer Standards（ GB / T 23349-2009）.