Apparatus and method for manufacturing cement slurry comprising foam
By designing a device with multiple foam inlets, the foam is introduced into the cement slurry, the problem of foam cutting and dispersion in the prior art is solved, and uniform mixing of foam in the cement slurry and low foam loss is achieved.
Patent Information
- Application Number
- CN202380061220.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-10-20
- Filing Date
- 2023-10-18
- Publication Date
- 2025-04-01
AI Technical Summary
The prior art, when introducing foam into cement slurry, tends to lead to shear and dispersion of foam, resulting in high foam loss and low efficiency density reduction.
A device is designed that includes a channel and a plurality of foam inlets, by combining the plurality of inlets of the foam into the channel with the cement slurry, the shear force of the foam is reduced to ensure that the foam is evenly mixed in the cement slurry.
Through this device, the foam maintains stability in the cement slurry, the foam loss is reduced, and the efficiency of the density is improved.
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Figure CN119744219A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a device for manufacturing cement slurry containing foam and a method for manufacturing cement slurry containing foam using the device. Background Art
[0002] Gypsum as a raw material occurs naturally in the form of calcium sulfate dihydrate (CASO4 2(H2O)). Gypsum-containing products, such as gypsum board, are prepared by forming a mixture of calcined or dehydrated gypsum, calcium sulfate hemihydrate (CASO4 0.5(H2O)), and water to form a settable slurry, which is then cast into a desired shape. The calcium sulfate hemihydrate reacts with water, rehydrates to dihydrate crystals, and then cures or dries to a solid state.
[0003] Gypsum products are commonly found throughout buildings due to their versatility, desirable mechanical properties and the possibility of achieving a high level of finish. Therefore, there is a need to produce lightweight gypsum products. Reductions in the amount of gypsum used significantly reduce the resource requirements of the manufacturing process, therefore reducing material costs. Therefore, the weight of these gypsum products is very important.
[0004] In order to provide a lightweight gypsum product, foam can be added to the settable slurry. However, the introduction of foam into the slurry results in shearing and dispersion of the foam. This dispersion results in high foam losses, creating an inefficient process that limits the degree of density reduction that can be achieved using this method. Foam losses are particularly prevalent when large amounts of foam are introduced into the slurry. Summary of the invention
[0005] According to a first aspect of the present invention, there is provided an apparatus for manufacturing a cement slurry containing foam, the apparatus comprising: a mixing chamber for mixing a cement material and water to form a cement slurry, a channel which is fluidly connected to the mixing chamber at a first end, the channel being used to receive the cement slurry from the mixing chamber, the channel extending from the first end and terminating at at least one second end; the channel comprising a first foam inlet for introducing foam into the channel; and the channel also comprising a second foam inlet for introducing foam into the channel.
[0006] The present invention provides a device for effectively and consistently combining foam with a cement slurry, such as plaster or gypsum slurry. When combined with the slurry via multiple inlets in a channel, the foam experiences sufficiently low shear forces to maintain foam stability. In the prior art, the mixing device inside the mixing chamber can apply very high shear rates within the slurry. These high shear rates can destroy bubbles and destabilize any foam in the mixing chamber. Therefore, introducing foam into the cement slurry in the mixing chamber can result in high levels of foam loss. The present invention solves this problem of the prior art because the use of a first foam inlet and a second foam inlet within the channel ensures that the foam is evenly mixed throughout the cement slurry with low levels of foam loss.
[0007] Preferably, the mixing chamber is a tangential mixer. Preferably, the tangential mixer comprises a single mixing member. Alternatively, the tangential mixer comprises a plurality of mixing members.
[0008] Preferably, the first foam inlet is located in the lower half of the channel. Alternatively, the first foam inlet is located in the upper half of the channel. Alternatively, the first foam inlet is located at the vertical midpoint of the channel.
[0009] Preferably, the first foam inlet is located on an outer wall of the channel, wherein the outer wall extends tangentially from the mixing chamber. Preferably, where the mixing chamber is a tangential mixer, the first foam inlet is located on an outer wall of the channel, wherein the outer wall extends tangentially from the tangential mixer.
[0010] Preferably, the second foam inlet is located on a wall of the channel substantially opposite the outer wall.The wall of the channel may be continuous, as in the case where the channel is circular, or different, as in the case where the channel is rectangular or square.
[0011] Preferably, the first foam inlet is located on a substantially opposite wall of the channel to the wall of the channel where the second foam inlet is located.Preferably, the second foam inlet is located on a substantially opposite side of the channel to the first foam inlet.
[0012] Preferably, the first foam inlet and the second foam inlet are located at the same vertical position in the channel. In such a configuration, the first foam inlet and the second foam inlet may be located at the same horizontal plane of the channel. In the case where the first foam inlet and the second foam inlet are located at the same vertical position in the channel, the distance between the base of the channel and the first foam inlet and the distance between the base of the channel and the second foam inlet will be the same, or the distance between the top of the channel and the first foam inlet and the distance between the top of the channel and the second foam inlet will be the same.
[0013] Preferably, the first foam inlet and the second foam inlet are positioned at the vertical midpoint of the channel.Here, the distance between the channel top and the foam inlet is the same as the distance between the channel base and the foam inlet.
[0014] Preferably, the first foam inlet and the second foam inlet are offset along the length of the channel. Preferably, the offset is at least 30mm. More preferably, the offset is at least 50mm. Still more preferably, the offset is at least 100mm. Still more preferably, the offset is at least 150mm.
[0015] Preferably, the first foam inlet is closer to the first end of the channel than the second foam inlet.Preferably, the distance between the first foam inlet and the first end of the channel is the same as the distance between the second foam inlet and the second end of the channel.
[0016] Preferably, the second foam inlet is located at least 200 mm from the first end of the channel.Preferably, the second foam inlet is located less than 250 mm from the first end of the channel.
[0017] Preferably, the maximum opening size of the first foam inlet and / or the second foam inlet is greater than or equal to 15 mm. More preferably, the maximum opening size of the first foam inlet and / or the second foam inlet is greater than or equal to 17.5 mm. Most preferably, the maximum opening size of the first foam inlet and / or the second foam inlet is greater than or equal to 20 mm.
[0018] Preferably, the maximum opening dimension of the first foam inlet is less than or equal to 25 mm. More preferably, the maximum opening dimension of the first foam inlet is less than or equal to 20 mm. Most preferably, the maximum opening dimension of the first foam inlet is less than or equal to 17.5 mm.
[0019] Preferably, the device is configured to introduce foam through the first foam inlet and the second foam inlet at a speed of 5.4 times or less of the speed of the cement slurry in the channel during use. More preferably, the device is configured to introduce foam through the first foam inlet and the second foam inlet at a speed of 3.4 times or less of the speed of the cement slurry in the channel during use. Still more preferably, the device is configured to introduce foam through the first foam inlet and the second foam inlet at a speed of 2.4 times or less of the speed of the cement slurry in the channel during use. Most preferably, the device is configured to introduce foam through the first foam inlet and the second foam inlet at a speed of 1.8 times or less of the speed of the cement slurry in the channel during use.
[0020] Preferably, the device is configured to introduce foam through the first foam inlet and the second foam inlet at a speed of two or more times the speed of the cement slurry in the channel in use. More preferably, the device is configured to introduce foam through the first foam inlet and the second foam inlet at a speed of three or more times the speed of the cement slurry in the channel in use. Even more preferably, the device is configured to introduce foam through the first foam inlet and the second foam inlet at a speed of four or more times the speed of the cement slurry in the channel in use.
[0021] Preferably, the device is configured to introduce foam through the first foam inlet and the second foam inlet at a speed of between 1.8 and 5.4 times the speed of the cement slurry in the channel, inclusive. More preferably, the device is configured to introduce foam through the first foam inlet and the second foam inlet at a speed of between 1.8 and 3.4 times the speed of the cement slurry in the channel, inclusive. Even more preferably, the device is configured to introduce foam through the first foam inlet and the second foam inlet at a speed of between 2.4 and 3.4 times the speed of the cement slurry in the channel, inclusive. Most preferably, the device is configured to introduce foam through the first foam inlet and the second foam inlet at a speed of 2.4 times the speed of the cement slurry in the channel, inclusive.
[0022] Preferably, at least one second end of the channel is connected to a dispensing hose.Preferably, the channel comprises a single second end.
[0023] Preferably, at least one second end of the channel is connected to the secondary chamber.
[0024] Preferably, the channel is substantially straight. Alternatively, the channel is substantially curved. Preferably, the channel has a substantially similar cross-sectional area throughout its length. Preferably, the channel has a substantially similar cross-sectional shape throughout its length. More preferably, the channel has a substantially similar cross-sectional area and a substantially similar cross-sectional shape throughout its length.
[0025] Preferably, the device comprises a third foam inlet. More preferably, the device comprises a fourth foam inlet. In selected embodiments, the plurality of foam inlets consists of four foam inlets.
[0026] Preferably, the four foam inlets are located along two orthogonal axes. More preferably, the orthogonal axes are offset along the length of the channel.
[0027] Preferably, the four foam inlets are evenly spaced along the length of the channel. More preferably, the four foam inlets are evenly spaced along the length of a portion of the channel.
[0028] Preferably, none of the four foam inlets is directly opposite another of the four foam inlets.Preferably, the four foam inlets are positioned at 90 degrees to each other around the periphery of the passageway.
[0029] Preferably, the axis of at least one foam inlet at the point where it joins the channel is perpendicular to the axis of the channel. More preferably, the axes of all foam inlets at the point where they join the channel are perpendicular to the axis of the channel. Thus, dispersion of the foam within the channel is improved. Preferably, the axis of at least one foam inlet intersects the axis of the channel at the point where it joins the channel.
[0030] Preferably, the first foam inlet has a substantially circular cross-section. In this case, the maximum opening dimension is the diameter of the circle. Alternatively, the first foam inlet has a substantially square or rectangular cross-section. In this case, the maximum opening dimension is the diagonal.
[0031] Preferably, the second foam inlet has a substantially circular cross-section. In this case, the maximum opening dimension is the diameter of the circle. Alternatively, the second foam inlet has a substantially square or rectangular cross-section. In this case, the maximum opening dimension is the diagonal.
[0032] Preferably, the channel comprises a circular cross-section.Alternatively, the channel comprises a rectangular or square cross-section.
[0033] Preferably, the cementitious material comprises at least one of calcium sulphate hemihydrate and calcium sulphate dihydrate. More preferably, the cementitious material consists essentially of calcium sulphate hemihydrate.
[0034] According to a second aspect of the present invention, a method for manufacturing a cement slurry containing foam is provided, the method comprising: providing an apparatus as described above; introducing cement material and water into a mixing chamber to form a cement slurry; and introducing foam into the cement slurry through a first foam inlet and a second foam inlet.
[0035] In this way, a method for efficiently and consistently combining foam with a cement slurry, such as a plaster or gypsum slurry, is provided. When combined with the slurry, the foam experiences sufficiently low shear forces to maintain foam stability. In the prior art, the mixing device inside the mixing chamber can apply very high shear rates within the slurry. These high shear rates can destroy bubbles and destabilize any foam in the mixing chamber. Therefore, introducing foam into the cement slurry in the mixing chamber can result in high levels of foam loss. The present invention solves this problem of the prior art because the use of multiple foam inlets ensures that the foam is evenly mixed throughout the cement slurry with low levels of foam loss.
[0036] Preferably, the foam is introduced into the cement slurry at a rate of 5.4 times or less of the cement slurry velocity in the channel. More preferably, the foam is introduced into the cement slurry at a rate of 3.4 times or less of the cement slurry velocity in the channel. Still more preferably, the foam is introduced into the cement slurry at a rate of 2.4 times or less of the cement slurry velocity in the channel, and still more preferably, the foam is introduced into the cement slurry at a rate of 1.8 times or less of the cement slurry velocity in the channel.
[0037] Preferably, the foam is introduced into the cement slurry at a rate of two or more times the velocity of the cement slurry in the channel. More preferably, the foam is introduced into the cement slurry at a rate of three or more times the velocity of the cement slurry in the channel. Still more preferably, the foam is introduced into the cement slurry at a rate of four or more times the velocity of the cement slurry in the channel.
[0038] Preferably, the foam is introduced into the cement slurry at a speed of 1.8 to 5.4 times (inclusive) the speed of the cement slurry in the channel. Still more preferably, the foam is introduced into the cement slurry at a speed between 1.8 to 3.4 times, inclusive, the speed of the cement slurry in the channel. Still more preferably, the foam is introduced into the cement slurry at a speed between 2.4 to 3.4 times, inclusive, the speed of the cement slurry in the channel. Most preferably, the foam is introduced into the cement slurry at a speed of 2.4 times the speed of the cement slurry. BRIEF DESCRIPTION OF THE DRAWINGS
[0039] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:
[0040] Figure 1 depicts an apparatus according to a first embodiment of the invention;
[0041] Figure 2 depicts a schematic diagram of a method according to a second aspect of the invention;
[0042] Figure 3 A theoretical foam efficiency factor (FEF)-distance graph is depicted to indicate foam stability at various distances of the foam inlet along the device;
[0043] Figure 4 The theoretical foam efficiency factor (FEF)-diameter graph is depicted to indicate the foam stability for various foam inlet diameters;
[0044] Figure 5 Density deviation-diameter graphs are plotted to indicate the mixing uniformity of the foam and cement slurry mixture for various foam inlet diameters;
[0045] Figure 6 depicts a foam inlet configuration within the scope of the present invention;
[0046] Figure 7 is a graph depicting the effect of various foam inlet configurations on density deviation measured within a slurry-foam mixture; and
[0047] Figure 8 Shear rate-distance and density deviation-distance graphs are plotted to indicate the shear forces experienced by the foam and the mixing uniformity of the foam and cement slurry mixture for various distances along the device from the foam inlet. DETAILED DESCRIPTION
[0048] Figure 1 An apparatus 100 for making a cement slurry containing foam is shown. The apparatus 100 comprises a mixing chamber 101 and a secondary chamber 102, the secondary chamber comprising a tank. The mixing chamber 101 is connected to the secondary chamber 102 via a channel 103.
[0049] The mixing chamber 101, here a tangential mixer, comprises a cement material inlet 104 for introducing at least one cement material (e.g. calcium sulfate hemihydrate or plaster) into the mixing chamber 101 and a first water inlet 105 for introducing water into the mixing chamber 101. In this way, cement material and water can be introduced into the mixing chamber 101. The mixing chamber comprises a mixing member, which comprises a plurality of blades or teeth. In use, the mixing member rotates in the mixing chamber 101, combining water and cement material to form cement slurry. After its formation, the cement slurry can leave the mixing chamber 101 and enter the channel 103 via the mixing chamber outlet 111. The mixing chamber outlet 111 ensures that the channel 103 is in fluid communication with the mixing chamber 101, so that the cement slurry can freely enter the channel 103 from the mixing chamber 101. The mixing chamber outlet 111 represents the first end of the channel 103.
[0050] The channel 103 comprises a foam inlet 106 for introducing foam into the channel 103. The foam inlet 106 is fluidly connected to the channel 103, ensuring that in use, foam can freely enter the channel 103 through the foam inlet 106. In use, foam is injected into the channel 103 via the foam inlet 106. In this way, downstream of the foam inlet 106, the channel comprises an increasingly homogeneous mixture of cement slurry and foam.
[0051] In the illustrated embodiment, the foam is a preformed aqueous foam generated in the foam generator 107. The foam generator includes a second water inlet 108 for introducing water into the foam generator 107, a soap inlet 109 for introducing soap into the foam generator 107, and an air inlet 110 for introducing air into the foam generator 107. The paths of the second water inlet 108 and the soap inlet 109 are joined and combined before entering the foam generator 107. Air, water, and soap are introduced into the foam generator 107 to generate foam.
[0052] The channel 103 extends from the mixing chamber outlet 111 and is substantially straight. The channel 103 terminates at a second end, which is a secondary chamber inlet 112. Therefore, the cement slurry leaving the mixing chamber 101 via the mixing chamber outlet 111 and the foam entering the channel via the foam inlet 106 are combined and mixed as they flow along the channel 103. Then, the mixed foam and cement slurry leave the channel 103 and enter the secondary chamber 102 via the secondary chamber inlet 112. In the secondary chamber 102, the cement slurry and foam are further mixed. When the foam is injected directly into the mixing chamber 101, the stability of the bubbles is reduced due to the movement of the mixing arm and the shear force present in the mixing chamber 101. Therefore, in order to reduce bubble damage, the foam inlet 106 is located in the channel 103 downstream of the mixing chamber outlet 111.
[0053] The foam inlet 106 is positioned so that the distance between the first end of the channel 103 (ie the end located near the mixing chamber outlet 111) and the foam inlet 106 is 100 mm. In this embodiment, the foam inlet is circular with a diameter of 15 mm.
[0054] The secondary chamber 102 is connected to a dispensing hose 113. The cement slurry and foam flow exiting the passage 103 and entering the secondary chamber 102 via the secondary chamber inlet 112 is further mixed as it passes through the secondary chamber 102 and then exits the secondary chamber 102 via the dispensing hose 113. Thus, there is a continuous fluid connection between the mixing chamber 101 and the dispensing hose 113, which continues through the mixing chamber outlet 111, the passage 103, the secondary chamber inlet 112, and the secondary chamber 102. In this embodiment, the dispensing hose 113 is split at a point along its length so that it includes a pair of elongated sections, each of which includes a dispensing hose outlet. Although in the present embodiment, the dispensing hose 113 is connected to the secondary chamber 102, in an alternative embodiment, it is contemplated that the dispensing hose 113 may be directly connected to the passage 103, thereby omitting the secondary chamber 102 from the device.
[0055] The present invention also relates to a method 300 of manufacturing a cement slurry containing foam, such as Figure 2 The method includes a providing device step 301, wherein a device as described above is provided. This is followed by an introducing slurry additive step 302, wherein cementitious material and water are introduced into the slurry chamber via their respective inlets. Next, in an introducing foam step 303, foam may be introduced into the cement slurry in the channel via the foam inlet.
[0056] Computer modeling was performed to demonstrate the advantages of the apparatus and methods described above.
[0057] Shear rate
[0058] Foam stability was evaluated by the foam efficiency factor (FEF), where FEF was calculated using the following equation:
[0059]
[0060] An FEF of 100 is preferred because it indicates that all of the foam was retained during manufacture of the cement product.
[0061] Foam stability and bubble collapse within the foam can also be indicated by the ratio between shear force and surface tension. Shear force acts to break the bubbles within the foam, and surface tension provides resistance to the shear force. The stability of each bubble depends on the shear rate and bubble size, and can be defined by the capillary number (Ca):
[0062]
[0063] where μ eff is the effective viscosity of cement paste, is the local shear rate, R b is the bubble radius and σ is the surface tension of the bubble. Each bubble remains stable below a critical value Ca. It has been found that a 100 μm bubble in an aqueous foam is stable below 3700 s. -1 It is stable at a shear rate of 3700s -1 is often considered the critical shear rate in such systems.
[0064] The theoretical FEF can be calculated by assuming that foam will be lost if it is exposed to shear rates above a critical shear rate during its introduction into the cement slurry.
[0065] Considering a device comprising a channel and a single foam inlet, computer simulations were performed to evaluate how the distance of the foam inlet from the mixing chamber affects the shear forces experienced by the foam and the foam stability. Figure 3 The estimated theoretical FEF (%) at the entry point of the foam into the channel is depicted for various locations of the foam inlet.
[0066] For a tangential mixer, a portion of the channel extends beyond the first end of the channel and is located in the mixing chamber. It should be understood that the first end of the channel is the point where the entire channel cross section exits the mixing chamber. Therefore, a negative distance value indicates that the foam inlet is located in the portion of the channel that is located in the mixing chamber. Figure 3 Based on the data, the channel was modeled as having a square cross-section with dimensions of 39 mm × 39 mm.
[0067] Numerical modeling of the slurry-foam blend was performed using a continuous single-phase model using the ANSYS Fluent computational dynamics package. In the framework of the model, the foamed cement slurry was modeled as an effective incompressible fluid with a non-Newtonian rheology that depends on the local air fraction. The cement slurry was modeled as an effective fluid with a 0% air fraction, while the foam was modeled as an effective fluid with a 100% air fraction. Herschel-Bulkley rheology was used in the model to describe the foam, slurry, and foamed slurry, and the coefficients used in the model were based on measurements performed with a laboratory rheometer.
[0068] from Figure 3 It can be seen that the foam entering from the inlet located within the channel experiences greater foam stability compared to the foam introduced into the mixing chamber. This increase in FEF is preferred because a reduced amount of foam is destroyed during the manufacture of the cementitious product. A higher FEF improves the overall efficiency of the manufacturing process.
[0069] Density deviation
[0070] In order to evaluate the uniformity of the slurry-foam mixture, and therefore the quality of the mix of cement slurry and foam, the calculated variation in the density of the slurry-foam mixture at various portions within the channel may be considered. In these calculations, a higher degree of density variation measured at a given point indicates a reduced uniformity of the slurry-foam mixture. Therefore, a low degree of density variation is desirable as it indicates that the device will provide a more consistent product.
[0071] To calculate the uniformity of the slurry-foam mixture, the flow of cement slurry, foam, and slurry-foam mixture is modeled. Cross sections are taken through the channel and the average density and density standard deviation are calculated within each cross section. The average density is taken over the volume or cross-sectional area and is not an average density over time. The density deviation is then calculated and is defined as:
[0072]
[0073] Perfect homogeneity within the slurry-foam mixture results in zero density deviation.
[0074] Foam inlet diameter
[0075] Computer modeling of foam inlet diameter was performed to evaluate the effect of inlet diameter on density deviation.
[0076] When selecting the foam inlet diameter within the device, a trade-off is made between mixing efficiency (which requires high shear rates to mix the foam with the cement slurry) and the stability of the foam (which is negatively affected by high shear rates). The effect of the foam inlet diameter on the average shear rate experienced by the foam at the point of entry into the slurry stream and the density deviation at the second end (outlet) of the channel is 2.34°, 2.37°, and 2.39°, respectively. Figure 4 and Figure 5 In order to obtain Figure 4 and Figure 5 Based on the data, the channel was modeled as having a square cross-section with dimensions of 39 mm × 39 mm.
[0077] Here, numerical modeling of slurry-foam blends is performed using a continuous single-phase model using the ANSYS Fluent computational dynamics software package. In the framework of the model, the foamed cement slurry is modeled as an effective incompressible fluid with a non-Newtonian rheology that depends on the local air fraction. The cement slurry is modeled as an effective fluid with 0% air fraction, while the foam is modeled as an effective fluid with 100% air fraction. Herschel-Bulkley rheology is used in the model to describe the foam, slurry, and foamed slurry, and the coefficients used in the model are based on measurements performed with a laboratory rheometer.
[0078] In the model, the volume flow rate of the foam is kept constant at 0.004 m 3 s -1 The volume flow rate of cement paste after foam insertion was modeled as 0.10 m 3 s -1 , the slurry velocity is modeled as 6.6ms -1 In order to inject foam into the cement slurry flow at a constant flow rate, the change in the foam inlet diameter requires a change in the velocity of the foam as it enters the channel. Figure 4 and 5 As shown, there is a high mixing efficiency region A and a high foam stability region B.
[0079] From the Figure 4 A review of the results shows that the theoretical FEF experienced by the foam increases as the foam inlet diameter increases from 5 mm to 31 mm, reaching an acceptable level for gypsum board production when the foam inlet diameter is equal to 15 mm. When the foam inlet diameter increases above 17.5 mm, a decrease in the average shear rate experienced by the foam is no longer observed, and the theoretical FEF remains high. Therefore, a high foam stability region B is found when the foam inlet diameter is 15 mm or greater.
[0080] from Figure 5As can be seen in FIG. 1 , it is found that the density deviation at the second end (outlet) of the channel gradually increases with the increase of the foam inlet diameter, wherein a small inlet diameter results in good penetration and mixing of the foam into the slurry flow. The high mixing efficiency region A appears at an inlet diameter of about 17.5 mm.
[0081] The intersection between the region of high mixing efficiency A and the region of high foam stability B exists at inlet diameters from about 15 mm to about 17.5 mm.
[0082] Speed Ratio
[0083] It has been found that the ratio between the velocity of the foam entering the cement slurry flow and the velocity of the cement slurry flow at the point where the foam enters the slurry flow affects the FEF of the final cement product.
[0084] Table 1
[0085]
[0086] From Table 1, it can be seen that a ratio of froth speed to slurry speed of 5.4 or less provides acceptable froth stability (sufficiently high FEF). It can also be seen that as the ratio of froth speed to slurry speed decreases, the FEF increases further, indicating an increase in froth stability.
[0087] Foam inlet configuration
[0088] Further modeling was performed to evaluate density deviations within the slurry-foam mixture for devices including channels with one, two, and four foam inlets arranged in various configurations.
[0089] Three configurations were modeled; an aligned configuration where all foam inlets were collinear along the length of the channel, a crossed configuration where the foam inlets were directly opposite each other, and an alternating configuration where the foam inlets were on alternating sides along the length of the channel.
[0090] In the aligned configuration, the foam inlets were positioned 35 mm apart from each other (between adjacent centers of each inlet), with the first foam inlet positioned adjacent to and 136 mm from the first end of the channel.Aligned configurations with two and four foam inlets were modeled.
[0091] In the cross configuration, each foam inlet is located 136 mm from the first end of the channel. In the two inlet cross configuration, a pair of opposing inlets is provided, the inlets being located on either side of the channel. In the four inlet cross configuration, each inlet is positioned equidistantly around the circumference of the channel so that two pairs of opposing inlets are provided.
[0092] In the alternating configuration, the foam inlets were spaced apart along the length of the channel.In the two inlet alternating configuration, a pair of opposing inlets were provided with the first foam inlet located 136 mm from the first end of the channel and the second foam inlet spaced 35 mm from the first inlet in a direction away from the mixing chamber.
[0093] In the four inlet alternating configuration, each inlet is positioned equidistantly around the circumference of the channel. The first foam inlet is located 136 mm from the mixing chamber. The second foam inlet, the third foam inlet, and the fourth foam inlet are positioned along the channel in a direction away from the first end of the channel. The first to fourth foam inlets are positioned along the channel with a distance of 35 mm between each adjacent inlet.
[0094] During modeling, the foam was first injected at 22 ms in a configuration with a constant total inlet area. -1 During the second round of modeling, the foam was introduced into the channel at different speeds through a foam inlet diameter of 15 mm. A consistent total volume flow rate was used for all models.
[0095] Foam inlet configuration Figure 6 The results are shown in Figure 2 and detailed in Table 2.
[0096]
[0097]
[0098] Table 2
[0099] Figure 7 The modeled density deviation in the slurry-foam mixture at the second end (outlet) of the channel is shown. Figure 7 Modeling data presented in , in all models the channel was considered to have a square cross section with sides of 39 mm. The velocity of the cement paste after the foam was inserted was modeled to be 6.6 ms -1 .
[0100] Here, numerical modeling of slurry-foam blends is performed using a continuous single-phase model using the ANSYS Fluent computational dynamics software package. In the framework of the model, the foamed cement slurry is modeled as an effective incompressible fluid with a non-Newtonian rheology that depends on the local air fraction. The cement slurry is modeled as an effective fluid with 0% air fraction, while the foam is modeled as an effective fluid with 100% air fraction. Herschel-Bulkley rheology is used in the model to describe the foam, slurry, and foamed slurry, and the coefficients used in the model are based on measurements performed with a laboratory rheometer.
[0101] exist Figure 7The calculated percentage density deviation is plotted for each scenario in FIG. 1 . The calculated density deviation for the control scenario is plotted as a dashed line on the graph.
[0102] From Table 2 and Figure 7 As can be seen in Figure 2, the crossed and alternating inlet configurations generally demonstrate improved homogeneity of the slurry-foam mixture compared to the aligned configuration. In other words, the modeled density deviations are lower for the crossed and alternating configurations when compared to the equivalent aligned configuration.
[0103] From Table 2 and Figure 7 It can also be seen that the alternating inlet configurations generally exhibit improved uniformity of the slurry-foam mixture compared to the crossed configuration. In other words, the modeled density deviations for the alternating configurations are lower when compared to the equivalent crossed configurations. Notably, all alternating configurations demonstrate reduced density deviations in the slurry-foam mixture compared to the control.
[0104] From Table 2 and Figure 7 It can also be inferred that increasing the number of foam inlets while maintaining the same total inlet area and foam injection rate increases the modeled density bias. This observation is consistent across all three configurations, as can be seen from comparing Scenarios 1 and 2, Scenarios 5 and 6, and Scenarios 9 and 10.
[0105] Locate the second entrance
[0106] Considering configurations with multiple inlets, for a fixed foam inlet diameter, the presence of two or more inlets allows for reducing the velocity of the foam entering the cement slurry while maintaining a constant volumetric flow rate of the foam entering the slurry flow. It was further investigated how the distance between the first end of the channel and the second foam inlet (i.e., the foam inlet away from the mixing chamber) affects the uniformity and stability of the foam. By positioning the second foam inlet away from the mixing chamber, the velocity of the slurry flow is reduced due to the rotation of the mixing member of the mixing chamber, so that the shear rate to which the foam is subjected when entering the slurry flow is reduced. Therefore, the foam efficiency factor can be increased, although the density deviation in the slurry-foam mixture increases with the reduction of the shear rate.
[0107] Figure 8 The average shear rate experienced by the foam at the point of entry into the slurry stream and the density deviation at the second end (outlet) of the channel relative to the location of the second foam inlet from the mixing chamber are shown for the configuration of Scenario 4. The velocity ratio is modeled as 1.7:1. It should be understood that the second foam inlet is the foam inlet that is distal to the mixing chamber. Again, there is a tradeoff between mixing efficiency (which requires high shear rates to mix the foam with the cement slurry) and the stability of the foam (which is negatively affected by high shear rates).
[0108] It was found that when the second foam inlet was more than 200 mm from the first end of the channel, the shear rate experienced by the foam was less than 3700 s -1 Therefore, positioning the second foam inlet at 250 mm or more from the first end of the channel helps improve the foam efficiency factor. However, as the shear rate experienced by the foam decreases as the position of the second inlet becomes farther away from the first end of the channel, the modeled density deviation becomes unacceptable when the second foam inlet is positioned greater than 250 mm from the first end of the channel. Therefore, positioning the second foam inlet in this area of the channel can provide a good balance between density deviation and foam efficiency.
[0109] The objects, aspects, features and / or embodiments of the present invention may be further understood by the following clauses:
[0110] Clause 1: An apparatus for making a cementitious slurry containing foam, the apparatus comprising: a mixing chamber for mixing a cementitious material and water to form a cementitious slurry, a passage fluidly connected to the mixing chamber at a first end, the passage for receiving the cementitious slurry from the mixing chamber,
[0111] The channel extends from the first end and terminates at at least one second end; the channel includes a first foam inlet for introducing foam into the channel; and the channel also includes a second foam inlet for introducing foam into the channel.
[0112] Clause 2: The device of clause 1, wherein the mixing chamber is a tangential mixer.
[0113] Clause 3: The device of clause 1 or clause 2, wherein the first foam inlet is positioned on an outer wall of the passage, wherein the outer wall extends tangentially from the mixing chamber.
[0114] Clause 4: The device of any preceding clause, wherein the second foam inlet is positioned on a side of the passageway substantially opposite the first foam inlet.
[0115] Clause 5: The device of any preceding clause, wherein the first foam inlet and the second foam inlet are located at the same vertical position within the channel.
[0116] Clause 6: Apparatus according to any preceding clause, wherein the first foam inlet and the second foam inlet are offset along the length of the channel.
[0117] Clause 7: The device of clause 6, wherein the offset is at least 50 mm, more preferably at least 100 mm, most preferably at least 150 mm.
[0118] Clause 8: The device of clause 6 or clause 7, wherein the first foam inlet is closer to the first end of the channel than the second foam inlet.
[0119] Clause 9: The device of any preceding clause, wherein the maximum opening dimension of the second foam inlet is greater than or equal to 15 mm.
[0120] Clause 10: The device of any of the preceding clauses, wherein the at least one second end of the channel is connected to a dispensing hose.
[0121] Clause 11: The device of any preceding clause, wherein the at least one second end of the channel is connected to a secondary chamber.
[0122] Clause 12: An apparatus according to any of the preceding clauses, wherein the apparatus is configured to introduce foam through the first foam inlet and the second foam inlet during use at a speed of 5.4 times or less of the speed of the cement slurry in the channel, more preferably at a speed of 3.4 times or less of the speed of the cement slurry in the channel, still more preferably at a speed of 2.4 times or less of the speed of the cement slurry in the channel, and most preferably at a speed of 1.8 times or less of the speed of the cement slurry in the channel.
[0123] Clause 13: A method of manufacturing a cement slurry containing foam, the method comprising: providing an apparatus according to any of the preceding clauses; introducing cement material and water into the mixing chamber to form a cement slurry; and introducing foam into the cement slurry through the first foam inlet and the second foam inlet.
[0124] Item 14: A method according to item 13, wherein the foam is introduced into the cement slurry at a speed of 5.4 times or less of the cement slurry speed in the channel, more preferably at a speed of 3.4 times or less of the cement slurry speed in the channel, still more preferably at a speed of 2.4 times or less of the cement slurry speed in the channel, and most preferably at a speed of 1.8 times or less of the cement slurry speed in the channel.
[0125] Clause 15: A method according to clause 13 or clause 14, wherein the foam is introduced into the cement slurry at a speed twice or more of the speed of the cement slurry in the channel, more preferably three times or more of the speed of the cement slurry in the channel, and even more preferably four times or more of the speed of the cement slurry in the channel.
Claims
1. A device for producing a cement slurry containing foam, the device comprising: A mixing chamber for mixing cementitious materials and water to form cement slurry, a passage fluidly connected to the mixing chamber at a first end, the passage being adapted to receive cement slurry from the mixing chamber, The channel extends from the first end and terminates at at least one second end; The passage includes a first foam inlet for introducing foam into the passage; and the passage further comprising a second foam inlet for introducing foam into the passage; It is characterized in that The first foam inlet and the second foam inlet are offset along the length of the channel.
2. The device according to claim 1, wherein: The mixing chamber is a tangential mixer.
3. An apparatus according to claim 1 or claim 2, wherein the first foam inlet is located on an outer wall of the passage, wherein the outer wall extends tangentially from the mixing chamber.
4. An apparatus according to any preceding claim, wherein the second froth inlet is positioned on a side of the passageway substantially opposite to the first froth inlet.
5. An apparatus according to any one of the preceding claims, wherein the first froth inlet and the second froth inlet are located at the same vertical position within the channel.
6. A device according to any one of the preceding claims, wherein: The offset is at least 50 mm, more preferably at least 100 mm, most preferably at least 150 mm.
7. An apparatus according to any preceding claim, wherein the first foam inlet is closer to the first end of the passage than the second foam inlet.
8. The device according to any one of the preceding claims, wherein the maximum opening dimension of the second foam inlet is greater than or equal to 15 mm.
9. The device according to any one of the preceding claims, wherein: The at least one second end of the passage is connected to a dispensing hose.
10. The device according to any one of the preceding claims, wherein: The at least one second end of the channel is connected to the secondary chamber.
11. An apparatus according to any one of the preceding claims, wherein the apparatus is configured to introduce foam through the first foam inlet and the second foam inlet during use at a speed of 5.4 times or less of the speed of the cement slurry in the channel, more preferably at a speed of 3.4 times or less of the speed of the cement slurry in the channel, still more preferably at a speed of 2.4 times or less of the speed of the cement slurry in the channel, and most preferably at a speed of 1.8 times or less of the speed of the cement slurry in the channel.
12. A method for producing a cement slurry containing foam, the method comprising: Providing a device as claimed in any one of the preceding claims; introducing cementitious material and water into the mixing chamber to form a cement slurry; and Foam is introduced into the cement slurry through the first foam inlet and the second foam inlet.
13. The method according to claim 12, wherein the foam is introduced into the cement slurry at a speed of 5.4 times or less of the cement slurry speed in the channel, more preferably at a speed of 3.4 times or less of the cement slurry speed in the channel, still more preferably at a speed of 2.4 times or less of the cement slurry speed in the channel, and most preferably at a speed of 1.8 times or less of the cement slurry speed in the channel.
14. The method according to claim 12 or 13, wherein the foam is introduced into the cement slurry at a speed twice or more of the cement slurry speed in the channel, more preferably three times or more of the cement slurry speed in the channel, and even more preferably four times or more of the cement slurry speed in the channel.