Gypsum heating apparatus
The gypsum heating apparatus addresses heat control and environmental issues in existing systems by using induction heating with insulating materials, resulting in efficient and emission-reduced gypsum heating.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SAINT GOBAIN PLACO SAS
- Filing Date
- 2025-12-16
- Publication Date
- 2026-07-23
AI Technical Summary
Existing gypsum heating systems face challenges in controlling heat application, suffer from heat loss, and have significant environmental impacts due to combustion-based heating methods.
A gypsum heating apparatus utilizing an induction heater surrounded by a conductive channel and insulating materials, which employs induction heating to efficiently and reliably heat gypsum with minimal heat loss and reduced emissions.
The apparatus provides consistent heat control, reduces heat loss, and lowers emissions, achieving faster heating times and energy savings in the gypsum manufacturing process.
Smart Images
Figure EP2025087299_23072026_PF_FP_ABST
Abstract
Description
[0001] GYPSUM HEATING APPARATUS
[0002] Field of the Disclosure
[0003] The present invention relates to a gypsum heating apparatus, more specifically to a gypsum heating apparatus comprising an induction heater. A method of heating gypsum using the apparatus is also described.
[0004] Background
[0005] Gypsum occurs naturally as a raw material in the form of calcium sulphate dihydrate (CaSC>42(H2O)). Gypsum containing products are prepared by forming a mixture of calcined or dehydrated gypsum, namely calcium sulphate hemihydrate (CaSO40.5(H2O)), with water, to form a settable slurry that is then applied on to, or used to make, different substrates, such as clay bricks, plasterboard or cast concrete. In the case of forming plasterboards, the slurry is then cast into a pre-determined shape. The calcium sulphate hemihydrate reacts with the water and becomes re-hydrated to the dihydrate crystal, which is then cured or dried to the solid state.
[0006] In the calcination process, the gypsum is dehydrated to form the calcium sulphate hemihydrate. This dehydration can occur in several stages. In some instances, the gypsum is preheated before calcination. In other systems, the preheating stage is omitted. The calcium sulphate hemihydrate produced in the calcination process can be categorised into two basic forms, alpha-calcium sulphate hemihydrate and beta-calcium sulphate hemihydrate. Beta-calcium sulphate hemihydrate is typically formed by calcining gypsum in air at ambient humidity or raised humidity and at ambient (i.e. atmospheric) pressure. On the other hand, alpha-calcium sulphate hemihydrate is produced from gypsum in steam or water under conditions of elevated temperature and pressure.
[0007] In present systems, both any preheating of gypsum and the calcination process itself use heat generated via combustion. Using the combustion of material as the heat source is undesirable, as the heating of the gypsum can be difficult to control. Additionally, the use of combustion poses significant environmental impacts that are desirably avoided.
[0008] Objects and aspects of the present disclosure seek to address at least the above issues associated with the currently available technology.Summary
[0009] According to a first aspect of the present invention, there is provided a gypsum heating apparatus, the gypsum heating apparatus comprising a channel fortransporting gypsum; the channel comprising a conductive material; and an induction heater, wherein the induction heater surrounds at least a portion of the channel.
[0010] In this way, there is provided an apparatus that uses induction heating to more efficiently and reliably heat gypsum during the manufacture of gypsum and / or plaster products.
[0011] Preferably, the conductive material is an electrically conductive material. Alternatively, the conductive material is a semiconductor.
[0012] Induction heating is a process in which a conductive material is heated when placed within a dynamic magnetic field to provide a simplified and cost-effective heating process. The use of induction heating is especially preferred as it provides heat rapidly after the start up of the apparatus. Additionally, induction heating provides a consistent heat to the contents of the channel with minimal heat loss due to the focused application of heat.
[0013] As such, in use, the described apparatus allows the effective heating of gypsum within the conductive channel with increased control, reduced heat loss and lower emissions.
[0014] Preferably, the gypsum heating apparatus further comprises a layer of insulating material positioned between the induction heater and the channel. Such a feature may be preferable as it may reduce heat loss from the channel increasing the efficiency of the apparatus. Preferably, the insulating layer comprises stone wool. Preferably, the insulating layer comprises glass wool. Preferably, the insulating layer comprises a mixture of stone and glass wool.
[0015] Preferably, the insulating layer has a thickness of less than or equal to 50 mm. More preferably, the insulating layer has a thickness less than or equal to 40 mm. Still more preferably, the insulating layer has a thickness less than or equal to 30 mm. Yet more preferably, the insulating layer has a thickness less than or equal to 20 mm. Most preferably, the insulating layer has a thickness less than or equal to 10 mm. Preferably, the insulating layer has a thickness greater than or equal to 5 mm. As such, the thickness of the insulating layer may be between 50 mm and 5 mm.
[0016] Preferably, the layer of insulating material surrounds at least a portion of the channel. More preferably, the layer of insulating material surrounds the channel along substantially its entire length.Preferably, the channel comprises a central channel axis and the induction heater comprises a central induction heater axis, wherein the central channel axis and the central induction heater axis are offset from one another. In such embodiments, the channel and the induction heater have central axes that are parallel, but not coaxial.
[0017] Preferably, in use, the central channel axis is below the central induction heater axis. In this way, in use, the gypsum at the base of the channel is closer to the induction heater.
[0018] In use, the gypsum is located at the bottom of the channel due to the impact of gravity. As such, where there is no offset between the central channel axis of the channel and the central induction heater axis of the induction heater, the temperature increase at the top of the channel may be far greater than the temperature at the base of the channel. As the gypsum acts to moderate the temperature rise in the base of the channel, it may be advantageous for the central channel axis and the central induction heater axis to be offset to assist in the gypsum within the heater reaching the required temperature. Additionally, such an arrangement may assist in preventing any overheating of the material at the top of the channel. Additionally, this offset creates additional space for a second insulating material between the insulating layer and the induction heater.
[0019] Preferably, the layer of insulating material has a variable thickness. More preferably, the layer of insulating material has a greater thickness substantially above the central channel axis than substantially below the central channel axis. In this way, the layer of insulating material both increases the efficiency of the gypsum heating apparatus and ensures that the correct spacing between the channel and the induction heater is maintained. Still more preferably, the layer of insulating material has a thickness in the range of 40 to 70 mm above the central channel axis, and a thickness in the range of 10 to 40 mm below the central channel axis. Yet more preferably, the layer of insulating material has a thickness in the range of 50 to 60 mm above the central channel axis, and a thickness in the range of 20 to 30 mm below the central channel axis.
[0020] Preferably, the gypsum heating apparatus comprises a secondary insulating material. Again, the use of a secondary insulating material may be advantageous in reducing heat loss for the channel, increasing the efficiency of the apparatus.
[0021] Preferably, the secondary insulating material comprises non-metallic material. More preferably the secondary insulating material consists of non-metallic material. Preferably, the secondary insulating material comprises wood and / or plastic.Preferably, the secondary insulating material has a thickness of less than or equal to 50 mm. More preferably, the secondary insulating material has a thickness less than or equal to 40 mm. Still more preferably, the secondary insulating material has a thickness less than or equal to 30 mm. Yet more preferably, the secondary insulating material has a thickness less than or equal to 20 mm. Most preferably, the secondary insulating material has a thickness less than or equal to 10 mm. Preferably, the secondary insulating material has a thickness greater than or equal to 5 mm. As such, the thickness of the secondary insulating material may be between 50 mm and 5 mm.
[0022] Preferably the secondary insulating material is located substantially above the central channel axis. More preferably, the secondary insulating material is located between the insulating layer and the induction heater. Alternatively, the secondary insulating material is located between the insulating layer and the channel. Preferably, the secondary insulating material and the insulating material partially fill the space between the channel and the induction heater. More preferably, the secondary insulating material and the insulating material fill the space between the channel and the induction heater.
[0023] The second insulating material both increases the efficiency of the gypsum heating apparatus and ensures that the correct spacing between the channel and the induction heater is maintained.
[0024] Preferably, the channel comprises an endless screw conveyor. Preferably, the channel comprises a rotary cylinder. Where the apparatus comprises an endless screw conveyor or a rotary cylinder, this may be advantageous in providing an efficient apparatus for the continuous heating of gypsum in a manufacturing process.
[0025] Preferably, the gypsum heating apparatus is a preheater. Here, the gypsum heating apparatus may be used to preheat gypsum before calcination in a subsequent calciner. In such embodiments, the channel may be connected to a calciner such that gypsum may pass from the channel directly or indirectly into a downstream calciner.
[0026] Preferably, the gypsum heating apparatus is a calciner. In such embodiments, the gypsum is calcined into calcium sulphate hemihydrate within the channel.
[0027] Preferably, the induction heater has a power of at least 15kW.
[0028] Preferably, the induction heater surrounds substantially the entire length of the channel. In such embodiments, the gypsum may be heated more efficiently as the entire length of the channel is used in the heating process.Preferably, the channel has a length of at least 2000 mm. Such a channel length may be preferable as it allows for sufficient time for the gypsum to be pre-heated or calcined.
[0029] According to a second aspect of the present invention, there is provided a method of heating gypsum, the method comprising, providing the gypsum heating apparatus as hereinbefore described, providing gypsum, inserting the gypsum into the channel and heating the gypsum with the induction heater.
[0030] In this way, there is provided a method with all the advantages previously described.
[0031] According to a third aspect of the present invention, there is provided a gypsum processing apparatus comprising at least one gypsum heating apparatus as previously described.
[0032] In this way, there is provided a gypsum processing apparatus with all the advantages previously described.
[0033] According to a fourth aspect of the present invention, there is provided a plasterboard manufacturing apparatus comprising the gypsum processing apparatus as previously described. In this way, there is provided a plasterboard manufacturing apparatus with all the advantages previously described.
[0034] According to a fifth aspect of the present invention, there is provided a plaster manufacturing apparatus comprising the gypsum processing apparatus as previously described. In this way, there is provided a plaster manufacturing apparatus with all the advantages previously described.
[0035] According to a sixth aspect of the present invention, there is provided the use of the gypsum heating apparatus as previously described in the heating of gypsum.
[0036] In this way, gypsum may be heated with the advantages already described.
[0037] Brief Description of the Drawings
[0038] The disclosure will be further described with reference to examples depicted in the accompanying figures in which:
[0039] Figure 1 is a schematic illustration of a gypsum heating apparatus according to the present invention;
[0040] Figure 2 is a cross section of a gypsum heating apparatus according to the present invention;Figure 3 is a graph illustrating the reduction in calculation time observed in a trail plant where an apparatus according to the present invention was used to pre-heat gypsum before calcination; and
[0041] Figure 4 is a cross section of a gypsum heating apparatus according to the present invention.
[0042] Detailed Description
[0043] The following description presents particular examples and serves to explain principles of the disclosure. However, the scope of the invention is not intended to be limited to the precise details of the examples, since variations will be apparent to a skilled person and are deemed to be covered by the description. Terms for components used herein should be given a broad interpretation that also encompasses equivalent functions and features.
[0044] Turning to Figure 1, there is depicted a gypsum heating apparatus 100 according to the present invention. Here, the gypsum heating apparatus comprises a channel (not shown) surrounded by an induction heater 120. Between the induction heater 120 and the channel is a layer of insulation 130. The layer of insulation 130 surrounds the channel and forms a barrier between the channel and the induction heater 120. As such, the layer of insulation 130 helps retain heat within the channel, such that the efficiency of the gypsum heater 100 is increased.
[0045] As can be seen in Figure 1 , the induction heater 120 comprises coils of wire that extend around the insulating layer 130 and the channel. In use, an electric current is passed through the coils of wire from a control unit 140. The passage of electric current through the coils of wire generates a magnetic field that heats the channel, as the channel includes a conductive material. As such, gypsum within the channel is heated.
[0046] Turning to Figure 2, there is again depicted a gypsum heating apparatus 100 comprising an induction heater 120 and an insulating layer 130. As in Figure 1, the insulating layer 130 surrounds the channel 110, forming a barrier between the channel 110 and the induction heater 120. As depicted in Figure 2, the channel 110 is an endless screw conveyor, with a central channel axis 115.
[0047] From this cross-sectional view, it can be seen that the central channel axis 115 of the channel 110 is offset from the centre of the induction heater 120. The central channel axis 115 of the channel 110 lies directly below the central induction heater axis of the induction heater 120,such that the central channel axis 115 of the conveyor 110 is offset from, but parallel with, the central induction heater axis of the induction heater 120.
[0048] Additionally, gypsum 1000 can be seen within the channel 110. As would be expected due to gravity, this gypsum 1000 lies predominantly in the bottom half of the channel 110. Additionally, a second insulating material 150 is located above the central channel axis 115 of the channel 110. Here, the second insulating material 150 is located between the insulating layer 130 and the induction heater 120. In the depicted embodiment, the second insulating material 150 is wood. Additionally, the second insulating material 150 only partially fills the space between the insulating layer 130 and the induction heater 120, though in other embodiments it is envisaged that this space may be filled in its entirety.
[0049] In the embodiment of the invention depicted in Figure 2, the channel 110 is not coaxial with the induction heater 120 to allow for improved heat management. As the gypsum 1000 is located at the bottom of the channel 110, without the offset between the central channel axis 115 of the channel 110 and the central induction heater axis of the induction heater 120 the temperature increase at the top of the channel would be far greater than the temperature at the base of the channel. As the gypsum 1000 acts to moderate the temperature rise in the base of the channel 110, the induction heater 120 and the channel 110 are offset to ensure the gypsum 1000 reaches the required temperature without overheating the material that forms the top of the channel. Additionally, this offset creates additional space for the second insulating material 150 between the insulating layer 130 and the induction heater 120. As can be seen in Figure 2, the second insulating material 150 is located above the central channel axis 115 of the channel 110. The second insulating material 150 both increases the efficiency of the gypsum heating apparatus 100 and ensure that the correct spacing between the channel 110 and the induction heater 120 is maintained.
[0050] Figure 3 is a graph showing the calcination time of a gypsum sample that was preheated using a gypsum heating apparatus according to the present invention. In Figure 3, the temperature of the kiln used for calcination is plotted on the Y axis, with the time since calcination process commenced plotted on the X axis. To produce this graph 7300 Kg of gypsum was preheated via induction power in a continuous process, with the gypsum moved through the induction heater via an endless screw conveyor.
[0051] In this graph, the dashed line represents the preheated sample, with the solid line representing gypsum that was at room temperature before the calcination process commenced. From a review of Figure 3, less energy input was required to complete the calcination process for thepreheated gypsum sample, with the preheated gypsum sample never falling to the same temperature low as the control sample. This difference is depicted in Figure 3 as (1). Additionally, for the preheated sample the calcination process completed more rapidly, with the preheated sample returning to 165 °C (taken as the termination of the calcination process) before the control sample. This difference is depicted in Figure 3 as (2). Extrapolating from these test values, it is estimated that the use of a gypsum heating apparatus according to the present invention in the preheating of gypsum before calcination may allow for:
[0052] • a reduction in overall energy usage during the calcination process of 15.6 kWh / tn (including the additional energy used in the preheating process) - a saving of 2.9%;
[0053] • a 3-minute reduction in the calcination batch time - an improvement of 5.8%; and • a 4.9% overall reduction in CO2 emissions.
[0054] Turning to Figure 4, there is a there is depicted a gypsum heating apparatus 400 comprising an induction heater 420 and an insulating layer 430. As in the apparatus of Figure 1, the insulating layer 430 surrounds the channel 410, forming a barrier between the channel 410 and the induction heater 420. The channel 410 is an endless screw conveyor, with a central channel axis 415.
[0055] From this cross-sectional view, it can be seen that the central channel axis 415 of the channel 410 is offset from the centre of the induction heater 420. The central channel axis 415 of the channel 410 lies directly below the central induction heater axis of the induction heater 420, such that the central channel axis 415 of the conveyor 410 is offset from, but parallel with, the central induction heater axis of the induction heater 420.
[0056] Additionally, gypsum 4000 can be seen within the channel 410. As would be expected due to gravity, this gypsum 4000 lies predominantly in the bottom half of the channel 410.
[0057] The insulating layer 430 has a greater thickness above the central channel axis 415 than below the central channel axis 415. In this way, the insulating layer offsets the central induction heater axis and the central channel axis 415, ensuring that the correct spacing between the channel 410 and the induction heater 420 is maintained. As described in relation to Figure 2, without the offset between the central channel axis 415 of the channel 410 and the central induction heater axis of the induction heater 420, the temperature at the top of the channel would be far greater than the temperature at the base of the channel due to the moderating effect of the gypsum 4000 on the temperature of the channel. The insulating layer430 both increases the efficiency of the gypsum heating apparatus 400 and ensures that the correct spacing between the channel 410 and the induction heater 420 is maintained.
Claims
Claims1. A gypsum heating apparatus, the gypsum heating apparatus comprising;a channel for transporting gypsum; the channel comprising a conductive material; and an induction heater;wherein the induction heater surrounds at least a portion of the channel, wherein, the channel comprises a central channel axis; andthe induction heater comprises a central induction heater axis;characterised in thatthe central channel axis and the central induction heater axis are offset from one another.
2. The gypsum heating apparatus of claim 1, wherein the gypsum heating apparatus further comprises a layer of insulating material positioned between the induction heater and the channel.
3. The gypsum heating apparatus of claim 2, wherein the layer of insulating material surrounds at least a portion of the channel.
4. The gypsum heating apparatus of any one preceding claim, wherein, in use, the central channel axis is below the central induction heater axis.
5. The gypsum heating apparatus of any one preceding claim, wherein the gypsum heating apparatus comprises a secondary insulating material.
6. The gypsum heating apparatus of claim 5, wherein the secondary insulating material is located substantially above the central channel axis.
7. The gypsum heating apparatus of claim 4, wherein the gypsum heating apparatus comprises a layer of insulating material positioned between the induction heater and the channel, the layer of insulating material surrounds at least a portion of the channel, andwherein the layer of insulating material has a variable thickness.
8. The gypsum heating apparatus of claim 7, wherein the layer of insulating material has a greater thickness substantially above the central channel axis than substantially below the central channel axis.
9. The gypsum heating apparatus of any one preceding claim, wherein the channel comprises an endless screw conveyor.
10. The gypsum heating apparatus of any one preceding claim, wherein the gypsum heating apparatus is a preheater.
11. The gypsum heating apparatus of any one preceding claim, wherein the gypsum heating apparatus is a calciner.
12. The gypsum heating apparatus of any one preceding claim, wherein the induction heater surrounds substantially the entire length of the channel.
13. The gypsum heating apparatus of any one preceding claim, wherein the channel has a length of at least 2000 mm.
14. A method of heating gypsum, the method comprising:providing the gypsum heating apparatus of any preceding claim;providing gypsum;inserting the gypsum into the channel; andheating the gypsum with the induction heater.