TW476661B - Impeller draft tube agitation for gas-liquid mixing using stirred tank reactor - Google Patents

Abstract

An improved design for the agitation system in stirred tank reactors for gas-liquid reactions is disclosed. The improvement involves the use of a draft tube with axial impeller(s) located inside the draft tube and redial impeller(s) located outside the draft tube.

Description

476661 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 ____-__ B7___ V. Description of the Invention (1) The present invention relates to an improved design of a system for energizing gas-liquid reactions in a stirred tank reactor. In particular, the invention relates to a system comprising a draft tube, one or more axial impellers and one or more radial impellers. The novel agitation design provides improved contact between the liquid and gas phases within the reactor. Stirred tank reactors (STRs) are very popular in chemical processes such as fermentation, hydrogenation, phosgenation, neutralization, gasification and organic oxidation. In this stirred tank reactor, The gas and liquid phases are in close contact for mass transfer. The design of this STR has important effects on bubble dispersion, interface area ("a"), bubble surface transients, and mass transfer coefficient "KL". The design of the STR also has an impact on the power required to run the impeller system at a specific rate. It has been published in the art that many different mixing systems attempt and achieve maximum mass transfer between the gas and liquid phases. These include U.S. Patent Nos. 4,231,974, 5,108,662, 5,371,283, 5,451,349, 5,523,474, 5,536,875, and 5,696,285. These conventional hybrid experiments can be improved because they neither have the best mass transfer coefficient nor can they minimize this power requirement. The invention includes a deflector along with both axial and radial impellers. The (or) axial impeller train is disposed inside the cylinder formed by the deflector tube, and the (or) radial impeller train is disposed below the cylinder formed by the deflector tube. The fluid flow and mass transfer characteristics of such a system are superior to those of a conventional agitation system. This paper size applies to China National Standard (CNS) A4 (210 X 297 mm) (Please read the precautions on the back before filling this page) Order -------- Line!

I 4 476661

V. Description of the invention (2) Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs

Further advantages and features of the present invention will be apparent from reading the detailed description of the present invention and referring to the following drawings. Brief Description of the Drawings Fig. 1 is a cross-sectional view of a device corresponding to the present invention. Figure 2 is a graph of the observed KLa versus gas flow rate for three different agitation rates in a system with a draft tube. Fig. 3 'is a graph of the observed KLa versus gas flow rate for three different actuation rates in a system without a diversion tube. As seen in FIG. 1, the present invention includes a transmission shaft 1; at least one axial impeller 2 attached to the transmission shaft 1 to move fluid in a direction generally parallel to the transmission shaft; and attached to the transmission shaft At least one radial impeller 3 of 1 moves the fluid in a direction generally perpendicular to the transmission shaft 11; and a deflector 4, which is a generally open cylinder. As clearly shown in the first circle, when the agitation system 5 is placed in a stirred tank reactor 10, the transmission shaft 1 extends through the flow guide tube 4, and the one or more axial impellers 2 are It is disposed in the duct tube 4, and the one or more radial impellers 3 are disposed outside the duct tube 4. The agitating tank reactor 10 having the agitating system 5 must be arranged in an upright form, as shown in FIG. 1, so that the radial impellers 3 are disposed below the guide tube 4. Similarly, as shown in Fig. 1, the inlet of the deflector 4 is preferably tilted away from the drive shaft 1, but this is not necessary. When the transmission shaft 1 rotates around its shaft 11, the axial impellers 2 are moved in a direction generally parallel to the transmission shaft 11 to apply the Chinese National Standard (CNS) A4 to the paper contents Specifications (210 X 297 mm). 11! 11!-I _ I II I! F Please read the notes on the back before filling this page) A7

V. Description of the invention (3) (Please read the notes on the back before filling in this page) and move through the guide tube 4. Axial impeller trains are generally known in the art and any such impeller can be used in the present invention. For example, a double spiral impeller, such as described in U.S. Patent No. 5,108,662, or an airfoil blade impeller, such as described in U.S. Patent No. 4,231,974, may be used in the present invention. Other suitable axial impellers include oblique blade turbines, high-efficiency impellers (such as the A-310 model of Lightnin Mixing Co., Chemineer,

Inc. HE-3 and ΕΚΑΤΟ Rueher and Mischtechnik GmbH

VlSC〇pr〇P), single screw or marine propeller (such as Lightnin Mixing

Co. A-315 or A-320, Chemineer, Inc. MT-4 or MY-4). Usually the number of axial impellers depends on the viscosity of the working medium. The more viscous the working medium, the more axial impellers are required. It is contemplated that the present invention may include one to several axial impellers 2, but preferably two. Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs at the same time when the transmission shaft 1 rotates around its axis π, the radial impellers 3 act to move the reactor contents away from the transmission shaft 1 and When the radial impeller 3 is disposed below the guide tube 4, the radial impeller 3 faces the outer surface of the guide tube 4. The centerline of the (etc.) radial impeller must be far enough below the end of the guide tube to avoid substantial interference. Usually this is in the range from about 1/8 of the radial impeller diameter distance to about 7/8 of the radial impeller diameter distance, and is preferably about 2/3. Radial impellers are also generally known in the art, and any design can be used in the present invention. Radial impellers generally suitable for the present invention include flat blade impellers, Rushton lmpeliers, SCABA (SRGT) impellers, and BT-6 models of Chemineer, Inc. The optimum number of radial impellers used depends on the liquid. The paper size is in accordance with China National Standard (CNS) A4 (210 X 297 mm) 6

Description of the Invention (Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs

The ratio of body southness to the diameter of the groove is determined. In most cases, a single radial impeller will be used in the present invention, but in some reactors, such as high fermentation tanks, most radial impellers can be used. Diversion tubes and their variations are also widely known in the art, and those teachings are generally applicable to the present invention. For example, the draft tube can be slotted to provide liquid back to the center of the draft tube if the liquid level does not exceed the top of the draft tube for some reason. In addition, it is advantageous to use an upright guide vane on the inner surface of the guide pipe to change the direction of the tangential flow to the axial flow. If a guide vane is used in the guide pipe, it is preferable that the guide vane has a width of the inner diameter of the guide pipe of 0.8 to 01 and a gap of the inner diameter of the guide pipe of 0.016 to 0.021. Moreover, the use of the deflector blades near the bottom of the cylinder formed by the deflector is particularly seen in U.S. Patent No. 5,536,875 and can also be used in the present invention. Although the size of the diversion tube 4 is not important to the present invention, it has been found that the optimal radius of the diversion tube is 0.707 of the groove radius. The use of a guide tube of this radius allows the cross-sectional area of the groove inside the guide tube to be equal to the cross-sectional area of the groove outside the guide tube. As can be seen in Figure 1, the guide tube 4 optionally contains a conical funnel section 6 at the inlet end of the guide tube. It is believed that this part will help direct the flow of the reactor contents. The bevel angle must be between 30 and 60 degrees, with 45 degrees being optimal. The hypotenuse must not be too long, as this restricts the flow around the top of the duct. It is preferred if the length of the hypotenuse is from 0 to about 1/4 of the inner diameter of the diversion tube, and a length of about 1/12 is most preferred. The invention can be used in stirred tank reactors of any size. A structural support attached to the side of the reactor wall can be used to adapt the guide tube to the paper size of China National Standard (CNS) A4 (210 X 297 male «) I ^ -------- ^» — — — — 1 — I 1 ^ (Please read the notes on the back before filling out this page) 476661 A7 V. Description of the invention (held in place, as known in the conventional technology. Along the wall of the reactor Alternatively, guide vanes may be used, as notified in the conventional technique. If guide vanes are used, four guide vanes spaced apart from each other by about 90 ° are preferred. Any known technique may be used. Devices to bring the reactive gas into the tank. These include ring sprayers and preferably tubular or nozzle sprayers. Printed by the Consumer Property Cooperative of the Intellectual Property Bureau of the Ministry of Economics. Specific details of the structure of the invention, such as materials, dimensions Etc. are not to be considered as a limitation of the present invention. Instead, these details can be adjusted as required to produce a preferred embodiment for any particular application. The effects of the present invention can be seen in the following examples: Example Use a transient technique to measure The mass transfer coefficient. This dynamic outgassing technique consists of injecting the reactor with pure nitrogen until all oxygen has been desorbed from the working medium. After that, the injected gas quickly changes from nitrogen to oxygen. The transient oxygen concentration is then measured. These measurements can then be used to calculate the volume mass transfer coefficient (KLa) of the system. Such physical techniques can be applied to a homogeneous mixing system and KLa to small values due to the slow induction time of the dissolved oxygen probe gas. Usually these Physical technology can be applied to KLa < 1 / r, where τ: is the induction time of the dissolved oxygen detection gas. An ASME disc bottom plexiglastm groove with an inner diameter of 0.045m (0.08m3) is used to perform the gas- Liquid mixing experiment. Four flat guide vanes spaced 90 ° apart are used to promote axial mixing. The agitation system includes two high-efficiency downward pumping axial impellers (Model A-310 of Lightnin Mixing Ltd.) and one Radial Gas Dispersion Rushton Disc Turbine (Please read the precautions on the back before filling this page) Order -------- Line | _ -1 · «I ^ 1 ^ 1 ϋ · 1 ϋ I n mmM9 ft — A—- The paper size applies the Chinese National Standard (CNS) A4 specification (210 X 297 male *) 476661 A7 B7 V. Description of the invention (6) (Lightnin R-100). Sprayed through a ring-shaped sprayer set under the radial impeller The gas. Deionized water was used as the working medium. The speed and torque of the agitator were measured by a proximity flow meter and a dynamometer, respectively, and the degree of oxygen dissolved in the water was measured by two oxygen sensors ( The electric sensing DO probe has a sensing time of 2 seconds for 95% saturation. The degree of agitation (gassed power is 0.26-2.6 watt / kg) is sufficient to produce a 0.012-0.046 m / s (that is, 1-5 VVM ) Uniform gas dispersion at surface gas velocity. A CAMILEtm 2000 data detection system was used to collect all data. First determine the KLa of a system without a duct at different gas flow rates and drive shaft speeds (power). Use ANSI / ASCE Standard 2-91 titled "Measurement of Oxygen Transfer in Clean Water" with non-linear regression (known as JMP in the statistical suite software, owned by SAS Institute, Cary, North Carolina, USA) In order to determine the correlation between the mass transfer coefficient KLa (l / sec) and the surface gas velocity Vsg (m / sec). These results are shown in Table 1 and illustrated graphically in Figure 2. — — — — — — — — — — — — — — ^ · 1111111 ^ «— — — — — 1 — (Please read the notes on the back before filling out this page) Printed on paper by Employees’ Cooperatives, Intellectual Property Bureau, Ministry of Economic Affairs Standards are applicable to China National Standard (CNS) A4 specifications (210 X 297 mm) 9 476661 Α7 Β7 V. Description of the invention (7) Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs, Table 1. There is no mass transfer coefficient for the diversion tube Speed N [rpm] Gas flow rate Q [scfm] Power per mass ε [w / kg] Surface gas velocity Vsg [m / s] Mass transfer coefficient KLa [l / sec] 300 4 2.66 0.0122 0.063 300 6 2.30 0.0182 0.070 300 9 2.14 0.0274 0.077 300 12 2.21 0.0365 0.081 250 4 1.66 0.0122 0.057 250 6 1.55 0.0182 0.058 250 9 1.49 0.0274 0.068 250 12 1.52 0.0365 0.072 250 15 1.49 0.0456 0.074 200 4 1.06 0.0122 0.043 200 6 1.02 0.0182 0.046 200 9 0.95 0.0274 0.053 200 12 0.96 0.0365 0.064 200 15 0.94 0.0456 0.067 Then a diversion tube with an inner diameter of 0.3m (to achieve the annular area within and around the diversion tube Of about the same superficial gas velocity) disposed within the mixing system. Then measure κρ at different gas flow rates and drive shaft speed (power). The results with this diversion tube are shown in Table 2 and illustrated in Figure 3. '' This paper size applies to China National Standard (CNS) A4 (210 X 297 mm) JH0 -------- Order-!!! line, * ------------- ----- (Please read the precautions on the back before filling this page) 10 476661 A7 _B7_ V. Description of Invention (8) Table 2

N [rpm] Qfscfm] 300 4 300 6 300 9 300 12 300 15 250 4 250 6 250 9 250 12 250 15 200 4 200 6 200 9 200 12 200 15 With the mass transfer coefficient speed of the guide tube gas flow rate per Mass power Surface gas velocity Mass transfer coefficient ε [w / kg] Vsg [m / s] KLa [l / sec] 2.21 0.0121 0.075 1.85 0.0182 0.081 1.53 0.0273 0.094 1.50 0.0365 0.099 1.45 0.0456 0.099 1.28 0.0121 0.062 1.08 0.0182 0.069 0.90 0.0273 0.075 0.85 0.0365 0.083 0.88 0.0456 0.092 0.70 0.0121 0.045 0.65 0.0182 0.051 0.61 0.0274 0.059 0.60 0.0365 0.063 0.52 0.0456 0.069 — — — — — — — — — — — — — — — — — — — ^ · 1111111 (Please read the first Please fill in this page for attention) Printed by the Consumer Cooperative of Intellectual Property Bureau of the Ministry of Economic Affairs

From these results, it can be seen that the presence of the deflector increases the KLa beyond the KLa of a conventional system without a deflector, increases the gas holdup and reduces the power pumped by the same motor speed. This paper size is in accordance with Chinese National Standard (CNS) A4 (210 X 297 mm) 11 476661 A7 _B7_ V. Description of the invention (9) Component number comparison 1 ... drive shaft 2 ... axial impeller 3 ... radial impeller 4 ... guide Flow tube 6 ... Tapered funnel part 10 ... Stirred tank reactor 11 ... Shaft (Please read the precautions on the back before filling this page) Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 1 i ϋ > 1 ·· II ϋ ϋ ϋ II -II ϋ I ϋ > 1 ϋ ϋ ϋ ϋ ϋ ϋ ^ 1 ϋ ϋ ϋ ϋ · ϋ ϋ. This paper size applies to China National Standard (CNS) A4 (210 X 297) Mm) 12

Claims (1)

4/6661 A8B8C8D8 Patent application scope Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs A type of agitation system suitable for use in a stirred tank reactor, including ... a a drive shaft; b at least attached to the drive shaft An axial impeller for moving fluid in a direction generally parallel to the drive shaft; c. At least one radial impeller attached to the drive shaft for moving fluid in a direction generally perpendicular to the drive shaft; d · — A deflector, which is shaped as a cylinder and has an opening at both ends of the cylinder; wherein the transmission shaft extends through the deflector, and the axial impeller train is arranged in the deflector cylinder, and the radial direction An impeller train is arranged outside the guide tube cylinder. 2. The system according to item 丨 of the patent application scope, wherein the transmission shaft is arranged in an upright form, and the radial impeller train is arranged below the guide tube. 3. The system according to claim 2 of the stated patent scope, wherein the diversion tube further includes a conical funnel-shaped portion on the top of the cylinder. 4. According to the system in item 2 of the scope of patent application, the impeller system is in the form of a double spiral. 5. The system according to item 2 of the scope of patent application, wherein the pumping impeller system is a high-efficiency impeller. 6. Green according to item 2 of the patent application, which has two axial impellers. 7. The system according to item 2 of the scope of patent application, wherein the diversion tube includes a cutout to allow liquid to enter the inner shirt I π of the diversion tube.卩 without going over the top of the tube. < Please read the precautions on the back before filling this page) # · Order-i-line · This paper size is applicable to China National Standard (CNS) A4 (210 X 297 Public Love 1 13