Flue gas desulfurization system with ionic liquid method coupled with catalytic method

Abstract

The invention relates to a flue gas desulfurization system with an ionic liquid method coupled with a catalytic method. The technical problem that the content of sulfur dioxide in desulfurized flue gas fluctuates greatly when large-scale to-be-desulfurized flue gas with high content of sulfur dioxide is treated by an ionic liquid flue gas desulfurization technology can be solved. Comprising an ionic liquid method flue gas desulfurization device which is used for receiving to-be-desulfurized flue gas and absorbing sulfur dioxide in the to-be-desulfurized flue gas by using a prepared ionic liquid as an absorbent so as to output primary desulfurized flue gas; the catalytic flue gas desulfurization device is used for receiving the first-stage desulfurized flue gas, absorbing residual sulfur dioxide in the first-stage desulfurized flue gas through a catalyst, converting the residual sulfur dioxide into sulfuric acid existing on the catalyst, and outputting second-stage desulfurized flue gas; wherein the content of sulfur dioxide in the first-stage desulfurized flue gas is 500 mg / Nm < 3 > to 1500 mg / Nm < 3 >, and the content of sulfur dioxide in the second-stage desulfurized flue gas is 50 mg / Nm < 3 > or less.

Description

Technical Field

[0001] The invention relates to the technical field of flue gas desulfurization, and in particular to an ionic liquid coupled catalytic flue gas desulfurization system. Background Art

[0002] Ionic liquid flue gas desulfurization technology uses ionic liquid with specific anion and cation structure as absorbent, and achieves flue gas desulfurization by absorbing sulfur dioxide through the absorbent. This technology has the advantages of large sulfur dioxide absorption capacity, good selectivity, low vapor pressure, high thermal stability, and absorbent recyclable regeneration. Ionic liquid can achieve directional regulation of performance by adjusting the anion and cation structure. High-purity sulfur dioxide products can be obtained during the regeneration of the absorbent, and can be input into adjacent sections as a raw material for preparing sulfuric acid. Ionic liquid desulfurization technology can adapt to flue gas with a wide sulfur content range to be desulfurized. Generally speaking, flue gas with a sulfur dioxide content (volume fraction) of 0.02%-5% to be desulfurized can be applied to ionic liquid desulfurization. In view of this, ionic liquid desulfurization technology is currently mainly used to treat large-scale flue gas with a high sulfur dioxide content to be desulfurized.

[0003] However, the inventors noticed that when the ionic liquid desulfurization method is used to treat a large amount of flue gas with a high sulfur dioxide content, not all of the flue gas to be desulfurized will come into contact with the absorbent, and a small part of the flue gas to be desulfurized will always escape from the absorbent, which leads to a large fluctuation in the sulfur dioxide content in the desulfurized flue gas after desulfurization by the ionic liquid method. For example, a coal-fired power generation unit using high-sulfur coal is designed to discharge a flue gas flow rate of 2450000Nm 3 / h, the sulfur dioxide content in the flue gas to be desulfurized is designed to be 12000mg / Nm 3 The designed desulfurization efficiency of ionic liquid flue gas desulfurization is ≥99.58%; however, the sulfur dioxide content in the desulfurized flue gas after ionic liquid flue gas desulfurization is actually not stable, and the peak value of the sulfur dioxide content in the desulfurized flue gas sometimes fluctuates up to several hundred milligrams per standard cubic meter. Summary of the invention

[0004] The purpose of the present invention is to provide an ionic liquid coupled catalytic flue gas desulfurization system, which can solve the technical problem that the sulfur dioxide content in the desulfurized flue gas has large fluctuations when the ionic liquid flue gas desulfurization technology is used to treat large-scale flue gas to be desulfurized with a high sulfur dioxide content.

[0005] In the first aspect, an ionic liquid coupled catalytic flue gas desulfurization system is provided, comprising: an ionic liquid flue gas desulfurization device, the ionic liquid flue gas desulfurization device is used to receive the flue gas to be desulfurized and absorb the sulfur dioxide in the flue gas to be desulfurized using the configured ionic liquid as an absorbent, and then output a first-stage desulfurized flue gas; a catalytic flue gas desulfurization device, the catalytic flue gas desulfurization device is used to receive the first-stage desulfurized flue gas and absorb the remaining sulfur dioxide in the first-stage desulfurized flue gas through a catalyst and convert it into sulfuric acid present on the catalyst, and then output a second-stage desulfurized flue gas; wherein the content of sulfur dioxide in the first-stage desulfurized flue gas is 500 mg / Nm 3 -1500mg / Nm 3 The sulfur dioxide content in the secondary desulfurized flue gas is 50 mg / Nm 3 the following.

[0006] As an optimization and / or instantiation of the above-mentioned ionic liquid coupled catalytic flue gas desulfurization system, further: the content of sulfur dioxide in the first-stage desulfurized flue gas is 1000±200 mg / Nm 3 .

[0007] As an optimization and / or instantiation of the above-mentioned ionic liquid coupled catalytic flue gas desulfurization system, further: the content of sulfur dioxide in the secondary desulfurized flue gas is 30 mg / Nm 3 the following.

[0008] As an optimization and / or instantiation of the above-mentioned ionic liquid coupled catalytic flue gas desulfurization system, further: the ionic liquid flue gas desulfurization device includes a desulfurization absorption tower and a regeneration tower, the desulfurization absorption tower is used to absorb the sulfur dioxide in the flue gas to be desulfurized through the absorbent and output the first-level desulfurized flue gas, and the regeneration tower is used to analyze the sulfur dioxide in the absorbent from the desulfurization absorption tower to produce a sulfur dioxide product and a regenerated absorbent.

[0009] As an optimization and / or instantiation of the above-mentioned ionic liquid coupled catalytic flue gas desulfurization system, it is further provided that: assuming that the absorbent after fully absorbing sulfur dioxide is a rich liquid and the absorbent after regeneration is a lean liquid, a rich liquid pump, a lean-rich liquid pump, a lean-liquid heat exchanger and a lean liquid cooler are provided between the desulfurization absorption tower and the regeneration tower, the rich liquid outlet of the desulfurization absorption tower is connected to the rich liquid inlet of the regeneration tower via the rich liquid pump and the lean-rich liquid heat exchanger in sequence, the lean liquid outlet of the regeneration tower is connected to the lean liquid inlet of the desulfurization absorption tower via the lean liquid pump, the lean-rich liquid heat exchanger and the lean liquid cooler in sequence, and the rich liquid output from the rich liquid outlet of the desulfurization absorption tower and the lean liquid output from the lean liquid outlet of the regeneration tower are heat exchanged via the lean-rich liquid heat exchanger.

[0010] As an optimization and / or instantiation of the above-mentioned ionic liquid coupled catalytic flue gas desulfurization system, further: the bottom liquid outlet of the regeneration tower is connected to a reboiler, the outlet of the reboiler returns to the bottom of the regeneration tower, the top sulfur dioxide gas outlet of the regeneration tower is connected to a condenser, the outlet of the condenser is connected to a gas-liquid separator, and the liquid outlet of the gas-liquid separator returns to the top of the regeneration tower through a reflux pump.

[0011] As an optimization and / or instantiation of the above-mentioned ionic liquid coupled catalytic flue gas desulfurization system, further: a packed washing tower and an electric precipitator are also provided before the desulfurization absorption tower, and the flue gas to be desulfurized first passes through the packed washing tower and the electric precipitator in sequence before entering the desulfurization absorption tower.

[0012] As an optimization and / or instantiation of the above-mentioned ionic liquid coupled catalytic flue gas desulfurization system, further: the absorbent is composed of 7%-9% by mass of N-hydroxyethylethylenediamine sulfate, 1%-1.5% of piperazine activator, 0.1%-0.3% of hydroquinone antioxidant and the rest of water, the sulfur dioxide absorption temperature of the absorbent is 30°C-45°C, the regeneration temperature is 90°C-105°C, and the molar ratio of sulfate ion to N-hydroxyethylethylenediamine of the N-hydroxyethylethylenediamine sulfate is 0.4-0.5.

[0013] As an optimization and / or instantiation of the above-mentioned ionic liquid coupled catalytic flue gas desulfurization system, further: the catalytic flue gas desulfurization device adopts a catalytic flue gas desulfurization tower, which performs flue gas desulfurization through multiple desulfurization reactors; each desulfurization reactor has an air inlet, an exhaust port, a liquid discharge port and a catalyst located in the desulfurization reactor, and each desulfurization reactor is provided with a spraying device for a regeneration liquid for washing and regenerating the catalyst. During desulfurization, the flue gas enters the desulfurization reactor from the air inlet and is desulfurized by the catalyst and then discharged from the exhaust port. The sulfur dioxide in the flue gas reacts on the catalyst to form sulfuric acid. When the catalyst is washed and regenerated, the sulfuric acid is recovered by spraying the regeneration liquid on the catalyst and then discharged from the liquid discharge port; the catalytic flue gas desulfurization tower comprises a vertical column of desulfurization reactors, an air inlet pipe network, an exhaust pipe network and a regeneration liquid circulation system; the vertical column of desulfurization reactors comprises a tower support structure, and the multiple desulfurization reactors are provided with a tower support structure. The desulfurization reactors are distributed on the tower support structure; the air intake network includes a vertically arranged air intake main pipe and air intake branches respectively connecting the air intake main pipe with the air inlets of the desulfurization reactors; the exhaust network includes a vertically arranged exhaust main pipe and exhaust branches respectively connecting the exhaust main pipe with the exhaust ports of the desulfurization reactors; a regeneration liquid circulation system, the regeneration liquid circulation system includes at least one regeneration liquid tank and a regeneration liquid circulation control network connected between the at least one regeneration liquid tank and the desulfurization reactors, the regeneration liquid circulation control network has an output side control network, an input side control network and a regeneration liquid driving device, the output side control network can introduce the regeneration liquid in the selected regeneration liquid tank into the regeneration liquid spraying device of the selected desulfurization reactor, the input side control network can introduce the regeneration liquid output from the discharge port of the selected desulfurization reactor into the selected regeneration liquid tank, and the regeneration liquid driving device can provide the required power to the regeneration liquid.

[0014] As an optimization and / or instantiation of the above-mentioned ionic liquid coupled catalytic flue gas desulfurization system, further: the flue gas to be desulfurized comes from a coal-fired generator using high-sulfur coal.

[0015] Catalytic flue gas desulfurization technology is an existing flue gas desulfurization technology. The basic principle of catalytic flue gas desulfurization technology is: sulfur dioxide, water, and oxygen in the flue gas to be desulfurized are adsorbed on the catalyst (usually an activated carbon-based desulfurization catalyst) and react to generate sulfuric acid under the catalytic action of the active components; when the sulfuric acid attached to the desulfurization catalyst reaches a certain level, the desulfurization catalyst can be washed with a regeneration liquid (usually dilute sulfuric acid and / or water) to remove the attached sulfuric acid on the desulfurization catalyst and release the active sites of the desulfurization catalyst; the used regeneration liquid can be reused as a by-product (usually dilute sulfuric acid).

[0016] Ionic liquid flue gas desulfurization technology uses specific ionic liquid as an absorbent to directly absorb sulfur dioxide and regenerate high-purity sulfur dioxide for the production of chemical products such as sulfuric acid; while catalytic flue gas desulfurization technology directly converts sulfur dioxide, water and oxygen into sulfuric acid on the catalyst surface, and uses regeneration liquid (dilute sulfuric acid or water) to wash the sulfuric acid produced on the catalyst surface to restore the catalyst activity. There are essential differences between ionic liquid flue gas desulfurization technology and catalytic flue gas desulfurization technology in desulfurization mechanism, final product and process equipment, and they are currently independently applied in different engineering practices.

[0017] The advantages of catalytic flue gas desulfurization technology are stable, safe and reliable operation, and the ability to accurately control the sulfur dioxide content in the desulfurized flue gas. In addition, the process flow of catalytic flue gas desulfurization technology is short, with less equipment and therefore a small footprint; it is easy to operate; due to the small amount of equipment and short process, only regeneration requires frequent intermittent operation on a daily basis, which can be operated by operators of other production units, and there is no need to consider operator costs at all. Another significant advantage of catalytic technology is that the catalyst accelerates the reaction process but is not consumed itself. Compared with the ionic liquid flue gas desulfurization technology, which requires the addition of absorbents, the desulfurizer of catalytic flue gas desulfurization technology basically does not need to be added, and only repeated regeneration is required, which further reduces operating costs. In addition, catalytic flue gas desulfurization technology is suitable for desulfurization when the temperature of the flue gas to be desulfurized is low.

[0018] The ionic liquid method coupled catalytic flue gas desulfurization system of the present invention uses the catalytic flue gas desulfurization device as a supplement to the ionic liquid flue gas desulfurization device, which can well make up for the disadvantage of the ionic liquid flue gas desulfurization technology that the sulfur dioxide content in the desulfurized flue gas has a large fluctuation when treating a large-scale flue gas to be desulfurized with a high sulfur dioxide content. Since the catalytic flue gas desulfurization technology is suitable for achieving desulfurization when the temperature of the flue gas to be desulfurized is relatively low, the primary desulfurized flue gas does not need to be heated before entering the catalytic flue gas desulfurization device.

[0019] In addition, the ionic liquid coupled catalytic flue gas desulfurization system of the present invention controls the content of sulfur dioxide in the primary desulfurized flue gas to 500 mg / Nm 3 -1500mg / Nm 3 The sulfur dioxide content in the secondary desulfurized flue gas is controlled to 50 mg / Nm 3 The purpose of this design is to appropriately reduce the desulfurization efficiency of the ionic liquid flue gas desulfurization device based on the desulfurization performance of the catalytic flue gas desulfurization device. By appropriately reducing the desulfurization efficiency of the ionic liquid flue gas desulfurization device, the sulfur dioxide content in the first-stage desulfurized flue gas is controlled at 500-1500mg / Nm 3Within this range, the consumption of ionic liquid and regeneration energy consumption can be significantly reduced, the cost of absorbent replenishment and equipment maintenance can be reduced, and at the same time, the operating fluctuations of the ionic liquid device under high load can be reduced, and a reasonable division of labor of the two-stage desulfurization device can be achieved, which not only ensures the overall desulfurization effect of the system and the stable compliance of emission indicators, but also optimizes the overall operating cost.

[0020] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. Additional aspects and advantages provided by the present invention will be partially given in the following description, partially become apparent from the following description, or be learned through practice. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings constituting a part of this specification are used to assist the understanding of the present invention. The contents provided in the drawings and the related descriptions in this specification can be used to explain the present invention, but do not constitute improper limitations on the present invention.

[0022] Figure 1 The present invention is a schematic structural diagram of an ionic liquid coupled catalytic flue gas desulfurization system according to an embodiment of the present invention.

[0023] Figure 2 for Figure 1 The structural schematic diagram of the ionic liquid flue gas desulfurization device is shown in. DETAILED DESCRIPTION

[0024] The present invention is described clearly and completely below in conjunction with the accompanying drawings. A person skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it should be particularly noted that:

[0025] The technical solutions and technical features provided in each section, including the following description, can be combined with each other without conflict. In addition, where possible, these technical solutions, technical features and related combinations can be assigned specific technical themes and protected by relevant patents.

[0026] The embodiments of the present invention involved in the following description are generally only a part of the embodiments rather than all the embodiments. Based on these embodiments, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of patent protection.

[0027] The terms "include", "comprises", "have" and any variations thereof in this specification and the corresponding claims and related parts are intended to cover non-exclusive inclusions. Other related terms and units can be reasonably interpreted based on the relevant content provided in this specification.

[0028] Figure 1The present invention is a schematic structural diagram of an ionic liquid coupled catalytic flue gas desulfurization system according to an embodiment of the present invention. Figure 2 for Figure 1 The schematic diagram of the structure of the ionic liquid flue gas desulfurization device is shown in FIG. Figure 1-Figure 2 As shown, the ionic liquid coupled catalytic flue gas desulfurization system comprises: an ionic liquid flue gas desulfurization device 1, wherein the ionic liquid flue gas desulfurization device 1 is used to receive the flue gas to be desulfurized and absorb the sulfur dioxide in the flue gas to be desulfurized using the configured ionic liquid as an absorbent, thereby outputting a first-stage desulfurized flue gas; a catalytic flue gas desulfurization device 2, wherein the catalytic flue gas desulfurization device 2 is used to receive the first-stage desulfurized flue gas and absorb the remaining sulfur dioxide in the first-stage desulfurized flue gas through a catalyst and convert it into sulfuric acid present on the catalyst, thereby outputting a second-stage desulfurized flue gas; wherein the content of sulfur dioxide in the first-stage desulfurized flue gas is 500 mg / Nm 3 -1500mg / Nm 3 The sulfur dioxide content in the secondary desulfurized flue gas is 50 mg / Nm 3 the following.

[0029] Among them, the ionic liquid flue gas desulfurization device 1 includes a desulfurization absorption tower 11 and a regeneration tower 12. The desulfurization absorption tower 11 is used to absorb sulfur dioxide in the flue gas to be desulfurized through the absorbent and output the first-level desulfurized flue gas. The regeneration tower 12 is used to analyze the sulfur dioxide in the absorbent from the desulfurization absorption tower 11 to produce sulfur dioxide products and regenerated absorbent.

[0030] More specifically, assuming that the absorbent after fully absorbing sulfur dioxide is a rich liquid and the absorbent after regeneration is a lean liquid, a rich liquid pump 13, a lean liquid pump 14, a lean-rich liquid heat exchanger 15 and a lean liquid cooler 16 are provided between the desulfurization absorber 11 and the regeneration tower 12. The rich liquid outlet of the desulfurization absorber 11 is connected to the rich liquid inlet of the regeneration tower 12 via the rich liquid pump 13 and the lean-rich liquid heat exchanger 15 in sequence, and the lean liquid outlet of the regeneration tower 12 is connected to the lean liquid inlet of the desulfurization absorber 11 via the lean liquid pump 14, the lean-rich liquid heat exchanger 15 and the lean liquid cooler 16 in sequence. The rich liquid output from the rich liquid outlet of the desulfurization absorber 11 and the lean liquid output from the lean liquid outlet of the regeneration tower 12 are heat exchanged via the lean-rich liquid heat exchanger 15.

[0031] In addition, the bottom liquid outlet of the regeneration tower 12 is connected to the reboiler 16, the outlet of the reboiler 16 returns to the bottom of the regeneration tower 12, the top sulfur dioxide gas outlet of the regeneration tower 12 is connected to the condenser 17, the outlet of the condenser 17 is connected to the gas-liquid separator 18, and the liquid outlet of the gas-liquid separator 18 returns to the top of the regeneration tower 12 through a reflux pump.

[0032] In addition, a packing washing tower 3 and an electric precipitator 4 are provided before the desulfurization absorption tower 11. The flue gas to be desulfurized first passes through the packing washing tower 3 and the electric precipitator 4 in sequence before entering the desulfurization absorption tower. The packing washing tower 3 can not only remove dust in the flue gas, but also cool the flue gas to be desulfurized to meet the working requirements of the desulfurization absorption tower 11.

[0033] The working principle of the ionic liquid flue gas desulfurization device 1 is as follows: the flue gas to be desulfurized first passes through a packed scrubber 3 and an electrostatic precipitator 4 for pretreatment to remove dust and moisture in the flue gas, and cool the flue gas to be desulfurized, and then enters a desulfurization absorption tower 11, where it is reversely contacted with an absorbent (lean liquid) sprayed from the top of the tower, and sulfur dioxide in the flue gas is absorbed by the absorbent to generate a rich liquid, and the treated flue gas (primary desulfurized flue gas) is discharged from the top of the tower; the absorbent (rich liquid) rich in sulfur dioxide is sent by a rich liquid pump 13 to a lean-rich liquid heat exchanger 15 for heat exchange with a high-temperature lean liquid from a regeneration tower 12, and then enters the regeneration tower 12, where it is heated by a bottom reboiler 16. The heat supplied is used to resolve the absorbed sulfur dioxide. The resolved sulfur dioxide gas is cooled by the tower top condenser 17 and then enters the gas-liquid separator 18. The separated liquid is returned to the top of the regeneration tower 12 through the reflux pump, while the gaseous sulfur dioxide is output as a product. The regenerated absorbent (lean liquid) is transported by the lean liquid pump 14, and is successively passed through the lean-rich liquid heat exchanger 15 to heat the rich liquid and the lean liquid cooler 16 to cool to a suitable temperature, and then returned to the top of the desulfurization absorption tower 11 for recycling. The entire system realizes the desulfurization of flue gas and the recycling of absorbent by the absorption-resolution-circulation method, and can reduce the sulfur dioxide content in the flue gas from the initial concentration to 500 mg / Nm 3 -1500mg / Nm 3 within the range.

[0034] The sulfur dioxide content in the first-stage desulfurized flue gas is 500mg / Nm 3 -1500mg / Nm 3 The requirement is equivalent to reducing the desulfurization efficiency for the ionic liquid flue gas desulfurization device 1. The sulfur dioxide content in the flue gas to be desulfurized is 12000 mg / Nm 3 To calculate, the sulfur dioxide content in the first-stage desulfurized flue gas is 500mg / Nm 3 -1500mg / Nm 3 , which is equivalent to setting the desulfurization efficiency of the ionic liquid flue gas desulfurization device 1 to 87%-96%. Compared with the desulfurization efficiency index of 99.5% or more that the ionic liquid flue gas desulfurization device usually needs to achieve, the desulfurization efficiency requirement for the ionic liquid flue gas desulfurization device 1 in this embodiment is lower, which can significantly reduce the consumption of ionic liquid and regeneration energy consumption, reduce the cost of absorbent replenishment and equipment maintenance, and reduce the operation fluctuation of the ionic liquid device under high load.

[0035] Compared with the desulfurization efficiency index of 99.5% or more that the ionic liquid flue gas desulfurization device usually needs to achieve, in this embodiment, the desulfurization efficiency of the ionic liquid flue gas desulfurization device 1 can be reduced by adjusting the formula of the absorbent, thereby significantly reducing the use cost of the ionic liquid.

[0036] In a specific embodiment, the absorbent is composed of 7%-9% by mass of N-hydroxyethylethylenediamine sulfate, 1%-1.5% of piperazine activator, 0.1%-0.3% of hydroquinone antioxidant and the rest of water. The sulfur dioxide absorption temperature of the absorbent is 30°C-45°C, the regeneration temperature is 90°C-105°C, and the molar ratio of sulfate ion of the N-hydroxyethylethylenediamine sulfate to N-hydroxyethylethylenediamine is 0.4-0.5.

[0037] Among them, since the molar ratio of sulfate to N-hydroxyethylethylenediamine in N-hydroxyethylethylenediamine sulfate is 0.4-0.5, it means that the free amine content is relatively high, which enhances the initial absorption capacity of SO2 and is conducive to the rapid removal of SO2 in flue gas.

[0038] The above-mentioned absorbent is composed of four components: the main component N-hydroxyethylethylenediamine sulfate serves as the core absorption component, which provides strong initial SO2 absorption capacity through its high free amine content; the piperazine activator is used to improve the mass transfer effect and the absorption kinetic rate; the hydroquinone serves as an antioxidant to prevent the solution from degrading; and the balance water serves as a solvent. This formula combination can achieve the desired desulfurization effect under a specific sulfate to amine molar ratio (0.4-0.5) conditions.

[0039] Among them, the catalytic flue gas desulfurization device 2 adopts a catalytic flue gas desulfurization tower 21, and the catalytic flue gas desulfurization tower 21 performs flue gas desulfurization through multiple desulfurization reactors; each desulfurization reactor has an air inlet, an exhaust port, a liquid discharge port and a catalyst located in the desulfurization reactor, and each desulfurization reactor is provided with a spraying device for a regeneration liquid for washing and regenerating the catalyst. During desulfurization, the flue gas enters the desulfurization reactor from the air inlet and is discharged from the exhaust port after being desulfurized by the catalyst. The sulfur dioxide in the flue gas reacts on the catalyst to form sulfuric acid. When the catalyst is washed and regenerated, the sulfuric acid is recovered by spraying the regeneration liquid on the catalyst and then discharged from the liquid discharge port; the catalytic flue gas desulfurization tower includes a vertical column of desulfurization reactors, an air inlet pipe network, an exhaust pipe network and a regeneration liquid circulation system; the vertical column of desulfurization reactors includes a tower support structure, and the multiple desulfurization reactors are distributed on the tower support structure On the top; the air intake network includes a vertically arranged air intake main pipe and various air intake branches which respectively connect the air intake main pipe with the air inlets of various desulfurization reactors; the exhaust network includes a vertically arranged exhaust main pipe and various exhaust branches which respectively connect the exhaust main pipe with the exhaust ports of various desulfurization reactors; a regeneration liquid circulation system 22, the regeneration liquid circulation system includes at least one regeneration liquid tank and a regeneration liquid circulation control network connected between the at least one regeneration liquid tank and each desulfurization reactor, the regeneration liquid circulation control network has an output side control network, an input side control network and a regeneration liquid driving device, the output side control network can introduce the regeneration liquid in the selected regeneration liquid tank into the regeneration liquid spraying device of the selected desulfurization reactor, the input side control network can introduce the regeneration liquid output from the discharge port of the selected desulfurization reactor into the selected regeneration liquid tank, and the regeneration liquid driving device can provide the required power to the regeneration liquid.

[0040] The applicant of the present invention has made detailed introductions to the catalytic flue gas desulfurization device 2 in patent documents with publication numbers CN214764545U, CN114653202A, CN114797450A, etc. The contents of these patent documents are cited here to illustrate the working mode of the catalytic flue gas desulfurization device 2, which will not be repeated here.

[0041] In summary, the catalytic flue gas desulfurization device 2 is fully capable of controlling the sulfur dioxide content in the secondary desulfurized flue gas to 50 mg / Nm 3 Below, even controlled at 30mg / Nm 3 the following.

[0042] Example

[0043] Use Figure 1-Figure 2The ionic liquid coupled catalytic flue gas desulfurization system shown in the figure, wherein the absorbent is composed of 8% by mass of N-hydroxyethylethylenediamine sulfate, 1.25% of piperazine activator, 0.1% of hydroquinone antioxidant and the rest of water, the sulfur dioxide absorption temperature of the absorbent is 30°C-45°C, the regeneration temperature is 90°C-105°C, and the molar ratio of sulfate ion of the N-hydroxyethylethylenediamine sulfate to N-hydroxyethylethylenediamine is 0.4.

[0044] After testing, the sulfur dioxide content in the first-level desulfurized flue gas is 1000±200mg / Nm 3 That is, the sulfur dioxide content in the primary desulfurized flue gas is controlled at 800g / Nm 3 Up to 1200g / Nm 3 Fluctuates within the range.

[0045] The catalytic flue gas desulfurization device 2 is used to stably control the sulfur dioxide content in the secondary desulfurized flue gas to 30 mg / Nm 3 the following.

[0046] Comparative Example

[0047] Still using Figure 1-Figure 2 The ionic liquid coupled catalytic flue gas desulfurization system shown in the figure, wherein the absorbent is composed of 28% by mass of N-hydroxyethylethylenediamine sulfate, 2.5% of piperazine activator, 0.5% of hydroquinone antioxidant and the rest of water, the sulfur dioxide absorption temperature of the absorbent is 25°C-30°C (controlled in a lower temperature range to improve the absorption efficiency), the regeneration temperature is 95°C-105°C, and the molar ratio of sulfate ion to N-hydroxyethylethylenediamine of the N-hydroxyethylethylenediamine sulfate is 0.8 (sufficient active sites can be maintained within this range).

[0048] After testing, the sulfur dioxide content in the first-stage desulfurized flue gas has obvious fluctuations, and the valley value of the sulfur dioxide content in the first-stage desulfurized flue gas is 50g / Nm 3 Around, peak value is 200g / Nm 3 about.

[0049] The catalytic flue gas desulfurization device 2 is used to stably control the sulfur dioxide content in the secondary desulfurized flue gas to 30 mg / Nm 3 the following.

[0050] Although the SO2 content in the primary desulfurized flue gas is relatively high, the SO2 content in the secondary desulfurized flue gas is in the same range as that in the comparative example. However, in the above example, the operating cost of the ionic liquid flue gas desulfurization device is significantly reduced due to the significant reduction in the amount of reagents used.

[0051] The above is a description of the relevant contents of the present invention. A person skilled in the art will be able to implement the present invention based on these descriptions. Based on the above contents of this specification, all other embodiments obtained by a person skilled in the art without making creative work should fall within the scope of the present invention.

Claims

1. Ionic liquid coupled catalytic flue gas desulfurization system, characterized by: include: An ionic liquid flue gas desulfurization device, which is used to receive the flue gas to be desulfurized and absorb the sulfur dioxide in the flue gas to be desulfurized using the configured ionic liquid as an absorbent, and then output a first-stage desulfurized flue gas; A catalytic flue gas desulfurization device, which is used to receive the primary desulfurized flue gas and absorb the remaining sulfur dioxide in the primary desulfurized flue gas through a catalyst and convert it into sulfuric acid present on the catalyst, thereby outputting a secondary desulfurized flue gas; The sulfur dioxide content in the primary desulfurized flue gas is 500 mg / Nm 3 -1500mg / Nm 3 The sulfur dioxide content in the secondary desulfurized flue gas is 50 mg / Nm 3 the following.

2. The ionic liquid coupled catalytic flue gas desulfurization system according to claim 1, characterized in that: The content of sulfur dioxide in the primary desulfurized flue gas is 1000±200 mg / Nm 3 .

3. The ionic liquid coupled catalytic flue gas desulfurization system according to claim 1, characterized in that: The sulfur dioxide content in the secondary desulfurized flue gas is 30 mg / Nm 3 the following.

4. The ionic liquid coupled catalytic flue gas desulfurization system according to claim 1, characterized in that: The ionic liquid flue gas desulfurization device comprises a desulfurization absorption tower and a regeneration tower. The desulfurization absorption tower is used to absorb sulfur dioxide in the flue gas to be desulfurized through the absorbent and output the first-level desulfurized flue gas. The regeneration tower is used to analyze sulfur dioxide in the absorbent from the desulfurization absorption tower to produce sulfur dioxide product and regenerated absorbent.

5. The ionic liquid coupled catalytic flue gas desulfurization system according to claim 4, characterized in that: Assuming that the absorbent after fully absorbing sulfur dioxide is rich liquid and the absorbent after regeneration is lean liquid, a rich liquid pump, a lean liquid pump, a lean-rich liquid heat exchanger and a lean liquid cooler are provided between the desulfurization absorber and the regeneration tower. The rich liquid outlet of the desulfurization absorber is connected to the rich liquid inlet of the regeneration tower via the rich liquid pump and the lean-rich liquid heat exchanger in sequence, and the lean liquid outlet of the regeneration tower is connected to the lean liquid inlet of the desulfurization absorber via the lean liquid pump, the lean-rich liquid heat exchanger and the lean liquid cooler in sequence. The rich liquid output from the rich liquid outlet of the desulfurization absorber and the lean liquid output from the lean liquid outlet of the regeneration tower are heat exchanged via the lean-rich liquid heat exchanger.

6. The ionic liquid coupled catalytic flue gas desulfurization system according to claim 4, characterized in that: The bottom liquid outlet of the regeneration tower is connected to a reboiler, the outlet of the reboiler returns to the bottom of the regeneration tower, the top sulfur dioxide gas outlet of the regeneration tower is connected to a condenser, the outlet of the condenser is connected to a gas-liquid separator, and the liquid outlet of the gas-liquid separator returns to the top of the regeneration tower through a reflux pump.

7. The ionic liquid coupled catalytic flue gas desulfurization system according to claim 4, characterized in that: A packing washing tower and an electric precipitator are also arranged before the desulfurization absorption tower. The flue gas to be desulfurized first passes through the packing washing tower and the electric precipitator in sequence before entering the desulfurization absorption tower.

8. The ionic liquid coupled catalytic flue gas desulfurization system according to claim 1, characterized in that: The absorbent is composed of 7%-9% by mass of N-hydroxyethylethylenediamine sulfate, 1%-1.5% of piperazine activator, 0.1%-0.3% of hydroquinone antioxidant and the rest of water. The sulfur dioxide absorption temperature of the absorbent is 30°C-45°C, the regeneration temperature is 90°C-105°C, and the molar ratio of sulfate group of the N-hydroxyethylethylenediamine sulfate to N-hydroxyethylethylenediamine is 0.4-0.

5.

9. The ionic liquid coupled catalytic flue gas desulfurization system according to any one of claims 1 to 8, characterized in that: The catalytic flue gas desulfurization device adopts a catalytic flue gas desulfurization tower, which desulfurizes the flue gas through multiple desulfurization reactors; Each desulfurization reactor has an air inlet, an exhaust port, a liquid discharge port, and a catalyst located in the desulfurization reactor. Each desulfurization reactor is provided with a spraying device for a regeneration liquid for washing and regenerating the catalyst. During desulfurization, flue gas enters the desulfurization reactor from the air inlet and is discharged from the exhaust port after being desulfurized by the catalyst. The sulfur dioxide in the flue gas reacts on the catalyst to form sulfuric acid. When the catalyst is washed and regenerated, the sulfuric acid is recovered by the regeneration liquid sprayed on the catalyst and then discharged from the liquid discharge port. The catalytic flue gas desulfurization tower comprises a vertical row of desulfurization reactors, an air intake pipe network, an exhaust pipe network and a regeneration liquid circulation system; The vertical row of desulfurization reactors comprises a tower support structure, and the plurality of desulfurization reactors are distributed on the tower support structure; The air intake pipe network comprises a vertically arranged air intake main pipe and air intake branch pipes respectively connecting the air intake main pipe to the air intake ports of the desulfurization reactors; The exhaust pipe network comprises a vertically arranged exhaust main pipe and exhaust branch pipes respectively connecting the exhaust main pipe to the exhaust ports of the desulfurization reactors; A regeneration liquid circulation system, wherein the regeneration liquid circulation system comprises at least one regeneration liquid tank and a regeneration liquid circulation control pipeline network connected between the at least one regeneration liquid tank and each desulfurization reactor, wherein the regeneration liquid circulation control pipeline network comprises an output side control pipeline network, an input side control pipeline network and a regeneration liquid driving device, wherein the output side control pipeline network can introduce the regeneration liquid in the selected regeneration liquid tank into the regeneration liquid spraying device of the selected desulfurization reactor, and the input side control pipeline network can introduce the regeneration liquid output from the discharge port of the selected desulfurization reactor into the selected regeneration liquid tank, and the regeneration liquid driving device can provide the required power to the regeneration liquid.

10. The ionic liquid coupled catalytic flue gas desulfurization system according to claim 1, characterized in that: The flue gas to be desulfurized comes from a coal-fired generator using high-sulfur coal.

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