Polyaluminium Chloride (Industrial) - China

Brief Overview

Polyaluminium Chloride (PAC) is an inorganic polymer coagulant, commonly used in water treatment as a yellow solid powder. It outperforms other aluminum salts such as aluminum chloride, aluminum sulfate, and various forms of Polyaluminium chlorisulfate and Polyaluminium chloride due to their lower charge compared to PAC.

Manufacturing Process

Two methods are used for producing Polyaluminium Chloride (PAC) - the Gypsum process and the Pressure process, with the latter being extensively employed in Europe and Latin America. The steps involved in the Pressure process are outlined below: 1. Mixing the press cake with Hydrochloric acid. This stage requires press cake as a raw material containing aluminum metal, alumina chloride, alumina trihydrate, and aluminum sulfate. The press cake is combined with concentrated hydrochloric acid in an agitated tank. The press cake consists of approximately 9% (w/w) aluminum and 12% (w/w) sulfate. It dissolves in the hydrochloric acid solution. The reactor's temperature reaches approximately 150°C, and the pressure is high. 2. Combining the resulting product with aluminum hydroxide. In the initial phase, hydrogen is released as a byproduct, which is an explosive and hazardous substance. Typically, the industry introduces aluminum hydroxide in the subsequent step. The amalgamation of aluminum hydroxide and hydrochloric acid yields aluminum chlorohydrate (ACH). This reaction establishes 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. To achieve stable PAC, a minimum of 9 weeks at 30°C is required for precipitation. Any water present during the process evaporates in the reactor, producing steam. Ultimately, Polyaluminium chloride contains more than 50% Al2O3.

Water Treatment Industry

Polyaluminium chloride is utilized for purifying drinkable water and handling wastewater, functioning as a powerful flocculant in wastewater treatment. Its effectiveness lies in removing impurities such as heavy metals, organic compounds, and colloidal particles. PAC holds numerous advantages over other coagulant chemicals. Its heightened charge facilitates quicker reactions, leading to the formation of larger flocs that aid in simpler filtration processes. PAC demonstrates efficiency across a wide pH range, reducing the need for frequent filter cleaning, addressing health worries, and demanding lower doses than other chemical coagulants.