WAYS OF CLEANING OF GASES
OXYGEN-CONVERTER OF MANUFACTURE
Kanenko
G.M., Pikonec G.А.
Oxygen - converter
process is leading steel-smelting
process in the world as usual.
The world manufacture of converter
steel has made 964,8 million tones
or 63,3 % from the general manufacture
in 2003 year .
Converter
manufacture of Ukraine includes 6 shops
with 19 converters in capacity 2
х
350 tones, 2
х
250 tones, 12
х
(150 - 170 tones), 3
х
65 tones. A technological level in
converter
shops as a whole high enough, best of
them are included into the number of
leading
converter
shops of the world.
Converter manufacture, as well as any
another, is a source of pollution of the
surrounding natural environment. The
primary problems of it are reduction of
emissions, dumps and decrease of waste
products. The essence of the given
problems consists in use of secondary
power and material resources, the modern
equipment.
Thus, an important aspect, without which
technical rearmament hardly possible, is
decision of the questions of increase of
a technological level, an ecological
safety, savings of resources and
energy.
The problems of resources savings solved
extremely slowly: many decades expenses
of raw material and energy on unit of
metal products on 30 - 50 % exceed the
best world achievements.
Researches and experience confirm the
rationality of the decision of a
two-uniform problem for decrease of
expenses of primary resources and sharp
reduction at the expense of it harmful
emissions in an atmosphere on all
metallurgical cycle - from extraction of
ore before release of rolling products.
PHYSICAL AND CHEMICAL PROPERTIES
CONVERTER OF GASES
The process in the oxygen converter
proceeds intensively. Plentiful gas
evolution is one of the main lacks of
this manufacture. Clearing of gases and
their previous cooling continue to
remain
difficult problems. Various ways of
application
converter
gases are possible. Burning gas above
the converter in boilers of a special
design, receive
steam. Catching of gas after cooling and
clearing allows using it as fuel in
power assemblies or as a reducer in
technological processes.
In
converter
gas, in the negligible quantity (up to 1
%) contains nitrogen, hydrogen and
oxygen. The basic component is CO (up to
90 %) and
СО2
(up
to 10 %). Such structure of gas causes
high heat of his combustion (8,5-9,2
МDg/m³)
and toxicity. The gas mix, which
contains more of 12 % CO, becomes
explosive at concentration of oxygen of
more than 5 %.
The maintenance of sulfur in
converter
gases depends appreciably on its
maintenance into lime and changes from
105 mg / m ³ to 206 mg / m ³.
An output of gases, their structure is
variable
on course smelting. The quantity of
converter
gas, got out of the converter, makes
60-80 m³. The temperature of converter
gas ≈ 1400-1800˚C also is close to
temperature of metal. The high
temperature of gas on an output from the
converter causes significant losses of
physical heat with gases and is an
essential share in thermal balance
конвертерной
smelting (up to 10 %).
Converter
gas is high-quality technological and
power fuel. These features are necessary
for take into account at a choice of
system and a way of tap and use. At tap
of gas without access of air pulverous
particles have larger sizes. According
to these features, the circuit of gas
purification gets out. At finer
fractions of a dust, the requirement to
the gas purification raise. The
temperature of gas before gas
purification should not exceed 200-300˚С.
As temperature of gas at an output from
the oxygen converter ≈1600˚C before gas
purification of them it is necessary to
cool.
Probably some ways of cooling:
-
diluting of
air;
-
injection of water;
-
the equipment of
gas duct
water-cooled fireplaces or screens;
-
development of fallow in the waste-heat
boilers at the expense of physical heat
of converter
gases or products of their combustion.
More often, these ways are combining.
The way of cooling and a design of the
cooling equipment essentially are
influence on technological process the
smelting of steel and parameters of
converter manufacture.
Gases allocate from oxygen converters
the various ways, at which the size of
coefficient of the charge of air on an
input is various:
-
at full burning gas with access of air
– α > 1;
-
with access of air and partial burning
of gas – 0 < α <1;
-
without access of air and without
burning gas – α = 0.
Gases on an output from the oxygen
converter contain energy ≈ 0,95-1,05 MDg/t
steel (20 % of physical heat and 80 % of
chemical energy).
Use of heat of gases allows saving 30
thousand tones conditional fuel on 1
million
tones
steel. At use of heat of
converter
gas it is possible to receive hot water
and sated water fallow in coolers with
reburning (α > 1). The fallow direct for
technological needs of the enterprise or
after overheat – for development of the
electric power.
In systems without reburning
converter
gases (α = 0) or with partial reburning
in radiation boilers use up to 10 % of
chemical energy and physical heat of gas
with subsequent his catching and burning
as fuel in power or technological
assemblies. After cooling and cleaning
without reburning, the
converter
gas can be use as fuel and chemical raw
material. Without clearing and cooling,
it is possible to use for heating
charge
materials
of converter
smelting and as a reducer iron-ore raw
material.
In our country, basically, systems of
tap of gases with full or partial
reburning CO in the converter are
applying. In these circuits, chemical
energy departed
converter
gases is not use and lost.
Application converter gas as fuel is one
of reserves of fuel and energy
resources. However, his application is
complicated for the following reasons:
1. Inconstancy
of an output
converter
gas (on time and on quantity)
2. Sharp
shakings of structure of gas during the
various periods smelting
3. An
opportunity inflow air that can result
to formation to a mix gases and oxygen
and explosion of using assembly.
WAYS OF CLEANING OF DEPARTED GASES
At a choice of devices of gas
purification, it is necessary to take
into account distinction of fractional
structure of a dust in products of
combustion (ОCG
with reburning) and
converter
gas (ОCG
without reburning), these systems acting
in gas paths. The special attention is
giving hermetic sealing flue
in the latter case in connection with
toxicity oxide the carbon (II), making
about 90 % of
converter
gas.
The exhaust path consists of a
boiler-cooler, devices of wet gas
purification with system of separation
and tap of sludge, a supercharger of
gas, afterburner devices or
gasholder, armatures, gas mains (with a
supercharger and additional cleaning in
the electrofilter) to the consumer.
Cooled and cleaned
converter
gas can be caught with subsequent use;
if catching is not stipulated he should
be burnt on candles. In
converter
shops of domestic factories,
converter
gas is not catch.
The basic circuit of tap and cleaning
the converter
gas without reburning CO with use of his
chemical energy after the gas
purification, used by one of factories
of Japan consists in the following. The
cooled gas acts in jet washers, then
after coagulation of a dust in pipes
Venturi, he is cleaning in centrifugal
scrubbers and goes in gasholder or to a
chimney. Before outburst in the
atmosphere, gas burns by help of special
torches.
USE OF PHYSICAL HEAT CONVERTER GAS
Converter
gas from the converter acts in exhaust a
path where his physical heat realizes
for reception fallow in a boiler-cooler.
In quality
ОCG
without reburning apply
radioactive-convective boilers with
screens, in which gas cools up to 500 –
600˚С.
After a boiler-cooler before gas
purification additional cooling is
carried out by injection of water in
flue. In the offered circuit the
opportunity of use of physical heat and
chemical energy converter gas is
provided: physical heat is used in a
boiler - cooler for development fallow,
and gas can be applied as high-quality
fuel after cleaning of a dust.
For the maximal realization of power
resources in oxygen converter shop is
necessary to use
generating set, into which structure
enter storage, evaporative and
deaerational of installation, and also
auxiliaries.
Thus, the offered circuit provides the
closed contour: a boiler-cooler
–
the power unit – a boiler-cooler.
At effective
converter
gas in
ОCG
without reburning the power unit
develops uses of physical heat of fallow
and a condensate for power and
technological consumers, and also for
own needs of shop.
USE OF CHEMICAL ENERGY DEPARTING
CONVERTER GASES
Chemical energy of departing gases is
rational for using for restoration
pellets. On figure 5.1 the basic circuit
of use
converter
gas is submitted as a reducer. At the
expense of underpressure created by a
supercharger
converter
gas is selected from flue
ОCG
at temperature 950 - 1050˚С
and through bypass
газоход
goes to the regenerative device; then
passes through a layer
железорудных окатышей,
heats up them up to 750 – 850˚С
and restores up to a degree of
metallization of 95 %. The fulfilled gas
with temperature 550 – 650˚С
and the maintenance CO about 35 % acts
in the gas purification placed in bypass
flue
behind the regenerative device, in
spray catcher, and then a supercharger
moves on a candle. The rest CO, formed
at restoration
oxides
iron up to iron metal, reburning on a
candle.
From the regenerative device the raw
material is unloaded periodically during
a purge of the converter or during the
interblowing-off period in intermediate
coated the capacity located before
batcher. Before next fusible the portion
hot metallized pellets is loaded into
the converter.
Use
converter
gas for restoration of iron from
iron-ore
pellets, passing domain process, gives
economy of scarce and expensive
reducers. In comparison with use of a
breakage application metallized pellets
provides purer iron and simplifies
transportation and loading of materials
the converter. However, additional
capital expenses are necessary for this
purpose in shop which volume defines a
level of economic efficiency of system.
The important problem is heating and
refinement
converter
breakage from nonferrous metals
polluting it. The significant amount of
the physical and chemical heat contained
in
converter
gases, allows solving this problem at
the expense of heat departing
converter
gases and by that sharply to lower power
consumption
converter
steel.
SYSTEMS OF GAS
PURIFICATIONS
In systems of gas purification
industrial check was passed with the
following devices: scrubbers, turbulent
scrubbers (big, small, etc.), named also
pipes
Venturi;
dry electrostatic filters, wet
electrostatic filters, foamy filters,
cyclones-spray separators and dry,
hydromechanical filters, fabric (hose)
filters.
From the listed devices the basic are
turbulent scrubbers (pipes
Venturi),
electrostatic filters, fabric filters.
Scrubbers, foamy filters and cyclones
apply, as a rule, in a combination with
pipes
Venturi
and electrofilters.
The temperature of gases after a cooler,
i.e. before system of clearing, is
defining by its type. Therefore, at
metal scrubbers the temperature of gases
can reach 400°С.
If a scrubber with fire-resistant liner,
the temperature can be much higher.
Turbulent
scrubbers, executed from carbonaceous
steel, reliably work at temperature of
acting gas 350 - 400°С.
Dry electrostatic filters work well at
constant temperature of acting gases
(approximately 140 – 160°С)
and humidity of gas about 70
g/m³.
Therefore, as a rule, in front of dry
electrofilters establish the stabilizer
in which in a stream of gases water
automatically injects or it is blown
fallow for maintenance of the required
temperature and humidity. The
maintenance of combustible components in
the gases acting in electrofilters
should be much less than the bottom
limit of ignition of a corresponding
component. Therefore, electrostatic
filters cannot work in system of tap of
gases without reburning.
At use fabric (hose)
filters show even more rigid
requirements to temperature of entering
gases, she should be within the limits
of 100 – 110°С
and do not exceed 150°С.
At higher temperatures durability of a
filtering fabric sharply reduced. In
case of application of wet systems
cleanings gases do not show such
requirements to fluctuations of
temperature of entering gases and
maintenances in them CO.
The system of cleaning of gases
predetermines to a certain extent
circuit exhaust of a path. The ways of
tap and cooling in turn influence
considerably system and dimensions
gas purification. Therefore, for
concrete objects of the circuit of
cooling and system of cleaning it is
necessary to choose after the careful
analysis.
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