A device and method for zero-emission flue evaporation of desulfurized wastewater and synergistic removal of SO3 / HCl
By combining the main flue evaporation technology and alkaline absorbent to capture SO3/HCl in the rotary atomization drying tower of desulfurization wastewater, the problems of high cost of desulfurization wastewater treatment and great impact on boiler thermal efficiency in the prior art are solved, and low energy is achieved Desulfurization wastewater is consumed with zero emissions and reduced pollutants.
Patent Information
- Application Number
- CN202010035907.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2020-01-14
- Publication Date
- 2024-12-17
- Estimated Expiration
- 2040-01-14
AI Technical Summary
The existing desulfurization wastewater treatment technology has problems such as high construction investment, high operating costs, difficulty in completely evaporating desulfurization wastewater, and a great impact on boiler thermal efficiency, especially under low load conditions.
Based on the original rotary atomization drying tower of desulfurization wastewater, combined with the main flue evaporation technology, the hot flue gas contact between the rotary atomization drying tower and the SCR denitrification reactor and the air preheater is evaporated and in the main flue duct SO3/HCl was captured using alkaline absorbents, and the heat of hot flue gas before the air preheater was evaporated to reduce the load on the boiler.
The low-energy consumption desulfurization wastewater is achieved, which reduces the impact on the boiler thermal efficiency, and reduces the generation of pollutants in the subsequent wet desulfurization system through alkaline absorbents, simplifying the device structure and operation process.
Smart Images
Figure CN113185045B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of zero emission of desulfurization wastewater from coal-fired units, and in particular to a device and method for zero emission flue evaporation of desulfurization wastewater and coordinated removal of SO3 / HCl. Background Art
[0002] The limestone-gypsum desulfurization process has become the standard configuration of coal-fired power plants. However, during the operation of this process, desulfurization wastewater containing various impurities will be produced.
[0003] Due to its strong corrosiveness, high turbidity, excessive heavy metal content, high salt content, large fluctuations in water quality, and unstable water volume, desulfurization wastewater treatment is difficult. So far, although the more mature process chemical precipitation method can effectively remove metal ions, the effluent still contains a large amount of chloride ions. Therefore, desulfurization wastewater zero discharge technology has emerged, such as evaporation crystallization technology, main flue evaporation technology, and rotary atomization drying technology. The above methods have certain defects in the treatment of desulfurization wastewater, such as the high construction investment and operation costs of traditional evaporation crystallization technology. Flue evaporation technology is to spray wastewater into the flue between the air preheater and the dust collector, and use hot flue gas to completely evaporate the wastewater, and convert pollutants in the wastewater into solids such as crystals or salts. However, due to low-temperature modification, the flue distance between the air preheater and the electrostatic precipitator is small. If the desulfurization wastewater is completely evaporated by the main flue, the purpose of complete evaporation may not be achieved. The desulfurization wastewater rotary atomization drying tower extracts a stream of hot flue gas between the SCR denitrification reactor and the air preheater, and evaporates the wastewater through the rotary atomization drying tower. If the desulfurization wastewater is completely evaporated by the rotary atomization drying tower, it may cause excessive load on the boiler. Summary of the invention
[0004] Based on the above problems, the present invention transforms the existing desulfurization wastewater rotary atomization drying device and provides a device and method for zero-emission flue evaporation of desulfurization wastewater and synergistic removal of SO3 / HCl.
[0005] In order to achieve the above object, the specific technical solution adopted by the present invention is as follows:
[0006] A device for zero-emission flue evaporation of desulfurized wastewater and synergistic removal of SO3 / HCl, comprising an SCR denitration reactor, an air preheater, a dust collector, and a desulfurization tower connected to the main flue in sequence, and also comprising a rotary atomization drying tower, a triple box, a stirring tank, a wastewater lifting pump, a high-position feed box, an injection device, and a salt recovery and processing system, wherein:
[0007] One end of the rotary atomization drying tower is connected to the main flue between the SCR denitration reactor and the air preheater through a first bypass flue, and the other end is connected to the main flue between the air preheater and the dust collector through a second bypass flue; the salt recovery and processing system is connected to the bottom discharge port of the rotary atomization drying tower;
[0008] The inlet end of the triple box is connected to the desulfurization tower, and a tee is arranged at the outlet end of the triple box; the first port of the tee is connected to the outlet end of the triple box; the second port of the tee is connected to the high-position feeding box through the wastewater lifting pump, and the high-position feeding box is connected to the rotary atomization drying tower; the third port of the tee is connected to the stirring tank, and the stirring tank is connected to the injection device through the wastewater lifting pump, an alkaline absorbent is added in the stirring tank, and the injection device is arranged in the main flue between the air preheater and the dust collector.
[0009] Furthermore, the spraying device is a dual-fluid atomizing nozzle.
[0010] Furthermore, the rotary atomization drying tower comprises: a drying tower body, a rotary atomizer and a flue gas distributor; the rotary atomizer is connected to the high-position feed box, and the flue gas distributor is connected to the first bypass flue.
[0011] Furthermore, the distance between the injection device and the second bypass flue and the interface with the main flue is 1 meter to 2 meters, and is in a direction away from the air preheater.
[0012] A method for zero-emission flue evaporation of desulfurization wastewater and synergistic removal of SO3 / HCl, characterized by comprising the following steps:
[0013] Step 1, the desulfurization wastewater generated during the wet desulfurization process is first tempered to a weakly alkaline state by adding lime slurry through the triple box, and the pH value of the desulfurization wastewater after tempering is 9 to 10;
[0014] Step 2: At the outlet end of the triple box, a portion of the conditioned desulfurized wastewater is transported to the high-position feed box by the wastewater lift pump through the second port of the tee, flows into the rotary atomizing drying tower by gravity, and is fully contacted with the hot flue gas extracted between the SCR denitration reactor and the air preheater. The wastewater is quickly evaporated, and the water evaporates into the flue gas, and is discharged into the main flue through the second bypass flue. Most of the inorganic salts evaporated and precipitated fall into the bottom discharge port of the rotary atomizing drying tower and are transported to the salt recovery and treatment system;
[0015] In step 3, the remaining conditioned desulfurized wastewater enters the stirring tank through the third port of the tee, an alkaline absorbent is added therein, and then the wastewater is transported to the injection device through the wastewater lifting pump and sprayed into the main flue for evaporation. During the evaporation of the wastewater, the alkaline absorbent reacts with HCl and SO3 in the flue gas and is captured, and enters the dust collector together with the flue gas discharged from the second bypass flue, and the fine inorganic salt particles precipitated by the evaporation of the wastewater are captured by the dust collector.
[0016] Furthermore, the amount of desulfurized wastewater transported to the rotary atomizing drying tower through the second port of the tee is 1 / 2 to 2 / 3 of the total amount of wastewater; the amount of desulfurized wastewater transported to the main flue through the third port of the tee via the injection device is 1 / 3 to 1 / 2 of the total amount of wastewater.
[0017] Furthermore, the alkaline absorbent is one or two of NaOH, Ca(OH)2, Na2CO3, and NaHCO3, and the molar ratio of the alkaline absorbent to the total amount of SO3+HCl in the flue gas is 2:1.
[0018] Furthermore, the inlet flue gas temperature entering the rotary atomization drying tower is 280-350° C., and the flue gas extraction amount is 1% to 3% of the main flue gas amount.
[0019] Furthermore, the average particle size of the desulfurization wastewater sprayed into the rotary atomization drying tower is less than 60 μm, and the residence time in the rotary atomization drying tower is not less than 20 seconds.
[0020] Furthermore, the average particle size of the desulfurization wastewater sprayed into the main flue is less than 50 μm, and the residence time in the main flue at the inlet of the dust collector is not less than 0.75 s.
[0021] The beneficial effects of the present invention are:
[0022] The invention has a simple structure and is easy to operate. It combines the main flue evaporation technology with the original desulfurization wastewater rotary atomization drying tower to solve the defect that the main flue evaporation technology alone is difficult to completely treat the desulfurization wastewater under low load, and effectively reduces the impact on the thermal efficiency of the boiler.
[0023] In the present invention, most of the desulfurization wastewater is evaporated by a rotary atomization drying tower, using the heat of the hot flue gas before the air preheater, without the need for additional steam, and is a low-energy consumption technology; only a small amount of hot flue gas needs to be extracted, which has little impact on the original boiler system and achieves the purpose of recovering the salt in the bottom slag of the drying tower.
[0024] In the present invention, a part of the desulfurization wastewater is conditioned by a triple box and then an alkaline absorbent is added to a stirring tank to absorb HCl and SO3. The alkaline desulfurization wastewater absorbs HCl and SO3 during evaporation, thereby reducing the amount of desulfurization wastewater generated in the subsequent wet desulfurization system. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 It is a schematic diagram of the process flow of the present invention.
[0026] In the accompanying drawings, the components represented by the reference numerals are listed as follows:
[0027] SCR denitrification reactor, 2. air preheater, 3. rotary atomization drying tower, 4. dust collector, 5. desulfurization tower, 6. triple box, 7. stirring tank, 8. wastewater lifting pump, 9. high-level feeding box, 10. injection device, 11. salt recovery and treatment system, 12. main flue, 13. first bypass flue, 14. second bypass flue. DETAILED DESCRIPTION
[0028] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.
[0029] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "center", "inside", "outside", "top", "bottom", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.
[0030] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0031] like Figure 1 As shown, the present invention provides a zero-emission desulfurization wastewater and coordinated SO3 / HCl removal device based on flue gas waste heat evaporation, comprising an SCR denitration reactor 1, an air preheater 2, a dust collector 4, and a desulfurization tower 5 connected to a main flue 12 in sequence, and also comprising a rotary atomization drying tower 3, a triple box 6, a stirring tank 7, a wastewater lifting pump 8, a high-level feed box 9, a dual-fluid atomization nozzle 10 and a salt recovery and processing system 11, wherein:
[0032] The rotary atomization drying tower 3 comprises: a drying tower body, a rotary atomizer and a flue gas distributor; the rotary atomizer is connected to the high-position feed box 9, and the flue gas distributor is connected to the first bypass flue 13; one end of the rotary atomization drying tower 3 is connected to the main flue 12 between the SCR denitration reactor 1 and the air preheater 2 through the first bypass flue 13, and the other end is connected to the main flue 12 between the air preheater 2 and the dust collector 4 through the second bypass flue 14; the salt recovery and processing system 11 is connected to the bottom discharge port of the rotary atomization drying tower 3;
[0033] The inlet end of the triple box 6 is connected to the desulfurization tower 5, and a tee is provided at the outlet end of the triple box 6; the first port of the tee is connected to the outlet end of the triple box 6; the second port of the tee is connected to the high-position feed box 9 through the wastewater lifting pump 8, and the high-position feed box 9 is connected to the rotary atomization drying tower 3; the third port of the tee is connected to the stirring tank 7, and the stirring tank 7 is connected to the dual-fluid atomization nozzle through the wastewater lifting pump 8, and the dual-fluid atomization nozzle is arranged in the main flue 12 between the air preheater 2 and the dust collector 4;
[0034] The distance between the dual-fluid atomizing nozzle and the interface between the second bypass flue 14 and the main flue 12 is 1 meter to 2 meters, and is in a direction away from the air preheater 2 .
[0035] The present invention also provides a method for zero-emission of desulfurization wastewater and synergistic removal of SO3 / HCl based on flue gas waste heat evaporation, comprising the following steps:
[0036] Step 1, the desulfurization wastewater generated during the wet desulfurization process is first tempered to a weakly alkaline state by adding lime slurry through the triple box 6, and the pH value of the desulfurization wastewater after tempering is 9 to 10;
[0037] Step 2, at the outlet end of the triple box 6, a portion of the conditioned desulfurized wastewater is transported to the high-position feed box 9 by the wastewater lift pump 8 through the second port of the tee, flows into the rotary atomizing drying tower 3 by gravity, and is fully contacted with the hot flue gas extracted between the SCR denitration reactor 1 and the air preheater 2, the wastewater is quickly evaporated, the water evaporates into the flue gas, and is discharged into the main flue through the second bypass flue 14, and most of the evaporated inorganic salts fall into the bottom discharge port of the rotary atomizing drying tower 3 and are transported to the salt recovery and treatment system 11;
[0038] In step 3, the remaining conditioned desulfurized wastewater enters the stirring tank 7 through the third port of the tee, in which an alkaline absorbent is added, and then transported to the dual-fluid atomizing nozzle through the wastewater lifting pump 8, and sprayed into the main flue 12 for evaporation. During the evaporation of the wastewater, the alkaline absorbent reacts with HCl and SO3 in the flue gas and is captured, and enters the dust collector 4 together with the flue gas discharged from the second bypass flue 14, and the fine inorganic salt particles precipitated by the evaporation of the wastewater are captured by the dust collector 4.
[0039] In a more preferred embodiment, a flow regulating valve is installed on the three-way, so that the amount of desulfurized wastewater delivered to the rotary atomization drying tower 3 through the second port of the three-way is 1 / 2~2 / 3 of the total amount of wastewater; the amount of desulfurized wastewater delivered to the main flue 12 through the third port of the three-way through the injection device 10 is 1 / 3~1 / 2 of the total amount of wastewater, and the ratio of desulfurized wastewater discharged from the two ports is adjusted in real time according to the boiler load. When the boiler load is high, the evaporation treatment capacity of the desulfurized wastewater in the main flue 12 is appropriately increased, that is, the amount of wastewater discharged through the third port of the three-way is made to reach 1 / 2 of the total amount of desulfurized wastewater through the flow regulating valve.
[0040] In a more preferred embodiment, the alkaline absorbent is one or two of NaOH, Ca(OH)2, Na2CO3, and NaHCO3, and the molar ratio of the alkaline absorbent to the total amount of SO3+HCl in the flue gas is 2:1.
[0041] In a more preferred embodiment, the average particle size of the desulfurization wastewater sprayed into the rotary atomization drying tower 3 is less than 60 μm, and the residence time in the rotary atomization drying tower 3 is not less than 20 seconds.
[0042] In a more preferred embodiment, the average particle size of the desulfurization wastewater injected into the main flue 12 is less than 50 μm, and the residence time in the main flue 12 at the inlet of the dust collector 4 is not less than 0.75 s.
[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims
1. A device for zero-emission flue evaporation of desulfurized wastewater and synergistic removal of SO3 / HCl, comprising an SCR denitrification reactor (1), an air preheater (2), a dust collector (4), and a desulfurization tower (5) connected in sequence to a main flue (12), characterized in that: It also includes a rotary atomizing drying tower (3), a triple box (6), a stirring tank (7), a wastewater lifting pump (8), a high-position feed box (9), an injection device (10) and a salt recovery and processing system (11), wherein: One end of the rotary atomizing drying tower (3) is connected to the main flue (12) between the SCR denitration reactor (1) and the air preheater (2) through a first bypass flue (13), and the other end is connected to the main flue (12) between the air preheater (2) and the dust collector (4) through a second bypass flue (14); the salt recovery and treatment system (11) is connected to the bottom discharge port of the rotary atomizing drying tower (3); the distance between the injection device (10) and the interface of the second bypass flue (14) and the main flue (12) is 1 meter to 2 meters, and is in a direction away from the air preheater (2); The rotary atomization drying tower (3) comprises: a drying tower body, a rotary atomizer and a flue gas distributor; the rotary atomizer is connected to the high-position feed box (9), and the flue gas distributor is connected to the first bypass flue (13); The inlet end of the triple box (6) is connected to the desulfurization tower (5), and a tee is provided at the outlet end of the triple box (6); the first port of the tee is connected to the outlet end of the triple box (6); the second port of the tee is connected to the high-position feed box (9) through the wastewater lifting pump (8), and the high-position feed box (9) is connected to the rotary atomization drying tower (3); the third port of the tee is connected to the stirring tank (7), and the stirring tank (7) is connected to the injection device (10) through the wastewater lifting pump (8), and an alkaline absorbent is added to the stirring tank (7), and the injection device (10) is arranged in the main flue (12) between the air preheater (2) and the dust collector (4).
2. The device for zero-emission flue evaporation of desulfurized wastewater and synergistic removal of SO3 / HCl according to claim 1, characterized in that: The spraying device (10) is a dual-fluid atomizing nozzle.
3. A method for zero-emission flue evaporation of desulfurized wastewater and synergistic removal of SO3 / HCl, using the device for zero-emission flue evaporation of desulfurized wastewater and synergistic removal of SO3 / HCl as claimed in claim 1 or claim 2, characterized in that: The method comprises the following steps: Step 1, the desulfurization wastewater generated during the wet desulfurization process is first tempered to a weakly alkaline state by adding lime slurry through the triple box (6), and the pH value of the desulfurization wastewater after tempering is 9 to 10; Step 2, at the outlet end of the triple box (6), a portion of the conditioned desulfurized wastewater is transported to the high-position feed box (9) by the wastewater lift pump (8) through the second port of the tee, flows into the rotary atomizing drying tower (3) by gravity, and is fully contacted with the hot flue gas extracted between the SCR denitration reactor (1) and the air preheater (2), the wastewater is rapidly evaporated, the water evaporates into the flue gas, and is discharged into the main flue (12) through the second bypass flue (14), and most of the inorganic salts evaporated fall into the bottom discharge port of the rotary atomizing drying tower (3) and are transported to the salt recovery and treatment system (11); In step 3, the remaining conditioned desulfurized wastewater enters the stirring tank (7) through the third port of the tee, is added with an alkaline absorbent, and then is transported to the injection device (10) through the wastewater lifting pump (8) and sprayed into the main flue (12) for evaporation. During the evaporation of the wastewater, the alkaline absorbent reacts with HCl and SO3 in the flue gas and captures them, and enters the dust collector (4) together with the flue gas discharged from the second bypass flue (14). The dust collector (4) captures the fine inorganic salt particles precipitated by the evaporation of the wastewater.
4. The method for zero-emission flue evaporation of desulfurization wastewater and synergistic removal of SO3 / HCl according to claim 3, characterized in that: The amount of desulfurized wastewater transported to the rotary atomizing drying tower (3) through the second port of the tee is 1 / 2 to 2 / 3 of the total amount of wastewater; the amount of desulfurized wastewater transported to the main flue (12) through the third port of the tee via the injection device (10) is 1 / 3 to 1 / 2 of the total amount of wastewater.
5. The method for zero-emission flue evaporation of desulfurization wastewater and synergistic removal of SO3 / HCl according to claim 3, characterized in that: The alkaline absorbent is one or two of NaOH, Ca(OH)2, Na2CO3, and NaHCO3, and the molar ratio of the alkaline absorbent to the total amount of SO3+HCl in the flue gas is 2:
1.
6. The method for zero-emission flue evaporation of desulfurization wastewater and synergistic removal of SO3 / HCl according to claim 3, characterized in that: The inlet flue gas temperature entering the rotary atomization drying tower (3) is 280-350° C., and the flue gas extraction amount is 1%-3% of the main flue gas amount.
7. The method for zero-emission flue evaporation of desulfurization wastewater and synergistic removal of SO3 / HCl according to claim 3, characterized in that: The average particle size of the desulfurization wastewater sprayed into the rotary atomization drying tower (3) is less than 60 μm, and the residence time in the rotary atomization drying tower (3) is not less than 20 seconds.
8. The method for zero-emission flue evaporation of desulfurization wastewater and synergistic removal of SO3 / HCl according to claim 3, characterized in that: The average particle size of the desulfurization wastewater injected into the main flue (12) is less than 50 μm, and the residence time in the main flue (12) at the inlet of the dust collector (4) is not less than 0.75 s.