mixer

Abstract

A mixer and method for mixing a cement slurry configured to calculate a volume of the cement slurry in the mixer to improve the mixing process and / or produce an improved cement product, the mixer including a sensor for measuring a parameter of the slurry in the mixer, the parameter of the slurry being used to calculate the volume of the slurry in the mixer.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to mixers and processes for mixing, monitoring, and delivering cement slurries. [Background technology]

[0002] During the manufacture of cement boards, cement slurry is mixed in and dispensed from a mixer. If the volume of the slurry in the mixer is too large or too small, the volume deviation can cause problems in the manufacturing process and / or the cement board product itself. For example, if the volume of the slurry in the mixer is different from what was expected, the slurry may contain lumps and / or the cement product may contain undesirable voids.

[0003] Generally, a slurry mixer includes a mixing element for mixing the slurry. In addition, the slurry mixer may include a scraper for removing accumulated slurry from the wall of the mixer. This may make it difficult to access the slurry mixer and monitor the volume of the slurry inside.

[0004] Current methods for controlling and / or monitoring the slurry volume fraction in a mixer use estimates based on an ideal mixer without stagnation zones or short circuits. In reality, mixers are not ideal, and it would be useful to monitor the actual mixer volume and slurry volume fraction. With this in mind, one could add pigment to the slurry and use a camera to calculate the pigment concentration in the slurry and estimate the slurry volume fraction. However, this method contaminates the slurry with pigment and cannot be applied continuously. Furthermore, contact between the slurry and sensitive equipment in the mixer could damage that equipment. Therefore, current methods, whether based on theoretical calculations of the average residence time or a more physical approach, cannot provide a continuous, reliable measurement of the slurry volume fraction in a mixer. Summary of the Invention [Problem to be solved by the invention]

[0005] Aspects of the present disclosure seek to provide a mixer and mixing process that alleviates these problems associated with prior known systems, and in particular, to provide an improved mixer and mixing process that allows for monitoring of the volume of slurry within the mixer. [Means for solving the problem]

[0006] According to a first aspect of the present disclosure, there is provided a mixer for mixing a cement slurry, the mixer comprising: an inlet for receiving a cementitious material and water; a mixing member configured to mix the cementitious material and the water to produce a cement slurry; an outlet for delivering the cement slurry; a sensor configured to measure a parameter of the cement slurry; and a processor configured to calculate a volume of the cement slurry in the mixer using the parameter measurements.

[0007] In this manner, the mixer allows for monitoring of the volume of the slurry within the mixer without contaminating the slurry, avoiding process and product problems.

[0008] In some embodiments, the processor is further configured to calculate a slurry volume fraction of the mixer, the slurry volume fraction being calculated according to the following formula:

number

[0009] In this manner, the slurry volume fraction can be used to determine improved mixer sizes and geometries for various line speeds to optimize the slurry volume fraction and avoid process and product issues. Additionally, calculating the slurry volume fraction makes it easier to compare and adjust mixers of various sizes.

[0010] In some embodiments, the processor is further configured to vary at least one of input parameters, process parameters, and discharge parameters of the mixer in response to the calculated volume of cement slurry in the mixer and / or the slurry volume fraction of the mixer. In this manner, the volume of the slurry in the mixer can be adjusted to improve the process and product. For example, if the volume of the slurry is larger than a desired volume, the input rate of the slurry components into the mixer can be decreased or the output rate of the slurry from the mixer can be increased. If the volume of the slurry is smaller than a desired volume, the input rate of the slurry components into the mixer can be increased or the output rate of the slurry from the mixer can be decreased. In some embodiments, the input parameters are selected from the list consisting of line speed, input rate of the slurry components into the mixer, input volumetric flow rate (e.g., volume of material entering the mixer per second), input temperature (e.g., temperature of one or more materials entering the mixer), or slurry composition. In some embodiments, the process parameter is a mixing speed (e.g., the speed of one or more mixing elements in a mixer) or a mixing temperature (e.g., the temperature of the slurry in the mixer). In some embodiments, the discharge parameter is selected from the list consisting of line speed, mixer discharge speed (e.g., the speed of material exiting the mixer), discharge volumetric flow rate (e.g., the volume of material exiting the mixer per second), discharge temperature (e.g., the temperature of the slurry exiting the mixer), and exit cross-sectional area.

[0011] In some embodiments, the mixer comprises a base and a lid, the base and the lid being connected by at least one sidewall. In some embodiments, the mixer is a closed system. In this manner, conditions within the mixer can be more easily controlled.

[0012] In some embodiments, the mixer comprises a scraper configured to remove accumulated slurry from the walls of the mixer, in this manner reducing the risk of parts of the slurry sticking to the walls of the mixer and improving the consistency of the slurry.

[0013] In some embodiments, the sensor comprises an infrared camera. In this manner, the infrared camera (hereinafter IR camera) can provide direct visualization of the profile of the slurry within the mixer. The location of the slurry within the mixer can also be determined. The combination of the profile and location allows for direct visualization and / or estimation of the volume of the slurry occupying the mixer.

[0014] In some embodiments, the mixer includes an IR window configured to transmit infrared light from the cement slurry inside the mixer to an external IR camera. In this manner, the IR camera can visualize the slurry inside the mixer through the IR window without requiring an IR camera in the mixer itself. A camera inside the mixer would likely contaminate the slurry, making it highly susceptible to damage, at least from abrasive slurries. In this manner, the IR camera can be used to calculate the volume of the slurry in the mixer without coming into contact with the slurry. Separating the sensor from the slurry protects the camera from damage caused by abrasive slurries and the harsh conditions inside the mixer. Furthermore, separating the sensor from the slurry protects the slurry from contamination by the sensor.

[0015] In some embodiments, the IR window is located in the lid of the mixer. In alternative embodiments, the IR window is located in the base of the mixer.

[0016] In some embodiments, the IR window comprises a ceramic. In some embodiments, the IR window comprises zinc sulfide. In this manner, the IR window is adapted for harsh industrial environments. In some embodiments, the IR window is made of zinc sulfide.

[0017] In some embodiments, the infrared camera is attached to a camera holder. In some embodiments, the camera holder is configured to be moved by a user. In this manner, the user can optimize the measurement by moving the camera holder and IR sensor to optimize the field of view. In some embodiments, the camera holder is attached to the mixer. In this manner, the camera has a constant view of the slurry, allowing for consistent analysis of the slurry.

[0018] In some embodiments, the sensor may include at least one thermocouple. In this manner, the temperature of the slurry and the presence or absence of the slurry at a point within the mixer may be determined. In some embodiments, the mixer includes at least one hole for accommodating the at least one thermocouple.

[0019] In some embodiments, an array of thermocouples can be used. When an array of thermocouples is used, they can provide a direct measurement of the profile of the slurry within the mixer. The location of the slurry within the mixer can also be determined. The combination of profile and location allows for direct visualization and / or estimation of the volume of slurry occupying the mixer.

[0020] In some embodiments, the sensor may include an IR camera and at least one thermocouple, in which case both the IR camera and the at least one thermocouple may be used to monitor the volume of the slurry in the mixer and more accurately determine the volume of the slurry in the mixer.

[0021] In some embodiments, the mixer is configured to measure a parameter of the slurry substantially continuously. In this manner, the volume and / or volume fraction of the slurry in the mixer can be continuously monitored without having to interrupt the mixing process to perform the measurement. Furthermore, the volume and / or volume fraction of the slurry in the mixer is related to the mean residence time (MRT) of the slurry in the mixer. The MRT is an important parameter to consider to avoid the risk of lumps in the slurry. Gypsum slurries used in cement board production have a short initial set time, often less than 50 seconds, and therefore, lumps can be a significant issue in cement board production. The MRT is also an important parameter for assessing whether the water gauge of the slurry is too high. A high water gauge can lead to high levels of breakage in the mixer, which can lead to process and product issues. Therefore, continuously measuring the volume and / or volume fraction of the slurry in the mixer allows for the MRT to be continuously calculated.

[0022] In some embodiments, the cementitious material added to the mixer is calcium sulfate hemihydrate. In this aspect, the mixer can be used to mix calcium sulfate hemihydrate slurries in the production of plasterboard.

[0023] According to a second aspect of the present disclosure, there is provided a process for manufacturing a cement board, the process including: generating a slurry of water and a cementitious material, mixing the slurry in a mixer, measuring parameters of the slurry in the mixer and calculating a volume of the slurry in the mixer, depositing the slurry to form a board precursor, and drying the board precursor to form a cement board. In this aspect, the volume of the slurry in the mixer can be monitored to provide improvements to the manufacturing method and product.

[0024] In some embodiments, the process further comprises calculating a slurry volume fraction from the volume of the slurry, the slurry volume fraction being calculated according to the following formula:

number

[0025] In this manner, the slurry volume fraction can be used to determine improved mixer sizes and geometries for various line speeds to optimize the slurry volume fraction and avoid process and product issues. Additionally, calculating the slurry volume fraction makes it easier to compare and adjust mixers of various sizes.

[0026] In some embodiments, the process further includes varying at least one of a mixer input parameter, a process parameter, and a discharge parameter in response to the calculated volume and / or slurry volume fraction. In this manner, the volume of the slurry in the mixer can be adjusted to improve the process and product. For example, if the volume of the slurry is larger than the desired volume, the input rate of the slurry components into the mixer can be decreased, or the discharge rate of the slurry from the mixer can be increased. If the volume of the slurry is smaller than the desired volume, the input rate of the slurry components into the mixer can be increased, or the discharge rate of the slurry from the mixer can be decreased. In some embodiments, the input parameter is selected from the list consisting of line speed, input rate of the slurry components into the mixer, input volumetric flow rate (e.g., volume of material entering the mixer per second), input temperature (i.e., temperature of one or more materials entering the mixer), or slurry composition. In some embodiments, the process parameter is a mixing speed (e.g., speed of one or more mixing elements in the mixer) or a mixing temperature (e.g., temperature of the slurry in the mixer). In some embodiments, the discharge parameter is selected from the list consisting of line speed, mixer discharge rate (e.g., velocity of material exiting the mixer), discharge volumetric flow rate (e.g., volume of material exiting the mixer per second), discharge temperature (e.g., temperature of the slurry exiting the mixer), and exit cross-sectional area.

[0027] In some embodiments, the measurement of the slurry parameters is substantially continuous. In this manner, the volume and / or volume fraction of the slurry in the mixer can be continuously monitored without the need to interrupt the mixing process to perform the measurement. Furthermore, continuous measurement allows for estimation of the mean residence time (MRT) of the slurry in the mixer. The MRT is an important parameter to consider to avoid the risk of lumps in the slurry. Gypsum slurries used in cement board production have a short initial set time, often less than 50 seconds, and therefore, lumps can be a significant issue in cement board production. The MRT is also an important parameter for assessing whether the water gauge of the slurry is too high. A high water gauge can lead to high levels of breakage in the mixer, which can lead to process and product problems.

[0028] In some embodiments, the process further includes varying the composition of the cement slurry depending on the calculated volume of the slurry in the mixer. In this manner, the composition of the slurry can be adjusted to match the volume of the slurry in the mixer, reducing process and product issues. Thus, an improved mixing process and cement board product is provided. For example, the amount of superplasticizer used in the slurry can be increased or decreased to reduce the risk of lumps in the slurry or undesirable voids in the cement board.

[0029] In some embodiments, the cementitious material is calcium sulfate hemihydrate. In this aspect, the method can be used to mix a calcium sulfate hemihydrate slurry in the production of plasterboard.

[0030] The present disclosure will be further explained with reference to examples illustrated in the accompanying drawings. [Brief explanation of the drawings]

[0031] [Figure 1]FIG. 2 is a diagram of an infrared camera system for one embodiment of the mixer of the present invention. [Figure 2] FIG. 2 is a diagram of an infrared camera system for one embodiment of the mixer of the present invention. [Figure 3] 1 is an image captured by an IR camera according to an embodiment of the present invention. [Figure 4] 1 is a graph showing the relationship between the position and time of a slurry measured by an IR camera according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] The following description presents specific examples and, together with the drawings, serves to explain the principles of the present disclosure. However, the scope of the present invention is not limited to the exact details of the examples, as variations will be apparent to those skilled in the art and are deemed to be covered by this description. Terms relating to components used in this specification should be interpreted broadly to encompass equivalent functions and features. In some cases, alternative terms for structural features may be provided, but such terms are not intended to be exhaustive.

[0033] Descriptive terms should also be interpreted in the broadest possible manner; for example, the term "comprising" as used herein means "consisting at least in part of," and in interpreting each statement herein containing the term "comprising," features other than the feature preceded by that term may be present. Related terms (such as "comprise" and "comprises") should be interpreted in the same manner. Terms of direction, such as "vertical," "horizontal," "upper," "lower," "upper," "lower," "upper," and "lower" are typically used with reference to figures for convenience of description and are not intended to be ultimately limiting, as equivalent functionality can be achieved with alternative dimensions, orientations, and / or directions.

[0034] Although the description herein refers to examples of particular combinations of features, it is contemplated that further combinations of features that are compatible between embodiments and with each other are possible. Indeed, separate features may function as inventions independently of other features and need not necessarily be implemented as a complete combination.

[0035] In one embodiment of the present invention, the mixer includes an IR camera mounted on a camera holder attached to the mixer. The mixer includes a lid, a base, and at least one sidewall connecting the lid and the base. The mixer further includes an IR window in the mixer lid. The IR window is configured to transmit infrared light from the slurry inside the mixer to the external IR camera. The IR window comprises zinc sulfide and has a thickness of 5 mm. The camera holder is movable to allow a user to position the IR camera to optimize the field of view through the IR window. The IR window is positioned 4 cm from the side of the mixer's internal casing wall.

[0036] Cementitious materials, water, additives, and other ingredients are added to a mixer to produce a slurry. The cementitious materials are hot when added, and the hydration reaction of the cementitious materials is exothermic. Therefore, IR imaging can be used to determine the volume of the slurry in the mixer due to its higher temperature. As the slurry is mixed in the mixer, centrifugal force pushes the slurry toward the edges of the mixer. The slurry forms a donut shape, and the thickness of the donut can be characterized with IR imaging. To observe the tilt of the donut, the IR window requires a field of view of at least 10 cm. The IR camera is positioned at an angle such that there is an angle α between the camera's field of view β and the camera's vertical height γ to avoid camera reflections within the IR window. The distance between the 10 cm field of view and the base of the camera holder is defined as δ. The camera's field of view β is calculated using the following equation:

number

[0037] The camera orientation φ is given by:

number

[0038] By analyzing the IR images, the location of the slurry decay profile can be identified and the volume of the slurry in the mixer determined.

[0039] As an alternative to an IR camera and window, the mixer is equipped with a thermocouple and a hole to accommodate the thermocouple to capture the thermal profile of the slurry.

[0040] Figure 1 is a schematic diagram of an IR system according to one embodiment of the present invention, showing the field of view of an IR camera 101 through an IR window 102 to a slurry 103 in a mixer 100.

[0041] 2 is a schematic diagram of an IR system according to one embodiment of the present invention. An IR camera 101 receives infrared light from a cement slurry 103 through an IR window 102. The IR window 102 is positioned 4 cm from the inside sidewall 104 of the mixer 100. The IR camera 101 is mounted on a camera holder 105 attached to the mixer 100.

[0042] Figure 4 shows the position of the slurry as measured by the IR camera versus time. The observed fluctuations can be linked to changes in the slurry volume fraction in the mixer.

Claims

1. A mixer for mixing cement slurry, comprising: an inlet for receiving cementitious material and water; a mixing member configured to mix the cementitious material with water to produce a cement slurry; an outlet for delivering the cement slurry; a sensor configured to measure a parameter of the cement slurry; a processor configured to calculate a volume of the cement slurry in the mixer using the parameter measurements; wherein the sensor includes an array of thermocouples.

2. A mixer for mixing cement slurry, comprising: an inlet for receiving cementitious material and water; a mixing member configured to mix the cementitious material with water to produce a cement slurry; an outlet for delivering the cement slurry; a sensor configured to measure a parameter of the cement slurry; a processor configured to calculate a volume of the cement slurry in the mixer using the parameter measurements; Equipped with the sensor includes an infrared camera; the mixer includes an IR window configured to transmit infrared light from the cement slurry inside the mixer to an IR camera outside; Mixer.

3. The processor is further configured to calculate a slurry volume fraction of the mixer, the slurry volume fraction being calculated according to the following formula: [Equation 1] 3. The mixer of claim 1 or claim 2, wherein the mixer is defined according to:

4. 4. The mixer of claim 1, claim 2, or claim 3, wherein the processor is further configured to vary at least one of input parameters, process parameters, and discharge parameters of the mixer in response to the calculated volume of cement slurry in the mixer and / or the slurry volume fraction of the mixer.

5. The mixer of claim 4 , wherein the feed parameter is selected from the list consisting of line speed, feed rate, feed volumetric flow rate, feed temperature, or slurry composition.

6. 6. The mixer according to claim 4 or claim 5, wherein the process parameter is a mixing speed or a mixing temperature.

7. 7. The mixer of claim 4, claim 5, or claim 6, wherein the discharge parameter is selected from the list consisting of mixer discharge rate, discharge volume, discharge temperature, or exit cross-sectional area.

8. 1. A process for producing cement board, comprising: forming a slurry of water and cementitious material; mixing the slurry in a mixer; measuring a parameter of the slurry in the mixer using a sensor and calculating a volume of the slurry in the mixer; depositing the slurry to form a board precursor; drying the board precursor to form a cement board; Including, the sensor includes an array of thermocouples; process.

9. 1. A process for producing cement board, comprising: forming a slurry of water and cementitious material; mixing the slurry in a mixer; measuring a parameter of the slurry in the mixer using a sensor and calculating a volume of the slurry in the mixer; depositing the slurry to form a board precursor; drying the board precursor to form a cement board; Including, the sensor includes an infrared camera; the mixer includes an IR window configured to transmit infrared light from the cement slurry inside the mixer to an IR camera outside; process.

10. The process further includes calculating a slurry volume fraction from the volume of the slurry, the slurry volume fraction being calculated according to the following formula: [Equation 2] 10. The process of claim 8 or claim 9, wherein the process is defined according to

11. 11. The process of claim 8, claim 9, or claim 10, further comprising varying at least one of a mixer input parameter, a process parameter, and a discharge parameter in response to the calculated volume and / or slurry volume fraction.

12. A process according to any one of claims 8 to 11, wherein the measurement of the parameter of the slurry is substantially continuous.

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