Ultra-low NOx control system for EDC cracking furnace flue gas

Abstract

The utility model discloses an EDC cracking furnace flue gas ultralow NOx control system which is characterized by comprising an EDC cracking furnace (1), a hearth (11) and a chimney (12) arranged at the top of the hearth (11), and the hearth (11) comprises a radiation section (111), a convection section (112) and a preheating section (113); the combustor (2) is installed on the side portion of the radiation section (111) and comprises a first-stage combustion section (21) and a second-stage combustion section (22), the first-stage combustion section (21) is used for conducting combustion after natural gas and air are premixed, and the second-stage combustion section (22) is used for conducting combustion on pure natural gas; the ammonia spraying device (3) is used for spraying ammonia gas into the convection section (112); and the SCR device (4) is positioned between the convection section (112) and the preheating section (113). Compared with the prior art, the ultra-low emission of nitrogen oxides can be realized.

Description

Technical Field

[0001] This utility model relates to the field of flue gas emission control and treatment technology, specifically to an ultra-low NOx control system for EDC pyrolysis furnace flue gas. Background Technology

[0002] Gas-fired boilers produce large amounts of nitrogen oxides (NOx) during combustion, such as NO. The large emissions of NOx lead to serious air pollution problems such as acid rain, photochemical smog, and ozone pollution, further endangering human health.

[0003] In the context of "dual carbon" (carbon dioxide, carbon emissions, and carbon sequestration), energy conservation and emission reduction are particularly important. Ultra-low emissions of nitrogen oxides (NOx) in flue gas can be achieved through tail-end flue gas denitrification and source combustion control. Selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) are currently mature and effective tail-end flue gas denitrification technologies. Among them, SCR denitrification technology is a commonly used method for NOx emission control in gas-fired boilers. For details, please refer to Chinese patent application number CN202411073019.9, "A Novel π-Type Boiler SCR Denitrification Device".

[0004] In addition, low-NOx combustion technology is a more economical and green NOx control method. It can achieve low-NOx combustion by using technologies such as staged combustion, flue gas recirculation, and humidified combustion. For details, please refer to Chinese patent application number CN202411503216.X, "A Low-NOx Combustion Device".

[0005] Traditional EDC pyrolysis furnaces do not strictly control nitrogen oxide emissions from the combustion flue gas, and therefore cannot achieve ultra-low nitrogen oxide emissions. Utility Model Content

[0006] The technical problem to be solved by this utility model is to provide an ultra-low NOx control system for EDC pyrolysis furnace flue gas that can achieve ultra-low emissions of nitrogen oxides, in light of the current state of the technology.

[0007] The technical solution adopted by this utility model to solve the above-mentioned technical problems is: an ultra-low NOx control system for EDC pyrolysis furnace flue gas, characterized in that: it includes...

[0008] EDC pyrolysis furnace includes a furnace chamber and a chimney located at the top of the furnace chamber. The furnace chamber includes a radiation section, a convection section and a preheating section connected sequentially from bottom to top.

[0009] The burner, installed on the side of the radiant section, includes a primary combustion section and a secondary combustion section. The primary combustion section is used for combustion of premixed natural gas and air, and the secondary combustion section is used for combustion of pure natural gas.

[0010] Ammonia injection device, used to spray ammonia gas into the convection section; and

[0011] The SCR device is installed inside the furnace and located between the convection section and the preheating section.

[0012] To facilitate the adjustment of the pressure inside the furnace, an induced draft fan is installed at the chimney, and multiple online pressure monitors are arranged at intervals inside the furnace.

[0013] To facilitate the adjustment of the pressure inside the furnace, the number of burners is at least two, and they are arranged at intervals along the vertical direction. The furnace is equipped with multiple online temperature monitors arranged at intervals.

[0014] To simplify the structure, all the burners are connected in parallel and connected to the main natural gas pipeline.

[0015] To facilitate adjustment of the premixed air volume, an air conditioning device is installed at the primary combustion section to adjust the amount of air premixed with natural gas.

[0016] To spray ammonia gas into the convection section, the ammonia injection device includes:

[0017] Ammonia vaporizer, used to vaporize ammonia water into ammonia gas; and

[0018] The injector is installed in the convection section and close to the SCR device, and is connected to the ammonia vaporizer via an ammonia delivery pipe.

[0019] To ensure the supply of ammonia water, the ammonia injection device also includes...

[0020] An ammonia storage tank is connected to the ammonia vaporizer via an ammonia delivery pipe; and

[0021] A delivery pump, installed on the ammonia water delivery pipe, is used to deliver ammonia water from the ammonia water storage tank to the ammonia water vaporizer.

[0022] To provide a heat source for ammonia vaporization, the ammonia injection device also includes...

[0023] An ammonia injection blower is connected to the ammonia vaporizer via an air supply pipe; and

[0024] A heater is installed on the air supply duct to heat the airflow transported in the air supply duct.

[0025] To facilitate real-time monitoring of oxygen and combustible content within the furnace and to allow for adjustment of burner parameters, it also includes...

[0026] An online oxygen content monitor is used to monitor the oxygen content inside the furnace; and

[0027] An online combustible material monitor is used to monitor the combustible material content in the furnace.

[0028] To monitor the nitrogen oxide content inside the chimney in real time and facilitate the control of the EDC pyrolysis furnace operation, an online NOx monitor is also included to monitor the nitrogen oxide content inside the chimney.

[0029] Compared with the prior art, the advantages of this utility model are as follows: through the staged and premixed combustion of the burner, it is possible to reduce the generation of nitrogen oxides while ensuring the normal operation of the EDC pyrolysis furnace and the furnace temperature. The nitrogen oxides generated during operation are further treated by the ammonia injection device and the SCR device, which is of great significance for achieving ultra-low NOx emissions from the EDC pyrolysis furnace. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of an embodiment of the ultra-low NOx control system for EDC pyrolysis furnace flue gas of this utility model;

[0031] Figure 2 for Figure 1 Schematic diagram of the middle burner;

[0032] Figure 3 for Figure 1 A schematic diagram of the ammonia injection unit. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0034] In the specification and claims of this utility model, terms indicating direction, such as "front," "rear," "upper," "lower," "left," "right," "side," "top," and "bottom," are used to describe various exemplary structural parts and elements of this utility model. However, the use of these terms is merely for the purpose of explanation and is based on the exemplary orientations shown in the accompanying drawings. Since the embodiments disclosed in this utility model can be arranged in different orientations, these terms indicating direction are for illustrative purposes only and should not be regarded as limitations. For example, "upper" and "lower" are not necessarily limited to directions opposite to or consistent with the direction of gravity.

[0035] like Figures 1 to 3 The image shows a preferred embodiment of the ultra-low NOx control system for EDC pyrolysis furnace flue gas of this utility model. This ultra-low NOx control system for EDC pyrolysis furnace flue gas includes an EDC pyrolysis furnace 1, a burner 2, an ammonia injection device 3, an SCR device 4, an online oxygen content monitor 5, an online combustible material monitor 6, and an online NOx monitor 7.

[0036] The EDC pyrolysis furnace 1 includes a furnace chamber 11 and a chimney 12 located at the top of the furnace chamber 11. Specifically, the furnace chamber 11 includes a radiation section 111, a convection section 112, and a preheating section 113 connected sequentially from bottom to top; an induced draft fan 121 is installed at the chimney 12. In addition, multiple online pressure monitors (not shown in the figure) and multiple online temperature monitors (not shown in the figure) are arranged at intervals inside the furnace chamber 11.

[0037] There are three burners 2, arranged vertically at intervals on the side of the radiant section 111. All burners 2 are connected in parallel and connected to the main natural gas pipeline, which is equipped with pressure and flow regulating devices. Specifically, as shown... Figure 2 As shown, each burner 2 includes a primary combustion section 21 and a secondary combustion section 22 arranged in parallel. The primary combustion section 21 is used for combustion of natural gas premixed with air, and the secondary combustion section 22 is used for combustion of pure natural gas. In addition, an air conditioning device 211 is installed at the primary combustion section 21 to adjust the amount of air premixed with natural gas.

[0038] The ammonia injection device 3 is used to spray ammonia gas into the convection section 112. In this embodiment, as shown... Figure 3 As shown, the ammonia injection device 3 includes an ammonia vaporizer 31, an ammonia storage tank 32, a transfer pump 33, an ammonia injection fan 34, and a heater 35. Specifically, the ammonia vaporizer 31 is used to vaporize ammonia water into ammonia gas at 150-300°C; the ammonia water storage tank 32 is connected to the ammonia vaporizer 31 through the ammonia water delivery pipe 321; the delivery pump 33 is installed on the ammonia water delivery pipe 321 and is used to deliver ammonia water from the ammonia water storage tank 32 to the ammonia vaporizer 31, and the outlet of the delivery pump 33 is equipped with an independent flow regulating device; the ammonia injection fan 34 is connected to the ammonia vaporizer 31 through the air supply pipe 341, and the outlet of the ammonia injection fan 34 is equipped with an independent flow regulating device; the heater 35 is installed on the air supply pipe 341 and is used to heat the airflow delivered in the air supply pipe 341; the injector 36 is installed in the convection section 112 and is connected to the ammonia vaporizer 31 through the ammonia gas delivery pipe 361, and each independent nozzle of the injector 36 is equipped with an independent flow regulating device.

[0039] The SCR device 4 is installed inside the furnace 11 and located between the convection section 112 and the preheating section 113, with the aforementioned injector 36 arranged close to the SCR device 4.

[0040] The oxygen content online monitor 5 is installed between the radiation section 111 and the convection section 112 of the furnace 11 to monitor the oxygen content in the furnace 11.

[0041] The combustible material online monitoring instrument 6 is installed between the radiation section 111 and the convection section 112 of the furnace 11 to monitor the combustible material content in the furnace 11.

[0042] The NOx online monitor 7 is installed inside the chimney 12 to monitor the nitrogen oxide content inside the chimney 12.

[0043] In addition, the above-mentioned EDC pyrolysis furnace flue gas ultra-low NOx control system also has a controller. The online pressure monitor and online temperature monitor inside the above-mentioned EDC pyrolysis furnace 1, as well as the induced draft fan 121, burner 2, ammonia injection device 3, SCR device 4, oxygen content online monitor 5, combustible material online monitor 6 and NOx online monitor 7 are all connected to the controller.

[0044] The working principle of this embodiment is as follows:

[0045] After the EDC pyrolysis furnace 1 is started, the induced draft fan 121 is started in conjunction with the online pressure monitor to control the pressure in the furnace 11 at a slightly negative pressure state (-0.5 to 0 kPaG);

[0046] Next, each burner 2 is ignited step by step, and the temperature change of the furnace 11 is monitored by the online temperature monitor. The natural gas flow and pressure are controlled to increase the load. The natural gas pressure is controlled at 0.01-0.3 MPaG, and the furnace 11 temperature is controlled at 150-800℃. After the load and temperature stabilize, the amount of premixed air in the first combustion section 21 of each burner 2 is adjusted one by one.

[0047] The oxygen content and combustible content changes in the furnace 11 are monitored in real time by the online oxygen content monitor 5 and the online combustible content monitor 6. Based on the oxygen content and combustible content, the air intake of the first-stage combustion section 21 of the burner 2 is adjusted to adjust the oxygen content in the furnace 11 to 0.5-5%, maintain a certain oxygen-deficient combustion, and control the generation of nitrogen oxides.

[0048] After the oxygen content and combustibles in the furnace 11 are adjusted, the number and position of burners 2 are adjusted according to the feedback from the online temperature monitor in order to achieve uniform temperature in the furnace 11 and control the inlet temperature of the SCR device 4. The denitrification reaction temperature range is 180 to 350°C.

[0049] After the temperature and oxygen content in the furnace 11 are stabilized, the ammonia injection device 3 and the SCR device 4 are started. The ammonia water feed rate is adjusted to 0.3-10 kg / h according to the NOx online monitoring instrument 7. The ammonia water is then evenly mixed with the flue gas through the ammonia injection device 3 before entering the SCR device 4 to achieve ultra-low NOx emission control.

[0050] This application adjusts the premixed air volume of several burners 2 to regulate the overall oxygen content within the furnace 11, maintaining a certain oxygen-deficient environment within the furnace 11. It also controls a certain reducing environment within the furnace 11 through staged combustion of the burners 2, reducing nitrogen oxide emissions. Simultaneously, based on measurements from multiple real-time monitoring devices, the overall operating status of the EDC pyrolysis furnace 1 is controlled by adjusting the status of several burners 2. In practical implementation, this application can achieve nitrogen oxide emissions of less than 50 mg / m³ without the SCR device 4 in operation. 3 After the SCR unit is put into operation, nitrogen oxide emissions can be controlled at 10 mg / m³. 3 The following approach effectively reduces nitrogen oxide emissions and the operating cost of SCR units, providing an effective energy-saving and emission-reduction retrofit technology solution for EDC pyrolysis furnaces. While maintaining the normal operation of EDC pyrolysis furnaces, it reduces the generation of nitrogen oxides and lowers the operating cost of SCR units.

Claims

1. An EDC cracking furnace flue gas ultra-low NOx control system, characterized in that: The EDC cracking furnace (1) comprises a furnace chamber (11) and a chimney (12) arranged at the top of the furnace chamber (11), wherein the furnace chamber (11) comprises, from bottom to top, a radiation section (111), a convection section (112) and a preheating section (113); The burner (2) is arranged at the side of the radiation section (111) and comprises a primary combustion section (21) and a secondary combustion section (22), wherein the primary combustion section (21) is used for burning natural gas mixed with air, and the secondary combustion section (22) is used for burning pure natural gas; The ammonia injection device (3) is used for injecting ammonia into the convection section (112); The SCR device (4) is arranged in the furnace chamber (11) and located between the convection section (112) and the preheating section (113). The chimney (12) is provided with an induced draft fan (121), and the furnace chamber (11) is provided with multiple online pressure monitors arranged at intervals. The number of the burners (2) is at least two, which are arranged at intervals in the vertical direction, and the furnace chamber (11) is provided with multiple online temperature monitors arranged at intervals.

2. The EDC cracking furnace flue gas ultra-low NOx control system of claim 1, wherein: All the burners (2) are connected in parallel and connected to a natural gas main pipe (20).

3. The EDC cracking furnace flue gas ultra-low NOx control system of claim 1, wherein: The air adjusting device (211) is arranged at the primary combustion section (21) and used for adjusting the amount of air mixed with natural gas.

4. The EDC cracking furnace flue gas ultra-low NOx control system of claim 3, wherein: The ammonia injection device (3) comprises 5. The EDC cracking furnace flue gas ultra-low NOx control system of claim 1, wherein: An ammonia water gasifier (31) used for gasifying ammonia water into ammonia gas; and 6. The EDC cracking furnace flue gas ultra-low NOx control system of claim 1, wherein: An injector (36) arranged in the convection section (112) and close to the SCR device (4), which is connected to the ammonia water gasifier (31) through an ammonia gas delivery pipe (361). The ammonia injection device (3) further comprises An ammonia water storage tank (32) connected to the ammonia water gasifier (31) through an ammonia water delivery pipe (321); and 7. The EDC cracking furnace flue gas ultra-low NOx control system of claim 6, wherein: A delivery pump (33) arranged on the ammonia water delivery pipe (321) and used for delivering ammonia water from the ammonia water storage tank (32) to the ammonia water gasifier (31). The ammonia injection device (3) further comprises An ammonia injection fan (34) connected to the ammonia water gasifier (31) through an air supply pipe (341); and 8. The EDC cracking furnace flue gas ultra-low NOx control system of claim 6, wherein: A heater (35) arranged on the air supply pipe (341) and used for heating the airflow delivered in the air supply pipe (341). Further comprising An oxygen content online monitor (5) used for monitoring the oxygen content in the furnace chamber (11); and 9. The EDC cracking furnace flue gas ultra-low NOx control system of any one of claims 1 to 8, wherein: A combustible online monitor (6) used for monitoring the combustible content in the furnace chamber (11). Further comprising a NOx online monitor (7) used for monitoring the nitrogen oxide content in the chimney (12). ​ 10. The EDC cracking furnace flue gas ultra-low NOx control system of any one of claims 1-8, wherein: ​

Images