TECHNICAL FIELD
[0001] The present invention relates to a method for prevention of formation powdery slag
or more particularly to a method for checking disintegration of slag by reducing the formation of gamma di-calcium silicate in the ladle furnace by mixing the additive mixture of composition of defined chemistry.
BACKGROUND OF THE INVENTION
[0002] Steelmaking process involves removing impurities from hot metal by treating it
with oxygen and the impurities form oxides which are known as slag. Slags are essential in high temperature metallurgical processing to purify molten metal with minimal cost. Large volume of slags is produced annually during different metallurgical processes, leading to important economic and ecological issues regarding their afterlife. To maximise the recycling potential, slag processing has become an integral part of the valorisation chain. Nonetheless, disintegration of steel slags produced during steelmaking hinders the valorisation and increases considerably the landfilling cost.
[0003] Slag produced after the steelmaking process is over, mostly contains di-calcium
silicate (C2S). C2S formed at high temperature when gets cooled down, goes through different phase transformations. Due to volume expansion of C2S below 500 degree centigrade, (gamma phase of C2S) slag gets fragile and disintegrates to form powder like structure which is very fine in nature. The adverse impact is, slag flies with wind and pollute environment as well as making the area unsafe by settling on stairs and other machineries. If the disintegrations of slag can be prevented, then it can be used for different purposes as value added product. Considering the stringent environmental regulation, this problem is in focus to reduce the environmental impact of steelmaking slag dust.
[0004] As can be seen in Figure 1, a lot of dust is generated after the slag gets cooled
down, which flies into the atmosphere creating environmental hazard and reduces the usability of slag. Mostly in Silicon killed grades of steel, the final slag contains lots of di-calcium silicate (2CaO_SiO2 or C2S). It is well established that this kind of slag disintegration is driven by the presence of di-calcium silicate in the slag. This mineral undergoes several phase transformations

from one polymorph to another when the slag is cooled as shown in Figure 2. The polymorphic transformation from β-Ca2SiO4 to γ-Ca2SiO4 of the slag which takes place at ~450 o C is accompanied by a volume expansion of about 12%, which generates high internal stresses finally causing the disintegration of the slag.
[0005] Hence, there is always a long felt need to provide an alternative solution to check
disintegration of slag.
[0006] The present invention meets the long felt need.
OBJECTS OF THE INVENTIOIN
[0007] It is therefore an object of the present invention to provide method for preventing
the formation of gamma phase of di-calcium silicate during cooling of slag produced in LD furnace.
[0008] Another object of the present invention is to provide a method for controlling the
formation of powdery slag by mixing of an additive composite.
[0009] Yet another object of the present invention to provide method for preventing the
formation of powdery slag with respect to time of addition during the steelmaking process to achieve the desired result.
[0010] Further object of the present invention is to provide method for preventing the
formation of powdery slag, where easily available ingredients have been used.
[0011] Another object of the present invention method for preventing the formation of
powdery, which is economic, effective yet environment friendly.
SUMMARY OF THE INVENTION
[0012] This summary is provided to introduce concepts related to a process to utilize non-
coking coal for producing a metallurgical coke. 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.
[0013] The present invention provides a method for prevention of disintegration of slag
by reducing the formation of gamma di-calcium silicate in the ladle furnace, said method comprises the steps of :
i. Addition of an additive material to the LF, the additive material comprising silica
(SiO2), sodium oxide and potassium oxide (Na2O+ K2O), calcium oxide (CaO) and
aluminium oxide (Al2O3)
ii. Reduction in basicity of slag is less than < 1.6 (please let us have a range) and increase
in alumina percentage >8%
iii. Purging an inert gas for a duration of 2-5 minutes
wherein the suitable time of addition of the additive material is just after the treatment
in the ladle furnace to optimize the effectiveness.
[0014] In an aspect there is provided, an innovative solution to control the formation of
powdery slag during cooling of slags produced during production of Si-killed steel grades through Basic Oxygen Furnace route. For this purpose, a suitable additive/material was used and added in the ladle furnace (LF), so that the formation of gamma di-calcium silicate formation can be prevented, which is the main component for the powdery slag formation. The said additive/material helps in arresting the formation of gamma di-calcium silicate and hence the slag after treatment remains solid. The quantity and time of addition of the said material is very important and determines the extent of solid slag formation in the process.
[0015] In one aspect, the additive material was added in the quantity of 10-12% of the LF
slag or the preferred quantity of additive was 10%
[0016] In one aspect, the reduction in basicity of slag is 1.4-1.6.
[0017] In one aspect, the increase in alumina percentage is 8-10%.

[0018] In one aspect, the inert gas is argon.
[0019] In one aspect, the additive material added is 0.5-1.5 mm and it is added in granule
form.
[0020] In one aspect, the bulk density of the additive is 0.9-1.2 kg/dm3.
[0021] 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.
[0022] It is to be understood that the aspects and embodiments of the disclosure described
above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.
[0023] The foregoing summary is illustrative only and is not intended to be in any way
limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] 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 processes that are consistent with the subject matter herein, wherein:
[0025] The accompanying drawings, which are incorporated in and constitute a part of this
disclosure, illustrate exemplary embodiments and, together with the description, serve to explain the disclosed principles. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the

figures to reference like features and components. Some embodiments of system and/or methods in accordance with embodiments of the present subject matter are now described, by way of example only, and with reference to the accompanying figures, in which:
[0026] Figure 1 illustrates the photo of disintegrated slag in slag pit.
[0027] Figure 2 illustrates flow sheet of formation of gamma phase of di-calcium silicate.
[0028] Figure 3 illustrates schematic diagram of steel making process.
[0029] Figure 4 illustrates determination of melting temperature of the LF slag and the said
additive material.
[0030] Figure 5 illustrates laboratory results after treatment with the said material.
[0031] Figure 6 illustrates the improvement after addition of the said material.
[0032] The figure depict embodiments of the disclosure for purposes of illustration only.
One skilled in the art will readily recognize from the following description that alternative embodiments of the methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0033] In the present document, the word "exemplary" is used herein to mean "serving as an
example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.
[0034] While the disclosure is susceptible to various modifications and alternative forms,
specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the disclosure to the forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.

[0035] The terms “comprises”, “comprising”, “includes” or any other variations thereof,
are intended to cover a non-exclusive inclusion, such that a setup, device or method that includes a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a system or apparatus proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or method.
[0036] In the following detailed description of the embodiments of the disclosure,
reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.
[0037] The description of preferred embodiment provides a method for prevention of
disintegration of slag due to formation of di-calcium silicate in ladle slag (LF) during cooling of slag produced in LF.
[0038] For this purpose, a suitable composition of additive was added in the ladle furnace
slag so that, formation of gamma di-calcium silicate can be prevented, which is the main component for the powdery slag formation.
[0039] The compound used in steelmaking process reduced the dust formation by upto
80% by arresting the formation of gamma C2S.
[0040] The chemical composition of the additive material was as follows:
SiO2 – 70-75 wt% Na2O+K2O – 4-8 wt% CaO – 1-3 wt%

Al2O3 – 15-20 wt%
[0041] The additive mixture is added to arrest the formation of gamma phase of di-calcium
sulphate in the ladle furnace slag. The optimum quantity of said additive is 10-12%, more preferably 10% of the LF slag.
[0042] The method for preventing the disintegration of slag comprises the steps of :
i. Addition of an additive material to the LF, the additive material comprising silica
(SiO2), sodium oxide and potassium oxide (Na2O+ K2O), calcium oxide (CaO) and
aluminium oxide (Al2O3)
ii. Reduction in basicity of slag is less than < 1.6 (please let us have a range) and increase
in alumina percentage >8%
iii. Purging an inert gas for a duration of 2-5 minutes
Wherein the suitable time of addition of the additive material is just after the treatment
in the ladle furnace to optimize the effectiveness.
Generally argon gas has used as inert gas.
[0043] The said additive/material helps in arresting the formation of gamma di-calcium
silicate and hence the slag after treatment remains solid. The quantity and time of addition of the said material is very important and determines the extent of solid slag formation in the process.
[0044] Figure 3 illustrates the schematic diagram of steel making process.
[0045] To prevent the disintegration of Si killed steelmaking slag, different additives were
tried in the laboratory. The additive material was chosen based on the chemical composition and melting characteristics observed in heating microscopy.
[0046] The melting behavior is show in Figure 4 and it can be seen that the additive has
much lower melting temperature than LF slag. This lower melting temperature helps in complete mixing of the slag in a short duration which is a prime requirement for plant processes. The primary aim was to get the basicity of the slag < 1.6 and at the same time increasing the alumina % in the slag to >8%.

[0047] Further, figure 5 also shows the result in laboratory addition.
[0048] It can be seen that 10% addition of the additive helps in making the powder solid.
The compound was added at the last stage of steel treatment in ladle furnace to enhance the effectiveness of the compound. Based on the laboratory studies plat trial was carried out for several heats to validate the same.
Example
Plant Trial:
[0049] Based on laboratory studies, additives were selected where the slag disintegration
was successfully controlled. Percentage addition which is required was also optimised in laboratory experiment. It was also considered that the kinetics and mixing phenomena will be different in actual plant conditions. Based on this hypothesis it was decided to add different quantities of additive during plant trial to obtain meaningful results. Time of addition of certain compound was also found to be critical and there are chances of pickup of elements in steel, which may change the steel specs being cast. The following trials were conducted at LF
• Trial with the compound
o % addition = 8-12% of slag weight
o Time of addition - Just after completion of treatment in LF followed by mild purging with argon
[0050] The result obtained after addition of the material on slag solidification is shown in
Figure 6. It can be seen that >80% of the slag is solid after addition of the additive material during the steelmaking process.
[0051] Figure 6 illustrates the nature of slag after addition of the additives. i.e >8%.
The technical advantages of the embodiment are as given blow:
[0052] The present disclosure provides a method to control the formation of powdery slag during cooling of slag produced during production of Si killed steel grades through basic oxygen furnace route.

[0053] The present disclosure provides a method to control the formation of powdery slag
by preventing the formation of gamma form of di-calcium silicate in LF slag.
[0054] The present disclosure provides a method to control the formation of powdery slag
by mixing of suitable additive mixture of preferred chemistry.
[0055] The said additive/material helps in arresting the formation of gamma di-calcium
silicate and hence the slag after treatment remains solid.
[0056] The quantity and time of addition of the said material is very important and
determines the extent of solid slag formation in the process.
Equivalents:
[0057] The specification has described a process to utilize non-coking coal for producing
a metallurgical coke. The illustrated steps are set out to explain the exemplary embodiments shown, and it should be anticipated that ongoing technological development will change the manner in which particular functions are performed. These examples are presented herein for purposes of illustration, and not limitation. Further, the boundaries of the functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternative boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the disclosed embodiments. Also, the words "comprising," "having," "containing," and "including," and other similar forms are intended to be equivalent in meaning and be open-ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.
[0058] Finally, the language used in the specification has been principally selected for
readability and instructional purposes, and it may not have been selected to delineate or

circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based here on. Accordingly, the embodiments of the present invention are intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.

We claim:
1. A method for prevention of disintegration of slag by reducing the formation of gamma di-
calcium silicate in the ladle furnace, said method comprises the steps of
i) Addition of an additive material to the LF, the additive material comprising silica
(SiO2), sodium oxide and potassium oxide (Na2O+ K2O), calcium oxide (CaO) and aluminium oxide (Al2O3)
ii) Reduction in basicity of slag is less than < 1.6 (please let us have a range) and
increase in alumina percentage >8%
iii) Purging an inert gas for a duration of 2-5 minutes
wherein the suitable time of addition of the additive material is just after the treatment in the ladle furnace to optimize the effectiveness.
2. The method as claimed in claim 1, wherein the additive material was added in the quantity of 10-12% of the LF slag.
3. The method as claimed in claim 1, wherein the preferred quantity of additive was 10%.
4. The method as claimed in claim 1 , wherein the reduction in basicity of slag is 1.4-1.6.
5. The method as claimed in claim 1, wherein increase in alumina percentage is 8-10%.
6. The method as claimed in claim 1, wherein the inert gas is argon.
7. The method as claimed in claim 1, wherein the additive material added is 0.5-1.5 mm.
8. The method as claimed in claim 1, wherein the additive material added is in granule form.
9. The method as claimed in claim 1, wherein the bulk density of the additive is 0.9-1.2 kg/dm3.

10. An additive mixture for prevention of disintegration of powdery slag, during cooling of
slags produced in Si killed steelmaking process in ladle furnace (LF), said mixture comprises:
i) Silica (SiO2)
ii) Sodium Oxide and Potassium Oxide (Na2O + K2O)
iii) Calcium Oxide (CaO)
iv) Aluminium Oxide (Al2O3)
11. The additive mixture as claimed in claim 10, wherein said additive comprises:
i) SiO2 - 70-75 wt%
ii) Na2O + K2O - 4-8 wt%
iii) CaO - 1-3 wt%
iv) Al2O3 - 15-20 wt%
12. The additive mixture as claimed in claim 10, wherein the said additive was added to arrest the formation of gamma phase of di-calcium sulphate in the ladle furnace slag.
13. The additive mixture as claimed in claim 10, wherein the optimum quantity of said additive is 10-12% for making powdered solid.