Double-calcium-based wet desulphurization adjusting process

Abstract

The invention belongs to the field of environmental protection, and discloses a double-calcium-based wet desulphurization adjusting process which comprises the following steps: step 1, measuring the concentration of sulfur dioxide in a tail gas input pipe; 2, the spraying amount of the first spraying module and the spraying amount of the second spraying module are adjusted according to the concentration of sulfur dioxide, so that the content of sulfur dioxide in tail gas exhausted by the tail gas exhaust pipe is lower than 15 mg / Nm < 3 >; the pH value of spraying liquid of the first spraying module is controlled between 6.5 and 6.8; and the pH value of the spraying liquid of the second spraying module is controlled between 4.8 and 5.5. According to the process, absorption of sulfur dioxide and oxidation of sulfite are fully considered, a double-spraying structure is adopted, double balance of absorption and oxidation is achieved based on different pH values, the process can improve the unit load and reduce the use amount of a desulfurizing agent, and the process can meet the tail gas absorption treatment requirements under the conditions of high flow and high concentration.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection, and particularly to a double calcium-based wet desulfurization adjustment process. Background Art

[0002] Currently, for the removal of acidic gases from the flue gas of major coal-fired power plants, the metallurgical industry, and chemical reaction tail gases, when the concentration of acidic gases increases, the circulating volume of the circulating absorption liquid in the conventional tail gas treatment process increases sharply, resulting in a significant increase in the gas-phase resistance of the tail gas treatment system and a significant increase in the power consumption of the circulating deacidification slurry. Moreover, it is difficult to meet the discharge standards for tail gas treatment.

[0003] In the patent application with the publication number CN106474895A and the theme of a method and device for deeply removing sulfur oxides from flue gas, a multi-layer spraying module is used for spraying. Among them, the upper spraying module sprays a desulfurizing agent, and the lower spraying module sprays a calcium hydroxide solution and a calcium carbonate slurry; through this method, the full absorption of sulfur dioxide is achieved.

[0004] This solution sprays a desulfurizing agent (such as a calcium hydroxide solution) in the upper spraying module, which can effectively improve the absorption efficiency of sulfur dioxide. However, the pH difference between it and the calcium carbonate slurry sprayed in the lower layer is too large, seriously affecting the process of oxidizing sulfite to sulfate, resulting in too large a pH fluctuation in the system, and the slurry at the bottom of the tower needs to be re-oxidized after being discharged to recover gypsum.

[0005] In the patent application with the publication number CN109078476A and the theme of a wet desulfurization system and method using a double calcium-based desulfurizing agent, a slaked lime (calcium hydroxide) supply tank is used to adjust the pH value of the spraying module, and its main purpose is still to improve the absorption efficiency of sulfur dioxide by increasing the pH value.

[0006] This solution cannot balance the absorption of sulfur dioxide and the oxidation of sulfite, significantly affecting the absorption efficiency and oxidation efficiency.

[0007] The problem to be solved by this solution is: how to develop a tail gas absorption system with balanced absorption and oxidation. Summary of the Invention

[0008] The purpose of the present invention is to provide a double calcium-based wet desulfurization adjustment process. This process fully considers the absorption of sulfur dioxide and the oxidation of sulfite, adopts a double spraying structure, and realizes the double balance of absorption and oxidation based on different pH values. This process can increase the unit load, reduce the usage amount of desulfurizing agent, and can meet the tail gas absorption and treatment requirements under high flow rate and high concentration.

[0009] To achieve the above object, the present application discloses a double calcium-based wet desulfurization regulation process, and the process involves a desulfurization tower; the desulfurization tower includes a tower body, a tail gas input pipe is connected to the middle of the tower body, and a tail gas discharge pipe is provided at the top of the tower body; a first spray module and a second spray module are provided inside the tower body; a first circulation pump and a second circulation pump are connected to the lower part of the tower body, the first circulation pump is connected to the second spray module, and the second circulation pump is connected to the first spray module; an absorber input pipe for inputting calcium hydroxide solution is connected to the inlet of the second circulation pump; a flow meter and a control valve are connected to the absorber input pipe;

[0010] The process includes the following steps:

[0011] Step 1: Measure the sulfur dioxide concentration in the tail gas input pipe;

[0012] Step 2: Adjust the spray amounts of the first spray module and the second spray module according to the sulfur dioxide concentration so that the sulfur dioxide content in the tail gas discharged from the tail gas discharge pipe is lower than 15 mg / Nm 3 ;

[0013] The pH value of the spray liquid of the first spray module is controlled between 6.5 and 6.8; the pH value of the spray liquid of the second spray module is controlled between 4.8 and 5.5.

[0014] When the first spray module descends to the position of the second spray module, it mixes with the liquid sprayed by the second spray module. Through comprehensive calculation, the pH at this time is 5.4 to 5.8, and this pH range has the best oxidation effect on sulfite ions; at the same time, this pH control strategy can also keep the bottom slurry stable.

[0015] The present invention fully considers the defects of the prior art. By adopting the above scheme, it can take into account both the absorption of sulfur dioxide and the oxidation of sulfite ions, improve the stability of the pH slurry at the bottom of the tower, and the oxidation of sulfite ions at the bottom of the tower is relatively complete.

[0016] The pH difference between the upper and lower spray modules of the present invention is small. Through actual measurement, after the pH of the calcium hydroxide / calcium carbonate solution reaches 6.8, an absorption efficiency close to 99.5% can be achieved (reference Figure 1 ); at the same time, when independently examining the relationship between the pH value and the liquid-gas ratio, we found that when the pH is close to 7, the liquid-gas ratio can be reduced to 12 (reference Figure 2 ); this also means that by controlling the pH difference between the two layers of spray modules, the liquid-gas ratio can be significantly reduced while maintaining a high oxidation efficiency.

[0017] In the above process, the full-load treatment flow rate of the desulfurization tower is 100%;

[0018] When the flow rate in the tail gas input pipe is 30 - 50%, and the content of sulfur dioxide in the tail gas is lower than 8000 mg / m 3 , control the total liquid-gas ratio to be 10 - 15, and the liquid distribution ratio of the first spray module and the second spray module to be 1:10 - 20;

[0019] When the flow rate in the tail gas input pipe is 50 - 80%, and the content of sulfur dioxide in the tail gas is lower than 8000 mg / m 3 , control the total liquid-gas ratio to be 15 - 20, and the liquid distribution ratio of the first spray module and the second spray module to be 1:10 - 20;

[0020] When the flow rate in the tail gas input pipe is 80 - 100%, and the content of sulfur dioxide in the tail gas is lower than 8000 mg / m 3 , control the total liquid-gas ratio to be 20 - 25, and the liquid distribution ratio of the first spray module and the second spray module to be 1:10 - 20.

[0021] In the above process, when the flow rate in the tail gas input pipe is 30 - 50%, and the content of sulfur dioxide in the tail gas is higher than 8000 mg / m 3 and lower than 10000 mg / m 3 , control the total liquid-gas ratio to be 10 - 15, and the liquid distribution ratio of the first spray module and the second spray module to be 1:10 - 15;

[0022] When the flow rate in the tail gas input pipe is 50 - 80%, and the content of sulfur dioxide in the tail gas is higher than 8000 mg / m 3 and lower than 10000 mg / m 3 , control the total liquid-gas ratio to be 15 - 20, and the liquid distribution ratio of the first spray module and the second spray module to be 1:5 - 10;

[0023] When the flow rate in the tail gas input pipe is 80 - 100%, and the content of sulfur dioxide in the tail gas is higher than 8000 mg / m 3 and lower than 10000 mg / m 3 , control the total liquid-gas ratio to be 20 - 25, and the liquid distribution ratio of the first spray module and the second spray module to be 1:3 - 5.

[0024] In the normal production process, the concentration of sulfur dioxide generally ranges from 8000 mg / m 3 to 10000 mg / m 3 , and the flow rate fluctuation will be relatively larger. Therefore, during the production process, the fluctuations of the flow rate and the concentration of sulfur dioxide in the tail gas have an impact on the absorption of sulfur dioxide and the oxidation of sulfite. Controlling the distribution ratio of the first spray module and the second spray module and the liquid-gas ratio is the guarantee for maintaining effective absorption of sulfur dioxide and a relatively high oxidation degree of sulfite.

[0025] When the concentration of sulfur dioxide is relatively low, the tail gas input volume is used as the main consideration criterion, and the above object is achieved by controlling the total liquid-gas ratio;

[0026] When the concentration of sulfur dioxide is relatively high, while using the tail gas input volume as the main consideration criterion, carefully control the liquid-gas ratio and distribution ratio to achieve the absorption of sulfur dioxide and the oxidation of sulfite.

[0027] Preferably, the liquid-gas ratio is adjusted by means of dynamic adjustment. The liquid-gas ratio increases with the increase in flow rate, and when the concentration of sulfur dioxide reaches a certain level, the liquid distribution ratio is adjusted by considering the tail gas flow rate factor.

[0028] Through the above scheme optimization, the system can be maintained at a low liquid-gas ratio level, reducing the power of the machine pump, increasing the unit load by 5 - 6%, and the concentration of sulfur dioxide at the outlet is lower than 15mg / Nm 3 , approaching the ultra-low emission index (the ultra-low emission index is ≤ 35mg / Nm 3 , and the ultra-ultra-low emission index is ≤ 15mg / Nm 3 ).

[0029] That is, the advantages of the above optimization are as follows: 1. By adjusting the pH, controlling the liquid-gas ratio for different working conditions, and optimizing the liquid distribution ratio, it is possible to significantly save desulfurization agents and reduce the concentration of sulfur dioxide at the outlet; 2. According to different working conditions, flexible response to the unit load can be achieved; 3. The present invention can significantly increase the unit load and achieve relatively sufficient absorption of sulfur dioxide and oxidation of sulfite under high-flow and high-concentration working conditions.

[0030] In the above process, the pH value of the slurry at the bottom of the tower body is 4.8 - 5.5; if the pH value of the slurry is lower than 4.8, calcium carbonate or calcium carbonate slurry is additionally supplemented to the bottom of the tower body.

[0031] By controlling the pH of the slurry at the bottom of the tower, the liquid pH during the oxidation process can be maintained between 5.4 and 5.8. Therefore, the quality of the oxidation process is closely related to the pH of the slurry at the bottom of the tower and the pH of the first spraying module.

[0032] In the above process, a gas distribution module for inputting air is provided at the bottom of the tower body.

[0033] The gas distribution module is a first gas distribution module for generating nano microbubbles and a second gas distribution module for inputting air to the bottom of the tower body;

[0034] The flow rate of the air input by the gas distribution module is 0.5 - 1 vol‰ of the tail gas treatment flow rate of the desulfurization tower; the volume ratio of the gas distribution volume of the first gas distribution module to the gas distribution volume of the second gas distribution module is 5 - 10:90 - 95.

[0035] In the present invention, both the first air distribution module and the second air distribution module are used to input air. During the upward movement of micro-nano bubbles, the pressure is reduced and the bubbles burst, releasing the internal energy of the gas and enhancing the catalytic effect of oxygen on sulfite ions.

[0036] In the above process, an alloy tray for enhancing gas-liquid mass transfer is provided below the second spray module.

[0037] Preferably, a Venturi rod is provided between the first spray module and the second spray module, and the Venturi rod is used to improve the mass transfer effect between the spray liquid of the first spray module and the flue gas.

[0038] One core innovation of the present invention lies in the use of a Venturi rod. By adding a Venturi rod, the flue gas velocity is greatly increased. Due to the wall adhesion effect of the slurry, that is, the spray liquid of the first spray module adheres to the Venturi rod. When the flue gas contacts at a high speed, the original slurry surface is stripped, forming a new gas-liquid contact surface and breaking the original two-phase mass transfer surface, thus accelerating the gas-liquid two-phase mass transfer rate, that is, improving the absorption of SO2.

[0039] By controlling the spray pH of the first spray module and the combination of the Venturi rod, the absorption efficiency of sulfur dioxide in the absorption stage can be significantly improved;

[0040] In addition, a sloping plate separation layer and a stirrer are provided at the bottom of the tower body; the sloping plate separation layer is located above the air distribution module; the stirrer is a suspension pump. When it is necessary to supplement calcium carbonate slurry to the bottom of the tower, calcium carbonate slurry can be supplemented to the bottom of the tower through a slurry supplement pipeline.

[0041] The stirrer keeps the inside of the tower body in a turbulent mixing state, enabling the micro-nano bubbles generated by the first air distribution module to be dispersed into the tower body, and the micro-nano bubbles to come into full contact with the bottom liquid of the tower, so that the oxidation reaction can be fully carried out at the bottom of the tower body;

[0042] Through the cooperation of the alloy tray, the first air distribution module, the second air distribution module, and the stirrer of the present invention, the oxidation reaction can be kept relatively sufficient during the bottom of the tower and the spraying process;

[0043] By the Venturi rod and the pH control of the first spray module, the absorption effect of sulfur dioxide can be significantly improved, thereby providing a better oxidation basis for subsequent oxidation and further promoting the smooth progress of the oxidation reaction.

[0044] In the above process, the tower height of the tower body is 35 m to 45 m; the tower diameter is 3 to 17 m.

[0045] In the above process, the height difference between the first spray module and the second spray module is 5 to 18 m.

[0046] The beneficial effects of this application are as follows:

[0047] The pH difference of the upper and lower spray modules of the present invention is small. By controlling the pH difference between the two-layer spray modules, the liquid-gas ratio can be significantly reduced while maintaining a high oxidation efficiency.

[0048] Furthermore, by controlling the liquid-gas ratio and distribution ratio under different sulfur dioxide concentrations in the flue gas, the system can be maintained at a low liquid-gas ratio level, reducing the power of the machine pump. The unit load is increased by 5-6%, and the concentration of sulfur dioxide at the outlet is lower than 15 mg / Nm 3 , approaching the ultra-low emission standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a relationship diagram between the slurry pH value and the sulfur dioxide absorption rate;

[0050] Figure 2 It is a relationship diagram between the slurry pH value and the liquid-gas ratio;

[0051] Figure 3 It is a microscopic photo of the gypsum discharged from the bottom of the tower before transformation;

[0052] Figure 4 It is a microscopic photo of the gypsum discharged from the bottom of the tower after transformation;

[0053] Figure 5 It is a schematic structural diagram of the system of Embodiment 2 of the present invention;

[0054] Figure 6 It is a schematic structural diagram of the system of Embodiment 3 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0055] Next, the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. In the description of the present invention, it should be noted that for those conditions not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0056] Embodiment 1

[0057] To clearly illustrate the technical solution of the present invention, the system involved in the process of the present invention will be described first. This system is mainly a desulfurization tower; specifically refer to Figure 5, the desulfurization tower includes a tower body 1, a tail gas inlet pipe 2 is connected to the middle of the tower body 1, and a tail gas discharge pipe 3 is provided at the top of the tower body 1; a first spraying module 4 and a second spraying module 5 are arranged in the tower body 1; a first circulation pump 6 and a second circulation pump 7 are connected to the lower part of the tower body 1, the first circulation pump 6 is connected to the second spraying module 5, and the second circulation pump 7 is connected to the first spraying module 4; an absorbent inlet pipe 8 for inputting calcium hydroxide solution is connected to the inlet of the second circulation pump 7; a flow meter and a control valve are connected to the absorbent inlet pipe 8. The pH value of the slurry at the bottom of the tower body 1 is 4.8 - 5.5; if the pH value of the slurry is lower than 4.8, calcium carbonate slurry is additionally replenished into the bottom of the tower body 1 through a slurry replenishment pipeline 15; in addition, a discharge pump 16 is also connected to the tower body 1, which is used to discharge part of the saturated slurry into the gypsum production system, and at the same time, calcium carbonate slurry is additionally replenished into the tower bottom through the slurry replenishment pipeline 15. A gas distribution module for inputting air is provided at the bottom of the tower body 1, an alloy tray 10 for enhancing gas-liquid mass transfer is provided below the second spraying module 5, the tower height of the tower body 1 is 40 m; the diameter of the tower body 1 is 7 m; the height difference between the first spraying module 4 and the second spraying module 5 is 12 m, the height of the first spraying module is 30 m, and the height of the second spraying module is 18 m. A Venturi rod 12 is arranged between the first spraying module 4 and the second spraying module 5, and the Venturi rod 12 is used to improve the mass transfer effect between the spraying liquid of the first spraying module 4 and the flue gas. The pH value of the spraying liquid of the first spraying module 4 is controlled between 6.5 and 6.8; the pH value of the spraying liquid of the second spraying module 5 is controlled between 4.8 and 5.5.

[0058] The first circulation pump 6 and the second circulation pump 7 independently control the spraying pH values of the first spraying module 4 and the second spraying module 5 respectively. The first spraying module 4 and the second spraying module 5 are equipped with independent pH probes to detect the pH value of the spraying slurry. Correspondingly, a pH sensor is also provided in the slurry pool at the bottom of the tower to detect the pH in the slurry pool. When the pH value exceeds the fluctuation range, calcium hydroxide solution is actively added to maintain the stability of the pH value in the slurry pool.

[0059] The oxidation process of sulfite is related to two factors: the pH value of the spraying liquid in the second spraying module 5 and the pH value in the slurry pool. The former is involved in the oxidation process, and the latter is involved in the oxidation and crystallization processes. There is no strict limit on the air distribution volume of the air distribution module. Preferably, the air supply volume of the air distribution module and the flue gas flow rate are preferably controlled at about 1:1000 - 2000. By continuously supplying air or oxygen, the oxidation and crystallization process is accelerated. The unreacted oxygen participates in the oxidation process of sulfite in the spraying liquid of the second spraying module 5. Due to the larger contact area, its oxidation rate will be faster. More specifically, in Example 2, a common air distribution module 9 is used for air distribution, and the air distribution flow rate is 1 vol‰ of the flue gas flow rate; in Example 3, a micro-nano bubble air distribution module 11 and a common air distribution module 9 are used for air distribution, and the air distribution flow rate ratio of the micro-nano bubble air distribution module 11 to the common air distribution module 9 is 5:95. The micro-nano bubbles referred to in the present invention refer to bubbles with a diameter of less than 500 nm as the main bubble composition, which is a kind of gas that can release the internal energy of the bubble after pressure loss, and it is prepared with air.

[0060] In addition, in Example 3, a sloping plate separation layer 13 and a stirrer 14 are also provided at the bottom of the tower body; the sloping plate separation layer 13 is located above the air distribution module; the stirrer 14 is a suspension pump;

[0061] The structural schematic diagram of Example 3 is referred to Figure 6 .

[0062] Example 2

[0063] It is carried out using the system of Example 1. The pH value of the spraying liquid in the first spraying module is controlled between 6.5 and 6.8 through the second circulation pump, and the pH value of the spraying liquid in the second spraying module is controlled between 4.8 and 5.5 through the first circulation pump. The pH of the slurry in the slurry pool at the bottom of the tower is dynamically controlled at 4.8 - 5.5; if the pH value of the slurry is lower than 4.8, calcium hydroxide is additionally replenished to the bottom of the tower body. When the first spraying module descends to the position of the second spraying module, it mixes with the liquid sprayed by the second spraying module. Through comprehensive measurement, the pH at this time is 5.4 to 5.8, and this pH range has the best oxidation effect on sulfite; at the same time, this pH control strategy can also keep the bottom slurry stable.

[0064] Its overall control strategy is:

[0065] Taking the full-load treatment flow rate of the desulfurization tower as 100%, the full-load treatment capacity is 300,000 m 3 / h;

[0066] When the flow rate in the tail gas input pipe is 30 - 50%, the content of sulfur dioxide in the tail gas is lower than 8000 mg / m 3When the time is reached, control the total liquid-gas ratio to be 10 - 15, and the liquid distribution ratio of the first spray module and the second spray module is 1:10 - 20;

[0067] When the flow rate in the tail gas input pipe is 50 - 80%, and the content of sulfur dioxide in the tail gas is lower than 8000 mg / m 3 When the time is reached, control the total liquid-gas ratio to be 15 - 20, and the liquid distribution ratio of the first spray module and the second spray module is 1:10 - 20;

[0068] When the flow rate in the tail gas input pipe is 80 - 100%, and the content of sulfur dioxide in the tail gas is lower than 8000 mg / m 3 When the time is reached, control the total liquid-gas ratio to be 20 - 25, and the liquid distribution ratio of the first spray module and the second spray module is 1:10 - 20;

[0069] When the flow rate in the tail gas input pipe is 30 - 50%, and the content of sulfur dioxide in the tail gas is higher than 8000 mg / m 3 and lower than 10000 mg / m 3 When the time is reached, control the total liquid-gas ratio to be 10 - 15, and the liquid distribution ratio of the first spray module and the second spray module is 1:10 - 15;

[0070] When the flow rate in the tail gas input pipe is 50 - 80%, and the content of sulfur dioxide in the tail gas is higher than 8000 mg / m 3 and lower than 10000 mg / m 3 When the time is reached, control the total liquid-gas ratio to be 15 - 20, and the liquid distribution ratio of the first spray module and the second spray module is 1:5 - 10;

[0071] When the flow rate in the tail gas input pipe is 80 - 100%, and the content of sulfur dioxide in the tail gas is higher than 8000 mg / m 3 and lower than 10000 mg / m 3 When the time is reached, control the total liquid-gas ratio to be 20 - 25, and the liquid distribution ratio of the first spray module and the second spray module is 1:3 - 5.

[0072] Since the situation where the concentration of sulfur dioxide in the flue gas exceeds 10000 mg / m 3 is not common, it is not considered in this embodiment. When such a situation occurs, it can be processed according to the situation of the maximum flue gas flow rate, which can meet the relevant requirements.

[0073] We divide the above working conditions into low sulfur dioxide concentration working conditions (sulfur dioxide < 8000 mg / m 3 ), medium and high sulfur dioxide concentration working conditions (8000 mg / m 3 ≤ sulfur dioxide < 10000 mg / m 3 ); the control strategies for the above working conditions are completely different strategies;

[0074] For the working condition of low sulfur dioxide concentration, only the tail gas flow needs to be considered. The total liquid-gas ratio is controlled according to the tail gas flow, and the liquid distribution ratio is fixed at an appropriate value.

[0075] For the working conditions of medium and high sulfur dioxide concentrations, not only the total liquid-gas ratio (with the tail gas flow as the consideration index) needs to be considered, but also the intelligent adaptation of the liquid distribution ratio is required. More specifically, when the tail gas flow is larger, the spraying amount of the first spraying module needs to be increased to improve the absorption effect. At the same time, after the first spraying module absorbs sulfur dioxide, the pH value decreases, which will increase the amount of liquid flowing through the second spraying module. This part of the liquid will reduce the pH value impact of the high-flow tail gas on the liquid sprayed by the second spraying module and maintain the liquid pH value of the second spraying module near the target value.

[0076] Through the above optimization, under different working conditions, using the above strategy for treatment, sampling the tail gas from the tail gas discharge pipe, the sulfur dioxide content in the tail gas is lower than 15 mg / Nm 3 , reaching the ultra-low emission standard.

[0077] Example 3

[0078] Generally the same as Example 2, the difference is that a micro-nano bubble gas distribution module, an inclined plate separation layer and a stirrer are added.

[0079] Operation test

[0080] This equipment was tested in a power plant in the mainland. It has two sets of independent units of the same specification, named Unit 1 and Unit 2 respectively, and the two units carried out experiments synchronously; Unit 1 used the system of the present invention and the process of Example 2, and Unit 2 used the process of Example 3;

[0081] The desulfurization tower before transformation also has a first spraying module and a second spraying module. Both the first spraying module and the second spraying module are connected to pumps to dynamically supplement calcium hydroxide solution to keep the pH of the spraying slurry constant at 5.5; according to the statistics of the original data, the average unit load of the desulfurization tower before transformation was 525.47 MW, and the average outlet SO2 was 32.139 mg / Nm 3 .

[0082] After nearly 3 months of synchronous operation, the following information was collected, referring to Table 1;

[0083] Table 1 Operation statistical data table

[0084] Average unit load <![CDATA[Average value of exported SO2]]> Unit 1 (Example 2) 555.85 MW <![CDATA[14.822mg / Nm 3 > Unit 2 (Example 3) 558.61 MW <![CDATA[11.408mg / Nm 3 >

[0085] Microscopic image reference of the gypsum discharged from Unit 1 Figure 3 , microscopic image reference of the gypsum discharged from Unit 2Figure 4 。

[0086] It can be found from the above results that after adopting the system and process of the present invention, the unit load has increased by 5-6%, and the content of sulfur dioxide at the outlet has decreased by 18-20 mg / Nm 3 。

[0087] By adopting micro-nano bubbles for gas distribution and combining with a suspension pump for auxiliary stirring, the oxidation effect of sulfite can be improved. Through the sufficient oxidation of sulfite, the concentration of sulfite in the bottom liquid of the tower can be reduced and converted into sulfate. A good liquid composition of the bottom liquid of the tower will make the first spray module and the second spray module more effective in absorbing sulfur dioxide; from the corresponding comparison of the gypsum photos generated in Example 2 and Example 3, it can be seen that the gypsum generated in Example 3 has better uniformity and fuller crystal particles, indicating that its oxidation degree is more thorough.

Claims

1. A double calcium-based wet desulfurization adjustment process, characterized in that: The process involves a desulfurization tower; the desulfurization tower comprises a tower body, the middle of the tower body is connected to a tail gas input pipe, and the top of the tower body is provided with a tail gas discharge pipe; a first spray module and a second spray module are provided in the tower body; a first circulation pump and a second circulation pump are connected to the lower part of the tower body, the first circulation pump is connected to the second spray module, and the second circulation pump is connected to the first spray module; an absorbent input pipe for inputting a calcium hydroxide solution is connected to the inlet of the second circulation pump; a flow meter and a control valve are connected to the absorbent input pipe; The process comprises the following steps: Step 1: Determine the sulfur dioxide concentration of the tail gas inlet pipe; Step 2: Adjust the spraying volume of the first spray module and the second spray module according to the sulfur dioxide concentration so that the sulfur dioxide content in the tail gas discharged from the tail gas exhaust pipe is lower than 15 mg / Nm 3 ; The pH value of the spray liquid of the first spray module is controlled between 6.5 and 6.8; the pH value of the spray liquid of the second spray module is controlled between 4.8 and 5.

5.

2. The process according to claim 1, characterized in that The full load processing flow of the desulfurization tower is 100%; When the flow rate in the tail gas inlet pipe is 30-50%, the sulfur dioxide content in the tail gas is less than 8000 mg / m 3 When the total liquid-gas ratio is controlled to be 10-15, the liquid distribution ratio of the first spray module and the second spray module is 1:10-20; When the flow rate in the tail gas inlet pipe is 50-80%, the sulfur dioxide content in the tail gas is less than 8000 mg / m 3 When the total liquid-gas ratio is controlled to be 15-20, the liquid distribution ratio of the first spray module and the second spray module is 1:10-20; When the flow rate in the tail gas inlet pipe is 80-100%, the sulfur dioxide content in the tail gas is less than 8000 mg / m 3 When the total liquid-gas ratio is controlled to be 20-25, the liquid distribution ratio of the first spray module and the second spray module is 1:10-20.

3. The process according to claim 2, characterized in that When the flow rate in the tail gas inlet pipe is 30-50%, the sulfur dioxide content in the tail gas is higher than 8000 mg / m 3 And less than 10000mg / m 3 When the total liquid-gas ratio is controlled to be 10-15, the liquid distribution ratio of the first spray module and the second spray module is 1:10-15; When the flow rate in the tail gas inlet pipe is 50-80%, the sulfur dioxide content in the tail gas is higher than 8000 mg / m 3 And less than 10000mg / m 3 When the total liquid-gas ratio is controlled to be 15-20, the liquid distribution ratio of the first spray module and the second spray module is 1:5-10; When the flow rate in the tail gas inlet pipe is 80-100%, the sulfur dioxide content in the tail gas is higher than 8000 mg / m 3 And less than 10000mg / m 3 When the total liquid-gas ratio is controlled to be 20-25, the liquid distribution ratio of the first spray module and the second spray module is 1:3-5.

4. The process according to claim 1, characterized in that The pH value of the slurry at the bottom of the tower body is 4.8-5.5; if the pH value of the slurry is lower than 4.8, additional calcium carbonate slurry is added to the bottom of the tower body.

5. The process according to claim 4, characterized in that An air distribution module for inputting air is arranged at the bottom of the tower body.

6. The process according to claim 5, characterized in that The air distribution modules are a first air distribution module for generating nano-micro bubbles and a second air distribution module for inputting air into the bottom of the tower body; The flow rate of air input by the air distribution module is 0.5-1 vol‰ of the exhaust gas treatment flow rate of the desulfurization tower; the volume ratio of the air distribution volume of the first air distribution module to the air distribution volume of the second air distribution module is 5-10:90-95.

7. The process according to claim 5, characterized in that An alloy tray for enhancing gas-liquid mass transfer is provided below the second spray module.

8. The process according to claim 7, characterized in that A venturi rod is provided between the first spray module and the second spray module, and the venturi rod is used to improve the mass transfer effect between the spray liquid of the first spray module and the flue gas.

9. The process according to claim 8, characterized in that The tail gas inlet pipe is located above the packing layer and below the alloy tray.

10. The process according to claim 1, characterized in that The tower body has a height of 35m to 45m; a diameter of the tower body is 3 to 17m, and a height difference between the first spray module and the second spray module is 5 to 18m.

Images