INTRODUCTION
Topicality of theme
Last years in connection with education
and accumulation of a significant amount
of a waste and necessity of the decision
of environmental problems value of their
utilization is increase. Prevailing in
steel-smelting manufacture
oxygen-converter process develops in a
direction material and energy economy.
In the waste of converter manufacture
except metals among nonmetallic
resources: secondary fire-resistant
materials, slags, sludges and a dust.
Special attention it is necessary to
give sludges converter manufacture,
which are investigated less other
secondary resources. Besides sludges
converter manufactures are most hard
utilization. Difficulties in utilization
of these sludges arise because of the
raised maintenance in them of nonferrous
metals, especially zinc and the lead,
which maintenance frequently exceeds in
scarce zinc and lead ores, which in
Ukraine practically are not present.
The purposes
-
to develop actions for decrease in
negative influence of a waste of
converter manufacture on
environment;
-
to develop resource economy
technology for converter
repartition;
-
to improve available schemes of
preparation of secondary material
resources of converter manufacture
to utilization, having provided with
that fuller utilization of the given
waste;
-
to prove economic efficiency from
introduction resource economy
technologies and use of essentially
new schemes of preparation of a
waste to utilization.
Tasks
-
to consider sources and
metallurgical value of a secondary
material waste of converter
manufacture;
-
to consider process of formation of
production wastes;
-
to reveal dependence of quantity of
a formed waste on a kind of used
treatment facilities and applied
technology of melt converter steel;
-
to formulate the basic directions of
increase of ecological safety of
converter manufacture;
-
to estimate economic benefit at
transition converter manufactures on
more perfect technology production
of steel and utilization of
wastes;
-
to state a complex estimation of the
developed technology production to
converter steel and utilization of
production wastes.
Scientific novelty of work consists that
earlier examined the questions,
concerning utilization of a waste of
steel-smelting manufacture as a whole.
The given work considers resource
economy technologies and ways of
utilization of a waste of converter
manufacture.
Practical value of work consists that
the considered technological actions
ecologically and economically
expediently to introduce at the
metallurgical enterprises of Ukraine
thereby raising ecological safety of
converter manufacture.
ANALYSIS OF RESOURCE SAVING AND
IMPROVEMENT OF TECHNOLOGY OF UTILIZATION
OF SECONDARY RESOURCES OF
OXYGEN-CONVERTER MANUFACTURE OF STEEL AT
THE METALLURGICAL ENTERPRISES OF UKRAINE
One of decrease
ways of material capacity production and
economy of a source of raw materials is
increase of level of use of production
wastes which are inevitably formed both
in sphere of production of goods, and in
consumption sphere. The
factory
floor experience
shows, that use of
a waste converter manufacture is
technically realizable and economic.
Despite spent job level of use of
secondary material resources still is
insufficiently high for the various
reasons, but first of all in the absence
of objects of the corresponding
preparation, not enough the developed
technologies, absence of the
systematized literature and first of all
help character.
Now the basic method of use sludge gas
purifications of converters is their
additive to agglomeration mix.
For utilization on agglomeration factory
converter sludge must be preliminary
dehydrated. Now the most rational scheme
of dehydration is the scheme providing a
condensation sludge of a pulp in radial
thickeners, filtering on vacuum-filters
and drying in siccative drums. At
presence at the enterprise in enough of
a dry waste (lime, agglomerate
elimination etc.) it is possible to
replace drying with mixing sludges with
this waste.
The cheme of
utilization sludges of converter
manufaction
Sometimes converter sludge on
agglomeration factory it is used without
mechanical and thermal dehydration, it
is direct in the form of a dense pulp
after a condensation (300—700 g/l) in
radial thickeners or in hydrocyclones
and radial thickeners. Sludge in the
sprayed kind moves in a mixing drum of
agglomeration factory. Advantage of such
way — low capital expenses and working
costs. A necessary condition of
successful operation of schemes is the
reliable automatic dosage of sludge in a
mixing drum depending on humidity mix
and density condensed sludge.
For returning of sludge of gas
purifications in the converter it is
necessary its preliminary fragmentation.
There are also methods of fragmentation,
developed specially for converter
sludges.
The fragmentation of sludge for
converter manufacture it is applied in
the following scheme. Gas purification
sewage converter shops arrives in a trap
where the largest particles are
besieged. Having poured traps gets
through the mixing chamber to a radial
thickener. In the mixing chamber limy
milk also moves. Plums of a radial
thickener goes on a reuse to gas
purification system, and condensed
sludge - on a funnel feeding drum-type
vacuum-filter. 28–32 % dehydrated to
humidity sludge from the vacuum-filter
and the large fraction caught in a trap,
the tape conveyor move in a feeder of
the rotating tubular furnace where are
carried out drying of sludge, it balling
and roasting of pellets at temperature
1150˚С.
The pellets are cooled in cooling drum
and are loaded into the railway car.
The prospective volume of use of sludge
of converter gas purifications is
utilized as the additive to
agglomeration mix. For returning the
sludge in converter manufacture it is
necessary to develop, leaning against
foreign experience, the effective scheme
of preparation sludges, which would
allow to receive a conditioned material
in a kind of pellets or briquettes. Such
scheme would allow to remove a problem
of without zinc-plating of converter
sludges for which till now there is no
cheap technology of removal of zinc.
In another way
utilizations ferriferous dusts and
sludges of converter manufacture
their inclusion in charge makeup is by
manufacture of cement and other building
materials, and also of some paints, for
example, ochre and dyes.
Pulp and dehydrated
sludge can use only on agglomeration
factory (or factories on manufacture of
pellets) as only in mix these
manufactures
it is possible to submit the humidified
materials. In particular, the pulp can
be submitted
to mixing drums of these manufactures.
Thus, as the requirement for moisture on
agglomeration factory can
exceed quantity
of moisture arriving with a pulp,
sometimes it is necessary even
to add moisture in the amalgamator.
However because of increase in expenses
of a pas transportation is expedient for
using this method only at a close
arrangement in
territory
of the enterprise steel-smelting
and agglomeration shops.
One
of perspective methods of preparation of
sludges to utilization is drying of the
sprayed pulp
in a stream
(preferably) heated gases. At method
test
good results, however a method yet have
been received has not found introduction
in manufacture. This method is expedient
for combining with giving received at
its use
dense (pastelike) sludges in mixers
(drums-pelletizers) of agglomeration
factory: sludge with moisture load 40 –
50 % (on weight) are sprayed by evolvent
atomizers
that provides uniform humidifying of
mix. Last way is attractive the
simplicity, however there are the
difficulties connected with a dosage of
sludges. For the purpose of increase of
reliability of the specified way careful
study of a method of a dosage and
processing of assemblages of the dosing
device are made.
Recently
in connection with an intensification
oxygen-converter
process carrying out from the unit with
gases of large fractions of a dust
departing from it
has amplified. Therefore it is necessary
to spend classification of sewage
before their receipt on the basic
constructions. Radial sediment bowls are
most widely
applied to dehydration of converter
sludges, for example, by diameter 30 m,
which at specific load 2 m3
/ (m2·h) allow to receive the
clarified water with the residual
maintenance of a suspension which are
not exceeding 200 mg/l.
The preparation
of
converter sludges to utilization in
agglomeration mix is expedient for
making together with
a waste containing iron. In a case when
at the metallurgical enterprise are
available martin
and converter manufacture,
it is the most expedient
to make
their
joint preparation
sludges to utilization.
The converter slagsб
from which even
metal
is rather full taken, contain a number
of valuable elements. They are rather
rational for using in metallurgy, for
example in agglomeration and
blast-furnace productions and foundry
manufacture, as a gumboil instead of
limestone.
Now in our country and abroad converter
slags process mainly
in a firm status. Them split up, subject
to rough selection of metal, sometimes
again split up and separate. Way of
processing widely tested and introduced
in manufacture converter in a liquid
status is not present till now some
slags. Only at separate factories test
semiindustrial or industrial granulation
installations.
Depending on time of stay in bowls (from
the moment of filling to canting) and
volume their slag can arrive for
processing in liquid or in a firm
status. It is shown, what even later 2 h
after filling to 80 % a liquid melt in a
bowl remains in a liquid
status.
From steel-smelting slags for use as a
turnaround product in metallurgical
repartition the greatest interest
represents slag of converter
manufacture. Converter slag incorporates
such components valuable to
metallurgical repartition as CaO, MgO,
MnO, CaF2, Al2O3,
FeO. Besides, in converter slag of
current manufacture contains from 3 to 9
% of iron in a kind of «prill».
Basicity of final converter slag is at
level 2,8 – 3,5, and maintenance
СаО
and in converter slag is in limestone
approximately at one level (46 – 52 %).
It allows using converter slag instead
of limestone in furnaces and
cupola-furnaces foundry shops.
As show thermodynamic calculations, heat
expenses on dissociation limestone and
reception of slag liquid melt
approximately in 1,5 - 1,7 times more
than at application of converter slag.
If to consider also that limestone the
natural material,
which
stocks,
finally, are limited, and converter slag
is
a manufacture withdrawal, advantage of
its use in metallurgical repartition
instead of
limestone undoubtedly.
Processing converter slag of current
manufacture is made
on a stationary site of conversion slag
with use
of a way of thermocrushing. Separate
processing
of liquid slag and ladle leavings
is provided. Technology of primary
processing
converter slags on a stationary site
concerns:
-
slag
transportation on a site;
- slag plums in
holes-trenches;
- movement slag
carriage in section for knockout ladle
leavings
and knockout of the last;
-
thermocrushing and cooling of slag by
water;
- working out
of the cooled down slag by a dredge;
- extraction of
the large-sized scrap metal;
-
transportation of the cooled down slag
by motor transport on
a crushing-and-sorting
site.
On a stationary site of conversion
liquid slag only from converters goes.
Plums of slag from converters it is made
in the pure, prepared bowls without
fight of a brick, industrial dust, scrap
metal and other waste. The bowls filled
with slag in as much as possible short
terms (that the quantity of liquid slag
in a bowl by the moment of canting was
not less than 50 %) arrive on a
stationary site.
The technology of thermocrushing
switches on leyel-by-leyel pouring of
liquid slag to depth of a layer of slag
1,5 – 2 m in special sections, an
irrigation water with the expense 0,1 –
0,15
m3/th
on 1m2 the areas after
canting of every portion slag. In
holes-sections the thermocrushed slag is
developed by a dredge and shipped or is
direct in auto dump-body trucks or is
formed in a temporary stack. The
fractional structure the thermocrushed
slag supposes direct loading of slag in
blast furnaces without additional
crushing.
The thermocrushed converter slag can be
used in mix blast furnaces and cupola
furnace; the crushed ladle leavings can
be used in mix blast furnaces, and also
after crushing on the
crushing-and-sorting plant -200 – in
agglomeration mix (fraction <10 mm).
It is shipped to consumers thermocrushed
slag, on a chemical compound should have
СаО
not less than 45 %, SiO2 no
more than 20 %, Fecom not
less than 10 %, humidity no more than 7
%. The maintenance of extraneous
impurity should not exceed 5 %.
The operational experience of Enakievsky
metallurgical plant shows that in
agglomeration mix it is possible to use
converter slag of fraction of 0-10 mm
with the expense of agglomerate of 30-50
kg/t without deterioration of technical
and economic
indicators
of work agglomeration factory. To blast
furnaces and cupola furnaces of foundry
shops goes converter slag of fraction of
10-40 mm. At use converter slag in
martin furnaces instead of limestone at
the expense of earlier formation slag
fuller removal of phosphorus in slag is
observed.
SUMMARY
Thus, from the economic and ecological
points of view
the
use
highly effective gas-purifying systems
with the organization full and complex
utilization of waste will allow to
increase technical and economic
indicators
of manufacture of steel and considerably
to lower
environmental contamination level. Use
of
converter slag instead of limestone in
metallurgical repartition
very favorably as will allow to lower
the expense natural mix materials and
coke and also to reduce emissions of
carbonic gas and a dust. The
organization of the processes
supervising movement of zinc in
metallurgical processes, will allow to
lower essentially
negative
influence of zinc on technology of
domain manufacture at utilization dust,
which to fly out at the steel-smelting
units, and also it is rational to solve
a question of reception of additional
quantity of scarce zinc from
a ferrous metallurgy
waste. The complex approach to the
decision of environmental problems
converter manufactures will allow
improving essentially ecological
conditions at metallurgical combines of
the country.
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