JP2003182844A - Pneumatic transportation of powder - Google Patents

Abstract

(57) [Summary] An object of the present invention is to suppress pressure loss in pneumatic transportation. The bleeding is performed in the middle of a transportation pipe, and the bleeding is performed.
The flow rate of the carrier gas₁, Flow rate of carrier gas before bleeding
To V₁, The minimum flow velocity required for pneumatic transportation is V_CAnd when
The amount of bleed air ΔQ is calculated as ΔQ / Q₁≤ (V₁-V_C) / V₁Full
Set to add. That is, the cross-sectional area of the pipe flow path is S
Then, the flow velocity V of the carrier gas after extracting ΔQ_TwoIs below
Flow velocity V_CIt is sufficient if it is at least_Two= V₁−ΔQ /
S ≧ V_CFrom this, the above equation is derived. So before
If the above expression is satisfied, the flow velocity of the carrier gas after bleeding is
V_CAs described above, the flow velocity of the carrier gas after bleeding
Speed V _CIf bleeding is performed so as to maintain a value in the vicinity, the pressure loss will be
It will be kept to the minimum necessary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for pneumatically transporting a granular material in which a granular material is suspended and transported in a carrier gas flowing in a pipe.

[0002]

2. Description of the Related Art A method in which a powder or granular material is suspended in a carrier gas or a carrier gas flowing in a pipe and transported is called pneumatic transportation. Even if the carrier gas is a gas other than air, such as nitrogen, it is generally called air transportation, which is a well-known technique. In this pneumatic transportation, if there is a space for arranging piping, it is possible to flexibly transport a relatively long distance of several tens of meters to several hundreds of meters or more by bending the route, and transport by a conveyor. Since it can be transported without problems such as dust generation and moisture absorption, which may occur in some cases, and chemical changes due to contact with the atmosphere, it is widely used in industry.

[0003]

However, during long-distance transportation, there are restrictions due to pressure loss in the piping and the economical efficiency of the means for supplying carrier gas having a pressure corresponding to the pressure loss. There is a limit to the transportation capacity of the piping. In other words, not only the carrier gas but also the pressure loss due to the particles contacting the inner wall of the pipe at a relative speed, and the pressure loss accompanying the lifting of the particles at a certain speed against gravity add to the transportation distance. The pressure loss in the pipeline is large.

Further, since the pressure loss is generally proportional to the square of the conveying speed, a design is made to reduce the conveying speed to suppress the pressure loss. At the same time, however, a minimum carrier gas flow rate is required to suspend the powdery particles. Since it is necessary to secure it, there is a limit to suppressing the transport speed. Therefore, a high-pressure gas of several kgf / cm ² G to 10 kgf / cm ² G or more is sometimes used as the carrier gas. As a result, equipment costs, operating costs, management such as inspection / maintenance / inspection, and maintenance costs become a problem, and the usable pressure is restricted, and the transportation distance or the transportation capacity at the time of design is constrained.

Further, there is a problem of abrasion of the inner wall of the pipe due to the granular material, and since this abrasion is generally proportional to the cube of the transportation speed, one of the effective means for the abrasion is to reduce the carrier gas flow velocity. Has become. From the above, in designing an air transportation system, it is important to suppress the flow velocity as much as possible after ensuring the minimum flow velocity required for floating transportation of powdery particles. FIG. 6 schematically shows the relationship between the pressure inside the pipe, the flow velocity of the carrier gas, and the pressure loss of each part in the transport pipe when the pipe inner diameter is constant. The carrier gas expands as the pressure decreases, the flow velocity of the carrier gas increases accordingly, and the pressure loss further increases and the pressure decreases. As a result, the pressure loss increases at an accelerated rate.

In order to prevent this, generally, the diameter of the pipe on the downstream side of the air transportation system is enlarged to suppress the increase in the flow velocity. By the way, one ideal way to reduce pressure loss in pneumatic transportation is to maintain the lower limit gas flow velocity required for floating transportation, and to achieve this, the pipe diameter should be continuously adjusted in accordance with the expansion of the carrier gas due to pressure loss. Need to expand to. However, since the standard size of the pipe diameter is intermittent, it is necessary to manufacture special pipes in order to do this, which is not practical in view of economy.

Therefore, it is necessary to use a commercially available piping material conforming to the JIS standard and to gradually expand the diameter of the piping at an appropriate position of the transportation pipeline, but if the dimension is increased by one step, the flow velocity decreases. Remarkable. Table 1 shows the JIS standard for pressure piping, which is often used for pneumatic transportation.
In the following pipes, if the pipe size is increased by one step, the cross-sectional area becomes 1.30 to 1.77 times, so the flow velocity immediately after the pipe diameter expansion portion is 1 / 1.30 to 1/1. 77 ≒
It becomes 0.77 to 0.56 times.

[0008]

[Table 1]

Here, the flow velocity after expansion of the pipe diameter must be equal to or higher than the lower limit flow velocity required for floating transportation. Therefore, according to the current piping standards, as described above, after expanding the pipe diameter, 23 to 44
Since a sudden decrease in the flow rate of 10% cannot be avoided, as shown in FIG.
_It must be 1.30 to 1.77 times _C or more.
This means that it is unavoidable to transport at a carrier gas flow velocity that causes pressure loss to be unnecessarily large in the transport section before expansion of the pipe diameter, and the transport limit in long-distance pneumatic transport is made smaller. It is one of the reasons for this.

On the other hand, in a facility in which powder particles are blown into a molten metal through an immersion lance, a part of the carrier gas is separated and discharged outside the path in the middle of the powder particle transportation pipeline. , A method and a device for controlling the pressure and the flow rate of a pipeline have been proposed. These are disclosed, for example, in JP-A-60-181218 or JP-A-5-1950.
As disclosed in Japanese Patent No. 31, the purpose of the present invention is to reduce excess carrier gas, which has a bad influence on control and operation, before injection, when a powder or granular material is blown into the molten metal.

Although these are not intended as techniques for suppressing pressure loss in pneumatic transportation in general, it is possible to reduce the flow velocity in the pipe by expanding the pipe diameter by reducing the amount of gas after the extraction portion. Therefore, it can also be a means for suppressing pressure loss. However, there is no mention of how to select the extraction amount or the pipe diameter, and an accurate selection method for these is desired. Therefore, the present invention has been made by paying attention to the above-mentioned unsolved problems of the related art, and it is possible to suppress the pressure loss in pneumatic transportation and to perform pneumatic transportation in an ideal state in which only a necessary minimum pressure loss occurs. It is an object of the present invention to provide a method for pneumatically transporting powder and granules.

[0012]

[Means for Solving the Problems] To achieve the above object
In addition, the method for pneumatically transporting the granular material according to claim 1 of the present invention is:
Entraining powder particles in the carrier gas flowing in the transportation pipeline
Along with the transportation, a certain amount of the
Air of powder and granules so that the gas to be sent is extracted outside the transportation pipeline.
In the transportation method, the extraction amount of the carrier gas is ΔQ / Q
₁≤ (V₁-V _C) / V₁Can be set to satisfy
It is characterized by. However, ΔQ is the extraction amount, Q₁Is extraction
Flow rate of generous carrier gas, V₁Is the flow of carrier gas before extraction
Speed, V_CIs the minimum load required to float the particles due to pneumatic transportation.
It is a gas flow velocity (hereinafter, referred to as a lower limit flow velocity).

That is, when the cross-sectional area of the pipe flow path is S,
The flow velocity V ₂ of the carrier gas after extracting the extraction amount ΔQ may be equal to or higher than the lower limit flow velocity V _C , so V ₂ = V ₁ −ΔQ / S ≧
It becomes V _C , and the above formula is derived from this. Therefore, if the above equation is satisfied, the flow velocity of the carrier gas after extraction is the lower limit flow velocity V _C.
As described above, the lower limit flow velocity V _C is secured and pneumatic transportation is possible. Further, in the pneumatic transportation method of the powdery or granular material according to claim 2 of the present invention, the flow velocity of the carrier gas in the transportation pipeline before and after extraction is the maximum carrier gas flow rate before extraction / minimum carrier gas after extraction. The extraction amount of the carrier gas is controlled so as to satisfy the flow velocity <1.77.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a schematic configuration diagram showing an example of an air transportation device to which the present invention is applied. In the figure, reference numeral 1 denotes a pressure tank, in which the powder particles 2 are stored.
When the aeration gas 3 is supplied into the pressurizing tank 1 from the bottom of the pressurizing tank 1, the fluidity of the granular material 2 in the pressurizing tank 1 is increased, and in this state, when the valve 4 is opened,
Due to the pressure in the pressure tank 1, the powder and granules 2 are compressed into the pressure tank 1.
And is discharged into the transportation pipeline 5. The transport pipeline 5 is formed of a single-diameter transport pipeline, and the granular material 2 discharged into the transport pipeline 5 mixes with the carrier gas 6 in the transport pipeline 5 and floats in the carrier gas 6. And the transport line 5
It is designed to be transported inside.

A plurality of extraction lines 10 are formed at appropriate places on the transportation line 5, and the extraction lines 10 are formed.
A bleed valve 11 and a flow meter 12 are provided in the. And, although not shown, the transportation pipeline 5 of the extraction pipeline 10
On the side, for example, a porous member having pores that has air permeability but does not allow the powder or granular material 2 to pass therethrough is provided, and the carrier gas 6 that has passed through this porous member is the extraction valve 11 and the flowmeter 1.
2 is discharged to the outside of the transportation pipeline 5 via the 2 and the extracted gas amount Δ
Q is measured by the flow meter 12, and the extraction valve 11 is adjusted so as to extract a predetermined amount of the carrier gas 6 based on the detection value of the flow meter 12.

Carrier gas 6 extracted by this extraction valve 11
The bleed gas amount ΔQ is set so as to satisfy the following equation (1). In the equation, Q ₁ is the carrier gas flow rate of the carrier gas 6 before extraction (m ³ / sec), V ₁ is the flow velocity of the carrier gas 6 before extraction (m / sec), and V _C is necessary for pneumatic transportation. The lower limit flow velocity (m / sec). ΔQ / Q ₁ ≦ (V ₁ −V _C ) / V ₁ (1) That is, the carrier gas flow rate in the transportation pipeline 5 after extraction is Q ₂ ,
Assuming that the flow velocity of the carrier gas 6 after extraction is V ₂ and the flow passage cross-sectional area of the transportation pipeline 5 is S, the flow velocity of the carrier gas 6 after extraction must be equal to or higher than the lower limit flow velocity V _C required for air transportation. Therefore, the following equation (2) is established.

V ₂ = V ₁ −ΔQ / S ≧ V _C (2) The following formula (3) is derived from the formula (2), and the formula (3) is divided by the carrier gas flow rate Q ₁ before the extraction. Expression (1) can be obtained. ΔQ ≦ (V ₁ −V _C ) × S (3) Therefore, the extraction gas amount ΔQ and the carrier gas flow rate Q before extraction are determined.
_If the ratio with 1 satisfies the above formula (1), the flow velocity V ₂ of the carrier gas 6 after extraction is the lower limit flow velocity V required for pneumatic transportation.
It will be possible to secure _C or higher.

Since the pressure loss in the transportation pipeline 5 is proportional to the square of the transportation speed, it is desirable to make the transportation speed smaller. Therefore, in the above formula (1),
By setting the extraction gas amount ΔQ so that the right side and the left side are equal, the pressure loss in the transportation pipeline 5 after the extraction can be minimized. Further, the wear of the pipe can be suppressed by suppressing the gas flow velocity in the pipeline. In particular,
When using a pipe conforming to the JIS standard as shown in Table 1 as the transport pipe 5, in order to reduce the gas flow velocity by enlarging the pipe diameter, one having an inner diameter of 25 A or more generally used for pneumatic transportation. , The cross-sectional area ratio with the pipe whose pipe diameter is one step higher is 1.30 to 1.7.
7, the flow velocity V of the carrier gas 6 immediately before the pipe diameter expansion position is V.
_{For No. 1} , in order to maintain the flow velocity immediately after the pipe diameter expansion position at the lower limit value V _C or more required for floating transportation, it is necessary to satisfy the following expression (4).

[0019]     V₁≧ (1.30 to 1.77) V_C                        …… (4) In other words, if the carrier gas flow rate is constant,
When the gas is not extracted, the gas flow velocity V₁Is
In the section (5), the pipe diameter cannot be expanded.
That is, the pressure loss cannot be reduced.     V₁<(1.30 to 1.77) V_C                        …… (5) On the other hand, when bleeding is performed, if the formula (1) is satisfied,
Good, gas velocity V ₁Is (1.30 to 1.77) V_C
Even if, the extraction gas amount ΔQ satisfies the above equation (1)
If set like this, it is possible to reduce the gas flow velocity.
The pressure loss can be reduced.

Therefore, it is possible to reduce the gas flow velocity even in the velocity region of the gas flow velocity which cannot be dealt with by the method of enlarging the pipe diameter, that is, in the section of the equation (5). Therefore, when the extraction gas amount ΔQ is adjusted within the section where the pipe diameter is constant and the gas flow velocity is adjusted according to the following equation (6), the pressure loss reduction effect in the velocity range that cannot be handled by the pipe diameter expansion method is obtained. Can be planned. Note that V _MAX in the equation is the flow velocity at the time of extraction, that is, the maximum flow velocity in the section before extraction. Further, V _MIN in the equation is the flow velocity after extraction, that is, the minimum flow velocity in the section after extraction.

V _MAX / V _MIN <[(1.30 to 1.77) V _C ] / V _C = (1.30 to 1.77) (6) Therefore, V _MAX / V _MIN <1. This is particularly effective when 77 is used as the control target for reducing the flow velocity.

[0022]

EXAMPLES Examples of the present invention will be described below. As the transportation pipeline 5, a transportation pipe having a pipe diameter of 25 A conforming to the JIS standard (carbon steel pipe for pressure piping STPG-sch80 inner diameter 2
5 mm), and iron oxide powder was pneumatically transported as a powder or granular material. The gas temperature of the carrier gas 6 is 300K. The lower limit flow rate V _C required for floating transportation is 10 m / s, and the carrier gas flow rate is 2 Nm ³ / min.

FIG. 2 shows the relationship between the transport distance of the transport pipe 5 and
Change in carrier gas flow velocity V and pressure loss per unit transport distance
Loss, and the absolute gas pressure is 7.4 kgf /
cm ²The gas flow velocity V is 10 m at a place below −ab
/ S or more, but unit transportation as the transportation distance L increases
Pressure loss per distance increases and absolute gas pressure is 3.7
kgf / cm²The gas flow velocity V becomes 2 when the temperature is about −ab or less.
The flow velocity becomes 0 m / s or more, and the wear becomes remarkable.

Here, there is a method of reducing the gas flow velocity by enlarging the diameter of the pipe in order to suppress pressure loss and wear due to an increase in the flow velocity. In this case, since the transportation pipe having a pipe diameter of 25 A is used, the pipe is expanded to one stage of 25 A in Table 1, that is, 32 A (inner diameter 32.9 mm). At this time, since it is necessary to ensure that the flow velocity immediately after expansion to 32A is equal to or lower than the lower limit flow velocity V _C (= 10 m / s), the flow velocity immediately before expansion is required to be 17.4 m / s or more, that is, transportation. Absolute gas pressure in the pipe 5 is 4.3kg
The pipe diameter cannot be expanded in the section of f / cm ² -ab or more.

Assuming that the gas densities are the same, the pressure loss per unit transport distance when the pipe diameter is constant is proportional to the square of the gas flow velocity, so the lower limit flow velocity V _C (= 1) required for transport.
Compared with the case of transporting at 0 m / s), just before expansion,
The pressure loss increases by (17.4 / 10) ² ≈3.0 times. On the other hand, when reducing the flow rate by performing extraction without changing the pipe diameter, since the extracted gas amount ΔQ may be set so as to satisfy the expression (1), for example, the flow velocity V ₁ of the immediately preceding extraction If V ₁ = 17.4 m / s, from the above formula (1), the extraction gas amount ΔQ is (17.4-10) /17.4≈ of the carrier gas flow rate Q ₁ before extraction.
It may be 0.43 times or less.

That is, the maximum flow velocity reaches 17.4 m / s.
It is possible to perform bleeding before
Can be reduced, and the flow velocity after extraction is the lower limit flow rate.
Speed V _CCan be kept above. Therefore, before and after extraction
It is possible to make the ratio of the large flow velocity to the minimum flow velocity less than 1.74 times.
Yes, that is, because the flow velocity ratio can be reduced,
By extracting air before the fluctuation range of the flow velocity becomes large,
Can suppress fluctuations in flow velocity, that is, suppress pressure loss.
Can be controlled. In addition, the gas flow velocity is set to the lower limit flow velocity V_CWith
Since it can be maintained close to the air,
Can be sent.

That is, in this example, the bleeding of the carrier gas is such that the flow rate of the carrier gas in the transportation pipeline before and immediately after the bleeding is “1.0 ≦ maximum carrier gas flow rate / minimum carrier required for floating”. By extracting air from the carrier gas so as to satisfy “gas flow velocity ≦ 1.74”, air transportation with reduced pressure loss became possible. FIG. 3 shows the lower limit flow rate V _C when the minimum flow velocity before extraction (the flow velocity at the highest pressure location in the same pipe diameter section) is 10 m / s.
(= 10 m / s), the carrier gas flow velocity V with respect to the transport distance L and the pressure loss per unit transport distance when the ratio of the maximum / minimum flow velocity immediately after extraction in the same section and 1.4 is increased. Is shown.

In order to increase the ratio of maximum / minimum flow velocity immediately after bleeding to 1.4 times, the gas flow velocity V is 10 × 1.4 = 14 m /
At a location of s (pressure 4.85 kgf / cm ² -ab), the carrier gas may be extracted by (14-10) /14≈0.285 times the carrier gas amount (that is, 28.5% or less). Figure 3
In this case, the extraction air is divided into two parts, and the gas flow velocity V is 1
20% (0.4 Nm ³ / min) of air was extracted at a location L ₁ where the pressure was 4 m / s (pressure 4.85 kgf / cm ² -ab). This bleeding reduced the gas flow velocity V to 11.2 m / s. After bleeding, the gas flow velocity increases with a decrease in the pipe pressure due to the pressure loss, but the pipe pressure is 4.26 kgf.
/ Cm ² −ab The remaining at the place L ₂ (0.3 Nm ³ /
min), the carrier gas flow velocity V after the bleeding decreased to 10.2 m / s. That is, the carrier gas flow velocity V after extraction was ensured to be equal to or higher than the lower limit flow velocity V _C.

In this way, in the case of extracting air, as shown by the solid line in FIG. 3, it is possible to reduce the carrier gas flow rate V by extracting air at the location L ₁ where the carrier gas flow rate V is 14 m / s. Therefore, the carrier gas flow velocity V can be further reduced by extracting air again at L ₂ . In contrast,
When the pipe diameter is expanded from 25 A to 32 A, as shown by the broken line in FIG. 3, the gas pipe diameter cannot be expanded up to the place L ₂ where the carrier gas flow velocity V is 17.4 m / s, that is, However, the carrier gas flow velocity V cannot be reduced.

Therefore, the extracted air can reduce the pressure loss as compared with the pressure loss when the diameter of the pipe is expanded. Specifically, the area between L _{1 and} L _{2 in} FIG. 3 is hatched. It is possible to reduce the pressure loss more than the indicated part.
Further, since the carrier gas flow rate can be reduced at a time point when the carrier gas flow rate V is smaller, that is, the carrier gas flow rate can be reduced before the pressure loss becomes larger and the pressure loss can be effectively suppressed. be able to.

Further, since the carrier gas flow velocity V can be suppressed, wear of the transportation pipe 5 can also be suppressed.
In addition, in the above-mentioned embodiment, the case where the bleeding is performed twice at the places L ₁ and L ₂ has been described, but it is also possible to perform the bleeding twice or more. Thus, pneumatic transportation can be performed while suppressing an increase in the carrier gas flow velocity V over a long distance section where the pipe diameter is constant. At this time, it is also possible to control the gas flow velocity V to a value close to the lower limit flow velocity V _C by adjusting the extraction location and the extraction amount, and by doing so, the pressure loss can be suppressed to the necessary minimum and the efficiency can be improved. Can be pneumatically transported.

Further, for example, as shown in FIG. 4, the gas flow velocity V is 14 m / s (pressure 4.85 kgf / cm ² -ab).
28% may be extracted at the location L ₁ where the flow rate after extraction is equal to the lower limit flow rate V _{C. In} this case, the next extraction may be performed at the location L ₂ or gas. You may perform in the place where the flow velocity V becomes 14 m / s again. Further, as shown in FIG. 5, when the gas flow velocity V reaches a certain level, that is, when the pressure loss reaches a certain level, the bleeding may be performed. The pressure loss can be suppressed while maintaining the stability of pneumatic transportation.

[0033]

As described above, according to the present invention,
By adjusting the extraction amount, the flow rate of the carrier gas after extraction can be made equal to or higher than the lower limit flow rate required for pneumatic transportation, so that the flow rate of the carrier gas after extraction becomes a value close to the lower limit flow rate. By adjusting the extraction amount in this manner, the pressure loss can be suppressed to the necessary minimum without changing the pipe diameter of the transportation pipe. Further, it is possible to reduce the flow velocity of the carrier gas even in the flow velocity range that cannot be realized by the method of changing the pipe diameter of the transportation pipe, and it is possible to further suppress the pressure loss.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of an air transport device for powder or granular material according to the present invention.

FIG. 2 is an explanatory diagram showing changes in carrier gas flow velocity and pressure loss with respect to a transportation distance when a pipe diameter is enlarged.

FIG. 3 is an explanatory diagram showing changes in a carrier gas flow velocity and a pressure loss with respect to a transportation distance, which is used for explaining an operation of the present invention.

FIG. 4 is another embodiment of the present invention.

FIG. 5 is another embodiment of the present invention.

FIG. 6 is an explanatory diagram showing changes in a pipe pressure, a carrier gas flow velocity, and a pressure loss with respect to a transportation distance.

FIG. 7 is an explanatory view showing changes in carrier gas flow velocity and in-pipe pressure by a conventional pipe diameter enlarging method.

[Explanation of symbols]

1 Pressurized tank 2 powder 5 transportation pipelines 6 Carrier gas 10 extraction line 11 Bleed valve 12 Flowmeter

Claims (2)

[Claims] 1. A carrier gas flowing in a transportation pipeline is transported while entraining powder particles in the carrier gas, and a predetermined amount of the carrier gas is extracted outside the transportation pipeline in the middle of the transportation pipeline. In the pneumatic transportation method of powdery or granular material, the air extraction amount of the carrier gas is set so as to satisfy the following expression. ΔQ / Q ₁ ≦ (V ₁ −V _C ) / V ₁ where ΔQ is the extraction amount, Q ₁ is the flow rate of the carrier gas before extraction, V ₁ is the flow rate of the carrier gas before extraction, and V _C is the air transportation. Therefore, it is the minimum carrier gas flow velocity required to float the powder. 2. The powder according to claim 1, wherein the extraction amount of the carrier gas is controlled so that the flow velocity of the carrier gas in the transportation pipeline before and after the extraction will satisfy the following equation. Pneumatic transportation method of granules. Maximum carrier gas flow rate before extraction / minimum carrier gas flow rate after extraction <1.77