Title of Invention | A PROCESS OF PRODUCING IRON BEARING CHARGE MATERIAL AND HYDRAULIC BINDER FROM LIQUID BOF SLAG |
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Abstract | The invention relates to a process of producing iron bearing charge material and hydraulic binder from liquid BOF slag, comprising the steps of: -removing the liquid slag having a temperature between 1650°C to 1400°C from the steel making vessel to a slag pot; -fluidizing the slag by adding fluorspar in a range between 0 to 5 wt% in the molten slag during the removing step; -cooling the slag by rapid quenching from a temperature of 1500°C to 1250°C via one of granulation method and water spraying on the slag layer; the cooled slag being crushed to size between 1 mm to 3 mm size; -separating a metallic portion of the liquid BOF slag by passing the crushed slag via a magnetic separator, the separated metallic slag being useable as charge material in an iron/steel making process; and -crushing the left-over non-metallic portion out of said liquid BOF slag along with 5% gypsum to a size range of 3000 to 3500 blain after separating the metallic portion therefrom, the ground non-metallic slag being useable as a hydraulic binder. |
Full Text | FIELD OF INVENTION The invention relates to a process of converting a liquid BOF slag being a waste material generated during steel making, to obtain cementitious properties suitable for various construction applications. More particularly, the invention relates to a process of producing iron bearing charge material and hydraulic binder from liquid BOF slag. BACKGROUND OF THE INVENTION During the production of steel, a waste in the form of slag is generated, the tonnage of which varies with the process of steel production but is typically between 10 to 20% of the steel produced. Depending on the type of hot metal and / or steel making practice adopted, the following compounds may be present in BOF slag: CaO - 45-55%, Fe(t) - 16-20%, SiO2 - 14-16%, P205 - 2.5-3.5%, etc. Nearly 100 million tones of steel making slags are produced annually worldwide. This slag is generally put into low-end uses such as land filling, road making, ballast, etc. directly or subsequent to some treatment. Since steel slags contain significant amounts of Calcium oxides of silica and iron, such low-end applications do not do justice to its potential usage. The recycling of this slag into iron making processes is restricted because of its higher proportion of P205, which virtually reports to blast furnace hot metal. At the same time, the fact that nearly half of the slag is made up of CaO and nearly one - fifth of iron oxide(s), implies that it could be put to use more profitably than done hitherto. OBJECTS OF THE INVENTION An object of the present invention is to propose a process for producing iron bearing charge material and hydraulic binder from liquid BOF slag. Another object of the present invention is to propose a process for producing iron bearing charge material and hydraulic binder from liquid BOF slag which is suitable for use in part or complete replacement of cement. A further object of the present invention is to propose a process for producing iron bearing charge material and hydraulic binder from liquid BOP slag which is easy to perform and does not require costly machinery. SUMMARY OF THE INVENTION Accordingly, there is provided a process of producing iron bearing charge material and hydraulic binder from liquid BOF slag which comprises the steps of: treating the slag and suitably cooling the liquid slag by granulation or direct quenching by pouring it into a pool of water, thereby converting the phases and their morphology to obtain in the B.O.F slags cementitious properties nearly conforming to the hydraulic binder. The ground slag thus produced is suitable for part / complete replacement of cement depending upon the strength and application requirements. It can be used as a hydraulic binder in masonry blocks, flat sheets, tiles and as a mortar in various applications. Also as a blend in cement manufacture. EX: HOLLOW BRICK Test results (as per IS 2185) of the hollow bricks made out of the hydraulic binder using hand moulding equipment are shown below: P - Ground Slag with 5% Gypsum S - River Sand D - Chips Dust (-4.5mm) C - Chips (-6mm) DETAILED DESCRIPTION OF THE INVENTION After the steel has been tapped into the steel ladle, the slag is removed from the stee(making vessel in a slag pot. In course of removal of the slag from the vessel, the slag is fluidized by adding flour spar of sufficient quantity in the slag pot. This enables the assimilation of the unmixed lime and also to some extent carryover metal to settle at the bottom of the slag pot. The pot is transferred to a nearest quenching pit to quench the slag. Alternatively, the slag pot taken to a granulation pit, where the molten slag is granulated through a runner. Then the quenched / granulated slag is crushed to -3mm size and passed through a magnetic separator to separate the metallic fraction of the slag. The rest non - metallic slag is then crushed with or without gypsum to 3500 blain depending upon the application. The magnetically separated metallic portion is suitable for iron bearing charge material in iron and steel making processes. The ground slag is suitable for varying applications including hydraulic binder in masonry blocks, flat sheets, and tiles and as a blend in cement manufacture and as a mortar in various applications. EXPERIMENTAL WORK Pilot scale experimentation in a running plant was carried out to establish the process parameters necessary to obtain the cementecious phases by controlled cooling. Various aspects of the process that lead to instant flaking of the treated slag were identified. The range of process parameters has been listed below. The exact temperatures ranges and method of cooling are shown below: WE CLAIM: 1. A process of producing iron bearing charge material and hydraulic binder from liquid BOF slag, comprising the steps of: -removing the liquid slag having a temperature between 1650°C to 1400°C from the steel making vessel to a slag pot; -fluidizing the slag by adding fluorspar in a range between 0 to 5 wt% in the molten slag during the removing step; -cooling the slag by rapid quenching from a temperature of 1500°C to 1250°C via one of granulation method and water spraying on the slag layer; the cooled slag being crushed to size between 1 mm to 3 mm size; -separating a metallic portion of the liquid BOF slag by passing the crushed slag via a magnetic separator, the separated metallic slag being useable as charge material in an iron/steel making process; and -crushing the left-over non-metallic portion out of said liquid BOF slag along with 5% gypsum to a size range of 3000 to 3500 blain after separating the metallic portion therefrom, the ground non-metallic slag being useable as a hydraulic binder. 2. The process as claimed in claim 1, wherein the slag is dried to a minimum extent after cooling and before crushing. 3. The process as claimed in claim 1, wherein the processed slag exhibits the phases of a'-2Cao.SiO2(0-25%)/ (3-2Cao.SiO2 (20-50%), 3CaO.SiO2 (0- 15%), 2CaO.Fe203 (20-40%), and complex phases of CaO, MgO, SiO2, FeO and Al2O3 (minor). 4. A process of producing iron bearing charge material and hydraulic binder from liquid BOF slag, as substantially described herein. The invention relates to a process of producing iron bearing charge material and hydraulic binder from liquid BOF slag, comprising the steps of: -removing the liquid slag having a temperature between 1650°C to 1400°C from the steel making vessel to a slag pot; -fluidizing the slag by adding fluorspar in a range between 0 to 5 wt% in the molten slag during the removing step; -cooling the slag by rapid quenching from a temperature of 1500°C to 1250°C via one of granulation method and water spraying on the slag layer; the cooled slag being crushed to size between 1 mm to 3 mm size; -separating a metallic portion of the liquid BOF slag by passing the crushed slag via a magnetic separator, the separated metallic slag being useable as charge material in an iron/steel making process; and -crushing the left-over non-metallic portion out of said liquid BOF slag along with 5% gypsum to a size range of 3000 to 3500 blain after separating the metallic portion therefrom, the ground non-metallic slag being useable as a hydraulic binder. |
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00543-kol-2006-correspondence other.pdf
00543-kol-2006-description complete.pdf
543-kol-2006-correspondence.pdf
543-kol-2006-description (complete).pdf
543-kol-2006-examination report.pdf
543-kol-2006-reply to examination report.pdf
543-kol-2006-specification.pdf
Patent Number | 244793 | ||||||||
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Indian Patent Application Number | 543/KOL/2006 | ||||||||
PG Journal Number | 52/2010 | ||||||||
Publication Date | 24-Dec-2010 | ||||||||
Grant Date | 20-Dec-2010 | ||||||||
Date of Filing | 05-Jun-2006 | ||||||||
Name of Patentee | TATA STEEL LIMITED | ||||||||
Applicant Address | JAMSHEDPUR | ||||||||
Inventors:
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PCT International Classification Number | C21C 5/30 | ||||||||
PCT International Application Number | N/A | ||||||||
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