The hydrometallurgical desulphurization of lead battery paste is a chemical reaction at low temperatures (40-50 °C) by means of the lead sulfate (PbSO4) contained in the paste that is converted into lead carbonate (PbCO3), according to the following reaction:
PbSO4 + Na2CO3 → PbCO3 + Na2SO4
The desulphurization of lead battery paste, integrated into the traditional pyro-metallurgical process lead battery recycling, has several advantages:
- lower energy consumption, because of the lower operating temperature of furnaces;
- higher yield of lead, due to the lower content of this element in the slag;
- lower environmental impact, due to the lower content of sulfur dioxide in the flue and lower waste production;
- lower raw material consumption, due to the lower amount of iron in the charge and lower production of slag;
- higher life-cycle for the furnace refractory bricks.
In fact, if the lead sulfate of the lead battery paste is desulphurated by-means of an hydrometallurgical pretreatment, the reduced furnace temperature is about 1000°C, considerably lower than 1360°C of the traditional process. In the desulphurization reactor the calcination temperature of lead carbonate, which is converted into PbO releasing CO2, is about 600-700 °C. At temperatures not much higher, the lead oxide is reduced to metallic lead, reacting with carbon monoxide in the furnace, with industrially acceptable kinetics. The slag from the furnace contains very little sulfur dioxide and the produced waste, in the hypothetical case of total absence of sulfates in charge, does not contain sulfides and its lead content is significantly reduced.
An additional benefit of the desulphurization of lead battery paste is the production of large quantities of sodium sulfate (Na2SO4) that meets the severe market specifications for its use in the paper, soap and glass industry.
Alternatively the STC process can also be operated for the extraction of sodium sulphate directly as Glauber’s salt, a valuable product in the paper industry.
Desulphurization cost analysis
STC has created a detailed cost analysis for the desulphurization plant of battery paste for lead battery recycling.
Changing the marked fields you can calculate your personal cost analysis.
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