CN108607239A - Spiral microchannel demulsification control method on the basis of Dean Secondary Flows - Google Patents

Abstract

The present invention discloses a helical microchannel demulsification control method based on Dean's secondary flow in the field of liquid-liquid two-phase separation technology. The optimal Dean secondary flow in the microchannel is controlled as the basis. When the De number is controlled between 6.5 and 8, the fluid flow rate is controlled according to the size of the spiral microchannel used, so that the demulsification occurs in the spiral microchannel. Dean secondary flow with best results. The beneficial effect of the present invention is: take the size of the spiral microchannel that adopts as benchmark to control the speed that the fluid flows through, when the De number of Dean's secondary flow in the spiral microchannel is controlled at 6.5～8, the spiral microchannel can be made The Dean secondary flow with the best effect on demulsification appears in the process, thus avoiding the operation of repeatedly adjusting the liquid flow rate, and can directly determine the liquid flow rate to achieve the best demulsification effect, further improving the demulsification efficiency and demulsification quality.

Description

Demulsification Control Method of Spiral Microchannel Based on Dean's Secondary Flow

technical field

The invention relates to the technical field of liquid-liquid two-phase separation, in particular to a spiral microchannel demulsification control method based on Dean secondary flow.

Background technique

Liquid-liquid two-phase separation is an important operation unit in the chemical process, and the corresponding high-efficiency separation equipment is an indispensable part of many important processes. Liquid-liquid two-phase separation is widely used in various important processes such as crude oil collection, petroleum transportation, reaction separation, extraction, and sewage treatment. With the introduction of the national environmental protection concept and the development of modern industry, there is a higher demand for new demulsification technology with wide application range, environmental friendliness, high separation efficiency and low energy consumption.

At present, more advanced separation technologies include cyclone separation, electric demulsification, inclined plate sedimentation, membrane method, biological method, etc. Among them, the microchannel demulsification method is more representative, such as CN104001349A. The microchannel demulsification separator adopts A three-dimensional helical microchannel, hydrophilic channel plate and hydrophobic channel plate were created. The liquid-liquid two-phase mixture spirals forward along the microchannel, passing through the hydrophilic channel plate and hydrophobic channel plate continuously, which promotes the collision and aggregation of the dispersed phase droplets. And, so that the two-phase mixture finally separated. The paper only mentions the droplet inertial migration mechanism with Dean secondary flow coupling in the helical channel, but the effect of this mechanism on demulsification is not clear, and the demulsification effect of the three-dimensional helical microchannel cannot be fully exerted, so it is necessary Do further research on this.

Contents of the invention

In order to overcome the deficiencies such as the influence of the Dean secondary flow on the demulsification without consideration of the existing spiral microchannel, resulting in poor demulsification effect, the technical problem to be solved by the present invention is: to provide a spiral microchannel based on the Dean secondary flow Channel breakage control method.

The technical solution adopted by the present invention to solve its technical problems is:

The spiral microchannel demulsification control method based on Dean's secondary flow comprises the following steps:

a. Assemble a three-dimensional spiral microchannel demulsification device, use a syringe pump or a plunger pump to connect the liquid to be treated with the liquid inlet hole of the demulsification device, and connect the liquid outlet hole of the demulsification device to the liquid storage container through a pipeline;

b. Start the syringe pump or plunger pump to make the liquid flow through the spiral microchannel. The dispersed phase droplets in the emulsion are subjected to the shear force of the microchannel, the vortex directional migration of the spiral microchannel, and the interface between hydrophilic and hydrophobic surfaces. Promote the collision and polymerization of adjacent droplets to form large droplets, and settle and separate from the emulsion to achieve demulsification;

c. Adjust the flow rate of the syringe pump or the plunger pump to achieve the best demulsification effect, wherein the flow rate of the syringe pump or the plunger pump is controlled on the basis of the best Dean secondary flow in the spiral microchannel. The De number of Dean secondary flow in the spiral microchannel is: where the Reylow number Re is:

where d _i is the spiral diameter, d _c is the equivalent diameter of the pipe, Re is the Reynolds number, ρ is the emulsion density, v is the fluid velocity, μ is the viscosity coefficient,

When the De number is controlled between 6.5 and 8, the fluid flow rate can be controlled according to the size of the spiral microchannel used, so that the Dean secondary flow with the best effect on demulsification can appear in the spiral microchannel.

Furthermore, the fluid flow rate can also be used as a quantitative measure before demulsification, and the De number can be satisfied by selecting the appropriate size of the helical microchannel, so that the Dean secondary flow that has the best effect on demulsification appears in the helical microchannel.

Further, the De number in step c is 7.2.

The beneficial effects of the present invention are: control the speed of the fluid flow based on the size of the adopted spiral microchannel, when the De number of the Dean secondary flow in the spiral microchannel is controlled at 6.5 to 8, the spiral microchannel can be The Dean secondary flow which has the best effect on demulsification appears in the process, thus avoiding the operation of repeatedly adjusting the liquid flow rate, and can directly determine the liquid flow rate to achieve the best demulsification effect, further improving the demulsification efficiency and quality.

Detailed ways

Below in conjunction with embodiment the present invention is further described.

The spiral microchannel demulsification control method based on Dean's secondary flow comprises the following steps:

a. Assemble a three-dimensional spiral microchannel demulsification device, use a syringe pump or a plunger pump to connect the liquid to be treated with the liquid inlet hole of the demulsification device, and connect the liquid outlet hole of the demulsification device to the liquid storage container through a pipeline;

b. Start the syringe pump or plunger pump to make the liquid flow through the helical microchannel. The water droplets are subjected to the shear force of the microchannel, the directional migration of the eddy current of the helical microchannel, and the interfacial action of the hydrophilic and hydrophobic surfaces to promote the generation of adjacent water droplets. Collision polymerization forms large water droplets, which settle and separate from the emulsion to achieve demulsification;

c. Adjust the flow rate of the syringe pump to achieve the best demulsification effect, wherein the flow rate of the syringe pump is controlled for the purpose of forming the best Dean secondary flow in the spiral microchannel, and the Dean secondary flow in the spiral microchannel The De number is: where the Reylow number Re is:

where d _i is the spiral diameter, d _c is the equivalent diameter of the pipe, Re is the Reynolds number, ρ is the emulsion density, v is the fluid velocity, μ is the viscosity coefficient,

When the De number is controlled between 6.5 and 8, the fluid flow rate can be controlled according to the size of the spiral microchannel used, so that the Dean secondary flow with the best effect on demulsification can appear in the spiral microchannel.

The structure of the three-dimensional spiral microchannel described in the article is roughly the same as that of the microchannel with the publication number CN104001349A, and the basic usage method is similar. However, when the treatment liquid is introduced, the existing method is to continuously adjust the liquid by observing the separation in the liquid storage container. The flow rate is until the separation is stable; and the liquid flow rate in the present application is to make the Dean secondary flow with a De number of 6.5 to 8 appearing in the three-dimensional helical microchannel as a benchmark. After theoretical analysis and a large number of comparative experiments, it can be concluded that the Dean secondary flow with De number between 6.5 and 8 can achieve the best demulsification effect. Therefore, during the demulsification operation, the flow rate of the liquid can be directly calculated through the De number and the size of the three-dimensional helical microchannel adopted, without repeated adjustments, which can greatly improve the demulsification efficiency and quality.

The peak of the De number is 7.2, that is, when the De number is less than 7.2, as the De number increases, the coalescence between droplets can be promoted, and the demulsification efficiency increases; when the De number is greater than 7.2, as the De number increases, It is not conducive to the coalescence between droplets, and the demulsification efficiency decreases, and the demulsification efficiency reaches the highest when De is equal to 7.2.

Before the demulsification, the fluid flow rate can also be used as a quantitative, and by selecting the appropriate size of the helical microchannel to meet the Dean number between 6.5 and 8, so that the Dean II which has the best effect on demulsification appears in the helical microchannel. secondary flow.

Example:

The spiral microchannel adopts: a flat spiral microchannel with a channel width of 5 mm, a channel height of 200 μm, and a spiral diameter of 5 mm. Calculated according to the above formula:

When the inlet volume flow rate is 8mL/min, the De number is 7.2, and the demulsification efficiency of a single passage through the channel can reach 25%;

When the inlet volume flow rate is 4mL/min, the De number is 3.6, and the demulsification efficiency of a single pass through the channel can reach 16%;

When the inlet volume flow rate is 12mL/min, the De number is 10.8, and the demulsification efficiency of a single pass through the channel can reach 14%.

It can be seen that when the De number is 7.2, the demulsification efficiency is the highest and reaches the peak value.

The present invention controls the velocity of the fluid flowing through based on the size of the spiral microchannel adopted, so that the De number of the Dean secondary flow in the spiral microchannel is controlled at 6.5 to 8, and the demulsification occurs in the spiral microchannel. The Dean secondary flow with the best effect avoids the operation of repeatedly adjusting the liquid flow rate, and can directly determine the liquid flow rate to achieve the best demulsification effect, further improving the efficiency and quality of demulsification, and has good practicability and It also fills the technical gap in this field and provides a theoretical basis for similar research.

Claims (3)

1. take Dean secondary flow as the benchmark spiral microchannel demulsification control method, it is characterized in that, may further comprise the steps: a. Assemble a three-dimensional spiral microchannel demulsification device, use a syringe pump or a plunger pump to connect the liquid to be treated with the liquid inlet hole of the demulsification device, and connect the liquid outlet hole of the demulsification device to the liquid storage container through a pipeline; b. Start the syringe pump or plunger pump to make the liquid flow through the spiral microchannel, and the dispersed phase droplets of the emulsion are subjected to the shear force of the microchannel, the eddy current directional migration of the spiral microchannel, and the interfacial interaction between the hydrophilic and hydrophobic surfaces , promote the collision and polymerization of adjacent droplets to form large droplets, and settle and separate from the emulsion to achieve demulsification; c. Adjust the flow rate of the syringe pump or the plunger pump to achieve the best demulsification effect, wherein the flow rate of the syringe pump or the plunger pump is controlled on the basis of the best Dean secondary flow in the spiral microchannel. The De number of Dean secondary flow in the spiral microchannel is: where the Reynolds number Re is: where d _i is the spiral diameter, d _c is the equivalent diameter of the pipe, Re is the Reynolds number, ρ is the emulsion density, v is the fluid velocity, μ is the viscosity coefficient, When the De number is controlled between 6.5 and 8, the fluid flow rate can be controlled according to the size of the spiral microchannel used, so that the Dean secondary flow with the best effect on demulsification can appear in the spiral microchannel. 2. the helical microchannel demulsification control method based on Dean's secondary flow as claimed in claim 1, is characterized in that: before carrying out demulsification, also can fluid flow rate as quantitative, and by selecting the helical microchannel of suitable size To satisfy the De number, so that the Dean secondary flow with the best effect on demulsification appears in the spiral microchannel. 3. the helical microchannel demulsification control method based on Dean secondary flow as claimed in claim 1 or 2, characterized in that: the De number in the step c is 7.2.