Scale-up Methods for Fast Competitive Chemical Reactions in Pipeline Mixers
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- 作者：Rupert Anthony (Tony) Taylor ; W. Roy Penney ; and Hanh X. Vo
- 刊名：Industrial & Engineering Chemistry Research
- 出版年：2005
- 出版时间：August 3, 2005
- 年：2005
- 卷：44
- 期：16
- 页码：6095 - 6102
- 全文大小：192K
- 年卷期：v.44,no.16(August 3, 2005)
- ISSN：1520-5045
文摘
An experimental study investigated the scale-up methods for fast competitive/consecutivereactions in static mixers. Twelve-element Kenics helical element mixers of 1/8-, 1/4-, and 1/2-in.-diameters were tested using the fourth Bourne reaction system as a test reaction. The fourthBourne reaction is a parallel reaction system where the acid-catalyzed hydrolysis of 2,2-dimethoxypropane (DMP) is conducted in parallel with the neutralization of HCl with NaOH.With very rapid mixing, the HCl catalyst is neutralized by NaOH and minimal hydrolysis ofDMP occurs. The main feed contained 200 mol/m3 of DMP and 210 mol/m3 of NaOH (5%stoichometric excess relative to HCl in the side stream). The side stream, which was introducedthrough two radial cylindrical feed ports at the midpoint of the third mixer element, contained2000 mol/m3 of HCl. The two streams were combined in the mixer at a volumetric flow ratio of10:1, main to side. By analysis of the reactor effluent for DMP hydrolysis products of acetoneand methanol, the effectiveness of the mixer-reactor in promoting the acid-base reaction wasquantified. The parameters used to evaluate the static mixer performance at different sizes are(1) the Reynolds number (experiment Re varied from 550 to 17 000), (2) the turbulent energydissipation rate, and (3) the residence time in the mixer. At low flow rates and low energydissipation, micromixing controlled and equal power dissipation was an acceptable scale-upcriterion. At high flow rates and high energy dissipation, mesomixing controlled and equalresidence time was the proper scale-up criterion. The recommended scale-up procedure is asfollows: (1) Maintain geometrical similarity. (2) Maintain the following parameters constant:(A) ratio of the main to side feed rates, (B) ratio of the main to side feed velocities, (C) ratio ofthe reagent concentration in the main and side feeds, (D) number of mixing elements in themixer, and (E) side feed orientation and location relative to the mixing elements. (3) Analyzethe experimental data to determine the controlling mixing mechanism, either micromixing ormesomixing: (A) for micromixing control, scale-up using equal power dissipation; (B) formesomixing control, scale-up using equal mixer residence time.