CN102444901A - Coal power plant combined type heat pipe flue gas waste heat recovery system and method - Google Patents

Abstract

The invention discloses a combined heat pipe flue gas waste heat recovery system and method of a coal power plant. The system includes a boiler, a dust collector, an induced draft fan, a booster fan, a combined heat pipe heat exchanger assembly, and a desulfurization tower that are sequentially connected through pipelines. and chimney; the method includes: in the flue system of the coal power plant, adding a combined heat pipe heat exchanger assembly to recover the heat and water vapor of the flue system; between the induced draft fan and the booster fan of the flue system , leading to the bypass flue, connected to the flue system between the desulfurization tower and the chimney. The combined heat pipe flue gas waste heat recovery system and method of the coal power plant described in the present invention can overcome the defects of poor energy saving, poor environmental protection, high cost, poor reliability and large occupied space in the prior art, so as to achieve good energy saving and environmental protection. , low cost, good reliability, small footprint and wide application range.

Description

A combined heat pipe flue gas waste heat recovery system and method for a coal power plant

technical field

The invention relates to the technical field of energy conservation and environmental protection of coal power plants, in particular to a combined heat pipe flue gas waste heat recovery system and method of coal power plants.

Background technique

In recent years, my country's energy demand has shown a rigid growth. Due to the constraints of domestic resource guarantee capacity and environmental capacity, as well as global energy security and the impact of climate change response, resource and environmental constraints have been increasingly strengthened, and the situation of energy conservation and emission reduction is very severe.

According to my country's "Twelfth Five-Year Plan" put forward the requirements of energy conservation and emission reduction goals. In terms of energy saving, by 2015, the national energy consumption per 10,000 yuan of GDP will drop to 0.869 tons of standard coal (calculated at the price in 2005), which is 16% lower than the 1.034 tons of standard coal in 2010. During the "Twelfth Five-Year Plan" period, Realize energy saving of 670 million tons of standard coal. In terms of emission reduction, by 2015, the national chemical oxygen demand and sulfur dioxide emissions will be controlled at 23.476 million tons and 20.864 million tons respectively, which are 8% lower than in 2010; the national ammonia nitrogen and nitrogen oxide emissions will be controlled at 2.380 million tons and 20.462 million tons, down 10% from 2010 respectively. The realization of the goals of the national "Twelfth Five-Year Plan" requires all walks of life in the country to actively respond, tap the potential deeply, and intensify efforts in energy conservation and emission reduction, especially the power industry, which is a large energy-consuming consumer. The coal consumption of boilers in the power industry accounts for a large proportion of the national energy consumption. Because of this, various energy recovery devices are more and more widely used in boiler combustion systems.

At present, it can be seen from the various heat losses of the boiler that the exhaust heat loss is the largest one, generally 5-8% of the boiler efficiency, and with the increase of the boiler's operating life, this loss is even higher, which can be Up to 10~15%. Therefore, flue gas waste heat recovery technology is the energy-saving technology with the most obvious energy-saving benefits and the fastest effect. It recycles part of the energy lost in the smoke exhaust to improve boiler efficiency, thereby improving energy utilization and reducing production costs. It is also the most direct and economical means to reduce pollutant emissions and protect the environment. In addition, according to the requirements of the national environmental protection policy, coal-fired boilers must have a flue gas desulfurization system. So far, several flue gas desulfurization technologies have been applied at home and abroad, but limestone-gypsum wet technology is the main method for flue gas desulfurization of large-scale thermal power plants. The preferred process for flue gas desulfurization in coal-fired power plants.

However, the operating temperature in the limestone-gypsum wet desulfurization process is relatively low, and it is far away from the designed exhaust gas temperature of the boiler. Usually, water spraying is required to cool the flue gas temperature in the desulfurization system, which not only loses the exhaust gas temperature and desulfurization temperature. The heat of the flue gas between the power plants increases the water consumption of the power plant and the water vapor content in the net flue gas. The increase in flue gas emissions also affects the environmental protection of the surrounding environment of the power plant; During the wet desulfurization process of the boiler, the flue gas heat at the boiler outlet is basically not recycled, and the pressure on operating energy consumption and environmental protection emissions is increased. Therefore, a flue gas cooling technology is needed to solve the problems of waste heat recovery and environmental protection emissions. question.

It can be seen that according to the actual operation of coal-fired boilers in the power industry, it is necessary to develop a flue gas cooling waste heat recovery technology to recover the heat between the design exhaust temperature of the boiler and the desulfurization process temperature, so as to achieve energy saving and emission reduction in power plants. environmental pollution requirements. Therefore, using flue gas low-temperature waste heat recovery technology to make full use of the waste heat before the flue gas enters the absorption tower has become an important topic for energy saving and emission reduction in power systems.

In the area before the desulfurization tower of the coal-fired boiler flue gas system in thermal power plants, low-temperature waste heat recovery and utilization of flue gas can reduce the temperature of the flue gas to below the acid dew point. Technical issues that need to be resolved. At present, the flue gas waste heat recovery technology applied in this area usually adopts the improved low-pressure economizer technology, that is, the spiral finned tube heat exchanger technology; and other applications evolved due to different system connections and circulation methods technology, such as boiler flue gas deep cooling waste heat recovery system (for details, please refer to the patent document with publication number CN101709879A).

A typical system of this technology, as shown in Figure 1, includes chimney 1, FGD outlet baffle 2 (that is, double louver baffle door), No. 1 absorption tower 3, boiler 4, dust collector 5, induced draft fan 6, FGD Entry baffle 7 (i.e. double louver type baffle door), booster fan 8, flue gas cooler 9, oxidation fan 10, low pressure cylinder 11, generator 12, JD6 (i.e. #6 low pressure heater) 13, JD7 ( That is, #7 low-pressure heater) 14, JD8 (that is, #8 low-pressure heater) 15, condensate pump 16 and condenser 17; boiler 4, dust collector 5, induced draft fan 6, FGD inlet baffle 7, booster fan 8 , Flue gas cooler 9 and No. 1 absorption tower 3 are sequentially connected through pipelines; oxidation fan 10, No. 1 absorption tower 3, FGD outlet baffle 2 and chimney 1 are sequentially connected through pipelines; medium pressure cylinder and low pressure cylinder 11. Condenser 17, condensate pump 16, JD8 15, JD7 14, JD6 13 and JD1 (i.e. #1 low-pressure heater) are sequentially connected through pipelines, and generator 12 is connected to the rotor of low-pressure cylinder 11; in JD8 15 Between JD7 14, a pipe is drawn, connected to the flue gas cooler 9; and from the flue gas cooler 9, another pipe is drawn, connected between JD7 14 and JD6 13; between JD8 15 and the flue gas cooler 9 Between JD7 14 and JD6 13, a second valve is installed; between the flue gas cooler 9 and JD6 13, a third valve is installed.

In the system shown in Figure 1, a set of gas-liquid spiral finned tube heat exchanger (smoke-water heat exchanger) is added in the flue before the booster fan 8 and No. 1 absorption tower 3. The water side is connected in parallel to a low-pressure heater of a certain stage of the steam turbine reheating system, and part or all of the condensed water is drawn from the low-pressure inlet of a certain stage, and sent to the smoke-water heat exchanger to absorb the heat of the exhaust gas and reduce the temperature of the exhaust gas, while itself being heated , Return to the low-pressure heater system after raising the temperature, and enter the next level of low-pressure heating after the outlet of this level of low-pressure heating is collected with the remaining condensed water. Because its system is connected in parallel in the heater circuit, replacing part of the low-pressure heater, it is also an integral part of the steam turbine thermal system (see the summary report of the flue gas waste heat recovery project of Shanghai Waigaoqiao No. 3 Power Plant).

The above technology is developed on the basis of the traditional low-pressure economizer, and the following improvements have been made mainly in terms of the material of the spiral finned tube and the temperature of the heated condensate:

(1) Corrosion-resistant material ND steel (namely 09CrCuSb steel) is used as the heating surface pipe. However, practice has proved that the corrosion resistance life of ND steel is only 3~4 times that of ordinary carbon steel, and because in the complex flue gas environment, there are not only SO ₃ ^- , SO ₄ ^- , but also F ^- and Cl ^- , so much Under acid corrosion conditions, ND steel can only delay corrosion, but cannot resist corrosion;

(2) The heated condensed water is adjusted from above the acid dew point to the low-speed corrosion area between the acid dew point and the water dew point. The temperature range in this area is small. When the boiler operates under variable operating conditions, the condensed water flow rate is greatly adjusted, and it is easy to deviate from the optimal economic condition of the entire regenerative heating system, resulting in a decline in the energy-saving benefits of waste heat recovery, and at the same time, excessive diversion of condensed water It is also easy to affect the operation safety of the low pressure heater. In addition, when the type of coal used in the power plant changes, the low-speed corrosion area will deviate from the design working conditions, and the temperature range of the originally designed condensate intake point is difficult to adjust to the working conditions.

Moreover, there are still some problems with low-pressure economizer technology, such as:

⑴The low-pressure economizer technology has a single heating medium. Since the temperature of the working fluid entering the low-pressure economizer system has certain requirements and the adjustment margin is small, when selecting the working fluid, the condensate can only be drawn from the turbine condensate system at the inlet or outlet of a certain low-pressure heater as source of water. In other words, the low-pressure economizer cannot directly heat other working fluids, and recover the heat of the flue gas to other systems in the power plant that require more waste heat;

(2) Low-pressure economizer technology uses sensible heat transfer to recover heat, which is several orders of magnitude lower than latent heat transfer. At the same time, the inlet temperature of the heating medium is required to be high. Due to the high inlet temperature of the refrigerant, the heat exchange equipment is limited. Therefore, in the case of the same recovered heat, the smaller heat transfer temperature difference and lower heat transfer efficiency determine that a larger heat transfer area needs to be designed, which not only increases the layout space, but also increases the equipment investment;

(3) In order to save the layout space, the low-pressure economizer still adopts spiral finned tubes, but it is inevitable that there will be sticky ash deposits in the flue gas condensation area. These ash deposits are usually deposited at the fin intervals and are difficult to clean, even if soot blowers are installed The device is also difficult to remove. Over time, it will definitely affect the heat exchange efficiency, and it will also lead to an increase in the acid concentration around the pipe wall, which will intensify the corrosion;

⑷The low-pressure economizer is a serpentine tube row connected to the inlet and outlet headers. It is an integral heat exchanger. If there is a corrosion leak in the tube bundle, the entire system must stop working immediately. If the entire system is not isolated in time, A large amount of soda and water will leak into the flue gas system, resulting in dust accumulation and corrosion of subsequent equipment, increased fan load, increased power consumption, and in severe cases, the desulfurization system cannot operate.

To sum up, in the process of realizing the present invention, the inventor found that there are at least the following defects in the prior art:

(1) Poor energy saving: In the process of wet desulfurization of coal-fired boilers, the heat of flue gas at the boiler outlet is basically not recycled, and the operating energy consumption is increased;

In the low-pressure economizer technology, since the low-pressure economizer cannot directly heat other working fluids, it cannot recover the heat of the flue gas to other systems in the power plant that require more waste heat; the sensible heat transfer method is used to recover heat, which is better than the latent heat transfer The recovery efficiency is several orders of magnitude lower; in order to save the layout space, spiral finned tubes are still used, and it is inevitable that there will be sticky dust in the flue gas condensation area, and it is difficult to clean, which will affect the heat exchange efficiency;

(2) Poor environmental protection: In the process of wet desulfurization of coal-fired boilers, the operating energy consumption and environmental protection discharge pressure are relatively large;

(3) High cost: In the low-pressure economizer technology, sensible heat transfer is used to recover heat, and the inlet temperature of the heating medium is required to be high, while the high inlet temperature of the refrigerant limits the heat transfer temperature difference of the heat exchange equipment. In the case of the same amount of heat, a smaller heat transfer temperature difference and lower heat transfer efficiency require a larger heat transfer area and increase equipment investment;

In addition, in order to save the layout space, spiral finned tubes are still used. In the flue gas condensation area, there will inevitably be sticky ash deposits and it is difficult to remove, which will lead to an increase in acid concentration around the tube wall, intensified corrosion, and increased equipment maintenance. and replacement costs;

(4) Poor reliability: In the low-pressure economizer technology, the serpentine tubes connected to the inlet and outlet headers form an integral heat exchanger. If there is any corrosion and leakage in the tube bundle, the entire system must stop working immediately;

At the same time, if the entire system is not isolated in time, a large amount of soda water will leak into the flue gas system, resulting in dust accumulation and corrosion of subsequent equipment, increased fan load, and increased power consumption. In severe cases, the desulfurization system cannot operate;

⑸Large space occupation: In the low-pressure economizer technology, sensible heat transfer is used to recover heat, and the inlet temperature of the heating medium is required to be high. Since the high inlet temperature of the refrigerant limits the heat transfer temperature difference of the heat exchange equipment, therefore, in In the case of the same recovered heat, a smaller heat transfer temperature difference and lower heat transfer efficiency require a larger heat transfer area and increase the layout space.

Contents of the invention

The purpose of the present invention is to solve the above problems and propose a coal power plant combined heat pipe flue gas waste heat recovery system to achieve the advantages of good energy saving, good environmental protection, low cost, good reliability, small footprint and wide application range .

In order to achieve the above object, the technical solution adopted in the present invention is: a coal power plant combined heat pipe flue gas waste heat recovery system, including a boiler, a dust collector, an induced draft fan, a booster fan, and a combined heat pipe heat exchange system that are sequentially connected through pipelines. components, desulfurization towers and chimneys.

Further, in the horizontal direction, the combined heat pipe heat exchanger assembly includes a finned heat pipe heat exchanger, a controllable heat pipe heat exchanger, and a corrosion-resistant heat pipe heat exchanger arranged sequentially from left to right. Here, the corrosion-resistant heat pipe heat exchanger may be an enamel heat pipe heat exchanger, or a heat pipe heat exchanger coated with anti-corrosion paint.

Further, in the vertical direction, the combined heat pipe heat exchanger assembly includes an upper part and a lower part, the upper part is the cold source working fluid side, the lower part is the flue gas side, and a with partitions;

On the flue gas side, there is a flue gas side inlet for connecting with a booster fan, a flue gas side outlet for connecting with a desulfurization tower, and a steam communication pipe connected with a controllable heat pipe heat exchanger; A regulating valve (or control valve) is provided on the steam communication pipe;

On the side of the cold source working medium, there is a cold source working medium side inlet for inputting the cold source working medium, a cold source working medium side outlet for outputting the cold source working medium, and a controllable heat pipe heat exchanger Connected condensate manifold.

Further, the above coal power plant combined heat pipe flue gas waste heat recovery system also includes a bypass flue; the bypass flue is drawn from between the induced draft fan and the booster fan, and is connected between the desulfurization tower and the chimney.

Further, the above coal power plant combined heat pipe flue gas waste heat recovery system also includes first to fourth baffles, the first baffle is connected between the desulfurization tower and the chimney, and the second baffle is connected between the dust collector 5 and the fan 6, the third baffle is set in the bypass flue 23, and the fourth baffle is set between the bypass flue 23 and the booster fan 8.

Further, in the boiler, an air preheater is arranged close to the pipeline connected to the dust remover.

At the same time, another technical solution adopted by the present invention is: a coal power plant combined heat pipe flue gas waste heat recovery method matched with the above-mentioned coal power plant combined heat pipe flue gas waste heat recovery system, including:

In the flue system of coal power plants, a combined heat pipe heat exchanger assembly is added to recover the heat and water vapor of the flue system;

Between the induced draft fan and the booster fan of the flue system, a bypass flue is drawn and connected to the flue system between the desulfurization tower and the chimney.

Further, the combined heat pipe heat exchanger assembly is co-located between the booster fan and the desulfurization tower of the flue system to recover heat and water vapor in the flue gas between the booster fan and the desulfurization tower.

Further, in the horizontal direction, the combined heat pipe heat exchanger assembly includes a finned heat pipe heat exchanger, a controllable heat pipe heat exchanger, and a corrosion-resistant heat pipe heat exchanger arranged sequentially from left to right;

In the vertical direction, the combined heat pipe heat exchanger assembly includes an upper part and a lower part, the upper part is the cold source working medium side, the lower part is the flue gas side, and a partition is arranged between the cold source working medium side and the flue gas side ;

On the flue gas side, there is a flue gas side inlet for connecting with a booster fan, a flue gas side outlet for connecting with a desulfurization tower, and a steam communication pipe connected with a controllable heat pipe heat exchanger; A regulating valve is provided on the steam communication pipe;

On the side of the cold source working medium, there is a cold source working medium side inlet for inputting the cold source working medium, a cold source working medium side outlet for outputting the cold source working medium, and a controllable heat pipe heat exchanger Connected condensate manifold.

Furthermore, the method for recovering waste heat from flue gas of combined heat pipes in coal power plants described above, and the system for recovering waste heat from flue gas from combined heat pipes in coal power plants that matches this method can be applied to steam turbine heat recovery systems, desalinated water systems, heat supply systems, etc. system, and air preheating system.

In the above coal power plant combined heat pipe flue gas waste heat recovery system and method, the combined heat pipe heat exchanger assembly is installed between the booster fan and the desulfurization tower of the coal-fired power plant (powdered coal boiler) to recover part of the waste heat of the flue gas ( Sensible heat) and the heat of condensation (latent heat) released by the condensation of part of the water vapor in the flue gas to recover the waste heat of the flue gas to the maximum; The humidity of the flue gas is reduced, which reduces the workload of the mist eliminator and the corrosion of the chimney by the flue gas, and also reduces the pollution to the environment. The above-mentioned combined heat pipe flue gas waste heat recovery system and method of coal power plants have the following characteristics:

⑴Improved the efficiency of the flue gas waste heat recovery heat exchanger; in the case of unlimited installation space, the above coal power plant combined heat pipe flue gas waste heat recovery system and method can recover more flue gas waste heat;

⑵Expand the application range of flue gas waste heat recovery heat exchanger; the recovered waste heat can not only be used in the steam turbine heat recovery system, but also in the desalinated water system, heating system and air preheating system, etc.;

⑶Improve the safety and reliability of the flue gas waste heat recovery heat exchanger; in the whole system, the hot and cold fluids flow outside the tube and are completely separated. A single heat tube works independently without affecting each other, and is easy to disassemble and replace; even a single tube The failure of the heat pipe will not affect the continuous operation of the system, and the doping of cold and hot fluid will not occur, which will not endanger the operation safety of the boiler;

⑷The flue gas can be reduced below the water dew point, and the dust in the flue gas will adhere to the surface of the enamel heat pipe, so the system has a certain dust removal effect;

(5) The temperature of the flue gas can be reduced to 50-60°C, which meets the requirements of the wet desulfurization process for the flue gas temperature, reduces the amount of water required for cooling the flue gas, and saves a lot of water resources.

The coal power plant combined heat pipe flue gas waste heat recovery system and method of each embodiment of the present invention, because the system includes boilers, dust collectors, induced draft fans, booster fans, combined heat pipe heat exchanger components, desulfurization tower and chimney; the method includes: in the flue system of the coal power plant, adding a combined heat pipe heat exchanger assembly to recover the heat and water vapor of the flue system; Between, the bypass flue is drawn, connected to the flue system between the desulfurization tower and the chimney; the combined heat pipe heat exchanger assembly can make the cold and hot fluids in the entire flue system flow outside the heat pipe and be completely separated , a single heat pipe works independently, does not affect each other, and is easy to disassemble and replace; even if a single heat pipe fails, it will not affect the flue system to continue to work, and there will be no doping of cold and hot fluids, which will not endanger the operation safety of the boiler; through the combined heat pipe The humidity of the net flue gas obtained by desulfurization of the flue gas after the heat exchanger module is reduced, which is beneficial to reduce the workload of the demister and the corrosion of the flue gas to the chimney, and reduce the pollution to the environment; it can be applied to the steam turbine heat recovery system , desalinated water system, heating system, and air preheating system, in the case of unlimited installation space, the recovered flue gas waste heat is large; thus it can overcome the poor energy saving, poor environmental protection, high cost and reliability of the existing technology In order to achieve the advantages of good energy saving, good environmental protection, low cost, good reliability, small space occupation and wide application range.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

The technical solutions of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the description, and are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention. In the attached picture:

Figure 1 is a schematic diagram of the working principle of a coal-fired boiler flue gas system in a thermal power plant based on low-pressure economizer technology;

Fig. 2a and Fig. 2b are the structural representations of heat pipe;

Fig. 3 is a schematic diagram of the working principle of the combined heat pipe flue gas waste heat recovery system of a coal power plant according to the present invention;

Fig. 4 is a partial structural schematic diagram of a coal power plant combined heat pipe flue gas waste heat recovery system according to the present invention;

Fig. 5a is a cross-sectional view in the front direction of the combined heat pipe heat exchanger assembly in the combined heat pipe flue gas waste heat recovery system of the coal power plant according to the present invention;

Fig. 5b is a side view of the combined heat pipe heat exchanger assembly in the combined heat pipe flue gas waste heat recovery system of the coal power plant according to the present invention;

Figure 5c is a partially enlarged schematic diagram of part E in Figure 5a;

6 is a schematic diagram of the working principle of applying the combined heat pipe flue gas waste heat recovery system and method of the coal power plant of the present invention to the steam turbine heat recovery system;

Fig. 7 is a schematic diagram of the working principle of applying the combined heat pipe flue gas waste heat recovery system and method of the coal power plant of the present invention to the desalinated water system;

Fig. 8 is a schematic diagram of the working principle of applying the combined heat pipe flue gas waste heat recovery system and method of the coal power plant of the present invention to the heating system;

Fig. 9 is a schematic diagram of the working principle of applying the combined heat pipe flue gas waste heat recovery system and method of the coal power plant of the present invention to the air preheating system.

In conjunction with the accompanying drawings, the reference signs in the embodiments of the present invention are as follows:

1-chimney, 2-FGD exit baffle, 3-absorption tower No. 1, 4-boiler, 5-dust collector, 6-induced fan, 7-FGD entrance baffle, 8-boosting fan, 9-flue gas cooling Device, 10-oxidation fan, 11-low pressure cylinder, 12-generator, 13-JD6, 14-JD7, 15-JD8, 16-condensate pump, 17-condenser, 18-shell, 19-suction core , 20-steam channel, 21-first baffle, 22-air preheater, 23-bypass flue, 24-flue gas side, 25-cold source working medium side, 26-desulfurization tower, 27-regulating valve , 28-gas collecting pipe, 29-cold source working medium side outlet, 30-finned heat pipe heat exchanger, 31-controllable heat pipe heat exchanger, 32-corrosion-resistant heat pipe heat exchanger, 33-cold source working medium Side inlet, 34-flue gas side inlet, 35-flue gas side outlet, 36-condensed water connecting pipe, 37-steam connecting pipe, 38-demister, 39-deaerator, 40-heat exchange station, 41- Steam turbine, 42-blower; 43-baffle; A-evaporating section, B-insulating section, C-condensing section, D-liquid return direction in the liquid-absorbing core.

Detailed ways

The preferred embodiments of the present invention will be described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

System embodiment

According to an embodiment of the present invention, as shown in Fig. 2a to Fig. 5c, a coal power plant combined heat pipe flue gas waste heat recovery system is provided.

As shown in FIG. 3 , this embodiment includes a boiler 4 , a dust collector 5 , an induced draft fan 6 , a booster fan 8 , a combined heat pipe heat exchanger assembly, a desulfurization tower 26 and a chimney 1 that are sequentially connected through pipelines.

Here, in the combined heat pipe heat exchanger assembly, the heat pipe is a high-efficiency heat exchange element that is filled with a working medium in the closed tube shell 18 and uses the phase change of the medium to absorb and release heat for heat exchange. The structure of the heat pipe can be See Figures 2a and 2b. In Fig. 2a and Fig. 2b, the heat pipe includes a cylindrical tube shell 18, and a liquid-absorbing core 19 that is close to the tube shell 18 and is axially arranged on the inner wall of the tube shell 18; the internal passage of the liquid-absorbing core 19 is a steam channel, The liquid backflow direction in the liquid-absorbing core 19 is shown by the arrow D in Fig. 2a. In the axial direction, from left to right, the heat pipe can be evenly divided into three sections, namely evaporation section A, adiabatic section B and condensation section C.

As a closed shell, the heat pipe has various shapes, and its inner surface is inlaid with a porous liquid-absorbing core 19 (such as a capillary liquid-absorbing core). Gas phase working medium. The external heat source adds heat in the evaporation section A to evaporate the working medium in the evaporation section A; the resulting pressure difference drives the steam from the evaporation section A to the condensation section C, where the steam condenses and releases the latent heat of vaporization out; the condensed liquid-phase working medium returns to the evaporation section A by its own gravity and capillary pressure, and evaporates again. In this way, the heat pipe continuously transfers the latent heat of vaporization from the evaporating section to the condensing section C without burning the wick dry. As long as the working medium flow channel is not blocked and the liquid phase working medium can return to the evaporation section, this process will continue.

In the above implementation, the coal power plant combined heat pipe flue gas waste heat recovery system also includes a bypass flue 23, a first baffle 21, a second baffle, a third baffle, a fourth baffle and an air preheater 22 ; Wherein, the bypass flue 23 is drawn between the induced draft fan 6 and the booster fan 8, and is connected between the desulfurization tower 26 and the chimney 1; the first baffle plate 21 is connected between the desulfurization tower 26 and the chimney 1, and the second The second baffle is connected between the dust collector and the fan, the third baffle is set in the bypass flue, the fourth baffle is set between the bypass flue and the booster fan, and the air preheater 22 is co-located on the boiler 4 In, and close to the pipeline connected to the dust collector 5.

As shown in Fig. 4 and Fig. 5a-Fig. 5c, in the horizontal direction, the above-mentioned combined heat pipe heat exchanger assembly includes a finned heat pipe heat exchanger 30, a controllable heat pipe heat exchanger arranged sequentially from left to right 31 and heat exchanger 32 of corrosion-resistant heat pipe. In the vertical direction, the combined heat pipe heat exchanger assembly includes an upper part and a lower part. The upper part is the cold source working fluid side 25, and the lower part is the flue gas side 24. There are partitions 43 .

On the flue gas side 24, there is a flue gas side inlet 34 for connecting with the booster fan 8, a flue gas side outlet 35 for connecting with the desulfurization tower 26, and a steam that is connected with the controllable heat pipe heat exchanger 31. A communication pipe 37; on the steam communication pipe 37, a regulating valve 27 is provided; in cooperation with the regulating valve 27, a gas collecting pipe 28 communicating with the steam communication pipe 37 is also provided. On the cold source working medium side 25, there is a cold source working medium side inlet 33 for inputting the cold source working medium, a cold source working medium side outlet 29 for outputting the cold source working medium, and a controllable heat pipe heat exchanger 31 is matched with the connected condensed water connecting pipe 36.

In the above embodiments, the coal power plant combined heat pipe flue gas waste heat recovery system mainly uses heat pipe technology to recover and process the waste heat and moisture of the flue gas discharged from the pulverized coal furnace.

In the combined heat pipe flue gas waste heat recovery system of a coal power plant, the main working process of the combined heat pipe heat exchanger assembly is as follows:

(1) The first part: use the finned heat pipe heat exchanger 30 to recover the waste heat of the flue gas, reduce the temperature of the flue gas to above the acid dew point, and ensure that this part will not be corroded by the acid dew. In order to prevent dust accumulation, the design ensures that the flue gas flow rate is 8-10m/s, and the finned heat pipe heat exchanger 30 has a certain self-cleaning ability. Ash;

(2) The second part: controllable heat pipe heat exchanger 31, add a system to control the temperature of the heat pipe wall, and control it above the dew point temperature (5-10°C); connect the evaporation section of each heat pipe to the gas collecting pipe , add a regulating valve at the outlet of the gas collecting pipe, so as to realize the adjustable and controllable wall temperature of the heat pipe; control the wall temperature of this part of the heat pipe heat exchanger to be slightly higher than the acid dew point (5-10 ℃), so as to ensure that this part will not be Acid dew corrosion, the measures to prevent dust accumulation are the same as the first part;

(3) The third part: the enamel light pipe heat pipe constitutes the last part of the flue gas waste heat recovery system. In this part, the temperature of the flue gas is lowered below the water dew point, so that the sensible heat of the flue gas can be recovered to the maximum extent and part of the flue gas can be recovered. The heat of condensation of water vapor. Enamel is used to prevent the acid dew corrosion of the heat exchanger, that is, to coat a layer of acid-resistant enamel on the ordinary carbon steel pipe. Because the enamel layer is very thin, the general thickness is 0.3mm, so it is closely combined with carbon steel and has little effect on the heat transfer effect. The heat transfer coefficient of the enamel tube is greater than or equal to 48.3W/(m ² ·℃). Compared with the carbon steel tube, the relative reduction rate of the heat transfer coefficient is less than 7.14%. The accumulated dust on the surface will adhere to it. According to the smooth surface of the enamel, the dust can be cleaned by spraying water.

In the above embodiments, the combined heat pipe heat exchanger assembly belongs to the indirect heat exchanger, which is generally installed in the flue area between the booster fan 8 and the desulfurization tower 26 of the boiler flue gas system of a coal-fired power plant. The side 24 is connected in series with the flue of the original system, and the heated working medium side (that is, the cold source working medium side 25 ) is connected in parallel with any thermal system pipe in the power plant. Among them, the heated working medium can be any working medium that needs to be heated in the power plant (such as desalted water, condensed water, heating water, boiler air supply, etc.).

During the operation of the boiler, all or part of the working fluid diverted from a certain thermal system in the power plant absorbs the heat in the exhaust smoke of the boiler through the combined heat pipe heat exchanger assembly, thereby increasing its own temperature, and the working fluid with increased temperature is regenerated Converging with the working medium in the original thermal system pipeline, the heat in the exhaust smoke of the boiler is transferred to the thermal system, thereby replacing part of the heat provided by steam heating in the thermal system, and reducing the self-consumption steam of the power plant. At the same time, on the flue gas side 24 of the boiler 4, the hot flue gas from the air preheater 22 on the heating surface at the rear of the boiler 4 enters the combined heat pipe heat exchanger after being dedusted by the dust collector 5 and boosted by the booster fan 8 In the components, the heat is released to the heated working medium, and the temperature of the flue gas after heat exchange is greatly reduced, which meets the process temperature requirements required by the desulfurization reaction, and will directly enter the desulfurization tower 26 for high-efficiency desulfurization, and the desulfurized flue gas The low-temperature clean flue gas is discharged into the atmosphere through the chimney 1.

For example, the boiler of a 300MW subcritical unit is a 1025t/h pulverized coal boiler, the boiler efficiency is 91.27%, the exhaust gas temperature after booster fan 8 is 130°C, and the flue gas volume is 102.98×10 ⁴ Nm ³ /h. Install a coal-fired power plant (powdered coal furnace) combined heat pipe heat exchanger assembly between the booster fan 8 and the desulfurization tower 26 to reduce the temperature of the flue gas to 80°C, and the recovered flue gas waste heat is used to heat the heat recovery system. It can heat 393t/h condensate from 45°C to 75°C, recover 49.58GJ of heat per hour, save 1.844tce/h, reduce the standard coal consumption of power generation by 2.64gce/kwh, and save standard coal per year based on 5000 hours of operation 9220tce, reducing CO ₂ emissions by 24,156t, SO2 emissions by 78t, and NO _X emissions by 68t.

As another example, the boiler of a 300MW subcritical unit is a 1025t/h pulverized coal boiler, the boiler efficiency is 91.27%, the exhaust gas temperature after the booster fan is 130°C, and the flue gas volume is 102.98×10 ⁴ Nm ³ /h. The calculated acid dew point is 81.21°C, and the water dew point is 42°C. Install a coal-fired power plant (powdered coal furnace) combined heat pipe heat exchanger assembly between the booster fan 8 and the desulfurization tower 26 to reduce the flue gas temperature to 42°C and heat 695t/h condensed water from 45°C to 95°C, recover 146GJ of heat per hour, save 5.43tce/h, reduce the standard coal consumption of power generation by 18.11gce/kWh, calculate according to the annual operation of 5000 hours, save 27167tce of standard coal, reduce _CO2 emissions by 71178t, _SO2 emissions by 231t , NO _X emissions 201t.

The coal power plant combined heat pipe flue gas waste heat recovery system of the above embodiment has the following characteristics:

(1) In front of the desulfurization tower 26, the combined heat pipe heat exchanger assembly is applied, and the condensation heat of part of the water vapor in the flue gas is recovered by using the heat pipe technology, so as to realize the controllable and adjustable wall temperature of the controllable heat pipe heat exchanger 31;

⑵Diversification of heating medium, waste heat can be recovered to heat the desalinated water system, steam turbine heat recovery system, heating system and air preheating system;

(3) Combined heat pipe technology and enamel anti-corrosion technology (that is, finned heat pipe heat exchanger + controllable heat pipe heat exchanger + enamel heat pipe heat exchanger) are used to recover the waste heat of flue gas;

⑷In the combined heat pipe flue gas waste heat recovery system of the entire coal power plant, the hot and cold fluids flow outside the pipe and are completely separated. A single heat pipe works independently without affecting each other, and is easy to disassemble and replace; even if a single heat pipe fails, it will not affect the system Continue to work without doping of hot and cold fluids, and will not endanger the operation safety of the power generation system;

(5) The third part of the combined heat pipe flue gas waste heat recovery system in coal power plants can reduce the flue gas below the water dew point and recover the condensation heat released by the condensation of part of the water vapor in the flue gas;

⑹The flue gas can be reduced below the water dew point, and the dust in the flue gas will adhere to the surface of the enamel heat pipe, so the combined heat pipe flue gas waste heat recovery system of the coal power plant has a certain dust removal effect;

⑺The temperature of the flue gas can be reduced to 50-60°C, which meets the requirements of the wet desulfurization process for the flue gas temperature, reduces the amount of water required for cooling the flue gas, and saves a lot of water resources;

⑻ After the flue gas passes through the combined heat pipe flue gas waste heat recovery system of the above-mentioned coal power plant, the humidity of the net flue gas obtained by desulfurization is reduced, which reduces the workload of the demister and the corrosion of the flue gas on the chimney, and also reduces pollution of the environment.

method embodiment

According to an embodiment of the present invention, a coal power plant combined heat pipe flue gas waste heat recovery method matching the above coal power plant combined heat pipe flue gas waste heat recovery system is provided, including:

In the flue system of coal power plants, a combined heat pipe heat exchanger assembly is added to recover the heat and water vapor of the flue system;

Between the induced draft fan 6 and the booster fan 8 of the flue system, a bypass flue 23 is drawn and connected between the desulfurization tower 26 and the chimney 1 of the flue system.

Among them, the above-mentioned combined heat pipe heat exchanger assembly is arranged between the booster fan 8 and the desulfurization tower 26 of the flue system to recover the heat and water vapor in the flue gas between the booster fan 8 and the desulfurization tower 26 deal with. Here, the structure and performance of the combined heat pipe heat exchanger assembly can refer to the relevant description of the combined heat pipe heat exchanger assembly in the system embodiment, and will not be repeated here.

The coal power plant combined heat pipe flue gas waste heat recovery method of the above embodiment, and the coal power plant combined heat pipe flue gas waste heat recovery system matched with the coal power plant combined heat pipe flue gas waste heat recovery system (see Figures 2a-5c) The system embodiment shown and its related descriptions) can be applied to steam turbine heat recovery system, desalinated water system, heating system, and air preheating system.

Below, in conjunction with Figures 6-9, the specific application of the combined heat pipe flue gas waste heat recovery system of the above coal power plant and the coal power plant combined heat pipe flue gas waste heat recovery method matched with the above coal power plant combined heat pipe flue gas waste heat recovery system , for example.

Fig. 6 is a schematic diagram of the working principle of applying the combined heat pipe flue gas waste heat recovery system and method of the above-mentioned coal power plant to the steam turbine heat recovery system. In Fig. 6, the equipment before the boiler 4 to the booster fan 8 is omitted, and the steam turbine heat recovery system includes a booster fan 8, a combined heat pipe heat exchanger assembly, a mist eliminator 38, a desulfurization tower 26, a chimney 1, multiple Low-level heating equipment, low-pressure cylinder 11 and generator 12; booster fan 8, flue gas side 24 of the combined heat pipe heat exchanger assembly and desulfurization tower 26 are connected through pipelines in turn; mist eliminator 38 is installed in desulfurization tower 26 After the top of the pipe, it is connected to the chimney 1 through the pipeline; the generator 12 is connected with the low-pressure cylinder 11, and the low-pressure cylinder 11 is connected with the multi-stage low-pressure equipment; Between the inlets, the lead pipe is connected to the cold source working medium side inlet 33 of the combined heat pipe heat exchanger assembly; the pipe drawn from the cold source working medium side outlet 29 of the combined heat pipe heat exchanger assembly is from the next stage It is introduced between the low-supply outlet and the next-level low-supply inlet.

In Figure 6, the flue gas waste heat recovery system including the combined heat pipe heat exchanger assembly is applied to the steam turbine heat recovery system, which can recover the waste heat of the flue gas and heat the condensed water with the recovered flue gas waste heat.

Fig. 7 is a schematic diagram of the working principle of applying the coal power plant combined heat pipe flue gas waste heat recovery system and method of the above embodiment to the desalinated water system. In Fig. 7, the equipment before the boiler 4 to the booster fan 8 is omitted, and the desalinated water system includes a booster fan 8, a combined heat pipe heat exchanger assembly, a desulfurization tower 26, a mist eliminator 38, a chimney 1, and an oxygen removal system. 39, the first valve, the second valve and the third valve; the booster fan 8, the flue gas side 24 of the combined heat pipe heat exchanger assembly and the desulfurization tower 26 are connected through pipelines in turn; the mist eliminator 38 is installed in the desulfurization After the top of the tower 26, it is connected to the chimney 1 through the pipeline; the desalted water is connected to the deaerator 39 through the pipeline equipped with the second valve, and the pipeline equipped with the first valve is drawn from the pipeline away from the deaerator 39 from the second valve. To the cold source working medium side inlet 33 of the combined heat pipe heat exchanger assembly; the cold source working medium side outlet 29 of the combined heat pipe heat exchanger assembly is connected to the second valve and the oxygen removal through the pipeline equipped with the third valve. device 39 between.

In Figure 7, the flue gas waste heat recovery system including the combined heat pipe heat exchanger assembly is applied to the desalinated water system, and the desalinated water is used as the cold source working medium to recover the waste heat of the flue gas, and use the recovered flue gas waste heat to heat and remove brine.

Fig. 8 is a schematic diagram of the working principle of applying the coal power plant combined heat pipe flue gas waste heat recovery system and method of the above embodiment to the heating system. In Fig. 8, the equipment before boiler 4 to booster fan 8 is omitted, and the heating system includes booster fan 8, combined heat pipe heat exchanger assembly, desulfurization tower 26, mist eliminator 38, chimney 1, heat exchange Station 40, first valve, second valve, third valve, steam turbine 41 and generator 12; booster fan 8, flue gas side 24 of combined heat pipe heat exchanger assembly and desulfurization tower 26 are connected through pipelines in sequence; After the mist device 38 is installed on the top of the desulfurization tower 26, it is connected to the chimney 1 through the pipeline; the generator 12, the steam turbine 41 and the heat exchange station 40 are connected in sequence; the heating return water is connected to the combination through the pipeline equipped with the first valve The cold source working medium side inlet 33 of the type heat pipe heat exchanger assembly is connected to the heat exchange station 40 through a pipeline equipped with a second valve; the cold source working medium side outlet 29 of the combined heat pipe heat exchanger assembly is equipped with The pipe of the third valve is connected to the heating water output end of the heat exchange station 40 .

In Figure 8, the flue gas waste heat recovery system including the combined heat pipe heat exchanger assembly is applied to the heating system, and the heating return water is used as the cold source working medium, which can recover the waste heat of the flue gas and heat it with the recovered flue gas waste heat Heating return water is used as heating water.

Fig. 9 is a schematic diagram of the working principle of applying the coal power plant combined heat pipe flue gas waste heat recovery system and method of the above embodiment to the air preheating system. In Fig. 9, the equipment before the boiler 4 to the booster fan 8 is omitted, and the air preheating system includes a booster fan 8, a combined heat pipe heat exchanger assembly, a desulfurization tower 26, a demister 38, a chimney 1, and a blower 42. The first valve and the second valve; the booster fan 8, the flue gas side 24 of the combined heat pipe heat exchanger assembly and the desulfurization tower 26 are connected through pipelines in turn; the demister 38 is installed on the top of the desulfurization tower 26 , connected to the chimney 1 through a pipe; the air is connected to the cold source working medium side inlet 33 of the combined heat pipe heat exchanger assembly through the pipe equipped with the first valve; the cold source working medium side outlet of the combined heat pipe heat exchanger assembly 29, the output combustion air is connected to the air blower 42 through the pipeline equipped with the second valve.

In Figure 9, the flue gas waste heat recovery system including the combined heat pipe heat exchanger assembly is applied to the air preheating system, and air is used as the cold source working medium to recover the waste heat of the flue gas and heat the air with the recovered flue gas waste heat , to obtain combustion air for use by the blower.

The coal power plant combined heat pipe flue gas waste heat recovery system and method of the above embodiments have the following beneficial effects:

(1) Good energy saving: through the combined heat pipe flue gas waste heat recovery system, part of the sensible heat in the waste heat of the flue gas and the condensation heat released by condensation of water vapor are recovered to maximize the recovery of the waste heat of the flue gas, and the temperature of the flue gas is reduced to 50-60 ℃, the flue gas temperature that meets the requirements of the wet desulfurization process, greatly reduces the amount of water consumed by desulfurization to reduce the flue gas temperature, and saves a lot of water resources; recovering the waste heat of the flue gas can improve the efficiency of the unit, reduce the coal consumption of power generation, save fuel and save Water resources, play a good role in energy saving and emission reduction;

(2) Good environmental protection: in the third part of the combined heat pipe flue gas waste heat recovery system of the above-mentioned coal power plant, part of the water vapor will condense on the surface of the enamel heat pipe, and the dust will adhere to it to play a certain role in dust removal, and at the same time enter the desulfurization tower The flue gas temperature meets the technological requirements of wet desulfurization, and there is no need to spray water to cool down. Therefore, the dust content and water content in the clean flue gas are reduced, and the pollution to the environment is reduced. In addition, the entire flue gas recovery system can reduce energy consumption, which also reduces CO ₂ , SO ₂ , and NO _X emissions, resulting in huge environmental benefits;

(3) Improvement of safety and reliability: In the coal power plant combined heat pipe flue gas waste heat recovery system and method of the above embodiment, the safety of the equipment is first considered, the first part works above the acid dew point of the flue gas, and a blower is installed Ash equipment, which not only ensures the safety of the equipment, but also ensures the efficiency of the equipment; the second part adopts the controllable wall temperature design, so that the temperature of the recovered flue gas of the equipment is as close as possible to the acid dew point but higher than the acid dew point, and also avoids acid dew Influenced by corrosion, soot blowing equipment is also installed to ensure the heat exchange efficiency of the equipment; the third part works below the acid dew point or even below the water dew point, adopts enamel-plating measures to prevent acid dew corrosion of the equipment, and adopts according to the characteristics of enamel The method of spraying water to remove dust ensures the heat exchange efficiency of the equipment;

In addition, in the combined heat pipe flue gas waste heat recovery system of the entire coal power plant, the hot and cold fluids flow outside the pipe and are completely separated. The single heat pipe works independently without affecting each other, and is easy to disassemble and replace; even if a single heat pipe fails, it will not It will affect the continuous operation of the entire heat exchanger, and there will be no doping of hot and cold fluids, which will not endanger the operation safety of the boiler, so the reliability of equipment operation is greatly enhanced;

⑷ Reducing the burden of the demister: Since the flue gas is no longer sprayed to cool down in the desulfurization tower, the moisture content in the clean flue gas is reduced, which changes the working conditions of the demister during the desulfurization process and ensures the demisting effect , to avoid the occurrence of chimney rain to ensure that the purified flue gas will not pollute the surrounding environment;

⑸Reduce the corrosion of flue gas on the chimney: the flue gas with low temperature and high humidity is the most corrosive to the chimney. Less water spray or no water spray will greatly reduce the humidity of the flue gas, so it also reduces the corrosion of the chimney to ensure the normal operation of the system.

Finally, it should be noted that: the above is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it still The technical solutions recorded in the foregoing embodiments may be modified, or some technical features thereof may be equivalently replaced. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A coal power plant combined heat pipe flue gas waste heat recovery system, characterized in that it includes a boiler, a dust collector, an induced draft fan, a booster fan, a combined heat pipe heat exchanger assembly, a desulfurization tower and a chimney connected sequentially through pipelines . 2. The combined heat pipe flue gas waste heat recovery system of a coal power plant according to claim 1, characterized in that, in the horizontal direction, the combined heat pipe heat exchanger assembly includes finned heat exchanger components arranged sequentially from left to right Heat pipe heat exchanger, controllable heat pipe heat exchanger and corrosion-resistant heat pipe heat exchanger. 3. The coal power plant combined heat pipe flue gas waste heat recovery system according to claim 2, characterized in that, in the vertical direction, the combined heat pipe heat exchanger assembly includes an upper part and a lower part, and the upper part is a cold source working fluid side, the lower part is the flue gas side, and a partition is provided between the cold source working fluid side and the flue gas side; On the flue gas side, there is a flue gas side inlet for connecting with a booster fan, a flue gas side outlet for connecting with a desulfurization tower, and a steam communication pipe connected with a controllable heat pipe heat exchanger; A regulating valve is provided on the steam communication pipe; On the side of the cold source working medium, there is a cold source working medium side inlet for inputting the cold source working medium, a cold source working medium side outlet for outputting the cold source working medium, and a controllable heat pipe heat exchanger Connected condensate manifold. 4. The coal power plant combined heat pipe flue gas waste heat recovery system according to any one of claims 1-3, characterized in that the system also includes a bypass flue; the bypass flue, the self-induced fan and It is drawn between the booster fan and connected between the desulfurization tower and the chimney. 5. The coal power plant combined heat pipe flue gas waste heat recovery system according to claim 4, characterized in that the system also includes first to fourth baffles, the first baffles are connected between the desulfurization tower and the chimney, The second baffle is connected between the dust collector and the fan, the third baffle is arranged in the bypass flue, and the fourth baffle is arranged between the bypass flue and the booster fan. 6. The coal power plant combined heat pipe flue gas waste heat recovery system according to claim 5, characterized in that, in the boiler, an air preheater is provided in conjunction with the pipeline connected to the dust collector. 7. A coal power plant combined heat pipe flue gas waste heat recovery method matched with the coal power plant combined heat pipe flue gas waste heat recovery system according to claim 1, characterized in that it comprises: In the flue system of coal power plants, a combined heat pipe heat exchanger assembly is added to recover the heat and water vapor of the flue system; Between the induced draft fan and the booster fan of the flue system, a bypass flue is drawn and connected to the flue system between the desulfurization tower and the chimney. 8. The combined heat pipe flue gas waste heat recovery method of coal power plant according to claim 7, characterized in that the combined heat pipe heat exchanger assembly is co-located between the booster fan and the desulfurization tower of the flue system, The heat and water vapor in the flue gas between the booster fan and the desulfurization tower are recovered. 9. The combined heat pipe flue gas waste heat recovery method of a coal power plant according to claim 8, characterized in that, in the horizontal direction, the combined heat pipe heat exchanger assembly includes finned heat exchanger components arranged sequentially from left to right Heat pipe heat exchanger, controllable heat pipe heat exchanger and corrosion-resistant heat pipe heat exchanger; In the vertical direction, the combined heat pipe heat exchanger assembly includes an upper part and a lower part, the upper part is the cold source working medium side, the lower part is the flue gas side, and a partition is arranged between the cold source working medium side and the flue gas side ; On the flue gas side, there is a flue gas side inlet for connecting with a booster fan, a flue gas side outlet for connecting with a desulfurization tower, and a steam communication pipe connected with a controllable heat pipe heat exchanger; A regulating valve is provided on the steam communication pipe; On the side of the cold source working medium, there is a cold source working medium side inlet for inputting the cold source working medium, a cold source working medium side outlet for outputting the cold source working medium, and a controllable heat pipe heat exchanger Connected condensate manifold. 10. The method for recovering waste heat from flue gas of combined heat pipes in coal power plants according to any one of claims 7-9, characterized in that the method and the system matching the method can be applied to steam turbine heat recovery systems, Demineralized water system, heating system, and air preheating system.

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