RU2311393C2 - Installation for production of mullite - Google Patents

Abstract

FIELD: chemical industry; ceramic industry; construction materials industry; devices for production of mullite, ceramic material, refractory and construction materials.

SUBSTANCE: the invention is pertaining to the installations of the high-temperature treatment of the topaz concentrate for production of mullite and may be used in the industry at production of the ceramic material, the refractory and construction materials, and also in the chemical industry. The installation for production of mullite consists of the furnace including the exterior and interior stacks located coaxially with formation of the heating chamber and supplied with the plasma generators connected by their outlets with the heating chamber, and the gas circulation circuit, which using the gas counter flow to the granules movement is switching on the activator of consumption. The heating chamber is supplied with the sets of nozzles connected to the activator of consumption and located so, that to provide the horizontal and vertical circulation of the gas in the heating chamber and its feeding into the layer of the granules through the holes executed in the wall of the interior stack. The furnace inlet is connected with the inlet of the granules drying furnace, and the outlet - with the receiving hopper equipped with the circuit of circulation of the gas cooling the granules. The internal stack of the furnace is made with the alternating in pairs protrusions, under which there are the holes connecting the internal stack with the heating chamber. Each next pair of the protrusions is shifted with respect to the previous one by 90°. The installation allows to provide conditions for production of the qualitative fibrillar and (or) needle-shaped mullite crystals in the continuous mode.

EFFECT: the invention allows to provide conditions for production of the qualitative fibrillar and (or) needle-shaped mullite crystals in the continuous mode.

3 cl, 5 dwg

Description

The invention relates to plants for the high-temperature processing of topaz concentrate to obtain mullite and can be used in industry for the production of ceramic, refractory and building materials, as well as in the chemical industry.

Known industrial firing lump topaz ores in rotary kilns. The mullite content in the obtained materials was low, since a mixture of mullite with cristobalite was obtained (Pole G.J., J. Amer. Soc., 1944, v. 27 No. 6).

A known method of producing mullite from topaz concentrate by firing in a rotary drum furnace (RF Application No.2000103140, IPC V03B 7/00, publ. 10.01.2002).

The design of this method does not allow to provide optimal conditions for mass transfer and heat transfer between the gas phase and topaz ore, which negatively affects the quality of the obtained mullite.

A known method of producing mullite according to US patent No. 5340516, IPC B32B 3/12; СВВ 35/10, 1994, according to which a granulator is used to form granules of a given shape, a drying oven for drying granules and a furnace for burning granules to obtain the desired mullite-containing product.

However, the design of the process described in the description of the patent, does not provide a product on an industrial scale.

The objective of the invention is to develop an installation for producing mullite from topaz concentrate, which provides mullite in the form of the most valuable forms - fibrous and (or) needle crystals, with a high content of the target substance in the final product.

The problem is solved in that, in the installation, the mullite synthesis furnace is made of external and internal shafts arranged coaxially with the formation of a heating chamber, and is equipped with plasma generators communicated with the exits of the heating chamber and a gas circulation circuit in countercurrent to the movement of the granules, including a flow inducer, while the heating chamber is equipped with groups of nozzles connected to a flow driver and arranged to ensure horizontal and vertical circulation of gas in the heating chamber and its supply to the granule layer through openings, Making a wall in the interior of the mine. The mullite synthesis furnace is communicated with an inlet with an outlet of a pellet drying furnace, and with an outlet with a receiving hopper equipped with a circulation loop of a cooling granule of gas. The inner shaft is made with alternating pairs of protrusions, under which are placed holes communicating the inner shaft with a heating chamber, with each subsequent pair of protrusions offset by 90 ° relative to the previous one.

Figure 1 schematically shows the proposed installation; figure 2 is a section aa in figure 1; figure 3 is a section bB in figure 1; figure 4 is a section bb in figure 3; figure 5 - section GG in figure 1.

The installation comprises a granulator 1, a rotary drum drying oven 2 with a metering unit 3, in communication with the output of a shaft furnace 4 for the synthesis of mullite in a moving layer of granules. The drying oven 2 is equipped with a fitting 32 for exhaust gases from furnaces 2 and 4.

The mullite synthesis furnace 4 contains a vertical metal housing 5, inside of which coaxially external 6 and internal 7 ceramic shafts are placed with the formation of a heating chamber 8 between the side walls of the shafts 6 and 7.

Between the outer shaft 6 and the metal casing 5 there is a layer of thermal insulation 9.

The inner shaft 7 is made with protrusions 10 alternating in pairs in height, with each subsequent pair of protrusions offset by 90 ° relative to the previous one.

The furnace is heated by gas, heated with water-cooled plasma generators 11, supplied to the heating chamber 8 through openings 12 in the shaft 7, shielded by protective ceramic rings 13 (FIGS. 2 and 3), cooled by gas (not shown).

The chamber 8 is in communication with the internal cavity of the shaft 7 by a system of holes 14 made directly under the protrusions 10.

The chamber 8 is equipped with nozzles 15, providing horizontal circulation of the heating gas in the chamber, as well as nozzles 16, providing vertical circulation of the heating gas in the chamber. To intensify the vertical circulation of the heating gas channels 17 are provided, made in the shaft 6 or formed using a vertical partition 18.

The furnace is equipped with a gas circulation circuit in countercurrent to the movement of the granules, including nozzles 19, a gas extraction nozzle 22 located in the upper part of the shaft 7, and a gas supply nozzle 31 located in the lower part of the furnace, and a piping system connected to the collector 30 and nozzle 31 with a flow driver 20 and a heat exchanger 21.

In addition to the circulating gas flow through the granules, a supply of heating gas to the volume of moving granules is organized directly from the chamber 8, for which nozzles 19 are provided, oriented towards the holes 14 and connected to the gas manifold 30. The collector 30 is placed in the insulation layer 9.

The lower part of the furnace is in communication with the receiving hopper 23 of the target product, equipped with a mechanism for the regulated delivery of the product 24 to the transport container 25. The receiving hopper is equipped with an air-gas mixture circulation circuit for cooling the target product, including the upper nozzle 29 for gas extraction and the lower nozzle 28 for supplying gas to the hopper as well as a flow inducer 26 and a heat exchanger 27.

All parts in contact with gas at temperatures above 300 ° C are made of alundum or mullite ceramics.

The installation is provided with devices (temperature, flow, pressure, etc.) for measuring various parameters and controlling processes in the furnace (not shown).

The furnace operates as follows.

From topaz concentrate in granulator 1, granules are formed in the form of rings or flakes with wall thicknesses from 1.5 to 3 mm, which are sent to the drying oven 2 through the metering loading unit 3. The drying oven must be heated to 300 ° C, and from the nozzle 32 carry out the selection of gases generated by heating.

The granules that pass through the drying furnace 2 enter the furnace 4 and are poured into the hopper 23. To prevent overheating of the discharge device 10, it is filled with the granules cooling circuit turned on.

After filling the hopper 23 include plasma heating of the furnace.

Warming up begins when the plasma generators 11 are operated with compressed air, followed by replacing the air with the gas produced in the synthesis furnace, when the gas circuit is turned on with the heat exchanger 21 and the flow inducer 20. The gases are taken into the circulation circuit through the nozzle 22.

Gas from the flow inducer 20, supplied to the manifold 30, is distributed into the nozzles of the horizontal circulation 15, the vertical circulation 16 and the gas supply nozzle 19 into the volume of the moving granules. In addition, gas from the flow inducer 20 is supplied to the nozzle 31, to the plasma generators 11, to protect the rings 13 (in a plasma jet stream) into the openings 12.

The furnace for producing mullite 4 is preheated to 800 ° C. The air heated in the plasma generator with a mass-average temperature of more than 3500 ° C, and during further operation, the gas enters through the nozzle 13 into the heating chamber 8. In the nozzle 13 and the chamber 8, the plasmoid mixes with the gas flow moving in them and gives it excess heat, and and with further work and granules inside the furnace. The movement of gas in the chamber and its supply to the internal cavity of the furnace is carried out by groups of nozzles. The nozzles 15 rotate the gas in the chamber, the nozzles 16 return the “cooled” gas from the upper part of the chamber to the areas of the fittings 13, and the nozzles 19 pump “hot” gas into the internal cavity of the furnace through the holes 14 located in the lower part of the chamber 8. Through the holes 14, located in the upper part of the chamber 8, the "cooled" gas from the internal cavity of the furnace partially returns to the chamber 8.

After heating the furnace to a temperature of 800 ° C, the supply of granules to the furnace is resumed, continuing heating.

In order to prevent freezing of granules in the active mullitization zone, the furnace is filled with granules while part of the granules is taken from the unloading device 23. After the furnace is filled, the granules are selected with loading and the furnace is heated to ensure that the temperature in the moving granules is at least 1300 ° С. Since the granules discharged during filling did not pass the full processing cycle, they are returned to the loading unit by mixing with the original granules.

In the steady-state stationary mode, the exposure time of the granules in the furnace is set, controlling their selection and loading according to the results of the analysis of the thermochemical processing of granules.

The discharge of granules from the furnace is carried out in a transport container 25.

During heating and mullitization, more than 60 kg of gas is released per 100 kg of loaded granules, consisting of a mixture of hydrogen fluoride, silicon tetrafluoride, water vapor, etc. In a steady-state process in a furnace, this mixture containing hydrogen fluoride is necessary for the conversion of topaz concentrate to mullite. The supply of the mixture provides a circulation circuit, taking gas from the nozzle 22 and distributing it into the nozzle 31, into the plasma generators 11, into all nozzles and to cool the rings 13 with the help of a flow inducer 20.

Plasma heating allows you to reuse the gases emitted during mullitization with minimal dilution, and the nozzle system provides intensification of heat and mass transfer in the furnace.

Example.

With a capacity of two plasma generators up to 65 kW each and loading 100 kg of granules per hour into the furnace, about 80 kg / hour of gas with a temperature of about 300 ° C is removed from the furnace by a gas circulation circuit, which is cooled in the heat exchanger 21 and then distributed using a flow inducer in the following way:

25-30 kg of gas enters the plasma generators, is heated to a temperature of more than 3500 ° C and is supplied to the chamber 8, being the energy source for heating the furnace 4;

10-12 kg of gas is supplied to protect the rings 13 from plasmoid radiation;

up to 15 kg of gas enters the nozzle 31 for heat recovery from moving towards the granules.

The remaining 25-30 kg of gas are distributed from the collector 30 to the nozzles, ensuring the transfer of gas energy received from the flow rate 20 directly in the contours of horizontal and vertical gas movement in chamber 8, as well as in the gas circulation loop through the volume of granules. At the same time, the gas, passing through the collector 30 and nozzles heated to 500-800 ° С, is heated to 400-600 ° С and then mixes in the ratio 1: 8-12 with the gas volumes in the circulation circuits inside the furnace (in different circuits its coefficient ejection), heated to 1400 ° С-1600 ° С, acquiring the operating temperature.

The excess gas formed in the furnace 4 enters the drying furnace 2, gives off heat to the initial granules and, together with the gases obtained in the drying furnace (mainly water vapor), is taken from the nozzle 32 for further processing to isolate valuable components.

This embodiment allows us to provide conditions for obtaining high-quality fibrous and (or) needle-shaped mullite crystals in a continuous mode, since the installation provides:

a) the temperature in the oven from 300 ° C to 1400 ° C;

b) maintaining at all stages of the transformation of the granules into mullite-containing material necessary for the course of the reactions of the composition of the gas mixture with the provision of a counterflow of gas and granular material;

d) the use of topaz concentrate granulated with the addition of an organic binder as a starting material;

e) holding the granular material for a long time at a stabilized temperature, ensuring maximum conversion of the initial composition of the granules into fibrous and (or) needle mullite through chemical reactions with a circulating fluorine-containing gas.

Claims (3)

1. Installation for producing mullite from topaz concentrate, containing a granulator, an oven for drying the obtained granules and a mullite synthesis furnace, characterized in that the mullite synthesis furnace is made of external and internal shafts placed coaxially with the formation of a heating chamber, and is equipped with plasma generators communicating with outputs with a heating chamber, and a gas circulation circuit countercurrent to the movement of the granules, including a flow inducer, while the heating chamber is equipped with groups of nozzles connected to a flow inducer and placed to provide m of horizontal and vertical gas circulation in the heating chamber and its supply to the granule layer through openings made in the wall of the inner shaft. 2. Installation according to claim 1, characterized in that the mullite synthesis furnace is communicated with an input with an outlet of a granule drying oven, and an output with a receiving hopper equipped with a circulation loop of a cooling gas granule. 3. Installation according to claim 1 or 2, characterized in that the inner shaft is made with alternating pairs of protrusions, under which are placed holes communicating the inner shaft with a heating chamber, with each subsequent pair of protrusions offset by 90 ° relative to the previous one.

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