The undesulfurized lead paste and surplus industrial water (desulfurized lead paste washing water, evaporation condensate water) of the workshop are added to the desulfurization reaction tank to prepare lead mud slurry. Sodium carbonate was put into the desulfurization reaction, and after the reaction was completed, the desulfurized lead paste (lead carbonate) and the sodium sulfate solution with the concentration of about 20% were obtained by press filtration. The desulfurized lead paste is rinsed and sent to the smelting unit. The principle of desulfurization is as follows:

PbSO4+Na2CO3→PbCO3+Na2SO4

H2SO4+Na2CO3→H2O+CO2  +Na2SO4