CN112879893A - Waste heat recovery system, waste heat recovery method and boiler system - Google Patents
Waste heat recovery system, waste heat recovery method and boiler system Download PDFInfo
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- CN112879893A CN112879893A CN202110319403.2A CN202110319403A CN112879893A CN 112879893 A CN112879893 A CN 112879893A CN 202110319403 A CN202110319403 A CN 202110319403A CN 112879893 A CN112879893 A CN 112879893A
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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
- F22D1/003—Feed-water heater systems
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES
- F23J15/00—Arrangements of devices for treating smoke or fumes
- F23J15/06—Arrangements of devices for treating smoke or fumes of coolers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
- F24D15/00—Other domestic- or space-heating systems
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
- F28F19/02—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers by using coatings, e.g. vitreous or enamel coatings
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
- F28F19/02—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers by using coatings, e.g. vitreous or enamel coatings
- F28F19/06—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers by using coatings, e.g. vitreous or enamel coatings of metal
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
- F24D2200/00—Heat sources or energy sources
- F24D2200/16—Waste heat
- F24D2200/18—Flue gas recuperation
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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
- Y02E20/30—Technologies for a more efficient combustion or heat usage
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- General Engineering & Computer Science (AREA)
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- Thermal Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
Abstract
The invention relates to a waste heat recovery system, a waste heat recovery method and a boiler system, aiming at solving the technical problem that the smoke discharge of an air duct is blocked due to easy corrosion, rusting and ash blockage of a heat exchanger in the traditional waste heat recovery process on the premise of not increasing the cost too much. The heat exchanger comprises a tubular shell connected in series with a flue, and a first heat exchanger and a second heat exchanger which are arranged in the shell; the temperature of the first heat exchange medium is higher than the dew point temperature of water vapor in the flue gas when the water vapor is condensed on the outer surface of the first heat exchanger; the first heat exchanger is a finned tube heat exchanger made of common carbon steel; the second heat exchanger is positioned at the downstream of the first heat exchanger along the flow direction of the flue gas, a second internal pipeline is arranged in the second heat exchanger, the second internal pipeline is provided with a cooling water inlet and a cooling water outlet, the cooling water inlet is connected with a water supply system for supplying a second heat exchange medium, the second heat exchange medium carries out secondary heat exchange with the flue gas in the second internal pipeline, and a large amount of water vapor in the flue gas is condensed on the outer surface of the second heat exchanger; the second heat exchanger is a light pipe heat exchanger made of high-corrosion-resistant materials.
Description
Technical Field
The invention relates to a waste heat recovery system, a waste heat recovery method and a boiler system.
Background
With the continuous deepening of the policy of energy conservation and emission reduction in China, the original coal-fired boiler for providing steam for enterprises or residents is gradually replaced by a gas-fired boiler taking natural gas as fuel, taking a certain industrial park as an example, 3 gas-fired boilers can generate 150 tons of steam per hour, the consumption capacity is huge, the temperature of the combusted tail gas is around 110-150 ℃, the main component of the natural gas is methane CH4, and according to the combustion chemical formula: CH4+2O2 ═ CO2+2H2O, 1m3After full combustion of the natural gas, the heating value is about 35.88MJ without regard to condensation. When the condensation heat release is considered, the heat value can reach 39.82MJ due to the fact that a large amount of heat is released when water vapor is condensed, and therefore, the waste heat recovery is of great significance due to the fact that the combustion tail gas contains a large amount of heat energy.
The traditional waste heat recovery system is seriously corroded and can block a flue, and therefore, a fin tube type condenser made of ND corrosion-resistant steel is changed into the waste heat recovery system as a tail gas, but the tail gas still generates acid corrosion within two years, and the tail gas contains more nitrogen oxides and water vapor after natural gas is fully combusted. When the waste heat recovery condenser is used, water vapor in tail gas is separated out due to condensation and is combined with nitrogen oxides to generate nitric acid solution. Due to the structural action of the fins, the acidic corrosive solution collects liquid drops outside the fin tubes of the heat exchanger, so that the fins are gradually corroded to generate metal oxides (rust). The fluffy oxides are accumulated outside the condenser, so that the air duct is gradually blocked, the air outlet resistance in the pipeline is increased, the performance working point of the tail gas fan is changed, and the air volume is obviously reduced.
If the finned heat exchanger processed by the high-corrosion-resistance material is adopted, the investment cost is too high and far exceeds the budget due to the fact that the finned tube type structure is complex, a large number of used materials are used, and the high-corrosion-resistance material is expensive.
Disclosure of Invention
The invention aims to provide a waste heat recovery system, which solves the technical problem that the smoke discharge of an air duct is blocked due to easy corrosion, rusting and ash blockage of a heat exchanger in the traditional waste heat recovery process on the premise of not increasing the cost too much; the invention also aims to provide a boiler system using the waste heat recovery system; the invention also aims to provide a waste heat recovery method which can solve the technical problem that the smoke discharge of an air duct is blocked due to easy corrosion, rusting and ash blockage of a heat exchanger in the traditional waste heat recovery process.
The technical scheme of the waste heat recovery system is as follows:
a waste heat recovery system comprising:
the first heat exchanger is arranged in the flue and is provided with a first internal pipeline, a first heat exchange medium is filled in the first internal pipeline, and the temperature of the first heat exchange medium is higher than the dew point temperature of water vapor in the flue gas when the water vapor is condensed on the outer surface of the first heat exchanger, so that the water vapor in the flue gas cannot be condensed on the surface of the first heat exchanger, an acidic solution cannot be formed, the corrosion of the acidic solution on the surface of the first heat exchanger is avoided, and the first heat exchanger cannot block a smoke exhaust channel due to corrosion and rusting; the first heat exchanger is a finned tube heat exchanger made of common carbon steel, and a first heat exchange medium exchanges heat with the flue gas for the first time; because the corrosion of the first heat exchanger can be avoided by controlling the temperature of the first heat exchange medium, the finned tube heat exchanger with high heat exchange efficiency is selected for the first heat exchanger to improve the heat exchange efficiency, and the common carbon steel material is selected as the material of the first heat exchanger, so that the cost of the first heat exchanger can be greatly reduced;
the second heat exchanger is arranged in the flue and is positioned at the downstream of the first heat exchanger along the flow direction of the flue gas, a second internal pipeline is arranged in the second heat exchanger, the second internal pipeline is provided with a cooling water inlet and a cooling water outlet, the cooling water inlet is connected with a water supply system for supplying a second heat exchange medium, the second heat exchange medium performs secondary heat exchange with the flue gas in the second internal pipeline, and a large amount of water vapor in the flue gas is condensed on the outer surface of the second heat exchanger; the second heat exchanger is a light pipe heat exchanger made of high-corrosion-resistant materials. The second heat exchanger is a place where a large amount of condensation is carried out according to design requirements, and condensation can generate a large amount of acid solution, so that the second heat exchanger is made of high-corrosion-resistant materials to be basically corrosion-resistant, and then the light pipe heat exchanger is selected, and the characteristic that the surface of the light pipe heat exchanger is smooth is utilized, so that the acid solution formed after condensation is prevented from being accumulated on the outer surface of the second heat exchanger, and the possibility of corrosion is further reduced; on the other hand, because the condensation is a violent phase change process, finned tubes are not needed to improve the heat exchange efficiency.
Therefore, through design, in a high-temperature area of the condenser, due to no water analysis, the finned tube made of common materials can be combined with common anticorrosion measures to inhibit acid corrosion, and the low-wind-resistance anticorrosion heat exchange tube, namely the elliptical finned tube, is adopted to design and manufacture the condenser in the high-temperature area; in the low temperature region, a large amount of dilute nitric acid solution is formed because a large amount of water is separated out. Therefore, in this region, stainless steel light pipes which are corrosion resistant and relatively high in cost are selected to design and manufacture the condenser module in the region.
On the basis of the scheme, the waste heat recovery system is further improved as follows, the waste heat recovery system comprises a shell, a spray pipe is further arranged in the shell corresponding to the second heat exchanger, an inlet of the spray pipe is connected with an external water supply system, a plurality of nozzles are arranged on the spray pipe towards one side of the second heat exchanger, the water spray range of the nozzles covers the second heat exchanger, and a water outlet is further formed in the shell below the second heat exchanger. Because the second heat exchanger is a designed large-amount condensation area, a large amount of acid solution can be formed, if the acid solution is adhered to the outer surface of the second heat exchanger, although the second heat exchanger is made of a high-corrosion-resistant material, the acid solution still can affect the corrosion resistance of the hot end of the second heat exchanger, and therefore the second heat exchanger needs to be washed away; on the other hand, the surface of the second heat exchanger is wet after condensation, so that dust in the flue gas is easily adsorbed, and the dust and the acidic solution are prevented from forming slurry and adhering to the surface of the second heat exchanger, so that the subsequent cleaning is inconvenient, the heat exchange efficiency of the second heat exchanger is influenced, even a ventilation channel on the surface of the second heat exchanger is blocked, and the blockage is avoided, so that the cleaning is required in time, and therefore, the arrangement of the spray pipe is very important, and the spray pipe can play an important role in corrosion prevention and dust blockage prevention of the second heat exchanger; meanwhile, the shower pipe can be washed to facilitate the collection of the acid solution, so that the acid solution can be reused.
On the basis of the scheme, the heat exchanger is further improved in that a water collecting tank is further arranged below the second heat exchanger on the shell, and the water outlet is arranged at the lower part of the water collecting tank. The setting up of water catch bowl makes things convenient for the quick gathering and the timely discharge of solution on the one hand, and on the other hand also prevents that acid solution from flowing to first heat exchanger department to avoid the corruption to first heat exchanger.
On the basis of the scheme, the material of the second heat exchanger is corrosion-resistant stainless steel or nonmetal.
On the basis of the scheme, the waste heat recovery system is further improved as follows, the waste heat recovery system further comprises a third heat exchanger for water-water heat exchange, the third heat exchanger is provided with a hot end pipeline and a cold end pipeline, the first heat exchange medium flows through the hot end pipeline, the second heat exchange medium flows through the cold end pipeline, and the first heat exchange medium and the second heat exchange medium perform third heat exchange in the third heat exchanger. The third heat exchanger is arranged to facilitate the control of the temperature of the first heat exchange medium, and further improve the temperature of the second heat exchange medium, so that the heat recovery efficiency is improved.
On the basis of the scheme, the cross section of the first inner pipeline of the first heat exchanger is oval, and the length direction of the oval extends along the flow direction of the flue gas. Such setting has reduced the windage on the one hand, and on the other hand has also improved the area of contact and the contact time of first heat exchanger and flue gas to improve heat exchange efficiency.
On the basis of the scheme, the light pipe inner core of the second heat exchanger is of a drawer type detachable structure so as to be convenient to clean.
On the basis of the scheme, the shell is further improved by comprising a first part and a second part which are spliced with each other, the first heat exchanger and the third heat exchanger are positioned in the first part, and the second heat exchanger is positioned in the second part. Such an arrangement may facilitate transportation.
On the basis of the scheme, the outer surface of the first heat exchanger is further improved to be provided with hot galvanizing and/or electroplated layers. The hot galvanizing and/or electroplating layer is arranged to avoid the corrosion of the acid solution on the surface of the first heat exchanger when the temperature of the first heat exchange medium is not raised to be higher than the dew point temperature, so that a certain corrosion prevention effect is achieved.
The technical scheme of the boiler system is as follows:
boiler system, including boiler body, the flue and the inlet tube that link to each other with boiler body, still include waste heat recovery system, waste heat recovery system includes:
the first heat exchanger is arranged in the flue and is provided with a first internal pipeline, a first heat exchange medium is filled in the first internal pipeline, and the temperature of the first heat exchange medium is higher than the dew point temperature of water vapor in the flue gas when the water vapor is condensed on the outer surface of the first heat exchanger, so that the water vapor in the flue gas cannot be condensed on the surface of the first heat exchanger, an acidic solution cannot be formed, the corrosion of the acidic solution on the surface of the first heat exchanger is avoided, and the first heat exchanger cannot block a smoke exhaust channel due to corrosion and rusting; the first heat exchanger is a finned tube heat exchanger made of common carbon steel, and a first heat exchange medium exchanges heat with the flue gas for the first time; because the corrosion of the first heat exchanger can be avoided by controlling the temperature of the first heat exchange medium, the finned tube heat exchanger with high heat exchange efficiency is selected for the first heat exchanger to improve the heat exchange efficiency, and the common carbon steel material is selected as the material of the first heat exchanger, so that the cost of the first heat exchanger can be greatly reduced;
the second heat exchanger is arranged in the flue and is positioned at the downstream of the first heat exchanger along the flow direction of the flue gas, a second internal pipeline is arranged in the second heat exchanger, the second internal pipeline is provided with a cooling water inlet and a cooling water outlet, the cooling water inlet is connected with a water supply system for supplying a second heat exchange medium, the second heat exchange medium performs secondary heat exchange with the flue gas in the second internal pipeline, and a large amount of water vapor in the flue gas is condensed on the outer surface of the second heat exchanger; the second heat exchanger is a light pipe heat exchanger made of high-corrosion-resistant materials. The second heat exchanger is a place where a large amount of condensation is carried out according to design requirements, and condensation can generate a large amount of acid solution, so that the second heat exchanger is made of high-corrosion-resistant materials to be basically corrosion-resistant, and then the light pipe heat exchanger is selected, and the characteristic that the surface of the light pipe heat exchanger is smooth is utilized, so that the acid solution formed after condensation is prevented from being accumulated on the outer surface of the second heat exchanger, and the possibility of corrosion is further reduced; on the other hand, because the condensation is a violent phase change process, finned tubes are not needed to improve the heat exchange efficiency.
Therefore, through design, in a high-temperature area of the condenser, due to no water analysis, the finned tube made of common materials can be combined with common anticorrosion measures to inhibit acid corrosion, and the low-wind-resistance anticorrosion heat exchange tube, namely the elliptical finned tube, is adopted to design and manufacture the condenser in the high-temperature area; in the low temperature region, a large amount of dilute nitric acid solution is formed because a large amount of water is separated out. Therefore, in this region, stainless steel light pipes which are corrosion resistant and relatively high in cost are selected to design and manufacture the condenser module in the region.
On the basis of the scheme, the waste heat recovery system is further improved as follows, the waste heat recovery system comprises a shell, a spray pipe is further arranged in the shell corresponding to the second heat exchanger, an inlet of the spray pipe is connected with an external water supply system, a plurality of nozzles are arranged on the spray pipe towards one side of the second heat exchanger, the water spray range of the nozzles covers the second heat exchanger, and a water outlet is further formed in the shell below the second heat exchanger. Because the second heat exchanger is a designed large-amount condensation area, a large amount of acid solution can be formed, if the acid solution is adhered to the outer surface of the second heat exchanger, although the second heat exchanger is made of a high-corrosion-resistant material, the acid solution still can affect the corrosion resistance of the hot end of the second heat exchanger, and therefore the second heat exchanger needs to be washed away; on the other hand, the surface of the second heat exchanger is wet after condensation, so that dust in the flue gas is easily adsorbed, and the dust and the acidic solution are prevented from forming slurry and adhering to the surface of the second heat exchanger, so that the subsequent cleaning is inconvenient, the heat exchange efficiency of the second heat exchanger is influenced, even a ventilation channel on the surface of the second heat exchanger is blocked, and the blockage is avoided, so that the cleaning is required in time, and therefore, the arrangement of the spray pipe is very important, and the spray pipe can play an important role in corrosion prevention and dust blockage prevention of the second heat exchanger; meanwhile, the shower pipe can be washed to facilitate the collection of the acid solution, so that the acid solution can be reused.
On the basis of the scheme, the heat exchanger is further improved in that a water collecting tank is further arranged below the second heat exchanger on the shell, and the water outlet is arranged at the lower part of the water collecting tank. The setting up of water catch bowl makes things convenient for the quick gathering and the timely discharge of solution on the one hand, and on the other hand also prevents that acid solution from flowing to first heat exchanger department to avoid the corruption to first heat exchanger.
On the basis of the scheme, the material of the second heat exchanger is corrosion-resistant stainless steel or nonmetal.
On the basis of the scheme, the waste heat recovery system is further improved as follows, the waste heat recovery system further comprises a third heat exchanger for water-water heat exchange, the third heat exchanger is provided with a hot end pipeline and a cold end pipeline, the first heat exchange medium flows through the hot end pipeline, the second heat exchange medium flows through the cold end pipeline, and the first heat exchange medium and the second heat exchange medium perform third heat exchange in the third heat exchanger. The third heat exchanger is arranged to facilitate the control of the temperature of the first heat exchange medium, and further improve the temperature of the second heat exchange medium, so that the heat recovery efficiency is improved.
On the basis of the scheme, the cross section of the first inner pipeline of the first heat exchanger is oval, and the length direction of the oval extends along the flow direction of the flue gas. Such setting has reduced the windage on the one hand, and on the other hand has also improved the area of contact and the contact time of first heat exchanger and flue gas to improve heat exchange efficiency.
On the basis of the scheme, the light pipe inner core of the second heat exchanger is of a drawer type detachable structure so as to be convenient to clean.
On the basis of the scheme, the shell is further improved by comprising a first part and a second part which are spliced with each other, the first heat exchanger and the third heat exchanger are positioned in the first part, and the second heat exchanger is positioned in the second part. Such an arrangement may facilitate transportation.
On the basis of the scheme, the outer surface of the first heat exchanger is further improved to be provided with hot galvanizing and/or electroplated layers. The hot galvanizing and/or electroplating layer is arranged to avoid the corrosion of the acid solution on the surface of the first heat exchanger when the temperature of the first heat exchange medium is not raised to be higher than the dew point temperature, so that a certain corrosion prevention effect is achieved.
The waste heat recovery method adopts the following technical scheme:
a method of waste heat recovery, the method comprising:
the flue gas heat exchanger comprises a first heat exchanger and a second heat exchanger which are sequentially arranged in a flue along the flow direction of flue gas, wherein the first heat exchanger is a finned tube heat exchanger made of common carbon steel and provided with a first internal pipeline, the second heat exchanger is a light tube heat exchanger made of high-corrosion-resistant material and provided with a second internal pipeline, and the second internal pipeline is provided with a cooling water inlet and a cooling water outlet;
filling a first heat exchange medium in the first heat exchanger, and controlling the temperature of the first heat exchange medium to be higher than the dew point temperature of vapor in the flue gas when the vapor is condensed on the outer surface of the first heat exchanger;
a second heat exchange medium with the temperature lower than the dew point temperature of the water vapor in the flue gas when the water vapor is condensed on the surface of a second heat exchanger is introduced through the cooling water inlet;
the flue gas in the flue exchanges heat with the first heat exchange medium and the second heat exchange medium when passing through the first heat exchanger and the second heat exchanger respectively, and water vapor in the flue gas is greatly condensed on the outer surface of the second heat exchanger.
Furthermore, a third heat exchanger is arranged between the first heat exchanger and the second heat exchanger, the third heat exchanger is provided with a hot end pipeline and a cold end pipeline, a first heat exchange medium flowing out of the first heat exchanger flows through the hot end pipeline and flows back to the first heat exchanger again, a second heat exchange medium flowing out of a cooling water outlet of the second heat exchanger flows through the cold end pipeline, and the first heat exchange medium and the second heat exchange medium are subjected to third heat exchange in the third heat exchanger.
The invention has the beneficial effects that: firstly, for a first heat exchanger, the temperature of a first heat exchange medium in the first heat exchanger is adjusted to be higher than the dew point temperature of the condensation of water vapor in tail gas, so that the condensation phenomenon of the water vapor at the first heat exchanger can not occur, and the outer surface of the first heat exchanger adopts common corrosion prevention schemes such as hot galvanizing or electroplating and the like, so that the corrosion prevention purpose of the first heat exchanger is realized, and therefore, a finned tube heat exchanger made of common carbon steel can be selected safely, and the surface of the first heat exchanger can not rust due to the fact that the finned tube heat exchanger can not be condensed, and the problem of preventing the flue from being blocked is solved; secondly, for the second heat exchanger, because the second heat exchanger is in a low-temperature region, the temperature of a second heat exchange medium in the second heat exchanger is low, the second heat exchanger is a core region for condensation heat exchange, and a large amount of condensed water is inevitably generated on the outer surface of the second heat exchanger, so that a large amount of dilute nitric acid solution can be formed, the second heat exchanger is a core region which is corroded, and the corrosion resistance of the second heat exchanger needs to be well improved; in addition, in order to prevent the acid solution from being accumulated on the surface of the second heat exchanger, a smooth-surface non-groove light pipe heat exchanger is selected, so that the acid solution cannot be accumulated on the surface of the heat exchanger for a long time; moreover, in order to prevent the acid solution from being bonded to the surface of the second heat exchanger after being combined with the dust, a spray pipe is arranged, and a water outlet is also formed in the lower part of the second heat exchanger, so that the outer surface of the second heat exchanger is regularly washed, the dust and the acid solution are washed down and discharged from the water outlet, and the outer surface of the second heat exchanger and the inner wall surface of the flue are prevented from being corroded; the design of the above anticorrosion measures has the advantages of excellent anticorrosion and flue blockage prevention on the premise of low cost, simple structure and high heat exchange efficiency; the corrosion of the waste heat recovery system is mainly electrochemical corrosion, the contents of the discharged gases of various boilers and gas turbines are different, the environmental pressures are different, the dew points (condensation-generating temperatures) are different, when the temperature of a certain point of the heat exchange device is lower than the condensation temperature, dew condensation can be generated, so that the heat exchanger is corroded, all the temperatures of the heat exchanger are higher than the dew point temperature by controlling the temperature of a cold-side medium of the heat recovery device, and the heat recovery quantity of a common heat exchanger can be reduced to the maximum extent by using common materials.
Drawings
FIG. 1 is a schematic diagram of the working principle of an embodiment 1 of the waste heat recovery system of the present invention;
FIG. 2 is a schematic front view of a waste heat recovery system;
FIG. 3 is a front view of a first heat exchanger and a second heat exchanger;
FIG. 4 is a left side view of FIG. 3;
FIG. 5 is a schematic diagram of the working principle of embodiment 2 of the waste heat recovery system of the present invention;
in the figure: 1-a first heat exchanger, 11-a circulating water inlet, 12-a circulating water outlet, 2-a circulating water pump, 3-a constant pressure tank, 4-a spray pipe, 41-a nozzle, 42-a spray water inlet, 43-a water outlet, 44-a water collecting tank, 5-a second heat exchanger, 51-a cooling water inlet, 52-a cooling water outlet, 6-a third heat exchanger and 7-a fourth heat exchanger; 8-first heat exchange medium, 9-second heat exchange medium, 20-front water chamber of heat exchanger, 30-rear water chamber of heat exchanger, and 40-shell.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
It is noted that relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The features and properties of the present invention are described in further detail below with reference to examples.
the waste heat recovery system is used for waste heat recovery of tail gas of a gas boiler or a coal-fired boiler, and is provided with a shell 40, wherein the shell 40 is in a pipeline shape and is connected in a tail gas pipeline in series, namely, two ends of the shell are in sealed butt joint with a tail gas pipe respectively, so that the tail gas of the boiler can pass through the waste heat recovery system, the tail gas is discharged after heat exchange is carried out, heat in the tail gas is transferred to a heat transfer medium of the waste heat recovery system, heating is carried out by utilizing the heat of the heat transfer medium, and the like.
The waste heat recovery system includes: the first heat exchanger is arranged in the flue and is provided with a first internal pipeline, a first heat exchange medium is filled in the first internal pipeline, and the temperature of the first heat exchange medium is higher than the dew point temperature of water vapor in the flue gas when the water vapor is condensed on the outer surface of the first heat exchanger, so that the water vapor in the flue gas can not be condensed on the surface of the first heat exchanger, an acid solution can not be formed, the corrosion of the acid solution on the surface of the first heat exchanger can be avoided, and the first heat exchanger can not block a smoke exhaust channel due to corrosion and rusting; the first heat exchanger is a finned tube heat exchanger made of common carbon steel, and a first heat exchange medium exchanges heat with the flue gas for the first time; because the corrosion of the first heat exchanger can be avoided by controlling the temperature of the first heat exchange medium, the finned tube heat exchanger with high heat exchange efficiency is selected for the first heat exchanger to improve the heat exchange efficiency, and the common carbon steel material is selected as the material of the first heat exchanger, so that the cost of the first heat exchanger can be greatly reduced; the second heat exchanger is arranged in the flue and is positioned at the downstream of the first heat exchanger along the flow direction of the flue gas, a second internal pipeline is arranged in the second heat exchanger, the second internal pipeline is provided with a cooling water inlet and a cooling water outlet, the cooling water inlet is connected with a water supply system for supplying a second heat exchange medium, the second heat exchange medium performs secondary heat exchange with the flue gas in the second internal pipeline, and a large amount of water vapor in the flue gas is condensed on the outer surface of the second heat exchanger; the second heat exchanger is a light pipe heat exchanger made of high-corrosion-resistant materials. The second heat exchanger is a place where a large amount of condensation is carried out according to design requirements, and condensation can generate a large amount of acid solution, so that the second heat exchanger is made of high-corrosion-resistant materials to be basically corrosion-resistant, and then the light pipe heat exchanger is selected, and the characteristic that the surface of the light pipe heat exchanger is smooth is utilized, so that the acid solution formed after condensation is prevented from being accumulated on the outer surface of the second heat exchanger, and the possibility of corrosion is further reduced; on the other hand, because the condensation is a violent phase change process, finned tubes are not needed to improve the heat exchange efficiency.
Therefore, through design, in a high-temperature area of the condenser, due to no water analysis, the finned tube made of common materials can be combined with common anticorrosion measures to inhibit acid corrosion, and the low-wind-resistance anticorrosion heat exchange tube, namely the elliptical finned tube, is adopted to design and manufacture the condenser in the high-temperature area; in the low temperature region, a large amount of dilute nitric acid solution is formed because a large amount of water is separated out. Therefore, in this region, stainless steel light pipes which are corrosion resistant and relatively high in cost are selected to design and manufacture the condenser module in the region.
The waste heat recovery system comprises a shell, a spray pipe is arranged in the shell and corresponds to the second heat exchanger, an inlet of the spray pipe is connected with an external water supply system, a plurality of nozzles are arranged on the spray pipe and face one side of the second heat exchanger, the water spray range of the nozzles covers the second heat exchanger, and a water outlet is formed in the shell and below the second heat exchanger. Because the second heat exchanger is a designed large-amount condensation area, a large amount of acid solution can be formed, if the acid solution is adhered to the outer surface of the second heat exchanger, although the second heat exchanger is made of a high-corrosion-resistant material, the acid solution still can affect the corrosion resistance of the hot end of the second heat exchanger, and therefore the second heat exchanger needs to be washed away; on the other hand, the surface of the second heat exchanger is wet after condensation, so that dust in the flue gas is easily adsorbed, and the dust and the acidic solution are prevented from forming slurry and adhering to the surface of the second heat exchanger, so that the subsequent cleaning is inconvenient, the heat exchange efficiency of the second heat exchanger is influenced, even a ventilation channel on the surface of the second heat exchanger is blocked, and the blockage is avoided, so that the cleaning is required in time, and therefore, the arrangement of the spray pipe is very important, and the spray pipe can play an important role in corrosion prevention and dust blockage prevention of the second heat exchanger; meanwhile, the shower pipe can be washed to facilitate the collection of the acid solution, so that the acid solution can be reused. A water collecting tank is also arranged below the second heat exchanger on the shell, and a water outlet is arranged at the lower part of the water collecting tank. The setting up of water catch bowl makes things convenient for the quick gathering and the timely discharge of solution on the one hand, and on the other hand also prevents that acid solution from flowing to first heat exchanger department to avoid the corruption to first heat exchanger.
The second heat exchanger is made of corrosion-resistant stainless steel or nonmetal. The waste heat recovery system further comprises a third heat exchanger for water-water heat exchange, the third heat exchanger is provided with a hot end pipeline and a cold end pipeline, the first heat exchange medium flows through the hot end pipeline, the second heat exchange medium flows through the cold end pipeline, and the first heat exchange medium and the second heat exchange medium perform third heat exchange in the third heat exchanger. The third heat exchanger is arranged to facilitate the control of the temperature of the first heat exchange medium, and further improve the temperature of the second heat exchange medium, so that the heat recovery efficiency is improved. The cross section of the first inner pipeline of the first heat exchanger is oval, and the oval length direction extends along the smoke flow direction. Such setting has reduced the windage on the one hand, and on the other hand has also improved the area of contact and the contact time of first heat exchanger and flue gas to improve heat exchange efficiency. The light pipe inner core of the second heat exchanger is of a drawer type detachable structure so as to be convenient to clean.
The shell comprises a first part and a second part which are spliced with each other, the first heat exchanger and the third heat exchanger are positioned in the first part, and the second heat exchanger is positioned in the second part. Such an arrangement may facilitate transportation.
The outer surface of the first heat exchanger is provided with hot galvanizing or electroplated layers. The hot galvanizing or the electroplating layer is arranged to avoid the corrosion of the acid solution on the surface of the first heat exchanger when the temperature of the first heat exchange medium is not raised to be higher than the dew point temperature, so that a certain corrosion prevention effect is achieved.
More specifically:
as shown in fig. 1 to 4, the waste heat recovery system includes a housing 40 and a first heat exchanger 1, a second heat exchanger 5, and a third heat exchanger 6 installed in the housing 40. Wherein:
the first heat exchanger 1 is a tube fin type air-water heat exchanger made of common carbon steel, tube fins of the first heat exchanger are elliptical finned tubes, the windward side of the first heat exchanger is small, the heat exchange area is large, the wind resistance outside the tubes can be fully reduced on the premise of ensuring the heat exchange efficiency, the overall structure better conforms to the field synergy principle, and the heat transfer coefficient of the first heat exchanger is superior to that of a common circular finned tube. Meanwhile, in order to ensure the corrosion resistance of the heat exchanger in the area, the outside of the finned tube is galvanized. Through high-temperature hot galvanizing, the fins and the base pipe are wrapped by the zinc layer at the same time, and the protection of the zinc layer can ensure that the fin and the base pipe have antirust and anticorrosive performances while the high-efficiency heat transfer between metals is kept. The following table is a table of performance parameters of the elliptical finned tube heat exchanger (first heat exchanger 1):
the body of first heat exchanger 1 is last to have circulating water import 11 and circulating water export 12, and what match with first heat exchanger 1 has an inner loop pipeline, and the inner loop pipeline includes circulating water pump 2, level pressure jar 3, converter and pipeline etc. and wherein the setting of level pressure jar 3 is for stabilizing water pressure. The pipeline is connected with a circulating water inlet 11 and a circulating water outlet 12 of the first heat exchanger 1 to form a closed-loop internal circulation pipeline, a circulating water pump 2, a constant pressure tank 3 and the like are arranged on the internal circulation pipeline, under the control of a frequency converter, the circulating water pump 2 operates according to a set rotating speed, so that a heat exchange medium (generally water, referred to as a first heat exchange medium 8) in the internal circulation pipeline circularly flows according to a set flow velocity (flow rate), and exchanges heat with high-temperature flue gas (generally around 110-. Meanwhile, the internal circulation pipeline is also connected with the third heat exchanger 6, performs heat exchange with another heat exchange medium (cooling water heated by the second heat exchanger 5, referred to as a second heat exchange medium 9) in the third heat exchanger 6, transfers the heat to the second heat exchange medium 9, and realizes temperature control of the first heat exchange medium 8; through the control of converter and circulating water pump 2 to 8 velocity of flow (flows) of first heat transfer medium and with the heat exchange of second heat transfer medium 9 promptly, realized the control to 8 temperatures of first heat transfer medium for 8 temperatures of first heat transfer medium are a little higher than dew point temperature (the condensation temperature of the vapor in the tail gas on 1 outer pipe wall of first heat exchanger), when guaranteeing that tail gas can not condense in vapor, 8 temperatures of first heat transfer medium are as low as possible, thereby improve 1 heat exchange efficiency of first heat exchanger.
In order to facilitate the control of the water temperature in the internal circulation pipeline, a temperature detection sensor is arranged on the internal circulation pipeline, a temperature range which can ensure that the water vapor in the tail gas is condensed and can also ensure that the heat exchange efficiency is higher is set, for example, 65-75 c is set as the temperature range, when the temperature sensor detects that the actual temperature is lower than 65 c, it is necessary to control the rotation speed of the circulating water pump 2, the flow is slower, so that the heat exchange time of the first heat exchange medium 8 and the high-temperature tail gas is prolonged, thereby increasing the temperature of the first heat exchange medium 8, whereas if the actual temperature is detected to be higher than 75 c, the rotating speed of the circulating water pump 2 needs to be controlled, so that the flow speed is fast, the heat exchange time of the first heat exchange medium 8 and the high-temperature tail gas is shortened, and the purpose of controlling the water temperature of the first heat exchange medium 8 within a set range is achieved.
It should be noted that: the reason why the water vapor in the exhaust gas is prevented from condensing on the outer surface of the first heat exchanger 1 is that the exhaust gas contains a large amount of nitrogen oxides and water vapor after the natural gas is sufficiently combusted. When the tail gas passes through the first heat exchanger 1, if the temperature of the first heat exchange medium 8 in the first heat exchanger 1 is lower than the dew point temperature, water vapor in the tail gas is separated out due to condensation and is combined with nitrogen oxides to generate a nitric acid solution. Due to the structural action of the fins, the acidic corrosive solution collects liquid drops outside the fin tubes of the heat exchanger, so that the fins are gradually corroded to generate metal oxides (rust). The fluffy oxides are accumulated outside the first heat exchanger 1, so that an air channel is gradually blocked, the air outlet resistance in the pipeline is increased, the performance working point of the tail gas fan is changed, and the air volume is obviously reduced. In the scheme of the invention, the temperature of the first heat exchange medium 8 is controlled to be slightly higher than the dew point through the arrangement of the internal circulation pipeline and the third heat exchanger 6, so that an acidic corrosive solution cannot be condensed on the outer surface of the first heat exchanger 1, and the corrosion problem of the first heat exchanger 1 is avoided.
High anticorrosive material, for example stainless steel or the heat exchange tube of taking special cladding can effectively be able to bear the corrosion of rare nitric acid, but because its price is more expensive, if all use high anticorrosive material to make the heat exchanger, probably lead to the heat exchanger investment cost far beyond the budget. Considering the cost, first heat exchanger 1 itself can choose ordinary carbon steel material not corrosion-resistant for use, owing to avoided first heat exchanger 1 surface corrosion through 8 temperature's of first heat transfer medium control, does not worry again under the prerequisite of anticorrosive problem, chooses for use the heat exchanger that the cross section is oval fin tube structure for the purpose of improving heat exchange efficiency. In other words, the temperature of the entire flow field of the exhaust gas as it passes through the condenser is calculated according to software simulation. And in different temperature intervals, different materials are selected for use as the heat exchange tube material, so that the heat exchanger structure with the heat exchange tube material coupled with the temperature field is realized. In the high-temperature area of the condenser, because no water is analyzed, the finned tube made of common materials can be combined with common anticorrosion measures to inhibit acid corrosion. In the low temperature region, a large amount of dilute nitric acid solution is formed because a large amount of water is separated out. Therefore, in this region, stainless steel light pipes, which are corrosion resistant but costly, are selected for the design of the condenser module in which the region is fabricated (see below for further details).
The high-temperature flue gas further enters a second heat exchanger 5 after passing through the first heat exchanger 1. As shown in fig. 3, the second heat exchanger 5 is a light-pipe air-water heat exchanger made of stainless steel, and a body of the heat exchanger is provided with a cooling water inlet 51 and a cooling water outlet 52 for the second heat exchange medium 9 to flow through, and the second heat exchange medium 9 is mainly used for heating the second heat exchange medium 9 to a required temperature, and the second heat exchange medium 9 is an output product of the waste heat recovery system, and can be used for heating or a water supply system of a gas boiler, so that the gas boiler can consume a little fuel when producing steam. In the second heat exchanger 5, as the temperature of the second heat exchange medium 9 in the second heat exchanger is lower than the dew point temperature, a large amount of heat is released by condensation of water vapor in the flue gas, and the heating power during the whole condensation can account for about 11% of the full heat value of the natural gas at most. In order to ensure reliable construction, a certain margin is reserved, and the flue gas temperature is recovered to 50 ℃. In the second heat exchanger 5, since the flue gas is mainly saturated steam, a large amount of heat is released along with condensation, and a large amount of condensed water is separated out. At this time, a large amount of acidic solution is generated outside the heat exchange tube.
The second-stage heat exchanger is a condensation heat exchange core area, and because the phase change of condensation heat exchange is severe and the heat exchange amount is large, the heat exchange efficiency is not required to be increased by adopting fins, and the light tube made of stainless steel or glass is directly adopted in consideration of the requirements on cost and corrosion resistance. The following table is a table of performance parameters for the bare tube heat exchanger (second heat exchanger 5):
as shown in fig. 3 and 4, since the acid solution is formed on the surface of the second heat exchanger 5, the acid solution is unfavorable to the heat exchanger on the surface of the heat exchanger, and dust is easily accumulated, a spray pipe 4 is disposed between the first heat exchanger 1 and the second heat exchanger 5, a plurality of spray nozzles 41 are disposed at intervals on the spray pipe 4, the spray nozzles 41 are disposed toward the second heat exchanger 5, high-pressure water is supplied by an external water supply pump, supplied to the spray pipe 4 through a spray water inlet 42, high-pressure water mist is sprayed out through the spray nozzles 41 in a tapered range to wash off the outer surface of the second heat exchanger 5 on-line, so as to wash off the dust and the acid solution on the surface of the second heat exchanger 5, a water collection tank 44 structure similar to a funnel is disposed at the lower portion of the housing 40 corresponding to the second heat exchanger 5, a water discharge port 43 is disposed at the lower portion of the water collection tank structure for discharging the washed off, it is therefore contemplated that the acidic solution may be filtered, purified, etc. to form a more pure acidic solution for subsequent use. In other embodiments, the material of the light pipe may be replaced by a corrosion-resistant material such as glass or ceramic.
Meanwhile, due to the separation of the condensed water, dust and impurities are very easily polluted in the area, so that the drawer type core body is adopted in the design, the maintenance and the cleaning are convenient, and the efficiency of the heat exchange tube and the cleanliness in the area are improved.
The third heat exchanger 6 is an auxiliary heat exchanger for exchanging heat between the internal heat exchange media (the first heat exchange medium 8 and the second heat exchange medium 9) of the first heat exchanger 1 and the second heat exchanger 5, the plate heat exchanger adopts a plate heat exchanger with a multi-layer plate stack structure, is a water-water heat exchanger, does not participate in heat exchange with tail gas, and has the main function of matching with an internal circulation pipeline system to conveniently control the temperature of the first heat exchange medium 8, and secondly, can perform secondary heating on the second heat exchange medium 9 to further improve the temperature of the second heat exchange medium 9.
In other words, the first heat exchanger 1 and the third heat exchanger 6 can be regarded as one first-stage heat exchanger, the second heat exchanger 5 is a second-stage heat exchanger, the first-stage heat exchanger is provided with internal circulation medium temperature control (namely provided with a plate heat exchanger, namely the third heat exchanger 6), namely, three streams of fluid exist in the first-stage heat exchanger, and the heat medium (the first heat exchange medium 8), the cold medium (the second heat exchange medium 9) and the high-temperature flue gas form two heat transfer states among the three. As shown in fig. 1, the three heat exchangers are integrated into a single structure. In order to meet the on-site transportation limit of the equipment and consider the convenience of equipment transportation and installation, the equipment is split into at least two templates.
On the other hand, the system is also provided with a water leakage alarm module and a water shortage alarm module, and when water leakage of a pipeline or water shortage in the heat exchanger is detected, alarm prompts are respectively carried out so as to ensure that maintenance personnel can timely collect message prompts.
When in use: as shown in figure 1, high temperature tail gas (110-, and at the same time, the speed of water circulation of the internal circulation pipeline is controlled, so that the temperature of the first heat exchange medium 8 is reduced to 70 ℃, and the temperature can be ensured not to be condensed but to have the highest heat exchange efficiency when the heat exchange is carried out with the high-temperature tail gas (110-; and the temperature of the second heat exchange medium 9 is raised to about 80 ℃, and the second heat exchange medium 9 can be guided into the water inlet pipeline of the gas-fired boiler at the moment, so that the gas consumption of the gas-fired boiler is reduced, and the second heat exchange medium can also be guided into an urban heating pipeline to realize heating and can also be used for other purposes.
The waste heat recovery system has the following characteristics:
1. the heat recovery efficiency is high, the energy utilization rate of the gas boiler can be improved as much as possible, firstly, the temperature of the first heat exchange medium 8 in the first heat exchanger 1 is controlled to be as low as possible on the premise that the temperature is higher than the dew point and the first heat exchange medium is not easy to corrode, so that the heat exchange efficiency is higher when the first heat exchange is carried out on the first heat exchange medium and the tail gas; secondly, the first heat exchanger 1 adopts finned tubes with oval cross sections, and the heat exchange efficiency is further improved because the width of the finned tubes in the wind direction is wider on the premise of meeting the requirement of smaller wind resistance, and the heat exchange time is longer and the heat exchange area is larger; in addition, the first heat exchanger 1 does not condense, so that a heat exchanger with fins is selected, the heat exchange efficiency of the fins is high, and the heat recovery efficiency is improved; moreover, the first heat exchange medium 8 also realizes heat exchange with the second heat exchange medium 9 through the third heat exchanger 6, so that the temperature of the second heat exchange medium 9 serving as an output product is further increased, and the heat recovery efficiency is further improved; more importantly, the heated first heat exchange medium 8 is used as raw material water of the gas boiler, so that the fuel quantity required by the gas boiler when heating the first heat exchange medium 8 is obviously reduced compared with the fuel quantity required by the original cooling water used as raw material, namely, the energy dissipation during subsequent long-distance conveying is avoided, and the starting point temperature of the gas boiler during steam production is increased, so that the energy utilization rate is improved; therefore, the waste heat recovery system has high heat recovery efficiency, and can improve the energy utilization rate of the gas-fired boiler as much as possible.
2. The anti-corrosion and anti-wind channel blockage method comprises the steps that firstly, for a first heat exchanger 1, the temperature of a first heat exchange medium 8 in the first heat exchanger is adjusted to be higher than the dew point temperature of water vapor condensation in tail gas, so that the water vapor can not be condensed at the first heat exchanger 1, and common anti-corrosion schemes such as hot galvanizing or electroplating are adopted on the outer surface of the first heat exchanger 1, so that the anti-corrosion purpose of the first heat exchanger 1 is realized, the finned tube heat exchanger made of common carbon steel can be selected safely, and no condensation can occur, so that an acid solution can not be formed, the surface of the first heat exchanger 1 can not rust, and the problem of preventing the flue blockage is solved; secondly, for the second heat exchanger 5, because the second heat exchanger 5 is in a low-temperature region, and the temperature of the second heat exchange medium 9 in the second heat exchanger is low, the second heat exchanger 5 is a core region for condensation heat exchange, and a large amount of condensed water is inevitably generated on the outer surface of the second heat exchanger 5, so that a large amount of dilute nitric acid solution can be formed, therefore, the second heat exchanger 5 is a core region which is corroded, and the corrosion resistance of the second heat exchanger is good, and the second heat exchanger 5 is integrally made of corrosion-resistant materials such as stainless steel and the like to play a main corrosion resistance role; in addition, in order to prevent the acid solution from being accumulated on the surface of the second heat exchanger 5, a smooth-surface non-groove light pipe heat exchanger is selected, so that the acid solution cannot be accumulated on the surface of the heat exchanger for a long time; furthermore, in order to prevent the acidic solution from bonding to the surface of the second heat exchanger 5 after being combined with the dust, the spraying pipe 4 is arranged, and the water outlet 43 is also arranged at the lower part of the spraying pipe, so that the outer surface of the second heat exchanger 5 is regularly washed, the dust and the acidic solution are washed down and discharged from the water outlet 43, and the corrosion of the outer surface of the second heat exchanger 5 and the inner wall surface of the flue is avoided; the design of the above anticorrosion measures has the advantages of excellent anticorrosion and flue blockage prevention on the premise of low cost, simple structure and high heat exchange efficiency; the corrosion of the waste heat recovery system is mainly electrochemical corrosion, the contents of the discharged gases of various boilers and gas turbines are different, the environmental pressures are different, the dew points (condensation-generating temperatures) are different, when the temperature of a certain point of the heat exchange device is lower than the condensation temperature, dew condensation can be generated, so that the heat exchanger is corroded, all the temperatures of the heat exchanger are higher than the dew point temperature by controlling the temperature of a cold-side medium of the heat recovery device, and the heat recovery quantity of a common heat exchanger can be reduced to the maximum extent by using common materials.
On the basis of the two characteristics, the novel energy-saving environment-friendly energy-saving device has the advantages of long service life of products, long service life, good economical efficiency and capability of reducing the investment recovery period.
The working principle of the whitening here is as follows: after passing through the second heat exchanger 5, most of moisture in the tail gas is condensed and separated out, the temperature of the tail gas is about 40 ℃, if the tail gas is directly discharged through a chimney, because the temperature of the tail gas is lower (lower than the dew point), when the tail gas is contacted with the inner wall of the chimney, because the temperature of the inner wall of the chimney is lower, saturated water vapor can be further condensed, so that an acid solution can be generated on the inner wall of the chimney, the corrosion of the inner wall of the chimney is easily caused, and when the tail gas is positioned near a smoke exhaust port of the chimney, the tail gas is contacted with cold air and is condensed to form white fog; in the scheme, the fourth heat exchanger 7 is arranged behind the second heat exchanger 5, so that a part of the heated second heat exchange medium 9 can be guided to be heated by the tail gas, the temperature of the tail gas is higher than the dew point temperature, namely the temperature of the tail gas is higher than the dew point temperature when the tail gas is near the smoke exhaust port of the chimney and the smoke exhaust port of the chimney, condensation cannot occur, and after the tail gas is further diffused into the atmosphere, although the temperature of the tail gas is lower than the dew point temperature, the diffused water vapor is relatively dispersed, water mist cannot be formed, and therefore white mist cannot occur, and the purpose of whitening is achieved. According to the scheme, additional energy is not required to be utilized for heating the tail gas, the temperature of the tail gas is utilized to be reversely heated for the tail gas after heat exchange, and therefore whitening is achieved.
It should be noted that: in the scheme, the tail gas is heated to be higher than 60 ℃ through regenerative heating after being reduced from 150 ℃ to 40 ℃, the regenerative process is not a repeated process, and the scheme is different from the scheme that the tail gas is directly reduced from 150 ℃ to 60 ℃, because the tail gas is a large amount of condensation processes carried out at the second heat exchanger 5 in the process of reducing the temperature to 40 ℃, most of water vapor in the tail gas is condensed and separated out in the process, therefore, the air is only heated in the subsequent regenerative process, the energy consumption of heating is low, and the humidity of the tail gas can be effectively reduced. It can be seen that the reduction from 60 ℃ to 40 ℃ and the heating from 40 ℃ to 60 ℃ in this solution are irreversible processes, since the moisture content in the exhaust gas is different in the two processes, the former having a large energy variation, and the latter having a small energy variation due to the phase transition process involving little water. This is also an ingenious aspect of the present solution.
Through this scheme, can realize protecting rear end chimney internal face material not corroded, reduce the humidity of discharging fume, prevent that vapor from appearing, and realize taking off white. In addition, the scheme achieves the extreme effect of heat recovery, and increases the utilization rate of heat as much as possible on the premise of meeting the requirement of whitening.
In use, as shown in fig. 5, the difference from example 1 is that the second heat exchange medium 9 (about 80 ℃) having passed through the third heat exchanger 6 is not directly introduced into the steam boiler feed water, but the exhaust gas (40 ℃ and 100% humidity) is heated by the fourth heat exchanger 7 to obtain an exhaust gas temperature of about 50 ℃ and a humidity of about 70%, while the temperature of the second heat exchange medium 9 is lowered to about 75 ℃, and the second heat exchange medium 9 (about 75 ℃) is subsequently introduced into the steam boiler feed water.
Specific embodiments of the boiler system of the present invention: take gas boiler system as an example, the system includes boiler body, water softener, water tank, oxygen-eliminating device, steam-distributing cylinder, feed pump, oxygen pump, continuous blowdown flash tank, combustor, flue, pipeline and waste heat recovery system, and waste heat recovery system's specific structure is the same with the structure in the above-mentioned embodiment, no longer explains repeatedly.
The waste heat recovery method comprises the following steps:
the flue gas heat exchanger comprises a first heat exchanger and a second heat exchanger which are sequentially arranged in a flue along the flow direction of flue gas, wherein the first heat exchanger is a finned tube heat exchanger made of common carbon steel and provided with a first internal pipeline, the second heat exchanger is a light tube heat exchanger made of high-corrosion-resistant material and provided with a second internal pipeline, and the second internal pipeline is provided with a cooling water inlet and a cooling water outlet; filling a first heat exchange medium in the first heat exchanger, and controlling the temperature of the first heat exchange medium to be higher than the dew point temperature of vapor in the flue gas when the vapor is condensed on the outer surface of the first heat exchanger; a second heat exchange medium with the temperature lower than the dew point temperature of the water vapor in the flue gas when the water vapor is condensed on the surface of a second heat exchanger is introduced through the cooling water inlet; the flue gas in the flue exchanges heat with the first heat exchange medium and the second heat exchange medium when passing through the first heat exchanger and the second heat exchanger respectively, and water vapor in the flue gas is greatly condensed on the outer surface of the second heat exchanger.
And a third heat exchanger is arranged between the first heat exchanger and the second heat exchanger, the third heat exchanger is provided with a hot end pipeline and a cold end pipeline, a first heat exchange medium flowing out of the first heat exchanger flows through the hot end pipeline and flows back to the first heat exchanger again, and a second heat exchange medium flowing out of a cooling water outlet of the second heat exchanger flows through the cold end pipeline, so that the first heat exchange medium and the second heat exchange medium exchange heat for the third time in the third heat exchanger.
The above description is only a preferred embodiment of the present invention, and not intended to limit the present invention, the scope of the present invention is defined by the appended claims, and all structural changes that can be made by using the contents of the description and the drawings of the present invention are intended to be embraced therein.
Claims (9)
1. A waste heat recovery system, comprising:
the first heat exchanger is arranged in the flue and is provided with a first internal pipeline, a first heat exchange medium is filled in the first internal pipeline, and the temperature of the first heat exchange medium is higher than the dew point temperature of vapor in the flue gas when the vapor is condensed on the outer surface of the first heat exchanger; the first heat exchanger is a finned tube heat exchanger made of common carbon steel,
the first heat exchange medium exchanges heat with the flue gas for the first time;
the second heat exchanger is arranged in the flue and is positioned at the downstream of the first heat exchanger along the flow direction of the flue gas, a second internal pipeline is arranged in the second heat exchanger, the second internal pipeline is provided with a cooling water inlet and a cooling water outlet, the cooling water inlet is connected with a water supply system for supplying a second heat exchange medium, the second heat exchange medium performs secondary heat exchange with the flue gas in the second internal pipeline, and a large amount of water vapor in the flue gas is condensed on the outer surface of the second heat exchanger; the second heat exchanger is a light pipe heat exchanger made of high-corrosion-resistant materials.
2. The waste heat recovery system of claim 1, wherein the second heat exchanger is made of corrosion-resistant stainless steel or a non-metal.
3. The heat recovery system of claim 1, further comprising a third heat exchanger for exchanging heat between water and water, the third heat exchanger having a hot side pipeline and a cold side pipeline, the first heat exchange medium flowing through the hot side pipeline, the second heat exchange medium flowing through the cold side pipeline, the first heat exchange medium and the second heat exchange medium exchanging heat for a third time in the third heat exchanger.
4. The waste heat recovery system of claim 1, wherein the first internal pipe of the first heat exchanger has an oval cross-sectional shape, and the length of the oval cross-sectional shape extends in the direction of the flue gas flow.
5. A heat recovery system as recited in claim 1, wherein the optical tube core of the second heat exchanger is a drawer-type removable structure to facilitate cleaning.
6. A waste heat recovery system as claimed in claim 1, wherein the outer surface of the first heat exchanger is galvanized and/or electroplated.
7. A boiler system comprising a boiler body, a flue and a water inlet pipe connected to the boiler body, characterized in that it further comprises a waste heat recovery system as claimed in any one of claims 1-6, and that the heated second heat exchange medium is led into the water inlet pipe.
8. A method of waste heat recovery, the method comprising:
the flue gas heat exchanger comprises a first heat exchanger and a second heat exchanger which are sequentially arranged in a flue along the flow direction of flue gas, wherein the first heat exchanger is a finned tube heat exchanger made of common carbon steel and provided with a first internal pipeline, the second heat exchanger is a light tube heat exchanger made of high-corrosion-resistant material and provided with a second internal pipeline, and the second internal pipeline is provided with a cooling water inlet and a cooling water outlet;
filling a first heat exchange medium in the first heat exchanger, and controlling the temperature of the first heat exchange medium to be higher than the dew point temperature of vapor in the flue gas when the vapor is condensed on the outer surface of the first heat exchanger;
a second heat exchange medium with the temperature lower than the dew point temperature of the water vapor in the flue gas when the water vapor is condensed on the surface of a second heat exchanger is introduced through the cooling water inlet;
the flue gas in the flue exchanges heat with the first heat exchange medium and the second heat exchange medium when passing through the first heat exchanger and the second heat exchanger respectively, and water vapor in the flue gas is greatly condensed on the outer surface of the second heat exchanger.
9. The waste heat recovery method of claim 8, wherein a third heat exchanger is disposed between the first heat exchanger and the second heat exchanger, the third heat exchanger has a hot end pipeline and a cold end pipeline, the first heat exchange medium flowing out of the first heat exchanger flows through the hot end pipeline and flows back to the first heat exchanger again, the second heat exchange medium flowing out of the cooling water outlet of the second heat exchanger flows through the cold end pipeline, and the first heat exchange medium and the second heat exchange medium exchange heat for a third time in the third heat exchanger.
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| CN202110319403.2A CN112879893A (en) | 2021-03-25 | 2021-03-25 | Waste heat recovery system, waste heat recovery method and boiler system |
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| CN202110319403.2A CN112879893A (en) | 2021-03-25 | 2021-03-25 | Waste heat recovery system, waste heat recovery method and boiler system |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114184065A (en) * | 2021-12-20 | 2022-03-15 | 北京瑞晨航宇能源科技有限公司 | High-temperature plate heat exchanger and temperature control method |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114184065A (en) * | 2021-12-20 | 2022-03-15 | 北京瑞晨航宇能源科技有限公司 | High-temperature plate heat exchanger and temperature control method |
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