WO2007078215A1 - Swirling-type furnace operating method and a swirling-type furnace - Google Patents

Abstract

The invention relates to heat engineering and can be used for designing and reconstructing furnaces for industrial boilers. More advantageously the inventive furnace can be used for burning coarsely dispersed broken combustibles, coal and schist. The invective swirling-type furnace operating method consists in returning the controllable amount of a coal-ash mixture from an ash catcher located behind a combustion to the internal surface thereof. Said swirling-type furnace comprises a combustion chamber provided with a sloping bottom which is formed by slops of lower parts of the walls thereof, a bottom-blowing device arranged under the sloping bottom mouth and an inclined burner which is used for supplying a fuel-air mixture and is fixed to the combustion chamber wall. The furnace is provided with the ash catcher located behind the combustion chamber and a recirculation ash channel, whose one end communicates with the ash catcher and the other with the combustion chamber internal space. The output openings of the channel are positioned between the sloping bottom mouth and the fuel supply burner or/and in a secondary combustion area, provided with an additional burner which is used for supplying the coal-ash mixture from the ash channel to the combustion chamber and is arranged therein. The ash catcher is selected according to a condition of catching particles whose size is greater than 0.5 mm. The ash channel can be provided with fly ash transporting and sorbent supply means.

Description

 METHOD OF OPERATION OF VORTEX FURNACE AND VORTEX FURNACE

Technical field

The invention relates to heat engineering, namely to furnaces for burning coarsely ground fuel, and can be most successfully used for burning crushed coal fuel and oil shale. State of the art

The main parameters of industrial furnaces are their economic and environmental characteristics, the first of which are determined primarily by the completeness of fuel combustion and fuel preparation costs, and the second - mainly with the quality of the flue gases discharged into the atmosphere.

From the point of view of completeness of burning non-ground fuel and environmental characteristics, good results are shown by circulating fluidized bed furnaces.

Known firebox (RF patent N ° 2094700) with a dense fluidized bed located in its lower part.

The furnace works as follows.

The fuel is fed into the ablation return estrus and, together with the dispersion material, enters the firebox on the fluidized bed grate. The air heated in the air heater is pressurized under the fluidized bed grate, forming a fluidized bed of a mixture of fuel and dispersed material. Speed

SUBSTITUTE SHEET (RULE 26) the air in the cross section of the furnace is selected so as to provide pneumatic transport of small particles of dispersed material and burnable fuel particles to the exit window of the furnace, from where they enter the high-temperature cyclone. The solid phase of the flue gases separated in the cyclone through the non-mechanical valve returns to the furnace, to the boundary of the fluidized bed, and the cleaned flue gases are sent to the transition duct, convection shaft, air heater and then to the chimney. The return to the fluidized bed of unburned particles of fuel allows for sufficiently complete combustion.

The disadvantage of such furnaces is the low temperature pressure due to the low temperatures in the combustion chamber, which does not allow the generation of high parameters steam, which are necessary for the economical conditions of the boiler plant. A significant part of the existing furnaces has high-temperature combustion modes, but to ensure them it is necessary to finely grind the fuel. This leads to high operating costs, causes the danger of slagging and an increase in the content of NOx in the flue gases.

Known vortex low-emission furnace (RF patent 2067724), containing a combustion chamber with at least one tilted down burner mounted on its wall for supplying an air-fuel mixture, with a prismatic cold funnel having a slotted mouth formed by slopes of the walls of the lower part of the combustion chamber, and placed under the mouth of a cold funnel with a lower blast input device. The burner is made in the form of at least two channels arranged one above the other for supplying a fuel-air mixture. Each of the channels is equipped with a device for regulating the fuel-air ratio, and these devices are selected such that the ratio of the amount of air to the amount of fuel for the upstream channel is always greater than for the downstream channel. The method of operation of this furnace includes the supply of ground fuel mixed with air through both channels of the burner, and the air supply through the input device of the lower blast. Excess amount is supplied to the top of the combustion chamber

SUBSTITUTE SHEET (RULE 26) oxygen at a sufficiently high load of this zone by fuel particles coming from the upstream burner channel. This leads to a relatively high combustion temperature with an excess of oxygen in this zone and a fairly efficient afterburning of fuel. The loading of the middle part of the furnace is carried out mainly from the downstream channel with insufficient oxygen.

As a result of the interaction of the flow of the air-fuel mixture flowing from this channel and the air coming from the lower blast input device, a vortex zone is formed, the main part of which is characterized by an insufficient oxygen content and a relatively low maximum temperature and acts as a recovery zone. Fuel of a given fractional composition is supplied to each channel, which is ensured, for example, by using a dust concentrator. In this case, finely dispersed fuel is fed into the upstream channel, which manages to burn near this channel, creating the required temperature level, and into the downstream relatively coarse fuel, which successfully burns into vortex zone.

Thus, in the known furnace, multiple circulation of fuel particles occurs in the low-temperature reduction zone and, at the same time, afterburning of fine particles carried out from the vortex zone in the high-temperature, oxygen-enriched zone.

Such a furnace successfully operates when using dust preparation systems, i.e. subject to preliminary grinding of fuel using, for example, mill separators. Existing cooking systems usually provide a fineness of dust (residue on a R90 sieve) for lignite and shale 40-60%, for hard coal 15 = 40%. Obviously, to obtain such a fine fuel requires significant energy costs, the use of special expensive equipment. In addition, pulverized fuel is an explosive substance. In the event that, when a well-known furnace is used, large-sized crushed fuel is fed into the burners (usually the maximum size of a piece of fuel after the crusher is 35 mm, and for high-moisture fuels - up to 25 mm), the last

SUBSTITUTE SHEET (RULE 26) by the action of gravitational forces, it sinks into the lower part of the furnace, while the upper part of the furnace is practically unloaded with fuel, and the temperature in this upper part is not high enough for afterburning the particles of fuel carried out from the vortex zone. To ensure multiple circulation of large particles of fuel and the creation of a vortex zone requires a significant increase in the flow velocity of the lower blast air. This not only causes a decrease in economic characteristics, but also leads to a sharp increase in heat loss with mechanical burning, since fuel particles are dried during circulation, some are destroyed and carried out (fired) by a powerful stream of lower blast into the upper part of the furnace, before they burn out. Since the temperature in the upper part of the furnace is reduced, these particles cool down and stop burning. Standard, most common, design. The furnace involves the location of superheaters in the upper part of the furnace, and, since the convective surfaces described above turn out to be underloaded, it becomes difficult to ensure the rated temperature of superheated steam supplied to the turbine.

SUMMARY OF THE INVENTION

The objective of the present invention is to provide a method of operation of a vortex furnace, ensuring the operation of the vortex furnace when a coarse coarse fuel is fed into the furnace chamber while at the same time increasing the completeness of fuel combustion and increasing the heat load of convective surfaces.

Another objective of the invention is the creation of a swirl chamber, providing the implementation of the method.

The first task is solved by the fact that in the method of operation of a vortex furnace, including a combustion chamber having a vortex zone and an afterburning zone, a lower blast device and means for collecting a coal-ash mixture from exhaust gases, including supplying a fuel-air mixture and lower air to the furnace blast in accordance with the invention

SUBSTITUTE SHEET (RULE 26) the fuel-air mixture, including coarse crushed fuel, is fed into the vortex zone of the chamber, and an adjustable amount of coal-ash mixture trapped from the exhaust gases is returned to the selected zone of the internal space of the combustion chamber.

The coal-ash mixture, caught from the exhaust gases by an ash collector, is a mixture of ash and coke particles. The return of a controlled amount of coal-ash mixture to the combustion chamber allows to increase the residence time of unburned coal particles contained in the coal-ash mixture in the combustion chamber, which significantly increases the completeness of fuel combustion.

Fuel can be returned to the vortex zone. In this case, effective afterburning is ensured as a result of repeated circulation of especially large particles of fuel.

Fuel can be returned to the afterburning zone, which is most often located in the upper part of the combustion chamber. In this case, efficient loading of the inner space of the combustion chamber with a coal-ash mixture is ensured, which includes unburned but already prepared as a result of the previous cycle fuel particles. Due to the operation of returning unburned, but warmed up, dried, and partially destroyed fuel particles to the afterburning zone, the heat load of the corresponding convective surfaces is increased.

A vortex furnace, in which the method is implemented, in addition to the basic structural elements inherent in all vortex furnaces (a combustion chamber with a cold funnel formed by slopes of the lower parts of the walls of the combustion chamber, a lower blast device installed under the mouth of the cold funnel, an air-fuel burner tilted down mixtures mounted on the wall of the combustion chamber) includes, in accordance with the invention, an ash collector installed behind the combustion chamber and a circulating ash channel provided with means for transporting ablation ortovki. One end of the circulating ash channel communicates with the ash collector, and the other with the internal space of the combustion chamber.

SUBSTITUTE SHEET (RULE 26) b

The channel outlet is located in the area of the selected zone of the internal space of the combustion chamber.

In an eddy furnace of this design, practically unprepared fuel can be used, i.e. dust preparation operations are completely excluded, which significantly reduces the operating costs of such a furnace. This is ensured by the fact that, due to the presence of an ash collector and a circulating ash channel, unburned fuel particles are returned to the furnace, which can happen many times, up to complete burning. This achieves an increase in the completeness of fuel combustion and an increase in heat load.

It is advisable that the flow channel of the coal-ash mixture is installed in the ash channel.

It is advisable that the ash channel was equipped with a means for introducing the sorbent. The outlet of the circulating ash channel can be placed between the mouth of the cold funnel and the burner for supplying fuel. In this case, the fuel is returned to the vortex zone of the furnace. It is advisable to install an additional burner on the wall of the combustion chamber in the afterburning zone. In this case, the outlet of the circulating ash channel can be combined with the specified burner. When using this design, the fuel is returned to the afterburning zone, which ensures an increase in the load of heat transferring surfaces.

The best embodiment of the invention

The invention is illustrated in the drawing, which schematically depicts a swirl chamber made according to the invention and implementing the claimed method. As can be seen from the drawing, the vortex furnace includes a prismatic combustion chamber I with a cold funnel 2. The cold funnel 2 is formed by the slopes of the walls of the combustion chamber 1.

Under the mouth 3 of the cold funnel 2, a lower blast device 4 s is installed

SUBSTITUTE SHEET (RULE 26) an air nozzle 5. A burner 6. a downward inclined burner is installed on the wall of the chamber 1. Behind the combustion chamber 1, an ash collector 7 is installed along the flue gas. The ash collector 7 can be made in any known manner, for example, can be made in the form of a cyclone, or have a louvered structure. A branching ash channel 8 is installed between the ash collector 7 and combustion chamber 1, the inlet 9 of which communicates with the ash collector 7. Through the outlet openings 10a and 106, the ash channel communicates with the internal space of the combustion chamber: through the hole 10a with a vortex zone (indicated by “W” in the drawing ) and, through an additional burner 11 located on the wall of the combustion chamber 1, with a afterburning zone (indicated by “P” in the drawing). The gold channel 8 is equipped with a regulator 12 for the supply of coal-ash mixture. The controller 12 can be performed in any known manner, for example, in the form of a gate. Depending on the features used. fuel, the return of the ash-coal mixture can be carried out both in one of the zones (vortex or afterburning zone), and in both. The quantity of the mixture and the direction are regulated using the above-mentioned regulators 12 and 13.

The location of the additional burner is selected depending on the location of the afterburning zone, preferably at its highest temperature. . parts .. In the case of the invention as shown in FIG. 1, an additional burner 11 for feeding the coal-ash mixture is placed in the upper part of the combustion chamber 1, since with such a structural solution of the combustion chamber, the afterburning zone is located in the upper part of the furnace.

In other cases, for example in invert furnaces, the afterburning zone may also be located in the lower part. fireboxes.

If necessary, the ash channel can be equipped with means for feeding the sorbent (not shown in Fig.).

The furnace works as follows.

Fuel after crushing (without using a dust preparation system) is fed into the combustion chamber 1 through the burner 6. The size of the fuel particles is limited only by the geometric parameters of the burner 6 for supplying the fuel-air mixture.

SUBSTITUTE SHEET (RULE 26) Small particles burn in the exhaust pipe, larger ones are sent together with air to the lower part of the combustion chamber. As a result of the interaction of the fuel-air stream from burner b and the stream of lower blast emerging from the mouth 3 of the cold funnel 2, a vortex zone is formed in which, as a result of repeated circulation, large particles of fuel are burned. As it burns out and cracks, the fuel particles are crushed, become lighter, their windage increases, the speed of soaring decreases, and some of them, not having time to burn out, are carried out to the top of the furnace. At the exit of the combustion chamber 1, flue gases enter the ash collector 7, which collects particles of ash and unburned fuel. Trapped particles are accumulated in the hopper of the ash collector 7, and then the transport air flow through the ash channel 8 and the outlet openings 10a, 106 and the additional burner 11 are fed into the selected zone — into the afterburning zone through the burner 11 and the vortex zone through the hole 10a. Air quantity air speed the flow necessary for afterburning the supplied ash-coal mixture and preventing its removal by the lower blast air flow are regulated in the usual way.

An adjustable amount of the coal-ash mixture (product) captured is returned to the selected zone. ash collector 7. The amount of product returned to the selected zone is determined by the characteristics of the fuel (ash content, particle size, yield of volatiles, etc.) and the product (content of unburned carbon and fractional composition). The more unburned carbon and the smaller the particle size in the product, the greater the proportion of the product returned to the afterburning zone, and the larger the unburned particles, the greater the proportion of the product returned to the vortex zone.

When using fuel with low ash content, most of the coal-ash mixture caught by the ash collector is returned to the selected zone, and when using high-ash fuel, the proportion of the returned mixture is reduced.

If high-volatile fuels are used, product return to the furnace can be reduced.

SUBSTITUTE SHEET (RULE 26) The amount of returned mixture is regulated using the flow controller 13. Ensuring a high airflow velocity of the lower blast to prevent failure and maintaining large particles in the vortex zone is not particularly difficult, and since the inventive method and the described furnace design provide the return to the selected zone of almost all unburned particles and their subsequent complete afterburning, a high completeness of combustion is ensured fuel.

The returned particles are a mixture of ash and unburned particles of fuel (coke), and the fuel practically does not contain any volatile or water vapor, i.e., it enters the selected zone of the furnace as if it had undergone thorough preparation in dust-preparation devices. Thus, the inventive method of operation of a vortex furnace and a vortex furnace allow you to burn crushed fuel without the use of dust preparation devices, with a high degree of combustion, while ensuring the receipt of steam required high parameters.

In the event that it is necessary to use a sorbent, the inventive furnace has one more advantage: since, as is well known, far from all the sorbent supplied to the combustion chamber manages to react completely, unreacted particles are captured by the ash collector and returned to the combustion chamber together with entrainment. Thus, the sorbent is used repeatedly.

Industrial applicability

The claimed technical solution allows you to reconstruct existing furnace units, while increasing their environmental and economic characteristics.

As shown by experiments, this design can operate on various types of solid fuels, including shale. When conducting tests on existing boilers using the claimed technical solutions, coal fuel of the following fractional composition was used: residue on a sieve with a mesh size of 5 mm - from 5 to 15%, s

SUBSTITUTE SHEET (RULE 26) mesh sizes of 1 mm - 50-70%. The maximum piece size was 25 mm. Energy consumption for own needs (for traction, blasting, fuel supply) decreased from 9.18 kWh / tpa to 7.9 kWh / tpa, or by 15%.

SUBSTITUTE SHEET (RULE 26)

Claims

CLAIM 1. The method of operation of a vortex furnace, including a combustion chamber having a vortex zone and an afterburning zone, a lower blast device and means for collecting a coal-ash mixture from exhaust gases, comprising supplying a fuel-air mixture and lower blast air to the furnace, characterized in that the fuel-air mixture, including coarse crushed fuel, is fed into the vortex zone of the chamber, and an adjustable amount of the coal-ash mixture trapped from the exhaust gases is returned to the selected zone of the chamber’s interior space and I. 2. The method of operation of the vortex furnace according to Claim 1, in that the vortex zone is selected by the selected zone of the internal space of the combustion chamber. 3. The method of operation of the vortex furnace pop.l, characterized in that the afterburning zone is selected by the selected zone of the internal space of the combustion chamber. 4. A vortex furnace, including a combustion chamber with a cold funnel formed by slopes of the lower parts of the walls of the combustion chamber, a lower blast device installed under the mouth of the cold funnel, a burner for supplying a fuel-air mixture mounted on the wall of the combustion chamber, the furnace being equipped with an ash collector installed behind the combustion chamber, a circulation ash channel equipped with a means for transporting fly ash, with one end of the specified channel communicates with the specified ash collector, and the other with friction space of the combustion chamber, while an outlet opening of said channel is placed in the selected location area of internal space of the combustion chamber zones. 5. The vortex furnace according to claim 4, characterized in that a coal-ash mixture flow regulator is installed in the ash channel. SUBSTITUTE SHEET (RULE 26) 6. Vortex furnace according to claim 4, characterized in that the ash channel is equipped with means for introducing a sorbent 7. Vortex furnace according to claim 4 to _3, characterized in that the outlet of the circulating ash channel is located between the mouth of the cold funnel and the burner for supplying fuel, and the ash collector is selected from the condition of catching particles of more than 0.5 mm. 8. The vortex furnace according to claim 4, characterized in that an additional burner is installed on the wall of the combustion chamber in the afterburning zone, the outlet of the circulating ash channel is aligned with the specified burner, and the ash collector is selected from the conditions for catching particles of more than 0.5 mm. SUBSTITUTE SHEET (RULE 26)