Claims:We Claim:

1. CDQ fine enriched agglomerate composition comprising:

metallurgical/mineral/slag waste in amounts of 80-85 wt% ;
CDQ fines in amounts of 10-12 wt% ;
silica based activated mineral binders in amounts of 2-3 wt%; and

moisture in amounts of 10-12 wt%.
2. CDQ fine enriched agglomerate composition as claimed in claim 1 in the form of micro-pellets /micro granules wherein said silica based activated mineral binders comprise 50-55% SiO2, 16-18% Al2O3, 13-16% Fe2O3, 1-3% CaO, 2.5-3.5% MgO, 2-3 % Na2O, and 0.1-0.5% K2O by wt.

3. CDQ fine enriched agglomerate composition as claimed in anyone of claims 1 or 2 wherein said silica based activated mineral binders has cation exchange capacity and is a powdery material (85-90% passing through 200-230 mesh BSS sieve) having minimum surface area of 300-310 m2/kg (Blaine number).

4. CDQ fine enriched agglomerate composition as claimed in anyone of claims 1 to 3, having cold strength of the micro granules in the range of 0.60 to 1.7 kg/pellet and the drop number in the range of 8-35 drops from 0 to 24 hrs of curing.

5. CDQ fine enriched agglomerate composition as claimed in anyone of claims 1 to 4, wherein said metallurgical/mineral/slag waste include selectively blast furnace dust and sludge, basic oxygen furnace (BOF) dust and slag, bag filter dust from iron and steel making process, limestone and dolomite fines.
6. Silica based activated mineral binder comprising 50-55% SiO2, 16-18% Al2O3, 13-16% Fe2O3, 1-3% CaO, 2.5-3.5% MgO, 2-3 % Na2O, and 0.1-0.5% K2O by wt., preferably having cation exchange capacity and powdery material (85-90% passing through 200-230 mesh BSS sieve) having minimum surface area of 300-310 m2/kg (Blaine number).

7. A process for manufacture of CDQ fine enriched agglomerate composition comprising:
(a) mixing of 80-85 wt% of metallurgical/mineral/slag waste with 10-12 wt% CDQ fines, 2-3 wt% silica based activated mineral binders and 4-6 wt% moisture to form a homogenized mix .
(b) pelletizing the homogenized mix to form an agglomerated mass; and
(c) Curing of agglomerated mass by exposing to atmospheric air for 24 - 48 hours.

8. A process as claimed in claim 7 carried out following the sequence of addition of raw materials as follows;

i- Corex/DRI/BOF Sludge, ii- Coke dry quenched fines, iii- BOF slag, iv- Silica based activated mineral binder, v- Lime and dolomite fines, vi -BOF/BF dust, and vii –Moisture;
such that the sludge binds the coke dry quenched fines and the binder used thereafter strengthens the sludge along with CDQ fines, with said agglomerated mass obtained in the form or pellets or micro-granules.
9. A process as claimed in anyone of claims 7 to 8, wherein the granulometry size of the agglomerate is about
-25 µ -25µ +45µ +45µ -7 5µ +75µ -150µ +150µ -1mm +1mm -3mm
25-30% 30-45% 10-15% 14-16 % 16-18% 5-6%
10. A process as claimed in anyone of claims 7 to 9 wherein in step (b), the dry mixture is fed to a drum granulator if the agglomerated mass is desired to be obtained in the form pellets or micro-granules.

Dated this the 5th day of February, 2016
Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)

, Description:FIELD OF THE INVENTION

The present invention relates to coke dry quenched (CDQ) fine enriched agglomerate composition and a process for its manufacture including micro-pellets or micro-granules of CDQ fines, ferrous ores or mineral fines by using activated silica based mineral binder for metallurgical application. More particularly, the present invention is directed to provide CDQ fines based agglomerate or micro-pellets for efficient usage of carbon values along with process waste materials for utilization in steel plant process produced by a process involving CDQ fines along with various iron and steel making process waste (i.e., dust and sludges) along with silica based activated mineral binder in selective proportions. The invention is related to a method for recycling of CDQ fines generated from coke making along with iron-bearing dusts, sludge and iron making slag back into a micro-agglomeration process, and more particularly, it relates to a method for recycling of iron-bearing waste materials, slag and CDQ fines back into a sintering process which contributes fuel, iron and flux values in sinter making.

BACKGROUND OF THE INVENTION

Coke is one of the major raw materials for Blast Furnace (BF) and the quality of coke is one of the significant factors affecting BF performance with respect to the production of hot metal and coke rate. It is a well known fact that consistency of coke quality is also a requirement for higher productivity and smooth functioning of BF.

A significant amount of coke fines is generated during quenching (i.e., rapid cooling) of coke by coke dry quenching (CDQ) process in coke making. This dust, if not evacuated in-time can cause severe maintenance problems and environmental concerns. These fines cannot be directly used in as generated condition in metallurgical processes because of very fine size.

It is also well known in the art of iron and steel making that iron-bearing dust and sludges, generated by Blast furnace, Corex process, Steelmaking furnaces and fines generated in coke ovens are valuable waste materials suitable for recycling back into iron making process. Such waste materials contain iron bearing materials in significant proportion (up to 35-45% by weight) and are very essential to recover, recycle and reuse as feed to iron making process for natural resource conservation and environment protection. However, in the case of wet sludge, and especially in the case of wet BOF scrubber sludge, Corex sludge, high moisture content makes the wet sludge very difficult to handle in a recycling stream.

Japanese Patent No. 8135731 dated 8th April 1981 (C1. C22 B1/ 14) by Jpn. Kokai Tokkyo Koho (Sumitomo Metal Ind. Ltd.) describes production of cold iron ore briquettes using cement (OPC) by hardening at 90 °C for 24 hours and drying at 90°C for 1 hour to get crushing strength of the order of 256 kg. The present invention differs in the sense that the raw mix, binder and curing cycle are completely different.

Furui Takeo et al. (Nippon Steel Corp.), Japan Kokai 7711103 (C1. C22B1/14), 27th Jan. 1977 Patent discloses the use of cement clinker and limestone mixture as binder which is mixed with iron ore material by grinding for production of non-sintered pellets. However, in present invention, silica based activated mineral binder is used.

US Patent No. 5496392; Simms et al. is directed to a method of recycling industrial waste. The recycle iron bearing material is either pelletized or formed into briquettes. The patent mentions that such briquettes are charged cold into steel making furnace and heated to temperature. The patent is absent of any teaching that would suggest charging such iron bearing revert into other agglomeration process also the binder and waste mix is different from that of present invention.

US Patent Nos. 5114474, 4725307, and 4711662 outline mixing of wet sludge and dust with molten slag to produce reverts. The mixture is crushed for recycling after the slag cools and solidifies.

Thus none of the prior arts disclosed use of CDQ fines and recycling the same along with iron bearing wastes back into a stage of iron and steel making processes for effective recovery with economic benefit. There has been thus a need in the existing art for recycling of CDQ fines generated from coke making along with iron-bearing dusts, sludge and iron making slag back into a process for production of micro-pellets or micro-granulations for cost effective utilization in iron and steel making process favouring preservation of scarce iron rich ores on one hand while also ensuring effective utilization of such micro-pellets in sintering process which contributes fuel, iron and flux values in sinter making.

OBJECTS OF THE INVENTION

The basic object of the present invention is directed to provide CDQ fine enriched agglomerate composition in the form of micro-pellets or micro-granules from iron bearing waste materials, CDQ fines, BOF slag, lime and dolo fines using silica based activated mineral binders for metallurgical applications and a process for micro-pelletization/granulation thereof.

A further object of the present invention is directed to a process of producing CDQ fine enriched agglomerate composition or micropellets/micro granules by recycling of CDQ fines along with iron bearing waste materials, BOF slag, lime and dolo fines in selective proportions wherein silica based activated mineral is used as binders to obtain desired strength and other properties of the micro-pellets/granules suitable for application in sintering process or other metallurgical applications.

A still further object of the present invention is directed to a process of micro- granulation from iron bearing waste materials, CDQ fines, BOF slag, lime and dolo fines using silica based activated mineral binders wherein inherent moisture content in raw materials of around 4-6 % can be effectively accommodated by the process and additional moisture (4-6%) is added in Eirich mixture depending on the inherent moisture in dust, sludge and CDQ fines.

A still further object of the present invention is directed to a process of producing CDQ fine enriched agglomerate composition or micro granules from iron bearing waste materials, CDQ fines, BOF slag, lime and dolo fines using silica based activated mineral binders wherein water absorption capacity of the binder causes the quick absorption of water at lower binder dosage.

A still further object of the present invention is directed to a process of micro pelletization/granulation from iron bearing waste materials, CDQ fines, BOF slag, lime and dolo fines using silica based activated mineral binders wherein cation exchange capacity of the binder makes it prone to attract towards the rest of the mix which is predominantly anionic facilitating uniform and homogeneous mixing.

A still further object of the present invention is directed to a process of micro-granulation from iron bearing waste materials, CDQ fines, BOF slag, lime and dolo fines using silica based activated mineral binders wherein hydration of the binder stretched the voids (tetrahedral and octahedral) which results in excessive swelling leading multifold increased surface area through shearing mechanism.

A still further object of the present invention is directed to a process of micro granulation from iron bearing waste materials, CDQ fines, BOF slag, lime and dolo fines using silica based activated mineral binders wherein in order to achieve desired strength of the micro pellets, CDQ fines are fed over the wet sludge to create a thin uniform layer which in turn gets covered with other process waste feed and the binder helps in making the inter-particles (CDQ fines and other wastes) bondage stronger.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to CDQ fine enriched agglomerate composition comprising:
metallurgical/mineral/slag waste in amounts of 80-85 wt% ;
CDQ fines in amounts of 10-12 wt%, ;
silica based activated mineral binders in amounts of 2-3 wt%; and
moisture in amounts of 10-12 wt%.

A further aspect of the present invention is directed to said CDQ fine enriched agglomerate composition in the form of micro-pellets /micro granules wherein said silica based activated mineral binders comprise 50-55% SiO2, 16-18% Al2O3, 13-16% Fe2O3, 1-3% CaO, 2.5-3.5% MgO, 2-3 % Na2O, and 0.1-0.5% K2O by wt.

A still further aspect of the present invention is directed to said CDQ fine enriched agglomerate composition wherein said silica based activated mineral binders has cation exchange capacity and is a powdery material (85-90% passing through 200-230 mesh BSS sieve) having minimum surface area of 300-310 m2/kg (Blaine number).

Another aspect of the present invention is directed to said CDQ fine enriched agglomerate composition having cold strength of the micro granules in the range of 0.60 to 1.7 kg/pellet and the drop number in the range of 8-35 drops from 0 to 24 hrs of curing.

Yet another aspect of the present invention is directed to said CDQ fine enriched agglomerate composition wherein said metallurgical/mineral/slag waste include selectively blast furnace dust and sludge, basic oxygen furnace (BOF) dust and slag, bag filter dust from iron and steel making process, limestone and dolomite fines.

A further aspect of the present invention is directed to Silica based activated mineral binder comprising 50-55% SiO2, 16-18% Al2O3, 13-16% Fe2O3, 1-3% CaO, 2.5-3.5% MgO, 2-3 % Na2O, and 0.1-0.5% K2O by wt., preferably having cation exchange capacity and powdery material (85-90% passing through 200-230 mesh BSS sieve) having minimum surface area of 300-310 m2/kg (Blaine number).

A still further aspect of the present invention is directed to a process for manufacture of CDQ fine enriched agglomerate composition comprising:

(a) mixing of 80-85 wt% of metallurgical/mineral/slag waste with 10-12 wt% CDQ fines, 2-3 wt% silica based activated mineral binders and 4-6 wt% moisture to form a homogenized mix.

(b) pelletizing the homogenized mix or form an agglomerated mass; and

(c) Curing of agglomerated mass by exposing to atmospheric air for 24 - 48 hours.

A still further aspect of the present invention is directed to said process carried out following the sequence of addition of raw materials as follows;
i- Corex/DRI/BOF Sludge, ii- Coke dry quenched fines, iii- BOF slag, iv- Silica based activated mineral binder, v- Lime and dolomite fines, vi -BOF/BF dust, and vii –Moisture;
such that the sludge binds the coke dry quenched fines and the binder used thereafter strengthens the sludge along with CDQ fines, with said agglomerated mass obtained in the form or pellets or micro-granules.

Another aspect of the present invention is directed to said process wherein the granulometry size of the agglomerate is about
-25 µ -25µ +45µ +45µ -7 5µ +75µ -150µ +150µ -1mm +1mm -3mm
25-30% 30-45% 10-15% 14-16 % 16-18% 5-6%

Yet another aspect of the present invention is directed to said process wherein in step (b), the dry mixture is fed to a drum granulator if the agglomerated mass is desired to be obtained in the form pellets or micro-granules.

The above and other objects and advantages of the present invention are described hereunder with reference to the following accompanying non limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPNAYING DRAWINGS

Fig.1: a schematic diagram of the process flow for micro-pelltization according to the present invention indicating the sequence of raw material addition.

Fig.2a: represents graphically the compression strength of micropellets produced according to the present invention at different % of CDQ fines and silica based activated mineral binder at 0 hours of curing.

Fig.2b: represents graphically the compression strength of micropellets produced according to the present invention at different % of CDQ fines and silica based activated mineral binder after 24 hours of curing.

Fig.3a: represents graphically the Drop number of micropellets at different percentage of CDQ fines and silica based activated mineral binder at 0 hours.

Fig.3b: represents graphically the Drop number of micro pellets at different percentage of CDQ fines and Silica based activated mineral binder after 24 hours.

Fig.4: illustrate the result of EPMA analysis of micro granules/pellets (Electron Probe Micro-analyzer) JXA-8230 wherein the photomicrographs of micropellets along with elemental mapping of carbon in micro-granules are presented.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

The present invention deals with CDQ fine enriched agglomerate composition and a process of producing such agglomerate including micro-pelletization of CDQ fines along with various iron and steel making process waste (i.e., dust and sludges) along with silica based activated mineral binder. The said process consists of mixing of 80-85 wt% of metallurgical/mineral/slag waste with 10-12 wt% CDQ fines, 2-3 wt% silica based activated mineral binders and 4-6 wt% moisture to form a homogenized mix, micro pelletizing it to form an agglomerated mass, and curing the agglomerated mass for 1 - 2 days by exposing to atmospheric air.

Accompanying Figure 1 shows the process of micro-pelletization and the various equipments used in the process. Dust and sludge contain appreciable amount of carbon and iron. However, the CDQ fines contain high carbon and low volatile matters with high calorific value. The preferred embodiment according to the present invention as illustrated in Figure 1 shows micro-pelletization process wherein bunker-1 contains steel & iron making sludge and bunker-2 holds CDQ fines. Bunker-3 contains basic oxygen steel making slag. Lime & dolo fines, Bag filter dust and Silica based activated mineral binder are stored in bunker 4, 5 and 6 respectively. The moisture content in raw materials is around 4-6 % and additional moisture (4-6%) is added in Eirich mixture depending on the inherent moisture in dust, sludge and CDQ fines.

Silica based activated mineral binder and water (moisture) is the ingredients mixed with different kinds of metallurgical and mineral fines in formulation of mixtures for manufacture of micro-granules. The silica based activated mineral binder is a powdery material (85-90% passing through 200-230 mesh BSS sieve) having minimum surface area of 300-310 m2/kg (Blaine number).

The cation exchange capacity of the binder makes is prone to attract towards the rest of the mix which is predominantly anionic. This phenomenon helps in uniform and homogeneous mixing. The water absorption capacity of the binder causes the quick absorption of water at lower binder dosage. The hydration of the binder stretched the voids (tetrahedral and octahedral) which results in excessive swelling leading multifold increased surface area through shearing mechanism.

Depending on the type of iron bearing waste materials, CDQ fines, moisture and other ingredients are mixed to make homogenized mixtures in dry or semi wet condition. CDQ fines addition alters the strength of the micro-pellets due to poor wettability and stickiness to binder as well as process waste materials. To overcome this problem, the CDQ fines are fed over the wet sludge to create a thin uniform layer which in turn gets covered with other process waste feed. The binder helps in making the inter-particles (CDQ fines and other wastes) bondage stronger.

Dry or semi wet mixture consisting of particle size up to -25 micron to 3 mm is fed to the drum or disc granulator devices for manufacture of fine ball or micro-granules by adding required quantity of water. Balling time of the mixture is 4 to 6 minutes for manufacture of +0.15 to -6 mm diameter micro-pellets. The final moisture in micro-pelletization is maintained in the range of 10 - 12%.

Depending upon the feed constituents, composition and application, higher strength in the micropellets can be achieved using higher percentage of binder. Figures 2a, 2b and 3a, 3b show the effect of binder on micro-pellet’s strength and drop number. Silica based activated mineral binder plays a significant role to develop the cold strength by hydration in the agglomerated product. The binder composition is 50-55% SiO2, 16-18% Al2O3, 13-16% Fe2O3, 1-3% CaO, 2.5-3.5% MgO, 2-3 % Na2O, and 0.1-0.5% K2O by weight. Figure 4 shows the elemental carbon mapping of micropellets which reveals that the CDQ fines is uniformly distributed throughout the matrix of micro-granules.

Experimental Results:

The invention of the present process has been established by conducting series of laboratory scale experiments to produce micro-granules from different combination of CDQ fines, Fe-bearing materials, mineral fines, blast furnace dust and sludge, basic oxygen furnace (BOF) dust and slag, Corex and DRI sludge, lime & dolo fines with varying percentage of silica based activated mineral binder.

The agglomerated products have been examined to evaluate the physical and metallurgical properties as presented in following table I suitable for various applications.

Table I:

Binder, % CDQ Fines, % GCS, kg/pellet Drop No. Moisture, %
Curing,Hrs 0 24 0 24 0 24
3 6 1.4 1.7 35 32 10.5 9.5
8 1.2 1.4 23 20 10.2 9.2
10 1.1 1.3 22 18 10.3 9.1
12 1.1 1.2 22 18 10.4 9
2.5 6 1.1 1.4 22 20 11.4 10.1
8 1.2 1.3 21 18 11.3 10.1
10 1 1.2 20 19 11.2 10.2
12 0.8 0.9 18 17 11.1 10
2.3 6 1 1.2 20 19 11.5 10.1
8 0.9 1.1 19 18 11.4 10.1
10 0.9 1.1 18 17 11.4 10
12 0.9 1 17 16 11.1 10
2 6 0.9 1 14 11 11.8 10
8 0.8 1 13 10 11.7 10.1
10 0.7 0.9 11 9 11.6 10.2
12 0.7 0.8 11 8 11.6 10.2

It is thus possible by way of the present invention to provide micro-pellets/micro-granules from iron bearing waste materials, CDQ fines, BOF slag, lime and dolo fines using silica based activated mineral binders for metallurgical applications and a process for micro-pelletization/granulation thereof. The invention is related to a method for recycling of CDQ fines generated from coke making along with iron-bearing dusts, sludge and iron making slag back into a micro-pelletization process involving the steps of mixing, pelletizing and curing, directed to recycling of iron-bearing waste materials, slag and CDQ fines back into a sintering process which contributes fuel, iron and flux values in sinter making.