RU2022624C1 - Method of cleaning and removing fuel gases - Google Patents

Abstract

FIELD: removal of fuel gases. SUBSTANCE: optimal water discharge for atomizers 14 and 15 is measured when boiler unit operates at mean mode of load. Then gate 17 is set in such a manner that temperature detectors 16 indicate optimal temperature. When boiler unit changes to complete mode of load, temperature of gases to be removed increases in gas duct 10. Command for opening valve 19 is received for increasing water discharge and for opening gate 17 for increasing supply of heated air. In this case two-flare atomizer 14 has hollow flares in Venturi tube, and two-flare atomizer 15 has contrary hollow flare and direct volumetric flare. EFFECT: improved efficiency. 1 dwg

Description

 The invention relates to methods for cleaning and removal of flue gases, mainly from boiler units, but can also be used in other industries, for example in the steel industry.

 A known method of purification and removal of flue gases from a boiler operating from coal combustion, in which flue gases are sequentially treated with water in an ash collector with Venturi pipes, is separated in droplet eliminators, and then through exhaust fans, suction and pressure ducts are led into an exhaust pipe. A sufficiently high efficiency of ash collection in the known method is ensured mainly through the use of a new technologically and constructively type droplet eliminator, namely a wet, multi-lead, annular, equipped with a cylindrical insert. Such a droplet eliminator has a high material consumption and cost, and also requires increased water consumption for film irrigation of the outer and inner surfaces of the cylinders, which serves as an obstacle to its widespread adoption, especially when reconstructing the flue gas treatment system of an existing boiler unit, when it is necessary to dismantle existing droplet eliminators beforehand.

 The closest to the proposed technical essence and the achieved result is a method of cleaning and exhausting flue gases, which includes sequentially treating the flue gas with water in an ash collector with venturi pipes, separating it in droplet eliminators, mixing with heated air at the outlet of the latter and exhausting gas through smoke exhausters that suction and pressure ducts in the exhaust pipe.

The known method provides effective cleaning of flue gases from dust, in particular due to the organization of more efficient mixing of gas flows, the use of series-connected high-speed dust concentrators in the form of cyclones and additional dust coagulation at the inlet and outlet of the venturi. However, the advantages of the known method are fully manifested only when cleaning and removing flue gases from ferrous metallurgy units. Known attempts to introduce a similar technological scheme for the cleaning and removal of flue gases for boilers (for example, at the Irkutsk TPP-10), which works on the combustion of coal and equipped with an air heating system, were unsuccessful. The reasons for this are as follows: firstly, the boiler operates in various, significantly different load conditions, for example, from 60 to 100% of its capacity, and therefore it is not possible to manually perform such adjustment of shut-off and control valves, in which the entire width a range of changes in the operation mode of the boiler unit would ensure the simultaneous fulfillment of two conditions, namely, achieving a degree of gas purification from ash not lower than the specified one and maintaining a given optimal temperature of the exhaust gases in n open gas ducts, in which condensate does not form in the latter, as well as in the chimney, and, in addition, the necessary dispersion of the exhaust gases in the upper atmosphere is ensured;
secondly, the burning of coal is inevitably accompanied by the formation of ash, and the ash content of coal from some deposits is very significant. The negative role of ash is manifested both in connection with its abrasive properties, and in connection with the property, when in contact with water, to form calcium compounds, which tend to be deposited on the walls. Therefore, the use of the known method for a boiler burning coal will inevitably cause, on the one hand, accelerated abrasive wear of serially connected cyclones and associated pipelines, and on the other hand, can lead to the formation of strong deposits, for example, in the zone of ejection of zologase concentrate and inside the droplet eliminator, in the installation zone of the cyclone. All this will ultimately reduce the efficiency of cleaning and removing gases from the boiler.

 The purpose of the invention is to increase the efficiency of purification and removal of gases from a boiler unit operating on coal combustion and equipped with an air heating system, in a wide range of changes in its operation mode.

 This goal is achieved due to the fact that in the known method of cleaning and exhausting flue gases, including sequential treatment of flue gases with water in an ash collector with venturi pipes, separation in droplet eliminators, mixing with heated air at the outlet of the latter and exhaust gas through smoke exhausters, suction and pressure gas ducts into the exhaust pipe, water is centrally sprayed in each venturi in succession in four zones, in the first zone - towards the gas flow with the placement of the border of the irrigation zone within two-thirds of the length onfusor from the beginning of the neck, in the second zone - along the gas flow with the location of the border of the irrigation zone within the neck, in the third zone - towards the gas flow with the location of the border of the irrigation zone in the diffuser at a distance from the neck end of 0.4-0.8 of the neck diameter , in the fourth zone - in the diffuser with the irrigation zone border placed at a distance from the neck end of at least one of its diameter, in the first three zones water is sprayed in the form of hollow torches, in the last zone - in the form of a volumetric torch, while the water flow for all s n and the flow rate of preheated air continuously and automatically synchronously adjusted up or down in magnitude of deviation, respectively, in higher or lower gas temperature in the pressure ducts optimal.

 The drawing schematically shows a device for implementing the proposed method.

 The scheme includes boiler 1, gas duct 2, confuser 3, neck 4 and diffuser 5 of the Venturi pipe, gas duct 6, centrifugal drop catcher 7, suction duct 8, exhaust fan 9, pressure duct 10, exhaust pipe 11, air heating system 12 of boiler 1, duct 13, two-flare nozzle 14 mounted along the axis of the confuser 3 and forming oppositely directed hollow flares, two-flare nozzle 15 installed along the axis of the diffuser 5 and forming oppositely directed torches, one of which is hollow and the other is voluminous and smoke is directed along the direction O gas, the temperature sensors 16, slide valve 17, check valves 18, valve 19, actuator 20, an electronic temperature controller 21.

 The method is as follows. Empirically determine the position of the two-nozzle nozzles 14 and 15 on the axes of the confuser 3 and the diffuser 5 of the venturi so that the boundaries of all irrigation zones from four flares with minimum and maximum water flow are on the walls of the venturi within the limits indicated above. In this case, there should not be such a situation when a torch does not form the boundaries of the irrigation zone on the wall of the Venturi pipe, since this would mean that part of the water used to form the corresponding torch is not used efficiently because not all of the smoke gas in this case is irrigated. It has been established that if in the confuser 3 the boundary of the irrigation zone of the first torch of the first zone is at such a distance from the neck 4 that exceeds two thirds of the length of the confuser 3, this will inevitably lead to the formation of ash on the wall of the confuser 3 in its middle part. If the boundary of the irrigation zone of the second torch extends beyond the neck 4, then this will significantly affect the operation of the installation. Moreover, if the border of the irrigation zone is placed within confuser 3, the gas flow rate will decrease, which will entail a decrease in stiffness (speed of the water droplets making up the torch) and the first torch, which will not reach the walls of confuser 3 and, accordingly, the entire volume of passing gas will be irrigated by a sprayed torch, resulting in reduced ash collection efficiency. If the boundary of the irrigation zone of the second plume is placed within the diffuser due to the high gas flow rate, at least a large part of the plume will not reach the walls of the diffuser, which will also entail a reduction in the efficiency of ash collection.

 If in the third irrigation zone located within the diffuser 5, the boundary of the irrigation zone will be less than 0.4 of its diameter from the neck 4, then due to the high gas flow velocity not all water droplets of the torch will reach the wall of the diffuser 5, which is equivalent to reduce the amount of ash particles caught. If, due to insufficient pressure in the nozzle, the boundary is at a distance of more than 0.8 of its diameter from the neck 4, this will adversely affect the stiffness of the torch and lead to a decrease in the distribution density of the water droplets constituting it, which will ultimately reduce the efficiency of ash collection.

 If in the fourth irrigation zone, also located within the diffuser 5, the boundary of the irrigation zone is shifted to the neck 4 by a distance of less than one of its diameter, then again, due to the high velocity of the gas flow, the volumetric plume will not fully open and irrigation density will not be uniform over the entire cross-sectional area, which will accordingly reduce the efficiency of gas purification.

 When the boiler unit 1 is in the average load mode, for example, 75% of the power, the optimal water flow rate for nozzles 14 and 15 is determined experimentally. The optimal flow rate will correspond to the minimum one that provides the set degree of gas purification from ash, for example 98.5%. After that, the gate 17 is installed so that the temperature sensors 16 in the pressure duct 10 record the optimum temperature, determined by the known method described in the literature, or based on the operating experience of boiler unit 1. Then, the boiler unit 1 is transferred to another load mode, for example 100% power. This will lead to an increase in the ash concentration, as well as to an increase in the temperature of the exhaust gases in the pressure duct 10, depending on the temperature deviation from the optimum temperature in the electronic temperature controller 21, a command is issued to the actuator 20, automatically opening the valve 19 to increase the flow rate of water and the gate 17 for increase the consumption of heated air from the air heating system 12.

 The degree of opening of the valve 19 is synchronized with the degree of opening of the gate 17, based on the fact that the increased flow rate of water to the nozzles ensures the degree of purification of flue gases having a higher ash concentration (98.5%), and the increased flow rate of heated air mixed with the exhaust gases in the upper part of the droplet eliminator 7, completely compensates for the overcooling of flue gases in the venturi, which will happen when the sensors 16 record a predetermined optimal temperature.

 After that, the boiler unit 1 can be operated in a wide range of changes in its operation mode while maintaining high efficiency of cleaning and removal of flue gases.

Claims (1)

 METHOD FOR CLEANING AND DISCHARGE OF SMOKE GASES, including sequentially treating flue gases with water in an ash collector with venturi pipes, separating them in droplet eliminators, at the outlet of which mixing flue gas with heated air and exhausting gas through smoke exhausters, suction and pressure flues into an exhaust pipe, characterized in that , in order to improve the efficiency of cleaning and removing gases from a boiler that runs on coal combustion and is equipped with an air heating system in a wide range of changes in its operating mode, I spray water centrally t in each Venturi pipe sequentially in four zones, in the first zone towards the gas flow with the location of the irrigation zone border within 2/3 of the length of the confuser from the beginning of the neck, in the second zone - along the gas flow with the location of the border of the irrigation zone within the neck, in the third zone - towards the gas flow with the location of the border of the irrigation zone in the diffuser at a distance from the end of the neck 0.4 - 0.8 of the diameter of the neck, in the fourth zone - in the diffuser with the location of the border of the irrigation zone at a distance from the end of the neck, at least more than one diameter, in the first three zones, water is sprayed in the form of hollow torches, in the last zone - in the form of a volumetric torch, while the flow rate of water for all zones and the flow rate of heated air are continuously automatically and synchronously adjusted to a greater or lesser extent in terms of deviation, respectively up or down the temperature of the gases in the pressure ducts from the optimum.