Boiler tail gas treatment device

Abstract

The utility model discloses a boiler tail gas treatment device, a low-nitrogen combustor of a gas-fired boiler is provided with a main combustion chamber and an outer-layer combustion chamber, a fuel gas pipeline comprises a main feeding pipeline and an auxiliary feeding pipeline which are connected in parallel, the main feeding pipeline is communicated with the main combustion chamber, and the auxiliary feeding pipeline is communicated with the outer-layer combustion chamber. The low-nitrogen combustor is communicated with an air inlet pipeline, the flue gas circulating pipeline is communicated with the preheated air pipeline and is provided with a variable-frequency fan and a valve, the device adopting the scheme can enable tail gas emission to meet the current emission standard, the tail gas treatment effect is remarkable, and ultralow emission of tail gas NOx can be realized.

Description

Technical Field

[0001] This utility model relates to the field of exhaust gas treatment, specifically to a boiler exhaust gas treatment device. Background Technology

[0002] Boilers are crucial equipment in the chemical industry, generating significant amounts of exhaust gas during operation. This exhaust gas can severely harm the environment and human health. With increasing environmental awareness, national emission standards for exhaust gases are becoming increasingly stringent. Since January 1, 2020, Shandong Province has implemented a new standard, the "Shandong Province Boiler Air Pollutant Emission Standard" (DB37 / 2374-2018), which stipulates that nitrogen oxide concentrations in flue gas from gas-fired boilers in key control areas must be ≤100 mg / m³. To address the environmental impact of boiler emissions, the retrofitting of some gas-fired boilers is urgently needed. Effectively controlling low NOx emissions in flue gas is of paramount importance for achieving long-term environmentally friendly operation of gas-fired boiler exhaust gas treatment.

[0003] Currently, common low-NOx retrofit technologies include burner modification / replacement, SCR technology, SNCR technology, and full combustion technology. These technologies are all relatively complex and costly. The choice and adjustment of a low-NOx retrofit solution must be based on the specific circumstances of the boiler. It must be compatible with the existing boiler combustion technology while also considering increasingly stringent environmental standards to ensure that the retrofitted boiler meets low-NOx emission requirements and that the low-NOx retrofit effect is long-lasting and stable.

[0004] Some existing gas-fired boilers that do not meet the exhaust emission requirements can reduce the nitrogen oxide content in the flue gas by reducing the workload, adjusting the excess air coefficient, or one of the aforementioned common technologies to meet the new flue gas emission standards. However, this wastes the company's existing resources. With the increasing emphasis on environmental protection by the country, single technologies and simple process adjustments can no longer meet the ever-changing new environment, ultimately resulting in the company's environmental emissions failing to meet standards. Utility Model Content

[0005] In view of the shortcomings of the existing technology, the technical problem to be solved by this utility model is to provide a boiler exhaust gas treatment device that meets the current emission standards, has a significant exhaust gas treatment effect, and can achieve ultra-low NOx emissions.

[0006] To solve the above problems, this utility model provides the following technical solution:

[0007] A boiler exhaust gas treatment device includes a fuel gas inlet pipeline, a gas-fired boiler, an air preheater, and a chimney connected in sequence. The gas-fired boiler is equipped with a low-NOx burner, which has a main combustion chamber and an outer combustion chamber. The fuel gas pipeline includes a main feed pipeline and a secondary feed pipeline connected in parallel. The main feed pipeline is connected to the main combustion chamber, and the secondary feed pipeline is connected to the outer combustion chamber. The secondary feed pipeline is equipped with a shut-off valve. The low-NOx burner is connected to an air inlet pipeline, which includes a blower. The outlet of the blower is connected to the air inlet of the air preheater, and the air outlet of the air preheater is connected to the air inlet of the low-NOx burner through a preheated air pipeline. A circulating gas outlet is provided on one side of the chimney, which is connected to the preheated air pipeline through a flue gas circulation pipeline. The flue gas circulation pipeline is equipped with a variable frequency fan and a valve.

[0008] This device introduces flue gas from the chimney into the low-NOx burner via a variable frequency fan, achieving controllable flue gas recirculation. Simultaneously, a secondary feed line for fuel gas enters the outer combustion chamber, enabling staged combustion. Fuel staged combustion involves first mixing a portion of the fuel with air to form a pre-combustion zone, then adding the remaining fuel to complete the main combustion process. This reduces the formation of localized high-temperature zones and lowers NOx formation. Flue gas recirculation involves reintroducing a portion of the combusted flue gas into the combustion zone, mixing it with fresh air before further combustion. Inert gases in the flue gas (such as carbon dioxide and water vapor) dilute the oxygen concentration, lowering the combustion temperature and thus reducing NOx formation. This dual design of staged combustion and flue gas recirculation significantly reduces NOx emissions, achieving ultra-low NOx emissions significantly below emission standards and resolving the issue of excessive flue gas emissions.

[0009] The technical solution of this utility model also includes a pressure gauge and a flame arrester sequentially installed at the outlet of the shut-off valve of the auxiliary feed pipeline. The gas intake volume in the auxiliary feed pipeline can be adjusted by adjusting the opening of the shut-off valve, and the pressure gauge and flame arrester are used to improve the safety of the pipeline.

[0010] The technical solution of this utility model also includes valves at both the inlet and outlet ends of the variable frequency fan. The purpose of installing valves at the inlet and outlet ends of the variable frequency fan is to control and optimize the fan's operating state, ensuring the safe and efficient operation of the system. Specifically, the inlet valve controls the intake volume and fan inlet pressure, and facilitates the shut-off of the air supply to ensure safety. The outlet valve controls the outlet volume and fan outlet pressure and prevents airflow back to the fan.

[0011] To improve the convenience of valve adjustment, the technical solution of this utility model also includes that the valves at the air inlet and outlet of the variable frequency fan are one or a combination of butterfly valves and pendulum valves.

[0012] To achieve more precise control of exhaust gas composition, the technical solution of this utility model also includes a flue gas analyzer in the boiler exhaust gas device. The flue gas analyzer includes a sampling probe fixed inside the chimney, which is connected to the gas analyzer via a sampling pipeline. The gas analyzer is electrically connected to the controller. The controller and the flue gas analyzer can monitor and adjust the air-fuel ratio in real time, monitor the exhaust gas composition and content, and ensure optimal combustion conditions. The flue gas analyzer is a device for continuous real-time monitoring of flue gas composition, measuring the concentrations of NOx, SOx, CO, CO2, O2, and other components in the flue gas. In this device, the flue gas analyzer is mainly used to determine the oxygen concentration in the exhaust gas. Based on this concentration value, the frequency of the variable frequency fan and the opening of the shut-off valve are adjusted, thereby regulating the flue gas circulation volume and the fuel gas intake volume of the auxiliary feed pipeline to achieve standard exhaust gas emissions.

[0013] The technical solution of this utility model also includes that the variable frequency fan and valve of the flue gas circulation pipeline, as well as the blower of the air intake pipeline, are all electrically connected to the controller.

[0014] Preferably, the technical solution of this utility model further includes that the shut-off valve is a butterfly valve or a pendulum valve, the shut-off valve is equipped with a position sensor, and the shut-off valve is electrically connected to the controller. The controller and the position sensor can monitor and adjust the intake air volume of fuel gas in real time, thereby adjusting the optimal combustion conditions.

[0015] The boiler exhaust gas treatment method of the above-mentioned device includes the following steps:

[0016] (1) Close the shut-off valve of the auxiliary feed pipeline and the valve of the flue gas circulation pipeline, start the gas boiler and flue gas analyzer, and the tail gas after the fuel gas combustion in the boiler is discharged through the chimney after the waste heat is recovered by the air preheater.

[0017] (2) After the gas boiler has been running normally for 30-60 minutes, open the valve of the flue gas circulation pipeline, adjust the frequency of the variable frequency fan to 0Hz, start the variable frequency fan, and slowly increase the frequency of the variable frequency fan according to the oxygen content value in the flue gas analyzer to stabilize the oxygen content value at 4%;

[0018] (3) Open the shut-off valve of the auxiliary feed line. A portion of the fuel gas enters the outer combustion chamber through the auxiliary feed line. Adjust the opening of the shut-off valve according to the NOx concentration value in the flue gas analyzer until the NOx concentration value meets the emission standards.

[0019] The beneficial effects of this utility model are as follows: Compared with the prior art, the purpose of this utility model is to provide a boiler exhaust gas treatment device that meets current emission standards and has a significant exhaust gas treatment effect, achieving ultra-low NOx emissions. This device introduces the chimney exhaust gas into the low-NOx burner via a variable frequency fan, achieving controllable flue gas recirculation. Simultaneously, a secondary feed line for fuel gas enters the outer combustion chamber, achieving combustion staged combustion. This device features a dual design of fuel staged combustion and flue gas recirculation, enabling ultra-low NOx emissions from gas-fired boilers. On the one hand, it significantly reduces pollution, promotes green practices, and saves energy; on the other hand, it controls the gas-fired boiler exhaust gas emission values ​​within standards, with NOx concentrations far below 100 mg / m³, providing a long-term solution for gas-fired boiler retrofitting needs. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the boiler exhaust gas treatment device in a specific implementation.

[0022] Among them, 1 is a gas-fired boiler, 2 is an air preheater, 3 is a chimney, 4 is a low-NOx burner, 5 is the main combustion chamber, 6 is the outer combustion chamber, 7 is the main feed line, 8 is the auxiliary feed line, 9 is a shut-off valve, 10 is a pressure gauge, 11 is a flame arrester, 12 is a controller, 13 is a blower, 14 is a preheated air line, 15 is a flue gas circulation line, 16 is a variable frequency fan, 17 is a butterfly valve, 18 is a sampling probe, and 19 is a gas analyzer. Detailed Implementation

[0023] To enable those skilled in the art to better understand the technical solutions of this utility model, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of this utility model.

[0024] In the description of this utility model, it should be understood that the terms "center", "horizontal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the purpose of simplifying the description of this utility model 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 utility model.

[0025] As shown in the attached drawings, a boiler exhaust gas treatment device includes a fuel gas inlet pipeline, a gas-fired boiler 1, an air preheater 2, and a chimney 3 connected in sequence. The gas-fired boiler 1 is equipped with a low-NOx burner 4, which has a main combustion chamber 5 and an outer combustion chamber 6. The fuel gas pipeline includes a main feed pipeline 7 and a secondary feed pipeline 8 connected in parallel. The main feed pipeline 7 is connected to the main combustion chamber 5, and the secondary feed pipeline 8 is connected to the outer combustion chamber 6. The secondary feed pipeline 8 is equipped with a shut-off valve 9, which is a pendulum valve. A pressure gauge 10 and a flame arrester 11 are sequentially installed at the outlet of the shut-off valve 9.

[0026] The low-NOx burner 4 is connected to an air intake pipeline, which includes a blower 13. The outlet of the blower 13 is connected to the air inlet of the air preheater 2. The air outlet of the air preheater 2 is connected to the air intake of the low-NOx burner 4 through a preheated air pipeline 14. A circulating air outlet is provided on one side of the chimney 3. The circulating air outlet is connected to the preheated air pipeline 14 through a flue gas circulation pipeline 15. A variable frequency fan 16 is provided in the flue gas circulation pipeline 15. Both the inlet and outlet of the variable frequency fan 16 are equipped with butterfly valves 17.

[0027] The boiler exhaust gas system is equipped with a flue gas analyzer, which includes a sampling probe 18 fixed inside the chimney. The sampling probe 18 is connected to a gas analyzer 19 via a sampling pipeline, and the gas analyzer 19 is electrically connected to a controller 12. The variable frequency fan 16, butterfly valve 17, shut-off valve 9, and blower 13 of the air intake pipeline of the flue gas circulation pipeline 15 are all electrically connected to the controller.

[0028] The boiler exhaust gas treatment method using the above-mentioned device includes the following steps:

[0029] (1) Close the shut-off valve of the auxiliary feed pipeline and the valve of the flue gas circulation pipeline, start the gas boiler and flue gas analyzer, and the tail gas after the fuel gas combustion in the boiler is discharged through the chimney after the waste heat is recovered by the air preheater.

[0030] (2) After the gas boiler has been running normally for 30 minutes, open the valve of the flue gas circulation pipeline, adjust the frequency of the variable frequency fan to 0Hz, start the variable frequency fan, and slowly increase the frequency of the variable frequency fan according to the oxygen content value in the flue gas analyzer to stabilize the oxygen content value at 4%;

[0031] (3) Open the shut-off valve of the auxiliary feed line. A portion of the fuel gas enters the outer combustion chamber through the auxiliary feed line. Adjust the opening of the shut-off valve according to the NOx concentration value in the flue gas analyzer until the NOx concentration value meets the emission standards. In this embodiment, the NOx concentration in the exhaust gas is lower than 50 mg / m3.

[0032] The device in this embodiment features a dual design of fuel grading and flue gas recirculation, enabling ultra-low emissions of nitrogen oxides (NOx) from gas-fired boilers. On the one hand, it is highly effective in reducing pollution, promoting green practices, and saving energy; on the other hand, it can control the emission values ​​of gas-fired boilers within the standard range, providing a long-term solution for the retrofitting of gas-fired boilers.

[0033] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, it is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the present invention, and all such modifications or substitutions should be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the scope of the claims.

Claims

1. A boiler exhaust gas treatment device, comprising a fuel gas inlet pipe, a gas-fired boiler, an air preheater, and a chimney connected in sequence, characterized in that: The gas-fired boiler is equipped with a low-NOx burner, which has a main combustion chamber and an outer combustion chamber. The fuel gas pipeline includes a main feed pipeline and a secondary feed pipeline connected in parallel. The main feed pipeline is connected to the main combustion chamber, and the secondary feed pipeline is connected to the outer combustion chamber. The secondary feed pipeline is equipped with a shut-off valve. The low-NOx burner is connected to an air intake pipeline, which includes a blower. The outlet of the blower is connected to the air inlet of the air preheater, and the air outlet of the air preheater is connected to the air intake of the low-NOx burner through a preheated air pipeline. A circulating gas outlet is provided on one side of the chimney. The circulating gas outlet is connected to the preheated air pipeline through a flue gas circulation pipeline. The flue gas circulation pipeline is equipped with a variable frequency fan and valves.

2. The boiler exhaust gas treatment device according to claim 1, characterized in that: A pressure gauge and a flame arrester are sequentially installed at the outlet of the shut-off valve of the secondary feed pipeline.

3. The boiler exhaust gas treatment device according to claim 1, characterized in that: The variable frequency fan is equipped with valves at both the air inlet and outlet.

4. The boiler exhaust gas treatment device according to claim 3, characterized in that: The valves at the air inlet and outlet of the variable frequency fan are one or a combination of butterfly valves and pendulum valves.

5. The boiler exhaust gas treatment device according to any one of claims 1-4, characterized in that: The boiler exhaust gas device is equipped with a flue gas analyzer, which includes a sampling probe fixed inside the chimney. The sampling probe is connected to the gas analyzer through a sampling pipeline, and the gas analyzer is electrically connected to the controller.

6. The boiler exhaust gas treatment device according to claim 5, characterized in that: The variable frequency fan and valves of the flue gas circulation pipeline, as well as the blower of the air intake pipeline, are all electrically connected to the controller.

7. The boiler exhaust gas treatment device according to claim 5, characterized in that: The shut-off valve is a type of butterfly valve or pendulum valve. The shut-off valve is equipped with a position sensor and is electrically connected to the controller.

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