A New Route for Treating Neutral
Leaching Residue
Caio César Spindola de Oliveira, Daniel Dayrell Pereira,
Felipe Ramos Pereira Mendes and Mateus Felipe Louredo Araujo
Abstract In the zinc smelter process, more specifically in the acid leaching step,
sulfuric acid is added to the neutral leach residue until 45–60 g/L free acidity is
reached, usually retrieving 92% of the zinc contained in the residue. However, it
also makes iron and other impurities soluble. Because of that, the solution must go
to some iron removal step (jarosite, for example). In this work, we compared this
method to the sulfatation process. By simulating a roaster gas outlet (8% of SO 2 ), at
650 °C, in a fluidized bed reactor (2 kg/h), we were able to solubilize 96.6% of the
zinc and only 2.9% of the iron. That means, no excess acid was required in order to
obtain the zinc, and less acid was spent with iron (less residue was obtained as well
because hematite occupies 67% less mass than jarosite). With these results, we may
improve acid balance, residue reduction, and raw materials consumption in a zinc
plant.
Keywords Sulfatation · Neutral underflow · Zinc recovery
Introduction
Conventional Leaching Process
In the traditional zinc RLE (roasting, leaching, and electrowinning) process, after
roasting the zinc sulfide concentrate, the obtained zinc calcine (zinc oxide) is mixed
C. C. S. de Oliveira (B) · D. D. Pereira · F. R. P. Mendes · M. F. L. Araujo
Nexa Resources, BR040, km 284, Tres Marias/MG 39206-000, Brazil
e-mail: caio.oliveira@nexaresources.com
D. D. Pereira
e-mail: daniel.pereira@nexaresources.com
F. R. P. Mendes
e-mail: ext.felipe.mendes@nexaresources.com
M. F. L. Araujo
e-mail: mateus.araujo.ma1@nexaresources.com
© The Minerals, Metals & Materials Society 2020
A. Siegmund et al. (eds.), PbZn 2020: 9th International Symposium
on Lead and Zinc Processing, The Minerals, Metals & Materials Series,
https://doi.org/10.1007/978-3-030-37070-1_72
827
Leaching Residue
Caio César Spindola de Oliveira, Daniel Dayrell Pereira,
Felipe Ramos Pereira Mendes and Mateus Felipe Louredo Araujo
Abstract In the zinc smelter process, more specifically in the acid leaching step,
sulfuric acid is added to the neutral leach residue until 45–60 g/L free acidity is
reached, usually retrieving 92% of the zinc contained in the residue. However, it
also makes iron and other impurities soluble. Because of that, the solution must go
to some iron removal step (jarosite, for example). In this work, we compared this
method to the sulfatation process. By simulating a roaster gas outlet (8% of SO 2 ), at
650 °C, in a fluidized bed reactor (2 kg/h), we were able to solubilize 96.6% of the
zinc and only 2.9% of the iron. That means, no excess acid was required in order to
obtain the zinc, and less acid was spent with iron (less residue was obtained as well
because hematite occupies 67% less mass than jarosite). With these results, we may
improve acid balance, residue reduction, and raw materials consumption in a zinc
plant.
Keywords Sulfatation · Neutral underflow · Zinc recovery
Introduction
Conventional Leaching Process
In the traditional zinc RLE (roasting, leaching, and electrowinning) process, after
roasting the zinc sulfide concentrate, the obtained zinc calcine (zinc oxide) is mixed
C. C. S. de Oliveira (B) · D. D. Pereira · F. R. P. Mendes · M. F. L. Araujo
Nexa Resources, BR040, km 284, Tres Marias/MG 39206-000, Brazil
e-mail: caio.oliveira@nexaresources.com
D. D. Pereira
e-mail: daniel.pereira@nexaresources.com
F. R. P. Mendes
e-mail: ext.felipe.mendes@nexaresources.com
M. F. L. Araujo
e-mail: mateus.araujo.ma1@nexaresources.com
© The Minerals, Metals & Materials Society 2020
A. Siegmund et al. (eds.), PbZn 2020: 9th International Symposium
on Lead and Zinc Processing, The Minerals, Metals & Materials Series,
https://doi.org/10.1007/978-3-030-37070-1_72
827