Description:TECHNICAL FIELD:
Present disclosure relates in general to a field of metallurgy. Particularly, but not exclusively, the present disclosure relates manufacturing of ultra-low carbon steels. Further embodiments of the present disclosure disclose a RH degassing vessel and a configuration of a gas-purging module for the RH degassing vessel for manufacturing the low carbon steels.

BACKGROUND OF THE DISCLOSURE:

Generally, in a series of refining steps for manufacturing clean steel/interstitial free steel, vacuum degassing by an RH degassing process is employed. The RH degassing process is a secondary refining process that is configured to remove dissolved gases such as hydrogen/carbon present in the molten metal to enable the production of high-grade steel. Processes that remove the dissolved gasses in the molten steel are necessary for the production of high-grade steels. The said RH process is suitable for quickly degassing from large quantities of molten steel. Generally, the RH degassing process features a vacuum chamber equipped with two snorkels that may be immersed into the ladle accommodating molten metal.

In the method for degassing molten metal in the RH degasser, the molten metal is conveyed from a casting ladle into the inlet snorkel above the level of steel bath. The argon gas rises in the immediate vicinity of the wall of the RH degasser. The conveyance of the liquid steel is facilitated by the volume enlargement because of argon in the riser pipe and by the pressure difference between the outer air pressure and the negative pressure in the evacuation vessel. The argon bubbles entrain the molten steel and ensure a uniform circulation of the molten steel. The partial pressure is simultaneously lowered, and the decarburization reaction is accelerated. The steel taken into the evacuation vessel is sprayed.

However, in the conventional method/system of introducing the argon in the inlet nozzle faces several downsides. Primarily, the recirculation rate of the molten metal into the degasser deteriorates due to larger argon bubbles. The argon bubbles having larger dimensions fail to capture sufficient surface area, which leads to lower recirculation rates. Thus, effecting the degassing efficiency.

The present disclosure is directed to overcome one or more limitations as stated above or any other limitations associated with the conventional arts.

SUMMARY OF THE DISCLOSURE

One or more shortcomings of the conventional arts are overcome by an apparatus and a method as claimed and additional advantages are provided through the provision of apparatus and the method as claimed in the present disclosure.

Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.

In one non-limiting embodiment of the disclosure, a gas-purging module for a RH degassing vessel is disclosed. The module includes a tube having an inlet end and an outlet end. The outlet end is receivable in a provision defined in an inlet snorkel of the RH degassing vessel. The tube extends in a refractory lining surrounding the inlet snorkel and defines a flow path extending from the inlet end to the outlet end. The outlet end is defined with a plurality of apertures of pre-determined dimension to induce gas bubbles into the inlet snorkel to increase recirculation rate of molten metal within the RH degassing vessel.

In an embodiment of the disclosure, the plurality of apertures defines a partial opening to the interior of the inlet snorkel.

In an embodiment of the disclosure, the inlet end of the tube is fluidly connected to a blow pipe to channelize inert gas from an inert gas unit to the tube. The inert gas is argon.

In an embodiment of the disclosure, the plurality of apertures in the gas purging module ranges from 5 to 8.

In an embodiment of the disclosure, the gas bubbles induced into the inlet snorkel is of 1mm diameter.

In another non-limiting embodiment, a RH degassing vessel is disclosed. The vessel includes a vacuum chamber defined with an inlet snorkel and an outlet snorkel each surrounded by a refractory lining. The inlet snorkel is structured to accommodate a plurality of gas purging modules. The plurality of gas purging modules is distributed along a circumference of the inlet snorkel at a plurality of levels. Each of the plurality of gas purging modules includes a tube having an inlet end and an outlet end. The outlet end is receivable in a provision defined in the inlet snorkel of the RH degassing vessel. The tube extends in the refractory lining surrounding the inlet snorkel and defines a flow path extending from the inlet end to the outlet end. The outlet end is defined with a plurality of apertures of pre-determined dimension to induce gas bubbles into the inlet snorkel to increase recirculation rate of molten metal within the RH degassing vessel.

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.

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 ACCOMPANYING FIGURES

The novel features and characteristics of the disclosure are set forth in the appended claims. The disclosure itself, however, as well as a preferred mode of use, further objectives, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:

FIG.1 illustrates an exemplary schematic view of a gas purging module surrounded by a refractory lining, in accordance with an embodiment of the present disclosure.

FIG.2 illustrates a sectional view of a RH degassing vessel with plurality of gas-purging module of FIG.1.

FIG.3 illustrates outlet end of the gas purging module of FIG.1 with plurality of apertures.

FIG.4 illustrates comparison of inert gas volume fraction as a function of snorkel height and plumes of inert gas volume fractions.

FIG.5 illustrates a graphical representation of circulation rates for various aperture dimensions.
The figures 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 structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION

The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the claims of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent processes do not depart from the spirit and scope of the disclosure as set forth in the appended claims. The novel features which are believed to be characteristic of the disclosure, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

Embodiments of the present disclosure discloses a gas purging module for a RH degassing vessel. The gas purging module may be designed to be used in an inlet snorkel of the RH degassing vessel to induce inert gas into the vessel. The configuration of the gas purging module significantly improves recirculation rate of molten metal into the degassing vessel from a ladle and from the vessel to the ladle. The RH degassing vessel includes a vacuum chamber defined with the inlet snorkel and an outlet snorkel. The inlet and the outlet snorkel may be surrounded by a refractory lining. The inlet snorkel may be structured to accommodate the plurality of gas purging modules. In an embodiment, the plurality of gas purging modules may be distributed along a circumference of the inlet snorkel at a plurality of levels. The plurality of levels may include a first level and a second level, and the plurality of gas purging modules may range from 6 to 12 modules. In an embodiment, each of the plurality of gas purging modules may be spaced apart equidistantly from each other along the circumference of the inlet snorkel.

In an embodiment, each of the plurality of gas purging modules includes a tube defined with an inlet end and an outlet end. The outlet end of the gas purging module may be receivable in a provision defined in the inlet snorkel. Further, the inlet end of the tube may be fluidly connected to a blow pipe to channelize inert gas from an inert gas unit to the tube. The tube may extend within the refractory lining that is surrounding the inlet snorkel of the RH degassing vessel. The outlet end of the tube may be defined with a plurality of apertures of pre-determined dimension. The plurality of apertures may define a partial opening to the interior of the inlet snorkel. Further, the plurality of apertures may be designed to induces gas bubbles into the inlet snorkel to increase recirculation of molten metal within the RH degassing vessel. The gas induced into the inlet snorkel may be an inert gas such as argon.

The terms “comprises…. a”, “comprising”, or any other variations thereof used in the specification, are intended to cover a non-exclusive inclusion, such that an assembly that comprises 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 method. In other words, one or more elements in an assembly proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the assembly.

Henceforth, the present disclosure is explained with the help of one or more figures of exemplary embodiments. However, such exemplary embodiments should not be construed as limitation of the present disclosure.

The following paragraphs describe the present disclosure with reference to FIG(s) 1 to 5. In the figures, the same element or elements which have similar functions are indicated by the same reference signs. For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to specific embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated methods, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention pertains.

The following detailed description is merely exemplary in nature and is not intended to limit application and uses. Furthermore, there is no intention to be bound by any theory presented in the preceding background or summary or the following detailed description. It is to be understood that the disclosure may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices or components illustrated in the attached drawings and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions or other physical characteristics relating to the embodiments that may be disclosed are not to be considered as limiting, unless the claims expressly state otherwise. Hereinafter, preferred embodiments of the present disclosure will be described referring to the accompanying drawings. While some specific terms directed to a specific direction will be used, the purpose of usage of these terms or words is merely to facilitate understanding of the present invention referring to the drawings. Accordingly, it should be noted that the meanings of these terms or words should not improperly limit the technical scope of the present invention.

Embodiments of the disclosure discloses a system for producing ultra-low carbon steels. Among various other components employed in the system, RH degassing vessel may be a component of significant importance to decarbonize/reduce carbon content in steels. The RH degassing vessel in the corresponding figures is generally indicated by referral numeral 10. The RH degassing vessel (10) may also be referred to as degassing vessel/vessel (10) and may be interchangeably used hereinafter in the present disclosure. The term RH degassing vessel refers to Rurhstahl Heraeus degassing vessel. The present disclosure is directed towards improving circulation rate of molten metal within the vessel (10) when in operation which will be elucidated henceforth.

Referring in general to FIGS.1 and 2 which schematic view of the RH degassing vessel. In a series of refining steps for manufacturing ultra-low carbon steel, in many cases, vacuum degassing by RH method may be carried out on molten metal. For the process of vacuum degassing, the RH degassing vessel (10) may be employed. In an embodiment, the RH degassing vessel (10) may include one or more portions defined internally. The one or more portions may include a vacuum chamber (V) and one end i.e., a bottom portion of the vacuum chamber (V) may be defined with an inlet snorkel (2a) and an outlet snorkel (2b). In an embodiment, the inlet snorkel (2a) and the outlet snorkel (2b) may also be referred to as immersion tubes as they may be immersed into molten metal. The inlet snorkel (2a) and the outlet snorkel (2b) extend downward from the bottom portion of the vessel (10). In an embodiment, walls of the inlet snorkel (2a) and the outlet snorkel (2b) are surrounded by a refractory lining (3). The walls of the snorkels (2a and 2b) may be encompassed by the refractory lining (3). During the RH process, the inlet snorkel (2a) and the outlet snorkel (2b) may be immersed into the molten metal in a ladle (4). Subsequently, inner portion of the vacuum chamber (V) may be evacuated. Further, an inert gas may be blown into the inlet snorkel (2a).

Once, the inert gas is introduced into the inlet snorkel (2a), the molten metal moves up in the inlet snorkel (2a). The molten metal moving up in the inlet snorkel (2a) passes inside the vacuum chamber (V). Further, the molten metal flows out of the vacuum chamber (V) and moves down to the ladle (4) through the outlet snorkel (2b). The flow of molten metal into the vacuum chamber (V) and out of the vacuum chamber (V) may be illustrated by the arrows as shown in FIG.1.

As discussed above, the inert gas may be induced into the inlet snorkel (2a) through a plurality of gas-purging modules (1). Each of the plurality of gas-purging modules (1) may be receivable in a provision defined in an inlet snorkel (2a) of the RH degassing vessel. In an embodiment, the provisions are defined along the circumference of the inlet snorkel (2a). The plurality of provisions may be through apertures defined equidistantly from each other along the circumference of the inlet snorkel (2a). The plurality of provisions may be defined at one or more levels on the inlet snorkel. The one or more levels include a first level (h1) and a second level (h2). In an embodiment, the number of provisions in each of the plurality of levels (h1 and h2) may be determined based on the number of gas-purging modules (1) to be positioned at the respective levels. Each of the plurality of gas purging modules (1) [also referred to as purging modules] may be received by the plurality of provisions by ingressing the purging modules (1) through the refractory lining (3) surrounding the inlet snorkel (2). Each of the plurality of provisions defined at the plurality of levels (h1 and h2) may receive each of the plurality of gas-purging modules (1). In an exemplary embodiment, at the first level (h1) six gas purging modules (1) may be arranged and in second level (h2) six gas purging modules (1) may be arranged.

Each of the plurality of gas-purging modules (1) may include a tube (T) [as shown in FIG.2]. The tube (T) may be defined with an inlet end (I) and an outlet end (O). The outlet end (O)may be receivable in the provision defined in the inlet snorkel (2). The tube (T) may be made of materials such as but not limiting to carbon steel and the like. Shape of the tube (T) may be substantially annular. The inlet end (I) of the tube (T) may be fluidly connectable to a blow pipe (A). The blow pipe (A) may be configured to channelize the inert gas from an inert gas unit to the inlet snorkel (2) through the tube (T). The inert gas supplied to the inlet snorkel (2a) according to the present disclosure may be argon but not limiting to the same. Argon gas may be supplied from the inert gas unit to the inlet snorkel (2a) through the tube. The outlet end (O) of the tube (T) may be closed by an enclosure (E) and such enclosure (E) may be defined with a plurality of apertures (5). The plurality of apertures (5) defined on enclosure (E) at the outlet end (O) may be of pre-determined dimension. In an embodiment, the pre-determined dimension of the each of the plurality of apertures (5) may be 1mm in diameter.

The plurality of apertures (5) may define a partial opening towards the interior of the inlet snorkel (2a). The number of apertures in enclosure (E) of the outlet end (O) of the gas purging module (1) may be at least one of 5 or 8 [as shown in FIG.3]. The plurality of apertures (5) may generate gas bubbles of similar diameter i.e., of 1mm and induce the same in the inlet snorkel (2a). In an embodiment, the inert gas may act as a lift gas and aid in recirculation of molten metal. The inert gas introduced in the inlet snorkel (2a) may expand and rise up. The expansion and rising of the inert gas may increase the velocity of the molten metal. Since, each of the gas-purging modules (1) include a plurality of apertures (5), the amount of inert gas bubbles induced into the inlet snorkel (2a) increases. Increase in the bubble formation may increase the amount of molten metal to be lifted from the ladle (4) to the vacuum chamber (V). As the inert gas bubbles induced are of smaller dimension (i.e., 1mm) and more gas bubbles are induced, the surface area captured by the inert gas bubbles significantly increases. The decreased size of the inert gas bubbles may aid to significant increase the circulation rate by capturing more surface area at each time during lifting of molten metal. Increase in circulation rate in turn increases the decarbonization process within the degassing vessel (10). The decarbonization process decreases the concentration of carbon concentration in the molten metal to manufacture ultra-low carbon steels.

Exemplary Experimental analysis

Following paragraphs may be illustrate exemplary experimental results illustrating test parameters improving recirculation of molten metal within the RH degassing vessel (10). Reference is now made to FIG.4 henceforth. The gas volume fraction of the induced inert gas in the inert snorkel (2a) may be an important parameter to understand fluid flow in vacuum degassing process. In order to illustrate the evolution of the gas volume fraction as a function of its travelling distance along the inlet snorkel (2a), simulation has been conducted at cross sectional planes at three different heights, one at the first level (h1) of six nozzles, second level (h2) of another six nozzles and third at up-leg. It is evident from the FIG. 4 that. till the second level (h2) is reached, the gas column expand but remain as individual gas plumes. After that that as the height increase, the gas columns expand but remain as individual gas plumes. Once the height increases, the gas columns expand and collide to form ring like structure [as shown in FIG.4]. By increasing the inert gas bubble distribution and flow rates, more bubbles will form and travel to the center faster creating the ring structure much earlier. This process may help to lift the molten metal significantly faster in turn increasing the circulation rate, thus faster decarbonization.

Rate of decarbonization depends on reaction surface area which in turn depends on circulation rate of molten metal. The decarbonization performance of RH-degasser vessel (10) depends mainly on the circulation rate which may be defined as the amount of molten metal flowing into and out of the vessel (10) in a minute and may be governed by equation,

• Q = 3.8*10-3 Du0.3 Dd1.1 G0.31 H0.5
Where, Q is circulation rate of molten metal in the vessel (10), ton/minute,
Du is upleg internal diameter, cm,
Dd is downleg internal diameter, cm,
H is lift gas injection depth, cm,
G is total inert gas injection rate in upleg, Nl/min.

Three different sizes of inert gas bubbles were simulated keeping the flowrate constant with the same inlet snorkel (2a) design. The experiment is carried out to compare the circulation rates between different inert gas bubble sizes. From the results, it can be observed that as the bubble size decreased, the circulation rate increases. The smaller the bubble, more surface area may be captured. FIG.5 indicates circulation rate in tons/min for three different bubble sizes i.e., 6mm, 3mm and 1mm.

In an embodiment, the configuration of the gas-purging module (1) of the present disclosure may significantly improve the recirculation rate of molten metal. Thus, increasing decarbonization efficiency in the RH vessel (10).

It is to be understood that a person of ordinary skill in the art may develop a system of similar configuration without deviating from the scope of the present disclosure. Such modifications and variations may be made without departing from the scope of the present disclosure. Therefore, it is intended that the present disclosure covers such modifications and variations provided they come within the ambit of the appended claims and their equivalents.

Equivalents

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

It will be understood by those within the art that, in general, terms used herein, are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding the description may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated in the description.

Referral Numerals:
Description Reference number
Gas purging module 1
Inlet snorkel and outlet snorkel 2a and 2b
Refractory lining 3
Ladle 4
Apertures 5
Inert gas pipe A
Tube T
Enclosure E

Claims:We claim:

1. A gas-purging module (1) for a RH degassing vessel (10), the gas-purging module (1) comprising:
a tube (T) having an inlet end (I) and an outlet end (O) receivable in a provision defined in an inlet snorkel (2) of the RH degassing vessel (10), wherein the tube (T) extends in a refractory lining (3) surrounding the inlet snorkel (2) and defines a flow path extending from the inlet end (1) to the outlet end (O),
wherein, the outlet end (O) is defined with a plurality of apertures (5) of pre-determined dimension to induce gas bubbles into the inlet snorkel (2a) to increase recirculation rate of molten metal within the RH degassing vessel.

2. The module (1) as claimed in claim 1, wherein the plurality of apertures (5) defines a partial opening to the interior of the inlet snorkel (2).

3. The module (1) as claimed in claim 1, wherein the inlet end (I) of the tube (T) is fluidly connected to a blow pipe to channelize inert gas from an inert gas unit to the tube (T).

4. The module (1) as claimed in claim 1, wherein the inert gas is argon.

5. The module (1) as claimed in claim 1, wherein the plurality of apertures (5) in the gas purging module (1) ranges from 5 to 8.

6. The module (1) as claimed in claim 1, wherein diameter of each of the plurality of apertures (5) is 1mm.

7. The module (1) as claimed in claim 1, wherein the gas bubbles induced into the inlet snorkel (2a) is of 1mm diameter.

8. A RH degassing vessel (10) comprising:
a vacuum chamber (V) defined with an inlet snorkel (2a) and an outlet snorkel (2b) each surrounded by a refractory lining (3), wherein the inlet snorkel (2a) is structured to accommodate a plurality of gas purging modules (1), the plurality of gas purging modules (1) is distributed along a circumference of the inlet snorkel (2a) at a plurality of levels (h1 and h2), each of the plurality of gas purging modules (1) comprises:
a tube (T) having an inlet end (I) and an outlet end (O) receivable in a provision defined in an inlet snorkel (2) of the RH degassing vessel (10),
wherein the tube (T) extends in the refractory lining (3) surrounding the inlet snorkel (2) and defines a flow path extending from the inlet end (1) to the outlet end (O),
wherein, the outlet end (O) is defined with a plurality of apertures (5) of pre-determined dimension to induce gas bubbles into the inlet snorkel (2a) to increase recirculation rate of molten metal within the RH degassing vessel.

9. The vessel (10) as claimed in claim 8, wherein the plurality of levels (h1 and h2) includes a first level (h1) and a second level (h2).

10. The vessel (10) as claimed in claim 8, wherein the plurality of gas purging modules (1) ranges from 6 to 12 modules along the circumference of the inlet snorkel (2a) in each of the plurality of levels.

11. The vessel (10) as claimed in claim 8, wherein each of the plurality of gas purging modules (1) are spaced apart equidistantly from each other along the circumference of the inlet snorkel (2a).

12. The vessel (10) as claimed in claim 8, wherein the inlet end (I) of the tube (T) is fluidly connected to a blow pipe to channelize inert gas from an inert gas unit to the tube (T).

13. The vessel (10) as claimed in claim 8, wherein the inert gas is argon.

14. The vessel (10) as claimed in claim 8, wherein the plurality of apertures (5) in each if the plurality of gas purging module (1) is 5 to 8.

15. The vessel (10) as claimed in claim 8, wherein diameter of each of the plurality of apertures (5) is 1mm.

16. The vessel (10) as claimed in claim 1, wherein the gas bubbles induced into the inlet snorkel (2) is of 1mm.