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B. Saxén et al.
Introduction
Industrias Peñoles is a Mexican company founded in 1887 constituted by the mines
and metals—chemicals divisions. The metals division operates the most important
non-ferrous metallurgical complex in Latin America and one of the most important
worldwide, which is located in northern Mexico in the city of Torreón Coahuila.
Metallurgica Met-Mex Peñoles has a lead smelter, a lead–silver refinery, and an
electrolytic zinc refinery where lead and zinc concentrates from Peñoles and Fresnillo
groups are processed. The main products of the metallurgical complex are refined
zinc, lead, silver, and gold as well as a series of by-products such as sulfuric acid,
cadmium, bismuth, ammonium sulfate, and liquid sulfur dioxide.
The zinc refinery began operations in 1973, with an annual installed capacity of
105,000 ton. Due to increasing demand for this metal, the plant annual capacity was
increased to 240,000 ton in 2006. The production of zinc concentrates with high
iron content by Peñoles mines also increased; however, the main characteristic of
these materials is the lower recovery of zinc in the roasting–leaching–electrowinning
process. An alternative to process these materials without sulphuric acid production
and high zinc recovery was searched, and the direct leaching (DL) technology met
the requirements established by Peñoles. The first steps in the DL project were
taken already in 2004 with concentrate leaching tests at Outotec laboratories. As the
first tests showed good results, bigger scale tests including continuous piloting of
both leaching and residue treatment steps were carried out, and engineering studies
were executed. After also some inactive periods, Peñoles made the decision for DL
expansion early 2015 followed by detail engineering, delivery, installations, and
finally process start-up late 2018.
In the coming years the quality of zinc concentrates available in Mexico will be
lower due to the increase in impurities content, as well as the variation in mineralogical composition and the decrease in particle size. One of the main objectives
of Industrias Peñoles is the processing of all the concentrates produced by Fresnillo
group in Met-Mex Peñoles metallurgical complex, to achieve this goal a strategic
plan with the objective of defining technological alternatives for the processing of
zinc concentrates of Fresnillo group was done.
An analysis of the technologies available for the purge of iron showed Outotec Pure
Jarosite precipitation process being the best option. With this technology Peñoles will
be able to process zinc concentrates with high content of values (Au, Ag and Zn),
as well as impurities. The Pure Jarosite process, including also the roaster feed pretreatment system (FPS), was piloted at Outotec in parallel with basic engineering
during 2016. This provided necessary information for the investment decision which
was made early 2017. The implementation of these process changes is now going
on.
This paper presents the DL process and its implementation at Torreón plant. In
addition, the features and application of Pure Jarosite process and the roaster FPS
are described.
B. Saxén et al.
Introduction
Industrias Peñoles is a Mexican company founded in 1887 constituted by the mines
and metals—chemicals divisions. The metals division operates the most important
non-ferrous metallurgical complex in Latin America and one of the most important
worldwide, which is located in northern Mexico in the city of Torreón Coahuila.
Metallurgica Met-Mex Peñoles has a lead smelter, a lead–silver refinery, and an
electrolytic zinc refinery where lead and zinc concentrates from Peñoles and Fresnillo
groups are processed. The main products of the metallurgical complex are refined
zinc, lead, silver, and gold as well as a series of by-products such as sulfuric acid,
cadmium, bismuth, ammonium sulfate, and liquid sulfur dioxide.
The zinc refinery began operations in 1973, with an annual installed capacity of
105,000 ton. Due to increasing demand for this metal, the plant annual capacity was
increased to 240,000 ton in 2006. The production of zinc concentrates with high
iron content by Peñoles mines also increased; however, the main characteristic of
these materials is the lower recovery of zinc in the roasting–leaching–electrowinning
process. An alternative to process these materials without sulphuric acid production
and high zinc recovery was searched, and the direct leaching (DL) technology met
the requirements established by Peñoles. The first steps in the DL project were
taken already in 2004 with concentrate leaching tests at Outotec laboratories. As the
first tests showed good results, bigger scale tests including continuous piloting of
both leaching and residue treatment steps were carried out, and engineering studies
were executed. After also some inactive periods, Peñoles made the decision for DL
expansion early 2015 followed by detail engineering, delivery, installations, and
finally process start-up late 2018.
In the coming years the quality of zinc concentrates available in Mexico will be
lower due to the increase in impurities content, as well as the variation in mineralogical composition and the decrease in particle size. One of the main objectives
of Industrias Peñoles is the processing of all the concentrates produced by Fresnillo
group in Met-Mex Peñoles metallurgical complex, to achieve this goal a strategic
plan with the objective of defining technological alternatives for the processing of
zinc concentrates of Fresnillo group was done.
An analysis of the technologies available for the purge of iron showed Outotec Pure
Jarosite precipitation process being the best option. With this technology Peñoles will
be able to process zinc concentrates with high content of values (Au, Ag and Zn),
as well as impurities. The Pure Jarosite process, including also the roaster feed pretreatment system (FPS), was piloted at Outotec in parallel with basic engineering
during 2016. This provided necessary information for the investment decision which
was made early 2017. The implementation of these process changes is now going
on.
This paper presents the DL process and its implementation at Torreón plant. In
addition, the features and application of Pure Jarosite process and the roaster FPS
are described.