Dry Impermeable Castable Refractory For Electrolytic Cell

August 17, 2018

Dry impermeable castable refractory for aluminium electrolytic cell is a specialized product, dry impermeable castable refractory can effectively prevent the aluminum liquid from penetrating and form a protective layer,thus increasing the overall operation time of aluminum electrolytic cell.

Product Introduction

The dry impermeable castable refractory use clay clinker as refractory aggregate, Grade III bauxite clinker as refractory powder, add superfine powder, use CA-50 cement as binder, and dispersant and silica or feldspar are added.Its main properties are Al2O3 44%, SiO2 49%, bulk density≥2.23g/cm3, cold crushing strength after burning  are 40mpa and 70mpa respectively at 110 °C  and 1000°C.This dry impermeable castable refractory is used between the carbon brick on the side wall of aluminium electrolytic cell and the heat insulation layer, which can prevent the penetration of Naf and Na and also protect the insulation layer.

The dry impermeable castable refractory has a critical particle size of 3mm and the mass ratio of aggregate is about 6:4. It’s directly laid on the bottom insulation layer and has a thickness of 100-150mm. The penetration depth measurement: 300g of dry impermeable castable refractory is put into a graphite crucible, oscillated for 5 min under pressure,and the height H1 of the vibrating material was measured, then put into cryolite 200g of high molecular ratio,sealed crucible, heated to 950℃ in an electric furnace, the holding time is 96h. The temperature naturally cools to room temperature, pick it out, cuts the profile and analyzes, measures the remaining height H2 after anti-seepage material and cryolite reaction, the immersion depth(H1-H2) is calculated, which is essentially the height of the reation, that is, the impermeability of the material.

Dry impermeable castable refractory is also known as chemical baffle, also called as dry penetration-proof castable. It is not incapable of being immersed by itself, but it can react with the electrolyte components in place to form a dry baffle, which can prevent the electrolyte from continuing to penetrate downward. That is, after the reaction with fluoride, an impermeable solid layer of glassy layer is formed. The data with this characteristic contains a group of minerals containing calcium silicate or calcium aluminium silicate, during which certain minerals react with fluorine-fed molten salts at 900℃, and all the reaction products are solid compounds, resulting in coherent drying of the molten salts.

The dry powder impermeable castable refractory has better anti-seepage effect, which can reduce power consumption, reduce furnace construction cost and extend the life of the tank.

Product Application

The special function data of the aluminium electrolytic cell furnace construction have remarkable effect on improving technical and economic indicators of the electrolytic cell and extending service life of the electrolytic cell. Therefore,in a short years, it has been implemented rapidly.Now, more than 60% of the electrolytic aluminum plants have chosen dry impermeable castable refractory. Others can also used in a power station boiler, melting furnace, heating furnace, soaking furnace, heat treatment furnaces and induction furnaces lining in different parts.

Development of a new type of aluminium electrolytic dry impermeable castable

The dry impermeable castable refractory for aluminium electrolysis was used in the experiment of rare earth molten salt electrolysis, and the dry impermeable castable refractory can prevent the penetration of LiF in the electrolyte but can not prevent the penetration of LaF3. The dry impermeable castable refractory for aluminum electrolysis is used as a matrix, and the penetration proof effect of the modified anti-seepage material is studied by adding components such as CaO, MgO, La2O3, Fe2O3 and Sic.

The dry impermeable castable refractory construction and testing methods

Dry impermeable castable refractory needs to be compacted when used. The compact density is one of important goals affecting the use of dry impermeable castables refractory for aluminum electrolysis cells. The dry impermeable castables refractory with high density is more resistance to electrolyte penetration. Based on the compact density and the planned thickness of the dry impermeable castable refractory, it is estimateed that an electrolytic cell requires about the quality of the dry impermeable castable refractory. In YS/T 456-2003,the high frequency shaking table method is adopted to measure compact density. However, during high frequency oscillation, coarse particles are easy to reach the lower part of measuring cylinder, and the fine powder is vibrated to the surface, and it is difficult to vibrate. Since the dry impermeable castable refractory is a dry granular substance,it is easy to segregate the particles and fine powder during the oscillation test, and can not reach the tightest packing condition,failing to obtain the actual compact density, and being sued with the aluminum electrolytic cell. The practice methods for dry impermeable castable refractory do not match. The modified YS/T 456-2014 has improved the testing method of compact density which can make dry impermeable castable refractory reach the most tight accumulation, which can reflect the compact density level of dry impermeable castable refractory after practical construction. YS/T 456-2003 regular compaction density is 1.85-1.93g/cm3, YS/T 456-2014 regular compaction density is 1.93g/cm3, further ensuring the anti-seepage quality of dry impermeable castable refractory.

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