Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
1, Field of the Invention
This invention relates to a powdery desulfurizing
agent comprising quicklime, diamide lime and calcium carbide
as main ingredients. More specifically t the invention
pertains to a powdery desulfurizer composition comprising
quicklime, diamide lime and calcium carbide as main in-
gredients, which is e~pecially effective in injection
desulfurization of molten iron.
The diamide lime is a mixture consisting essential-
ly of calcium carbonate and carbon.
The term "molten iron" as used herein, denotes
a molten mass of pig iron, cast iron, steel, etc.
2. Description of the Prior Art.
As is well known, desulfurization of molten iron
is an important trea~ment for obtaining iron and steel
products having excellent properties, and numerous
desulfurizing agents and desulfurizing methods have been
proposed heretogore.
Calcium carbide has by far the best desulfuriz-
ing ability, and desulfurizers comprising calcium carbide
as a main ingredient have gained widespread acceptance.
Production of calcium carbide, however, entails high
electric power consumption, and it has become necessary
to re-assess calcium carbide as a desulfurizer from an
economical viewpoint in order to cope with the recent
rise in energy cost. On the other hand, quicklime is known
as one of cheaper desulfurizers. Although the iron and
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steel industry desires commercial utilization of quicklime,
its very low desulfuriæing performance has made it difficult
to meet various high-level requirements ~n the present-day
de~ulfurization of molten iron.
A method which comprises adding a certain powdery
desulfurizing agent to molten iron and mechanically ~tirr~
ing the mixture and a method which comprises injecting a
certain powdery desulfurizing agent into molten iron u~in~
a carrier gas are well known for desulfurization of molten
iron. The injection de~ulfurizing method has gained
widespread acceptance because of its excellent operat,ional
ease and desulfurizing efficiency. Specifically, the
injection de~ulfurizing method comprises carrying a powdery
desulfurizing agent on a stream of a carrier gas such a
dry nitrogen, and injecting it into molten iron through
a lance submerged in molten iron. According to a widely
accepted practice of injection desulfuriæation, a torpedo
car which has received molten pig iron from a bla~ ~urnace,
for example, is stopped for a while at a desulfurizing
station on its way to a steel-makin~ factory, and a powdery
desulfurizing agent is injected into molten iron in the
torpedo car during this stop. Furthermore1 injection
desulfurization in an open ladle has been put into opera-
tion in recent years in place of the mechnically ~tirrin~
desulfurizing met~od (e.g., the so-called KR ~ethod in an
open ladle) because of its excellent operational ease and
de~ulfurizing efficiency.
The term "injection desulfurization", as used
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in the present application, is a term contrastive with
"desulfurization methods which involve preaddition of
desulfurizers or mechanical stirring desulfurization",
etc., and specifically denotes a method of desulfurization
which comprises injecting a powdery desulfurizing agent
together with a carrier gas into molten iron beneath its
surface.
The injected desulfurizing agent escapes from
the carrier gas in molten iron and makes contact with the
molten iron, whereupon it reacts with sulfur in the molten
iron. Then, the desulfurizing agent and/or its reaction
product with sulfur rise through the molten iron and
finally float as desulfurization slag on the surface of
the molten iron. The molten iron is sufficiently moved
and stirred by the carrier gas and/or gases which may be
evolved from gas~enerating substances in the powdery
desulfurizing agent, and as a result, the chances of the
desulfurizer to encounter sulfur in molten iron are enhanc-
ed, and the residual sulfur content in the molten iron
is geometrically uniformed.
Methods for improving the desulfurizing ability
of quicklime have been proposed, for example, in Japanese
Laid-Open Patent Publications Nos. 38209/1979, 50414/1979,
86416/1979, and 86417/1979 which are directed mainly to
size reduction of CaO crystals constituting quicklime so
as to increase its contact area and thereby improve its
reactivity. It has been found, however, that when quiok-
lime treated by the methods disclosed in these prior patent
documents is used in injection desulfurization of molten
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iron, its transportability on a stream of a carrier gas
is very poor, a large amount of the carrier gas is requir-
ed, and therefore injection of the qui.cklime in high con-
centrations and flne dispersion in the carrier gas is
difficult, and consequently that the advantage of the
finely divided CaO crystals cannot be utilized and the
expected desulfurizing effect cannot be obtained. It is
thus seen that although the reduction o~ the particle size
of a desulfurizing agent has greatly to do with an increase
in desulfurizing ability, its desulfurizing performance
is not directly eoYerned by its particle size, but also
it is greatly affected by the transportability of the
desulfurizing agent on a carrier gas.
In the injection desulfurizing method, the powdery
desulfurizing agent is injected into molter. iron in a form
suspended in carrier gas. That part of the powdery de-
sulfurizing agent which has escaped out of the gas bubbles
of the gas stream makes direct contact with the molten
iron and reacts with sulfur in the molten iron, but that
portion of the desulfurizing agent which remains enclosed
within the gas bubbles rises as such and floats on the
surface of the molten iron without contributing to the
desulfurization reaction or spurts out of the molten iron
together with the gas.
In order to increase the proportion of the
desulfurizer powder which participates in the desulfuriza
tion reaction and to increase its reactivity, it is
desirable to minimize the amount of the carrier gas,
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thereby preventing the desulfurizing agent from being
enclosed within the gas bubbles. The amount of the
carrier gas required for injection, however, depends upon
the gas transportability of the powdery desulfurixin~ agent,
and a desulfurizing agent which has poor gas transport-
ability requires a large amount of a carrier gas for
injection. Accordingly, even a desul~urizing agent having
high reactivity cannot give the desired desulfurizing
effect in injection desulfurization if its transportability
on a carrier gas i3 poor.
Furthermore, when the desulfurizing agent has
poor ga~ tranqportability, great fluctua~ion occurs in
the concentration of the desulfuriæing agent in the carrier
gas in injection desulfurization to cause a pulsating
movement of the desulfurizer carrier gas stream which
frequently becomes an operational trouble. For example,
injection of an excess.ively larg0 amount of the powdery
desulfurizing agent into molten iron ak a time, results
in an excessively large amount of gas evolution at a time
in the molten iron and thus increases vibration o~ a
torppedo car, an open ladble, etc. The fluctuations in
the concentration of the desulf'urizing agent also can
result in the desulfurizing agent blocking up the lance
pipes, or the molten iron splashing vigorously out of the
torppedo car, etc, and thus causing undesirable phenomena
such as the pollution of the working environment, exposure
to danger, and economical loss.
The present inventors made various investi.ga-
tions in order to improve the performance of quicklime in
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injec-tion desulEuriza-tion with special attention to the poor gas transportability
of various quicklime desulEurizers so far proposed, and unexpectedly found tha-t
a powdery desulfurizing composition comprising a specified amoun-t of powdery
quicklime and a specified amount of powdery diamide lime gives ~ complete solu-
-tion to the aforesaid various problems associated with quicklime.
It has recently been found however that the desulfurizing ability of
-the said desulfurizer composi-tion is not enough in the production of ultralow
sulfur iron having a sulfur content of 0.010% or less which is especially
required in steel making, and a further improvement is desired.
SUMMARY OF THE IN~ENTION
The present inventors furthered their investigations in order -to
improve the desulfurizing ability of the powdery desulfurizer composition of
the above patent application for production of ultralow sulfur iron by injection
desulfurizing method, and unexpectedly found that a powdery desulfurizer compo-
sition comprising quicklime, diamide lime and calcium carbide permits a marked
increase in the xatio of calcium carbide utilized by -the incorporation of quick-
lime and diamide lime, exhibits an equivalen-t desulfurizing abili-ty to conven-
tional powdery desulfurizer compositions consisting mainly of calcium
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carbide in amounts equal to, or less than, the amounts of
the conventional calcium carbide desulfurizer compositions,
and can give ultralow sulfur within short desulfurizing
treatment times, and also it can be provided at low cost.
According to this invention there is provided
a powdery desulfurizer composition for use in in~ection
desulfrization of molten iron, said composition comprising
quicklime, diamide lime and calcium carbide.
In a preferred embodiment, the composition of
this invention further comprises not more than 10 parts
by weight of a carbonaceous material and~or 2 to 8 parts
by weight of one or more desulfuriæation aids 7 particular~
ly fluorspar, per 100 parts by weight of the quicklime,
diamide lime and calcium carbide combined.
DETAILED DESCRIPTION OF THE INVEN~ION
The "quicklime", as used in the pre~ent appli-
cation, denotes lime containing calcium oxide in an
amount of at least 60% by weight, preferably at least
70% by weight, more preferably at least 80% by weight ?
most preferably at least 90% by weight.
Quicklime is generally obtained by çalcining
lime materials containing calcium carbonate as a main
component, such as limestone, calcite, marble and shells
of shellfish in such a thermal decomposition device as a
vertical kiln fired by heavy oil, gases or their mixtures,
or a rotary kiln, and is supplied in suitable degrees ~f
purity and suitable extents o~ calcining depending upon
the end uses. For industrial use, there are, for example,
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quicklime for steel-making, quicklime for chemical industry
(production of calcium carbide, bleaching agents and paper
pulp), quicklime for agriculture, and quicklime for
construction work. Usually, quicklime is marketed as
special grade (CaO content 90% by weight or more), first
grade (CaO content 80% or more), second grade (CaO content
70% by weight or more), and third grade (CaO content 60%
by weight or more). Quicklime o~ any of the~e grades
can be used in the desulfurizer composition of this in-
vention. However, quicklime containing calcium oxide inan amount of at least 60% by weight, preferably at least
70% by weight, more preferably at least 80% by weight,
most preferably at least 90% by weight can be used with
good results in injection desulfurization of molten iron.
The term "diamide lime", as used in this inven~
tion, denotes a mixture of fine calcium carbonate and
carbon precipitated from an aqueous solution or aqueous
suspension by a chemical reaction. A typical example of
the '1diamide lime" is a by-product filtration residue in
the production of dicyanidamide. In this process ? an
aqueous suspension of calcium cyanamide is reacted with
carbon dioxide gas and cyanamide is extracted. The filtra_
tion residue obtained generally contains 70 to 90% by
weight of calcium carbonate, 5 to 15% by weight of carbon
and impurities such as iron oxide, aluminum oxide, silicon
oxide and magnesium oxide. In the production of thiourea
from calcium cyanamide, a similar by-product is obtained.
Thus, genera].ly, filtration residues obtained in the
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extraction of cyanamide from calcium cyanamide have much
the same composition.
The term "calcium carbide", as used herein gen-
erally denotes indus~rial carbide. Usually, it is market~
ed in grades capable of generating about 275 to about
300 literstkg of acetylene and having a CaC2 content
of about 75 to about 82%. These industrial grades of
carbide can ~e used without any restriction. In addlt:ion
to CaC2, the industrial carbide contain free carbon,
silica SiO2, iron oxide~ quicklime 7 magnesium oxide,
aluminum oxide, calcium carbonate, calcium fluoride,
calcium phosphide, etc.
The weight proportions of the quicklime, diamide
lime and calcium carbide constituting the desulfurizer
composition of this invention are not particularly restrict-
ed. Advantageously, the composition consisting of 90 to
60% by weight of quicklime and diamide lime combined and
10 to 40% by weight of calcium carbide with the amount of
quicklime being 30 to 80 parts by wei~ht and the amount
of the diamide being 70 to 20 parts by weight provided
that the total amount of the quicklime and diamide lime is
100 parts by weight. Especially preferably, the compos~-
tion of this invention comprises 85 to 65% by weight of
quicklime and diamide lime combined and 15 to 35% by
weight of calcium carbide with the amount of quicklime
being 40 to 60 parts by weight and the amount of the
diamide lime being 60 to 40 parts by weight provided that
total amount of the quicklime and diamide lime is 100 parts
by weight.
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If the amount of quicklime and diamide lime in
the powdery desulfurizer composition exceeds 90% by
weight, the amount of calcium carbide decreases and the
desulfurizing ability of the composition tends to decrease.
Accordingly, to obtain ultralow sulfur iron, a large
amount of the desulfurizer composition must be injected
into molten iron, and the desulfurizing treatment is
tlme-consumin~. As a result, this affects the time
schedule of a continuous casting process, etc. If the
total amount of quicklime and diamide lime is less than
60% by weight, the amount of the calcium carbide increases
and accordin~ly, the amount of that portion of the calcium
carbide which does not contribute to the desulfurizing
action of the composition increases. Thus, the decrease
of the unit consumption and the shortening of the
desulfurizing time are achieved to a lesser extent than
the desulfurizer composition of this invention containing
10 to 40% by wei~ht of calcium carbide, and such a com-
position is economically disadvantageous. In order to
obtain a powdery desulfurizer composition of the invention
which fully exhibits the desulfurizing ability of calcium
carbid0, permits decreasing of the unit consumption and
the shortenin~ of the desulfurizing time and which is
economically advantageous, the total amount of quicklime
and diamide lime is especially preferably 85 to 65% by
weight.
Wh~n the total amount of quicklime and diamide
lime i~ taken as 100 parts by weight, it is preferred
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that the amount of quicklime is 30 to 80 parts by weight,
and the amount of the diamide lime is 70 to 20 parts by
weight. If the proportion of the diamide lime exceeds
70 parts by weight, the amount of gases generated from
the desulfurizer composition in molten iron increases and
the molten iron tends to splash. Also, the consequently
decrease of quicklime tends to decrease the desul~urizing
ability of the composition. If the proportion of diamide
lime is less than 20 parts by weight, the gas transport-
ability of the resulting composition is reduced, andinjection of the desulfurizer composition, which exhibits
the inherent excellent desulfurizing ability of quicklime,
in high concentrations is difficult. In order to have
the inherent excellent desulfurizing ability of quicklime
exhibited fully without the problems of splashing and
gas transportability, it is preferred that the amount of
quicklime is 40 to 60 parts by weight and the amount of
the diamide lime is 60 to ~0 parts by weight with the
total amount of these being 100 parts by weight.
The quicklime, diamide lime and calcium carbide
and a carbonaceous material to be described hereinbelow
preferably have a particle sizes of mainly not more than
60 microns. In the present application, the e~pres~ion
"mainly not more than 60 microns'7 means that the propor-
tion of particles having a particle diameter of not more
than 60 microns is at least 80% by weight, preferably at
least 90% by weight, and in particular, the proportion
of particles ha~ing particle diameters of not more than
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40 microns is at least ~0% by weight, preferably at least
90% by weight. If the particle diameter is mainly above
60 microns t the particles are too coarse to secure good
gas transportability, and thus the concentration of the
powdery desulfurizer compositioll in a carrier gas during
injection can fluctuate greatly, and the surface area of
the particles per unit weight decreases. Hence, the
desulfurizing abilities of quicklime and calcium carbide
cannot be utilized fully.
The desulfurizer composition of the invention
can be injected with a carrier gas into molten iron by
using known devices such as a device adapted to feed the
powdery desulfurizer in specified portions down from its
tank into an injection pipe line by means of a rotary
valve and transport it on the carrier gas (e.g., Japanese
~aid~Open Patent Publication No. 102515J1975), or a
device adapted to fluidize the powdery desulfurizer placed
in a pressure vessel and inject it by using the carrier
gas.
The desulfurizer composition of this invention
is suitable for use in many injection desulfurization
msthods using various devices including the aforesaid
devices. Even when a relatively large amount of the
carrier gas is used as in Japanese Patent Publications
Nos. 6454tl974 and 1967J1974 in which the proportion of
the amount of the carrier gas is about 100 Nl per
kilogram of the powdery desulfurizer composition, the
desulfurizer composition of the invention can be used by
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properly selecting the injection arJgles or lance declina-
tions, the number of injection places, the geometrical
locations of injection, etc.
The "apparatus for dispensing a flowable solid
material from a pressure vessel" disclosed in Japanese
Laid-Open Patent Publication No. 31518/1979 is one of
especially preferred injection devices which leads to full
utilization of the effect of the powdery desulfurizer
composition of this invention. This device has gained
widespread commercial acceptance because it permits in-
jection into molten iron of the powdery desulfuriæing a~ent
in high concentrations. If the amount of the carrier gas
per unit amount of the powdery desulfurizer is small, the
total amount of the carrier gas required for injecting can
be small. Accordingly, the degree of temperature lowering
of molten iron is small, and the apparatus can be small-
sized. In injection desulfurization using this type of
the device, the proportion of the carrier gas can be
suitably not more than 10 Nl, preferably 2 to 10 Nl,
for example 5 Nl, per kilogram of the powdery desulfurizer
composition. At such a low carrier gas proportion, the
gas transportability of the powdery desulfurizer composi-
tion is of utmost importance. The powdery desulfurizer
composition of this invention having excellent gas
transportability is most effective under such conditions.
Accordingly, the powdery desulfurizer com-
position of the invention is suitable for use in an
injection desulfurizing method particularly the one which
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comprises fluidiæing the powdery desulfurizer composition
in a pressure vessel, and injecting it into molten iron
using a carrier gas ir. an amount of not more than 10 Nl
per kilogram of the desulfurizer composition.
The present inventors have also found unexpected-
ly that when fine quicklime is produced by calcining
diamide lime, and this quicklime is used in combination
with diamide lime, the resulting composition ha~ more
improved gas transportability and further improved
desulfuriæing ability.
Japanese Laid-Open Patent Publications Nos.
50414/1979 and 86417/1979 cited above disclose that by
calcining diamide lime under special conditions, quicklime
having good desulfurizabilit~ can be obtained. However,
calcining of diamide lime to obtain the aforesaid quick-
lime does not require any special calcining conditions
although no clear reason can be assigned. Quicklime
obtained by calcining diamide lime until its CaO content
reaches at least 60% by weight, preferably at least 70%
by weight, more preferably at least 80% by weight, most
preferably at least 90/~ by weight can be used with good
results in injection desulfurization of molten iron.
However, fluidized calcination under oxygen-excessive
atomosphere can be used preferably to produce the quick-
lime for this invention.
The quicklime obtained by calcining diamide limemay be mixed in any desired proportions with quicklimes
from other more conventional lime sources. But since
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the quicklime obtained by calcining of cliamide li~e
imparts better gas transportability and greater desulfuriz-
ing ability, it is preferred to use 90 to 60% by weight
of quicklime obtained by calcini.ng diamide lime and diamide
amide combined and 10 to 40% by weight of calcium carbide
with the amount of the quicklime obtained by calcining
diamide lime being 30 to 80 part;s by weight and the amount
of diamide lime being 70 to 20 parts by weight provided
that the total amount of the quicklime and diamide is lO0
parts by weight. More preferably, these components are
used in a particle diameter of mainly not more than 60
microns. It is especially preferred to use 85 to 65% by
weight of quicklime obtained by calcining diamide lime
and diamide lime combined and 15 to 35% by weight of
calcium carbide with the amount of the quicklime obtained
by calcining diamide lime being 40 to 60 parts by weight
and the amount of the diamide lime being 60 to ~O~h by
weight provided that the total amount of these components
is 100 parts by weight.
In accordance with this invention, it has also
been found that when not more than lO parts by weight,
preferabl~ 3 to lO parts by weight, of a carbonaceous
material is added to lO0 parts by weight of a powdery
desulfurizer composition composed of quicklime, diamide
lime and calcium carbide, the resulting mixture shows more
improved gas transportability and desulfurizing ability
suitable for use in desulfurization of molten iron.
Examples of the carbonaceous material are
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graphite, coal, coke, petroleum coke, and charcoal. There
is no particular restriction on its kind and properties.
It is desirable however that such a carbonaceous material
should have a low sulfur content and a low water content
so as to use it with quicklime. Coal and coke are
preferred carbonaceous materials in view of their ready
availab.ility and low cost. The carbonaceous material
desirably has a particle diameter of mainly not more than
60 microns as stated hereinabove.
If the amount of the carbonaceous material ex-
ceeds 10 parts by weight per 100 parts by weight of the
powdery desulfurizer composition composed of quicklime,
diamide lime and calcium carbide, the amount of the
carbonaceous material in exhaust gases from, for ex-
ample, an open ladle in the injection desulfurization
process increases to cause various working environmental
troubles such as higher exhaust gas temperature, flushing
danger, and/or the increase amount of carbon monoxide.
The powdery desulfurizer composition for molten
iron of this invention is inexpensive and exhibits excel-
lent desulfurizing performance in injection desulfuriza-
tion with effects comparable to conventional calcium
carbide desulfurizer compositions. Its desulfurizing
effect can be further improved by using it in combination
with various conventional desulfurizing agents and
desulfurization aids Examples of these conventional
materials include calcium cyanamide t fluor-ide compounds
such as fluorspar or cryolite; oxide, hydroxide, carbo-
nate or other compounds of sodium, magnesium or
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aluminum; calcium hydroxide, powders of synthetic resins,
and compounds capable of liberating water or hydro~en in
the desulfurization system. Fluorspar and cryolite are
preferred, and fluorspar is especially preferred. The
amount of fluorspar and the other conventional materials
mentioned above is 2 to 8 parts by weight, pre~erably 3
to 6 parts by weight, per 100 parts by weight of the
desulfurizer composition composed of quicklime, diamide
lime, and calcium carbide. In addition to increasine the
desulfurizing ability of the desulfurizer composition
further, fluorspar permits easy removal of the slag after
desulfurization. The reason for this is not entirely
clear, but it is theorized that fluorspar prevents adhesion
of calcium silicate to the surface of the lime powder,
and decreases the viscosity of the slag.
When the amount of fluorspar and the other
conventional materials exceeds 8 parts by weight, re-
fractories will be heavily damaged, and if it is less than
2 parts by weight, the degree of improvement of desulfuriz-
ing ability and slag removability is small.
Fluorspar which may be used in this inventioncontains about 80 to about 98% by weight of CaF2 and up
to about 16% by weight of SiO2, ~e203, MgO, etc.
The following Examples and Comparative Fxamples
illustrate the present invention more specifically.
Examples 1 to 22 and Comparative Examples 1 and 2
In each run, the various materials shown in
Table 1 or 2 were mixed uniformly in an inert atmosphere
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to form a powdery desulfurizer composition.
The powdery desulfurizer composition was injected
at a rate of 80 to 150 kg/min. through a lance into a tor-
pedo ladle having a capacity of 350 T filled with 300 to
330 T oP molten iron having a sulfur content of 0.035 to
0.040% by means of the injection device described in
Japanese ~aid~Open Patent Publication No. 31518/1974 using
dry nitro~en gas as a carrier gas.
The results of the desulfurization are shown in
Tables 1 and 2.
The amounts of quicklime t(quicklime)lDL,
(quicklime)2DL, or (quicklime)*l, diamide lime and calcium
carbide in Tables 1 and 2 are by weight % based on the
total amount of these three components, and the amounts of
the carbonaceous material and fluorspar are expressed by
parts by weight per 100 parts by weight of the quicklime,
diamide lime and calcium carbide combined.
The material~ used in these examples were as
follows:
1) Qulcklime
Quicklime suitable ~or calcium carbide produc-
tion 7 which has a CaO co~tent of 95%.
2) Diamide lime
Diamide lime obtained as a by-product in the
production of dicyanidamide rrom calcium cyanamide. Its
chemical composition is: CaC03 85% by weight, C 10% by
weight, SiO2 1.8% by weigllt, A1203 1.3% by weight, Fe203
0.8% by weight, MgO 0.7/0 by weight, and others 0.4% by
weight.
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3) tQuicklime)lDL
Obtained by calcining the diamide lime mentioned
in paragraph 2) above in the fluidized state at 1000C
for 30 seconds in excess air using CO gas as a fuel. Its
chemical composition is: CaO 72% by weight t CaCO3 23% by
weight, C 1.5% by weight, SiO2 1.4% by weight, A1~03 0.9%
by weight, and others 1.2% by weight.
4) (Quicklime)2DL
The diamide lime mentioned in paragraph ~) above
was calcined under the same conditions as in 3) above
except that the calcining time was changed to 45 seconds.
The chemical composition of the product was: CaO 90% by
weight, CaC03 2.1% by weight, C 0.3% by weight, SiO2 2.7%
by weight, A12O3 1.7% by weight, Fe203 1.0% by weight,
and others 2.2% by weight.
5) (Quicklime)~
The diamide lime described in Table 1, Example,
Calcination No. 4 of the specification of Japanese Laid-
Open Patent Publication Mo. 86417/1979 was calcined in a
nitrogen gas atmosphere at 950C for 60 seconds.
6) Calcium carbide
Industrial carbide having the chemical composi-
tion: CaC2 ~0% by weight, CaO 13% by weight, SiO2 2% by
weight and others 5% by weight.
7) Carbon
Obtained by pulverizing commercially available
coke. It has a carbon content of 86% by weight.
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8) Fluorspar
Obtained by pulverizing imported fluor4par in
the same way as in the preparation of the carbonaceous
substance. This fluorspar had the following chemical com-
position: CaF2 90% by weight, SiO2 8.5% by weight, Fe2O3
1.0% by weight, and MgO 0.3% by weight.
The particle size distributions (%) of the quick-
lime, diamide lime, ~quicklime)lDL, (quicklime)2DL,
calcium carbide and carbon used in these examples were as
tabulated below. The tquicklime)* contained at least 85%
by weight of particles having a size of 145 mesh or smaller.
Quick_ D1amide (quick_ (QuiCk-L Calcium
Size lime lime 1 _ 2 carbide Carbon
70 mesh and 2.0 1.0 1.5 0.5 1.0 1.0
larger sizes
70 - 145 1.0 0.5 0.5 0.5 1.0 0.
145 - 250 1.5 1.0 1.0 l.O 1.5 1.5
250 - 350 2.5 0.5 0 0.5 1.5 0.5
350 mesh 93.0 97.0 97. 97~ 95~ 96.5
and smaller
sizes
The terms used in Tables 1 and 2 have the
following meanings.
(a) Unit consumption
Weight (~g) of the powdery desulfurizer
composition injected into molten iron
Weight (T) of molten iron treated
(b) Carrier gas ratio
Flow rate (Nl/min.) of the carrier gas
desulfurizer composi~ion
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(c) Injection pressure
The pressure (kg/çm ) of the carrier gas to be
connected to the discharging exit point when the desulfu-
rizer composition is carried on the carrier gas and
lnjected into molten ircn (corresponding to a relatively
low pressure P3 connected to the discharge opening 4 in
Figure 2 of Japanese L,aid-Open Patent Publication No.
31518/1979).
(d) Desulfurizing ability
Sl ~ S2 (=QS)
Unit
consumption
Sl = sulfur content (%) of molten iron before
desulfurization
S2 - sulfur content (%) of molten iron after
desulfurization
Comparative Example 3
.
~ esulfurization was carried out under the same
conditions as in Examples 1 to 22 except that a powdery
desulfurizer composition composed of 40% by wei~ht of
(quicklime)lDL, 40% by weight of diamid lime, 20% by weight
of calcium carbide, and 15 parts by weight of carbon per
100 parts by weight of the quicklime, diamide lime, and
calcium carbide combined was used. During the injection
operation, the temperature of the exhaust gas became
exceedingly high, and the operation was too dangerous to
~5 continue. Thus, this composition cannot be used for
praçtical purposes.
~: ;
'7 ~)
- 22 -
Comparative Example 4
A powdery desulfurizer composition composed of
50% by weight of quicklime, 50% by weight of calcium
carbide was prepared and examined by fundamental injection
desulfurization test, Its gas transportability was found
to be so bad that it was quite unsuitable for injection
into molten iron.
7 ~ f)
- 23 ~
Table 1
Ex- Desulfurizer composition
ample _ _
(Ex.) Quick- (Quick- (Quick- Diamide Calcium Carbo-
or lime lime)lDL lime)* lime carbide naceous
Com~ substance
para- _ _ ~ _ _
Exive wt.% wt.% wt.% wt.% wt,% parithtby
ample - r~ - - - - -
CEx.l 60 _ _ 40 _
Ex. 155 _ _ 40 5 _
" 240 _ _ 50 10
" 320 _ _ 60 20
" 424 _ _ 56 20
" 5 _ 24 _ 56 20
" 6 _ _ ~ 56 20
i' 740 _ 40 20
" 8 _ 40 _ 40 20
" 964 _ _ 16 20
" 10 _ 64 ~ 16 20
" 1168 _ _ 12 20
" 1235 _ _ 35 30 _
" 1325 _ _ 35 40
" 1420 _ _ 30 50
CEx.2_ _ _ 10 90 _
Ex.15_ 40 40 20 5
" 1640 _ _ 40 2010
" 17 _ 40 ~ 40 20 _
(to be continued)
~7 ,~ 7
- 24 -
Table 1 (continued)
_ ~__ __~_
Ex~ Desulfur- Gas De~ulfuriæation re~ult~
ample ization transportability
(Ex.) conditions
or ~ _ _ _ _ ~
Com- S content Carrier Injectlon S content Unit De~ulfur-
para- of molten gas preC7sure of molten con- izing
tive iron be- ratio iron af- sump- ability
Ex- fore de- ter de- tion
ample sulfuriza- sulfur~
(CEx.) tion (Sl) (Sa2)ion
_ ,. _ __ ____
%Nl/kg kg/cmC % kg/T AS/kg
_ _ -- -- ____ __
CEx. 1 0.0407 3.1 0.018 5.2 0.0042
Ex. 1 0.0366 3.0 0,010 4.8 0.0054
" 2 0.0385 2.9 0.008 4.2 0.0071
" 3 0.0365 2.7 0 t 010 4.6 0.0057
" 4 0.0365 2.8 0.007 4.1 0.0071
" 5 0.0365 2.6 0.005 4.2 0.0074
" 6 0.0355 2.6 0.006 4.2 0.0071
" 7 0.0395 2.8 0.006 4.1 0.0080
" 8 0.0404 2.7 0.005 4.0 0.00~8
" 9 0.0388 3.1 0.007 4.4 0.0070
" 10 0.0375 2.7 0.006 ~.3 0.0072
" 11 0.03710 3.0 0.010 5.0 0.0054
7l 12 0'0396 3.0 0.005 4.0 0-00~5
" 13 0.0386 3.1 0.005 3.8 0.0087
" 14 0.0367 2.7 0.009 4.1 0.0066
CEx. 2 0.03812 4.2 0.011 5.1 0.0053
~x. 15 0.0374 2.6 0.003 3.7 0.0092
16 0.0384 2.7 0.004 3.8 0.0092
0 0384 2.6 0.002 3.6 0.0100
I :~ 6~76
25 -
t~ o
~ ~ ~ C~ o o o
~ . . ~ _ _ O O O O O
L ~rl ~ 3~ ~ ~) O CO ~D ~O In
.~ ~ 8 tn ~ ~ ~ r~
., ~ a) a)
3 O J~
~ ~ ~ ~ a) 3 ~^~ ~ o o Oo o o
u~ O ~ ~0 ~ ~ ~ tQ O O O O O
a tn Or~ rl _
o ~
~ ~ ,3 ~ ~D t~
~ l ~ ~ ~ ~
~ . _ _ ___ _.. I
Sc~ ~ bO
S:: '~ rl ~ LS~ ~ ~ ~ ~
~ c~ ~
H 8 ~ ~ r l ~ O ~ a~ c~ ~ t~
,-I-rl l~~ s:~ O ~r-l~rl~ ~ O O O O O
ID I SO ~ ~ O S ~ N
D a) N ~~ ~ a~ $ ~ ~ O O O O O
a ~tn o ~rl n ~,1
. D
.,1 ~ i I I u~, ~
_______ ~ ~ . ....... ___
~-~1 ~
.0 ~ O ~ ~ ~ I i Lf~
~ td ~ ~ ~ ~
.~ C.) ~ ~ ,, ~ ;3
o.~.~1 ~e o o o o o
~ g 3 N N N N
N
~~ ~l? ~ ~D O O O O
3a',l ~ _ .
~ ~ ~ ;~ o o o o
rl ~ ~ N ~ ~ 3 ;1'
, . _ _ , ,
I ~ t~ a~ o ~1
.....
` ~
. . .
,~ ' ' ' .
3 ~ ~
_ 26 -
As shown in Tables 1 and 2 7 the powdery desul~u-
rizer compositions of' the invention in Examples 1 to 22
did not cause pulsating movement at relatively low injec-
tion pressures, and exhibited excellent gas transportabi:Li-
ty with a carrier gas ratio of less than 10 Nl/kg, andfurthermore, they scarcely caused splashing of molten
iron from the torpedo ladle. Moreover since the powdery
pulverizer composition could be injected at hi~h, con-
centrations, the inherent desu:Lfurizing ability of quick-
lime was fully utilized, and the ratio o~ calcium carbideutilized increases. The desulfurizing ability reached
about 0.0055 to 0.0100, and the desulfurized molten iron
has the sulfur content of less than 0.01%.
The powdery desulfurizer composition of Example
7 is best in gas transportability and desulfurizing ability
among those obtaine~ in Examples 4, 7 and 9. The powdery
desulfurizer compositions of Examples 5, 8 and 10 prepared
by using (quicklime)lDL are better than those obtained in
Examples 4, 7 and g, and the desulfurizer composition of
Example 8 is better in desulfurizing ability than those of
Examples 5 and 10. The composition of Example 6 prepared
by using the (quicklime)~ was slightly inferior in
performance to the composition obtained in Example 5. The
powdery desulfurizing compositions obtained in Examples
15 to 17 which contain carbon exhibit especially good gas
transportability and desulfurizing ability.
The desulfurizer composition of Example 3
consisting mainly of diamide lime causes a tendency to
~' "' ' ~ ' .
.
~` , . .
- 27 -
slight increase of splashing. The composition of Example
ll consisting mainly of quicklime show.s a tendency to
reduced gas transportability and reduced stirring of molten
iron by the evolved gases. However, the desulfurizing
abilities of the compositions of Examples 3 and ll are
satisfactory. The composition of Rxample 14 consisting
mainly of calcium carbide does not show increased de-
sulfurizing ability corresponding to an increase in the
amount of calcium carbide.
The compositions of Examples 18 and 19 which
contain the (quicklime)2DL show better desulfurizattion
results than those containing (quicklime)lDL, and the
compositions of Examples 20 to 22 which further contain a
carbon and/or fluorspar show much better desulfurization
results.
Referenti_l Examples l and 2
De~ulfurization was performed by using the
same desulfurizier composition as in Example 17 under the
conditions shown in Table 3. The results are shown in
Table 3.
28
Table 3
__
_ _ _
Gas transporting Desulfur- Desulfurization results
Ex or conditions ization
e . x. conditions
_ . __ _ __
Carrier Injection S content S content Unit Desulfur
gas pressure in molten of molten con- izing
ratio iron iron sump_ ability
(Nl/kg) before de~ after de- tion (~S/kg)
sulfuriz;a- sulfuriza-
tion (%) tion (%)
. _ __
Ex 17 4 2.60.038 0.002 3.6 0.0100
REexf1 20 2.90.034 0.013 3.9 0.0054
Ex. 2 60 2.80 036 0.017 4.3 0.0044
It is seen from Table 3 that the powdery
desulfurizing composition obtained in Example 17 which is
used at a small carrier gas ratio shows the best desulfur-
izing performance. As stated hereinabove, the powdery
desulfurizing composition shows especially good
desulfurizing performance when the carrier gas ratio is
not more than 10 Nl per kg of the desulfurizer composition,
and this value is suitable for good injection desulfur-
ization.
