Types and Processing Methods of Lightweight Insulating Bricks

Bricks can be produced by carving lightweight natural porous rocks into smaller chunks.

Brick bodies are composed of natural porous and lightweight materials.

Add easily combustible materials, such as rice husk and sawdust, to form a porous structure. Sublimable substances, like naphthalene, should also be included.

 Add foaming agent such as rosin soap for a porous surface, then fire the structure for maximum impact. This should create an uneven and porous finish.

Chemical reactions with foaming agents inorganic can produce porous structures.

In general, methods 3 and 4 tend to be the most preferred options.

 Below are the most frequently employed strategies for preparing thermal insulation materials:

(1) Hollow sphere bonding method

Binders are used to form and adhere porous lightweight aggregate, then dried and baked at appropriate temperatures. This method yields low-cost products with simple processing steps; however, due to thermal expansion differences between binder and aggregate the product may crack or even collapse during repeated cold/hot processes.

2) Pre-Embedded Filling Burning Method:

This method is the go-to way for producing porous, lightweight thermal insulation at low costs and with minimal production processes required. Common additives used include sawdust and cork powder as combustible additives.

Foaming by chemical reaction is one method available.

This method uses a mixture of pore-forming powder and slurry that produces a chemical reaction to release body material, producing a porous, flowing slurry. After casting and drying a green body is created that is heated to high temperatures before being calcined for heat insulation purposes at temperatures between 55%-75% porosity. Calcined pure oxide heat-insulating products with 55%-75% porosity can then be manufactured. According to literature (1) this can also produce heat insulating products made with 55%-75% porosity; common chemical reactions include mixing sodium carbonate with acid to produce CO2, caustic soda with aluminum or acid with aluminium producing hydrogen gas for production of heat-insulation products with 55%-75% porosity.

These reactions take longer to react at lower temperatures and take more time for foaming to occur, due to a large residual amount and low melting points reducing strength of brick production costs. Aluminum production costs increase accordingly.

(4) Removing pre-embedded substances:

Method involves adding volatile substances to a slurry, then sublimating these volatile elements under certain conditions to form pores.

(5) Foam pre-mixed casting method

Foaming agents such as protein, rosin or saponin esters can be added to slurry mixtures to form porous foam that can then be poured, molded, dried and fired to produce lightweight insulation refractory materials with porous surfaces and lightweight density. Their performance on heat insulation products and refractories produced with this technique varies considerably based on which physical foaming agent is chosen as part of this method.

Foaming substances include rosin gum, waste animal hair, resin soap, hydrolyzed coagulated blood, petroleum aluminum-sulfonate (PAS), lignosulfonate and protein hydrolyzate - these materials being easy to use, having low equipment costs and adaptability features; plus being suitable for production of lightweight high-porosity insulation materials insulating firebrick  with low density; these processes have since received increased interest among industry producers of lightweight insulation materials.

Two primary production techniques used today for creating lightweight insulation materials are embedding filler burning and foam pre-mixed casting. While both techniques produce lightweight insulation materials with similar strength and thermal conductivity characteristics, their strength and thermal conductivity differ considerably between products made using either method.

Combustible materials are used to create lightweight insulation materials through combustion. As air diffuses into bricks along pore channels to provide oxygen, and combustibles are discharged into material through such channels forming continuous pores; with increasing number and size of pores. However, their microstructure remains looser while their strength remains lower compared with foam materials.

Classification and characteristics of lightweight insulating bricks

Industrial furnaces often employ refractory bricks with no material with good thermal properties attached, in order to improve thermal efficiency by minimizing heat loss, reduce temperature of outside air and improve environmental conditions - this practice is known as insulation.

Industrial applications typically call for insulation materials of three types: fiber, porous and granular. Heat-insulating and fireproof materials may also be classified depending on whether they come into contact with environments with temperatures reaching high temperatures.

(1) Fire-resistant lightweight materials. "Lightweight refractories" refers to materials with low volume density and thermal conductivity as well as high porosity that have low volume density but can withstand temperatures and loads, along with a lower thermal conductivity and thermal emissivity rating than regular refractories.

1) Refractory lightweight bricks with high porosity. Alumina hollow ball and its products are the most commonly-used pore-lightweight refractories.

Fiber insulation and refractory material consists of ceramic fiber cotton in various grades and products, among others.

Insulating lightweight material. Insulating lightweight material (ILM) is a lightweight refractory material designed to provide heat insulation. To avoid heat loss and protect the steel structure supporting the furnace body, this layer should often be installed with its opposite facing side exposed against heat loss.