MXPA00002945A - Method for monitoring the wear and extending the life of blast furnace refractory lining - Google Patents

Abstract

A method is provided for on-line monitoring of the wear of a refractory lining of a blast furnace. The method includes determining the wear line of the lining from signals provided by temperature probes located in groups, e.g., group (10, 12, 14), group (16, 18, 20), group (22, 24, 26), embedded at spaced locations across the thickness of the refractory lining. Other methods disclosed include:a method of determining the thickness of a protective layer of solidified metal skull formed on the refractory hearth, a method of determining the conditions of heat transfer between a refractory lining and a metal shell of a blast furnace and between the metal shell and cooling water applied to the shell, and a method of extending the life of refractory lining.

Description

METHOD FOR MONITORING WEAR AND PROLONGING THE LIFE OF REFRACTORY HIGH OVEN COATINGS TECHNICAL FIELD The present invention is a method for extending the life of a refractory blast furnace lining, and particularly a method that includes on-line monitoring of campaign peak and current average signals of a plurality of thermocouples embedded at spaced locations in the refractory lining and of a plurality of thermocouples placed at spaced locations in a metal shell of the furnace, calculating from those signals the wear line of the refractory lining and the thickness of a layer of solidified metal film formed on an inner surface of the refractory, and then determine the conditions of heat transfer in the shell, for example, whether or not a space has been formed between the shell and the shell and whether or not it is sufficient to cool the shell with water.

ANTECEDENTS OF THE TECHNIQUE Normally, the iron furnace is constructed of a metal shell with a refractory brick lining. The life of the refractory brick lining determines the length of time that the furnace can be kept running before the furnace has to be stopped to install a new refractory. The longer life of the refractory decreases the cost of the refractory and increases the achieved productivity of the furnace. More expensive refractory bricks have been used to extend the length of a furnace "campaign". The injection or application with a gun of a refractory material between the refractory brick and the metal shell has also been used as a measure of repair to close the spaces that sometimes form between the shell and the brick. The spaces between the brick and the shell reduce the heat transfer and cause increased wear of the refractory brick. The patent of US Pat. No. 4,510,793 describes the use of a ceramic rod in a furnace wall that wears away with the coating. The wear of the bar and the coating is detected ultrasonically by generating ultrasonic pulses in the bar and detecting the reflection of the pulses from the internal end of wear of the bar. Japanese published application 1-290709 discloses thermocouples embedded in the refractory in the interior and bottom side of the wall of a blast furnace. From the temperatures measured by the thermocouples, calculations are performed to determine the compacting state of coke in the center of the furnace. When the compacting of coke is inadequate for preferential flow of molten iron in the central part of the furnace, changes are made in the amount, grain size or heat characteristics of the coke charged in the furnace.

The patent of E.U.A. 4,358,953, Horiuchi et al, describes a method for monitoring the wear of refractory blast furnace lining walls by monitoring temperatures at different points through the refractory thickness and analyzing the delay time between firing signals representing internal phenomena of the furnace and the output signals of the temperature probe. This patent also discloses a prior art method for determining the degree of wear from a one-dimensional heat transfer analysis. An apparatus for monitoring the temperature distribution in the refractory is also described. A similar apparatus is described in the patent of E.U.A. 4,412,090, Kawate et al, and in the U.S. patent. 4,442,706, Kawate, et al. It is also known to use one-dimensional and two-dimensional heat transfer calculations for refractory temperature distributions and then compare them with the measured temperatures to calculate the remaining refractory and film thickness. A method of this type is described in a literature document entitled "Evaluation of Mathematical Model for Estimating Refractory Wear and Solidified Layer in the Blast Furnace Hearth", by Suh Young-Keun et al, ISIJ, 1994, pages 223-228. However, there was no previous method that used measured temperatures to calculate the thickness of the brick and the film directly so that the interaction between the temperatures measured in all locations in a vertical plane is taken into account simultaneously. In addition, there was no previous method that could be used online without human intervention for signal problems with space formation, insufficient cooling in the shell, and perception of irregular erosion profiles "in the form of an elephant" and erosion profiles "in bowl shape ", to be able to correct the measurements during the operation of the oven and thus prolong the life of the refractory. Other patents related to the measurement of wall thickness and / or temperature include E.U.A. 2,264,968; 2,987,685; 2,994,219; 3,018,663; 3,307,401; 3,512,413; 4,217,544; 4,248,809 and 4,539, 846.

BRIEF DESCRIPTION OF THE INVENTION The invention relates to a method for prolonging the life of the refractory lining of the interior of a metal shell of a blast furnace. The method includes placing the thermocouples in the refractory at a plurality of spaced sites and monitoring the signals produced by the thermocouples during operation of the furnace. Periodically, an average of the temperature readings at each thermocouple location is determined and recorded. The maximum temperature reading from the beginning of a furnace campaign is also determined and recorded. From the current average and maximum field temperature readings of the thermocouple signals, an on-line determination is made, that is to say during the furnace operation, to know if there is a solidified protective layer of metal film on the inside of the refractory and the thickness of the film. If a protective layer of solidified metal film does not exist, or does not have insufficient thickness, a determination is made if there is a space between the refractory and the metal shell of the furnace and the location of the space or if the cooling of the shell of metal is insufficient. Thus, some steps are followed during operation of the furnace, based on the results of said calculations, to fill said spaces with refractory, to restore sufficient cooling of the shell or to form a protective solidified layer of sufficient thickness on the internal surface of the shell. refractory. The method of the invention also includes performing a movable limit calculation directly from the temperatures measured in all locations of the thermocouple in a vertical plane simultaneously to perceive irregular erosion profiles, for example erosion "in the form of an elephant" and "in bowl shape "of the refractory.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross section of the half of a blast furnace crucible showing the arrangement of thermocouples in the refractory and the metal shell of the furnace crucible area. Figure 2 is a schematic side elevational view of the area of the blast hole of a blast furnace illustrating the placement of thermocouples in said area. Figure 3 is a flow diagram of the steps that are followed according to the method of this invention. Figure 4 is a graphical representation of the wear of the refractory lining of the blast furnace crucible and of the formation of solidified metal film determined in accordance with the method of the invention. Figure 5 is a schematic representation of two adjacent surface temperatures of refractory metal shell, TIR and TIS, determined by two different analyzes, with TIR substantially greater than TIS, indicating that the presence of a space between the refractory and the shell of metal. Figure 6 is a schematic representation of the two adjacent refractory metal shell surface temperatures, TIR and TIS, with TIS substantially greater than TIR, indicating insufficient cooling of the metal shell.

DETAILED DESCRIPTION OF THE INVENTION With reference to Figure 1, thermocouples are embedded to measure the temperature, preferably thermocouples, in the refractory and in the metal shell of a blast furnace in the crucible area. The thermocouples 10 and 12 are placed on the side wall of the crucible refractory at two known positions through the thickness in a radial direction of the furnace. At least one thermocouple 14 is placed in a known position in the metal shell in line with thermocouples 10 and 12 in the refractory. This first group of thermocouples is preferably placed in the elevation of a casting hole of the furnace and in the vicinity of the casting hole. A second group of thermocouples 16, 18 and 20 is positioned in vertically aligned positions substantially with the first group at an elevation above the upper surface 21 of the crucible bed. A third group of thermocouples 22, 24 and 26 is placed substantially in vertically aligned positions with respect to the first two groups at an elevation in the corner of the side wall of the crucible where the side wall meets the crucible bed. The groups of thermocouples are placed on the floor of the crucible, that is, in the bed of the crucible, in two known elevations with their hot joints vertically aligned. A pair of thermocouples 28 and 30 is placed on the centerline of the oven. A second pair of thermocouples 32 and 34 is placed a third of the inside of the metal shell on the side wall of the crucible. A third pair, 36 and 38 is placed two-thirds away from that location. It is preferred that the thermocouples in this arrangement be placed in spaced locations around the periphery of the furnace, with concentrated thermocouple coverage in the areas of potentially higher wear such as around the casting hole. Referring to Figure 2, more specifically illustrates the placement of thermocouples around the area of the casting hole of the furnace. Two groups of thermocouples 40 and 42 are located on either side of the casting hole around the elevation of the casting hole. These thermocouples may be in line in a horizontal direction normal to the plane of the pattern or spaced about 10 cm apart in vertical direction as shown in Fig. 2. At an intermediate elevation above the top surface of the crucible bed, locate five groups of thermocouples 44, 45, 48, 50 and 52 in the area of the casting hole. Five other thermocouple groups 54, 56, 58, 60 and 62 are located around the elevation of the corner of the side wall and the top surface of the crucible bed. The thermocouples in the last two groups may be spaced by about 0.6096 meters in a horizontal direction in the plane of Figure 2. As shown in Figure 3, the readings taken from the plurality of thermocouples embedded in the refractory and the shell they are used as input in a computer program to perform a sequence of heat transfer calculations. The current average and maximum field temperatures of these thermocouples are introduced in a heat transfer model that translates these inputs into a heat flow. From this information, a one-dimensional heat transfer model calculates the location of the hot metal solidification isotherm, for example 1148.8 ° C for blast furnace iron. The solidification isotherm resulting from this calculation is used as the initial limit in a two-dimensional heat transfer model. The two-dimensional heat transfer program is repeated until a final limit of the solidification isotherm is determined by minimizing the difference between the measured and predicted temperatures at each measurement point. The calculations of two-dimensional heat transfer are made based on the following two equations: 5tV fffty íí Idxdr ^ = 0 5T where T is the temperature at the location where the radius coordinate from the center line of the furnace is r, and the height coordinate is x. Using the average and maximum temperatures, the heat transfer calculation sequence provides two abutting surfaces of solidification isotherms, Ih and I, respectively, as shown in Figure 4. The adjoining surface Ih is closer to the hot side in comparison with him The abutting surface of the isotherm le, which is closer to the cold side, represents the wear profile of the refractory lining, while representing the film formation between the hot metal and the lining. The distance between Ih and it represents the thickness of the solidified film. The presence of the film prevents the coating from being directly attacked by hot metal and allows to prolong the life of the blast furnace crucible. The beginning of an irregular erosion profile at the corner is illustrated in Figure 4, where an "elephant-shaped" erosion begins to form as indicated by a larger erosion 62 at the corner, than erosion 64 at the corner. adjacent side wall. The method of this invention makes it possible to determine the irregular erosion "in the form of an elephant" in an on-line calculation using a movable limit calculation that takes into account the interaction between the temperatures measured in all locations in a vertical plane simultaneously. The maximum field thermocouple readings represent the last erosion profile of the refractory brick. Generally, the maximum field readings correspond to the highest heat flow and the minimum refractory thickness calculated. These readings can be applied to determine the critical isotherm corresponding to the current erosion profile of the brick, le. The average thermocouple readings represent the current condition inside the crucible. The average temperatures of the last hours recorded at each location are used to determine the current position of the critical isotherm and to calculate TIR and TIS, for the purposes described hereinafter, at all locations in the furnace crucible. The position of the current critical isotherm, Ih, in relation to the isotherm corresponding to the calculated maximum refractory erosion profile, relates the presence and the relative thickness of the protective film on the internal surface of the refractory at each location. In general, when the thermocouple current average readings approach the maximum field temperatures, le ~ Ih, this indicates that there is no protective film layer on the inner surface of the brick. After calculating the critical isotherms, at each location, the calculated values of TIR and TIS are used to determine the presence of a space between the shell and the brickwork of the crucible and the presence of a formation in the shell of the furnace. where, TIR = Calculated surface temperature of adjacent shell as calculated from the hot side TIS = Calculated temperature of adjacent shell surface as calculated from the side cooled with water Ti = Temperature measured from location 1, see figures 5 and 6 T2 = Temperature measured from location 2, see figures 5 and 6 Ts = Measured shell temperature L, = Relative position of the adjacent shell surface with reference to the coordinate system Li = Relative position of the thermocouple 1 with reference to the coordinate system L2 = Relative position of the thermocouple 2 with reference to the coordinate system Ls = Relative position of the shell thermocouple with reference to the coordinate system K1 (T) = Thermal conductivity as a function of temperature between locations 1 and 2 K, (T) = Thermal conductivity between the adjacent surface of the shell and the location 2 Ks (T) = Thermal conductivity of the shell Given these calculated values, the program then uses logical comparison establishments to indicate the conditions of potential precaution and conducts appropriate action to solve any indicated problem. As shown in Figure 5, TIR and TIS are calculated and compared to determine if a space has been formed. TIR is calculated according to the above formula from temperatures T-i and T2 at thermocouple locations 1 and 2 in Figure 5 (corresponding, for example, to thermocouples 10 and 12 in Figure 1). TIS is calculated using the above formula from the temperatures Ts, Ti and T2 (where Ts corresponds to thermocouple 14 of Figure 1). The following relation is used for said comparison: Yes (TIR-TIS) >; pre-established limit (10 ° C in one case), then a space has been formed between the refractory and the metal shell. The preset limit can typically be selected within the range of -6.6 ° C to 48.8 ° C. Corrective action can be taken to fill the space, for example with a high conductivity injection material to re-establish contact with the cooled shell. As shown in Figure 6, TIR and TIS are calculated and compared to determine if a formation in the shell has occurred. The following relationship is used for said comparison: Yes (TIS - TIR) > pre-established limit (10 ° C in one case), then the water cooling of the shell is insufficient. Again, the preset limit can normally be selected within the range of -6.6 to 48.8 ° C. It is possible to take measures to verify a problem in the water system or to determine if a potential formation has formed on the outer surface of the shell that is interfering with the proper heat transfer. After determining the cause of the problem, steps can be taken to remove the formation or restore the proper water flow in this area to improve heat removal efficiency. Conventional measures can be taken to correct these problems, for example, the surface of the shell can be cleaned by sandblasting to remove any formation or other measures can be taken to correct the insufficient water flow or high water temperature. When a space is not formed between the refractory and the shell and when the cooling of the shell is sufficient and therefore there is no solidified metal film formed in the refractory lining of the furnace, or the thickness of the film is insufficient to serve as For refractory protection, steps can be taken to form a solidified metal film of sufficient thickness to serve as protection for the refractory or form additional refractory on the surface of the lining. Such measurements can take the form of injection materials or titanium housing charge in the furnace to protect the inner surface of the crucible, or reduce the production and adjust the speed to form a solidified metal film of sufficient thickness.

Industrial application The invention can be applied to blast furnaces to produce iron for the steel industry as well as blast furnaces to produce non-ferrous metals.

Claims (10)

NOVELTY OF THE INVENTION CLAIMS

1. - A method for monitoring the wear of a refractory lining of a blast furnace where the refractory lining has temperature probes embedded therein, comprising the steps of: a) measuring the temperatures at different points through the thickness of the refractory lining by means of the temperature probes embedded in it; b) calculating the location of a solidification isotherm of the hot metal in said furnace using a one-dimensional heat transfer approach; c) use the one-dimensional heat transfer approach as the initial limit to start a movable limit calculation from a two-dimensional heat transfer model; and d) continuing to repeat the two-dimensional heat transfer model until a final limit of said solidification isotherm is determined by minimizing the difference between the measured temperature and a predicted temperature by said two-dimensional heat transfer model at each temperature measurement point; said final limit of the solidification isotherm indicates the position of a wear surface of the refractory lining for the purpose of monitoring its wear.

2. A method for determining the thickness of a protective layer of solidified metal film formed on the refractory crucible of a blast furnace wherein the refractory crucible has temperature probes embedded in locations spaced in radial directions from the center of the furnace and in several elevations through the thickness of the floor and the walls thereof, comprising the steps of: a) periodically measuring the temperatures in said locations spaced in said radial directions and through the thickness of the floor and walls of the furnace crucible by the probes of temperature embedded in it; b) determine the maximum temperature recorded for each temperature probe since the beginning of a furnace campaign and the average temperature recorded by each temperature probe for a current period of time; c) analyzing the relationship of said maximum and current average temperatures of said temperature probes embedded in the walls of the crucible correlated with the radial distance between the temperature probes and the center of the furnace and the ratio of said maximum temperatures of campaign and current average of said temperature probes embedded in the crucible floor correlated with the elevation distance between the location of the temperature probes in the crucible floor to be able to predict the location of the wear line of the refractory crucible from the location of a solidification isotherm closest to a metal shell, and predicting the location of the inner surface of a solidified metal film liner, said refractory crucible from an isotherm closest to the hot side of the furnace away from the metal shell, and d) determine the thickness of the protective layer of solidified metal film each from the distance between the predicted wear line of the refractory crucible and the predicted internal surface of the metal film.

3. A method according to claim 2, further characterized in that said analysis is performed by calculating the location of said solidification isotherms by using a one-dimensional heat transfer approach, using this approach as the initial limit to start a calculation of a movable limit from a two-dimensional heat transfer model, and continue repeating the two-dimensional heat transfer model until a final limit of each solidification isotherm is determined, minimizing the difference between the temperature measured at each probe location of temperature and a predicted temperature in said location based on the repetitions of the model of two-dimensional heat transfer. 4.- A method to determine the heat transfer conditions between a refractory lining and a metal shell cooled with water from a blast furnace, wherein at least one group of temperature probes is embedded in spaced locations in a radial direction of the furnace, said group of temperature probes include at least two temperature probes located in the refractory lining and at least one temperature probe. temperature in the metal shell cooled with water from the furnace, comprising the steps of: a) from the temperature difference between the temperature probes of said group aligned in a radial direction in the refractory lining, determine the temperature in the adjacent surface between the refractory lining and the metal shell, said adjacent surface temperature is designated TIR; b) from the sum of the temperature of the temperature probe embedded in the metal shell and the temperature difference between the temperature probes aligned in a radial direction in the refractory lining, determining a second temperature in said adjoining surface, said adjoining surface temperature is designated TIS; and c) compare the TIR and TIS values to determine the difference between them. 5. A method according to claim 4, further characterized in that a determination is made to verify if there is a space between the refractory lining and said metal shell where the temperature TIR is substantially greater than the temperature TIS. 6. A method according to claim 4, further characterized in that a determination is made to verify if the cooling of the metal shell is insufficient when the temperature TIS is substantially greater than the temperature TIR. 7. A method to prolong the life of a refractory lining of a blast furnace crucible, wherein the refractory lining of said crucible has temperature probes embedded in radially spaced locations from the center of the furnace crucible and in several elevations through the thickness of the floor and walls of the furnace crucible, comprising the steps of: a) periodically measuring the temperatures in said locations spaced in said radial directions and through the thickness of the crucible refractory lining by embedded temperature probes in the same; b) determine the maximum temperature recorded for each temperature probe since the beginning of a furnace campaign and the average temperature recorded by each temperature probe for a current period of time; c) analyzing the relatiop of said maximum and current average temperatures of said temperature probes embedded in the walls of the crucible correlated with the radial distance between the temperature probes and the center of the furnace crucible and the ratio of said temperatures of maximum of campaign and current average of said temperature probes embedded in the floor of the crucible correlated with the elevation distance between the temperature probes and the floor to be able to predict the location of the wear line of the refractory lining from the location of a solidification isotherm closer to a metal shell, and predicting the location of the inner surface of a protective coating layer of solidified metal film, said refractory crucible from an isotherm closest to the hot side of the furnace away from the metal shell; d) determining the thickness of the solidified metal film during operation of the actual furnace from the distance between the wear line of the refractory lining and the inner surface of the metal film; and e) maintaining sufficient thickness of said protective layer of solidified metal film during operation of said furnace to prolong the life of the refractory lining of said furnace crucible. 8. A method according to claim 7, further characterized in that said analysis is performed by calculating the location of said solidification isotherms using a one-dimensional heat transfer approach, using this approach as the initial limit to start a movable limit calculation from a model of two-dimensional heat transfer, and continue repeating the model of two-dimensional heat transfer to determine a final limit of each solidification isotherm, minimizing the difference between the temperature measured at each temperature probe location and a predicted temperature in said location based on the repetitions of the two-dimensional heat transfer model. 9. A method according to claim 7, further characterized by comprising temperature probes embedded in a metal shell cooled with water from the furnace crucible aligned at the same elevation with the temperature probes on the walls of the furnace crucible, and wherein said step of maintaining a protective layer includes the step of maintaining adequate heat transfer from the walls of the crucible refractory to the metal shell of the furnace crucible and from the metal shell to cooling water applied to the metal shell; said step of maintaining adequate heat transfer includes determining a first temperature at the abutting surface between the refractory lining of the crucible and the metal shell from the temperature difference between at least two temperature probes aligned in a radial direction at the refractory crucible walls, said adjoining surface temperature is designated TIR; determining a second temperature to said abutting surface from the sum of the temperature of at least one of the temperature probes embedded in the metal shell and the temperature difference between said temperature probes aligned in the same radial direction as the temperature probe in said shell, said second adjacent surface of temperature is designated TIS; compare the values of TI R and TIS to determine the difference between them; and in the case of a substantial difference between TIR and TIS take corrective action to minimize the difference. 10. A method for making in-line determinations of irregular erosion profiles of a refractory lining of a blast furnace where the refractory lining has temperature probes embedded therein, comprising the steps of: a) measuring temperatures at different points through the thickness of the refractory lining in a plurality of elevations by the temperature probes embedded in the liner; b) initially calculate the location of a solidification isotherm of the hot metal in the furnace; and c) from the initial estimated isotherm location perform a movable limit calculation to determine the final limit by minimizing the difference between the measured temperature and a predicted temperature by said movable limit calculation at all temperature probe locations in a vertical plane simultaneously, in order to make in-line determinations of irregular erosion profiles of said refractory lining.