Some standard content:
Static mixer settings
HG/T20570.20—95
Compiled by: Process System Design Technology Center of the Ministry of Chemical Industry Approved by: Ministry of Chemical Industry
Implementation date: September 1, 1996
Compiled by:
Lu Zhenmin (specially invited), Xu Bin (specially invited), Gong Ren, Process System Design Technology Center of the Ministry of Chemical Industry
Auditor:
Wang Qingyu, China Huanqiu Chemical Engineering Company
Process System Design Technology Center of the Ministry of Chemical Industry Feng Shuyuan, Center for Design and Technology
1.0.1 Scope of application
1 Scope and type of application
Static mixers are used in liquid-liquid, liquid-gas, liquid-solid, gas-gas mixing, emulsification, neutralization, absorption, extraction, reaction and enhanced heat transfer processes. They can be used in a wide range of fluid viscosity (about 10°mPa·s) and in different flow patterns (laminar flow, transitional flow, smooth flow, complete flow). They can be operated intermittently or continuously, and are easy to directly enlarge. The following classification is briefly described. 1.0.1.1 Liquid-liquid mixing: From laminar flow to flow or fluids with a viscosity ratio as large as 1:10°mPa·s can achieve good mixing, the minimum diameter of the dispersed droplets can reach 1~2um, and the size distribution is uniform. 1.0.1.2 Liquid-gas mixing: The liquid-gas two-phase components can cause continuous renewal and full contact of the phase interface, thereby replacing the bubble tower or part of the sieve plate tower. 1.0.1.3 Liquid-solid mixing: a small amount of solid particles or powder (solids account for about 5% of the liquid volume) and liquid are forced to fully disperse under flow conditions to achieve the extraction or decolorization of the liquid. 1.0.1.4 Gas-gas mixing: cold and hot gas mixing, mixing of gases of different components. 1.0.1.5 Enhanced heat transfer: compared with the empty pipe, the heat transfer coefficient of the static mixer is increased by 8 times for hot gas cooling or cold gas heating with a very small heat transfer coefficient: 5 times for viscous fluid heating, and 8.5 times for condensation in the presence of a large amount of non-condensable gas; for polymer melts, it can reduce the temperature and viscosity gradient of the melt on the pipe section.
1.0.2 Types and structures of static mixers
1.0.2.1 This regulation is compiled based on five types of static mixer series products: SV, SX, SL, SH and SK (Note).
1.0.2.2Since the internal structures of the mixing units are different, the application occasions and effects are also different, the selection should be based on different application occasions and technical requirements. 1.0.2.3The use and performance comparison of five types of static mixers are shown in Table 1.0.2-1 and Table 1.0.2-2, and the structural diagram is shown in Figure 1.0.2. The static mixer consists of three parts: the outer shell, the internal parts of the mixing unit and the connecting flange.
Product application table of five types of static mixersWww.bzxZ.net
Table 1.0.2-1
Applicable to liquid-liquid, liquid-gas, gas-gas mixing, emulsification, reaction, absorption, extraction, and enhanced heat transfer processes with viscosity <10°mPa·s
d (Note) 3.5, suitable for clean media
d≥5, the application medium may be accompanied by a small amount of non-adhesive impurities. Applicable to medium and high viscosity liquid-liquid mixing with viscosity <10°mPa·s, reaction and absorption processes or mixing of polymer fluids, reaction processes, and better use effect when the processing volume is large. Applicable to chemical, petroleum, grease and other industries, viscosity 10°mPa·s or accompanied by mixing of polymer fluids, heat exchangers for simultaneous heat transfer, mixing and heat transfer reactions, heating or cooling viscous products and other unit operations. Applicable to mixing, emulsification, color matching, injection molding spinning, heat transfer and other processes in fine chemicals, plastics, synthetic fibers, mining and metallurgy and other departments. It is especially suitable for clean media with small flow and high viscosity (<10*mPa·s) with high mixing requirements. It is suitable for medium and high viscosity (≤10°mPa·s) fluids or liquid-solid mixing, reaction, extraction, absorption, plastic color matching, extrusion, heat transfer and other processes in chemical, petroleum, oil refining, fine chemicals, plastic extrusion, environmental protection, mining and metallurgy departments. It is especially suitable for viscous media with small flow and impurities. Performance comparison table of five types of static mixers Capacity
Dispersion and mixing effect
(Note ④) (enhancement multiple)
Applicable media conditions
(viscosity mPa·s)
Pressure drop comparison
(AP multiple)
Clean fluid
Table 1.0.2-2
Clean fluid
Fluids with impurities Fluids with impurities Fluids with impurities
Laminar flow pressure drop 18.6~23.5
(AP multiple)
(Note)
Complete flow pressure drop
(AP multiple)
2.43~4.47
=7~8 times
AP empty
Note: ①The five types of static mixers are classified and selected according to the provisions of the industry standard "Static Mixer" (JB/T7660-95). ②dh-unit hydraulic diameter, mm.
③Comparison conditions are the same medium, length (mixing equipment), the same or similar specifications, and the flow rate is 0.15m/s~0.6m/s when the pressure drop is not considered. The enhancement multiple compared with the empty pipe. ④18.6 times refers to AP when d≥5, and 23.5 times refers to △P when d<5. 512
(a) SV type
(c) SL type
(e) sK type
Figure 1.0.2 Structural diagram
(b) sx type
(d) H type
2.0.1 Flow pattern selection
2 Determination of main technical parameters
Determine the fluid flow pattern according to the fluid properties and mixing requirements. The flow pattern is controlled by the apparent empty tube inner diameter flow rate. 2.0.1.1 For the mixing, heat transfer and slow chemical reaction of medium and high viscosity fluids, it is suitable to operate under laminar flow conditions, and the fluid flow rate is controlled at 0.1~0.3m/s
2.0.1.2 For the mixing, extraction, neutralization, heat transfer and medium-speed reaction of low and medium viscosity fluids, it is suitable to work under transition flow or flow conditions, and the fluid flow rate is controlled at 0.3~0.8m/s. 2.0.1.3 For the mixing, emulsification, rapid reaction, pre-reaction and other processes of low-viscosity and difficult-to-mix fluids, it is suitable to work under end flow conditions, and the fluid flow rate is controlled at 0.8~1.2m/s2.0.1.4 For gas-gas and liquid-gas mixing, extraction, absorption, and enhanced heat transfer processes, the gas flow rate is controlled to work under full flow conditions of 1.2~14m/s. 2.0.1.5 For liquid-solid mixing and extraction, it is suitable to work under flow conditions. When designing and selecting, in principle, the liquid flow rate should be greater than the sedimentation velocity of the largest solid particles in the liquid. The sedimentation velocity of solid particles in liquid is calculated by Stokes' law:
V number of particles = d'g(e-1)/18 Vp
P reduced volume
V teaching - sedimentation velocity, m/s
d - maximum diameter of particles, m;
P number of particles, P reduced volume - density of particles and liquid under operating conditions, kg/m; u dynamic viscosity of liquid under operating conditions, mPa·sg
- acceleration of gravity, 9.81m/s2.
2.0.2 Relationship between mixing effect and length of static mixer (2.0.1)
The length of static mixer is determined by: first, the requirements of the process itself, and second, it is determined by basic experiments and practical application experience. Note ①.
2.0.2.1 Under flow conditions, the mixing effect has nothing to do with the length of the mixer, that is, after the length of the mixer is given, the mixing effect will not change significantly. The recommended length to tube diameter ratio is L/D=7~10 (SK type mixing length is equivalent to L/D=10~15). 2.0.2.2 Under transition flow conditions, the recommended length to tube diameter ratio is L/D10~15. 2.0.2.3 Under laminar flow conditions, the mixing effect is related to the length of the mixer, and the generally recommended length is L/D-10~514
2.0.2.4 For the extraction process that requires both uniform mixing and rapid stratification, under the condition of controlled flow type, the mixer length is L/D=7~10.
2.0.2.5 The volume percentage and viscosity ratio of the continuous phase and the dispersed phase of the fluid. If there is a huge difference, the mixing effect is related to the length of the mixer, and the upper limit (largest value) of the above recommended length is generally taken. 2.0.2.6 For emulsification, mass transfer, and heat transfer processes, the mixer length should be determined separately according to the process requirements. Note: ① The relationship between the mixing effect and the mixer length listed above refers to the data of liquid-liquid, liquid-gas, and liquid-solid mixing processes. For gas-gas mixing processes, the mixing is relatively easy, and L/D=2~5 is sufficient under the condition of complete flow. 2.0.3 Pressure drop calculation formula for static mixers For processes with high system pressure, the pressure drop generated by static mixers is relatively small and will not have a major impact on process pressure. However, for processes with low system pressure, pressure drop calculations must be performed after setting up static mixers to meet process requirements.
2.0.3.1 Pressure drop calculation formula for SV, SX, and SL types: fPen2L
(2.0.3-1)
(2.0.3—2)
The hydraulic diameter (d) is defined as the ratio of 4 times the void volume of the mixing unit to the wetted surface area (mixing unit and pipe wall area):
d=4(DL—AA8)/(2AA+元DL)
AP—pressure drop per unit length of static mixer, Paf—friction coefficient;| |tt||Pe—density of continuous phase fluid under working conditions, kg/m; - flow rate of mixed fluid (measured by inner diameter of empty tube), m/s; e-porosity of static mixer, e=1-A8; ds-hydraulic diameter, m
Re. Reynolds number;
p—viscosity of continuous phase under working conditions, Pa·s; L-length of static mixer, m;
—total single surface area of mixing unit, m\
A-SV type, single surface area of mixing unit per m2 volume, m/m. (2.0.3-3)
—material thickness of mixing unit, m, generally 8=0.0002m; D-inner diameter of tube, m.
The relationship between friction coefficient (f) and Reynolds number (Re) is shown in Table 2.0.3-1 and Figure 2.0.3. 2.0.3.2 SH and SK type pressure drop calculation formula AP=f
Rep=Dpeu/u
(2.0.3-4)
(2.0.3-5)
The relationship between the friction coefficient (f) and the Reynolds number (Rep) is shown in Table 2.0.3-2 and Figure 2.0.3. The pressure drop calculation value of the relationship formula allows a deviation of ±30%, which is applicable to liquid-liquid, liquid-gas, and liquid-solid mixing. SV, SX, and SL type static mixers f and Re. Relationship Mixer type
Laminar flow zone
Transition flow zone
Full flow zone
Complete turbulent zone
Relationship
Relationship
Re≤23
f=139/Ree
23
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