【作者】 李平；

【导师】 梁斌； 吴鸿欣；

【作者基本信息】 四川大学 ， 化学工程， 2003， 硕士

【摘要】 随着我国大化肥装置不断上马(目前已有30套)，加之进口化肥的冲击以及农民种田积极性降低，化肥销售日趋困难。为了赢得较好的化肥销售市场，各大化肥厂必须千方百计提高尿素质量。除了尿素的化学含量外，尿素颗粒的结块、粉尘含量等外观质量是影响尿素销售的重要因素。 根据国内外成功经验，结合了多年来建峰化工厂在防尿素结块与粉化方面的工作，指出了对尿素的水分、粉尘及强度控制是防止尿素结块与粉化的关键。通过造粒喷头的结构和性能剖析，筛选出两种造粒喷头进行性能测试，结果表明，可以根据季节变化选择不同喷头。 论文分析了添加甲醛对强度的影响，给出了SNAM尿素生产工艺添加甲醛最适宜控制量。还研究了晶种造粒对提高尿素颗粒强度的作用机理，并提出了添加造粒晶种的工艺流程。通过试验采用了一种新型防结块剂，结果表明，其对控制尿素产品的水分有明显的效果。 设计了利用尿素喷头内设温度探头，对喷头内液位进行自动探测，自动调节造粒喷头转速，充分保证了造粒质量。从控制尿素水分角度出发，推出了根据气候变化情况计算尿素出塔控制温度的经验公式。通过详细的计算分析，建立起了针对60万吨／年大化肥尿素造粒装置的百叶窗开度自动控制理论，并在DCS系统开发了百叶窗开度自动控制程序。更多还原

【Abstract】 With increasing capacity of urea fertilizer production, enlarging import and lowering growth of farm requirement, fertilizer urea is meeting great challenges in domestic market of China. Urea producers must pay more attention on the qualities of urea in order to keep their market share. Beside the chemical composition, the appearance qualities, such as, caking properties and dust content, are very important for the vendition of urea product.Based on the analysis of successful experience over the world and progress of Jianfeng Plant in the prevention of caking and pulverization of urea, it was found that the control of moisture, dust and mechanic strength is the key for the prevention of caking and pulverization of urea. The effects of sprayer structure on the mechanic properties of granulated urea were studied. Two potential sprayers were tested. The results show that different sprayers should be switched in different seasons.The influence of adding formaldehyde on the granule strength of urea was investigated. An optimal adding amount of formaldehyde was recommended for the SNAM urea production process. Furthermore, the affecting mechanism of crystal seeds on the granule urea was discussed. A new granulation process with crystal seeds was proposed. Considering the moisture controlling in storage of urea, a new anti-caking additive was used. It obviously lowered the moisture adsorption in the storage period.A temperature sensor was fixed inside the sprayer. It was used to detect the melted urea level inside the sprayer. The temperature detected was back fed to theDCS to control the rotation speed of sprayer. It ensures the spraying urea is distributed uniformly inside the tower. The moisture content of granule urea is an important factor for the mechanic properties of urea granule. To control the moisture content in granule, a formula was developed to calculate the granule temperature at the outlet of granulation tower according to different climate condition. The model was used to be an objective function for the control of air velocity in the tower. A systematic model for controlling blinds of air stream was built up for the 600 kt/a urea device in Jianfeng Plant and automatic regulation was realized.更多还原