JP2000351620A - Microsilica having exactly adjusted bulk density, its production and production apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a microsilica having an exactly adjusted bulk density and a method and in apparatus for producing the microsilica. SOLUTION: A microsilica is fed to a closed space and compressed air is sprayed on the microsilica from below in a flow rate to cause the fluidization of the microsilica. The microsilica is fed to the closed space continuously or substantially continuously and discharged from the closed space continuously or substantially continuously. The weight of the microsilica in the closed space and the level of the microsilica in the closed space are continuously recorded. The bulk density of the microsilica in the closed space is measured based on the recorded weight of the microsilica in the closed space and the recorded level of the microsilica in the closed space. The weight of the microsilica fed to the closed space is recorded and the discharge of the microsilica having a preset bulk density from the closed space is controlled so as to retain the set bulk density of the microsilica in the closed space.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to the production of micro-silica having a strictly controlled bulk weight.

[0002]

BACKGROUND OF THE INVENTION In the production of materials having high silicon contents, such as silicon, ferrosilicon, silicon carbide, and other silicon-containing alloys, in a smelting furnace, a significant amount of silicon is converted to silicon dioxide. Silicon oxide is generated. Similar forms of silicon are recovered from the production of molten oxides such as mullite, zirconia and zircon mullite. This silicon dioxide is extremely fine and is generally called microsilica (trade name of Applicant Company, chemical name: Silicon Flower).

[0003] Due to the extremely lightweight nature of the microsilica, it does not remain in the refining process, but rather is discharged from the refining process together with the exhaust gas into the flue of the furnace. Since the emitted dust becomes environmental pollution, it is necessary to collect this dust from the fumes from the smelting furnace. Typical dry methods used in this context consist of bag house filters and the like.

The recovered very fine microsilica having a typical weight-to-volume of 150-300 kg / m ³ has to be treated. Various uses of microsilica are known as refractory ceramics, concrete and rubber fillers and non-solidifying materials for fertilizers. If this material is used for these special applications, of course, it usually needs to be transported to its end user. The transportation cost is prohibitively high because microsilica is very light and finely divided.

From the description of US Pat. No. 4,126,424,
Reversible to increase the bulk density of microsilica consisting of charging microsilica in an enclosed space and injecting pressurized air from below into microsilica at a flow rate that causes fluidization in a batch process for at least 5 hours The waterless system is known.

The system described in US Pat. No. 4,126,424 has been in commercial use for more than 20 years,
There are two main disadvantages. First, the scheme is a batch scheme that limits the capabilities of the scheme. Second, it is difficult to control the final bulk density of the densified microsilica produced in this manner. Third, this known approach makes this material difficult to disperse in certain end-use applications.
It tends to produce the densified microsilica having a high bulk density of 50- 700 kg / m in the range of ^3.

[0007]

SUMMARY OF THE INVENTION It is a primary object of the present invention to provide a microsilica having a strictly (evenly) adjusted bulk density, a method and apparatus for continuously producing the same.

[0008]

SUMMARY OF THE INVENTION Accordingly, the present invention provides microsilica in an enclosed space and injects compressed air from below into the microsilica at a flow rate to cause fluidization of the microsilica. In the production of microsilica having a strictly controlled bulk density, the microsilica is continuously or substantially continuously charged into the enclosed air and continuously or substantially continuously discharged from the enclosed space. And
The weight of the microsilica in the enclosed space and the level of the microsilica in the enclosed space are continuously recorded, and the bulk density of the microsilica in the enclosed space is determined by the recorded weight of the microsilica in the enclosed space and the volume of the microsilica in the enclosed space. Measure based on the recorded level of microsilica, record the weight of microsilica charged in the enclosed space, and discharge the densified microsilica set from the enclosed space to the microsilica in the enclosed space. The present invention relates to a method for producing micro silica having a strictly adjusted bulk density, which is adjusted to maintain a set bulk weight.

In a preferred embodiment of the present invention, the bulk weight of the microsilica in the enclosed space is from 425 kg / m ³ to 550 kg / m ^{3.
When it is} less than ³ (excluding 550 kg / m ³ ), micro silica is discharged from the closed space.

In another preferred embodiment, the microsilica is charged at the top of the enclosed space and discharged at or near the bottom of the enclosed space.

The weight of the microsilica in the closed space is weighed and recorded when the closed space is emptied and the weighing cell disposed in the closed space, and the weight of the microsilica in the closed space is thereby recorded. Can be easily recorded as microsilica charged in the enclosed space.

The level of microsilica in the enclosed space is recorded in the usual way, for example by using an ultrasonic measuring device.

According to the present invention, microsilica can be continuously densified to a predetermined bulk density.

To start the process, microsilica is charged into the enclosed space and the flow of compressed air through the bottom of the fluidized bed is started. The weight of the microsilica is then monitored by recording the weight of the microsilica in the enclosed space and the level of the microsilica in the enclosed space. When the bulk weight of the microsilica in the enclosed space reaches a preset value, on the one hand, it starts a continuous or substantially continuous discharge from the enclosed space and at the same time further microsilica in the enclosed space. Is started continuously or substantially continuously, where the weight of the microsilica discharged over a certain time interval becomes equal to the weight of the microsilica supplied to the enclosed space.

[0015]

FIG. 1 shows a silo 1 having a fluidized bed 2 and a device 3 for supplying fluidized air to the fluidized bed 2. Part of the silo wall is notched on the drawing. The silo 1 is provided with four groups of load cells for recording silo weight. The signal from the load cell is recorded in the computer 5. At the top of Silo 1,
A level indicator 6 is provided for recording the level of microsilica in the silo. This level indicator is preferably an ultrasonic measuring device. The signal from the level indicator is also recorded in the computer 5. Based on the signals from the load cell 4 and the level indicator 6, the bulk density of the microsilica in the silo is calculated at short intervals.

Untreated microsilica having a low bulk density is charged into silo 1 through inlet opening 7. The weight of the microsilica loaded in the silo 1 is recorded on the computer 5. The microsilica having the adjusted bulk density is discharged from the silo 1 through the discharge opening 8. Discharge opening 8
The weight of the microsilica discharged through is recorded in the computer 5.

Finally, the silo 1 has a filter 9 and an outlet opening 10 for air from the silo 1 at the top of the silo. The micro silica collected from the air by the filter 9 is returned to the silo 1.

To start the process, fluidized bed 2 is supplied with air through air supply pipe 3 and through microsilica inlet opening 7 until a fluidized bed of microsilica having a set level 11 is established in the silo. Microsilica is charged into the silo. Recording of the weight of microsilica and the level of microsilica in silo 1 is started, and then the bulk density is calculated and monitored by computer 5. Initially, no microsilica is discharged until the calculated bulk density of the microsilica in silo 1 reaches a set value. When the microsilica reaches this set value, the discharge of the microsilica having the adjusted bulk density through the discharge opening 8 is started, and the weight of the discharged microsilica is recorded. Furthermore, the charging of the untreated microsilica is simultaneously started through the microsilica inlet opening 7.

The weight of microsilica charged into the silo is kept at about the same level as the weight of micros discharged from the silo. If the bulk weight measured during microsilica discharge tends to decrease, the microsilica discharge rate is reduced as well as the untreated microsilica charge rate. If the measured bulk weight of the microsilica tends to increase upon discharge, the microsilica discharge rate is increased as well as the microsilica charge rate. This method and the regulated fluctuations of the fluidizing air flow result in a continuous or substantially continuous charge of untreated microsilica and a steady state process with a predetermined and tightly controlled bulk density. can get.

[0020]

EXAMPLE Microsilica having a bulk density of 250 kg / m ³ and obtained from the production of silicon in an electric smelting furnace is shown in FIG.
Was inserted into the silo 1 shown in FIG. At the same time, compressed air at room temperature is supplied to the fluidized bed bottom 2 through the supply device 3. The air flow is regulated to fluidize the microsilica in the silo. Starting amount of micro silica is 1
Silo 1 to obtain the level of microsilica
To supply. Before the supply of microsilica, the silo 1 is weighed by the weighing cell 4 and the weighing of the silo is performed continuously throughout the test. The level of microsilica is measured by a level indicator 6,
When the microsilica level 11 drops, another microsilica is fed to silo 1. The bulk weight of microsilica in the silo was calculated by computer based on the recorded weight of microsilica and microsilica level 11. This calculation was performed at very short time intervals. The purpose of this example is to produce microsilica having a bulk density of 450 kg / m ³ . Therefore, silo 1
When the bulk density of the micro silica in this
Discharge of treated microsilica having a bulk density of kg / m ³ was started through discharge opening 8. The weight of the discharged microsilica was continuously recorded, and a weight of microsilica corresponding to the weight of the discharged microsilica was charged through the inlet opening 7. The amount of the discharged microsilica was adjusted based on the measured bulk weight of the microsilica in the silo 1 so that the bulk weight in the silo 1 was kept as close to 450 kg / m ³ as possible. In other words, a stable operation of continuously producing microsilica having a bulk density of 450 kg / m ³ was obtained.

[0021]

According to the present invention, from 425 kg / m ³ to 550 kg
Microsilica having a bulk density of less than / m ³ can be easily obtained by operation in a continuously stable state.

The use of microsilica having a bulk density within the above specified range facilitates homogeneous and dispersed addition of microsilica to a mixture for various products,
In addition, the transportation and storage costs of the microsilica can be reduced.

[Brief description of the drawings]

FIG. 1 shows an outline of an apparatus suitable for carrying out an example of a production method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silo 2 Fluidized bed 3 Air injection device 4 Load cell 5 Computer 6 Level indicator 7 Inlet opening 8 Outlet opening 9 Filter 10 Air outlet 11 Setting level

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Otaru Realm Norway 4626 Kristiansan S. Cartea 20 Ei (72) Inventor Svein Zytrestatd Norway 4630 Kristiansand S.S. SOMELOGT 10 F term (reference) 4G072 AA25 BB05 GG01 GG03 HH14 HH40 LL05 MM03 QQ03 RR11 RR17 TT04 UU07 UU08 UU30

Claims (7)

[Claims] 1. A bulk weight is characterized by being prepared from 425 kg / m ³ to less than 550 kg / m ^3, strictly microsilica having a bulk density adjusted. 2. A strictly controlled bulk density for supplying microsilica to the enclosed space and for injecting compressed air from below into the microsilica at a flow rate to cause fluidization of the microsilica. In the production of microsilica, the microsilica is continuously or substantially continuously charged into the enclosed air and discharged continuously or substantially continuously from the enclosed space, and the microsilica in the enclosed space is The weight and microsilica level in the enclosed space were continuously recorded and the bulk density of the microsilica in the enclosed space was recorded by the recorded weight of the microsilica in the enclosed space and the microsilica in the enclosed space. Measure based on the level, record the weight of the microsilica charged in the enclosed space, and discharge the microsilica having a predetermined bulk density from the enclosed space. A process for producing microsilica having a strictly controlled bulk density, characterized in that the outlet is adjusted to maintain the set bulk weight of the microsilica in the enclosed space. 3. The bulk weight of the microsilica in the closed space is
From 425 kg / m ³ when it is less than 550 kg / m ^3, the preparation of micro-silica having a strictly regulated bulk density according to claim 1, wherein consisting in discharging the microsilica from the enclosed space. 4. The strictly controlled bulk density microsilica according to claim 1, comprising charging the microsilica from the top of the enclosed space and discharging the microsilica from or near the bottom of the enclosed space. Manufacturing method. 5. The method of claim 1, wherein the weight of the microsilica in the closed space is recorded in a weighing cell disposed in the closed space. 6. The weight of the microsilica in the closed space,
5. The strictly regulated method according to claim 4, wherein the measurement of the bulk density based on the level of the microsilica in the enclosed space is performed by a computer receiving a signal from a weighing cell and a level indicator of the microsilica in the enclosed space. Production method of micro silica having high bulk density. 7. A strictly controlled bulk density for supplying microsilica to the enclosed space and for injecting compressed air from below into said microsilica at a flow rate to cause fluidization of said microsilica. A fluidized-bed furnace for producing microsilica, comprising a load cell and a level indicator connected to a computer in a closed space of the fluidized-bed furnace, the production of microsilica having a strictly adjusted bulk density. For fluidized bed furnace.