Method and system for measuring the setting time of gypsum board

Abstract

A computer-implemented method (5000) for in-line, real-time monitoring of the time-temperature profile of gypsum board (1013) continuously produced in a gypsum board production line (1000). The method (5000) receives as input signals S-IR from infrared sensors (2001a-d) positioned at predetermined distances along the gypsum board production line (1000) between the molding stage (1001) and the cutting stage (1003) of the gypsum board production line (1000), and also receives as input the speed S-GB of the gypsum board (1013) continuously produced on the gypsum board production line (1000). The method (5000) provides as output a corrected time-temperature profile (CTT) of the continuously produced gypsum board (1013). The method (5000) further includes the steps of: (a) Converting (5001) signals from a group of infrared sensors (2001a-d) into a time-temperature profile based on the speed S-GB of gypsum board (1013) continuously produced on a gypsum board production line (1000); (b) processing the time-temperature profile through a correlation model (CM) and / or a physical model PM to calculate a corrected time-temperature profile (CTT) (5002);

Description

[Technical Field]

[0001] The present invention relates to a method and system for real-time, in-line monitoring of the set time-temperature profile of continuously produced gypsum board. [Background technology]

[0002] Gypsum boards are a well-known application of gypsum (calcium sulfate dihydrate CaSO4·2(H2O)) for wall and ceiling systems. They consist of a gypsum core sandwiched between two cover sheets, usually paper-based sheets.

[0003] The source material of the gypsum crystalline matrix of the gypsum core is calcium sulfate hemihydrate CaSO40.5(H2O), also known as "stucco," which is produced by the dehydration or calcination of gypsum CaSO42(H2O) to remove 1.5 molecules of water.

[0004] In a typical industrial production line, calcined calcium sulfate hemihydrate, known as stucco, is fed into a storage bin, and water is added to form a slurry. A foaming agent may also be added, and / or air may be blown into the slurry to create pores. Once prepared, the slurry is poured between two large rolls of cover sheet, such as a paper-based sheet, and formed into a single continuous board, which is the precursor to individual gypsum boards.

[0005] The continuous board is then conveyed to a cutting station while the stucco hydrates and hardens, after which it is finally cut into individual gypsum boards of various lengths by cutting blades. Setting time (also called set time) is an important parameter in the continuous board manufacturing process.

[0006] It is essential that the slurry in continuously produced gypsum boards be sufficiently set before the cutting process. Boards that have not had sufficient time to stiffen may be too soft to cut cleanly. They may sag during the cutting stage and / or be torn, crushed, or shredded by the cutting blade, such as a knife blade. On the other hand, continuous boards that are fully set may be too tough for the cutting blade and may break or crack when cut. Such defects can cause production to stop.

[0007] The setting time of the continuous board depends on several parameters, such as the chemical composition of the board (e.g., the nature of the stucco, moisture content, accelerators, other additives, foaming agents), the thickness and / or thermal conductivity of the slurry and / or cover sheet, the humidity and / or temperature of the surrounding environment, etc.

[0008] In practice, conveyor speed and / or drying power or time must be adjusted to ensure that the continuously produced gypsum board exhibits adequate strength or stiffness when it reaches the cutting stage for clean cutting. If this is not the case, the cutting stage may need to be postponed or advanced until or before the continuous board has sufficiently hardened or stiffened. The conveyor running speed may need to be slowed or increased. In the first case, if the continuous board is not sufficiently hardened, the production rate of the gypsum board may be reduced. In the second case, if the continuous board is too stiff, the risk of board breakage may increase.

[0009] The ASTM C 472 standard provides two different definitions of set time: Vicat set and temperature rising set (TRS), since the set of the slurry is an exothermic hydration reaction.

[0010] For Vicat set, the ASTM C 472 standard discloses a method for measuring by dropping a penetrating needle into the slurry. The set time is considered complete when the needle no longer penetrates the slurry. However, the set time does not determine the time for complete hydration of the gypsum.

[0011] For the temperature rise set (TRS), the ASTM C 472 standard also discloses how to measure it by monitoring the temperature of the slurry in the insulating block. The set time is the time elapsed from the first addition of water to the gypsum to the time when the maximum temperature rise is achieved. The measured set time is assumed to correspond to the hydration time of the slurry.

[0012] A common practice on production lines is to perform ex situ set time measurements for Vicat set and / or temperature rising set (TRS) on samples collected from the production line.

[0013] U.S. Patent No. 4,496,515 (United States Gypsum Co., US), issued January 29, 1985, discloses a method for cutting continuous gypsum board, in which the continuous board is cut with a high-pressure, high-velocity fluid, i.e., water or oil blade, immediately after initial stiffening and before the temperature rise set or solidification period (also called Vicat set). The use of high-pressure, high-velocity fluid for cutting, instead of knives, allows for cutting of relatively soft boards and avoids the aforementioned drawbacks associated with using knives.

[0014] U.S. Patent Application Publication No. 2004052297 [RAYTEK [US]], published March 18, 2004, describes a system and method for real-time in-line monitoring of the temperature of the slurry at different locations within a continuously produced gypsum board. Time-temperature data is recorded by infrared sensors positioned along the gypsum board between the forming and cutting stages and displayed to an operator. An algorithm may further be implemented to compensate for changes in ambient air temperature by an operator-provided product of a compensation variable and the difference between the temperature measured by the infrared sensors and the measured ambient air temperature.

[0015] WO 2017078952 [[UNITED STATES GYPSUM CO[US]]], published May 11, 2017, discloses a system and method for monitoring the setting of a slurry in continuously produced gypsum board by measuring the relative sag height in the continuously produced gypsum board over an unsupported span in a conveyor. The measured relative sag height is correlated to the hydration rate of the slurry.

[0016] Chinese Patent Application Publication No. 110757645 [BEIJING NEW BUILDING MAT PLC], dated February 7, 2020, discloses a method for measuring the setting time of a sampled slurry during hydration, in which the temperature of the slurry is recorded over time, and the initial and final setting times are measured from the time-temperature curve by the tangent method.

[0017] U.S. Patent Application Publication No. 2017363524 [[UNITED STATES GYPSUM CO[US]]], published June 9, 2020, discloses a method and system based on in-line measurement of the setting time of a slurry on a production line using a force gauge. The force gauge measures the resistance force along the normal axis of the gypsum board.

[0018] The measured resistance force is then correlated with compressive strength and hydration ratio from a mapping between the recorded resistance data and a database containing hydration ratio values ​​determined from temperature rising set (TRS) data or Vicat set data measured ex situ on samples collected according to ASTM C 472 standard.

[0019] The system may further rely on an in-line, continuous, real-time temperature rise monitoring system with infrared sensors along the production line, and a processor configured to generate time-temperature curves and store the time-temperature data in a database, which is then used as the basis for further correlations between measured forces and percent hydration values ​​derived from the time-temperature data. [Prior art documents] [Patent documents]

[0020] [Patent Document 1] U.S. Patent No. 4,496,515 [Patent Document 2] US Patent Application Publication No. 2004052297 [Patent Document 3] International Publication No. 2017078952 [Patent Document 4] Chinese Patent Application Publication No. 110757645 [Patent Document 5] US Patent Application Publication No. 2017363524 [Non-Patent Document 1] Standard Test Methods for Physical Testing of Gypsum, Gypsum Plaster, and Gypsum Concrete, ASTM C 472 - 99, American Society for Testing and Materials Summary of the Invention [Problem to be solved by the invention]

[0021] One drawback of the common practice of performing ex-situ measurements on samples collected from the production line is that it takes too much time. Production interruptions during the cutting stage cannot be avoided during the measurements. Furthermore, it can be difficult to implement real-time feedback control based on this ex-situ, time-consuming practice.

[0022] Methods that rely on in-line contact sensors, such as force gauges, to measure the strength of the slurry in the production line require the installation of additional mechanical sensors on the production line, which not only can incur additional costs but also requires further calibration based on ex-situ conventional measurements of TRS and Vicat set to ensure that the in-line mechanical measurements are representative of the setting or hydration time of the slurry.

[0023] Furthermore, contact measurements can be very difficult at high line speeds and / or with lightweight gypsum boards because they are in direct contact with the continuous board surface, which can cause surface defects.

[0024] Meanwhile, a real-time in-line monitoring system with infrared sensors along the production line before the cutting stage can also be used as support for mechanical sensor calibration through TRS / mechanical resistance correlation.

[0025] However, the temperature profile from the infrared sensor can be too noisy and can show various deviations compared to the ex-situ TRS measurements. These discrepancies can be due, for example, to changes in the temperature of the ambient air surrounding the production line, to changes in the heat capacity or thickness of the board (e.g., due to moisture content or cover sheet properties), and / or to inherent drift and / or inaccuracy of the infrared sensor.

[0026] Another drawback of conventionally using infrared sensors along a production line is that, because infrared sensors are typically placed before the cutting stage and the cutting process is performed before the continuous board reaches its full rigidity or strength, only a portion of the set time-temperature profile or curve is captured, i.e., only the portion of the curve before the maximum temperature plateau. The remaining time-temperature profile or curve can be interpolated, but the interpolation can often be inaccurate due to a lack of data, especially near the inflection points of the time-temperature curve. Therefore, inaccurate estimates of set time can occur.

[0027] Therefore, there is a need for a simple method and system that allows for real-time, in-line monitoring of the setting time-temperature profile of continuously produced gypsum board, while also being suitable for high production throughput and not interfering with the gypsum board during its hardening / stiffening stage. [Means for solving the problem]

[0028] The above-mentioned technical problems are solved by the invention as set forth in the claims.

[0029] In a first aspect of the invention, a method is provided for in-line, real-time monitoring of the time-temperature profile of gypsum boards continuously produced in a gypsum board manufacturing line.

[0030] In second and third aspects of the present invention there are provided a data processing system having means for performing a method according to the first aspect of the invention, and a computer program comprising instructions which, when executed by a computer, cause the computer to perform a method according to the first aspect of the invention.

[0031] In a fourth aspect of the invention, there is provided a system for implementing the method according to the first aspect of the invention.

[0032] In a fifth aspect of the invention, a feedback control system for hydration of continuously produced gypsum board in a gypsum board manufacturing line is provided. [Effects of the Invention]

[0033] First, the present invention eliminates discrepancies between the temperature signal from the infrared sensor and the true temperature data that can be derived from ex-situ TRS measurements. The time-temperature monitored by the present invention is relatively accurate and relatively reliable.

[0034] And as a second advantage, the risk of incorrect or erroneous interpolation of unacquired portions of the time-temperature profile is reduced or even eliminated.

[0035] A third advantage is that the present invention does not rely on contact measurements, eliminating the risk of surface imperfections.

[0036] A fourth advantage is that it can be easily implemented on existing manufacturing lines at minimal cost.

[0037] As a fifth advantage, the method and system according to the present invention can be implemented as part of a feedback control system for the hydration of continuously produced gypsum board. [Brief explanation of the drawings]

[0038] [Figure 1] FIG. 1 is a schematic diagram of a gypsum board production line equipped with a system according to a second embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram of Detail I of the gypsum board production line of FIG. 1 between the molding stage and the cutting stage. [Figure 3] FIG. 3 is a plot of an example time-temperature curve generated from measurements by infrared sensors and temperature rising sets (TRS) along a production line. [Figure 4] FIG. 4 is a plot of an example of the time-temperature signal of an infrared sensor at each location along a production line. [Figure 5] FIG. 5 is a data flow diagram of a computer implementing the classification method according to the first aspect of the invention. [Figure 6] FIG. 6 is a physical data flow diagram of a processing data system implementing the method according to the first aspect of the invention. [Figure 7] FIG. 7 is a plot of an obtained time-temperature profile according to an example embodiment. [Figure 8] FIG. 8 is a plot of a time-temperature profile from a TRS and a parameterized fitting sigmoid function and its first derivative as the fitting model for the acquired time-temperature profile, according to an example embodiment. [Figure 9] FIG. 9 is a plot of the corrected time-temperature profile, the corrected parameterized fitted sigmoidal function, and their corrected first derivatives, according to an example embodiment. [Figure 10] FIG. 10 is a plot of the target hydration time compared to the corrected first derivative of the acquired time-temperature profile, according to an example embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0039] Referring to FIG. 1, a typical industrial production line 1000 for gypsum board includes a forming or molding stage 1001, a setting or curing stage 1002, a cutting stage 1003, a drying stage 1004, a control stage 1005, and a stacking and packaging stage 1006.

[0040] During forming or molding 1001, calcined calcium sulfate hemihydrate, known as stucco, is provided to a receiving bin 1007 where water is added to the stucco to form a slurry. A blowing agent and other additives, such as set accelerators, may also be added to bin 1007. Air may also be blown into the slurry.

[0041] Once prepared, the slurry is poured through nozzles 1008 onto a bottom cover sheet 1009, such as a sheet of paper, which is unwound onto a conveyor belt 1010. A top cover sheet 1011, such as a sheet of paper, is then unwound onto the slurry, and the sandwiched slurry is conveyed between rollers 1012 (extruders) which define the thickness of a single continuously produced board 1013.

[0042] In the setting or hardening stage 1002, the continuously produced board is conveyed a predetermined distance at a predetermined speed to allow time for the setting or hardening reaction to occur in the slurry before the board reaches a cutting station 1014 in the cutting stage 1003, where it is finally cut by a cutting blade into single pieces of gypsum board 1015 of various lengths.

[0043] During the drying step 1004, the single or individual pieces of board are inverted and continuously conveyed to the dryer 1016. At the exit of the dryer 1016, the pieces are inspected in a control step 1005, arranged in stacks, and packaged in a stacking and packaging step 1006 before being stored and / or shipped to the customer.

[0044] As explained above, to cleanly cut the continuously produced boards 1013 at the cutting station 1004, the slurry must be sufficiently solidified or set to prevent it from being too soft and sagging, crushing, or shredding, or too hard and cracking or breaking when cut.

[0045] The time required for the slurry to set or harden may depend on several parameters, such as the chemical composition of the board (e.g., the nature of the stucco, moisture content, accelerators, other additives, foaming agents), the thickness and / or thermal conductivity of the slurry and / or cover sheet, the humidity and / or temperature of the surrounding environment, etc.

[0046] It is common practice to adjust the speed of the production line (i.e., the speed of the conveyor 1010) to allow sufficient time for the slurry to solidify or harden sufficiently so that the continuously produced gypsum board 1013 has the necessary strength or rigidity when it reaches the cutting stage for clean cutting.

[0047] The time required for complete solidification or setting of the slurry (hereinafter referred to as the set time) can be interpreted as the set time in the context of the temperature rise set (TRS), as defined in the ASTM C 472 standard, i.e., the time elapsed from the time water is first added to the gypsum to the time when the maximum temperature rise is obtained.

[0048] However, the time during which the continuously produced gypsum board 1013 will have the necessary stiffness or strength to be able to be cleanly cut at the cutting station 1014 may be shorter than the set time defined in ASTM C 472, depending on the components of the continuously produced gypsum board, such as the properties and / or thickness of the cover sheet and / or slurry. However, the stiffening time may coincide with the set time or may be slightly longer.

[0049] Therefore, in the context of the present disclosure, the time considered for the setting or hardening of the slurry in the setting or hardening step 1002 can be either the stiffening time or the setting time, which is referred to as the "hydration time."

[0050] As illustrated in Figure 2, which is a detailed representation of the setting or curing stage 1002 of the production line 1000 depicted in Figure 1, the production line may be provided with an array of infrared sensors 2001a-d for in-line, real-time temperature measurement of the continuously produced gypsum board 1013. An example of an infrared sensor may be an IRT C.03-K-80F 27C sensor manufactured by EXERGEN®.

[0051] Infrared sensors 2001a-d may transmit their temperature-related signals via wired or wireless connections to a data processing system, such as computer 2002. Computer 2002 is configured to generate a time-temperature curve or profile along the continuously produced gypsum board.

[0052] An example of time-temperature curves (IRS dots) acquired by six infrared sensors between the rolling mill 1012 and the cutting station 1014 is plotted in Figure 3. For comparison, a time-temperature curve or profile 3002 from a set of temperature rises (TRS lines) measured on an ex-situ sample collected according to ASTM C 472 is also shown. Not only may the infrared sensors 2001a-e not be able to collect a complete time-temperature curve or profile corresponding to the TRS curve or profile, but the time-temperature curves so measured and generated may be subject to significant deviations; the infrared sensors may indicate that the continuously produced board 1013 is much cooler than that observed in the ex-situ TRS measurements.

[0053] Furthermore, the region around the inflection point (IP) of the temperature rise set (TRS) profile is not accurately reproduced by the temperature signal from the infrared sensor, however, this region is an important feature of the time-temperature profile because it is the point where the sign of the curvature changes and the slurry may begin to solidify or harden and reach its optimum strength or stiffness for clean cutting.

[0054] Furthermore, the signals from the infrared sensors 2001a-e may be corrupted by noise, as shown in Figure 4, which represents the time-temperature signal of each infrared sensor 2001a-e at each position along the production line during the solidification stage 1002. For each sensor, the standard deviation may vary from 0.4°C to 0.7°C, which leads to an uncertainty of 4-7% within the 10°C interval in which the inflection point (IP) may occur.

[0055] As previously explained, any discrepancies observed between the time-temperature curves generated by processing the signals of the infrared sensors 2001a-d and the reference TRS time-temperature curves or profiles may be due to, for example, changes in the temperature of the ambient air surrounding the production line, changes in heat capacity or board thickness (e.g., from the moisture content or nature of the cover sheet), and / or inherent drift and / or inaccuracy of the infrared sensors.

[0056] A significant disadvantage is that any attempt to interpolate the complete time-temperature curve from infrared sensor measurements may lead to inaccurate estimation of set time, as can be done from TRS measurements. This is why conventional methods for in-line real-time monitoring of set time do not rely on infrared sensor measurements along the production line 1000 during the set stage, but rather use them as a complement or supplement to measurements of physical properties, such as resistance force or board height, by contact sensors, such as force gauges, or optical devices, such as lasers.

[0057] Therefore, a need remains for a simple method and system for real-time, in-line, and reliable monitoring of the set time-temperature profile of continuously produced gypsum board that can be suitable for high production throughput, can not interfere with the curing / stiffening stage of the gypsum board, and can be easily implemented into existing manufacturing lines at minimal cost.

[0058] In this regard, and referring to Figure 5, in a first aspect of the present invention, a computer-implemented method 5000 is provided for in-line, real-time monitoring of the time-temperature profile of continuously produced gypsum boards 1013 in a gypsum board production line 1000. The method 5000 takes as input signals S-IR from infrared sensors 2001a-d positioned at predetermined distances along the gypsum board production line between the molding stage 1001 and the cutting stage 1003 of said gypsum board production line 1000, and further inputs the speed S-GB of continuously produced gypsum boards 1013 on the gypsum board production line 1000. The method 5000 provides as output a corrected time-temperature profile CTT of the continuously produced gypsum boards 1013. The method 5000 further includes the steps of: (a) Converting 5001 the signals of the infrared sensors 2001a-d into a time-temperature profile based on the speed S-GB of the gypsum board 1013 continuously produced on the gypsum board production line 1000. (b) Processing 5002 the time-temperature profile through a correlation model CM and / or a physical model PM to calculate a corrected time-temperature profile CTT.

[0059] The correlation model CM is obtained from a mapping between time-temperature profiles acquired by the same infrared sensors 2001a-d and time-temperature profiles from ex-situ measurements of a set of temperature rises in at least one gypsum board having similar physicochemical characteristics to the continuously produced gypsum board 1013.

[0060] The physical model PM is obtained from a mapping between heat flow calculated from time-temperature profiles acquired by the same infrared sensor group 2001a-d and heat flow calculated from time-temperature profiles from ex-situ measurements of a set of temperature rises in at least one gypsum board having similar physicochemical characteristics to the continuously produced gypsum board 1013.

[0061] In step (a), the signals of the infrared sensors 2001a-d are converted into a time-temperature profile based on the speed S-GB of the gypsum boards 1013 continuously produced on the gypsum board production line 1000. In other words, the acquisition frequency of the infrared sensors may be adjusted so that the sensors acquire temperature signals on the same area of ​​the continuously produced gypsum boards as it is transported in front of each infrared sensor on the production line. Adjusting the acquisition frequency can help reduce the risk of over-sampling or under-sampling temperature data on the gypsum boards.

[0062] For example, if the acquisition frequency is lower than the inverse of the speed S-GB, the infrared sensors will not acquire a signal on the same area of ​​the board as it is transported in front of the sensors, and the area of ​​the board where the temperature signal was acquired by the first sensor may have passed the solidification stage before the last infrared sensor can acquire a temperature signal there. A direct disadvantage is that the temperature signal acquired may then not be representative of the temperature profile of the gypsum board as it is transported in the solidification stage.

[0063] An example of converting the signals of the infrared sensors 2001a-d into a time-temperature profile based on the speed S-GB of the gypsum boards 1013 continuously produced on the gypsum board production line 1000 can be to adjust the acquisition frequency of the infrared sensors to the inverse of the speed S-GB of the gypsum boards, where the acquisition time represents the time scale of the temperature profile of the gypsum boards.

[0064] Step (b) of processing the time-temperature profile may be performed by using the correlation model CM and the physical model PM alone or in combination, i.e., by using the correlation model CM alone, the physical model PM alone, or both in sequence.

[0065] According to the present invention, both the correlation model CM and the physical model PM are obtained from a mapping between time-temperature profiles or features or parameters thereof obtained by infrared sensors 2001a-d and time-temperature profiles or features or parameters thereof obtained by ex-situ measurements of a set of temperature increases on at least one gypsum board having similar physicochemical characteristics to the continuously produced gypsum board 1013. Examples of physicochemical characteristics may include the chemical composition of the gypsum board slurry (e.g., stucco properties, water content, accelerators, other additives, foaming agents) and / or the chemical composition of the cover sheet, the thickness of the slurry and / or the cover sheet, etc.

[0066] The infrared sensor group includes at least two sensors. In a particularly advantageous embodiment, the input S-IR signal can be the signal of at least four, preferably at least six, and more preferably at least eight sensors. The greater the number of infrared sensors, the more representative the curvature of the time-temperature profile generated from the infrared sensor group signals will be compared to the time-temperature profile obtained from the TRS measurement. In particular, the curvature in the region of the inflection point will be more accurate.

[0067] In certain embodiments, the correlation model CM may be a supervised or unsupervised learning algorithm trained on a historical database including time-temperature profiles from the infrared sensors and time-temperature profiles from ex-situ measurements of the set of temperature rises. This historical database may enable the correlation model CM to identify correlations between the signals of the infrared sensors 2001a-d converted into time-temperature profiles based on the speed S-GB of the gypsum board 1013 continuously produced on the gypsum board production line 1000 in step (a). Thus, the correlation model CM may enable adjustments of the infrared sensors to be calculated based on the historical database including the time-temperature profiles from the infrared sensors and time-temperature profiles from ex-situ measurements of the set of temperature rises.

[0068] Examples of correlation models can be linear models, such as ridge regression, polynomial regression, decision tree regression, support vector machine regression, or ensemble methods, such as random forest regression, gradient tree boosting. Artificial neural networks can also be used.

[0069] In certain embodiments, the physical model PM is a correction factor calculated from a comparison of the first derivative of the time-temperature profile at the inflection point of the time-temperature profile to the first derivative of the time-temperature profile at the inflection point of the time-temperature profile from ex-situ measurements of a set of increasing temperatures.

[0070] In the context of this disclosure, an inflection point of a time-temperature profile is a point where the curvature of the time-temperature profile changes sign, and the first derivative is the slope of the tangent to the curve at the point of interest. As shown in Figure 3, the first derivative at an inflection point is the slope (FD) of the tangent to the curve at the inflection point (IP).

[0071] According to Fourier's law, the first derivative can be considered as a representative value of the heat flow generated by the exothermic hydration reaction in the slurry. At the inflection point (IP), this heat flow is at a maximum since the value of the slope of the tangent line (FD) reaches a maximum, which indicates that the hydration reaction is nearly complete and the board has reached the correct strength or stiffness to be able to cut cleanly.

[0072] An example of a correction factor calculated from a comparison of the first derivative at the inflection point of the time-temperature profile with the first derivative at the inflection point of the time-temperature profile from an ex-situ measurement of a set of increasing temperatures is the ratio between said first derivatives, which may be linear, e.g., a polynomial, or a non-linear function thereof.

[0073] In certain embodiments, the method may further include calculating a hydration time from the corrected time-temperature profile CTT. Among other advantages already mentioned, the method according to the first aspect of the present invention makes it possible to obtain a time-temperature profile representative of a time-temperature profile obtained by ex-situ measurements of an increasing set of temperatures from an infrared sensor. The corrected time-temperature profile thus makes it possible to calculate a hydration time representative of the slurry in continuously produced gypsum board.

[0074] Advantageously, the hydration time calculated from the corrected time-temperature profile may be the time elapsed from the point corresponding to the minimum temperature before the temperature starts to rise to the point at which the maximum temperature rise is reached, and the hydration time thus calculated may be representative of the hydration time defined in Section 11 of the ASTM C 472 standard.

[0075] In certain embodiments, the method may further include calculating a percentage of the hydration time in the cutting stage from the corrected temperature profile (CTT). As described above, the time at which the continuously produced gypsum board 1013 has the stiffness or strength required for clean cutting at the cutting station 1014 may be equal to or shorter than the set time defined in ASTM C 472. As a result, the hydration level at which the continuously produced gypsum board 1013 exhibits the stiffness or strength required for clean cutting may be equal to or shorter than the aforementioned standard hydration time. This hydration level may be expressed as a percentage of the hydration time in the cutting stage. For example, it may be the ratio of the elapsed time at which the continuously produced gypsum board 1013 reaches the cutting stage to the hydration time calculated according to the aforementioned embodiment.

[0076] The first aspect of the present invention is computer-implemented. Thus, referring to Figure 6, in a second aspect of the present invention there is provided a data processing system 6000 having means for performing a method according to any embodiment of the first aspect of the present disclosure.

[0077] A first example of a means for performing a method may be a device 6001 that can be instructed to automatically perform a sequence of arithmetic or logical operations to perform a task or action. Such a device may have one or more central processing units (CPUs) and at least one controller adapted to perform these operations.

[0078] The device may further include other electronic components, such as an input / output interface 6003, a non-volatile or volatile storage device 6002, and a bus, which are communication systems for transferring data between components within the computer or between computers. One of the input / output devices may be a user interface for human-machine interaction, such as a graphical user interface for displaying human-understandable information. In this regard, an example of device 6001 may be computer 2002 illustrated in FIG. 2.

[0079] An advantage of the method according to the first aspect of the present invention is that it may require low computational and data storage resources, and a second example of the means may be an on-board system, such as a low-power computer board, such as a single-board computer, which allows real-time applications.

[0080] In a third aspect, there is provided a computer program I6001 comprising instructions which, when executed by a computer, cause the computer to perform a method according to any embodiment of the first aspect of the invention.

[0081] Any kind of programming language, either compiled or interpreted, may be used to implement the steps of the method of the invention. The computer program may be part of a software solution, i.e. part of a collection of executable instructions, codes or scripts etc. and / or part of a database.

[0082] In particular embodiments, a computer program may be stored on a non-transitory computer-readable medium 6002. Thus, such non-transitory computer-readable medium 6002 may include instructions that, when executed by a computer, cause the computer to perform a method according to any embodiment described herein.

[0083] The computer readable medium 6002 may preferably be a non-volatile storage device or memory, such as a hard disk drive or a flash / non-flash solid state drive, etc. The computer readable medium may also be a removable or non-removable storage medium as part of the computer.

[0084] Alternatively, the computer readable medium 6002 may be a volatile memory within a removable medium, which may facilitate deployment of the present invention across many production sites.

[0085] In a fourth aspect of the present invention, referring to FIGS. 2, 5, and 6, a system is provided for real-time and in-line measurement of the setting time-temperature profile of gypsum boards 1013 continuously produced in a manufacturing line 1000, wherein the system comprises: - a group of infrared sensors 2001a-d, arranged at a predetermined distance along the gypsum board production line between the molding stage 1001 and the cutting stage 1003 of said gypsum board production line 1000; a processor 2002, 6000 configured to execute a computer program I6001, said computer program I6001 comprising instructions for executing a method according to any embodiment of the first aspect of the invention, It has.

[0086] In certain embodiments, the infrared sensor group 2001a-d may have at least four sensors, preferably at least six sensors, preferably at least eight sensors, preferably at least nine sensors, preferably at least twelve sensors, and preferably at least fifteen sensors. The number of infrared sensors may depend on the desired level and / or the possibility of interpolating parts of the time-temperature profile not acquired by the infrared sensors. As a general rule, the more infrared sensors there are, the more representative the curvature of the time-temperature profile generated from the signals of the infrared sensor group will be compared to the time-temperature profile from the TRS measurement. Six, preferably eight, sensors may be considered an interesting compromise in terms of accuracy.

[0087] In an advantageous embodiment, the infrared sensor group may further comprise at least one, preferably at least two, infrared sensors 2003 immediately after the cutting stage 1003. By providing additional data, the additional infrared sensors located after the cutting stage 1003 may help to better sample the time-temperature profile after the inflection point (IP) and thus to better reproduce its curvature. As illustrated in Figure 2, at least one, preferably at least two, infrared sensors 2003 may be located at the exit of the cutting station 1014.

[0088] In certain embodiments, the infrared sensors 2001a-d, 2003 may be configured such that the infrared sensors 2001a-d, 2003 are spaced along the gypsum board production line at a distance equal to or less than 60 seconds, preferably equal to or less than 40 seconds, and more preferably equal to or less than 30 seconds, multiplied by the rate at which gypsum boards are continuously produced on the production line. Such placement may provide valuable sampling of the time-temperature profile along the continuously produced gypsum boards.

[0089] In certain embodiments, the infrared sensor clusters 2001a-d may be configured such that the infrared sensors are positioned less than 1 meter, preferably less than 0.5 meters, from the gypsum board surface.

[0090] In accordance with the overall disclosure, the system of the fourth aspect of the present invention may be advantageously used in a manufacturing line 1000 for continuously produced gypsum board 1013 profiles. In an advantageous embodiment, the system may be implemented either as a control system for monitoring the time-temperature profile of the continuously produced gypsum board 1013 or as a feedback control system for controlling the hydration level of the continuously produced gypsum board 1013.

[0091] Therefore, in a fifth aspect of the present invention, there is provided a feedback control system for the hydration of continuously produced gypsum boards 1013 in a production line (1000), said feedback system comprising: - a system according to any embodiment of the fourth aspect of the present invention; a control device configured to adjust the line speed of the production line 1000 between the molding stage 1001 and the cutting stage 1003 and / or the level of a set accelerator in the slurry, thereby maintaining a constant level of hydration of the gypsum board between the molding stage 1001 and the cutting stage 1003 and / or during the cutting stage 1002 based on a hydration time rate calculated from a corrected set time-temperature profile of at least one position between the molding stage 1001 and the cutting stage 1003; It has.

[0092] In an advantageous embodiment, the percentage of hydration time is calculated during the cutting step 1003 .

[0093] All embodiments of the first to fifth aspects of the present invention described in this disclosure may be combined unless they are deemed technically incompatible by a person skilled in the art. [Example]

[0094] In the example shown, 14 infrared sensors were placed at predetermined distances between the molding stage and the cutting stage of a gypsum board production line that continuously produces gypsum board at a production speed of 37 m / min. The temperature of the gypsum board was continuously measured at regular intervals at a frequency equivalent to the inverse of the speed of the gypsum board.

[0095] Figure 7 plots the temperature T (filled circles, left vertical axis) acquired by each infrared sensor as a function of distance D from the forming stage. The acquisition error is on the order of the magnitude of the symbols. In Figure 7, for simplicity and explanation, the temperature profile is represented as a function of distance, but it can equivalently be represented as a function of time by multiplying the distance by the board speed.

[0096] An equivalent but easier way to express the obtained temperatures is to convert them into relative temperature rise rates TR, which are also plotted in Figure 7 (open circles, right vertical axis). This conversion can be performed with the following equation:

[0097]

number

[0098] where T is the temperature currently acquired by a specific infrared sensor, and Tmin and Tmax are the minimum and maximum temperatures acquired by all infrared sensors, respectively. The reason for using the temperature rise rate TR instead of the temperature T is to eliminate relative temperature fluctuations that may arise from the ambient environment of the production line.

[0099] The obtained temperature rise rate TR is then modeled with a parametric sigmoid function according to the following equation and the parameters listed in Table 1:

[0100]

number

[0101] where t is time, and a, b, k, n, G, and C are fitting parameters.

[0102] [Table 1]

[0103] The fitted data (open circles, left vertical axis) and the parametrized fitted sigmoid function (dashed line, left vertical axis) are plotted in Figure 8. The first derivative of the fitted sigmoid function (dotted line, right vertical axis) is also plotted. This first derivative, which is representative of the heat flow, exhibits a maximum value S at the inflection point of the fitted sigmoid function at a distance of approximately 133 m.

[0104] FIG. 8 also plots the first derivative of the time-temperature profile (solid line) (here converted to a temperature rate TR-distance D profile). It is obtained from ex-situ measurements of a set of temperature ramps performed on a gypsum slurry sampled just before the casting stage. This first derivative is representative of the heat flow through the sample during solidification. It shows a maximum value E at the inflection point of the sigmoid function at a distance of approximately 167 m. Sampling of the slurry and ex-situ measurements of a set of temperature ramps can be performed at regular intervals, for example every two hours, to predict any deviations, for example due to changes in the operating parameters of the production line and / or the chemistry, i.e., composition, of the slurry.

[0105] As shown in Figure 8, the two maxima S and E of the first derivative (dotted and solid lines) do not coincide and are separated from each other by a distance ΔD of about 34 m. This discrepancy indicates that the infrared sensor is not calibrated and cannot accurately monitor the temperature of the continuously produced gypsum board.

[0106] A first, but very simple correlation model for correcting the temperature rate obtained can be an offset affine function that offsets the temperature rate TR by a value of ΔD=+34m. The affine function can be expressed as:

[0107]

number

[0108] where TRcorr is the corrected temperature rate, TRmeas is the temperature rate measured by the infrared sensor, and ΔD is an offset coefficient, e.g., +34 here.

[0109] This correction with a simple offset affine function is shown in Figure 9. Plotted are the corrected temperature rate (filled squares, left vertical axis), the corrected fitted sigmoid function (dot-dot-dashed line), and the corrected first derivative (dotted line, right vertical axis) of the fitted sigmoid function (dot-dashed line, right vertical axis).

[0110] As further shown in Figure 9 , the correction makes the maximum S′ of the corrected first derivative of the fitted sigmoid function (dotted-dashed line, right vertical axis) coincide with the maximum E of the first derivative of the time-temperature profile (solid line) obtained from ex situ measurements of the temperature ramp set.

[0111] Such a correction may be satisfactory in some practical cases. However, it may be ineffective in other cases, especially when the general trend in the temperature measured by the infrared sensor does not follow a sigmoid or sigmoid-like curve. In that case, the shape of the first derivative may deviate strongly from the first derivative of a time-temperature profile obtained from ex-situ measurements of a set of increasing temperatures. In this case, a more sophisticated correlation model may be required.

[0112] An example of a more sophisticated correlation, not fully detailed here, may be based on a fitting function that reproduces the first derivative of a time-temperature profile obtained from ex-situ measurements of a set of temperature rises, and this may then be subjected to mathematical integration to reconstruct a time-temperature profile from which individual correction factors may be derived for each infrared sensor.

[0113] In the present illustrative example, besides the offset correction, a relatively good correction can be further considered for optimal monitoring of the temperature rise rate TR by the infrared sensor. In Fig. 9, the corrected first derivative of the fitted sigmoid function (dotted-dashed line, right vertical axis) and the first derivative of the time-temperature profile obtained from ex-situ measurements of the temperature rise set (solid line) do not completely overlap in their shape or curvature. For such purpose, an advanced correlation model, such as that briefly described above, can be advantageously implemented.

[0114] According to some embodiments of the present invention, monitoring the time-temperature profile of continuously produced gypsum board can be used in a feedback control system. An example of use is shown in Figure 10. The target hydration time T is represented by the black arrow at a distance of approximately 150 m, which corresponds to the position where 50% of the hydration time of the gypsum board needs to reach 60% of the hydration time at the cutting stage for a clean cut.

[0115] To reach the target value T, the maximum S' of the corrected first derivative of the fitted sigmoid function (dotted-dashed line, right vertical axis) should be located at 150 m, not after about 167 m. Among several improvements to shift the maximum S' to the target T, it may be worth adjusting the diapower, the line speed, and / or the content of solidification promoters in the slurry.

[0116] While the present invention has been described in connection with preferred embodiments and examples, it should be understood that various modifications, additions, and variations may be made to the present invention by those skilled in the art without departing from the spirit and scope of the invention as defined in the claims.

Claims

1. A computer-implemented method (5000) for in-line, real-time monitoring of the time-temperature profile of continuously produced gypsum boards (1013) in a gypsum board manufacturing line (1000), comprising: Here, the method (5000) receives as input signals S-IR from a group of infrared sensors (2001a-d) arranged at a predetermined distance along the gypsum board production line between the molding stage (1001) and the cutting stage (1003) of the gypsum board production line (1000), and further receives as input a speed S-GB of the gypsum boards (1013) continuously produced on the gypsum board production line (1000); wherein said method (5000) provides as output a corrected time-temperature profile (CTT) of said continuously produced gypsum board (1013), said method (5000) comprising the following steps: (a) converting (5001) the signals of the infrared sensors (2001a-d) into a time-temperature profile based on the speed S-GB of the gypsum boards (1013) continuously produced on the gypsum board production line (1000); (b) processing said time-temperature profile through a correlation model (CM) and / or a physical model PM to calculate a corrected time-temperature profile (CTT) (5002); Further comprising: wherein the correlation model (C-M) is obtained from a mapping between the time-temperature profile acquired by the same infrared sensor group (2001a-d) and the time-temperature profile obtained by ex-situ measurement of a set of temperature rises on at least one gypsum board having similar physicochemical characteristics as the continuously produced gypsum board (1013); wherein the physical model (P-M) is obtained from a mapping between heat flow calculated from time-temperature profiles acquired by the same infrared sensor group (2001a-d) and heat flow calculated from time-temperature profiles obtained by ex-situ measurements of a set of temperature rises on at least one gypsum board having similar physicochemical characteristics to the continuously produced gypsum board (1013).

2. 2. The method of claim 1, wherein the correlation model (C-M) can be a supervised or unsupervised learning algorithm trained on a historical database including time-temperature profiles from an infrared sensor and time-temperature profiles from ex-situ measurements of a set of temperature rises.

3. 3. The method of claim 1 or 2, wherein the physical model (P-M) is a correction factor calculated from a comparison between the first derivative at the inflection point of the time-temperature profile and the first derivative at the inflection point of the time-temperature profile from an ex-situ measurement of the temperature ramp set.

4. The method according to any one of claims 1 to 3, wherein the method may further comprise the step of calculating a hydration time from the corrected time-temperature profile (CTT).

5. The method according to any one of claims 1 to 4, wherein the method may further comprise the step of calculating the percentage of hydration time in the cutting stage from the corrected temperature profile (CTT).

6. A data processing system (6000) having means for performing the method according to any one of claims 1 to 5.

7. A computer program (I6001) comprising instructions that, when said program is executed by a computer, cause said computer to perform the method according to any one of claims 1 to 5.

8. A system for real-time, in-line measurement of the setting time-temperature profile of gypsum boards (1013) continuously produced in a manufacturing line (1000), comprising: wherein the system comprises: - a group of infrared sensors (2001a-d) arranged at a predetermined distance along the gypsum board production line between the molding stage (1001) and the cutting stage (1003) of the gypsum board production line (1000); a processor (2002), (6000) configured to execute a computer program (I6001); and A system wherein the computer program comprises instructions for carrying out the method according to any one of claims 1 to 5.

9. The system of claim 8, wherein the group of infrared sensors (2001a-d) has at least four sensors, preferably at least six sensors, preferably at least eight sensors, preferably at least nine sensors, preferably at least twelve sensors, preferably at least fifteen sensors.

10. 10. The system according to claim 8 or 9, wherein the infrared sensor group further comprises at least one, preferably at least two, infrared sensors (2003) immediately after the cutting stage (1003).

11. The system according to any one of claims 8 to 10, wherein the infrared sensor groups (2001a-d, 2003) are configured such that the infrared sensor groups (2001a-d, 2003) are spaced apart along the gypsum board production line (1000) at a distance equal to or less than 60 seconds, preferably equal to or less than 40 seconds, and more preferably equal to or less than 30 seconds, multiplied by the speed of the gypsum boards being continuously produced on the production line.

12. The system according to any one of claims 8 to 11, wherein the infrared sensor group (2001a-d, 2003) may be configured such that the infrared sensors are positioned less than 1 meter, preferably less than 0.5 meters, from the surface of the gypsum board.

13. Use of the system according to any one of claims 8 to 12 in a manufacturing line (1000) for continuously produced gypsum boards (1013).

14. A feedback control system for the hydration of continuously produced gypsum boards (1013) in a manufacturing line (1000), said feedback system comprising: a system according to any one of claims 8 to 12; a control device configured to adjust the line speed of the production line (1000) between the molding stage (1001) and the cutting stage (1003) and / or the level of set accelerator in the slurry, thereby maintaining a constant level of hydration of the gypsum board between the molding stage (1001) and the cutting stage (1003) and / or during the cutting stage (1002) based on a hydration time rate calculated from a corrected setting time-temperature profile for at least one position between the molding stage (1001) and the cutting stage (1003); A feedback control system having:

15. 15. The feedback control system of claim 14, wherein the hydration time percentage is calculated during the cutting step (1013).

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