Desulfurization wastewater reduction system based on low-grade flue gas concentration and operation method thereof

Abstract

The invention discloses a desulfurization wastewater reduction system based on low-grade flue gas concentration and an operation method thereof.The system comprises a dust remover, a desulfurization tower, a booster fan, a supergravity rotating bed, a wastewater tank, a wastewater circulating pump and a wastewater discharge pump, and a flue gas outlet of the dust remover is divided into a first pipeline and a second pipeline; a first pipeline is sequentially connected with a booster fan and a supergravity rotating bed, a second pipeline is connected with a desulfurizing tower, a gas phase outlet pipeline of the supergravity rotating bed is connected with the second pipeline in a converging mode, a liquid phase outlet of the supergravity rotating bed is connected with a waste water tank, and a pipeline at the bottom of the waste water tank is circularly connected with the supergravity rotating bed through a waste water circulating pump. And another pipeline at the bottom of the wastewater tank is connected with a subsequent treatment device through a wastewater discharge pump. The low-temperature flue gas waste heat is utilized to reduce and concentrate the desulfurization waste water, a large amount of steam energy is not required to be introduced, the energy consumption is reduced, and waste heat recycling of a power plant is realized while reduction of the desulfurization waste water is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of desulfurization wastewater treatment, and in particular relates to a desulfurization wastewater reduction system based on low-grade flue gas concentration and an operation method thereof. Background Art

[0002] The limestone-gypsum wet flue gas desulfurization process is currently the most widely used and mature desulfurization technology in the world. In order to ensure the working efficiency of the slurry, reduce system corrosion and ensure the quality of gypsum, the chloride ion concentration should be controlled. The control limit is generally 8000-20000 mg / L. To control the chloride ion concentration, a certain amount of desulfurization wastewater needs to be discharged regularly and fresh absorption liquid needs to be added. The desulfurization wastewater quality of wet desulfurization in coal-fired power plants has the following characteristics: ① It is weakly acidic, with a pH of 5 to 6.5; ② The suspended solids are relatively high, at 10000mg / L to 60000mg / L; ③ Cl - Generally, it is between 8000mg / L and 20000mg / L, and is highly corrosive; ④ It contains a large amount of metal ions, such as Ca 2+ Mg 2+ Etc., the total amount reaches 20000mg / L~50000mg / L; ⑤ The content of heavy metals (Hg, Cr, Pb, Ni, Cd) is high.

[0003] Common desulfurization wastewater reduction processes are divided into membrane concentration and thermal concentration. The membrane concentration process requires a pre-treatment device to soften the incoming water, which has the disadvantage of high requirements for incoming water. Affected by various factors such as coal quality and boiler load, the quality of desulfurization wastewater is unstable, and the difficulty of pre-treatment increases; the service life of the membrane is limited and needs to be cleaned or replaced frequently, and there is a risk of membrane polarization.

[0004] Thermal concentration can be divided into steam thermal concentration and low-temperature flue gas waste heat concentration. Among them, steam thermal concentration uses power plant steam as a heat source to evaporate and concentrate desulfurization wastewater, which has problems such as complex system, high energy consumption, high investment cost, complex composition of mixed salt products, great difficulty in handling, short cleaning cycle, and easy scaling. Low-temperature flue gas waste heat concentration uses low-temperature flue gas waste heat to achieve concentration and reduction of desulfurization wastewater, without the need to introduce a large amount of steam energy, saving costs, but low-temperature flue gas waste heat concentration requires the installation of a concentration tower, which has problems such as large footprint, high infrastructure cost, and poor gas-liquid mass transfer effect. Summary of the invention

[0005] In view of the above problems, the object of the present invention is to provide a desulfurization wastewater reduction system based on low-grade flue gas concentration and an operation method thereof.

[0006] The specific technical solutions are as follows: A desulfurization wastewater reduction system based on low-grade flue gas concentration comprises a dust collector, a desulfurization tower, a booster fan, a supergravity rotating bed, a wastewater tank, a wastewater circulation pump and a wastewater efflux pump, wherein the flue gas outlet of the dust collector is divided into a first pipeline and a second pipeline, the first pipeline is connected to the booster fan and the supergravity rotating bed in sequence, the second pipeline is connected to the desulfurization tower, the gas phase outlet pipeline of the supergravity rotating bed is merged and connected with the second pipeline, the liquid phase outlet of the supergravity rotating bed is connected to the wastewater tank, a pipeline at the bottom of the wastewater tank is circulatedly connected to the supergravity rotating bed through a wastewater circulation pump, and another pipeline at the bottom of the wastewater tank is connected to a subsequent treatment device through a wastewater efflux pump.

[0007] Furthermore, the liquid phase outlet pipeline of the ultra-gravity rotating bed extends into the wastewater tank, and the distance between the end of the pipeline and the bottom of the wastewater tank is no more than 300 mm; the top of the wastewater tank is connected with a desulfurization wastewater inlet pipeline.

[0008] Furthermore, the ultra-gravity rotating bed is composed of 2-5 rotors.

[0009] An operating method of a desulfurization wastewater reduction system based on low-grade flue gas concentration comprises the following steps: 1) The desulfurized wastewater in the wastewater tank is transported to the supergravity rotating bed through the wastewater circulation pump; 2) The low-temperature flue gas after passing through the dust collector is pressurized by the booster fan and then transported to the supergravity circulating bed; 3) The desulfurized wastewater and low-temperature flue gas are in countercurrent contact in the supergravity rotating bed for gas-liquid mass transfer. The heat of the flue gas is transferred to the desulfurized wastewater, and the desulfurized wastewater transfers mass to the flue gas to achieve the concentration of the desulfurized wastewater; 4) The concentrated desulfurization wastewater flows from the liquid phase outlet pipeline of the supergravity rotating bed to the wastewater tank; 5) The saturated wet flue gas returns to the desulfurization tower from the gas phase outlet at the top of the supergravity rotating bed; 6) The concentrated wastewater in the wastewater tank is discharged to the subsequent treatment device through the wastewater discharge pump.

[0010] Furthermore, the temperature of the low-temperature flue gas in step 2) is 85-140°C.

[0011] Furthermore, the operating conditions of the high gravity rotating bed in step 3) are high gravity factor 60-150, liquid-gas ratio 0.8-2 L / m 3 , empty bed gas velocity 2~3.5m / s.

[0012] Furthermore, a cross-sectional area ratio of the first pipeline to the second pipeline is 1:5-15.

[0013] The beneficial effects of the present invention are: 1) The waste heat of low-temperature flue gas is used to reduce and concentrate the desulfurization wastewater, without the need to introduce a large amount of steam energy, thus reducing energy consumption. While reducing the desulfurization wastewater, the waste heat of the power plant is reused; 2) The use of an ultra-gravity rotating bed enhances the gas-liquid mass transfer effect, effectively reduces the size of the equipment, reduces the system footprint, and simplifies the process flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the system structure of the present invention.

[0015] In the figure: 1. dust collector; 2. desulfurization tower; 3. booster fan; 4. supergravity rotating bed; 5. wastewater tank; 6. wastewater circulation pump; 7. wastewater effluent pump; 11. first pipeline; 12. second pipeline. DETAILED DESCRIPTION

[0016] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention is not limited thereto.

[0017] like Figure 1 As shown, a desulfurization wastewater reduction system based on low-grade flue gas concentration includes a dust collector 1, a desulfurization tower 2, a booster fan 3, a supergravity rotating bed 4, a wastewater tank 5, a wastewater circulation pump 6 and a wastewater effluent pump 7. The flue gas outlet of the dust collector 1 is divided into a first pipeline 11 and a second pipeline 12. The first pipeline 11 is connected to the booster fan 3 and the supergravity rotating bed 4 in sequence, and the second pipeline 12 is connected to the desulfurization tower 2. The gas phase outlet pipeline of the supergravity rotating bed 4 is connected to the second pipeline 12. The liquid phase outlet pipeline of the bed 4 extends into the wastewater tank 5, and the distance between the end of the pipeline and the bottom of the wastewater tank 5 is not more than 300 mm. A pipeline at the bottom of the wastewater tank 5 is circulatedly connected to the supergravity rotating bed 4 through a wastewater circulation pump 6. Another pipeline at the bottom of the wastewater tank 5 is continuously connected to the subsequent treatment device through a wastewater efflux pump 7. The top of the wastewater tank 5 is connected to the desulfurization wastewater inlet pipeline. The supergravity rotating bed 4 is composed of 2-5 rotors. The cross-sectional area ratio of the first pipeline 11 and the second pipeline 12 is 1:5~15.

[0018] Example

[0019] An operating method of a desulfurization wastewater reduction system based on low-grade flue gas concentration comprises the following steps: 1) The desulfurized wastewater with a calcium ion concentration of 58 mmol / L in the wastewater tank 5 is transported to the supergravity rotating bed 4 through the wastewater circulation pump 6. The flow rate of the desulfurized wastewater is 10m 3 / h; 2) After passing through the dust collector 1, the low-temperature flue gas at 130°C is pressurized by the booster fan 3 and transported to the supergravity circulating bed 4. The flow rate of the low-temperature flue gas is 11134m 3 / h, liquid-gas ratio is 0.9L / m 3 ; 3) The super gravity factor of the super gravity rotating bed 4 is 87, and the empty bed gas velocity is 3.5 m / s. The desulfurized wastewater and the low-temperature flue gas are in countercurrent contact in the super gravity rotating bed 4 for gas-liquid mass transfer. The heat of the flue gas is transferred to the desulfurized wastewater, and the desulfurized wastewater transfers mass to the flue gas to achieve the concentration of the desulfurized wastewater. The concentration ratio of the desulfurized wastewater is 5 times. 4) The concentrated desulfurized wastewater flows from the liquid phase outlet pipeline of the supergravity rotating bed 4 to the wastewater tank 5, wherein the calcium ion concentration is 290mmol / L; 5) The saturated wet flue gas at 83°C is returned to the desulfurization tower 2 from the gas phase outlet at the top of the supergravity rotating bed 4; 6) The concentrated wastewater in the wastewater tank 5 is discharged to the subsequent treatment device through the wastewater discharge pump 7.

Claims

1. A desulfurization wastewater reduction system based on low-grade flue gas concentration, characterized in that: The invention comprises a dust collector (1), a desulfurization tower (2), a booster fan (3), a supergravity rotating bed (4), a wastewater tank (5), a wastewater circulation pump (6) and a wastewater discharge pump (7). The flue gas outlet of the dust collector (1) is divided into a first pipeline (11) and a second pipeline (12). The first pipeline (11) is connected to the booster fan (3) and the supergravity rotating bed (4) in sequence. The second pipeline (12) is connected to the desulfurization tower (2). The gas phase outlet pipeline of the supergravity rotating bed (4) is connected to the second pipeline (12). The liquid phase outlet of the supergravity rotating bed (4) is connected to the wastewater tank (5). A pipeline at the bottom of the wastewater tank (5) is connected to the supergravity rotating bed (4) through the wastewater circulation pump (6). Another pipeline at the bottom of the wastewater tank (5) is connected to a subsequent treatment device through the wastewater discharge pump (7).

2. A desulfurization wastewater reduction system based on low-grade flue gas concentration as claimed in claim 1, characterized in that: The liquid phase outlet pipeline of the ultra-gravity rotating bed (4) extends into the wastewater tank (5), and the distance between the end of the pipeline and the bottom of the wastewater tank (5) is no more than 300 mm; the top of the wastewater tank (5) is connected to the desulfurization wastewater inlet pipeline.

3. A desulfurization wastewater reduction system based on low-grade flue gas concentration as claimed in claim 2, characterized in that: The ultra-gravity rotating bed (4) is composed of 2 to 5 rotors.

4. An operating method of a desulfurization wastewater reduction system based on low-grade flue gas concentration as claimed in claim 3, characterized in that: The steps include: 1) The desulfurized wastewater in the wastewater tank (5) is transported to the supergravity rotating bed (4) via the wastewater circulation pump (6); 2) The low-temperature flue gas after passing through the dust collector (1) is pressurized by the booster fan (3) and then transported to the supergravity circulating bed (4); 3) The desulfurized wastewater and low-temperature flue gas are countercurrently contacted in the supergravity rotating bed (4) to carry out gas-liquid mass transfer, the heat of the flue gas is transferred to the desulfurized wastewater, and the desulfurized wastewater transfers mass to the flue gas, thereby achieving the concentration of the desulfurized wastewater; 4) The concentrated desulfurized wastewater flows from the liquid phase outlet pipeline of the supergravity rotating bed (4) to the wastewater tank (5); 5) The saturated wet flue gas is returned to the desulfurization tower (2) from the gas phase outlet at the top of the supergravity rotating bed (4); 6) The concentrated wastewater in the wastewater tank (5) is discharged to a subsequent treatment device through a wastewater discharge pump (7).

5. The method for operating a desulfurization wastewater reduction system based on low-grade flue gas concentration according to claim 4, characterized in that: The temperature of the low-temperature flue gas in step 2) is 85-140°C.

6. The method for operating a desulfurization wastewater reduction system based on low-grade flue gas concentration according to claim 4, characterized in that: The operating conditions of the high gravity rotating bed (4) in step 3) are high gravity factor 60-150, liquid-gas ratio 0.8-2 L / m 3 , empty bed gas velocity 2~3.5m / s.

7. The method for operating a desulfurization wastewater reduction system based on low-grade flue gas concentration according to claim 4, characterized in that: The cross-sectional area ratio of the first pipeline (11) to the second pipeline (12) is 1:5-15.

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