What can aluminum powder do in aerated brick production line? In aerated concrete production line of all countries of the world, the vast majority are using metal method to produce gas, while in the metal method, metal powders real for industrial production, only aluminium powder (aluminum powder paste).
Internationally used aluminium powder as foaming agent, China used to be dominated by using aluminum powder, now except for introducing a few to offline, most have switched to aluminum powder paste.
First, aluminum powder’s gas reaction
Aluminum powder’s specific gravity is only 2.7, under standard conditions, per 1g Al produce 1.241 hydrogen, thus using aluminum powder to conduct gas reaction has the advantages of less use, low cost and so on. In addition, aluminum production is larger, sources are more widely and for aerated concrete production were better control on the process, is the most commonly used material for gas release.
Alumina is stable in air and water, and aluminum products used in our everyday life has purified aluminium oxide protection film can prevent aluminum being further oxidized, alumina in acid or alkaline environments can react with acids or bases, generates new salt, causes the coating destroyed. The commonly used aluminium powder, its particle surface always has oxidized, produces alumina protective film, preventing the aluminium contact with water, only after eliminating the oxide film, aluminium powder can react, swapping out the hydrogen in the water. Therefore, we say that aluminium powder as foaming agent should be conducted the gas release reaction in an alkaline environment.
Second, aluminium powders production process and its main characteristics
Aluminum powder is forming by dissolved aluminum ingot, using compressed air sprayed into fine powder, and then after the election, gets granular powder joins in the closed ball to levigate. In order to prevent aluminum powder oxidized during the grinding process, and thus cause a fire explosion, except for the specially designed of ball mill system, ensure tight seal and pump into the ammonia protection, it also should be adding a certain amount of stearic acid in the aluminum powder, make aluminum powder pulverized and form of stearic acid protective layer on the particle surface in the pulverized process. Now, it usually uses gas former aluminium powder paste, in the grounding process does not add stearic acid, nor ammonia protection, but joined the media and various additives for grinding, the finely ground aluminium paste through centrifugalizing enrichment into paste. Grinding media has two kinds, one is a mineral oil, aluminum powder paste made from it called oily aluminum powder paste; the other is water, the forming aluminum powder paste called aluminium powder paste. The raw material of aluminum powder paste are most taking the scrap of packaging aluminum, this material has a high purity and low prices, made aluminum powder paste was accepted by the majority of enterprises. But the fineness and dispersion of aluminum powder paste tend to affect the quality of aerated concrete products.
Stearic acid in aluminum powder surface must be removed while used, that is degreased. Common methods have baking method and chemical method. Baking method is not much used, chemical method is based on mixing chemical degreaser and aluminum powder to get rid of stearic acid on the surface. Conventional chemical defatting agents has dibutyl naphthalene sulfonate, advanced epoxy ethane fatty alcohols, saponin powder or saponin plant extracts and ordinary detergent and so on.
Article Source:http://www.mhcmp.com
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