Zhalehrajabi Ehsan, Lau Kok Keong, Ku Shaari Ku Zilati, Zahraee Seyed Mojib, Seyedin Seyed Hadi, Azeem Babar, Shaaban Azizah
Department of Chemical Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar 32610, Perak, Malaysia.
CO2 Research Centre (CO2RES), Institute of Contaminant Management, Universiti Teknologi PETRONAS, Bandar Seri Iskandar 32610, Perak, Malaysia.
Materials (Basel). 2019 Jul 20;12(14):2320. doi: 10.3390/ma12142320.
Granulation is an important step during the production of urea granules. Most of the commercial binders used for granulation are toxic and non-biodegradable. In this study, a fully biodegradable and cost-effective starch-based binder is used for urea granulation in a fluidized bed granulator. The effect of binder properties such as viscosity, surface tension, contact angle, penetration time, and liquid bridge bonding force on granulation performance is studied. In addition, the effect of fluidized bed process parameters such as fluidizing air inlet velocity, air temperature, weight of primary urea particles, binder spray rate, and binder concentration is also evaluated using response surface methodology. Based on the results, binder with higher concentration demonstrates higher viscosity and higher penetration time that potentially enhance the granulation performance. The viscous Stokes number for binder with higher concentration is lower than critical Stokes number that increases coalescence rate. Higher viscosity and lower restitution coefficient of urea particles result in elastic losses and subsequent successful coalescence. Statistical analysis indicate that air velocity, air temperature, and weight of primary urea particles have major effects on granulation performance. Higher air velocity increases probability of collision, whereby lower temperature prevents binder to be dried up prior to collision. Findings of this study can be useful for process scale-up and industrial application.
造粒是尿素颗粒生产过程中的一个重要步骤。大多数用于造粒的商业粘结剂有毒且不可生物降解。在本研究中，一种完全可生物降解且具有成本效益的淀粉基粘结剂被用于流化床造粒机中进行尿素造粒。研究了粘结剂性能（如粘度、表面张力、接触角、渗透时间和液桥粘结力）对造粒性能的影响。此外，还使用响应面方法评估了流化床工艺参数（如流化空气入口速度、空气温度、初级尿素颗粒重量、粘结剂喷雾速率和粘结剂浓度）的影响。基于结果，较高浓度的粘结剂表现出较高的粘度和较长的渗透时间，这可能会提高造粒性能。较高浓度粘结剂的粘性斯托克斯数低于临界斯托克斯数，这会增加聚并速率。尿素颗粒较高的粘度和较低的恢复系数导致弹性损失并随后成功聚并。统计分析表明，空气速度、空气温度和初级尿素颗粒重量对造粒性能有主要影响。较高的空气速度增加了碰撞概率，而较低的温度可防止粘结剂在碰撞前干燥。本研究的结果可用于工艺放大和工业应用。
