Flue gas dry burning system for power plant

Abstract

The utility model discloses a power plant flue gas dry burning system which comprises a boiler, a denitration device, a rotary air preheater, a flue gas air heater, a dust remover, an induced draft fan, a desulfurizing tower and a chimney which are connected in sequence, the dry burning system is arranged between the denitration device and the dust remover, and hot air of the dry burning system is used for carrying out dry burning on the flue gas air heater. According to the utility model, effective dry burning of the flue gas air heater is realized under the condition that the exhaust gas temperature is hardly influenced, and the flue gas air heater has the advantages of good dry burning effect, high dry burning efficiency, easiness in flexible regulation and control and energy conservation; hot air is introduced into the outer wall of the heat exchange pipe of the smoke air heater through the specific dry burning system for dry burning, and the response rate of dry burning is further improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of coal-fired boiler systems in power plants, and in particular relates to a flue gas dry burning system in power plants. Background Art

[0002] During operation of a power plant's coal-fired boiler system, when the temperature of the cold air mixed with the low-temperature raw flue gas is above the flue gas's acid dew point, the heat exchanger plate wall temperature upon entering the flue gas is lower than the acid dew point, inevitably causing low-temperature corrosion. The lower the cold air temperature, the more severe the corrosion. To ensure efficient denitrification, a moderate excess of ammonia must be injected into the chemical reaction. The presence of SO₃ inevitably produces ammonium bisulfate, which crystallizes on metal surfaces with wall temperatures below 147°C. As the efficiency of the denitrification system decreases, the amount of ammonia injected inevitably increases. Combined with factors such as uneven flow fields, the amount of ammonium bisulfate crystallizes, further increasing the risk of ammonium bisulfate blockage in the heat exchanger. Ammonium bisulfate blockage reduces heat exchange performance and raises exhaust gas temperatures, resulting in increased flue gas volume flow, resistance, induced draft fan energy consumption, increased ash resistivity, reduced electrostatic precipitator efficiency, increased water consumption in the desulfurization process, increased net flue gas temperature and moisture content, increased chimney corrosion risk, increased white smoke generation, and reduced desulfurization tower dust removal and desulfurization efficiency. Therefore, it is urgent to solve the problems of ammonium bisulfate blockage and low-temperature corrosion in heat exchangers. Dry burning to increase the wall temperature of the heat exchanger can effectively alleviate the blockage of ammonium bisulfate.

[0003] Document CN109210555A discloses an online dry burning and clearing technology for denitrification air preheaters in power plant boilers. Communication damper doors are installed on the communication air ducts of the air preheaters on both sides to adjust the air volume of the air channels on both sides of the air preheaters. During normal operation, the communication damper doors are open. The variable frequency instructions of the discrete control system are used to operate and close fan A, or part of the communication damper doors of fan A or B. The air volume of fan A or fan B can be adjusted, and the deviation of the air volume between fan A and fan B can be further adjusted to increase the temperature of the air preheater tube wall on side A or side B. By increasing the temperature of the air preheater tube wall on one side above the critical temperature, ammonium bisulfate is vaporized again and precipitated from the ash scale and carried away by the flue gas. At the same time, the adhesion strength of the ash scale layer is reduced and falls off, effectively alleviating the blockage of ammonium bisulfate.

[0004] However, the dry-burning effect of the aforementioned dry-burning system needs to be further optimized, and it is not convenient to precisely control it. Utility Model Content

[0005] In response to the problems mentioned in the background technology, the purpose of the present utility model is to provide a power plant flue gas dry burning system.

[0006] The utility model adopts the following technical solutions.

[0007] A power plant flue gas dry burning system comprises a boiler, a desulfurization device, a rotary air preheater, a flue gas heater, a dust collector, an induced draft fan, a desulfurization tower and a chimney connected in sequence. A dry burning system is provided between the desulfurization device and the dust collector, and hot air from the dry burning system is used to dry burn the flue gas heater.

[0008] As a preferred solution, the flue gas heater is composed of N flue gas heating units, and each flue gas heating unit corresponds to a set of independently controllable cold air damper doors and dry-burning air dampers.

[0009] Furthermore, the dry burning system includes:

[0010] A flue gas bypass is provided with a heater, the inlet of the flue gas bypass is connected to the flue gas channel upstream of the rotary air preheater, and the outlet of the flue gas bypass is connected to the flue gas channel at the outlet of the flue gas heater;

[0011] The dry burning air channel passes through the heater, and the hot air outlet of the dry burning air channel is connected to the flue gas heater.

[0012] Furthermore, the dry burning air channel has a dry burning air branch pipe 1 and a dry burning air branch pipe 2. The dry burning air branch pipe 1 is connected to the primary air inlet of the flue gas heater, and the dry burning air branch pipe 2 is connected to the secondary air inlet of the flue gas heater.

[0013] Furthermore, the dry burning air channel has a dry burning air branch pipe 1 and a dry burning air branch pipe 2. The dry burning air branch pipe 1 is connected to the primary air introduction channel of the flue gas heater, and the dry burning air branch pipe 2 is connected to the secondary air introduction channel of the flue gas heater.

[0014] Furthermore, a dry burning air damper door and a dry burning air adjustment door are provided upstream of the heater on the dry burning air channel, a dry burning air damper main door is provided downstream of the heater on the dry burning air channel, and dry burning air branch doors are respectively provided on the dry burning air branch pipelines.

[0015] Furthermore, the first dry-burning air branch pipe is connected to the downstream of the cold primary air damper door on the primary air introduction channel, and the second dry-burning air branch pipe is connected to the downstream of the cold secondary air damper door on the secondary air introduction channel.

[0016] Furthermore, an inlet dry-burning flue gas main gate and a dry-burning flue gas regulating gate are provided upstream of the heater on the flue gas bypass, and an outlet dry-burning flue gas main gate is provided downstream of the heater on the flue gas bypass.

[0017] Furthermore, it also includes a hot primary air bypass and a hot secondary air bypass. The hot primary air bypass is connected from the hot primary air outlet of the flue gas heater and connected to the primary air channel of the rotary air preheater, and finally connected to the boiler; the hot secondary air bypass is connected from the hot secondary air outlet of the flue gas heater and connected to the secondary air channel of the rotary air preheater, and finally connected to the boiler.

[0018] Beneficial effects: The utility model can realize effective dry burning of the flue gas heater without affecting the exhaust gas temperature, and has the advantages of good dry burning effect, high dry burning efficiency, easy and flexible regulation, and energy saving; the utility model introduces hot air through a specific dry burning system to dry burn the outer wall of the heat exchange tube of the flue gas heater, and also improves the response rate of dry burning. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 2 is a diagram of a power plant flue gas dry combustion system in an embodiment. DETAILED DESCRIPTION

[0020] The following is a clear and complete description of the technical solutions of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] Example 1

[0022] Combine Figure 1 As shown, a power plant flue gas dry combustion system includes a boiler 21, a desulfurization device 19, a rotary air preheater 18, a flue gas heater 17, a dust collector 22, an induced draft fan 23, a desulfurization tower 24, and a chimney 25, which are connected in sequence. A dry combustion system is provided between the desulfurization device 19 and the dust collector 22. Hot air from the dry combustion system dry-combusts the flue gas heater 17. The flue gas heater 17 is composed of N flue gas heating units (or flue gas heating modules), each of which corresponds to a set of independently controllable cold air dampers and dry combustion dampers.

[0023] In this embodiment, the dry burning system includes:

[0024] A flue gas bypass 20 is provided with a heater 7. The inlet of the flue gas bypass 20 is connected to the flue gas passage upstream of the rotary air preheater 18, and the outlet of the flue gas bypass 20 is connected to the flue gas passage at the outlet of the flue gas heater 17;

[0025] The dry burning air channel 26 passes through the heater 7 , and the hot air outlet of the dry burning air channel 26 is connected to the flue gas heater 17 .

[0026] The dry-burning air duct 26 includes a dry-burning air branch line 1 31 and a dry-burning air branch line 2 32. Dry-burning air branch line 1 31 connects to the primary air inlet of the flue gas heater 17, while dry-burning air branch line 2 32 connects to the secondary air inlet of the flue gas heater 17. The dry-burning air duct 26 includes a dry-burning air branch line 1 31 and a dry-burning air branch line 2 32. Dry-burning air branch line 1 31 connects to the primary air inlet 61 of the flue gas heater 17, while dry-burning air branch line 2 32 connects to the secondary air inlet 62 of the flue gas heater 17. The primary air inlet 61 is equipped with a cold primary air shutoff door 13 and a blower 15, while the secondary air inlet 62 is equipped with a cold primary air shutoff door 14 and a blower 16.

[0027] A dry-burning air damper door 5 and a dry-burning air adjustment door 6 are provided upstream of the heater 7 in the dry-burning air duct 26 (specifically, the dry-burning air duct 26 has two inlet air ducts, each equipped with a fan 4 and a dry-burning air damper door 5, with one in use and one in reserve). A dry-burning air damper main door 8 is provided downstream of the heater 7 in the dry-burning air duct 26, and dry-burning air branch doors are provided on the dry-burning air branch pipes (a dry-burning air branch door 9 is provided on dry-burning air branch pipe 1 31 , and a dry-burning air branch door 10 is provided on dry-burning air branch pipe 2 32 ). Dry-burning air branch pipe 1 31 connects to the downstream side of the cold primary air damper door 11 on the primary air inlet duct 61 , and dry-burning air branch pipe 2 32 connects to the downstream side of the cold secondary air damper door 12 on the secondary air inlet duct 62 .

[0028] Among them, an inlet dry-burning flue gas main gate 2 and a dry-burning flue gas regulating gate 1 are arranged upstream of the heater 7 on the flue gas bypass 20, and an outlet dry-burning flue gas main gate 3 is arranged downstream of the heater 7 on the flue gas bypass 20.

[0029] In this embodiment, it also includes a hot primary air bypass 51 and a hot secondary air bypass 52. The hot primary air bypass 51 is connected to the primary air channel of the rotary air preheater 18 from the hot primary air outlet of the flue gas heater 17 and is finally connected to the boiler 21; the hot secondary air bypass 52 is connected to the secondary air channel of the rotary air preheater 18 from the hot secondary air outlet of the flue gas heater 17 and is finally connected to the boiler 21.

[0030] When the boiler is in normal operating condition: the dry burning system is not put into use, and a flue gas heater 17 is connected in series at the flue gas side outlet of the rotary air preheater 18 to form a composite air preheater; the cold air coming out of the blower 15 and the blower 16 is first heated by the flue gas heater 17 and the hot flue gas at the outlet of the rotary air preheater 18, and then the heated hot air is heated for a second time through the rotary air preheater 18 and the high-temperature flue gas at the outlet of the de-binding device 19 (that is, it is heated by heat exchange in the rotary air preheater 18), thereby increasing the air temperature entering the boiler to assist combustion, while reducing the flue gas temperature of the rotary air preheater 18 and the flue gas heater 17, thereby improving boiler efficiency.

[0031] When the dry burning system is in use, the heater 7 starts to run, and the high-temperature flue gas from the inlet of the rotary air preheater 18 and the low-temperature air introduced by the fan 4 exchange heat through the heater 7 pipe box to form high-temperature hot air. The high-temperature hot air enters the individual module of the flue gas heater 17 through the dry burning air duct, and heats the individual module for dry burning. When the dry burning of one module is completed, the next module is dry burned in turn until the dry burning of all modules is completed.

[0032] Follow the steps below to dry burn (dry burning method 1):

[0033] 1. Open the inlet dry burning smoke main door 2, outlet dry burning smoke main door 3, and dry burning smoke regulating door 1 of the smoke inlet of heater 7 in sequence, and then heater 7 starts working;

[0034] 2. Open the dry-burning air damper door 5, the dry-burning air adjustment door 6, and the fan 4 in sequence;

[0035] 3. Open the dry-burning air main door (item 8);

[0036] 4. Dry-burn the primary air duct box of the flue gas heater 17: close the cold primary air damper door 11 of the primary air duct box channel of each flue gas heater 17 in turn, and open the corresponding dry-burning air branch door 9. At this time, adjust the dry-burning air regulating door 6 and the frequency of the fan 4 according to the set value based on the required dry-burning hot air flow rate; after the dry-burning hot air enters the duct box channel, when the duct box temperature reaches the set temperature and time, open the cold primary air damper door 11 of the duct box channel, close the corresponding dry-burning air branch door 9, and the dry-burning of the duct box is completed; then close the cold primary air damper door 11 of the second duct box channel, open the dry-burning air branch door 9 of the corresponding duct box channel, and dry-burn the second duct box channel; repeat the above process until the dry-burning of all primary air duct boxes is completed, open all cold primary air damper doors 11, and close the dry-burning air branch door 9;

[0037] 5. Dry-burn the secondary air duct box of the flue gas heater 17: close the cold secondary air damper door 12 of the secondary air duct box channel of each flue gas heater 17 in turn, and open the corresponding dry-burning air sub-door 10. At this time, according to the required dry-burning hot air flow rate, adjust the corresponding dry-burning air regulating door 6 and the frequency of the fan 4 according to the set value; after the dry-burning hot air enters the duct box channel, when the duct box temperature reaches the set temperature and time, open the cold secondary air damper door 12 of the duct box channel, close the corresponding dry-burning air sub-door 10, and the dry-burning of the duct box is completed; then close the cold secondary air damper door 12 of the second duct box channel, open the dry-burning air sub-door 10 of the corresponding duct box channel, and dry-burn the second duct box channel; repeat the above process until the dry-burning of all secondary air duct boxes is completed, open all the cold secondary air damper doors 12, and close the dry-burning air sub-door 10;

[0038] 6. Close the dry-burning air damper main door 8;

[0039] 7. Close the dry-burning fan damper door 5, dry-burning air adjustment door 6, and fan 4 in sequence;

[0040] 8. The heater 7 body starts to dry burn, and the dry burning is completed when the temperature of the tube box reaches the set temperature and time;

[0041] 9. Close the inlet dry burning flue gas main door 2, outlet dry burning flue gas main door 3, and dry burning flue gas regulating door 1 in sequence, and stop the heater 7;

[0042] 10. The overall dry burning of the system is completed.

[0043] In addition to the aforementioned dry burning method 1, during actual operation, the opening conditions of valves, damper doors, etc. can be flexibly adjusted as needed to achieve dry burning in other ways.

[0044] The dry burning system of the present invention can realize effective dry burning of the flue gas heater without almost affecting the exhaust gas temperature, and has the advantages of good dry burning effect, high dry burning efficiency, easy and flexible regulation, and energy saving; the system introduces hot air through a specific dry burning system to dry burn the outer wall of the heat exchange tube of the flue gas heater, and also improves the response rate and time of dry burning (the time from starting regulation to reaching the target dry burning temperature). The response time of dry burning can be controlled within one minute.

Claims

1. A power plant flue gas dry burning system, characterized by: The invention comprises a boiler (21), a desulfurization device (19), a rotary air preheater (18), a flue gas heater (17), a dust collector (22), an induced draft fan (23), a desulfurization tower (24), and a chimney (25) connected in sequence. A dry burning system is provided between the desulfurization device (19) and the dust collector (22), and hot air from the dry burning system is used to dry burn the flue gas heater (17).

2. The power plant flue gas dry burning system according to claim 1, characterized in that: The flue gas heater (17) is composed of N flue gas heating units, each of which corresponds to a set of independently controllable cold air damper doors and dry-burning air dampers.

3. The power plant flue gas dry burning system according to claim 1, characterized in that: The dry burning system comprises: A flue gas bypass (20) is provided with a heater (7), an inlet of the flue gas bypass (20) is connected to a flue gas passage upstream of the rotary air preheater (18), and an outlet of the flue gas bypass (20) is connected to a flue gas passage at an outlet of the flue gas heater (17); The dry burning air channel (26) passes through the heater (7), and the hot air outlet of the dry burning air channel (26) is connected to the flue gas heater (17).

4. The power plant flue gas dry burning system according to claim 3, characterized in that: The dry burning air channel (26) has a dry burning air branch line 1 (31) and a dry burning air branch line 2 (32). The dry burning air branch line 1 (31) is connected to the primary air inlet of the flue gas heater (17), and the dry burning air branch line 2 (32) is connected to the secondary air inlet of the flue gas heater (17).

5. The power plant flue gas dry burning system according to claim 4, characterized in that: The dry burning air channel (26) comprises a dry burning air branch line 1 (31) and a dry burning air branch line 2 (32), wherein the dry burning air branch line 1 (31) is connected to the primary air introduction channel (61) of the flue gas heater (17), and the dry burning air branch line 2 (32) is connected to the secondary air introduction channel (62) of the flue gas heater (17).

6. The power plant flue gas dry burning system according to claim 5, characterized in that: A dry-burning air damper door and a dry-burning air regulating door (6) are provided upstream of the heater (7) on the dry-burning air passage (26); a dry-burning air damper main door (8) is provided downstream of the heater (7) on the dry-burning air passage (26); and dry-burning air branch doors are provided on the dry-burning air branch pipes.

7. The power plant flue gas dry burning system according to claim 6, characterized in that: The dry-burning air branch line 1 (31) is connected to the downstream of the cold primary air damper door (11) on the primary air introduction channel (61), and the dry-burning air branch line 2 (32) is connected to the downstream of the cold secondary air damper door (12) on the secondary air introduction channel (62).

8. The power plant flue gas dry burning system according to any one of claims 3 to 7, characterized in that: An inlet dry burning smoke main door (2) and a dry burning smoke regulating door (1) are provided upstream of the heater (7) on the smoke bypass (20), and an outlet dry burning smoke main door (3) is provided downstream of the heater (7) on the smoke bypass (20).

9. The power plant flue gas dry burning system according to claim 8, characterized in that: The hot primary air bypass (51) and the hot secondary air bypass (52) are further included. The hot primary air bypass (51) is connected from the hot primary air outlet of the flue gas heater (17) to the primary air channel of the rotary air preheater (18), and finally connected to the boiler (21); the hot secondary air bypass (52) is connected from the hot secondary air outlet of the flue gas heater (17) to the secondary air channel of the rotary air preheater (18), and finally connected to the boiler (21).

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