606
D. Fonseca et al.
[1, 2]. Reasons for this are that most lead is used in easily recyclable and economically viable applications, such as lead-acid batteries, and the energy consumption is
almost 50% lower compared to primary production [3].
Short rotary furnaces (SRF) used for secondary lead production are highly versatile and have become popular in Europe. These kilns can perform similar functions
compared to the blast furnace, however with higher flexibility due to the possibility
of handling fine material. Its main disadvantage is the short life of the refractory
lining [4].
Common fluxes used in rotary furnace smelting are shredded iron scrap or steel
turnings and sodium carbonate (soda ash). A high sodium slag is used in many cases
due to its low melting point and low viscosity, promoting good separation of slag and
bullion [4]. In addition, the amount of volatilized lead could be reduced by operating
at lower temperatures, and sulfur can be easily captured into the slag through the
formation of sodium sulfide:
PbSO 4 + 4CO → PbS + 4CO 2
(1)
PbS + CO + Na 2 CO 3 → Pb + Na 2 S + 2CO 2
(2)
CO 2 + C → 2CO
(3)
Owing to the increased fuel consumption (Eq. 3) and the high cost of soda ash, a
higher proportion of iron in the flux material is commonly employed [4]. In addition,
restrictive environmental legislations hamper the disposal of high soda slags due to
their high toxic compound content. Thus, new slags based on low soda and increased
calcium and silica contents are being adopted [3].
In the case of lead-acid battery recycling, SRF are typically used. The refractories
in the furnace lining suffer severe wear, and the service life generally varies between
12 and 14 months, depending on the operation process and thickness of the working
lining [3]. Magnesia-chromite bricks (60–80% MgO) are the preferred choice for
the furnace lining due to their high resistance to extreme chemical attack. However,
the use of alternative CaO-rich slags accelerates refractory wear and significantly
reduces lining lifetime of magnesia-chromite bricks [3, 5].
The present study attempts to simulate the SRF environment in a laboratory scale
rotary drum furnace and provides a comparison of the slag wear resistance of six
different refractory grades. The main goal is to deepen the knowledge of the wear
phenomena of refractories exposed to different slag chemistries employed in secondary lead production. This would allow refractory producers to provide optimal
brick lining solutions based on the slag chemistry of each furnace.
D. Fonseca et al.
[1, 2]. Reasons for this are that most lead is used in easily recyclable and economically viable applications, such as lead-acid batteries, and the energy consumption is
almost 50% lower compared to primary production [3].
Short rotary furnaces (SRF) used for secondary lead production are highly versatile and have become popular in Europe. These kilns can perform similar functions
compared to the blast furnace, however with higher flexibility due to the possibility
of handling fine material. Its main disadvantage is the short life of the refractory
lining [4].
Common fluxes used in rotary furnace smelting are shredded iron scrap or steel
turnings and sodium carbonate (soda ash). A high sodium slag is used in many cases
due to its low melting point and low viscosity, promoting good separation of slag and
bullion [4]. In addition, the amount of volatilized lead could be reduced by operating
at lower temperatures, and sulfur can be easily captured into the slag through the
formation of sodium sulfide:
PbSO 4 + 4CO → PbS + 4CO 2
(1)
PbS + CO + Na 2 CO 3 → Pb + Na 2 S + 2CO 2
(2)
CO 2 + C → 2CO
(3)
Owing to the increased fuel consumption (Eq. 3) and the high cost of soda ash, a
higher proportion of iron in the flux material is commonly employed [4]. In addition,
restrictive environmental legislations hamper the disposal of high soda slags due to
their high toxic compound content. Thus, new slags based on low soda and increased
calcium and silica contents are being adopted [3].
In the case of lead-acid battery recycling, SRF are typically used. The refractories
in the furnace lining suffer severe wear, and the service life generally varies between
12 and 14 months, depending on the operation process and thickness of the working
lining [3]. Magnesia-chromite bricks (60–80% MgO) are the preferred choice for
the furnace lining due to their high resistance to extreme chemical attack. However,
the use of alternative CaO-rich slags accelerates refractory wear and significantly
reduces lining lifetime of magnesia-chromite bricks [3, 5].
The present study attempts to simulate the SRF environment in a laboratory scale
rotary drum furnace and provides a comparison of the slag wear resistance of six
different refractory grades. The main goal is to deepen the knowledge of the wear
phenomena of refractories exposed to different slag chemistries employed in secondary lead production. This would allow refractory producers to provide optimal
brick lining solutions based on the slag chemistry of each furnace.