Polyaluminium Chloride

About Polyaluminium Chloride
Polyaluminium Chloride (PAC) is an inorganic polymer coagulant. It is a yellow solid powder that is widely used in water treatments. PAC is better than other aluminum salts such as aluminium chloride, aluminium sulphate, and other various forms of Polyaluminium chlorisulfate and Polyaluminium chloride that they have lower charge than PAC.
Manufacturing Process
These are 2 methods for polyalumunium chloride production or manufacturing process, the Gypsum process, and the Pressure process. The pressure process is widely used in Europe and Latin America. These are the following steps:
1. Mixing the press cake with Hydrochloric acid.
This process needs press cake as a raw material that containd aluminium metal, alumina chloride, alumina tryhidrate, and aluminium sulphate. The press cake mixes with concentrated hydrochloric acid that they are blended in an agitated tank. The press cake contains about 9% (w/w) aluminium and 12% (w/w) sulphate. The cake is solute in hydrochloric acid solution. The temperature of this reactor reach about 150oC and the pressure is high.
2. Mixing the product with aluminium hydroxide
The first process is releasing hydrogen as a side product. It is an explosive and hazardous substance. The industry usually adds the aluminium hydroxide in the second process. The combination of aluminium hydroxide and hydrochloric acid produces aluminium chlorohydrate (ACH). This reaction determines the value of m and n in the Polyalumunium chloride molecules. This reaction happens at 500 kPa and 170oC.
Precipitating the solution
Pressure and temperature of olyalumunium chloride sink into the standard level. Stable PAC needs at least 9 weeks at 30o to precipitate. The presence of water during the process will be evaporated in the reactor that produces steam. Finally, Polyalumunium chloride contains more than 50% Al2O3.