Sirok / Blagojevic / Bullen Mineral Wool

Production and Properties
1. Auflage 2008
ISBN: 978-1-84569-445-6
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: Adobe DRM (»Systemvoraussetzungen)

E-Book, Englisch, 192 Seiten

Reihe: Woodhead Publishing Series in Metals and Surface Engineering

Mineral wool has a unique range of properties combining high thermal resistance with long-term stability. It is made from molten glass, stone or slag that is spun into a fibre-like structure which creates a combination of properties that no other insulation material can match. It has the ability to save energy, minimize pollution, combat noise, reduce the risk of fire and protect life and property in the event of fire.Mineral wool: Production and properties describes the technological process of mineral wool production and the physical characteristics of the melt and theoretical bases of multiregression and dimensionless theory. This is followed by the introduction of the fibre cooling model in the blow-away flow and the influence of temperature in the melt film (on the rotating centrifuge wheels) on the thickness of forming fibres.The second part predominantly focuses on the use of computer-aided visualisation: tools for the diagnostics of fibre and primary layer formation. Special attention is given to the study of aerodynamic characteristics of the airflow which significantly influences the quality of the final product.Mineral wool: Production and properties is suitable for engineers, researchers and for graduate and postgraduate students who want to broaden their knowledge of experimental methods in this field. - Describes the technological process of mineral wool production and the physical characteristics - Focuses on the use of computer-aided visualisation and discusses aerodynamic characteristics of the airflow - Essential for engineers, researchers and students to gain knowledge of experimental methods in this field

Autoren/Hrsg.

Sirok, B.

Blagojevic, B.

Bullen, P.

Leseproben

1 INTRODUCTION
Publisher Summary
The technology of mineral wool is composed of particular complex technological subsystems. Mineral wool is a general name for many inorganic insulation materials made of fibers. It is usually divided into different subgroups depending on the raw materials it is made of, such as rock wool, glass wool, and slag wool. There are several methods for mineral wool fiber production with a wide variation in the quality and quantity of the final product. This chapter provides an overview of the book, “Mineral Wool,” which aims to tackle the most important segments of the technological process of mineral wool production. The book presents the physical and chemical characteristics of mineral wool fiberization and primary layer formation, and describes the basic variables of the process as well as their reciprocal phenomenological dependences. It also describes the applied experimental procedures and the adapted methods that are appropriate for monitoring of real technological procedures of mineral wool production. The relation to the energy sources, their use and the burdening of environment with by-products are undergoing a significant change. With the new perspective a change of attitude towards the efficiency of all energy conversion processes in production and consumption has taken place. A large part of energy conversions is tightly connected with heat transfer, where the process efficiency is influenced by introducing insulation materials. The use and development of the latter has significantly increased, and the amount of those which are based on classical technologies with modified technological procedures is also increasing. The technology of mineral wool also belongs to such procedures. It is composed of particular complex technological subsystems. Mineral wool is a general name for many inorganic insulation materials made of fibres. It is usually divided into different subgroups depending on raw materials it is made of, such as rock wool, glass wool and slag wool. There are several methods for mineral wool fibre production with a wide variation in the quality and quantity of the final product, Ohberg [1,2]. The main process areas which are also shown in Fig. 1.1are:
Fig. 1.1 Production process of mineral wool. • supplying raw materials and energy sources, • melting, • fiberisation and collecting, • primary layer formation, • finishing (binder application, curing, cutting, packing, etc.) Supplying raw materials and energy sources The most frequently used raw materials for mineral wool production are diabase, dolomite, granite, basalt, limestone, etc. Because of its amorphous structure, mineral wool has excellent sound and thermal insulation properties. The energy source is coke. Raw materials and coke are charged into a silo from which they are weighted on a conveyor belt that transports them to the top of the cupola furnace. 1. Melting and fiberisation sources: Pos. 1 Cupola Pos. 2 Spinning machine – centrifuge 2. Primary layer formation: Pos. 3 Collection chamber Pos. 4 Conveyor belt Pos. 5 Primary balance 3. Mineral wool layer formation: Pos. 6 Pendulum system – transversal layer arrangement Pos. 7 Superficial and loading balance Pos. 8 Squeezer Pos. 9 Curing chamber 4. Finishing: Pos.10 Cooling zone Pos.11 Suction from the cooling zone Melting
In the cupola (Fig. 1.1 – pos.1), coke is combusted releasing heat that is utilised for heating and melting raw materials. Most rock melts have temperatures in the range from 1300-1600°C. The cupola furnace is a system for melting magma rocks and supplements. In the cupola furnace, several chemical and thermodynamic processes take place. Coke is most frequently used as an energy source; however, electric and gas furnaces are also used for melting rocks. Melting furnaces serve not only for melting rocks, but also for reaching the homogeneity of melts in the temperature range 1400-1600°C. In the melting process it is intended to acquire the desired chemical substances which influence the material characteristics, such as viscosity and surface tension of the melt. Fiberisation – Centrifuge
The most commonly used mineral wool production process is the fiberisation process (Fig. 1.2) of molten rock on fast rotating spinning machines (wheels) (Fig. 1.1 – pos.2) where the melt is spun into fibres. This machine uses several cylindrical rotors onto which the melt is directed and which fiberise the melt with or without the help of stripping air. The fibres are mixed with an organic binder and collected on the conveyor belt as wool. The literature [1] also provides the description of other methods which can be used for fiberisation. These methods are V-shaped blowing nozzle, the Downey method and the Sillan process. The V-shaped blowing nozzle, giving a high percentage of unfiberised material and the fibre diameter distribution, was very broad. This led to the development of the Downey rotor which provides a controlled distribution of the melt.
Fig. 1.2 Fiberisation process of mineral wool. The most commonly used mineral wool production process is the fiberisation process of molten rock on fast rotating spinning wheels (Trdi et al. [3], Angwafo et al. [4] and Westerlund et al. [5]). Molten rock enters through a siphon neck in a homogenisation reservoir. Over the weir and the directing channel, the molten rock falls under gravity onto the rotating wheel of the spinning machine. With blow-in air led coaxially over the wheels, the fibres are transported away from the spinning machine and are thrown into the collection chamber where they solidify into fibres which have the diameter of about 5 mm and length of approx. 10 mm. The formation mechanism, as mentioned in reference [5], was described by Eisenklam [6]. Fibres are formed from the molten film on spinning wheels. The forming and motion of fibres depend on inertial, viscous and surface tension forces, whereas the solidification process depends on thermodynamic and mass properties of the melt. The quality of the final product depends on the structure of fibres and on the proportion of solidified shots in the mineral wool. The fibre structure is characterised by its thickness (diameter), its length, and the variation of both respective quantities. Material that did not transform into fibres remains in the form of solidified shots which arise from an incomplete fiberisation process [3,4]. Primary layer formation – collection chamber
The fibres formed on the centrifuge are transported by the air flow of the nozzle outlet into the interior of the collection chamber (Fig. 1.1 – pos.3), where the primary layer of mineral wool is being formed on the perforated conveyor belt. A homogenous turbulence field forms a thin layer of intertwined fibres (Fig. 1.3) which are damped with phenol formaldehyde pitch. As the dispersed drop flow, the pitch is added into the outlet flow in the area of fibre formation. The geometrical structure of intertwined fibres and the homogenous binder distribution on the fibre surface significantly influence the quality of the final product.
Fig. 1.3 Primary layer formation in the collection chamber. Conveyor belt and primary balance
The primary layer leaves the collection chamber and passes over the intermediate belt (Fig. 1.1 – pos.4) onto the primary balance (Fig. 1.1 – pos.5) which measures the mass flow of mineral wool. Apart from performing this measurement, the basic function of the primary balance is to diagnose the transversal distribution of mineral wool surface density in the primary layer. The balance is designed to enable the combination of four independent simultaneously measured values of gravity force of the primary layer and to detect the density fluctuations of mineral wool in the primary layer [7,75]. Pendulum
The function of the pendulum (Fig. 1.1 – pos. 6) is to periodically fold and load the primary layer into a stack of mineral wool, which moves in the process direction. The pendulum oscillation frequency, the velocity of the primary layer and conveyor belt velocity (Fig. 1.1 – pos.7) form a multilayered structure of mineral wool which then enters the area of the process balance where the measurements...