Dolomite Refractory


Dolomite Refractory

INTRODUCTION


Dolomite is a calcium and magnesium double carbonate (CaCO3, MgCO3). It is a key raw material in the iron and steel, ferroalloys, glass, alloy steels, and fertilizer industries, among other industries. There are also dolomite chip flooring tiles accessible. Dolomite brick has a number of characteristics that make it an excellent refractory lining for a cement rotary kiln. The strong refractoriness of dolomite bricks allows them to withstand the high temperatures and stresses of the burning zone, as well as alkali and decreasing environment corrosion resistance and excellent coat ability. Ultimately, the environmental protection of the materials utilized is one of the dolomite brick’s best features. Dolomite is a type of limestone that is high in magnesium (CaMgCO3). It can be found in nature. With the use of silicate binders and wax, calcined dolomite brick particles are joined. The mixture is then molded into bricks, which are subsequently air dried and charred for roughly a day at temperatures ranging from 1200 to 1560°C to produce stabilized dolomite bricks. Basic slag doesn’t seem to bother these bricks.

Dolomite refractory

Properties:

1. Dolomite bricks are porous, softer, and have a lower strength than magnesia bricks.

2. They can withstand temperatures of up to 2300 ℃ without pressure as well as up to 1650 ℃ with pressure.

The most essential aspect of a basic brick is its coating formation. In practice, if the kiln conditions are favourable, a coating will form. The most significant distinction between the various sorts of bricks used in this situation is how well they will cling onto coating once it has been produced. During the campaign, the clinker coating on the refractory lining is not always present. Thermal stress may be the reason of some or all coating degradation. When the lining’s covering is destabilized, the brick beneath it is exposed to a rapid temperature fluctuation, exposing the brick to serious thermal shock. Standard dolomite was limited for a long time to the region where a stable coating formed over the refractory lining, and blackouts were few. The creation of zirconia enhanced grades, on the other hand, has greatly improved the thermal shock resistance of dolomite bricks. Since zirconia is relatively non-reactive with dolomite, it was selected.

Zirconia is corrosion resistant to clinker minerals present in cement kilns and has a high refractoriness. As a result, the zirconia-enriched dolomite grades exhibit outstanding thermal flexibility and thermal shock resistance. Finally, chemical reaction resistance is the most significant need for a refractory lining material used during burning zone of a cement rotary kiln, which is the zone with the maximum temperatures.

Dolomite bricks are the top pick for these situations. At a temperature of about 1450° C, the melting phases of the clinker react with the lime in the refractory brick material to generate the minerals alite and belite, which have very high melting temperatures (2000 and 2130° C). A firm and steady coating forms on the surface of the dolomite bricks as a result of this reaction. The creation of the coating will lessen the wear on the brick surface. Furthermore, the coating protects the clinker burden in the kiln from temperature losses, resulting in decreased heat losses through the shell. Thermal losses will be drastically decreased, specifically in the hottest area, the burning area. As a result, dolomite bricks are the best choice for the cement rotary kiln’s burning zone.


Manufacturing Procedure:

Rotary kilns create dead burnt refractory dolomite. For dead burning, high-grade dolomite with combined contaminants of less than 3% is usually chosen. Because high purity dolomite is challenging to densify in a rotary kiln, mineralizers are commonly used to aid dead burning. Iron oxide is a frequent ingredient in cosmetics. The manufacturing procedure varies depending on the grade of D.B. dolomite that is preferred. A standard process is employed in most European factories, which uses rotary kilns lined in the hot zone with basic bricks and burnt with powdered coal. The hot zone reaches temperatures of almost 1760 °C. For combustion management, continuous gas sampling equipment is installed in the kilns, which allows to measure and record the oxygen, combustible materials, and carbon dioxide components of the kiln exit gases. In the fabrication of dead burnt dolomite, the latter is especially crucial in establishing uniform quality of the product, optimum use of dead burning agents, and better fuel utilization.

Upon dead burning, the dolomite is condensed in rotary or reciprocating recuperative coolers. The air used for condensation is heated and then used as secondary air in the kilns for burning. It is absolutely essential to use a slightly higher firing temperature when D.B. dolomite is manufactured with an ingredient in order to shrink the dolomite in a reasonable time-cycle in the kiln. This was achieved by enhancing the kiln’s thermal efficiency. This was achieved by enhancing the kiln’s thermal efficiency. The use of insulating brick-back of the fundamental lining in the hot zone and the best usage of secondary air from the recuperative condensers, to pick up as much of the available heat as feasible from the cooling of the product, are two ways to achieve improved efficiency. Some other type of refractory dolomite is termed as ‘stabilized’ dolomite. It is made using a procedure similar to that used to make Portland clinker. In a ball mill, dolomite and serpentine are pulverized to a slurry with small quantities of appropriate stabilizing agents. In a rotating kiln with a temperature of around 1760°C, the slurry is burnt to a dense mature clinker. The maximum capacity of a vertical or shaft kiln that uses coke admixed with dolomite as fuel is fixed at 100 tons per day. These kilns are frequently employed in the United States and the United Kingdom, as well as Scandinavia and other European countries. In the steel-producing nations, remarkable progress has been achieved in the automation of kilns. Temperatures of up to 2300°C can be tolerated by D.B. dolomite. When basic slag is used to purify steel, it is typically employed as a refractory material. It’s used in open fireplace furnaces for both new fireplace installs and fireplace maintenance. These hearths are made of rammed dolomite and tar-dolomite ramming mixtures. Dolomite refractories are also used in electrical furnaces and the cement industry’s clinker producing process.


APPLICATIONS

Dolomite is a mineral with few application. Dolostone, on the contrary, offers a wide range of applications because it can be mined in large quantities. The most prevalent application of Dolostone is in the construction industry. It’s pulverized and compressed for use as a road base, cement and asphalt aggregate, railroad ballast, rip-rap, and filler, among other things. It’s also used to produce cement, and it’s chiseled into specific-size chunks known as “dimension stone.” Dolomite’s interaction with acid also tends to make it beneficial. It’s utilized in the chemical industry to neutralize acids, as well as in stream restoration projects and as a soil conditioner. Dolomite is often used as a source of magnesia (MgO), as a livestock feed supplement, as a sintering agent and fluid in metal processing, and as a component of glass, bricks, and ceramics. Numerous lead, zinc, and copper deposits have dolomite as their host rock. When heated, acidic hydrothermal solutions rise from depths through some kind of fracture system and collide with a dolomitic rock unit, those deposits develop. These solutions react with the dolomite, causing a pH reduction that leads metals to precipitate out of solution. Dolomite is often used as a reservoir rock for oil and gas. A volume drop happens during the transformation of calcite to dolomite.

This can lead to the formation of pore spaces in the rock, which can be filled with oil or natural gas that migrates in from other rock units. As a result, dolomite is a reservoir rock and an oil and gas drilling target. After calcination, dolomite is used as a refractory in lining for burners such as basic open-hearth steel furnaces and basic Bessemer converters (as a substitute for magnesite refractories). For lining, LD furnaces require high purity dead-burnt dolomite bricks, while dolomite is required for fettling and refractory operations in mini-steel plants. In the iron and steel, ferro-alloys, and glass industries, dolomite, like limestone, is used as a fluid. At a few steel companies, dolomite is no longer utilized in blast furnaces, and its usage in the production of self-fluxing sinters has been shown to be adequate for blast-furnace charge. It’s used in the restoration of magnesia and the formation of magnesium metal; in the manufacture of basic magnesium carbonate (also referred as “technical carbonate”), “block magnesia” or “magnesia alba,” which is used in pipe and boiler wrappings as well as in other heat resistance, and even in the medical products, rubber, and chemical industries; and in the manufacture of paper, leather, glass, potteries, and high-magnesium alloys. It is also used as a soil conditioner to rectify acidity in agriculture. It is used as a filler in fertilizers, paints and coatings, and in coal mines to control dirt. It is not only used as a building stone, but also as chips and powder in the manufacture of flooring tiles.