Production of highly soluble foliar fertilizer in a spouted bed dryer

ABSTRACT The drying process can be useful to change the particulate structure, improving the powder solubility. In this study, we investigated the drying of foliar fertilizer in a spouted bed using polyethylene pellets as inert particles to improve its solubility. A 23 factorial experimental design was used to evaluate how the powder yield and moisture were affected by the feeding time, intermittency time, and feed atomizer position. The spouting instability caused powder retention on the bed wall, which decreased the powder recovery efficiency by 2.3-26.6%. Although the powder recovery efficiency was low, the solubility time was reduced by 5.9 times, probably due to particle agglomeration, which increased the amorphous phase of the fertilizer. Design alterations, suggested by the CFD data, can increase spouted bed stability and facilitate centralized spouting. Based on this, the spouted bed drying technique was applied, and it effectively increased the solubility of commercial fertilizer, thus, incorporating more desirable characteristics for field applications.摘要 干燥工艺可改变颗粒结构，提升粉体溶解度。本研究以聚乙烯颗粒（polyethylene pellets）作为惰性颗粒（inert particles），在喷动床（spouted bed）中对叶面肥进行干燥处理以提升其溶解度。采用2³因子实验设计，考察进料时间、间歇时间与进料雾化器位置对粉体收率与含水率的影响。喷动不稳定会导致粉体附着于床壁，使粉体回收率降低2.3%~26.6%。尽管粉体回收率较低，但粉体溶出时间缩短了5.9倍，这可能源于颗粒团聚提升了肥料的非晶相占比。计算流体动力学（CFD）数据表明，对装置进行改造可提升喷动床稳定性，促进集中喷动。基于上述结果，本研究应用喷动床干燥工艺，有效提升了商品叶面肥的溶解度，使其具备更适宜田间应用的特性。