Advanced Technology Available for the Abatement of Mercury Pollution
133
the rest is released into the atmosphere (Habashi 1992a). Occasionally, the Hg,
As, Se and Te present in S02 are vented directly into the atmosphere or these
elements will pass into the sludge in many countries including the former Soviet
Union, Canada, USA, Australia and South America (Dyvik 1995). The global
atmospheric discharge of Hg from mining and metallurgical industries was
estimated to be between 134 (median value) to 170 t a-I in 1983 (Nriagu and
Pacyna 1988; Pirrone et al. 1996), whereas in 1992 it was 267 t a -I (Pirrone et al.
1996). Global consumption of zinc and copper concentrates were 14 X lOb and
35 x 10 6 t a-I respectively, while the production of H2 S0 4 was 143 X lOb tin 1995,
of which 60% was high quality H2 S0 4 according to the market standards
(Boliden Chemtrade, Zug, Switzerland, 1996, pers. comm.). If there were no
developments in technology, then 20 000 t a -I Hg would enter into the
ecosystem from the non-ferrous metallurgical industry alone (Habashi 1992b).
In the past, problems of Hg emissions from ferro-alloys production, scrap
remelting, iron and steel facilities and also from the traditional gold-winning
process in the Amazon territory have been highlighted (Maim et al. 1990;
Habashi 1992a; Dyvik 1995; Cleary 1996). It is necessary to control the Hg
emissions from these sources by available technology.
Due to the seriousness of the Hg problem in the metallurgical industry and
stringent legal regulations, continuous research since the 1960s in the Nordic
countries, Europe, North America and Japan has promoted the development of a
number of processes which are commercially adopted to recover or remove Hg
from gases in the metallurgical industry. Nine processes have been examined in
this study.
3
Removal of Mercury from the Gas Phase
The form of Hg in a process guides the selection of the Hg removal technology. In
the metallurgical industry, most of the Hg is released in the elemental form (HgO).
The processes for Hg removal from smelter gases are based on precipitationfiltration and adsorption-filtration methods (Habashi 1978). In the former, Hgo
reacts with concentrated H2S0 4 , HgCl2 or amorphous solid elemental Se to form
insoluble Hg slurry compounds in scrubbers which may be filtered to recover Hg
and other metals such as Se. In the latter method, gases are filtered through
activated carbon, zeolite or selenium. The Hg removal processes are described
below.
3.1
The Outokumpu Process
In the early 1970S, Outokumpu Oy, a multimetal production company, developed
an Hg recovery process from roaster gases based on precipitation-filtration
methods at the Kokkola Zinc Plant in Finland. In this process, the roaster gases at
133
the rest is released into the atmosphere (Habashi 1992a). Occasionally, the Hg,
As, Se and Te present in S02 are vented directly into the atmosphere or these
elements will pass into the sludge in many countries including the former Soviet
Union, Canada, USA, Australia and South America (Dyvik 1995). The global
atmospheric discharge of Hg from mining and metallurgical industries was
estimated to be between 134 (median value) to 170 t a-I in 1983 (Nriagu and
Pacyna 1988; Pirrone et al. 1996), whereas in 1992 it was 267 t a -I (Pirrone et al.
1996). Global consumption of zinc and copper concentrates were 14 X lOb and
35 x 10 6 t a-I respectively, while the production of H2 S0 4 was 143 X lOb tin 1995,
of which 60% was high quality H2 S0 4 according to the market standards
(Boliden Chemtrade, Zug, Switzerland, 1996, pers. comm.). If there were no
developments in technology, then 20 000 t a -I Hg would enter into the
ecosystem from the non-ferrous metallurgical industry alone (Habashi 1992b).
In the past, problems of Hg emissions from ferro-alloys production, scrap
remelting, iron and steel facilities and also from the traditional gold-winning
process in the Amazon territory have been highlighted (Maim et al. 1990;
Habashi 1992a; Dyvik 1995; Cleary 1996). It is necessary to control the Hg
emissions from these sources by available technology.
Due to the seriousness of the Hg problem in the metallurgical industry and
stringent legal regulations, continuous research since the 1960s in the Nordic
countries, Europe, North America and Japan has promoted the development of a
number of processes which are commercially adopted to recover or remove Hg
from gases in the metallurgical industry. Nine processes have been examined in
this study.
3
Removal of Mercury from the Gas Phase
The form of Hg in a process guides the selection of the Hg removal technology. In
the metallurgical industry, most of the Hg is released in the elemental form (HgO).
The processes for Hg removal from smelter gases are based on precipitationfiltration and adsorption-filtration methods (Habashi 1978). In the former, Hgo
reacts with concentrated H2S0 4 , HgCl2 or amorphous solid elemental Se to form
insoluble Hg slurry compounds in scrubbers which may be filtered to recover Hg
and other metals such as Se. In the latter method, gases are filtered through
activated carbon, zeolite or selenium. The Hg removal processes are described
below.
3.1
The Outokumpu Process
In the early 1970S, Outokumpu Oy, a multimetal production company, developed
an Hg recovery process from roaster gases based on precipitation-filtration
methods at the Kokkola Zinc Plant in Finland. In this process, the roaster gases at