Transformation method for changing calcium-process desulfurization system into ammonia-process desulfurization system

Abstract

The invention provides a transformation method for changing a calcium-process desulfurization system into an ammonia-process desulfurization system, which comprises the following steps: transforming a calcium-process desulfurization tower in the calcium-process desulfurization system into an ammonia-process desulfurization tower of the ammonia-process desulfurization system, so that the interior of the ammonia-process desulfurization tower sequentially comprises an oxidation section, a cooling section, an absorption section, a washing section and a demisting section from bottom to top, the absorption section is subjected to diameter expansion transformation, so that the gas velocity is reduced, the ammonia desulfurization absorption effect is improved, and the working condition requirement of an ammonia desulfurization system is met. According to the transformation method, an original calcium-process desulfurization system is fully utilized, the old utilization rate can be increased, the transformation old utilization rate can reach 80% or above, the cost is reduced, and the transformation effect is improved.

Description

Technical Field

[0001] This invention relates to the field of flue gas desulfurization technology, specifically to a method for modifying a calcium-based desulfurization system into an ammonia-based desulfurization system. Background Technology

[0002] Currently, most flue gas desulfurization devices in thermal power units adopt the limestone-gypsum wet method (also known as the calcium method), which uses limestone ultrafine powder to prepare a slurry as the desulfurization raw material, and the desulfurization product is desulfurized gypsum (CaSO4·2H2O). However, the limestone-gypsum wet method has the following problems: (1) Calcium desulfurization is a process of "removing one waste and producing three wastes", that is, while removing SO2, solid waste gypsum, desulfurization wastewater and greenhouse gas CO2 are generated; (2) The annual production of desulfurized gypsum by calcium desulfurization in China is about 90 million tons. Except for a small portion used in the construction industry, most of the desulfurized gypsum is stored or landfilled as solid waste without anti-seepage treatment, and a large amount of desulfurized gypsum is prone to secondary pollution during the storage process; (3) Calcium desulfurization depends on Limestone (CaCO3) is used as a desulfurizing agent. The reaction between limestone and SO2 produces CO2. For every ton of SO2 removed, 0.7 tons of CO2 are produced. This additional carbon emission is contrary to the national strategic goal of carbon peaking and carbon neutrality. (4) The large-scale mining of limestone has damaged the green mountains and clear waters. The shortage of limestone resources has further increased the cost of desulfurization. (5) A large amount of high-salt wastewater will be generated during the calcium desulfurization process. In order to achieve the requirement of "zero discharge" of wastewater, the cost of zero discharge treatment of wastewater is relatively high.

[0003] In contrast, ammonia desulfurization uses liquid ammonia or ammonia water as the desulfurizing agent to desulfurize flue gas. This route produces no wastewater, waste residue, or waste gas, does not increase carbon dioxide emissions, and the byproduct ammonium sulfate can be sold as fertilizer, supporting agricultural development. Moreover, the electricity consumption of ammonia technology is nearly 40% lower than that of the calcium method, turning overall operating costs from negative to positive.

[0004] Therefore, for flue gas desulfurization systems of thermal power units, in order to minimize the retrofit cost and maximize the environmental and economic benefits after the retrofit, it is necessary to develop a retrofit method to change the calcium desulfurization system to an ammonia desulfurization system. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention provides a method for converting a calcium-based desulfurization system to an ammonia-based desulfurization system. This method involves modifying the calcium-based desulfurization tower in the calcium-based desulfurization system into an ammonia-based desulfurization tower. The ammonia-based desulfurization tower comprises, from bottom to top, an oxidation section, a cooling section, an absorption section, a water washing section, and a demister section. The absorption section is enlarged to reduce gas velocity and improve the absorption effect of the ammonia-based desulfurization, thereby meeting the operating requirements of the ammonia-based desulfurization system. The modification method of the present invention makes full use of the original calcium-based desulfurization system, increasing the utilization rate (up to 80%), reducing costs, and improving the modification effect.

[0006] To achieve this objective, the present invention adopts the following technical solution: The purpose of this invention is to provide a method for converting a calcium-based desulfurization system into an ammonia-based desulfurization system. The method includes: converting the calcium-based desulfurization tower in the calcium-based desulfurization system into an ammonia-based desulfurization tower in the ammonia-based desulfurization system. The ammonia-based desulfurization tower includes, from bottom to top, an oxidation section, a cooling section, an absorption section, a water washing section, and a demisting section. The absorption section is enlarged to reduce the gas velocity and improve the absorption effect of the ammonia-based desulfurization.

[0007] It should be noted that in the modified ammonia desulfurization tower of this invention, the oxidation section and cooling section are completely isolated by a partition plate, while the cooling section, absorption section, and washing section are connected by separate gas-liquid separators, achieving the effect of flue gas being connected from bottom to top but the absorbent liquid not being interconnected; the ammonia source, oxygen source, and absorbent liquid collected by the gas-liquid separator at the bottom of the absorption section are independently introduced into the oxidation section, and the slurry in the oxidation section is returned to the absorption section as the ammonia absorption liquid; in addition, the original flue gas inlet is located in the cooling section. The cooling section has a discharge port at its bottom and a cooling absorbent inlet at its top. The discharge port is connected to the cooling absorbent inlet and the ammonium sulfate treatment module via a circulation pipeline and an ammonium sulfate collection pipeline, respectively. The original absorbent inlet is replaced with an ammonia absorbent inlet and / or a water washing circulation inlet, while the original process water inlet remains unchanged. Liquid circulation pipelines are added from the bottom of the water washing section to the top of the absorption section and from the bottom of the absorption section to the top of the cooling section to achieve overall water balance. In other words, the original calcium desulfurization slurry pool at the bottom of the calcium desulfurization tower is reused and converted into the oxidation section of the ammonia desulfurization tower, ensuring rapid, efficient, and complete oxidation of ammonium sulfite to ammonium sulfate. This effectively saves investment and operating costs, and also improves the reliability of the device. The original flue gas inlet, cooling section, demister section, and process water inlet of the calcium desulfurization tower are all reused and converted, achieving a 100% reuse rate for the original calcium desulfurization tower.

[0008] It should be noted that the empty tower gas velocity under ammonia desulfurization conditions is relatively low, generally not exceeding 3.5 m / s. Based on the actual characteristics of the project, a velocity of u = 2~3.5 m / s is preferred. The empty tower gas velocity under calcium desulfurization conditions is relatively high, generally not less than 3.8 m / s. This means that the diameter of the original calcium desulfurization tower cannot meet the requirements of ammonia desulfurization, and the original calcium desulfurization tower needs to be enlarged. However, the modification method described in this invention only requires enlarging the absorption section to meet the modification requirements. It can adapt to the empty tower gas velocity requirements under ammonia desulfurization conditions, extend the flue gas residence time, ensure sufficient contact and reaction between the gas and liquid phases, and control ammonia escape at the source.

[0009] This invention provides a method for converting a calcium-based desulfurization system to an ammonia-based desulfurization system. The method involves modifying the calcium desulfurization tower in the calcium-based system into an ammonia-based desulfurization tower. The ammonia-based desulfurization tower comprises, from bottom to top, an oxidation section, a cooling section, an absorption section, a water washing section, and a demister section. The absorption section is enlarged to reduce gas velocity and improve the absorption effect of the ammonia-based desulfurization, thereby meeting the operating requirements of the ammonia-based desulfurization system. This method fully utilizes the original calcium-based desulfurization system, increasing the reuse rate (up to 80%), reducing costs, and improving the conversion effect.

[0010] As a preferred embodiment of the present invention, the diameter of the absorption section of the ammonia desulfurization tower satisfies the formula... Where D is the tower diameter of the absorption section, in meters; Q is the flue gas volume under ammonia-based desulfurization conditions, in cubic meters per second. 3 / s; u is the empty tower gas velocity under ammonia desulfurization conditions, in m / s.

[0011] It should be noted that the flue gas volume Q under the ammonia desulfurization operation is often consistent with the flue gas volume under the calcium desulfurization operation before the modification, which can ensure the flue gas desulfurization capacity; the empty tower gas velocity under the ammonia desulfurization operation is generally no more than 3.5m / s, and u=2~3.5m / s is preferred according to the actual characteristics of the project.

[0012] As a preferred technical solution of the present invention, the diameter expansion modification includes: dividing the tower body of the calcium desulfurization tower above the original flue gas inlet and inserting a newly added diameter expansion absorption section as the absorption section of the ammonia desulfurization tower.

[0013] It should be noted that the modification method described in this invention adopts the method of inserting a newly added diameter-expanding absorption section, which can add an absorption section of an ammonia desulfurization tower to the original calcium desulfurization tower. This not only improves the desulfurization effect of the original calcium desulfurization technology, but also allows the absorption section of the ammonia desulfurization tower to be further subdivided into multiple sub-absorption sections according to actual needs, further improving the desulfurization effect. Moreover, by using the method of inserting a newly added diameter-expanding absorption section, the diameter-expanding absorption section can be prefabricated on the ground in advance, which can significantly reduce the modification period. Compared with the diameter-expanding modification of the entire original calcium desulfurization tower, the modification investment can be saved by about 15-20%.

[0014] As a preferred technical solution of the present invention, the tower body of the calcium desulfurization tower is divided at a distance of 2-6m above the top of the original flue gas inlet. The distance of 2-6m above the top of the original flue gas inlet is, for example, 2m, 2.5m, 3m, 3.5m, 4m, 4.5m, 5m, 5.5m or 6m, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0015] As a preferred technical solution of the present invention, the diameter-expanding absorption section includes an upper transition section, a middle section, and a lower transition section; the height of the middle section is 9-18m, for example, 9m, 9.5m, 10m, 10.5m, 11m, 11.5m, 12m, 12.5m, 13m, 13.5m, 14m, 14.5m, 15m, 15.5m, 16m, 16.5m, 17m, 17.5m, or 18m, etc.; the angle between the outer inclined surface of the upper transition section and the lower transition section and the vertical direction is 25-45 degrees, for example, 25 degrees, 27 degrees, 30 degrees, 31 degrees, 33 degrees, 35 degrees, 38 degrees, 40 degrees, or 45 degrees, etc., but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0016] It should be noted that the present invention does not impose too many restrictions on the height of the upper transition section and the lower transition section of the expansion absorption section. Those skilled in the art can make reasonable selections according to the actual tower connection process used. For example, the height of the upper transition section and the lower transition section can be set independently to 1-3m.

[0017] It should be noted that the height of the expansion absorption section described in this invention is related to the number of spray layers in the absorption section under the ammonia desulfurization condition. The number of spray layers required under the ammonia desulfurization condition is set according to the SO2 concentration of the original flue gas. The higher the number of spray layers in the absorption section, the higher the height of the expansion absorption section, which is unrelated to the diameter of the original calcium absorption tower.

[0018] As a preferred technical solution of the present invention, the modification method further includes: using a main pipe for diversion control of the absorption circulation pump in the calcium desulfurization system, so as to achieve one pump for multiple spray layers without replacing the small pump.

[0019] It should be noted that the modification method described in this invention involves the transformation of the circulation system. The original calcium-based absorption circulation pump has a large spray volume, and ammonia is much more reactive than calcium carbonate. By fully utilizing the original circulation pump motor and replacing the pump head, the spray volume and head requirements of the ammonia absorption process are met. Without changing the motor, the power supply and distribution system of the original calcium-based desulfurization system does not need adjustment, significantly reducing modification costs. Furthermore, to adapt to the original calcium-based high-flow circulation pump, the circulation pipeline route is changed from a branch pipe to a main pipe. A single circulation pump can meet the spray requirements of at least two absorption spray layers without replacing the circulation pump, saving 20% ​​of the modification investment. This invention's modification of the circulation system utilizes the original circulation pump, reducing modification costs, and also reduces the number of operating circulation pumps, lowering the system failure rate and ensuring long-term stable system operation.

[0020] As a preferred technical solution of the present invention, the modification method further includes: adopting a main pipe for the oxidation fans in the calcium desulfurization system, and adding at least one more oxidation fan according to the actual operating conditions. This is because the oxidation fans in the calcium desulfurization system suffer from insufficient airflow and pressure head. By adopting a main pipe and appropriately adding at least one more oxidation fan according to the operating requirements, the technical effect of fully utilizing and modifying the existing oxidation fans can be achieved. For example, the original centrifugal oxidation fan (flow rate 224 m³ / h) 3 / min (pressure increased to 87kPa), the old motor was reused, the compressor head was replaced, the pressure head was increased to 100kPa, and the flow rate was 202m³ / min. 3 / min, add a magnetic levitation oxidation fan, the new magnetic levitation oxidation fan has a pressure boost of 100kPa and a flow rate of 101m³ / min. 3 / min.

[0021] It should be noted that the flow rates of the oxidation fan and circulating pump in the original calcium-based desulfurization system are mismatched with those in the modified ammonia-based desulfurization system. The conventional approach, to adapt to the new process requirements, is to replace the original oxidation fan and replace the pump head of the circulating pump while retaining the motor. This eliminates the need for flow rate adjustments during operation, but replacing the oxidation fan and modifying the circulating pump increases costs. This invention uses a master pipe system, requiring only adjustment of pipeline valves during operation, which significantly reduces modification costs.

[0022] As a preferred technical solution of the present invention, the modification method further includes: modifying the gypsum treatment module in the calcium desulfurization system into the ammonium sulfate treatment module in the ammonia desulfurization system, reusing and modifying the original hydrocyclone, and adding a centrifuge, a dryer and a packaging machine in sequence at the outlet of the hydrocyclone.

[0023] It should be noted that the modification method described in this invention includes the modification of the by-product system. The original calcium gypsum treatment complex is modified by local strengthening and adjustment, and then reused and transformed into an ammonium sulfate production complex for ammonia desulfurization by-products. This can save about 20% of the modification investment. For example, the original vacuum dryer in the calcium desulfurization system can be replaced with an atmospheric pressure dryer suitable for drying ammonium sulfate.

[0024] It should be noted that the modification method described in this invention can transform the original demisting section of the desulfurization tower into a water-washing demisting section, utilizing the original desulfurization tower's shell, support beams, and demister, thereby significantly reducing modification investment and shortening the modification period. Furthermore, by adopting the modification method described in this invention, the existing electrical instrumentation system can be largely reused, and the electrical system adopts low-voltage zone control technology, reducing electrical system investment and improving system operation safety, stability, and operational flexibility. This approach can save approximately 10% of modification investment.

[0025] Compared with existing technical solutions, the present invention has at least the following beneficial effects: (1) This invention provides a method for converting a calcium-based desulfurization system into an ammonia-based desulfurization system. The method involves converting the calcium-based desulfurization tower in the calcium-based desulfurization system into an ammonia-based desulfurization tower, such that the ammonia-based desulfurization tower comprises, from bottom to top, an oxidation section, a cooling section, an absorption section, a water washing section, and a demisting section. The absorption section is enlarged to reduce gas velocity and improve the absorption effect of the ammonia-based desulfurization, thereby meeting the operating requirements of the ammonia-based desulfurization system. This method fully utilizes the original calcium-based desulfurization system, increasing the utilization rate (up to 70%), reducing costs, and improving the conversion effect.

[0026] (2) The modification method described in this invention can reduce the discharge of desulfurization wastewater, reduce limestone mining, and generate almost no carbon dioxide and solid waste gypsum. After the modification is completed, the discharge of desulfurization wastewater will be reduced by at least 0.25 tons / 10,000 kWh, the CO2 emission will be reduced by at least 0.7 tons / 1 ton of SO2, the solid waste gypsum emission will be reduced by at least 2.6 tons / 1 ton of SO2, and the limestone mining will be reduced by at least 1.8 tons / 1 ton of SO2. Moreover, after the modification is completed, the by-product of ammonia desulfurization is ammonium sulfate fertilizer, which can turn waste into treasure, realize the recycling of resources and create economic benefits.

[0027] (3) The modification method described in this invention can recover the modification investment by saving about 2-3 years of calcium desulfurization operation costs after modification, and is suitable for widespread use. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the transformation of the calcium-based desulfurization tower into an ammonia-based desulfurization tower in the transformation method described in Embodiment 1 of the present invention. Detailed Implementation

[0029] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0030] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows: Example 1 (Technical upgrade of 2x300MW ammonia desulfurization to ammonium sulfate production to calcium desulfurization project) This embodiment provides a method for converting a calcium-based desulfurization system to an ammonia-based desulfurization system, the method comprising: Tower renovation: Reference Figure 1 The original calcium desulfurization system had a calcium desulfurization tower with a diameter of 13.1m and a height of 39.5m. At a point 3.5m above the original flue gas inlet, corresponding to a height of 23m for the calcium desulfurization tower, the tower was divided. The lower section was converted into a cooling section for an ammonia desulfurization tower, with a gas-liquid separator installed near the division point. The upper section was converted into a water washing section for an ammonia desulfurization tower, with a gas-liquid separator installed near the sealing point. An expansion absorption section was prefabricated on the ground and modified... The absorption section of the ammonia desulfurization tower includes an upper transition section, a middle section, and a lower transition section. The middle section has a height of 13.3m. The angle between the outer inclined planes of the upper and lower transition sections and the vertical direction is 31 degrees, and their heights are both 2m. This is used to achieve a transition and connection with the original calcium desulfurization tower. Compared to the original calcium desulfurization tower's height of 39.5m, the height of the modified ammonia desulfurization tower is 56.8m. The flue gas volume Q under ammonia desulfurization conditions is set to 1952197m³. 3 / h, the empty tower gas velocity u under the ammonia desulfurization condition is set to 2.88 m / s, which is significantly lower than the empty tower gas velocity of 4.02 m / s under the original calcium desulfurization condition. According to the formula The calculated tower diameter of the middle section of the expanded absorption section is 15.5m.

[0031] Slurry pool reuse and renovation: At the height of the original calcium desulfurization tower at 12m, an oxidation section is formed by installing a partition plate inside the calcium desulfurization tower, which is isolated from the cooling section. This transforms the bottom slurry pool of the calcium desulfurization tower into an oxidation section. The original tower oxidation air inlet is modified, and an oxidation air distributor is added inside. A reflux port is added to the side of the oxidation section, and ammonia addition components are installed.

[0032] Circulation system modification: A circulation reflux tank equipped with a jet vortex pump is added. The slurry collected in the lower part of the cooling section is introduced into the circulation reflux tank, and the jet vortex pump ensures thorough mixing. The slurry in the circulation reflux tank is divided into two parts: one part is returned to the cooling section by the circulation pump for cooling and concentrating the flue gas, and the other part enters the ammonium sulfate treatment module for recovering ammonium sulfate products. The inlet and outlet of the jet vortex pump are located 0.3m~1m above the bottom plate of the circulation reflux tank, and the jet vortex pump is a centrifugal pump with a flow rate of 700m³ / h. 3 / h, the outlet tangentially enters the tower body. Furthermore, the original calcium-based desulfurization tower's absorption spray is equipped with four absorption circulation pumps, corresponding to the four spray layers, with a flow rate of 4000 m³ / h. 3 / h. After the conversion to an ammonia-based desulfurization tower, the original two absorption circulation pumps can be idled or kept on standby. The remaining two absorption circulation pumps will be reused, with the motors and pump heads remaining unchanged. The outlet pipelines of the absorption circulation pumps will be modified, with branch pipes branching off from the outlet header to connect to the spray layers of the four modified absorption towers. One absorption circulation pump will connect to the first and second spray layers of the absorption section via the outlet header, while the other absorption circulation pump will connect to the third and fourth spray layers of the absorption section via the outlet header. The flow rate of the branch pipes will be adjusted by valves on the branch pipes.

[0033] Oxidation system modification: The oxidation fan corresponding to the absorption tower in the original calcium desulfurization system has a flow rate of 224 m³ / h. 3 / min, pressure increased to 87kPa, oxidation blower was modified, old motor was reused, pump head replaced, the modified oxidation blower flow rate is 202m³ / min. 3 The flow rate is 101 m³ / min, with a pressure increase of 100 kPa. A new magnetic levitation oxidation fan is added to the existing calcium oxidation fan using a main pipe system and connected in parallel with it. 3 / min, pressure increased by 100KPa. The newly added magnetic levitation oxidation fan outlet is connected in parallel with the original centrifugal oxidation fan outlet and merged into the main pipe.

[0034] Byproduct system upgrade: The existing calcium-process gypsum treatment complex will be reused. The gypsum dewatering, limestone preparation, and wastewater treatment units within the existing gypsum treatment complex will be demolished, and a new ammonium sulfate solid-liquid separation, drying, and packaging unit will be constructed. Specifically, the main high-load equipment of the original gypsum treatment complex is located on the first floor, while the high-load equipment of the ammonium sulfate treatment complex, such as centrifuges and drying towers, is located on the second floor and above. Due to insufficient load-bearing capacity on the second floor and above of the original gypsum treatment complex, local reinforcement measures will be implemented on the floor slabs, beams, columns, and support joints that bear the loads of the centrifuges, drying towers, etc., to reuse the existing gypsum treatment complex and meet the installation requirements of the equipment in the ammonium sulfate downstream system.

[0035] Electrical system upgrade: Reuse existing electrical instruments to reduce electrical system investment and improve system safety, stability and operational flexibility.

[0036] After actual testing, the modified ammonia desulfurization system is operating normally, and the flue gas volume Q under ammonia desulfurization conditions is set to 1952197 m³. 3 / h, equivalent to 1347937 Nm³ under standard conditions 3 / h, the average SO2 concentration in the inlet flue gas is 4000 mg / Nm³. 3 With an annual operating time of 6000 hours, the SO2 concentration in the purified flue gas is ≤35mg / Nm³. 3 The SO2 removal rate is above 99.0%; the project utilizes the heat of flue gas to concentrate and crystallize ammonium sulfate products, with an annual output of 134,000 tons of ammonium sulfate fertilizer, which meets the GB / T 535-2020 standard.

[0037] The modification method described in this embodiment reduces construction steps such as complete tower dismantling and replacement of large equipment. The desulfurization tower body, desulfurization equipment, civil engineering, and comprehensive building are all 100% reused; power supply and distribution are also 100% reused; instrumentation reuse rate exceeds 70%; and the overall reuse rate exceeds 80%. Compared to traditional overall modification schemes, the construction period can be shortened by approximately 50%, significantly reducing equipment purchase and dismantling / reconstruction costs. The modification cost is equivalent to less than 30% of building a new ammonia-based desulfurization facility of the same scale. After adopting the modification method of this embodiment, the core design parameters are comparable to those of a newly built ammonia-based desulfurization system, ensuring desulfurization efficiency and controlling ammonia escape from the source, guaranteeing long-term, stable system operation. Based on the operating cost savings after converting from calcium-based to ammonia-based desulfurization, the owner can recover their investment in 2-3 years. After the renovation, wastewater discharge will be reduced by 84,000 tons / year, gypsum discharge by 172,000 tons / year, CO2 emissions by 44,000 tons / year, limestone mining by 117,000 tons / year, electricity consumption by 15 million kWh / year, and ammonium sulfate fertilizer production by 134,000 tons / year; it has significant social and environmental benefits.

[0038] In contrast, if the prefabricated absorption section on the ground is not expanded during the tower modification, the gas velocity in the absorption section will be too high, resulting in the following negative effects: (1) The gas velocity is too high, the residence time of flue gas in the absorption zone is reduced, and the effective reaction time of acidic gases such as SO2 with ammonia droplets / liquid film is insufficient, resulting in a decrease in desulfurization efficiency. (2) The high-speed airflow will carry a large number of absorbent droplets out of the absorption zone, which not only causes physical loss of ammonia and reactants, but more importantly, these large number of entrained droplets contain ammonium salts and unreacted absorbent ammonia, which will cause the demister to be overloaded and blocked, resulting in a decrease in demister efficiency, ammonia escape from the chimney tail gas and particulate matter exceeding the standard, a sharp increase in demister pressure difference, rapid blockage of demister channels, a large increase in system resistance, a surge in induced draft fan power consumption, and a large number of droplets scouring the demister, resulting in a shortened service life of the demister. (3) Excessive air velocity can easily cause the airflow distributor to deviate from the design conditions, resulting in channeling and flow deviation in the tower. In some areas, the air velocity is extremely high, resulting in poor contact effect; in some areas, dead zones may form, reducing the effective mass transfer area and lowering the overall efficiency. (4) Droplets and crystal particles carried in the high-speed airflow will cause severe scouring and wear on the internal components of the absorption tower (such as spray layer nozzles, trays, distributors, etc.), shortening their service life. (5) Increased consumption of absorbent (ammonia) is caused by the decrease in desulfurization efficiency and physical entrainment losses, requiring more ammonia to ensure that the SO2 concentration at the outlet does not exceed the standard, directly leading to an increase in operating costs. (6) Increased power consumption, increased system resistance (especially demister pressure difference), and significantly increased power consumption of the induced draft fan.

[0039] This invention provides a method for converting a calcium-based desulfurization system to an ammonia-based desulfurization system. The method involves modifying the calcium desulfurization tower in the calcium-based system into an ammonia-based desulfurization tower. The ammonia-based desulfurization tower comprises, from bottom to top, an oxidation section, a cooling section, an absorption section, a water washing section, and a demister section. The absorption section is enlarged to reduce gas velocity and improve the absorption effect of the ammonia-based desulfurization, thereby meeting the operating requirements of the ammonia-based desulfurization system. This method fully utilizes the original calcium-based desulfurization system, increasing the reuse rate (up to 70%), reducing costs, and improving the conversion effect.

[0040] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0041] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0042] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0043] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for converting a calcium-based desulfurization system to an ammonia-based desulfurization system, characterized in that, The modification method includes: The calcium desulfurization tower in the calcium desulfurization system is modified into an ammonia desulfurization tower in the ammonia desulfurization system. The ammonia desulfurization tower includes, from bottom to top, an oxidation section, a cooling section, an absorption section, a water washing section, and a demisting section. The absorption section is enlarged to reduce the gas velocity and improve the absorption effect of ammonia desulfurization.

2. The modification method according to claim 1, characterized in that, For the absorption section of the ammonia desulfurization tower, the tower diameter of the absorption section satisfies the formula... ; Where D is the tower diameter of the absorption section, in meters; Q is the flue gas volume under ammonia-based desulfurization conditions, in cubic meters per second. 3 / s; u is the empty tower gas velocity under ammonia desulfurization conditions, in m / s.

3. The modification method according to claim 1 or 2, characterized in that, The diameter expansion modification includes: dividing the tower body of the calcium desulfurization tower above the original flue gas inlet and inserting a newly added diameter expansion absorption section as the absorption section of the ammonia desulfurization tower.

4. The modification method according to claim 1, characterized in that, The modification method also includes: using a main pipe for diversion control of the absorption circulation pump in the calcium desulfurization system to achieve one pump for multiple spray layers.

5. The modification method according to claim 1, characterized in that, The modification method also includes: using a main pipe for the oxidation fan in the calcium desulfurization system, and adding at least one oxidation fan according to the actual working conditions.

6. The modification method according to claim 1, characterized in that, The modification method also includes: modifying the gypsum treatment module in the calcium desulfurization system into the ammonium sulfate treatment module in the ammonia desulfurization system, reusing and modifying the existing hydrocyclone, and adding a centrifuge, dryer and packaging machine in sequence at the outlet of the hydrocyclone.

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