【作者】 程峰；

【导师】 叶世超；

【作者基本信息】 四川大学 ， 化学工程， 2003， 硕士

【摘要】 造粒技术广泛应用于国民经济的众多产业部门。振动流化床造粒可有效克服传统流化床或喷动床造粒颗粒粒度分布宽、动力消耗高的缺点，特别适合于中小生产规模的层式造粒过程。因此开展本课题研究，开发实用的造粒新技术以装备生产过程，不仅具有重要的学术价值，而且具有良好的应用前景。 本文以尿素或油菜籽颗粒为晶种，以不同浓度的尿素溶液为喷雾料浆，对振动流化床喷雾造粒特性进行了实验研究。实验在晶种上喷涂尿素熔融液或不同浓度的尿素溶液，使其以层式机理长大。着重研究了晶种类别、料液流量、料液浓度、流化气速、振动强度、喷嘴高度、雾化气压力等因素对颗粒成长的影响。实验结果表明：在u_f=1.86 u_mf操作气速下，油菜籽晶种颗粒生长速率明显高于尿素晶种；增大料液流量、料液浓度，减低喷嘴高度均有利于颗粒长大；本实验条件下，料液流量在u_f=1.5～2 u_mf时应小于8.5kg／h；保证颗粒处于正常流态化的前提下，较低的流化气速有利于造粒，流化气速过大或过小均不利于颗粒的生长，实验中一般控制在1.5～2 u_mf左右；适度振动有利于颗粒的生长，能够显著降低操作气速，可有效减轻粉尘生成量，克服结块现象，但振动强度过高颗粒生长速率反而减低，一般控制Γ=1～2为宜。 依据颗粒层式成长机理，根据物质守恒原理建立了颗粒层式生长的数学模型，提出了粒径长大的计算式。将粒径的理论预测值与实验测定值进行了比较，结果表明，两者间的误差在±8.8％以内，从而验证了模型的正确性。更多还原

【Abstract】 Granulating technique has been applied widely in many industries. The vibrated fluidized bed granulation will effectively overcome these disadvantages of wide distribution of particle size and high dissipation of energy, existing in the traditional fluidized bed and the spout-fluidized bed. The granulation technique in VFB is especially suitable for the medium and small scales process of layering granulation. Accordingly, investigating the granulation characteristics in VFB, developing new practical technique of granulation for the producing process have important scientific value and extensive application prospect.In this paper, urea particles and oil-vegetable seeds as initial particles are used to study granulation process in a vibrated fluidized bed, where the initial particles grow in a layered manner by spraying melt Urea solution on them and reached the required granule size. The coating efficiency and the particle’s size are measured under various experimental conditions. The effects of particle type, liquid spraying rate, liquid concentration, fluidizing gas velocity, vibrated intensity, nozzle position and atomization air pressure on the growth of particles have been analyzed and discussed. The experimental results show that at fluidizing gas velocity u=1.86umf, the oil-vegetable seeds get higher growth rate than the urea particles. Higher liquid spraying rate and higher urea solution concentration, lower nozzle position are preferred conditions for the growth of particles. However,liquid spraying rate should be limited to less than 8.5kg/h for u= 1.5-2.0 umf. On the premise that the particles were fluidized normally, lower gas velocity is fit for the particles growth. Gas velocity should be ranged from 1.5 to 2.0umf. Appropriate vibrated intensity is a preferred condition for the growth of particles, which can reduce gas velocity greatly, and deal with the crushing and the conglomeration of particles effectively. But the particles growth rate is decreased along with the overage vibrated intensity, should be ranged from 1 to 2.A mathematical model for the particles layering growth is developed based on the mechanism of layering growth and law of conservation of mass. A formula for calculating the particle diameter was also deduced. Comparing the predicated values with the experimental values, the results show that the deviation between them is ± 8.8%. Therefore the precision of the model is proved .更多还原