Mixer

Abstract

A mixer and method for mixing cementitious slurries configured to calculate the volume of cementitious slurry in the mixer in order to produce an improved mixing process and / or an improved cementitious product. The mixer includes a sensor for measuring a parameter of the slurry in the mixer for calculating a volume of the slurry in the mixer.

Description

Technical Field

[0001] The present disclosure generally relates to mixers and methods for mixing, monitoring, and dispensing cementitious slurries. Background Art

[0002] During cement board manufacturing, cementitious slurry is mixed within and dispensed from a mixer. If the volume of slurry in the mixer is too large or too small, these volume deviations may cause problems with the manufacturing process and / or the cement board product itself. For example, where the volume of slurry in the mixer deviates from what is expected, the slurry may include lumps and / or the cementitious product may include undesirable voids.

[0003] Generally, a slurry mixer includes a mixing member that mixes the slurry. Additionally, the slurry mixer may include a scraper that cleans the deposited slurry from the walls of the mixer. As a result, the slurry mixer is difficult to access, and therefore, monitoring the slurry volume therein may be challenging.

[0004] Current methods for controlling and / or monitoring the slurry volume fraction within a mixer use estimates based on an ideal mixer with no stagnant 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, pigment can be added to the slurry and a camera can be used to calculate the concentration of the pigment within the slurry and estimate the slurry volume fraction. However, this method causes the slurry to be contaminated with pigment and cannot be applied continuously. In addition, any contact between the slurry and sensitive equipment within the mixer can damage the equipment. Therefore, current methods, whether based on theoretical calculations of mean residence time or based on more physical methods, cannot provide continuous and reliable measurement of the slurry volume fraction within the mixer.

[0005] Aspects of the present disclosure seek to provide mixers and mixing processes that alleviate these problems of prior known systems. Specifically, aspects of the present disclosure seek to provide improved mixers and mixing processes that are capable of monitoring the volume of slurry in the mixer. Summary of the invention

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

[0007] In this way, the mixer allows the volume of slurry in the mixer to be monitored without contaminating the slurry in order to avoid process and product problems.

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

[0009]

[0010] In this way, the slurry volume fraction can be used to determine improved mixer size and geometry for different line speeds to optimize the slurry volume fraction, thereby avoiding process and product problems. In addition, calculating the slurry volume fraction allows for simpler comparison and adjustment of mixers of different sizes.

[0011] In some embodiments, the processor is further configured to change at least one of the input parameters, process parameters, and output parameters of the mixer in response to the calculated volume of cementitious slurry in the mixer and / or the slurry volume fraction of the mixer. In this way, the volume of slurry in the mixer can be adjusted to improve the process and product. For example, if the volume of the slurry is higher than desired, the input rate of the slurry components into the mixer can be reduced or the rate at which the slurry is output from the mixer can be increased. If the volume of the slurry is lower than desired, the rate at which the slurry components are input into the mixer can be increased, or the rate at which the slurry is output from the mixer can be reduced. In some embodiments, the input parameter is selected from a list consisting of: line speed, the rate at which the slurry components are input into the mixer, input volume flow rate (e.g., the volume of material entering the mixer per second), input temperature (e.g., the temperature of one or more materials entering the mixer), or the composition of the slurry. In some embodiments, the process parameter is a mixing speed (e.g., the speed of one or more mixing components in the mixer) or a mixing temperature (e.g., the temperature of the slurry in the mixer). In some embodiments, the output parameter is selected from a list consisting of: line speed, mixer output speed (e.g., the speed of material leaving the mixer), output volume flow rate (e.g., the volume of material leaving the mixer per second), output temperature (e.g., the temperature of the slurry leaving the mixer), outlet cross section.

[0012] In certain embodiments, the mixer comprises a base and a lid, wherein the base and the lid are connected by at least one sidewall. In certain embodiments, the mixer is a closed system. In this way, the conditions in the mixer can be more easily controlled.

[0013] In some embodiments, the mixer comprises a scraper configured to remove deposited slurry from the walls of the mixer. In this way, the risk of part of the slurry settling on the walls of the mixer is reduced and the consistency of the slurry is improved.

[0014] In some embodiments, the sensor includes an infrared camera. In this way, the infrared camera (hereinafter referred to as the IR camera) can provide a direct visualization of the slurry profile in the mixer. The position of the slurry in the mixer can also be determined. The combination of profile and position allows direct visualization and / or estimation of the slurry volume occupied in the mixer.

[0015] In some embodiments, the mixer includes an IR window that is configured to allow infrared radiation to be transmitted from the cementitious slurry within the mixer to an external IR camera. In this way, the IR camera is able to visualize the slurry in the mixer through the IR window without requiring an IR camera in the mixer itself. Including a camera within the mixer may contaminate the slurry and is very susceptible to damage from at least the abrasive slurry. In this way, the infrared camera can be used to calculate the volume of the slurry in the mixer without coming into contact with the slurry. Separating the sensor and slurry protects the camera from damage caused by the abrasive slurry and the harsh conditions within the mixer. In addition, separating the sensor and slurry protects the slurry from contamination from the sensor.

[0016] In some embodiments, the IR window is located on the lid of the mixer. In alternative embodiments, the IR window is located on the base of the mixer.

[0017] In some embodiments, the IR window comprises ceramic. In some embodiments, the IR window comprises zinc sulfide. In this way, the IR window is suitable for harsh industrial environments. In some embodiments, the IR window consists of zinc sulfide.

[0018] In some embodiments, the infrared camera is mounted on a camera holder. In some embodiments, the camera holder is configured to be moved by a user. In this way, the user can move the camera holder and IR sensor to optimize the field of view and thus the measurement. In some embodiments, the camera holder is attached to the mixer. In this way, the camera has a constant view of the slurry, which allows for consistent analysis of the slurry.

[0019] In some embodiments, the sensor may include at least one thermocouple. In this way, the temperature of the slurry and its presence or absence at a certain point within the mixer can be determined. In some embodiments, the mixer includes at least one hole to accommodate at least one thermocouple.

[0020] In some embodiments, an array of thermocouples may be used. Where an array of thermocouples is used, these thermocouples may provide a direct measurement of the slurry profile in the mixer. The position of the slurry in the mixer may also be determined. The combination of profile and position allows for direct visualization and / or estimation of the slurry volume occupied in the mixer.

[0021] In some embodiments, the sensor may include an IR camera and at least one thermocouple. In this way, both the IR camera and at least one thermocouple may be used to monitor the volume of the slurry in the mixer to more accurately determine the volume of the slurry in the mixer.

[0022] In some embodiments, the mixer is configured to measure the parameters of the slurry substantially continuously. In this way, the volume and / or slurry volume fraction of the slurry in the mixer can be continuously monitored without interrupting the mixing process to measure. In addition, the volume and / or slurry volume fraction of the slurry in the mixer is related to the mean residence time (MRT) of the slurry in the mixer. MRT is an important parameter considered to avoid the risk of agglomeration in the slurry. Gypsum slurry used for cement board production has a fast initial setting time, typically less than 50 seconds, and therefore the formation of lumps may be an important problem in cement board production. MRT is also an important parameter for evaluating whether the water level of the slurry is too high. If the water level is too high, it may cause a high level of disintegration in the mixer, which may cause problems with the process and the product. Therefore, continuous measurement of the volume and / or slurry volume fraction of the slurry in the mixer allows continuous calculation of the MRT.

[0023] In some embodiments, the cementitious material added to the mixer is calcium sulfate hemihydrate. In this way, the mixer can be used to mix calcium sulfate hemihydrate slurry in gypsum board production.

[0024] According to a second aspect of the present disclosure, there is provided a method for manufacturing a cement board, the method comprising: forming a slurry of water and cement material; mixing the slurry in a mixer; measuring parameters of the slurry in the mixer and calculating the 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 way, the volume of the slurry in the mixer can be monitored to provide improved production methods and products.

[0025] In some embodiments, the method further comprises calculating a slurry volume fraction from the slurry volume, wherein the slurry volume fraction is defined according to the following formula:

[0026]

[0027] In this way, the slurry volume fraction can be used to determine improved mixer size and geometry for different line speeds to optimize the slurry volume fraction, thereby avoiding process and product problems. In addition, calculating the slurry volume fraction allows for simpler comparison and adjustment of mixers of different sizes.

[0028] In some embodiments, the method further comprises changing at least one of an input parameter, a process parameter, and an output parameter in response to the calculated volume and / or slurry volume fraction. In this way, 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 higher than desired, the input rate of the slurry component into the mixer can be reduced or the rate at which the slurry is output from the mixer can be increased. If the volume of the slurry is lower than desired, the rate at which the slurry component is input into the mixer can be increased, or the rate at which the slurry is output from the mixer can be reduced. In some embodiments, the input parameter is selected from a list consisting of: line speed, the rate at which the slurry component is input into the mixer, input volume flow rate (e.g., the volume of material entering the mixer per second), input temperature (i.e., the temperature of one or more materials entering the mixer) or the composition of the slurry. In some embodiments, the process parameter is a mixing speed (e.g., the speed of one or more mixing components in the mixer) or a mixing temperature (e.g., the temperature of the slurry in the mixer). In some embodiments, the output parameter is selected from a list consisting of: line speed, mixer output speed (e.g., the speed of material leaving the mixer), output volume flow rate (e.g., the volume of material leaving the mixer per second), output temperature (e.g., the temperature of the slurry leaving the mixer), outlet cross section.

[0029] In some embodiments, the measurement of the parameters of the slurry is substantially continuous. In this way, the volume and / or slurry volume fraction of the slurry in the mixer can be continuously monitored without interrupting the mixing process to measure. In addition, continuous measurement allows the mean residence time (MRT) of the slurry in the mixer to be estimated. MRT is an important parameter considered to avoid the risk of caking in the slurry. Gypsum slurry used for cement board production has a fast initial setting time, typically less than 50 seconds, and therefore the formation of lumps may be an important problem in cement board production. MRT is also an important parameter for evaluating whether the water level of the slurry is too high. If the water level is too high, it may cause a high level of disintegration in the mixer, which may cause problems with the process and product.

[0030] In some embodiments, the method further comprises changing the composition of the cementitious slurry in response to the calculated volume of the slurry in the mixer. In this way, the composition of the slurry can be adjusted to accommodate the volume of the slurry in the mixer so as to reduce process and product problems. Improved mixing methods and cement board products are thus provided. For example, the amount of fluidizing agent 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.

[0031] In some embodiments, the cementitious material is calcium sulfate hemihydrate. In this way, the method can be used to mix calcium sulfate hemihydrate slurry in gypsum board production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present disclosure will be further described with reference to the examples depicted in the accompanying drawings, in which:

[0033] Figure 1 is a diagram of an infrared camera system of an embodiment of a mixer of the present invention;

[0034] Figure 2 is a diagram of an infrared camera system of an embodiment of the mixer of the present invention; and

[0035] Figure 3 is an image captured by an IR camera in an embodiment of the present invention; and

[0036] Figure 4 is a graph showing the relationship between the position of the slurry and time as measured by an IR camera of an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The following description presents specific examples and is related to the Figure 1 The invention is intended to explain the principles of the present disclosure. However, the scope of the invention is not intended to be limited to the precise details of the embodiments, as variations will be apparent to the skilled person and are considered to be covered by the description. The terms for components used herein should be given a broad interpretation, which also encompasses equivalent functions and features. In some cases, alternative terms for structural features may be provided, but these terms are not intended to be exhaustive.

[0038] Descriptive terms should also be given the broadest possible interpretation; for example, the term "comprising" as used in this specification means "consisting at least in part of...", so that each statement in this specification including the term "comprising" is interpreted that there may also be features in addition to the one or more features beginning with the term. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner. Directional terms such as "vertical", "horizontal", "upper", "lower", "top", "bottom", "upper" and "lower" are generally used for ease of explanation and are not intended to be ultimately limiting if an equivalent function can be achieved with alternative sizes, orientations and / or directions.

[0039] The description herein relates to examples with specific combinations of features, however, it is contemplated that further combinations and cross-combinations of compatible features between embodiments will be possible. In fact, isolated features can function as the present invention independently of other features, and do not necessarily need to be implemented as a complete combination.

[0040] In an embodiment of the present invention, a mixer includes an IR camera mounted on a camera bracket attached to the mixer. The mixer includes a cover, a base, and at least one side wall connecting the cover and the base. The mixer also includes an IR window on the cover of the mixer. The IR window is configured to allow infrared radiation to be transmitted from the slurry inside the mixer to the external IR camera. The IR window includes zinc sulfide and has a thickness of 5 mm. The camera bracket is removable to allow a user to position the IR camera to optimize the field of view through the IR window. The IR window is located 4 cm from the side of the inner shell wall of the mixer.

[0041] Cementitious material, water, additives, and other materials are added to a mixer to form a slurry. The cementitious material is hot when added, and the hydration of the cementitious material is exothermic. Therefore, due to the higher temperature of the slurry, IR imaging can be used to determine the volume of the slurry in the mixer. As the slurry is mixed in the mixer, the slurry is pushed to the edge of the mixer due to centrifugal force. The slurry forms a donut shape, and the thickness of the donut shape can be characterized using IR imaging. In order to observe the slope of the donut, the IR window requires a field of view of at least 10 cm. The IR camera is positioned at an angle so that there is an angle α between the field of view β of the camera and the vertical height γ of the camera to avoid reflections of the camera in the IR window. The distance between the 10 cm field of view and the base of the camera mount is defined as δ. The field of view β of the camera is determined using the following formula:

[0042]

[0043] The camera's orientation φ is determined using the following formula:

[0044]

[0045] The IR images can be analyzed to determine the location of the decreasing profile distribution of the slurry and then determine the volume of the slurry in the mixer.

[0046] As an alternative to an IR camera and window, the mixer includes a thermocouple and an aperture to accommodate the thermocouple in order to capture the thermal profile of the slurry.

[0047] Figure 1 is a schematic diagram of an IR system according to an embodiment of the present invention. Figure 1 The field of view of the IR camera 101 through the IR window 102 to the slurry 103 in the mixer 100 is shown.

[0048] Figure 2 1 is a schematic diagram of an IR system of an embodiment of the present invention. An IR camera 101 receives infrared radiation from a cementitious slurry 103 through an IR window 102. The IR window 102 is located 4 cm from an inner side wall 104 of the mixer 100. The IR camera 101 is mounted on a camera bracket 105 attached to the mixer 100.

[0049] Figure 4 The relationship between the slurry position measured by the IR camera and time is shown. The observed changes are related to the changes in the slurry volume fraction of the mixer.

Claims

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

2. A mixer for mixing cementitious slurry, the mixer comprising: an inlet for receiving cementitious material and water; a mixing member configured to mix a cementitious material and water to form a cementitious slurry; an outlet for dispensing cementitious slurry; a sensor configured to measure a parameter of the cementitious slurry; and a processor configured to calculate a volume of cementitious slurry in a mixer using the parameter measurements; wherein The sensor comprises an infrared camera; and The mixer includes an IR window configured to allow infrared radiation to be transmitted from the cementitious slurry within the mixer to an external IR camera.

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

4. A mixer according to claim 1, claim 2 or claim 3, wherein the processor is further configured to change at least one of the input parameters, process parameters and output parameters of the mixer in response to the calculated volume of cementitious slurry in the mixer and / or the slurry volume fraction of the mixer.

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

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

7. A mixer according to claim 4, claim 5 or claim 6, wherein: The output parameter is selected from the list consisting of mixer output speed, output volume, output temperature or outlet cross section.

8. A method for manufacturing a cement board, the method 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 plate precursor; and drying the board precursor to form a cement board; in The sensor includes an array of thermocouples.

9. A method for manufacturing a cement board, the method 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 plate precursor; and drying the board precursor to form a cement board; wherein The sensor comprises an infrared camera; and The mixer includes an IR window configured to allow infrared radiation to be transmitted from the cementitious slurry within the mixer to an external IR camera.

10. The method according to claim 8 or claim 9, wherein the method further comprises calculating a slurry volume fraction from the slurry volume, wherein the slurry volume fraction is defined according to the following formula:

11. The method of claim 8, claim 9 or claim 10, wherein the method further comprises changing at least one of an input parameter, a process parameter and an output parameter in response to the calculated volume and / or slurry volume fraction.

12. The method of any one of claims 8 to 11, wherein the measuring of the parameter of the slurry is substantially continuous.

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