Title of Invention	A PROCESS FOR PRODUCING COLD BONDED PELLETS FROM SOLID WASTES GENERATED IN INTEGRATED STEEL PLANTS
Abstract	A cold-bonded agglomeration process for recycling of the wastes/by-products generated in integrated steel plants, whereby various steel plant by-products, carbonaceous material and other ingredients such as slimes, BF flue dust, COREX sludge, BOF sludge, BOF dust, continuous caster and hot strip mill scale could be advantageously reused within the steel plant. The green balls/pellets obtained using pelletising disc from wasted materials are preferably in the size range of 5-25mm diameter and of desirable properties suitable for recycling through blast furnace, COREX, hot metal pre-treatment, cupola, LD converter etc. The method of recycling is directed to reducing the cost of steel produced by reusing mineral values recovered from the waste material/by-products, control industrial pollutants/environmental hazards and thus providing scope for its wide scale industrial application in integrated steel plants.

Title of Invention

A PROCESS FOR PRODUCING COLD BONDED PELLETS FROM SOLID WASTES GENERATED IN INTEGRATED STEEL PLANTS

Abstract

A cold-bonded agglomeration process for recycling of the wastes/by-products generated in integrated steel plants, whereby various steel plant by-products, carbonaceous material and other ingredients such as slimes, BF flue dust, COREX sludge, BOF sludge, BOF dust, continuous caster and hot strip mill scale could be advantageously reused within the steel plant. The green balls/pellets obtained using pelletising disc from wasted materials are preferably in the size range of 5-25mm diameter and of desirable properties suitable for recycling through blast furnace, COREX, hot metal pre-treatment, cupola, LD converter etc. The method of recycling is directed to reducing the cost of steel produced by reusing mineral values recovered from the waste material/by-products, control industrial pollutants/environmental hazards and thus providing scope for its wide scale industrial application in integrated steel plants.

Full Text	FORM 2 THE PATENT ACT 1970 (39 OF 1970) & The Patent Rules, 2003 COMPLETE SPECIFICATION (See Section 10 and Rule 13) 1 TITLE OF THE INVENTION : A PROCESS FOR PRODUCING COLD BONDED PELLETS FROM SOLID WASTES GENERATED IN INTEGRATED STEEL PLANTS. 2 APPLICANT (S) Name : JSW Steel Limited. I Nationality : An Indian Company. Address : Jindal Mansion, 5-A, Dr. G. Deshmukh Marg ,Mumbai - 400 026, State of Maharastra, India. 3 PREAMBLE TO THE DESCRIPTION COMPLETE The following specification particularly descibes the invention and the manner in which it is to be performed. i FIELD OF THE INVENTION: The present invention relates to a method of recycling of the various solid wastes generated in an integrated steel plant and, in particular, to a process for producing cold bonded pellets using pelletising disc from such solid wastes generated in an integrated steel plant. Advantageously, the process of the invention provides for benefit utilization of waste materials such as slimes from beneficiation plant, BF dust, sludge from Corex and BOF, mill scale from mills and the like by way of cold bond agglomeration involving pelletisation. The invention would thus serve in reducing the cost of steel produced through possible beneficial utilization of mineral values from waste materials. Also, importantly the above process of the invention would take care of serious problems of handling and disposal of such environmentally hazardous waste of steel plants and favour in protecting the environment apart from recovery and utilization of the waste to make the steel manufacture more cost-effective. Moreover, the invention would favour preserving the scare and limited natural resources by way of providing for its most effective utilization and value addition in steel industry. BACKGROUND ART: It is well known in the field of iron and steel making processes especially in large integrated steel plants that the same involves processing of iron ore, coal, coke and fluxes to produce iron and steel which is usually carried out through a number of unit processes like agglomeration, coke making, iron making, steel making, casting and rolling/forging etc, whereby one or more wastes or by-products are generated. The specific amount of such wastes generated depend on various factors such as the quality of raw materials, level of technology applied in practice, operating philosophy including dealing with and considerations for the environmental pollution and waste disposal/handling etc. The average specific rate of waste generation in an integrated steel plant is in the order of 800 kg per ton of crude steel produced and include slag from iron/steel making process, slimes, BOF and COREX sludges, BF flue dust and BOF dust, scales formed in continuous caster and the hot strip mill etc. These wastes are rich in mineral contents and pose environmental concern relating to handling and disposal thereof. Stringent regulations relating to restriction on emission of industrial pollutants and the increasing costs of primary sources of materials have made it imperative to maximize recycling of by-products and wastes generated in an integrated steel plant. 2 Several techniques have been applied to recycle the steel plant waste, of which cold bond agglomeration using briquetting process is the most commonly adopted method. In this process, the steel plant wastes such as the slag, sludge, scales etc. are mixed thoroughly with a binder and are sent to briquetting press. In the briquetting process requisite amount of load is applied to compact the mass and provide adequate strength to the agglomerated mass. However, such conventional briquetting process had the inherent disadvantage with respect to the non-uniform size of the agglomerated mass and non-homogeneity in composition making it difficult for recycling in various unit processes like blast furnace, Corex, hot metal pre-treatment, cupola, LD converter etc. There has been thus a continuing need to develop an alternative to briquetting process of agglomeration such as to provide agglomerated masses of favorable size capable for diverse requirement for recycling in different unit processes in the integrated steel plants and effectively control the handling and disposal of solid wastes. OBJECTS OF THE INVENTION: It is thus the basic object of the present invention to provide an alternative agglomeration process involving pelletisation of the waste generated in integrated steel plants rich in mineral to provide benefit utilization of the waste by way of diverse requirement for recycling in different unit processes in the integrated steel plants. Another object of the present invention is directed to recycling of waste generated in an integrated steel plant and in the process reduce the cost of steel produced by providing avenues for reuse of the valuable mineral containing waste materials in steel plants. Yet further object of the present invention is directed to provide an alternative agglomeration process involving pelletisation of the waste generated in integrated steel plants which is rich in mineral which on one hand would be favouring effective utilization of the waste and on the other hand more importantly address the issue of environmental hazards of handling and disposal of such mineral containing wastes. A further object of the present invention is directed to provide an alternative agglomeration process involving pelletisation of the waste generated in integrated steel plants which is rich in mineral which would favour effective utilization and also preservation of scare natural 3 resources by avoiding the unwanted wastage of valuable minerals which has limited resource all over the world. Yet further object of the present invention is directed to achieve a method of recycling of solid wastes generated from various unit processes in steel making in order to efficiently handle the solid wastes, recovering scarce minerals and importantly further adhere to stringent regulations regarding disposal of industrial wastes/pollutants. A further object of the present invention is directed to a method of recycling of solid wastes obtained as by-products of various unit processes in order to utilize the minerals contained in the wastes are re-used to save scarce natural reserves/resources rather than disposing them to environment as industrial pollutants. A further object of the present invention directed to a recycling process of the solid wastes or by-products generated in an integrated steel plant such that the by products/wastes obtained from various processes such as the slime, BF flue dust, Corex sludge, steel plant waste products like BOF sludge, BOF dust, scales obtained from continuous caster and hot strip mill etc. could be advantageously pelletlized and provided in a form suitable for its reuse by the steel industry. A still further object of the present invention directed to a method of recycling the wastes/byproducts generated in an integrated steel plant such as to obtain cold bonded pellets of desired uniform size range and composition having requisite strength properties to satisfy the requirements for intended use of these pellets as input to different unit processes. A still further object of the present invention directed to a method of recycling the wastes/byproducts generated in an integrated steel plant such as to obtain cold bonded pellets which would be rich in iron due to presence of slime which is a by-product of iron ore beneficiation as also the scales obtained from continuous caster or hot strip mill, such that the use of fresh iron ore is minimized in iron/steel making. 4 SUMMARY OF THE INVENTION: Thus according to the basic aspect of the invention there is provided a process for producing cold bonded pellets from solid wastes generated in an integrated steel plant comprising: i) providing a through mix of said solid wastes from the integrated steel plant in sizes of less than 100 mesh; ii) adding to the solid waste a binder material in the range of 5-25% and adding water thereto to maintain a moisture level of 8-15% by wt of the total mix to provide a wet mix; iii) obtaining from said wet mix green balls /pellets in the size range of 5 - 25 mm and having a moisture of 9 - 18%; and iv) subjecting the green balls/pellets to drying and curing for desired strength and moisture content. According to another aspect of the present invention there is provided a process for producing cold bonded pellets from solid wastes generated in an integrated steel plant comprising: i) providing a thorough mix of said solid wastes from the integrated steel plant in sizes of less than 100 mesh; ii) adding to the solid waste a cement binder material preferably selected from Portland cement and slag cement in the range of 5-25% and adding water thereto to maintain a moisture level of 8-15% by wt of the total mix to provide a wet mix; iii) obtaining from said wet mix green balls /pellets in a balling/pelletising disc in the size range of 5 - 25 mm and having a moisture of 9 - 18%; and iv) subjecting the green balls/pellets to an initial drying for initial strength ; v) subjecting the thus dried balls/ pellets to curing for desired strength and moisture content; and vi) subjecting the cured balls/pellets having a moisture content of upto 25% to drying in air such as to retain moisture of only upto 10%. Another aspect of the present invention is directed to a process for producing cold bonded pellets from solid wastes wherein the said solid wastes from the integrated steel plant comprise revert materials including slimes from beneficiation plant in amounts of upto 100 % 5 by wt. of the composition ,BF dust in amounts of upto 50 % by wt. of the composition, sludge from Corex and BOF in amounts of upto 50 % by wt. of the composition, mill scale from the mills in amounts of upto 50 % by wt. of the composition and other steel plant wastes in amounts of upto 10% by wt. of the composition which are mixed thoroughly in a mixer. A still further aspect of the present invention is directed to said process for producing cold bonded pellets from solid wastes wherein in the said balling /peiletizing disc moisture of about 1-3% is added for preparation of the balls/pellets. According to yet further aspect of the present there is provided a process for producing cold bonded pellets from solid wastes wherein the green balls/pellets are initially dried for a period ranging from 4 to 24 hrs. such as to achieve said initial strength. According to the a still further aspect there is disclosed a process for producing cold bonded pellets from solid wastes wherein the dried green balls/pellets are cured by spraying water such that the balls/pellets are always wet or by completely dipping them in water for a period varying from 3 to 10 days. A still further aspect of the present process provides for producing cold bonded pellets from solid wastes wherein the cured balls/pellets containing a moisture level of upto 25% are dried in air to remove moisture for a period of 0 to 10 days such as to retain moisture less than 10%. According to yet another aspect there is disclosed cold bonded pellets from solid wastes produced by the process of the present invention comprising 10-15% Slag Cement, 30-60% BOF Sludge and 30-60% Slimes. Preferably, the said cold bonded pellets from solid wastes comprises of selective chemical constituents selected from Fe : up to 60 %;FeO :up to 5 %;SiO2: up to 10 %;AI2O3: up to 7 %;CaO: up to 15 % and MgO up to 5 %. According to another preferred aspect the said Cold bonded pellets from solid wastes obtained according to the process of present invention comprises: Cold Properties : Tumbler Index (+6.3mm), % in the range of 50 to 95; 6 CCS, Kg in the range of 20 to 120; and High Temperature Properties: RDI (-6.3mm), % in the range of 5 to 25; RDI (-0.5 mm), % in the range of 5 to 25; Metallisation in the range of 50 to 100;and Crushing strength of DRI in the range of 20 to 200 kg According to a still further aspect of the present invention there is provided a method of recycling solid wastes converted to cold bonded pellets obtained following the processes according to the present invention, in steel plant selectively through blast furnace, Corex, hot metal pretreatment, cupola, LD converter and the like. The present invention and its objects and advantages are described in greater detail with reference to the accompanying illustrative non-limiting examples as follows: DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO ACCOMPANYING EXAMPLES: The present invention is directed to an efficient method of recycling of solid wastes and byproducts obtained from different unit processes carried out in an large integrated steel plant such slimes from beneficiation plant, BF dust, sludge from Corex and BOF, mill scale from the mills and the like. Importantly, the invention provides for an alternative agglomeration process involving pelletising of the above solid waste mix for advantageous re utilization by the steel industry avoiding unwanted disposal causing environmental problems and in the process also taking care of the need for environment friendly recycling of steel plant wastes and the like. The pellets produced by the process of the invention comprise of minerals and ingredients that are rich in minerals so that the reuse of these pellets further reduces the requirement of fresh quantity of iron ore for basic iron/steel manufacturing plants and make the steel making simple and cost-effective. The present method of cold bonded agglomeration is an effective alternative to the conventional agglomeration process in a briquetting press where the mix of ingredients comprising steel plant wastes/by-products along with a binder material are subjected to required amount of pressure for compacting the mixed mass in presence of the binder. The 7 unique cold bonded agglomeration process according to the present invention developed involves simple collection and mixing of the wastes/by-products of different intermediate/unit processes in an integrated steel plant such as the slimes rich in iron content obtained as the by-product of iron ore beneficiation, blast furnace flue dust, COREX sludge, steel making plant wastes including BOF sludge, BOF dust and scales from continuous caster and the hot strip mill, all being fed to a mixer for through mixing. The constituents are mixed in desired proportions as per the requirement and availability. Water is added to the above mix to maintain desired total moisture content Slag cement or ordinary Portland cement is added to the mix as a binder for hardening. The materials are mixed thoroughly and the blend is subjected to pelletizing in a standard balling disc for converting it into pellets. Green balls with varying sizes ranging from 5-25mm are made from this mix, using the balling disc are produces which are initially dried, then cured and again dried to achieve the desired properties suitable for re-cycling through blast furnace, COREX, hot metal pre-treatment, cupola, LD converter etc. The cold bonded agglomeration process of the present invention for recycling/conversion of solid wastes/by-products of integrated steel plants into pellets having desired properties making them suitable for reuse as raw material feed in appropriate proportion to any of the unit processes wherever required such as the blast furnace, COREX, hot metal pre-treatment, Cupola, LD converter etc. to recover the minerals/iron which would otherwise have been wasted creating industrial pollution. The process of the invention is detailed hereunder in greater detail by way of the following exemplary illustration: EXAMPLE: The waste material and the binder involved in the process are as in Table I hereunder: Table I Waste Material recycled Content in wt. % Slimes 0-100 Mill Scale 0-50 Sludge from COREX and BOF 0-50 BF flue dust 0-50 Other Steel Plant Wastes 0-10 Binder: Portland/Slag Cement 5-25 (of the above blend) 8 The pelletization process according to the process of the present invention was carried out as follows: 1. Firstly, the revert materials used for recycling containing slimes from ore beneficiation plant, BF dust, Sludge from COREX and BOF, mill scales from the hot strip mills and the continuous caster, obtained in less than 100 mesh size were mixed thoroughly, the constituents being selectively mixed; After thorough mixing of the basic ingredients, water was next added to the mix to maintain the moisture between 8-15% by weight of the total mix; 2. In the following step, the wet mix was then sent to standard balling/pelletizing disc, to make green balls/pellets. At this stage further 1-3% moisture was added as per the requirements to prepare balls/pellets of desired size. The green balls/pellets were obtained in the size range of 5-25mm having total moisture content of 9-18%; 3. The green balls/pellets were then initially dried for duration ranging from 4 to 24 hours, based on the requirement of initial strength of pellets. 4. The dried green balls /pellets were cured by spraying water so that the same remained always wet or by completely dipping the same in water for a period varying from 3 to 10 days. 5. The cured balls/pellets which contained moisture up to 25% were next dried in air to remove the moisture which continued for about 0 to 10 days so as to retain moisture content at a level less than 10% by wt. 6. The dried balls/pellets were sent for chemical analysis and tested for cold tumbler test, cold crushing strength, high temperature properties, such as Reduction Degradation Index (RDI-6.3mm,%) and (RDI-0.5mm,%), metallization, degree of reduction and crushing strength of reduced material. The properties of cold bonded pellets obtained from a typical blend comprising 10-15% Slag Cement, 30-60% BOF Sludge and 30-60% Slimes is shown in following Table II and III. 9 Table II CHEMICAL ANALYSIS COMPOUND PRESENT WT. % Fe(Total) 51.36 FeO 30.76 SiO2 7.38 Al2O3 4.24 CaO 10.37 MgO 1.21 Table III: COLD PROPERTIES Tumbler Index(+6.3mm,%) 83 CCS, kg 50 HIGH TEMPERATURE PROPERTIES RDI (-6.3mm),% 13.1 RDI (-0.5mm),% 12.2 Metallisation 96 Crushing strength of DRI 100 The cement based cold bonded agglomerated pellets thus produced following the above process of the invention are found suitable for use as feed to either of the unit processes for iron/steel making like BF, COREX, hot metal pre-treatment, Cupola or LD Converter, depending on the chemical and high temperature properties achieved in the pellets produced, facilitating reduction in use of fresh charge of ore. It is thus possible by way of the present invention to obtain cement based cold bonded pellets produced by agglomeration in a standard balling disc, to enable advantageous recycling of the wastes/by-products produced in various unit processes in iron and steel making, rolling/forging or casting in large integrated steel plants. The invention therefore would on one hand enable effective utilization of the waste and oh the other hand favour avoiding environmental hazards in disposal of such mineral containing wastes apart from also favouring substantial saving of scarce natural reserve of ore/minerals and meet the much desired objective of making steel production environment friendly , simple and cost-effective. 10 WE CLAIM: 1. A process for producing cold bonded pellets from solid wastes generated in an integrated steel plant comprising: i) providing a through mix of said solid wastes from the integrated steel plant in sizes of less than 100 mesh; ii) adding to the solid waste a binder material in the range of 5-25% and adding water thereto to maintain a moisture level of 8-15% by wt of the total mix to provide a wet mix; iii) obtaining from said wet mix green balls /pellets in the size range of 5 - 25 mm and having a moisture of 9 - 18%; and iv) subjecting the green balls/pellets to drying and curing for desired strength and moisture content. 2. A process for producing cold bonded pellets from solid wastes generated in an integrated steel plant comprising: i) providing a through mix of said solid wastes from the integrated steel plant in sizes of less than 100 mesh; ii) adding to the solid waste a cement binder material preferably selected from Portland cement and slag cement in the range of 5-25% and adding water thereto to maintain a moisture level of 8-15% by wt of the total mix to provide a wet mix; iii) obtaining from said wet mix green balls /pellets in a balling/pelletising disc in the size range of 5 - 25 mm and having a moisture of 9 - 18%; and iv) subjecting the green balls/pellets to an initial drying for initial strength ; v) subjecting the thus dried balls/ pellets to curing for desired strength and moisture content; and vi) subjecting the cured balls/pellets having a moisture content of upto 25% to drying in air such as to retain moisture of only upto 10%. 3. A process for producing cold bonded pellets from solid wastes as claimed in anyone of claims 1 or 2 wherein the said solid wastes from the integrated steel plant comprise revert materials including slimes from beneficiation plant in amounts of upto 100 % by 11 wt. of the composition ,BF dust in amounts of upto 50 % by wt. of the composition, sludge from Corex and BOF in amounts of upto 50 % by wt. of the composition, mill scale from the mills in amounts of upto 50 % by wt. of the composition and other steel plant wastes in amounts of upto 10% by wt. of the composition which are mixed thoroughly in a mixer. 4. A process for producing cold bonded pellets from solid wastes as claimed in anyone of claims 1 to 3 wherein in the said balling /palletizing disc moisture of about 1-3% is added for preparation of the balls/pellets. 5. A process for producing cold bonded pellets from solid wastes as claimed in anyone of claims 1 to 4 wherein the green balls/pellets are initially dried for a period ranging from 4 to 24 hrs. such as to achieve said initial strength. 6. A process for producing cold bonded pellets from solid wastes as claimed in anyone of claims 1 to 5 wherein the dried green balls/pellets are cured by spraying water such that the balls/pellets are always wet or by completely dipping them in water for a period varying from 3 to 10 days. 7. A process for producing cold bonded pellets from solid wastes as claimed in claim 6 wherein the cured balls/pellets containing a moisture level of upto 25% are dried in air to remove moisture for a period of 0 to 10 days such as to retain moisture less than 10%. 8. Cold bonded pellets from solid wastes obtained by the process as claimed in anyone of claims 1 or 7 such as to comprise: Cold Properties : Tumbler Index (+6.3mm),% in the range of 50 to 95; CCS, Kg in the range of 20 to 120; and High Temperature Properties: RDI (-6.3mm),% in the range of 5 to 25; RDI (-0.5 mm).% in the range of 5 to 25; 12 Metallisation in the range of 50 to 100; and Crushing strength of DRI in the range of 20 to 200 kg 9. A method of recycling cold bonded pellets obtained following the processes as claimed in anyone of claims 1 to 7 in steel plant selectively through blast furnace, Corex, hot metal pretreatment, cupola, LD converter and the like. 10. A process for producing cold bonded pellets from solid wastes generated in an integrated steel plant and its use in steel making substantially as here in described and illustrated with reference to the accompanying Examples. Dated this 9th day of August, 2007 13 ABSTRACT A PROCESS FOR PRODUCING COLD BONDED PELLETS FROM SOLID WASTES GENERATED IN INTEGRATED STEEL PLANTS. A cold-bonded agglomeration process for recycling of the wastes/by-products generated in integrated steel plants, whereby various steel plant by-products, carbonaceous material and other ingredients such as slimes, BF flue dust, COREX sludge, BOF sludge, BOF dust, continuous caster and hot strip mill scale could be advantageously reused within the steel plant. The green balls/pellets obtained using pelletising disc from waste materials are preferably in the size range of 5-25mm diameter and of desirable properties suitable for recycling through blast furnace, COREX, hot metal pre-treatment, Cupola, LD converter etc. The method of recycling is directed to reducing the cost of steel produced by reusing mineral values recovered from the waste material/by-products, control industrial pollutants/environmental hazards and thus providing scope for its wide scale industrial application in integrated steel plants. 14

Full Text

FORM 2
THE PATENT ACT 1970
(39 OF 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)
1 TITLE OF THE INVENTION :
A PROCESS FOR PRODUCING COLD BONDED PELLETS FROM SOLID WASTES GENERATED IN INTEGRATED STEEL PLANTS.
2 APPLICANT (S)

Name : JSW Steel Limited.
I
Nationality : An Indian Company.
Address : Jindal Mansion, 5-A, Dr. G. Deshmukh Marg ,Mumbai - 400 026,
State of Maharastra, India.
3 PREAMBLE TO THE DESCRIPTION
COMPLETE
The following specification particularly descibes the invention and the manner in which it is to
be performed.
i

FIELD OF THE INVENTION:
The present invention relates to a method of recycling of the various solid wastes generated in an integrated steel plant and, in particular, to a process for producing cold bonded pellets using pelletising disc from such solid wastes generated in an integrated steel plant. Advantageously, the process of the invention provides for benefit utilization of waste materials such as slimes from beneficiation plant, BF dust, sludge from Corex and BOF, mill scale from mills and the like by way of cold bond agglomeration involving pelletisation. The invention would thus serve in reducing the cost of steel produced through possible beneficial utilization of mineral values from waste materials. Also, importantly the above process of the invention would take care of serious problems of handling and disposal of such environmentally hazardous waste of steel plants and favour in protecting the environment apart from recovery and utilization of the waste to make the steel manufacture more cost-effective. Moreover, the invention would favour preserving the scare and limited natural resources by way of providing for its most effective utilization and value addition in steel industry.
BACKGROUND ART:
It is well known in the field of iron and steel making processes especially in large integrated steel plants that the same involves processing of iron ore, coal, coke and fluxes to produce iron and steel which is usually carried out through a number of unit processes like agglomeration, coke making, iron making, steel making, casting and rolling/forging etc, whereby one or more wastes or by-products are generated. The specific amount of such wastes generated depend on various factors such as the quality of raw materials, level of technology applied in practice, operating philosophy including dealing with and considerations for the environmental pollution and waste disposal/handling etc. The average specific rate of waste generation in an integrated steel plant is in the order of 800 kg per ton of crude steel produced and include slag from iron/steel making process, slimes, BOF and COREX sludges, BF flue dust and BOF dust, scales formed in continuous caster and the hot strip mill etc. These wastes are rich in mineral contents and pose environmental concern relating to handling and disposal thereof. Stringent regulations relating to restriction on emission of industrial pollutants and the increasing costs of primary sources of materials have made it imperative to maximize recycling of by-products and wastes generated in an integrated steel plant.
2

Several techniques have been applied to recycle the steel plant waste, of which cold bond agglomeration using briquetting process is the most commonly adopted method. In this process, the steel plant wastes such as the slag, sludge, scales etc. are mixed thoroughly with a binder and are sent to briquetting press. In the briquetting process requisite amount of load is applied to compact the mass and provide adequate strength to the agglomerated mass. However, such conventional briquetting process had the inherent disadvantage with respect to the non-uniform size of the agglomerated mass and non-homogeneity in composition making it difficult for recycling in various unit processes like blast furnace, Corex, hot metal pre-treatment, cupola, LD converter etc.
There has been thus a continuing need to develop an alternative to briquetting process of agglomeration such as to provide agglomerated masses of favorable size capable for diverse requirement for recycling in different unit processes in the integrated steel plants and effectively control the handling and disposal of solid wastes.
OBJECTS OF THE INVENTION:
It is thus the basic object of the present invention to provide an alternative agglomeration process involving pelletisation of the waste generated in integrated steel plants rich in mineral to provide benefit utilization of the waste by way of diverse requirement for recycling in different unit processes in the integrated steel plants.
Another object of the present invention is directed to recycling of waste generated in an integrated steel plant and in the process reduce the cost of steel produced by providing avenues for reuse of the valuable mineral containing waste materials in steel plants.
Yet further object of the present invention is directed to provide an alternative agglomeration process involving pelletisation of the waste generated in integrated steel plants which is rich in mineral which on one hand would be favouring effective utilization of the waste and on the other hand more importantly address the issue of environmental hazards of handling and disposal of such mineral containing wastes.
A further object of the present invention is directed to provide an alternative agglomeration process involving pelletisation of the waste generated in integrated steel plants which is rich in mineral which would favour effective utilization and also preservation of scare natural
3

resources by avoiding the unwanted wastage of valuable minerals which has limited resource all over the world.
Yet further object of the present invention is directed to achieve a method of recycling of solid wastes generated from various unit processes in steel making in order to efficiently handle the solid wastes, recovering scarce minerals and importantly further adhere to stringent regulations regarding disposal of industrial wastes/pollutants.
A further object of the present invention is directed to a method of recycling of solid wastes obtained as by-products of various unit processes in order to utilize the minerals contained in the wastes are re-used to save scarce natural reserves/resources rather than disposing them to environment as industrial pollutants.
A further object of the present invention directed to a recycling process of the solid wastes or by-products generated in an integrated steel plant such that the by products/wastes obtained from various processes such as the slime, BF flue dust, Corex sludge, steel plant waste products like BOF sludge, BOF dust, scales obtained from continuous caster and hot strip mill etc. could be advantageously pelletlized and provided in a form suitable for its reuse by the steel industry.
A still further object of the present invention directed to a method of recycling the wastes/byproducts generated in an integrated steel plant such as to obtain cold bonded pellets of desired uniform size range and composition having requisite strength properties to satisfy the requirements for intended use of these pellets as input to different unit processes.
A still further object of the present invention directed to a method of recycling the wastes/byproducts generated in an integrated steel plant such as to obtain cold bonded pellets which would be rich in iron due to presence of slime which is a by-product of iron ore beneficiation as also the scales obtained from continuous caster or hot strip mill, such that the use of fresh iron ore is minimized in iron/steel making.
4

SUMMARY OF THE INVENTION:
Thus according to the basic aspect of the invention there is provided a process for producing cold bonded pellets from solid wastes generated in an integrated steel plant comprising:
i) providing a through mix of said solid wastes from the integrated steel plant in sizes
of less than 100 mesh;
ii) adding to the solid waste a binder material in the range of 5-25% and adding
water thereto to maintain a moisture level of 8-15% by wt of the total mix to
provide a wet mix;
iii) obtaining from said wet mix green balls /pellets in the size range of 5 - 25 mm
and having a moisture of 9 - 18%; and
iv) subjecting the green balls/pellets to drying and curing for desired strength and
moisture content.
According to another aspect of the present invention there is provided a process for producing cold bonded pellets from solid wastes generated in an integrated steel plant comprising:
i) providing a thorough mix of said solid wastes from the integrated steel plant in
sizes of less than 100 mesh;
ii) adding to the solid waste a cement binder material preferably selected from
Portland cement and slag cement in the range of 5-25% and adding water thereto
to maintain a moisture level of 8-15% by wt of the total mix to provide a wet mix;
iii) obtaining from said wet mix green balls /pellets in a balling/pelletising disc in the
size range of 5 - 25 mm and having a moisture of 9 - 18%; and
iv) subjecting the green balls/pellets to an initial drying for initial strength ;
v) subjecting the thus dried balls/ pellets to curing for desired strength and moisture
content; and
vi) subjecting the cured balls/pellets having a moisture content of upto 25% to drying
in air such as to retain moisture of only upto 10%.
Another aspect of the present invention is directed to a process for producing cold bonded pellets from solid wastes wherein the said solid wastes from the integrated steel plant comprise revert materials including slimes from beneficiation plant in amounts of upto 100 %
5

by wt. of the composition ,BF dust in amounts of upto 50 % by wt. of the composition, sludge from Corex and BOF in amounts of upto 50 % by wt. of the composition, mill scale from the mills in amounts of upto 50 % by wt. of the composition and other steel plant wastes in amounts of upto 10% by wt. of the composition which are mixed thoroughly in a mixer.
A still further aspect of the present invention is directed to said process for producing cold bonded pellets from solid wastes wherein in the said balling /peiletizing disc moisture of about 1-3% is added for preparation of the balls/pellets.
According to yet further aspect of the present there is provided a process for producing cold bonded pellets from solid wastes wherein the green balls/pellets are initially dried for a period ranging from 4 to 24 hrs. such as to achieve said initial strength.
According to the a still further aspect there is disclosed a process for producing cold bonded pellets from solid wastes wherein the dried green balls/pellets are cured by spraying water such that the balls/pellets are always wet or by completely dipping them in water for a period varying from 3 to 10 days.
A still further aspect of the present process provides for producing cold bonded pellets from solid wastes wherein the cured balls/pellets containing a moisture level of upto 25% are dried in air to remove moisture for a period of 0 to 10 days such as to retain moisture less than 10%.
According to yet another aspect there is disclosed cold bonded pellets from solid wastes produced by the process of the present invention comprising 10-15% Slag Cement, 30-60% BOF Sludge and 30-60% Slimes.
Preferably, the said cold bonded pellets from solid wastes comprises of selective chemical constituents selected from Fe : up to 60 %;FeO :up to 5 %;SiO2: up to 10 %;AI2O3: up to 7 %;CaO: up to 15 % and MgO up to 5 %.
According to another preferred aspect the said Cold bonded pellets from solid wastes
obtained according to the process of present invention comprises:
Cold Properties :
Tumbler Index (+6.3mm), % in the range of 50 to 95;
6

CCS, Kg in the range of 20 to 120; and
High Temperature Properties:
RDI (-6.3mm), % in the range of 5 to 25;
RDI (-0.5 mm), % in the range of 5 to 25;
Metallisation in the range of 50 to 100;and
Crushing strength of DRI in the range of 20 to 200 kg
According to a still further aspect of the present invention there is provided a method of recycling solid wastes converted to cold bonded pellets obtained following the processes according to the present invention, in steel plant selectively through blast furnace, Corex, hot metal pretreatment, cupola, LD converter and the like.
The present invention and its objects and advantages are described in greater detail with reference to the accompanying illustrative non-limiting examples as follows:
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO ACCOMPANYING EXAMPLES:
The present invention is directed to an efficient method of recycling of solid wastes and byproducts obtained from different unit processes carried out in an large integrated steel plant such slimes from beneficiation plant, BF dust, sludge from Corex and BOF, mill scale from the mills and the like. Importantly, the invention provides for an alternative agglomeration process involving pelletising of the above solid waste mix for advantageous re utilization by the steel industry avoiding unwanted disposal causing environmental problems and in the process also taking care of the need for environment friendly recycling of steel plant wastes and the like. The pellets produced by the process of the invention comprise of minerals and ingredients that are rich in minerals so that the reuse of these pellets further reduces the requirement of fresh quantity of iron ore for basic iron/steel manufacturing plants and make the steel making simple and cost-effective.
The present method of cold bonded agglomeration is an effective alternative to the conventional agglomeration process in a briquetting press where the mix of ingredients comprising steel plant wastes/by-products along with a binder material are subjected to required amount of pressure for compacting the mixed mass in presence of the binder. The
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unique cold bonded agglomeration process according to the present invention developed involves simple collection and mixing of the wastes/by-products of different intermediate/unit processes in an integrated steel plant such as the slimes rich in iron content obtained as the by-product of iron ore beneficiation, blast furnace flue dust, COREX sludge, steel making plant wastes including BOF sludge, BOF dust and scales from continuous caster and the hot strip mill, all being fed to a mixer for through mixing. The constituents are mixed in desired proportions as per the requirement and availability. Water is added to the above mix to maintain desired total moisture content Slag cement or ordinary Portland cement is added to the mix as a binder for hardening. The materials are mixed thoroughly and the blend is subjected to pelletizing in a standard balling disc for converting it into pellets. Green balls with varying sizes ranging from 5-25mm are made from this mix, using the balling disc are produces which are initially dried, then cured and again dried to achieve the desired properties suitable for re-cycling through blast furnace, COREX, hot metal pre-treatment, cupola, LD converter etc.
The cold bonded agglomeration process of the present invention for recycling/conversion of solid wastes/by-products of integrated steel plants into pellets having desired properties making them suitable for reuse as raw material feed in appropriate proportion to any of the unit processes wherever required such as the blast furnace, COREX, hot metal pre-treatment, Cupola, LD converter etc. to recover the minerals/iron which would otherwise have been wasted creating industrial pollution.
The process of the invention is detailed hereunder in greater detail by way of the following exemplary illustration:
EXAMPLE:
The waste material and the binder involved in the process are as in Table I hereunder:
Table I

Waste Material recycled Content in wt. %
Slimes 0-100
Mill Scale 0-50
Sludge from COREX and BOF 0-50
BF flue dust 0-50
Other Steel Plant Wastes 0-10
Binder: Portland/Slag Cement 5-25 (of the above blend)
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The pelletization process according to the process of the present invention was carried out as follows:
1. Firstly, the revert materials used for recycling containing slimes from ore beneficiation plant, BF dust, Sludge from COREX and BOF, mill scales from the hot strip mills and the continuous caster, obtained in less than 100 mesh size were mixed thoroughly, the constituents being selectively mixed; After thorough mixing of the basic ingredients, water was next added to the mix to maintain the moisture between 8-15% by weight of the total mix;
2. In the following step, the wet mix was then sent to standard balling/pelletizing disc, to make green balls/pellets. At this stage further 1-3% moisture was added as per the requirements to prepare balls/pellets of desired size. The green balls/pellets were obtained in the size range of 5-25mm having total moisture content of 9-18%;
3. The green balls/pellets were then initially dried for duration ranging from 4 to 24 hours, based on the requirement of initial strength of pellets.
4. The dried green balls /pellets were cured by spraying water so that the same remained always wet or by completely dipping the same in water for a period varying from 3 to 10 days.
5. The cured balls/pellets which contained moisture up to 25% were next dried in air to remove the moisture which continued for about 0 to 10 days so as to retain moisture content at a level less than 10% by wt.
6. The dried balls/pellets were sent for chemical analysis and tested for cold tumbler test, cold crushing strength, high temperature properties, such as Reduction Degradation Index (RDI-6.3mm,%) and (RDI-0.5mm,%), metallization, degree of reduction and crushing strength of reduced material.
The properties of cold bonded pellets obtained from a typical blend comprising 10-15% Slag Cement, 30-60% BOF Sludge and 30-60% Slimes is shown in following Table II and III.
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Table II

CHEMICAL ANALYSIS
COMPOUND PRESENT WT. %
Fe(Total) 51.36
FeO 30.76
SiO2 7.38
Al2O3 4.24
CaO 10.37
MgO 1.21
Table III:

COLD PROPERTIES
Tumbler Index(+6.3mm,%) 83
CCS, kg 50
HIGH TEMPERATURE PROPERTIES
RDI (-6.3mm),% 13.1
RDI (-0.5mm),% 12.2
Metallisation 96
Crushing strength of DRI 100
The cement based cold bonded agglomerated pellets thus produced following the above process of the invention are found suitable for use as feed to either of the unit processes for iron/steel making like BF, COREX, hot metal pre-treatment, Cupola or LD Converter, depending on the chemical and high temperature properties achieved in the pellets produced, facilitating reduction in use of fresh charge of ore.
It is thus possible by way of the present invention to obtain cement based cold bonded pellets produced by agglomeration in a standard balling disc, to enable advantageous recycling of the wastes/by-products produced in various unit processes in iron and steel making, rolling/forging or casting in large integrated steel plants. The invention therefore would on one hand enable effective utilization of the waste and oh the other hand favour avoiding environmental hazards in disposal of such mineral containing wastes apart from also favouring substantial saving of scarce natural reserve of ore/minerals and meet the much desired objective of making steel production environment friendly , simple and cost-effective.
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WE CLAIM:
1. A process for producing cold bonded pellets from solid wastes generated in an integrated
steel plant comprising:
i) providing a through mix of said solid wastes from the integrated steel plant in sizes
of less than 100 mesh;
ii) adding to the solid waste a binder material in the range of 5-25% and adding
water thereto to maintain a moisture level of 8-15% by wt of the total mix to
provide a wet mix;
iii) obtaining from said wet mix green balls /pellets in the size range of 5 - 25 mm
and having a moisture of 9 - 18%; and
iv) subjecting the green balls/pellets to drying and curing for desired strength and
moisture content.
2. A process for producing cold bonded pellets from solid wastes generated in an integrated
steel plant comprising:
i) providing a through mix of said solid wastes from the integrated steel plant in sizes
of less than 100 mesh;
ii) adding to the solid waste a cement binder material preferably selected from
Portland cement and slag cement in the range of 5-25% and adding water thereto
to maintain a moisture level of 8-15% by wt of the total mix to provide a wet mix;
iii) obtaining from said wet mix green balls /pellets in a balling/pelletising disc in the
size range of 5 - 25 mm and having a moisture of 9 - 18%; and
iv) subjecting the green balls/pellets to an initial drying for initial strength ;
v) subjecting the thus dried balls/ pellets to curing for desired strength and moisture
content; and
vi) subjecting the cured balls/pellets having a moisture content of upto 25% to drying
in air such as to retain moisture of only upto 10%.
3. A process for producing cold bonded pellets from solid wastes as claimed in anyone of
claims 1 or 2 wherein the said solid wastes from the integrated steel plant comprise
revert materials including slimes from beneficiation plant in amounts of upto 100 % by
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wt. of the composition ,BF dust in amounts of upto 50 % by wt. of the composition, sludge from Corex and BOF in amounts of upto 50 % by wt. of the composition, mill scale from the mills in amounts of upto 50 % by wt. of the composition and other steel plant wastes in amounts of upto 10% by wt. of the composition which are mixed thoroughly in a mixer.
4. A process for producing cold bonded pellets from solid wastes as claimed in anyone of claims 1 to 3 wherein in the said balling /palletizing disc moisture of about 1-3% is added for preparation of the balls/pellets.
5. A process for producing cold bonded pellets from solid wastes as claimed in anyone of claims 1 to 4 wherein the green balls/pellets are initially dried for a period ranging from 4 to 24 hrs. such as to achieve said initial strength.
6. A process for producing cold bonded pellets from solid wastes as claimed in anyone of claims 1 to 5 wherein the dried green balls/pellets are cured by spraying water such that the balls/pellets are always wet or by completely dipping them in water for a period varying from 3 to 10 days.
7. A process for producing cold bonded pellets from solid wastes as claimed in claim 6 wherein the cured balls/pellets containing a moisture level of upto 25% are dried in air to remove moisture for a period of 0 to 10 days such as to retain moisture less than 10%.
8. Cold bonded pellets from solid wastes obtained by the process as claimed in anyone of claims 1 or 7 such as to comprise:
Cold Properties :
Tumbler Index (+6.3mm),% in the range of 50 to 95;
CCS, Kg in the range of 20 to 120; and
High Temperature Properties:
RDI (-6.3mm),% in the range of 5 to 25;
RDI (-0.5 mm).% in the range of 5 to 25;
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Metallisation in the range of 50 to 100; and
Crushing strength of DRI in the range of 20 to 200 kg
9. A method of recycling cold bonded pellets obtained following the processes as claimed in anyone of claims 1 to 7 in steel plant selectively through blast furnace, Corex, hot metal pretreatment, cupola, LD converter and the like.
10. A process for producing cold bonded pellets from solid wastes generated in an integrated steel plant and its use in steel making substantially as here in described and illustrated with reference to the accompanying Examples.
Dated this 9th day of August, 2007
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ABSTRACT
A PROCESS FOR PRODUCING COLD BONDED PELLETS FROM SOLID WASTES GENERATED IN INTEGRATED STEEL PLANTS.
A cold-bonded agglomeration process for recycling of the wastes/by-products generated in integrated steel plants, whereby various steel plant by-products, carbonaceous material and other ingredients such as slimes, BF flue dust, COREX sludge, BOF sludge, BOF dust, continuous caster and hot strip mill scale could be advantageously reused within the steel plant. The green balls/pellets obtained using pelletising disc from waste materials are preferably in the size range of 5-25mm diameter and of desirable properties suitable for recycling through blast furnace, COREX, hot metal pre-treatment, Cupola, LD converter etc. The method of recycling is directed to reducing the cost of steel produced by reusing mineral values recovered from the waste material/by-products, control industrial pollutants/environmental hazards and thus providing scope for its wide scale industrial application in integrated steel plants.
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Patent Number

270057

Indian Patent Application Number

1567/MUM/2007

PG Journal Number

48/2015

Publication Date

27-Nov-2015

Grant Date

26-Nov-2015

Date of Filing

13-Jul-2007

Name of Patentee

JSW STEEL LIMITED

Applicant Address

JINDAL MANSION, 5-A, DR. G. DESHMUKH MARG, MUMBAI

Inventors:

#	Inventor's Name	Inventor's Address
1	PEDDOLLA PRACHETHAN KUMAR	JSW STEEL LIMITED, R&D AND SS, VIDYANAGAR, TORANAGALLU, BELLARY-583275.
2	RAJAN MADHU	JSW STEEL LIMITED, R&D AND SS, VIDYANAGAR, TORANAGALLU, BELLARY-583275.

PCT International Classification Number

C22B7/00; C22B19/00; C22B21/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA