CN109939531A - A method and device for simultaneously removing SO2 and NOx by using ionic liquid - Google Patents

Abstract

The invention belongs to the technical field of coal _- fired flue gas purification, and discloses a method and a device for simultaneously removing SO2 and _NOx by utilizing ionic liquid. The method comprises the following steps: S1 flue gas passes through a condenser and a first compressor for condensation and pretreatment; SO ₂ and NO _x in the gas can be absorbed and separated at the same time, and the purified flue gas is discharged to S3 to release the pressure of the rich liquid that absorbs SO ₂ and NO _x , and then complete the analysis of the absorbent, and send it to the absorption tower for reuse. The invention also discloses a corresponding device. The invention utilizes the ionic liquid to realize the integrated and effective removal of SO ₂ and NO _x in the coal-fired flue gas under specific conditions. Small, compact, cost-effective and reusable absorbent.

Description

A method and device for simultaneously removing SO2 and NOx by using ionic liquid

technical field

The invention belongs to the technical field of coal _- fired flue gas purification, and more particularly, relates to a method and a device for simultaneously removing SO2 and NOx by utilizing ionic liquid.

Background technique

The flue gas produced by coal combustion contains acid gases such as sulfur oxides (SO _x and NO _x ) and nitrogen oxides (NO _x ). major source of human health. At present, researchers have been continuously working on developing various high-efficiency and low-emission control technologies for SO2 and NOx in coal-fired flue gas, but most of them focus on single pollutant control technologies. The removal of SO ₂ in the flue gas mainly adopts the relatively mature wet flue gas desulfurization technology, and the removal of NOx mainly adopts the selective catalytic reduction technology (SCR) and low NOx combustion technology, but these technologies are complicated in process and high in cost. At the same time, the boiler efficiency is significantly reduced. Among the existing flue gas purification technologies at home and abroad, the desulfurization and denitrification processes that have been industrially applied are basically independent operating systems. In terms of combined desulfurization and denitrification, the desulfurization and denitrification devices are simply connected in series to integrate desulfurization and denitrification. There are fewer denitrification methods. The use of the same process to achieve integrated and coordinated removal of multiple pollutants is a highly competitive coal-fired flue gas purification technology, which has many advantages such as small footprint, compact structure, low investment, economical and environmental protection, and so on.

Ionic liquids have excellent characteristics such as extremely low vapor pressure, good chemical and thermal stability, adjustable structure, and reuse. They are green flue gas purification absorbents. _A large number of studies have shown that ionic liquids have good selectivity and high absorption capacity for SO2 absorption, and this research has been partially applied in pilot scale. Compared with the absorption and separation of SO ₂ , there are few studies on the removal of NO _x from flue gas using ionic liquids. Therefore, there is an urgent need in the art to propose a method for simultaneously removing SO ₂ and NO _x by using ionic liquid, so as to realize the integrated and effective removal of SO ₂ and NO _x in coal-fired flue gas.

SUMMARY OF THE INVENTION

In view of the above defects or improvement needs of the prior art, the present invention provides a method and device for simultaneously removing SO ₂ and NO _x by using ionic liquid, the purpose of which is to realize the integration of SO ₂ and NO _x in coal-fired flue gas effective removal.

In order to achieve the above object, according to one aspect of the present invention, a method for simultaneously removing _SO and NO using ionic liquid _is provided, comprising the steps of:

S1 performs condensation and pressurization pretreatment on the flue gas at the tail of the boiler, and part of the NO _x in the flue gas is oxidized by O ₂ at the condensation temperature and pressure;

S2 performs secondary pressurization treatment on the flue gas in step S1, and then enters the absorption tower loaded with absorbent, the acid gas SO ₂ in the flue gas and the oxidized NO _x are absorbed and separated at the same time, and the purified flue gas is discharged;

S3 feeds the absorbent that has absorbed SO ₂ and NO _x into the desorption tower for pressure release, and completes the desorption of the absorbent under heating conditions. The desorbed absorbent can be sent to the absorption tower for reuse. The enriched SO ₂ and _NOx gas can be utilized as a chemical raw material.

Further, the absorbent is an ionic liquid, and the ionic liquid can be selected from conventional ionic liquids or functional ionic liquids.

Further, the anion of the ionic liquid is one or more of nitrate anion, acetate anion, thiocyanate anion, diazolium anion or tetrazolium anion.

Further, the concentration of the ionic liquid is 40wt% to 100wt%, preferably, the concentration of the ionic liquid is 70wt%.

Further, in step S1, the temperature of the condensation is 30°C to 50°C, preferably, the optimum temperature of the condensation is 40°C.

Further, in step S1, the pressure of the pressurized pretreatment is 4 bar to 10 bar, and preferably, the pressure of the pressurized pretreatment is 7 bar.

Further, in step S2, the pressure of the secondary boosting treatment is 10 bar to 30 bar, and preferably, the pressure of the secondary boosting treatment is 20 bar.

According to another aspect of the present invention, there is provided a device for realizing the method for simultaneously removing SO ₂ and NO _x by using ionic liquid, the device comprises an absorption tower and a desorption tower, and the two are circulated through a heat exchanger connection; where,

The absorption tower is communicated with the analysis tower through a rich liquid pump and a heat exchanger, so that the rich liquid after absorbing SO ₂ and NO _x flows from the absorption tower to the analysis tower;

The analysis tower is communicated with the absorption tower through a lean liquid pump and a heat exchanger, so that the ionic liquid can be recycled from the analysis tower to the absorption tower for reuse.

Further, a first compressor and a second compressor are arranged between the absorption tower and the flue gas pipeline at the tail of the boiler, wherein the first compressor is used for pressurizing the flue gas at the tail of the boiler, and the The second compressor is used to secondary pressurize the flue gas before it enters the absorption tower.

Further, a stirrer is provided inside the absorption tower, and a back pressure valve is also provided on one side of the absorption tower.

In general, compared with the prior art, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

1. The method of the present invention utilizes ionic liquids to realize the integrated and effective removal of SO ₂ and NO _x in coal-fired flue gas under specific conditions.

2. In the method of the present invention, the whole process makes full use of the conditions of compression and condensation of pressurized air and pressurized oxygen-enriched combustion power plants and the oxidizing atmosphere existing in the flue gas. Before entering the absorption tower, a large amount of NO gas is oxidized to NO ₂ by O ₂ in the flue gas, and then SO ₂ in the flue gas and the oxidized NO ₂ are dissolved in the ionic liquid absorbent to achieve the effect of synergistic removal, and in the release The absorbent can be regenerated after autoclaving.

3. The method of the present invention, wherein the simultaneous removal efficiencies of SO ₂ and NO _x are 98% and 93%, respectively, which has the advantages of economical efficiency and reusability.

4. In the method of the present invention, the ionic liquid directly participates in the main reaction liquid of the absorption reaction, and simultaneously absorbs SO ₂ and NO _x in the coal-fired flue gas, without the need for additional catalysts.

5. In the method of the present invention, the original flue gas is compressed to 10-30 bar by a compressor, the pressure after the pressurization is regulated by the back pressure valve at the outlet of the absorption tower reactor, and the O ₂ in the compressed flue gas is used for NO oxidation.

6. The method of the present invention makes full use of the conditions of compression and condensation in the power plant and the oxidizing atmosphere in the flue gas in the whole process, and has the advantages of small footprint, compact structure, economical efficiency and reusable absorbent.

Description of drawings

1 is a schematic flowchart of a method for simultaneously removing SO ₂ and NO _x by utilizing an ionic liquid according to an embodiment of the present invention;

2 is a schematic diagram of a dynamic high-pressure reaction device involved in a method for simultaneously removing SO ₂ and NO _x by utilizing an ionic liquid according to an embodiment of the present invention;

Fig. 3 is the individual denitration curve of ionic liquid according to the embodiment of the present invention;

Fig. 4 is the _NOx outlet concentration curve of ionic liquid synergistic desulfurization and denitrification according to the embodiment of the present invention;

Fig. 5 is the outlet concentration curve of SO ₂ in the collaborative desulfurization and denitration of ionic liquid according to the embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as there is no conflict with each other.

FIG. 2 is a schematic diagram of a dynamic high-pressure reaction device involved in a method for simultaneously removing SO ₂ and NO _x by using an ionic liquid according to an embodiment of the present invention. The device includes an absorption tower and a desorption tower, which are cyclically connected through a heat exchanger, wherein the absorption tower is communicated with the desorption tower through a rich liquid pump and a heat exchanger, so that the rich liquid after absorbing SO ₂ and NO _x can be removed from the absorption tower. The tower flows to the analysis tower; at the same time, the analysis tower is connected with the absorption tower through the lean liquid pump and heat exchanger, which is convenient for the ionic liquid to flow back from the analysis tower to the absorption tower for reuse. In addition, a first compressor and a second compressor are arranged between the absorption tower and the flue gas pipeline at the tail of the boiler, wherein the first compressor is used for pressurizing the flue gas at the tail of the boiler, and the second compressor is used for the flue gas The gas is pressurized a second time before entering the absorption tower. There is a stirrer inside the absorption tower, which is convenient for stirring the absorbent (such as ionic liquid), so that the SO ₂ and NO _x in the flue gas can be fully absorbed. There is a back pressure valve on one side of the absorption tower, which is used to discharge the purified flue gas after absorbing SO ₂ and NO _x . The desorption tower is lined with polytetrafluoroethylene, and the rich liquid is transported to the desorption tower through the heat exchanger to release the pressure, and the desorption of the absorbent is completed under heating conditions. The decomposed absorbent can be sent to the absorption tower for reuse, while The enriched SO ₂ and NO _x gases after analysis can be used as chemical raw materials for subsequent use.

As shown in FIG. 1 , an embodiment of the present invention provides a method for simultaneously removing SO ₂ and NO _x by using an ionic liquid, including the following steps:

(1) The first-stage flue gas pretreatment: the boiler tail flue gas is condensed and pressurized through the condenser and the first compressor, and part of the NO in the flue gas is oxidized to NO ₂ by O ₂ under the condensation temperature and pressure;

(2) Simultaneous desulfurization and denitrification in the second stage: the flue gas is pressurized twice by the second compressor before entering the absorption tower; then it enters the absorption tower reactor loaded with absorbent, and the acid gas SO ₂ in the flue gas is oxidized and oxidized The NO ₂ can be absorbed and separated at the same time, and the purified flue gas is discharged;

(3) The regeneration of the absorption liquid in the third stage: the rich liquid is transported through the heat exchanger to the decompression tower lined with PTFE for pressure release, and the desorption of the absorbent is completed under heating conditions, and the decomposed absorbent can be sent into The absorption tower is reused, and the SO ₂ and NO _x gas enriched after analysis can be used as chemical raw materials for subsequent use.

Preferably, in the above step (1), the pretreatment conditions are a condensation temperature of 30-50° C. and a pressure of 4-10 bar.

Preferably, in the above step (2), the secondary pressurization reaches a pressure of 10-30 bar; the pressure after the pressurization is regulated by the back pressure valve at the outlet of the absorption tower reactor. In the method of the present invention, the original flue gas is compressed to 10-30 bar by a compressor, the pressure after supercharging is regulated by the back pressure valve at the outlet of the absorption tower reactor, and the O ₂ in the compressed flue gas is used for NO oxidation.

Preferably, in the above step (2), the absorbent is an ionic liquid, and the ionic liquid can be selected from conventional and functional ionic liquids, wherein the anions can be selected from nitrate anions [NO ₃ ], acetate anions [AC], Thiocyanate anion [SCN], diazonium anion [IM], tetrazolium anion, etc.; or a mixed solution of the above ionic liquid and water, and the ionic liquid concentration is 40wt% to 100wt%. In the method of the present invention, the ionic liquid directly participates in the main reaction liquid of the absorption reaction, and simultaneously absorbs SO ₂ and NO _x in the coal-fired flue gas, without the need for additional catalysts.

Preferably, in the above step (3), the pressure release process means that the pressure is gradually reduced to 1 bar.

The whole process makes full use of the conditions of compression and condensation of pressurized air and pressurized oxygen-enriched combustion power plants and the oxidizing atmosphere in the flue gas. NO gas is oxidized to NO ₂ by O ₂ in the flue gas, then SO ₂ in the flue gas and the oxidized NO ₂ are dissolved in the ionic liquid absorbent to achieve a synergistic removal effect, and the absorbent can be regenerated after the pressure is released and heated . The method can effectively realize the integration of desulfurization and denitrification of coal-fired flue gas, wherein the simultaneous removal efficiencies of SO ₂ and NO _x are 98% and 93%, respectively, and have the advantages of economical efficiency and reusability.

Example 1

The removal performance experiment of ionic liquid for _NOx in simulated flue gas was carried out on a dynamic high pressure reaction device, including simulated flue gas pretreatment system, reactor main body and flue gas online detection system, as shown in Figure 1. In the NO removal experiment, the initial concentration of O ₂ in the simulated flue gas was controlled at about 5.5%, and the initial concentration of NO was controlled at about 1000 ppm. The selected absorbent is ionic liquid [C ₄ mim][AC]. The outlet concentration curve of NO _x at 1.0 MPa is shown in Figure 3, and the removal efficiency is about 84%.

Example 2

_The synergistic removal performance experiment of ionic liquid for SO2 and _NOx in simulated flue gas was carried out on a dynamic high pressure reaction device, including simulated flue gas pretreatment system, reactor main body and flue gas online detection system, as shown in Fig. 1. In the experiment of simultaneous removal of NO and SO ₂ by ionic liquids, the initial concentration of O ₂ was controlled at around 5.5%, and the initial concentrations of NO and SO ₂ were controlled at around 1000 ppm and 1500 ppm, respectively. The selected absorbent is ionic liquid [C ₄ mim][AC]. The outlet concentration curves of each component gas at 1.0 MPa are shown in Figures 4 and 5. The simultaneous removal efficiencies of SO ₂ and NO _x are 98%, respectively. % and around 93%.

Example 3

The flue gas at the tail of the boiler is condensed and pretreated by pressure, and part of the _NOx in the flue gas is oxidized by O ₂ under the condensation temperature and pressure; The flue gas is subjected to secondary pressurization treatment, and then enters the absorption tower loaded with ionic liquid, the acid gas SO ₂ and oxidized NO _x in the flue gas are absorbed and separated at the same time, and the purified flue gas is discharged; The anion in the solution is thiocyanate anion, the concentration of the ionic liquid is 40 wt %, and the pressure of the secondary pressurization treatment is 10 bar.

The absorbent that has absorbed SO ₂ and NO _x is fed into the desorption tower for pressure release, and the desorption of the absorbent is completed under heating conditions. The desorbed absorbent can be sent to the absorption tower for reuse, and the enriched SO ₂ and NO after desorption _X gas can be used as a chemical raw material.

Example 4

The flue gas at the tail of the boiler is condensed and pretreated by pressure, and part of the _NOx in the flue gas is oxidized by O ₂ under the condensation temperature and pressure; the temperature of the condensation is 40°C, and the pressure of the pretreatment is 7bar The flue gas is subjected to secondary pressurization treatment, and then enters the absorption tower loaded with ionic liquid, the acid gas SO ₂ and oxidized NO _x in the flue gas are absorbed and separated at the same time, and the purified flue gas is discharged; The anion in the solution is diazolium anion, the concentration of the ionic liquid is 70 wt %, and the pressure of the second pressurization treatment is 20 bar.

The absorbent that has absorbed SO ₂ and NO _x is fed into the desorption tower for pressure release, and the desorption of the absorbent is completed under heating conditions. The desorbed absorbent can be sent to the absorption tower for reuse, and the enriched SO ₂ and NO after desorption _X gas can be used as a chemical raw material.

Example 5

The flue gas at the tail of the boiler is condensed and pretreated by pressure, and part of the _NOx in the flue gas is oxidized by O ₂ under the condensation temperature and pressure; The flue gas is subjected to secondary pressurization treatment, and then enters the absorption tower loaded with ionic liquid, the acid gas SO ₂ and oxidized NO _x in the flue gas are absorbed and separated at the same time, and the purified flue gas is discharged; The anion in the solution is diazolium anion, the concentration of the ionic liquid is 100 wt %, and the pressure of the secondary pressurization treatment is 30 bar.

The absorbent that has absorbed SO ₂ and NO _x is fed into the desorption tower for pressure release, and the desorption of the absorbent is completed under heating conditions. The desorbed absorbent can be sent to the absorption tower for reuse, and the enriched SO ₂ and NO after desorption _X gas can be used as a chemical raw material.

Those skilled in the art can easily understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (10)

_1. a method of utilizing ionic liquid to remove SO and NO simultaneously, _is characterized in that, comprises the steps: S1 performs condensation and pressurization pretreatment on the flue gas at the tail of the boiler, and part of the NO _x in the flue gas is oxidized by O ₂ at the condensation temperature and pressure; S2 performs secondary pressurization treatment on the flue gas in step S1, and then enters the absorption tower loaded with absorbent, the acid gas SO ₂ in the flue gas and the oxidized NO _x are absorbed and separated at the same time, and the purified flue gas is discharged; S3 feeds the absorbent that has absorbed SO ₂ and NO _x into the desorption tower for pressure release, and completes the desorption of the absorbent under heating conditions. The desorbed absorbent can be sent to the absorption tower for reuse. The enriched SO ₂ and _NOx gas can be utilized as a chemical raw material. 2. a kind of method that utilizes ionic liquid to simultaneously remove SO and NO according to claim ₁ , _is characterized in that, described absorbent is ionic liquid, and this ionic liquid can select conventional type or functional type ionic liquid . 3. a kind of method that utilizes ionic liquid to simultaneously remove SO ₂ and NO according to claim 2, _is characterized in that, the anion of described ionic liquid is nitrate anion, acetate anion, thiocyanate anion, two One or more of azole anions or tetrazolium anions. 4 . The method for simultaneously removing SO ₂ and NO _x by utilizing ionic liquid according to claim 2 or 3, wherein the concentration of the ionic liquid is 40wt% to 100wt%, preferably, the ionic liquid The concentration of the liquid was 70 wt%. 5 . The method for simultaneously removing SO ₂ and NO _x by utilizing ionic liquid according to claim 1 , wherein in step S1 , the temperature of the condensation is 30° C. to 50° C., and preferably, the The optimum temperature for condensation is 40°C. 6 . The method for simultaneously removing SO ₂ and NO _x by utilizing ionic liquid according to claim 1, wherein in step S1, the pressure of the pressurized pretreatment is 4bar～10bar, preferably, the The pressure of the pressurized pretreatment was 7 bar. 7 . The method for simultaneously removing SO ₂ and NO _x by utilizing ionic liquid according to claim 1, characterized in that, in step S2, the pressure of the secondary pressurization treatment is 10bar～30bar, preferably, The pressure of the secondary boosting process was 20 bar. 8. a device for realizing the method for simultaneously removing SO with ionic liquid as claimed in any one of claims 1-7, it _is characterized in that, this device comprises absorption tower and desorption tower, _two or through a heat exchanger to achieve cyclic connection; among them, The absorption tower is communicated with the analysis tower through a rich liquid pump and a heat exchanger, so that the rich liquid after absorbing SO ₂ and NO _x flows from the absorption tower to the analysis tower; The analysis tower is communicated with the absorption tower through a lean liquid pump and a heat exchanger, so that the ionic liquid can be recycled from the analysis tower to the absorption tower for reuse. 9 . The device according to claim 8 , wherein a first compressor and a second compressor are arranged between the absorption tower and the flue gas pipeline at the tail of the boiler, wherein the first compressor uses For pressurizing pretreatment of the flue gas at the tail of the boiler, the second compressor is used for secondary pressurizing the flue gas before entering the absorption tower. 10 . The device according to claim 8 or 9 , wherein a stirrer is provided inside the absorption tower, and a back pressure valve is also provided on one side of the absorption tower. 11 .