CN205650072U - Dual cycle desulfurization absorption tower - Google Patents

Abstract

The utility model provides a double-cycle desulfurization absorption tower, which includes an absorption tower slurry pool, a lower loop spray layer, and a demister from bottom to top. An inlet flue is arranged between the absorption tower slurry pool and the lower loop spray layer. There is an outlet flue above the demister, and the slurry in the slurry pool of the absorption tower is transported to the spray layer of the lower loop through the slurry circulation pump of the lower loop. An oxidation device is also installed outside the slurry pool of the absorption tower. The spray layer of the lower loop and the demister A liquid collecting bucket and an upper circuit spray layer are arranged in sequence from bottom to top between the foggers. Outside the slurry tank of the absorption tower, there is also a feeding tank outside the tower, and the slurry in the feeding tank outside the tower is transported by the upper circuit slurry circulation pump. To the spray layer of the upper circuit, the overflow slurry from the feeding tank outside the tower flows back into the slurry pool of the absorption tower through the pipeline. The use of this desulfurization tower can not only meet the desulfurization requirements of ultra-low emissions in power plants today, but also effectively reduce the operating cost of the desulfurization system.

Description

A double cycle desulfurization absorption tower

technical field

The utility model relates to an environmental protection equipment, in particular to a double-cycle desulfurization absorption tower.

Background technique

In the next 50 years, the situation that China's power energy structure is dominated by coal-fired generating units will not change. And SO2 is one of the main air pollutants in coal _- fired power plants, which will lead to air pollution. Today, domestic thermal power plants are basically equipped with flue gas desulfurization devices to meet flue gas emission standards. Among them, limestone-gypsum wet flue gas desulfurization technology is the most widely used, and its desulfurization efficiency can reach more than 98%. This method has become the mainstream process of flue gas desulfurization in thermal power plants.

In the limestone-gypsum wet flue gas desulfurization process, the desulfurization absorption tower is basically a traditional countercurrent spray tower. The structure of the desulfurization absorption tower is shown in Figure 1. It includes the absorption tower slurry tank, the lower circuit spray layer, and the demister from bottom to top. There is an inlet flue between the absorption tower slurry tank and the lower circuit spray layer. There is an outlet flue above the fogger, and the slurry in the slurry tank of the absorption tower is transported to the spray layer of the lower loop through the slurry circulation pump of the lower loop, and an oxidation device is installed outside the slurry of the absorption tower. Among them, the function of the slurry pool is to store the desulfurization agent slurry, which is composed of limestone, calcium sulfate and calcium sulfite; the flue gas absorption area is formed between the upper part of the slurry pool and the spray layer of the lower circuit, and the flue gas contacts the desulfurization slurry in this area , to complete gas-liquid mass transfer to remove SO ₂ ; the demister area is the area of the demister above the spray layer of the lower circuit to form the demist area, in which the net flue gas is removed from the entrained water and then discharged out of the desulfurization tower.

The desulfurization process of flue gas in this type of absorption tower is as follows: the slurry circulation pump pumps the slurry in the slurry pool of the desulfurization tower and sends it to the spray pipe above the flue gas absorption area, and the slurry is atomized by the nozzle on the spray pipe and then sprayed out. Contact with the high-temperature raw flue gas entering the lower part of the absorption zone (without flue gas heat exchanger: 110~150°C, with flue gas heat exchanger: 80~90°C ₎ , and the SO2 in the raw flue gas dissolves in the spray In the slurry; in the slurry tank, the SO ₂ in the liquid phase reacts with the dissolved CaCO ₃ in series to form CaSO ₃ , and the CaSO ₃ is oxidized by the blown air to form CaSO ₄ ; after countercurrent contact with the atomized slurry in the spray layer, the smoke is entrained More slurry droplets, at this time, most of the droplets are separated and removed by the demister in the tower, and the purified flue gas is discharged from the outlet flue at the top of the tower.

_In the above process, the flue gas desulfurization is realized through the absorption and oxidation of SO2 in the flue gas, while the absorption and oxidation of SO2 are realized by _three main reaction processes occurring in the slurry in the countercurrent spray tower, respectively It is limestone dissolution reaction, SO ₂ absorption reaction, CaSO ₃ generation and oxidation reaction. The absorption reaction of SO ₂ is in the absorption zone, and the gas-liquid mass transfer is completed in the countercurrent contact between the flue gas and the atomized desulfurization slurry, and the dissolution reaction of limestone and the formation and oxidation of CaSO ₃ are carried out in the slurry pool below the absorption zone. The above-mentioned reaction degree is closely related to the pH value of the slurry in the tower, so the control of the reaction conditions directly affects the progress of the entire desulfurization reaction, but the most difficult thing at present is the control of the reaction conditions. The reason is that the three types of reactions have different requirements on the slurry pH environment, and even restrict each other. For example, the high pH environment of the slurry is conducive to the absorption of SO2. When the pH value reaches ₆ , the slurry has the best absorption effect on SO2 _; but the low pH environment of the slurry is conducive to the dissolution _of limestone and the oxidation of CaSO3. When the pH value of the slurry is When it is lower _than 3.5, the oxidation rate and dissolution rate are extremely high, but it is very difficult for the slurry to absorb SO2 at this time.

In summary, it can be seen that there are design defects in this desulfurization tower: the setting of a single slurry tank will inevitably lead to a compromise selection of the pH value of the slurry, and the suppression of the absorption capacity of the slurry to SO2, that is, the selection of the pH value is based _on improving the slurry. The dissolution of limestone and the oxidation of CaSO ₃ sacrifice the maximum absorption capacity of the slurry to SO ₂ to a certain extent, and the desulfurization capacity of the system is limited.

With the implementation of ultra-low emissions from coal-fired power plants across the country, in order to ensure a high desulfurization rate of the desulfurization system, traditional spray desulfurization towers generally adopt measures such as increasing the liquid-gas ratio and increasing the number of spray layers in the design. However, a series of problems are also derived: the increase of the liquid-gas ratio increases the amount of slurry entrained in the flue gas after the gas-liquid contact, the phenomenon of "gypsum rain" is more likely to occur, and the dust content of the flue gas increases; at the same time, the volume of the slurry tank and The amount of slurry circulation also increases correspondingly, resulting in an increase in the power consumption of the circulating pump and the oxidation fan; the increase in the number of spray layers will lead to an increase in the height of the absorption tower, which will eventually lead to an increase in the cost of the desulfurization device, desulfurization power consumption, and operating costs. Power plants bring heavy operating and economic burdens. Therefore, it is very necessary and meaningful to seek a desulfurization absorption tower with high desulfurization efficiency and strong adaptability to _SO2 load changes.

Utility model content

Purpose of the utility model: In order to overcome the above-mentioned defects, the utility model provides a double-cycle desulfurization absorption tower, which consists of two circulation loops working at different pH values, so as to improve the utilization rate of limestone and the removal rate of SO ₂ .

Technical scheme of the utility model:

A double-cycle desulfurization absorption tower, which includes the absorption tower slurry pool, the lower loop spray layer, and the demister from bottom to top. There is an inlet flue between the absorption tower slurry pool and the lower loop spray layer. There is an outlet flue, and the slurry in the slurry tank of the absorption tower is transported to the spray layer of the lower circuit through the slurry circulation pump of the lower circuit. An oxidation device is also installed outside the slurry tank of the absorption tower. From the bottom to the top, there are liquid collecting buckets (which can collect the upper sprayed slurry and allow the flue gas to pass through) and the upper circuit spray layer. The slurry in the material tank is transported to the spray layer of the upper circuit through the slurry circulation pump of the upper circuit, the slurry pool of the absorption tower, the spray layer of the lower circuit and the slurry circulation pump of the lower circuit constitute the lower circulation circuit, and the feeding tank outside the tower, the spray layer of the upper circuit and the upper circuit The loop slurry circulation pump constitutes the upper circulation loop. The overflow slurry from the feeding tank outside the tower flows back into the slurry pool of the absorption tower through the pipeline, and the air is blown into the slurry pool of the absorption tower through the oxidation device to perform forced oxidation on the slurry.

The upper circuit spray layer is 2-4 layers.

The pH value of the slurry in the lower circulation loop is 4-5. The pH value of the slurry in the upper circulation loop is 6-7. The two circulation loops operate at different pH values.

The demister is a two-stage demister, which removes mist droplets carried by the flue gas. The demisters are equipped with flushing water pipes and nozzles, which are flushed regularly to avoid blockage of the demisters.

With the above technical scheme, when the raw flue gas enters the absorption tower, it flows from bottom to top and first passes through the spray area of the lower circuit, and contacts with the desulfurization absorbent sprayed downward in countercurrent. Each layer of spraying corresponds to a slurry circulation pump, and the slurry circulation pump pumps the bottom slurry of the slurry pool (pH 4~5) in the absorption tower to the spray layer. In this area, while initially removing SO ₂ , the flue gas temperature can be lowered to quickly reach the saturated flue temperature, and at the same time, HF and HCl in the flue gas can be washed away together. The complete oxidation of CaSO ₃ and the formation of CaSO ₄ are mainly completed in the lower circulation loop.

After the pre-washing of the lower circulation loop, the flue gas from bottom to top passes through the guide blades of the liquid collecting bucket and continues upward into the upper circulation loop. The flue gas contacts the atomized slurry sprayed by the spray layer of the upper loop in countercurrent contact. When the pH value is 6~7, because the slurry contains excess CaCO ₃ and has a large buffer capacity, almost all SO ₂ in the flue gas can be absorbed and removed by the atomized slurry sprayed by the spray layer of the upper circuit. The buffering effect enables the system to be automatically controlled within a stable optimum pH range, which does not fluctuate with changes in flue gas flow and SO ₂ load.

Beneficial effect:

Compared with the prior art, the utility model has the following advantages:

1. Composed of two circulation loops working at different pH values, so that the absorption and oxidation of SO ₂ can be carried out under the best chemical conditions, and the slurry can complete the large-capacity absorption of SO ₂ and the complete removal of CaSO ₄ Oxygenated. The feeding tank in the upper absorption area has a strong buffer capacity due to the high pH value of the slurry, which can effectively ensure the highest _SO2 removal rate, and even if the _SO2 load changes significantly, it will not cause fluctuations in the desulfurization rate. In the slurry pool at the lower part of the absorption tower, the low pH value of the slurry is conducive to the dissolution of limestone and the oxidation of CaSO ₃ , which is beneficial to improving the utilization rate of limestone and the purity of gypsum.

2. The upper circulation loop operates at a high pH value. At the same desulfurization rate, compared with the traditional countercurrent spray tower, the required liquid gas is smaller, which reduces the flow rate of the slurry circulation pump. And in the slurry tank of the absorption tower, the oxidation condition of the gypsum generation area is good, which can effectively reduce the liquid level of the slurry tank and the pressure head of the oxidation fan.

Therefore, the use of this kind of desulfurization tower can not only meet the desulfurization requirements of ultra-low emissions in today's power plants, but also effectively reduce the operating cost of the desulfurization system.

Description of drawings

Fig. 1 is a structural schematic diagram of an existing desulfurization absorption tower.

Fig. 2 is the structural representation of double circulation desulfurization absorption tower of the present utility model;

Among them: 1. Absorption tower slurry pool; 2. Oxidation device; 3. Inlet flue; 4. Lower circuit spray layer; 5. Liquid collection bucket; 6. Upper circuit spray layer; 7. Demister; 8. Exit flue; 9. Upper loop slurry circulation pump; 10. Feeding tank outside the tower; 11. Lower loop slurry circulation pump.

detailed description

Below in conjunction with accompanying drawing and specific embodiment, further set forth the utility model, should be understood that these embodiments are only used for illustrating the utility model and are not intended to limit the scope of the utility model, after having read the utility model, those skilled in the art will understand this utility model The modifications of various equivalent forms of the utility model all fall within the scope defined by the appended claims of the present application.

Example 1

As shown in Figure 2, a double-cycle desulfurization absorption tower includes the absorption tower slurry pool 1, the lower loop spray layer 4, the demister 7, the absorption tower slurry pool 1 and the lower loop spray layer 4 from bottom to top. There is an inlet flue 3 between them, and an outlet flue 8 is arranged above the mist eliminator 7. The slurry in the slurry pool 1 of the absorption tower is transported to the spray layer 4 of the lower loop through the slurry circulation pump 11 of the lower loop, and the slurry pool 1 of the absorption tower is transported to the spray layer 4 of the lower loop. An oxidation device 2 is also provided, and a liquid collection bucket 5 is arranged sequentially from bottom to top between the lower circuit spray layer 4 and the demister 7 (which not only collects the upper sprayed slurry but also allows the flue gas to pass through) and The upper circuit spray layer 6, the absorption tower slurry pool 1 is also provided with a tower external feeding tank 10, the slurry in the tower external feeding tank 10 is transported to the upper circuit spray layer 6 through the upper circuit slurry circulation pump 9, and the absorption tower slurry pool 1. The lower circuit spray layer 4 and the lower circuit slurry circulation pump 11 constitute the lower circulation circuit, the tower external feeding tank 10, the upper circuit spray layer 6 and the upper circuit slurry circulation pump 9 constitute the upper circulation circuit, and the tower external feeding tank 10 The overflow slurry flows back into the slurry pool 1 of the absorption tower through the pipeline, and the air is blown into the slurry pool 1 of the absorption tower through the oxidation device 2, and the slurry is forcibly oxidized.

The upper circuit spray layer is 2-4 layers.

The pH value of the slurry in the lower circulation loop is 4-5. The pH value of the slurry in the upper circulation loop is 6-7. The two circulation loops operate at different pH values.

The demister is a two-stage demister, which removes mist droplets carried by the flue gas. The demisters are equipped with flushing water pipes and nozzles, which are flushed regularly to avoid blockage of the demisters.

When the original flue gas enters the absorption tower, it flows from bottom to top and first passes through the lower circuit spray layer 4, and then contacts with the desulfurization absorbent sprayed downwards in countercurrent, and cools down to the saturation temperature. Each layer of spraying corresponds to a slurry circulation pump, and the slurry circulation pump pumps the bottom slurry of the slurry pool (pH 4~5) in the absorption tower to the spray layer. The slurry in the lower circuit spray layer 4 comes from the absorption tower slurry pool 1, and is sent to the lower circuit spray layer 4 through the lower circuit slurry circulation pump 10. In this area, while initially removing SO ₂ , the temperature of the flue gas can be reduced to make it It quickly reaches the saturated flue temperature, and at the same time, it can wash away the HF and HCl in the flue gas. In the lower circulation loop, the complete oxidation of CaSO ₃ and the generation of CaSO ₄ are mainly completed, and the pH value of the slurry in this area is controlled at about 4~5. The air needed for CaSO3 oxidation is provided by oxidation device ₂ .

After the pre-washing of the lower circulation loop, the flue gas from bottom to top passes through the guide vanes of the liquid collecting bucket 5, and continues to enter the upper circulation loop upwards, and the flue gas is in countercurrent contact with the atomized slurry sprayed by the upper loop spray layer 6 . The slurry in the spray layer 6 of the upper circuit comes from the feeding tank 10 outside the tower, and is sent to the upper absorption area by the slurry circulation pump 9 of the upper circuit. On the loop. When the pH value is 6~7, because the slurry contains excess CaCO ₃ and has a large buffer capacity, almost all SO ₂ in the flue gas can be absorbed and removed by the atomized slurry sprayed by the spray layer 6 of the upper circuit. This kind of buffering effect makes the system automatically control in a stable optimum pH value range, which does not fluctuate with the change of flue gas flow and SO ₂ load.

The overflow slurry from the feeding tank 10 outside the tower flows into the slurry pool 1 of the absorption tower through a pipeline. The newly replenished limestone slurry can be added to the feeding tank 10 outside the tower separately, or can be added to the slurry pool 1 of the absorption tower at the same time.

A two-stage mist eliminator 7 is installed on the upper part of the absorption tower to remove the slurry droplets carried in the flue gas. The two-stage demisters 7 are provided with flushing water pipes and nozzles, which are regularly flushed to avoid blockage of the demisters.

Claims (3)

1. A double-cycle desulfurization absorption tower, which includes the absorption tower slurry pool (1), the lower loop spray layer (4), the demister (7), the absorption tower slurry pool (1) and the lower loop spray layer from bottom to top. There is an inlet flue (3) between the shower layers (4), an outlet flue (8) above the mist eliminator (7), and the slurry in the absorption tower slurry pool (1) passes through the lower loop slurry circulation pump (11 ) to the lower circuit spray layer (4), and an oxidation device (2) is provided outside the absorption tower slurry pool (1), characterized in that the lower circuit spray layer (4) and demister (7) A liquid collecting bucket (5) and an upper circuit spray layer (6) are arranged sequentially from bottom to top, and an external feeding tank (10) is provided outside the slurry pool (1) of the absorption tower, and the external feeding The slurry in the tank (10) is transported to the upper loop spray layer (6), the absorption tower slurry pool (1), the lower loop spray layer (4) and the lower loop slurry circulation pump (11) via the upper loop slurry circulation pump (9) The lower circulation loop is formed, the feeding tank outside the tower (10), the upper loop spray layer (6) and the upper loop slurry circulation pump (9) constitute the upper circulation loop, and the overflow slurry from the feeding tank outside the tower (10) flows back through the pipeline In the slurry pool (1) of the absorption tower. 2. A double-cycle desulfurization absorption tower according to claim 1, characterized in that, the spray layer (6) of the upper circuit is 2-4 layers. 3. A dual-cycle desulfurization absorption tower according to claim 1, characterized in that the demister (7) is a two-stage demister.