自然循环蒸发器循环推动力及传热研究
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摘要
蒸发器是广泛应用于化工蒸发单元操作的化工设备,耗能巨大。传统蒸发器在运转过程中，加热管原料液侧容易出现析晶污垢，大大降低传热系数。论文首先介绍了污垢类型，结垢机理及影响结垢速度的主要因素，污垢所造成的经济损失及控制，防止和清洗方法。
论文从结构上对蒸发器进行改进，改型后可算为一种新型蒸发器。其主要改进包括将加热室从原来的上升管内沸腾段的下方移到了循环管的中下部较好地利用了空间，降低设备高度；加装副加热室增加其汽化量，增大循环推动力；加装助推器以利启动，也是负压效保证循环流速所必需；添加纽带这种除垢防垢和传热强化元件。然后进行了纽带除垢防垢的可行性试验，得出了其在线防垢及强化传热功能能否发挥的关键－流速条件及纽带螺距等结构因素对纽带转动快慢的的影响。运用因次分析方法得出了插有纽带管段阻力计算准数关联式，并通过具体实验求出参数值，得出压力降的具体准数关联式表达式，据此调节阀门开度以模拟热态试验工况条件。
冷态试验先假定沸腾段蒸发为平衡蒸发，在此前提下推导了理论循环计算压头公式。然后通过实测数据计算的压头与理论压头比较，得出沸腾段蒸发为不平衡蒸发的结论，且不平衡蒸发程度在35％-50％之间，并通过热态试验加以验证。
热态试验中以常压效为例进行了试验，由于这种蒸发器是逆循环，又特别提出了具体操作步骤及注意事项。试验的结果表明不平衡蒸发程度为55％左右，证明了冷态模型确使较好的反映实际情况以及在常压效中纽带在无助推条件下可以平稳转动发挥其在线清洗和强化传热功能。
As chemical equipments, evaporators are widely used in chemical plants. A large amount of heating energy is cost in it. During the operation of traditional evaporators, however, crystal fouling is often found on the inside of the heating pipes. This paper analyzes the type of the fouling, the fouling mechanism and the main factors that influence the fouling rate. A narration about the economic loss resulting from the fouling has been made. How to control, to prevent and to clean the fouling are introduced.
This paper aims at improving the structure of traditional evaporators as followed. Firstly, the heating chamber is employed to circulating pipe from the ascending pipe to make fuller use of the space and to reduce the height of the equipment；secondly, an auxiliary heating chamber is installed to enhance the circular drive；thirdly, a roll booster is used to start the circulation and to guarantee the vacuum unit working safely；fourthly, A type of twisted stripe was introduced which can prevent, clean the fouling and enhance the heating effect. On that base, an experiment is conducted to prove the possibility for the twisted stripe cleanness. A series of data are acquired. The data show the necessary circling velocity is vital for the twisted stripes to work. Through dimension-analyzing method, the relating equation of resisting force that exists in the heating tube with a twisted stripe is achieved. Those unknown coefficients in the equation are attained by another experimentation. Then we can draw the detailed expressing equation. According to
the equation, We adjust the opening-degree of the valve to simulate the working condition of an evaporator in the factory.
On the assumption that the evaporation is a complete process in the mocking experiment, the theoretical circling prompting-force equation is achieved. By comparing the result from the theoretical equation with the practical, we find there is a great gap between them, and their proportion is largely the same, about 35%-50%. So we can conclude that the evaporating process in the boiling tube in the evaporator is not a hundred-percent one.
During the process of the heating trial, some special procedures are mentioned because of the particularity of circulation. The experiment result shows the degree of evaporation is nearly 55%. It also proves the self-rotational twisted stripe can rotate smoothly to full function.
论文从结构上对蒸发器进行改进，改型后可算为一种新型蒸发器。其主要改进包括将加热室从原来的上升管内沸腾段的下方移到了循环管的中下部较好地利用了空间，降低设备高度；加装副加热室增加其汽化量，增大循环推动力；加装助推器以利启动，也是负压效保证循环流速所必需；添加纽带这种除垢防垢和传热强化元件。然后进行了纽带除垢防垢的可行性试验，得出了其在线防垢及强化传热功能能否发挥的关键－流速条件及纽带螺距等结构因素对纽带转动快慢的的影响。运用因次分析方法得出了插有纽带管段阻力计算准数关联式，并通过具体实验求出参数值，得出压力降的具体准数关联式表达式，据此调节阀门开度以模拟热态试验工况条件。
冷态试验先假定沸腾段蒸发为平衡蒸发，在此前提下推导了理论循环计算压头公式。然后通过实测数据计算的压头与理论压头比较，得出沸腾段蒸发为不平衡蒸发的结论，且不平衡蒸发程度在35％-50％之间，并通过热态试验加以验证。
热态试验中以常压效为例进行了试验，由于这种蒸发器是逆循环，又特别提出了具体操作步骤及注意事项。试验的结果表明不平衡蒸发程度为55％左右，证明了冷态模型确使较好的反映实际情况以及在常压效中纽带在无助推条件下可以平稳转动发挥其在线清洗和强化传热功能。
As chemical equipments, evaporators are widely used in chemical plants. A large amount of heating energy is cost in it. During the operation of traditional evaporators, however, crystal fouling is often found on the inside of the heating pipes. This paper analyzes the type of the fouling, the fouling mechanism and the main factors that influence the fouling rate. A narration about the economic loss resulting from the fouling has been made. How to control, to prevent and to clean the fouling are introduced.
This paper aims at improving the structure of traditional evaporators as followed. Firstly, the heating chamber is employed to circulating pipe from the ascending pipe to make fuller use of the space and to reduce the height of the equipment；secondly, an auxiliary heating chamber is installed to enhance the circular drive；thirdly, a roll booster is used to start the circulation and to guarantee the vacuum unit working safely；fourthly, A type of twisted stripe was introduced which can prevent, clean the fouling and enhance the heating effect. On that base, an experiment is conducted to prove the possibility for the twisted stripe cleanness. A series of data are acquired. The data show the necessary circling velocity is vital for the twisted stripes to work. Through dimension-analyzing method, the relating equation of resisting force that exists in the heating tube with a twisted stripe is achieved. Those unknown coefficients in the equation are attained by another experimentation. Then we can draw the detailed expressing equation. According to
the equation, We adjust the opening-degree of the valve to simulate the working condition of an evaporator in the factory.
On the assumption that the evaporation is a complete process in the mocking experiment, the theoretical circling prompting-force equation is achieved. By comparing the result from the theoretical equation with the practical, we find there is a great gap between them, and their proportion is largely the same, about 35%-50%. So we can conclude that the evaporating process in the boiling tube in the evaporator is not a hundred-percent one.
During the process of the heating trial, some special procedures are mentioned because of the particularity of circulation. The experiment result shows the degree of evaporation is nearly 55%. It also proves the self-rotational twisted stripe can rotate smoothly to full function.
引文
[1] 姚玉英，黄凤廉，陈常贵等．化工原理，天津科学技术出版社，1992.
[2] Hans Muller-Steinhagen．Fouling of Heat Exchanger Surface, Chemistry & Industry, 1995, (3).
[3] A.P.WATKINSON. Fouling of Augmented Heat Transfer Tubes, Heat Transfer Engineering, 1990, (11).
[4] 日本实用节能机器全书编委会．实用节能全书（译本），化工出版社，北京，1987.
[5] 陆震维，陈玉梅．化工装置清洗技术现状和展望，化工进展，1992，(4)．
[6] 黄祥健，电厂真空冷凝器自转式塑料纽带清洗技术，湘潭大 学硕士论文，2000．
[7] 胡修慈．侧沸式蒸发器及其循环计算，化工机械，1980，(5)．
[8] 杨祖荣，W.J.Frederick．蒸发器中结垢速率研究，化工学报，1992，(2)．
[9] 郑成，李宽宏．垂直管道浸取器的空气升液研究．化学反应工程与工艺，1995，(3)．
[10] 戴干策，陈敏恒．化工流体力学，化学工业出版社，1988．
[11] 张正荣．传热学（第二版），北京，1983．
[12] 赵景利，王秀珍等． 对自然循环蒸发器的技术改造与开发，化学工程，1993，(3)．
[13] 王兆中．论列文蒸发器改为反循环的必要性，海湖盐与化工，1988，(4)．
[14] 卢赤杰．外沸腾自然循环蒸发器，化学工程，1991，(5)．
[15] 沈慧云．强制循环蒸发装置及运行情况，氯碱工业，1985，(3)．
[16] 顾全德．关于蒸发设备防垢问题的研究，海盐与化工，1981，(1)．
[17] 沈自求，沙庆云等．易结垢盐类溶液蒸发的防垢与强化，新疆化工，1991，(4)．
[18] в.т.гаряжа等．煮糖过程的强化，轻工出版社．1989，4．
[19] 胡修慈．外沸式蒸发器的循环计算，河北工学院学报，1980，(4)．
[20] 沈自求，徐维勤，丁洁．中国专利，CN85102830．
[21] 李道杰，姜新月，王进印等．碳酸钾生产过程中蒸发节能技术研究，化工机械，1987，(5)．
[22] 刘素云，大庆石油化工总厂有相变换热器的调研报告．全国化工炼油机械有相变研讨会．1991，1．
[23] 刘素云，大庆石油化工总厂稀释蒸汽发生塔中压蒸汽再沸器(Ei-235)泄漏原因分析及改进措施．1989，9．
[24] 罗运禄，崔乃英等．窄缝蒸发器的初步实验及其结果，甘蔗糖业，1989，(5)．
[25] K．SANDQUIST，Rheological properties and evaporation of black liquor at high dry-solids content，pulp & paper，1984，(3)．
[26] 污垢的防治与对策．科学出版社，1995．
[27] 朱冬生，卜穗安，谭盈科．管壳式换热器的防垢、强化传热技术，海湖盐与化工，1995，(5).
[2] Hans Muller-Steinhagen．Fouling of Heat Exchanger Surface, Chemistry & Industry, 1995, (3).
[3] A.P.WATKINSON. Fouling of Augmented Heat Transfer Tubes, Heat Transfer Engineering, 1990, (11).
[4] 日本实用节能机器全书编委会．实用节能全书（译本），化工出版社，北京，1987.
[5] 陆震维，陈玉梅．化工装置清洗技术现状和展望，化工进展，1992，(4)．
[6] 黄祥健，电厂真空冷凝器自转式塑料纽带清洗技术，湘潭大 学硕士论文，2000．
[7] 胡修慈．侧沸式蒸发器及其循环计算，化工机械，1980，(5)．
[8] 杨祖荣，W.J.Frederick．蒸发器中结垢速率研究，化工学报，1992，(2)．
[9] 郑成，李宽宏．垂直管道浸取器的空气升液研究．化学反应工程与工艺，1995，(3)．
[10] 戴干策，陈敏恒．化工流体力学，化学工业出版社，1988．
[11] 张正荣．传热学（第二版），北京，1983．
[12] 赵景利，王秀珍等． 对自然循环蒸发器的技术改造与开发，化学工程，1993，(3)．
[13] 王兆中．论列文蒸发器改为反循环的必要性，海湖盐与化工，1988，(4)．
[14] 卢赤杰．外沸腾自然循环蒸发器，化学工程，1991，(5)．
[15] 沈慧云．强制循环蒸发装置及运行情况，氯碱工业，1985，(3)．
[16] 顾全德．关于蒸发设备防垢问题的研究，海盐与化工，1981，(1)．
[17] 沈自求，沙庆云等．易结垢盐类溶液蒸发的防垢与强化，新疆化工，1991，(4)．
[18] в.т.гаряжа等．煮糖过程的强化，轻工出版社．1989，4．
[19] 胡修慈．外沸式蒸发器的循环计算，河北工学院学报，1980，(4)．
[20] 沈自求，徐维勤，丁洁．中国专利，CN85102830．
[21] 李道杰，姜新月，王进印等．碳酸钾生产过程中蒸发节能技术研究，化工机械，1987，(5)．
[22] 刘素云，大庆石油化工总厂有相变换热器的调研报告．全国化工炼油机械有相变研讨会．1991，1．
[23] 刘素云，大庆石油化工总厂稀释蒸汽发生塔中压蒸汽再沸器(Ei-235)泄漏原因分析及改进措施．1989，9．
[24] 罗运禄，崔乃英等．窄缝蒸发器的初步实验及其结果，甘蔗糖业，1989，(5)．
[25] K．SANDQUIST，Rheological properties and evaporation of black liquor at high dry-solids content，pulp & paper，1984，(3)．
[26] 污垢的防治与对策．科学出版社，1995．
[27] 朱冬生，卜穗安，谭盈科．管壳式换热器的防垢、强化传热技术，海湖盐与化工，1995，(5).