CN210480872U - High-temperature furnace for preparing hexagonal boron nitride - Google Patents

Abstract

The utility model relates to a high temperature furnace of preparation hexagonal boron nitride, specific saying so one kind is with the high temperature induction furnace of response mode preparation hexagonal boron nitride under high temperature. Including induction coil (5), anti-oxidant heat preservation (9), graphite crucible and flue component, the utility model discloses when satisfying the preparation that uses the induction furnace to carry out hexagonal boron nitride, can handle polluting gases such as ammonia, cyanamide that the side reaction produced at the normal position, also prevent polluting gases to corrode equipment simultaneously, increased the running life of equipment, used with the cooperation of cigarette storehouse, a small amount of polluting gases that do not handle have got into the scope that the cigarette storehouse can hold.

Description

High-temperature furnace for preparing hexagonal boron nitride

Technical Field

The utility model relates to a high temperature furnace for preparing hexagonal boron nitride, specific saying so one kind is with the high temperature induction furnace of response mode preparation hexagonal boron nitride under high temperature.

Background

At present, in the preparation of hexagonal boron nitride, melamine or urea is generally used as a nitrogen source and reacts with boron sources such as boric acid and borax in a heating state. In the heating process, the boron source and the nitrogen source have complex physical and chemical actions, amorphous boron nitride can be formed when the temperature reaches about 850 ℃, and the amorphous boron nitride is subjected to crystal form transformation to form hexagonal boron nitride at the temperature of over 1200 ℃. Because the reaction process is mainly solid-phase reaction and then gas-solid reaction, a molten pool cannot be formed in the system, and the common heating kilns are heating furnaces indirectly heated by alloy heating wires, silicon carbide and molybdenum silicide heating elements, such as resistance furnaces, tunnel kilns and the like.

With the development of science and technology, the requirement of the material industry on the crystallinity of boron nitride is increased, and the preparation temperature needs to be increased to over 1600 ℃ to prepare boron nitride with higher crystallinity. It is difficult to stably operate the heating furnace based on the above-described heating body at this temperature. In order to be able to reach higher temperatures, induction furnaces are used industrially which can operate stably at around 2000 ℃ on the principle of induction heating.

The induction furnace is generally applied to occasions requiring high-temperature heating of more than 1000 ℃ such as steel making, non-ferrous metal smelting and the like. The induction system uses a hollow copper pipe to make a coil pipe, the inside of the copper pipe is cooled by cooling water, after the copper pipe is electrified, eddy current is induced in nearby conductive materials and is finally converted into a large amount of heat, so that the conductive materials become a heating body to be heated. In the smelting industry, the material is conductive, so that an additional induction heating body is not needed, the crucible is made of a material which is resistant to high temperature and scouring of the molten liquid, and a heat insulation layer is arranged between the copper pipe and the crucible. The material usually generates smoke under high temperature heating at thousands of degrees, mainly solid particles of various metal oxides, silicon dioxide and the like, and a small amount of gases of carbon monoxide, sulfur dioxide and the like, so a smoke warehouse (dust collection hood) is used for collecting the smoke and purifying the smoke in the subsequent process.

In the field of boron nitride, graphite, which is resistant to high temperature and conductive, is used as a crucible and also as an induction heating element because a molten pool is not formed in the crucible. When the induction furnace works at normal temperature to 2000 ℃, a heat-insulating layer needs to be constructed, and the graphite crucible needs to be protected from being oxidized. And gas is continuously generated in the whole sintering process of the boron nitride, so a flue and a smoke warehouse are required to be configured.

According to the research of Carmen Hoffendahl and the like, various gas byproducts such as water vapor, nitrogen, ammonia gas, hydrogen cyanide, cyanamide and the like can be generated in the reaction stage of the boron source and the nitrogen source, which is not existed in the metal smelting industry. The gas production stage mainly occurs at about (650-. Meanwhile, the polluting gas reacts with moisture in the air, so that the copper coil of the induction furnace is corroded greatly and even corroded through the coil, and the shutdown is caused.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a high temperature furnace of preparation hexagonal boron nitride, because main polluting gas by-product is all combustible, consequently the utility model discloses set up the nozzle dish at the high temperature furnace gas outlet end, burnt polluting gas before the flue gas gets into dust pelletizing system. The pollution of ammonia gas and cyanide as byproducts is obviously reduced, and a small amount of incompletely combusted polluting gas enters the range which can be accommodated by the smoke warehouse.

Meanwhile, above 1000 ℃, partial byproducts volatilize and are condensed into liquid drops on the flue, and the liquid drops flow back to the graphite crucible along the wall of the flue to pollute the raw materials. Therefore, the utility model discloses increased a molten drop and accepted the dish on the material layer under the flue, prevented that the liquid drop from instiling into and forming the pollution in the material.

The purpose of the utility model can be realized by the following technical scheme: a high-temperature furnace for preparing hexagonal boron nitride comprises an induction coil 5, an anti-oxidation heat-preservation layer 9, a graphite crucible and a flue component, wherein the graphite crucible comprises a graphite crucible bottom 6, a graphite crucible wall 7 and a graphite crucible cover 11 and is embedded into the anti-oxidation heat-preservation layer 9; the graphite crucible cover 11 is provided with a flue gas outlet, a protective gas inlet and a temperature measuring hole which are symmetrical left and right;

the induction coil 5 is fixed by a furnace ring support 10 and is poured and protected by refractory cement 3, and an electrode 18 interface and circulating cooling water interfaces 4 and 12 are reserved on the refractory cement 3;

the flue component comprises a flue tube seat 15, a flue tube 16, a burner nozzle disc 19 and a molten drop receiving disc 14; wherein, the chimney seat 15 is annular, is positioned above the smoke outlet of the graphite crucible cover 11, and extends out of the anti-oxidation heat-preservation layer 9; the chimney 16 is arranged on the chimney seat 15, a groove is arranged above the chimney 16, the burner disk 19 is erected on the groove of the chimney 16 and can be conveniently moved, and the molten drop receiving disk 14 is placed on the material right below the chimney 16.

The anti-oxidation heat-insulation layer 9 is formed by compounding powdery high-temperature-resistant materials and reducing materials; the powdery high-temperature resistant material is thermal cracking carbon black, and the reducing material is alumina powder.

The burner disk 19 is provided with an igniter and is supplied with gas by the gas pipeline 4.

The utility model has the advantages that:

the utility model discloses when satisfying the preparation that uses the induction furnace to carry out hexagonal boron nitride, can handle polluting gases such as ammonia, cyanamide that the side reaction produced at the normal position, also prevent simultaneously that polluting gases from corroding equipment, increased the running life of equipment, used with the cooperation of cigarette storehouse, a small amount of polluting gases that do not handle have got into the scope that the cigarette storehouse can hold.

Meanwhile, the structure of the burner disk which is convenient to use and disassemble can be disassembled after pollutant gas is treated, so that the burner is prevented from being burnt out after the temperature of the furnace body is raised to over 1000 ℃. The utility model discloses the molten drop that sets up accepts the dish and can effectively prevent to fire when hexagonal boron nitride the molten drop of flue condensation drop into the material in and form the pollution.

Drawings

The present invention will be further described with reference to the accompanying drawings.

Fig. 1 is a schematic view of the overall structure of the present invention;

fig. 2 is a schematic structural view of the burner disk of the present invention.

1, refractory bricks; 2, a base; 3, refractory cement; 4, a cooling water inlet pipe; 5 an induction coil; 6 graphite crucible bottom; 7 graphite crucible wall; 8, raw materials; 9 an anti-oxidation heat-insulation layer; 10, supporting a furnace ring; 11 a graphite crucible cover; 12 cooling water outlet pipe; 13, a temperature measuring tube; 14 a droplet receiving pan; 15 a chimney seat; 16 chimney; 17 gas protection tube; 18 electrodes; 19 a burner disk; 20, supporting frames; 21 an igniter; 22 gas pipe.

Detailed Description

A high-temperature furnace for preparing hexagonal boron nitride comprises an induction coil 5, an anti-oxidation heat-preservation layer 9, a graphite crucible and a flue component, wherein the graphite crucible comprises a graphite crucible bottom 6, a graphite crucible wall 7 and a graphite crucible cover 11 and is embedded into the anti-oxidation heat-preservation layer 9; the graphite crucible cover 11 is provided with a flue gas outlet, a protective gas inlet and a temperature measuring hole which are symmetrical left and right;

the induction coil 5 is fixed by a furnace ring support 10 and is poured and protected by refractory cement 3, and an electrode 18 interface and circulating cooling water interfaces 4 and 12 are reserved on the refractory cement 3;

the flue component comprises a flue tube seat 15, a flue tube 16, a burner nozzle disc 19 and a molten drop receiving disc 14; wherein, the chimney seat 15 is annular, is positioned above the smoke outlet of the graphite crucible cover 11, extends out of the anti-oxidation heat-preservation layer 9, and prevents the powdery heat-preservation material from falling into the crucible from the flue; the chimney 16 is located on the chimney seat 15, a groove is formed in the upper portion of the chimney 16 and used for supporting a burner disk, the burner disk 19 is erected on the groove of the chimney 16 and can be conveniently moved, and a molten drop receiving disk 14 is placed on the material 8 under the chimney 16 to prevent smoke from condensing into molten drops on the chimney and dropping into the material to pollute the material.

The oxidation-resistant heat-insulating layer 9 is formed by compounding a powdery high-temperature-resistant material and a reducing material, the powdery high-temperature-resistant material is thermal cracking carbon black, and the reducing material is alumina powder, so that the heat-insulating structure cannot be damaged by the graphite crucible at high temperature, the oxidation speed of the graphite crucible can be slowed down by self-oxidation, and the service life of the graphite crucible is prolonged;

the burner disk 19 is provided with an igniter 21 and is supplied with gas by a gas pipeline 22.

When the high-temperature furnace works, a graphite crucible is filled with a material 8, a molten drop receiving disc 14 is placed in the center of the material, a crucible cover 11 is covered, a flue component is assembled, a temperature measuring instrument and a gas protection gas circuit are communicated, and an anti-oxidation heat-preservation layer 9 is covered on the crucible cover until only a pipeline of the temperature measuring instrument, a pipeline of the gas protection gas circuit and a chimney base 15 are exposed. Circulating water is introduced into the induction coil 5, and the temperature is raised after the circulation water is electrified. And (3) heating to about 300 ℃, then starting gas, starting an igniter to ignite the burner, and burning the ammonia gas, hydrogen cyanide, cyanamide and the like generated by the reaction into harmless nitrogen and carbon dioxide until the gas production process is finished at about 900 ℃.

And extinguishing the burner after the gas production process is finished, and removing the burner disc by using a tool to prevent the burner from being burnt out by further heating of the high-temperature furnace. And introducing protective gas, and controlling according to process parameters to finish high-temperature sintering.

And after sintering is completed, cutting off the power and cooling, removing the flue member and the antioxidant insulating layer 9 after cooling, opening the crucible cover 11, discharging, cleaning the molten drop receiving disc 14, and supplementing the burnt antioxidant powder material. Completing the implementation of one cycle.

The foregoing is merely exemplary and illustrative of the structure of the invention, and various modifications, additions and substitutions as described in the detailed description may be made by those skilled in the art without departing from the structure or exceeding the scope of the invention as defined in the claims.

Claims (2)

1. The high-temperature furnace for preparing the hexagonal boron nitride is characterized by comprising an induction coil (5), an anti-oxidation heat-insulation layer (9), a graphite crucible and a flue component, wherein the graphite crucible comprises a graphite crucible bottom (6), a graphite crucible wall (7) and a graphite crucible cover (11) which are embedded in the anti-oxidation heat-insulation layer (9); a flue gas outlet, a protective gas inlet and a temperature measuring hole which are symmetrical from side to side are arranged on the graphite crucible cover (11);

the induction coil (5) is fixed by a furnace ring support (10) and is poured and protected by refractory cement (3), and an electrode (18) interface and circulating cooling water interfaces (4, 12) are reserved on the refractory cement (3);

the flue component comprises a flue tube seat (15), a flue tube (16), a burner disk (19) and a molten drop receiving disk (14); wherein, the chimney seat (15) is annular and is positioned above the smoke outlet of the graphite crucible cover (11) and extends out of the anti-oxidation heat preservation layer (9); the chimney (16) is arranged on the chimney seat (15), a groove is arranged above the chimney (16), the burner disk (19) is erected on the groove of the chimney (16) and can be conveniently moved, and the molten drop receiving disk (14) is placed on the material right below the chimney (16).

2. A high temperature furnace for producing hexagonal boron nitride according to claim 1, characterized in that the burner plate (19) is provided with an igniter (21) supplied by a gas line (22).

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