Zero emission and recovery system for flue gas pollutants of thermal power plant

Abstract

The invention relates to the technical field of flue gas treatment, in particular to a thermal power plant flue gas pollutant zero emission and recovery system which comprises a pretreatment unit, a desulfurization, denitrification and decarbonization integrated unit, a deep purification unit and a pollutant recovery unit which are communicated in sequence. The control system is electrically connected with the pretreatment unit, the desulfurization, denitrification and decarbonization integrated unit, the deep purification unit and the pollutant recovery unit respectively; the pretreatment unit is used for cooling and dedusting flue gas discharged from the thermal power plant; the desulfurization, denitrification and decarburization integrated unit is used for carrying out desulfurization, denitrification and decarburization synchronous treatment on the pretreated flue gas; the deep purification unit is used for carrying out residual pollutant removal treatment on the flue gas subjected to desulfurization, denitrification and decarbonization treatment, so that the pollutant concentration in the flue gas meets the zero emission requirement; the pollutant recovery unit is used for separating, purifying and recovering generated pollutant products; the control system is used for monitoring operation parameters of all the units in real time and automatically adjusting the operation state.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flue gas treatment, in particular to a flue gas pollutant zero-emission and recovery system for thermal power plants. BACKGROUND

[0002] Thermal power plants burn coal, natural gas and other fuels to produce a large amount of flue gas, which contains SO2, NO x , CO2, particulate matter and other pollutants. Direct emission of flue gas will exacerbate environmental problems such as acid rain and greenhouse effect. The existing flue gas treatment technology mostly adopts a segmented treatment mode of "desulfurization + denitrification + dust removal" (e.g. limestone-gypsum method for desulfurization, SCR method for denitrification, and electric dust removal for dust removal). The existing technology has the following disadvantages: the system is dispersed, the land occupation is large, the equipment investment and operation energy consumption are high; the desulfurization product gypsum has low purity and is easy to cause secondary pollution, the denitrification process does not recover pollutants, CO2 is not effectively treated, and it is difficult to achieve "zero emission"; each system is independently controlled, the coordination is poor, and the operation fluctuation is easy to occur, resulting in a decrease in treatment efficiency.

[0003] Therefore, there is an urgent need for an integrated, efficient and recyclable flue gas pollutant zero-emission system to solve the defects of the existing technology. SUMMARY

[0004] The present application relates to the technical field of flue gas treatment, in particular to a flue gas pollutant zero-emission and recovery system for thermal power plants.

[0005] The present application provides a flue gas pollutant zero-emission and recovery system for thermal power plants, which comprises a pretreatment unit, a desulfurization-denitrification-decarbonization integrated unit, a deep purification unit and a pollutant recovery unit connected in sequence, and a control system electrically connected with the pretreatment unit, the desulfurization-denitrification-decarbonization integrated unit, the deep purification unit and the pollutant recovery unit respectively; the pretreatment unit is used for cooling and dust removal treatment of flue gas discharged from the thermal power plant; the desulfurization-denitrification-decarbonization integrated unit is used for simultaneous desulfurization, denitrification and decarbonization treatment of the pretreated flue gas; the deep purification unit is used for residual pollutant removal treatment of the flue gas after desulfurization, denitrification and decarbonization treatment, so that the pollutant concentration in the flue gas meets the zero-emission requirement; the pollutant recovery unit is used for separation and purification recovery of pollutant products generated in the desulfurization, denitrification and decarbonization process; and the control system is used for real-time monitoring of the operation parameters of each unit and automatic adjustment of the operation state.

[0006] Preferably, the pretreatment unit comprises a flue gas cooler and an electrostatic precipitator connected in sequence; the flue gas cooler is an indirect heat exchange cooler, which is internally provided with a serpentine heat exchange pipe through which cooling water is passed; and the dust collection electrode of the electrostatic precipitator is made of stainless steel, and the discharge electrode is made of tungsten wire.

[0007] Preferably, the outlet flue gas temperature of the flue gas cooler is controlled at 80-120℃, and the dust removal efficiency of the electrostatic precipitator is ≥99.5%.

[0008] Preferably, the integrated desulfurization, denitrification, and decarbonization unit includes a composite adsorption desulfurization section, an SCR catalytic denitrification section, and an amine liquid absorption decarbonization section arranged sequentially along the flue gas flow direction; the composite adsorption desulfurization section is filled with a calcium-based activated carbon composite adsorbent, the SCR catalytic denitrification section is provided with a vanadium-titanium catalyst, and the absorbent introduced into the amine liquid absorption decarbonization section is an N-methyldiethanolamine solution.

[0009] Preferably, the operating temperature of the composite adsorption desulfurization section is 80-150℃, and the operating pressure is 0.1-0.3MPa; the operating temperature of the SCR catalytic denitrification section is 280-400℃, the reducing agent is ammonia, and the ammonia-nitrogen molar ratio is 1.0-1.2; the operating temperature of the amine liquid absorption decarbonization section is 40-60℃, and the mass concentration of the N-methyldiethanolamine solution is 20%-30%.

[0010] Preferably, the deep purification unit includes a molecular sieve adsorption tower, which is filled with 13X type molecular sieves. The molecular sieve adsorption tower operates using pressure swing adsorption, with an adsorption pressure of 0.15-0.25 MPa and a desorption pressure of 0.02-0.05 MPa.

[0011] Preferably, the SO2 concentration in the flue gas exiting the deep purification unit is ≤5 mg / m³. 3 NO x Concentration ≤5mg / m 3 CO2 concentration ≤100mg / m³ 3 Particulate matter concentration ≤1mg / m³ 3 .

[0012] Preferably, the pollutant recovery unit includes a desulfurization product recovery subunit, a denitrification product recovery subunit, and a decarbonization product recovery subunit, which are respectively connected to the integrated desulfurization, denitrification, and decarbonization unit. The desulfurization product recovery subunit includes a filter press and a dryer for processing the desulfurization slag generated in the composite adsorption desulfurization section into gypsum products. The denitrification product recovery subunit includes an absorption tower and a distillation tower for converting NO2 generated in the SCR catalytic denitrification section into nitric acid and purifying it. The decarbonization product recovery subunit includes a compressor unit and a cooler for compressing and cooling the CO2 desorbed in the amine liquid absorption decarbonization section into liquid carbon dioxide.

[0013] Preferably, the gypsum product produced by the desulfurization product recovery subunit has a purity of ≥95%; the nitric acid mass fraction produced by the denitrification product recovery subunit is ≥68%; and the liquid carbon dioxide produced by the decarbonization product recovery subunit has a purity of ≥99.9%.

[0014] Preferably, the control system includes a PLC controller, temperature sensors, pressure sensors, flow sensors, and pollutant concentration sensors respectively installed at the inlet and outlet of each unit, and a drive module connected to each actuator; the PLC controller receives the detection signals from each sensor and controls the drive module to adjust the operating parameters of each actuator to realize the automated operation of the system.

[0015] Beneficial effects: This invention adopts a series structure of "pretreatment + integrated desulfurization, denitrification, and decarbonization + deep purification + pollutant recovery," replacing the traditional segmented treatment mode. This significantly reduces the system's footprint, lowers equipment investment costs and operating energy consumption, and overcomes the shortcomings of existing decentralized systems. The integrated unit enables simultaneous desulfurization, denitrification, and decarbonization. Combined with the deep purification unit, it can control the concentration of flue gas pollutants within the zero-emission requirement. Simultaneously, the pollutant recovery unit separates and purifies the products, avoiding secondary pollution from desulfurization gypsum and achieving NO... x The system utilizes CO2 resources, overcoming the limitations of existing technologies that lack recycling and struggle to achieve zero emissions. The control system monitors the parameters of each unit in real time and adjusts them automatically, improving system coordination, avoiding the decline in processing efficiency caused by operational fluctuations, and ensuring the overall processing is stable and reliable. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a block diagram showing the overall structure of the present invention.

[0018] Explanation of reference numerals in the attached diagram: 1-Pretreatment unit, 101-Flue gas cooler, 102-Electrostatic precipitator, 2-Integrated desulfurization, denitrification and decarbonization unit, 201-Composite adsorption desulfurization section, 202-SCR catalytic denitrification section, 203-Amine liquid absorption decarbonization section, 3-Deep purification unit, 301-Molecular sieve adsorption tower, 4-Pollutant recovery unit, 401-Desulfurization product recovery subunit, 402-Denitrification product recovery subunit, 403-Decarbonization product recovery subunit, 5-Control system. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] Example 1 This embodiment uses a 600MW coal-fired power plant as an example, whose flue gas emissions are 1.2×10⁻⁶. 5 m 3 / h (standard conditions), the pollutant concentration in the original flue gas is: SO2 2800 mg / m³ 3 NO x 850mg / m 3 CO2 12% (volume fraction), particulate matter 35g / m³ 3 The flue gas temperature is 180-220℃. The specific structure and operation process of the zero-emission and recovery system for flue gas pollutants using this invention are as follows: 1.1 System Composition The system includes a pretreatment unit 1, an integrated desulfurization, denitrification and decarbonization unit 2, a deep purification unit 3, a pollutant recovery unit 4 and a control system 5. Each unit is connected in sequence through flue gas pipes and material pipes. The control system 5 is electrically connected to the sensors and actuators of each unit through cables.

[0023] 1.2 Operating parameters and procedures of each unit 1.2.1 Preprocessing Unit Equipment composition: an indirect serpentine flue gas cooler 101 connected in sequence, and a stainless steel dust collecting electrode-tungsten wire discharge electrode electrostatic precipitator 102.

[0024] Operating parameters: Flue gas cooler: 30℃ circulating cooling water is introduced into the serpentine heat exchange tubes, and the flue gas at the inlet temperature of 180-220℃ is cooled to 100℃ (control range 80-120℃) through indirect heat exchange. After the cooling water outlet temperature rises to 65℃, it enters the cooling tower for cooling circulation.

[0025] Electrostatic precipitator: When a DC voltage of 60kV is applied, the dust removal efficiency reaches 99.8% (≥99.5%), and the particulate matter concentration in the outlet flue gas is reduced to 0.07g / m³. 3 .

[0026] 1.2.2 Integrated Desulfurization, Denitrification, and Decarbonization Unit Along the flue gas flow direction, a composite adsorption desulfurization section 201, an SCR catalytic denitrification section 202, and an amine liquid absorption decarbonization section 203 are sequentially arranged as follows: Composite adsorption desulfurization section: Filled with calcium-based activated carbon composite adsorbent (CaO mass percentage 30%, activated carbon mass percentage 70%), operating temperature 120℃ (80-150℃), operating pressure 0.2MPa (0.1-0.3MPa).

[0027] SO2 in the flue gas reacts with the adsorbent to form CaSO3 and CaSO4, achieving a desulfurization efficiency of 99.8% and reducing the outlet SO2 concentration to 5.6 mg / m³. 3 .

[0028] SCR catalytic denitrification section: The device incorporates a vanadium-titanium catalyst (V2O5-WO3 / TiO2, with V2O5 accounting for 1.5% by mass), operates at a temperature of 320℃ (280-400℃), uses liquid ammonia as a reducing agent, and controls the ammonia-nitrogen molar ratio to be 1.1 (1.0-1.2).

[0029] NO x Under the action of a catalyst, it reacts with NH3 to produce N2 and H2O, achieving a denitrification efficiency of 99.4%, and reducing NO at the outlet. x The concentration decreased to 5.1 mg / m³. 3 .

[0030] Amine liquid absorption and decarbonization section: A 25% (20%-30%) N-methyldiethanolamine (MDEA) solution was introduced, the operating temperature was 50℃ (40-60℃), and the gas-liquid ratio was 150:1.

[0031] MDEA solution reacts with CO2 to form carbamate, achieving a decarbonization efficiency of 99.9% and reducing the outlet CO2 volume fraction to 0.012% (corresponding to a concentration of approximately 100 mg / m³). 3 ).

[0032] 1.2.3 Deep Purification Unit Equipment: 13X type molecular sieve adsorption tower 301 with single tower and double bed, adopting the "adsorption-pressure equalization-desorption-washing" pressure swing adsorption (PSA) process, with a single cycle of 120s.

[0033] Operating parameters: Adsorption pressure 0.2MPa (0.15-0.25MPa), desorption pressure 0.03MPa (0.02-0.05MPa), adsorption temperature 40℃.

[0034] Treatment effect: Further removal of residual SO2 and NO x The concentrations of pollutants in the outlet flue gas, including CO2 and particulate matter, are consistently maintained at: SO2 ≤ 3 mg / m³. 3 NO x ≤4mg / m 3 CO2 ≤ 80 mg / m³ 3 Particulate matter ≤0.8mg / m³ 3 It meets the zero emission requirements (less than 1 / 10 of the "Special Emission Limit" in GB13223-2011 "Emission Standard of Air Pollutants for Thermal Power Plants").

[0035] 1.2.4 Pollutant Recovery Unit It includes three sub-units, which respectively recover desulfurization, denitrification, and decarbonization products: Desulfurization product recovery subunit 401: The adsorbent that has failed in the composite adsorption desulfurization section (mainly containing CaSO3 and CaSO4) is hydraulically conveyed to a filter press (filtration pressure 0.8MPa, filter cake moisture content ≤20%), and then enters a dryer (hot air temperature 150℃, drying time 2h) to obtain gypsum product (CaSO4•2H2O) with a purity of 96.5% (≥95%), with a yield of about 2.8t / h, which can be used in building material production.

[0036] Denitrification product recovery subunit 402: Unreacted NH3 and trace amounts of NO2 in the SCR catalytic denitrification section are absorbed by an absorption tower (with 5% dilute nitric acid as the absorbent) to generate ammonium nitrate solution, which is then sent to a distillation tower (operating pressure 0.1 MPa, top temperature 120℃) for distillation to obtain industrial-grade nitric acid with a mass fraction of 69.2% (≥68%), with a yield of approximately 0.3 t / h.

[0037] Decarbonization product recovery subunit 403: The rich liquid from the amine absorption and decarbonization section is desorbed into high-concentration CO2 (99.5% purity) in a desorption tower (desorption temperature 120℃, pressure 0.15MPa). Then, it is compressed by a compressor unit (three-stage compression, outlet pressure 8.0MPa) and cooled by a cooler (cooled to 25℃) to obtain liquid carbon dioxide with a purity of 99.95% (≥99.9%), with a yield of about 11.2t / h. It can be used for food-grade CO2 or chemical raw materials.

[0038] 1.2.5 Control System Core equipment: Siemens S7-400 PLC controller, equipped with a 10-inch touch screen operating interface.

[0039] Monitoring and control: Temperature sensors (measuring range 0-300℃, accuracy ±1℃), pressure sensors (0-1MPa, accuracy ±0.01MPa), and particulate matter concentration sensors are installed at the inlet and outlet of the pretreatment unit. SO2 and NO are installed at the inlets and outlets of each section of the integrated unit. x CO2 concentration sensor (accuracy ±2%FS), flow sensor (0-2×10 5 m 3 / h, accuracy ±1%) The PLC controller receives signals from various sensors in real time and adjusts the cooling water flow rate of the flue gas cooler, the voltage of the electrostatic precipitator, the injection volume of the SCR reducing agent, the circulation volume of the MDEA solution, and the valve switching sequence of the molecular sieve adsorption tower through the drive module to achieve automated operation of the system with an operational stability of over 98% and no manual intervention required.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A zero-emission and recovery system for flue gas pollutants from a thermal power plant, characterized in that, The system includes a pretreatment unit, an integrated desulfurization, denitrification, and decarbonization unit, a deep purification unit, and a pollutant recovery unit connected in sequence, as well as a control system electrically connected to each of the pretreatment unit, the integrated desulfurization, denitrification, and decarbonization unit, the deep purification unit, and the pollutant recovery unit. The pretreatment unit is used to cool and remove dust from the flue gas discharged from the thermal power plant. The integrated desulfurization, denitrification, and decarbonization unit is used to simultaneously desulfurize, denitrify, and decarbonize the pretreated flue gas. The deep purification unit is used to remove residual pollutants from the flue gas after desulfurization, denitrification, and decarbonization to ensure that the pollutant concentration in the flue gas meets the zero-emission requirement. The pollutant recovery unit is used to separate, purify, and recover the pollutant products generated during the desulfurization, denitrification, and decarbonization processes. The control system is used to monitor the operating parameters of each unit in real time and automatically adjust the operating status.

2. The zero-emission and recovery system for flue gas pollutants in thermal power plants according to claim 1, characterized in that, The pretreatment unit includes a flue gas cooler and an electrostatic precipitator connected in sequence; the flue gas cooler is an indirect heat exchange cooler with a serpentine heat exchange tube inside, through which cooling water flows; the dust collecting electrode of the electrostatic precipitator is made of stainless steel, and the discharge electrode is made of tungsten wire.

3. The zero-emission and recovery system for flue gas pollutants in thermal power plants according to claim 2, characterized in that, The outlet flue gas temperature of the flue gas cooler is controlled at 80-120℃, and the dust removal efficiency of the electrostatic precipitator is ≥99.5%.

4. The zero-emission and recovery system for flue gas pollutants in thermal power plants according to claim 1, characterized in that, The integrated desulfurization, denitrification, and decarbonization unit includes a composite adsorption desulfurization section, an SCR catalytic denitrification section, and an amine liquid absorption decarbonization section arranged sequentially along the flue gas flow direction. The composite adsorption desulfurization section is filled with a calcium-based activated carbon composite adsorbent, the SCR catalytic denitrification section is equipped with a vanadium-titanium catalyst, and the absorbent liquid introduced into the amine liquid absorption decarbonization section is an N-methyldiethanolamine solution.

5. The zero-emission and recovery system for flue gas pollutants in thermal power plants according to claim 4, characterized in that, The operating temperature of the composite adsorption desulfurization section is 80-150℃, and the operating pressure is 0.1-0.3MPa; the operating temperature of the SCR catalytic denitrification section is 280-400℃, the reducing agent is ammonia, and the ammonia-nitrogen molar ratio is 1.0-1.2; the operating temperature of the amine liquid absorption decarbonization section is 40-60℃, and the mass concentration of the N-methyldiethanolamine solution is 20%-30%.

6. The zero-emission and recovery system for flue gas pollutants in thermal power plants according to claim 1, characterized in that, The deep purification unit includes a molecular sieve adsorption tower, which is filled with 13X type molecular sieves. The molecular sieve adsorption tower operates using pressure swing adsorption, with an adsorption pressure of 0.15-0.25 MPa and a desorption pressure of 0.02-0.05 MPa.

7. The zero-emission and recovery system for flue gas pollutants in a thermal power plant according to claim 6, characterized in that, The SO2 concentration in the flue gas exiting the deep purification unit is ≤5 mg / m³. 3 NO x Concentration ≤5mg / m 3 CO2 concentration ≤100mg / m³ 3 Particulate matter concentration ≤1mg / m³ 3 .

8. The zero-emission and recovery system for flue gas pollutants in a thermal power plant according to claim 1, characterized in that, The pollutant recovery unit includes a desulfurization product recovery subunit, a denitrification product recovery subunit, and a decarbonization product recovery subunit, which are respectively connected to the integrated desulfurization, denitrification, and decarbonization unit. The desulfurization product recovery subunit includes a filter press and a dryer, used to process the desulfurization slag generated in the composite adsorption desulfurization section into gypsum products. The denitrification product recovery subunit includes an absorption tower and a distillation tower, used to convert NO2 generated in the SCR catalytic denitrification section into nitric acid and purify it. The decarbonization product recovery subunit includes a compressor unit and a cooler, used to compress and cool the CO2 desorbed in the amine liquid absorption decarbonization section into liquid carbon dioxide.

9. The zero-emission and recovery system for flue gas pollutants in a thermal power plant according to claim 8, characterized in that, The gypsum product produced by the desulfurization product recovery subunit has a purity of ≥95%; the nitric acid produced by the denitrification product recovery subunit has a mass fraction of ≥68%; and the liquid carbon dioxide produced by the decarbonization product recovery subunit has a purity of ≥99.9%.

10. The zero-emission and recovery system for flue gas pollutants in a thermal power plant according to claim 1, characterized in that, The control system includes a PLC controller, temperature sensors, pressure sensors, flow sensors, and pollutant concentration sensors respectively installed at the inlet and outlet of each unit, and a drive module connected to each actuator. The PLC controller receives the detection signals from each sensor and controls the drive module to adjust the operating parameters of each actuator, thereby realizing the automated operation of the system.

Images