Features of spray dried process: The features of pressure type spray dried method is determined by the operating principle of pressure type atomizer. The output product after pressure type spray dried process is porous fine particle or hollow fine particle, which show the features of superiors dustproof and flowing property. Owing to its bigger contact area between itself and surrounding water than other powder products, it shows better wettabiliy and quicker water purifying speed. Spray granulation is to dry polyaluminium chloride and atomize to be minute particle simultaneously. Polyaluminium chloride is water soluble substance and shows features of good thermal stability and high solubility. Polyaluminium chloride solution with 40-50% solid content on drying is introduced to high pressure pump, atomized in atomizer of dryer to be minute fogdrop which is then dried to be granular products. Dehydration and granulation are made simultaneously in this process. Features: This product possess the following advantages compared with other coagulants: 1. Wider application, better water adaption. 2. Quickly shaping big alum bubble, and having good precipitation. 3. Better adaption to PH value (5-9), and little declining range of PH value and alkalinity of water after treatment. 4. Keeping stable precipitation effect at lower water temperature. 5. Higher alkalization than other aluminium salt and iron salt, and little erosion to equipments.