Denitration system adopting novel dry powder denitration agent and denitration method

Abstract

The invention discloses a denitration system adopting a novel dry powder denitration agent and a denitration method.The denitration system comprises a stock bin, a feeding device, a fluidized bed pyrolysis device and a cyclone separator, the dry powder denitration agent is stored in the stock bin, the feeding device is used for conveying the dry powder denitration agent to the fluidized bed pyrolysis device, and the cyclone separator is used for separating the dry powder denitration agent from the fluidized bed pyrolysis device; the dry powder denitration agent is pyrolyzed into pyrolysis gas in the fluidized bed pyrolysis device, the cyclone separator is arranged at the downstream of the fluidized bed pyrolysis device, the pyrolysis gas is separated into a gas-phase substance and a solid-phase substance through the cyclone separator, the gas-phase substance is sprayed into flue gas through the ammonia spraying grid, and the solid-phase substance enters the fluidized bed pyrolysis device. According to the denitration system, the dry powder type denitration agent is utilized, the dry powder denitration agent is directly pyrolyzed, the denitration reaction process time is remarkably shortened, the energy consumption and the operation cost are reduced, and meanwhile potential safety hazards of a traditional technology are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of denitration in thermal power plants, and in particular to a denitration system and a denitration method using a novel dry powder denitrifier. Background Art

[0002] Traditional denitrification technologies in thermal power plants generally use liquid ammonia, urea, or aqueous ammonia as reducing agents, but these solutions have significant drawbacks. Liquid ammonia, a major hazard and a potential safety hazard during storage and transportation, has been gradually phased out in recent years. While urea and aqueous ammonia are relatively safe, their denitrification reactions require hydrolysis or thermal decomposition to produce ammonia gas, resulting in a long reaction delay. This limits denitrification efficiency due to operating conditions, making precise control difficult, especially during rapid changes in unit load. Furthermore, urea thermal decomposition consumes significant amounts of heat energy, and the transportation and storage costs of aqueous ammonia are high, resulting in poor overall economic efficiency. Summary of the Invention

[0003] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0004] To this end, embodiments of the present invention provide a denitration system and a denitration method using a novel dry powder denitrifier.

[0005] In a first aspect, the present invention proposes a denitration system using a novel dry powder denitrifier, comprising:

[0006] a silo in which the dry powder denitrification agent is stored;

[0007] A feeding device, the feeding device is arranged downstream of the silo, and the feeding device is used to transport the dry powder denitrification agent to the fluidized bed pyrolysis device;

[0008] a fluidized bed pyrolysis device, wherein the fluidized bed pyrolysis device is arranged downstream of the feeding device, and the dry powder denitrification agent is pyrolyzed into pyrolysis gas in the fluidized bed pyrolysis device;

[0009] A cyclone separator is provided downstream of the fluidized bed pyrolysis device. The pyrolysis gas is separated into gaseous matter and solid matter by the cyclone separator. The gaseous matter is sprayed into the flue gas through the ammonia injection grid, and the solid matter enters the fluidized bed pyrolysis device.

[0010] Furthermore, the feeding device uses compressed air as a carrier to transport the dry powder denitrification agent to the fluidized bed pyrolysis device.

[0011] Furthermore, the pneumatic conveying velocity of the dry powder denitrifier is 18 to 30 m / s.

[0012] Furthermore, the feeding device is a frequency conversion controlled screw feeder.

[0013] Further, the hot air from the boiler provides heat source for the fluidized bed pyrolysis device, and the pyrolysis temperature of the fluidized bed pyrolysis device is 150 - 300 °C.

[0014] Further, the gaseous substances include ammonia and carbon dioxide, and the solid substances enter the fluidized bed pyrolysis device for re-pyrolysis.

[0015] Further, the dry powder denitration agent includes ammonium carbamate, corrosion inhibitor and stabilizer. Among them, the mass proportion of ammonium carbamate is 95% - 97.5%, the mass proportion of the corrosion inhibitor is 2% - 3%, and the mass proportion of the stabilizer is 0.1% - 2%.

[0016] Further, the particle size of the dry powder denitration agent is 0.1 - 1 mm.

[0017] Further, the ammonia injection grid is distributed in multiple stages in the flue.

[0018] In a second aspect, the present invention provides a denitration method, which uses the denitration system proposed in the first aspect above, and includes the following steps:

[0019] (1) The feeding device pneumatically conveys the dry powder denitration agent stored in the silo to the fluidized bed pyrolysis device;

[0020] (2) In the fluidized bed pyrolysis device, the dry powder denitration agent is pyrolyzed into pyrolysis gas under the action of hot air at 150 - 300 °C from the boiler;

[0021] (3) The pyrolysis gas is separated into gaseous substances and solid substances under the action of a cyclone separator;

[0022] (4) The gaseous substances are sprayed into the flue gas through the ammonia injection grid arranged in the flue and undergo selective catalytic reaction with the nitrogen oxides in the flue gas.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] The denitration system of the present invention uses a dry powder type denitration agent, directly pyrolyzes the dry powder denitration agent, significantly shortens the denitration reaction process time, reduces energy consumption and operation costs, and at the same time avoids the safety hazards of traditional technologies.

[0025] The present invention uses the hot air from the boiler as the heat source for pyrolyzing the dry powder denitration agent, reducing energy consumption.

[0026] The ammonia injection grid of the present invention adopts a multi-stage distribution layout in the flue to ensure the turbulent mixing effect of the pyrolysis gas ammonia and the flue gas. Description of the Drawings

[0027] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the following description of embodiments in conjunction with the accompanying drawings, in which:

[0028] Figure 1 It is a schematic diagram of a denitration system using a novel dry denitration agent of the present invention.

[0029] Description of reference numerals:

[0030] 1. Silo; 2. Feeding device; 3. Air compressor; 4. Fluidized bed pyrolysis device; 5. Cyclone separator; 6. Ammonia injection grid; 7. Boiler. Detailed implementation manners

[0031] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0032] The following describes a denitration system and a denitration method using a novel dry denitration agent proposed by the present invention in conjunction with the accompanying drawings.

[0033] As Figure 1 shown, the denitration system using a novel dry denitration agent of the present invention includes a silo 1, a feeding device 2, a fluidized bed pyrolysis device 4, and a cyclone separator 5.

[0034] The silo 1 is used to store the dry denitration agent. The dry denitration agent takes ammonium carbamate as the main active substance and also includes a corrosion inhibitor and a stabilizer. Among them, the mass ratio of ammonium carbamate is 95% - 97.5%, the mass ratio of the corrosion inhibitor is 2% - 3%, and the mass ratio of the stabilizer is 0.1% - 2%.

[0035] In some embodiments, the corrosion inhibitor includes alcohol amide substances. The alcohol amide substances include polyisobutylene maleic acid diethanolamide, oleic acid diethanolamide, and stearic acid diethanolamide, or other suitable alcohol amide substances.

[0036] In some embodiments, the stabilizer includes benzotriazole derivatives. The benzotriazole derivatives include benzotriazole isobutylimine, benzotriazole, and benzotriazole propylimine, or other suitable benzotriazole derivatives.

[0037] In some embodiments, the particle size of the dry denitration agent is 0.1 - 1 mm. The particle size of the dry denitration agent within a suitable range enables the pyrolysis efficiency, conveying rate, and economy to be in a relatively high range; when the particle size of the dry denitration agent is too large, the particle pyrolysis requires a relatively high energy consumption, and at the same time, it brings difficulties to pneumatic conveying; when the particle size of the dry denitration agent is too small, the production cost of the denitration agent is relatively high.

[0038] The dry powder denitrifier of the present invention uses ammonium carbamate as the main active substance. The pyrolysis temperature of ammonium carbamate is about 100-200°C lower than that of urea, the pyrolysis energy consumption is reduced by more than 30%, and the reaction rate is increased by 40%, and it can quickly respond to load changes.

[0039] The present invention adopts a denitrification agent in the form of dry powder. The dry powder has stable physical properties, no risk of deliquescence or agglomeration, and its storage and transportation safety is significantly better than liquid ammonia and ammonia water.

[0040] The dry powder denitrifier of the present invention contains a corrosion inhibitor, which can effectively inhibit the corrosion of pipelines during the pyrolysis process and extend the service life of the equipment.

[0041] The feeding device 2 is arranged downstream of the silo 1. In the present invention, the feeding device 2 is used to transport the dry powder denitrification agent to the downstream fluidized bed pyrolysis device 4.

[0042] In some embodiments, the feeding device 2 uses compressed air as a carrier to transport the dry powder denitrification agent to the fluidized bed pyrolysis device 4. That is, the feeding device 2 is connected to the air compressor 3. During the feeding process, the compressed air at the outlet of the air compressor 3 mixes with the dry powder denitrification agent, and the dry powder denitrification agent is transported to the fluidized bed pyrolysis device 4 by air force.

[0043] It is understandable that the pressure of the compressed air and the flow rate of the dry powder denitrification agent can be adjusted according to specific working conditions.

[0044] In some embodiments, the pneumatic conveying velocity of the dry powder denitrification agent is 18 to 30 m / s. The present invention controls the pneumatic conveying velocity of the dry powder denitrification agent at 18 to 30 m / s to achieve high pneumatic conveying efficiency. When the pneumatic conveying velocity of the dry powder denitrification agent is too high, pipeline resistance is high and energy consumption is high. When the pneumatic conveying velocity of the dry powder denitrification agent is too low, the solid transport volume is small, and environmental emission requirements cannot be met.

[0045] In some embodiments, the feeding device 2 is a variable frequency controlled spiral feeder, which can control the flow rate of the dry powder denitrification agent according to specific working conditions.

[0046] The fluidized bed pyrolysis device 4 is arranged downstream of the feeding device 2. The feeding device 2 uses pneumatic conveying to transport the dry powder denitrification agent to the fluidized bed pyrolysis device 4. The dry powder denitrification agent is pyrolyzed into pyrolysis gas in the fluidized bed pyrolysis device 4. The pyrolysis gas includes ammonia and carbon dioxide.

[0047] In some embodiments, the hot air from the boiler 7 provides a heat source for the fluidized bed pyrolysis device 4 , and the pyrolysis temperature of the fluidized bed pyrolysis device 4 is 150-300° C.

[0048] A cyclone separator 5 is arranged downstream of the fluidized bed pyrolysis device 4. The pyrolysis gas is separated into gas-phase substances and solid-phase substances by the cyclone separator 5. The gas-phase substances include ammonia and carbon dioxide. The gas-phase substances are injected into the flue gas through an ammonia injection grid 6, and the ammonia in the gas-phase substances undergoes a selective catalytic reduction reaction with the nitrogen oxides in the flue gas.

[0049] The solid-phase substances include dust and unpyrolyzed denitration agent. The solid-phase substances enter the fluidized bed pyrolysis device 4, and the solid-phase substances entering the fluidized bed pyrolysis device 4 are pyrolyzed again.

[0050] The ammonia injection grid 6 is arranged in the flue duct, between the economizer of the boiler and the SCR denitration reactor. In some embodiments, the ammonia injection grid 6 is distributed in multiple stages in the flue duct. The ammonia injection grid 6 distributed in multiple stages is arranged in the flue duct, so that the gas-phase substances are evenly injected into the flue gas, thereby fully reacting with the nitrogen oxides in the flue gas.

[0051] The denitration method of the present invention uses the denitration system adopting the novel dry denitration agent of the present invention, and comprises the following steps:

[0052] (1) The feeding device 2 pneumatically conveys the dry denitration agent stored in the silo 1 to the fluidized bed pyrolysis device 4;

[0053] (2) In the fluidized bed pyrolysis device 4, the dry denitration agent is pyrolyzed into pyrolysis gas under the action of hot air at 150-300 °C from the boiler 7;

[0054] (3) The pyrolysis gas is separated into gas-phase substances and solid-phase substances under the action of the cyclone separator 5;

[0055] (4) The gas-phase substances are injected into the flue gas through the ammonia injection grid 6 arranged in the flue duct to carry out a selective catalytic reaction with the nitrogen oxides in the flue gas.

[0056] Among them, step (1) is the conveying process of the dry denitration agent. The feeding device 2 conveys the dry denitration agent to the fluidized bed pyrolysis device 4 with gas as the carrier. In some embodiments, the feeding device 2 is a spiral feeder with frequency conversion control, and the flow rate of the dry denitration agent can be controlled according to the specific working conditions. In some embodiments, the carrier gas of the dry denitration agent is compressed air, which is provided by the air compressor 3.

[0057] Step (2) is the pyrolysis process of the dry denitration agent. The dry denitration agent is pyrolyzed into pyrolysis gas at high temperature in the fluidized bed pyrolysis device 4, and the pyrolysis temperature is 150-300 °C. The hot air from the boiler 7 provides heat source for the pyrolysis process of the dry denitration agent.

[0058] Step (3) is the gas-solid separation process of the pyrolysis gas. The pyrolysis gas is separated into gas-phase substances and solid-phase substances under the action of the cyclone separator 5. The gas-phase substances include ammonia and carbon dioxide, and the solid-phase substances include dust and incompletely pyrolyzed denitration agent.

[0059] In step (4), the gaseous substance is sprayed into the flue gas for selective catalytic reaction, that is, ammonia reacts with nitrogen oxides in the flue gas to remove nitrogen oxides in the flue gas. The gaseous substance is provided by the ammonia injection grid 6 and sprayed into the flue gas. The ammonia injection grid 6 is arranged in the flue and is located between the economizer of the boiler and the SCR reactor. Among them, the economizer of the boiler and the SCR reactor are commonly used equipment in the denitration system and will not be elaborated here.

[0060] The following will illustrate the present invention with a specific embodiment.

[0061] The denitration agent powder with a particle size of 0.1 mm is pneumatically transported to the silo in a dense phase. A screw feeder is installed at the lower part of the silo, and the output range of the screw feeder is 0 - 4 t / h. Under the normal load of the boiler, the screw feeder continuously transports the denitration agent powder to the pneumatic conveying pipeline at a speed of 1.2 t / h. Under the action of the air compressor, the compressed air at 0.4 MPa transports the denitration agent powder through the pneumatic conveying pipeline to the pyrolysis furnace. The gas velocity is 30 m / s, and the solid conveying capacity is 1.2 t / h. The hot air from the boiler enters the fluidized bed pyrolysis device from the top of the fluidized bed pyrolysis device, providing continuous heat for pyrolysis and maintaining the stable operation of the fluidized bed pyrolysis device at about 300 °C. The ammonia gas after pyrolysis, carrying uncompletely pyrolyzed particles or solid impurities, enters the cyclone separator from the outlet of the fluidized bed pyrolysis device. The solid part is captured by the cyclone separator and returned to the fluidized bed pyrolysis device, and the gas part containing ammonia gas enters the boiler for denitration reaction.

[0062] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms can be directed to different embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0063] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0064] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A denitration system using a new type of dry denitration agent, characterized in that, Comprising: A silo, in which dry denitration agent is stored; A feeding device, which is arranged downstream of the silo and is used to convey the dry denitration agent to a fluidized bed pyrolysis device; A fluidized bed pyrolysis device, which is arranged downstream of the feeding device, and the dry denitration agent is pyrolyzed into pyrolysis gas in the fluidized bed pyrolysis device; A cyclone separator, which is arranged downstream of the fluidized bed pyrolysis device. The pyrolysis gas is separated into gas-phase substances and solid-phase substances by the cyclone separator. The gas-phase substances are sprayed into the flue gas through an ammonia injection grid, and the solid-phase substances enter the fluidized bed pyrolysis device.

2. The denitration system according to claim 1, characterized in that, The feeding device conveys the dry denitration agent to the fluidized bed pyrolysis device by taking compressed air as a carrier.

3. The denitration system according to claim 1, characterized in that, The pneumatic conveying flow rate of the dry denitration agent is 18 - 30 m / s.

4. The denitration system according to claim 1, characterized in that, The feeding device is a variable-frequency controlled screw feeder.

5. The denitration system according to claim 1, wherein Hot air from the boiler provides heat source for the fluidized bed pyrolysis device, and the pyrolysis temperature of the fluidized bed pyrolysis device is 150 - 300 °C.

6. The denitration system according to claim 1, wherein, The gas-phase substances include ammonia and carbon dioxide, and the solid-phase substances enter the fluidized bed pyrolysis device to be pyrolyzed again.

7. The denitration system according to claim 1, characterized in that, The dry denitration agent includes ammonium carbamate, corrosion inhibitor and stabilizer. Among them, the mass ratio of ammonium carbamate is 95% - 97.5%, the mass ratio of the corrosion inhibitor is 2% - 3%, and the mass ratio of the stabilizer is 0.1% - 2%.

8. The denitration system according to claim 1, wherein, The particle size of the dry denitration agent is 0.1 - 1 mm.

9. The denitration system according to claim 1, characterized in that, The ammonia injection grid is distributed in multiple stages in the flue.

10. A denitrification method, characterized in that, Using the denitration system according to any one of claims 1 - 9, comprising the following steps: (1) The feeding device pneumatically conveys the dry denitration agent stored in the silo to the fluidized bed pyrolysis device; (2) In the fluidized bed pyrolysis device, the dry denitration agent is pyrolyzed into pyrolysis gas under the action of hot air at 150 - 300 °C from the boiler; (3) The pyrolysis gas is separated into gas-phase substances and solid-phase substances under the action of the cyclone separator; (4) The gas-phase substances are sprayed into the flue gas through the ammonia injection grid arranged in the flue and undergo selective catalytic reaction with nitrogen oxides in the flue gas.

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