RU2791072C1 - Cyclone furnace for heat treatment of fine materials - Google Patents

Abstract

FIELD: heat treatment of bulk materials.

SUBSTANCE: invention can be used in sintering and pulp and paper production, metallurgy, waste management, chemical and sugar industries, energy, building materials and other industries. A cyclone furnace for heat treatment of finely ground material in the form of limestone, dolomite, gypsum, magnesite, pyrite cinders, slag contains a housing with an upper loading device, tangentially located burners, a central exhaust pipe and a lower unloading device, while the burners are distributed along the height and circumference of the furnace, and the furnace is made with the possibility of introducing material into the furnace in a dosed manner through the burner tunnel of the upper burner device.

EFFECT: improving the quality of the finished product, the possibility of firing raw materials of a wide fractional composition up to 15 mm.

3 cl, 1 dwg

Description

The invention relates to devices for heat treatment of bulk materials and can be used in sintering and pulp and paper production, metallurgy, waste management, chemical and sugar industries, energy, building materials and other industries.

Known installation, consisting of two stepped rotary kilns with self-supply of fuel and heated air, heat exchangers drum, grate or cyclone types, cyclone dust collector. These rotary kilns provide a fairly uniform heat treatment of the material, have high productivity (Tsibin IP and other Start-up, commissioning and thermal testing of furnaces and dried refractory industry. M., Metallurgy, 1978, p. 256).

The disadvantage of the installation is the high specific fuel consumption (for example, for rotating lime kilns - 200-220 kg of reference fuel / t), high dust removal of the material (10-30%), which necessitates the installation of bulky dust removal systems with cyclone heaters and separators. One of the main disadvantages of rotary kilns is the limitation on the fraction of the fired material, which should not be less than 10-20 mm.

Cyclone-type furnaces can be used to intensify the process of heat treatment of bulk materials.

A cyclone kiln for the production of powdered lime is known, containing a cylindrical body with gas burners, central loading and a bottom outlet of flue gases and material (see AS USSR No. 1502937, publ. 23.08.1989, Bull. No. 31).

The disadvantage of this design of the cyclone furnace are:

- blowing the material with air into the working space reduces the possibility of regulating the productivity of the furnace and maintaining the required temperature level of the firing process;

- when the material is blown from top to bottom along the axis of the furnace, due to the speed of the air flow, the initial vector of motion of the particles of the material is formed, directed downward, which reduces the time spent by the material in the furnace;

- reverse reactions of recarbonization due to the joint removal of flue gases and burned material from the kiln, which leads to a deterioration in the quality (activity) of the resulting lime.

Known cyclone furnace for heat treatment of finely divided material, consisting of a cylindrical body, a working chamber, tangentially arranged blast nozzles with loading devices (see AS USSR No. 1364843, publ. 07.01.1988, bull. No. 1). In the working chamber, a hollow cylindrical insert made of heat-resistant steel is coaxially installed, in the upper part of which gas nozzles are installed. Dust and gas flow (flue gases and burnt material) is removed from the furnace through the flue.

The disadvantage of this design of the cyclone furnace are:

- injection of material into the furnace space by the air involved in the combustion of the fuel coming through the tuyeres of the central insert limits the ability to control the productivity of the furnace and maintain the required temperature level of the firing process;

- when using this design of the cyclone kiln during the roasting of carbonate materials to produce lime, recarbonization reactions will also occur with a deterioration in the quality (activity) of the final product due to the joint removal of flue gases and the burnt material from the kiln;

- difficulty in separating the flows of fine material and flue gases.

The closest analogue to the claimed invention is a cyclone limestone kiln, containing a housing with a top loading device, tangentially arranged burners, a central exhaust pipe, a cooler and a bottom unloading device (see A.C. USSR No. 520500, publ. 07/05/1976 g ., Bull. No. 25).

This method is taken as a prototype.

The disadvantages of the prototype are:

- made in the lining of the housing cooling channel complicates the design of the prototype and leads to the removal of heat energy from the firing zone of the cyclone furnace, which leads to excessive fuel consumption. At present, a fairly large number of refractory materials operating at temperatures above +1500°C are known and successfully used.

- the design of the socket of the central exhaust pipe in combination with the umbrella-reflector leads to a decrease in the cross section of the cylindrical profile of the internal space of the cyclone furnace, which leads to an increase in the velocity of the mixture of the gas flow of the combustion products of the fuel and the fired material and an increase in the dust removal of the fired material from the furnace;

- uneven temperature field along the height of the furnace, due to the location of the burners only in the upper part of the furnace.

The objective of the present invention is to create such a method of heat treatment of fine material, mainly carbonate rocks, which will allow industrial firing:

- carbonate rocks of fraction 0-15 mm in the form of limestone and dolomite into commercial fine lime;

- dust entrainment of cyclone and bag filters of rotating and shaft kilns for burning limestone and dolomite into commercial fine lime;

- gypsum stone fraction 0-15 mm into commercial fine-dispersed estrich-gypsum;

- carbonate sludge from dumps of sludge storage facilities for chemical water treatment of thermal power plants into marketable fine lime;

- pyrite cinders (waste from the processing of iron pyrite (FeS ₂ , pyrite) into sulfuric acid) fraction 0-15 mm to obtain commercial iron ore concentrate;

- natural magnesite (MgCO ₃ ) fraction 0-15 mm into commercial caustic magnesite MgO.

The problem is solved by the proposed cyclone furnace for heat treatment of finely divided material in the form of limestone, dolomite, gypsum, magnesite, pyrite cinders, slag, containing a housing with an upper loading device, tangentially located burners, a central exhaust pipe and a lower unloading device, while burners distributed over the height and circumference of the furnace, while the furnace is configured to introduce material into the furnace in a dosed manner, through the burner tunnel of the upper burner device.

In a particular embodiment, the furnace is configured to co-feed finely ground material and additional ground fuel into the burner tunnel of the upper burner device.

In a particular case, the furnace is configured to jointly supply finely divided material to the burner tunnel of the upper burner device and add the gas phase of the pyrolysis or gasification process of alternative fuel - RDF, SRF, TDF or combustible waste.

The problem is solved by the proposed design of the cyclone furnace for firing fine materials (Figure 1). It consists of a lined furnace body - 1, a feeder of the fired material - 2 with a screw - 3, a hopper - 4 and a feeder - 5, burners - 6.1, 6.2, 6.3 tangentially located along the height of the furnace, inserted into the burner tunnels - 12, central exhaust pipe - 7, fan - 8 for supplying cold air to the auger unloading device - 16, fan - 9 for supplying cold air to the ejector - 10, crusher - grinder of feedstock - 11, working space of the furnace - 13, peepers - 14, air duct - 15 heated air outlet from the unloader and air duct - 21 heated air outlet from the heat exchanger - 19, fan - 20 for cold air supply to the heat exchanger, smoke exhauster - 22, dust settling cyclone - 17 with an unloading valve - 18, bag filter - 23.

The oven works as follows. The feedstock through the crusher-grinder 11 is fed into the receiving hopper of the boot device 2. Together with the feedstock, in order to reduce the consumption of process fuel, additional solid crushed fuel, such as coal, sawdust, sunflower husk, alternative waste fuel (RDF, SRF or TDF). The prepared raw material is loaded immediately into the receiving hopper of the loading device 2, from where the auger 3 is metered into the burner tunnel 12 of the upper burner 6.1, and with the flow of combustion products is blown into the working space of the furnace 13. A pre-prepared gas-air mixture is introduced through the tangential burners 6.1, 6.2, 6.3, providing a cyclonic effect inside the furnace. Material particles blown in by the 6.1 charging burner are swirled by the flow, fired and, braking against the refractory walls of the cylindrical shaft 1, accumulate in the lower part of the furnace, from where they are gradually unloaded by the 16 unloader. The 16 unloader is equipped with a cooler in which the heat of the finished product is used to heat the air combustion supplied by the fan 8 and going to the burners. Flue gases, partially dedusted, enter the central gas outlet channel 7 and are discharged from the furnace by a jet pump based on the ejector 10 to the dust settling cyclone 17, where they are additionally dedusted and enter the heat exchanger 19 to heat the combustion air. In the ejector 10, as an ejecting agent, cold air is supplied by a fan 9, which makes it possible to partially reduce the temperature of the combustion products and increase the volume of hot gases supplied to the heat exchanger for heating the combustion air. The combustion air supplied by the fan 20, passing through the heater 17 and being heated, enters the burner 10.

From the hopper 4 through the feeder 5, various additives or light products of gasification or pyrolysis of alternative fuels (RDF, SRF, TDF fuel, coal, sawdust, sunflower husks, lignins and other combustible waste) can be additionally supplied together with the fired material.

The use of a distributed input of the coolant along the height of the furnace and the circumference of the furnace makes it possible to have a uniform temperature field in the reaction zone. The dynamic jet movement of flue gases from the combustion of fuel and air supplied through tangentially located burners creates a centrifugally swirling downward two-phase flow of heat carrier and material in the furnace, which increases the residence time of the particles of the fired material in the reaction zone of the furnace by an order of magnitude. The tangential supply of material through the burner tunnel together with the products of combustion makes it possible to give centrifugal acceleration to the particles of the material, which additionally increases the residence time of the particles of the material to be fired in the reaction zone of the furnace. This technical solution makes it possible to expand the fractional composition of the fired particles, thereby reducing the cost of separating the material during grinding, the cost of catching it from flue gases and their subsequent dedusting. The roasting of carbonate rocks together with the gases supplied for afterburning from pyrolysis and gasification of alternative fuels provides partial neutralization of pollutants (sulfur, halides, and others) in the flow of suspended heated fine calcium oxide.

In the process of full-scale tests of a pilot cyclone-type kiln manufactured by NPO Science-Intensive Technologies LLC (TIN 7804451380), the most suitable screening fraction of flux limestone for firing into commercial lime was determined, which is 0.2-0.4 mm. A fraction of 0-0.2 mm in such modes is burned tightly, so it must be fired in the same cyclone furnace, but under other, milder modes (burner flame temperature not more than +1000°C). It was also confirmed the expediency of installing an ejector at the outlet of the furnace to create additional vacuum during the evacuation of flue gases and their partial cooling.

Claims (3)

1. A cyclone furnace for heat treatment of finely divided material in the form of limestone, dolomite, gypsum, magnesite, pyrite cinders, slag, containing a body with an upper loading device, tangentially located burners, a central exhaust pipe and a lower unloading device, characterized in that the burners distributed over the height and circumference of the furnace, while the furnace is configured to introduce material into the furnace in a dosed manner, through the burner tunnel of the upper burner device. 2. The cyclone furnace according to claim 1, characterized in that the furnace is configured to jointly supply finely divided material and additional crushed fuel to the burner tunnel of the upper burner device. 3. The cyclone furnace according to claim 1, characterized in that the furnace is configured to jointly supply finely divided material into the burner tunnel of the upper burner device and add the gas phase of the pyrolysis or gasification process of alternative fuel - RDF, SRF, TDF or combustible waste.

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