Flue gas ozone denitration and denitration waste liquid treatment system

Abstract

The utility model relates to flue gas treatment technical field especially, relates to a kind of flue gas ozone denitration and denitration waste liquid processing system, it includes gas distributor, caustic washing tower, lye circulating washing spray component, by setting water washing section, and circulating water washing spray component is provided at water washing section, circulating water washing spray component carries out spray washing to the flue gas of entering water washing section, removes nitrate and nitrite entrained in flue gas, avoids the secondary pollution formed by nitrate and nitrite entrained in flue gas in large quantities;By setting denitration waste liquid processing component, the denitration waste liquid generated in caustic washing tower is handled, and nitrate and steam condensate water are obtained, avoid denitration waste liquid to be discharged into water body and cause water pollution.Processed emission flue gas NOx≤50mg / Nm 3 , particulate matter≤5mg / Nm 3 , reach ultra-low emission limit value requirement, and the obtained sodium nitrate reaches the requirement of first-grade product.

Description

Technical Field

[0001] This utility model relates to the field of flue gas treatment technology, and in particular to a flue gas ozone denitrification and denitrification waste liquid treatment system. Background Technology

[0002] The flue gas ozone denitrification process uses ozone to oxidize low-valence NO in flue gas into high-valence NO that is soluble in solution. X Ozone is mainly generated by an ozone generator, which primarily consumes oxygen. When the flue gas temperature is in the range of 20–200 °C, the denitrification efficiency can reach over 90%, achieving ultra-low emission standards, with nitrogen oxide emissions after denitrification ≤50 mg / m³. 3 The presence of dust and sulfides in flue gas does not significantly affect ozone depletion or NOx removal efficiency; the denitrification reaction is fast, and oxidation can occur instantaneously at low concentrations; it has low requirements for on-site civil engineering, equipment layout, and other aspects; no waste gas is generated during the denitrification process; and the ozone dosage can be precisely controlled based on the nitrogen oxide content in the flue gas, achieving the goal of accurately removing NO from the flue gas. Due to these characteristics, flue gas ozone denitrification technology is widely used. Although flue gas ozone denitrification has many advantages, it involves mixing ozone with flue gas. The nitrogen oxides in the flue gas react with the ozone to oxidize the water-insoluble NO in the flue gas into water-soluble NO2, N2O5, and other higher-valence nitrogen oxides. Therefore, alkaline solutions or substances are needed in an alkaline scrubbing tower to wash away these higher-valence nitrogen oxides in the flue gas. This involves transferring these higher-valence nitrogen oxides to the liquid phase to form nitrates and nitrites. Over time, the concentration of nitrates and nitrites formed from the washed flue gas increases, leading to secondary pollution caused by a large amount of nitrates and nitrites carried in the scrubbed flue gas. Furthermore, the denitrification wastewater generated in the alkaline scrubbing tower needs to be discharged, which can also cause water pollution if released into water bodies. Utility Model Content

[0003] The technical problem solved by this utility model is to provide a flue gas ozone denitrification and denitrification wastewater treatment system. The system washes the flue gas after ozone denitrification, that is, washes away the large amount of nitrates and nitrites carried in the flue gas and transfers them to water to avoid secondary pollution. At the same time, the denitrification wastewater generated by alkaline washing is treated to recover nitrates from the denitrification wastewater to obtain nitrate products, and the water in the denitrification wastewater is recovered for reuse to avoid water pollution.

[0004] The technical solution adopted by this utility model to solve its technical problem is: a flue gas ozone denitrification and denitrification waste liquid treatment system, including a gas distributor, an alkaline scrubbing tower, and an alkaline circulating scrubbing spray assembly. The gas distributor is provided with a first flue gas inlet, an ozone inlet, and a flue gas outlet. The lower half of the alkaline scrubbing tower is an alkaline scrubbing section, and the lower part of the alkaline scrubbing section is provided with an alkaline inlet and a second flue gas inlet. The flue gas outlet is connected to the second flue gas inlet through a first pipe. The alkaline circulating scrubbing spray assembly is located at the alkaline scrubbing section and sprays and scrubs the flue gas entering the alkaline scrubbing section. The alkaline inlet is connected to the alkaline circulating scrubbing spray assembly. The upper half of the alkaline scrubbing tower is a water scrubbing section, and the water scrubbing section is provided with a circulating water scrubbing spray assembly. The circulating water scrubbing spray assembly sprays and scrubs the flue gas entering the water scrubbing section. The top of the water scrubbing section is provided with a flue gas outlet.

[0005] It also includes a denitrification waste liquid treatment component, which includes a denitrification waste liquid pretreatment tank, a filter press, an oxidation tank, and an evaporator crystallizer. The upper and middle parts of the denitrification waste liquid pretreatment tank are provided with a waste liquid inlet, a chemical inlet, and a waste clear liquid overflow inlet. The bottom of the denitrification waste liquid pretreatment tank is provided with a first waste slurry outlet. The upper and middle parts of the oxidation tank are provided with a waste clear liquid inlet and an oxidant inlet. The bottom of the oxidation tank is provided with a second waste slurry outlet.

[0006] The lower part of the alkaline washing section is equipped with a waste liquid outlet. The waste liquid outlet is connected to the waste liquid inlet through a second pipe, and a first conveying pump is installed on the second pipe. The first waste slurry outlet is connected to the feed inlet of the filter press through a third pipe, and a second conveying pump is installed on the third pipe. The waste clear liquid overflow outlet is connected to the waste clear liquid inlet through a ninth pipe. The second waste slurry outlet is connected to the feed inlet of the evaporator crystallizer through a fourth pipe, and a third conveying pump is installed on the fourth pipe.

[0007] Furthermore, the circulating water washing spray assembly includes a circulating water pipe, on which a circulating water tank and a water washing circulation pump are installed;

[0008] The lower part of the washing section is equipped with a water washing circulation interface. One end of the circulation water pipe is connected to the water washing circulation interface, and the other end of the circulation water pipe is equipped with a water washing spray nozzle. The water washing spray nozzle is located inside the upper part of the washing section.

[0009] Furthermore, a filtrate return interface is also provided in the upper middle part of the denitrification waste liquid pretreatment tank. The filtrate return interface is connected to the filtrate outlet of the filter press through the sixth pipe, and the filtrate outlet of the filter press is higher than the position of the filtrate return interface.

[0010] Furthermore, the steam condensate outlet of the evaporator crystallizer is connected to the circulating water pipe via a seventh pipe.

[0011] Furthermore, the position of the waste liquid overflow port is higher than the position of the waste liquid inlet port.

[0012] The beneficial effects of this invention are as follows: By setting a water washing section at the top of the alkaline washing tower, and installing a circulating water washing spray assembly, the circulating water washing spray assembly sprays and washes the flue gas entering the water washing section, removing nitrates and nitrites entrained in the flue gas, thus reducing the large amount of nitrates and nitrites entrained in the flue gas and avoiding secondary pollution of the flue gas; by setting up a denitrification wastewater treatment assembly, the denitrification wastewater generated in the alkaline washing tower is treated to obtain nitrates and steam condensate, with nitrates as the product; the steam condensate is returned to the water washing section for recycling and is not discharged externally, avoiding the discharge of denitrification wastewater into water bodies and causing water pollution, thereby significantly reducing the pollution of the flue gas ozone denitrification system. Furthermore, the flue gas ozone denitrification and denitrification wastewater treatment system of this invention has a simple structure, and the NOx content in the emitted flue gas after treatment by this system is ≤50mg / Nm³. 3 Particulate matter ≤5mg / Nm 3 The process meets ultra-low emission limits, and the obtained sodium nitrate meets the requirements of Grade I in GB / T 4553-2002. The condensate can be returned to the washing section for recycling, and there is no waste liquid discharge. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the present invention;

[0014] The following are labeled as follows: Gas distributor 1, Alkali washing tower 2, First pipeline 3, Flue gas outlet 4, Denitrification waste liquid pretreatment tank 5, Filter press 6, Oxidation tank 7, Evaporator crystallizer 8, Second pipeline 9, First transfer pump 10, Third pipeline 11, Second transfer pump 12, Fourth pipeline 13, Third transfer pump 14, Ozone generator 15, Fifth pipeline 16, Flue gas conveying pipeline 17, Alkali supply tank 18, Through the eighth pipeline 19, Fourth transfer pump 20, Alkali circulation pipeline 21, Alkali circulation pump 22, Circulating water pipe 23, Circulating water tank 24, Water washing circulation pump 25, Sixth pipeline 26, Seventh pipeline 27, Ninth pipeline 28. Detailed Implementation

[0015] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0016] like Figure 1As shown, the present invention relates to a flue gas ozone denitrification and denitrification wastewater treatment system, comprising a gas distributor 1, an alkaline scrubbing tower 2, and an alkaline circulating scrubbing spray assembly. The gas distributor 1 is provided with a first flue gas inlet, an ozone inlet, and a flue gas outlet. The lower half of the alkaline scrubbing tower 2 is an alkaline scrubbing section, and the lower part of the alkaline scrubbing section is provided with an alkaline inlet and a second flue gas inlet. The flue gas outlet is connected to the second flue gas inlet through a first pipe 3. The alkaline circulating scrubbing spray assembly is located at the alkaline scrubbing section and sprays and scrubs the flue gas entering the alkaline scrubbing section. The alkaline inlet is connected to the alkaline circulating scrubbing spray assembly. The upper half of the alkaline scrubbing tower 2 is a water scrubbing section, and the water scrubbing section is provided with a circulating water scrubbing spray assembly. The circulating water scrubbing spray assembly sprays and scrubs the flue gas entering the water scrubbing section. The top of the water scrubbing section is provided with a flue gas outlet 4.

[0017] It also includes a denitrification waste liquid treatment component, which includes a denitrification waste liquid pretreatment tank 5, a filter press 6, an oxidation tank 7, and an evaporator crystallizer 8. The upper and middle parts of the denitrification waste liquid pretreatment tank 5 are provided with a waste liquid inlet, a chemical inlet, and a waste clear liquid overflow inlet. The bottom of the denitrification waste liquid pretreatment tank 5 is provided with a first waste slurry outlet inlet. The upper and middle parts of the oxidation tank 7 are provided with a waste clear liquid inlet and an oxidant inlet. The bottom of the oxidation tank 7 is provided with a second waste slurry outlet inlet.

[0018] The lower part of the alkaline washing section is provided with a waste liquid outlet. The waste liquid outlet is connected to the waste liquid inlet through the second pipe 9, and the second pipe 9 is equipped with a first conveying pump 10. The first waste slurry outlet is connected to the feed port of the filter press 6 through the third pipe 11, and the third pipe 11 is equipped with a second conveying pump 12. The waste clear liquid overflow outlet is connected to the waste clear liquid inlet through the ninth pipe 28. The second waste slurry outlet is connected to the feed port of the evaporator crystallizer 8 through the fourth pipe 13, and the fourth pipe 13 is equipped with a third conveying pump 14.

[0019] The denitrification process of this utility model's flue gas ozone denitrification and denitrification waste liquid treatment system is as follows: For example... Figure 1As shown, flue gas enters gas distributor 1 through the first flue gas inlet, and ozone enters gas distributor 1 through the ozone inlet. In gas distributor 1, after the flue gas and ozone are mixed evenly, the ozone reacts with NO in the flue gas. Utilizing the strong oxidizing property of ozone, the nitrogen oxides (mainly NO) in the flue gas can be oxidized into higher oxidation state acidic nitrogen oxide gases. The main reactions are: NO + O3 → NO2 + O2, NO2 + O3 → N2O5. After the low oxidation state NO in the flue gas is oxidized into higher oxidation state acidic gases, the alkaline solution circulating washing spray assembly sprays and washes the flue gas entering the alkaline washing section. The alkaline solution and flue gas come into counter-current contact (flue gas from bottom to top, alkaline solution from top to bottom). The nitrogen oxides in the flue gas are absorbed by the solution, achieving the purpose of denitrification. The main reactions are as follows: 2NO2 + NaOH → NO + NaNO3, NO + NO2 + NaOH → NaNO2, 2NO2 + NaOH → NaNO2 + NaNO3, N2O5 + NaOH → NaNO 3； After the alkaline solution circulating washing spray assembly sprays and washes the flue gas entering the alkaline washing section, it enters the water washing section. The circulating water washing spray assembly sprays and washes the flue gas entering the water washing section. The water and flue gas come into counter-current contact (flue gas from bottom to top, water from top to bottom), removing the nitrates and nitrites carried in the flue gas. After the flue gas meets the standards, it is discharged through the flue gas emission port 4.

[0020] The treatment process for the denitrification wastewater generated in the alkali washing tower is as follows: (Example) Figure 1 As shown, the denitrification waste liquid is sequentially fed into the denitrification waste liquid pretreatment tank 5 via the first transfer pump 10 through the waste liquid outlet, the second pipe 9, and the waste liquid inlet. The chemical (Ca(NO3)2) enters the denitrification waste liquid pretreatment tank 5 through the chemical inlet. The main reaction in the denitrification waste liquid pretreatment tank 5 is as follows: Ca(NO3)2 + NaSO4 → CaSO4↓ + NaNO3. The resulting waste slurry is then fed into the filter press 6 via the second transfer pump 12 through the first waste slurry outlet, the third pipe 11, and the feed inlet of the filter press 6. The filter press 6 separates the solid and liquid in the waste slurry, obtaining filter residue (sodium nitrate) and filtrate. The upper waste liquid from the denitrification waste liquid pretreatment tank 5 enters the oxidation tank 7 via the waste liquid overflow outlet, the ninth pipe 28, and the waste liquid inlet. The oxidant (H2O2) enters the oxidation tank 7 through the oxidant inlet. The main reaction in the oxidation tank 7 is as follows: NaNO2 + H2O2 → NaNO3 + ... H2O, the waste slurry after the reaction is passed through the third transfer pump 14, the second waste slurry outlet, the fourth pipeline 13, and the feed port of the evaporator crystallizer 8. After the waste slurry is treated in the evaporator crystallizer 8, solid sodium nitrate and steam condensate are obtained.

[0021] Specifically, to facilitate the delivery of ozone to the gas distributor 1, this invention also includes an ozone generator 15, which is connected to the ozone inlet interface via a fifth pipe 16. It is impossible for the ozone generated by the ozone generator 15 to enter the gas distributor 1 via the fifth pipe 16 and the ozone inlet interface.

[0022] To facilitate the delivery of flue gas to the gas distributor 1, this invention also includes a flue gas delivery pipe 17, which is connected to the first flue gas inlet. Flue gas would normally enter the gas distributor 1 via the flue gas delivery pipe 17 and the first flue gas inlet (but this is not always possible).

[0023] To facilitate the addition of alkaline solution to alkaline washing tower 2, for example... Figure 1 As shown, this utility model also includes an alkali supply tank 18, which is connected to the alkali inlet port via an eighth pipe 19, and a fourth delivery pump 20 is installed on the eighth pipe 19. The alkali is placed in the alkali supply tank 18, and then fed into the alkali washing tower 2 via the eighth pipe 19 through the fourth delivery pump 20. To facilitate metering and control of the amount of alkali added, the fourth delivery pump 20 is preferably a metering pump.

[0024] The function of the alkaline solution circulating washing spray assembly is to spray and wash the flue gas entering the alkaline washing section. In order to ensure the effectiveness of the alkaline solution circulating washing spray assembly, the preferred structure of the alkaline solution circulating washing spray assembly of this utility model is as follows: the alkaline solution circulating washing spray assembly includes an alkaline solution circulating pipe 21, an alkaline solution circulating pump 22 is installed on the alkaline solution circulating pipe 21; an alkaline solution circulating interface is provided at the lower part of the alkaline washing section, one end of the alkaline solution circulating pipe 21 is connected to the alkaline solution circulating interface, and an alkaline solution spray port is provided at the other end of the alkaline solution circulating pipe 21. The alkaline solution spray port is located inside the upper part of the alkaline washing section, and an alkaline solution circulating tank is provided inside the lower part of the alkaline washing section. The alkaline solution inlet interface and the alkaline solution circulating interface are both connected to the alkaline solution circulating tank. The working process of the alkaline solution circulating washing spray assembly is as follows: the alkaline solution circulating pump 22 operates, transporting the alkaline solution through the alkaline solution circulating pipe 21 to the alkaline solution spray nozzle. The alkaline solution is sprayed out through the alkaline solution spray nozzle and moves downward, contacting and reacting with the upward moving flue gas. The nitrogen oxides in the flue gas are absorbed by the solution, achieving the purpose of denitrification. Excess alkaline solution falls into the alkaline solution circulating tank under the action of gravity for recycling. The alkaline solution supply tank 18 replenishes the alkaline solution circulating tank. When the alkalinity in the alkaline solution circulating tank drops to the set alkalinity concentration, it forms denitrification waste liquid, which is discharged to the denitrification waste liquid treatment assembly for treatment.

[0025] The function of the circulating water scrubbing spray assembly is to spray and scrub the flue gas entering the scrubbing section, removing nitrates and nitrites entrained in the flue gas. To ensure the effectiveness of the circulating water scrubbing spray assembly, further steps are needed. Figure 1As shown, the circulating water washing spray assembly includes a circulating water pipe 23, a circulating water tank 24, and a water washing circulation pump 25. A water washing circulation interface is located at the lower part of the washing section. One end of the circulating water pipe 23 is connected to the water washing circulation interface, and the other end of the circulating water pipe 23 is provided with a water washing spray nozzle. The water washing spray nozzle is located inside the upper part of the washing section. A broken tower tray is located inside the lower part of the washing section, and the broken tower tray has an interface for washing water to flow into the circulating tank. The washing circulation tank is connected to the water washing circulation interface. The working process of this circulating water washing spray assembly is as follows: the water washing circulation pump 25 transports the circulating water from the circulating water tank 24 to the water washing spray nozzle through the circulating water pipe 23. The water is sprayed out through the water washing spray nozzle and moves downwards, contacting the upward-moving flue gas to remove nitrates and nitrites entrained in the flue gas. The flue gas then falls into the washing circulation tank under gravity, and the circulating water pipe 23 is then recycled back to the circulating water tank 24.

[0026] The filter press 6 separates the solid and liquid in the waste slurry to obtain filter residue (calcium sulfate) and filtrate. The upper middle part of the denitrification waste liquid pretreatment tank 5 is also equipped with a filtrate return interface. The filtrate return interface is connected to the filtrate outlet of the filter press 6 through the sixth pipe 26, and the filtrate outlet of the filter press 6 is higher than the position of the filtrate return interface.

[0027] To further ensure that the entire flue gas ozone denitrification and denitrification wastewater treatment system has no wastewater discharge, the steam condensate outlet of the evaporator crystallizer 8 is connected to the circulating water pipe 23 via the seventh pipe 27. The steam condensate generated in the evaporator crystallizer 8 is transported to the circulating water pipe 23 via the seventh pipe 27 for use as a washing circulating liquid. Furthermore, a liquid transfer pump can also be installed in the seventh pipe 27.

[0028] The evaporator crystallizer 8 can be a single-effect evaporator, a double-effect evaporator, a triple-effect evaporator, an MVR evaporator, etc.

[0029] To reduce transportation costs, the waste liquid overflow port is positioned higher than the waste liquid inlet port.

[0030] The NOx concentration in the flue gas treated by the flue gas ozone denitrification and denitrification wastewater treatment system of this invention is ≤50mg / Nm³. 3 Particulate matter ≤5mg / Nm 3 The process meets ultra-low emission limits, and the obtained sodium nitrate meets the requirements of Grade I in GB / T 4553-2002. The condensate can be returned to the washing section for recycling, and there is no waste liquid discharge.

Claims

1. A flue gas ozone denitrification and denitrification wastewater treatment system, comprising a gas distributor (1), an alkaline scrubbing tower (2), and an alkaline circulating scrubbing spray assembly, wherein the gas distributor (1) is provided with a first flue gas inlet, an ozone inlet, and a flue gas outlet; the lower half of the alkaline scrubbing tower (2) is an alkaline scrubbing section, and the lower part of the alkaline scrubbing section is provided with an alkaline inlet and a second flue gas inlet; the flue gas outlet is connected to the second flue gas inlet via a first pipe (3); the alkaline circulating scrubbing spray assembly is located at the alkaline scrubbing section, and the alkaline circulating scrubbing spray assembly sprays and scrubs the flue gas entering the alkaline scrubbing section; the alkaline inlet is connected to the alkaline circulating scrubbing spray assembly; characterized in that: The upper part of the alkaline washing tower (2) is the water washing section. A circulating water washing spray assembly is installed in the water washing section. The circulating water washing spray assembly sprays and washes the flue gas entering the water washing section. A flue gas discharge port (4) is installed at the top of the water washing section. It also includes a denitrification waste liquid treatment component, which includes a denitrification waste liquid pretreatment tank (5), a filter press (6), an oxidation tank (7) and an evaporator crystallizer (8). The upper and middle parts of the denitrification waste liquid pretreatment tank (5) are provided with a waste liquid inlet, a chemical inlet, and a waste clear liquid overflow inlet. The bottom of the denitrification waste liquid pretreatment tank (5) is provided with a first waste slurry outlet inlet. The upper and middle parts of the oxidation tank (7) are provided with a waste clear liquid inlet and an oxidant inlet. The bottom of the oxidation tank (7) is provided with a second waste slurry outlet inlet. The lower part of the alkaline washing section is provided with a waste liquid outlet interface. The waste liquid outlet interface is connected to the waste liquid inlet interface through the second pipe (9). The second pipe (9) is provided with a first conveying pump (10). The first waste slurry outlet interface is connected to the feed port of the filter press (6) through the third pipe (11). The third pipe (11) is provided with a second conveying pump (12). The waste clear liquid overflow interface is connected to the waste clear liquid inlet interface through the ninth pipe (28). The second waste slurry outlet interface is connected to the feed port of the evaporator crystallizer (8) through the fourth pipe (13). The fourth pipe (13) is provided with a third conveying pump (14).

2. The flue gas ozone denitrification and denitrification wastewater treatment system as described in claim 1, characterized in that: The circulating water washing spray assembly includes a circulating water pipe (23), on which a circulating water tank (24) and a water washing circulation pump (25) are provided; The lower part of the washing section is provided with a water washing circulation interface. One end of the circulation water pipe (23) is connected to the water washing circulation interface, and the other end of the circulation water pipe (23) is provided with a water washing spray nozzle. The water washing spray nozzle is located inside the upper part of the washing section.

3. The flue gas ozone denitrification and denitrification wastewater treatment system as described in claim 1, characterized in that: The upper middle part of the denitrification waste liquid pretreatment tank (5) is also provided with a filtrate return interface. The filtrate return interface is connected to the liquid outlet of the filter press (6) through the sixth pipe (26), and the liquid outlet of the filter press (6) is higher than the position of the filtrate return interface.

4. The flue gas ozone denitrification and denitrification wastewater treatment system as described in claim 1, characterized in that: The steam condensate outlet of the evaporator crystallizer (8) is connected to the circulating water pipe (23) through the seventh pipe (27).

5. The flue gas ozone denitrification and denitrification wastewater treatment system as described in any one of claims 1 to 4, characterized in that: The overflow port for waste liquid is positioned higher than the inlet port for waste liquid.

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