Title of Invention

"A PROCESS FOR THE MANUFACTURE OF COMPOSITE BRIQUETTES OF IRON AND STEEL PLANT WASTES BY COLD BRIQUETTING"

Abstract

The present invention provides a process for the manufacture of composite briquettes of iron and steel plant wastes by cold briquetting, which are otherwise unutilised and are an environmental hazard. The steel plant wastes used in cold briquetting of the present invention are in a combination of iron ore fines of - 6 mm size, flue dust of - 3 mm size, mill scale of - 6 mm size and coke fines of - 6 mm size. The combination of inorganic binders used on the basis of wt % of charge materials are: pyrophilite in the range of 5 - 10%, cement/granulated slag of (-100µ size) in the range of 5 - 10% and activated commercial grade sodium silicate (Na2O :SiO2 ≈1:1) in the range of 3 - 7%. The composite briquettes obtained by the process of the present invention using different binder combinations have sufficient green strength (above 4 drops), cold-crushing strength of above 250 kg/briquette for cylindrical briquettes and above 130 kg/briquette for elliptical briquettes and RDI of below 30%, and are suitable for charging into blast furnace for further processing.

Full Text

This invention relates to a process for the manufacture of composite briquettes of iron and steel plant wastes by cold briquetting. The present invention particularly relates to a process for cold briquetting of steel plant wastes such as iron ore fines, flue dust, mill scale, coke fines and the like with an improved binder matrix, consisting of a combination of different in-organic binders, to make composite briquettes. The briquettes thus obtained have adequate green strength, cold-crushing strength and RDI and are suitable as blast furnace charge. Iron and Steel industries, operating all over he world, produce waste materials like, slag, mill-scale and flue dust besides generating a huge quantity of iron ore and coke fines. These wastes cause a lot of storage and environmental related problems besides wastage of valuable resources. In recent times, efforts have been made to utilise these fines employing agglomeration techniques like, pelletisation and briquetting as part of zero waste concept. Worldwide, for the 700 million tons of steel produced annually, an estimated 30 million tons of recycle wastes are generated. A typical Indian integrated steel plant of 3 million tons per annum capacity generates around 100,000 tons of iron oxide fines, 55.000 tons of coke fines, 15,000 tons of flue dust and 17,000 tons of mill-scale. In the known prior art, a few of the steel plants abroad, specially U.S.A., utilise the ore fines generated during steel making, through briquetting method using various organic and/or inorganic binders. National Steel Corporation, Great lakes division, Chicago, U.S.A. recycle the revert dust/sludges and other materials generated from iron and steel making process through briquetting using inorganic blast furnace binder containing sodium silicate. , Gary Works, U.S.A. use molasses-cement as binder to produce briquettes which are used as charge for blast furnace and steel making furnaces. U.S. Steel, Edgar, U.S.A., use cement-molasses binder for briquetting revert materials like basic oxygen furnace (BOF) sludge, flue dust. The molasses based binder system causes operational problems like bad odour and ammonia- phenol build-up in recycle water stream. Bethlehem Steel Corporation, U.S.A., use cement as binder for extrusion of BOF dust. National Recovery Systems Inc., U.S.A., developed a process to recycle waste oxides in the steel industry by cold bonded rolled briquettes. National Recovery System USA has developed a briquetting process using an inorganic binder for briquetting steel plant revert materials like BOF dust, BOF sludge and flue dust. The main disadvantages of the above briquetting processes, referred above, are that the binders used causes (i) bad odour, (ii) ammonia-phenol build up in recycle water system, (iii) requirement of extensive gas cleaning, (iv) lower strength of briquettes at high temperature and (v) decrease in strength of briquettes under reducing atmosphere encountered in blast furnace. Further the above processes do not use coke fines in briquetting of waste oxides from blast furnace / steel industries. The main object of the present invention is to provide a process for the manufacture of composite briquettes of iron and steel plant wastes by cold briquetting, which obviates the drawbacks of the hitherto known prior art. Another object of the present invention is to provide a process for cold briquetting of iron and steel plant wastes with an improved inorganic binder system, a combination of inorganic binders, which obviates the drawbacks of the hitherto known prior art. Yet another object of the present invention is to provide a process for cold briquetting of iron and steel plant wastes which are otherwise unutilised and are an environmental hazard. Still another object of the present invention is to provide a process for the manufacture of composite briquettes of iron and steel plant wastes, by cold briquetting, which are suitable for charging into blast furnace for further processing. Still yet another object of the present invention is to provide a process for the manufacture of composite briquettes of iron and steel plant wastes, by cold briquetting, which have green strength (above 4 drops), cold-crushing strength of above 250 kg/briquette for cylindrical briquettes and above 130 kg/briquette for elliptical briquettes and RDI of below 30%. In the present invention there is provided a process for the manufacture of composite briquettes of iron and steel plant wastes, which are otherwise unutilised and are an environmental hazard, by cold briquetting with an improved inorganic binder matrix. The steel plant wastes used in cold briquetting of the present invention are in a combination of iron ore fines of - 6 mm size, flue dust of - 3 mm size, mill scale of - 6 mm size and coke fines of - 6 mm size. The combination of inorganic binders used on the basis of wt % of charge materials are: pyrophilite in the range of 5 - 10%, cement/granulated slag of (-100 [i size) in the range of 5 - 10% and activated commercial grade sodium silicate (Na2O :SiO2 ≈1:1) in the range of 3 - 7%. The composite briquettes obtained by the process of the present invention using different binder combinations have sufficient green strength (above 4 drops), cold-crushing strength of above 250 kg/briquette for cylindrical briquettes and above 130 kg/briquette for elliptical briquettes and RDI of below 30%, and are suitable for charging into blast furnace for further processing. Accordingly the present invention provides a process for the manufacture of composite briquettes of iron and steel plant wastes by cold briquetting, which comprises the steps: I. dry mixing of iron and steel plant wastes such as iron ore fines, flue dust, mill scale, coke fines; II. adding a binder matrix to the dry mix, of iron and steel plant wastes obtained in step (i), and subjecting it to thorough mixing, characterised in that the said binder matrix essentially consisting of inorganic binders such as pyrophilite, cement / ground granulated slag of steel plant and activated commercial grade sodium silicate (Na20 : Si02 «1:1) and are used in a combination on the basis of wt % of charge materials such as: pyrophilite in the range of 5 - 10%, cement/granulated slag of -100 µ size in the range of 5 - 10% and activated commercial grade sodium silicate (Na2O :SiO2 ≈1:1) in the range of 3 - 7%; III. adding water to the above said resultant dry mix, obtained in step (ii), and subjecting it to further mixing to obtain a charge mixture dough; IV. cold briquetting the resultant charge mixture dough obtained in step (iii), by known method in a briquetting machine or briquetting roll press by applying a vertical compression load of the order of 350-450 kg/cm2 and 100-200 kg/cm2 to obtain the cylindrical and elliptical briquettes, respectively, and curing the such briquettes so obtained, under natural conditions for a period of 3-6 days. In an embodiment of the present invention, the steel plant wastes are in a combination of iron ore fines of - 6 mm size, flue dust of - 3 mm size, mill scale of - 6 mm size and coke fines of - 6 mm size. In another embodiment of the present invention, the vertical compression load used in briquetting machine for making cylindrical briquettes is preferably 400 kg/cm2 In yet another embodiment of the present invention, the vertical compression load used in briquetting roll press for making elliptical briquettes is preferably 150 kg/cm2 In a further embodiment of the present invention, the composite briquettes obtained have green strength of above 4 drops, cold-crushing strength of above 250 kg/briquette for cylindrical briquettes and above 130 kg/briquette for elliptical briquettesand (Reduction degradation Index) RDI of below 30%, and are suitable for charging into blast furnace for further processing. The novel features of the present invention have been realised by the non-obvious inventive step of providing a combination of iron and steel plant wastes as charge materials, such as iron ore fines of - 6 mm size, flue dust of - 3 mm size, mill scale of - 6 mm size and coke fines of - 6 mm size and improved inorganic binder matrix consisting of a combination of inorganic binders used on the basis of wt % of charge materials such as pyrophilite in the range of 5 -10%, cement/granulated slag of steel plant of -100 µ size in the range of 5 - 10% and activated commercial grade sodium silicate (Na2O :SiO2 ≈1:1) in the range of 3 - 7%. In a co-pending patent application no. 1224/del/2002, we have described and claimed an improved inorganic binder matrix useful for cold briquetting of iron and steel plant wastes. The improved inorganic binder matrix enables making composite briquettes using steel plant wastes like iron ore fines, flue dust, mill scale, coke fines by cold briquetting and these briquettes are suitable for charging into blast furnace for further processing. The improved inorganic binder matrix is a novel synergistic mixture of inorganic binders essentially consisting of pyrophilite, cement/granulated slag and activated sodium silicate in a ratio in the range of 5 to 10 : 5 to 10 : 3 to 7, respectively. The following examples are given to illustrate how the process of the present invention is carried out in actual practice and should not be construed to limit the scope of the invention. Example-1 750g of iron ore fines, lOOg mill-scale, 50g flue-dust and lOOg coke fines were mixed thoroughly and then 50g of pyrophilite (5% by weight of charge), 50g of cement (5% by weight of charge) were added and again mixed. 40g of activated sodium silicate (4% by weight of charge) was added to the above charge mix and mixed thoroughly by adding suitable amount of water. Composite briquettes of cylindrical shape were made using this mix in a briquetting machine by applying a vertical compression load of 400 kg/cm2. The cylindrical briquettes obtained were of the size of 28 mm diameter and of 30 mm height. The briquettes were subjected to natural curing for 5 days. The briquettes were found to have green strength of 4 drops, cold crushing strength of 260 kg/briquette after curing and RDI of 23%. Example-2 750g of iron ore fines, lOOg mill-scale, 50g flue-dust and lOOg coke fines were mixed thoroughly and then lOOg of pyrophilite (10% by weight of charge), 50g of cement (5% by weight of charge) were added and again mixed. 40g of activated sodium silicate (4% by weight of charge) was added to the above charge mix and mixed thoroughly by adding suitable amount of water. Composite briquettes of cylindrical shape were made using this mix in a briquetting machine by applying a vertical compression load of 400 kg/cm2. The cylindrical briquettes obtained were of the size of 28 mm diameter and of 30 mm height. The briquettes were subjected to natural curing for 5 days. The briquettes were found to have green strength of 6 drops, cold crushing strength of 265 kg/briquette after curing and RDI of 8%. Example-3 750g of iron ore fines, lOOg mill-scale, 50g flue-dust and lOOg coke fines were mixed thoroughly and then 50g of pyrophilite (5% by weight of charge), lOOg of cement (10% by weight of charge) were added and again mixed. 40g of activated sodium silicate, (4% by weight of charge) was added to the above charge mix and mixed thoroughly by adding suitable amount of water. Composite briquettes of cylindrical shape were made using this mix in a briquetting machine applying a vertical compression load of 400 kg/cm2. The cylindrical briquettes obtained were of the size of 28 mm diameter and of 30 mm height. The briquettes were subjected to natural curing for 5 days. The briquettes had green strength of 4 drops, cold crushing strength of 350 kg/briquette after curing and RDI of 20%. Example-4 750g of iron ore fines, lOOg mill-scale, 50g flue-dust and lOOg coke fines were mixed thoroughly and then 50g of pyrophilite (5% by weight of charge), 50g of ground granulated slag (5% by weight of charge) were added and again mixed. 40g of activated sodium silicate (4% by weight of charge) was added to the above charge mix and mixed thoroughly by adding suitable amount of water. Composite briquettes of cylindrical shape were made using this mix in a briquetting machine applying a vertical compression load of 400 kg/cm2. The cylindrical briquettes obtained were of the size of 28 mm diameter and of 30 mm height. The briquettes were subjected to natural curing for 5 days. The briquettes have green strength of 4 drops, cold crushing strength of 280 kg/briquette after curing and RDI of 22%. Example-5 750g of iron ore fines, lOOg mill-scale, 50g flue-dust and lOOg coke fines were mixed thoroughly and then 50g of pyrophilite (5% by weight of charge), lOOg of ground granulated slag (10% by weight of charge) were added and again mixed. 40g of activated sodium silicate (4% by weight of charge) was added to the above charge mix and mixed thoroughly by adding suitable amount of water. Composite briquettes of cylindrical shape were made using this mix in a briquetting machine applying a vertical compression load of 400 kg/cm2. The cylindrical briquettes obtained were of the size of 28 mm diameter and of 30 mm height. The briquettes were subjected to natural curing for 5 days. The briquettes had green strength of 5 drops, cold crushing strength of 285 kg/briquette after curing and RDI of 20%. Example-6 750g of iron ore fines, lOOg mill-scale, 50g flue-dust and lOOg coke fines were mixed thoroughly and then 50g of pyrophilite (5% by weight of charge), 50g of cement (5% by weight of charge) were added and again mixed. 30g of activated sodium silicate (3% by weight of charge) was added to the above charge mix and mixed thoroughly by adding suitable amount of water. Composite briquettes of cylindrical shape were made using this mix in a briquetting machine applying a vertical compression load of 400 kg/cm2. The cylindrical briquettes obtained were of the size of 28 mm diameter and of 30 mm height. The briquettes were subjected to natural curing for 5 days. The briquettes had green strength of 4 drops, cold crushing strength of 265 kg/briquette after curing and RDI of 15%. Example-7 750g of iron ore fines, lOOg mill-scale, 50g flue-dust and lOOg coke fines were mixed thoroughly and then 50g of pyrophilite (5% by weight of charge), 50g of cement (5% by weight of charge) were added and again mixed. 70g of activated sodium silicate (7% by weight of charge) was added to the above charge mix and mixed thoroughly by adding suitable amount of water. Composite briquettes of cylindrical shape were made using this mix in a briquetting machine applying a vertical compression load of 400 kg/cm2. The cylindrical briquettes obtained were of the size of 28 mm diameter and of 30 mm height. The briquettes were subjected to natural curing for 5 days. The briquettes had green strength of 5 drops, cold crushing strength of 350 kg/briquette after curing and RD! of 9%. Example-8 750g of iron ore fines, lOOg mill-scale, 50g flue-dust and lOOg coke fines were mixed thoroughly and then 50g of pyrophilite (5% by weight of charge), 50g of ground granulated slag (5% by weight of charge) were added and again mixed. 30g of activated sodium silicate (3% by weight of charge) was added to the above charge mix and mixed thoroughly by adding suitable amount of water. Composite briquettes of cylindrical shape were made using this mix in a briquetting machine applying a vertical compression load of 400 kg/cm2. The cylindrical briquettes obtained were of the size of 28 mm diameter and of 30 mm height. The briquettes were subjected to natural curing for 5 days. The briquettes had green strength of 4 drops, cold crushing strength of 330 kg/briquette after curing and RDI of 7.5 kg of iron ore fines, 1 kg of mill-scale, 0.5 kg of flue dust and 1 kg of coke fines ere mixed thoroughly and then 0.7 kg of pyrophilite (7% by weight of charge), 0.7 kg of cement (7% by weight of charge) were added and again mixed. 0.5 kg of activated sodium silicate (5% by weight of charge) was added to the above charge mix and mixed thoroughly by adding suitable amount of water. Composite briquettes of elliptical shape were made using this mix in a briquetting roll press by applying a load of 150 kg/cm2. The elliptical briquettes obtained were of 50 mm x 35 mm x 15 mm size. The briquettes were subjected to natural curing for 5 days. The briquettes had green strength of 5 drops, cold crushing strength of 140 kg/briquette after curing and RDI of 22%. Example-10 7.5 kg of iron ore fines, 1 kg of mill-scale, 0.5 kg of flue dust and 1 kg of coke fines were mixed thoroughly and then 0.7 kg of pyrophilite (7% by weight of charge), 0.7 kg of ground granulated slag (7% by weight of charge) were added and again mixed. 0.5 kg of activated sodium silicate (5% by weight of charge) was added to the above charge mix and mixed thoroughly by adding suitable amount of water. Composite briquettes of elliptical shape were made using this mix in a briquetting roll press by applying a load of 150 kg/cm2. The elliptical briquettes obtained were of 50 mm x 35 mm x 15 mm size. The briquettes were subjected to natural curing for 5 days. The briquettes had green strength of 4 drops, cold crushing strength of 188 kg/briquette after curing and RDI of 21%. Example-11 7.5 kg of iron ore fines, 1 kg of mill-scale, 0.5 kg of flue dust and 1 kg of coke fines were mixed thoroughly and then 0.5 kg of pyrophite (5% by weight of charge), 0.5 kg of cement (5% by weight of charge) were added and again mixed. 0.3 kg of activated sodium silicate (3% by weight of charge) was added to the above charge mix and mixed thoroughly by adding suitable amount of water. Composite briquettes of elliptical shape were made using this mix in a briquetting roll press by applying a load of 150 kg/cm2. The elliptical briquettes obtained were of 50 mm x 35 mm x 15 mm size. The briquettes were subjected to natural curing for 5 days. The briquettes had green strength of 4 drops, cold crushing strength of 145 kg/briquette after curing and RDI of 19%. Example-12 7.5 kg of iron ore fines, 1 kg of mill-scale, 0.5 kg of flue dust and 1 kg of coke fines were mixed thoroughly and then 0.5 kg of pyrophite (5% by weight of charge), 0.5 kg of ground granulated slag (5% by weight of charge) were added and again mixed. 0.3 kg of activated sodium silicate (3% by weight of charge) was added to the above charge mix and mixed thoroughly by adding suitable amount of water. Composite briquettes of elliptical shape were made using this mix in a briquetting roll press by applying a load of 150 kg/cm2. The elliptical briquettes obtained were of 50 mm x 35 mm x 15 mm size. The briquettes were subjected to natural curing for 5 days. The briquettes had green strength of 4 drops, cold crushing strength of 130 kg/briquette after curing and RDI of 25%. 14 The main advantages of the process of the present invention are : 1. Manufacture of composite briquettes by cold briquetting of iron and steel plant wastes, such as iron ore fines, flue dust, mill scale, coke fines, which are otherwise unutilised and are an environmental hazard. 2. The iron and steel plant wastes such as iron ore fines, flue dust, mill scale, coke fines can be cold briquetted and these briquettes are suitable for charging into blast furnace for further processing. 3. The process wherein the briquettes of various shapes such as cylindrical and elliptical briquettes have sufficient green strength, cold crushing strength and RDI for charging into the blast furnace. 4. The composite briquettes of iron and steel plant wastes manufactured by cold briquetting have green strength (above 4 drops), cold-crushing strength of above 250 kg/briquette for cylindrical briquettes and above 130 kg/briquette for elliptical briquettes and RDI of below 30%. 5. The process is cost effective. We claim: 1. A process for the manufacture of composite briquettes of iron and steel plant wastes by cold briquetting, which comprises the steps of: i) dry mixing of iron and steel plant wastes such as iron ore fines, flue dust, mill scale, coke fines; ii) adding a binder matrix to the dry mix of iron and steel plant wastes obtained in step (i), and subjecting it to thorough mixing, characterized in that the said binder matrix essentially consisting of inorganic binders such as pyrophilite, cement / ground granulated slag of steel plant and activated commercial grade sodium silicate (Na2O : SiO2≈1:1) and are used in a combination on the basis of wt % of charge materials such as: pyrophilite in the range of 5 - 10%, cement/granulated slag of -100 µ size in the range of 5 - 10% and activated commercial grade sodium silicate (Na2O :SiO2 ≈1:1) in the range of 3 - 7%; iii) adding water to the above said resultant dry mix, obtained in step (ii), and subjecting it to further mixing to obtain a charge mixture dough; iv) cold briquetting the resultant charge mixture dough obtained in step (iii), by known method in a briquetting machine or briquetting roll press by applying a vertical compression load of the order of 350-450 kg/cm2 and 100-200 kg/cm2 to obtain the cylindrical and elliptical briquettes, respectively, and curing the such briquettes so obtained, under natural conditions for a period of 3-6 days. 2. A process as claimed in claim 1, wherein the steel plant wastes used are in a combination of iron ore fines of - 6 mm size, flue dust of - 3 mm size, mill scale of - 6 mm size and coke fines of - 6 mm size. 3. A process as claimed in claim 1, wherein the vertical compression load used in briquetting machine for making cylindrical briquettes is preferably 400 kg/cm2 4. A process as claimed in claim 1, wherein the vertical compression load used in briquetting roll press for making elliptical briquettes is preferably 150 kg/cm2 5. A process for the manufacture of composite briquettes of iron and steel plant wastes by cold briquetting, substantially as herein described with reference to the examples.

Documents:

1223-DEL-2002-Abstract-(30-07-2008).pdf

1223-del-2002-abstract.pdf

1223-DEL-2002-Claims-(30-07-2008).pdf

1223-del-2002-claims.pdf

1223-DEL-2002-Correspondence-Others-(10-09-2008).pdf

1223-del-2002-correspondence-others.pdf

1223-del-2002-correspondence-po.pdf

1223-del-2002-description (complete)-10-09-2008.pdf

1223-del-2002-description (complete).pdf

1223-del-2002-form-1.pdf

1223-del-2002-form-18.pdf

1223-DEL-2002-Form-2-(10-09-2008).pdf

1223-del-2002-form-2.pdf

1223-del-2002-form-3.pdf