Apparatus and method for manufacturing cement slurry comprising foam and channel for apparatus

Abstract

There is provided an apparatus (100) for manufacturing a cement slurry comprising foam, the apparatus (100) comprising: a mixing chamber (101) for mixing a cement material and water to form a cement slurry, a channel (103) fluidly connected to the mixing chamber (101) at a first end, the channel (103) for receiving the cement slurry from the mixing chamber (101), the channel (103) extending from the first end and terminating at a second end; a portion of the channel (103) between the foam inlet (106) and the second end has a length of 400 mm to 1200 mm (inclusive), wherein the foam inlet (106) is positioned such that a distance between the first end of the channel (103) and the foam inlet (106) is less than 25% of a distance between the first end of the channel (103) and the second end of the channel (103). A cement slurry channel (103) and a method of manufacturing a cement slurry are also provided.

Description

Technical Field

[0001] The present invention relates to an apparatus for producing cement slurry containing foam. The present invention also relates to a method for producing cement slurry containing foam using the apparatus. Background Art

[0002] Gypsum is a raw material composed of calcium sulfate dihydrate (CaSO 4 2(H 2 O)) occurs naturally. It is formed by calcining or dehydrated gypsum, i.e. calcium sulfate hemihydrate (CaSO 4 0.5(H 2 O)) is mixed with water to form a settable slurry which is then cast into a desired shape to prepare gypsum-containing products, such as gypsum board. Calcium sulfate hemihydrate reacts with water to rehydrate into dihydrate crystals which then cure or dry into 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. One method of combining the foam with the slurry is to mix the foam and slurry in a mixing chamber. However, the mixing process can result in shearing and breaking of the bubbles, causing the foam to be unstable as the bubbles disperse. This dispersion results in high foam losses, resulting in an inefficient process that can limit the extent of density reduction achieved using the process. 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 fluidly connected to the mixing chamber at a first end, the channel for receiving the cement slurry from the mixing chamber, the channel extending from the first end and terminating at a second end; the channel comprising a foam inlet for introducing foam into the channel; wherein the portion of the channel between the foam inlet and the second end has a length of 400 mm to 1200 mm, inclusive.

[0006] The present invention provides an apparatus and method for efficiently and consistently combining foam with a cement slurry, such as a plaster or gypsum slurry. 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 the bubbles and destabilize any foam in the mixing chamber. Therefore, the introduction of 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 length of the passage between the foam inlet and the second end ensures that the foam is evenly mixed throughout the cement slurry with low levels of foam loss.

[0007] Additionally, the length of the channel prevents an unnecessary increase in the back pressure experienced by the fluid in the device that occurs when the length of the channel is longer than described herein. Furthermore, the reduction in channel length allows for easier installation of the device, providing a more compact solution.

[0008] Preferably, the portion of the channel between the foam inlet and the second end has a length of 400 mm to 600 mm, inclusive.

[0009] Preferably, the channel comprises a mixing section comprising a first dimension and a second dimension, the first dimension being perpendicular to the second dimension and the first dimension being longer than the second dimension, wherein the foam inlet is configured to introduce foam into the channel in a direction substantially parallel to the second dimension.

[0010] This feature may be preferred because the relative sizes of the channels and the location of the foam input ensure that the foam is evenly mixed throughout the cement slurry with low levels of foam losses.

[0011] More preferably, the first dimension of the mixing cross-section is more than 1.1 times the second dimension of the mixing cross-section. Still more preferably, the first dimension of the mixing cross-section is more than 1.2 times the second dimension of the mixing cross-section. Still more preferably, the first dimension of the mixing cross-section is more than 1.4 times the second dimension of the mixing cross-section. Most preferably, the first dimension of the mixing cross-section is more than 1.5 times the second dimension of the mixing cross-section.

[0012] Preferably, the first dimension of the mixing cross-section is at most equal to 12 times the second dimension of the mixing cross-section. More preferably, the first dimension of the mixing cross-section is at most equal to 10 times the second dimension of the mixing cross-section. Still more preferably, the first dimension of the mixing cross-section is at most equal to 8 times the second dimension of the mixing cross-section. Most preferably, the first dimension of the mixing cross-section is at most equal to 6 times the second dimension of the mixing cross-section.

[0013] Preferably, the foam inlet is configured to introduce foam into the mixing section. Alternatively, the foam inlet is configured to introduce foam into the passage upstream of the mixing section.

[0014] Preferably, the mixing cross section extends at least 50% of the distance between the foam inlet and the second end. More preferably, the mixing cross section extends at least 75% of the distance between the foam inlet and the second end. Still more preferably, the mixing cross section extends at least 90% of the distance between the foam inlet and the second end. Most preferably, the mixing cross section extends between the foam inlet and the second end.

[0015] Preferably, the mixing cross section extends at least 50% of the distance between the first end and the second end. More preferably, the mixing cross section extends at least 75% of the distance between the first end and the second end. Still more preferably, the mixing cross section extends at least 90% of the distance between the first end and the second end. Most preferably, the mixing cross section extends between the first end and the second end.

[0016] Preferably, the foam inlet is located closer to the first end of the channel than the second end of the channel. More preferably, the foam inlet is located such that the distance between the first end of the channel and the foam inlet is less than 25% of the distance between the first end of the channel and the second end of the channel.

[0017] Preferably, the mixing chamber comprises a mixing member, wherein the mixing member is configured to rotate.Preferably, the first end of the passage is positioned such that, in use, cement slurry exits the mixing chamber in a direction tangential to the mixing member.

[0018] Preferably, the second end of the channel is connected to the dispensing hose. Preferably, the second end of the channel is connected to the secondary chamber. Preferably, the foam inlet is positioned so that the foam is injected transversely into the slurry flow in the channel. Preferably, the channel is substantially straight. Alternatively, the channel includes a curve, kink or bend.

[0019] 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.

[0020] Preferably, the foam inlet has a substantially circular cross-section.Alternatively, the foam inlet has a substantially square cross-section.

[0021] According to a second aspect of the present invention, a cement slurry channel is provided, which is configured to form a fluid connection with a cement slurry mixer, the cement slurry channel comprising a foam inlet, a first end and a second end, wherein the length of the channel portion between the foam inlet and the second end is 400 mm to 1200 mm, inclusive.

[0022] In this way, a cement slurry channel having the advantages described above is provided.

[0023] Preferably, the portion of the channel between the foam inlet and the second end has a length of 400 mm to 600 mm, inclusive.

[0024] According to a third aspect of the present invention, there is provided a method for manufacturing a cement slurry containing foam, 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 foam inlet.

[0025] Preferably, the foam is introduced into the cement slurry at a speed between three and five times the cement slurry speed, including three and five times. More preferably, the foam is introduced into the cement slurry at a speed between 3.5 and 4 times the cement slurry speed, including 3.5 and 4 times. Here, the speed considered is the average flow rate of the foam and cement slurry through the equipment, rather than the local speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0027] Figure 1 depicts a device according to a first embodiment of the invention;

[0028] Figure 2 depicts a schematic diagram of a method according to a third aspect of the invention;

[0029] Figure 3 and Figure 4 Density deviation-length graphs were plotted to indicate the mixing uniformity of the foam and cement slurry mixtures for various channel lengths;

[0030] Figure 5 A pressure-length graph is depicted to indicate back pressure in the channel; and

[0031] Figure 6 The outlet density deviation versus foam inlet position graph for a channel length of 519 mm is plotted to indicate the mixing uniformity of the foam and cement slurry mixture at various foam inlet positions. DETAILED DESCRIPTION

[0032] 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 for mixing the cement slurry from the mixing chamber 101 with the foam. The mixing chamber 101 is connected to the secondary chamber 102 by a channel 103. The secondary chamber 102 comprises a tank.

[0033] The mixing chamber 101 includes 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 includes a mixing member, which includes 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.

[0034] 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.

[0035] 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.

[0036] 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. In this way, 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 forces 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.

[0037] The foam inlet 106 is positioned so that the distance between the first end of the channel 103 (i.e., the end positioned adjacent the mixing chamber outlet 111) and the foam inlet 106 is less than 25% of the distance between the first end of the channel 103 and the second end of the channel 103 (i.e., the channel end adjacent the secondary chamber inlet 112).

[0038] 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 so that the secondary chamber 102 is omitted from the apparatus.

[0039] 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 apparatus step 301, wherein an apparatus 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.

[0040] Computer modeling was performed to demonstrate the advantages of the apparatus and methods described above.

[0041] Density deviation

[0042] 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 locations within the channel may be considered. In these calculations, a higher degree of density variation measured at a given point indicates a lack of uniformity in the slurry-foam mixture. Therefore, a low degree of density variation is desirable.

[0043] The flow of cement slurry, foam, and slurry-foam mixtures is modeled in order to calculate the uniformity of cement slurry and slurry-foam mixtures. Cross sections are taken through the channel and the average density and standard deviation of the density 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:

[0044]

[0045] Perfect homogeneity of the foam within the slurry flow with zero density deviation.

[0046] Figure 3 The density deviation calculated at the outlet of the distribution hose is shown. The distribution hose length is modeled as 900 mm. In order to obtain Figure 3 Based on the data from the experiment, the foam inlet was modeled in the channel at a fixed distance of 136 mm from the mixing chamber. In addition, the channel was modeled as a square cross section with dimensions of 39 mm and 39 mm.

[0047] Here, numerical modeling of slurry-foam hybrids 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.

[0048] from Figure 3 As can be seen in the graph, the distance between the foam inlet and the second end of the channel is short, below 400 mm, and then the density deviation measured at the outlet is high. Therefore, in the case where this distance is below 400 mm, the slurry-foam mixture leaving the equipment will be highly variable, resulting in inconsistent properties of any subsequently manufactured product.

[0049] Figure 3 It is also shown that the longer the distance between the foam inlet and the second end of the channel, the smaller the density variation seen at the outlet. Therefore, the longer distance between the foam inlet and the second end of the channel reduces the variability of the density of the slurry-foam mixture, while reducing the variation of any final product produced from the slurry-foam mixture.

[0050] Figure 4A channel with a total length of 2000 mm, a square cross-section and dimensions of 39 mm and 39 mm was modeled. Here, the foam inlet was modeled as introducing the foam into the cement slurry 136 mm from the first end of the channel. Numerical modeling of the slurry-foam mixing was 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 was modeled as an effective incompressible fluid with non-Newtonian rheology that depends on the local air fraction. The cement slurry was modeled as an effective fluid with 0% air fraction, while the foam was modeled as an effective fluid with 100% air fraction. Herschel-Bulkley rheology was used in the model to describe the foam, slurry and foam slurry, and the coefficients used in the model were based on measurements performed with a laboratory rheometer.

[0051] from Figure 4 It can be seen that with the introduction of foam, the calculated density deviation increases significantly before exhibiting an exponential decay along the length of the channel. Figure 4 It was demonstrated that a longer length between the foam inlet and the second end of the channel reduced any observed density variations within the slurry-foam mixture.

[0052] Back pressure in the channel

[0053] Backpressure is the force or resistance opposing the flow through the system. In the present invention, both the cement slurry and the foam experience backpressure opposing their flow through the channel to its second end.

[0054] Therefore, the length between the foam inlet and the second end of the channel cannot be optimized by considering the density deviation of the slurry-foam mixture alone. In any such optimization, the back pressure on both the foam and cement slurry needs to be considered as the distance between the foam inlet and the second end of the channel increases.

[0055] Figure 5 The change in back pressure as the length between the foam inlet and the second end of the channel increases is shown. It can be seen that as the distance between the foam inlet and the second end of the channel increases, the back pressure within the channel increases. The back pressure exerted by the flow of the slurry stream increases linearly with the channel length, which can be determined mathematically using an equation known in the literature as the Hagen-Poiseuille equation:

[0056]

[0057] Where ΔP is the back pressure, μ is the effective viscosity of the shear gypsum slurry (measured rheologically and equal to 1 Pa.s under these conditions), L is the length of the pipe, Q is the throughput and A is the cross-sectional area of ​​the pipe. In these experiments, the throughput used was 10 Ls -1This calculated back pressure is added to the back pressure already generated by the dispensing hose and the tank, which equals 0.8 bar. In addition, the back pressure is generated by the presence of the foam generator, which is in the range of 1 to 2 kPa. In order to ensure the stability of the industrial process, it is generally understood that this back pressure should not exceed 2 kPa.

[0058] Cross-sectional profile

[0059] The cross-sectional profile of the channel also affects the mixing characteristics of the slurry. To evaluate this, the density deviation of multiple cross-sectional profiles, each with the same channel length, has been numerically studied. The cross-sectional profile variations are shown in Examples 1 to 4. Examples 1 and 4 are rectangular cross-sections, Example 2 is a square cross-section, and Example 3 is a circular cross-section. Numerical modeling of slurry-foam mixing was 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 non-Newtonian rheology that depends on the local air fraction. The cement slurry is modeled as an effective fluid with a 0% air fraction, while the foam is modeled as an effective fluid with a 100% air fraction. Herschel-Bulkley rheology is used in the model to describe the foam, slurry, and foam slurry, and the coefficients used in the model are based on measurements made with a laboratory rheometer.

[0060] Each of Examples 1 to 4 has a similar cross-sectional area, such that the only substantial variation in each channel is the shape of the channel cross section. The dimensions of each of Examples 1 to 4 and their cross-sectional areas are detailed in Table 1.

[0061] Table 1

[0062] example Height(mm) Width(mm) Diameter(mm) <![CDATA[Area (mm 2 )]]> Example 1 30 50 - 1500 Example 2 39 39 - 1521 Example 3 - - 44 1521 Example 4 50 30 - 1500

[0063] Table 2 details the height-to-width ratio for each example and the density deviation at the dispense hose outlet of the dispense hose. The dispense hose length was 900 mm. The channel length was 360 mm, and the foam was modeled to be injected in a direction substantially parallel to the channel width and substantially perpendicular to the channel height.

[0064] Table 2

[0065] example Height:Aspect Ratio Density deviation (%) Example 1 1:1.7 2.59 Example 2 1:1 1.95 Example 3 1:1 1.11 Example 4 1.7:1 0.85

[0066] In each of Examples 1 to 4, the model predicts a similar degree of foam penetration. Therefore, in each case, the ratio between the velocity of the foam and the velocity of the cement paste is calculated to be similar. However, the differences in cross-sectional shape between Examples 1 to 4 do produce differences in density deviations, as shown in Table 2.

[0067] Table 2 shows that the foam is better dispersed in the slurry flow when the height of the channel between the foam inlet and the second end is greater than the width of the channel between the foam inlet and the second end, as seen in Example 4. In Example 4, the density deviation is lowest, indicating that the uniformity in the slurry-foam mixture is the best. Therefore, the modeling shows improved properties in the slurry-foam mixture when the first dimension of the mixing cross section is greater than the second dimension of the mixing cross section.

[0068] While the examples show that increasing the height of the channel relative to its width will result in a reduction in density bias, increasing the height of the channel beyond certain limits may make it more challenging to actually include in a device as the channel dimensions become incompatible with other aspects of the device.

[0069] That is, the height of the mixing chamber imposes a maximum functional height on the mixing chamber outlet, and in turn imposes a maximum height on the channel. In addition, the diameter of the foam inlet imposes a minimum width on the channel. In turn, a minimum channel height is imposed to maintain the desired aspect ratio of the channel.

[0070] For the simulations described herein, the foam inlet diameter was 15 mm. Therefore, taking into account the maximum height of the mixing chamber, the maximum channel height was 100 mm, maintaining a height:width ratio of 6.7:1.

[0071] The advantage of the minimum channel width limitation imposed by the foam inlet diameter is that the maximum channel height to width ratio can be calculated independently of the line speed or the size of the equipment. The ratio of the velocity of the foam introduced into the slurry to the velocity of the cement slurry is preferably 3 to 5. The maximum channel height to width ratio can be determined using the following calculation.

[0072] First, the velocity ratio of foam to cement slurry is Here, α is preferably between 3 and 5.

[0073] The velocity ratio can be calculated by considering the volume flow rates of cement slurry and foam (Q) and the cross-sectional area of ​​the foam inlet (A) and the cross-sectional area of ​​the channel (the foam cross-sectional area (A) and 泡沫 ) and the cross-sectional area of ​​cement paste (A 浆料 )) to determine.

[0074]

[0075] After calculation, Typically between 1 / 3 and 1 / 2. Therefore, the following calculation can be used to calculate the maximum channel aspect ratio for the foam inlet:

[0076]

[0077] The maximum channel aspect ratio imposed on the equipment is 12:1 with a foam to cement slurry velocity ratio of 5. That is, a small amount of foam with a high inlet foam velocity is introduced into the cement slurry. Further calculations must be performed to confirm that the maximum channel aspect ratio does not exceed the channel height limitation imposed by the maximum height of the mixing chamber.

[0078] Foam inlet position

[0079] The density deviation of the slurry is affected by the location of the foam inlet relative to the first end of the channel, wherein the density deviation indicates the mixing uniformity of the foam and cement slurry mixture. Therefore, a low density deviation at the first end of the channel is desirable.

[0080] Table 3 and Figure 6 The effect of the foam inlet position relative to the density deviation at the outlet of the dispensing hose as the channel length increases is shown. The dispensing hose length was modeled as 900 mm. To obtain the data in Table 3, the density deviation was calculated using the same Figure 3 In a similar manner to the data for , the channel was modeled as a square cross-section with dimensions of 39 mm and 39 mm.

[0081] The foam inlet position is the distance of the foam inlet from the first end of the channel as a percentage of the total channel length. For example, a 15% foam inlet position is the position of the foam inlet when the distance between the first end of the channel and the foam inlet is 15% of the distance between the first end of the channel and the second end of the channel. A 0% foam inlet position is when the foam inlet is directly at the first end of the channel.

[0082] At a given channel length, there is an associated back pressure opposing the flow of the slurry stream through the channel. Using the Hagen-Poiseuille equation outlined above, it is assumed that the back pressure exerted by the flow of the slurry stream increases linearly with the channel length. For example, Figure 6 A graph of the outlet density deviation relative to the foam inlet position is shown for a channel length of 519, where a back pressure of 1.14 bar is present.

[0083] It is desirable to minimize the outlet density deviation while also maintaining an acceptable back pressure in the channel. Although increasing the channel length can improve the mixing uniformity of the foam and cement slurry, the increase in channel length also increases the back pressure within the channel.

[0084] It will be appreciated that an outlet density deviation of less than 2.5% provides acceptable uniformity of the foam and cement slurry mixture.

[0085] Table 3

[0086]

[0087]

[0088] From Table 3 and Figure 6 It can be seen that it is advantageous for the foam inlet to be positioned such that the distance between the first end of the channel and the foam inlet is less than 25% of the distance between the first end of the channel and the second end of the channel.

[0089] At a given channel length, the density deviation is higher when the distance between the first end of the channel and the foam inlet is 35% of the distance between the first end of the channel and the second end of the channel, and the density deviation is even higher when the distance is 45% of the distance between the first end of the channel and the second end of the channel.

[0090] As described above, the percentage of the channel length between the foam inlet and the second end of the channel cannot be optimized by considering the density deviation of the slurry-foam mixture alone. In any such optimization, the back pressure on both the foam and the cement slurry needs to be considered as the distance between the foam inlet and the second end of the channel increases.

[0091] Table 3 shows that for any given foam inlet location, as the length of the channel increases, higher back pressures are experienced. For a given foam inlet location, the lowest and therefore most acceptable back pressure is when the channel length is 322 mm.

[0092] However, as shown in Table 3, when the total channel length is 322 mm, there is an unacceptably high density deviation at the outlet of the dispensing hose. A high degree of density variation measured at a given point indicates a lack of uniformity in the slurry-foam mixture. Therefore, a low degree of density variation is desirable. The table shows that channel lengths of 519 mm or greater exhibit a desirable level of density deviation.

[0093] When the total channel length becomes too high, unacceptable back pressure exists. It should be understood that back pressures less than 1.75 bar are generally acceptable, although back pressures closer to 1 bar are desirable. Table 3 shows that while scenarios 26 to 34 exhibit good density deviation characteristics, back pressures exceeding acceptable limits are experienced. In addition, scenarios 21 to 25 exhibit back pressures greater than desired.

[0094] Therefore, when the length of the channel is considered, there is a gain between improved outlet density deviation and improved back pressure.

[0095] The present invention will now be described in the following terms:

[0096] Item 1: 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 fluidly connected to the mixing chamber at a first end, the channel for receiving the cement slurry from the mixing chamber, the channel extending from the first end and terminating at a second end; the channel comprising a foam inlet for introducing foam into the channel; wherein the portion of the channel between the foam inlet and the second end has a length of 400 mm to 1200 mm, inclusive.

[0097] Item 2: An apparatus according to item 1, wherein the channel includes a mixing section, which includes a first dimension and a second dimension; the first dimension is perpendicular to the second dimension; the first dimension is longer than the second dimension; and wherein the foam inlet is configured to introduce foam into the channel in a direction substantially parallel to the second dimension.

[0098] Clause 3: The apparatus of clause 2, wherein the foam inlet is configured to introduce foam into the mixing section.

[0099] Clause 4: Apparatus according to clause 2 or clause 3, wherein the mixing section extends between the froth inlet and the second end.

[0100] Clause 5: The apparatus of any one of clauses 2 to 4, wherein the mixing cross section extends from the first end to the second end.

[0101] Clause 6: The device of any preceding clause, wherein the foam inlet is located closer to the first end of the channel than the second end of the channel.

[0102] Clause 7: The device of Clause 6, wherein the foam inlet is positioned such that a distance between the first end of the channel and the foam inlet is less than 25% of a distance between the first end of the channel and the second end of the channel.

[0103] Clause 8: Apparatus according to any preceding clause, wherein the mixing chamber comprises a mixing member, wherein the mixing member is configured to rotate.

[0104] Clause 9: Apparatus according to clause 8, wherein the first end of the passage is positioned such that, in use, the cement slurry exits the mixing chamber in a direction tangential to the mixing element.

[0105] Clause 10: The apparatus of any preceding clause, wherein the second end of the passage is connected to a dispensing hose.

[0106] Clause 11: The device of any preceding clause, wherein the second end of the channel is connected to a secondary chamber.

[0107] Clause 12: The device of any preceding clause, wherein the channel comprises a curve, kink or bend.

[0108] Item 13: A cement slurry channel configured to form a fluid connection with a cement slurry mixer, the cement slurry channel comprising a foam inlet, a first end and a second end, wherein the length of the portion of the channel between the foam inlet and the second end is 400 mm to 1200 mm, inclusive.

[0109] Clause 14: A method of making a cement slurry containing foam, the method comprising: providing an apparatus as claimed in any one of the preceding claims; introducing cementitious material and water into the mixing chamber to form a cement slurry; and introducing foam into the cement slurry through the foam inlet.

[0110] Clause 15: The method of Clause 14, wherein the foam is introduced into the cement slurry at a rate between three and five times the rate of the cement slurry, inclusive.

Claims

1. An apparatus for producing a cement slurry containing foam, the apparatus 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 the cement slurry from the mixing chamber, The passage extends from the first end and terminates at a second end; The passage includes a foam inlet for introducing foam into the passage; wherein the portion of the passage between the foam inlet and the second end has a length of 400 mm to 1200 mm, inclusive; Wherein the foam inlet is positioned such that a distance between the first end of the channel and the foam inlet is less than 25% of a distance between the first end of the channel and the second end of the channel.

2. The device according to claim 1, wherein: The passage includes a mixing cross-section, the mixing cross-section including a first dimension and a second dimension; The first dimension is perpendicular to the second dimension; the first dimension is longer than the second dimension; Wherein the foam inlet is configured to introduce foam into the channel in a direction generally parallel to the second dimension.

3. The device according to claim 2, wherein: The foam inlet is configured to introduce foam into the mixing section.

4. Apparatus according to claim 2 or claim 3, wherein the mixing section extends between the froth inlet and the second end.

5. The device according to any one of claims 2 to 4, wherein: The mixing section extends from the first end to the second end.

6. Apparatus according to any one of the preceding claims, wherein: The mixing chamber includes a mixing member, wherein the mixing member is configured to rotate.

7. Apparatus according to claim 6, wherein the first end of the passage is positioned such that, in use, the cement slurry exits the mixing chamber in a direction tangential to the mixing member.

8. Apparatus according to any one of the preceding claims, wherein: The second end of the passage is connected to a dispensing hose.

9. Apparatus according to any one of the preceding claims, wherein: The second end of the channel is connected to a secondary chamber.

10. Apparatus according to any one of the preceding claims, wherein: The passageway may include curves, kinks or bends.

11. A cement slurry channel configured to be fluidly connected to a cement slurry mixer, The cement slurry channel includes a foam inlet, a first end, and a second end. The cement slurry passage has a length of 400 mm to 1200 mm, inclusive, at a portion between the foam inlet and the second end.

12. A method for producing a cement slurry containing foam, the method comprising: Providing an apparatus as claimed in any one of the preceding claims; introducing cementitious material and water into a mixing chamber to form a cement slurry; and Foam is introduced into the cement slurry through the foam inlet.

13. The method of claim 12, wherein the foam is introduced into the cement slurry at a rate between three and five times the cement slurry rate, inclusive.

Images