JPH07110337B2 - Air flow type powder mixing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a powder mixing method used in industries such as the ceramic industry, food industry, and chemical industry that mix powders.

[Conventional Conventional Method] There is a fluidizing type mixing method as a conventional powder mixing method, and an example of a mixing apparatus according to this method is shown in FIGS. 5 and 6.

First, as shown in FIG. 5, the powder mixing chamber is divided into upper and lower two chambers by a porous partition plate 8 having air permeability. A plurality of types of powders 5 are supplied to the upper chamber 9 through the plurality of powder supply pipes 4 and filled on the partition plate 8. Lower chamber
The gas 6 is blown into the 10 by the fan 11, passes through the partition plate 8 and the powder layer 12 above it, and is guided to the upper space of the upper chamber 9. As the gas stream passes through the powder bed 12, it causes fluidization of the powder bed 12, which results in the mixing of the powders. Since the powder 5 is continuously supplied to the fluidized powder layer 12, the mixed powder is discharged from the powder discharge pipe 13 by overflow. The speed at which the gas 6 passes through the powder layer 12 is not so high as to suspend the powder in the gas flow, most of the particles remain at the upper part of the partition plate 8, and only a very small number of minute particles are gas. It is guided to the dust collector 7 such as a bag filter along with the flow.

The mixer shown in FIG. 6 is also a fluidizing type mixing device similar to that of FIG. 5, but the discharge method is different, and the mixer is drawn from below. The partition plate 8 has a cone shape so that the powder can easily flow down, and the fluidized powder is taken out of the mixer by an extracting device 14 such as a rotary feeder.

Such a fluidized type mixing device is used particularly when a large amount of powder is mixed.

In terms of shape, the present invention has a shape relatively similar to that of a calcination furnace used in a cement manufacturing plant as shown in FIGS. At the lower end of the intermediate portion 17 having the gas inlet duct 2a connected to the inverted cone-shaped lower portion 15 and the narrowed portion 18, a high temperature gas of at least 800 ° C. or more flows in from the gas inlet duct 2b which is grounded so as to be in contact with the inner wall, The powder is supplied from the powder supply pipe 4 in the middle part. Further, this calcination furnace is provided with a burner 26, and by the above-mentioned high temperature gas and heat given from this burner 26,
The cement raw material supplied inside undergoes a decarboxylation reaction, and is discharged together with the gas from the upper outlet duct 3. However, this calcination furnace is installed not for mixing the powders but for calcination (decarbonation) of the powders, and multiple types of powders to be calcined are supplied at the same time. There is no.
Further, as shown in the table, the present invention and the calcination furnace are operated under completely different conditions.

[Problems to be Solved by the Invention] The conventional mixing method described above has the following problems.

(1) Since the gas flows through the powder layer, the pressure loss is high relative to the air volume, and the power consumption of the fan is large.

(2) In order to improve the mixing efficiency, the residence time of the powder must be lengthened, and a large capacity mixing space is required.

For these reasons, the initial cost such as construction cost is high and a large occupied space is required.

An object of the present invention is to solve the problems of the conventional mixing method, to suppress the power consumption of the fan, to provide a compact and excellent mixing efficiency.

[Means for Solving the Problems] In the present invention, a plurality of powder supply pipes are provided in the periphery, a gas inlet duct is provided in a lower portion, and an outlet duct is provided in an upper portion. A kind of powder is introduced from the gas inlet duct, and is continuously supplied from the powder supply pipe into a gas that flows in the mixing tank at a speed at which the powder can be floated or more. An air flow characterized by evenly mixing a plurality of powders by collecting the powders carried out of the mixing tank through the outlet duct with a dust filter such as a bag filter installed downstream. Formula powder mixing method.

In the present invention, it is preferable to supply the mixture ratio of a plurality of powders (ratio of the weight flow rate of powder and gas) as 3 to 6 [kg powder / kg gas]. In addition, 15 to 30 from the gas inlet duct
Gas should flow in at a speed of [m / s]. Also, in the mixing tank, the gas is flowing at a speed that allows the powder to be suspended, and the supplied multiple types of powder are mixed by the gas flow while mixing with the gas through the outlet duct. It is carried out of the tank. A mixed powder can be obtained by collecting the powder floating in the gas flow with a dust collector such as a cyclone or a bag filter.

In the case of powder having a high temperature, the atmosphere or cold air is introduced from the gas inlet duct for the purpose of cooling at the same time as mixing.

In the present invention, the wind speed Vin in the gas inlet duct and the pressure loss in the mixing tank have the relationship shown in FIG.
When n is less than 15 [m / s] or exceeds 30 [m / s], the pressure loss in the mixing tank rapidly increases and the power consumption of the fan also increases. Further, the degree of mixing of powders (mixing degree) becomes smaller as the wind speed becomes higher as shown in FIG. 10, and increases as the wind speed becomes lower. Therefore, considering the two aspects of the pressure loss and the degree of mixing of the mixing tank, the range of the inlet wind speed Vin of 15 to 30 [m / s] is a low-cost and efficient mixing region.

On the other hand, the powder mixing ratio and the pressure loss in the mixing tank have the relationship shown in FIG. The pressure loss in the mixing tank increases directly up to a mixing ratio of 6 [kg powder / kg gas], but a sharp increase tends to occur above this. If the amount of gas is constant, the mixing ratio has the same meaning as the amount of powder processed, but as the mixing ratio increases, the pressure loss in the mixing tank also increases, and the power consumption of the fan also increases. Therefore, FIG. 12 is obtained by plotting the electric power amount per unit mixed powder on the vertical axis and plotting the relationship with the mixing ratio. Electric power consumption rate is 3 to 6 [kg powder / kg
Gas] shows the minimum, and it is understood that this range is the range of the optimum mixing ratio. Further, in the range of this mixing ratio,
Since the pressure loss between Vin and the mixing tank and the relationship between Vin and the mixing degree shown in Fig. 10 are established, the optimum operating condition of the mixing tank is finally that the inlet wind speed Vin is 15 to 30 [m / s ], The mixing ratio is 3 to 6
It becomes [kg powder / kg gas].

When the temperature of the powder to be supplied is 100 to 200 ° C., cold air such as the atmosphere is introduced from the inlet duct to cool the powder at the same time as mixing, so that the powder can be mixed and cooled. For example, the operating conditions described above (Vin = 15 to 30 [m /
s], mixing ratio = 3 to 6 [kg powder / kg gas]), when 120 ° C powder is mixed and cooled in the atmosphere at 15 ° C, the powder discharged from the mixing tank is up to around 70 ° C. It will be cooled. Further, as a matter of course, the present invention can be applied only for cooling the powder.

[Function] Two or more kinds of powders supplied from the plurality of powder supply pipes to the inside of the mixing tank fall near the central axis of the mixing tank and are connected to the lower part of the mixing tank depending on the speed of the powder at the time of supply. Colliding with the gas flow entering from the gas inlet duct that is present. Due to the collision with this gas flow, the supplied powder is dispersed and further mixed by the turbulent gas flow. The entire shape is such that it once expands from the gas inlet duct to the mixing tank to the outlet duct and then contracts again. Since the gas flow has a velocity distribution as shown in FIG.
As shown in the figure, part of the supply powder is carried with the gas through the gas outlet duct to the cyclone or bag filter downstream, but the remaining part falls from the vicinity of the wall with the slow gas flow velocity to the bottom of the mixing tank, It is carried upwards again by the gas flow coming from the gas inlet duct. Due to the existence of such a cycle, the mixing of the powder will be further promoted.

[Embodiment] FIGS. 1 and 2 schematically show an embodiment of the present invention.

In all examples, the mixing tank 1 has a gas inlet duct 2 and an outlet duct 3 connected to the lower part 15 and the upper part 16, respectively. Around the mixing tank 1, a plurality of powder supply pipes 4 are attached.

The mixing tank 1 is composed of an inverted cone-shaped lower portion 15 connected to the gas inlet duct 2, a cone-shaped upper portion 16 connected to the outlet duct 3, and a cylindrical intermediate portion 17 connecting them.
In another embodiment, the lower part 15 connected to the gas inlet duct 2 has an inverted two-stage cone shape, and the upper part 16 connected to the outlet duct 3 has a multi-stage cylindrical shape, and the mixture is mixed from a cone-shaped throttle portion connecting these. There is also a modified example in which the tank 1 is configured.

In the two embodiments described above, the gas and raw material flows are similar and will be described as follows. A plurality of kinds of powders 5 are supplied to the mixing tank 1 from a powder supply pipe 4 installed around the mixing tank 1 at a mixing ratio of 3 to 6 [kg powder / kg gas]. Fan from gas inlet duct 2 to mixing tank 1
Depending on 11, the gas 6 flows in at a wind speed of 18 to 30 [m / s].
The gas 6 rises in the mixing tank 1 at a speed higher than that at which the powder can be suspended in the gas, and the powder supplied by this gas flow is mixed in the mixing tank 1 and mixed with the gas flow. The powder carried to the outside of the tank is collected by a dust collector 7 such as a bag filter or a cyclone installed downstream.

Further, the powder is cooled by taking in cold air such as air from the gas inlet duct 2. When the powder temperature is 120 ° C, the atmospheric temperature is 15 ° C, and the mixing ratio is 3 to 6 [kg powder / kg gas] and the wind speed is 15 to 30 [m / s], the powder is cooled down to around 70 ° C. To be done.

[Advantages of the Invention] The present invention is as described above, and can provide a mixing method that suppresses the power consumption of a fan, is compact, and has excellent mixing efficiency. For example, at a processing capacity of 200 t / hr, when compared with the conventional fluidized type mixing method, the electric power consumption rate is about 1.0 kwh / t, which is about the same as the electric power consumption rate.
In contrast to mφ × 16 mH, the present invention has a much more compact size of 2 mφ × 7 mH. Further, when the temperature of the powder to be supplied is high, the powder can be cooled at the same time as the powder is mixed by inflowing cold air such as air from the inlet duct.

In summary, the present invention has the following effects.

(1) Since the gas does not flow through the powder layer as in the fluidized mixing method, the pressure loss is small and the power consumption of the fan is small.

(2) Since efficient mixing is possible, a large amount of powder can be mixed in a small-sized container.

(3) The powder can be mixed and cooled at the same time by taking in cold air such as air from the gas inlet duct.

[Brief description of drawings]

FIG. 1 is a front sectional view showing an embodiment of the present invention, FIG. 2 is a plan sectional view of FIG. 1, FIG. 3 is an explanatory view showing the behavior of powder in a mixing tank, and FIG. Explanatory drawing showing the wind speed distribution in the mixing tank, FIGS. 5 and 6 are conventional fluidized type mixing devices, FIG. 7 is a schematic view showing an example of a calcining furnace used in a cement manufacturing plant, and FIG. Is a plan sectional view of FIG. 7, FIG. 9 is an explanatory view showing the relationship between the inlet wind speed Vin in the gas inlet duct and the pressure loss of the mixing tank, and FIG. 10 is an explanatory view showing the relationship between Vin and the degree of mixing, FIG. 11 is an explanatory diagram showing the relationship between the powder mixing ratio and the pressure loss in the mixing tank, and FIG. 12 is an explanatory diagram showing the relationship between the powder mixing ratio and the electric power consumption rate of the fan. 1 ... Mixing tank, 2, 2a, 2b ... Gas inlet duct, 3 ... Exit duct, 4 ... Powder supply pipe, 5 ... Powder, 6 ... Gas, 7 ... Dust collector, 8 ...... Partition plate, 9 …… Upper chamber, 10 …… Lower chamber, 11 …… Fan, 12 …… Powder layer, 13 …… Powder discharge pipe, 14 …… Pulling device, 15 …… Lower part, 16… … Upper, 17 …… Middle part, 26 …… Burner.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Maruyama 1-12-32 Nishihonmachi, Ube City, Yamaguchi Prefecture Ube Headquarters, Ube Head Office (56) Reference Japanese Patent Publication No. 42-1691 (JP, B1)

Claims (4)

[Claims] 1. A mixing tank 1 having a plurality of powder supply pipes 4 in the periphery thereof, a gas inlet duct 2 in the lower portion, and an outlet duct 3 in the upper portion, and a plurality of types of powders. Is continuously supplied from the powder supply pipe 4 into a gas flowing from the gas inlet duct 2 and flowing at a speed at which the powder can be suspended in the mixing tank 1, and the gas is flowed out along with the gas flow. The powder carried to the outside of the mixing tank 1 through the duct 3 is collected by a dust collecting device 7 such as a bag filter installed downstream so that a plurality of powders are uniformly mixed. Air flow type powder mixing method. 2. The mixing tank 1 comprises an inverted two-stage cone-shaped lower portion 15 connected to the gas inlet duct 2, a cone-shaped upper portion 16 connected to the outlet duct 3, and a cylinder sandwiched between the upper portion 16 and the lower portion 15. The air flow type powder mixing method according to claim 1, wherein the air flow type powder mixing method is constituted by three parts of the intermediate portion 17 in the shape of a circle. 3. An air flow system according to claim 1, wherein high temperature powder is supplied into the mixing tank 1 and the powder is mixed and cooled at the same time by cold air flowing from the gas inlet duct 2. Powder mixing method. 4. The method according to claim 1, wherein the gas inlet velocity Vin is 15 to 30 m / s, and the mixture ratio of powder and gas [kg powder / kg gas] is 3 to 6. (3) The airflow type powder mixing method as described above.