High-temperature sintering furnace and preparation method and application thereof

Abstract

The application discloses a high-temperature sintering furnace and a preparation method and application thereof, and uses a stainless steel to weld a furnace body inner container, carbon fibers are wound outside the inner container, PAN and siloxane are brushed on surfaces of the carbon fibers, electromagnetic induction copper coils are sleeved outside the carbon fibers as heating sources, liquid nitrogen is passed through the inside of the copper coils, the liquid nitrogen is changed into nitrogen gas while cooling the copper pipes, and the nitrogen gas is passed into the furnace body to serve as a protective gas for material sintering. Compared with a traditional resistance wire heating furnace, the sintering furnace can reduce the weight of the furnace steel material, improve sintering efficiency and reduce energy consumption.

Description

Technical Field

[0001] This invention relates to the field of sintering furnace technology, specifically to a high-temperature sintering furnace that improves sintering efficiency, reduces material usage, and lowers sintering energy consumption, as well as its preparation method and application. Background Technology

[0002] Currently, lithium iron phosphate and lithium manganese iron phosphate cathode materials have become the most promising new generation of safe and environmentally friendly lithium-ion power battery cathode materials due to their advantages such as high specific capacity, low price, no environmental pollution, good safety and thermal stability. They can be widely used in new energy vehicles, energy storage equipment, uninterruptible power supplies, power tools and other fields, and have a very broad market prospect.

[0003] Lithium iron phosphate (LFP) and potassium manganese iron phosphate (MgFePO4) cathode materials are typically produced using resistance furnace synthesis equipment. With the continuous expansion of the market, the existing resistance furnace synthesis equipment has become the most significant obstacle to the rapid production of LFP and MgFePO4. To improve production efficiency, the current common practice is to lengthen and thicken the furnace chamber, but this increases weight and cost, increases heat capacity, increases energy consumption, and reduces heating efficiency. Furthermore, existing resistance furnace synthesis equipment uses only stainless steel as the furnace chamber, making electromagnetic induction heating impossible; it mostly relies on resistance wire heating, primarily transferring heat to the furnace chamber through thermal radiation, which is not conducive to rapid heating and results in low efficiency. Therefore, improvements are necessary. Thus, this invention addresses the aforementioned problems of the existing technology. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, this invention provides a high-temperature sintering furnace, its preparation method, and its application.

[0005] To achieve the above objectives, one objective of this invention is to provide a method for preparing a high-temperature sintering furnace, comprising the following steps:

[0006] Step 1: Weld stainless steel into the inner liner of the furnace.

[0007] Step 2: Wrap carbon fiber around the outside of the furnace inner liner, and brush the surface of the carbon fiber with polyacrylonitrile and siloxane.

[0008] Step 3: An electromagnetic induction copper coil is wrapped around the outside of the carbon fiber. Liquid nitrogen is passed through the inside of the copper coil. The liquid nitrogen turns into nitrogen gas while cooling the copper tube and is then passed into the furnace as a protective gas for the sintering of the material.

[0009] Step 4: When using it for the first time, heat the furnace body to 800℃ and keep it at that temperature to obtain the high-temperature sintering furnace. During heating, polyacrylonitrile carbonizes and solidifies the carbon fiber, and siloxane decomposes into a silicon dioxide oxygen barrier layer to protect the carbon fiber and prevent it from oxidizing at high temperature.

[0010] Another object of the present application provides a high-temperature sintering furnace, comprising a furnace body, further comprising an electromagnetic induction heating element and a cooling medium.

[0011] The furnace body comprises an inner furnace body on the inner side and carbon fibers on the outer side, the inner furnace body is welded by stainless steel, and the carbon fibers are wound on the outer side of the inner furnace body and are coated with a solidification layer and an oxygen barrier layer on the surface.

[0012] The electromagnetic induction heating element is hollow to form a medium channel and is sleeved on the outer side of the carbon fibers, one end of the medium channel is connected with a medium supply device, and the other end is communicated with the inner furnace body.

[0013] The cooling medium is filled in the medium channel, the cooling medium is used for cooling the electromagnetic induction heating element during heating and is gasified into the inner furnace body as a protective gas for material sintering during heating.

[0014] Preferably, the high-temperature sintering furnace is prepared by the preparation method.

[0015] Another object of the present application is to provide the use of the high-temperature sintering furnace or the high-temperature sintering furnace prepared by the preparation method in the synthesis of battery positive electrode materials and ceramic materials.

[0016] Compared with the prior art, the present application has the following advantages:

[0017] 1) The present application uses carbon fiber reinforced stainless steel furnace body, the use amount of stainless steel is saved by more than 30%, the thickness and weight of stainless steel are reduced, the material is saved, the overall inertia of the furnace body is greatly reduced, the energy consumed by the rotation of the furnace body is reduced, and the energy consumption is reduced.

[0018] 2) The carbon fibers on the outer side of the furnace body are directly heated by electromagnetic induction, the furnace body itself is heated at a high speed, the power saving is more than 10%, and the energy consumption is reduced.

[0019] 3) Liquid nitrogen is used through a copper coil, the temperature of the coil is reduced, and the liquid nitrogen is gasified itself, as a protective gas for material synthesis, and the energy use efficiency is further improved. BRIEF DESCRIPTION OF DRAWINGS

[0020] The present application will be further described below in combination with the drawings and examples:

[0021] Figure 1 The structure of the high-temperature sintering furnace of the present application is shown in the figure. DETAILED DESCRIPTION

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0023] Example

[0024] This invention provides an electromagnetic induction sintering furnace that improves sintering efficiency, reduces material usage, and lowers sintering energy consumption. Figure 1 As shown, the furnace includes a furnace chamber 1, an electromagnetic induction heating element 2, and a cooling medium. The furnace chamber 1 comprises an inner liner 11 and an outer carbon fiber 12. The inner liner 11 is welded from stainless steel. The surface of the carbon fiber 12 is coated with a polyacrylonitrile cured layer (not shown) and a silica oxygen barrier layer (not shown) and is wound around the outside of the inner liner 11. The electromagnetic induction heating element 2 is spirally sleeved on the outside of the carbon fiber 12, and the interior of the electromagnetic induction heating element 2 is hollow to form a medium channel (not shown). One end of the medium channel is connected to a medium feeding device (not shown), and the other end is connected to the inner liner 11. The cooling medium fills the medium channel and is used to cool the electromagnetic induction heating element 2 during the heating process. The cooling medium also vaporizes during heating and is introduced into the inner liner as a protective gas for the synthesis of the positive electrode material. By using carbon fiber to replace part of the stainless steel in the furnace chamber, the amount of stainless steel used is reduced, the furnace chamber is strengthened, and the weight and thickness of the furnace chamber 1 are reduced, thus reducing the overall rotational inertia of the furnace chamber 1. An electromagnetic induction heating element 2 is installed on the outside of the furnace chamber 1, enabling the furnace chamber 1 to generate its own heat through electromagnetic induction, reducing energy consumption and saving more than 10% of electricity. Preferably, the electromagnetic induction heating element 2 is a hollow copper coil. The cooling medium is liquid nitrogen, which not only cools the copper coil but also vaporizes upon heating to produce nitrogen gas. Nitrogen gas is a stable inert gas and can be used as a protective gas during the material synthesis process.

[0025] Additionally, preferably, such as Figure 1 As shown, multiple radially outwardly protruding protrusions 3 are provided on the outer wall of the furnace body, with these protrusions 3 spaced apart. The protrusions 3 are located between adjacent coils. The protrusions 3 serve two purposes: firstly, to strengthen the furnace structure, and secondly, to act as a limiting element, preventing the copper coils from directly contacting each other. Furthermore, there is a gap between the inner wall of the copper coils and the outer wall of the furnace body, i.e., between the outer side of the carbon fiber.

[0026] The high-temperature sintering furnace described in the above embodiment is prepared by the following method, specifically including the following steps:

[0027] Step 1: Weld a furnace inner liner 11 with a diameter of 3 meters and a length of 40 meters using 316 stainless steel.

[0028] Step 2, using as Figure 1 The carbon fiber cloth is wound outside the furnace barrel 1, and the surface of the carbon fiber cloth is brushed with polyacrylonitrile (PAN) and silicone (not limited, any silicone known to those skilled in the art and existing in the market can be used). Specifically, the PAN in the embodiment of the present application is dissolved using a 50% sodium thiocyanate aqueous solution until the concentration of the PAN is 10%-13%. The silicone is directly brushed, and the specific concentration is not limited.

[0029] Step 3, an electromagnetic induction copper coil is sleeved outside the carbon fiber cloth, liquid nitrogen is passed through the inside of the copper coil, and the liquid nitrogen is passed into the inner barrel 11 of the furnace body after being cooled into nitrogen gas and serving as a protective gas for the synthesis of the positive electrode material.

[0030] Step 4, the temperature of the furnace body is heated to 800℃ and kept for 24 hours, the PAN is carbonized and solidified carbon fiber, the silicone is decomposed into a silicon dioxide oxygen barrier layer to protect the carbon fiber. The required high-temperature sintering furnace is prepared.

[0031] The high-temperature sintering furnace prepared in the above embodiment has a unit energy consumption reduction of 10.3%. Specifically, compared with the traditional resistance furnace, the use amount of stainless steel of the furnace barrel is saved by more than 30%, and the power saving is more than 10%. The high-temperature sintering furnace prepared by the preparation method in the above embodiment is applied to the synthesis of the positive electrode material. In the following examples, only the lithium manganese iron phosphate positive electrode material is taken as an example for illustration. The specific steps are as follows:

[0032] Step 5, lithium dihydrogen phosphate (13 kg), manganese carbonate (167 kg), lithium carbonate (45 kg), magnesium hydroxide (1.6 kg), iron phosphate (180 kg), and starch (3.6 kg) are dissolved in water and uniformly dispersed.

[0033] Step 6, the dispersion liquid in step 5 is subjected to spray drying, the inlet air temperature is 240℃, and the outlet air temperature is 130℃, and the precursor is dried.

[0034] Step 7, the precursor enters the furnace barrel from the furnace head of the sintering furnace, is sintered at 800℃ under the protection of nitrogen for 4 hours, and the positive electrode material, lithium manganese iron phosphate, is synthesized.

[0035] The embodiment of the present application also provides the application of the high-temperature sintering furnace in the above embodiment or the high-temperature sintering furnace prepared by the preparation method in the above embodiment in the synthesis of the battery positive electrode material. When the battery positive electrode material is synthesized by using the high-temperature sintering furnace in the above embodiment, the unit energy consumption is reduced by 10.3% compared with the traditional resistance wire heating synthesis device, thereby verifying that the heating efficiency of the high-temperature sintering furnace in the embodiment of the present application is greatly improved in the synthesis of the battery positive electrode material. The high-temperature sintering furnace in the embodiment of the present application can be applied not only to the synthesis of the battery positive electrode material as described above, but also to the synthesis of ceramic materials.

[0036] It should be pointed out that the above are only the preferred embodiments of the present application, and do not limit the present application in any form. Any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application still falls within the scope of the technical solutions of the present application.

[0037] It should be understood that the above detailed description of the present application is only used for illustrative explanation or principle of the present application, and does not constitute a limitation of the present application. Therefore, any modification, equivalent replacement, improvement, etc. made without departing from the spirit and scope of the present application shall be included in the protection scope of the present application. In addition, the appended claims of the present application are intended to cover all changes and modifications falling within the scope and boundary of the appended claims, or the equivalent forms of such scope and boundary.

Claims

1. A method for preparing a high-temperature sintering furnace, characterized in that, Includes the following steps: Step 1: Weld stainless steel into the inner liner of the furnace. Step 2: Wrap carbon fiber around the outside of the furnace inner liner, and brush the surface of the carbon fiber with polyacrylonitrile and siloxane. Step 3: An electromagnetic induction copper coil is wrapped around the outside of the carbon fiber. Liquid nitrogen is passed through the inside of the copper coil. The liquid nitrogen turns into nitrogen gas while cooling the copper tube and is then passed into the furnace as a protective gas for the sintering of the material. Step 4: When using it for the first time, heat the furnace body to 800℃ and keep it at that temperature to obtain the high-temperature sintering furnace. During heating, polyacrylonitrile carbonizes and solidifies the carbon fiber, and siloxane decomposes into a silicon dioxide oxygen barrier layer to protect the carbon fiber and prevent the carbon fiber layer from oxidizing at high temperature.

2. The method for preparing a high-temperature sintering furnace according to claim 1, characterized in that, The carbon fiber is carbon fiber filament or carbon fiber cloth woven from carbon fiber twill.

3. The method for preparing a high-temperature sintering furnace according to claim 2, characterized in that, The axial thermal conductivity of the carbon fiber is greater than 30 W / m•K, and the elastic modulus is greater than 310 GPa; and / or The thickness of the carbon fiber is 0.05-0.5 mm.

4. The method for preparing a high-temperature sintering furnace according to any one of claims 1-3, characterized in that, The inner liner of the furnace is made of 309, 310, 314, 316 or 330 stainless steel.

5. A high-temperature sintering furnace prepared by the method according to any one of claims 1-4, comprising a furnace liner, characterized in that, It also includes electromagnetic induction heating elements and cooling media; The furnace liner includes an inner liner and an outer carbon fiber. The inner liner is welded from stainless steel. The carbon fiber is wrapped around the outer side of the inner liner and its surface is covered with a curing layer and an oxygen barrier layer. The electromagnetic induction heating element is hollow to form a medium channel and is sleeved on the outside of the carbon fiber. One end of the medium channel is connected to the medium feeding device and the other end is connected to the inner liner. The cooling medium is filled in the medium channel. The cooling medium is used to cool the electromagnetic induction heating element during the heating process and is vaporized during heating and introduced into the inner liner as a protective gas for material sintering.

6. The high-temperature sintering furnace according to claim 5, characterized in that, The cured layer is a polyacrylonitrile cured layer formed by curing polyacrylonitrile coated on the carbon fiber after heating at 800°C. The oxygen barrier layer is a silica oxygen barrier layer formed by heating siloxane coated on the carbon fiber at 800°C.

7. A high-temperature sintering furnace according to claim 5, characterized in that, The electromagnetic induction heating element is a copper coil.

8. A high-temperature sintering furnace according to claim 5, characterized in that, The cooling medium is liquid nitrogen, and the protective gas is nitrogen.

9. The application of the high-temperature sintering furnace according to any one of claims 5-8 or the high-temperature sintering furnace prepared by the preparation method according to any one of claims 1-4 in the synthesis of battery cathode materials and ceramic materials.

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