An intermediate storage type hot air powder feeding boiler system with a waste gas recovery device

Abstract

The present invention discloses an intermediate storage type hot air powder feeding boiler system with an exhaust gas recovery device, which includes an intermediate storage type hot air powder feeding boiler system, a fan, a spray tower, a pulverized coal dryer and a water coal slurry preparation process system. In the present invention, the exhaust gas is sent into the spray tower for pulverized coal recovery or to make water coal slurry, avoiding the exhaust gas entering the furnace as the tertiary air for combustion, fundamentally solving the problems such as disordered pulverized coal combustion, decreased boiler thermal efficiency, increased carbon content in fly ash caused by the characteristics of high exhaust gas velocity, low temperature, high humidity and low concentration of the exhaust gas. At the same time, the absence of the tertiary air structure simplifies the primary and secondary air regulation systems, which is beneficial to the organization of combustion in the furnace, strengthens the mixing of flue gas and powder, and thus has a high pulverized coal burnout degree, reduces the mechanical incomplete loss, decreases the production of nitrogen oxides, and improves the boiler combustion efficiency. In addition, the use of the spray tower to recover fine exhaust gas powder has high efficiency, good safety, little environmental pollution, and the collected water-powder mixture can also be made into water coal slurry to carry out diversified utilization of pulverized coal.

Description

Technical Field

[0001] The present invention relates to an intermediate storage type hot air powder feeding boiler system with an exhaust gas recovery device, belonging to the technical field of boilers. Background Art

[0002] When burning hard-to-burn anthracite, lean coal or inferior bituminous coal, most power plants widely adopt an intermediate storage type hot air powder feeding coal-fired boiler system. In the coal pulverizing system, pulverized coal with a particle size less than 10 μm generally cannot be separated by the fine powder separator and is led out from the upper part of the separator along with the drying medium, which is called exhaust gas. The amount of pulverized coal in it is about 10% of the coal grinding capacity. At present, most power plant boilers directly send the exhaust gas into the furnace through the tertiary air nozzle for combustion, which is called tertiary air, and its air volume accounts for about 10%-15% of the total air volume. The tertiary air nozzle is usually arranged on the topmost layer, and the primary and secondary air are below it. The tertiary air has the characteristics of high wind speed, low temperature, high humidity and fine pulverized coal. Research results show that the adoption of tertiary air will obviously have an adverse impact on the combustion stability of the boiler: (1) The tertiary air has a high wind speed and a large air volume, which is easy to disrupt the normal combustion air dynamic flow field in the furnace, causing combustion disorder and increasing the carbon content in fly ash; (2) The tertiary air has a low temperature and high humidity, and entering the furnace will cause more ineffective heat absorption, reduce the boiler efficiency, increase the nitrogen oxide content, and increase the high-temperature corrosion of the water wall and superheater; (3) The pulverized coal in the tertiary air is fine and the concentration is low, and a higher tertiary air speed needs to be maintained to prevent the flame from being too close to the nozzle and burning out the nozzle.

[0003] Many scholars have proposed some technical solutions for such problems: (1) Adding a set of exhausted gas treatment devices to the pulverized coal preparation system of utility boilers, mainly including bag filters, auxiliary powder silos, air locks, exhaust fans, etc. Such technical solutions mainly filter the exhausted gas through bag filters and recover fine pulverized coal, thus avoiding the reduction of boiler efficiency caused by directly sending the exhausted gas into the furnace for combustion. However, this solution requires a large number of additional devices and a relatively large cost investment. In addition, poor collection of fine powder or poor filtering effect of the dust collector during actual operation may lead to serious consequences (Chinese Utility Model No. 96242050.6; Chinese Utility Model No. 201220620806.7); (2) Using the non-uniformity at the outlet of the exhaust fan to divide the exhausted gas into two parts, thick and thin, and then sending them into the furnace for combustion through the primary and secondary air nozzles respectively. This technology has a simple structure and less investment, and solves problems such as the reduction of boiler efficiency caused by injecting tertiary air. However, the addition of the exhausted gas will cause the temperature of the primary and secondary air to decrease and the wind speed to increase, which is not conducive to the stable operation of the boiler (Chinese Invention No. 200410009997.3; Chinese Invention No. 201510222262.7). (3) Adjust the structure of the tertiary air nozzle to be arranged in two layers, upper and lower, reduce the original upper tertiary air volume, and utilize the high temperature and large heat load in the flame center area of the lower primary air main burner, where pulverized coal is more likely to ignite and burn out, reducing the carbon content in fly ash. However, the lower tertiary air is close to the primary air main burner, and its characteristics of low temperature and high humidity will affect the ignition and combustion of the pulverized coal air flow in the main burner. (Chinese Utility Model No. 201120172697.2;) Summary of the Invention

[0004] The object of this invention patent is to provide an intermediate storage type hot air powder feeding boiler system with an exhausted gas recovery device, which solves problems such as the reduction of thermal efficiency, high carbon content in fly ash, and high temperature corrosion of high temperature heating surfaces caused by factors such as low temperature, high wind speed, high humidity, and low concentration of the exhausted gas used as tertiary air in traditional coal-fired boilers.

[0005] To solve the above problems, this invention patent adopts the following technical solutions:

[0006] An intermediate storage type hot air powder feeding boiler system with an exhausted gas recovery device, comprising an intermediate storage type hot air powder feeding boiler system 29, a fan 20, a spray tower 23, a pulverized coal dryer 21, and a water coal slurry preparation process system 25;

[0007] The intermediate storage type hot air powder feeding boiler system 29 includes a raw coal bunker 1. A sluice gate 2 is provided at the bottom end of the raw coal bunker 1. The lower outlet of the sluice gate 2 is connected to the inlet of a coal feeder 3. The outlet of the coal feeder 3 is connected to the upper inlet of a downward drying pipe 5. The lower outlet of the downward drying pipe 5 is connected to the inlet of a coal mill 6. The outlet of the coal mill 6 is connected to the inlet of a coarse powder separator 8. An induced powder pipe 7 is provided above the inlet of the coarse powder separator 8, and the induced powder pipe 7 is connected to the inlet of the coal mill 6. The outlet of the coarse powder separator 8 is connected to the inlet of a fine powder separator 9. The bottom outlet of the fine powder separator 9 is connected to the inlet of a coal powder bunker 13 through a screw coal conveyor 11. The bottom outlet of the coal powder bunker 13 is connected to a primary air pipe 31 through a coal feeder 14. The inlet of a forced draft fan 26 is connected to the atmosphere, and the outlet is divided into two paths: the first path is connected to the inlet of an air preheater 28, and the second path is connected to the upper inlet of the downward drying pipe 5 through an air supply pipe 30. The outlet of the air preheater 28 is connected to a secondary air pipe 19 and a primary air fan 17. The secondary air pipe 19 is connected to a primary and secondary air burner 15. The outlet of the primary air fan 17 is connected to the inlet of a primary air box 16, and the outlet of the primary air box 16 is connected to the primary and secondary air burner 15 through the primary air pipe 31. The primary and secondary air burner 15 is arranged at the front end of the boiler 18, and the boiler 18 has no tertiary air burner.

[0008] The inlet of a fan 20 is connected to the upper outlet of the fine powder separator 9, and the outlet is connected to the waste gas inlet in the middle section of a spray tower 23. The upper part of the spray tower 23 is directly connected to the atmosphere, and a water and powder mixture collector is provided at the bottom and is connected to a coal powder dryer 21 and a water coal slurry process system 25 through a powder conveying pipe 22. The outlet of the coal powder dryer 21 is connected to the inlet of the screw coal conveyor 11.

[0009] The method for recovering exhausted gas is as follows: The exhausted gas is sent from the upper outlet of the fine powder separator 9 to the spray tower 23 through the fan 20 for gas-powder separation. The waste gas is directly discharged into the atmosphere from the upper part of the spray tower 23, and the fine coal powder captured by the water mist falls into the bottom collector due to gravity. There are two utilization methods for the water and powder mixture collected by the spray tower 23: The first utilization method is that the water and powder mixture is dried by the coal powder dryer 21 and then sent to the coal powder bunker 13 to participate in the subsequent combustion of the boiler. The second utilization method is that the water and powder mixture is concentrated and then made into water coal slurry through the water coal slurry process system 25.

[0010] Furthermore, a moisture discharge pipe 12 is provided between the screw coal conveyor 11 and the coal powder bunker 13, and the moisture discharge pipe 12 is connected to the powder conveying pipe 22 at the inlet end of the fine powder separator 9.

[0011] Furthermore, the spray tower 23 is a circulating water spray tower.

[0012] Furthermore, an explosion-proof door 10 is provided at the top of the fine powder separator 9.

[0013] Further, the water coal slurry preparation process system 25 mainly includes a water-powder mixture concentration process, an additive mixing process, and a strong stirring process. The water-powder mixture collected by the circulating water spray tower 23 is concentrated and then 1% additive is added, and water coal slurry is made through strong stirring and mixing, increasing the diversified utilization methods of coal.

[0014] The main working process of the intermediate storage hot air powder feeding boiler system with a waste gas recovery device of the present invention is as follows: Raw coal is fed from the raw coal bunker 1 into the downward drying pipe 5 through the coal feeder 3 for drying. After meeting the grinding requirements, it is sent to the coal mill 6 for grinding. The ground coal powder is sent into the coarse powder separator 8 for separation along with the drying hot air. The coarse powder that does not meet the furnace combustion standard is sent back to the coal mill 6 for re-grinding through the return powder pipe 7, and the rest is sent into the fine powder separator 9 from the upper outlet of the coarse powder separator 8 for further separation. The filtered fine powder is sent into the coal powder bunker 13 through the screw powder conveyor 11, and finally is sent into the furnace of the boiler 18 along with the primary air for combustion. The waste gas is sent from the upper outlet of the fine powder separator 9 into the circulating water spray tower 23 through the fan 20 for gas-powder separation. The waste gas is directly discharged into the atmosphere from the upper part of the circulating water spray tower 23, and the fine coal powder captured by the water mist falls into the bottom collector due to gravity, and then is sent to the coal powder dryer 21 through the powder conveying pipe 22 for drying, (or sent to the water coal slurry preparation process system 25 to carry out the diversified utilization of coal), and the dried coal powder is sent to the coal powder bunker 13 to participate in the subsequent combustion.

[0015] The present invention is different from the traditional intermediate storage hot air powder feeding boiler system in that the waste gas is sent into the boiler as the tertiary air for combustion. The present invention sends the waste gas into the circulating water spray tower for coal powder recovery or to make water coal slurry, avoiding problems such as disordered coal powder combustion, decreased boiler thermal efficiency, and increased carbon content in fly ash caused by the waste gas entering the furnace as the tertiary air for combustion. Compared with the prior art, the present invention has the following advantages and effects: (1) The boiler has no tertiary air burner, the structure is simple, and the operation and maintenance costs of the burner are reduced; (2) The absence of the tertiary air structure in the boiler can simplify the primary and secondary air adjustment systems. At the same time, it is beneficial to the organization of combustion in the furnace, strengthens the mixing of flue gas and powder, and thus the burnout degree of coal powder is high, the mechanical incomplete loss is reduced, the production of nitrogen oxides is reduced, and the combustion efficiency of the boiler is improved, etc. (3) Recycling the fine powder of the waste gas by using the circulating water spray tower has higher efficiency, better safety, and less environmental pollution compared with the traditional bag filter for recovering fine powder. In addition, the generated water-powder mixture is made into water coal slurry through the water coal slurry system, which can increase the diversified utilization methods of coal powder. Description of the Drawings

[0016] Figure 1 It is a schematic diagram of an intermediate storage hot air powder feeding boiler system with a waste gas recovery device of the present invention.

[0017] Wherein Figure 1 The markings are explained as follows:

[0018] 1 - Raw coal bunker; 2 - Damper

[0019] 3 - Coal feeder; 4 - Air lock

[0020] 5 - Downward drying pipe; 6 - Coal mill

[0021] 7 - Return powder pipe; 8 - Coarse powder separator

[0022] 9 - Fine powder separator; 10 - Explosion-proof door

[0023] 11 - Screw powder conveyor; 12 - Moisture discharge pipe

[0024] 13 - Pulverized coal bunker; 14 - Powder feeder

[0025] 15 - Primary and secondary air burners; 16 - Primary air box

[0026] 17 - Primary air fan; 18 - Boiler

[0027] 19 - Secondary air duct; 20 - Fan

[0028] 21 - Pulverized coal dryer; 22 - Powder conveying pipe

[0029] 23 - Circulating water spray tower; 24 - Exhaust gas

[0030] 25 - Coal water slurry preparation process system; 26 - Forced draft fan

[0031] 27 - Cold air inlet; 28 - Air preheater

[0032] 29 - Intermediate storage type hot air powder-feeding boiler system

[0033] 30 - Air supply duct; 31 - Primary air duct Specific embodiments

[0034] The accompanying drawings show an embodiment of an intermediate storage type hot air powder-feeding boiler system with an exhaust gas recovery device according to the present invention.

[0035] An intermediate storage type hot air powder-feeding boiler system with an exhaust gas recovery device in this embodiment includes an intermediate storage type hot air powder-feeding boiler system 29, a fan 20, a pulverized coal dryer 21, a circulating water spray tower 23, and a coal water slurry preparation system 25.

[0036] Among them, the intermediate storage type hot air powder feeding boiler system 29 mainly includes: a raw coal bunker 1, a sluice gate 2 is provided at the bottom end of the raw coal bunker 1, and the lower end outlet of the sluice gate 2 is connected to the left inlet of a coal feeder 3; the right end outlet of the coal feeder 3 is connected to the upper end inlet of a downward drying pipe 5; the lower end outlet of the downward drying pipe 5 is connected to the left end inlet of a coal mill 6; the right end outlet of the coal mill 6 is connected to the inlet of a coarse powder separator 8; an ash return pipe 7 is provided above the inlet of the coarse powder separator, and the ash return pipe 7 is connected to the left end inlet of the coal mill 6, and the upper outlet of the coarse powder separator 8 is connected to the inlet of a fine powder separator 9; the bottom outlet of the fine powder separator 9 is connected to the inlet of a coal powder bunker 13 through a screw coal conveyor 11, wherein a moisture discharge pipe 12 is provided between the screw coal conveyor 11 and the coal powder bunker and is connected to the powder conveying pipe 22 at the inlet end of the fine powder separator 9. The moisture discharge pipe can extract the water vapor in the screw coal conveyor and the coal powder bunker, prevent the coal powder from getting damp and caking, and prevent blockage or "jamming" phenomena. It can also keep the coal powder bunker and the coal conveyor under negative pressure to prevent powder spraying out from the unsealed parts; the bottom outlet of the coal powder bunker 13 is connected to a primary air pipe 31 through a coal feeder 14; the inlet of a forced draft fan 26 is connected to the atmosphere, and the outlet is divided into two paths: the first path is connected to the inlet of an air preheater 28, and the second path is connected to the upper inlet of the downward drying pipe 5 through an air supply pipe 30; the outlet of the air preheater 28 is connected to a secondary air pipe 19 and a primary air fan 17; the secondary air pipe 19 is connected to a primary and secondary air burner 15; the outlet of the primary air fan 17 is connected to the inlet of a primary air box 16, and the outlet of the primary air box 16 is connected to the primary and secondary air burner 15 through the primary air pipe 31; the primary and secondary air burner 15 is arranged at the front end of the boiler 18, and the boiler has no tertiary air burner.

[0037] The inlet of a fan 20 is connected to the upper outlet of the fine powder separator 9, and the outlet is connected to the waste gas inlet in the middle section of a spray tower 23; the upper part of the spray tower 23 is directly connected to the atmosphere, and a moisture mixture collector is provided at the bottom and is connected to a coal powder dryer 21 and a water coal slurry process system 25 through a powder conveying pipe 22; the outlet of the coal powder dryer 21 is connected to the inlet of the screw coal conveyor 11.

[0038] As a preferred embodiment of the present invention, the spray tower 23 is a circulating water spray tower. The circulating water spray tower can effectively filter the fine coal powder in the exhausted gas, and the filtered waste gas can be discharged into the atmosphere without secondary treatment. It also has the characteristics of simple structure and low operation cost.

[0039] As a preferred embodiment of the present invention, an explosion-proof door 10 is provided at the top of the fine powder separator 9. The explosion-proof door can effectively reduce the huge air pressure generated in the pipeline when the coal powder explodes, and prevent the equipment from being damaged by blasting.

[0040] The process in the water coal slurry process system 25 mainly includes the concentration of the water and powder mixture, the mixing of additives, and strong stirring. The water and powder mixture collected by the circulating water spray tower 23 is concentrated and then 1% of additives are added and mixed by strong stirring to make water coal slurry, so as to develop diversified utilization methods of coal.

[0041] The main working process of the system of the present invention is as follows: Raw coal is fed from the raw coal bunker 1 into the downcomer drying pipe 5 through the coal feeder 3 for drying. After meeting the grinding requirements, it is sent to the coal mill 6 for grinding. The ground coal powder is sent into the coarse powder separator 8 along with the drying hot air for separation. The coarse powder that does not meet the furnace combustion standard is sent back to the coal mill 6 through the return powder pipe 7 for re-grinding. The rest is sent into the fine powder separator 9 from the upper outlet of the coarse powder separator 8 for further separation. The filtered fine powder is sent into the coal powder bunker 13 through the screw coal powder conveyor 11 and finally sent into the furnace of the boiler 18 along with the primary air for combustion. The exhausted gas is sent from the upper outlet of the fine powder separator 9 into the circulating water spray tower 23 through the fan 20 for gas-solid separation. The waste gas is directly discharged into the atmosphere from the upper part of the circulating water spray tower 23. The fine coal powder captured by the water mist falls into the bottom collector due to gravity and is then sent to the coal powder dryer 21 through the powder conveying pipe 22 for drying (or sent to the coal water slurry preparation process system 25 to carry out the diversified utilization of coal). The dried coal powder is sent to the coal powder bunker 13 to participate in the subsequent combustion.

[0042] Through the above description, those skilled in the art can already implement it.

[0043] In addition, the content described in the specific embodiments in the specific implementation part of this specification is only an example of the present invention patent. Any equivalent transformation made according to the structure, features, and principles of the present invention patent concept is within the protection scope of the present invention patent. In the present invention, unless otherwise clearly specified and defined, the terms "connected", "communicated", and "connected" should be understood in a broad sense. Those skilled in the art of the present invention patent can make various modifications, supplements, or use similar methods to replace the described specific embodiments, as long as they do not deviate from the structure of the present invention or exceed the scope defined by this claim book, they should all belong to the protection scope of the present invention.

Claims

1. An intermediate storage type hot air powder feeding boiler system with a waste gas recovery device, characterized in that, It includes an intermediate storage type hot air powder feeding boiler system (29), a fan (20), a spray tower (23), a pulverized coal dryer (21) and a water coal slurry preparation process system (25); The intermediate storage type hot air powder feeding boiler system (29) includes a raw coal bunker (1). A sluice gate (2) is provided at the bottom end of the raw coal bunker (1). The lower outlet of the sluice gate (2) is connected to the inlet of a coal feeder (3). The outlet of the coal feeder (3) is connected to the upper inlet of a downcomer drying pipe (5). The lower outlet of the downcomer drying pipe (5) is connected to the inlet of a coal mill (6). The outlet of the coal mill (6) is connected to the inlet of a coarse powder separator (8). A return powder pipe (7) is provided above the inlet of the coarse powder separator (8), and the return powder pipe (7) is connected to the inlet of the coal mill (6). The outlet of the coarse powder separator (8) is connected to the inlet of a fine powder separator (9). The bottom outlet of the fine powder separator (9) is connected to the inlet of a coal powder bunker (13) through a screw coal powder conveyor (11). The bottom outlet of the coal powder bunker (13) is connected to a primary air pipe (31) through a coal feeder (14). The inlet of a forced draft fan (26) is connected to the atmosphere, and the outlet is divided into two paths: the first path is connected to the inlet of an air preheater (28), and the second path is connected to the upper inlet of the downcomer drying pipe (5) through an air supply pipe (30). The outlet of the air preheater (28) is connected to a secondary air pipe (19) and a primary air fan (17). The secondary air pipe (19) is connected to a primary and secondary air burner (15). The outlet of the primary air fan (17) is connected to the inlet of a primary air box (16). The outlet of the primary air box (16) is connected to the primary and secondary air burner (15) through the primary air pipe (31). The primary and secondary air burner (15) is arranged at the front end of the boiler (18), and there is no tertiary air burner in the boiler (18); The inlet of the fan (20) is connected to the upper outlet of the fine powder separator (9), and the outlet is connected to the waste gas inlet in the middle section of the spray tower (23). The upper part of the spray tower (23) is directly connected to the atmosphere. A water and powder mixture collector is provided at the bottom and is connected to the pulverized coal dryer (21) and the water coal slurry preparation process system (25) through a powder conveying pipe (22). The outlet of the pulverized coal dryer (21) is connected to the inlet of the screw coal powder conveyor (11); The method for recovering exhausted gas is as follows: The exhausted gas is sent from the upper outlet of the fine powder separator (9) to the spray tower (23) through the fan (20) for gas-powder separation. The waste gas is directly discharged into the atmosphere from the upper part of the spray tower (23). The fine pulverized coal captured by the water mist falls into the bottom collector due to gravity. There are two utilization methods for the water and powder mixture collected by the spray tower (23): The first utilization method is that the water and powder mixture is dried by the pulverized coal dryer (21) and then sent to the coal powder bunker (13) to participate in the subsequent combustion of the boiler. The second utilization method is that the water and powder mixture is concentrated and then made into water coal slurry through the water coal slurry preparation process system (25).

2. The intermediate storage hot air powder feeding boiler system with an exhaust gas recovery device according to claim 1, characterized in that A moisture discharge pipe (12) is provided between the screw coal powder conveyor (11) and the coal powder bunker (13), and the moisture discharge pipe (12) is connected to the powder conveying pipe (22) at the inlet end of the fine powder separator (9).

3. A medium-storage hot air powder-feeding boiler system with a waste gas recovery device according to claim 1, characterized in that, The spray tower (23) is a circulating water spray tower.

4. A medium storage hot air powder feeding boiler system with an exhaust gas recovery device according to claim 1, characterized in that, An explosion-proof door (10) is provided at the top of the fine powder separator (9).

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