Patent Application
20200354802
The present invention generally relates to vessels for melting metal. More specifically, it relates to systems and methods for controlling the operation and/or positioning of a lance and nozzle assembly relative to a molten metal bath in such a vessel.
In the steel industry, the Basic Oxygen Furnace (BOF) is the primary steelmaking vessel in a steel mill. A general goal in the industry is to improve quality control while also reducing production time and cost. However, a common impedance to being able to achieve that goal is the inability to determine, in real time, the temperature of the molten steel bath inside a BOF. As a result of lacking real time, accurate temperature data, target temperatures and chemistries are often missed. Failure to achieve the target temperatures and chemistries during the metal melting process can result in inefficiencies and may even result in having to reinitiate the heating process, resulting in significant economic impact. This lack of ability to determine temperature in real time results in a lack of efficiency that not only applies to BOF's in the steel industry, but also to electric arc furnaces (EAF's) as well as induction furnaces.
A BOF operates at very high temperatures. As a result, using temperature sensors inside the BOF to take temperature readings is not typically feasible. Furthermore, to the extent that using temperature sensors inside the BOF has been attempted, the high temperatures at which the BOF operates tend to substantially impact the life of the sensors.
There are a few temperature measuring approaches that have been attempted in the industry and have resulted in at least some measure of success. These approaches include the following: using a bomb thermocouple (i.e., temperature sensor); using a spring loaded thermocouple disposed in the tip of a lance; using an infrared camera to sense the temperature of the tip of a lance or the bath itself; and using a thermocouple installed in a tuyere (i.e., an air nozzle which is used to blow air into the molten bath in the BOF). While these approaches do provide for the measurement of temperature, the measurements that are taken are basically just a snapshot—a single temperature measurement taken at a specific point in time. Because the temperature of the molten metal bath in a BOF varies greatly with stratification of the level (height) of the bath and proximity to the heating element, none of these approaches effectively provide accurate temperature data with regard to the overall bath inside the BOF.
Generally speaking, each steel mill develops their own BOF process control strategies in an attempt to improve quality control while concurrently reducing production time and cost. In most facilities, static models are used to determine the amount of oxygen to be blown into the bath in the vessel and the charge to be applied to the furnace, based on initial and final heat information. While these models have improved the operators' chances of achieving the desired endpoint, they do not provide real time process information and therefore target temperatures and chemistries can still be missed. Failure to achieve the desired endpoint condition can be attributed to errors in model input conditions (e.g. the unknown composition of the scrap, uncertainties in hot metal temperature and chemistry, etc.) as well as the inability of the model itself to accurately represent the physics of the conversion process. Changes in furnace volume can also result in distance variations between the tip of the lance and the top surface of the molten metal bath—a phenomenon that affects bath stirring characteristics and carbon oxidization rates. Alleviating the missed endpoint condition requires corrective action, either while the steel remains in the BOF or during subsequent ladle treatment. Unfortunately, either corrective action translates to additional operating cost.
Because of the challenging environment in the BOF, it has been difficult to implement process sensors in this environment that can provide meaningful data over long sensor lifetimes. One of the primary objectives for requiring a temperature measurement is to rapidly and accurately measure the end-point melt temperature for quick tap operations. Gaining access to the melt surface through the slag layer represents the primary challenge associated with accurate endpoint temperature measurement.
One method is to install a temperature sensing device through a tuyere. This type of sensing device is adequate at the beginning of the life of the sensor, but quickly begins to deteriorate. A second type of temperature sensing device is an infrared camera located in the roof, sidewall or lance tip. The slag layer on top of the steel requires a high pressure gas to part it, and the resulting splashing of the slag creates difficulty in obtaining an accurate measurement.
As a matter of course, some molten metal is always left in the bottom of the BOF, between heats, to improve melting efficiency. After every heat, some of this metal and slag freezes, building a thickness on the bottom of the furnace. After a number of heats, this thickness builds substantially enough to warrant adjusting the height of the lance relative to the bath. If the lance is too low or too close to the bath, the tip can overheat or the lance can ingest slag that can plug the orifices. On the other hand, if the lance is too high, the oxygen will not penetrate the slag. To determine the height of the lance above a bath, some furnace operators measure the buildup using a system that uses lasers to calculate the available volume of vessel. This is an expensive and time-consuming process. Other operators place a disposable rod on the end of a lance, insert the lance to operating position, remove the lance and measure the length of melted rod to determine the actual distance to the bath. This method involves exposing personnel to unsafe conditions.
An objective of an embodiment of the present invention is to provide an improved system and method for controlling the operation and/or positioning of a lance and nozzle assembly with regard to a molten metal bath in a vessel.
Another objective of an embodiment of the present invention is to provide a system and method for continuously detecting and monitoring the temperature of a molten metal bath in a vessel.
Briefly, a preferred embodiment of the present invention provides a system and method for measuring and monitoring the temperature of a molten metal bath in a vessel, such as a BOF, and based on those temperatures, amend the position of a lance and nozzle assembly relative to the height of the molten metal bath. Specifically, at least one temperature sensor is disposed proximate the tip of a lance and nozzle assembly in order to continuously measure and monitor the temperature at the tip of the lance. Another temperature sensor may be placed in a position to measure the temperature of molten metal bath. Preferably, the at least one temperature sensor is configured to provide at least one signal to a processing unit (such as a control center), and the processing unit is configured to process the at least one signal and determine the temperature of the molten metal bath. The at least one temperature sensor can be either hard wired to the processing unit, or the at least one temperature sensor can be configured to wirelessly transmit the signals to the processing unit. Regardless, the system can be used to continuously monitor the temperature of the lance tip and/or molten metal bath over time. Moreover, the control center may be configured to operate and/or position the lance and nozzle assembly relative to the molten metal bath, based on signals received and processed by the control center via the at least one temperature sensor. It is contemplated that a single sensor, such as an infrared sensor, may measure the temperature of both the lance tip and the molten metal bath in order to carry out the systems and methods of this invention.
A preferred embodiment of the present invention comprises:
a system for operating and/or positioning a lance and nozzle assembly relative to a molten metal bath in a vessel, the system comprising:
at least one temperature sensor proximate a tip of the lance and nozzle assembly; and
a processing unit configured to receive at least one signal from the at least one temperature sensor, process said at least one signal to determine the temperature of the molten metal bath in the vessel, and operate and/or position the lance and nozzle assembly based on the temperature which has been determined by the processing unit based on the at least one signal which has been received by the at least one temperature sensor.
Another preferred embodiment of the present invention comprises:
a method for operating and/or positioning a lance and nozzle assembly relative to a molten metal bath in a vessel, the method comprising:
providing a first temperature sensor proximate to a tip of the lance and nozzle assembly, wherein the sensor is housed by the lance and nozzle assembly, wherein the first temperature sensor is configured to detect a temperature of the tip of the lance and nozzle assembly, and wherein the temperature is converted to tip temperature data;
providing a second temperature sensor on or within the vessel, wherein the second temperature sensor is configured to detect a temperature of the molten metal bath, and wherein the temperature is converted to bath temperature data;
sending the tip temperature data and the bath temperature data to a processing unit;
exchanging information between the processing unit and a process operations data module, wherein the information comprises the tip temperature data, the bath temperature data, and process operations data;
mapping the tip temperature data and bath temperature data to a corresponding active elevation of the lance and nozzle assembly;
comparing the active elevation to a preferred elevation of the lance and nozzle assembly;
moving the lance and nozzle assembly from the active elevation to the preferred elevation.
The organization and manner of the structure and operation of the invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings wherein like reference numerals identify like elements in which:
While this invention may be susceptible to embodiment in different forms, there are shown in the drawings and will be described herein in detail, specific embodiments with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that as illustrated.
As shown in
The at least one temperature sensor 16 can be either hard wired to the processing unit 18 (such as via hardwire, a fiber optic conductor, etc.), or the at least one temperature sensor 16 can be configured to wirelessly transmit the at least one signal to the processing unit 18 (such as via laser signals, a radio signal, etc.). Regardless, the system 10 can be used to continuously monitor the temperature of the molten metal bath 22 in the vessel 12 over time, and based on the temperature that has been detected, the processing unit 18 can change one or more operating conditions, during production, to arrive at the desired endpoint. The same temperature sensor 16 may also be effectively used, by the processing unit 18, to confirm that the conversion process has reached the desired endpoint condition. In some preferred embodiments, as will be described below, a sensor 16 is located at the tip of the lance and nozzle assembly 14 for detecting a temperature of the lance 14 tip and another sensor 16 is positioned near the molten metal bath 22 for detection of a temperature thereof. In either case, the utility of the real-time sensor (i.e., the at least one temperature sensor 16 and processing unit 18) is its ability to minimize the time and cost required to produce steel.
The temperature of the slag itself can be measured with the at least one temperature sensor 16 located in the lance and nozzle assembly 14 and the melt temperature inferred from this measurement. This temperature probe reading the inside of the copper tip can be a spring loaded thermocouple, or an IR camera. The time-resolved radiance from the slag and combustion of gases can be correlated to the temperature of the bath. The operating temperature profile exhibits a peak near the start of the heat and falls rapidly to a minimum approximately 250 seconds into the heat. From that point, the radiance gradually rises, while concurrently exhibiting local minima and maxima associated with: 1) variations in combustion activity below the lance; 2) addition of ore, lime, and stone throughout the heat; and 3) changes in lance height.
Since radiance is coupled with the heat release rate within the combustion zone, the data effectively received (by the processing unit 18 via the at least temperature sensor 16) provides feed-back information for modified lance practice and/or the time and rates of flux addition to arrive at a more uniform radiance level and greater integrated heat release rates at early times in the conversion process.
Tip sensor measurements (measurement of the temperature of a tip of the lance and nozzle assembly 12 taken by the processing unit 18 via the at least one temperature sensor 16) may also provide an indicator of end point bath carbon content. Based on empirical evaluation of data, it has been determined that measurements pertinent to bath carbon content are consequential only after the heat has progressed for approximately 1000 seconds or more. From this time forward, the radiance exhibits an initial maximum, followed by a decrease to a local minimum, rising again to a local maximum. For many heats, within 50 seconds after the second local maximum or 100 seconds of the local minimum, the carbon endpoint is reached. From a process control perspective, it is preferable to obtain bath carbon content information as soon as feasible before reaching the endpoint to allow time for process correction, if necessary. However, failing this approach, a thermally measured endpoint carbon measurement would also be useful.
Preferably, the processing unit 18 is configured to effectively use the at least one temperature sensor 16 in the lance and nozzle assembly 14 to calibrate the temperature of the lance while the lance is in a known position relative to the bath. Using the at least one temperature sensor 16, the relative position of the lance and nozzle assembly 12 relative to the bath can be determined by the processing unit 18, indirectly without having to take further measurements, make additional calculations, or exposing anyone to a risk in safety.
Providing at least one temperature sensor 16 in the lance and nozzle assembly 14 effectively provides a view into the vessel that can be used by the processing unit 18 to decrease process time and energy as well as positioning of the lance. With all the information that is typically collected, furnace owners still have operators manually make operational decisions thereby losing consistency between operators. The purpose of the present invention is to automate the real time data being collected with automated control of the lancing operations. This is done by sending data signals from the at least one temperature sensor 16 to the processing unit 18 via hardwire, fiber optic conductor, laser signals, radio signal, etc. The at least one temperature sensor 16 and the processing unit 18 collectively function to permit analysis of certain bath conditions which might be metallurgical, relate to sound and light, or be pyrometric, etc. This data is received and analyzed by the processing unit 18, and the resulting analysis causes commands to be sent to the lance carriage controls and oxygen valve stand for the beneficiation of the process.
The arrangement may be utilized with any gas lance or oxygen-oil or oxygen fuel burner lance where some form of sensor or information gathering means is to be incorporated. Preferably, a central tube of the lance and nozzle assembly provides a safe and yet effective construction and shielding means for the cable conductor. The arrangement may also be utilized with any signal or information transmittal method, such as but not limited to light usage or fiber optic transfer medium as well as the transmittal of an electrical signal by cable. The ability to measure the bath temperature in real-time allows the operator to see what the bath is doing over time, instead of relying upon single-point measurements taken, for example, with a thermocouple. This capability can be used to prevent overshoots, reduce processing time and optimize energy usage. Real-time temperature monitoring gives valuable insight into the transient behavior of the bath, thereby ensuring the ability of the measurement to accurately represent the bath as a whole. It provides a safe and economic manner in which the desired result may be achieved. It further automates the control of the oxygen blow and lance position ensuring consistency in operation between operators.
The present invention is directed to a combination of a lance and nozzle assembly for supplying gas to a basic oxygen furnace. The lance and nozzle include an arrangement to accommodate a temperature sensing device or unit which is adapted to transmit signals providing information in connection with the refractory or contents of the bath contained within the vessel. The arrangement includes a signal transmission by, for example, hard wire or radio transmission to a processing 18, such as a PLC, located in a control center. This PLC interprets the data to provide automatic control for operating or positioning the lance and nozzle assembly.
A: collecting tip temperature data via sensor 16 at the tip of the lance and nozzle assembly 14, wherein such data is provided to processing unit 18;
B: collecting bath temperature data via sensor(s) 16, such as that provided in one or more locations other than the lance and nozzle assembly 14, for the molten metal bath 22 in the vessel 12, wherein such data is provided to processing unit 18;
C: obtaining in process operations data module 26 process operations and parameters data from primary and sub systems of system 10, wherein the process operations and parameters data of the process operations data module 26 and data of processing unit 18 may be exchanged between unit 18 and module 26 either unidirectionally or bidirectionally;
D: providing information to lance elevation control 24 based on a comparison of data received by processing unit 18 against stored data;
E: amending the elevation position of the lance and nozzle assembly 14 in relation to the bath 22.
Mechanisms for obtaining tip temperature data from the tip of lance and nozzle assembly 14 include various means and methods, such as Op-T Temp, pyrometer, thermocouple, infrared temperature sensors, and resistance temperature detectors.
Mechanisms for obtaining bath temperature data from the metal bath 22 include continuous bath measurement, manual measurement, manual measurement, automated measurement, ultrasonic measurement, and probing.
The temperature data obtained at steps A and B are preferably mapped to a calculated lance and nozzle assembly 14 elevations 20 via an algorithm as such elevations 20 relating to an operating range at Step C. The operating ranges preferably correspond to a particular processing step in the metal making process of the vessel 12. Step C may comprise a feedback loop, and process operations data module 26 may be connected to and/or informed by an operator's station. Data comprising module 26, including process operations data, may include data from the primary and sub systems of the vessel 12, including anti-slop systems as well as normal operations practices input provided by operators at human machine interfaces.
At step D, the data processing unit 18 preferably calculates the lance and nozzle assembly 14 elevation 20 and amends the elevation 20 based on the temperature readings in the operating range at Step C. This step comprises the lance elevation control 24, which receives input from the processing unit 18. The elevation 20 is preferably the distance between the lance and nozzle assembly 14 tip and the surface of the molten metal bath 22.
Step E can be effectuated by various means including automated controls and manual operation controls as prompted by the lance elevation control 24.
Ideally, the present invention will maintain the elevation 20 at an optimal level depending on the operational stage of the vessel 12.
If the temperatures reach a critical level where the lance 14 is calculated by the system 10 processing unit 18 to be too close to the bath 22 the lance 14 can be alarmed for manual adjustment override, or it can be programmed to automatically adjust to a proper lance 14 height 20 to prevent damaging or dunking the lance 14 tip in relation to the steel bath 22.
Any of steps A-E can comprise a wired or wireless transmission of data.
It is contemplated that additional steps may be deployed the method described herein. The process described herein may be automated, manual, or semi-automated.
While specific embodiments of the invention have been shown and described, it is envisioned that those skilled in the art may devise various modifications without departing from the spirit and scope of the present invention.
This application claims the benefit of U.S. Provisional Patent Application No. 62/719,277 filed in the United States Patent and Trademark Office on Aug. 17, 2018.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2019/047116 | 8/19/2019 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62719277 | Aug 2018 | US |
