CZ2004488A3 - Method for making a concentrated heat exchange within revolving furnaces and apparatus for making the same - Google Patents

Abstract

The solution relates to efficient combustion of gaseous fuel and formation the thermochemical annealing / sintering process of refractory and other materials under rotary kiln conditions. The flame forms by stoichiometric combustion of a homogeneous mixture the balance of gas and air is directed obliquely to the surface of the annealed material in the form of a volumetric flow s adjustable radial and meridial sector angle v of the kinetic burning process, with a significant proportion radiant heat up to 55%, ensuring compliance technological conditions during annealing (sintering) of material. Equipment to create a focused and directed heat The replacement consists of a gas console burner whose length extends beyond the cooling zone with the necessary elements of various shapes and location

Description

Method for producing concentrated and directed heat exchange in rotary kilns and apparatus for its creation

Technical field

The invention relates to a method for efficient combustion of gaseous fuel and to the formation of a thermochemical process of annealing or sintering refractory and other materials under rotary kiln conditions.

BACKGROUND OF THE INVENTION

Known is a method of generating a thermodynamic process in the processing of powdered bulk materials in rotary kiln conditions that have gas combustion by an axially positioned diffusion burner whose axis is oriented horizontally or parallel to the furnace axis, with a single gas channel, with an opening angle control system / Walberg HS The application of natural gas for clinker burning: Cement-Wapno-Gips, Warsaw /, No.11 1967, pp. 331-337; Vaíberg G.S. Natural Gas in the Cement Industry, The State Press., 1962, p. 172; Vaíberg G.S. et al., Cement Production Intensification (Clinker Burning), 1971, p. 145 / or multichannel, with external air collector, with primary and secondary air intake ranging from 30 to 70% (Pillard Offenering GmbH-Rotary Kiln Virner, bulletin) , which are characterized by a thermal coefficient of useful power equal to 40 to 42% / Refractory production. Zpravodaj. Part 11, “Metallurgy”, 1965 page 199 /.

The thermal analysis of the work of existing rotary kilns is evaluated by the magnitude of the specific heat load of the cross-section of the sintering / annealing zone in light, kcal / m ³ , i.e. the amount of heat entering the sintering zone over an hour. / Anda WH.Cment Data Book. Internationale Verfahrentechniken der Zementindustrie, 2. Vollig neubearbeitete und erweiterte Auflage. 1977 Bauverlag GmbH Wiesbaden und Berlin, p. 335 /.

Under existing conditions, the thermal load of the free cross-section of rotary kilns is limited by the magnitude of the rate of combustion products. Increasing the furnace gas velocity not only worsens the heat exchange, but also causes the entrainment of large quantities of finely divided dispersed particles of the annealed material by the gas flow, the concentration of these particles increasing proportionally to the square of the gas flow velocity (Legrand J.). rotatif, Rhubarb materiaux Construction, No.544, p.23./

According to the data / Production of Refractory Materials, Proceedings, Volume 11, “Metallurgy”, Volume 1965, page 196 /, the total volume of drift is 35 to 45%.

• · • ··· · · · · · · ·

The thermal load of the sintering zone is characterized by the amount of heat passing from the combustion zone to the sintering zone, the length of which is determined by the amount of specific heat consumption for annealing.

From practical experience, the thermal load of the sintering / annealing zone is 3x10 ⁵ kcal / m ³ hours and attempts to increase this indicator by accelerating the annealing / sintering regime have led to an increase in the temperature of the waste gases and proportionally to their velocity. payload coefficient. / Anselm. W. Modelleichlichkeitsbetrachtungen von Drehofen, Zement-Kalk-Gips 11,1954, p.427 /.

At present, as it is known, the movement of heat from the combustion products gas to žíhanému / spékanému / material characteristic heat flux representing the amount of heat which receives the surface of 1 m ² for 1 hour. Under the conditions of existing rotary kilns, this surface, where the material to be treated is located, represents only 16 to 20% of the total surface to which the heat flow is directed by the heat transfer method known to sinter and / or anneal the materials.

The temperature of the combustion products along the length of the rotary kiln resulting from the known method of gas combustion appears to depend on an initial monotonous temperature rise to a maximum of 15-30% of the length of the furnace, followed by a monotonically decreasing temperature, and no temperature equilibrium zone to meet the temperature of the endothermic process of dissociating carbonaceous materials, which ultimately eliminates process optimization and is accompanied by considerable heat losses to the environment of up to 37 to 40%.

In addition, the known method of gas combustion, structurally in the position of the burner in the direction of the material moving beyond the boundaries of the cooling zone (recrystallization), adversely affects this process, as some thermal energy in the initial burner section is given to the cooled material.

Known designs of flame-forming combustion apparatus in the diffusion zone, as determined by the laws of chemical kinetics, depend on the properties of the flammable mixture, temperature, focus pressure, reagent concentration, and virtually little on diffusion aerodynamic processes.

Diffuse combustion (burning of premixed fuel and oxidant) is complex and the rate of combustion is limited by the rate of mixing - molecular diffusion, or summary / turbulent and molecular / diffusion.

Increasing the rate of diffuse combustion by increasing turbulent diffusion at the expense of burner flow rate, increases the rate of mixture formation, which may be higher than the rate of chemical combustion reactions, and the combustion process transforms from the diffusion region to kinetic across the so-called mid zone. The propellant is higher than the flame propagation rate, resulting in a loss of stabilization of the combustion process with subsequent flame detachment from the burner crater and ultimately the combustion must be interrupted.

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As is known, heat transfer takes place in three ways: radiation, convection and conduction, which have a specific heat transfer mechanism and are governed by different laws.

Of particular importance in the annealing / sintering / material rotary kilns are two types of heat transfer: convection and radiation.

The specific heat transfer by convection is defined by the granulometric characteristic of the powder materials according to the dust entrainment and radiation - using a low-temperature diffusion combustion process. According to literature data, the total proportion of heat given off by radiation in the presence of soot particles is, in the case of a long burner, i.e. a maximum of 18 to 20% of the total amount of heat received by the entire furnace surface and material 6 to 7%. In addition, the known design of burner devices that heat the refractory insulating layer of a furnace to practically the same temperature along its periphery does not create conditions for efficient heat exchange between it and the sintered material as the furnace is rotated. Therefore, some of the thermal energy received by the flame-resistant heat-insulating layer is lost due to thermal conductivity and radiation to the environment.

In this way, a comprehensive analysis of the operation of gas-fired rotary kilns shows that existing combustion engine solutions and heating space aerodynamics do not provide optimal high efficiency coefficients of efficiency and eliminate the possibility of controlling the direction and concentration of heat flow to the annealed zone. material, which is accompanied by considerable heat and material losses

The conversion of rotary kiln operation to a high-temperature gas-fired mode into a kinetic zone of 2100 to 2150 ° C with a glow proportion of 55 to 65% requires the creation and elaboration of complete aerodynamics of heater and special burner equipment ensuring heat flux concentration in the location sector of the annealed / sintered material, heating the gas supplied to the combustion plant and the air at the expense of the cooling zone's thermal energy.

The task was therefore to create an efficient annealing / sintering / heat / mass exchange process due to the principal change in flame aerodynamics and its orientation in the combustion chamber of the high-temperature gas combustion process with structural confirmation of its performance ensuring technological parameters of the thermodynamic annealing a homogeneous mixture, reaching the maximum temperature of the burner with the transformation of heat energy into the heat, producing a short and strong flame and improving the heating of the gas (up to its combustion) and air as a result of cooling of the burner equipment as well as the high partial pressure of the water vapor generated during combustion , increasing the degree of "blackness" of the flame as well as the rational utilization of the radiant capacities of the heat-resistant insulating layer of rotary kilns using the heat obtained from the flame - as a result of heat exchange with due to its "distribution" and "adhesion" in the zone of contact with the material being moved to heat it.

Radiation heat transfer in high-temperature furnaces is crucial because in this way 80 to 90% of all the heat produced by the heated material is transferred / AIEvdokimov, VVKosterin, Natural Gas in Color Metallurgy, "Metallurgy", M., 1972 62, 65, 141). The temperature of the flame may be higher than the temperature of the refractory furnace by 370 ° C or more to intensify the heating. When the air is heated from 273 to 770 ⁰ Kse, the flame spread rate increases 2 and more times, and fuel consumption decreases by 34% / Glinkov MA, Stepanov ME, VUZOV News Black metallurgy, 1961, no.9, p 143; Zaberežnyj, II, Use of heated air in furnaces of color metallurgy. "Metalurgizdat", 1958, Bašanov Ll et al. Non-ferrous metals. 1967, No.1, p.37 /.

In solving a complex task based on ways to increase the overall efficiency of the thermodynamic annealing / sintering / powdering process, combustion is located in the annealing / sintering / homogeneous mixture zone, corresponding to stoichiometric equality with complete premixing of gas and air, in the form of a pyramidal flame consisting of individual strands exiting the mixing chamber of the burner with a sector opening angle of 35 to 40 °, the axis of which is at right angles to the surface of a radially segmented layer of annealed / sintered material process. The rate of discharge of the mixture from the mixing chamber nozzles exceeds the rate of combustion, eliminating the retraction or skipping of flames into the burner interior (Stoliner, E.B., Pauleva, E.F: Report for Gas-fired Boiler Room Personnel. "Nedra", 1990, p.199).

In order to avoid overheating of the burner assembly, an annular burner structure is provided, including an outer annular gas collector, extending at the front to an inner gas collector disposed axially within the air collector and an effective cooling system on its outer surface, which supply gas to the mixing chamber, cooling the walls along its entire length by controlling the gas velocity mode at minimum friction resistance coefficient with boundary layer turbulization in the zone of increased heating of its walls from radiation / Šlichting, G., Boundary Layer Theory. .1969 pp. 569 /.

To reduce the hydraulic resistance of the air collector and reduce the electrical energy consumption of the respirator fan drive, the property of a gas stream ejected into the air collector space is used to transform kinetic energy to potential and potential to kinetic energy (Budrin, D.V., Glinkov, M.A., et al. Metallurgical furnaces. Part 1. State Technical Publishing House for Black and Color Metallurgy., M.1963, p.252 /, using ejection forces for the process of mixing gas with air at optimal gas flow rates in the mixing chamber /Butakov, S.E., Aerodynamics of Industrial Ventilation Systems. VNIIOT, Moscow 1949, p.86 ... 105 /.

To reduce the heat loss and costs of the electric drive of the smoke exhaust fan due to the uncontrolled air intake in the furnace head, volume control

• Excluded combustion products are installed by collector-type measuring devices corresponding to the volume of their formation and eliminating their transfer from the atmosphere of the hall.

The choice of geometry, design parameters of stream shape components and its orientation when burning a homogeneous stoichiometric mixture is determined by the conditions of achieving the target and depends on the properties of the annealed material, technological parameters of rotary kilns, air and gas pressure. mixing and transforming mixtures at the expense of energy / pressure / gas capabilities with minimal hydraulic resistance to the air supply system.

SUMMARY OF THE INVENTION

It is an object of the present invention that in order to create efficient heat exchange and heat exchange concentration of strong and short and high temperature flame and to conserve energy sources, the flame is produced by burning a homogeneous homogeneous mixture at stoichiometric equilibrium of gas and air. a pyramidal flame shape consisting of individual strands coming from the burner mixing chamber with an open angle of 35 to 40 degrees or more, the axis of which is oblique to the surface of the radially segmented layer of annealed material taking into account the possibility of additional heating of the surface of the refractory insulating layer in front of the moved roasted (annealed) material, whose length in the direction of its movement ensures the course of the thermodynamic process perpendicular to the surface of the annealed material in the form of a volumetric flow of different flame shape, with a controlled radial and sector angle in the kinetic combustion process, with a radiation ratio of about 55 to 55%, ensuring that the technological conditions during annealing (sintering) of the material are met. The bulk stream is made up of a number of individual radial streams with a homogeneous mixture flow rate exceeding the combustion rate.

The essence of the solution is that in order to associate the process of homogenization of the media and to save energy costs for air transport, the gas supply to the mixing zone is performed at the flow rate, sufficient to eject (entrain) air and maximum heat exchange.

Furthermore, the device for producing a concentrated and directed heat exchange consists of a radiating head, a gas burner, a jacket, internally walled with refractory bricks, a dust chamber, a support mechanism and a drive. To produce a controlled volume of heat, the gas burner is cantilevered, with a length that extends beyond the cooling zone. In order to reduce the air intake volumes from the surroundings, the flue gas chamber is equipped with a measurable collector. In order to heat the gas from the cooling zone, the gas burner is equipped with an external gas collector which is connected to the internal gas collector by a front radial-annular confuser.

6 · · · · · · · ·. Collector located axially in the air collector. The gas burner is equipped with a mixing chamber. The face radial-annular confuser has a cylindrical or elliptical shape.

Another principle is that the internal gas collector is equipped with air ejection nozzles. The mixing chamber is equipped with several rows of mixing outlet nozzles at the base of the nozzles, placed side by side or alternately (like a chessboard), the axes of which are oriented obliquely at an angle to the sintered material. The gas burner is equipped with an external gas collector, an air collector and a mixing chamber.

Another principle is that the front gas collector is equipped with several gas nozzles which are located in the air collector space and whose axes are directed parallel or at a meridian angle to the surface of the air collector. The front of the mixing chamber passes to a pyramid confuser equipped with a nozzle base, which may be flat, cylindrical or conical, directed at an angle to the axis of the rotating furnace.

The use of the proposed method of directed heat exchange by means of said combustion device provides the following advantages compared to existing methods:

significantly reduces energy sources for thermodynamic annealing (sintering) process increases heat exchange process efficiency decreases powder dust entrainment expands process application limits increases quality of use in the regulation of technological flow control of heat flow

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a rotary kiln. Fig. 2 - section A-A, fig. 3 longitudinal section of the burner device (variant I), fig. 4 fig. 4 - section B-B, fig. 5 - section C-C, fig. 6 - section D-D. Fig. 7 is a longitudinal section of the burner apparatus (variant II); Fig. 8 is a sectional view of E-E. Giant. 9 is a longitudinal section of the burner apparatus (variant III), FIG. 10 is a view F-F, and FIG. 11 is a section G-G. Fig. 12 is a longitudinal section of the burner apparatus (variant IV); Fig. 13 is a section H-H. Fig. 14 is a longitudinal section of the burner apparatus (variant V); Fig. 15 is a section of CH-CH.

Examples

Example 1

The rotary kiln (Fig. 1) with a radiating head 1, a gas burner 2 and a jacket 3 is internally lined with fire bricks, has a dust chamber 4, a flue gas chamber 5, a measurable collector 6, a support mechanism 7 and a drive 8.

• · · · · ·

The gas burner 2, variant I (Figs. 3, 4, 5, 6) has an external gas collector 9, a front radial-ring confuser 10, an internal gas collector 11 (Fig. 4), supplied with gas nozzles 12 (Fig. 6), an air collector. 13 with gas-air mixing chamber 14, mixing outlet nozzles 15. gas inlet throat 16 with gas meter 17 and shut-off flap 18, air inlet throat 19 with air meter 20 and shut-off throttle 21. The collector 9 with the circuit without mixing outlet nozzles 15 for the mixture discharge is equipped with turbulators 22. The burner device is equipped with a branch for the lighter 23 and moves by means of a reverse mechanism 24.

In the chamber 5 (Fig. 1) of the flue gas in the dust chamber 4 at the outlet of the combustion products from the rotating furnace there is a measurable collector 6 with an end throttle 27. The combustion products discharged from the dust chamber 4 downstream of the dust collection system are discharged into the atmosphere. .

The annealed (sintered) material 25 is displaced along the inner walled portion of the furnace shell 3 (FIG. 2) to which the flame stream 26 formed by the individual streams coming from the mixing nozzles 15 is directed perpendicularly.

The workflow is presented together for all examples.

Example 2

The rotary kiln is similar to Example 1. The gas burner 2, variant II (FIGS. 7, 8) has an elliptical radial-circular confuser whose nozzle base 33 is at an angle to the burner axis and mix mixing nozzles 15 are located thereon. The annealed (sintered) material 25 is displaced along the inner walled portion of the furnace shell 3 (FIG. 2) to which the flame stream 26 formed by the individual streams coming from the mixing nozzles 15 is directed perpendicularly.

Example 3

The rotary kiln is similar to Example 1. The gas burner 2, variant III (Figs. 9, 10, 11,) has a front nozzle base 33 whose plane is at an angle to the burner axis and is equipped with outlet mixing nozzles 15 and separator plates 30. .

Example 4

The rotary kiln is similar to Example 1. The gas burner 2, variant IV (Figs. 12, 13) has a front gas collector of circular shape 34, equipped with a continuous air duct 29 and outlet ports 12 of the mixture. The air duct 29 may be located both axially and radially.

Example 4

The rotary kiln is similar to Example 1. The gas burner 2, variant V (Fig. 14, 15) has an inclined confuser 31 equipped with mixing outlet nozzles 15 at the front of the mixing chamber 14.

The inner diameter of the sheath 3 is formed by a drying zone - "A", a heating zone - "B", a calcining zone - "C", an annealing / sintering / "D" zone and a cooling zone ·

The procedure of operation in rotary kilns is implemented as follows:

In gas burners 2 - variant I or variant II - the gas is fed through the gas supply system - gas supply neck 16, shut-off flap 18 and metering device 17 to the external gas collector 9 and further through a radial-ring confuser 10 to the internal gas collector H and air nozzles 12 to the mixing chamber 14. At the same time, air flows from the blowing fans through the duct system, the shut-off throttle 21, the air measuring device 20 and the air inlet 19 to the air collector 13 and into the mixing chamber 14 where the mixing process takes place. of gases with the formation of a homogeneous gas-air mixture.

The prepared homogeneous mixture with the mixing outlet nozzles 15 introduces sintering / roasting / "D" to the combustion chamber. The mixture is ignited by lighter 23.

In the gas burner 2 (variant 111), the gas is fed through the gas supply system - gas supply orifice 16, shut-off flap 18 and metering device 17 to the external gas collector 9 and further to the mixing chamber 14. At the same time , a shut-off throttle valve 21, an air metering device 20, and an air inlet 19 to the air collector 13, and then to a mixing chamber 14, where the mixing process takes place to form a homogeneous gas-air mixture. / roasting / "D". The mixture is ignited by lighter 23. The uniformity of the rate of flow of the mixture is stabilized by the plates 30.

In the gas burner 2 - variants IV and V - gas is fed via the gas supply assembly, the gas supply port 16, the shut-off flap 18 and the metering device 17 to the gas collector 34 and the gas nozzle 12 to the mixing chamber 14 where the mixing process takes place. homogeneous gas-air mixtures. The gas-air mixture is fed through the mixing outlet nozzles 15 to the combustion space of the sintering / roasting / "D" zone. The mixture is ignited by lighter 23.

In the gas burner 2, variant V, gas flows from the mixing chamber 14 to the inclined confuser and through the mixing outlet nozzles 15 to the combustion space of the sintering / roasting / "D" zone. The mixture is ignited by lighter 23.

The formed flue gas flows perpendicularly (variant I) or obliquely (variants II, III, IV and V) to the plane of placement of the sintered material 25 in the form of a volumetric flame of different shapes generated by separate streams exiting the mixing outlet nozzles 15 as a result of oxygenation. thereby creating the conditions for an efficient thermodynamic annealing / sintering / workpiece process. The volume flow of flue gas, acting on the surface of the annealed material under the influence of the vacuum created by the smoke extractor, alters the path of movement in the meridial direction and in this way produces a high temperature gas flow in the zone. in which the material to be processed is located, thereby increasing the heat exchange efficiency of the convection.

Directing the volumetric flow to the material placement plane allows the burner device to be removed from the high temperature zone, thus avoiding overheating and deformation.

In the long-term operation of said burner devices, depending on the temperature conditions, the front part on which the mixing outlet nozzles 15 and possibly the mixing chamber 14 are located can be protected by a heat-insulating refractory material.

The cone shape of the confuser 31 of the burner device (varinta V) is used under high-temperature production conditions.

Claims (14)

PATENT CLAIMS A method for producing concentrated and directed heat exchange in rotary kilns by the method of combustion of gas in one or many channel (ring) burners whose flame is oriented horizontally or or parallel to the furnace axis (layer of annealed material) in a low temperature diffusion mode of combustion. 18 to 20% of radiation generated by heat dissipation interrupted in a radial direction over the furnace surface (specific heat flux), characterized in that the furnace flame forms a homogeneous mixture in the furnace by stoichiometric equilibrium of gas and air and directed obliquely to the sintered surface The material in the form of a volumetric stream with adjustable radial and meridian sector angles in the kinetic combustion process mode, with a significant proportion of radiant heat, preferably 40 to 60%, ensuring that the technological conditions during annealing (sintering) of the material are met. Method according to claim 1, characterized in that the volumetric flame stream is formed from a number of individual streams, with an air-gas mixture flow rate exceeding the combustion rate. Method according to claims 1 and 2, characterized in that the gas supply to the mixing zone is carried out at a flow velocity sufficient to eject the air and the maximum heat exchange. Apparatus for generating a concentrated and directed heat exchange according to claims 1 to 3 in rotary kilns, comprising a radiator head, a gas burner, a sheath, internally walled refractory bricks, a dust chamber, a support mechanism and a drive, characterized in that the gas burner (2) is cantilevered, with a length that extends beyond the cooling zone. Device according to claims 1 to 4, characterized in that the flue gas chamber (5) is equipped with a measurable collector (6). Apparatus according to claims 1 and 5, characterized in that the gas burner (2) is provided with an external gas collector (9), which is connected to the internal gas collector (11) axially in the air collector by a front radial-annular confuser (10). collector (13). • · Device according to claim 6, characterized in that the gas burner (2) is provided with a mixing chamber (14). Apparatus according to claim 6, characterized in that the front radially-annular confuser (10) has a cylindrical or elliptical shape. Apparatus according to claim 6 to 8, characterized in that the inner gas collector (11) is equipped with nozzles (12) for ejecting air. Apparatus according to claims 6 to 9, characterized in that the mixing chamber (14) is provided with a plurality of mixing outlet nozzles (15) on a nozzle base (33) arranged regularly side by side or alternately (like a chessboard) whose axes are oriented obliquely at an angle to the sintered material (25). Device according to claims 6, 7, characterized in that the gas burner (2) is equipped with an external gas collector (9), an air collector (13) and a mixing chamber (14). Device according to claim 11, characterized in that the front gas collector (34) is equipped with a plurality of gas nozzles (12) located in the space of the air collector (13) and whose axes are directed parallel or at meridian angle to the surface air collector (13). Apparatus according to claims 7 and 10, characterized in that the front part of the mixing chamber (14) passes into a pyramid-shaped confuser (31) which is equipped with a nozzle base (33) which can be flat, cylindrical or conical directed below angle to the axis of the rotating furnace. Apparatus according to claims 10 and 13, characterized in that the axes of the rows of the mixing outlet nozzles (15) are parallel to each other or checkered and form a sector with an overall opening angle of 30 to 40 or more degrees.