Anhydrous Salt Crystallizer for Lead Battery Recycling

The anhydrous salt crystallizer is a fundamental part of the desulphurization plant of lead battery paste. The crystallizer carries out the crystallization of a watery sodium sulphate solution and the accretion of the crystal grains by reduction solubility of salt Na2SC>4 through increasing of the solution`s temperature.

The crystallizer for lead battery recycling is completely produced in stainless steel AISI 304, and is composed of the following parts:

• A cylindric body that receives the solution to be treated from the top. The sedimentation zone in this body permits to continuously draw off the clarified part of the solution from the top. This part is sent to an external device that concentrates it through evaporation. The saturated solution re-enters the cylindric body containing the crystallization germs of Na2SC>4 • 10 H2O in suspension;
• A shell and tube exchanger in the cylindric body, feeded with steam, that releases thermal energy to the crystal germ solution. The heating causes a supersaturation of the system (drivingforce), supporting the new nucleation that the accretion of the crystalline grains presents in suspension with consequent precipitation of larger crystals;
• A propeller agitator. This agitator maintains the suspension in mechanical agitation and allows the crystals to grow up to the desired size. In this way it is possible to carry out a classification of the created crystals. The agitator is moved by an electric triphase motor and its speed is controlled by an inverter;
• A conical bottom with a final stem for the crystal collecting.

A pump draws the suspension containing the crystals from the crystallizer`s bottom and sends it to a centrifuge for the final separation. The process is continuously controlled through temperature and pressure sensors.

The motor of the crystallizer reactor for lead battery recycling can be activated via the monitoring system developed on PC, both in manual and automatic mode. In manual mode, start/stop is controlled by the user, while in automatic mode start/stop will be managed by the control software developed on PLC. In both cases the actual supply will only be present if the disconnector placed on board of the machine is not in the service position.