A system for realizing controllable furnace temperature adjustment and efficient denitration by using flue gas recirculation

Abstract

The present application relates to a kind of controllable furnace temperature adjustment and high-efficiency denitration system using flue gas recirculation, belong to boiler combustion and flue gas purification technical field;Including boiler, temperature adjustment flue gas fan, temperature adjustment flue gas wind box, temperature adjustment flue gas cyclone nozzle, the flue of boiler is connected with the inlet of temperature adjustment flue gas fan by connecting flue;Temperature adjustment flue gas wind box is installed on the hearth outside of boiler, and temperature adjustment flue gas cyclone nozzle is fixedly arranged on the wall of hearth, temperature adjustment flue gas cyclone nozzle is communicated with temperature adjustment flue gas wind box, temperature adjustment flue gas cyclone nozzle is located between the burnout zone and SNCR reaction zone of hearth;Flue gas conveying pipeline is arranged between the outlet of temperature adjustment flue gas fan and temperature adjustment flue gas wind box;The problem that the present SNCR denitration technology is caused by the fact that the temperature of reaction zone cannot be controlled to be always in effective window and leads to poor denitration effect is solved.

Description

Technical Field

[0001] This invention belongs to the field of boiler combustion and flue gas purification technology, specifically relating to a system for controlling in-furnace temperature regulation and efficient denitrification by utilizing flue gas recirculation. Background Technology

[0002] Selective non-catalytic reduction (SNCR) denitrification technology is widely used in denitrification systems and devices for small pulverized coal boilers due to its low investment and small footprint. Its principle involves injecting a denitrification reducing agent (such as urea or ammonia) into the furnace region where the temperature is within the reaction "window" range (typically 900℃-1100℃). In this region, the reducing agent reacts with NO... x The reaction produces N2, CO2, and H2O. If the temperature is too high, the reducing agent is easily oxidized to produce additional NO. x This leads to an increase in the consumption of denitrifying agents; if the temperature is too low, the reaction efficiency will drop sharply, leading to an increase in the consumption of denitrifying agents and a significant increase in ammonia slip.

[0003] Ash and slag buildup on the heating surfaces of a boiler furnace has a significant impact on the furnace temperature distribution and furnace outlet temperature. For some small pulverized coal boilers that are not equipped with soot blowing devices or whose soot blowing devices are not operating well, ash and slag are prone to accumulate on the heating surfaces. Increased boiler load and prolonged operation will lead to changes in the furnace temperature distribution and an increase in the flue gas temperature at the furnace outlet. The temperature in the denitrification agent injection zone will deviate from the effective reaction temperature window, resulting in reduced reaction efficiency, increased denitrification agent consumption, and increased production costs. Summary of the Invention

[0004] This invention overcomes the shortcomings of existing technologies and proposes a controllable furnace temperature regulation and efficient denitrification system that utilizes flue gas recirculation; it solves the problem that the current SNCR denitrification technology has poor denitrification effect because it cannot control the temperature of the reaction zone to always be within the effective window.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution.

[0006] A system for controllable in-furnace temperature regulation and efficient denitrification using flue gas recirculation includes a boiler, a temperature-regulating flue gas fan, a temperature-regulating flue gas box, and temperature-regulating flue gas swirl nozzles. The boiler's exhaust flue is connected to the inlet of the temperature-regulating flue gas fan via a connecting flue. A temperature-regulating flue gas box is installed on the outside of the boiler's furnace. Temperature-regulating flue gas swirl nozzles are fixedly installed on the furnace wall and are connected to the temperature-regulating flue gas box. The temperature-regulating flue gas swirl nozzles are located between the combustion zone and the SNCR reaction zone of the furnace. A flue gas conveying pipeline is provided between the outlet of the temperature-regulating flue gas fan and the temperature-regulating flue gas box.

[0007] Furthermore, a flue gas temperature sensor and a flue gas flow sensor are installed on the flue gas conveying pipeline.

[0008] Furthermore, the boiler furnace contains, in sequence, a main combustion zone, a burnout zone, and an SNCR reaction zone along the flue gas flow direction.

[0009] Furthermore, denitrification agent nozzles are installed on the walls of the SNCR reaction zone in the furnace, located upstream inside the SNCR reaction zone.

[0010] Furthermore, a reaction zone temperature sensor is installed in the SNCR reaction zone of the furnace, and the reaction zone temperature sensor is located in the horizontal plane where the denitrification agent nozzle is located.

[0011] Furthermore, two symmetrical temperature-regulating flue gas boxes are fixedly installed on the outside of the furnace, and two or more temperature-regulating flue gas swirl nozzles are installed on the furnace walls corresponding to the two temperature-regulating flue gas boxes.

[0012] Furthermore, the outer end of the temperature-regulating flue gas swirl nozzle is connected to the inside of the temperature-regulating flue gas wind box, and the inner end of the temperature-regulating flue gas swirl nozzle is connected to the inside of the furnace.

[0013] Furthermore, the outside of the flue gas conveying pipe is covered with insulation material.

[0014] Furthermore, the temperature-regulating flue gas is taken from the flue after the boiler's dust collector and induced draft fan.

[0015] The beneficial effects of this invention compared to the prior art are as follows: 1. Achieve controllable furnace temperature in the SNCR reaction zone: By injecting temperature-regulating flue gas into the wall between the combustion zone and the SNCR reaction zone in a swirling counter-current manner, the flue gas temperature in the SNCR reaction zone inside the furnace can be effectively regulated, so that the flue gas temperature in the SNCR reaction zone is maintained in the optimal reaction window zone (900℃-1100℃), creating the best temperature conditions for SNCR denitrification.

[0016] 2. No interference with upstream combustion and burnout process: The recirculated flue gas is injected downstream of the burnout zone, which will not affect the aerodynamic field and temperature field of the main combustion and burnout zone, ensuring the combustion stability and burnout characteristics of pulverized coal.

[0017] 3. No increase in oxygen content: The temperature-regulating flue gas is recirculated flue gas, which will not change the oxygen concentration distribution in the furnace or affect the characteristics of staged combustion. Attached Figure Description

[0018] The present invention will now be described in further detail with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram showing the connection between the temperature-regulating flue gas swirl nozzle, the denitrification agent nozzle, and the boiler. Figure 3This is a plan view of the boiler at the temperature-regulating flue gas swirl nozzle. Among them, 1 is the boiler, 2 is the dust collector, 3 is the induced draft fan, 4 is the temperature-regulating flue gas fan, 5 is the temperature-regulating flue gas box, 6 is the temperature-regulating flue gas swirl nozzle, 7 is the flue gas conveying pipeline, 8 is the main combustion zone, 9 is the combustion zone, 10 is the SNCR reaction zone, 11 is the flue gas temperature sensor, 12 is the flue gas flow sensor, 13 is the denitrification agent nozzle, and 14 is the reaction zone temperature sensor. Detailed Implementation

[0019] To make the technical problems to be solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail with reference to the embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The technical solutions of this invention are described in detail below with reference to the embodiments and accompanying drawings, but the scope of protection is not limited thereto.

[0020] like Figure 1 As shown in Figure 3, this invention provides a system for controllable in-furnace temperature regulation and efficient denitrification using flue gas recirculation. The system includes a boiler 1, with a dust collector 2 and an induced draft fan 3 sequentially installed at the boiler 1's exhaust port. The induced draft fan 3 draws the flue gas discharged from the boiler 1 outwards, while the dust collector 2 removes dust from the flue gas. A temperature-regulating flue gas fan 4 is installed at the outlet of the induced draft fan 3. A temperature-regulating flue gas box 5 is installed outside the furnace of the boiler 1. A temperature-regulating flue gas swirl nozzle 6 is fixedly installed on the furnace wall, connected to the temperature-regulating flue gas box 5. The temperature-regulating flue gas swirl nozzle 6 is located between the combustion zone 9 and the SNCR reaction zone 10 of the furnace. A flue gas conveying pipe 7 is installed between the outlet of the temperature-regulating flue gas fan 4 and the temperature-regulating flue gas box 5.

[0021] Inside the furnace of boiler 1, along the direction of flue gas flow, there are a main combustion zone 8, a burnout zone 9, and an SNCR reaction zone 10 arranged sequentially, wherein the main combustion zone 8 is located upstream of the burnout zone 9, and the burnout zone 9 is located upstream of the SNCR reaction zone 10.

[0022] A flue gas temperature sensor 11 and a flue gas flow sensor 12 are installed on the flue gas conveying pipeline 7. The flue gas temperature sensor 11 is used to measure the temperature of the temperature-controlled flue gas output by the temperature-controlled flue gas fan 4, and the flue gas flow sensor 12 is used to measure the volume of the temperature-controlled flue gas output by the temperature-controlled flue gas fan 4.

[0023] A denitrification agent nozzle 13 is installed on the wall of the SNCR reaction zone 10 in the furnace. The denitrification agent nozzle 13 is located upstream inside the SNCR reaction zone 10, ensuring that the denitrification agent injected into the nozzle 13 can enter the SNCR reaction zone 10 with the flue gas flowing inside the furnace. A reducing agent (such as urea or ammonia) is injected into the SNCR reaction zone 10 through the denitrification agent nozzle 13. The reducing agent reacts with NO in the flue gas. x The efficient reaction generates N2, CO2 and H2O, thereby achieving denitrification.

[0024] Two symmetrical temperature-regulating flue gas boxes 5 are fixedly installed on the outside of the furnace. Two or more temperature-regulating flue gas swirl nozzles 6 are installed on the furnace walls corresponding to each of the two temperature-regulating flue gas boxes 5. The temperature-regulating flue gas swirl nozzles 6 are connected to the temperature-regulating flue gas box 5 on the same side. One outer end of the temperature-regulating flue gas swirl nozzle 6 is connected to the inside of the temperature-regulating flue gas box 5, and one inner end of the temperature-regulating flue gas swirl nozzle 6 is connected to the inside of the furnace. The temperature-regulating flue gas swirl nozzles 6 are arranged in an opposing manner, and the flue gas velocity at the temperature-regulating flue gas swirl nozzles 6 is designed to be 25m / s-30m / s to ensure that the temperature-regulating flue gas can be quickly and uniformly mixed with the high-temperature flue gas in the furnace.

[0025] A reaction zone temperature sensor 14 is installed in the SNCR reaction zone 10 of the furnace. The reaction zone temperature sensor 14 is located in the horizontal plane where the denitrification agent nozzle 13 is located. The reaction zone temperature sensor 14 is used to measure the reaction temperature of the SNCR reaction zone 10 in the area where the denitrification agent nozzle 13 is located.

[0026] The outside of the flue gas conveying duct 7 is covered with insulation material to prevent heat loss and condensation of the temperature-regulating flue gas. The flow rate of the temperature-regulating flue gas inside the flue gas conveying duct 7 is designed to be 12m / s-15m / s.

[0027] The working principle of this invention is as follows: The induced draft fan 3 draws the flue gas discharged from the boiler 1 outwards, and the discharged flue gas passes through the dust collector 2 for dust removal. The flue gas drawn out from the outlet of the induced draft fan 3 is low-temperature flue gas, with a temperature range of 120-150℃. The temperature-regulating flue gas fan 4 transports a portion of the low-temperature flue gas drawn out by the induced draft fan 3 into the flue gas conveying pipe 7. The low-temperature flue gas transported into the flue gas conveying pipe 7 is the temperature-regulating flue gas, which is used to regulate the temperature of the flue gas in the furnace. The temperature-regulating flue gas fan 4 adopts frequency conversion control, and the amount of temperature-regulating flue gas is precisely controlled by adjusting the frequency of the temperature-regulating flue gas fan 4.

[0028] Temperature-regulating flue gas enters the temperature-regulating flue gas box 5 through the flue gas conveying pipe 7, and then is injected into the furnace between the combustion zone 9 and the SNCR reaction zone 10 through the temperature-regulating flue gas swirl nozzle 6. The temperature-regulating flue gas ejected from the temperature-regulating flue gas swirl nozzle 6 mixes with the high-temperature flue gas flowing out of the combustion zone 9 inside the furnace. The temperature of the mixed flue gas is lower than that of the high-temperature flue gas inside the furnace. The temperature-regulating flue gas swirl nozzle 6 adopts an opposing arrangement, and the flue gas velocity at the temperature-regulating flue gas swirl nozzle 6 is designed to be 25m / s-30m / s to ensure that the temperature-regulating flue gas can be quickly and uniformly mixed with the high-temperature flue gas inside the furnace.

[0029] The low-temperature temperature-regulating flue gas mixes with the high-temperature flue gas in the furnace in the area between the combustion zone 9 and the SNCR reaction zone 10, and then flows into the interior of the SNCR reaction zone 10, thus lowering the reaction temperature inside the SNCR reaction zone 10. The reaction zone temperature sensor 14, installed in the SNCR reaction zone 10, can measure the reaction temperature in the area where the denitrification agent nozzle 13 is located. Based on the temperature value fed back by the reaction zone temperature sensor 14, the frequency of the temperature-regulating flue gas fan 4 can be adjusted accordingly, thereby regulating the amount of temperature-regulating flue gas incorporated. The amount of temperature-regulating flue gas incorporated is monitored in real time by the flue gas flow sensor 12. The purpose of adjusting the temperature-regulating flue gas fan 4 is to maintain the flue gas temperature in the area where the denitrification agent nozzle 13 is located at the high end of the optimal reaction temperature range, i.e., 1100℃.

[0030] When the boiler load increases or ash and slag buildup on the furnace heating surface causes the flue gas temperature at the furnace outlet to rise, resulting in the temperature sensor 14 in the reaction zone measuring a temperature exceeding 1100℃ in the area where the denitrification agent nozzle 13 is located, the injection volume of temperature-regulating flue gas is increased by increasing the frequency of the temperature-regulating flue gas fan 4. After the low-temperature temperature-regulating flue gas mixes with the high-temperature flue gas in the furnace, the temperature of the SNCR reaction zone 10 is controlled within the window range of 900℃-1100℃.

[0031] When the temperature sensor 14 in the reaction zone measures that the temperature in the area where the denitrification agent nozzle 13 is located is below 1100℃, the frequency of the temperature-regulating flue gas fan 4 is reduced, the amount of low-temperature temperature-regulating flue gas added is reduced, and the temperature in the reaction zone is raised back to the optimal window range.

[0032] Through the above operational adjustments, the temperature of SNCR reaction zone 10 remained stable within the optimal reaction window. At this temperature, the reducing agent (such as urea or ammonia) injected through denitrification agent nozzle 13 reacts with NO in the flue gas. x The efficient reaction generates N2, CO2, and H2O, ensuring the high denitrification efficiency of the SNCR system, while effectively controlling the consumption of denitrification agent and reducing ammonia slip.

[0033] Since the temperature-regulating flue gas injection point is located downstream of the combustion zone 9, this input method will not interfere with the combustion stability and aerodynamic field of the upstream main combustion zone 8, nor will it change the oxygen concentration in the furnace, thus ensuring the combustion efficiency and combustion characteristics of the pulverized coal.

[0034] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A system for controllable in-furnace temperature regulation and efficient denitrification using flue gas recirculation, characterized in that: The boiler (1), temperature regulating flue gas fan (4), temperature regulating flue gas box (5), and temperature regulating flue gas swirl nozzle (6) are included. The flue gas exhaust duct of the boiler (1) is connected to the inlet of the temperature regulating flue gas fan (4) through a connecting flue. The temperature regulating flue gas box (5) is installed on the outside of the furnace of the boiler (1). The temperature regulating flue gas swirl nozzle (6) is fixedly installed on the wall of the furnace. The temperature regulating flue gas swirl nozzle (6) is connected to the temperature regulating flue gas box (5). The temperature regulating flue gas swirl nozzle (6) is located between the combustion zone (9) and the SNCR reaction zone (10) of the furnace. A flue gas conveying pipe (7) is provided between the outlet of the temperature regulating flue gas fan (4) and the temperature regulating flue gas box (5).

2. The system for controllable in-furnace temperature regulation and efficient denitrification using flue gas recirculation as described in claim 1, characterized in that: A flue gas temperature sensor (11) and a flue gas flow sensor (12) are installed on the flue gas conveying pipe (7).

3. The system for controllable in-furnace temperature regulation and efficient denitrification using flue gas recirculation as described in claim 1, characterized in that: Inside the furnace of the boiler (1), along the direction of flue gas flow, there are a main combustion zone (8), a burnout zone (9), and an SNCR reaction zone (10).

4. The system for controllable furnace temperature regulation and efficient denitrification using flue gas recirculation as described in claim 1, characterized in that: A denitrification agent nozzle (13) is provided on the wall of the SNCR reaction zone (10) in the furnace. The denitrification agent nozzle (13) is located upstream inside the SNCR reaction zone (10).

5. The system for controllable furnace temperature regulation and efficient denitrification using flue gas recirculation according to claim 4, characterized in that: A reaction zone temperature sensor (14) is installed in the SNCR reaction zone (10) of the furnace. The reaction zone temperature sensor (14) is located in the horizontal plane where the denitrification agent nozzle (13) is located.

6. The system for controllable in-furnace temperature regulation and efficient denitrification using flue gas recirculation according to claim 1, characterized in that: Two symmetrical temperature-regulating flue gas boxes (5) are fixedly installed on the outside of the furnace. Two or more temperature-regulating flue gas swirl nozzles (6) are installed on the furnace walls corresponding to the two temperature-regulating flue gas boxes (5).

7. A system for controllable furnace temperature regulation and efficient denitrification using flue gas recirculation as described in claim 6, characterized in that: One end of the temperature-regulating flue gas swirl nozzle (6) is connected to the inside of the temperature-regulating flue gas wind box (5), and one end of the temperature-regulating flue gas swirl nozzle (6) is connected to the inside of the furnace.

8. The system for controllable in-furnace temperature regulation and efficient denitrification using flue gas recirculation according to claim 1, characterized in that: The outside of the flue gas conveying pipe (7) is covered with thermal insulation material.

9. A system for controllable in-furnace temperature regulation and efficient denitrification using flue gas recirculation as described in claim 1, characterized in that: The temperature-regulating flue gas is taken from the flue after the dust collector (2) and induced draft fan (3) of the boiler (1).

Images