Perlite insulation material

At very low temperatures with hquid air and similar substances, the tank may have double walls with the interspace evacuated. The weh-known Dewar flask is an example. Large tanks and even pipe hues are now built this way. An alternative is to use double walls without vacuum but with an insulating material in the interspace. Perlite and plastic foams are two insulating materials employed in this way. Sometimes both insulation and vacuum are used. 

Table 11. Properties of heat insulation materials obtained by synthesis of PE on perlite [ 18]...

The superhigh-filled composite materials obtained by PE polymerization on formed perlite particles present in the amount of 80 to 95% by mass can be used to advantage as heat insulation materials (see Table 11). 

The main features of these concepts are freestanding inner tank and bottom in 9% nickel steel and aluminium suspended deck, with all penetrations from the tank roof. Pump wells are either supported from the tank base (as for type a+b) or from the roof (type c). The insulation material is usually perlite. Further specific features ... 

The containers used for transporting and storing the majority of cryogenic liquids are insulated cryogenic tankers, liquid cylinders, and stationary storage tanks. These containers are similar in design to a Thermos bottle. There is an inner vessel, which contains the cryogenic product, and an outer vessel. The space between the two vessels is under a vacuum and usually contains a wrapped insulation material such as aluminized Mylar, or it may contain a powdered insulation such as expanded perlite. The liquid cylinders, usually 160-250 L in capacity, are constructed to a... 

Double-wall tanks are known in various designs. In the simplest version an inner tank designed for storage temperature and pressure is surrounded by a second tank. The annular space between the two walls is filled with insulation material, for example, Perlite. The main purpose of the outer shell is to contain and hold the insulation. Today s usual practice is to design the outer shell to the same standard as the inner shell. This so-called double-integrity tank concept provides an additional safety measure as the outer tank can hold the full content if the inner shell fails. 

As discussed in previous sections, it is important to minimize the heat leak into the cryogenic section of the ASU. This is accomplished by containing the equipment in an insulated enclosure termed a coldbox. The coldbox is a structural steel frame which is paneled with metal sheeting and provides structural support for the equipment and also containment for the insulation. There are essentially two different types of insulation material used in ASUs. The first and most popular is perlite. The perlite coldboxes are insulated in the field with perlite blown in from the top of the coldbox. The second insulation material is rock wool. Rock wool has to be packed manually. 

Although in refractory practice there are hundreds of heat insulation materials, the list of heat insulation materials for the lining of reduction cells is rather limited. For one thing, economic considerations add some limitations, but for another, the heat insulation materials in reduction cells should withstand mechanical compression loads without deformation at temperatures up to 900 °C for a long time, and numerous inexpensive fiber heat insulation materials don t correspond to this requirement. In the Hall-Heroult reduction cell, the heat insulation materials should withstand the pressure of the layer of the electrolyte, the layer of molten aluminium, cathode carbon blocks (taking into account collector bars), and the refractory layer. Currently, only four or five heat insulation materials are used in the lining of reduction cells diatomaceous (moler) and perlite bricks, vermiculite and calcium silicate blocks (slabs), and sometimes lightweight fireclay bricks (but their thermal conductivity is relatively big, while the cost is not small) and fiber fireclay bricks. 

Perlite heat insulation materials may be made cement-bonded (without firing) and fired clay-bonded. The service temperature of good perlite-based heat insulation materials may be up to 1,200 °C and is determined by the binder. 

The range of heat insulation materials is rather broad. Heat insulation materials that can withstand relatively high mechanical loads - this list includes lightweight fireclay bricks, vermiculite slabs, perlite bricks, calcium silicate boards, and diatomaceous bricks - are used for the heat insulation of the bottom. The pressure on the walls is lower, so it is possible to use fiber-based boards (in addition to the above-mentioned materials). Sometimes lightweight castables with fillers, such as lightweight fireclay, vermiculite, and fiber, are also used for heat insulation. 

More advanced insulations are also under development. These insulations, sometimes called superinsulations, have R that exceed 20 fthh-°F/Btu-m. This can be accomplished with encapsulated fine powders in an evacuated space. Superinsulations have been used commercially in the walls of refrigerators and freezers. The encapsulating film, which is usually plastic film, metallized film, or a combination, provides a barrier to the inward diffusion of air and water that would result in loss of the vacuum. The effective life of such insulations depends on the effectiveness of the encapsulating material. A number of powders, including silica, milled perlite, and calcium silicate powder, have been used as filler in evacuated superinsulations. In general, the smaller the particle size, the more effective and durable the insulation packet. Evacuated multilayer reflective insulations have been used in space applications in past years. 

Cementitious materials use a hydraulically setting cement such as Portland cement as a binder with a filler material of good insulation properties, e.g., verminculite, perlite, etc. Concrete us frequently used for fireproofing because it is easily installed, readily available, is quite durable and generally economical compared to other methods. It is heavy compared to other materials and requires more steel to support that other methods. 

These can be inorganic materials such as calcium silicate, mineral wool, diatomaceous earth or perlite and mineral wool. If provided as an assembly they are fitted with steel panels or jackets. These are woven noncombustible or flame retardant materials the provide insulation properties to fire barrier for the blockage of heat transfer. 

A powder insulation system consists of a finely divided particulate material such as perlite, expanded Si02, calcium silicate, diatomaceous earth, or carbon black packed between the surfaces to be insulaed. When used at 0.1 MPa gas pressure (generally with an inert substance), the powder reduces both convection and radiation and, if the particle size is sufficiently small, can also reduce the mean free path of the gas molecules. 

Gas-Filled Porous Insulations. Table I shows some of the results of tests on porous or vesicular materials. One test sample was 1-in. thick sintered perlite, evacuated to 4 X 10 torr. The other was a foam-filled honeycomb, f in. thick, in a helium atmosphere tested between room and liquid-hydrogen temperatures. The heat flux for this sample reached 600 Btu/hr-ft-, which approached the design limit of the apparatus. In another test the foam-filled honeycomb sample was filled with nitrogen and allowed to cryopump. 

Phosphoric acid or aluminium add phosphates can be used to bond asbestos sheets [42], glass wool [43], vermiculite [44], fly ash [45], mica [46] or perlite [47] to make building materials or electrically insulating compositions. Phosphoric acid and caldum aluminate can be combined to produce a strong cement for sparking plugs [48]. 

The storage vessel is insulated either by a pure vacuum alone or by one of several evacuated insulations such as perlite, santocel, fiberglas or a combination of fiberglas and metal foil. Li recent months improvements of the latter type of insulation have resulted in superior insulating systems which are fabricated by custom lamination of various reflectors and separating materials. The typical storage vessel is shown in Fig. 2. 

Perlite (rhyolitic obsidian) Aggregate in plasters, loose-fill insulation, filtration medium, paint filler, oil-well drilling muds, inert packing materials. 

In recent years the increasing use of liquefied gases in industry, as rocket propellants, and as low-temperature baths, to mention only a few. and the practical results of transporting gases in liquid form, have necessitated a search for more efficient schemes for low-temperature insulation. Evacuated powders are one scheme that shows promise. Powder insulation, in either evacuated or unevacuated systems, refers to the use of materials with a low bulk solid conduction, in a finely divided state. Examples are silica aerogel (Santocel, Cab-0-Sil,Syloid), calcium silicate (Microcel), diatomaceous earths, perlite, etc. 

In order to provide a true comparison of these results on fibrous insulations with some of the well-known granular materials, the data for Fig. 4 were run. These values for Santocel and perlite are in satisfactory agreement with those published by others [2], even though different means of testing may have been used. This agreement serves as a reassurance of the validity of data obtained by the heat meter equipment. 

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