Zero emission method of wastewater in lead-zinc metallurgical refinery

Abstract

The invention belongs to the field of wastewater treatment of non-ferrousmetal metallurgy, which is suitable for wastewater treatment with high content of Zn, Cd, Mg and Cl. The metallurgical wastewater adopts a two-section neutral reaction, namely (1) in a first-section neutral reaction tank, the supernatant which is produced by a second-section neutralization and Mg-precipitated is reacted withmetallurgical wastewater, the pH value of the final point is equal to 7.5 to 8, the precipitate flows at the bottom, after pressing and filtering, zinc leaching is returned so as to recover Zn and Cd, and the supernatant part enters into the second-section neutral reaction, and the other part enters into filtering procedure; (2) in a second-section neutral reaction tank, the supernatant which is produced by the first-section neutralization is reacted with lime milk, the pH value of the final point is equal to 12 to13, the precipitate flows at the bottom, after pressing and filtering, filteredslag containing Ca and Mg is conveyed to a slag dam for stockpiling; and (3) the pH value of the other part of supernatant produced by the first-section neutralization is adjusted to 5.5 to 6.5 with dilute sulphuric acid, a combined film is used for filtering, and various produced filtering water is conveyed to corresponding procedures in a lead-zinc metallurgical refinery. The zero emission method has high recovery rate of Zn and Cd and has the Zn metallurgical system with high content of Ca and Mg and no return slag.

Description

technical field [0001] The invention belongs to the treatment technology of lead-zinc smelting wastewater, and is especially suitable for treating wastewater containing high Zn, Cd, Mg, and Cl. The recovery rate of Zn and Cd is high, and the waste residue containing high Ca and Mg is not returned to the zinc smelting system. technical background [0002] For the treatment of lead-zinc smelter wastewater, a one-stage lime milk neutralization method is usually adopted at home and abroad, so that the heavy metal ions in the wastewater can form hydroxides and precipitate into the slag. The supernatant water containing heavy metal ions can meet the national discharge standards and can be discharged into rivers . Since this supernatant water still contains high Cl - (400~500mg / L), Ca 2+ (700~800mg / L), SO 4 2- (2500~3500mg / L), except that a small part can be reused for pyrometallurgy water-quenching slag and silver flotation make-up water, for hydromethod zinc smelting with lar...

AI Technical Summary

Problems solved by technology

However, sodium carbonate must be added to remove calcium below 3mg / L before filtration, and then sand filtration, activated carbon filtration, cation exchange, and ultrafiltration can enter reverse osmosis filtration, which increases the consumption of sodium carbonate and increases production costs. Into the sodium ion, its disadvantages are obvious

[0005] Shaoguan Smelter adopts the process of "one-stage neutralization + chemical decalcification + pretreatment (sand filtration + activated carbon 2+ , Mg 2+ , SO 4 2- etc.), the output "sodium fresh water" can be reused for production, which is applicable to pyro-smelting plants, but this method cannot remove Cl in wastewater - The monovalent ion represented by Cl - The harm to zinc electrolysis cannot be solved by this law

The foreign ions brought in by chemical decalcifiers accumulate in the wastewater, which cannot achieve zero discharge of wastewater, but can only achieve the purpose of reducing discharge.

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