Model NF - Nanofiltration Skid System for Lead Battery Recycling
The nano-filtration system is part of the crystallization process of decahydrated sodium sulphate (Glauber's Salt) operating in the desulphurization unit of lead battery recycling plants.
The nano-filtration system treats the mother liquors comingfrom the crystallization of the dechydrated salt (feeding liquid), which contain still 5% of sodium sulphate in solution, and re-introduces them into the crystallization process with a concentration higher than 15% (concentrated liquid). The permeate (diluted liquid), instead, is sent to the process water collecting tank of the lead battery recycling plant.
The incoming solution is filtered in a mechanical cartridge filter in order to remove solid particles that would obstruct the osmosis membranes in shorter times compared to the regular period. Afterwards the solution enters in the multistage centrifugal pump for pressurization. The pressurization is necessary because the membranes of the nano-filtration need high pressure to be able to have permeate flows corresponding to project specification. The solution enters two parallel membranes first and then two vessels located in series.
Each of the four vessels produces a permeate current which is collected in a single basin. The connections for the concentrate and the permeate are located in front of the skid. Each vessel has three membrane modules of nano-filtration 8040 (8 inches diameter rated for 40 inches length) connected in series.
The plant is equipped with analog and digital instrumentation for its operation. The switchboard is installed on the front side and controls the electric feeding as well as the commands through PLC.
The nano-filtration plant of the lead battery recycling process operates at a pressure of maximum 50 bar: the pressure equipment has lower characteristics than the limits fixed by the PED (Pressure Equipment Directive) and therefore make part of the exemptions of art. 3 comma 3 of the same directive.