連續攪拌槽反應器
連續攪拌槽反應器(英語:,簡稱CSTR),也可以稱作vat-reactor或是backmix reactor,是化學工程中一個常見的化學反應器模型。CSTR通常是指在使用continuous agitated-tank reactor要達到指定出料條件時用來估計關鍵操作變數的模型[notes 1] 。該數學模型適用於所有流体:液體、氣體和漿體。
CSTR的行為通常會以連續理想攪拌槽反應器(Continuous Ideally Stirred-Tank Reactor,CISTR)建模,所有由CISTR進行的計算皆已假設其為完美攪拌。在一個完美攪拌的反應器中,出料的組成會與反應器內的組成一致,而組成與滯留時間及反應速率有關。以工程方面來說,一般會假設滯留時間是攪拌時間的5-10倍。CISTR模型通常用於簡化工程計算並可用於描述及研究反應器。然而實際上,反應只能接近而無法達到完美狀態,特別是在具工業規模的反應器中。
反應模型
假設反應為理想情況(完美攪拌),則在體積為的反應器內物料(莫耳數為)的總質量平衡可表示成:
(累積量=進料-出料+生成)
如果要建立一個非等溫或是單一反應的系統時,則必須要考慮額外的控制變數。如果系統被認為處於不穩定狀態,那麼就必須求解微分方程或是耦合微分方程組。
CSTR是一類具有多重穩態、極限循環和混沌等複雜行為的系統。
應用
CSTR通常應用於廢水處理過程中。CSTR可以促進稀釋速率,使它們能抵抗鹼性或酸性的揮發性脂肪酸廢棄物。與其他類型的反應器相比,CSTR的效率較低,因為它們需要更大的反應器體積以達到與其他反應器模型(如塞流反應器)相同的反應速率。
參見
- 層流反應器
- 微反應器
- 連續振動阻隔反應器
- 塞流反應器
備註
- Chemical reactors often have significant heat effects, so it is important to be able to add or remove heat from them. In a CSTR (continuous stirred tank reactor) the heat is added or removed by virtue of the temperature difference between a jacket fluid and the reactor fluid. Often, the heat transfer fluid is pumped through agitation nozzle that circulates the fluid through the jacket at a high velocity. The reactant conversion in a chemical reactor is a function of a residence time or its inverse, the space velocity. For a CSTR, the product concentration can be controlled by manipulating the feed flow rate, which changes the residence time for a constant chemical reactor. Occasionally the term "continuous" is misinterpreted as a modifier for "stirred", as in 'continuously stirred'. This misinterpretation is especially prevalent in the civil engineering literature. As explained in the article,"continuous" means 'continuous-flow' — and hence these devices are sometimes called, in full, continuous-flow stirred-tank reactors (CFSTR's).
參考資料
- Schmidt, Lanny D. . New York: Oxford University Press. 1998. ISBN 0-19-510588-5.
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