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What is Dolomite Refractory

Writer:Mr. Roger SunNumber of visits: Date:2/21/2017

Dolomite refractoryr is made of dolomite as the main raw material with a CaO content of over 40% and MgO of over 30%.

The chemical composition of dolomite is MgCO3.CaCO3.It used be calcined at high temperature (1500-1600℃)before used.

The main mineralogical compositions of calcined dolomite clinker are periclase (MgO) and α -CaO.

Dolomite clinker crushed to a certain size is called metallurgical dolomite sand and can be used to make brick.

1) Tar dolomite brick

Tar dolomite brick is made uf metallurgical dolomite sand as the raw material and tar or asphalt(7-10%) as a binding agent,by ramming.It can be used directly without firing . Itcan used at high temperature . Tar and asphalt decompose and emit volatilies and fixed carbon remains.

The main characteristics of tar dolomite brick include:

A. Hydration

The hydration of dolomite brick is more serious than that of the magnesia brick. CaO and H2O react and form Ca(OH)2. The volume is expanded and doubled, which do damage to the brick. After calcinated at high temperature , the hydration of dolomite will be reduced,but a large amount of free CaO in the brick will absorb water in the air if stored for too long and will be gradually hydrated. Therefore , it should be used as soon as possible.

B.Other properties

Tar dolomite brick is a basic refractory , with strong resistance to alkaline slag but poor resistance to acidic slag. The softening starting temperature under load is relatively low, only 1500-1570℃.

Tar dolomite brick has better thermal shock resistance than magnesia brick and can be air cooled for 20times.This is because the binding agent (fixed carbon) has good thermal stability. Since tar or asphalt can be softened at a low temperature after heated, when preheating the kiln, don't stay at 500 ℃ for too long to prevent the softening and deformation.

2)Stable dolomite brick

To overcome the drawback of CaO hydration, SiO2 silica powder and diatomaceous earth can be added into the ingredient.After calcined ,CaO and Sio2 can form stable compounds :3Cao SiO2 and 2CaO.SiO2. CaO is not in a free state , so it no longer reacts with water.

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