Flue gas desulfurization treatment system for oxidizing slurry outside desulfurization tower

Abstract

The utility model belongs to the technical field of flue gas purification, and particularly relates to a flue gas desulfurization treatment system for oxidizing slurry outside a desulfurization tower. The system comprises a desulfurizing tower, an oxidizing tower and a filtering device which are sequentially communicated, and the desulfurizing tower is a non-oxidizing device type desulfurizing tower. According to the utility model, the slurry is oxidized outside the desulfurization tower, so that the operation pressure of the desulfurization tower is reduced, the desulfurization effect is improved, the gypsum dehydration difficulty is reduced, and the purity is improved. Meanwhile, the structure in the tower is simplified, the slurry amount during operation of the desulfurizing tower is reduced, and the size of the desulfurizing tower is reduced.

Description

Technical Field

[0001] This utility model belongs to the field of flue gas purification technology, specifically relating to a flue gas desulfurization treatment system that oxidizes slurry outside the desulfurization tower. Background Technology

[0002] With rapid industrialization, air pollution has become an increasingly prominent problem. Flue gas generated in kilns in steel, cement, building materials, glass, and metallurgical industries contains large amounts of pollutants such as sulfur dioxide, nitrogen oxides, and particulate matter, posing a significant threat to human health and the ecological environment. Simultaneously, the construction of ultra-large-scale power generation units places considerable demands on desulfurization equipment. The large volume of flue gas requires correspondingly larger desulfurization towers, increasing construction costs and adding to operational instability. Utility Model Content

[0003] To address the shortcomings of existing technologies, this invention provides a flue gas desulfurization system that oxidizes the slurry outside the desulfurization tower. By oxidizing the slurry outside the desulfurization tower, this invention reduces the operating pressure of the tower, improves the desulfurization effect, reduces the difficulty of gypsum dewatering, and increases purity. Simultaneously, it simplifies the tower's internal structure, reduces the amount of slurry during tower operation, and decreases the tower's volume.

[0004] The technical solution provided by this utility model is as follows:

[0005] A flue gas desulfurization system for oxidizing slurry outside a desulfurization tower includes a desulfurization tower, an oxidation tower, and a filtration device arranged in sequence, wherein the desulfurization tower is a desulfurization tower without an oxidation device.

[0006] In the above technical solution:

[0007] After the raw flue gas passes through a dust removal device to remove dust, it enters a desulfurization tower for limestone wet desulfurization. Inside the desulfurization tower, sulfur dioxide reacts with limestone to produce calcium sulfite, which removes sulfur dioxide from the flue gas. Then, the slurry containing a high amount of calcium sulfite is sent to an oxidation tower for oxidation to produce calcium sulfate. Calcium sulfate continuously precipitates and crystallizes from the slurry into large gypsum particles, which are separated by a filtration device to obtain high-purity gypsum. The filtrate is returned to the desulfurization tower to continue the desulfurization reaction.

[0008] Desulfurization tower: Limestone wet desulfurization is adopted. Sulfur dioxide in flue gas is fully dissolved in the slurry and reacts with limestone to generate calcium sulfite, which dissolves in the slurry, thereby removing sulfur dioxide from the flue gas.

[0009] Oxidation tower: The calcium sulfite generated from desulfurization is sent into the oxidation tower for oxidation treatment, which oxidizes the calcium sulfite into calcium sulfate. The calcium sulfite and limestone in the slurry gradually decrease, while the calcium sulfate gradually increases, and finally the calcium sulfate crystallizes out to saturation.

[0010] Filtration device: The calcium sulfate in the slurry is filtered and collected, and the filtrate is returned to the desulfurization tower to participate in the desulfurization reaction.

[0011] A desulfurization tower without an oxidation device is a desulfurization tower that does not have an oxidation device, such as a gas-liquid two-phase countercurrent spray tower without an oxidation device. Existing technologies can be used; for example, the oxidation device can be omitted from existing desulfurization towers and gas-liquid two-phase countercurrent spray towers.

[0012] Main reaction equations inside the desulfurization tower:

[0013] SO2 + H2O → H2SO3

[0014] CaCO3 + H2SO3 → CaSO3 + CO2 + H2O

[0015] CaSO3 + H2SO3 → Ca(HSO3)2

[0016] Main reaction equations in the oxidation tower:

[0017] CaSO3 + 1 / 2O2 → CaSO4

[0018] Ca(HSO3)2+1 / 2O2→CaSO4+H2O+SO2

[0019] CaSO4 + 2H2O → CaSO4·2H2O

[0020] Furthermore, it also includes at least one desulfurization tower, with each desulfurization tower connected in parallel and respectively connected to the oxidation tower.

[0021] Based on the above technical solutions, when two or more desulfurization towers share an oxidation tower, the slurry storage capacity of the system can be reduced, and the investment in oxidation air equipment can be reduced. Since there is no oxidation air system inside the desulfurization tower, the liquid level of the slurry inside the desulfurization tower can be lowered, the liquid storage capacity of the desulfurization tower can be reduced, and the height of the desulfurization tower can be reduced, thereby reducing the construction cost and difficulty of the desulfurization tower.

[0022] Specifically: Each desulfurization tower has a tower body, and the tower body is equipped with a circulating pump, a spray layer and a demisting layer.

[0023] Based on the above technical solution, the oxidation system of the desulfurization tower is moved externally, eliminating the need for an oxidation system within the tower itself; that is, a complex oxidation air system is no longer installed within the slurry. When the oxidation air ducts are arranged within the slurry, scaling, blockage, and corrosion of the aeration ports easily occur, leading to uneven air distribution. This is especially problematic for many high-sulfur units, where the oxidation air system operates at high pressure, resulting in poor desulfurization efficiency, difficulty in gypsum dewatering, and low purity. Without an oxidation air system, the desulfurization tower has a simpler internal structure. Because there is no need to oxidize the slurry, there is no aeration and oxidation time between the slurry and air, reducing the slurry volume during operation and thus decreasing the tower's overall volume.

[0024] Specifically: The oxidation tower is a gas-liquid two-phase countercurrent spray tower.

[0025] Based on the above technical solution, the main function of the oxidation tower is to fully oxidize the desulfurization slurry fed into the desulfurization tower to generate gypsum crystals, followed by solid-liquid separation. The oxidation tower adopts a gas-liquid two-phase countercurrent spray tower, ensuring sufficient contact time and area between the air and the slurry. A certain pressure is maintained inside the oxidation tower; the oxidation air pressure should be greater than the desulfurization tower pressure. Finally, the oxidation air enters the desulfurization tower after passing through the oxidation tower.

[0026] Furthermore, an oxygen content detector is installed at the exhaust outlet of the oxidation tower.

[0027] Furthermore, the exhaust outlet of the oxidation tower is equipped with a regulating valve.

[0028] Furthermore, a circulation pump connected to the inlet pipeline is installed at the lower part of the oxidation tower.

[0029] Furthermore, the oxidation tower is connected to an oxidation fan.

[0030] Based on the above technical solution, an oxygen content detector is installed at the exhaust outlet of the oxidation tower. Air is added to the oxidation tower at an appropriate oxygen content to ensure the oxygen content inside the tower remains above 19%. Traditional desulfurization tower oxidation systems use submerged aeration. The oxidation of the slurry is affected by factors such as temperature, pressure, pH, and density within the tower. The oxidation air pipes inside the tower are approximately 5-7 meters below the slurry surface, requiring oxidation blowers to provide oxidation air at a pressure of approximately 100 kPa. This necessitates high-head Roots blowers or high-speed centrifugal chillers to provide high-pressure air, resulting in high energy consumption. When the oxidation air pipes malfunction, slurry deposits and scale at the pipe openings, clogging the air distribution ports. In contrast, external oxidation uses a spray method, and the oxidation process is unaffected by the operating conditions of the desulfurization tower. The oxidation air only needs to provide a pressure of approximately 10 kPa, which can be provided by ordinary blowers. Furthermore, the oxidation tower outlet valve can be adjusted to maintain a balanced pressure of 5-10 kPa throughout the tower, reducing redundant air waste and saving blower energy. Meanwhile, the oxidation tower is equipped with a corresponding slurry circulation pump and spraying equipment to ensure that the slurry is in full contact with the oxidizing air and to ensure that the oxidation tower has sufficient oxidation effect.

[0031] When the slurry is oxidized outside the oxidation tower, the pH of the oxidation tower is relatively stable. Since the oxidation and crystallization of gypsum takes place inside the tower, the process is not affected by the outside world. The resulting gypsum crystals have a larger particle size and better dehydration properties. The desulfurization tower continuously supplies slurry to the oxidation tower, which will not cause the reaction of gypsum saturation in the slurry to inhibit the dissolution of calcium carbonate. Since the gypsum content in the slurry inside the desulfurization tower is relatively small, the density of the slurry will be reduced, reducing the deposition of slurry at the bottom of the desulfurization tower, and at the same time reducing the energy consumption of the circulating pump and the wear of the blades.

[0032] When the oxidation tower oxidizes the slurry outside the tower, the desulfurization tower continuously supplies slurry to the oxidation tower. The slurry in the desulfurization tower has a low gypsum saturation. After the spray desulfurization process, the droplets carried by the clean flue gas contain less gypsum, making it less likely to precipitate and crystallize. It is also easy to wash away, reducing the clogging of the demister, improving the service life of the demister and improving the dust removal and demisting effect.

[0033] Specifically:

[0034] The filtration device includes at least a hydrocyclone and a filtrate tank;

[0035] The oxidation tower is connected to the hydrocyclone, and the hydrocyclone is connected to the filtrate tank;

[0036] The hydrocyclone has an overflow port, which is connected to the oxidation tower via a reuse pipeline.

[0037] Furthermore, a dewatering belt conveyor is also provided between the hydrocyclone and the filtrate tank.

[0038] The gypsum crystals that have grown through oxidation and crystallization are initially separated by a hydrocyclone. Larger particles are sent to a belt dewatering machine for liquid-solid separation, while smaller crystals are returned to the oxidation tower to continue growing.

[0039] Furthermore, the filtrate tank is also connected to each of the desulfurization towers via a reuse pipeline.

[0040] When the slurry is oxidized outside the oxidation tower, the pH value of the slurry in the desulfurization tower can be appropriately increased to improve the desulfurization effect. As the slurry is continuously sent to the oxidation tower for oxidation, the amount of calcium sulfite and unreacted calcium carbonate in the oxidized slurry is reduced. When it returns to the desulfurization tower, it can better dissolve sulfur dioxide and calcium carbonate, thus promoting the desulfurization reaction.

[0041] This utility model also discloses a flue gas desulfurization treatment method using an external oxidation slurry in a desulfurization tower, wherein the flue gas desulfurization is performed using the aforementioned external oxidation slurry flue gas desulfurization treatment system.

[0042] Specifically, the flue gas desulfurization treatment method for external oxidation slurry of the desulfurization tower includes the following steps:

[0043] Limestone wet desulfurization is carried out inside the desulfurization tower;

[0044] The oxidation of calcium sulfite takes place inside the oxidation tower;

[0045] The gypsum is separated within the filtration device.

[0046] The flue gas treatment system provided by this utility model has a simple structure, is easy to manufacture, is safe and reliable to use, and is easy to implement and promote. This technical solution can reduce investment costs, increase operational stability, achieve more stable desulfurization results, produce higher quality gypsum as a desulfurization product, and is more conducive to the resource utilization of desulfurized gypsum.

[0047] Compared with existing technologies, this invention reduces the internal structure of the desulfurization tower by removing the oxidation system outside the tower, lowering the liquid level of the slurry inside the tower, reducing the height of the desulfurization tower, and simplifying the arrangement of oxidation air ducts within the tower, thus reducing the manufacturing cost of the desulfurization tower. Furthermore, it replaces the original bubbling oxidation method that introduced air into the slurry with spray oxidation, increasing the gas-liquid ratio, reducing the amount of oxidation air, and saving energy consumption of the oxidation blower. Additionally, by simplifying the structure of existing desulfurization towers, manufacturing costs and maintenance complexity can be reduced. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the flue gas desulfurization treatment system for oxidizing slurry outside the desulfurization tower provided by this utility model.

[0049] Figure 2 This is a flowchart of a flue gas desulfurization system for oxidizing slurry outside a desulfurization tower, provided by this utility model.

[0050] Appendix Figure 1 The structures represented by each label are listed below:

[0051] 1. Desulfurization tower; 2. Oxidation tower; 3. Filtration tank; 4. Dewatering belt conveyor; 5. Oxidation fan; 6. Hydrocyclone. Detailed Implementation

[0052] The principles and features of this utility model are described below. The embodiments given are only used to explain this utility model and are not intended to limit the scope of this utility model.

[0053] Unless otherwise specified, the test methods used in the embodiments are conventional methods; unless otherwise specified, the materials and reagents used are commercially available.

[0054] Example 1

[0055] like Figure 1 As shown, the flue gas desulfurization treatment system for oxidizing slurry outside the desulfurization tower includes a desulfurization tower 1, an oxidation tower 2, and a filtration device connected in sequence.

[0056] Desulfurization tower 1 is a gas-liquid two-phase countercurrent spray tower without an oxidation device.

[0057] Oxidation tower 2 is connected to oxidation fan 5. A circulation pump connected to the inlet pipeline is installed at the bottom of oxidation tower 2.

[0058] The filtration device includes a hydrocyclone 6, a dewatering belt conveyor 4, and a filtrate tank 3, which are connected in sequence. The oxidation tower 2 is connected to the hydrocyclone 6. The hydrocyclone 6 has an overflow port, which is connected to the oxidation tower 2 through a reuse pipeline.

[0059] Based on this technical solution, after the raw flue gas passes through a dust removal device to remove dust, it enters a desulfurization tower for limestone wet desulfurization. In the desulfurization tower, sulfur dioxide reacts with limestone to produce calcium sulfite, which removes sulfur dioxide from the flue gas. Then, the slurry containing more calcium sulfite is sent to an oxidation tower for oxidation to produce calcium sulfate. Calcium sulfate continuously precipitates and crystallizes from the slurry into large gypsum particles, which are then separated by a filtration device to obtain gypsum with higher purity.

[0060] Example 2

[0061] Based on Example 1, such as Figure 1 As shown, the system also includes a desulfurization tower 1, and the two desulfurization towers 1 are connected in parallel and connected to the oxidation tower 2 respectively.

[0062] Based on this technical solution, the slurry storage capacity of the system can be reduced, and the investment in oxidation air equipment can be reduced.

[0063] Example 3

[0064] Based on Example 2, such as Figure 1 As shown, an oxygen content detector is installed at the exhaust outlet of oxidation tower 2, and a regulating valve is installed at the exhaust outlet of oxidation tower 2.

[0065] Based on this technical solution, an oxygen content detector is installed at the exhaust outlet of the oxidation tower. By appropriately replenishing the air in the oxidation tower according to the oxygen content, the oxygen content in the oxidation tower is ensured to be above 19%. The pressure of 5-10 kPa in the entire oxidation tower can be maintained by adjusting the outlet valve of the oxidation tower, thereby reducing the waste of redundant air.

[0066] Example 4

[0067] Based on Example 3, such as Figure 1 As shown, the filtrate tank 3 is also connected to each desulfurization tower 1 through a reuse pipeline.

[0068] Based on this technical solution, when the oxidized slurry is returned to the desulfurization tower, it can better dissolve sulfur dioxide and calcium carbonate, thus promoting the desulfurization reaction.

[0069] Example 1

[0070] Flue gas desulfurization is performed using a flue gas desulfurization system with external oxidation slurry in the desulfurization tower.

[0071] SO2 in raw flue gas: 3000 mg / m³ 3 .

[0072] SO2 in the treated flue gas < 20 mg / m³ 3 .

[0073] The purity of the obtained gypsum is ≥95%.

[0074] The process can be referenced. Figure 2 .

[0075] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A flue gas desulfurization system for oxidizing slurry outside a desulfurization tower, characterized by: The system comprises a desulfurization tower (1), an oxidation tower (2) and a filter device connected in sequence, wherein the desulfurization tower (1) is an oxidation device-free desulfurization tower.

2. The flue gas desulfurization treatment system that oxidizes slurry outside desulfurization tower according to claim 1, characterized in that: The system further comprises at least one desulfurization tower (1), each of which is connected in parallel with the oxidation tower (2).

3. The flue gas desulfurization system of oxidizing slurry outside the desulfurization tower according to claim 2, characterized in that: Each desulfurization tower (1) has a tower body provided with a circulating pump, a spraying layer and a demisting layer.

4. The flue gas desulfurization treatment system that oxidizes slurry outside desulfurization tower according to claim 2, characterized in that: The oxidation tower (2) is a gas-liquid two-phase countercurrent spraying tower.

5. The flue gas desulfurization system of claim 4, wherein: An oxygen content detector is installed at the exhaust outlet of the oxidation tower (2); And / or, an adjusting valve is arranged at the exhaust outlet of the oxidation tower (2).

6. The flue gas desulfurization system of claim 2, wherein: The filter device comprises at least a cyclone (6) and a filtrate tank (3); The oxidation tower (2) is connected with the cyclone (6), and the cyclone (6) is connected with the filtrate tank (3); The cyclone (6) has an overflow port connected with the oxidation tower (2) through a recycling pipeline.

7. The flue gas desulfurization system of oxidizing slurry outside the desulfurization tower according to claim 6, characterized in that: A dehydration belt conveyor (4) is further arranged between the cyclone (6) and the filtrate tank (3).

8. The flue gas desulfurization system of oxidizing slurry outside the desulfurization tower according to claim 6, characterized in that: The filtrate tank (3) is further connected with each desulfurization tower (1) through a recycling pipeline.

9. The flue gas desulfurization system of oxidizing slurry outside the desulfurization tower according to claim 4, characterized in that: A circulating pump connected with a liquid inlet pipeline is arranged at the lower part of the oxidation tower (2).

10. The flue gas desulfurization system of oxidizing slurry outside the desulfurization tower according to claim 4, characterized in that: An oxidation air blower (5) is connected with the oxidation tower (2).

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