JP2012091978A - Method for manufacturing perlite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing high durability perlite that undergoes a small change in the bulk density and does not lose its lightness and hollow state peculiar to perlite after manufacturing.SOLUTION: The method for manufacturing perlite includes pulverizing natural glassy rocks as a raw material and foaming by heating, wherein the water content in the raw material is adjusted to 3.6-5.0 wt.% and the raw material is foamed by temperature rising from this water content state to an expansion temperature within 60 seconds. For example, a raw material having a particle size of ≤0.5 mm is used, the water content in the raw material is adjusted to 3.6-5.0 wt.% at ≤300°C, and the raw material is foamed by temperature rising from this water content state to 800-1,200°C within 60 seconds.

Description

The present invention relates to a method for producing a highly durable pearlite. The present invention provides a method for producing a highly durable pearlite that improves the strength of the pearlite and has a small change in bulk density that does not lose the light weight and hollow state that are the characteristics of the pearlite after production.

Perlite is a weight reduction material used for weight reduction. For example, the weight can be reduced by mixing pearlite into mortar, roof tiles, and outer wall materials.

In pearlite manufacturing, rhyolite (pearlite, obsidian, etc.), which is acid volcanic rock, is crushed and heated and foamed to produce products. In the process of heating and foaming, an airflow firing furnace or a rotary kiln is used. In an air-flow firing furnace, foaming is performed by contact of a high-temperature gas or a flame formed in the furnace with a raw material for a fraction of a second to several tens of seconds. In the rotary kiln, the raw material is heated by the radiant heat of the furnace wall, the burner frame, and the hot gas in the furnace while sliding on the rotary kiln furnace wall, and foaming is performed. The rotary kiln has an advantage that the foaming time is as long as several minutes to several tens of minutes, and uniform foaming is performed.

Perlite foams at a ratio of several to five times the raw material particles, and the thickness of the surface shell is several microns, which is very thin. For this reason, it is weak against the pressure from the outside. In particular, after pearlite is manufactured, it is often sent pneumatically through the transport pipe for storage in silos, etc. At this time, the transport speed is approximately several m / sec, which is quite fast. In addition to the straight pipe portion, there are bent portions at various locations, and the pearlite being transported collides with the bent portion and breaks, so that the hollow state is lost and the bulk density gradually increases.

In order to increase the strength of pearlite, one measure is to reduce the expansion ratio and make the shell thicker, and there is a method of firing pearlite at a low temperature. However, since firing at a low temperature narrows the width of the foaming temperature region, heating is insufficient and unfoamed particles are easily formed. Therefore, the manufactured pearlite is likely to cause material separation, resulting in uneven quality. On the other hand, when fired at a high temperature, excessive foaming occurs and the strength decreases.

Therefore, it is known to control foaming of pearlite in order to improve the quality of pearlite (Patent Documents 1 and 2). Pearlite made from pearlite becomes foaming agent when the water in pearlite becomes the foaming agent, and when it reaches the melting point temperature, the water vaporizes and foams. The thickness becomes thinner and the strength becomes weaker. Therefore, a manufacturing method is known in which preheating is performed in advance to control the amount of water in the pearlite, and then heating to the foaming temperature.

As a method for reducing unfoamed raw materials for uniform firing, it is known to use a mixture of two types of foamed raw materials having different bulk densities after foaming (Patent Document 3). In this method, the bulk density is controlled by mixing and using raw materials having different bulk densities that foam optimally at the same temperature.

JP-A-7-277851 JP 2007-320805 A Japanese Patent No. 3528390

As a means for producing highly durable pearlite, when performing multiple firings such as pre-firing, a corresponding firing furnace is required, and the firing installation tends to be large, and installation space and equipment costs are excessive. Burden and complicated operation of the apparatus. In addition, when different types of raw materials are used, different raw material supply silos, supply paths, mixing facilities, and the like are required. In this case as well, large-scale equipment installation is required. In any case, the mixing of unfoamed particles is inevitable.

When unfoamed particles are mixed, the pearlite tends to be damaged during storage or transportation, and the density of the manufactured pearlite tends to increase. In addition, when fired at a low temperature so as to have high strength, the number of unfoamed particles tends to increase, and the quality of pearlite decreases. Even if the pearlite shell is made thicker and stronger, if unexpanded particles are present, the expanded particles collide with the unexpanded particles and the pearlite is damaged, and the weight reduction and the hollow state cannot be maintained. Thus, in the conventional manufacturing method, there was a problem that there was much quantity of the unexpanded particle which is a cause of breakage.

The present invention solves the problem that the pearlite is damaged by unfoamed particles and the bulk density is increased at the downstream side after manufacture of pearlite, that is, at the time of pneumatic transportation, storage, product transportation, end product production, etc. Provided is a production method that suppresses damage after production and suppresses an increase in bulk density by reducing foam particles as much as possible.

According to this invention, the manufacturing method of the pearlite which consists of the following structures is provided.
[1] A method for producing pearlite using natural glassy rock as a raw material, crushing the raw material, heating and foaming, and adjusting the water content in the raw material to 3.6 to 5.0 wt%. A method for producing pearlite, wherein the foaming is performed by raising the temperature from the above state to the foaming temperature within 60 seconds.
[2] The moisture content in the raw material is adjusted to 3.6 to 5.0 wt% at 300 ° C. or lower, and the temperature is increased from 800 ° C. to 1200 ° C. within 60 seconds from the state of the moisture content, and foamed. ] The manufacturing method of the pearlite described in.
[3] The method for producing pearlite according to [1] or [2] above, wherein a raw material having a particle size of 0.5 mm or less is used.

In the production method of the present invention, the moisture content of the raw material is adjusted to a predetermined range, and the temperature rising rate up to the foaming temperature is controlled to a predetermined rate or more. Specifically, the amount of moisture in the raw material is adjusted to 3.6 to 5.0 wt%, and the temperature is raised from this moisture amount state to the foaming temperature within 60 seconds, so the amount of unexpanded particles is 15 wt% or less. Furthermore, since excessive foaming is also suppressed, it is possible to manufacture a high-quality pearlite that has a remarkably small change in bulk density during pneumatic feeding.

The production method of the present invention is a method for producing pearlite in which natural glassy rock is used as a raw material, and the raw material is pulverized, heated and foamed, and the water content in the raw material is adjusted to 3.6 to 5.0 wt%. The method for producing pearlite is characterized in that foaming is performed by raising the temperature from the state of the water content to the foaming temperature within 60 seconds.

In the production method of the present invention, (i) the water content in the raw material is adjusted to 3.6 to 5.0 wt% at 300 ° C. or less, and the temperature is raised from 800 ° C. to 1200 ° C. within 60 seconds. And (b) an embodiment using a raw material having a particle size of 0.5 mm or less.

In the production method of the present invention, the natural glassy rock used as a raw material may be pearlite, pine stone, obsidian, shirasu, and the like. The raw material preferably has a particle size of 0.5 mm or less. When the particle size is larger than this, unfoamed particles tend to increase.

In the production method of the present invention, the moisture content of the raw material is adjusted to a predetermined range. Specifically, the water content in the raw material is adjusted to 3.6 to 5.0 wt%. This water content is calculated from the weight loss when the raw material dried at 100 ° C. is heated to 1000 ° C. If the water content of the raw material is less than 3.6 wt%, the number of unfoamed particles increases, and if it exceeds 5 wt%, the amount of excessive foaming and rupture increases.

In the production method of the present invention, the moisture content of the raw material is adjusted to a predetermined range, and the temperature rising rate up to the foaming temperature is controlled to a predetermined rate or more. Specifically, the raw material temperature before heating is set to 300 ° C. or lower, the water content in the raw material is adjusted to 3.6 to 5.0 wt% at 300 ° C. or lower, and the water content is set to 800 ° C. within 60 seconds. Heat rapidly to above. Since the foaming temperature of pearlite is approximately 800 ° C. to 1200 ° C., it is heated to this temperature within 60 seconds.

When the raw material temperature before heating exceeds 300 ° C. and the temperature rising time to 800 ° C. or more exceeds 60 seconds, the moisture in the raw material is decomposed and the moisture contributing to foaming is reduced, so that the unfoamed portion increases. The residence time at 800 ° C. to 1200 ° C. is preferably 1 second to 180 seconds. When the residence time is 1 second or less, heat is not easily transferred to relatively large particles, and unfoamed easily. On the other hand, when the residence time is 180 seconds or more, the foamed particles melt and sinter and the hollow state is impaired.

As the heating means, an electric furnace, a rotary kiln, an airflow firing furnace, a fluidized bed firing furnace, or the like can be used, but an airflow firing furnace or a fluidized bed firing furnace is preferable in order to achieve the above-described rate of temperature rise.

The unexpanded particles refer to particles that are not expanded and particles that are insufficiently expanded, and specifically, particles whose expanded state does not reach the expansion standard. The foaming standard is a standard that distinguishes unfoamed particles from foamed particles. The foaming state varies depending on the production conditions such as the type of raw material and heating conditions, so specific foaming standards depending on the production conditions and the desired foaming state. Can be determined.

For example, the bulk density and the floating rate (ratio of floating in water when thrown into water) can be used as an index for foaming. Generally, nacreous particles with a bulk density of about 1.0 g / cm ³ are used as raw materials and heated to 800 ° C. to obtain expanded particles with an overall bulk density of about 0.2 g / cm ³ and a floating rate of about 85%. Can do. This value may be used as the foaming standard.

For example, the entire foamed particles having a floating rate of 85% include a non-floating portion corresponding to 100% -85% = 15%, and this non-floating portion is generally unfoamed with a bulk density of 1.0 g / cm ³ or more. Particles. When there are many such heavy particles, the tendency to destroy the surrounding light foam particles becomes large. Therefore, when the bulk density is used as an index, for example, a bulk density of 1.0 g / cm ³ is used as a foaming standard, and a raw material that reduces this amount is used. In this case, for example, when the number of particles having a bulk density of 1.0 g / cm ³ or more is increased, the particles having a large bulk density are heavier than the light foam particles having a small bulk density. When it receives, it is easy to destroy the surrounding light foam particles by impacting them.

Since the pearlite obtained by the production method of the present invention has few unexpanded particles, the expanded particles are difficult to be destroyed, so the change in bulk density due to handling during transportation or use is small.

Moreover, the pearlite by the manufacturing method of this invention is a high quality pearlite which has few unexpanded particles and consists of expanded particles which have a uniform bulk density. Since unexpanded particles are larger in density and heavier than expanded particles, if there are many unexpanded particles, material separation is likely to occur in the entire pearlite. For this reason, when products such as tiles and wall materials are processed by mixing pearlite, problems such as variations in mass occur between products. Since the pearlite of the present invention has few unexpanded particles and is formed of expanded particles having a uniform bulk density, material separation does not occur in the entire pearlite, and such a problem does not occur.

Even in the pearlite produced by the method of the present invention, some unfoamed particles are present, and when this is removed, pearlite having further excellent durability can be obtained. As a removal method, in order to remove the unexpanded particles based on the foam specific gravity or apparent specific gravity, a dry or wet specific gravity separator, a centrifugal specific gravity separator, an inertia force dust collector, or the like may be used. On the other hand, in order to remove unfoamed particles based on the rate of increase with respect to the raw material particle size, for example, a sieve having a pore diameter (sieving mesh) corresponding to the foaming standard rate is used, and the sieve residue is adapted, Can be removed.

The manufactured perlite is often stored in product silos, etc., but transportation to the silo is mainly by transportation with compressed air. In this transportation, pearlite is caused to flow through the transport pipe by compressed air, so that the pearlite flowing in the pipe is subjected to air pressure. In addition, since there is a vertical part or a curved part in the middle of the path, the pearlite flowing in the pipe often comes into contact with the pipe wall and is damaged due to friction. Furthermore, impact and pressure are applied to the pearlite during loading into the silo, storage, and transportation by truck or lorry vehicle.

When a lot of unexpanded particles are mixed in perlite during storage during transportation, the unexpanded particles are heavier than the expanded particles, so the unexpanded particles are lightened by impact or pressure during transportation, loading, storage, etc. The rate of collision with the foamed particles and their destruction increases. Since conventional pearlite has a large number of unexpanded particles, the ratio of the expanded particles to be destroyed during transportation is high, and the bulk density is significantly increased. On the other hand, since the pearlite of the present invention has very few unexpanded particles, the destruction by the unexpanded particles hardly occurs.

Since pearlite is a lightweight aggregate having a space inside, the weight of the material can be reduced by mixing it with building materials such as mortar, wall materials, roof tiles and the like. Moreover, since it has a cavity inside, it is also used as a heat insulating material. Since the pearlite produced by the method of the present invention has a very small change in bulk density, a high-quality lightweight building material can be obtained by blending it with a building material or the like.

The Example of this invention is shown with a comparative example. The water content, bulk density, and floating rate were measured as follows.
[Moisture content] Calculated from the weight loss when the raw material dried at 100 ° C was heated to 1000 ° C.
[Bulk density] Fill a container with a constant volume S (cm ³ ), grind the portion protruding from the opening, measure the total weight G1, subtract the weight G2 of the container from this, and weight the powder G3 (g) The powder weight G3 [G3 / S] g / cm ³ with respect to the volume S was defined as the bulk density.
[Floating rate] Floating rate is about 10 g of sample placed in a 200 ml graduated cylinder, water is added, and after stirring well, let stand until it is free of water turbidity. The volume Vb (cm 3) of the sample was measured, and the floating rate was calculated from Va / (Va + Va) × 100 (vol%).

[Example 1]
The raw materials of the components shown in Table 1 were used to pulverize to a maximum particle size of 0.3 mm, adjust the particle size, put in an airflow firing furnace, heat and foam to produce pearlite.
Table 1 shows the measurement results of the floating rate and bulk density of the fired pearlite. Perlite made from pearlite a to d having a moisture content of 3.6 to 5 wt% has a floating rate of more than 85%, and therefore the ratio of unfoamed raw material is 15 wt% or less (A1 to A4). The pearlite made from the pearlite e has a floating rate of 80.1% (B1), and the pearlite made from the pearlite f has a floating rate of 84.5% (B2), both of which have a low floating rate. This is probably because pearlite B1 made from pearlite e having a moisture content of 6% was ruptured by overfoaming, and pearlite B2 made from pearlite f was made less foamed due to its low moisture content.

About this manufactured pearlite, pearlite is transported with air at a transportation speed of 30m / sec using eight 90 ° bends and a pneumatic transportation pipe with a total length of 5m, and the density and the floating rate before and after transportation are measured. Compared before and after transportation.

Table 2 shows the measurement results of the bulk density before and after the pearlite was pneumatically fed.
Since A1 to A4 measured for the bulk density before and after pumping have little unfoamed content, the difference in bulk density before and after pneumatic feeding is small. On the other hand, B2 with many unexpanded particles has a large difference between before and after pumping, and it is considered that the hollow pearlite particles were damaged.

Table 3 shows the product quality when a mortar board using the above pearlite (A1 to A4, B1 to B2) was produced. When a mortar was prototyped with actual equipment using the above-mentioned pearlite, the pearlite (A1 to A4) made from pearlite a to d had a pearlite amount of a predetermined density compared to the designed amount of pearlite. The amount of perlite (B1, B2) made from nacre e and f is required to exceed 140% of the design amount. The product quality in the table is a comparison of the amount of pearlite used to obtain the product density set when the product is manufactured, and the amount used according to the design value is 100%.

[Example 2]
The nacre b used in Example 1 was heated by changing the temperature rising time from the temperature before heating (raw material temperature) to the foaming temperature (800 ° C.). The results are shown in Table 4. When the raw material temperature is 280 ° C., the floating rate exceeds 85%, but when the raw material temperature is 400 ° C., the floating rate is less than 85%. This is considered that when the temperature before heating is 400 ° C., the moisture in the raw material is decomposed and volatilized, and the foamed components are reduced, so that unexpanded particles are increased.

Further, when the temperature rising time to the foaming temperature is 60 seconds or less, the floating rate is hardly changed (C1 to C7). If the temperature rising time exceeds 120 seconds, the floating rate will decrease. This is thought to be due to the fact that the moisture in the raw material decomposes and volatilizes to reach the foaming temperature, the foaming component is reduced, and the amount of unfoamed particles is increased.

Claims (3)

A method for producing pearlite which uses natural glassy rock as a raw material, pulverizes the raw material, heats and foams, and adjusts the water content in the raw material to 3.6 to 5.0 wt%. A method for producing pearlite, wherein the foaming is performed by raising the temperature to a foaming temperature within 60 seconds.
The moisture content in the raw material is adjusted to 3.6 to 5.0 wt% at 300 ° C or lower, and the temperature is raised from 800 ° C to 1200 ° C within 60 seconds from the state of the moisture content, and foamed. A manufacturing method of pearlite.
The method for producing pearlite according to claim 1 or 2, wherein a raw material having a particle size of 0.5 mm or less is used.