A denitration flexible regulation system for improving the drying output of a high-moisture lignite boiler

Abstract

The application discloses a denitration flexible regulation system for improving the drying output of a high-moisture lignite boiler, and aims at solving the problems of low denitration efficiency and large ammonia escape amount in the drying output of the boiler for the lignite with high moisture content.The system comprises a boiler, a denitration bypass flue (a bypass flue with a heat exchanger), a bypass flue heat exchanger, an air preheater, a heat exchanger hot air flue, a denitration device, a heat pipe heat exchanger, a boiler outlet flue, a coal mill and a series of flue gas passages and baffle doors / valves.The application sets the denitration bypass flue at a suitable position of the boiler diversion chamber and sets the bypass flue heat exchanger in the denitration bypass flue, heat exchange is carried out between the high-temperature flue gas in the bypass flue heat exchanger and the hot primary air at the outlet of the preheater, the drying output of the coal mill is improved, the flue gas temperature at the inlet of the denitration device is improved at low load, the denitration efficiency is improved, and the wide load flexibility is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of flexibility adjustment systems of denitration for improving the dry output of high moisture lignite boiler. BACKGROUND

[0002] For the pulverized coal boiler unit of lignite in the thermal power industry, due to the actual use of coal moisture deviates (higher) from the original design coal moisture or seasonal factors affecting the moisture content of boiler coal, it will cause the dry output of the coal mill system equipped by the boiler to be insufficient, affecting the normal operation performance index and environmental protection index of the boiler, this phenomenon is more obvious when high load operation. While low load operation, the dry output of the coal mill can usually meet the needs of the boiler operation, but the inlet flue gas temperature of the denitration device is lower than the recommended temperature of the denitration catalyst operation, causing low denitration efficiency, large ammonia escape amount and other problems. The common solution is to set up a boiler denitration bypass flue to increase the flue gas temperature at the inlet of the denitration device. At the same time, under the environment of deep peak regulation, the low load operation of the boiler will cause the outlet flue gas temperature of the preheater to be too low, causing cold end corrosion of the preheater, causing economic and operational risks. SUMMARY

[0003] The purpose of the present application is to solve the problems of low denitration efficiency and large ammonia escape amount in the dry output of lignite boiler, and to provide a kind of flexibility adjustment systems of denitration for improving the dry output of high moisture lignite boiler. The heat of the boiler flue gas is used to increase the temperature of the hot primary air at the outlet of the preheater, to increase the dry output of the coal mill, and to have the denitration device wide load flexible operation and avoid the cold end corrosion of the preheater.

[0004] The present application relates to a kind of flexibility adjustment systems of denitration for improving the dry output of high moisture lignite boiler. It comprises a boiler, a denitration bypass flue, a bypass flue heat exchanger, an air preheater, a heat exchanger hot air duct, a denitration device, a heat pipe heat exchanger, a boiler outlet flue and a coal mill.

[0005] The denitration bypass flue is respectively communicated with the boiler and the outlet of the boiler outlet flue, and the flue gas outlets of the denitration bypass flue and the boiler outlet flue are communicated with the flue gas inlet of the denitration device. The flue gas outlet of the denitration device is communicated with the flue gas inlet of the air preheater, and the flue gas outlet of the air preheater is communicated with the flue gas inlet of the heat pipe heat exchanger.

[0006] The hot air outlet of the heat pipe heat exchanger is communicated with the cold end air inlet of the air preheater. The hot primary air outlet of the air preheater is communicated with the heat exchanger hot air duct. The hot air inlet of the bypass flue heat exchanger is communicated with the heat exchanger hot air duct. The air outlet of the bypass flue heat exchanger is communicated with the air inlet of the coal mill. The air outlet of the coal mill is communicated with the air inlet of the burner of the boiler.

[0007] Further, the bypass flue heat exchanger is provided with a baffle door to adjust the heat exchange amount.

[0008] Further, the bypass flue, the bypass flue of the bypass flue heat exchanger, the heat exchanger hot air flue and the boiler outlet flue are all provided with a flue gas and air baffle door.

[0009] Further, when the boiler is in high load operation, the high-temperature flue gas drawn from the boiler by the denitration bypass flue enters the bypass flue heat exchanger to heat all or part of the hot primary air drawn in by the air preheater and through the heat exchanger hot air flue, further improves the temperature of the hot primary air, and then the high-moisture lignite is dried in the coal mill, and finally introduced into the boiler burner.

[0010] Further, when the boiler is in low load operation, the flue gas heat drawn from the boiler by the denitration bypass flue is mixed with the flue gas of the boiler outlet flue by cutting off the air baffle door of the bypass flue heat exchanger or by adjusting part of the flue gas to pass through the heat exchanger bypass, thereby improving the temperature of the flue gas entering the denitration device, and finally the flue gas passes through the air preheater and the heat pipe heat exchanger to enter the downstream equipment.

[0011] Further, the bypass flue heat exchanger is provided with an adjustment bypass.

[0012] The denitration flexibility adjustment system for improving the drying output of high-moisture lignite boiler of the present application utilizes the denitration bypass flue arranged at a suitable position such as the boiler turning chamber, and the bypass flue heat exchanger arranged inside, to utilize the high-temperature flue gas therein to exchange heat with the hot primary air at the outlet of the preheater, thereby improving the drying output of the coal mill, and at the same time, under low load, the temperature of the flue gas entering the denitration device is improved, the denitration efficiency is improved, and the wide load flexibility is achieved, and the heat pipe heat exchanger is arranged below the air preheater to improve the cold end temperature of the air preheater to avoid cold end corrosion.

[0013] The present application has the following beneficial effects:

[0014] 1. The adjustment system of the present application has the effect of improving the drying output of the coal mill of high-moisture lignite boiler;

[0015] When the boiler is in high load operation, the high-temperature flue gas drawn from the boiler by the denitration bypass flue enters the bypass flue heat exchanger (provided with an adjustment bypass), further heats all or part of the hot primary air drawn in by the air preheater and through the heat exchanger hot air flue, further improves the temperature of the hot primary air, and then the high-moisture lignite is dried in the coal mill, thereby improving the drying output of the coal mill, and finally introduced into the boiler burner.

[0016] 2. The adjustment system of the present application has the effect of wide load operation flexibility of the denitration device;

[0017] When the boiler is running at low load, the heat of the high-temperature flue gas drawn out of the boiler by the denitration bypass flue is used to mix directly with the flue gas of the boiler outlet flue in the case of cutting off the air valve of the bypass flue heat exchanger (equipped with a regulating bypass) or directly passing part of the flue gas through the bypass flue of the heat exchanger, thereby increasing the flue gas temperature at the inlet of the denitration device and improving the flexibility of the operation of the denitration device.

[0018] 3. Compared with the conventional denitration bypass flue device, the regulating system of the present application can flexibly adjust the relationship between the coal mill drying output of the lignite boiler and the operation of the denitration, and can separately adjust the air volume and the flue gas volume passing through the heat exchanger.

[0019] The present application can flexibly adjust the flue gas volume (heat source) and the air volume (cold source) entering each device through the adjustable denitration bypass flue and the regulating capacity of the bypass flue heat exchanger (equipped with a regulating bypass) to meet the different requirements for the coal mill drying output and the flexibility of the denitration under different loads.

[0020] 4. It is beneficial for the cold end treatment of the air preheater.

[0021] The regulating system of the present application uses the flue gas heat at the outlet of the air preheater through the heat pipe heat exchanger to increase the air temperature at the inlet of the cold end of the preheater, thereby avoiding the risk of corrosion of the cold end of the air preheater, and the effect is more obvious when the depth of the peak regulation is run.

[0022] The present application uses the denitration bypass flue arranged at a suitable position such as the boiler turning chamber, and internally arranges the bypass flue heat exchanger, uses the high-temperature flue gas drawn out by the bypass flue heat exchanger to exchange heat with the hot primary air at the outlet of the preheater, increases the coal mill drying output, and at the same time, has the effect of increasing the flue gas temperature at the inlet of the denitration device under low load, improving the denitration efficiency and the flexibility of the wide load denitration operation, and the feature is that the flue gas volume and the air volume passing through the bypass flue heat exchanger can be flexibly adjusted to adjust the outlet temperature of the flue gas and the hot air. And the heat pipe heat exchanger is arranged below the air preheater to increase the cold end temperature of the air preheater and avoid the corrosion of the cold end, thereby meeting the long-term stable operation requirements of the boiler unit during the depth of the peak regulation. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The present application is a denitration flexibility regulating system for improving the drying output of the high-moisture lignite boiler. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear and explicit, the spirit of the present application will be described in detail below, and any person skilled in the art can make changes and modifications to the technology taught by the present application content after understanding the embodiments of the present application content, which does not deviate from the spirit and scope of the present application content.

[0025] The schematic embodiments of the present application and their descriptions are used to explain the present application, but not as a limitation of the present application.

[0026] Embodiment 1

[0027] The system comprises a boiler 1, a denitration bypass flue 2 (with a heat exchanger bypass flue), a bypass flue heat exchanger (equipped with an adjusting bypass) 3, an air preheater 4, a heat exchanger hot air flue 5, a denitration device 6, a heat pipe heat exchanger 7, a boiler outlet flue 8, a coal mill 9 and a series of smoke and air passages and baffle doors / valves.

[0028] When the boiler 1 is running at high load, the high-temperature flue gas from the boiler 1 is introduced into the bypass flue heat exchanger (equipped with an adjusting bypass) 3 to further heat all or part of the hot primary air introduced through the heat exchanger hot air flue 5, thereby increasing the temperature of the hot primary air and introducing it into the coal mill 9 to dry the high-moisture lignite, and finally introducing it into the boiler 1 burner.

[0029] When the boiler 1 is running at low load, the high-temperature flue gas from the boiler 1 is introduced into the bypass flue heat exchanger (equipped with an adjusting bypass) 3 to further heat all or part of the hot primary air introduced through the heat exchanger hot air flue 5, thereby increasing the temperature of the hot primary air and introducing it into the coal mill 9 to dry the high-moisture lignite, and finally introducing it into the boiler 1 burner.

[0030] In some extreme load or extreme operating conditions, the proportion of flue gas passing through the bypass flue heat exchanger (equipped with an adjusting bypass) 3 in the denitration bypass flue 2 and the proportion of hot air temperature passing through the heat exchanger hot air flue 5 into the bypass flue heat exchanger 3 can be adjusted to meet the requirements of the coal mill 9 drying output and the denitration device 6 operating flue gas temperature of the high-moisture lignite-fired boiler.

Claims

1. A denitration flexibility adjustment system for enhancing the drying capacity of a high-moisture lignite boiler, characterized by It comprises a boiler (1), a denitration bypass flue (2), a bypass flue heat exchanger (3), an air preheater (4), a heat exchanger hot air flue (5), a denitration device (6), a heat pipe heat exchanger (7), a boiler outlet flue (8) and a coal mill (9). The denitration bypass flue (2) is communicated with the boiler (1) and the boiler outlet flue (8) respectively, and the flue gas outlets of the denitration bypass flue (2) and the boiler outlet flue (8) are communicated with the flue gas inlet of the denitration device (6); the flue gas outlet of the denitration device (6) is communicated with the flue gas inlet of the air preheater (4), and the flue gas outlet of the air preheater (4) is communicated with the flue gas inlet of the heat pipe heat exchanger (7). The hot air outlet of the heat pipe heat exchanger (7) is communicated with the cold end air inlet of the air preheater (4); the hot primary air outlet of the air preheater (4) is communicated with the heat exchanger hot air flue (5); the hot air inlet of the bypass flue heat exchanger (3) is communicated with the heat exchanger hot air flue (5); the air outlet of the bypass flue heat exchanger (3) is communicated with the air inlet of the coal mill (9); the air outlet of the coal mill (9) is communicated with the air inlet of the burner of the boiler (1); when the boiler (1) is operated at high load, the high-temperature flue gas drawn from the boiler (1) by the denitration bypass flue (2) is used to heat the whole or part of the hot primary air drawn into the coal mill (9) by the air preheater (4) and the heat exchanger hot air flue (5) through the bypass flue heat exchanger (3), so that the temperature of the hot primary air is further increased, and the high-moisture lignite is dried in the coal mill (9), and finally introduced into the burner of the boiler (1); when the boiler (1) is operated at low load, the flue gas drawn from the boiler (1) by the denitration bypass flue (2) is used to mix with the flue gas of the boiler outlet flue (8) to increase the temperature of the flue gas entering the denitration device (6) under the condition that the air baffle door of the bypass flue heat exchanger (3) is cut off or part of the flue gas directly passes through the heat exchanger adjustment bypass, and finally the flue gas passes through the air preheater (4) and the heat pipe heat exchanger (7) to enter the downstream equipment.

2. A system for denitration flexibility regulation for increasing the drying capacity of a high-moisture lignite boiler according to claim 1, characterized in that The bypass flue heat exchanger (3) is provided with a baffle door to adjust the heat exchange amount.

3. A system for denitration flexibility regulation for increasing the drying capacity of a high-moisture lignite boiler according to claim 1, characterized in that The denitration bypass flue (2), the bypass flue of the bypass flue heat exchanger (3), the heat exchanger hot air flue (5) and the boiler outlet flue (8) are all provided with flue gas and air baffle doors.

4. A system for denitration flexibility regulation for increasing the drying capacity of a high-moisture lignite boiler according to claim 1, characterized in that The bypass flue heat exchanger (3) is provided with an adjustment bypass.

Images