JPH06331535A - Measuring method of pulverulent-body adhesion force in fluid state - Google Patents

Abstract

PURPOSE:To measure a pulverulent-body adhesion force in a comparatively weak or fluid state by using a fluid layer not only at room temperature and under normal pressure but also in an industrial usage atmosphere by operating the pulverulent-body adhesion force of a pulverulent body in which a fluidization state whose minimum fluidization velocity and air-bubble start velocity are different under a measuring condition exists. CONSTITUTION:A primary regression line which has been found from a pulverulent-body differential pressure at a minimum fluidization velocity Umf, an air-bubble start velocity Umb, a pulverulent-body stationary-layer height Hlp, a pulverulent-body average particle size dp and a superficial velocity at the Umf of lower is extended, a pulverulent-body differential- pressure estimation point at the Umb is found, the difference DELTAP* between a pulverulent-body differential pressure at the Umb and a pulverulent-body differential pressure at the Umf is measured, and a pulverulent-body adhesion force deltaf is found by the following formula: sigmaf=DELTAP*/4*(Umf<0.5>+Umb<0.5>/Umb<0.5>*dp/Hlp. By the definition formula, the pulverulent-body adhesion force of a weak powder or in a fluid state can be measured not only at room temperature and under normal pressure but also in an industrial usage atmosphere. When the pulverulent- body adhesion force is used, a method of keeping the fluid state optimum, e.g. of making the distribution of a particle size optimum, can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus design for handling powder (for example, a dust collector, powder transportation, etc.) and an industry for controlling the flow state of powder (for example, Fluidized Catalyst Crack).
ing, acrylonitrile, oxychlorination, fluidized bed reaction of maleic anhydride, etc., fluidized bed combustion, etc.).

[0002]

2. Description of the Related Art In the present specification, a particle refers to each grain and a powder refers to an aggregate of particles. The powder formed by the mutual interparticle force has a force for keeping the shape of the powder, and a certain amount of stress is required to break the powder. The stress necessary for breaking the powder is hereinafter referred to as the powder adhesive force.

The powder adhesion is described in, for example, the Handbook of Powder Engineering, First Edition p.9.
As shown in 0-270, it is important as one of the basic properties of powder. Conventionally, various devices for measuring the powder adhesion force in the non-fluid state have been developed, and the main measurement method is the tensile rupture method,
There are shear method and rupture fracture method. These methods require compression molding of the powder as a preparation for the measurement of the powder adhesive force. (Refer to p.126-129 for the first edition of Powder Engineering Handbook) In this case, the powder cannot stay on the measuring cell unless it can be compression molded, and industrially fluidized bed reaction, such as FCC, acrylonitrile, and methacrylonitrile production. It has not been possible to measure powders with a relatively small powder adhesion, as used in.

The conventional method for measuring the adhesive force of powder is a method for measuring the adhesive force of a cake-like powder which is compression-molded, and is used in a fluidized state which is industrially used, for example, in a fluidized bed or pneumatic transportation. It has been impossible to measure the powder adhesion force of the above with conventional technology. Generally, the powder adhesive force changes depending on the powder porosity, and the powder adhesive force, the powder porosity, the mutual particle force, the particle coordination number, and the average particle diameter are σ _f , ε, Φ, k, and d, respectively.
_{If p} , then the Rumpf equation (Rumpf, C
hem. Ing. Tech., 30, 144 (1958)).

[0005]

## EQU2 ## σ _f = (1-ε) / π * k * Φ / d _p ² (2) where the average particle size is the powder The distribution was obtained by the laser light diffraction method shown in p.24 of the first edition of the Engineering Handbook, and the median diameter was used. Generally, the powder porosity is the smallest in the compressed state, and then increases in the stationary state and the fluidized state in that order.

[0006] As an example of a method for estimating the powder adhesion force in a state where the powder porosity is high, that is, in a fluidized state, several types of powder having a low porosity, that is, a powder in a compressed state, are used by a conventional method, for example, a tensile fracture method. There is a method of measuring the body adhesion force and estimating the powder adhesion force in a fluid state according to the equation (2) (for example, Tubaki and Jimbo, Powder Technology, 37,
219-227 (1984)). However, since the above estimation method is an extrapolation-based estimation, the error in the measured data greatly affects the estimated value, and the relationship between the particle coordination number and the powder porosity is still unclear, so It has the drawback of large errors. Therefore, it is not possible at present to estimate or extrapolate the powder adhesive force in the fluid state from the measurement result of the powder adhesive force in the compressed state.

On the other hand, as a method for measuring the powder adhesion force which does not require compression molding, for example, a method using static electricity has been reported (Pontius and Snyder, Powder Technolog).
y, 68,159-162 (1991)). However, since it requires an electric charge, the device becomes complicated and compression molding is unnecessary, but it is still stationary measurement, and it is impossible to measure in a fluid state that is industrially used. Is.

FIG. 1 schematically shows the range of measurement of the powder adhesive force of the prior art. As shown in FIG. 1, the method for measuring the powder adhesion force in the state where the compression-molded powder has a small porosity includes the tensile fracture method, the shear method, and the rupture fracture method described above.
In addition, as a method for measuring the powder adhesion force in a state where the powder porosity is relatively large without performing compression molding in a stationary state, the electrostatic method and the like described above are also available. However, the prior art has not developed a method for measuring the powder adhesion force in the flow state of the powder, that is, the state where the powder porosity is large.

Further, the prior art measurement in an industrial use atmosphere such as high temperature and high pressure has a drawback that the apparatus becomes complicated.

[0010]

The object of the present invention is to obtain a relatively weak powder adhesion force of 5 Pa or less, or a powder adhesion force in a fluidized state, which has been impossible to date, in the fluidized bed. The purpose is to measure not only at room temperature and atmospheric pressure but also in an industrial use atmosphere.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted earnest researches on a method for measuring a relatively weak powder adhesive force and a powder adhesive force in a fluidized state in an industrial use atmosphere. Introducing a gas such as air or nitrogen, the minimum fluidization rate and bubble initiation rate are different under the measurement conditions, and between the minimum fluidization rate and bubble initiation rate,
There is a state in which air bubbles do not occur and the powder expands (hereinafter referred to as a uniform fluidized state). When the powder is fluidized, the energy given by the introduced gas to the powder and the powder are uniform. It was found that the powder adhesive force can be calculated by the energy used for breaking the powder when expanding in the fluidized state, and the present invention has been completed.

That is, the present invention provides a method for measuring the powder adhesion force of a powder in which there is a fluidized state in which the minimum fluidization rate and the bubble initiation rate are different under the measurement conditions, and the minimum fluidization rate (U _mf ) , Bubble start velocity (U _mb ), powder static bed height (H _lp ), powder average particle size (d _p ), and the linear regression line obtained from powder differential pressure at superficial velocity below U _mf , U _mb, a powder differential pressure prediction point is obtained, and a difference (ΔP ^* ) between the powder differential pressure at the U _{mb and} the powder differential pressure at U _mf is measured.

[0013]

[Formula 3] σ _f = ΔP ^* / 4 * (U _mf ^0.5 + U _mb ^0.5 ) / U _mb ^0.5 * d _p / H _lp (1) The powder adhesion force (σ _f ) is obtained by And the method of measuring the powder adhesion force. Hereinafter, the powder measured in the present invention will be described in detail the present invention, it is possible to flow by inserting a flowing gas such as air or nitrogen, and the minimum fluidization speed and bubble initiation speed are different, The particle shape is not limited as long as there is a uniform fluidization state.For example, as shown in p.70-73, the first edition of reaction engineering of fluidized beds, a classification map of powders focusing on fluidization characteristics. Any powder may be used as long as it is a powder belonging to group A in the above. For example, the group A having a particle size of about 10 to 150 μm
Belong to. However, there is no problem even if the powder has a particle size range and a particle density range in this powder classification as long as the powder has the characteristics of group A.

Here, the powders belonging to group A in the powder classification map are particle density, flowing gas density, and average particle diameter as ρ _s , ρ, and d _p , respectively, and their units are g / cm ^3. , G / cm ³ , and μm, the following formula (3) is satisfied, and Geldart, Powder Technology, 7, 285
-292 (1973) refers to the powder located on the right side of the empirically obtained lines P to Q shown in Fig.3.

[0015]

Equation 4] _{(ρ s -ρ) * d p} ≦ 225 ····················· (3) illustrating the present invention with reference to FIGS To do. However, these drawings do not limit the scope of the present invention. In FIG. 2, 1 is a fluidized bed main body, 2 is a pressure guiding tube for measuring a differential pressure, 3 is a differential pressure gauge, 4 is a flowing gas, 5 is a ruler for measuring the height of the powder bed in the fluidized bed, and 6 is a measurement. Powder, 7 is a fluidized gas disperser. The fluidized bed of No. 1 may be any one as long as the measured powder inside can be observed from the outside and has sufficient strength to withstand the measurement conditions. For example, transparent glass or the like is used. The column diameter may be such that the powder to be flowed does not cause slugging, but it is preferably a column diameter of 4 inches or more, which reduces the effect of the column wall. The tower height may be higher than the height at which the flowing powder does not jump out.

Two pressure guiding tubes, one at the lower part of the fluidized bed,
The other is attached above the surface of the powder bed of 6, but the upper pressure guiding tube is for detecting the pressure in the fluidized bed, and the pressure at the tip of the upper pressure guiding tube is the same as the pressure in the fluidized bed. In this case, the upper pressure guiding tube may not be installed in the fluidized bed. The fluid gas of No. 4 may be any fluid as long as the powder can be fluidized, and for example, air or nitrogen is used. The gas disperser of No. 7 may be any as long as it can disperse the introduced gas uniformly in the fluidized bed and has sufficient strength to withstand the measurement conditions. It is sufficient that the powder to be measured in 6 has an amount corresponding to the height at which the minimum fluidization speed and the bubble initiation speed can be measured, and the ratio of the powder static height to the fluidized bed column diameter is usually about 1 to 4. .

FIG. 3 schematically shows changes in powder differential pressure, powder height and powder adhesion force when the superficial velocity of the flowing gas is changed. As shown in FIG. 3, when the superficial velocity of the fluidizing gas is increased, the powder does not flow below the minimum fluidization speed, and the powder differential pressure increases due to the superficial velocity (hereinafter, the minimum flow rate). The change in the powder pressure difference below the conversion rate due to the superficial velocity is called slope 1.) Thereafter, the powder expands, and the differential pressure thereafter shows a constant value irrespective of the superficial velocity (hereinafter, the change in the powder differential pressure above the minimum fluidization velocity due to the superficial velocity is called slope 2). .

The minimum fluidization speed is the first version of reaction engineering for fluidized beds.
As shown in p.19, it can be obtained by changing the superficial velocity and measuring the powder differential pressure to obtain the slope 1 and slope 2, and extrapolating the respective slopes to obtain the intersection points. Further, the method of measuring the bubble initiation speed may be any method as long as it can measure the lowest superficial velocity at which bubbles are first produced, for example, gradually increasing the superficial velocity, and observing the formation of bubbles visually for the first time. Measured points and collapsing tests (Abrahamsenand Geldart, P
owder Technology, 26, 47 (1980)) to determine the highest point of emulsion phase height (Kono et al., P
owder Technology, 53, 69 (1987)).

The height of the powder stationary layer refers to the height from directly above the gas disperser 7 to the surface of the powder layer in the state where the powder has not started to flow due to the flowing gas. Any method may be used as long as it can be measured, and for example, it is measured by a ruler attached to the outside. For the average particle diameter, the distribution was determined by the laser light diffraction method shown in p.24 of the First Edition of Powder Engineering Handbook, and the median diameter was used.

Further, ΔP ^* in the equation (1) is obtained by extrapolating the powder pressure difference up to the bubble start speed along the slope 1 shown in FIG. 3 to obtain the powder pressure difference value at the bubble start speed. To be Powder differential pressure value and slope 2 at the bubble start speed
It is defined as the difference from the powder differential pressure value of. Hereinafter, the idea that the inventors derived the formula (1) will be shown.

When the superficial velocity changes from the minimum fluidization velocity to the bubble initiation velocity, the energy (E _D ) used for expanding the powder is the minimum fluidization velocity to the bubble initiation velocity. When the difference between the extrapolated value along the slope 1 shown in FIG. 3 and the powder differential pressure value of the slope 2 at a superficial velocity (U ₀ ) between them is ΔP ′, it can be defined by the equation (4), Figure 3
It corresponds to the area surrounded by e to f to g.

[0022]

[Equation 5]

Further, at the same superficial velocity (U ₀ ) between the minimum fluidization velocity and the bubble initiation velocity, the powder adhesion force (σ _f (U
o)) is Ergun's formula (see Chemical Engineering II Mechanical Operation 2nd Edition p.14) and Rumpf's formula, where the powder adhesion force at bubble initiation velocity and the bubble initiation velocity are σ _f and U _mb , respectively. (See Rumpf, Chem. Ing. Tech., 30, 144 (1958)), and can be expressed by the following equation (5).

[0024]

[Equation 6] σ _f (Uo) = σ _f * U _mb * U ₀ ^-0.5・ ・ ・ ・ ・ ・ (5) Superficial velocity is the minimum fluidization velocity ~ bubbles Change between start speeds,
Loss of powder adhesion energy (Eσ) per unit time when the powder expands can be expressed by the equation (6) using the above equation (5) and is surrounded by a to b to c to d in FIG. Equivalent to the area covered.

[0025]

[Equation 7]

Here, the formula (4) is the energy of the entire powder layer, and the formula (6) is the energy per layer in the powder layer. Therefore, the energy balance of E _D and E σ can be expressed by the following equation (7) when the average particle diameter and the powder stationary layer height are d _p and H _lp , respectively.

[0027]

[Equation 8] E _D = Eσ * d _p / H _lp ..... (7) Therefore, the powder adhesion force at the bubble initiation speed is It can be expressed by the following equation (1).

[0028]

[Formula 9] σ _f = ΔP ^* / 4 * (U _mf ^0.5 + U _mb ^0.5 ) / U _mb ^0.5 * d _p / H _lp (1) According to this definition formula, it has been impossible until now. The weak powder adhesion or the powder adhesion in the fluid state can be measured not only at room temperature and atmospheric pressure, but also in an industrial use atmosphere. In the industry of designing and controlling the flow state of powder, it is possible to carry out a method for keeping the flow state optimum, for example, optimization of particle size distribution.

[0029]

【Example】

[0030]

Example 1 An FCC catalyst was used as the measurement powder.
The fluidized bed used for the measurement has a tower diameter of 10.2 cm and a tower height of 1.5.
It is made of 5 m quartz. The amount of the charged powder was introduced so that the height of the powder stationary layer was 13.8 cm. Air was used as the flowing gas, and the measurement was performed at room temperature and atmospheric pressure. The minimum fluidization rate was determined by the above method, and as a result, a value of 0.6 cm / s was obtained, and ΔP at that time was 1210 Pa. ΔP * was 687 Pa calculated by the above method. The bubble initiation velocity was gradually increased by increasing the superficial velocity, and the point at which bubbles were first observed was determined. As a result, 0.9 cm / s was obtained. The height of the powder stationary layer was visually measured using a ruler attached to the outside, and as a result, it was 13.8 cm. The average particle size was measured by a laser light diffraction method, and the median size thereof was 65 μm. The powder adhesion σ _f was determined to be 0.15 Pa from these values. Table 1 shows a list of the above measurement results.

[0031]

[Example 2] Glass beads were used as the measurement powder, and the measurement was performed in the same manner as in Example 1. As a result, the powder adhesion was determined to be 0.03 Pa. Similarly, Table 1 shows a list of measurement results.

[0032]

Example 3 Starch powder was used as the measurement powder, and Example 1 was used.
Using the same method as above, the powder adhesion was determined to be 0.02 Pa. Similarly, Table 1 shows a list of measurement results.

[0033]

Example 4 As a measurement powder, a mixed powder obtained by adding 5% by weight of calcium carbonate to an FCC catalyst was used, and the measurement was carried out by the same method as in Example 1. As a result, the powder adhesion force was 0.
It was determined to be 32 Pa. Similarly, Table 1 shows a list of the measurement results, and the measurement results of the powder bulk density and the powder adhesion force are also shown in FIG.

[0034]

[Example 5] Carbon black was used as the measurement powder, and the measurement was conducted in the same manner as in Example 1. As a result, the powder adhesion was determined to be 0.08 Pa. Similarly, Table 1 shows a list of the measurement results, and the measurement results of the powder bulk density and the powder adhesion force are also shown in FIG.

[0035]

Example 6 An FCC catalyst was used as the measurement powder.
The fluidized bed used for the measurement has a tower diameter of 10.2 cm and a tower height of 1.5.
It is made of 5 m quartz. The amount of the charged powder was introduced so that the height of the powder stationary layer was 15.7 cm at room temperature.
Air was used as the flowing gas. The measuring device is heated by an electric furnace attached to the outer wall of the fluidized bed, and the temperature is measured by inserting an aromel chromel thermocouple into the powder layer and measuring 100, 20.
It was measured at each point under atmospheric pressure of 0, 300, 400, 500, 600 ° C. The minimum fluidization rate and ΔP ^* were determined by the above method. The bubble initiation velocity gradually increased the superficial velocity, and the point at which bubbles were first observed was determined. The height of the powder stationary layer is
It was visually measured using a ruler attached to the outside. The average particle diameter was measured by a laser light diffraction method at room temperature, and the median diameter thereof was 65 μm. Table 2 shows the measured values at each temperature. From these values, it can be seen that the powder adhesive force σ _f can be measured even under high temperature conditions.

[0036]

[Reference Example 1] As a reference example, a powder adhesion measuring device by the conventional tensile rupture method is used, and a commercially available Cohitester manufactured by Hosokawa Micron Co. is used.
The measurement was tried using the same FCC catalyst, glass beads, and starch powder as those of No. 3. However, all the powders used could not be measured because the powders could not be compression molded.

[0037]

[Reference Example 2] As the measurement powder, a mixed powder obtained by adding 5% by weight of calcium carbonate to the same FCC catalyst as in Example 4 was used. The measuring method was a powder adhesion measuring device by the tensile rupture method, and the same Cohitester manufactured by Hosokawa Micron Co., Ltd. as used in Reference Example 1 was used, and the bulk density was changed, and four points were measured. Figure 4 shows the measurement results of powder bulk density and powder adhesion.
Shown in.

[0038]

Reference Example 3 As the measurement powder, the same carbon black as in Example 5 was used. The measurement method was the same as that used in Reference Example 1, using a Cohitester manufactured by Hosokawa Micron Co., Ltd., and the bulk density was changed, and four points were measured. The measurement results of the powder bulk density and the powder adhesive force are shown in FIG.

As is clear from Examples 4 and 5 and Reference Examples 2 and 3, the present invention enables the measurement of a region which could not be measured by the conventional method.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

EFFECTS OF THE INVENTION It is possible to measure not only the powder adhesion force of 5 Pa or less or the powder adhesion force in a fluid state at room temperature and atmospheric pressure, which is relatively weak, which could not be measured by the prior art, but also in an industrial atmosphere. Therefore, it is important to design powder handling equipment (eg dust collector, powder transportation, etc.), which is important for powder handling industry, and to control powder flow condition (eg Fluidized Catalyst Cracking, acrylonitrile). , Oxychlorination, fluidized bed reaction of maleic anhydride, etc., fluidized bed combustion, etc.) can be carried out by a method for maintaining an optimum fluidized state, for example, optimization of particle size distribution.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a conventional technique for measuring powder porosity, powder existing state, and powder adhesive force.

FIG. 2 is a diagram of a measuring device for powder adhesion.

FIG. 3 is a relationship diagram between a powder pressure difference and a powder pressure difference.

FIG. 4 is a graph showing the relationship between powder bulk density and powder adhesion.

[Explanation of symbols]

 1: Fluidized bed main body 2: Pressure guiding tube 3: Differential pressure gauge 4: Flowing gas 5: Ruler 6: Measuring powder 7: Disperser

Claims (1)

[Claims] 1. A method for measuring the powder adhesion force of a powder having a fluidized state in which the minimum fluidization rate and the bubble initiation rate are different under the measurement conditions, wherein the minimum fluidization rate (U _mf ), bubble initiation Velocity (U _mb ), powder static bed height (H _lp ), average particle diameter (d _p ), and the linear regression line obtained from the powder differential pressure at superficial velocity below U _mf ,
seeking powder differential pressure predicted point in _mb, the measured difference in powder differential pressure ([Delta] P ^*) the powder differential pressure and U _mf in U _mb, the following equation (1), Equation 1] sigma _f = ΔP ^* / 4 * (U _mf ^0.5 + U _mb ^0.5 ) / U _mb ^0.5 * d _p / H _lp (1) The powder adhesive force (σ _f ) is obtained by the _formula (1). Measuring method.