FORM 2
THE PATENTS ACT 1970
39 OF 1970
&
THE PATENT RULES 2003
COMPLETE SPECIFICATION
(SEE SECTIONS 10 & RULE 13)
1. TITLE OF THE INVENTION
A METHOD FOR PERFORMING A DESULFURIZATION OF SPONGE IRON
IN A DRI KILN
2. APPLICANTS (S)
NAME NATIONALITY ADDRESS
JINDAL STEEL & Indian Kharsia Road, Raigarh - 496001
POWER LIMITED
Company (CG), Chhattisgarh, India
3. PREAMBLE TO THE DESCRIPTION
COMPLETE SPECIFICATION
The following specification particularly describes the invention and the manner in
which it is to be performed.

A METHOD FOR PERFORMING A DESULFURIZATION OF SPONGE
IRON IN A DRI KILN TECHNICAL FIELD
[0001] The present subject matter relates to iron production, in particular, the present subject matter relates to a desulphurization method within coal-based direct reduction process that results in a production of sponge iron with acceptable sulfur content and involves an application of calcined lime (CaO).
BACKGROUND
[0002] Traditionally, for producing various grades of steels or special steels, sulphur content by weight in steel as low as possible is a must requirement in all practices. DRI production is an intermediate stage for the production of steel. A significant limitation in achieving controlled chemistry in DRI final product is the Sulphur level which inherently remains present in the coal (Reducing Agent source) itself in forms like Pyrite (FeS2), Sphalerite (ZnS), Galena (PbS), Chalcopyrite (CuFeS2), Pyrrhotite, Arsenopyrite (FeAsS), etc.
[0003] The production of various grades of steels or specialty steels necessitates minimizing the sulfur content by weight in the steel. Iron production serves as the intermediary stage for steel manufacturing, and therefore, reducing sulfur content in iron is imperative for producing steel with lower sulfur levels.
[0004] A preferred maximum percentage is desirable for Sponge Iron for achieving desired chemistry of steel. General practice for producing solid sponge iron is achieved by removing oxygen from the ore. The technique of Direct Reduction varies according to the type of reducing

agents employed and the metallurgical vessel in which they are reduced. A conventional coal-based DR process utilizes a Horizontal kiln. The kiln is provided with an inside refractory lining to protect the shell and has a slope towards the discharge end. For supplying atmospheric air for operations to carry out, primary and secondary air sources are available throughout the length of the kiln at calculated length intervals.
[0005] The production of solid sponge iron (Direct Reduced Iron or DRI) conventionally involves the removal of oxygen from the ore through a reduction process. The kiln features an internal refractory lining to safeguard the shell and maintains a slope of 2.5%-3.0% toward the discharge end.
[0006] The conventional process in practice is directly reducing ore containing oxides of iron in a rotary kiln using coal as the solid carbonaceous feed, where feeding of coal is done both at the feed end & the discharge end/injection end of the kiln, which is acting as both fuel and helps in reduction. Furthermore, in the conventional coal-based Direct Reduction process, the introduction of iron-bearing material takes place at the feeding end of the rotary kiln. The hot reducing gases flow from the discharge end to the feeding end. To regulate the sulfur content in the final product of the kiln (Direct Reduced Iron or DRI), dolomite or limestone is introduced at the feeding end.
[0007] In current conventional coal-based Direct Reduction (DR) processes, coal used often comes with a higher percentage of sulfur and desulfurization is conducted during the reduction process through the addition of limestone or dolomite as flux material. This practice aims to manage sulfur content in the DRI produced. Increasing the flux dosage at the feeding end is a common approach to mitigate the rise in sulfur

content; however, this adjustment often comes at the expense of a reduction in the overall production rate.
[0008] There is a need for a solution to overcome above mentioned drawbacks.
SUMMARY
[0009] This summary is provided to introduce concepts related to a method for performing a desulfurization of a sponge iron in a coal based Direct Reduction (DR) kiln. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0010] In an embodiment, the present subject matter provides a method for performing a desulfurization of a sponge iron in a coal based Direct Reduction (DR) kiln. The method includes feeding a first predetermined amount of Iron Bearing Raw materials in a DR kiln from a feed end. The method includes feeding a second predetermined amount of coal into the DR kiln from the feed end. The method includes feeding a third predetermined amount of coal into the DR kiln from the injection end. The method includes rotating the DR Kiln at a pre-determined value of Rotations Per Minute (RPM) to obtain an output, characterized in that, feeding a predetermined quantity of Calcined Lime as a flux material from the injection side in the DR kiln for de-sulfurization. The output obtained is sponge iron with a minimum quantity of Sulfur
[0011] In an aspect of the present subject matter, the sponge iron consists of sulfur in a quantity ranging upto 0.03% by weight.
[0012] In an aspect of the present subject matter, the Calcined lime charged through the injection end ranges between 3 mm- 10 mm in size,

the Iron-bearing-raw-material ranges between 5mm-18mm is size, and the coal ranges up to 25 mm in size.
[0013] In an aspect of the present subj ect matter, the method further includes separating the output of the kiln into a magnetic Sponge Iron and non-magnetic products, and the non-magnetic products termed as char.
[0014] In an aspect of the present subject matter, the DRI kiln is rotated at 0.28-0.36 RPM.
[0015] In an aspect of the present subject matter, a temperature of the feed end of the kiln is maintained between a range of 8000-9000C and the injection end/ a kiln outlet end is heated to a temperature ranging between 1000-1150°C while producing the sponge iron.
[0016] In an aspect of the present subj ect matter, the method further includes supplying atmospheric air inside the kiln from a plurality of air sources while the kiln is being rotated.
[0017] In an aspect of the present subject matter, feeding the predetermined amount of Calcined lime from the injection side eliminates the need for feeding of the limestone/dolomite from the feed end and vacating a considerable space that may be used to feed in more IBRM.
[0018] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE FIGURES
[0019] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and methods that are consistent with the subject matter as claimed herein, wherein:
[0020] Fig. 1 illustrates a schematic block diagram depicting a method for performing a desulfurization of a sponge iron in a coal based DR kiln, in accordance with an embodiment of the present subject matter;
[0021] Fig. 2 illustrates an operational flow diagram depicting a process for performing a desulfurization of a sponge iron in a coal based DRI kiln, in accordance with an embodiment of the present subject matter;
[0022] Fig. 3 illustrates a diagram depicting a DRI plant, in accordance with an embodiment of the present subject matter;
[0023] Fig. 4 illustrates a diagram depicting a DRI kiln, in accordance with an embodiment of the present subject matter; and
[0024] Fig. 5 illustrates a diagram depicting a section view of a horizontal kiln, in accordance with an embodiment of the present subject matter.
DETAILED DESCRIPTION
[0025] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations

of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the present disclosure as defined by the appended claims.
[0026] As used in the description herein and throughout the claims that follow, the meaning of “a”, “an”, and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0027] Fig. 1 illustrates a schematic block diagram depicting a method 100 for performing a desulfurization of a sponge iron in a coal based DR kiln, in accordance with an embodiment of the present subject matter. Iron production may be only an intermediate step in the production of steel from natural resources like iron ore, coal, or the like.
[0028] At block 102, the method 100 includes feeding a first predetermined amount of Iron Bearing Raw materials in a DR kiln from a feed end.
[0029] At block 104, the method 100 includes feeding a second predetermined amount of coal into the kiln from the feed end.
[0030] At block 106, the method 100 includes feeding a third predetermined amount of coal into the kiln from the injection end.
[0031] At block 108, the method 100 includes rotating the Kiln at a pre-determined value of Rotations Per Minute (RPM) to obtain an output.
[0032] At block 110, the method 100 includes feeding a predetermined quantity of Calcined Lime (CaO) from the injection side in the kiln for de-sulfurization, wherein the output obtained is sponge iron with a minimum quantity of sulfur.

[0033] Fig. 2 illustrates an operational flow diagram depicting a process 200 for performing a desulfurization in a coal based DR kiln, in accordance with an embodiment of the present subject matter. The process 200 may include maintaining a sulfur level preferably below 0.03% by wt, in DRI. The process 200 may include introducing an additional supply of Calcined lime against limestone/dolomite for scavenging or controlling the sulphur levels in the DRI products produced. During a reduction process, oxygen from Iron ore is removed inside the kiln.
[0034] At step 202, the process 200 may include feeding a first predetermined amount of Iron Bearing Raw materials in a DR kiln from a feed end. In a preferred embodiment, the Iron-bearing-raw-material may range between 5mm-18mm is size. In a preferred embodiment, a temperature of the feed end of the kiln may be maintained between a range of 8000-9000C.
[0035] At step 204, the process 200 may include feeding a second predetermined amount of coal into the kiln from the feed end.
[0036] At step 206, the process 200 may include feeding a third predetermined amount of coal into the kiln from the injection end. The coal may range up to 20mm in size.
[0037] Along with the addition of Calcined lime from the injection side, the vacant volume available at the feed end in place of limestone may accommodate an extra amount of iron ore such that the iron ore feed rate may be increased by 2.25 T/hr (31.25 to 33.50) leading to an overall increase in throughput.
[0038] At step 210, the process 200 may include rotating the Kiln at a pre-determined value of Rotations Per Minute (RPM) to obtain an output. The output obtained is sponge iron with a minimum quantity of

Sulfur. The sponge iron may consist of sulfur in a quantity ranging between 0.02-0.03 %. The DR kiln may be rotated at 0.28-0.36 RPM.
[0039] At step 212 the process 200 may include separating the output of the kiln into a magnetic Sponge Iron and non-magnetic products. The non-magnetic products may be termed as char. In a preferred embodiment, the injection end/a kiln outlet end may be heated to a temperature ranging between 1000-1150°C while producing the sponge iron. Further, a saved heat due to skipping a calcination may be utilized successfully increasing iron ore fed into the system at a higher rate.
[0040] The process 200 may include:
a. Iron Ore / Pellet: Fe grade: 64% & above, Size: 5-18 mm or
6- 20 mm
b. Feed Coal: 5-25 mm
c. Limestone / Dolomite: 1-6 mm
d. Injection Coal lump: 5-20 mm
e. Injection Coal Fine: -5mm
f. Retention time in DRI kiln: 8-10 hrs @ 0.33 rpm
g. Retention time in Cooler: 2-2:30 hrs @ 0.8 rpm
h. Overall timing in the process: 8-12 hours
i. Temperature attained in kiln at feed end : 800-850°C and at
discharge end : 1000-1100°C j. Final DRI Product: Fe(M) = > 80% & Sulfur = 0.03% or
below
[0041] Fig. 3 illustrates a diagram 300 depicting a DR plant, in accordance with an embodiment of the present subject matter. The DR plant may include a kiln section, and a production separation unit. The

kiln section may include a feed end and an injection end. The feed end may receive a first predetermined amount of Iron Bearing Raw materials (iron-ore pellets) and a second predetermined amount of coal.
Fe(T) SiOI A120 LO] Moist l"18 -18+15 ln"c "
% % 3% S% P% % urf TI Al ™ mm% WS Sin
~63J2 TT6 HI n.OO 0.062 0.19 ISO (OtO K6 19.86 7.23
4 93.89 4.63 2
~6X46 T07 106 n.OO 0.060 0.21 2770~~ ""(MIO 372 21.03 5.51
I | | 6 | | | | | | |__j_J I
Table 1 depicts chemical & size analysis of incoming iron ore pellet
[0042] To that understanding, the product separation unit may be used for separating the output of the DR kiln into a magnetic Sponge Iron and non-magnetic products.
[0043] The temperatures of different heating zones may be measured and controlled using thermocouples mounted throughout a length of the kiln. Gradually as the charge moves along the kiln in a cascading motion aided by rotation. Preheating zone may account for about 30% -50% of the kiln length, wherein both moisture and volatile matter present in the feed mixture may be removed from the feed material. The heat required in the preheating zone may be provided by the combustion of part of the coal. The kiln rotates at a low rpm for homogeneous reduction of burden materials in it. The final output may be sent to a rotating cooler where it may be cooled by indirect cooling by spraying water on the cooler’s shell avoiding re-oxidation of the final DRI produced as it may be quite unstable at that high temperature.
[0044] Furthermore, screening may be done for 3mm and above sized products. Products may then be separated in magnetic separator as

magnetic & non-magnetic where the magnetic product may be used as feed material for steel making.
[0045] Fig. 4 illustrates a diagram 400 depicting a DR kiln, in accordance with an embodiment of the present subject matter. The DR kiln may include a feed end, and an injection end. The feed end may receive a first predetermined amount of Iron Bearing Raw materials (iron-ore pellets) and a second predetermined amount of coal. The injection end may be configured to receive a third pre-determined amount of flux material (Calcined lime), a third predetermined amount of coal.
[0046] In a preferred embodiment, limestone Calcination reactions may usually take place at or above a thermal decomposition temperature. The thermal decomposition temperature is defined as a temperature at which a standard Gibbs free energy is equal to zero for decomposition reaction. The thermal decomposition temperature is characterized as the temperature at which the standard Gibbs free energy for the decomposition reaction (Eqn-1) equals zero.
CaCO3 (s) = CaO (s) + CO2 (g) ΔHR = +168KJ/mol, 1000~1100 °C.
(Eqn-1)
[0047] The standard Gibbs free energy of the reaction may be approximated as ΔG° = 177100 - 158 T (J/mol). The standard free energy of the reaction may be zero when the temperature T is equal to 1121 K or 848 °C. Hence the chemical decomposition reaction for pure CaCO3 (limestone) may start at 850 °C. The Calcination of CaCO3 may be a highly endothermic reaction, requiring 755 M Cal of heat input to produce a ton of calcined lime at standard state. The reaction may begin when the temperature is above a dissociation temperature of carbonates in the limestone. The temperature typically may be between 850 °C and 1340°C.

The CaCO3 added as a sulfur-controlling agent may quickly transform to CaO after calcination that captures sulfur and holds the sulfur as CaS and/or CaSO4 so that it may be removed. The feeding of CaCO3 as a sulfur-controlling agent undergoes transformation to CaO during calcination. This converted CaO serves as a sulfur-capturing agent, binding sulfur in the form of CaS and/or CaSO4. This strategic transformation prevents the sulfur from combining with iron during the reduction process. A drop in a feed rate of the control agent below a minimum level may cause a proportional rise in a sulfur content of DRI product produced and the resulting contamination may show up rapidly in only a few hours of kiln operation. Sulfur levels in the DRI may rise high even with the proper control agent feed rate. It is thus vital that an adequate sulfur-controlling agent should be fed feed rate to the kiln be maintained. The appropriate rate depends on the total sulfur input with the 5 input raw materials and the provision of the excess CaO required. Since the reaction is endothermic, limestone calcination may take some energy from the system leading to an extra requirement of energy in the form of fuel. The addition of direct CaO (calcined lime) in place of CaCO3 (limestone) may also be helpful in a sense that the energy spent in a form of fuel may be saved as a quantity of coal required per ton DRI. Lesser quantity of fuels may indirectly help in controlling impurities throughout the operation. Reactions including S from coal with limestone & calcined lime:
CaCO3 (s) = CaO (s) + CO2 Limestone
decomposition
CaO + SO2 +1/2O2 = CaSO4 or
CaO + SO2 = CaS + O2

[0048] Fig. 5 illustrates a diagram 500 depicting a section view of a horizontal kiln, in accordance with an embodiment of the present subject matter. Each source of raw materials used throughout the present subject matter may be kept constant. Along with a general practice of feeding all raw materials from a feed end, an additional introduction of calcined lime/dolomitic lime may be done through an injection side of the kiln without disturbing any other parameters.
[0049] Furthermore, all examples recited herein are principally
intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor(s) to furthering the art and are to be construed as being without limitation to such specifically recited examples and conditions. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.
[0050] While the detailed description describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions, or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

I/We Claim:
1. A method (100) for performing a desulfurization of a sponge iron in a coal
based Direct Reduction (DR) kiln, the method (100) comprising:
feeding a first predetermined amount of Iron Bearing Raw materials (IBRM) in the kiln from a feed end;
feeding a second predetermined amount of coal into the kiln from the feed end;
feeding a third predetermined amount of coal into the kiln from the injection end of the kiln;
rotating the kiln at a pre-determined value of Rotations Per Minute (RPM) to obtain a reduced product,
characterized in that,
feeding a predetermined quantity of Calcined Lime from the injection side into the kiln for de-sulfurization, wherein the output obtained is sponge iron with a minimum quantity of Sulfur.
2. The method (100) as claimed in claim 1, wherein the sponge iron consists of sulfur less than 0.03 % by weight.
3. The method (100) as claimed in claim 1, wherein the calcined lime charged through the injection end ranges between 3 mm- 10 mm in size, the IBRM ranges between 5mm-18mm is size, and the coal ranges up to 25mm in size.
4. The method (100) as claimed in claim 1, further comprising:
separating the reduced product of the DRI kiln into a magnetic Sponge Iron and non-magnetic products, wherein the non-magnetic products are char.
5. The method (100) as claimed in claim 1, wherein the DRI kiln is rotated at 0.28-0.36 RPM.
6. The method (100) as claimed in claim 1, wherein a temperature of the feed end of the DRI kiln is maintained between a range of 8000-9000C and the injection

end/ a kiln outlet end is heated to a temperature ranging between 1000-1150°C while producing the sponge iron.
7. The method (100) as claimed in claim 1, further comprising:
supplying atmospheric air inside the DRI kiln while the DRI kiln is being rotated from a plurality of air sources.
8. The method (100) as claimed in claim 1, wherein feeding the predetermined
amount of CaO from the injection side eliminates the need for feeding of the
limestone/dolomite from the feed end and vacating a considerable space that
may be used to feed in more IBRM.