Claims:We Claim:

1. A pre-reduced iron agglomerate suitable for feed as metallic iron source for iron and steel making comprising iron oxide waste sludge agglomerate comprising: 0.3-2.0% polymeric binder, 60-85% iron oxide waste sludge, 0.04%-1.7% zinc, 0.8%-2.5%.% alkali and 10-30% carbon, wherein the iron oxide waste sludge agglomerate is indurated in the temperature range of 1000 to 1400 0C to form the pre-reduced iron agglomerate comprising 35 to 75% metallic elemental iron, 0.001 to 0.10% of zinc and 0.01 to 0.11 % alkali.

2. The pre-reduced iron agglomerate as claimed in claim1 having melting characteristics including deformation temperature in the range of 1326 to 14030C and flow temperature in the range of 1403 to 15440C.

3. The pre-reduced iron agglomerate as claimed in anyone of claims 1 to 2, wherein said polymeric binder is selected from the group consisting of the cellulose amine and combination thereof;

said iron oxide waste sludge includes one or more of mill scale, open-hearth or electric arc furnace flue sludge, oily scale, steel melting shop sludge, directly reduced iron (DRI) sludge, blast furnace gas cleaning sludge, COREX sludge, basic oxygen furnace (BOF) sludge and combination thereof; and

said carbon source is carbon waste selected from the group consisting of carbon black, coke, coke breeze, coal, and combination thereof from various plants such as coke dry quenching plant and COREX.

4. The pre-reduced iron agglomerate as claimed in anyone of claims 1 to 3, wherein said oxide waste sludge agglomerate is a briquette.

5. The pre-reduced iron agglomerate as claimed in anyone of claims 1 to 4 having strength in the range of 200-250kg/cm2 and has 35% to 75% of elemental iron.

6. A method of steel-making involving pre-reduced iron agglomerate as claimed in claim 1 to 5 comprising the steps of:

i) providing 0.3-2.0% polymeric binder, 60-85% iron oxide waste sludge, 0.04-1.7% zinc, 0.8-2.5% alkali and 10-30% carbon;
ii) dewatering of iron oxide waste sludge;
iii) mixing the polymeric binder, iron oxide waste sludge and carbon source to form a mixture and adjust the moisture to 5-15%;
iv) forming iron oxide waste sludge agglomerate from the mixture by cold extrusion;
v) indurating the iron oxide waste sludge agglomerate at a temperature of 1000-1400oC and reducing iron oxide in the iron oxide waste sludge agglomerate to elemental iron and removing substantially all zinc and alkali impurities to produce the pre-reduced iron agglomerate suitable for feed as metallic iron source for steel making;
vi) transferring the thus obtained pre-reduced iron agglomerate to a furnace;
vii) heating thepre-reduced iron agglomerate in the furnace; and
viii) depositing the pre-reduced iron agglomerate into molten steel.

7. The method as claimed in claim 6, wherein the furnace is heated at a temperature of 1000-1600oC and furnace is a rotary hearth furnace, puddling furnace, reverberatory furnace, Bessemer converter, open hearth furnace, basic oxygen furnace, electric arc furnace or electric induction furnace.

8. The method as claimed in claims 6 to 7, wherein the iron oxide waste sludge agglomerate is indurated for 30 to 90 minutes.

Dated this the 6th day of October, 2020
Anjan Sen
Of Anjan Sen & Associates
(Applicant’s Agent)
IN/PA-199

, Description: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 :
IRON OXIDE WASTE SLUDGE AGGLOMERATES AND METHOD OF USING THE SAME IN STEEL MAKING PROCESS.



2 APPLICANT (S)

Name : JSW STEEL LIMITED.

Nationality : An Indian Company incorporated under the Companies Act, 1956.

Address : JSW CENTRE,
BANDRA KURLA COMPLEX,
BANDRA(EAST),
MUMBAI-400051,
MAHARASHTRA,INDIA.



3 PREAMBLE TO THE DESCRIPTION

COMPLETE

The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION

The present invention relates to iron oxide waste sludge agglomerates by recycling of iron oxide wastes generated at steel plant, to be converted to pre-reduced iron agglomerates and using the same in iron and steel making.

BACKGROUND OF THE INVENTION

Process wastes generations in the form of sludge and dusts containing iron, carbon, lime, alkalies, zinc etc. are inevitable in steel plant operations. The quantity of process wastes being substantial, it is pertinent to develop a suitable process / technology for utilization of the same. Recycling of wastes helps in cost reduction, resource conservation and mitigating the environmental issues. Major process wastes are Steel Melt Shop (SMS) sludge and dust, Direct reducing gas (DRI) sludge, Electrostatic Precipitator (ESP) dust, Cyclone dust, Bag filter dusts, Blast Furnace Gas Cleaning Plant (GCP) sludge, COREX sludge,Linz-Donawitz(LD) slag sludge, mill scale, Cold Rolling Mill (CRM) dust which contain substantial iron and carbon values. These dust and sludge contain35-75% of iron and 10-25% of carbon. A major part of these wastes are already being utilized in agglomeration and steelmaking processes. However, certain process wastes containing impurities such as zinc, alkali, silica, alumina etc. are not being utilized.

The presence of Zn and alkalies causes operational difficulties in blast furnace. SMS sludge contains major iron oxide in the form of FeO (~30-45%) which is more suitable for use in steel making as coolant. High FeO content of SMS sludge as pellet feed has adverse impact on pellet properties. The ultra-fine size of these particles requires proper handling and suitable agglomeration process for conversion into usable form.

Patent No. GB1463477A describes the process of agglomeration of steel plant waste dust to produce a hardened agglomerate made from steel plant waste dust containing a hydratable material selected from over burnt lime, a hydratable slag material or a mixture thereof, by preparing a moistened mixture including the steel plant waste dust, 2 to 20 wt.% of an oxide, hydroxide or carbonate of calcium or magnesium, or a mixture thereof, as a bonding agent, and 0 to 5 wt% of a silica-containing material capable of reacting with the bonding agent to form silicate bonds, therewith, the weight percentages being based on the total weight of dry solids in the moistened mixture, hydrothermally hardening the masses by contacting them with saturated or substantially saturated steam at a temperature of 100 to 244oC. for a period of time sufficient to form hardened and integrally bonded masses, and cooling the hardened masses.

Patent No. US3895088A describes the method of agglomerating steel plant dusts by using binders of lime and calcium hydroxide and siliceous material such as silica.Steel plant waste dust means finely divided, iron-rich, solid particulates and fines, preferably containing about 30-80 weight per cent iron, which are recovered as by-products from steel making processes and include dust collected from the fumes from basic oxygen furnace (BOF), openhearth, blast furnace, and electric furnace processes.

Patent No. CA1036361A describes the method of developing highly crush-resistant hardened agglomerates produced from steel plant waste dusts by forming a moistened mixture including one or more of such dusts along with 2 - 20 wt% of a bonding agent, such as lime or calcium hydroxide, and about 0.5 -5 wt% of a siliceous material, such as silica; aging the moistened mixture at an elevated temperature for a sufficient time to hydrate the over burned lime and/or slag contained therein; forming the aged mixture in discrete, green agglomerates; adjusting the moisture content of the green agglomerates to about 5 wt% or less; and then hydro-thermally hardening the green agglomerates to a hardened form, The crushing or compressive strength of the hardened agglomerates can be further increased by subjecting them to a drying step to remove at least a portion of the moisture contained therein immediately after the hydrothermal hardening step.

All the above 3 prior arts describe the method of agglomeration of steel plant wastes in the form of fines with binders of lime and silica. None of the prior arts disclose the use of sludge for agglomeration. The present invention discloses the agglomeration of steel plant sludge which is having moisture of 20-25% and rich in iron and carbon using organic binder for adhesion.

OBJECT OF THE INVENTION

The main object of the present invention is to provide the iron oxide waste sludge agglomerate that is converted to pre-reduced iron agglomerate suitable as feed to iron and steel making process.

A further object of the present invention is to provide said pre-reduced iron agglomerate wherein carbon source is carbon waste.

It is another object of the present invention to provide the iron oxide waste sludge agglomerate that is converted into pre-reduced iron agglomerates substantially free of zinc and alkali impurities.

It is yet another object of the present invention to provide the pre-reduced iron agglomerate that is having good strength required for handling and transportation.

A still further object of the present invention is to provide iron containing agglomerates/briquettes that acts as a replacement of pellet and direct reduced iron.

A further object of the present invention is to recycle iron bearing wastes into agglomerates suitable for iron and steel making to thereby save loss of iron.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to a pre-reduced iron agglomerate suitable for feed as metallic iron source for iron and steel making comprising iron oxide waste sludge agglomerate comprising: 0.3-2.0% polymeric binder, 60-85% iron oxide waste sludge, 0.04-1.7% zinc, 0.8-2.5% alkali and 10-30% carbon. The iron oxide waste sludge agglomerate is indurated in the temperature range of 1000 to 1400 0C to form the pre-reduced iron agglomerate comprising 35 to 75 % metallic elemental iron, 0.001 to 0.10% of zinc and 0.01 to 0.11 % alkali.

A still further aspect of the present invention is directed to the pre-reduced iron agglomerate having melting characteristics including deformation temperature in the range of 1326 to 1403 0C and flow temperature in the range of 1403 to 1544 0C.

A still further aspect of the present invention is directed to the polymeric binder selected from the group consisting of the cellulose amine and combination thereof. The iron oxide waste sludge includes one or more of mill scale, open-hearth or electric arc furnace flue sludge, oily scale, steel melting shop sludge, directly reduced iron (DRI) sludge, blast furnace gas cleaning sludge, COREX sludge, basic oxygen furnace (BOF) sludge and combination thereof. Thecarbon source is carbon waste selected from the group consisting of carbon black, coke, coke breeze, coal, and combination thereof from various plants such as coke dry quenching plant and COREX.

The pre-reduced iron agglomerate having strength in the range of 200-250kg/cm2 and has 35 to 75 % of elemental iron.

A still further aspect of the present invention is directed to a method of steel-making involving pre-reduced iron agglomerate. Firstly, providing 0.3-2.0% polymeric binder, 60-85% iron oxide waste sludge, 0.04%-1.7% zinc, 0.8%-2.5% % alkali and 10-30% carbon, Secondly, dewatering of iron oxide waste sludge. Thirdly, mixing the polymeric binder, iron oxide waste sludge and carbon source to form a mixture and adjust the moisture to 5-15%. Fourthly, forming iron oxide waste sludge agglomerate from the mixture by cold extrusion. Fifthly, indurating the iron oxide waste sludge agglomerate at a temperature of 1000-1400 oC and reducing iron oxide in the iron oxide waste sludge agglomerate to elemental iron and removing substantially all zinc and alkali impurities to produce the pre-reduced iron agglomerate suitable for feed as metallic iron source for steel making. Sixthly, transferring the thus obtained pre-reduced iron agglomerate to a furnace. Seventhly, heating the pre-reduced iron agglomerate in the furnace. Lastly, depositing the pre-reduced iron agglomerate into molten steel.

A still further aspect of the present invention is directed to the furnace is heated at a temperature of 1000-1600 oC and furnace is a rotary hearth furnace, puddling furnace, reverberatory furnace, Bessemer converter, open hearth furnace, basic oxygen furnace, electric arc furnace or electric induction furnace.

A still further aspect of the present invention is directed to the iron oxide waste sludge agglomerate is indurated for 30 to 90 minutes.

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

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 illustrates the flow chart of method of steel-making process involving pre-reduced iron agglomerate obtained of iron oxide waste sludge agglomerate according to present invention;

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

The accompanying figure together with the detailed description below forms part of the specification and serves to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention.

The present invention is now discussed in more detail referring to the drawings that accompany the present application. In the accompanying drawings, like and/or corresponding elements are referred to by like reference numbers.

Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or the like parts.

Before describing in detail embodiments that are in accordance with the invention, it should be observed that the embodiments reside primarily for development of extruded agglomerates/briquettes from wastes generated at steel making plants. The agglomerates have adequate strength and high iron content. These iron containing agglomerates are suitable for being used as feed in steel making process. The iron containing briquettes acts as a replacement of pellet and direct reduced iron. Extracting iron-bearing products from steelmaking wastes and returning them to the production cycle is expected to reduced iron losses.In the present invention iron oxide present in steel making plant waste is converted into iron metallic. The developed agglomerate is used in steel making as a scrap replacement and also in smelting reduction iron making.

The basic aspect of the present invention is directed to a pre-reduced iron agglomerate suitable for feed as metallic iron source for iron and steel making comprising iron oxide waste sludge agglomerate comprising: 0.3-2.0% polymeric binder, 60-85% iron oxide waste sludge, 0.04%-1.7% zinc, 0.8-2.5%% alkali and 10-30% carbon. The iron oxide waste sludge agglomerate is indurated in the temperature range of 1000 to 1400 0C to form the pre-reduced iron agglomerate comprising 35 to 75% metallic elemental iron, 0.001 to 0.10% of zinc and 0.01 to 0.11 % alkali. The iron oxide waste sludge agglomerate substantially has no zinc and alkali impurities and the iron oxide is reduced to elemental iron, when the iron oxide waste sludge agglomerate is indurated at temperature of 1000-1400oC.The iron oxide waste sludge agglomerate is a briquette.

The polymeric binder is selected from the group consisting of the cellulose amine and combination thereof.

The iron oxide waste sludge includes steel plant waste sludge. The steel plant waste means sludge recovered as by-products from steel-making processes. The steel plant wastes preferably containing 30 to 80 weight percent of iron, recovered as by-products from steel making processes. It includes sludge collected from mill scale, open-hearth or electric arc furnace flue, oily scale, steel melting shop, directly reduced iron (DRI), blast furnace gas cleaning, COREX sludge and basic oxygen furnace (BOF).

Mill scale consists primarily of metallic iron, some iron oxides and contamination from hot top refractories. The larger particles are screened out and can be returned directly to the blast furnace. The fine particles require agglomeration before they can be returned to the process. Mill scale fines are brittle flakes consisting mainly of iron oxides, derived as by-products from steel manufacturing. The content of iron in oily scale reaches 70-80%, in metallurgical sludge 10–30%. Mill scale consists primarily of metallic iron containing some iron oxides and contamination from hot top refractories. Around 500 tons of SMS sludge is generating daily from SMS sludge contains Fe, (total)% of 45.0-55.0%, Alkali (Na2O+K2O) of 0.4-1.0 % and Zinc (Zn) of 0.06-0.10 % and the same is used in micropelletization but due to the presence of impurities blast furnace is facing operational problems such as refractory damage and tuyere failure. SMS sludge contains iron in the form of FeO (~42.0%) which is pre reduced form and more suitable to use in steel making as a scrap replacement in the form of briquettes. FeO present in it can be converted to Fe met by using carbon rich wastes such as coke fines, carbon recovery plant sludge or low grade thermal coal. Around 1000 tons of BFgas cleaning plant sludge is generating daily from BF currently it is going to iron removal plant for iron recovery. The problem with this sludge is high zinc (0.05-0.1%) and alkali (1.0-1.5%).

The carbon source is carbon waste. The carbon waste is selected from the group consisting of carbon black, coke, coke breeze, coal, and combination thereof from various plants such as coke dry quenching plant and COREX. The carbon acts as solid reductant. The carbon promote reduction and provide more efficient operation of the agglomerates during steel making process. The solid reductant such as carbon remains substantially intact in the hardened agglomerate. Hence, it is available for the conversion of iron oxide to metallic iron, and the reduction of any zinc and/or lead oxides which may be present in the agglomerate. The hardened agglomerates can then be metallized, i.e. the iron oxide converted into metallic iron, and the zinc and/or lead removed, i.e. their oxides reduced, by heating to an elevated temperature of 1000-1400oC without additional reducing agents. The solid reductant should contain free carbon and supply sufficient carbon, in conjunction with the free carbon present in the steel plant waste sludge, to convert all the iron oxide into metallic iron and reduce the zinc and/or lead oxides during the subsequent indurating step. Preferably, the amount of solid reductant used is slightly in excess of that stoichiometrically required; however, this excess is desirably kept to a minimum to preventing necessary reductions in the compressive strength of the agglomerate and dilution of the resultant iron content of the agglomerate. The size of coal is below 150 microns and metallurgical coke fines is below 3mm. Around 130 tons of coke fines are generating daily from coke oven 3&4 and presently these are using in micropellet plant as carbon source. These fines are having carbon content of more than 85% which can be used in the current extrusion process as reducing agent. Around 1000 tons of CSP coal (below 6mm size) is generating from COREX. This coal contains carbon of 55-60%, VM of 23-27% and rest ash content. Currently these coals are being sent to thermal power plant as a fuel source.

In order to convert the FeO of sludge to Fe (met), carbon is added for the briquettes. Huge quantity of lean grade coal fines isgenerated from COREX units and carbon slurry generated from carbon recovery plant of iron recovery plant can be tried as carbon. The following reaction is to be undergone for making the proposed pre reduced pellets:
FeO (steel plant waste) +C ?Fe (met) + CO

The amount of water added will vary depending upon the-physical and chemical characteristics of the particular steel plant waste used and the particular agglomeration technique employed.

The iron oxide waste sludge agglomerates are preferably formed into relatively compact configurations, such as cylinders, spheres, egg shapes, pillows, etc. and are desirable substantially devoid of any thin sections or sharp angularity which might be susceptible to fracture or breakage during handling. The configuration of the agglomerates is also preferably controlled so that they do not become tightly compacted when stacked together, and thereby prevent the passage of a heated moisture-laden fluid between them during the subsequent hydrothermal hardening step. When briquetting is used, the agglomerates are preferably in a pillow. It should be appreciated, however, that larger agglomerates can be formed. The time should be sufficient to obtain hardening and bonding of the individual particles of the agglomerate.

The pre-reduced iron agglomerate having melting characteristics including deformation temperature in the range of 1326 to 14030C and flow temperature in the range of 1403 to 1544 0C.

The present invention is also directed to the method of steel-making process by using iron oxide waste sludge agglomerate. FIG. 1 illustrates the flowchart of method 100 of steel-making process. In step 102, 0.3-2.0% polymeric binder, 60-85% iron oxide waste sludge, 0.04%-1.7% zinc, 0.8%-2.5% alkali and 10-30% carbon is provided. In step 104, the iron oxide waste sludge is dewatered. Dewatering is done by various methods such as evaporation. In step 106, the polymeric binder, iron oxide waste sludge and carbon is mixed to form a mixture and the moisture is adjusted to 5-15%.In step 108, the iron oxide waste sludge agglomerate is formed from the mixture by cold extrusion. In cold extrusion process the screw pushes the material forward and die at 45oC angle will extrudes iron oxide waste sludge agglomerate. The screw speed is 5-20 rpm preferably 10 rpm and with pug speed of 5-20 rpm preferably 10 rpm. The cold strength of the cold extruded iron oxide waste sludge agglomerate is around 100 kg/cm2. The cold extruded iron oxide waste sludge agglomerate size is 15mm diameter and 25mm length. In step 110, the iron oxide waste sludge agglomerate is indurated at a temperature of 1000-1400oC and reducing iron oxide in the iron oxide waste sludge agglomerate to elemental iron and substantially all zinc and alkali impurities are removed to form a pre-reduced iron agglomerate. The iron oxide waste sludge agglomerate is indurated for 30 to 90 minutes. In step 112, the pre-reduced iron agglomerate is transferred to a furnace. The furnace is heated at a temperature of 1000-1600oC. The furnace is a rotary hearth furnace, puddling furnace, reverberatory furnace, bessemer converter, open hearth furnace, basic oxygen furnace, electric arc furnace and electric induction furnace. In step 114, the pre-reduced iron agglomerate is heated in the furnace. Lastly, in step 116, the pre-reduced iron agglomerate is deposited into molten steel.

Attempts have been made to define the nature of the bonding achieved by a process employing the present invention. The pre-reduced iron agglomerate strength is 200-250kg/cm2 and has 35-75% of elemental iron. It has been established that the slag bonding between the agglomerate particles increases the strength.

The pre-reduced iron agglomerate is a feed as iron source for smelting reduction furnace as a replacement of hot direct reduced iron. The pre-reduced iron agglomerate is a feed as metallic iron source for steel melting shop as a replacement of coolant iron ore or mill scale briquettes.

The pre-reduced iron agglomerate has reducibility index (RI) of 80% and reduction degradation index (RDI) of 15%.

In this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article or composition that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article or composition. An element proceeded by "comprises...a" does not, without more constraints, preclude the existence of additional identical elements in the process, method, article or composition that comprises the element.

In the present specification, when a part “includes” a certain component, it means that the component may further include other components, not to exclude other components, unless specifically stated otherwise.

Although not defined differently, all terms including technical terms and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present invention pertains. Commonly used dictionary-defined terms are additionally interpreted as having meanings consistent with related technical documents and currently disclosed contents, and are not interpreted as ideal or very formal meanings unless defined.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art to which the present invention pertains can easily practice. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

In addition, unless otherwise specified, % means weight%.

Advantages and features of the present invention, and methods for achieving them will be clarified with reference to embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only the embodiments allow the disclosure of the present invention to be complete, and are conventional in the art to which the present invention pertains. It is provided to fully inform the knowledgeable person of the scope of the invention, and the invention is only defined by the scope of the claims. The same reference numerals refer to the same components throughout the specification.

Thus, in some embodiments, well-known techniques are not specifically described to avoid obscuring the present invention. Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used as meanings commonly understood by those skilled in the art to which the present invention pertains.

The present invention is described further hereinafter by reference to a series of examples.

Experiments that were actually performed are now described by way of following examples.

Example I: Chemical Analysis of Steel Plant Wastes
Table 1 shows the iron oxide waste sludge generated from steel making processes.
Table 1: Iron oxide waste sludge generated from steel making processes
Name of
the waste Generation,
Tonnes per day Fe, % Type of waste Impurity
Sludge
Steel melting shop sludge 400-450 45-50 Iron rich in sludge Zinc: 0.06-1.0
and Alkali
(Na2O+K2O): 0.8-1.2
BF gas cleaning plant (GCP) sludge 300-350 40-45 Slurry Zinc: 0.5-1.0
COREX sludge 400-450 40-45 Sludge Zinc: 0.3-0.5 and alkali: 0.5-1.0

The chemical composition and size analysis of steel plant waste sludge are listed in Tables 2 and 3 respectively.
Table 2: Chemical analysis of waste generated from steel making plant
% of ingredient % in CaO,
% MgO,
% SiO2,
% MnO,
% Al2O3,
% Na2O,
% K2O,
% ZnO,
% Fe
,% Zn,
%
SMS sludge 50 13.19 3.35 2.36 0.70 0.66 0.47 0.27 0.04 56.0 0.06
BF GCP sludge 20 11.46 5.22 4.28 0.96 1.06 1.13 1.17 1.73 47.10 0.27

Table 3: Size analysis of waste generated from steel making plant
+6mm,
% +3mm
-6mm,% +2mm
-3mm, % +1mm
-2mm, % +500
-1000µ, % +220
-500, % +150,
-220, % +125
-150, % +75
-125, % -75µ, %
SMS sludge 0.0 0.0 0.0 0.0 0.0 1.0 3.0 7.0 17.0 72.0
BF GCP sludge 0.0 0.0 0.0 0.0 0.0 2.0 8.0 10.0 15.0 62.0

There are 2 types of carbon sources that are available in the plant are coke dry quenching fines and COREX coal fines. CDQ fines were utilized in sintering process through micropellet route as a carbon source and whereas COREX coal fines are not using anywhere and sent to power plant at lower cost. Both CDQ fines and COREX coal fines and found that metallization % is more when used coal fines compared to CDQ fines. Because of the above two reasons COREX coal is selected as reductant. Table 4 show the proximate analysis of carbon waste.
Table 4: Proximate analysis of carbon waste
COREX coal fines CDQ fines
Fixed Carbon, % 58.0 84.5
Volatile Matter, % 30.0 3.0
Ash, % 12.0 12.5

Example 2: Method of preparation of pre-reduced iron agglomerate

The iron The polymeric binder, iron oxide waste sludge, water and carbon was provided. The iron oxide waste sludge was dewatered. The steel melting shop sludge was selected as iron oxide waste sludge and COREX coal fines was used as carbon. The polymeric binder, iron oxide waste sludge, water and carbon was mixed to form a mixture and moisture was adjusted to 5-15%. An iron oxide waste sludge agglomerate is formed from the mixture by cold extrusion. In cold extrusion process the screw pushes the material forward and die at 45o C angle will extrudes iron oxide waste sludge agglomerate. The screw speed is 5-20 rpm preferably 10 rpm and with pug speed of 5-20 rpm preferably 10 rpm. The cold extruded iron oxide waste sludge agglomerate size is 15mm diameter and 25mm length.Table 5 shows the operating parameters of cold extrusion.

Table 5: Cold extrusion operating parameters
Description Parameter Description Parameter
Binders Polymer binder Mixer screw speed, rpm 10
Size of agglomerate 15mm x 25mm Pug speed, rpm 10
Batch size 10 kg moisture, % 15
Mixing time 5 min Curing period, hours Atmospheric for 48 hrs

The iron oxide waste sludge agglomerate is indurated at a temperature of 1000-1400oC and reducing iron oxide in the iron oxide waste sludge agglomerate to elemental iron and substantially all zinc and alkali impurities are removed to form a pre-reduced iron agglomerate. The iron oxide waste sludge agglomerate is indurated for 30 to 90 minutes.

Example 3: Influence of carbon on metallization in pre-reduced iron agglomerate

The carbon percentage was varied from 10-30% in the pre-reduced iron agglomerate to study the influence of carbon on metallization that is conversion of FeO to elemental iron. Table 6 shows the influence of carbon, time and temperature on metallization in pre-reduced iron agglomerate.

Table 6: Influence of carbon, time and temperature on metallization in pre-reduced iron agglomerate
Carbon Temperature, oC 1000 1100 1200 1300
Time, min % Metallization
10% 30 5.0 10.0 14.0 21.0
45 7.0 13.0 18.0 27.0
60 11.0 15.9 26.7 34.0
75 10.0 17.0 26.0 35.0
90 10.0 15.0 27.0 34.0
20% 30 8.0 15.0 19.0 32.0
45 10.0 17.0 21.0 37.0
60 14.0 18.0 30.0 47.4
75 14.0 21.0 29.0 47.0
90 15.0 20.0 30.0 47.0
30% 30 10.0 17.0 23.0 38.0
45 15.0 21.0 27.0 44.0
60 17.0 25.0 34.0 48.0
75 18.0 25.0 35.0 48.0
90 20.0 24.0 35.0 47.5

The optimum metallization that is 47.4%was observed at induration of 1300oC for 60 min with 20% of carbon. Low metallization is due to lower heating rate (5oC per minute) and burning of carbon during heating process. This is also due to static reduction process compared to conventional DRI making process such as Rotary kiln or Midrex.
Example 4: Evaluation of properties of iron oxide waste sludge agglomerate and pre-reduced iron agglomerate
Table 9 shows the chemical analysis of iron oxide waste sludge agglomerate and pre-reduced iron agglomerate. Chemical analyses of the samples were determined by X-Ray Fluorescence (XRF, Thermo-Scientific, Model No. ARL 9900). Moisture content was measured by calculating the percent weight difference after oven drying at 1100 oC.Cold Compressive Strength (CCS) of the extruded agglomerate was measured by placing the extruded agglomerate in a compressive testing machine and applying load at a constant speed until the pellet breaks (IS: 8604 - 1977). The maximum load applied where the pellet breaks is recorded in kilograms.

Table 7: Chemical analysis of iron oxide waste sludge agglomerate and pre-reduced iron agglomerate
Iron Oxide Waste Sludge Agglomerate Pre-reduced iron agglomerate
SiO2,% 1.98 1.53
Al2O3,% 0.74 0.43
CaO,% 9.62 5.76
MgO,% 0.97 0.82
TiO2,% 0.09 0.05
Na2O,% 0.55 0.11
K2O,% 0.48 0
P2O5,% 0.20 0.18
SO3,% 0.30 0.18
ZnO, % 0.08 0.00
LOI, %(Inc. C) 21.78 0.45
C, % 14.0 0.24
MnO, % 0.65 0.35
Fe(M) ,% 4.07 28.45
FeO,% 51.92 46.44
Fe2O3, % 6.57 15.25
Fe, total % 43.71 59.0
Zn, % 0.06 0.001
Metallization, % 9.31 47.4
CCS, Kg/briquette 85.0 124

Table 7 shows that 47.4% metallization was achieved and 98.3% Zinc was removed and 89.3% of alkali was also removed.
The melting characteristics were evaluated for iron oxide waste sludge agglomerate and pre-reduced iron agglomerate based on standard test method of using Ash fusion equipment (HESSE Instruments, Model No- EM201-17K) in oxidizing atmosphere. Table 8 shows the comparison of melting characteristics of iron oxide waste sludge agglomerate and pre-reduced iron agglomerate.

Table 8:Comparison of melting characteristics of iron oxide waste sludge agglomerate and pre-reduced iron agglomerate.
Iron oxide waste sludge agglomerate Pre-reduced iron
agglomerate.

Sintering temperature, o C 783 1141
Deformation temperature, o C 851 1326
Hemi Sphere temperature, o C 1350 1403
Flow temperature, o C 1448 1544
Deformation range 851-1350 1326-1403
Flow range 1350-1448 1403-1544

The deformation and flow temperature ranges of iron oxide waste sludge agglomerate was in the range of 851-1350oC& 1350-1448oC respectively. This result indicates that iron oxide waste sludge agglomerate will start deformation at 851oC and start melting beyond 1350oC.
The deformation and flow temperature ranges of pre-reduced iron agglomerate was 1326-1403oC and 1403-1544oC. This result indicates that pre-reduced iron agglomerate will start deformation at 1326oC and start melting beyond 1403oC. Process of pre reducing has increased the deformation temperature of 475oC and flow temperature of 96oC respectively.
The iron oxide waste sludge agglomerate and pre-reduced iron agglomerate was evaluated for different phases by using XRD. Table 9 shows various phases in iron oxide waste sludge agglomerate and pre-reduced iron agglomerate.
Table 9: Phase analysis of iron oxide waste sludge agglomerate and pre-reduced iron agglomerate
Phase Chemical Formula % (iron oxide waste sludge agglomerate) % (pre-reduced iron
agglomerate)
Hematite Fe2 O3 25.0 20.0
Magnetite Fe 3 O4 32.0 24.0
Wuestite Fe0.918 O1 31.0 8.0
Iron Fe1 12.0 48.0

It was observed that iron oxide waste sludge agglomerate and pre-reduced iron agglomerate contains Wuestite, Magnetite, Hematite, and Iron as the major phases. Iron in the form of oxide is converted to iron metallic due to the process of pre reducing in presence of heat and carbon as reducing agent.