Polyaluminium Chloride (Industrial) - India

Brief Overview

Polyaluminium Chloride (PAC) stands as an inorganic polymer coagulant, recognized as a yellow solid powder extensively employed in water treatment. It surpasses alternative aluminum salts like aluminum chloride, aluminum sulfate, and diverse versions of Polyaluminium chlorisulfate and Polyaluminium chloride due to their comparatively reduced charge in comparison to PAC.

Manufacturing Process

There exist two methods for producing Polyaluminium Chloride (PAC): the Gypsum process and the Pressure process. The Pressure process finds wide usage in Europe and Latin America. The steps involved are as follows: 1. Blending the press cake with Hydrochloric acid. This procedure requires press cake as a raw material containing aluminum metal, alumina chloride, alumina trihydrate, and aluminum sulfate. The press cake is mixed with concentrated hydrochloric acid in an agitated tank. The press cake comprises approximately 9% (w/w) aluminum and 12% (w/w) sulfate. The cake dissolves in the hydrochloric acid solution. The reactor's temperature reaches around 150°C, and the pressure is high. 2. Combining the resulting product with aluminum hydroxide. In the initial step, hydrogen is released as a byproduct, which is an explosive and hazardous substance. Typically, the industry introduces aluminum hydroxide in the subsequent phase. The interaction between aluminum hydroxide and hydrochloric acid yields aluminum chlorohydrate (ACH). This reaction determines the values of 'm' and 'n' in the Polyaluminium chloride molecules. The reaction occurs at 500 kPa and 170°C. 3. Precipitating the solution. The pressure and temperature of Polyaluminium chloride are reduced to standard levels. Achieving stable PAC necessitates at least 9 weeks at 30°C for precipitation. Any water present during the process evaporates in the reactor, generating steam. Ultimately, Polyaluminium chloride contains over 50% Al2O3.

Water Treatment Industry

Polyaluminium chloride finds application in treating potable drinking water and managing wastewater. It's widely recognized as a potent flocculant in wastewater treatment, capable of eliminating impurities like heavy metals, organic substances, and colloidal particles. PAC boasts several advantages over other coagulant chemicals. Its high charge enables faster reactions, fostering the creation of larger flocs for easier filtration. PAC proves efficient across a broad pH spectrum, decreasing the frequency of filter cleaning, reducing health concerns, and requiring lower dosages compared to alternative chemical coagulants.