CA1149618A - Process for the manufacture of desulfurizing agents for crude iron or steel melts - Google Patents
Process for the manufacture of desulfurizing agents for crude iron or steel meltsInfo
- Publication number
- CA1149618A CA1149618A CA000368479A CA368479A CA1149618A CA 1149618 A CA1149618 A CA 1149618A CA 000368479 A CA000368479 A CA 000368479A CA 368479 A CA368479 A CA 368479A CA 1149618 A CA1149618 A CA 1149618A
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- CA
- Canada
- Prior art keywords
- mixture
- cao
- weight
- calcium oxide
- particles
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
Abstract
PROCESS FOR THE MANUFACTURE OF DESULFURIZING AGENTS
FOR CRUDE IRON OR STEEL MELTS
ABSTRACT OF THE DISCLOSURE:
The present invention relates to a process for the manufacture of desulfurizing agents containing 1 - 6 %
by weight of chemically bonded water, based on calcium oxide-containing calcium carbide, for crude iron and steel melts. To this end, a molten mixture of calcium carbide and calcium oxide with a CaO content of 20 to 80 % by weight is produced, which is allowed to solidify into a block. Next, the block which still has an average temperature of more than 400° C, is rough-crushed to particles with a size of less than 150 mm and calcium oxide is added to the comminuted mixture, which still has a temperature of at least 400° C, in accordance with the CaO content desired in the end product. The mixture is finally ground in the presence of air or nitrogen with a moisture content of from 5 to 20 g/m3 (at 1.013 bar and 273.15 K) at temperatures below 100° C to particles with a size of less than 10 mm.
FOR CRUDE IRON OR STEEL MELTS
ABSTRACT OF THE DISCLOSURE:
The present invention relates to a process for the manufacture of desulfurizing agents containing 1 - 6 %
by weight of chemically bonded water, based on calcium oxide-containing calcium carbide, for crude iron and steel melts. To this end, a molten mixture of calcium carbide and calcium oxide with a CaO content of 20 to 80 % by weight is produced, which is allowed to solidify into a block. Next, the block which still has an average temperature of more than 400° C, is rough-crushed to particles with a size of less than 150 mm and calcium oxide is added to the comminuted mixture, which still has a temperature of at least 400° C, in accordance with the CaO content desired in the end product. The mixture is finally ground in the presence of air or nitrogen with a moisture content of from 5 to 20 g/m3 (at 1.013 bar and 273.15 K) at temperatures below 100° C to particles with a size of less than 10 mm.
Description
~96~8 The present invention relates to a process for the manufacture of desulfurizing agents containing 1 - 6 %
by weight of chemically bonded water, based on calcium oxide-containing calcium carbide, for crude iron and steel melts.
The desulfurization of crude iron and steel melts by means of calcium carbide (referred to hereinafter as carbide) containing calcium oxide (briefly referred to hereinafter as lime) is generally known (DE-PS 1 160 457, DE-PS 20 37 758).
Heretofore, it has been customary to prepare these desulfurizing agents by processes, wherein the required amount of finely divided lime was introduced into molten carbide in order to produce a homogeneous mixture in the melt, which was then allowed to cool and was comminuted.
Preferably, the finely divided lime was introduced into the stream of carbide tapped of~ from the furnace.
Although the amount of lime that can be introduced into the carbide melt is limited and there are risks associated with working with liquid carbide, it has long been hel~
in the art that this method could not be avoided since it was thoughtthat only a mixture of CaC2 and CaO pro-duced in the melt was ideally suited for desulfurizationof metal melts.
Desulfurizing agents based on calcium carbide that contain substances which split off water at the temperature '~
of the metal melt have already been described in DE-AS
22 52 795. These agents, which are mixtures of customary commercial carbide with, for example, Ca(OH)2 as the substance that splits off water, have the disadvantage that they are mixtures produced by mechanical mixing processes in which carbide particles exist separately from the Ca(OH)2 particles, so that the use of theæ products leads to higher consumption, irregular and vigorous gas reactions and a large variation as regards the desulfuriz-ing efficiency, rendering difficult any controlled use ofthese agents.
The present invention now unexpectedly provides a process for making a highly effective desulfurizing agent for crude iron and steel melts which process permits the disadvantages of prior art methods to be avoided and which comprises: thermally producing from lime and coke a molten starting mi2ture of carbide and calcium oxide with a CaO
content varying within the range 20 to 80 %; allowing the mixture to cool and solidify into a block; rough-crushing the solidified block while it still has anaverage temperature of more than 400 C, preferably of between 400 C and the solidification temperature of the melt, to particles with a size of less than 150 mm and calciu~ oxide; and admixing the comminuted mixture, which still has a temperature of at least 400 C, with a quantity of calcium oxide, necessary to establish in the mixture a total content of CaO corresponding to the CaO
content desired in the end product. Preferably, calcium ~961~3 oxide is added in a quantity necessary to establish in the mixture a total content of CaO of more than 45 O~G
up to 90 % by weight. Next, the mixture is gro~nd with intensive mixing and in the presence of air or nitrogen having a moisture content of 5 to 20 g/m3 (at 1.013 bar and 273.15 K) at temperatures below 100 C, preferably at 10 - 50 C, to particles with a size of less than 10 mm, preferably of less than 100 /um.
A preferred feature of the present process provides for the molten starting mixture of calcium carbide and calcium oxide to contain 20 to 45 % by weight of CaO, the mixture having been obtained ~rom lime and coke in known manner by thermal treatment. It is also possible, however, initially to produce a molten starting mixture of calcium carbide and calcium oxide with a CaO content of more than 45 % up to 80 % by weight, by introducing finely divided calcium oxide into an existing calcium carbide melt containing up to 45 % by weight of CaO
until establishment of a maximum CaO content of up to 80 % by weight, then allowing the whole to solidify into a block, and rough-crushing the latter at temperatures of above 400 C.
The present process permits inhibiting mixing the lime with a carbide melt and the di~ficulties associated therewith.
In addition to this, the present process has, inter alia, the following beneficial effects: It is not necessary for the composition of the burden to be set in each particular case ~or producing the carbide melt, nor is it necessary 6~
for the lime to be first ground to a certain particle size. Use can rather be made of a carbide block with a CaC2 : CaO weight ratio which may vary within wide limits, In other words, the carbide block may contain CaC2 and CaO in practically any ratio, and the lime can even be used in the form of coarse particles with a size within the range 8 to 60 mm, for example.
A further beneficial effect of the agent produced in accordance with this invention resides in the fact that on the surface each individual particle of Ca(OH)2 lies close to CaC2, with the result that the desulfurizing reaction is started very early and regularly. As a re-sult of this, smaller amounts of desulfurizing agents are required to be used for producing comparable de-sulfurization results, which incidentally are controllable.
The following Examples illustrate the invention:
The starting material was a melt as customarily usedfor the manufacture of commercial carbide, the melt con-taining 80 % by weight of CaC2 and 20 % by weight of CaO.A carbide block of corresponding composition was produced in known manner in a crucible by allowing this melt to cool.
After the block had cooled to an average temperature of approximately 600 C, it was rough-crushed to particles with a size of less than 150 mm and the carbide, still with a temperature of 500 C, was covered with a layer of sufficient lime with a particle size of 8 to 60 mm ~96~8 that the resulting mixture had a total CaO content of 50 ~ by weight.
Next, the mixture was ground in a rotary mill, while 1500 m3/h of air with a moisture content of 10 g/m3 (at 15 C) was passed therethrough. The throughput was 50Q kg/h at 50 C, and the mixture was ground to particles with a size of up to 100 /um.
1500 kg of this product was used for customary desul-furization of 300 000 kg of a crude iron melt th~ contained 0.03 % by weight of sulfur. The iron so treated contained 0.005 % by weight.
Calcium carbide was thermally produced in known manner from lime and coke, the lime/coke mi,~ture in the total burden being set at a weight ratio of approximately 110 : 40, corresponding to a carbide with a CaO content of approximately 45 % by weight.
CaO of a particle size of 3 - 8 mm was metered into the carbide tapped off, the CaO being used in a quantity necessary to establish an average content of approximately 80 % by wei~ht of CaO in the discharge crucible (approxi-mately 1.2 - 1.3 t of CaO per metric ton material tapped off).
After cooling the crucible to an average temperature of no less than 600 C, which was the case after 4 hours, the block was rough-crushed to particles with a size of less than 150 mm and a layer of sufficient lime of ~ 61 8 particles with a size of 8 to 60 mm was added to the hot mixture that the average CaO content was 90 % by weight. Next, the mixture was ground in a rotary mill, while 1500 m3/h of air with a moisture content of 10 g/m3 (at 15 C) w~s passed therethrough. The through-put was 500 kg/h at 50 C and the material was ground to particles with a size of less than 100 /um.
The mixture permitted the same desulfurization results to be produced, based on the calcium carbide content, as described in Example 1.
by weight of chemically bonded water, based on calcium oxide-containing calcium carbide, for crude iron and steel melts.
The desulfurization of crude iron and steel melts by means of calcium carbide (referred to hereinafter as carbide) containing calcium oxide (briefly referred to hereinafter as lime) is generally known (DE-PS 1 160 457, DE-PS 20 37 758).
Heretofore, it has been customary to prepare these desulfurizing agents by processes, wherein the required amount of finely divided lime was introduced into molten carbide in order to produce a homogeneous mixture in the melt, which was then allowed to cool and was comminuted.
Preferably, the finely divided lime was introduced into the stream of carbide tapped of~ from the furnace.
Although the amount of lime that can be introduced into the carbide melt is limited and there are risks associated with working with liquid carbide, it has long been hel~
in the art that this method could not be avoided since it was thoughtthat only a mixture of CaC2 and CaO pro-duced in the melt was ideally suited for desulfurizationof metal melts.
Desulfurizing agents based on calcium carbide that contain substances which split off water at the temperature '~
of the metal melt have already been described in DE-AS
22 52 795. These agents, which are mixtures of customary commercial carbide with, for example, Ca(OH)2 as the substance that splits off water, have the disadvantage that they are mixtures produced by mechanical mixing processes in which carbide particles exist separately from the Ca(OH)2 particles, so that the use of theæ products leads to higher consumption, irregular and vigorous gas reactions and a large variation as regards the desulfuriz-ing efficiency, rendering difficult any controlled use ofthese agents.
The present invention now unexpectedly provides a process for making a highly effective desulfurizing agent for crude iron and steel melts which process permits the disadvantages of prior art methods to be avoided and which comprises: thermally producing from lime and coke a molten starting mi2ture of carbide and calcium oxide with a CaO
content varying within the range 20 to 80 %; allowing the mixture to cool and solidify into a block; rough-crushing the solidified block while it still has anaverage temperature of more than 400 C, preferably of between 400 C and the solidification temperature of the melt, to particles with a size of less than 150 mm and calciu~ oxide; and admixing the comminuted mixture, which still has a temperature of at least 400 C, with a quantity of calcium oxide, necessary to establish in the mixture a total content of CaO corresponding to the CaO
content desired in the end product. Preferably, calcium ~961~3 oxide is added in a quantity necessary to establish in the mixture a total content of CaO of more than 45 O~G
up to 90 % by weight. Next, the mixture is gro~nd with intensive mixing and in the presence of air or nitrogen having a moisture content of 5 to 20 g/m3 (at 1.013 bar and 273.15 K) at temperatures below 100 C, preferably at 10 - 50 C, to particles with a size of less than 10 mm, preferably of less than 100 /um.
A preferred feature of the present process provides for the molten starting mixture of calcium carbide and calcium oxide to contain 20 to 45 % by weight of CaO, the mixture having been obtained ~rom lime and coke in known manner by thermal treatment. It is also possible, however, initially to produce a molten starting mixture of calcium carbide and calcium oxide with a CaO content of more than 45 % up to 80 % by weight, by introducing finely divided calcium oxide into an existing calcium carbide melt containing up to 45 % by weight of CaO
until establishment of a maximum CaO content of up to 80 % by weight, then allowing the whole to solidify into a block, and rough-crushing the latter at temperatures of above 400 C.
The present process permits inhibiting mixing the lime with a carbide melt and the di~ficulties associated therewith.
In addition to this, the present process has, inter alia, the following beneficial effects: It is not necessary for the composition of the burden to be set in each particular case ~or producing the carbide melt, nor is it necessary 6~
for the lime to be first ground to a certain particle size. Use can rather be made of a carbide block with a CaC2 : CaO weight ratio which may vary within wide limits, In other words, the carbide block may contain CaC2 and CaO in practically any ratio, and the lime can even be used in the form of coarse particles with a size within the range 8 to 60 mm, for example.
A further beneficial effect of the agent produced in accordance with this invention resides in the fact that on the surface each individual particle of Ca(OH)2 lies close to CaC2, with the result that the desulfurizing reaction is started very early and regularly. As a re-sult of this, smaller amounts of desulfurizing agents are required to be used for producing comparable de-sulfurization results, which incidentally are controllable.
The following Examples illustrate the invention:
The starting material was a melt as customarily usedfor the manufacture of commercial carbide, the melt con-taining 80 % by weight of CaC2 and 20 % by weight of CaO.A carbide block of corresponding composition was produced in known manner in a crucible by allowing this melt to cool.
After the block had cooled to an average temperature of approximately 600 C, it was rough-crushed to particles with a size of less than 150 mm and the carbide, still with a temperature of 500 C, was covered with a layer of sufficient lime with a particle size of 8 to 60 mm ~96~8 that the resulting mixture had a total CaO content of 50 ~ by weight.
Next, the mixture was ground in a rotary mill, while 1500 m3/h of air with a moisture content of 10 g/m3 (at 15 C) was passed therethrough. The throughput was 50Q kg/h at 50 C, and the mixture was ground to particles with a size of up to 100 /um.
1500 kg of this product was used for customary desul-furization of 300 000 kg of a crude iron melt th~ contained 0.03 % by weight of sulfur. The iron so treated contained 0.005 % by weight.
Calcium carbide was thermally produced in known manner from lime and coke, the lime/coke mi,~ture in the total burden being set at a weight ratio of approximately 110 : 40, corresponding to a carbide with a CaO content of approximately 45 % by weight.
CaO of a particle size of 3 - 8 mm was metered into the carbide tapped off, the CaO being used in a quantity necessary to establish an average content of approximately 80 % by wei~ht of CaO in the discharge crucible (approxi-mately 1.2 - 1.3 t of CaO per metric ton material tapped off).
After cooling the crucible to an average temperature of no less than 600 C, which was the case after 4 hours, the block was rough-crushed to particles with a size of less than 150 mm and a layer of sufficient lime of ~ 61 8 particles with a size of 8 to 60 mm was added to the hot mixture that the average CaO content was 90 % by weight. Next, the mixture was ground in a rotary mill, while 1500 m3/h of air with a moisture content of 10 g/m3 (at 15 C) w~s passed therethrough. The through-put was 500 kg/h at 50 C and the material was ground to particles with a size of less than 100 /um.
The mixture permitted the same desulfurization results to be produced, based on the calcium carbide content, as described in Example 1.
Claims (8)
THE CLAIMS:
1) A process for the manufacture of desulfurizing agents containing 1 - 6 % by weight of chemically bonded water, based on calcium oxide-containing calcium carbide, for crude iron and steel melts, which com-prises: producing from lime and coke a molten mixture of calcium carbide and calcium oxide having a CaO
content varying within the range 20 to 80 % by weight;
allowing the mixture to cool and solidify into a block; rough-crushing the solidified block while it still has an average temperature of more than 400° C
to particles with a size of less than 150 mm, admixing the comminuted mixture, which still has a temperature of at least 400 ° C, with a quantity of calcium oxide necessary to establish in the resulting mixture a total content of CaO corresponding to the CaO content desired in the end product, and then grinding the mixture with thorough agitation and in the presence of air or nitrogen with a moisture content of 5 to 20 g/m3 (at 1.013 bar and 273.15 K) at temperatures below 100° C to particles with a size of less than 10 mm.
content varying within the range 20 to 80 % by weight;
allowing the mixture to cool and solidify into a block; rough-crushing the solidified block while it still has an average temperature of more than 400° C
to particles with a size of less than 150 mm, admixing the comminuted mixture, which still has a temperature of at least 400 ° C, with a quantity of calcium oxide necessary to establish in the resulting mixture a total content of CaO corresponding to the CaO content desired in the end product, and then grinding the mixture with thorough agitation and in the presence of air or nitrogen with a moisture content of 5 to 20 g/m3 (at 1.013 bar and 273.15 K) at temperatures below 100° C to particles with a size of less than 10 mm.
2) The process as claimed in claim 1, wherein coarse particles of CaO with a size of 8 to 60 mm are added to the rough-crushed mixture.
3) The process as claimed in claim 1, wherein a quantity of CaO sufficient to produce a mixture containing more than 45 % up to 90 % by weight of CaO, is added to the rough-crushed mixture.
4) The process as claimed in claim 1, wherein the mixture is crushed at temperatures of between 400° C and the solidification temperature.
5) The process as claimed in claim 1, wherein the molten starting mixture of calcium carbide and calcium oxide with a CaO content of 20 to 45 % by weight is produced from lime and coke in customary manner by thermal treat-ment.
6) The process as claimed in claim 1, wherein the molten starting mixture of calcium carbide and calcium oxide with a CaO content of more than 45% up to 80 % by weight is produced by introducing finely divided calcium oxide into an existing calcium carbide melt containing up to 45 % by weight of CaO until establish-ment therein of a maximum CaO content of up to 80 %
by weight and then allowing the whole to solidify into a block.
by weight and then allowing the whole to solidify into a block.
7) The process as claimed in claim 1, wherein the mixture is ground at 10 - 50° C to particles with a size of less than 10 mm.
8) The process as claimed in claim 1, wherein the mixture is ground to particles with a size of less than 100 /µm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000368479A CA1149618A (en) | 1981-01-14 | 1981-01-14 | Process for the manufacture of desulfurizing agents for crude iron or steel melts |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000368479A CA1149618A (en) | 1981-01-14 | 1981-01-14 | Process for the manufacture of desulfurizing agents for crude iron or steel melts |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1149618A true CA1149618A (en) | 1983-07-12 |
Family
ID=4118914
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000368479A Expired CA1149618A (en) | 1981-01-14 | 1981-01-14 | Process for the manufacture of desulfurizing agents for crude iron or steel melts |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1149618A (en) |
-
1981
- 1981-01-14 CA CA000368479A patent/CA1149618A/en not_active Expired
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| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |