CN106290065B - A method and device for determining a non-Newtonian fluid stirring dead zone in a reactor - Google Patents

Abstract

The present invention relates to the method and devices that a kind of determining non-newtonian fluid stirs dead zone in reactor.The described method includes: obtaining the relation curve of the shear rate of the viscosity and reactor agitating device of material in reactor；The shear rate effect critical point of the relation curve is obtained according to preset algorithm；The shear rate of reactor agitating device is stirring dead zone when being less than the shear rate effect critical point.Described device is realized based on method as discussed above.The present invention can determine different stirring dead zones according to different non-newtonian fluids, so as to provide technical support for reactor design, parameter optimization and saving energy consumption.

Description

A method and device for determining a non-Newtonian fluid stirring dead zone in a reactor

technical field

The invention relates to a method and a device for determining a non-Newtonian fluid stirring dead zone in a reactor.

Background technique

The materials in the reactor are divided into two categories: Newtonian fluid and non-Newtonian fluid in terms of fluid properties. The fluid characteristics of Newtonian fluid are relatively clear, but the flow law of non-Newtonian fluid is more complicated. For non-Newtonian fluid, viscosity has an influence on its flow behavior. The greater the impact, the greater the viscosity, the easier it is to stick to the wall of the reactor, and the less likely it is to flow, thereby forming a dead zone and short flow in the reactor. It is difficult to directly, accurately and comprehensively predict the flow behavior and movement characteristics of materials in the reactor, making it difficult to improve and optimize the mixing effect of materials in the reactor. The reactor often has the phenomenon of uneven material mixing, resulting in obvious stratification, floating and dry crusting.

During the stirring operation, the dead zone reflects the material and is an important indicator for evaluating the stirring and mixing effect of the reactor. It can reflect the uniformity of mixing of the material in the reactor and the mass and heat transfer effect of the material in the reactor. Different researchers at home and abroad have different understandings and judgments on the dead zone in the reactor. In the exploration of the flow field in the stirred tank with straight inclined misaligned impellers, some scholars define the dead zone as the area where the velocity is less than or equal to 0.02m/s; in the numerical simulation of the anaerobic digestion reactor, the area where the velocity is less than 0.001m/s It is defined as the dead zone; in the CFD optimization of the maximum diameter of the blade-type stirring impeller in the high-viscosity system, the area where the velocity is less than 0.01v (blade velocity) is defined as the stirring dead zone. It can be seen that scholars do not have a unified scientific definition of the concept of dead zone. They only consider the problem from the perspective of fluid or stirring blade speed, and do not consider the problem in conjunction with the flow properties of the material in the reactor itself, so it often has limitations.

Contents of the invention

Aiming at the defects in the prior art, the present invention provides a method and device for determining the non-Newtonian fluid stirring dead zone in the reactor, which is used to solve the non-uniform stirring caused by non-Newtonian fluid under special circumstances in the prior art According to different non-Newtonian fluids, different stirring dead zones can be determined, which can provide technical support for reactor design, parameter optimization and energy saving.

In a first aspect, the present invention provides a method for determining a non-Newtonian fluid stirring dead zone in a reactor, the method comprising:

Obtain the relationship curve between the viscosity of the material in the reactor and the shear rate of the reactor stirring device;

Obtaining the shear rate effect critical point of the relationship curve according to a preset algorithm;

When the shear rate of the stirring device of the reactor is lower than the critical point of the shear rate effect, it is a stirring dead zone.

Optionally, the preset algorithm is a division method or a viscosity multiple method.

Optionally, the segmentation method includes:

Obtain the value range of material viscosity μ and shear rate γ;

Divide the value range into n equal parts, n=1, 2, ...;

When the shear rate γ satisfies: When , the shear rate γ _i is the critical point of shear rate effect.

Optionally, the viscosity multiple method includes:

Obtain the maximum viscosity value μ _max , limit viscosity value μ _min and reference viscosity μ ₁ of the material viscosity; the reference viscosity μ ₁ = m×μ _min ; m is a non-zero integer;

When the relationship curve falls into the range formed by the straight line y= _μ1 and the straight line y=μmin for the _first time, the corresponding shear rate is the critical point of the shear rate effect.

Optionally, the step of obtaining the relationship curve includes:

The HAAKE Viscotester-550 rotary viscometer is used to conduct rheological tests on materials with preset solid content to obtain the experimental curves of material viscosity and shear rate;

Sisko model equations were used to fit the experimental curves to obtain the material-shear stress equation, namely the relationship curve.

In the second aspect, the embodiment of the present invention also provides a device for determining the non-Newtonian fluid stirring dead zone in the reactor, the device comprising:

The relationship curve acquisition module is used to acquire the relationship curve between the viscosity of the material in the reactor and the shear rate of the reactor stirring device;

A critical point acquisition module, configured to obtain the shear rate effect critical point of the relationship curve according to a preset algorithm;

The stirring dead zone acquisition module is used for the stirring dead zone when the shear rate of the stirring device of the reactor is lower than the critical point of the shear rate effect.

Optionally, the critical point acquisition module acquires the shear rate effect critical point by a segmentation method or a viscosity multiple method.

Optionally, the critical point acquisition module is configured to perform the following steps:

Obtain the value range of material viscosity μ and shear rate γ;

Divide the value range into n equal parts, n=1, 2, ...;

When the shear rate γ satisfies: When , the shear rate γ _i is the critical point of shear rate effect.

Optionally, the critical point acquisition module is configured to perform the following steps:

Obtain the maximum viscosity value μ _max , limit viscosity value μ _min and reference viscosity μ ₁ of the material viscosity; the reference viscosity μ ₁ = m×μ _min ; m is a non-zero integer;

When the relationship curve falls into the range formed by the straight line y= _μ1 and the straight line y=μmin for the _first time, the corresponding shear rate is the critical point of the shear rate effect.

Optionally, the relationship curve acquisition module acquires the relationship curve through the following steps:

The HAAKE Viscotester-550 rotary viscometer is used to conduct rheological tests on materials with preset solid content to obtain the experimental curves of material viscosity and shear rate;

Sisko model equations were used to fit the experimental curves to obtain the material-shear stress equation, namely the relationship curve.

It can be seen from the above technical scheme that the present invention obtains the relationship curve between the viscosity of the material in the reactor and the shear rate of the reactor stirring device, and then adopts a preset algorithm to reach the critical point of the shear rate effect of the relationship curve, and the shear rate The difference between the velocity less than the critical point of the above-mentioned shear rate effect is regarded as the dead zone of stirring. It can be seen that the present invention can determine different dead zones according to different materials, so as to provide support for the design of the reactor, make the reactor work in the state of optimal efficiency, and save energy consumption.

Description of drawings

The features and advantages of the present invention will be more clearly understood by referring to the accompanying drawings, which are schematic and should not be construed as limiting the invention in any way. In the accompanying drawings:

Fig. 1 is a schematic flow chart of a method for determining a non-Newtonian fluid stirring dead zone in a reactor provided by an embodiment of the present invention;

Figure 2 is a schematic diagram of the principle of the segmentation method;

Fig. 3 is a schematic diagram of the principle of the limiting viscosity multiplier method;

Fig. 4 is a schematic diagram of the dead zone definition shown in Fig. 2 and Fig. 3 in an embodiment of the present invention;

Fig. 5 is a schematic diagram of the dead zone definition shown in Fig. 2 and Fig. 3 in another embodiment of the present invention;

Fig. 6 is a block diagram of a device for determining a non-Newtonian fluid stirring dead zone in a reactor provided by an embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

In the first aspect, an embodiment of the present invention provides a method for determining a non-Newtonian fluid stirring dead zone in a reactor, as shown in FIG. 1 , the method includes:

S1. Obtain the relationship curve between the viscosity of the material in the reactor and the shear rate of the reactor stirring device;

S2. Obtain the shear rate effect critical point of the relationship curve according to a preset algorithm;

S3. When the shear rate of the stirring device of the reactor is lower than the critical point of the shear rate effect, it is a stirring dead zone.

It should be noted that the materials in the reactor in the embodiment of the present invention are all non-Newtonian fluids with a certain solid content. Wherein, the solid content refers to the percentage of solid content in a certain mixture.

The preset algorithm in the embodiment of the present invention is the segmentation method or the viscosity multiple method.

Segmentation method: As shown in Figure 2, the data of the viscosity of the material in the reactor with the shear rate is measured experimentally, and the distribution is a discrete point. According to the experimental data, the material viscosity is μ∈[μ _min ,μ _max ], and the shear rate is γ∈[γ _min ,γ _max ]. Combining the relevant knowledge of discrete data, the viscosity μ∈[μ _min ,μ _max ] is divided into n equal parts, namely μ ₁ ,μ ₂ ,...μ _n (n=1,2,…), corresponding to The shear rate is γ ₁ , γ ₂ ,...γ _n . When the shear rate γ satisfies:

Then γ at this time is the critical point of shear rate effect γ ₀ .

Viscosity sum method: as shown in Figure 3, μ _min is the limit viscosity value of the material viscosity, μ _max is the maximum viscosity value of the material viscosity, μ ₁ =m×μ _min is the reference viscosity, and m is a non-zero integer. A straight line y=μ _min and a straight line y=μ ₁ are formed in the relation diagram. When the relationship curve falls into the range formed by the two straight lines for the first time, the shear rate at this time is the critical point γ ₀ of the shear rate effect.

The method for determining the non-Newtonian fluid stirring dead zone in the reactor provided by the embodiment of the present invention will be described in detail below by using the above two methods.

Embodiment one

In this example, the non-Newtonian fluid is fresh pig manure. A HAAKE Viscotester-550 rotational viscometer was used to conduct a rheological test on the fresh pig manure with a solid content of 24.92%, to obtain an experimental curve of viscosity and shear rate. According to the above experimental curve, the Sisko model equation was used to fit the viscosity-shear rate experimental curve, and the pig manure viscosity-shear stress equation was obtained as:

μ=0.0046+9.21·γ ^−0.6949 .

The viscosity of the above-mentioned fresh pig manure is μ∈[0.10,2.70], that is, the limit viscosity of pig manure is 0.10Pa·s.

As shown in Figure a in Figure 4, in the embodiment of the present invention, the viscosity range is equally divided, n=10, the shear rate γ ₁₀ =160.90s ^-1 at the tenth point, and its coordinates are (160.90, 0.2744), The shear rate at the ninth point is γ ₉ =59.35s ^-1 , and its coordinates are (59.35, 0.5441), and the shear rate at the eighth point is γ ₈ =33.11s ^-1 , and its coordinates are (33.11, 0.8139). According to the law of (γ _i -γ _i-1 )/γ _i ≥ 0.5, the shear rate is calculated by substituting the tenth, ninth and eighth points into the calculation, and it is verified by calculation that it satisfies

Thus, the critical point of shear rate effect γ ₀ is 160.90s ^-1 .

It should be noted that the above data of 0.50 in the embodiment of the present invention is set to illustrate the variation of discrete shear rates and adjacent shear rates in the experimental curve or relationship curve. Of course, those skilled in the art can make settings according to the usage scenario, which is not limited in the present invention.

As shown in figure b in Figure 4, the critical point γ ₀ of the shear rate effect is calculated by the viscosity multiplier method. Under the same condition of fresh pig manure, the shear rate of HAAKE Viscotester-550 rotational viscometer ranges from 0 to 600s ^-1 . The rheological experiment also used fresh pig manure with a solid content of 24.92%. The value of m is taken as 2.5, the straight line y=2.5×μmin and the relationship curve μ= _0.0046 +9.21·γ ^-0.6949 intersect for the first time at the point ( _165.76 , 0.27), that is to say, this intersection point is judged to be the critical point of shear rate effect γ0 is 165.76s ^-1 .

Embodiment two

In this example, the non-Newtonian fluid is raw sludge, and a HAAKE Viscotester-550 rotational viscometer is used to conduct a rheological test of the raw sludge with a solid content of 6.01%.

As shown in figure a of Figure 5, the raw sludge viscosity μ∈[0.10,4.09], that is, the limiting viscosity of raw sludge is 0.10Pa·s. For the range of viscosity μ∈[0.10,4.09], n=10 equal divisions are carried out, the shear rate at the tenth point is γ ₁₀ =177.34s ^-1 , and its coordinate is (177.34, 0.2778); Shear rate γ ₉ =80.38s ^-1 , and its coordinates are (80.38, 0.9030); at the eighth point, shear rate γ ₈ =50.60.11s ^-1 , and its coordinates are (50.60, 1.3025). According to the law of (γ _i -γ _i-1 )/γ _i ≥ 0.5, the shear rate is calculated by substituting the tenth, ninth and eighth points into the calculation, and it is verified by calculation that it satisfies:

Thus, the critical point of shear rate effect γ ₀ is 177.34s ^-1 .

As shown in figure a of Fig. 5, the critical point γ ₀ of the shear rate effect is determined by the limiting viscosity m multiplying rule. The shear rate range of HAAKEViscotester-550 rotational viscometer is 0～400s ^-1 . The rheological experiment also used raw sludge and fresh pig manure with a solid content of 6.01%. The value of m is taken as 5, and the straight line y=5× ^{μmin and the pig manure viscosity-shear rate curve μ=0.10+37.28·γ-0.8760} _intersect for the first time at the point (169.31, 0.50), that is, it is determined that the intersection point is the shear rate The effect critical point γ ₀ is 169.31s ^-1 .

In the second aspect, the embodiment of the present invention also provides a device for determining the non-Newtonian fluid stirring dead zone in the reactor, as shown in Figure 6, the device includes:

The relationship curve acquisition module M1 is used to acquire the relationship curve between the viscosity of the material in the reactor and the shear rate of the reactor stirring device;

The critical point obtaining module M2 is used to obtain the shear rate effect critical point of the relationship curve according to a preset algorithm;

Stirring dead zone acquisition module M3 is used for stirring dead zone when the shear rate of the reactor stirring device is lower than the critical point of the shear rate effect.

Optionally, the critical point acquisition module M2 acquires the shear rate effect critical point by using a division method or a viscosity multiple method.

Optionally, the critical point acquisition module M2 is configured to perform the following steps:

Obtain the value range of material viscosity μ and shear rate γ;

Divide the range of values into n equal parts, where n is a natural number;

When the shear rate γ satisfies: When , the shear rate γ _i is the critical point of shear rate effect.

Optionally, the critical point acquisition module M2 is configured to perform the following steps:

Obtain the maximum viscosity value μ _max , limit viscosity value μ _min and reference viscosity μ ₁ of the material viscosity; the reference viscosity μ ₁ = m×μ _min ; m is a non-zero integer;

When the relationship curve falls into the range formed by the straight line y= _μ1 and the straight line y=μmin for the _first time, the corresponding shear rate is the critical point of the shear rate effect.

Optionally, the relationship curve acquisition module M1 acquires the relationship curve through the following steps:

The HAAKE Viscotester-550 rotary viscometer is used to conduct rheological tests on materials with preset solid content to obtain the experimental curves of material viscosity and shear rate;

Sisko model equations were used to fit the experimental curves to obtain the material-shear stress equation, namely the relationship curve.

It can be seen from the above that the device provided by the embodiment of the present invention is implemented based on the method described above, so it can solve the same technical problem and achieve the same technical effect, which will not be repeated here.

In the present invention, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance. The term "plurality" means two or more, unless otherwise clearly defined.

Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention. within the bounds of the requirements.

Claims (4)

1. a method for determining non-Newtonian fluid stirring dead zone in reactor, it is characterized in that, described method comprises: Obtain the relationship curve between the viscosity of the material in the reactor and the shear rate of the reactor stirring device; Obtaining the shear rate effect critical point of the relationship curve according to a preset algorithm; When the shear rate of the reactor stirring device is less than the critical point of the shear rate effect, it is the dead zone of stirring; The preset algorithm is a segmentation method or a viscosity multiple method; Wherein, the segmentation method includes: Obtain the value range of material viscosity μ and shear rate γ; Divide the value range into n equal parts, n=1, 2, ...; When the shear rate γ satisfies: , the shear rate γ _i is the critical point of the shear rate effect; Described viscosity multiple method comprises: Obtain the maximum viscosity value μ _max , limit viscosity value μ _min and reference viscosity μ ₁ of the material viscosity; the reference viscosity μ ₁ = m×μ _min ; m is a non-zero integer; When the relationship curve falls into the range formed by the straight line y= _μ1 and the straight line y=μmin for the _first time, the corresponding shear rate is the critical point of the shear rate effect. 2. The method according to claim 1, wherein the step of obtaining the relationship curve comprises: The HAAKE Viscotester-550 rotary viscometer is used to conduct rheological tests on materials with preset solid content to obtain the experimental curves of material viscosity and shear rate; Sisko model equations were used to fit the experimental curves to obtain the material-shear stress equation, namely the relationship curve. 3. A device for determining non-Newtonian fluid stirring dead zone in reactor, is characterized in that, described device comprises: The relationship curve acquisition module is used to acquire the relationship curve between the viscosity of the material in the reactor and the shear rate of the reactor stirring device; A critical point acquisition module, configured to obtain the shear rate effect critical point of the relationship curve according to a preset algorithm; The stirring dead zone acquisition module is used for the stirring dead zone when the shear rate of the reactor stirring device is less than the critical point of the shear rate effect; The critical point acquisition module obtains the shear rate effect critical point by a segmentation method or a viscosity multiple method; Wherein, when the critical point acquisition module adopts the segmentation method, it is used to perform the following steps: Obtain the value range of material viscosity μ and shear rate γ; Divide the value range into n equal parts, n=1, 2, ...; When the shear rate γ satisfies: , the shear rate γ _i is the critical point of the shear rate effect; Or when the critical point acquisition module adopts the viscosity multiple method, it is used to perform the following steps: Obtain the maximum viscosity value μ _max , limit viscosity value μ _min and reference viscosity μ ₁ of the material viscosity; the reference viscosity μ ₁ = m×μ _min ; m is a non-zero integer; When the relationship curve falls into the range formed by the straight line y= _μ1 and the straight line y=μmin for the _first time, the corresponding shear rate is the critical point of the shear rate effect. 4. The device according to claim 3, wherein the relationship curve obtaining module obtains the relationship curve through the following steps: The HAAKE Viscotester-550 rotary viscometer is used to conduct rheological tests on materials with preset solid content to obtain the experimental curves of material viscosity and shear rate; Sisko model equations were used to fit the experimental curves to obtain the material-shear stress equation, namely the relationship curve.