A rotary air preheater with steam soot blowing device

Abstract

The present invention relates to a rotary air preheater with a steam soot blowing device, comprising a rotor, wherein the rotor is provided with flue gas, primary air and secondary air compartments, a heat exchange element and a steam soot blowing device, wherein the steam soot blowing device is arranged in the cold secondary air inlet air duct of the secondary air compartment, and the steam soot blowing device comprises a steam soot blower, a gun barrel and a nozzle assembly, wherein the nozzle assembly comprises a first nozzle assembly and a second nozzle assembly, wherein in the rotation direction of the rotor, the first nozzle assembly is located upstream of the second nozzle assembly, and the first nozzle assembly comprises a throttling tube and a nozzle; the second nozzle assembly comprises a distribution pipe and a nozzle, and the nozzle jet velocity is less than the nozzle jet velocity. The present invention improves the steam purging conditions, eliminates the influence of the backflow obstruction on the steam jet, improves the purging effect of the ammonium bisulfate deposited ash, reduces the hardness and bonding strength of the deposited ash, improves the shearing and flushing effect of the downstream high-speed and low-temperature steam jet on the deposited ash, and improves the removal effect of the ammonium bisulfate deposited ash.

Description

Technical Field

[0001] The invention relates to a rotary air preheater, in particular to a rotary air preheater with a steam soot blowing device. Background Art

[0002] The conventional rotor rotary air preheater for coal-fired power station boilers is divided into flue gas compartments, secondary air compartments and primary air compartments in the circumferential direction. The rotor consists of two layers of flat plate heat exchange elements. The rotation process passes through the flue gas compartments, secondary air compartments and primary air compartments in turn, and performs periodic heat storage and heat release processes: in the flue gas compartments, the high-temperature flue gas passes through the heat exchange elements from top to bottom, the flue gas heat release temperature decreases, and the heat storage temperature of the heat exchange elements increases; in the secondary air compartments and primary air compartments, the cold secondary air and cold primary air pass through the heat exchange elements from bottom to top, the cold air heat absorption temperature increases, and the heat release temperature of the heat exchange elements decreases. In the flue gas compartments, the ammonia escaping from the upstream SCR denitrification system and the SO3 in the flue gas are easy to form ammonium bisulfate deposition ash on the surface of the heat exchange elements at the cold end of the air preheater rotor, blocking the flue gas channels between the heat exchange elements.

[0003] In order to keep the passages between the heat exchange elements of the air preheater smooth, steam soot blowers are usually arranged above the heat exchange elements at the hot end of the flue gas compartment rotor and below the heat exchange elements at the cold end of the rotor. The steam jet is used to intermittently flush the surface of the heat exchange elements online, and the deposited ash on the surface is blown off by shearing. In the flue gas compartment, the flue gas flows through the heat exchange elements from top to bottom. The steam jet of the hot end steam soot blower blows downward downstream, and the steam jet of the cold end steam soot blower blows upward countercurrently. The steam pressure in the soot blower gun barrel is about 0.8-1.07MPa, and the temperature is about 300-350℃.

[0004] In order to improve the blowing effect of ammonium bisulfate ash deposits between the heat exchange elements of the air preheater, the steam soot blower has tried a variety of technical improvements:

[0005] Referring to the patent with publication number CN208566739, a rotary air preheater high-pressure water online cleaning device is disclosed, which contains high-pressure water and steam together to form a dual-fluid sootblower, and can separately spray high-pressure water and steam for sootblowing.

[0006] Refer to the patent publication number CN204881327 which discloses a steam sootblowing device for a rotary air preheater and the paper "Optimization of Blowing Trajectory and Operation Mode of Air Preheater Sootblower", both of which propose a rake-type multi-nozzle sootblower based on a single-tube nozzle to increase the residence time of the rotor heat exchange element passing through the steam blowing section.

[0007] Referring to the patent with publication number CN111623365, a rotary air preheater refined automatic sootblowing system and sootblowing control method is disclosed, an online monitoring method for dirt and blockage of heat exchange elements is proposed, and the steam sootblower is automatically put into operation according to the degree of dirtiness.

[0008] In the above-mentioned air preheater steam soot blower technology, CN204881327 increases the residence time of the steam purge section on the circumference of the air preheater rotor heat exchange element, but the effect of conventional steam soot blowers is limited for highly viscous deposited ash containing ammonium bisulfate, mainly because the jet steam still retains a central jet velocity of 80 to 120 m / s when reaching the surface of the heat exchange element, but due to the entrainment of the surrounding low-temperature flue gas, the purge steam temperature is reduced to about 100 to 150°C. In the face of highly viscous deposited ash containing ammonium bisulfate, even if the steam jet has a strong scouring and shearing effect, due to the low temperature of the jet steam, it is impossible to reduce the strength of the deposited ash by heating and gasifying the ammonium bisulfate in the deposited ash, which seriously reduces the purge effect of the steam soot blower on the deposited ash containing ammonium bisulfate. Summary of the invention

[0009] The object of the present invention is to provide a rotary air preheater with a steam soot blowing device, which firstly heats and gasifies the ammonium bisulfate in the ash deposited on the surface of the heating element by low-speed high-temperature steam, and then uses high-speed low-temperature steam to shear and remove the loose deposited ash that does not contain ammonium bisulfate.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] A rotary air preheater with a steam soot blowing device, comprising a rotor rotating around a central sleeve, wherein a flue gas compartment, a primary air compartment and a secondary air compartment are distributed in the rotor along its circumference, wherein the flue gas compartment, the primary air compartment and the secondary air compartment are sealed and spaced apart, wherein a heat exchange element is arranged on the rotor, wherein the air preheater further comprises a steam soot blowing device, wherein the steam soot blowing device is arranged in an air duct of a cold secondary air inlet of the secondary air compartment, wherein the steam soot blowing device comprises a steam soot blower, a gun barrel connected to the steam soot blower and extending along the radial direction of the rotor, and a nozzle assembly connected to the gun barrel, wherein the nozzle assembly comprises A first nozzle assembly and a second nozzle assembly, in the rotation direction of the rotor, the first nozzle assembly is located upstream of the second nozzle assembly, the first nozzle assembly includes a throttle tube connected to the barrel at one end and a nozzle connected to the other end of the throttle tube, a throttle shrinkage hole is arranged inside the throttle tube, the aperture of the throttle shrinkage hole is smaller than the diameter of the throttle tube, and the inlet diameter of the nozzle is smaller than the outlet diameter; the second nozzle assembly includes a distribution pipe connected to the barrel and at least one nozzle connected to the distribution pipe, and the steam jet velocity at the nozzle outlet is smaller than the steam jet velocity at the nozzle outlet.

[0012] Preferably, the gun barrel is movably arranged in the radial direction of the rotor.

[0013] Further preferably, a plurality of nozzle assemblies are provided, and the moving stroke of the gun barrel is the distance between two adjacent nozzle assemblies.

[0014] Preferably, the distance between the nozzle outlet and the lower surface of the heat exchange element is 10-15 mm; the distance between the nozzle outlet and the lower surface of the heat exchange element is 400-600 mm.

[0015] Preferably, the nozzle is a Venturi nozzle, the throat diameter of the Venturi nozzle is 6-10 mm, the outlet diameter is 8-12 mm, and the diffusion angle is 10-15°.

[0016] Preferably, when multiple nozzles are connected to the distribution pipe, the center distance between two adjacent nozzles is equal to 0.5-1 purge radius of the nozzles, the purge trajectories of the multiple nozzles overlap by 0.5-1 purge radius of the nozzles, and the purge radius of each nozzle is 50-100 mm.

[0017] Preferably, a resistance block is further provided inside the throttling tube, and the resistance block is located downstream of the throttling shrinkage hole.

[0018] Preferably, the throttling tube has a length of 400-500 mm and a tube diameter of 20-30 mm.

[0019] Preferably, the nozzle comprises a conical cavity whose bottom is connected to the throttling tube, and a top surface covering the top of the conical cavity, and a spray hole is provided on the top surface, such as a shower-type nozzle.

[0020] Further preferably, the top surface of the nozzle is arc-shaped.

[0021] More preferably, when the nozzle assemblies are arranged in multiple groups, the arc length of the top surface of the nozzle close to the steam soot blower is greater than the arc length of the top surface of the nozzle far from the steam soot blower.

[0022] More preferably, the top surface width of the nozzle is 1.0-1.5 times the nozzle jet sweep radius, and the top surface arc length of the nozzle is 1-6 times the nozzle jet sweep radius.

[0023] Further preferably, the diameter of the injection hole is 1-3 mm.

[0024] Further preferably, the total area of ​​the injection holes is 40-60% of the top surface area of ​​the nozzle.

[0025] Preferably, the first nozzle assembly, the second nozzle assembly and the gun barrel are connected via a three-way pipe.

[0026] Preferably, the distance between the three-way pipe and the gun barrel is 10-20 mm.

[0027] Preferably, the nozzle assemblies are provided in a plurality of groups, and the plurality of groups of nozzle assemblies are distributed along the length direction of the gun barrel.

[0028] Further preferably, the spacing between two adjacent groups of nozzle assemblies is equal, and the spacing between two adjacent groups of nozzles is 1-2 m.

[0029] Preferably, the aperture of the throttling shrinkage hole near the steam soot blower is larger than the aperture of the throttling shrinkage hole far away from the steam soot blower; the number of nozzles on the distribution pipe near the steam soot blower is not less than the number of nozzles on the distribution pipe far away from the steam soot blower.

[0030] Preferably, the center line of the throttle tube, the center line of the distribution tube and the center line of the nozzle extend along the axial direction of the rotor, and the center line of the barrel extends along the radial direction of the rotor.

[0031] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0032] The present invention improves the steam blowing conditions of the sootblower. The sootblower is arranged at the cold secondary air inlet duct of the secondary air compartment, corresponding to the heat exchange element sector with the highest temperature and the lowest ammonium bisulfate deposition area on the circumference of the air preheater rotor, and the steam jet is in the same direction as the cold secondary air, eliminating the backflow obstruction of the traditional steam jet, creating excellent conditions for the steam jet to shear and remove the ammonium bisulfate-containing deposited ash; the blowing effect of the ammonium bisulfate deposited ash is improved, the upstream high-temperature and low-speed steam jet heats and gasifies the ammonium bisulfate in the deposited ash on the surface of the heat exchange element, so that the dense deposited ash is changed into a fluffy structure, which greatly reduces the hardness and bonding strength of the deposited ash, improves the shearing and flushing effect of the downstream high-speed and low-temperature steam jet on the deposited ash, and effectively improves the removal effect of the ammonium bisulfate deposited ash. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Attached Figure 1 This is a schematic diagram of the main view of the rotary air preheater in this embodiment;

[0034] Attached Figure 2 Schematic diagram of a top view of a rotary air preheater in this embodiment;

[0035] Attached Figure 3 is a schematic front view of the nozzle assembly in this embodiment;

[0036] Attached Figure 4 Schematic diagram of temperature distribution on the circumference of the hot end and the cold end of the heat exchange element of the air preheater in this embodiment;

[0037] Attached Figure 5a is a cross-sectional view of the throttling tube;

[0038] Attached Figure 5b A cross-sectional view of a Venturi nozzle.

[0039] In the above attached figure:

[0040] 1. Rotor; 10. Center sleeve; 11. Flue gas compartment; 12. Primary air compartment; 13. Secondary air compartment; 130. Cold secondary air inlet duct; 131. Hot secondary air outlet duct; 14. Seal; 15. Heat exchange element; 150. Cold end bottom surface; 151. Cold end top surface; 152. Hot end top surface; 20. Steam soot blower; 21. Gun barrel; 22. Throttle tube; 220. Throttle shrinkage hole; 221. Resistance block; 23. Nozzle; 24. Distribution pipe; 25. Venturi nozzle; 26. Tee pipe; 30. Heating area; 31. Purge area; 4. Ammonium bisulfate deposition temperature range. DETAILED DESCRIPTION

[0041] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0043] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] like Figure 1 , 2 The rotary air preheater with steam soot blowing device shown in the figure comprises a rotor 1 rotating around a central sleeve 10, a flue gas compartment 11, a primary air compartment 12 and a secondary air compartment 13 are distributed along the circumference of the rotor 1, and the flue gas compartment 11, the primary air compartment 12 and the secondary air compartment 13 are separated by a fan-shaped seal 14, and a metal heat exchange element 15 is arranged on the rotor 1. The rotation process passes through the flue gas compartment 11, the secondary air compartment 13 and the primary air compartment 12 in sequence, and performs a periodic heat storage and heat release process: in the flue gas compartment 11, the high-temperature flue gas passes through the heat exchange element 15 from top to bottom, the flue gas heat release temperature decreases, and the heat storage temperature of the heat exchange element 15 increases; in the primary air compartment 12 and the secondary air compartment 13, the cold primary air and the cold secondary air pass through the heat exchange element 15 from bottom to top, the cold air heat absorption temperature increases, and the heat release temperature of the heat exchange element 15 decreases.

[0045] The air preheater also includes a steam soot blowing device, which is arranged in the cold secondary air inlet duct 130 of the secondary air compartment and close to the seal 14 on one side of the flue gas compartment 11.

[0046] like Figure 3As shown, the steam sootblowing device includes a steam sootblower 20 , a gun barrel 21 connected to the steam sootblower 20 and extending radially along the rotor 1 , and a plurality of nozzle assemblies connected to the gun barrel 21 .

[0047] The total length of the barrel 21 is equal to the radius of the rotor 1, and is divided into n sections at equidistant intervals of 1 to 2 m. According to the length of the sections, n groups of nozzle assemblies are arranged from the inside to the outside along the radial direction of the rotor 1, that is, from the end of the barrel 21 close to the central sleeve 10 to the outermost side of the rotor 1, the nozzle assembly number increases from the first group to the nth group. The barrel 21 is movably arranged in the radial direction of the rotor 1, and the moving stroke of the barrel 21 in the radial direction of the rotor 1 is the distance between two adjacent nozzle assemblies.

[0048] The nozzle assembly includes a first nozzle assembly and a second nozzle assembly, and in the rotation direction of the rotor, the first nozzle assembly is located upstream of the second nozzle assembly.

[0049] The first nozzle assembly includes a throttle tube 22 connected to the barrel 21 at one end, and a nozzle 23 connected to the other end of the throttle tube 22. The throttle tube 22 is provided with a throttle shrinkage hole 220 and a circular resistance block 221 located downstream of the throttle shrinkage hole 220. The throttle shrinkage hole 220 and the resistance block 221 are connected to the throttle tube 22 by nuts. The aperture of the throttle shrinkage hole 220 is smaller than the diameter of the throttle tube 22. The inlet diameter of the nozzle 23 is smaller than the outlet diameter. The length of the throttle tube 22 is 400-500 mm, and the diameter is 20-30 mm.

[0050] In this embodiment: the nozzle 23 includes a quadrangular pyramid cavity whose bottom is connected to the throttling tube 22, and an arc-shaped top surface covering the top of the cone cavity. A spray hole is opened on the top surface, and the distance between the top surface of the nozzle 23 and the lower surface of the cold end heat exchange element 15 is 10-15mm. The spray holes are evenly and densely distributed on the top surface of the nozzle 23, with a diameter of about 1-3mm, and the total area of ​​the spray holes is about 40%-60% of the top surface area of ​​the nozzle 23. Specifically, a shower-type nozzle can be used. In addition, the width of the arc-shaped top surface of the nozzle 23 in the radial direction of the rotor 1 is 1.0-1.5 times the jet steam purge radius of the Venturi nozzle 25, and the arc length is 1-6 times the jet steam purge radius of the Venturi nozzle 25, and the arc length increases with the increase of the nozzle assembly number.

[0051] After the high-pressure and high-temperature steam in the barrel 21 passes through the throttling shrinkage hole 220, the resistance block 221 and the nozzle 23, it is reduced in pressure and expanded into low-pressure and high-temperature steam under the principle of adiabatic no work and equal enthalpy. The steam temperature in the nozzle 23 is about 300°C, and the pressure is slightly higher than the static pressure of the external cold secondary air by 200-500Pa. The steam jet velocity at the outlet of the injection hole on the top surface of the nozzle 23 is about 20-30m / s, merging into a vertically upward low-speed and high-temperature steam jet, and the jet velocity entering the channel of the heat exchange element 15 at the cold end of the rotor 1 is about 15-23m / s, forming a steam heating area on the circumference. The low-speed and high-temperature steam jet velocities of nozzle assemblies with different numbers are equal, and the flow rate is set by the diameter size of the throttling shrinkage hole 220 in the throttling tube 22. As the nozzle assembly number increases from the 1st group to the nth group, the diameter of the throttling shrinkage hole 220 gradually increases.

[0052] The second nozzle assembly includes a distribution pipe 24 connected to the barrel 21 and at least one venturi nozzle 25 connected to the distribution pipe 24. The distribution pipe 24 can be a rake-type blowpipe, and 1 to 5 venturi nozzles 25 of the same model are arranged on each distribution pipe 24. As the nozzle assembly number increases from the first group to the nth group, the number of venturi nozzles 25 on the distribution pipe 24 gradually increases. The diameter of the throat of the venturi nozzle 25 is about 6 to 10 mm, the diameter of the outlet is about 8 to 12 mm, and the diffusion angle is 10 to 15°. Under the isentropic principle of adiabatic decompression expansion to do technical work, the outlet steam jet velocity reaches 1 to 2 times the Mach number, and the temperature is rapidly reduced to about 100 to 150°C. The expansion distance between the throat and the outlet of the venturi nozzle 25 is appropriately reduced, so that the outlet steam jet is in an incomplete expansion state, the steam jet temperature is greater than 120°C, and the pressure is about 0.2 to 0.3 MPa, which is higher than the ambient atmospheric pressure. The distance between the outlet of the Venturi nozzle 25 and the lower surface of the cold end heat exchange element 15 is about 400-600mm, the sweeping radius of the steam jet of a single Venturi nozzle 25 on the lower surface of the heat exchange element 15 is about 50-100mm, the center distance between two adjacent Venturi nozzles 25 is equal to 0.5-1 steam jet sweeping radius, and the steam jet sweeping trajectories of the same group of Venturi nozzles 25 overlap by 0.5-1 sweeping radius, forming a steam sweeping area along the circumference. After a large amount of surrounding cold secondary air is entrained along the way, the central velocity of the steam jet when it reaches the lower surface of the heat exchange element 15 is reduced to about 100-150m / s, the steam jet temperature gradually decreases, and the jet temperature is maintained close to 100℃ by gradually releasing the latent heat of steam vaporization.

[0053] The throttle tube 22, the distribution tube 24 and the barrel 21 are connected by a tee tube 26 through a nut, and the spacing between the tee tube 26 and the barrel 21 is 10-20 mm. The center line of the throttle tube 22, the center line of the distribution tube 24 and the center line of the venturi nozzle 25 extend along the axial direction of the rotor 1, and the center line of the barrel 21 extends along the radial direction of the rotor 1.

[0054] After throttling and reducing the pressure, the boiler steam enters the barrel 21 of the steam soot blower 20. After further reducing the pressure and expanding through the high- and low-speed nozzle assemblies, two vertically upward steam jets of low-speed and high-temperature and high-speed and low-temperature are formed at multiple radial positions of the rotor 1 in the cold secondary air duct. The steam flows in the same direction and downstream of the cold secondary air from bottom to top into the channel of the cold-end heat exchange element 15 of the upper rotor 1. During the circular rotation of the heat exchange element 15, the ammonium bisulfate in the deposited ash on the surface of the heat exchange element 15 is first vaporized in the heating area formed by the low-speed and high-temperature steam jet, and then the deposited ash is removed through the purge area formed by the high-speed and low-temperature steam jet. The vaporized ammonium bisulfate and the stripped deposited ash enter the boiler furnace with the hot secondary air.

[0055] The barrel 21 moves radially from the inside to the outside of the rotor 1, and the central angles corresponding to the arc lengths of the fan-shaped heating areas of the first to nth groups of nozzle assemblies are close, and the residence time of the heat exchange element 15 at the cold end of the rotor 1 in each group of steam heating areas is not less than 0.2s, and the residence time in each group of steam purge areas is not less than 0.2s. The barrel 21 can be advanced intermittently and retreated directly, and the advancement step length is 0.5 to 1 times the steam purge radius of the Venturi nozzle on the lower surface of the heat exchange element. The smaller the multiple, the greater the overlap of the purge trajectory. The residence time of each step length makes the air preheater rotor rotate 1 to 2 times. According to the degree to which the flue gas side differential pressure of the air preheater is higher than the design value displayed by the unit DCS online analyzer, the steam soot blower is put into operation once at different time intervals of every 8 hours, 1 day, and 1 week. The greater the degree to which the flue gas differential pressure is higher than the design value, the shorter the soot blowing interval should be.

[0056] The steam jet parameter design of the steam sootblowing device in this embodiment is described in detail below:

[0057] The throttle tube is marked as 1, the Venturi nozzle is marked as 2, the inlet of the throttle tube is marked as (1, 0), the throttle shrinkage hole is marked as (1, 1), and the outlet of the throttle tube is marked as (1, 2); the inlet of the Venturi nozzle is marked as (2, 0), the throat of the Venturi nozzle is marked as (2, 1), and the outlet of the Venturi nozzle is marked as (2, 2).

[0058] The steam flow rate of the throttle tube and the Venturi nozzle can be calculated according to the critical steam state at the throttle contraction hole and the throat position 1 of the Venturi nozzle using equations (1) to (3). Among them, h0 is obtained by looking up the enthalpy entropy diagram according to the steam pressure P0 and temperature T0. After the critical pressure P1 at the throat position of the throttle contraction hole and the Venturi nozzle is obtained by using the isentropic principle, the steam enthalpy h1 and specific volume v1 are obtained by looking up the enthalpy entropy diagram. The steam flow rate G1 of a single throttle tube or Venturi nozzle is designed as:

[0059]

[0060]

[0061]

[0062] Wherein: A1 is the cross-sectional area of ​​the throat of the throttle tube or the Venturi nozzle; c1 is the steam velocity at the throat of the throttle tube or the Venturi nozzle; v1 is the steam specific volume; h0 is the stagnation steam enthalpy in the barrel; P1 is the critical steam enthalpy at the throat of the throttle tube or the Venturi nozzle; P0 is the stagnation steam pressure in the barrel; P1 is the critical steam pressure at the throat of the throttle tube or the Venturi nozzle; γ is the superheated steam adiabatic coefficient.

[0063] The steam pressure at the nozzle outlet is about 200-500Pa higher than the external environment pressure. The steady flow steam before and after the throttling shrinkage hole in the throttling tube belongs to an isenthalpic process of adiabatic expansion without work. After the steam enthalpy is determined by the stagnation steam pressure P0 and temperature T0 in the barrel, the steam temperature and specific volume v after decompression expansion are obtained on the enthalpy-entropy diagram according to the steam pressure at the nozzle outlet. 1,2 , the steam velocity c of the injection hole on the top surface of the nozzle is calculated using formula (4): 1，2 for:

[0064]

[0065] Where: v 1,2 A is the specific volume of steam at the injection hole on the top surface of the nozzle; 1，2 is the surface area of ​​the top of the nozzle; φ is the flow area ratio of the injection hole.

[0066] The steady flow steam before and after the throat of the Venturi nozzle belongs to the isentropic process of adiabatic expansion and technical work. The enthalpy and entropy values ​​are determined by the stagnation steam pressure P0 and temperature T0 in the barrel. Assume that the steam pressure P0 at the outlet of the Venturi nozzle is 2,2 The initial value is the critical pressure P at the throat of the Venturi nozzle 2,1 0.5 times, the steam enthalpy, temperature and specific volume at the outlet of the Venturi nozzle are obtained from the enthalpy-entropy diagram, the outlet steam jet velocity is calculated using formula (5), the outlet steam flow rate is calculated using formula (6), and the flow deviation between the throat and the outlet of the Venturi nozzle is calculated using formula (7). When the deviation is greater than 5%, the outlet steam pressure is adjusted to 1.1 times the previous value, and the outlet steam flow rate is calculated again by checking the enthalpy-entropy diagram; when the deviation is less than -5%, the outlet steam pressure is adjusted to 0.9 times the previous value, and the outlet steam flow rate is calculated again by checking the enthalpy-entropy diagram; until the deviation between the two is no more than ±5%, the steam pressure, temperature and velocity at the nozzle outlet are determined:

[0067]

[0068]

[0069]

[0070] Where: h 2,2is the steam enthalpy at the outlet of the Venturi nozzle; c 2,2 A is the steam velocity at the outlet of the Venturi nozzle; 2,2 is the outlet area of ​​the Venturi nozzle; v 2,2 G is the specific volume of steam at the outlet of the Venturi nozzle; 2,2 is the steam flow rate at the outlet of the Venturi nozzle; G 2,1 is the steam flow rate at the throat of the Venturi nozzle; ξ is the steam flow deviation.

[0071] The steam at the outlet of the Venturi nozzle is a free jet. After determining the distance between the outlet of the Venturi nozzle and the lower surface of the heat exchange element at the cold end of the rotor, the steam sweep radius of a single Venturi nozzle is calculated using formula (8), the center velocity is calculated using formula (9), the jet flow rate along the jet is calculated using formula (10), and the jet temperature is calculated using formula (11). When the calculated value of the jet temperature is lower than 100°C, the steam outside the jet gradually releases the latent heat of vaporization so that the jet temperature is close to but not higher than 100°C:

[0072]

[0073]

[0074]

[0075]

[0076] Where: R is the steam purge radius of the Venturi nozzle; R2 is the outlet radius of the Venturi nozzle; s is the distance from the outlet of the Venturi nozzle to the lower surface of the heat exchange element at the cold end of the rotor; θ is the diffusion angle of the Venturi nozzle; c is the jet velocity at the center of the purge; G is the jet flow rate of the steam purge section; T a is the central jet temperature of the steam purge section; T e is the ambient temperature; T 2,2 is the steam temperature at the Venturi nozzle outlet.

[0077] After obtaining the steam flow of the throttle tube and the venturi nozzle in each set of nozzle assemblies, the steam consumption G of the steam soot blower is calculated using formula (12): total :

[0078]

[0079] Where: G 1，j is the steam flow rate of the throttling pipe of the jth group of nozzle assemblies; G 2，j，i is the steam flow rate of the ith venturi nozzle of the jth nozzle assembly; n is the total number of nozzle assemblies; m j is the total number of the Venturi nozzles in the jth group of nozzle assemblies; j is the number of the nozzle assembly; i is the number of the Venturi nozzle.

[0080] The flue gas side resistance of the air preheater recorded online by the unit DCS can reflect the degree of blockage of the air preheater rotor heat exchange element channel by the ammonium bisulfate deposited ash. However, since it is excessively affected by factors such as operating load, it is also necessary to evaluate the steam heating and blowing effects of the steam soot blower body.

[0081] (1) The nozzle assembly on the gun barrel forms a steam heating area and a purge area on the lower surface of the heat exchange element at the cold end of the air preheater rotor. The central angle corresponding to the circumferential arc length of each area can be calculated using equations (13) and (14) respectively. The central angles corresponding to n heating areas should be close, and the central angles corresponding to n purge areas should be close:

[0082]

[0083]

[0084] (2) The residence time of the air preheater rotor heat exchange element in the circumferential direction passing through the steam heating area and the purge area of ​​each nozzle assembly can be calculated using equations (15) and (16) respectively. The residence time of n heating areas should be close, and the residence time of n purge areas should be close:

[0085]

[0086]

[0087] (3) According to the steam flow rate of the throttling tube and the venturi nozzle, the heating steam flow rate and the purge steam flow rate of different groups of nozzle assemblies can be calculated using equations (17) and (18) respectively:

[0088] M 1,j =G 1，1,j (17)

[0089]

[0090] (4) After obtaining the heating steam flow rate and the purge steam flow rate of each set of nozzle assemblies, the steam receiving amount per unit area of ​​the heat exchange element on the circumference is calculated using equations (19) and (20) according to the heating and purge areas on the circumference of the air preheater rotor radial position where each set of nozzle assemblies is located:

[0091]

[0092]

[0093] (5) The relative deviation method is used to calculate the relative deviation of the amount of heating steam received by the heat exchange element per unit area of ​​the n sets of nozzle assemblies using formula (21), and the relative deviation of the amount of purge steam received by the heat exchange element per unit area of ​​the n sets of nozzle assemblies using formula (22). The relative deviation of the heating steam amount is generally required to be less than ±10%, and the relative deviation of the purge steam amount is less than ±20%:

[0094]

[0095]

[0096] In the formula: ɡ 1，j is the central angle of the jth group of heating areas; A rc，j is the arc length of the jth group of heating areas; R r，j is the air preheater rotor radius corresponding to the jth group of nozzle assemblies; 2，j is the central angle of the purge area of ​​the jth group; R i is the steam purge radius of the Venturi nozzle; Δτ 1，j is the time for the rotor cold end heat exchange element to stop at the jth group of heating areas; Δτ 2，j c is the time for the rotor cold end heat exchange element to stop at the jth group of purge areas; rpm is the air preheater rotor speed; M 1，j is the heating steam flow rate of the jth group of nozzle assemblies; G 1，1，j is the steam flow rate at the throttling hole of the jth group of nozzle assemblies; M 2，j is the purge steam flow rate of the jth group of nozzle assemblies; G 2，1，j,i is the steam flow rate at the throat of the ith venturi nozzle of the jth nozzle assembly; SFUA 1，j SFUA is the amount of heating steam received by the heat exchange element per unit area at the cold end of the rotor at the jth group of nozzle assemblies; 21，j RD is the amount of purge steam received by the heat exchange element per unit area at the cold end of the rotor at the jth group of nozzle assemblies; 1，j RD is the relative deviation of the heating steam volume of the jth group of nozzle assemblies; 2，j is the relative deviation of the purge steam volume of the jth group of nozzle assemblies.

[0097] The air preheater of a 1000MW unit is used as an example for further explanation.

[0098] 1) A 1000MW unit is equipped with two 34-VI(T)-2000-SMR type rotor rotary three-compartment air preheaters. The air preheater rotor diameter is 16400mm and the center sleeve diameter is 1560mm. The air preheater rotor is divided into two layers, the rotor hot end and the rotor cold end: the upper heat exchange element is made of low carbon steel, with a height of 1100mm and a thickness of 0.5mm; the lower heat exchange element is enameled Corten steel, with a height of 1000mm, a thickness of 1.2mm, and a flow porosity of about 78%.

[0099] 2) The central angle of the flue gas compartment is 165°, the secondary air compartment is 100°, the primary air compartment is 50°, and the three fan-shaped seals are 45° in total; the air preheater rotor rotates along the flue gas compartment-secondary air compartment-primary air compartment, with a speed of 1.2r / min. The cold secondary air temperature in the cold secondary air inlet duct at the bottom of the secondary air compartment under full load of the unit is 23°C, and the static pressure is 0.103140MPa.

[0100] 3) Under the rated load of the unit, the temperature distribution of the top surface of the heat exchange element at the hot end of the rotor, the top surface and the bottom surface of the heat exchange element at the cold end of the rotor in the circumferential direction is calculated, such as Figure 4 As shown. In the flue gas compartment, the inlet flue gas temperature is 364.8℃, the outlet flue gas temperature is 1231℃, and the ammonium bisulfate in the flue gas condenses and deposits on the surface of the rotor cold end heat exchange element with a temperature range of about 150-190℃. When the air preheater rotor heat exchange element leaves the flue gas compartment and enters the secondary air compartment, the heat exchange element temperature reaches the highest, and an ammonium bisulfate deposition area is formed about 400-600mm above the lower surface of the heat exchange element.

[0101] 4) A steam soot blower of this embodiment is arranged in the cold secondary air duct at the bottom inlet of the secondary air compartment, near the seal between the flue gas compartment and the secondary air compartment. The barrel is consistent with the radial length of the air preheater rotor of 7420 mm. The barrel length is 7420 mm. A total of 5 groups of nozzle assemblies are arranged from the gun head close to the center sleeve to the outside of the air preheater rotor, and the distance between adjacent nozzle assemblies is 1484 mm.

[0102] 5) The diameter of the gun barrel is 50mm. The relevant design parameters of the five groups of nozzle assemblies are shown in Table 1: The first group is located at a radius of 2264mm in the rotor radial direction, with a Venturi nozzle and a throttling shrinkage hole with a diameter of 5.4mm; the second group is located at a radius of 3748mm, with two Venturi nozzles and a throttling shrinkage hole with a diameter of 7.0mm; the third group is located at a radius of 5232mm, with two Venturi nozzles and a throttling shrinkage hole with a diameter of 8.2mm; the fourth group is located at a radius of 6716mm, with three Venturi nozzles and a throttling shrinkage hole with a diameter of 9.2mm; the fifth group is located at a radius of 8200mm, with four Venturi nozzles and a throttling shrinkage hole with a diameter of 10.3mm. The distance from the Venturi nozzle outlet to the lower surface of the rotor cold end heat exchange element is 500mm.

[0103] Table 1 Nozzle assembly design parameters:

[0104]

[0105] 6) The steam pressure in the barrel is 0.78MPa and the temperature is 310℃. After the throttling shrinkage hole or the throat of the Venturi nozzle is reduced in pressure and expanded, the steam pressure at the throttling tube outlet is 0.103MPa and the temperature is 302℃. The steam pressure at the Venturi nozzle outlet is 0.2MPa and the temperature is 150.5℃. See Table 2 for detailed data.

[0106] Table 2 Sootblower steam parameter changes:

[0107]

[0108] 7) The steam jet velocity at the outlet of the venturi nozzle is 547m / s, and the central velocity reaching the lower surface of the rotor cold end heat exchange element is reduced to 156m / s. The jet velocity at the 1 / 4 radius is 65m / s, and the purge radius is 58mm; the steam jet velocity at the outlet of the throttle tube is 25m / s, and the velocity entering the cold end rotor heat exchange element channel is reduced to 19.2m / s. The purge steam flow rate of the steam soot blower is 46.7kg / min, and the heating steam flow rate is 16.0kg / min, totaling 62.7kg / min. In the radial direction of the air preheater rotor, the relative deviation of the steam flow rate received by the unit area heat exchange element of the 5 groups of heating areas is -1.7%~2.0%, and the relative deviation of the steam flow rate received by the unit area heat exchange element of the purge area is -16.6%~16.4%. Detailed data are shown in Table 3.

[0109] Table 3 Sootblower steam jet parameters:

[0110]

[0111] 8) Consistent with the steam purge radius length of the Venturi nozzle, the barrel advancement step length is 58 mm, the advancement speed is 0.806 mm / s, the advancement stroke is 1484 mm, and the purge time is 1842 s.

[0112] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A rotary air preheater with a steam soot blowing device, comprising a rotor rotating around a central sleeve, wherein a flue gas compartment, a primary air compartment and a secondary air compartment are distributed along the circumference of the rotor, wherein the flue gas compartment, the primary air compartment and the secondary air compartment are sealed and spaced apart, and a heat exchange element is arranged on the rotor, wherein: The air preheater also includes a steam soot blowing device, which is arranged in the secondary air compartment cold secondary air inlet air duct, and the steam soot blowing device includes a steam soot blower, a gun barrel connected to the steam soot blower and extending along the radial direction of the rotor, and a nozzle assembly connected to the gun barrel, the center line of the gun barrel extends along the radial direction of the rotor, and the gun barrel is movably arranged in the radial direction of the rotor. The nozzle assembly includes a first nozzle assembly and a second nozzle assembly. In the rotation direction of the rotor, the first nozzle assembly is located upstream of the second nozzle assembly, and the second nozzle assembly is located upstream of the second nozzle assembly. A nozzle assembly includes a throttle tube connected to the gun barrel at one end and a nozzle connected to the other end of the throttle tube, a throttle shrinkage hole is arranged inside the throttle tube, the aperture of the throttle shrinkage hole is smaller than the diameter of the throttle tube, and the inlet diameter of the nozzle is smaller than the outlet diameter; the second nozzle assembly includes a distribution pipe connected to the gun barrel and at least one nozzle connected to the distribution pipe, the steam jet velocity at the nozzle outlet is smaller than the steam jet velocity at the nozzle outlet, and the center line of the throttle tube, the center line of the distribution pipe and the center line of the nozzle extend along the axial direction of the rotor.

2. The rotary air preheater with steam soot blowing device according to claim 1, characterized in that: The nozzle is a Venturi nozzle.

3. The rotary air preheater with steam soot blowing device according to claim 1, characterized in that: When a plurality of the nozzles are connected to the distribution pipe, the center distance between two adjacent nozzles is equal to 0.5-1 of the purge radius of the nozzles, and the purge trajectories of the plurality of nozzles overlap by 0.5-1 of the purge radius of the nozzles.

4. The rotary air preheater with steam soot blowing device according to claim 1, characterized in that: A resistance block is also arranged inside the throttling tube, and the resistance block is located downstream of the throttling shrinkage hole.

5. The rotary air preheater with steam soot blowing device according to claim 1, characterized in that: The nozzle comprises a conical cavity whose bottom is connected with the throttling tube, and a top surface covering the top of the conical cavity, wherein a spray hole is provided on the top surface.

6. The rotary air preheater with steam soot blowing device according to claim 1, characterized in that: The first nozzle assembly, the second nozzle assembly and the gun barrel are connected through a three-way pipe.

7. The rotary air preheater with steam soot blowing device according to claim 1, characterized in that: The nozzle assemblies are arranged in a plurality of groups, and the plurality of groups of nozzle assemblies are distributed along the length direction of the gun barrel, and the intervals between two adjacent groups of nozzle assemblies are equal.

8. The rotary air preheater with steam soot blowing device according to claim 1, characterized in that: The aperture of the throttling shrinkage hole close to the steam soot blower is larger than the aperture of the throttling shrinkage hole far from the steam soot blower; the number of nozzles on the distribution pipe close to the steam soot blower is not less than the number of nozzles on the distribution pipe far from the steam soot blower.

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