JPH0749100B2 - Method for producing inorganic spherical particles - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method and an apparatus for producing spheroidized particles from an inorganic powder raw material, and to a method for economically increasing or decreasing the production of spherical particles in a stable quality state. .

[Conventional technology]

Conventionally, as a technique for producing inorganic particles such as fused silica used as a sealing agent, for example, JP-A-62-241541 and JP-A-62-241542 provide inorganic powder to a fuel gas / oxygen burner. Then, after forming molten particles in the combustion area, cooling gas (for example, air) in the cooling area connected to it
A technique has been proposed in which the particles are blown and rapidly cooled to prevent fusion of particles.

[Problems to be solved by the invention]

In the prior art, when there was a demand to increase or decrease the production for the standard operation, it was possible to cope with this while keeping the quality at a high level, only within a narrow range where the burner load could be changed. That is, the fuel gas / oxygen burner used for these has a high burning rate, and when the flow velocity of the burner nozzle portion is lower than the burning rate, a flashback phenomenon occurs, and burner melting damage trouble occurs in an instant. Therefore, the changeable range of the combustion load is considered to be about 75 to 100%.

The amount of the inorganic powder raw material supplied to the burner can be easily increased / decreased (increased / decreased production), but if it is excessively supplied to the combustion load, the spheroidization rate will decrease due to the decrease in flame temperature, and good quality spherical particles will be produced. I can't get it.

On the other hand, in the case of production reduction, the supply amount of the powder raw material is reduced in proportion to the reduction of the combustion load, but this is limited by the lower limit value of the burner. If the supply amount of the powder raw material is further reduced under the condition of the lower limit fuel load, the powder will stay in the high temperature flame for a long time, and the fusion of the melts will cause coarsening and increase of the coarse particle ratio.

According to the study by the present inventors, the cooling gas supplied into the cooling chamber is discharged into the subsequent system from the lower side of the cooling chamber after spherical solidification, but a part of the cooling gas rises to the upper spherical chamber. I will do it.

It has been found that the increased cooling gas is caught in the combustion flame formed by the fuel gas / oxygen burner to lower the flame temperature and lower the melting effect of the inorganic powder raw material.

The present invention focuses on the fact that the flame temperature in the spheroidizing chamber can be freely controlled if the cooling gas supply amount is controlled from the above phenomenon, and the spheroidized particles by controlling the flame temperature by controlling the cooling gas supply amount. It is possible to easily increase or decrease the production.

[Means for solving problems]

The present invention includes (1) a high temperature flame and an inorganic powder raw material are brought into contact with each other in a spheroidizing chamber of a vertical furnace having a spheroidizing chamber and a cooling chamber for spheroidizing treatment, and then a cooling gas is supplied to cool the pulverizing chamber. In the method for producing inorganic spherical particles, the amount of cooling gas supplied is adjusted according to the amount of the inorganic powder raw material supplied to control the high temperature flame temperature.

The present invention will be described below by taking a facility for producing spherical particles of silica as an example.

The vitrification rate is used as an index that simply expresses the spheroidization rate. This is the true specific gravity of glass (2.21),
Focusing on the true specific gravity of quartz (2.65), it is estimated from the true specific gravity of the product (A) using the following formula.

Glass ratio (%) = (13.3 / A-5.02) x 100 Figure 1 shows the calculation results for the flame temperature and the temperature rise of the injected particles. The flame temperature is transmitted to silica as it passes through the burner port. It decreases due to heat, heat loss, and entrainment of surrounding gas.

Now, in the case of a flame (a) having a temperature distribution as shown in FIG.
For melting, a powder injection amount of 200 kg / H is suitable, but 120 kg / H is too high, that is, the particles are heated to a temperature higher than the melting point to cause coarsening due to coalescence of particles. Meanwhile 280 kg /
With H, the temperature is too low to reach the melting point, so the product has a low vitrification rate. The ideal flame temperature distribution when the injection amount is 120 kg / H is the flame temperature b shown by the dotted line in FIG. 1, and it is desirable that the flame temperature be lowered to the melting point at the distance where melting is completed.

As a result of the investigation, it was found that the flame of the thermal spray burner diffuses while entraining the surrounding gas, but entrains 1 to 5 times the amount of the combustion gas around the burner at 1 m from the burner. When surrounding gas is entrained 1.5 times as much as combustion gas at 1m from burner, ignore heat loss of flame and
Estimating the flame temperature at the m point, the flame temperature is 1480 ° C when the ambient temperature is 800 ° C, 1720 ° C when the ambient temperature is 1200 ° C, and the flame temperature is adjusted by changing the ambient gas temperature. I know what I can do. As a means for changing the ambient gas temperature, it was examined to increase or decrease the amount of cooling gas (clean air is used here) blown into the cooling chamber, and the results shown in FIG. 2 were obtained.

If this result is utilized, when the injection amount of the inorganic powder is small, the particles become high temperature and coalesce into coarse particles, so to prevent this, the flame temperature is lowered by increasing the cooling air flow rate, and the injection amount of the powder is reduced. When increasing, it is possible to stabilize the quality by decreasing the cooling air flow rate and raising the flame temperature.

However, if the amount of exhaust gas or temperature at the outlet of the cooling chamber fluctuates, the operation of the spherical particle separation equipment or gas treatment equipment in the subsequent process becomes unstable. Therefore, in the apparatus of the present invention, the heat and gas amounts of the entire process are balanced by separately replenishing the cooling chamber outlet pipe with an amount of gas corresponding to the increase or decrease of the cooling gas.

〔Example〕

In the apparatus example showing the embodiment of the present invention shown in FIG.
An inorganic powder raw material, fuel gas, and oxygen are injected into the spheroidizing chamber 1 from a thermal spray burner 3 provided on the ceiling of the spheroidizing chamber 1. Cooling gas is blown into the cooling chamber 2 connected to the lower side of the spheroidizing chamber through the regulating valve 6 to cool the high temperature flame and the molten particles from the spheroidizing chamber 1. The spherical particles and the combustion exhaust gas are sent from the lower part of the cooling chamber 2 to the particle and gas treatment process through the air feeding pipe 10. Discharge valves 8 and 9 for coarse particles are provided in the lower portion of the cooling chamber 2 to regularly discharge the inorganic molten material, the refractory material and the like that have fallen off.

Here, air is used as the cooling gas, and the air from the fan 4 is dust-removed by the filter and then blown into the cooling chamber 2 as the cooling gas through the control valve 6. In the device of the present invention, this cooling air is branched and the cooling chamber outlet air feeding pipe is branched.
A piping was provided so that 10 and spherical particles could be supplied through a control valve 7 to the upstream side of a cyclone 11 where primary separation was performed. The flow rate of the cooling air is adjusted by a thermometer 13 that detects the temperature of the gas rising in the spheroidizing chamber 1. When the injection amount of the inorganic powder raw material is large, the spheroidizing chamber temperature is increased due to the reduction of the cooling air, and conversely. When the injection amount of the powder raw material is small, the cooling air is increased and the spheroidizing chamber temperature is lowered.

In this way, it is possible to stably obtain a spherical product with a high vitrification rate while preventing coarsening due to fusion of the powder raw material, but the amount of gas discharged from the cooling chamber and the temperature change In a centrifugal separator such as a cyclone, the separated particle size distribution is different. Therefore, in this embodiment, cooling air can be supplied to the inlet side of the cyclone 11, and the cooling air flow rate is adjusted by the control valve 7. The particle size of particles separated from the cyclone 11 was controlled, and particle separation and gas treatment in the lower step were facilitated. Next, an example of operation by the above apparatus will be described.

As standard operation, LNG4 as fuel gas to the thermal spray burner 3
0 Nm ³ / H and 200 Nm ³ / H of oxygen were supplied, and 200 kg / H of silica as an inorganic powder raw material was sprayed on the high temperature flame. At this time, the spheroidizing chamber temperature is 850 to 950 ° C, and the cooling chamber 2
The fused silica was cooled by 3000 Nm ³ / H of cooling air blown into the glass, and the spherical silica was discharged through a pneumatic tube 10.

Example-1 In the above standard operation, the silica spray amount was 280 from 200 kg / H.
When it was increased to kg / H, the vitrification rate decreased to 82-87%, making it insufficient as a sealant. 900Nm to where the cooling air blown into the cooling chamber 2 from 3000Nm ³ / H ³ / H
Spheroidizing chamber temperature 13 from 850 to 900 ℃ to 1050 to
When the temperature was raised to 1100 ° C, the silica spray amount was 240 kg / while maintaining the vitrification rate of 94-96% of the product under the same combustion conditions.
I was able to increase to H.

This is a conventional fuel LPG 1Nm ³ silica spray amount 5kg 6k
It means that we could increase to g. However, since the outlet gas amount in the cooling chamber 2 decreased and the outlet gas temperature rose to a temperature as high as 350 ° C to 800 ° C, 1500 to 2000 Nm ³ / H upstream of the cyclone 11 in order to continue stable operation of the particle separation process. Cooling air was replenished from the control valve 7.

Example-2 On the other hand, when the thermal spraying amount of silica was reduced by 40% from 200 kg / H to 120 kg / H, the following operation was performed: The first stage: First, the fuel gas amount to the burner was reduced. It was reduced to the limit combustion load (75%) for stable operation. (At this time
LPG is to 30Nm ³ / H than 40Nm ³ / H, 150Nm than oxygen 200Nm ³ / H ³ /
Reduced to H), whereas the cooling air is reduced from 3000 Nm ³ / H 2200 nm to ³ / H, the sprayed amount became 150 kg / H than 200 kg / H. Second stage: further increase the spray amount by 12 while preventing coarsening of silica.
In order to reduce the amount to 0 kg / H, the cooling air volume to the cooling chamber 2 is set to 220
It was 3100-3300 Nm ³ / H from 0 Nm ³ / H. As a result, the spheroidizing chamber temperature 13 was 600 to 700 ℃, and the quality of vitrification rate of 94 to 97% could be maintained without increasing the coarsening ratio of the product.

〔The invention's effect〕

As described above, according to the present invention, it is possible to economically increase or decrease the production of spherical particles having stable quality.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the distance from the burner and the flame temperature and the spheroidizing particle temperature, and FIG. 2 is a diagram showing the relationship between the cooling air flow rate and the spheroidizing chamber surrounding gas temperature and the cooling chamber outlet gas temperature. FIG. 3 is an explanatory diagram of an example of a device showing an embodiment of the present invention. 1 ... Sphericalizing chamber, 2 ... Cooling chamber 3 ... Thermal spray burner, 4 ... Cooling air fan, 5 ... Dust filter, 6 ... Cooling air control valve, 7 ... Cyclone inlet air control valve, 8, 9 ... Coarse particle discharge valve, 10 ... pneumatic tube 11 ... cyclone 12 ... lower process for particle separation and gas treatment 13 ... spheroidizing chamber thermometer

Claims (1)

[Claims] 1. An inorganic substance in which a high temperature flame and an inorganic powder raw material are brought into contact with each other in a spheroidizing chamber of a vertical furnace having a spheroidizing chamber and a cooling chamber to perform spheroidizing treatment, and then a cooling gas is supplied to cool the inorganic substance. In the method for producing spherical particles, the amount of cooling gas supplied is adjusted in accordance with the amount of the inorganic powder raw material supplied to control the high temperature flame temperature.