A device and method for multi-stage venturi injection enhanced flue gas desulfurization

Abstract

The present invention provides a device and method for multi-stage venturi injection enhanced flue gas desulfurization, the device comprises an absorption tower body and a reverse injection tower connected to the absorption tower body at the lower end, a tail gas inlet is arranged at the upper part of the reverse injection tower, a tail gas outlet is arranged at the top of the absorption tower body, a liquid distributor and a multi-stage venturi injector are arranged in the reverse injection tower; the sulfur-containing tail gas enters the reverse injection tower and reacts and absorbs with droplets of different sizes injected by the first, second and third stage venturi injectors respectively, and part of the tail gas enters the venturi injectors of each stage through negative pressure self-absorption to form a self-circulation of the tail gas; the tail gas after the reaction enters the absorption tower body and is discharged. The flow field in the reverse injection tower is highly turbulent, the gas-liquid interweaving degree is high, the liquid column and the droplets injected by the three-stage injection collide in the process of falling and dispersing, and a new gas-liquid contact surface is continuously generated to enhance mass transfer; at the same time, the tail gas in the negative pressure self-absorption tower of the venturi injector is absorbed by the tail gas for multiple cycles, which greatly increases the tail gas absorption efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of flue gas desulfurization, and in particular relates to a device and method for multi-stage venturi injection enhanced flue gas desulfurization. Background Art

[0002] SO2 is one of the most common pollutants in the atmosphere. With the continuous development of industry, the emission of SO2 is also increasing. The large-scale emission of sulfur dioxide gas has led to the intensification of acid rain, which not only has a serious impact on the natural environment, but also has a direct impact on human health. If it cannot be effectively treated, it will aggravate the acidification of soil and water, destroy the ecological balance, and affect biodiversity.

[0003] With the enhancement of environmental awareness and the popularization of environmental protection laws and regulations, most sulfuric acid enterprises in my country have increased their investment in sulfuric acid tail gas treatment. Liquid column desulfurization tower has become the focus of attention due to its advantages of sufficient gas-liquid mass transfer and high desulfurization efficiency. However, in actual industrial production, there are still problems such as insufficient absorption efficiency of liquid column alkali washing tower, inability to discharge directly, and high alkali consumption.

[0004] CN202983508U discloses a multi-stage and multi-scale injection device for a liquid column tower, the process feature of which is that injection nozzles of different models and heights are arranged in the absorption tower, and multiple layers of dense droplets with increasing particle size are formed in the tower space in turn. Although the desulfurization efficiency of this technology is improved, the flue gas absorbed by this technology has a high mist content at the outlet, which increases the load of the subsequent demister and has little positive effect on energy saving and consumption reduction.

[0005] CN108579396A discloses a device and method for flue gas desulfurization, which includes an absorption tower body; a flue gas inlet is provided at the lower part of the absorption tower body, and a flue gas outlet is provided at the top; a slurry circulation device, a liquid column injection device, a high-efficiency atomization spray device and a demisting device are arranged in sequence from bottom to top; the liquid column injection device is arranged above the flue gas inlet, and includes a plurality of liquid column injection branches, the bottom end of each liquid column injection branch is connected to the slurry circulation device, and a liquid column injection nozzle is provided at the top; although this method has the characteristics of high desulfurization efficiency, its absorption liquid amount increases. In actual industry, the absorption liquid cost accounts for a large proportion of the liquid column tower, so the economic efficiency of this method in actual industry is relatively low. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a device and method for enhancing flue gas desulfurization by multi-stage Venturi injection. By setting three Venturi injectors with different structures, droplets of different sizes are generated, so that the flow field in the tower is turbulent and the gas-liquid interweaving degree is high; at the same time, the Venturi air intake port can directly absorb the tail gas in the tower through negative pressure, so that the tail gas in the tower can be circulated and absorbed multiple times, greatly increasing the tail gas absorption efficiency.

[0007] The present invention is achieved through the following technical solutions:

[0008] A device for enhancing flue gas desulfurization with multi-stage venturi injection, the device for enhancing flue gas desulfurization comprises an absorption tower body and a reverse injection tower whose lower end is connected to the side wall of the absorption tower body, the upper part of the reverse injection tower is provided with a tail gas inlet, the top of the absorption tower body is provided with a tail gas outlet, and the bottom end of the absorption tower body is used to store absorption liquid; in the reverse injection tower, a liquid distributor and a multi-stage venturi injector whose lower end is connected to the liquid distributor are installed below the tail gas inlet, the multi-stage venturi injector comprises a primary, secondary and tertiary venturi injectors for generating liquid columns of different heights and droplet sizes, the liquid inlet of the liquid distributor is connected to the bottom end of the absorption tower body through a circulation pipeline, and is used to transport the absorption liquid stored in the absorption tower body to the liquid distributor for distribution, and then spray droplets through the multi-stage venturi injector into the reverse injection tower to react and absorb with the tail gas, and a water pump is provided on the circulation pipeline.

[0009] The present invention is further configured such that the first-stage, second-stage and third-stage Venturi ejectors of the multi-stage Venturi ejector are three different structures of Venturi ejector devices, namely, high-spray column, middle-spray column and low-spray column Venturi ejector devices. The Venturi ejector devices each include a Venturi liquid inlet at the lower end and a Venturi liquid outlet at the upper end, and a self-priming air inlet is arranged on the side wall; the Venturi ejector device includes a water inlet section, a mixing section and a water outlet section connected in sequence, and the water inlet section and the water outlet section are connected to the Venturi liquid inlet and the Venturi liquid outlet respectively; the mixing section is radially provided with a throat connected to the mixing section, and the throat is connected to the self-priming air inlet; wherein:

[0010] The high-spray Venturi injection device is used to produce tiny droplets. The lengths of the water inlet section and the water outlet section are adjusted to 2-5 cm according to demand, the length of the mixing section is 3-6 cm, the aspect ratio of the mixing section is 5-7, and the throat diameter of the throat is 1-2 mm; preferably, two throats are opened radially opposite to each other in the mixing section; the throat tapering angle α of the water inlet section and the throat expanding angle β of the water outlet section are 25°-30°.

[0011] The middle spray column Venturi injection device is used to produce small droplets. The lengths of the water inlet section and the water outlet section are adjusted to 2-4 cm according to demand, the length of the mixing section is 3-5 cm, the aspect ratio of the mixing section is 4-6, and the throat diameter of the throat is 3-4 mm; preferably, a throat is opened in the radial direction of the mixing section; the throat taper angle α of the water inlet section and the throat taper angle β of the water outlet section are 30°-35°.

[0012] The low-spray Venturi injection device is used to produce large droplets. The lengths of the water inlet section and the water outlet section are adjusted to 1-3 cm according to demand, the length of the mixing section is 2-4 cm, the aspect ratio of the mixing section is 2-4, and the throat diameter of the throat is 5-6 mm; preferably, a throat is opened in the radial direction of the mixing section; the throat tapering angle α of the water inlet section and the throat expanding angle β of the water outlet section are 35°-40°.

[0013] The present invention is further configured such that a demister is arranged inside the absorption tower body above the connection between the absorption tower body and the reverse spray tower, for allowing the gas absorbed by the reverse spray tower to enter the absorption tower body and then be discharged from the tail gas outlet after being defogged by the demister.

[0014] The present invention is further configured such that a liquid adding port is provided on the side wall of the absorption tower body for introducing the absorption liquid required for the reaction of the flue gas desulfurization device into the bottom of the absorption tower body; the liquid adding port is connected to a liquid adding port valve for controlling the feeding of the absorption liquid into the absorption tower body.

[0015] The present invention is further configured such that a spray device is provided at the top of the reverse spray tower for spraying small droplets to react with the exhaust gas just entering the reverse spray tower; the spray device is connected to an external spray liquid pipeline, or is connected to a spray liquid pipeline connected to the bottom end of the absorption tower body; preferably, the spray liquid pipeline is connected to the circulation pipeline, and the absorption liquid in the absorption tower body is used for spraying the top of the reverse spray tower, and a spray device valve is provided on the spray liquid pipeline for controlling the feed of the spray liquid.

[0016] The present invention is further configured such that a main tower liquid outlet valve and a venturi liquid inlet valve are sequentially provided on the circulation pipeline along the water flow direction. According to actual operation requirements, the main tower liquid outlet valve and the venturi liquid inlet valve are provided as one or more valves; a liquid flow meter is provided on the circulation pipeline, and a first pressure gauge and a second pressure gauge are sequentially provided along the water flow direction for monitoring the flow rate and pressure on the circulation pipeline; a discharge pipeline is connected to the circulation pipeline, and a discharge outlet valve is provided on the discharge pipeline for controlling the discharge of the absorption liquid in the absorption tower body.

[0017] The present invention is further configured such that the discharge pipeline is arranged between the main tower liquid outlet valve and the Venturi liquid inlet valve on the circulation pipeline, and is arranged between the first pressure gauge and the second pressure gauge, so that the first pressure gauge and the second pressure gauge are used to monitor the pressure of the liquid outlet section and the circulation section on the circulation pipeline respectively.

[0018] The present invention also provides a method for enhancing flue gas desulfurization using the flue gas desulfurization device, and the specific steps are as follows:

[0019] Tail gas containing sulfur dioxide enters the tower from the tail gas inlet of the reverse spray tower, and reacts and absorbs with droplets of different sizes ejected from the first, second and third stage venturi ejectors respectively; part of the tail gas after reaction in the reverse spray tower enters the venturi ejector from the self-priming air inlet of each stage of venturi ejectors through negative pressure self-priming, thereby realizing self-circulation of the tail gas in the reverse spray tower; part of the tail gas after reaction enters the absorption tower body from the lower part of the reverse spray tower, and is discharged through the tail gas outlet.

[0020] The present invention is further configured such that after the tail gas containing sulfur dioxide enters the reverse spray tower, it first reacts with the small droplets sprayed by the spray device at the top of the reverse spray tower; and then reacts and absorbs with the droplets sprayed by the first, second and third stage venturi ejectors respectively. Specifically, the spray device generates a large number of tiny droplets with a diameter of 50-100 μm, which are first preliminarily absorbed by the tail gas entering the reverse spray tower.

[0021] The present invention is further configured such that, taking the height of the liquid distributor as a reference, the injection height of the liquid column of the multi-stage Venturi injector is 0.5-3.5 m, wherein:

[0022] The gas-liquid ratio of the first-stage Venturi ejector is 8-10, the injection height of the liquid column is 2.0-3.5m, and the highest point of the liquid column injection produces droplets with a diameter range of 120-250μm. Since the droplets produced have a small particle size and a large mass transfer specific surface area, the desulfurization process can be enhanced after spray absorption;

[0023] The gas-liquid ratio of the secondary venturi ejector is 3-5, the injection height of the liquid column is 1.0-2.5m, and small droplets with a diameter of 300-550μm are generated at the highest point of the liquid column injection, and the main mass transfer process of desulfurization in the reverse injection tower is completed within this range;

[0024] The gas-liquid ratio of the three-stage Venturi ejector is 1-3, the injection height of the liquid column is 0.5-1.0m, and droplets with a diameter in the range of 1000-2500μm are generated at the highest point of the liquid column injection. The droplet size is large, and a large number of sheet droplets are generated during the falling process of the liquid column. These large droplets can capture the droplets entrained in the gas phase and reduce the mist content in the gas phase.

[0025] The present invention is further configured such that, in order to ensure that the absorption liquid smoothly enters the multi-stage venturi ejector and generates an injection liquid column in the height range, a certain pressure needs to be provided by the water pump. Specifically, the head of the water pump is set to be above 20m.

[0026] The present invention is further configured such that after the reacted gas enters the absorption tower body, it is defogged by the demister and then discharged from the tail gas outlet.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention provides a device and method for enhancing flue gas desulfurization by multi-stage venturi injection. In the reverse spray tower section of the device, three-stage venturi injectors with different structures fixed on a liquid distributor are arranged to generate liquid columns and droplet sizes of different heights, respectively, so that the flow field in the reverse spray tower is turbulent and the gas-liquid interweaving degree is high; the three-stage injected liquid columns and droplets collide during the falling and dispersing process, thereby continuously generating new gas-liquid contact surfaces and enhancing mass transfer; at the same time, the self-priming air inlet of the venturi injector can pass through the negative pressure self-priming tower tail gas, so that the tail gas in the tower can be circulated and absorbed multiple times, forming a self-circulation of the tail gas in the reverse spray tower, which can greatly increase the tail gas absorption efficiency. Due to the sufficient mass transfer in the above flue gas desulfurization method, the consumption of absorption liquid can be greatly reduced.

[0029] Compared with the common liquid column tower, the multi-stage Venturi injection device of the present invention can realize the multi-stage and multi-scale injection droplet circulation desulfurization effect, and has the advantages of high desulfurization efficiency, good desulfurization effect, and low absorption liquid consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the process flow of multi-stage Venturi injection enhanced flue gas desulfurization according to the present invention;

[0031] Figure 2 This is a schematic diagram of the multi-stage Venturi droplet spraying principle of the present invention;

[0032] Figure 3 It is a cross-sectional view of the reverse spray tower of the present invention along the AA plane;

[0033] Figure 4 It is a schematic diagram of the external structure of the Venturi ejector of the present invention;

[0034] Figure 5 is a cross-sectional view of the internal structure of the Venturi ejector of the present invention;

[0035] Figure 6 It is a schematic diagram of the process of the desulfurization process of the liquid column tower enhanced by adding an air guide coil according to the present invention;

[0036] Figure 7 This is a front view of the air guide coil described in the present invention;

[0037] Figure 8 A side view of the air guide coil according to the present invention;

[0038] Fig. 9 It is a front view of the throttling orifice plate of the present invention;

[0039] Fig.10 A side view of the throttling orifice plate of the present invention;

[0040] Among them, 1-absorption tower body; 2-reverse spray tower; 3-tail gas inlet; 4-tail gas outlet; 5-liquid distributor; 6-multi-stage Venturi ejector; 6-1 first-stage Venturi ejector; 6-2 second-stage Venturi ejector; 6-3 third-stage Venturi ejector; 6-4 Venturi liquid inlet; 6-5 Venturi liquid outlet; 6-6 self-priming air inlet; 6-7 water inlet section; 6-8 mixing section; 6-9 water outlet section; 6-10 throat; 7-circulation pipeline; 7-1 water pump; 7-2 main tower liquid outlet valve; 7-3 Venturi liquid inlet valve; 7-4 first pressure gauge; 7-5 second pressure gauge; 7-6 liquid flow meter; 8-spraying device; 9-demister; 10-liquid filling port; 10-1 liquid filling port valve; 11-liquid discharge pipeline; 11-1 Drain valve; 12-spray liquid pipeline; 12-1 spray device valve; 13-air guide coil; 13-1 air guide disc; 13-2 air guide pipe; 14-throttling orifice; 15-fan. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below in conjunction with examples. It should be understood that the following examples are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by professionals and technicians in this field based on the content of the present invention still belong to the scope of protection of the present invention. Example 1

[0042] A multi-stage venturi injection enhanced flue gas desulfurization device of the present invention, such as Figure 1 As shown, the device for enhancing flue gas desulfurization includes an absorption tower body 1 and a reverse spray tower 2 whose lower end is connected to the side wall of the absorption tower body 1, a tail gas inlet 3 is provided at the upper part of the reverse spray tower 2, a tail gas outlet 4 is provided at the top of the absorption tower body 1, and the bottom end of the absorption tower body 1 is used to store absorption liquid; a spray device 8 is provided at the top of the reverse spray tower 2 for spraying small droplets to react with the tail gas just entering the reverse spray tower 2; Figure 2-3As shown, in the reverse spray tower 2, a liquid distributor 5 and a multi-stage venturi injector 6 whose lower end is connected and fixed to the liquid distributor 5 are installed below the tail gas inlet 3, and the multi-stage venturi injector 6 includes a first-stage venturi injector 6-1, a second-stage venturi injector 6-2 and a third-stage venturi injector 6-3. The liquid inlet of the liquid distributor 5 is connected to the bottom end of the absorption tower body 1 through a circulation pipeline 7, which is used to transport the absorption liquid stored in the absorption tower body 1 to the liquid distributor 5 for distribution, and then spray droplets through the multi-stage venturi injector 6 into the reverse spray tower 2 for reaction and absorption with the tail gas. A water pump 7-1 is provided on the circulation pipeline 7; in the absorption tower body 1, a demister 9 is arranged above the connection between the absorption tower body 1 and the reverse spray tower 2, which is used to allow the gas after reaction and absorption in the reverse spray tower 2 to enter the absorption tower body 1, and then be defogged by the above-mentioned demister 9 and discharged from the tail gas outlet 4.

[0043] Furthermore, the first-stage, second-stage and third-stage Venturi injectors 6-1, 6-2 and 6-3 of the multi-stage Venturi injector 6 are three different structures of Venturi injectors, namely high spray column, middle spray column and low spray column Venturi injectors 6-1, 6-2 and 6-3, respectively, for generating liquid columns of different heights and droplet sizes, combined with Figure 4-5 As shown, the Venturi injection device includes a Venturi liquid inlet 6-4 at the lower end and a Venturi liquid outlet 6-5 at the upper end, and a self-priming air inlet 6-6 is arranged on the side wall; the Venturi injection device includes a water inlet section 6-7, a mixing section 6-8 and a water outlet section 6-9 which are connected in sequence, and the water inlet section 6-7 and the water outlet section 6-9 are connected to the Venturi liquid inlet 6-4 and the Venturi liquid outlet 6-5 respectively; the mixing section 6-8 is radially provided with a throat 6-10 connected to the mixing section 6-8, and the throat 6-10 is connected to the self-priming air inlet 6-6.

[0044] The high-spray Venturi injection device 6-1 is used to produce tiny droplets. The lengths of the water inlet section 6-7 and the water outlet section 6-9 are adjusted to 2-5 cm according to demand, the length of the mixing section 6-8 is 3-6 cm, the aspect ratio of the mixing section 6-8 is 5-7, and the throat diameter of the throat 6-10 is 1-2 mm; preferably, two throats 6-10 are opened radially opposite to each other in the mixing section 6-8 to increase the air intake, that is, to increase the amount of internal circulating gas, and at the same time increase the injection height; the throat tapering angle α of the water inlet section 6-7 and the throat tapering angle β of the water outlet section 6-9 are 25°-30°.

[0045] The middle spray column Venturi injection device 6-2 is used to produce small droplets. The lengths of the water inlet section 6-7 and the water outlet section 6-9 are adjusted to 2-4 cm according to demand, the length of the mixing section 6-8 is 3-5 cm, the aspect ratio of the mixing section 6-8 is 4-6, and the throat diameter of the throat 6-10 is 3-4 mm; preferably, a throat 6-10 is opened radially in the mixing section 6-8; the throat tapering angle α of the water inlet section 6-7 and the throat tapering angle β of the water outlet section 6-9 are 30°-35°.

[0046] The low-spray Venturi injection device 6-3 is used to produce large droplets. The lengths of the water inlet section 6-7 and the water outlet section 6-9 are adjusted to 1-3 cm according to demand, the length of the mixing section 6-8 is 2-4 cm, the aspect ratio of the mixing section 6-8 is 2-4, and the throat diameter of the throat 6-10 is 5-6 mm; preferably, a throat 6-10 is opened radially in the mixing section 6-8; the throat tapering angle α of the water inlet section 6-7 and the throat tapering angle β of the water outlet section 6-9 are 35°-40°.

[0047] Furthermore, one of the throats 6-10 of the high-spray column Venturi injection device 6-1 is arranged in the same direction as the throat 6-10 of the middle-spray column Venturi injection device 6-2 and the throat 6-10 of the low-spray column Venturi injection device 6-3.

[0048] Furthermore, a liquid adding port 10 is provided on the side wall of the absorption tower body 1 for introducing the absorption liquid required for the reaction of the flue gas desulfurization device into the bottom of the absorption tower body 1; the liquid adding port 10 is connected to a liquid adding port valve 10-1 for controlling the feeding of the absorption liquid into the absorption tower body 1.

[0049] Furthermore, the circulation pipeline 7 is provided with a main tower liquid outlet valve 7-2 and a venturi liquid inlet valve 7-3 in sequence along the water flow direction. According to actual operation requirements, the main tower liquid outlet valve 7-2 and the venturi liquid inlet valve 7-3 are set to one or more; the circulation pipeline 7 is provided with a liquid flow meter 7-6, and a first pressure gauge 7-4 and a second pressure gauge 7-5 are provided in sequence along the water flow direction, which are used to monitor the flow rate and pressure on the circulation pipeline 7; the circulation pipeline 7 is connected to a discharge pipeline 11, and the discharge pipeline 11 is provided with a discharge valve 11-1, which is used to control the discharge of the absorption liquid in the absorption tower body 1.

[0050] Preferably, the discharge pipeline 11 is arranged between the main tower liquid outlet valve 7-2 and the Venturi liquid inlet valve 7-3 on the circulation pipeline 7, and is arranged between the first pressure gauge 7-4 and the second pressure gauge 7-5, so that the first pressure gauge 7-4 and the second pressure gauge 7-5 are used to monitor the pressure of the liquid outlet section and the circulation section on the circulation pipeline 7, respectively.

[0051] Furthermore, the spray device 8 is connected to an external spray liquid pipeline, or is connected to a spray liquid pipeline 12 connected to the bottom end of the absorption tower body 1; preferably, the spray liquid pipeline 12 is connected to the circulation pipeline 7, and the absorption liquid in the absorption tower body 1 is used for spraying the top of the reverse spray tower 2, and a spray device valve 12-1 is provided on the spray liquid pipeline 12 for controlling the feed of the spray liquid.

[0052] The process of strengthening flue gas desulfurization by using the flue gas desulfurization device all occurs in the reverse spray tower 2. The method of strengthening flue gas desulfurization is specifically described as follows:

[0053] The tail gas containing sulfur dioxide enters the tower from the tail gas inlet 3 of the reverse spray tower 2, and first reacts with the small droplets sprayed from the spray device 8 at the top of the reverse spray tower 2; then reacts and absorbs with the droplets sprayed from the first-stage, second-stage and third-stage venturi ejectors 6-1, 6-2 and 6-3 respectively; the reacted gas enters the absorption tower body 1 from the lower part of the reverse spray tower 2, and is discharged from the tail gas outlet 4 after passing through the demister 9.

[0054] Specifically, the multi-stage venturi ejector 6 generates droplets of different sizes by setting three levels of venturi ejectors with different structures fixed on the liquid distributor 5, so that the flow field in the reverse spray tower 2 is turbulent and the gas-liquid interweaving degree is high. By adjusting the liquid flow meter and pump pressure on the circulation pipeline 7, the height of the liquid column and the droplet size generated by the three venturi ejectors are controlled in conjunction with the different structures of the three-stage venturi ejectors; the three-stage ejected liquid column and droplets collide during the falling and dispersing process, thereby continuously generating new gas-liquid contact surfaces and strengthening mass transfer; at the same time, the self-priming air inlet 6-6 of the venturi ejector can pass through the negative pressure self-priming tower tail gas, which can make the tail gas in the tower circulate and absorb multiple times, and can greatly increase the tail gas absorption efficiency. Since this method has a relatively sufficient mass transfer, it can greatly reduce the consumption of absorption liquid.

[0055] Furthermore, the injection height of the liquid column of the multi-stage venturi injector 6 is 0.5-3.5m, and the injection height of the liquid column is based on the height of the venturi liquid outlet of the venturi injector, and the injection height is the height of the liquid column, wherein:

[0056] The gas-liquid ratio of the first-stage Venturi ejector 6-1 is 8-10, the injection height of the liquid column is 2.0-3.5m, and the highest point of the liquid column injection produces droplets with a diameter in the range of 120-250μm. Since the droplets produced have a small particle size and a large mass transfer specific surface area, the desulfurization process can be enhanced after spray absorption;

[0057] The gas-liquid ratio of the secondary venturi ejector 6-2 is 3-5, the injection height of the liquid column is 1.0-2.5m, and the highest point of the liquid column injection produces small droplets with a diameter in the range of 300-550μm, within which the main mass transfer process of desulfurization in the reverse spray tower 2 is completed;

[0058] The gas-liquid ratio of the three-stage Venturi injector 6-3 is 1-3, the injection height of the liquid column is 0.5-1.0m, and the highest point of the liquid column injection produces droplets with a diameter range of 1000-2500μm. The droplet size is large, and a large number of sheet droplets are generated during the falling process of the liquid column. These large droplets can capture the droplets entrained in the gas phase and reduce the mist content in the gas phase.

[0059] Furthermore, the spray device 8 generates a large number of tiny droplets with a diameter of 50-100 μm, which are first preliminarily absorbed by the tail gas entering the reverse spray tower 2 .

[0060] Furthermore, in order to ensure that the absorption liquid smoothly enters the multi-stage Venturi ejector 6 and generates an injection liquid column in the height range, a certain pressure needs to be provided by the water pump 7-1. Specifically, the head of the water pump 7-1 is set to be above 20m. Example 2

[0061] The flue gas desulfurization device and method described in Example 1 were used to treat the SO2 concentration of about 1500 mg / m 3 The sulfur-containing flue gas, the inlet flue gas flow rate is 50000 m 3 / h, wherein the specific structure and parameters of the flue gas desulfurization device are set as follows:

[0062] The absorbent is sodium hydroxide; the head of the water pump is set to 20m;

[0063] The length of the water inlet section and the water outlet section of the high-spray venturi injection device is 5 cm; the length of the mixing section is 5 cm, and the aspect ratio is 6; the throat diameter of the throat is 2 mm; the throat taper angle α of the water inlet section is 25°, and the throat taper angle β of the water outlet section is 25°;

[0064] The length of the water inlet section and the water outlet section of the middle spray column Venturi injection device is 4 cm; the length of the mixing section is 5 cm, the aspect ratio is 5, and the throat diameter of the throat is 3 mm; the throat taper angle α of the water inlet section is 30°, and the throat taper angle β of the water outlet section is 30°;

[0065] The lengths of the water inlet section and the water outlet section of the low-spray venturi injection device are 2 cm; the length of the mixing section is 3 cm, the aspect ratio is 2-4, and the throat diameter of the throat is 5-6 mm; the throat taper angle α of the water inlet section is 35°, and the throat divergence angle β of the water outlet section is 35°.

[0066] After several days of stable operation, the SO2 concentration and alkali consumption discharged from the exhaust gas outlet were tested, and the results are shown in the following table.

[0067]

[0068] Comparative Example 1

[0069] Taking the flue gas treatment device of a chemical plant in Nanjing as a comparative example, the same exhaust flue gas was treated at the same inlet flow rate as in Example 2. Its tail gas treatment system included a tail gas absorption tower, a water washing tower, a two-stage electrostatic precipitator and other equipment. Its tail gas absorption tower was a traditional liquid column tower, which adopted a traditional nozzle injection method.

[0070] After several days of stable operation, the SO2 concentration and alkali consumption discharged from the exhaust gas outlet were tested, and the results are shown in the following table.

[0071]

[0072] It can be seen from the above table that under the condition of almost the same SO2 inlet concentration, the SO2 concentration at the outlet of Example 2 is lower than that of Comparative Example 1, the absorption efficiency is significantly higher than that of Comparative Example 1, and its alkali consumption is also lower than that of Comparative Example 1. At the same time, the concentration of Comparative Example 1 can only reach the standard after passing through the secondary water washing tower, which is not higher than 200 mg / m 3 Therefore, the cost of SO2 tail gas absorption and treatment using Example 2 in actual production will be significantly lower.

[0073] Comparative Example 2

[0074] The flue gas desulfurization device and method described in Example 2 were used to treat sulfur-containing flue gas, and the same inlet flow rate as in Example 2 was used, except that the injector used for liquid column injection was not a Venturi injector, but a traditional liquid column nozzle of the same specification. After several days of stable operation, the SO2 concentration and alkali consumption discharged from the tail gas outlet were detected, and the results are shown in the following table.

[0075]

[0076] It can be seen from the above table that under the condition of almost the same SO2 inlet concentration, the SO2 concentration at the outlet of Example 2 is lower than that of Comparative Example 2, the absorption efficiency is significantly higher than that of Comparative Example 2, and its alkali consumption is also lower than that of Comparative Example 2. Therefore, the cost of SO2 tail gas absorption treatment using Example 2 in actual production will be significantly lower. Example 3

[0077] On the basis of Example 1, a device for strengthening the desulfurization of the liquid column tower by adding an air guide coil is further provided, such as Figure 6 As shown, the exhaust gas inlet 3 is connected to a fan 15 for blowing in the exhaust gas; the lower end of the reverse spray tower 2 is provided with an air guide coil 13, combined with Figure 7-8As shown, the air guide coil 13 includes an air guide disc 13-1 and a plurality of air guide pipes 13-2 connected to the air guide disc 13-1. The four sides of the air guide disc 13-1 are fixedly connected to the inner wall of the reverse spray tower 2. The air guide pipes 13-2 are immersed in the absorption liquid at the bottom of the absorption tower body 1, and are used to pass the gas absorbed by the liquid column reaction into the absorption liquid at the bottom of the absorption tower body 1 for aeration, so as to perform secondary enhanced reaction absorption; combined with Figure 9-10 As shown, a throttling orifice plate 14 is arranged below the demister 9 in the absorption tower body 1, which is used to increase the speed of the gas absorbed by the aeration reaction to an optimal demister speed range through the throttling orifice plate 14, and then discharge it from the tail gas outlet 4 after demistering by the demister 9.

[0078] Furthermore, the air guide plate 13 - 1 is vertically connected to the inner wall of the reverse spray tower 2 , and the air guide pipe 13 - 2 is immersed in the lower part of the absorption liquid at the bottom of the absorption tower body 1 .

[0079] Furthermore, the air guide coil 13 is made of PVC material, and the number and diameter of the air guide pipes 13-2 are adjusted according to the flue gas treatment capacity of the liquid column tower, wherein the diameter of the air guide pipes 13-2 is generally set to 1-5cm, and the number is adjusted according to the size of the air guide disc 13-2.

[0080] Furthermore, the throttling orifice plate 14 is made of polypropylene, the thickness of the orifice plate 14 is 3-5 cm, and the opening diameter ranges from 0.1-1.5 mm, which can be adjusted accordingly according to different demisters used.

[0081] The tail gas containing sulfur dioxide enters the tower from the tail gas inlet 3 of the reverse spray tower 2 through the fan 15, and first reacts with the small droplets sprayed from the spray device 8 at the top of the reverse spray tower 2; then reacts and absorbs with the droplets sprayed from the first-stage, second-stage and third-stage Venturi ejectors 6-1, 6-2 and 6-3 respectively; the reacted gas is passed from the air guide coil 13 at the bottom of the reverse spray tower 2 to the absorption liquid in the absorption tower body 1 under the pressure of the fan 15 to be aerated and undergo secondary reaction and absorption, while the absorption liquid in the reverse spray tower 2 is circulated to the absorption tower body 1 through the air guide coil 13; the reacted gas is accelerated by the throttling orifice plate 14 and then flows through the demister 9 to achieve the best demisting effect; the demisted gas is discharged from the tail gas outlet 4. Since this method allows the sulfur-containing tail gas to be absorbed by liquid column injection and then subjected to secondary aeration absorption, the desulfurization efficiency can be greatly improved; at the same time, the installation of a throttling orifice plate increases the gas flow rate, making the outlet gas mist content lower.

[0082] Furthermore, the gas flow rate after aeration through the air guide coil 13 is 0.5-1.0 m / s, and the gas flow rate increases to 2-4 m / s after passing through the throttling orifice plate 14, reaching the optimal demisting flow rate range.

[0083] This application is described in detail for the purpose of enabling those skilled in the art to understand the contents of this application and implement them. This is not intended to limit the scope of protection of this application. Any equivalent changes or modifications made according to the spirit of this application should be included in the scope of protection of this application.

Claims

1. A device for multi-stage venturi injection enhanced flue gas desulfurization, characterized in that: The device for enhancing flue gas desulfurization comprises an absorption tower body and a reverse spray tower whose lower end is connected to the side wall of the absorption tower body, wherein: The upper part of the reverse spray tower is provided with a tail gas inlet, the top of the absorption tower body is provided with a tail gas outlet, and the bottom end of the absorption tower body is used to store absorption liquid; In the reverse spray tower, a liquid distributor and a multi-stage venturi ejector in communication with the liquid distributor at the lower end are installed below the tail gas inlet, the multi-stage venturi ejector includes a first-stage, a second-stage and a third-stage venturi ejector for generating liquid columns of different heights and droplet sizes, the liquid inlet of the liquid distributor is in communication with the bottom end of the absorption tower body through a circulation pipeline, and a water pump is provided on the circulation pipeline; The first-stage, second-stage and third-stage Venturi injectors of the multi-stage Venturi injector are respectively high-spray column, middle-spray column and low-spray column Venturi injectors; the Venturi injectors all include a Venturi liquid inlet at the lower end and a Venturi liquid outlet at the upper end, a self-priming air inlet is arranged on the side wall, and the interior includes a water inlet section, a mixing section and a water outlet section which are connected in sequence, the water inlet section and the water outlet section are connected to the Venturi liquid inlet and the Venturi liquid outlet respectively, a throat connected to the mixing section is arranged radially of the mixing section, and the throat is connected to the self-priming air inlet; the high-spray column Venturi injector is used to produce tiny droplets, the middle-spray column Venturi injector is used to produce small droplets, and the low-spray column Venturi injector is used to produce large droplets.

2. The device for enhancing flue gas desulfurization according to claim 1, characterized in that: The lengths of the water inlet section and the water outlet section of the high-spray venturi injection device are 2-5 cm, the length of the mixing section is 3-6 cm, the aspect ratio of the mixing section is 5-7, two throats are radially opposite to each other in the mixing section, and the throat diameter of the throat is 1-2 mm; the throat tapering angle α of the water inlet section and the throat expanding angle β of the water outlet section are 25°-30°.

3. The device for enhancing flue gas desulfurization according to claim 1, characterized in that: The lengths of the water inlet section and the water outlet section of the middle spray column Venturi injection device are 2-4 cm, the length of the mixing section is 3-5 cm, the aspect ratio of the mixing section is 4-6, a throat is radially opened in the mixing section, and the throat diameter of the throat is 3-4 mm; the throat tapering angle α of the water inlet section and the throat expanding angle β of the water outlet section are 30°-35°.

4. The device for enhancing flue gas desulfurization according to claim 1, characterized in that: The lengths of the water inlet section and the water outlet section of the low-spray venturi injection device are 1-3 cm, the length of the mixing section is 2-4 cm, the aspect ratio of the mixing section is 2-4, a throat is radially provided in the mixing section, and the throat diameter of the throat is 5-6 mm; the throat tapering angle α of the water inlet section and the throat expanding angle β of the water outlet section are 35°-40°.

5. A method for enhancing flue gas desulfurization by multi-stage venturi injection using the device for enhancing flue gas desulfurization according to any one of claims 1 to 4, characterized in that: The specific steps are as follows: Tail gas containing sulfur dioxide enters the tower from the tail gas inlet of the reverse spray tower, and reacts and absorbs with droplets of different sizes ejected from the first-stage, second-stage and third-stage venturi ejectors respectively; part of the tail gas after reaction in the reverse spray tower enters the venturi ejector through negative pressure self-priming, thereby realizing self-circulation of the tail gas in the reverse spray tower; part of the tail gas after reaction enters the absorption tower body from the lower part of the reverse spray tower, and is discharged through the tail gas outlet.

6. The method for enhancing flue gas desulfurization according to claim 5, characterized in that: A spray device is provided at the top of the reverse spray tower, which produces a large number of tiny droplets with a diameter of 50-100 μm. After the tail gas containing sulfur dioxide enters the reverse spray tower, it first reacts with the small droplets sprayed by the spray device for preliminary absorption.

7. The method for enhancing flue gas desulfurization according to claim 5, characterized in that: Taking the height of the liquid distributor as a reference, the injection height of the liquid column of the multi-stage Venturi injector is 0.5-3.5m, wherein: The gas-liquid ratio of the first-stage Venturi ejector is 8-10, the injection height of the liquid column is 2.0-3.5m, and the highest point of the liquid column injection produces droplets with a diameter in the range of 120-250μm; The gas-liquid ratio of the secondary venturi ejector is 3-5, the injection height of the liquid column is 1.0-2.5m, and the highest point of the liquid column injection produces small droplets with a diameter in the range of 300-550μm; The gas-liquid ratio of the three-stage venturi ejector is 1-3, the injection height of the liquid column is 0.5-1.0m, and the highest point of the liquid column injection produces droplets with a diameter in the range of 1000-2500μm.

8. The method for enhancing flue gas desulfurization according to claim 5, characterized in that: The lift of the water pump is set to be above 20m.

9. The method for enhancing flue gas desulfurization according to claim 5, characterized in that: A demister is arranged in the absorption tower body above the connection between the absorption tower body and the reverse spray tower. After the reacted gas enters the absorption tower body, it is defogged by the demister and then discharged from the tail gas outlet.

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