CN110440234B - Comprehensive utilization adjustment system for low-grade heat of machine furnace and control method thereof - Google Patents
Comprehensive utilization adjustment system for low-grade heat of machine furnace and control method thereof Download PDFInfo
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- CN110440234B CN110440234B CN201910793504.6A CN201910793504A CN110440234B CN 110440234 B CN110440234 B CN 110440234B CN 201910793504 A CN201910793504 A CN 201910793504A CN 110440234 B CN110440234 B CN 110440234B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B1/00—Methods of steam generation characterised by form of heating method
- F22B1/02—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers
- F22B1/18—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being a hot gas, e.g. waste gas such as exhaust gas of internal-combustion engines
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B35/00—Control systems for steam boilers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22D—PREHEATING, OR ACCUMULATING PREHEATED, FEED-WATER FOR STEAM GENERATION; FEED-WATER SUPPLY FOR STEAM GENERATION; CONTROLLING WATER LEVEL FOR STEAM GENERATION; AUXILIARY DEVICES FOR PROMOTING WATER CIRCULATION WITHIN STEAM BOILERS
- F22D1/00—Feed-water heaters, i.e. economisers or like preheaters
- F22D1/16—Feed-water heaters, i.e. economisers or like preheaters with water tubes arranged otherwise than in the boiler furnace, fire tubes, or flue ways
- F22D1/20—Feed-water heaters, i.e. economisers or like preheaters with water tubes arranged otherwise than in the boiler furnace, fire tubes, or flue ways and directly connected to boilers
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery
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Abstract
The invention discloses a comprehensive utilization adjusting system of low-grade heat of a machine furnace and a control method thereof. The control method comprises the following steps: switching to operate in a heating mode and supplying heat from the boiler side to the low pressure heating unit on the turbine side when the exhaust temperature of the high-load boiler is high in summer; in winter or when the low-load boiler exhaust gas temperature is low, the operation is switched to be in a heating mode and the low-pressure heating unit at the side of the boiler side turbine is used for heating. The comprehensive cascade utilization adjustment system for the tail heat of the machine furnace greatly improves the comprehensive utilization rate of waste heat, improves the boiler efficiency and the unit efficiency, and solves the problems of cold end corrosion and blockage of the low-load air preheater.
Description
Technical Field
The invention relates to the technical field of boiler manufacturing and transformation, in particular to a comprehensive utilization and adjustment system for low-grade heat of a machine furnace and a control method thereof
Background
At present, the actual operation of the boiler has higher summer exhaust temperature than a design value, larger waste heat loss and lower winter exhaust temperature than the design value, and the cold end of the air preheater is corroded and blocked seriously. To solve the problem, some projects adopt that a flue gas heat exchanger is additionally arranged at a rear flue of the air preheater to recover flue gas waste heat, and meanwhile, an air heater is additionally arranged at an outlet of a blower to improve cold air temperature at an inlet of the air preheater, so that the purpose of recovering the flue gas waste heat is achieved, and risks of corrosion and blockage of a cold end of the air preheater are reduced.
However, for some power plants with low design exhaust gas temperature, the boiler exhaust gas temperature is very low in winter under low load, and the exhaust gas heat exchanger is not needed to recover waste heat at the moment, so that cold air at the inlet of the air preheater cannot be heated by the air heater to prevent corrosion and blockage at the cold end of the air preheater. While some power plants can solve the problem by adopting a hot air recirculation means or a steam heater means, the two modes reduce the economy of the whole unit and greatly increase the transformation cost of the power plant.
Disclosure of Invention
Aiming at the defects of the scheme of combining a flue gas heat exchanger (or a low-temperature economizer) with an air heater (or a warm air heater) and the defects of poor economy of the scheme of adopting a hot air recirculation or a steam air heater, the invention provides a comprehensive utilization and adjustment system for low-grade heat of a machine furnace and a control method thereof.
The invention provides a comprehensive utilization and adjustment system for low-grade heat of a machine furnace, which comprises an air preheating unit, a flue gas heat exchange unit, an air heating unit and a low-pressure heating unit at the side of a steam turbine, wherein the low-pressure heating unit comprises a low-pressure pipeline and a plurality of groups of low-pressure heaters which are arranged on the low-pressure pipeline in series;
the air side outlet of the air heating unit is connected with the air side inlet of the air preheating unit, and the flue gas side outlet of the air preheating unit is connected with the flue gas side inlet of the flue gas heat exchange unit;
the upstream of the low-adding pipeline is connected with a water supply side inlet of the flue gas heat exchange unit through a main water intake pipeline, a water supply side outlet of the flue gas heat exchange unit is connected with the midstream of the low-adding pipeline through a main water return pipeline and is connected with a water supply side inlet of the air heating unit through an air heating unit inlet pipeline, and a water supply side outlet of the air heating unit is connected with the main water intake pipeline through a first air heating unit outlet pipeline;
the water supply side outlet of the air heating unit is further connected with the main water return pipeline through the outlet pipeline of the second air heating unit, the downstream of the low-pressure pipeline is further connected with the main water intake pipeline through the heat collecting pipeline, and at least 1 group of low-pressure heaters are arranged between the connection point of the heat collecting pipeline and the low-pressure pipeline and the connection point of the main water return pipeline and the low-pressure pipeline.
According to one embodiment of the system for regulating the comprehensive utilization of low-grade heat of the machine furnace, the system further comprises a recirculation pipeline arranged between the main water return pipeline and the main water intake pipeline, and the recirculation pipeline is provided with a control valve.
According to one embodiment of the system for comprehensively utilizing and adjusting the low-grade heat of the machine furnace, the main water intake pipeline, the main water return pipeline, the air heating unit inlet pipeline, the first air heating unit outlet pipeline, the second air heating unit outlet pipeline and the heat intake pipeline are all provided with control valves, and the downstream of the main water intake pipeline is also provided with a booster pump.
According to one embodiment of the system for comprehensively utilizing and adjusting the low-grade heat of the machine furnace, the connection point of the outlet pipeline of the first air heating unit and the main water intake pipeline is positioned between the control valve and the booster pump on the main water intake pipeline;
the connection point of the recirculation pipeline and the main water return pipeline is positioned at the upstream of the control valve on the main water return pipeline, and the connection point of the recirculation pipeline and the main water intake pipeline is positioned between the control valve on the main water intake pipeline and the booster pump and at the upstream of the connection point of the outlet pipeline of the first air heating unit and the main water intake pipeline;
the connection point of the heat taking pipeline and the main water taking pipeline is positioned between the control valve and the booster pump on the main water taking pipeline and is positioned at the upstream of the connection point of the recirculation pipeline and the main water taking pipeline;
the connection point of the outlet pipeline of the second air heating unit and the main water return pipeline is positioned at the downstream of the control valve on the main water return pipeline.
According to one embodiment of the low-grade heat comprehensive utilization adjusting system of the machine furnace, the adjusting system further comprises a dust removing unit arranged at the upstream or downstream of the flue gas heat exchange unit, and an induced air unit, a desulfurization unit and a smoke discharging unit which are sequentially arranged at the downstream of the flue gas heat exchange unit.
According to one embodiment of the low-grade heat comprehensive utilization adjustment system of the machine furnace, the air heating unit is a primary air heater or a secondary air heater arranged in a cold air duct between the blower and the air preheating unit, the flue gas heat exchange unit is a flue gas heat exchanger arranged in a flue behind the air preheating unit, and the air preheating unit is an air preheater arranged in a tail flue of the boiler.
The invention also provides a control method of the system for comprehensively utilizing and adjusting the low-grade heat of the machine furnace, which is switched to operate in a heat supply mode and supplies heat from a low-pressure heating unit on the side of a turbine of the boiler when the exhaust temperature of the high-load boiler is higher in summer; in winter or when the low-load boiler exhaust gas temperature is low, the operation is switched to be in a heating mode and the low-pressure heating unit at the side of the boiler side turbine is used for heating.
According to one embodiment of the control method of the low-grade heat comprehensive utilization adjustment system of the machine furnace, the heat supply mode is as follows: and pumping low-temperature condensed water in the low-pressure pipeline, conveying the low-temperature condensed water to a smoke heat exchange unit through a main water intake pipeline for smoke waste heat recovery, conveying one part of the condensed water after temperature rise to an air heating unit through an inlet pipeline of the air heating unit for heating cold air, and returning the other part of the condensed water to the low-pressure pipeline through a main water return pipeline, wherein the condensed water after temperature reduction returns to the main water intake pipeline through an outlet pipeline of the first air heating unit.
According to one embodiment of the control method of the low-grade heat comprehensive utilization adjustment system of the machine furnace, the heating mode is as follows: and extracting high-temperature condensate and low-temperature condensate in the low-pressure pipeline, conveying the high-temperature condensate and the low-temperature condensate to a smoke heat exchange unit through a main water intake pipeline for smoke waste heat recovery, conveying all the heated condensate to an air heating unit through an inlet pipeline of the air heating unit for heating cold air, and returning the cooled condensate to the low-pressure pipeline through an outlet pipeline of the second air heating unit and a main water return pipeline.
According to one embodiment of the control method of the system for comprehensively utilizing and adjusting the low-grade heat of the machine furnace, the sum of the outlet flue gas temperature of the air preheating unit and the outlet air temperature of the air heating unit is used as an automatically controlled dependent variable, and when the adjusting system further comprises a recirculation pipeline arranged between a main water return pipeline and a main water intake pipeline, the flue gas waste heat is recovered by adjusting the flow of the main water intake pipeline, the heat intake pipeline and the recirculation pipeline to adjust the temperature and the flow of condensed water entering the inlet of the water supply side of the flue gas heat exchange unit.
Compared with the prior art, the invention has the following advantages:
1) In summer or when the exhaust temperature of the high-load boiler is higher, the waste heat of the tail smoke of the boiler can be effectively recovered; when the smoke exhaust temperature of the low-load boiler is low in winter, the heat of low-quality condensate water of the low-pressure heater system of the steam turbine can be used for heating the boiler for air supply, and the economy of the whole unit is greatly improved;
2) When the load of the unit and the external conditions change, the air conditioner can be freely switched in a heat supply mode or a heating mode without adding an external heat source, so that the cold air temperature at the inlet of the air preheater is effectively improved, and the risk of corrosion and blockage of a cold end heat exchange element of the air preheater is prevented;
3) Compared with other external heat sources such as a steam air heater, hot air recirculation and the like for heating cold air, the invention can improve the temperature of the flue gas at the outlet of the air preheater to a safer temperature without sacrificing the running economical performance of the unit.
Drawings
Fig. 1 shows a schematic structural diagram of a low-grade heat comprehensive utilization adjustment system of a machine furnace according to an exemplary embodiment of the present invention.
Reference numerals illustrate:
1. an air preheating unit; 2. a flue gas heat exchange unit; 3. a dust removal unit; 4. an induced air unit; 5. a desulfurization unit; 6. a smoke exhausting unit; 7. a control valve; 8. an air heating unit inlet line; 9. a main water intake pipeline; 10. a low-pressure pipeline; 11. a low pressure heater; 12. a main water return line; 13. an air heating unit; 14. a recirculation line; 15. a booster pump; 16. a blower; 17. a heat-taking pipeline; 18. a first air heating unit outlet line; 19. and a second air heating unit outlet pipeline.
Detailed Description
All of the features disclosed in this specification, or all of the steps in a method or process disclosed, may be combined in any combination, except for mutually exclusive features and/or steps.
Any feature disclosed in this specification may be replaced by alternative features serving the same or equivalent purpose, unless expressly stated otherwise. That is, each feature is one example only of a generic series of equivalent or similar features, unless expressly stated otherwise.
In the prior art, a flue gas heat exchanger (or a low-temperature economizer) and air heater (or a warm air heater) combined system adopted by some projects can solve the problems of higher flue gas temperature of a boiler in summer or a high-load boiler and corrosion and blockage of a cold end of the air heater, but can not only heat cold air by recycling flue gas waste heat under the condition of lower flue gas temperature of the boiler in winter or the low-load boiler, but also can prevent the blockage of the rotary heater by additionally adopting high energy consumption modes such as a steam warm air heater or hot air recirculation and the like, and the problems of energy waste and the like exist if the anti-blockage margin of the preheater is improved.
The invention provides a comprehensive utilization and adjustment system for low-grade heat of a machine furnace through system optimization on the basis of a flue gas heat exchanger and air heater system. The system has the advantages that the functions of recovering the flue gas waste heat to the inlet cold air of the air preheater and the low-adding system in summer or when the exhaust temperature of the high-load boiler is higher are reserved, the function of supplying heat to the side of the boiler through the steam turbine low-adding system in winter or when the exhaust temperature of the low-load boiler is lower is added, and the system can freely switch the working mode and automatically adjust according to the load and the change of external conditions.
The low-grade heat comprehensive utilization and adjustment system of the machine furnace is specifically described below.
Fig. 1 shows a schematic structural diagram of a low-grade heat comprehensive utilization adjustment system of a machine furnace according to an exemplary embodiment of the present invention.
As shown in fig. 1, according to an exemplary embodiment of the present invention, the system for adjusting low-grade heat comprehensive utilization of an engine furnace includes an air preheating unit 1, a flue gas heat exchange unit 2, an air heating unit 13, and a low-pressure heating unit on a turbine side, wherein the low-pressure heating unit includes a low-pressure pipe 10 and several groups of low-pressure heaters 11 serially arranged on the low-pressure pipe.
The air preheating unit 1 is preferably an air preheater arranged in the boiler tail flue for preheating the air entering the boiler. The air heating unit 13 is preferably a primary air heater or a secondary air heater arranged in the cool air duct between the blower 16 and the air preheating unit 1 for heating the inlet cool air of the air preheating unit. The flue gas heat exchange unit 2 is preferably a flue gas heat exchanger arranged in the flue after the air preheating unit 1 for recovering flue gas waste heat at the outlet of the air preheating unit 1.
In addition, the adjusting system of the invention can also comprise a dust removing unit 3 (such as a dust remover) arranged at the upstream or downstream of the flue gas heat exchanging unit 2, and an induced draft unit 4 (such as a draught fan), a desulfurization unit 5 (such as a desulfurization tower) and a smoke discharging unit 6 (such as a chimney) which are sequentially arranged at the downstream of the flue gas heat exchanging unit 2.
The air side outlet of the air heating unit 13 is connected with the air side inlet of the air preheating unit 1, the flue gas side outlet of the air preheating unit 1 is connected with the flue gas side inlet of the flue gas heat exchange unit 2, cold air heated by the air heating unit 13 enters the air preheating unit 1 to be preheated into hot air, and flue gas from the boiler economizer enters the flue gas heat exchange unit 2 to recover waste heat after heat exchange of the air preheating unit 1.
The upstream of the low-adding pipeline 10 is connected with a water supply side inlet of the flue gas heat exchange unit 2 through a main water intake pipeline 9, the water supply side outlet of the flue gas heat exchange unit 2 is connected with the midstream of the low-adding pipeline 10 through a main water return pipeline 12 and is connected with a water supply side inlet of the air heating unit 13 through an air heating unit inlet pipeline 8, and the water supply side outlet of the air heating unit 13 is connected with the main water intake pipeline 9 through a first air heating unit outlet pipeline 18.
Wherein, the water supply side outlet of the air heating unit 13 is also connected with the main water return pipeline 12 through the second air heating unit outlet pipeline 19, the downstream of the low-pressure adding pipeline 10 is also connected with the main water intake pipeline 9 through the heat collecting pipeline 17, and at least 1 group of low-pressure heaters are arranged between the connection point of the heat collecting pipeline 17 and the low-pressure adding pipeline 10 and the connection point of the main water return pipeline 12 and the low-pressure adding pipeline 10.
The invention adds the heat-collecting pipeline 17 and the outlet pipeline 19 of the second air heating unit on the basis of the flue gas heat exchanger combined air heater system scheme, thereby realizing the expected function through control. On the one hand, the heat-collecting pipeline 17 can extract part of high-temperature condensate water from the heat-collecting pipeline to enter the air heating unit to heat cold air when the exhaust temperature of the boiler is low, and can adjust the flow of the high-temperature condensate water extracted from the low-pressure heating unit according to the change of the exhaust temperature of the boiler, so that the exhaust heat of the boiler and the low-grade condensate water heat of the low-pressure heating unit are effectively utilized. On the other hand, two paths of outlet pipelines are arranged at the outlet of the air heating unit, so that the condensed water at the outlet of the air heating unit can be returned to the inlet of the booster pump or the low-pressure heating unit according to the running mode of the system.
The main water intake pipeline 9 is connected with the low-pressure pipeline 10 and the flue gas heat exchange unit 2 and is used for taking water of condensed water; the main water return pipeline 12 is connected with the flue gas heat exchange unit 2 and the low-pressure pipeline 10 and is used for returning condensate water. The heat-collecting pipeline 17 is connected with the low-pressure pipeline 10 and the main water-collecting pipeline, and is used for supplying high-temperature condensed water to the system by the low-pressure heating unit at the turbine side when the low-load smoke discharging temperature is low in winter, so as to supply heat to the boiler side. The first air heating unit outlet pipeline 18 is connected with the air heating unit 13 and the main water intake pipeline 9 and is used for backwater of condensate water at the outlet of the air heating unit; the second air heating unit pipeline 19 connects the air heating unit 13 with the main water return pipeline 12, and is also used for returning condensate water at the outlet of the air heating unit.
Furthermore, in order to adjust the inlet water temperature of the flue gas heat exchange unit, the inventive adjustment system may further comprise a recirculation line 14 arranged between the main water return line 12 and the main water intake line 9, the recirculation line 14 being provided with a control valve 7.
In order to realize control, the main water intake pipeline 9, the main water return pipeline 12, the air heating unit inlet pipeline 8, the first air heating unit outlet pipeline 18, the second air heating unit outlet pipeline 19 and the heat intake pipeline 17 are all provided with control valves 7, and the downstream of the main water intake pipeline 9 is also provided with a booster pump 15.
A control valve 7 is arranged on each condensate line for regulating the distribution of resistance of the line and regulating the flow of condensate while being able to shut off or open each line. The booster pump 15 is used for adjusting the total flow of the condensate entering the flue gas heat exchange unit 2 and overcoming the resistance of the condensate side of the system.
On the basis of this, the connection point of the first air heating unit outlet line 18 to the main water intake line 9 is preferably located between the control valve and the booster pump 15 on the main water intake line 9. The connection point of the recirculation line 14 to the main return line 12 is located upstream of the control valve on the main return line 12, the connection point of the recirculation line 14 to the main intake line 9 is located between the control valve on the main intake line 9 and the booster pump 15 and upstream of the connection point of the first air heating unit outlet line 18 to the main intake line 9.
The connection point of the heat-collecting pipeline 17 and the main water-collecting pipeline 9 is positioned between the control valve and the booster pump 15 on the main water-collecting pipeline 9 and is positioned upstream of the connection point of the recirculation pipeline 14 and the main water-collecting pipeline 9; the connection point of the secondary air heating unit outlet line 19 to the primary return line 12 is located downstream of the control valve on the primary return line 12.
Therefore, the invention can realize the comprehensive and reasonable utilization of heat of the boiler side and the steam turbine side, and particularly can realize the following two functions:
1) In summer or when the exhaust temperature of the high-load boiler is higher, the exhaust gas waste heat of the tail part is firstly recovered to the cold air at the inlet of the air preheating unit, and if the residual heat exists, the residual heat can be recovered to the condensate water of the low-pressure heating unit at the side of the steam turbine. In this mode, the boiler side supplies heat to the steam turbine side;
2) When the smoke exhaust temperature of the low-load boiler is low in winter, the low-pressure heating unit at the side of the turbine supplies heat to cold air at the inlet at the side of the boiler, so that the high-efficiency utilization of the heat of low-grade condensed water is realized. In this mode, the steam turbine side supplies heat to the boiler side.
The two working modes can be freely switched according to the changes of external conditions such as load, ambient temperature and the like, so that different control effects are realized. In addition, by increasing the temperature of the cold air at the inlet of the air preheating unit, the risk of corrosion and blockage of the heat exchange element at the cold end of the air preheating unit can be greatly reduced; the low-temperature dust removal effect of the dust removal unit can be greatly exerted by controlling the temperature of the inlet flue gas of the dust removal unit to be about 90 ℃, and the dust removal efficiency is improved.
The invention also provides a control method of the system for comprehensively utilizing and adjusting the low-grade heat of the machine furnace. According to an exemplary embodiment of the present invention, the control method includes: switching to operate in a heating mode and supplying heat from the boiler side to the low pressure heating unit on the turbine side when the exhaust temperature of the high-load boiler is high in summer; in winter or when the low-load boiler exhaust gas temperature is low, the operation is switched to be in a heating mode and the low-pressure heating unit at the side of the boiler side turbine is used for heating.
When the temperature of the exhaust gas of the summer or high-load boiler is higher, the system operates in a heat supply mode under the working condition, namely, when the temperature of the exhaust gas of the outlet of the air preheating unit is higher and the tail smoke has redundant heat, the system is used for recovering the smoke waste heat. The heat is reasonably regulated between the heating cold air and the heating condensed water, so that the waste heat as much as possible is ensured to be used for replacing high-quality energy required to be consumed by the boiler.
The heat supply mode is as follows: the low-temperature condensate water in the extraction low-pressure pipeline 10 is conveyed to the flue gas heat exchange unit 2 through the main water intake pipeline 9 for flue gas waste heat recovery, one part of the condensate water after temperature rising is conveyed to the air heating unit 13 through the air heating unit inlet pipeline 8 for heating cold air, the other part of the condensate water returns to the low-pressure pipeline 10 through the main water return pipeline 12, and the condensate water after temperature reducing is returned to the main water intake pipeline through the first air heating unit outlet pipeline 18.
When the system is operated under this condition, the control valve 7 on the main water intake line 9, the main water return line 12, the recirculation line 14 (if provided), the first air heating unit outlet line 18 are all open, and the heat intake line 17, the second air heating unit outlet line 19 are all closed.
When the smoke temperature of the low-load boiler is lower in winter, the system operates in a heating mode under the working condition, namely, when the temperature of the outlet smoke of the air preheating unit 1 is lower and the tail smoke does not have redundant heat, the steam turbine side of the system supplies heat to the boiler side. The cold air (comprising primary air and secondary air) at the inlet of the air preheating unit is heated by taking heat from the condensation water, so that the cold end corrosion and blockage of the air preheating unit are prevented, the heat after the preheating unit is recycled by the flue gas heat exchange unit and returned by the heating cold air, the final exhaust gas temperature of the boiler is ensured not to be increased, and the overall economy of a unit is improved.
The heating mode is as follows: the high-temperature condensate and the low-temperature condensate in the low-pressure adding pipeline 10 are extracted and conveyed to the smoke heat exchange unit 2 through the main water intake pipeline 9 for smoke waste heat recovery, the heated condensate is conveyed to the air heating unit through the air heating unit inlet pipeline 8 to heat cold air, and the cooled condensate is returned to the low-pressure adding pipeline 10 through the second air heating unit outlet pipeline 19 and the main water return pipeline 12.
When the system operates under the working condition, the control valves 7 on the main water return pipeline 12 and the first air heating unit outlet pipeline 18 are closed, the main water intake pipeline 9, the heat taking pipeline 17 and the second air heating unit outlet pipeline 19 are opened, the system can adjust the opening of the control valves on the main water taking pipeline 9 or the heat taking pipeline 17 according to the change of external conditions such as load, further adjust the water temperature (under the condition of not lower than 70 ℃ and the condition of being provided with) after the two pipelines of the pipeline and the recirculation pipeline 14, the temperature is controlled to be higher as much as possible, the corrosion of the flue gas heat exchange unit 2 is prevented), the condensed water after the two pipelines of the pipeline are mixed enters the flue gas heat exchange unit 2 and is further heated, all the condensed water from the flue gas heat exchange unit 2 enters the air heating unit 13 to heat the cold air from the blower 16, and the condensed water returns to the low-adding pipeline 10 through the second air heating unit outlet pipeline 19 and the main water return pipeline 12 after the temperature of the condensed water is reduced.
When the regulation system further comprises a recirculation line 14 arranged between the main water return line 12 and the main water intake line 9, it is also possible to regulate the temperature of the condensate entering the inlet of the water supply side of the flue gas heat exchange unit 2 by regulating the flow rates of the main water intake line 9, the heat intake line 17 and the recirculation line 14.
Therefore, the free switching of the system under each working condition can be realized, and the operation mode of the system is adjusted according to the exhaust smoke temperature of the outlet of the air preheating unit and the air temperature of the inlet of the blower. When the redundant heat of the tail flue gas of the boiler can be recovered, the heat can be recovered to a boiler side and a steam turbine side low-pressure system (heat supply mode operation); when the temperature of the tail flue gas of the boiler is low and the flue gas does not recover heat, the side of the boiler is supplemented with condensed water through the side low of the steam turbine (the operation of a heating mode).
And in winter, the cold air temperature at the inlet of the air preheating unit can be improved by the heat recovered by the flue gas heat exchange unit and the heat of the condensate water of the low-pressure heater at the side of the steam turbine without other auxiliary means, so that the economic performance of the unit can not be sacrificed even if the flue gas temperature at the outlet of the air preheating unit is controlled at a higher safety margin as long as the flue gas temperature after the flue gas heat exchange unit is ensured to be kept at a lower value.
In addition, when the unit load, the ambient temperature, the coal quality, the anti-blocking ash temperature requirement of the cold end of the preheater and the like change, the system can automatically adjust the outlet smoke temperature of the air preheating unit 1 and the outlet air temperature of the air heating unit 13, so that the safety of the air preheating unit is ensured, and as much heat as possible is sent back to the boiler to achieve the high-quality utilization of waste heat, and the running economical performance of the unit is ensured. When the outlet smoke temperature of the air preheating unit 1 is low, but the smoke waste heat can be recovered, the system can automatically adjust the opening of the control valves on the main water intake pipeline 9 and the recirculation pipeline 14 to adjust the inlet water temperature of the smoke heat exchange unit 2 to recover the smoke waste heat of the outlet of the air preheating unit 1.
The system can be used as an automatically controlled dependent variable through the sum of the outlet flue gas temperature of the air preheating unit 1 and the outlet air temperature of the air heating unit 13 (hereinafter referred to as cold end comprehensive temperature) required by different coal types, so that the automatic control system is designed by replacing high quality energy consumed by the original boiler with low quality heat at the tail parts of two layers of the machine furnace as much as possible.
For example, when the heating mode is operated, the control valve opening degree on the control heat collecting pipe 17 is 0%, the smaller the control valve opening degree on the main water collecting pipe 9 is, the less heat is supplied to the condensed water; when the opening of the regulating valve on the main water intake pipeline 9 is reduced to 0%, the waste heat recovered by the flue gas heat exchange unit is fully used for heating cold air, if the waste heat is still insufficient for heating the cold air, a control valve on the heat intake pipeline 17 is opened according to the requirement, the system operation mode transits to the heating mode, the larger the opening of the regulating valve on the heat intake pipeline 17 is, the more low-quality heat obtained by the boiler from the side of the steam turbine is, and when the waste heat exhausted by the boiler is increased, the reverse adjustment is only needed.
More preferably, the system adopts a main water intake pipeline and a heat intake pipeline, and a control valve on the main water intake pipeline and the heat intake pipeline can automatically adjust the opening according to the changes of load, ambient temperature, coal quality, the anti-ash blocking temperature requirement of the cold end of the preheater and the like, so as to adjust the operation mode of the system. The system is provided with two outlet pipelines at the outlet of the air heating unit, and the system operates in different working modes when the unit load, the ambient temperature, the coal quality, the anti-ash blocking temperature requirement of the cold end of the preheater and the like are changed, so that the opening of the two outlet pipelines can be automatically selected according to the water temperature of the outlet of the air heating unit.
In summary, the invention provides an optimizing and adjusting system and a control method for comprehensively and stepwise utilizing the tail heat of the machine furnace through system optimization, which not only reserves the functions of recovering the waste heat of the flue gas to the cold air at the inlet of the air preheating unit and to the low-adding system when the exhaust temperature of the high-load boiler is higher in summer or in low-load, but also increases the function of supplying heat to the boiler side through the low-adding system of the steam turbine when the exhaust temperature of the low-load boiler is lower in winter or in low-load, and the system can freely switch the working mode according to the load change, thereby organically and comprehensively considering the tail waste heat of the flue gas at the boiler side and the heat of the condensate water of the low-adding system of the steam turbine side, realizing the high-efficiency utilization of low-grade heat, achieving the aim of preventing the cold end corrosion blockage risk of the air preheater and improving the safety of unit operation.
The invention is not limited to the specific embodiments described above. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification, as well as to any novel one, or any novel combination, of the steps of the method or process disclosed.
Claims (6)
1. The system is characterized by comprising an air preheating unit, a flue gas heat exchange unit, an air heating unit and a low-pressure heating unit at the side of a turbine, wherein the low-pressure heating unit comprises a low-pressure pipeline and a plurality of groups of low-pressure heaters which are arranged on the low-pressure pipeline in series;
the air side outlet of the air heating unit is connected with the air side inlet of the air preheating unit, and the flue gas side outlet of the air preheating unit is connected with the flue gas side inlet of the flue gas heat exchange unit;
the upstream of the low-adding pipeline is connected with a water supply side inlet of the flue gas heat exchange unit through a main water intake pipeline, a water supply side outlet of the flue gas heat exchange unit is connected with the midstream of the low-adding pipeline through a main water return pipeline and is connected with a water supply side inlet of the air heating unit through an air heating unit inlet pipeline, and a water supply side outlet of the air heating unit is connected with the main water intake pipeline through a first air heating unit outlet pipeline;
the water supply side outlet of the air heating unit is also connected with a main water return pipeline through an outlet pipeline of the second air heating unit, the downstream of the low-pressure pipeline is also connected with the main water intake pipeline through a heat taking pipeline, and at least 1 group of low-pressure heaters are arranged between the connection point of the heat taking pipeline and the low-pressure pipeline and the connection point of the main water return pipeline and the low-pressure pipeline;
the adjusting system further comprises a dust removing unit arranged at the upstream or downstream of the flue gas heat exchange unit, and an induced draft unit, a desulfurization unit and a smoke discharging unit which are sequentially arranged at the downstream of the flue gas heat exchange unit;
the air heating unit is a primary air heater or a secondary air heater arranged in a cold air duct between the blower and the air preheating unit, the flue gas heat exchange unit is a flue gas heat exchanger arranged in a flue behind the air preheating unit, and the air preheating unit is an air preheater arranged in a boiler tail flue.
2. The system for integrated utilization and adjustment of low-grade heat of a furnace according to claim 1, further comprising a recirculation line disposed between the main water return line and the main water intake line, the recirculation line being provided with a control valve.
3. The system for comprehensively utilizing and adjusting low-grade heat of a machine furnace according to claim 2, wherein the main water intake pipeline, the main water return pipeline, the air heating unit inlet pipeline, the first air heating unit outlet pipeline, the second air heating unit outlet pipeline and the heat intake pipeline are all provided with control valves, and a booster pump is further arranged at the downstream of the main water intake pipeline.
4. The system for integrated utilization and adjustment of low-grade heat of a furnace according to claim 3, wherein the connection point of the outlet pipeline of the first air heating unit and the main water intake pipeline is positioned between the control valve and the booster pump on the main water intake pipeline;
the connection point of the recirculation pipeline and the main water return pipeline is positioned at the upstream of the control valve on the main water return pipeline, and the connection point of the recirculation pipeline and the main water intake pipeline is positioned between the control valve on the main water intake pipeline and the booster pump and at the upstream of the connection point of the outlet pipeline of the first air heating unit and the main water intake pipeline;
the connection point of the heat taking pipeline and the main water taking pipeline is positioned between the control valve and the booster pump on the main water taking pipeline and is positioned at the upstream of the connection point of the recirculation pipeline and the main water taking pipeline;
the connection point of the outlet pipeline of the second air heating unit and the main water return pipeline is positioned at the downstream of the control valve on the main water return pipeline.
5. A control method of the low-grade heat comprehensive utilization adjustment system of a machine furnace according to any one of claims 1 to 4, characterized in that in summer or when the high-load boiler exhaust gas temperature is high, switching is made to operate in a heating mode and heat is supplied from the low-pressure heating unit on the side of the turbine of the boiler; when the exhaust temperature of the low-load boiler is lower in winter, the low-pressure heating unit is switched to operate in a heating mode and is used for heating the side of the boiler to the turbine;
the heat supply mode is as follows: extracting low-temperature condensed water in the low-pressure pipeline, conveying the low-temperature condensed water to a smoke heat exchange unit through a main water intake pipeline for smoke waste heat recovery, conveying one part of the condensed water after temperature rise to an air heating unit through an inlet pipeline of the air heating unit for heating cold air, and returning the other part of the condensed water to the low-pressure pipeline through a main water return pipeline, wherein the condensed water after temperature reduction returns to the main water intake pipeline through an outlet pipeline of the first air heating unit;
the heating mode is as follows: and extracting high-temperature condensate and low-temperature condensate in the low-pressure pipeline, conveying the high-temperature condensate and the low-temperature condensate to a smoke heat exchange unit through a main water intake pipeline for smoke waste heat recovery, conveying all the heated condensate to an air heating unit through an inlet pipeline of the air heating unit for heating cold air, and returning the cooled condensate to the low-pressure pipeline through an outlet pipeline of the second air heating unit and a main water return pipeline.
6. The control method of the system for comprehensively utilizing and adjusting low-grade heat of a machine furnace according to claim 5, wherein the control method is characterized in that the sum of the outlet flue gas temperature of the air preheating unit and the outlet air temperature of the air heating unit is used as a dependent variable of automatic control, and when the adjusting system further comprises a recirculation pipeline arranged between a main water return pipeline and a main water intake pipeline, the flue gas waste heat is recovered by adjusting the flow rates of the main water intake pipeline, the heat intake pipeline and the recirculation pipeline to adjust the condensation water temperature and the flow rate entering the inlet of the water supply side of the flue gas heat exchange unit.
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| CN113137624B (en) * | 2021-04-02 | 2023-06-20 | 武瑞香 | Energy-saving utilization device of thermal power plant flue gas system |
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