A double calcium-based wet flue gas desulfurization conditioning process

Abstract

This application belongs to the field of environmental protection and discloses a dual-calcium-based wet desulfurization process. The process includes the following steps: Step 1: Measuring the sulfur dioxide concentration in the exhaust gas inlet pipe; Step 2: Adjusting the spray 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 exhaust gas emitted from the exhaust pipe is lower than 15 mg / Nm³. 3 The pH value of the spray solution in the first spray module is controlled between 6.5 and 6.8; the pH value of the spray solution in the second spray module is controlled between 4.8 and 5.5. This process fully considers the absorption of sulfur dioxide and the oxidation of sulfite, and adopts a dual-spray structure. Based on different pH values, it achieves a dual balance between absorption and oxidation. This process can increase the unit load, reduce the amount of desulfurizing agent used, and can meet the needs of tail gas absorption and treatment under high flow and high concentration conditions.

Description

Technical Field

[0001] This invention relates to the field of environmental protection, and in particular to a dual-calcium-based wet desulfurization regulation process. Background Technology

[0002] Currently, the removal of acidic gases from tail gas in major coal-fired power plants, metallurgical industries, and chemical reactions presents challenges. As the concentration of acidic gases increases, the circulation volume of the circulating absorption liquid in conventional tail gas treatment processes increases dramatically, resulting in a significant increase in the meteorological resistance of the tail gas treatment system and a substantial increase in the power consumption of the circulating deacidification slurry. Furthermore, it is difficult for the tail gas to meet emission standards.

[0003] In the patent application with publication number CN106474895A, which is entitled "A Method and Apparatus for Deep Removal of Sulfur Oxides from Flue Gas", a multi-layer spray module is used for spraying. The upper spray module sprays desulfurizing agent, the lower spray module sprays calcium hydroxide solution, and the lower spray module sprays calcium carbonate slurry. Through this method, the full absorption of sulfur dioxide is achieved.

[0004] The solution sprays a desulfurizing agent (such as calcium hydroxide solution) in the upper spray module, which can effectively improve the absorption efficiency of sulfur dioxide. However, the pH difference between the desulfurizing agent and the calcium carbonate slurry sprayed in the lower layer is too large, which seriously affects the process of sulfite oxidation to sulfate. This causes the pH fluctuation in the system to be too large, so that the slurry at the bottom of the tower needs to be oxidized again after discharge in order to recover gypsum.

[0005] In the patent application CN109078476A, which is entitled "A wet desulfurization system and method using a dual-calcium-based desulfurizing agent", a quicklime (calcium hydroxide) supply tank is used to adjust the pH value of the spray module. Its main purpose is to improve the absorption efficiency of sulfur dioxide by increasing the pH value.

[0006] This scheme cannot simultaneously absorb sulfur dioxide and oxidize sulfite, significantly affecting both absorption and oxidation efficiency.

[0007] The problem this solution aims to solve is: how to develop a tail gas absorption system that balances absorption and oxidation. Summary of the Invention

[0008] The purpose of this invention is to provide a dual-calcium-based wet desulfurization process that fully considers the absorption of sulfur dioxide and the oxidation of sulfite. It adopts a dual-spray structure and achieves a dual balance between absorption and oxidation based on different pH values. This process can increase the unit load, reduce the amount of desulfurizing agent used, and meet the needs of tail gas absorption and treatment under high flow and high concentration conditions.

[0009] To achieve the above objectives, this application discloses a dual-calcium-based wet desulfurization conditioning process, which relates to a desulfurization tower. The desulfurization tower includes a tower body, a tail gas inlet pipe connected to the middle of the tower body, and a tail gas outlet pipe 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 absorbent inlet 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 absorbent inlet pipe.

[0010] The process includes the following steps:

[0011] Step 1: Measure the sulfur dioxide concentration in the exhaust gas inlet pipe;

[0012] Step 2: Adjust the spray volume of the first and second spray modules according to the sulfur dioxide concentration to ensure that the sulfur dioxide content in the exhaust gas emitted from the exhaust pipe is below 15 mg / Nm³. 3 ;

[0013] The pH value of the spray liquid in the first spray module is controlled between 6.5 and 6.8; the pH value of the spray liquid in 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, the liquid sprayed from the second spray module mixes with it. According to comprehensive calculation, the pH at this time is 5.4 to 5.8. This pH range is the best for the oxidation of sulfite. At the same time, this pH control strategy can also keep the slurry at the bottom of the tower stable.

[0015] This invention fully considers the shortcomings of the prior art and adopts the above-mentioned solution, which can take into account both the absorption of sulfur dioxide and the oxidation of sulfite, improve the stability of the pH slurry at the bottom of the tower, and make the oxidation of sulfite in the slurry at the bottom of the tower more thorough.

[0016] The pH difference between the upper and lower spray modules of this invention is small. Actual calculations show that once the pH of the calcium hydroxide / calcium carbonate solution reaches 6.8, an absorption efficiency of nearly 99.5% can be achieved (reference). Figure 1 Meanwhile, when examining the relationship between pH and the liquid-to-gas ratio independently, we found that when the pH is close to 7, the liquid-to-gas ratio can be reduced to 12 (reference). Figure 2 This also means that by controlling the pH difference between the two spray modules, the liquid-to-gas ratio can be significantly reduced while maintaining a high oxidation efficiency.

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

[0018] When the flow rate in the exhaust gas inlet pipe is 30-50%, the sulfur dioxide content in the exhaust gas is less than 8000 mg / m³. 3 At that time, the total liquid-to-gas ratio is controlled at 10-15, and the liquid distribution ratio of the first spray module and the second spray module is 1:10-20;

[0019] When the flow rate in the exhaust gas inlet pipe is 50-80%, the sulfur dioxide content in the exhaust gas is below 8000 mg / m³. 3 At that time, the total liquid-to-gas ratio is controlled at 15-20, and the liquid distribution ratio of the first spray module and the second spray module is 1:10-20;

[0020] When the flow rate in the exhaust gas inlet pipe is 80-100%, the sulfur dioxide content in the exhaust gas is less than 8000 mg / m³. 3 At that time, the total liquid-to-gas ratio is controlled at 20-25, and the liquid distribution ratio of the first spray module and the second spray module is 1:10-20.

[0021] In the above process, when the flow rate in the exhaust gas inlet pipe is 30-50%, the sulfur dioxide content in the exhaust gas is higher than 8000 mg / m³. 3 And below 10000 mg / m 3 At that time, the total liquid-to-gas ratio is controlled at 10-15, and the liquid distribution ratio of the first spray module and the second spray module is 1:10-15;

[0022] When the flow rate in the exhaust gas inlet pipe is 50-80%, the sulfur dioxide content in the exhaust gas is higher than 8000 mg / m³. 3 And below 10000 mg / m 3 At that time, the total liquid-to-gas ratio is controlled at 15-20, and the liquid distribution ratio of the first spray module and the second spray module is 1:5-10;

[0023] When the flow rate in the exhaust gas inlet pipe is 80-100%, the sulfur dioxide content in the exhaust gas is higher than 8000 mg / m³. 3 And below 10000 mg / m 3 At that time, the total liquid-to-gas ratio is controlled at 20-25, and the liquid distribution ratio of the first spray module and the second spray module is 1:3-5.

[0024] In normal production processes, the concentration of sulfur dioxide is generally between 8000 mg / m³. 3 ~10000mg / m 3 The flow rate fluctuations are relatively large. Therefore, during the production process, the fluctuations in the flow rate and the concentration of sulfur dioxide in the exhaust gas affect the absorption of sulfur dioxide and the oxidation of sulfite. Controlling the distribution ratio of the first spray module and the second spray module, as well as the liquid-gas ratio, is the guarantee for maintaining effective absorption of sulfur dioxide and a high degree of oxidation of sulfite.

[0025] When the concentration of sulfur dioxide is low, the exhaust gas input volume is used as the main consideration, and the above purpose is achieved by controlling the total liquid-gas ratio.

[0026] When the concentration of sulfur dioxide is relatively high, while taking the amount of exhaust gas input as the main consideration, the liquid-to-gas ratio and distribution ratio should be carefully controlled to achieve the absorption of sulfur dioxide and the oxidation of sulfite.

[0027] Preferably, the liquid-gas ratio is adjusted dynamically, with the liquid-gas ratio increasing as the flow rate increases. When the sulfur dioxide concentration reaches a certain level, the liquid distribution ratio is adjusted based on the exhaust gas flow rate.

[0028] By optimizing the above schemes, the system can be maintained at a low liquid-to-gas ratio, reducing pump power, increasing unit load by 5-6%, and achieving an outlet sulfur dioxide concentration below 15 mg / Nm³. 3 Approaching ultra-low emission standards (ultra-low emission standard is ≤35mg / Nm³). 3 The ultra-low emission standard is ≤15mg / Nm³. 3 ).

[0029] In other words, the advantages of the above optimization are: 1. By adjusting the pH, controlling the liquid-to-gas ratio for different operating conditions, and optimizing the liquid distribution ratio, desulfurizing agent can be significantly saved and the outlet sulfur dioxide concentration can be reduced; 2. The unit load can be flexibly adjusted according to different operating conditions; 3. The present invention can significantly increase the unit load and achieve more sufficient absorption of sulfur dioxide and oxidation of sulfite under high flow and high concentration conditions.

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

[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 success 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 spray module.

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

[0033] The air distribution module consists of a first air distribution module for generating nano-microbubbles and a second air distribution module for inputting air to the bottom of the tower.

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

[0035] In this invention, both the first and second gas distribution modules are used to input air. By releasing the internal energy of the gas through the decompression and bursting of micro-nano bubbles during the ascent, the catalytic effect of oxygen on sulfite ions is improved.

[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 and the flue gas of the first spray module.

[0038] A core innovation of this invention lies in the use of a Venturi rod. By adding the 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 comes into contact with the slurry at high speed, the original slurry surface is peeled off, forming a new gas-liquid contact surface. This breaks the original two-phase mass transfer surface, thereby accelerating the gas-liquid two-phase mass transfer rate, which in turn improves the absorption of SO2.

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

[0040] In addition, an inclined plate partition layer and an agitator are provided at the bottom of the tower body; the inclined plate partition layer is located above the gas distribution module; the agitator is a suspension pump, and when calcium carbonate slurry needs to be added to the bottom of the tower, it can be added to the bottom of the tower through a slurry replenishment pipe.

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

[0042] By combining the alloy tray, the first gas distribution module, the second gas distribution module, and the agitator of this invention, the oxidation reaction can be maintained at a relatively sufficient level at the bottom of the tower and during the spraying process.

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

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

[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:

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

[0048] Furthermore, by controlling the liquid-to-gas ratio and distribution ratio at different sulfur dioxide concentrations in the flue gas, the system can be maintained at a low liquid-to-gas ratio, reducing pump power, increasing unit load by 5-6%, and achieving an outlet sulfur dioxide concentration below 15 mg / Nm³. 3 It is close to the ultra-low emission standard. Attached Figure Description

[0049] Figure 1 A graph showing the relationship between slurry pH and sulfur dioxide absorption rate;

[0050] Figure 2 A graph showing the relationship between slurry pH and gas-liquid ratio;

[0051] Figure 3 A microscope photograph of the plaster discharged from the bottom of the tower before the renovation;

[0052] Figure 4 Microscopic photograph of the plaster discharged from the bottom of the modified tower;

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

[0054] Figure 6 This is a schematic diagram of the system structure of Embodiment 3 of the present invention. Detailed Implementation

[0055] The present invention will now be clearly and completely described in conjunction with embodiments thereof. It should be noted that, unless specific conditions are specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0056] Example 1

[0057] To clearly illustrate the technical solution of this invention, the system involved in the process of this invention will first be described, which is mainly a desulfurization tower; see details below. Figure 5The desulfurization tower includes a tower body 1, with a tail gas inlet pipe 2 connected to the middle of the tower body 1 and a tail gas outlet pipe 3 at the top of the tower body 1. A first spray module 4 and a second spray module 5 are installed inside 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 spray module 5, and the second circulation pump 7 is connected to the first spray 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, additional calcium carbonate slurry is added to the bottom of the tower body 1 through a slurry replenishment pipe 15. Furthermore, a discharge pump 16 is connected to the tower body 1 to discharge a portion of the saturated slurry into the gypsum production system, while additional calcium carbonate slurry is added to the bottom of the tower through the slurry replenishment pipe 15. The bottom of the tower body 1 is equipped with an air distribution module for air input, and below the second spray module 5 is an alloy tray 10 for enhancing gas-liquid mass transfer. The tower body 1 has a height of 40m and a diameter of 7m. The height difference between the first spray module 4 and the second spray module 5 is 12m, with the first spray module having a height of 30m and the second spray module having a height of 18m. A Venturi rod 12 is provided between the first spray module 4 and the second spray module 5 to improve the mass transfer effect between the spray liquid and the flue gas in the first spray module 4. The pH value of the spray liquid in the first spray module 4 is controlled between 6.5 and 6.8; the pH value of the spray liquid in the second spray 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 spray pH value of the first spray module 4 and the second spray module 5. The first spray module 4 and the second spray module 5 are equipped with independent pH probes to detect the pH value of the sprayed slurry. Correspondingly, a pH sensor is also installed in the slurry tank at the bottom of the tower to detect the pH value in the slurry tank. 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 tank.

[0059] The oxidation process of sulfite is related to two factors: the pH value of the spray liquid in the second spray module 5 and the pH value in the slurry tank. The former involves the oxidation process, while the latter involves both oxidation and crystallization. The gas distribution volume of the gas distribution module is not strictly limited. Preferably, the air supply volume and flue gas flow rate of the gas distribution module are controlled at approximately 1:1000-2000. By continuously supplying air or oxygen, the oxidation and crystallization process is accelerated. Unreacted oxygen participates in the oxidation of sulfite by the spray liquid in the second spray module 5. Due to its larger contact area, the oxidation rate is faster. More specifically, Example 2 uses a conventional gas distribution module 9 for gas distribution, with a gas distribution flow rate of 1 vol‰ of the flue gas flow rate; Example 3 uses a micro-nano bubble gas distribution module 11 and a conventional gas distribution module 9 for gas distribution, with a gas distribution flow rate ratio of 5:95. The micro-nano bubbles referred to in this invention are gases composed mainly of bubbles with a diameter of less than 500 nm, which can release the internal energy of the bubbles after depressurization, and are prepared using air.

[0060] In addition, in embodiment 3, an inclined plate partition layer 13 and an agitator 14 are provided at the bottom of the tower body; the inclined plate partition layer 13 is located above the gas distribution module; the agitator 14 is a suspension pump.

[0061] Structural schematic diagram of Example 3 (see reference) Figure 6 .

[0062] Example 2

[0063] Using the system of Example 1, the pH value of the spray liquid from the first spray module is controlled between 6.5 and 6.8 by the second circulation pump, and the pH value of the spray liquid from the second spray module is controlled between 4.8 and 5.5 by the first circulation pump. The pH value of the slurry in the slurry pool at the bottom of the tower is dynamically controlled to be 4.8 to 5.5. If the pH value of the slurry is lower than 4.8, calcium hydroxide is added to the bottom of the tower. When the first spray module descends to the position of the second spray module, the spray liquid from the second spray module mixes with it. Based on comprehensive calculation, the pH value at this time is 5.4 to 5.8. This pH range is optimal for the oxidation of sulfite. At the same time, this pH control strategy can also keep the slurry at the bottom of the tower stable.

[0064] Its overall control strategy is as follows:

[0065] The desulfurization tower operates at full load with a flow rate of 100% and a capacity of 300,000 m³ / h. 3 / h;

[0066] When the flow rate in the exhaust gas inlet pipe is 30-50%, the sulfur dioxide content in the exhaust gas is less than 8000 mg / m³. 3At that time, the total liquid-to-gas ratio is controlled at 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 exhaust gas inlet pipe is 50-80%, the sulfur dioxide content in the exhaust gas is below 8000 mg / m³. 3 At that time, the total liquid-to-gas ratio is controlled at 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 exhaust gas inlet pipe is 80-100%, the sulfur dioxide content in the exhaust gas is less than 8000 mg / m³. 3 At that time, the total liquid-to-gas ratio is controlled at 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 exhaust gas inlet pipe is 30-50%, the sulfur dioxide content in the exhaust gas is higher than 8000 mg / m³. 3 And below 10000 mg / m 3 At that time, the total liquid-to-gas ratio is controlled at 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 exhaust gas inlet pipe is 50-80%, the sulfur dioxide content in the exhaust gas is higher than 8000 mg / m³. 3 And below 10000 mg / m 3 At that time, the total liquid-to-gas ratio is controlled at 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 exhaust gas inlet pipe is 80-100%, the sulfur dioxide content in the exhaust gas is higher than 8000 mg / m³. 3 And below 10000 mg / m 3 At that time, the total liquid-to-gas ratio is controlled at 20-25, and the liquid distribution ratio of the first spray module and the second spray module is 1:3-5.

[0072] Because the concentration of sulfur dioxide in the flue gas exceeds 10,000 mg / m³ 3 Such cases are rare, so they are not considered in this embodiment. When such cases occur, they can be handled according to the maximum flue gas flow rate, which can meet the relevant requirements.

[0073] We categorize the above operating conditions into low sulfur dioxide concentration conditions (sulfur dioxide < 8000 mg / m³). 3 ), medium to high sulfur dioxide concentration conditions (8000 mg / m³) 3 ≤Sulfur dioxide <10000 mg / m³ 3 The control strategies for the above operating conditions are completely different.

[0074] For low sulfur dioxide concentration conditions, only the exhaust gas flow rate needs to be considered. The total liquid-gas ratio can be controlled according to the exhaust gas flow rate, and the liquid distribution ratio can be fixed at an appropriate value.

[0075] For medium to high sulfur dioxide concentrations, it is necessary to consider not only the total liquid-to-gas ratio (with exhaust gas flow rate as the indicator) but also the intelligent adaptation of the liquid distribution ratio. More specifically, when the exhaust gas flow rate is higher, the spray volume of the first spray module needs to be increased to improve the absorption effect. At the same time, the pH value of the first spray module decreases after absorbing sulfur dioxide, which will increase the amount of liquid flowing through the second spray module. This liquid will reduce the impact of high-flow exhaust gas on the pH value of the liquid sprayed by the second spray module, and maintain the pH value of the liquid in the second spray module near the target value.

[0076] Through the above optimization, under different operating conditions, and using the above strategy, the sulfur dioxide content in the exhaust gas sample from the exhaust pipe is below 15 mg / Nm³. 3 To achieve ultra-low emission standards.

[0077] Example 3

[0078] It is largely the same as Example 2, except that it adds a micro-nano bubble distribution module, an inclined plate partition layer, and a stirrer.

[0079] Run test

[0080] The equipment was tested at a power plant in mainland China. It has two independent units of the same specifications, named Unit 1 and Unit 2 respectively. The two units were tested simultaneously. Unit 1 used the system of this invention and the process of Example 2, while Unit 2 used the process of Example 3.

[0081] The desulfurization tower before the upgrade also had a first spray module and a second spray module. Both the first and second spray modules were connected to pumps to dynamically replenish the calcium hydroxide solution, so as to keep the pH of the spray slurry constant at 5.5. According to the original data, the average unit load of the desulfurization tower before the upgrade was 525.47MW, and the average SO2 concentration at the outlet was 32.139mg / Nm³. 3 .

[0082] After nearly three months of synchronous operation, the following information was collected, see Table 1 for reference;

[0083] Table 1 Operational Statistics Table

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

[0085] Microscopic image of gypsum discharged from Unit 1 (reference) Figure 3 Microscopic image of gypsum discharged from Unit 2 (for reference) Figure 4 .

[0086] The results above show that after adopting the system and process of this invention, the unit load increased by 5-6%, and the outlet sulfur dioxide content decreased by 18-20 mg / Nm³. 3 .

[0087] By using micro-nano bubbles for gas distribution combined with a suspension pump for auxiliary stirring, the oxidation effect of sulfite can be improved. Through the full oxidation of sulfite, the concentration of sulfite in the bottom liquid can be reduced and converted into sulfate. The good liquid composition of the bottom liquid will make the absorption of sulfur dioxide by the first and second spray modules more effective. As can be seen from the corresponding gypsum photographs of Examples 2 and 3, the gypsum produced in Example 3 has better uniformity and fuller crystal particles, indicating that its oxidation degree is more thorough.

Claims

1. A dual-calcium-based wet desulfurization conditioning process, characterized in that, The process involves a desulfurization tower; the desulfurization tower includes a tower body, a tail gas inlet pipe connected to the middle of the tower body, and a tail gas outlet pipe 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; the inlet of the second circulation pump is connected to an absorbent inlet pipe for inputting calcium hydroxide solution; a flow meter and a control valve are connected to the absorbent inlet pipe; The process includes the following steps: Step 1: Measure the sulfur dioxide concentration in the exhaust gas inlet pipe; Step 2: Adjust the spray volume of the first and second spray modules according to the sulfur dioxide concentration to ensure that the sulfur dioxide content in the exhaust gas emitted from the exhaust pipe is below 15 mg / Nm³. 3 ; The pH value of the spray solution in the first spray module is controlled between 6.5 and 6.8; the pH value of the spray solution in the second spray module is controlled between 4.8 and 5.

5. The desulfurization tower is used at full load with a flow rate of 100%. When the flow rate in the exhaust gas inlet pipe is 30-50%, the sulfur dioxide content in the exhaust gas is below 8000 mg / m³. 3 At that time, the total liquid-to-gas ratio is controlled at 10-15, and the liquid distribution ratio of the first spray module and the second spray module is 1:10-20; When the flow rate in the exhaust gas inlet pipe is 50-80%, the sulfur dioxide content in the exhaust gas is below 8000 mg / m³. 3 At that time, the total liquid-to-gas ratio is controlled at 15-20, and the liquid distribution ratio of the first spray module and the second spray module is 1:10-20; When the flow rate in the exhaust gas inlet pipe is 80-100%, the sulfur dioxide content in the exhaust gas is less than 8000 mg / m³. 3 At that time, the total liquid-to-gas ratio is controlled at 20-25, and the liquid distribution ratio of the first spray module and the second spray module is 1:10-20; When the flow rate in the exhaust gas inlet pipe is 30-50%, the sulfur dioxide content in the exhaust gas is higher than 8000 mg / m³. 3 And below 10000 mg / m 3 At that time, the total liquid-to-gas ratio is controlled at 10~15, and the liquid distribution ratio of the first spray module and the second spray module is 1:10~15; When the flow rate in the exhaust gas inlet pipe is 50-80%, the sulfur dioxide content in the exhaust gas is higher than 8000 mg / m³. 3 And below 10000 mg / m 3 At that time, the total liquid-to-gas ratio is controlled at 15-20, and the liquid distribution ratio of the first spray module and the second spray module is 1:5-10; When the flow rate in the exhaust gas inlet pipe is 80-100%, the sulfur dioxide content in the exhaust gas is higher than 8000 mg / m³. 3 And below 10000 mg / m 3 At that time, the total liquid-to-gas ratio is controlled at 20-25, and the liquid distribution ratio of the first spray module and the second spray module is 1:3-5; When the first spray module descends to the position of the second spray module, the liquid sprayed by the second spray module mixes with the liquid sprayed by the second spray module, at which point the pH is 5.4 to 5.

8.

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

3. The process according to claim 2, characterized in that, The bottom of the tower is provided with an air distribution module for inputting air; the air distribution module is a first air distribution module for generating nano-microbubbles and a second air distribution module for inputting air to the bottom of the tower. The air flow rate input to the air distribution module is 0.5~1 vol‰ of the desulfurization tower tail gas treatment flow rate; 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; an alloy tray for enhancing gas-liquid mass transfer is provided below the second spray module; a Venturi rod is provided between the first spray module and the second spray module, the Venturi rod is used to improve the mass transfer effect between the spray liquid and the flue gas of the first spray module; the tail gas input pipe is located above the packing layer and below the alloy tray.

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

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