“UzACADEMIA” scientific-methodical journal 24
www.academiascience.uz The chemistry of the fuming process is described by the following main
reactions:
ZnO + C = Znvapor + CO (1)
ZnO + CO = Znvapor + CO2 (2)
Partial recovery from zinc stripping:
ZnO + Fe = Znvapor + FeO (3)
Zinc metal, boiling at 906 ° C, is removed from the slag in the form of steam.
Above the surface of the slag bath and in the gas flue, zinc is re-oxidized even by
carbon dioxide:
Znvapor + CO2 = ZnO + CO (4)
Vapors of cadmium and lead and volatile lead sulfide are also oxidized in the
furnace atmosphere. As a result, sublimates (fine dust) are almost entirely composed
of oxides. Up to 90-94% of Zn and 95-98% of lead, indium and cadmium are
extracted from slags by fuming. Fumes (dust) of fuming furnaces contain 15-20%
lead oxide, 70-75% zinc oxide, cadmium, indium and germanium.
The copper and precious metals contained in the slag can be recovered by
treating the liquid slags after fuming with sulfides in the presence of a reducing agent
to form a matte. Copper, gold and silver are extracted into matte [4].
Slag sublimation (fuming) furnace is a rectangular shaft-type furnace made
entirely of water-cooled caissons. Furnace width ~ 2.4; length 1.2-9.6 steel caissons
for holding the slag skull pins welded in a staggered pattern. On each long side of the
furnace, 11 to 36 tuyeres are installed.
Fuming is a periodic process. It includes four stages: pouring, heating, reduction
treatment and slag tapping. The throughput of the kiln at one time ranges from 35 to
90 tons and depends on the size of the kiln.
A fundamentally continuous fuming process is possible. However, the optimal
version of its industrial implementation has not yet been found.
Waelz slag is a process of reduction treatment of solid granular slags without
melting them at 1100-
1200 ° C. It is carried out in tubular rotary kilns. The reducing
agent is coke and furnace (furnace) gases containing CO. The chemical processes that
take place during Waelz are similar to those during fuming.
The Waelz process is ongoing. A well-mixed mixture of slag with a size of 3-5
mm and coke with a particle size of up to 15 mm is loaded into the upper head of the
furnace. When moving in the furnace for 2-3 hours, the components of the charge
interact and the volatile components sublime in the form of oxides. The remnants of
the processed charge (clinker) are unloaded in the lower head of the furnace.
Sublimates (Waelz-oxides) yield is 20-25%. Sublimates contain, %: Zn 60-65;
Pb 11-15; Cd 0.5-1.0. Copper, gold, silver and excess carbon remain in the clinker.
The process is characterized by high extraction of zinc, lead and cadmium into fumes.
“ILM-FAN VA TA’LIMDA INNOVATSION YONDASHUVLAR, MUAMMOLAR, TAKLIF VA YECHIMLAR”
MAVZUSIDAGI 9-SONLI RESPUBLIKA ILMIY-ONLAYN KONFERENSIYASI
