A waste heat boiler with integrated bypass regulation function
By setting up a flue gas direct passage and damper plate inside the waste heat boiler, combined with the SCR denitrification module, the problems of bypass corrosion and denitrification compatibility of the waste heat boiler were solved, achieving long-term stable operation and low-cost maintenance of the unit.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SINOPEC GUANGZHOU ENG CO LTD
- Filing Date
- 2024-11-26
- Publication Date
- 2026-05-26
AI Technical Summary
Conventional waste heat boiler bypass facilities are prone to corrosion and are incompatible with SCR denitrification, which makes it impossible for the unit to operate stably for a long period of time.
Design a waste heat boiler with integrated bypass function. By setting a flue gas direct passage and damper plate inside the waste heat boiler, combined with an SCR denitrification module, the flue gas can be directly passed and mixed inside the boiler, eliminating the need for external bypass facilities.
The corrosion problem of the bypass facilities was solved, the compatibility between the waste heat boiler and SCR denitrification was achieved, the long-term stable operation of the unit was guaranteed, and the investment cost and equipment damage risk were reduced.
Smart Images
Figure CN122083301A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of waste heat recovery technology, specifically relating to waste heat recovery boilers for flue gas in the fields of petrochemicals, metallurgy, thermal power, and waste incineration. Background Technology
[0002] Conventional flue gas waste heat boilers are generally equipped with a bypass so that when the waste heat boiler needs maintenance, the flue gas can be discharged through the bypass, ensuring the normal operation of the unit without interruption or reduction in output.
[0003] Waste heat boiler bypasses are typically isolated using water seal tanks or shut off using large flue gas butterfly valves, resulting in high investment costs. Because there is no flow in the bypass during normal operation, the flue gas in the bypass pipeline gradually cools down until the temperature drops below the SO3 dew point, leading to severe dew point corrosion in the bypass flue gas pipeline, water seal tank, or large butterfly valve, causing damage and leaks in the pipeline equipment.
[0004] With increasingly stringent environmental protection requirements, regenerated flue gas must undergo denitrification and desulfurization treatment before it can be emitted. Currently, the mainstream flue gas denitrification process uses the SCR method, with the denitrification catalyst placed between the superheater and economizer sections within the waste heat boiler. Because the waste heat boiler bypass spans the entire boiler, flue gas passing through the bypass during boiler maintenance lacks the denitrification treatment step and fails to meet emission standards. Therefore, it cannot be discharged through the bypass, rendering the bypass redundant. However, without a bypass, the unit would need to operate simultaneously with the waste heat boiler, or at a reduced processing capacity, affecting the long-term stable operation of the unit.
[0005] Chinese patent CN108087851 A discloses a dual-channel waste heat boiler. It ensures long-term operation by setting up a backup economizer section in the economizer section prone to failure and shutdown, allowing for switching maintenance during malfunctions. This solution requires multiple ultra-large valves, which have high sealing requirements, are difficult to manufacture, and are very expensive. Furthermore, the dead zone of the backup system is prone to flue gas dew point corrosion due to low temperatures. Summary of the Invention
[0006] This invention provides a waste heat boiler with integrated bypass function to solve the problems of easy corrosion of conventional waste heat boiler bypass facilities and incompatibility with SCR denitrification.
[0007] To achieve the above objectives, the technical solution of the present invention is as follows:
[0008] A waste heat boiler with integrated bypass function includes a waste heat boiler body and an internal flue gas direct passage. The waste heat boiler comprises a furnace body, superheated section heat extraction pipes, a flue gas direct passage, dampers, a denitrification module, and economizing section heat extraction pipes. The superheated section heat extraction pipes, denitrification module, and economizing section heat extraction pipes are all located inside the furnace body. The superheated section heat extraction pipes and economizing section heat extraction pipes are sequentially arranged along the flue gas flow direction to recover waste heat from the flue gas. A denitrification module is installed between the superheated section heat extraction pipes and the economizing section heat extraction pipes. A flue gas direct passage is provided between the superheated section heat extraction pipes and the economizing section heat extraction pipes, and a damper is installed inside the flue gas direct passage to open or close it. The denitrification module is equipped with an SCR denitrification catalyst, and the denitrification catalyst bed covers the entire cross-section of the boiler passage.
[0009] The superheated section heat extraction pipe can be configured as a single-stage or multi-stage heat extraction pipe, preferably 1-3 stages. The denitrification module can also be located between the multi-stage superheated section heat extraction pipes.
[0010] The heat extraction pipe in the coal-saving section can be configured as a single-stage or multi-stage heat extraction pipe, preferably a 1-3 stage heat extraction pipe.
[0011] High-temperature flue gas passes through the furnace body and exchanges heat with the steam or boiler feedwater in the heat exchange tubes; the flue gas bypass and bypass water seal tank (or shut-off valve) outside the waste heat boiler are eliminated.
[0012] Preferably, the waste heat boiler has one or more direct flue gas passages inside to replace the external bypass. The number of the multiple direct flue gas passages is not limited, but preferably, one is provided at intervals of 0.5-1m.
[0013] Preferably, the flue gas straight passage passes through the middle of the heat exchange pipe;
[0014] Preferably, the flue gas direct passage is controlled by a damper plate to open and close the passage.
[0015] Preferably, the flue gas direct passage is set up in stages with the heat extraction pipes of the superheated section and the heat extraction pipes of the economizing section, and each stage is equipped with an independent damper switch;
[0016] Preferably, a flue gas mixer can be installed between the flue gas direct passage and the denitrification module to mix the bypass high-temperature flue gas and the low-temperature flue gas after heat extraction, so as to prevent local high-temperature flue gas from damaging the subsequent denitrification module.
[0017] Preferably, each stage of the heat extraction pipe can be equipped with multiple flue gas direct passages to make the distribution of bypass flue gas on the cross section more uniform, so as to facilitate the mixing of high and low temperature flue gas.
[0018] Preferably, the form of the internal flue gas straight passage is determined according to the arrangement of the heat extraction tubes of the waste heat boiler. For square furnaces, it is preferable to use a partition to separate the square passage, but round tubes or other shapes that are easy to achieve in industry can also be used.
[0019] Preferably, the damper plate can be installed at any position within the flue gas direct passage;
[0020] The present invention has the following beneficial effects:
[0021] (1) Since the flue gas direct passage is surrounded by hot flue gas, there will be no low temperature operating conditions when there is no flow, and there is no problem of flue gas dew point corrosion.
[0022] (2) The waste heat boiler has a bypass function compatible with SCR denitrification. When one of the waste heat boilers is cut off online for maintenance, the flue gas emissions can still meet the standards, ensuring the long-term stable operation of the unit.
[0023] (3) The baffle of the flue gas direct passage does not need to be strictly sealed or pressure resistant. Thin baffles and damper plates are sufficient. The manufacturing and material requirements are not high, and the investment is far lower than the configuration of an external bypass with a water seal tank (or shut-off valve).
[0024] (4) The heat transfer load of the waste heat boiler can be adjusted by bypassing the flue gas side, eliminating the problem of steam overheating and overheating caused by changes in steam production, and realizing flexible distribution of the load of each heat exchange section of the waste heat boiler.
[0025] (4) The process is simpler and requires less space. Attached Figure Description
[0026] Figure 1 This is a schematic diagram of the structure of a waste heat boiler with integrated bypass function according to the present invention;
[0027] Figure 2 A schematic diagram of the structure of a waste heat boiler with integrated bypass function according to the present invention, which is equipped with two-stage superheated pipes and two flue gas direct passages;
[0028] Explanation of reference numerals in the attached diagram: 1. Furnace body; 2. Superheated section heat extraction pipes; 3. Flue gas straight passage; 4. Damper plate; 5. Denitrification module; 6. Economizer section heat extraction pipes; 7. Flue gas mixer. Detailed Implementation
[0029] The following is in conjunction with the appendix Figure 1-2 The technical solution of the present invention will be further described below.
[0030] As attached Figure 1-2The present invention provides a waste heat boiler with integrated bypass function, equipped with an SCR denitrification module, comprising a furnace body 1, superheated section heat exchange pipes 2, flue gas straight passage 3, damper plate 4, denitrification module 5, and economizing section heat exchange pipes 6. The superheated section heat exchange pipes 2, denitrification module 5, and economizing section heat exchange pipes 6 are all located inside the furnace body 1. A flue gas straight passage 3 passes through the superheated section heat exchange pipes 2 and the economizing section heat exchange pipes 6, and a damper plate 4 is installed inside the flue gas straight passage 3 to open or close the flue gas straight passage 3.
[0031] Preferably, a flue gas mixer 7 can be installed between the flue gas direct passage 3 and the denitrification module 5 to mix the bypass high-temperature flue gas and the low-temperature flue gas after heat extraction, so as to prevent the local high-temperature flue gas from damaging the subsequent denitrification module.
[0032] Preferably, each stage of the heat extraction pipe can be equipped with multiple flue gas straight-through channels 3, so that the bypass flue gas distribution on the cross section is more uniform, which is conducive to the mixing of high and low temperature flue gas. (See attached...) Figure 2 The image shows a typical implementation example where each stage of the heat extraction pipe has two direct flue gas passages.
[0033] The following is a brief introduction to the operation mode and effects of the waste heat boiler provided by this invention.
[0034] The waste heat boilers are configured in parallel, with units A and B connected. During normal operation, damper 4 is closed, and high-temperature flue gas enters the waste heat boilers in parallel through the flue gas inlet. It flows through the heat extraction tubes 2 in the hot section to heat the steam, then passes through the SCR denitrification module to remove NOx. After further recovering waste heat, it flows through the economizer tubes 6 to recover more waste heat before exiting the waste heat boilers through the flue gas outlet. During normal operation, the flue gas in the direct flue gas passage 3 does not flow. However, because the passage 3 is surrounded by high-temperature flue gas, the temperature inside the passage will not be lower than the surrounding flue gas temperature, thus preventing flue gas dew point corrosion.
[0035] When one of the waste heat boilers, A, malfunctions and needs to be shut off for maintenance, the damper plate 4 of the other waste heat boiler, B, which is still operating normally, is opened. The flue gas that originally flowed through waste heat boiler A passes through the flue gas direct passage 3 of waste heat boiler B, through the superheated section heat extraction pipe 2 and the economizer section heat extraction pipe 6, preventing excessive heat extraction and overheating of the heat extraction pipes and excessive pressure drop in the waste heat boiler when waste heat boiler B is operating alone. This bypass flue gas is mixed with the cold flue gas after normal heat extraction through the flue gas mixer 7, and then treated together by the SCR denitrification module to remove NOx. After passing the treatment, it can be discharged normally, achieving normal operation of the unit without reducing its treatment capacity.
[0036] The above are merely typical embodiments of the present invention. It should be noted that those skilled in the art can make several improvements or substitutions without departing from the principles described in the present invention, and these improvements or substitutions should also be considered within the scope of protection of the present invention.
Claims
1. A waste heat boiler with integrated bypass function, comprising a waste heat boiler body and an internal flue gas direct passage, characterized in that: The waste heat boiler consists of a furnace body, superheated section heat extraction pipes, a flue gas straight passage, a damper plate, a denitrification module, and economizing section heat extraction pipes. The superheated section heat extraction pipes, denitrification module, and economizing section heat extraction pipes are all located inside the furnace body. The superheated section heat extraction pipes and economizing section heat extraction pipes are sequentially arranged along the flue gas flow direction to recover waste heat from the flue gas. A denitrification module is installed between the superheated section heat extraction pipes and the economizing section heat extraction pipes. A flue gas straight passage is provided between the superheated section heat extraction pipes and the economizing section heat extraction pipes.
2. The waste heat boiler according to claim 1, characterized in that: The denitrification module is equipped with an SCR denitrification catalyst, and the denitrification catalyst bed covers the entire cross-section of the boiler passage.
3. The waste heat boiler according to claim 1, characterized in that: The superheated section heat extraction pipe and the coal-saving section heat extraction pipe can be configured as a single-stage or multi-stage heat extraction pipe.
4. The waste heat boiler according to claim 3, characterized in that: The heat extraction pipes in the superheated section and the heat extraction pipes in the economizing section are of level 1-3.
5. The waste heat boiler according to claim 3, characterized in that: The denitrification module is located in the heat extraction pipe room of the multi-stage superheated section.
6. The waste heat boiler according to claim 1, characterized in that: The waste heat boiler is equipped with one or more direct flue gas passages to replace the external bypass. When multiple passages are provided, they are arranged at intervals of 0.5-1m.
7. The waste heat boiler according to claim 1, characterized in that: The flue gas direct passage is controlled by a damper plate to open and close the passage.
8. The waste heat boiler according to claim 1, characterized in that: The flue gas direct passage is set up in stages according to the heat extraction pipes of the superheated section and the heat extraction pipes of the economizing section, and each stage is equipped with an independent damper switch.
9. The waste heat boiler according to claim 1, characterized in that: A flue gas mixer is installed between the flue gas direct passage and the denitrification module.
10. The waste heat boiler according to claim 1, characterized in that: The form of the internal flue gas straight passage is determined according to the arrangement of the heat extraction pipes of the waste heat boiler. For square furnaces, a partition is used to separate the square passage.