CLIAMS:We Claim:

1. A process for producing iron ore pellets involving iron oxide and carbon comprising:

i) providing iron ore fines with other additives mix in combination with Corex sludge as a source for carbon and iron for pellets;and
ii) subjecting the thus sourced pelletization ingredients to various steps of pelletization including
(a) providing green mix charge in balling disc to produce green pellets of size 8 to 16 mm in diameter;
(b) feeding the green mix pellets to indurating machine for indurating at a temperature range of 1250 to 1350 ºC to achieve required strength properties;
(c) transferring the cooled pellets after separation of hearth layer to stockpile for temporary storing or directly to furnace(BF, Corex or DRI producing unit) for consumption.

2. A process as claimed in claim 1 wherein said Corex sludge is in the form of slurry with solid : water ratio of 30: 70.

3. A process as claimed in anyone of claims 1 or 2 wherein said Corex sludge contains around 30-40 % Carbon with 28-43 % iron oxides.

4. A process as claimed in anyone of claims 1 to 3 wherein said Corex sludge comprises:

Elements/compound wt%
C 30 -40
S 0.50 - 1.50
P 0.10 - 0.22
SiO2 8-11
Fe(T) 20 - 30
Al2O3 4-7
CaO 5-8
MgO 2.5 - 4.5
TiO2 0.15 - 0.32
Na2O 0.01 -0.12
K2O 0.20 - 0.75
ZnO 0.15 - 0.45

5. A process as claimed in anyone of claims 1 to 4 wherein the said ingredients are seelctively used such that green pellets comprise an average iron content between 58 to 62 % and carbon content in the range of 0.9 to 1.3 % wherein the majority of the carbon content is driven out of said Corex sludge.

6. A process as claimed in anyone of claims 1 to 5 wherein the concentration of corex sludge is varied to vary the desired quality of the pellets.

7. A process as claimed in claim 6 wherein the concentration of the Corex sludge is varied in the range of 20 to 60 % of total slurry used ( 0.41-1.24% of total raw mix charge) which can suitably vary the pellet characteristics including (a) degree of reduction for pellets % (b) disintegration index (-6.3 mm) % (c ) porosity of pellets % and (d) Abrasion Index (0.5 mm) %.

8. A process as claimed in anyone of claims 1 to 7 comprising involving ageing inhibitors sourced from Corex sludge preferably selected from metal oxides including alumina, fine silica and other metal oxides of potassium, sodium and calcium.

9. A process as claimed in anyone of claims 1 to 8 wherein the Corex slurry containing water is involved as the substantial water content source for the said pelletization process.

10. A process as claimed in anyone of claims 1 to 9 wherein said corex sludge with sticky characteristic provides for effective utilization of Iron Ore fines for due adhering to the pellets volume or other iron ore agglomerate.

11. A process as claimed in anyone of claims 1 to 10 wherein the net energy consumption is substantially less than the conventional pellet making.
12. Iron ore pellets comprising iron content in the range of 58 to 62 % while the carbon content in the range of 0.9 to 1.3% wherein the majority of carbon content around 1 % of carbon may be sourced from corex sludge along with the rise in iron content by 0.6 to 1.0 %, depending on the chemical composition of sludge (Fe content in sludge varies from 20 – 30%).

13. Iron ore pellets as claimed in claims 12 wherein said pellets produced have enhanced operational properties including degree of reduction in the range of 94 to 97 % disintegration index in the range of 20 to 25, porosity in the range of 23 to 25 and abrasion index in the range of 16 to 22 %.

Dated this the 13th day of October, 2014
Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)

,TagSPECI:FIELD OF THE INVENTION

The present invention relates to a process for producing iron ore pellets by utilization of spent carbon and iron oxides available in sludge obtained as waste from Corex iron making process. More particularly, the present invention is directed to a method of reclaiming carbon content from metallurgical furnace sludge and utilizing the same in manufacturing of iron ore agglomerates/pellets. The waste generated during Corex iron making process containing high value of carbon of up to 300-400 kg/ton of sludge produced during the process and iron content of 200-300 kg/ton of sludge produced and hence it is prudent to use sludge in agglomeration process. The said carbon content serves as a component of fuel which otherwise is supplied from outside whereas the iron content increases the iron value of pellets.

BACKGROUND OF THE INVENTION

Pellet making is an agglomeration technique used industry wide for supplying in-situ raw material to the metallurgical furnaces such as Corex, Blast Furnace, Midrex, Finex, ITmk3, FINMET® and Circored® etc. These pellets essentially constitute of iron ore, fuel (generally a carbon bearing material), binder, flux and moisture in a stipulated ratio.

Corex, a commercially proven smelting reduction process, is an alternative route for hot metal production with plants operating in South Africa, South Korea, India and China. The process differs from the conventional blast furnace route as non-coking coal can be directly used for iron ore reduction and melting process, eliminating the need for coke oven plants. The use of lump ore or pellets also dispenses with the need for sintering plants. The Corex process is a two-stage process. In the first stage, the iron oxide is reduced in a reduction-shaft and in second stage; the reduced iron oxide is melted in the melter-gasifier using the energy generated from the gasification of coal. The reducing gas produced in this stage is used in the shaft furnace. Viewing the process from the coal route perspective, non-metallurgical coal is directly charged into the melter-gasifier via a lock-hopper system. Due to the high temperatures predominating in the dome of the melter-gasifier [in excess of 10000C], a portion of the hydrocarbons released from the coal during devolatilization are immediately dissociated to carbon monoxide and hydrogen. Combustion with oxygen injected into the melter-gasifier results in the generation of a highly efficient reducing gas.

The reducing gas exiting from the melter-gasifier consists mainly of CO and H2 laden with fine coal, ash and iron dust. This dust is largely removed from the gas stream in a hot gas cyclone and is then recycled to the process as it contains carbon and iron. The exhaust gas of scrubber is used by other users and particulate which are settled at bottom are sent to settling pond. The top gases from reduction shaft are sent to another scrubber and the settled particulates of this scrubber also go to settling pond. The product of this settling pond is known as Corex sludge.

It is thus well known that the waste sludge generated during Corex iron making process, contain high value of carbon and iron content. This waste is thus having a potential to serves as an appropriate substitute of carbon admixed from outside during Pellet making. Further, it can also enhance the iron content in the pellets.

There has been thus a need in the art to developing a process for utilization of Corex sludge in pellet making for recovery of iron value and carbon source. Present invention pertains to a novel process of Pellet making wherein it utilizes the spent carbon of Corex furnace and enhance iron content in pellets. The present invention describes an advantageous and effective streamlined process for the production of iron ore pellets by utilizing the discarded Corex Sludge.

OBJECTS OF THE INVENTION

The basic object of the present invention is thus directed to provide a process for producing iron ore pellets involving reclaiming carbon content from metallurgical furnace sludge in pellet making and also enhancing iron value by utilizing the carbon content present in Corex sludge as an indispensible component of pellets, which otherwise would be discarded under the conventional process of iron making.

A further object of the present invention is directed to provide a process for producing iron ore pellets utilizing Corex sludge as carbon source and also to enhance iron value in pellets wherein the pellets produced would have the required quality/properties such as degree of reduction, disintegration index, porosity and abrasion index etc. for advantageous use in blast furnace, corex and DRI producing units.

A still further object of the present invention is directed to provide a process for producing iron ore pellets utilizing Corex sludge as carbon source and also to enhance iron value in pellets wherein use of fresh water in pellet green mix making would be substantially cut down as a major chunk of the moisture content comes from the sludge utilized.

A still further object of the present invention is directed to provide a process for producing iron ore pellets utilizing Corex sludge as carbon source and enhancing iron value in pellets wherein sticky characteristic of Corex sludge used favour use of Iron Ore fines become easier as these fines are not dragged by any of the carrier such as wind and fines adhered to the pellets volume or other iron ore agglomerate.

A still further object of the present invention is directed to provide a process for producing iron ore pellets utilizing Corex sludge as carbon source and enhancing iron value in pellets wherein said sludge containing various metal oxides such as alumina, fine silica and other metals oxides of potassium, sodium and calcium, which act as aging inhibitor for the pellets as a result of which the life of the pallets is increased.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is thus directed to a process for producing iron ore pellets involving iron oxide and carbon comprising:

i) providing iron ore fines with other additives mix in combination with Corex sludge as a source for carbon and iron for pellets; and
ii) subjecting the thus sourced pelletization ingredients to various steps of pelletization including
(a) Providing green mix charge in balling disc to produce green pellets of size 8 to 16 mm in diameter;
(b) Feeding the green mix pellets to indurating machine for indurating at a temperature range of 1250 to 1350 ºC to achieve required strength properties;
(c) Transferring the cooled pellets after separation of hearth layer to stockpile for temporary storing or directly to furnace (BF, Corex or DRI producing unit) for consumption.

A further aspect of the present invention is directed to said process wherein said Corex sludge is in the form of slurry with solid:water ratio of 30:70.

A still further aspect of the present invention is directed to said process wherein said Corex sludge contains around 30-40 % Carbon with 28-43 % iron oxides.

Yet another aspect of the present invention is directed to said process wherein said Corex sludge comprises:

Elements/compound %
C 30 -40
S 0.50 - 1.50
P 0.10 - 0.22
SiO2 8-11
Fe(T) 20 - 30
Al2O3 4-7
CaO 5-8
MgO 2.5 - 4.5
TiO2 0.15 - 0.32
Na2O 0.01 -0.12
K2O 0.20 - 0.75
ZnO 0.15 - 0.45

A still further aspect of the present invention is directed to said process wherein the said ingredients are selectively used such that Green pellets comprise an average iron content between 58 to 62 % and carbon content in the range of 0.9 to 1.3 % wherein the majority of the carbon content is driven out of said Corex sludge.

A still further aspect of the present invention is directed to said process wherein the concentration of corex sludge is varied to vary the desired quality of the pellets.

A still further aspect of the present invention is directed to said process wherein the concentration of the Corex sludge is varied in the range of 20 to 60 % of total slurry used (0.41-1.24% of total raw mix charge) which can suitably vary the pellet characteristics including (a) degree of reduction for pellets % (b) disintegration index (- 6.3 mm) % (c ) porosity of pellets % and (d) Abrasion Index (0.5 mm) %.

According to an advantageous aspect of the present invention directed to said process comprising involving ageing inhibitors sourced from Corex sludge preferably selected from metal oxides including alumina, fine silica and other metal oxides of potassium, sodium and calcium.

A further aspect of the present invention is directed to said process wherein the Corex slurry containing water is involved as the substantial water content source for the said pelletization process.

A still further aspect of the present invention is directed to said process wherein said corex sludge with sticky characteristic provides for effective utilization of Iron Ore fines for due adhering to the pellets volume or other iron ore agglomerate.

A still further aspect of the present invention is directed to said process wherein the net energy consumption is substantially less than the conventional pellet making.

According to a further aspect of the present invention, the same is directed to iron ore pellets comprising iron content in the range of 58 to 62 % while the carbon content in the range of 0.9 to 1.3% wherein the majority of carbon content upto 1 % along with the iron content by 0.67 to 1.0% may be sourced from corex sludge depending on the excess carbon required after utilizing the carbon content of other raw mix used.

A still further aspect of the present invention is directed to iron ore pellets wherein said pellets produced have enhanced operational properties including degree of reduction in the range of 94 to 97 %; disintegration index in the range of 20 to 25 %; porosity in the range of 23 to 25 %; and abrasion index in the range of 16 to 22 %.

The objectives and advantages of the present invention are described hereunder in greater details with reference to the following accompanying non limiting illustrative drawings and example.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES

Figure 1: is the schematic flow chart showing the different steps in a conventional process of pellet making.

Figure 2: is the schematic flow chart showing the steps involved in the process of pellet making according to the present invention involving addition of Corex sludge slurry and thickener slurry as the input ingredient alongwith conventional inputs.

Figure 3(a)-(e): is the graphical presentation of properties of pellets such as (a)degree of reduction, (b)disintegration index, (c) abrasion index, (d)porosity, (e)Fe(T) etc observed in pellets produced according to the present invention using different concentration of Corex sludge.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURES

The present invention is directed to provide a process for pellet making utilizing the carbon source from waste obtained as Corex sludge wherein the net energy consumption is substantially less than the conventional pellet making and in addition the iron content in pellet product is also enhanced.

Accompanying Figure 1 is a schematic flow chart showing the different steps in a conventional process of pellet making. Conventional Pellet making is an agglomeration technique in which ingredients in desired particle size comprising iron ore, fuel (generally a carbon bearing material), binder, flux and moisture are provided in a stipulated ratio in a mixer. The green mix is then fed in a balling mill having balling discs to produce green pellets of desired size which are subjected to induration in an indurating machine at desired temperature to produce the pellets of desired characteristics suitable to feed the blast furnace, Corex and DRI producing units.

Accompanying Figure 2 is the schematic flow chart showing the steps involved in the process of pellet making according to the present invention involving addition of Corex sludge slurry and thickener slurry as the input ingredient alongwith conventional inputs.

In the process according to the present invention, the Corex sludge in the form of slurry with a solid/water ratio of 30:70 is sent to pellet plant for its effective utilization in green ball formation. In the present method Corex sludge is added in the mixer to produce green mix along with additives such as bentonite, flux, and coal/coke breeze as used in conventional pellet making, to produce green pellets. Since, Corex sludge contains carbon and iron oxides, the present invention is intended to utilize the carbon content present in Corex sludge as an indispensible component of pellets, which otherwise would be discarded under the conventional process of iron making. Coke breeze contains ~75% carbon with negligible moisture. Corex sludge contains around 30-40% Carbon with 28-43% iron oxides and balance the impurities. A typical composition of Corex sludge used for the purpose of the present invention is as shown in following Table 1.

Table 1: Analysis of Corex sludge used for the present invention, wt%

C S P SiO2 Fe(T) Al2O3 CaO MgO TiO2 Na2O K2O ZnO
31.17 1.28 0.14 10.17 28.68 5.93 5.38 2.83 0.28 0.12 0.51 0.41

The experiments conducted to produce pellets using Corex sludge slurry as an additive alongwith conventional inputs are illustrated with the following example:

Example:

According to an embodiment as per the process of the present invention, applicants take up to manufacture 1000 kg of pellet with its stipulated average iron content in between 58 to 62 % while keeping the carbon content in the range of 0.9 to 1.3% wherein the majority of carbon content will be extracted out of Corex sludge. The pellets are made using varying concentration of Corex sludge from 20 to 60 % of total slurry used ( 0.41-1.24% of total raw mix charge).

As evident from following Table 2, around 1 % of carbon may be sourced from corex sludge along with the rise in iron content by 0.6 to 1.0 %. Accordingly, 96.0 to 139.7 kg of corex slurry (solid to water ratio- 3: 7; Carbon: 31.17 %) that contains 28.9 to 41.7 kg of sludge and 67.4 to 97.3 kg of moisture is necessary to fulfill the requirement of 9.0 to 13.0 kg of carbon to produce 1000 kg of pellet that will further increase iron content in pellet by 0.83 to 1.20 % depending on the chemical composition of corex sludge. Requirement of the corex sludge sufficient enough for making an optimum quality of pellet is as under.

Table 2 : Carbon and iron oxides sourced from Corex sludge, %

Carbon content in Corex sludge 31.17
Iron content in Corex sludge 28.68
Coke needed for pellet making 1.30
Carbon needed for pellet making 0.98
Corex sludge needed 3.13
Corex slurry (Solid: Water::30:70) 10.43
Fe(T) increased due to addition of slurry 0.90

In addition to these constitutional benefits, the said Pellets also depict enhanced operational properties such as Degree of reduction, disintegration index, porosity and abrasion index etc. The improvement in the aforementioned properties are illustrated graphically in accompanying Figure 3(a) to (e) for the said embodiment, wherein pellet qualities with varying content of corex slurry from 0 to 60 % of total slurry used (i.e 0-1.24% of total raw mix charge) have been shown graphically in figures 3(a) to (d) and enhancement in Fe(T) content in pellet withincrease in corex slurry percentage has been shown in figure 3(e).

Thus according to the above example, following ingredients are provided as the raw mix charge in the mixer for producing 1000kg of green pellets:

Iron ore fines: 1074.45 kg or 93.51 wt%
Corex slurry having Corex sludge: 10.43 kg or 0.91 wt% of total raw mix and moisture: 7.30 kg or 70 wt% of corex sludge or 0.64 % of raw mixture;
Lime stone: 35.93 kg or 3.13 wt%;
Coal/coke breeze: 4.37 kg or 0.38 wt%;
Bentonite: 9.43 kg or 0.82 wt%.

In the above mix, the particle size of iron ore is 0 to 100 mesh size;
and particle size of other ingredients e.g. lime stone, coal/coke, bentonite is in the range of 0 to 200 mesh;

Following steps were implemented according to the proposed process of pellet making:
(i) Providing raw mix charge in mixer comprising:
Iron ore fines: 1074.45 kg or 93.51 wt%
Corex slurry having Corex sludge: 10.43 kg or 0.91 wt% of total raw mix and moisture: 7.30 kg or 70 wt% of corex sludge or 0.64 % of raw mixture;
Lime stone: 35.93 kg or 3.13 wt%;
Coal/coke breeze: 4.37 kg or 0.38 wt%;
Bentonite: 9.43 kg or 0.82 wt%.
Fresh process water : 7 to 9 wt%
(ii) Providing green mix charge in balling disc to produce green pellets of size 8 to 16 mm in diameter;
(iii) Feeding the green mix pellets to indurating machine for indurating at a temperature range of 1250 to 1350ºC to achieve required strength properties;
(iv) Transferring the cooled pellets after separation of hearth layer to stockpile for temporary storing or directly to furnace (BF , Corex or DRI producing unit) for consumption.

According to one aspect of the present invention , the same is directed to substantially cut down on fresh water use, as a substantial portion of the moisture content comes from the sludge utilized.

The present process heavily utilizes the discards of the Corex Iron making whereby the net energy consumption is substantially less than the conventional pellet making and in addition the process contribute to enhancement of iron content in pellet product. Importantly, due to the sticky characterstic of Corex Sludge used in present invention, utilization of Iron Ore fines become easier as fines are not dragged by any other carrier such as wind and iron fines adhered to the pellets volume or other iron ore agglomerate. Furthermore, the sludge also contains various metal oxides such as alumina, fine silica and other metals oxides of potassium, sodium and calcium which act as aging inhibitor for the pallets as a result of which the life of the pallets is increased.

It is thus possible by way of the present invention to provide a process for production of iron ore pellets utilizing the Corex sludge slurry favouring sourcing spent carbon upto 1.3 % from corex sludge while also enhancing and iron value of pellet product by about 1.20%, making the process energy efficient and economic while on one hand providing pellets with improved properties and enhanced iron value and on the other hand mitigating waste sludge handling and disposal problem.
We Claim:

1. A process for producing iron ore pellets involving iron oxide and carbon comprising:

i) providing iron ore fines with other additives mix in combination with Corex sludge as a source for carbon and iron for pellets;and
ii) subjecting the thus sourced pelletization ingredients to various steps of pelletization including
(a) providing green mix charge in balling disc to produce green pellets of size 8 to 16 mm in diameter;
(b) feeding the green mix pellets to indurating machine for indurating at a temperature range of 1250 to 1350 ºC to achieve required strength properties;
(c) transferring the cooled pellets after separation of hearth layer to stockpile for temporary storing or directly to furnace(BF, Corex or DRI producing unit) for consumption.

2. A process as claimed in claim 1 wherein said Corex sludge is in the form of slurry with solid : water ratio of 30: 70.

3. A process as claimed in anyone of claims 1 or 2 wherein said Corex sludge contains around 30-40 % Carbon with 28-43 % iron oxides.

4. A process as claimed in anyone of claims 1 to 3 wherein said Corex sludge comprises:

Elements/compound wt%
C 30 -40
S 0.50 - 1.50
P 0.10 - 0.22
SiO2 8-11
Fe(T) 20 - 30
Al2O3 4-7
CaO 5-8
MgO 2.5 - 4.5
TiO2 0.15 - 0.32
Na2O 0.01 -0.12
K2O 0.20 - 0.75
ZnO 0.15 - 0.45

5. A process as claimed in anyone of claims 1 to 4 wherein the said ingredients are seelctively used such that green pellets comprise an average iron content between 58 to 62 % and carbon content in the range of 0.9 to 1.3 % wherein the majority of the carbon content is driven out of said Corex sludge.

6. A process as claimed in anyone of claims 1 to 5 wherein the concentration of corex sludge is varied to vary the desired quality of the pellets.

7. A process as claimed in claim 6 wherein the concentration of the Corex sludge is varied in the range of 20 to 60 % of total slurry used ( 0.41-1.24% of total raw mix charge) which can suitably vary the pellet characteristics including (a) degree of reduction for pellets % (b) disintegration index (-6.3 mm) % (c ) porosity of pellets % and (d) Abrasion Index (0.5 mm) %.

8. A process as claimed in anyone of claims 1 to 7 comprising involving ageing inhibitors sourced from Corex sludge preferably selected from metal oxides including alumina, fine silica and other metal oxides of potassium, sodium and calcium.

9. A process as claimed in anyone of claims 1 to 8 wherein the Corex slurry containing water is involved as the substantial water content source for the said pelletization process.

10. A process as claimed in anyone of claims 1 to 9 wherein said corex sludge with sticky characteristic provides for effective utilization of Iron Ore fines for due adhering to the pellets volume or other iron ore agglomerate.

11. A process as claimed in anyone of claims 1 to 10 wherein the net energy consumption is substantially less than the conventional pellet making.
12. Iron ore pellets comprising iron content in the range of 58 to 62 % while the carbon content in the range of 0.9 to 1.3% wherein the majority of carbon content around 1 % of carbon may be sourced from corex sludge along with the rise in iron content by 0.6 to 1.0 %, depending on the chemical composition of sludge (Fe content in sludge varies from 20 – 30%).

13. Iron ore pellets as claimed in claims 12 wherein said pellets produced have enhanced operational properties including degree of reduction in the range of 94 to 97 % disintegration index in the range of 20 to 25, porosity in the range of 23 to 25 and abrasion index in the range of 16 to 22 %.

Dated this the 13th day of October, 2014
Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)

ABSTRACT

TITLE: A PROCESS FOR PRODUCING IRON ORE PELLETS INVOLVING IRON OXIDE AND CARBON SOURCED FROM COREX SLUDGE.

The present invention relates to a process for producing iron ore pellets by utilization of spent carbon and iron oxides available in Corex sludge obtained as waste from Corex iron making process. The process involves reclaiming carbon content from metallurgical furnace sludge and utilizing the same in manufacturing of iron ore agglomerates/pellets whereby carbon is sourced upto 1.3 % and iron value in pellets is enhanced by about 1.2%. The said carbon content serves as a component of fuel which otherwise is supplied from outside whereas the iron content increases the iron value of pellets, making the process energy efficient and economic while on one hand providing pellets with improved properties and enhanced iron value and on the other hand mitigating waste sludge handling and disposal problem.
(Figure 2)