Posted on 10/27/2015
In close cooperation with the company Dürr, the Swedish carmaker Volvo optimized the pretreatment of car bodies in its Gothenburg plant. The phosphate sludge that is removed from the pretreatment basin is fed into the chamber filter press using a flow and pressure regulated Turo® vortex pump. As a result of this regulation, a thick filter cake is generated, which helps extract a clear filtrate that can be fed back to the plant. The ideal filter cake must have a good dry substance prior to opening the filter press and must also be easily removable from the filter cloths. The phosphate sludge from this section of the plant contains cryolites that are difficult to dehydrate. It also has a pH value of 3 to 4 and can therefore be classified as an acidic cake.
One additional challenge at Volvo was to convert this acidic dry cake into a solid alkaline dry cake.Before opening the filter press, the dry cake is neutralized by injecting caustic soda into the special membrane filter plates. This is the first known application of its kind in the automotive industry. After the neutralization process, the treated dry filter cake reache...