Patent Application
20170362672
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The present invention pertains to the field of hot metal processing equipment and a method of using such equipment, for instance when making steel and iron.
The present invention relates to removal of impurities from a quantity of molten hot metal in a ladle during ironmaking, or alternatively, during steelmaking, as both processes use similar equipment and methods. References to steelmaking hence are also applicable to ironmaking and the use of the term “steelmaking” here is meant to include ironmaking as well. Slag is a term of art in the steelmaking industry referring to waste impurities produced when a desired metal has been separated from its raw ore, and typically floats to the surface of the molten metal. The impurities are skimmed off the surface of the molten or hot metal before the metal is sent for processing. Presence of impurities affects the quality and characteristics of the finished products, consolidating and efficiently removing impurities reduces production costs, and improves yield and metal quality.
Currently, steelmakers use two methods to separate waste or impurities from hot metal: (1) material methods that introduce desulfurizing agents deep into the hot metal to chemically bind the sulfur for easier removal, and (2) stirring methods that physically stir the hot metal by creating turbulence to agitate the body of metal so as to allow better distribution of desulfurizing agents and thus allow the desulfurizing agents to work more efficiently.
For material methods, material (desulfurizing agents) are commonly delivered into the hot metal via a typical “straight” through lance, one of many configurations of lances used in steelmaking, the lance consisting of a pipe or chamber with the majority of the length coated with a refractory material. The purpose of the refractory coating is to prevent the pipe from melting or distorting while submerged in the hot (molten) metal. This type of lance simply delivers the injected material to the bottom of the ladle with a minimum amount of stirring of the material into the hot metal. The only stirring gas available is provided by the gas which conveys the material into the ladle and/or the vaporization material.
A known issue with material methods using lances is the lack of uniform dispersion of material into the hot metal. The reagent is only present in sufficient quantities in around the lance itself, as the material-gas bubble typically will simply follow the lance exterior body up to the slag line, resulting in a decreased effectiveness in removing sulfur impurities from the entire body of hot metal. It is also known that a stirring gas without any material introduced into the hot metal also tends to follow the lance exterior body up to the slag line, reducing its effectiveness to stir the material into the hot metal.
Regarding the material and stirring methods, the prior art teaches that use of the stirring method is optional when using a material injection method, although steelmakers often use the stirring method in conjunction with the material method as this typically results in better mixing of reagent and thus increased removal of impurities from the hot metal.
Another type of material lance design is a “T” lance, in which the bottom of the main pipe is shaped like an inverted letter “T” so as to move the material away from the lance in two different directions. This process is an improvement over the other lance style since it moves the material away from the lance and thus improves distribution of the material to a degree by creating two reaction zone in the hot metal. While useful, U.S. Pat. No. 5,188,661 (Cook et al.) granted 23 Feb. 1993 discusses some of the drawbacks of the T lance, including the problem of uneven material distribution caused by blockages of one of the two ports and thus resulting in undesired splashing of the hot metal.
For stirring methods, a rotary lance has been developed to physically stir the hot metal, by rotating the lance while submerged in the hot metal via a motor and speed reducer system. The main drawback to this system is that it must be installed above a lance drive, which requires the lance drive to be of a substantial structure to be able to support the additional weight of the machinery needed to rotate the lance.
The prior art teaches the use of both material and stirring methods together, as well as separately, however in reality, most steelmakers are forced by economic reasons to use only one method as the capital investments required for both methods is often cost prohibitive. For instance, a highly effective material-stirring lance is described in U.S. Pat. No. 9,259,780 B2 (Waitlevertch et al.) granted 16 Feb. 2016, for which the present inventor is also a co-inventor, the main drawback of this system is the need for costly modifications to existing equipment in order to support the weight of the machinery required to rotate the lance, again adding to capital costs, and downtime to do such modifications.
What is needed is an improved lance that increases efficiency and requires no significant nor expensive investments or modification to existing equipment, and is cost effective for steelmakers.
In a first aspect of the invention, a multiple chamber material-stirring lance for removing impurities from a quantity of hot metal in a ladle during steel or ironmaking comprises at least one gas chamber formed with a gas connection pipe at a first end and terminating in at least one lower gas port, and at least one material chamber parallel to the gas chamber having a material connection pipe at a first end and terminating in at least one material discharge port at a second end, both chambers encased by a refractory coating so as to form a single lance body. The lower ports are gas permeable structures that restrict and regulate a flow of gas out of the gas chamber and configured such that the flow of gas introduced into the gas chamber and emitted through the gas permeable structures with a cfm of gas between 40 and 600 cfm into the quantity of hot metal form a plurality of bubbles smaller than a plurality of bubbles emitted from a gas permeable structure that does not restrict nor regulate the flow of gas out of the gas chamber.
In a second aspect of the invention, the material chamber terminates in a pipe having a pair of opposed material discharge ports forming an inverted T-configuration.
In yet a third aspect of the invention, the at least one material discharge port is positioned at a lowermost terminal end of the material chamber.
In yet a forth aspect of the invention, the gas chamber is further comprised of at least one body port formed into a length of the gas chamber, leading out of the gas chamber and exiting the refractory coating and wherein the at least one body port is a gas permeable structure that restricts and regulates the flow of gas out of the gas chamber, including porous plugs, directional plugs, and nozzles.
In yet a fifth aspect of the invention, a method of using a multiple chamber material-stirring lance having at least one material chamber and at least one gas chamber during a steel purification process, comprises the steps of positioning the multiple chamber material-stirring lance vertically into a quantity of hot metal inside a ladle, introducing a quantity of material into the material chamber, introducing a volume of stirring gas into the gas chamber, discharging the quantity of material from the material chamber through at least one material port and into the quantity of hot metal and discharging the volume of stirring gas through the lower ports where the exiting gas has a cfm between 40 and 600 cfm, where the discharged gas forms a plurality of bubbles simulating a boiling effect in the hot metal.
The features and advantages of the invention will become apparent from a consideration of the subsequent detailed description presented in connection with accompanying drawings, in which:
The following is a list of reference labels used in the drawings to label components of different embodiments of the invention, and the names of the indicated components.
Hot metal or molten metal: metal heated to a temperature such that the metal is in a liquid state, and includes metals commonly purified by heating in a ladle such as steel and iron
Material: desulfurization reagent or reagents
Port: when referring to a port of a gas chamber, a structure capable of passing gas, including but not limited to porous plugs, directional plugs, pipes, and nozzles, and when referring to a port of a material chamber, a structure that allows material to pass through.
A multiple chamber material-stirring lance 40 and method of use is shown in
Turning now to
A material chamber 43, located adjacent to the gas chamber, having a material connection pipe 42 at an uppermost end terminates in one or more material discharge ports 60 at a lowermost end of the material chamber 43. While not shown in the Figures, when a single material port 60 is used, the port exit opening is typically located at a lowermost terminal end of the material chamber (straight lance configuration). A lance refractory coating 46 covers and encases the exterior of the gas chamber to protect it from damage caused by submerging the multiple chamber material-stirring lance 40 into a quantity of hot metal 6 in a ladle 2, the lower ports 52 allowing gas present in the gas chamber 48 to exit the multiple chamber material-stirring lance 40.
a-h are side and top cross sectional views of a second embodiment of the multiple chamber material-stirring lance 40, where the gas chamber 48 is formed with at least one or more body ports 50 formed into a length of the gas chamber 48 above the lower ports 52. The body ports 50, like the lower ports 52, are directional and/or porous structures that emit relatively smaller gas bubbles as compared to an open pipe end that does not limit or otherwise alter the flow rate of the gas from the gas chamber. The inventor notes that gas ports, whether they are lower ports 52 or body ports 50, are structures that control the flow of gas out of the gas chamber and into the hot metal. In contrast, material ports 60 allow material, such as powdered reagent with a gas carrier such as nitrogen to freely exit the material ports without regulation. The array of body ports shown in
Turning now to
When the multiple chamber material-stirring lance 40 is in use, the material 5 is dispersed from the material ports 60 and stirring gas bubbles 11 emitted from the lower gas ports 52 and/or the plurality of body ports 50 create turbulence in the hot metal 6. The inventor notes that the lower gas ports 52 of the multiple chamber material-stirring lance can also be configured as an array of ports about the terminal end of the gas chamber 48, where a series of pipes radiate outwards from the chamber 48 with each pipe ending in porous and/or directional port structures that regulate the flow of gas so as to control the boiling effect of the stirring gas bubbles and to allow the creation of different stirring gas patterns, as desired.
The inventor notes that while the Figures show a single material chamber and a single gas chamber, it is possible to introduce multiple material and multiple gas chambers within a same lance body. The inventor notes the stirring gas can be introduced into the hot metal with or without material also being introduced, providing the mill operator flexibility of use of the multiple chamber material-stirring lance 40. The inventor stresses that his use of the term “port”, in the singular or plural, includes any gas permeable structure such as porous or directional plugs, nozzles, and pipes, and the Figures may show a particular type of port, such as a porous plug as an example of a suitable structure and is not meant to limit the meaning of “port” to only refer to the specific type of structures as shown in the Figures but is meant to illustrate one type of suitable port according to the invention. The inventor also notes that directional plugs, which have a gas permeable slit or slot are also suitable gas permeable structures for use with the invention. The term “porous plugs” also includes plate type porous material. Port size, regardless of the type of permeable structure used, varies between 0.125 to 5 inches (0.315 to 12.7 cm) in diameter and the lance can be manufactured so as to vary port sizes in a single lance, according to desires or needs of the mill operator. Varying port sizes will impact the volume of gas flowing through the ports relative each other.
The inventor notes the multiple chamber material-stirring lance 40 provides many benefits to the mill operator. The weight of the lance 40 for instance, is essentially the same as that of a standard prior art lance. Thus the multiple chamber material-stirring lance 40 can be installed onto an existing lance drive system with no structural modifications required. The only modifications to the lance drive system consist of an additional gas manifold and an additional hose to a top of the lance 40 to deliver gas to the lance 40, relatively simple and inexpensive modifications.
The mill operator using the multiple chamber material-stirring lance is afforded significant cost reductions and efficiency/quality increases. Steelmaking efficiency is improved without incurring the additional capital equipment cost as required by the prior art systems, and as the multiple chamber material-stirring lance 40 is a combined material and gas stirring lance, only a single lance must be replaced. The mill operator may use gas only, or have gas and material introduced into the hot metal simultaneously, or at different times or different frequencies, as desired, allowing the mill operator the most flexibility and functionality with a single lance, and represents significant cost savings for the mill operator, as a single lance (and its requisite equipment) can achieve a same or better results as the dual material lance systems previously patented, and without substantive capital investment by the mill operator.
It is to be understood the above-described arrangements are only illustrative of the application of the principles of the present invention. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the scope of the present invention. For instance, the invention is shown with chambers and the exterior lance body as being generally cylindrical in shape, with a circular cross section, however other shapes, such as triangular and hexagonal prisms, with triangular and hexagonal cross sections, cubes and cuboid, with square and rectangular cross sections, or other three dimensional shapes, even spherical or irregular can also be used. The inventor stresses that the combination of gas and material chambers in a single lance, the port configurations which maximize mixing of material within the hot metal, and the ability to control the volume and/or rate of flow of stirring gas via port size, type, and location are key features of the multiple chamber material-stirring lance. Whether the chambers have square or other shaped cross sections, or flat walls versus curved, are variations that are inconsequential to the functioning of the invention, and the circular cross sections shown in the Figures are not meant to exclude these other possible shapes for the coaxial chambers but are just an example of one possible useful shape.
The inventor also notes that the array of body ports shown in
Reference is made to and priority claimed from U.S. application Ser. No. 15/183,020 filed 15 Jun. 2016, and which itself claims priority from U.S. provisional application Ser. No. 62/180,826 filed 17 Jun. 2015
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15183020 | Jun 2016 | US |
| Child | 15432130 | US |
