CN215951481U - Low-temperature heat exchange island of blast furnace gas boiler - Google Patents
Low-temperature heat exchange island of blast furnace gas boiler Download PDFInfo
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- CN215951481U CN215951481U CN202122187761.0U CN202122187761U CN215951481U CN 215951481 U CN215951481 U CN 215951481U CN 202122187761 U CN202122187761 U CN 202122187761U CN 215951481 U CN215951481 U CN 215951481U
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Abstract
The utility model discloses a low-temperature heat exchange island of a blast furnace gas boiler, which is arranged behind a coal economizer of the blast furnace gas boiler and comprises a high-temperature air preheater, a gas heater, a low-temperature air preheater and a low-temperature coal economizer; the flue gas flowing out of the coal economizer of the blast furnace gas boiler sequentially passes through the high-temperature air preheater, the gas heater, the low-temperature air preheater and the low-temperature coal economizer to exchange heat, the combustion-supporting air is heated by the high-temperature air preheater or sequentially passes through the low-temperature air preheater and the high-temperature air preheater and then is sent into the gas burner of the boiler, and the gas is heated by the gas heater and then is sent into the gas burner of the boiler. Carry out overall management with blast furnace gas boiler flue gas low temperature waste heat and heat transfer medium, and make above-mentioned waste heat utilization equipment combine organically, through the rational arrangement of equipment, the hierarchical utilization of flue gas waste heat and the complementation of equipment performance, furthest reduces blast furnace gas boiler's exhaust gas temperature, improves the thermal efficiency of boiler by a wide margin.
Description
Technical Field
The utility model relates to the technical field of energy conservation and emission reduction, in particular to a low-temperature heat exchange island of a blast furnace gas boiler.
Background
The blast furnace gas is a byproduct generated in the iron making process, and mainly comprises CO, CO2, N2, H2, CH4 and the like. Blast furnace gas contains more non-combustible components, less combustible components and lower calorific value, and the components and the calorific value of the blast furnace gas are related to fuel used by a blast furnace, a smelting process and the like. Modern advanced iron-making processes reduce energy consumption, but the calorific value of the produced blast furnace gas is lower. The CO2 and N2 in the blast furnace gas do not participate in combustion to generate heat and can not support combustion, and on the contrary, the CO2 and N2 also absorb a large amount of heat generated in the combustion process, so that the theoretical combustion temperature of the blast furnace gas is lower and the combustion stability is poor. Meanwhile, after the blast furnace gas is combusted, a large amount of heat is carried by the high-content non-combustible gas to be discharged from the furnace, so that the thermal efficiency of the furnace using the blast furnace gas as fuel is low.
For a blast furnace gas boiler, a large amount of CO2 and N2 exist in blast furnace gas, the blast furnace gas does not participate in chemical reaction basically in the combustion process, the gas is almost transferred to flue gas generated by combustion in equal quantity, the flue gas generated by the combustion of the blast furnace gas is far more than that of a coal-fired boiler and other fuel boilers, and the heat loss of the flue gas discharged by the blast furnace gas boiler is larger than that of other boilers, so that the temperature of the flue gas discharged is reduced to the maximum extent, and the method has a particularly important significance for improving the heat efficiency of the blast furnace gas boiler and greatly improving the economic benefit of gas power generation.
The conventional method for utilizing the waste heat of the flue gas of the existing blast furnace gas boiler is to arrange a blast furnace gas heater at the tail of the flue gas of the boiler so as to reduce the exhaust gas temperature, improve the charging temperature of the blast furnace gas, improve the combustion stability of the gas, improve the combustion temperature of a hearth and strengthen the heat exchange between the flue gas in the boiler and a water-cooled wall.
After the blast furnace gas heater is arranged, the thermal efficiency of the boiler is greatly improved, and after the gas heater is arranged, the exhaust gas temperature is 140 ℃ below zero, but the waste heat utilization is still insufficient, and the thermal efficiency of the boiler is still low.
In addition, in the using process of the boiler, the generated waste heat is not effectively and comprehensively recycled, so a solution for improving the thermal efficiency of the blast furnace gas boiler and the economic benefit of the gas generator set is urgently needed.
SUMMERY OF THE UTILITY MODEL
The utility model aims to provide a low-temperature heat exchange island of a blast furnace gas boiler, aiming at the technical problem that the waste heat of the blast furnace gas is difficult to be comprehensively utilized in the prior art, and the technical problem is solved by overall management of the waste heat of the low-temperature flue gas of the blast furnace gas boiler and a heat exchange medium.
In order to achieve the purpose, the technical scheme provided by the utility model is as follows:
the utility model relates to a low-temperature heat exchange island of a blast furnace gas boiler, which comprises a gas heater, a low-temperature air preheater and a low-temperature economizer; the flue gas flowing through the heat exchange island can exchange heat; the gas used for the gas burner in the boiler can exchange heat with the flue gas through the gas heater to heat up, and the combustion air used for the gas burner in the boiler can exchange heat with the flue gas through the low-temperature air preheater to heat up.
According to the scheme, the waste heat of the low-temperature flue gas of the blast furnace gas boiler is comprehensively managed with the heat exchange medium, the boiler flue gas waste heat recovery equipment is organically combined, and the low-temperature flue gas waste heat recovery complete heat exchange island system independent of the boiler is established through reasonable arrangement and waste heat grading deep utilization of the blast furnace gas heater, the low-temperature combustion-supporting air preheater and the low-temperature economizer, so that the exhaust smoke temperature of the blast furnace gas boiler is reduced to the maximum extent, and the thermal efficiency utilization of the boiler is improved.
The flue gas is subjected to heat exchange and cooling through a gas heater, then is subjected to heat exchange and cooling through a low-temperature air preheater, and finally is subjected to heat exchange and cooling through a low-temperature economizer. The flue gas through multistage heat transfer cooling is discharged through the exhanst gas outlet, and the boiler flue gas is after the heat transfer cooling of low temperature heat transfer island classification this moment, and exhaust gas temperature drops by a wide margin, and boiler thermal efficiency obtains greatly promoting. The combustion-supporting air for the gas burner in the boiler can exchange heat with the flue gas through the low-temperature air preheater to heat up, and the gas for the gas burner in the boiler can exchange heat with the flue gas through the gas heater to heat up, so that the combustion temperature of the combustion-supporting air and the blast furnace gas is increased.
Furthermore, the gas heater, the low-temperature air preheater and the low-temperature economizer are arranged in series in the heat exchange island, and the flue gas flowing through the heat exchange island can sequentially pass through the gas heater, the low-temperature air preheater and the low-temperature economizer for heat exchange;
or the gas heater and the low-temperature air preheater are arranged in parallel in the heat exchange island, the flue gas flowing through the heat exchange island is divided into two flow directions, and the two flow directions flow into the low-temperature economizer for heat exchange after flowing through the gas heater and the low-temperature air preheater respectively.
Further, the device also comprises a high-temperature air preheater which is arranged outside or in the blast furnace gas boiler body; the flue gas flowing out of the economizer of the blast furnace gas boiler firstly exchanges heat through a high-temperature air preheater and then enters a gas heater; the combustion-supporting air is heated by the high-temperature air preheater or is heated by the low-temperature air preheater and the high-temperature air preheater in sequence and then is sent to the boiler gas burner. The utility model can be applied to the built blast furnace gas boiler, the high-temperature air preheater is integrated in the blast furnace gas boiler at the moment, and can also be applied to a newly-built blast furnace gas boiler, and the high-temperature air preheater can be arranged outside the shell of the blast furnace gas boiler at the moment, thereby being convenient for later maintenance.
The flue gas of boiler economizer export carries out the one-level heat transfer by the flue gas inlet through high temperature air heater after cooling down, gets into gas heater and carries out the second grade heat transfer cooling, carries out tertiary heat transfer cooling through low temperature air heater again, and at last, carries out the level four heat transfer cooling through low temperature economizer. The flue gas through multistage heat transfer cooling is discharged through the exhanst gas outlet, and the boiler flue gas is after the heat transfer cooling of low temperature heat transfer island classification this moment, and exhaust gas temperature drops by a wide margin, and boiler thermal efficiency obtains greatly promoting. The combustion-supporting air is heated by the low-temperature air preheater and the high-temperature air preheater and finally sent to the boiler gas burner, so that the combustion temperature of the combustion-supporting air and the blast furnace gas is increased.
The high-temperature air preheater is first-stage heat exchange equipment at a flue gas inlet of a low-temperature heat exchange island of a boiler, and adopts a tube type heat exchanger, and a heat exchange tube bundle mainly comprises a heat exchange tube and a tube plate. The flue gas passes through the heat exchange tube transversely to exchange heat with air in the tube.
Further, an air outlet of the low-temperature air preheater is communicated with an air inlet of the high-temperature air preheater through an air connecting pipeline, a combustion-supporting air bypass pipe is arranged in front of the air inlet of the low-temperature air preheater and the air connecting pipeline, and a combustion-supporting air bypass adjusting valve is arranged on the combustion-supporting air bypass pipe. The bypass adjusting valve is opened to reduce the amount of combustion-supporting air entering the low-temperature air preheater so as to properly increase the exhaust gas temperature of the boiler and reduce the degree of low-temperature dew point corrosion of equipment. Also can adopt the anticorrosion measure to the heat pipe which is at the temperature below the acid dew point of the flue gas.
The utility model relates to a gas heater, which is a second-stage heat exchange device for flue gas of a low-temperature heat exchange island of a boiler. In view of the characteristics of inflammability, explosiveness and toxicity of blast furnace gas, the gas heater adopts a heat pipe type heat exchanger, the safety and the reliability of the gas heater are determined by the characteristics of a heat pipe device structure, and the isolation and the respective sealing performance between the gas and flue gas fluid are ensured. According to the specific engineering situation, an integral heat pipe exchanger or a split heat pipe exchanger can be adopted.
The low-temperature air preheater is a third-stage heat exchange device which is a low-temperature working condition heat exchanger, and in order to ensure safe and long-term use of the device, a heat pipe heat exchanger is adopted, and an integral heat pipe heat exchanger or a split heat pipe heat exchanger can be adopted according to specific engineering conditions.
Furthermore, integral heat pipe exchanger includes a plurality of heat pipes, the heat pipe includes the heat pipe parent tube, the heat pipe parent tube is separated into flue gas side and heating gas side by the baffle, and the flue gas side is located flue gas flow path, and the heating gas side is located the gas flow path that needs the heating, be provided with working medium in the heat pipe parent tube.
The heat pipe is a gravity heat pipe and comprises a heat pipe base pipe, and fins can be arranged on the heat pipe base pipe to enhance the heat transfer effect; the heat pipe base pipe is a closed cavity, a certain negative pressure is firstly pumped in the closed pipe, and working medium is filled in the closed pipe. The heat quantity at the side of the flue gas is rapidly transferred to the side of the heating gas through the base pipe of the heat pipe, so that the heat transfer of the gas to be heated is completed, and the flue gas and the gas to be heated are separated from each other and do not leak. When the integral heat pipe heat exchanger is used as a gas heater, gas to be heated is gas, and when the integral heat pipe heat exchanger is used as a low-temperature air preheater, the gas to be heated is combustion air.
Furthermore, split type heat pipe exchanger includes flue gas heat exchanger tube bank and heating gas heat exchanger tube bank, flue gas heat exchanger tube bank and heating gas heat exchanger tube bank link to each other through tedge and downtake and form circulation circuit, flue gas heat exchanger tube bank sets up in flue gas flow path, heating gas heat exchanger tube bank sets up in the gas flow path that needs the heating. The number of the flue gas heat exchange tube bundles and the heating gas heat exchange tube bundles can be one row or multiple rows, and each row of tube bundles are respectively connected through an ascending tube and a descending tube to form a circulation loop which is independent of each corresponding tube bundle. When the split type heat pipe heat exchanger is used as a gas heater, gas to be heated is gas, and when the split type heat pipe heat exchanger is used as a low-temperature air preheater, the gas to be heated is combustion air. Fins can be arranged outside the heat exchange tubes of the heat exchange tube bundle, so that heat transfer is enhanced, and the heat exchange effect is improved. The flue gas heat exchange tube bundle and the heating gas heat exchange tube bundle are separately arranged according to the field condition, so that the separation effect of flue gas and heating gas is ensured, the blowby between the flue gas heat exchange tube bundle and the heating gas is avoided, the heat can be transferred remotely, and great flexibility is brought to the planning and arrangement of the device.
Furthermore, flue gas heat exchanger tube bank and heating gas heat exchanger tube bank all include header, a plurality of heat exchange tube and lower header, and the header of flue gas heat exchanger tube bank communicates with the header of heating gas heat exchanger tube bank through the tedge, and the lower header of flue gas heat exchanger tube bank communicates with the lower header of heating gas heat exchanger tube bank through the downcomer.
The low-temperature economizer is fourth-stage heat exchange equipment for the low-temperature island flue gas of the boiler. The tube bundle heat exchange element adopts a radial eccentric heat pipe, the radial eccentric heat pipe comprises an inner pipe and an outer pipe, a gap is arranged between the inner pipe and the outer pipe, the gap is a vacuum cavity, and working media are filled in the gap. Cold flow liquid enters from one end of the inner pipe of the radial eccentric heat pipe and flows out from the other end of the inner pipe of the radial eccentric heat pipe, the outer pipe is arranged in the smoke flowing channel, and smoke transversely sweeps across the outer pipe. The outer tube can be provided with fins to enhance the heat exchange effect.
And a condensed water flow regulating valve is arranged at an inlet of cold flow liquid of the low-temperature economizer, and the exhaust gas temperature of the boiler is controlled by regulating the flow of the cold flow liquid entering the low-temperature economizer, so that the degree of low-temperature dew point corrosion of equipment is reduced. In order to reduce corrosion, a corrosion prevention measure can be adopted for the heat pipe at the temperature below the acid dew point of the flue gas.
Furthermore, cold flow liquid entering the inner pipe of the low-temperature economizer for heat exchange can be determined according to specific conditions on site, steam turbine condensed water can be adopted for a gas boiler generator set, and the condensed water enters the blast furnace gas boiler deaerator after being heated, so that the steam extraction quantity of a steam turbine is reduced, and the output of the generator set is improved.
The utility model has the following beneficial effects:
the utility model provides a low-temperature heat exchange island of a blast furnace gas boiler, which carries out overall management on waste heat of low-temperature flue gas of the blast furnace gas boiler and a heat exchange medium, organically combines a high-temperature combustion-supporting air preheater, a low-temperature combustion-supporting air preheater, a blast furnace gas heater and a low-temperature economizer, establishes a low-temperature flue gas waste heat recovery complete system independent of the blast furnace through reasonable arrangement of equipment, graded utilization of flue gas waste heat and complementation of equipment performance, adopts flexible and changeable adjusting means, reduces the exhaust smoke temperature (90-95 ℃) of the blast furnace gas boiler to the maximum extent, and greatly improves the thermal efficiency of the boiler and the economic benefit of a gas generator set. Meanwhile, the structural style and the material (including anti-corrosion measures) of the heat exchange equipment in the low-temperature heat exchange island of the boiler are selected in a targeted manner according to the specific characteristics of cold and hot media and different areas of the flue gas temperature, so that the safe long-period operation of the waste heat utilization equipment is ensured.
After the waste heat of the flue gas of the blast furnace gas boiler is subjected to graded heat exchange and cooling by the high-temperature air preheater, the gas heater, the low-temperature air preheater and the low-temperature economizer in the low-temperature heat exchange island of the blast furnace gas boiler, the exhaust gas temperature of the boiler is greatly reduced, and the thermal efficiency of the boiler is greatly improved. In addition, the low-temperature heat exchange island of the blast furnace gas boiler provided by the utility model is independent from the outside of the boiler body, so that the equipment is convenient and quick to replace and maintain, and the cost is reduced. The utility model carries out overall management on the waste heat of the low-temperature flue gas of the blast furnace gas boiler and a heat exchange medium, integrates the waste heat and the heat exchange medium into a unified low-temperature heat exchange island for comprehensively utilizing heat, organically combines waste heat recovery equipment (such as an air preheater, a gas heater, a condensed water or external water heater and the like) of the boiler, and furthest reduces the exhaust gas temperature of the blast furnace gas boiler and improves the heat efficiency of the blast furnace gas boiler by deeply utilizing the waste heat of the flue gas of the boiler in a grading way.
The method is characterized in that:
(1) the low-temperature air preheater, the gas preheater and the low-temperature economizer all adopt heat pipe heat exchange elements, so that the high-efficiency heat exchange of flue gas-air, flue gas-gas and flue gas-cold flow liquid (such as condensed water of a power generation turbine) is realized, the separation sealing effect between cold and hot fluids is ensured, and the reliability and the safe use of equipment are ensured.
(2) The heat pipe base pipe of the heat pipe exchanger is provided with the fins to enhance the heat exchange effect, and the heat exchange area of the fins can be adjusted to control the heat flux density of heat exchange of the heat pipe, improve the wall surface temperature of the heat pipe and reduce the low-temperature corrosion degree of the heat pipe.
(3) The heat of the low-temperature flue gas is further absorbed and utilized by utilizing the higher heat exchange coefficient of the flue gas-condensed water and the proper temperature difference, so that the deep recovery of the waste heat of the flue gas is realized, and the temperature of the discharged flue gas is reduced to the lowest.
(4) By arranging the low-temperature economizer, the condensed water of the steam turbine is heated, and the waste heat in the flue gas is continuously recovered; meanwhile, condensed water enters the boiler deaerator after being heated, so that the steam extraction amount of the steam turbine is reduced, and the output of the generator set is improved.
(5) Because the heat pipe heat exchanger equipment consists of a plurality of heat pipe elements, the effect of the equipment is limited due to the failure of a few heat pipes, and the integral failure of the equipment cannot be caused.
(6) For low-temperature air preheaters and gas preheaters, if a split type heat pipe exchanger is adopted, the flue gas heat exchange tube bundle and the gas (air) heat exchange tube bundle are independent of each other, and fluid separation and sealing are easier to realize. When the heat exchanger operation thermal efficiency is reduced, online exhaust (non-condensable gas exhaust) can be performed according to the situation so as to repair the performance of the heat exchanger.
(7) Even if the heat pipes of the low-temperature air preheater and the gas preheater are accumulated with dust, corroded and invalid due to a small amount of heat pipes, the performance of the low-temperature air preheater and the performance of the gas preheater are reduced to some extent, the temperature of a smoke outlet is increased, the smoke exhaust temperature can be reduced through adjusting (increasing) the water amount of condensed water, and the boiler efficiency is ensured.
(8) For low load of the boiler and low temperature of the flue gas at the tail of the boiler, the flow of the condensed water of the low-temperature economizer can be adjusted besides the adjustment of the air bypass valve of the low-temperature air preheater, so that the dew point corrosion range of equipment is prevented from being expanded, the equipment is protected to be safe, and the adjusting means is flexible and reliable.
Drawings
Fig. 1 is a schematic view (elevation view) of a low-temperature heat exchange island of a blast furnace gas boiler provided by the utility model.
FIG. 2 is a top view of the low temperature heat exchange island of the blast furnace gas boiler provided by the present invention (only the low temperature side of the air/gas heat exchange equipment is seen).
FIG. 3 is a schematic view of a high temperature air preheater tube bundle of the present invention.
FIG. 4 is a schematic view of a heat pipe of the integral heat pipe exchanger of the present invention.
FIG. 5 is a schematic view of a radial eccentric heat pipe according to the present invention.
Fig. 6 is a cross-sectional view of fig. 5.
FIG. 7 is a schematic view of a split heat pipe exchanger according to the present invention.
Fig. 8 is a schematic view of a split heat pipe exchanger bundle of the present invention.
Fig. 9 is a schematic diagram of the parallel arrangement of the gas heater and the low temperature air preheater of the present invention in the heat exchange island.
Reference numerals in the drawings: 1. a flue gas inlet; 2. a high temperature air preheater; 3. a flue gas transition section I; 4. a gas heater; 5. a flue gas transition section II; 6. a low temperature air preheater; 7. a flue gas transition section III; 8. a low-temperature economizer; 9. a flue gas outlet; 10. a condensate flow rate regulating valve; 11. a dust remover;
12. an air bypass regulating valve; 13. an air connection duct;
14. a heat exchange pipe; 15. a tube sheet; 16. a heat pipe; 17. a partition plate; 18. a heat pipe base pipe; 19. gas (air) side fins; 20. a flue gas side fin; 21. a radial eccentric heat pipe; 22. an outer tube; 23. an inner tube (condensate tube); 24. a fin; 25. Working medium; 26. a condensed water inlet header; 27. a condensed water outlet header; 28. working medium; 29. a gas (air) side housing; 30. a gas (air) heat exchange tube bundle; 31. a down pipe; 32. working medium; 33. a flue gas heat exchange tube bundle; 34. a flue gas side shell; 35. a riser pipe; 36. 39, an upper header; 37. 40, heat exchange tubes; 38. and 41, a lower header.
Detailed Description
For a further understanding of the utility model, reference should be made to the following detailed description taken in conjunction with the accompanying drawings and examples.
The structure, proportion, size and the like shown in the drawings are only used for matching with the content disclosed in the specification, so that the person skilled in the art can understand and read the description, and the description is not used for limiting the limit condition of the implementation of the utility model, so the method has no technical essence, and any structural modification, proportion relation change or size adjustment still falls within the scope of the technical content disclosed by the utility model without affecting the effect and the achievable purpose of the utility model. Meanwhile, the terms such as "upper", "lower", "left", "right" and "middle" used in the present specification are for clarity of description only, and are not used to limit the implementable scope, and the relative relationship changes or adjustments may be considered to be within the implementable scope of the present invention without substantial technical changes; in addition, the embodiments of the present invention are not independent of each other, but may be combined.
Example 1
As shown in fig. 1 and 2, the low-temperature heat exchange island of the blast furnace gas boiler provided by the utility model can be regarded as a heat exchange device, and the heat exchange island is arranged behind an economizer of the blast furnace gas boiler on a low-temperature flue outside a boiler body. The heat exchange island can comprehensively manage the waste heat of the low-temperature flue gas of the blast furnace gas boiler and a heat exchange medium, organically combines the high/low-temperature air preheater, the blast furnace gas heater and the low-temperature economizer, and forms the low-temperature heat exchange island independent of the boiler through reasonable arrangement of the devices and graded deep utilization of the waste heat of the flue gas, thereby reducing the smoke exhaust temperature of the blast furnace gas boiler to the maximum extent, and greatly improving the heat efficiency of the boiler and the economic benefit of a gas generator set. Meanwhile, the structural style and the material (including anti-corrosion measures) of the heat exchange equipment in the low-temperature heat exchange island of the boiler are selected in a targeted manner according to the specific characteristics of cold and hot media and different areas of the flue gas temperature, so that the safe long-period operation of the waste heat utilization equipment is ensured, the equipment in the low-temperature heat exchange island is convenient and quick to replace and maintain, and the cost is reduced.
Specifically, as shown in fig. 1, the low-temperature heat exchange island of the blast furnace gas boiler provided by the present invention includes a flue gas inlet 1, a high-temperature air preheater 2, a flue gas transition section (a) 3, a gas heater 4, a flue gas transition section (a) 5, a low-temperature air preheater 6, a flue gas transition section (a) 7, a low-temperature economizer 8, a flue gas outlet interface 9, and soot blowers 11 disposed on the flue gas side of each heat exchange device and the blast furnace gas side, wherein the flue gas inlet 1, the high-temperature air preheater 2, the flue gas transition section (a) 3, the gas heater 4, the flue gas transition section (a) 5, the low-temperature air preheater 6, the flue gas transition section (a) 7, the low-temperature economizer 8, and the flue gas outlet interface 9 are sequentially disposed along the flow direction of flue gas in a flue.
The flue gas at the outlet of the boiler economizer is subjected to primary heat exchange and cooling through a flue gas inlet 1 and a high-temperature air preheater 2; the flue gas enters a gas heater 4 through a flue gas transition section (I) 3 to carry out secondary heat exchange and temperature reduction; then enters a low-temperature air preheater 6 through a flue gas transition section (II) 5 to carry out three-stage heat exchange and temperature reduction; and finally, the flue gas enters the last heat exchange equipment, namely a low-temperature economizer 9 through a flue gas transition section (III) 7 to carry out four-stage heat exchange and cooling, and finally, the flue gas subjected to the multi-stage heat exchange and cooling is discharged through a flue gas outlet 9, and the flue gas temperature of the boiler is greatly reduced to 90-95 ℃ after the boiler flue gas is subjected to heat exchange and cooling through a low-temperature heat exchange island.
In this embodiment, the combustion air is heated by the low-temperature air preheater 6 and further heated by the high-temperature air preheater 2 through the air connecting pipe 13 in a serial connection manner, and then the combustion air is sent to the boiler gas burner. It is also possible to feed only the combustion air heated in the high temperature air preheater 2 to the boiler gas burner.
Referring to fig. 3, the high-temperature air preheater 2 is a tubular heat exchanger, and includes a heat exchange tube 14 and a tube plate 15, wherein flue gas passes through the outside of the tube, flue gas passes through the inside of the air pass tube, and flue gas passes through the heat exchange tube transversely to exchange heat with air in the tube. Because of the flue gas temperature (the flue gas outlet is generally more than 200 ℃ after the equipment) and the air (preheated by the low-temperature air preheater) conditions of the high-temperature air preheater 2, the tubular heat exchanger made of common carbon steel can be adopted, and the heat exchanger does not generate low-temperature dew point corrosion.
After the flue gas is subjected to primary heat exchange and cooling with air through the high-temperature air preheater 2, the flue gas enters the coal gas heater 4 through the flue gas transition section (I) 3 to be subjected to secondary heat exchange and cooling. In view of the characteristics of inflammability, explosiveness and toxicity of blast furnace gas, the gas heater can adopt an integral heat pipe type heat exchanger which is beneficial to improving the safety and ensures the isolation between the gas and flue gas fluid and the respective tightness.
Referring to fig. 4, the gas heater 4 adopts an integral heat pipe heat exchanger, which comprises a plurality of heat pipes 16 arranged inside, the heat pipes comprise heat exchange base pipes 18, the heat exchange base pipes 18 are divided into a flue gas side and a gas side by partition plates 17, the upper sections of the heat pipe base pipes 18 are positioned in the gas passage, the lower sections of the heat pipe base pipes are positioned in the flue gas passage, and the partition plates play a role in sealing and separating, so that the flue gas and the gas can be ensured not to be mixed.
Preferably, an air side fin 19 may be disposed outside the heat pipe base pipe 18 in the gas passage, and a flue gas side fin 20 may be disposed outside the heat pipe base pipe 18 in the flue gas passage, so as to improve the heat exchange effect of the heat pipe 16. By adjusting the heat transfer area ratio of the heat pipe fins (the gas side fins 19 and/or the flue gas side fins 20), the wall temperature of the heat pipe 16 is increased, and the dew point corrosion degree of the pipe wall of the heat pipe 16 is reduced.
During operation, flue gas passes through the lower part of the heat pipe 16 in a transverse direction, the working medium 28 flowing in the heat pipe 16 absorbs heat and is vaporized into steam, the steam rises to the upper end of the heat pipe 16 under a slight pressure difference, and the steam is discharged to the coal gas side and is condensed into liquid. The condensate returns to the heated section along the inner wall of the heat pipe 16 under the action of gravity, is heated and vaporized again, and is circulated in such a way, so that heat is continuously transferred from the flue gas side to the coal gas side.
By the arrangement of the heat pipe 16, the heat exchange of the flue gas and the coal gas is carried out outside the pipe, and the heat transfer can be enhanced conveniently.
The low-temperature air preheater 6 of the present embodiment is arranged after the gas heater 4. The flue gas is cooled through the secondary heat exchange with the blast furnace gas by the gas heater 4, and then enters the low-temperature air preheater 6 for the tertiary heat exchange and cooling. Because the low-temperature air preheater 6 is positioned on the low-temperature side of the flue gas, in order to ensure the safe and long-acting effect of the equipment, the low-temperature air preheater 6 can adopt an integral heat pipe exchanger, and the integral heat pipe exchanger is favorable for ensuring the safety of the equipment and the isolation and the respective tightness between the air and the flue gas.
The structural characteristics of the low-temperature air preheater 6 equipment body are the same as the structure of the coal gas heater 4 body, and the structure can refer to the structure of the coal gas heater.
In order to avoid dew point corrosion, the heat pipe of the low-temperature air preheater 6 at the temperature below the dew point of the flue gas acid adopts an anti-corrosion measure, and an anti-corrosion layer can be arranged.
Referring to fig. 2, the combustion air outlet of the low temperature air preheater is communicated with the combustion air inlet of the high temperature air preheater through an air connecting pipeline 13, the combustion air enters from the combustion air inlet of the low temperature air preheater, and the air is heated by the low temperature air preheater 6 and then conveyed to the high temperature air preheater 2 through the air connecting pipeline 13 for further heating. In the embodiment, a combustion-supporting air bypass pipe is further arranged between a combustion-supporting air inlet of the low-temperature air preheater and the air connecting pipeline 13, and a combustion-supporting air bypass adjusting valve 12 is arranged on the combustion-supporting air bypass pipe, so that when the boiler is in low load and the exhaust gas temperature is too low, the bypass adjusting valve 12 is opened and adjusted, the flow of the combustion-supporting air entering the low-temperature air preheater is reduced, the combustion-supporting air can directly enter the high-temperature air preheater from the combustion-supporting air bypass pipe, the exhaust gas temperature of the boiler is properly increased, and the degree of low-temperature dew point corrosion of equipment is reduced.
The low-temperature economizer 8 of this embodiment arranges at boiler low temperature heat transfer island end for heat the steam turbine condensate water, carries out the level four heat transfer cooling to the flue gas, further reduces boiler exhaust gas temperature.
As shown in FIG. 5, the low-temperature economizer 8 is formed by combining a plurality of radial eccentric heat pipes 21, and a single radial eccentric heat pipe 21 comprises an inner pipe 23 and an outer pipe 22, wherein a vacuum cavity is formed between the inner pipe 23 and the outer pipe 22, and is filled with a working medium 25. The heat transfer of the flue gas side is enhanced by the heat receiving section of the radial eccentric heat pipe 21 by using the fins 24. The device has compact structure and small smoke flow resistance. Similarly, the structural parameters of the fins 24 on the radial eccentric heat pipes 21 are adjusted according to the characteristics of the flue gas, so that the density of the heat flow transmitted by the radial eccentric heat pipes 21 can be adjusted, and the degree of dew point corrosion of the pipe walls of the radial eccentric heat pipes 21 is effectively reduced. In order to improve the anticorrosion effect, the outer tube 22 and the fins 24 of the radial eccentric heat pipe 21 contacting with the flue gas adopt anticorrosion measures, and an anticorrosion layer can be arranged.
As shown in fig. 5 and 6, the radial eccentric heat pipe 21 is arranged in the flue gas channel, the flue gas transversely sweeps the outer pipe 22 and the fins 24 to heat the working medium 25 in the outer pipe 22, and heat is rapidly transferred to the inner pipe 23 through the working medium 25 to heat the condensed water. The inner pipe (condensed water pipe) 23 is not contacted with the smoke, and each radial eccentric heat pipe 21 has no welding line in the heat exchanger box body, thereby avoiding the leakage of condensed water. The heat of the flue gas indirectly heats the condensed water through the radial eccentric heat pipe, the flue gas and the condensed water are completely separated, the possibility that the condensed water of the low-temperature economizer leaks into a flue is avoided, and the series flow of cold fluid and hot fluid is effectively avoided.
The low-temperature economizer 8 is provided with a condensed water inlet header 26 and a condensed water outlet header 27, and condensed water enters and exits the radial eccentric heat pipe through the headers. The inlet of the condensate inlet header 26 may be provided with a condensate flow control valve 10 to control the flow of cold flow liquid entering the inlet header, thereby avoiding excessive flow and lowering the exhaust gas temperature. The condensed water enters the low-temperature economizer 8 from the condensed water inlet header 26, flows out from the condensed water outlet header 27 after being heated, and enters the boiler deaerator. The condensed water is heated and then sent into the deaerator, thereby reducing the steam extraction amount of the steam turbine and improving the output of the generator set. The condensate may also be replaced with low temperature feedwater or other fluids that are low in temperature.
Example 2
In this embodiment, basically the same as embodiment 1, different from the embodiment 1 in which the gas heater 4 and the low-temperature air preheater 6 are sequentially connected in series, as another embodiment, as shown in fig. 9, the gas heater 4 and the low-temperature air preheater 6 are arranged in parallel in the heat exchange island, the flue gas flowing through the heat exchange island is divided into two flow directions, that is, the flue gas flowing through the high-temperature air preheater 2 is divided into two flow directions, and the two flow directions of flue gas flow through the gas heater and the low-temperature air preheater respectively and then flow into the low-temperature economizer for heat exchange.
Example 3
The main difference between the embodiment and the embodiment 1 is that a split type heat pipe heat exchanger can be adopted as the gas heater 4 and the low-temperature air preheater 6 according to requirements. Other device types and arrangements are not changed.
Only the gas heater 4 and the low-temperature air preheater 6 are explained in terms of a split heat pipe heat exchanger, and other devices in the heat exchange island are not described again.
Referring to fig. 7 and 8, when the gas preheater 4 is installed as a split heat pipe exchanger, it includes a flue gas side shell 34, a flue gas heat exchange tube bundle 33, a gas side shell 29, and a gas heat exchange tube bundle 30, where the flue gas heat exchange tube bundle 33 and the gas heat exchange tube bundle 30 are connected by a riser 35 and a downcomer 31 to form a circulation loop.
The number of the flue gas heat exchange tube bundles 33 and the number of the coal gas heat exchange tube bundles 30 can be arranged in multiple rows, and the flue gas heat exchange tube bundles and the coal gas heat exchange tube bundles are respectively connected through the ascending tubes 35 and the descending tubes 31 to form independent circulation loops of each tube bundle.
The flue gas heat exchange tube bundle 33 consists of an upper header 39, heat exchange tubes 40 and a lower header 41; the coal gas heat exchange tube bundle 30 consists of an upper header 36, heat exchange tubes 37 and a lower header 38. The upper header of the flue gas heat exchange tube bundle is communicated with the upper header of the coal gas heat exchange tube bundle through an ascending tube 35, and the lower header of the flue gas heat exchange tube bundle is communicated with the lower header of the coal gas heat exchange tube bundle through a descending tube 31.
Fins are arranged outside the heat exchange tube 40 and the heat exchange tube 37, so that heat transfer is enhanced, and the heat exchange effect is improved.
The flue gas heat exchange tube bundle 33 and the coal gas heat exchange tube bundle 30 can be separately arranged according to the field condition, so that the separation effect of the flue gas and the coal gas is ensured, and the leakage of the flue gas and the coal gas is absolutely avoided. And can transfer heat in a long distance, thereby bringing greater flexibility to the planning and the arrangement of the device.
When the flue gas passes through the flue gas heat exchange tube bundle 33, the heat of the flue gas heats the working medium 32 in the flue gas heat exchange tube bundle 33. Working medium 32 is heated and vaporized, and is transferred to gas heat exchange tube bundle 30 along steam rising pipe 35 by the action of density difference, and the gas is heated. The vaporized working medium 35 transfers the latent heat of condensation to the gas to become condensate, and returns to the flue gas heat exchange tube bundle 33 through the downcomer 31 under the action of potential difference to be continuously heated by the flue gas, so that the energy transfer between the gas heat exchange tube bundle 30 and the flue gas heat exchange tube bundle 33 is formed by repeated circulation. The energy exchange between the coal gas and the flue gas is completed under the combined action of the multiple rows of heat exchange tube bundles.
For the low-temperature air preheater 6, in order to ensure the safe and long-acting effect of the equipment, the low-temperature air preheater 6 can adopt a split type heat pipe heat exchanger according to the requirement, the safety and the reliability of the heat pipe equipment are determined by the characteristics of the structure of the heat pipe equipment, and the isolation and the respective sealing performance between air and flue gas are ensured.
The structural characteristics of the low-temperature air preheater 6 equipment body are the same as the structure of the coal gas heater 4 body. The heat pipe of the low-temperature air preheater 6 at the temperature below the acid dew point of the flue gas adopts anti-corrosion measures.
It should be noted that, in the blast furnace gas boiler low-temperature heat exchange islands described in embodiments 1 and 2, in the concrete engineering application process, a flexible and variable method can be adopted, and three to four of the waste heat utilization devices are selected according to the field conditions, and are reasonably arranged to form the boiler low-temperature heat exchange island, so as to minimize the exhaust gas temperature of the boiler and maximize the thermal efficiency of the boiler.
Specifically, for the blast furnace gas boiler constructed in either embodiment 1 or embodiment 2, the high temperature air preheater 2 is integrated in the boiler body, and at this time, the low temperature heat exchange island of the blast furnace gas boiler according to the present invention includes the devices of the gas heater 4, the low temperature air preheater 6 and the low temperature economizer 8. The combustion air is preheated by the low-temperature air preheater 6 and then sent into the high-temperature air preheater 2 in the boiler through the air connecting pipeline 13. After the boiler flue gas is subjected to graded waste heat utilization by the low-temperature heat exchange island of the boiler, the exhaust gas temperature can be greatly reduced, and the thermal efficiency of the boiler and the output of a generator set can be improved.
For a newly-built blast furnace gas boiler, the complete waste heat utilization equipment of the low-temperature heat exchange island of the boiler can be completely utilized, and after the flue gas of the boiler is subjected to graded waste heat utilization by the equipment in the heat exchange island, the temperature of the flue gas is reduced to the maximum extent, the heat efficiency of the boiler is improved, and the output of a generator set is improved.
It should be noted that the key point of the present invention is to utilize the waste heat of multiple heat exchange objects for the flue gas of a blast furnace gas boiler, and although the specific heat exchanger types of the high-temperature air preheater, the gas heater, the low-temperature air preheater and the low-temperature economizer are described in the above embodiments 1 to 3, as long as the recovery of the waste heat between the corresponding heat exchange objects and the flue gas can be realized, the high-temperature air preheater, the gas heater, the low-temperature air preheater and the low-temperature economizer can all adopt different forms of heat exchangers, and are not limited to the specific heat exchanger forms listed and selected in the embodiments.
Comparative example
In addition, a comparative experiment is carried out on the embodiment, and on the basis of the same technical scheme of the embodiment 1, if a low-temperature air preheater and a low-temperature economizer are not arranged and only a gas heater is arranged, the final exhaust gas temperature is 130-155 ℃.
On the basis of the same technical scheme of the embodiment 1, if a low-temperature economizer is not arranged, a high-temperature air preheater, a coal gas heater and a low-temperature air preheater are arranged, and the final exhaust gas temperature is 115 ℃ below zero;
the utility model has been described in detail hereinabove with reference to specific exemplary embodiments thereof. It will, however, be understood that various modifications and changes may be made without departing from the scope of the utility model as defined in the appended claims. The detailed description and drawings are to be regarded as illustrative rather than restrictive, and any such modifications and variations are intended to be included within the scope of the present invention as described herein. Furthermore, the background is intended to be illustrative of the state of the art as developed and the meaning of the present technology and is not intended to limit the scope of the utility model or the application and field of application of the utility model.
More specifically, although exemplary embodiments of the utility model have been described herein, the utility model is not limited to these embodiments, but includes any and all embodiments modified, omitted, combined, e.g., between various embodiments, adapted and/or substituted, as would be recognized by those skilled in the art from the foregoing detailed description. The limitations in the claims are to be interpreted broadly based the language employed in the claims and not limited to examples described in the foregoing detailed description or during the prosecution of the application, which examples are to be construed as non-exclusive. Any steps recited in any method or process claims may be executed in any order and are not limited to the order presented in the claims. The scope of the utility model should, therefore, be determined only by the appended claims and their legal equivalents, rather than by the descriptions and examples given above.
Claims (10)
1. A low-temperature heat exchange island of a blast furnace gas boiler is characterized by comprising a gas heater, a low-temperature air preheater and a low-temperature economizer; the flue gas flowing through the heat exchange island can exchange heat; combustion-supporting air for a gas burner in a boiler can exchange heat with flue gas to heat through a low-temperature air preheater, and gas for the gas burner in the boiler can exchange heat with the flue gas to heat.
2. The blast furnace gas boiler low temperature heat exchange island of claim 1,
the gas heater, the low-temperature air preheater and the low-temperature economizer are arranged in the heat exchange island in series, and the flue gas flowing through the heat exchange island can sequentially pass through the gas heater, the low-temperature air preheater and the low-temperature economizer for heat exchange;
or the gas heater and the low-temperature air preheater are arranged in parallel in the heat exchange island, the flue gas flowing through the heat exchange island is divided into two flow directions, and the two flow directions flow into the low-temperature economizer for heat exchange after flowing through the gas heater and the low-temperature air preheater respectively.
3. The blast furnace gas boiler low-temperature heat exchange island of claim 1, further comprising a high-temperature air preheater, the high-temperature air preheater being disposed behind the economizer of the blast furnace gas boiler, the high-temperature air preheater being disposed outside or inside the body of the blast furnace gas boiler; the flue gas flowing out of the economizer of the blast furnace gas boiler firstly exchanges heat through a high-temperature air preheater and then enters a gas heater; the combustion-supporting air is heated by the high-temperature air preheater or is heated by the low-temperature air preheater and the high-temperature air preheater in sequence and then is sent to the boiler gas burner.
4. The low-temperature heat exchange island of a blast furnace gas boiler according to claim 3, wherein the high-temperature air preheater is a tubular heat exchanger comprising heat exchange tubes and a tube plate.
5. The blast furnace gas boiler low-temperature heat exchange island of claim 3, wherein an air outlet of the low-temperature air preheater is communicated with an air inlet of the high-temperature air preheater through an air connecting pipe, a combustion air bypass pipe is arranged in front of the air inlet of the low-temperature air preheater and the air connecting pipe, and a combustion air bypass adjusting valve is arranged on the combustion air bypass pipe.
6. The blast furnace gas boiler low-temperature heat exchange island of claim 1, 2, 3, 4 or 5, wherein the gas heater and the low-temperature air preheater adopt an integral heat pipe exchanger or a split heat pipe exchanger.
7. The low-temperature heat exchange island of the blast furnace gas boiler according to claim 6, wherein the integral heat pipe exchanger comprises a plurality of heat pipes, each heat pipe comprises a heat pipe base pipe, the heat pipe base pipe is divided into a flue gas side and a heating gas side by a partition plate, the flue gas side is positioned in the flue gas flow passage, the heating gas side is positioned in the gas flow passage to be heated, and a working medium is arranged in the heat pipe base pipe;
or the split type heat pipe exchanger comprises a flue gas heat exchange tube bundle and a heating gas heat exchange tube bundle, the flue gas heat exchange tube bundle and the heating gas heat exchange tube bundle are connected through an ascending tube and a descending tube to form a circulation loop, the flue gas heat exchange tube bundle is arranged in a flue gas flow channel, and the heating gas heat exchange tube bundle is arranged in a gas flow channel needing to be heated.
8. The blast furnace gas boiler low temperature heat exchange island of claim 7, wherein the flue gas heat exchange tube bundle and the heating gas heat exchange tube bundle each comprise an upper header, a plurality of heat exchange tubes and a lower header, the upper header of the flue gas heat exchange tube bundle is communicated with the upper header of the heating gas heat exchange tube bundle through an ascending tube, and the lower header of the flue gas heat exchange tube bundle is communicated with the lower header of the heating gas heat exchange tube bundle through a descending tube.
9. The blast furnace gas boiler low-temperature heat exchange island according to claim 1, 2 or 3, wherein the low-temperature economizer comprises a radial eccentric heat pipe; the radial eccentric heat pipe comprises an inner pipe and an outer pipe, a gap is formed between the inner pipe and the outer pipe, and working media are filled in the gap.
10. The blast furnace gas boiler low-temperature heat exchange island of claim 9, wherein condensed water is introduced into the inner pipe of the low-temperature economizer, and the heated condensed water is input into a deaerator of the blast furnace gas boiler.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116447597A (en) * | 2023-04-27 | 2023-07-18 | 张家港宏昌钢板有限公司 | Split type boiler gas heater |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116447597A (en) * | 2023-04-27 | 2023-07-18 | 张家港宏昌钢板有限公司 | Split type boiler gas heater |
| CN116447597B (en) * | 2023-04-27 | 2023-11-03 | 张家港宏昌钢板有限公司 | Split type boiler gas heater |
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