Mineral wool production

Contents

INTRODUCTION

1 GENERAL INFORMATION

1.1 General characteristics and properties of mineral wool

2. MINERAL WOOL TECHNOLOGY

2.1 Raw materials

2.2Bakes for production of silicate melt

2.3Silicate melt properties

2.4Melt-to-Fiber Processing Methods

2.5 Binders and methods of their mixing with mineral wool

2.6 Forming of mineral wool carpet

3. CALCULATION OF MIXTURE COMPOSITION FOR MINERAL WOOL PRODUCTION

3.1 Method of compiling and solving algebraic equations

3.2Specific approach method

3.3Accalculation of charge

3.3.1The method of compiling and solving equations

3.3.2Specific approach method

4. MINERAL BALANCE CALCULATION

5. PURPOSE OF MINERAL WOOL AND ARTICLES BASED ON IT

5.1Views of thermal insulation products from mineral wool

6. CONTROL OF PRODUCTION OF MINERAL WOOL AND PRODUCTS

7. LITERATURE

General characteristics and properties of mineral wool

Technical requirements for mineral wool are given in DSTU B B.2.7942000 (GOST 464093). Mineral wool (minvata, mineral wool insulation, stone wool) - fibrous heat-insulating material on a synthetic binder, obtained exclusively from mineral raw materials - silicate melts of rocks (silicate melts from blast furnace slags, mixtures of sedimentary and eruptive rocks are often used)Mineral wool, i.e. the mineral fiber produced by the industrial method, is very similar in its properties to asbestos fiber. It is characterized by considerable resistance to high temperatures and chemicals [3]. Mineral wool also has excellent heat and soundproofing properties. In construction, it can almost completely replace asbestos fiber. Currently, a significant amount of mineral wool is being produced, which is widely used in construction. The color of mineral wool is white, light gray, greenish, brown, dark brown. The high heat-insulating properties of mineral wool are due to the presence of a large number of air pores: porosity reaches 95-96%. The diameter of the wool fibers ranges from 1 to 10 μm. As the fiber diameter increases, the thermal conductivity increases, so the standard limits the fiber diameter to no more than 8 μm. The length of the fiber ranges from 2-3 mm to 20-30 cm. The average diameter of the fibers and their length depend on both the chemical composition of the melt and a number of technological factors. The longer the fiber, the more resilient and durable the products are. In addition to fibers, cotton wool contains melt particles that do not stretch into the fiber. These inclusions were called "kings." The shape of these particles is mainly spherical. Kings increase the thermal conductivity of mineral wool, being "bridges" of heat transfer. The bulk weight of the mineral wool depends on the average fiber diameter, the content of the kings and the degree of compaction. The standard provides for the determination of volumetric mass at a specific load of 0.002 MPa, which corresponds to the load experienced by cotton wool during operation. At the same specific load, the volume mass increases with increasing diameter and content of the kings. The standard provides for the production of wool grades 75, 100, 125. The content of kings larger than 0.25 mm is limited by the standard: for grades 75-12%; 100-20%, 125-25%. Water absorption of mineral wool when immersed in water is very high - up to 600%).. Hygroscopicity ranges from 0.2 to 2%. The mushroom resistance of mineral wool depends on the operating conditions. Mineral wool is not a favorable environment for the development of fungi. However, under the influence of organic acids emitted by fungi, mineral wool can break down. The mushroom resistance can be improved by increasing the acidity of the fibers. The sintering temperature of cotton wool is 700-800 ° C, respectively, the application temperature is 600-700 ° C. Decentration of cotton wool can occur already at 500 ° C.

Acidic cotton is less susceptible to decontamination. Mineral wool has fire-retarding properties due to incombustibility and low thermal conductivity. The thermal conductivity depends on the fiber diameter, bulk and the content of non-fiber inclusions in the wool. An increase in fiber diameter entails an increase in thermal conductivity. As the fiber diameter increases from 3 to 12 μm, the thermal conductivity increases by 10%.

The raw materials for the production of mineral wool are most often industrial waste - metallurgical, and fuel slags, ashes, ceramic glass scrap, silicate brick, etc., as well as rocks.

The grinding of the raw materials contributes to the acceleration of silicate-forming reactions and melt homogenization, which is necessary to obtain stable fiber properties.

Mineral wool carpet moulding

Mineral wool carpet is formed in fibre deposition chamber, which consists of metal frame lined with sheet steel, with thermal insulation. The bottom of the chamber is a mesh or plate conveyor with a width equal to the width of the chamber. Exhaust air is sucked from the chamber under the conveyor, which facilitates the deposition of cotton fibers on it.

Depending on the direction of the energy carrier during melt processing, the chamber may be horizontal and vertical. The length of the chamber depends on the method of fiber production. In blast methods, the chamber should be long to avoid swirls from the impact of the energy carrier flow on the end wall.

lubricant, mainly emulsifier, in amount of up to 1% of fibre weight is introduced into fibre deposition chamber to provide dusting and increase fibre elasticity. In some cases, a binder is introduced into the fiberization chamber by sputtering. To seal the cotton wool layer coming out of the chamber, a press roller is used at the outlet of the chamber. Upon exiting the fiberization chamber, the carpet is rolled into a roll in the event of the release of raw (coma) cotton or its transfer to an off-stream plant for processing into products. In loose form, mineral wool is not practical for the following reasons:

1) during transportation and storage of cotton wool is compacted and its heat-insulating properties are deteriorated;

2) laying loose cotton wool in the structure requires a lot of manual labor, and severe antihygienic conditions are created due to dusting and prickling of cotton wool;

3) heat insulation properties of the structure with loose mineral wool can be deteriorated as a result of compaction, from shocks, especially during vibration.

The listed disadvantages of loose mineral wool are largely eliminated when making articles from it [4].

Calculation of charge composition for mineral wool production

Initial data for calculation of charge are chemical compositions of raw materials and specified acidity modulus of mineral wool, which is determined by assignment of mineral wool, conditions of its service in design and method of melt processing into mineral fibre.

The composition of the charge is calculated by two methods:

• a method of compiling and solving a system of algebraic equations;

• by sequential approximation.

Sequential approximation method

This method is that, being set by the content of any one oxide in the received mineral wool and knowing the content of this oxide as a part of raw materials, as a certain sequence find quantity of separate parts of furnace charge. Such a component is usually one of the oxides, which determines the amount of acidity modulus, most often SiO2.

Of the two types of raw materials that make up the charge, one is considered the main and the other is considered additional corrective, the amount of which is expressed through X. Then set by the optimal content of SiO2 in the melt (a). Knowing the percentage of SiO2 mainly (b) and additional feedstock (c), the equation is:

a = in + X (b-b)

from where is determined

X = (a-b )/( b-b)

Having calculated the quantity of additional raw material (in unit fractions), it is found by subtracting it from the unit the quantity of main raw material (1-X). The percentage of individual chemical oxides in the charge is then determined as shown in the following example.

Let the SiO2 content in the main and additional feedstocks be n and m (%), then the content can be expressed by equality,%:

as part of charge

SiO2=n(1-X)+mX

The content of other oxides determining the acidity modulus, i.e. Al2O3, CaO, MgO, is also found.

Substituting the found values in these four oxides into the formula for determining the acidity modulus, it is found its value. If the acidity modulus is within the specified limits, then the calculation of the charge composition is completed, counting only the content of both raw materials with a fraction of one in weight percent, and correction for the moisture content of the materials is made.

If the obtained acidity modulus exceeds the specified values, then another value of SiO2 content in the charge composition is set and calculation is repeated. At excessively high value of Mk for recalculation lower content of SiO2 is taken, and at insufficient value of Mk lower content of CaO is taken in composition of charge.

Purpose of mineral wool and product based on it

In industrial construction, mineral wool products are mainly used as heat and sound insulating materials. Semi-rigid and rigid plates on synthetic binder are used for heat insulation of enclosing structures. Thermal insulation of coatings in industrial buildings is organized using hard plates and plates of increased rigidity, which make it possible to do without cement bracing during roofing operations. Products such as cords and bundles made of mineral wool.

The field of application of decorative and acoustic plates of the Akmigran type is sound insulation and aesthetic design of interiors in public and industrial buildings with a relative humidity of not more than 70%. For heat and sound insulation of industrial and energy equipment, mineral wool felt and mats, cylinders, semi-cylinders, segments, covering bars, etc. are used on a large scale.

The operating conditions of mineral wool heat insulation materials should exclude their humidification and free circulation through their air thickness, since in this case their heat insulation properties are sharply deteriorated. The load on mineral wool products should not exceed the permissible one, otherwise the product is deformed, compacted and does not fully meet its direct functional purpose. The temperature of use of mineral wool obtained from ordinary raw materials is 600... 700 ° С. The operating temperature of mineral wool products depends on the type of fiber, the binder used, the production technology and is: for products on bitumen binder - 60... 70 ° C, when lining with technical cardboard - up to 100 ° C; on a synthetic binder - 250... 350 ° C; on starch binder - up to 400 ° C; for harnesses and cords - up to 600 ° С.

The high technical and economic indicators of mineral wool and products based on it - good heat and sound insulation characteristics, relatively simple technology, the prevalence of raw materials, low cost - determine its wide implementation in various areas of the national economy.

According to VNIITeplosylation, the production of mineral wool and mineral wool products is currently more than 14.5 million m3/year, that is, about 56% of all thermal insulation materials produced in the country, and this figure will steadily increase.

In connection with the development of production and use in the construction of light enclosing structures, the production of new effective heat and sound insulation mineral wool materials has been mastered:

• high-rigidity mineral plates made by various methods, density 175... 250 kg/m3, compression strength 0.04 MPa and higher at 10% linear deformation, designed to insulate flat reinforced concrete coatings under a roll roof without ties, flat coatings from steel shaped flooring;

• solid mineral wool plates with a density of 250... 300 kg/m3 and a strength of 0.05... 1 MPa at 10% linear deformation for insulation of coatings on steel shaped flooring and for sheet assembly of walls of industrial buildings;

• reinforced self-supporting mineral wool plates with a density of 150 kg/m3 for insulation of rolling coatings from profiled asbestos-cement, steel, aluminum sheets.

Types of thermal insulation products from mineral wool

Depending on the type and degree of treatment of mineral wool, thermal insulation products based on it are divided into: loose materials - granular mineral wool; flexible roll products - piercing mats, mats on a synthetic binder (mineral wool felt); cord materials - bundles (cords); rigid piece products are plates, shells, covers, segments on organic and inorganic binding.

Even the simplest treatment of mineral wool - granulation - significantly improves its main operational qualities: reduces the number of kings, reduces average density, increases elasticity. It becomes possible to partially mechanize its placement in business, for example, with the help of pneumatic transport. Nevertheless, it has many drawbacks of "raw" mineral wool.

Flexible roll piercing mats with wool fibers unattached or partially attached to each other by means of a binder are made by inserting a mineral wool carpet into a flexible shell (water-resistant paper, fabric, mesh, polyethylene film, aluminum foil, etc.) followed by piercing them with threads, twine, wire, etc.

Flexible roll-on loose mats (felt) are made by bonding fibers to each other using a binder.

Flexible cords are obtained by packing mineral wool into a braid made of metal wire, cotton or synthetic threads.

All other types of mineral wool products are made using a binder, the type and amount of which depends on the degree of rigidity and mechanical strength of the obtained products.

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