RU2543648C1 - Plasma pulverised coal burner - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: plasma pulverised coal burner consists of two in-line coaxially located tubes of different diameter, internal tube 1 of the first stage and external tube 2 of the second stage, with electric-arc plasmotron 4 built in the end face of internal tube 1. In addition, the burner is provided with two individual adjustable air supply ducts: one for supply of additional air to internal tube 1 of the first stage, and the second one for supply of additional air to external tube 2 of the second stage. Air supply ducts are made in the form of tubes 6 and 7 with a tangential inlet, which are installed perpendicular to the in-line tubes: internal 1 and external 2, and rigidly attached to them. Dampers 18 and 19 are installed at the outlet of feeders 10 and 11 with a possibility of control of air mixture flow rates. Electric-arc plasmotron 4 is installed along the horizontal axis of internal tube 1.

EFFECT: invention allows controlling an excess air coefficient of a pulverised coal mixture in separated ducts for supply of a pulverised-coal mixture due to supply of supplementary air to the same ducts and controlling a process by electrothermochemical preparation in a burner.

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Description

The invention relates to energy and can be used for kindling boilers and stabilizing the combustion of a pulverized coal torch (backlight) in boilers, for example, energy and housing boilers, as well as for igniting finely divided solid fuels with preliminary electrothermochemical preparation (ETCP).

A device for oil-free kindling of a coal-fired boiler is known, which is a direct-flow type ignition burner consisting of an ETHP cylindrical chamber with a nozzle located on its side surface and a plasmatron located on this nozzle for introducing a plasma flow into this chamber. The design of the ETHP chamber consists of two coaxial pipes (internal stainless steel), the space between which is filled with a heat-resistant refractory heat-insulating material (chamotobeton, carborundum, etc.) called a muffle. The direct untwisted flow of the mixture arriving in the direction of the longitudinal axis of the chamber interacts with the low-temperature plasma stream introduced through the pipe perpendicular to the axis of the chamber. The air mixture in contact with the plasma stream heats up and ignites, heating the rest of the air mixture in the volume of the muffle chamber. The aerosol mixture heated to a temperature of self-ignition then enters the combustion chamber, where its combustion continues when mixed with secondary air. In this design, the residence time of the particles of coal dust in the chamber ECP is minimized and is determined by the linear velocity of the incoming flow of the air mixture. This installation has proven itself when using highly reactive coals (see Zhukov MF et al. Low-temperature plasma, vol. 16, Plasma oil-free kindling of boilers and stabilization of the combustion of a pulverized coal torch. - Novosibirsk: Nauka, 1995, p. 83-86, fig.3.5b).

The disadvantage of this installation is the impossibility of effectively regulating the process of ECP; making a muffle chamber is technically difficult and relatively expensive; the residence time of the coal dust particles in the ETC chamber is minimized and is determined by the linear velocity of the air mixture flow along the axis of the burner.

A device is known as part of a plant for implementing the method of oil-free kindling of an energy boiler and illuminating a pulverized coal torch, which provides for the separation of part of the mixture from the general stream, electrothermochemical preparation, followed by mixing the products of this process with the rest (main) part of the mixture in the furnace space. At the inlet of the burner, a device is installed to control two flows of aerosol mixture: the first - directed into the inner pipe for electrothermochemical preparation and the second - sent to the annulus, free of refractory heat-insulating material, for heat treatment and cooling of the inner pipe. In this regard, the inner pipe can be made of ordinary steel, which together with the rejection of the muffle reduces the cost of this type of burner and simplifies the manufacturing technology in this part of the burner (see patent RU No. 2180075, IPC F23D 1/00, H05H 1/32 , published on February 27, 2002, Bull. No. 6).

However, the presence of a nozzle for introducing the plasma flow increases the aerodynamic resistance to the flow of the air mixture in the annulus, and the presence of a device for regulating two flows of the air mixture inside the burner significantly complicates the design of this type and the technology of its manufacture.

Various variants of plasma dust-coal burners are also known, which are based on the idea of creating a method of plasma ignition of fuel using these burners, which provide reliable and stable plasma ignition with the minimum possible electric power supplied to the plasma torches. The pulverized coal mixture is fed into the thermochemical preparation chamber of the fuel through a swirling device or along a dust pipe bent along an arc of a circle, the center of which is located on the side opposite to the plasma torch. In this case, a region with an increased dust concentration is formed near the inner surface of the chamber for thermochemical fuel preparation, and a plasma jet is fed into the chamber in the direction along the radius of the transverse vertical section of the chamber or along the radius of the cross section separated from the transverse vertical section by an angle of no more than 15 ° (cm Patent RU No. 22210032, IPC F23D; F23Q, publ. 08/10/2003).

The disadvantages of these plasma pulverized coal burners are the bulkiness of the structures due to the presence of snails for supplying separated streams of pulverized coal mixtures, as well as snails for supplying secondary air, which greatly limits the possibility of incorporating such burners into the fuel supply system of boilers in operation, for example, E- type boilers 160-1.4-250KT.

Closest to the claimed invention in terms of technical nature and the achieved result is a vortex burner comprising a snail of secondary air, a snail of air mixture and coaxially arranged secondary air pipes, air mixture and the inner pipe of the air mixture. The internal mixture mixture tube is made in the form of a muffle, the length of which is 0.4-0.6 of the length of the mixture mixture pipe, with a plasma torch integrated in the end face and having a hole opposite the flame zone of the plasma torch, the terminal part of the mixture being 0.7 -0.8 inside lengths are studded and lined with refractory and wear-resistant material. The implementation of the internal mixture mixture tube in the form of a muffle with a plasmatron integrated in its end allows thermochemical preparation of pulverized coal for burning before it flows into the furnace volume, which in turn made it possible to refuse to use fuel oil for the kindling and stabilization of combustion. The length of the muffle, comprising 0.4-0.6 of the length of the mixture pipe, is optimal and provides the necessary degree of electrothermochemical preparation of the fuel. With a decrease in length, the efficiency of ETCPT decreases, and a "muffle" effect does not occur. With an increase in the length of the muffle, the mixing conditions of the main flow of the air mixture and the air mixture passing through the muffle deteriorate, as a result of which not all air mixture is subjected to thermochemical preparation. The lining of the inner surface of the mixture pipe by 0.7-0.8 of its length with a refractory and wear-resistant material is chosen so that it overlaps the muffle by half its length, which is sufficient to protect the mixture pipe from exposure to high temperatures. The presence of a hole in the muffle, covered by a gate, provides an controlled supply of aerosol particles to the combustion zone of the plasma torch, where it is heated and partially gasified (see patent RU No. 2171429, MGZH F23D, publ. July 27, 2001).

The disadvantages of the burner are: the presence of two snails, which limits the possibility of embedding such burners in the fuel supply system of boiler units; the impossibility of an efficient process regulation process for ECP and the need to manufacture a muffle chamber, which is a complex technological and expensive operation.

The problem solved by the invention is to expand the ability to integrate the proposed burner design into existing fuel systems of boilers of existing power plants, to regulate the coefficient of excess air of a coal-dust mixture, to establish optimal EHPT modes for various grades of coal and their mixtures.

The technical result of the invention is the ability to control the coefficient of excess air of the pulverized coal mixture in the separated supply channels of the pulverized coal mixture by supplying additional air to these channels, which makes it possible to regulate the process of ECPC in the proposed burner design and thereby affect its efficiency.

The technical result is achieved by the fact that a plasma pulverized coal burner, consisting of two coaxial, coaxially arranged pipes of various diameters, internal and external, with an electric arc plasma torch integrated in the end of the internal pipe on the flange, according to the invention is additionally equipped with two separate adjustable air supply channels: one for supplying additional air to the inner pipe of the first stage, and the second to supply additional air to the external pipe of the second stage, which are made of pipes with tangential inlet and installed perpendicular to the coaxial pipes: external and internal, and are rigidly connected to them, and the arc plasma torch is installed along the horizontal axis of the inner pipe, in addition, at the output of the feeders, each of which is installed above the pipe inlet with a tangential inlet, gates are installed with the possibility regulation of air mixture consumption, consisting of coal dust and air.

Distinctive essential features of the claimed invention are:

- the implementation of two separate adjustable air supply channels: one to supply additional air to the inner pipe, the other to supply additional air to the outer pipe, allows you to adjust the coefficient of excess air of the coal-dust mixture due to the additional air supply to the inner and outer pipes of the air mixture;

- the implementation of the air supply channels in the form of pipes with a tangential inlet, which are installed perpendicular to the coaxial pipes: internal and external, and rigidly connected to them, makes it possible to adjust the coefficient of excess air of the coal-dust mixture by additional air supply through pipes with a tangential entrance to the internal and external pipes ;

- the tangential feed of the mixture into the inner tube of the first stage creates a swirling swirl flow, thereby increasing the intensity of the interaction of the pulverized coal mixture with the plasma torch and, as a result, the efficiency of ECPT in the plasma torch;

- due to the presence of the above design differences, the principle of separation of the air mixture stream into two remains, and the main purpose of the air mixture stream directed to the outer pipe of the second stage is to cool the internal pipe of the first stage, where the main process of ECPT occurs, and the air mixture in the space formed by the internal the surface of the outer pipe and the outer surface of the inner pipe, where the first and second stage air mixtures are mixed, undergoes thermochemical preparation;

- installation of an arc plasma torch along the horizontal axis of the first stage inner pipe ensures efficient electrothermochemical treatment of a part of pulverized coal fuel mixtures entering the inner pipe of the first stage of the burner tangentially to the plasma torch of the plasma torch (see Fig. 1, item 5), while the plasma torch of the plasma torch extends along the axis of the inner tube of the first stage, which eliminates the possibility of contact of the plasma torch with the walls of the inner tube and its overheating and burning;

- installation of feeders in the form of bunkers with a pulverized coal mixture, each of which is located above the inlet of the pipes with a tangential inlet, provides the necessary supply of coal dust during the ignition of the boiler unit or stabilization of the combustion of the pulverized coal torch in the boiler furnace, in addition, if necessary, it allows the use of finely dispersed coal waste (dust, screening) in the first stage, and in the second stage - larger fractions of coal after crushing or grinding;

- the installation of gates at the output of the feeders provides the ability to control the flow of coal dust through the first and second stages of the plasma torch and, accordingly, to establish the optimal concentration of air mixture flows by controlling the flow rate of the air supply (see figure 1, pos. 8 and 9), which in turn allows you to adjust the length, temperature and intensity of the combustion of the pulverized coal torch in the furnace of the boiler, that is, the flow of air mixture, passed ETCP in a plasma torch (see figure 1, item 22).

Thus, the proposed set of design features allows to achieve a technical result, which consists in the possibility of controlling the coefficient of excess air of the pulverized coal mixture in two separate adjustable channels for supplying the pulverized coal mixture in them and supplying additional air to these channels, which makes it possible to regulate the process of ECPT in these burners and most affect its effectiveness.

From the prior art for scientific and technical literature and patent documentation, the applicant is not aware of technical solutions containing a combination of features similar or equivalent to those claimed, set forth in the claims of the present invention.

The essence of the claimed invention is illustrated in the drawing and photo, in which:

figure 1 schematically shows the device of a plasma pulverized coal burner;

photo 2 shows the plasma pulverized coal burner in working condition with the exit of the pulverized coal torch from the burner.

The proposed design of a plasma pulverized coal burner consists of two coaxially arranged pipes of various diameters: a metal inner pipe 1 with a diameter of, for example, 220 mm and a length of 1.5 m and a metal outer pipe 2 with a diameter of, for example, 270 mm and a length of 2.5 m. Inside the outer pipe 2 coaxially mounted metal inner pipe 1. The inner pipe 1 is the first stage of the burner, and the outer pipe 2 is the second stage of the burner. A flange 3 is installed at the end of the inner pipe 1 of the first stage, on which an electric arc plasma torch 4 of the EDP-212 type is mounted and fixed along the horizontal axis of the inner pipe 1, so that the plasma torch 5 of the electric arc plasma torch 4 is directed along the horizontal axis of the inner pipe 1 of the first stage (see Fig. 1). The inner pipe 1 of the first stage is made of ordinary steel. In the plasma pulverized coal burner, two separate adjustable channels for supplying air are additionally made: one for supplying additional air to the inner pipe 1 of the first stage, and the second to supply additional air to the external pipe 2 of the second stage. The channels for supplying additional air are made in the form of pipes 6 and 7 with a tangential inlet, which are installed perpendicular to the coaxial pipes: internal 1 and external 2. The pipes 6 and 7 with a tangential inlet are rigidly connected, for example, by welding with holes (not shown in Fig. 1 ) made in coaxial pipes: internal 1 and external 2, so that additional air and coal dust are fed tangentially by two flows into the coaxial pipes: internal 1 and external 2. In this case, the channel for supplying additional air and a coal-dust mixture, The pipe from the pipe 6 with a tangential inlet is a fuel line of the first stage, and the channel for supplying additional air and a coal-dust mixture made in the form of a pipe 7 with a tangential inlet is a fuel pipe of the second stage.

The supply of air mixtures 8 and 9, consisting of coal dust and air, into the inner pipe 1 of the first stage and the outer pipe 2 of the second stage is carried out through additionally installed separate adjustable pipes 6 and 7 with a tangential inlet. In this case, the flow of mixture 8 of the first stage is supplied through a pipe 6 with a tangential inlet, and the flow of mixture of the second stage 9 is supplied through a pipe 7 with a tangential inlet. Above the pipes 6 and 7 with a tangential inlet, feeders 10 and 11 are installed in the form of silos with a pulverized-coal mixture. The supply of additional air to the inner pipe 1 of the first stage and to the outer pipe 2 of the second stage is carried out through pipes 6 and 7 with a tangential inlet through the air supply nozzles 12 and 13, respectively, for the first and second stages, and the pulverized coal mixture from the feeders 10 and 11 is fed through nozzles 14 and 15 for introducing coal dust, respectively, of the first and second stage, into pipes 6 and 7 with a tangential inlet and then into the inner pipe 1 of the first stage and into the outer pipe 2 of the second stage. At the entrance of the nozzles 12 and 13 of the air inlet, respectively, for the first and second stages, there are installed gates: an air gate 16 of the first stage and an air gate 17 of the second stage. At the exit of the feeders 10 and 11, the sliders 18 and 19 are installed with the possibility of regulating the flow rate of the mixture. To regulate the coefficient of excess air in the supplied flows of mixtures 8 and 9, consisting of a pulverized coal mixture and air, tubes 6 and 7 with a tangential inlet for supplying primary additional air to them are additionally installed in the burner design.

The flow of aerosol mixture 20 of the first stage, which has undergone a plasma treatment in the inner pipe 1, consists of hot coal particles in the form of sparks and combustible gas released from coal particles during their interaction with plasma at a temperature of 1200-1500 ° C. In the space formed by the inner surface of the outer pipe 2 and the end part of the inner pipe 1, the flows 20 and 21 of the mixture of the first and second stages are mixed. The total flow of aerosol mixtures 22, which passed ETCP in a plasma pulverized coal burner, in the form of a burning torch leaves the external pipe 2 of the second stage into the furnace of the boiler (the latter is not shown in Fig. 1), where it continues to burn intensively with excess air.

In addition, the device has a power source 23, which is a thyristor three-phase converter (rectifier) AC to DC. The power source 23 has a power cable 24 with a plus sign and a power cable 25 with a minus sign, which are connected to an electric arc plasma torch 4.

A plasma pulverized coal burner operates as follows.

An electric arc plasma torch 4 is launched from a power source 23 through power cables 24 and 25. Coal dust from a feeder 10 is supplied by air to the inner pipe 1 of the first stage, on which an electric arc plasma torch 4 is installed, up to 20% of the total dust flow through the burner. Coal dust is fed tangentially, spirals along the inner wall of the pipe 1 and enters the plasma torch 5, burning along the horizontal axis of the inner pipe 1, where it partially ignites, and the plasma torch 5 is pulled into the outer pipe 2 - the first stage. After this, coal dust up to 80% of the total flow through the burner is also tangentially supplied by air from the second feeder 11, it is spirally twisted along the inner wall of the outer pipe 2 of the second stage of a larger diameter than the inner one. The bulk of the dust-air mixture, meeting with the first stage plasma dust-burning plasma torch 5, partially ignites, and the burning plasma torch 5 exits the second-stage external pipe 2 to the boiler furnace (the latter is not shown in Fig. 1), where, when there is an excess of air, the dust-coal is completely ignited a plasma torch 5 exiting the burner in the form of an output of a total flow of aerosol mixture 22. The regulation of the flow of additional air and pulverized coal dust, their ratio (concentration in the burner) is performed by the sliders 18 and 19 installed at the output of the feeders 10 and 11. The current control on the electric arc plasma torch 4 from 100 to 300 A and voltage from 200 to 300 V is made at the source power supply 23, which rectifies the alternating current into direct current. Joint regulation of the flow of air and coal through the burner, current and voltage on the electric arc plasma torch 4 allows you to adjust the length and temperature of the pulverized coal torch 22 at the outlet of the burner and, accordingly, adjust the power of the burner.

The air mixtures 8 and 9, controlled by the shutters 18 and 19, consisting of a pulverized coal mixture and air, through the pipes 6 and 7 with a tangential inlet enter the inner pipe 1 of the first stage and the outer pipe 2 of the second stage tangentially. The aerosol mixture stream (coal dust + air) entering the inner pipe 1 of the first stage is subjected to electrothermochemical preparation by plasma, and the aerosol mixture (pulverized coal + air) entering the outer pipe 2 of the second stage undergoes thermochemical preparation by removing heat from the outer wall inner pipe 1. In the space formed by the inner surface of the outer pipe 2 of the second stage and the end part of the inner pipe 1 of the first stage, there is a mixture of flows 20 and 21 of the mixture of the first and second stages. To control the coefficient of excess air in the supplied flows of the air mixture through the pipes 6 and 7 with a tangential inlet, primary additional air is supplied through the nozzles 12 and 13 of the air intake of the first and second stage, respectively.

The ability to control the coefficient of excess air of the pulverized coal mixture in additionally installed separate adjustable channels made in the form of pipes 6 and 7 with a tangential inlet for supplying the pulverized coal mixture from feeders 10 and 11 through nozzles 14 and 15 for introducing coal dust of the first and second stages, respectively, due to supplying additional air to these channels through the nozzles 12 and 13 of the air intake of the first and second stages, respectively, allows you to adjust the process EHPT in the proposed design of a plasma dust an oil burner and thereby affect its efficiency.

The present invention is a plasma pulverized coal burner - compared with the prototype (see patent RU No. 2171429, IPC F23D, publ. 07.27.2001) has the following advantages:

- simplification of the design of the device and the dimensions of the plasma pulverized coal burner, and in the prototype a pile of two snails;

- inside the plasma pulverized coal burner, electrothermochemical fuel preparation is carried out with the regulation of the excess air coefficient in the supplied air mixture flows, which allows optimizing the process of EHCP and integrating it into the existing fuel supply systems of the boilers of operating power plants;

- the manufacture of the inner pipe of the first stage of ordinary steel reduces the cost of manufacturing the burner, and in the prototype used high-temperature heat-insulating material for the lining of the inner pipe;

- the design of the plasma vortex burner allows you to fully automate the control processes of the air supply, coal dust, temperature and the length of the pulverized coal torch in the boiler furnace.

Claims (1)

A plasma dust-coal burner, consisting of two coaxial, coaxially arranged pipes of different diameters, an inner pipe and an outer pipe, with an electric arc plasma torch built into the end of the inner pipe on the flange, characterized in that the burner is additionally equipped with two separate adjustable air supply channels: one for supplying additional air into the inner pipe of the first stage, and the second to supply additional air to the outer pipe of the second stage, while the channels are made of pipes with tangential the input and are installed perpendicular to the coaxial pipes: external and internal, and are rigidly connected to them, and the arc plasma torch is installed along the horizontal axis of the internal pipe, in addition, at the output of the feeders, each of which is installed above the pipe inlet with a tangential inlet, there are sliders with the possibility of regulation air mixture costs consisting of coal dust and air.

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