Hydrogen-fueled boiler tail gas treatment device

Abstract

This utility model belongs to the technical field of exhaust gas treatment devices, specifically relating to an exhaust gas treatment device for hydrogen-fired boilers. It includes a hydrogen-fired steam boiler and an SCR denitrification system. The hydrogen-fired steam boiler has a burner at its bottom. The SCR denitrification system includes a denitrification tower, an exhaust pipe, a urea dissolving tank, a pyrolyzer, and a metering pump. The inlet of the denitrification tower is connected to the flue of the hydrogen-fired steam boiler, and an economizer is installed on the flue. The outlet of the denitrification tower is connected to the exhaust pipe. The urea dissolving tank is connected to the inlet of the pyrolyzer via the metering pump, and the outlet of the pyrolyzer is connected to the denitrification tower. This device has a reasonable structure and stable operation. By supplying urea solution to the pyrolyzer, ammonia is generated through pyrolysis. This ammonia reacts with nitrogen oxides in the flue gas in the denitrification tower, generating nitrogen and water. This effectively controls the concentration of nitrogen oxides in the exhaust gas to below 30 mg / Nm³, meeting environmental emission standards. It is suitable for the efficient removal of nitrogen oxides from the exhaust gas of hydrogen-fired boilers.

Description

Technical Field

[0001] This utility model belongs to the technical field of exhaust gas treatment devices, specifically relating to an exhaust gas treatment device for a hydrogen-fired boiler. Background Technology

[0002] The 200,000-ton ion-exchange membrane caustic soda project will generate 57 million Nm³ of nitrogen oxides during the production process. Hydrogen, of which 5.74 million Nm Hydrogen was used to synthesize 60,000 tons of high-purity hydrochloric acid, with an actual surplus of 51.26 million Nm³. This translates to 6408 Nm per hour. / h. The venting of large amounts of surplus hydrogen results in significant resource waste; therefore, a hydrogen-fired steam boiler project is being constructed. The process flow for the hydrogen-fired steam boiler is shown in the attached figure. Figure 2 As shown, the hydrogen output from the hydrogen processing distribution station is pre-treated by entering a precooler, cooler, and filter through pipelines. The treated hydrogen is then sent to the burner inlet at the bottom of the hydrogen boiler via a flame arrester. The heat generated heats the deoxygenated water in the boiler tubes (the deoxygenated water is pressurized by a feedwater pump and sent to the preheater at the top of the boiler, where it is preheated using the heat from the flue gas before entering the boiler tubes). The resulting qualified steam passes through an external steam-water separator at the top of the boiler and is then distributed to the plant's low-pressure steam network for use in chlor-alkali production, insulation, and living areas. This method of recovering and utilizing the heat generated from hydrogen combustion to produce steam, while the remaining hydrogen is pressurized and stored in tanks for sale, solves the steam requirement for production and fully utilizes the by-product hydrogen, achieving energy conservation, emission reduction, efficiency improvement, and reduced production costs, creating significant economic benefits for the company's production and operation.

[0003] However, with the upgrading of environmental standards, the emission standard for nitrogen oxides in the exhaust gas of hydrogen-fired boilers has been changed from <200mg / Nm³. Strictly limited to <30mg / Nm The originally designed hydrogen-fired boiler was shut down because it could not meet the new standards, resulting in a 2375 Nm³ / h boiler being decommissioned. / h of hydrogen gas is directly vented into the atmosphere—at a rate of 1Nm Based on a profit of 0.5 yuan per liter for hydrogen, the annual economic loss would reach 9.5 million yuan. At the same time, the release of hydrogen into the atmosphere poses a flammable and explosive safety hazard. Therefore, there is an urgent need for a hydrogen-fired boiler exhaust gas treatment device to solve the above problems. Utility Model Content

[0004] To address the aforementioned deficiencies in existing technologies, this utility model provides a hydrogen-fired boiler exhaust gas treatment device, comprising a hydrogen-fired steam boiler and an SCR denitrification system. A burner is installed at the bottom of the hydrogen-fired steam boiler. The SCR denitrification system includes a denitrification tower, an exhaust gas pipe, a urea dissolving tank, a pyrolyzer, and a metering pump. The inlet of the denitrification tower is connected to the flue of the hydrogen-fired steam boiler, and an economizer is installed on the flue. The outlet of the denitrification tower is connected to the exhaust gas pipe. The urea dissolving tank is connected to the inlet of the pyrolyzer via the metering pump, and the outlet of the pyrolyzer is connected to the denitrification tower. Optionally, the denitrification tower is internally equipped with multiple layers of honeycomb catalyst, with a total packing volume of 1.3m³. The honeycomb catalyst has an interlayer height of 2.65m, a single-layer resistance of 180Pa, a total resistance of 600Pa, a long-term tolerance temperature of 400℃, a short-term tolerance temperature of 420℃, and a chemical lifetime of more than 40,000 hours.

[0005] Optionally, the urea dissolving tank is equipped with an external steam heating jacket and an internal stirring assembly for preparing a 20% concentration urea solution.

[0006] Specifically, both the steam heating jacket and the stirring assembly are existing technologies; the steam heating jacket heats the urea dissolving tank through steam heat exchange; the stirring assembly includes a stirring motor, a stirring shaft connected to the stirring motor, and a stirring rod mounted on the stirring shaft, used to stir urea, pure water, and steam in the urea dissolving tank.

[0007] Optionally, the hydrogen-fired steam boiler is connected to a steam pipeline, and a steam-water separator and a steam distribution platform are sequentially installed on the steam pipeline.

[0008] Optionally, the hydrogen-fired steam boiler is connected to a drainage pipeline, and a steam trap, a cooling sewage pool, and a rainwater ditch are installed sequentially on the drainage pipeline.

[0009] Optionally, the hydrogen-fired boiler exhaust gas treatment device is also equipped with a combustion air pipeline and a hydrogen pipeline. The combustion air pipeline is equipped with a combustion air fan and a first automatic regulator, and the combustion air fan and the first automatic regulator are connected in sequence to one inlet of the burner. The hydrogen pipeline is equipped with a precooler, a cooler, a filter, and a second automatic regulator, and the precooler, cooler, filter, and second automatic regulator are connected in sequence to the other inlet of the burner.

[0010] In addition, the SCR denitrification system also includes the reactor body, static mixer, guide plate, rectifier plate, flue, electrical system and instrumentation control system, etc.

[0011] The design requirements for the catalyst are as follows: (1) This scheme uses a honeycomb catalyst that is resistant to clogging and poisoning.

[0012] (2) The catalyst should be able to operate for a long time at a flue gas temperature of 400℃, and should be able to withstand an operating temperature of 420℃ without any damage.

[0013] (3) While achieving the required denitrification efficiency, it can effectively prevent boiler fly ash from sticking, clogging and poisoning in the catalyst.

[0014] (4) The catalyst chemical lifetime is greater than 40,000 operating hours.

[0015] (5) The catalyst should be designed in a modular and standardized manner. The modules of each layer of the catalyst should be of uniform specifications and interchangeable to reduce the time required to replace the catalyst.

[0016] (6) The module adopts a carbon steel structural frame and is required to be well welded and sealed, and to be easy to transport, install and lift.

[0017] (7) A single boiler SCR system requires 1.3m³ of honeycomb catalyst. The reactor is arranged in a 2+1 layer configuration, with a cross-sectional area of ​​1.2 m² and a catalyst layer height of 2.65 m. The resistance of a single catalyst layer is 180 Pa, and the total resistance is 600 Pa.

[0018] The design requirements for electrical systems and instrumentation control systems are as follows: (1) The denitrification retrofit control system adopts independent PLC control and local control mode. The control room is equipped with an operator station and a local control system.

[0019] (2) The system can meet the requirements of safe and economical operation, monitoring, control and economic accounting of the entire denitrification system equipment, and meet the relevant national and international standards, safety, advanced and complete instrument and control system.

[0020] (3) It can monitor and control the denitrification system with the host computer display and PLC operator station display as the center. It can automatically scan and process relevant parameters; automatically alarm when parameters exceed the limit; and automatically complete the program start and stop of each local process system or auxiliary machine according to manual instructions. When the system malfunctions or accidents, it can ensure that the system can operate or stop under safe conditions through protection, interlocking or manual intervention.

[0021] This invention also includes other components that enable the normal operation of a hydrogen-fired boiler exhaust gas treatment device, all of which are conventional techniques in the field. Furthermore, any devices or components not specified in this invention employ conventional techniques in the field.

[0022] The working principle of this utility model is as follows: Hydrogen gas output from the hydrogen treatment process distribution station enters the precooler, cooler, and filter through pipelines for pretreatment. The treated hydrogen gas is then sent to the burner inlet at the bottom of the hydrogen-fired steam boiler through a flame arrester for combustion. The heat generated heats the deoxygenated water in the boiler tubes (the deoxygenated water is pressurized by a feed water pump and sent to the preheater at the top of the boiler, where it is preheated using the heat of the flue gas before entering the boiler tubes). The resulting qualified steam passes through the external steam-water separator at the top of the boiler and enters the distribution station, where it is distributed to the plant's low-pressure steam network for use in chlor-alkali production, insulation, and living areas. Subsequently, the flue gas discharged from the hydrogen-fired steam boiler enters the denitrification tower through the flue. Simultaneously, a 20% concentration urea solution prepared in the urea dissolving tank is sent to the pyrolyzer via a metering pump, where it is pyrolyzed into ammonia gas, which is then introduced into the denitrification tower. Under the action of a honeycomb catalyst, the ammonia gas reacts with nitrogen oxides in the flue gas to generate nitrogen gas and water. The treated tail gas is then discharged through the tail gas vent pipe.

[0023] The beneficial effects of this utility model are: (1) This scheme adopts the current mature, advanced, safe and reliable technology, and the design is scientific and reasonable, and the cost is more economical.

[0024] (2) This solution has high equipment utilization, long operating cycle, and low maintenance cost; it is easy to operate, observe, monitor, and maintain. (3) It can adapt to various load changes and start-up and shutdown times of the unit, and has no interference with boiler load and boiler operation mode. It can operate normally between the minimum and maximum values ​​of flue gas emission concentration.

[0025] (4) It can meet the requirements of automatic operation of the entire hydrogen-fired boiler system under various working conditions, and the system startup, normal operation monitoring and accident handling are fully automated.

[0026] (5) The layout design of all equipment and pipelines takes into account the realization of system functions and the convenience of operation.

[0027] (6) Environmental compliance: It can reduce NO in exhaust gas x Concentration controlled at <30 mg / Nm Ammonia slip < 8 ppm, dust content < 10 mg / Nm³ It fully meets the latest environmental standards.

[0028] (7) Resource recovery: enabling shut-down hydrogen-fired boilers to be put back into operation, 2375 Nm The vented hydrogen can be recovered, reducing economic losses by 9.5 million yuan per year, while avoiding the flammable and explosive risks of vented hydrogen.

[0029] (8) This scheme abandons the traditional ammonia preparation process and adopts the SCR denitrification process. The ammonia required for the SCR denitrification reaction comes from the urea solution, which can avoid the risk of ammonia leakage and explosion caused by ammonia preparation in the ammonia zone. At the same time, it can save steam consumption and reduce maintenance and valve replacement costs.

[0030] (9) The SCR reactor in this scheme is arranged after the boiler economizer. The arrangement is reasonable, simple and compact. The system resistance is low and the power consumption of the induced draft fan is low, which can reduce operating costs. Attached Figure Description

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] Figure 1 This is a schematic diagram of the overall structure of this utility model.

[0033] Figure 2 This is a schematic diagram of the structure of the hydrogen-fired boiler before the process modification. Detailed Implementation

[0034] The present invention will now be clearly described with reference to the accompanying drawings and specific embodiments. This description is merely for explaining the present invention and is not intended to limit it. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art based on the embodiments of the present invention without inventive effort to obtain all other embodiments should be included within the protection scope of the present invention.

[0035] Example like Figure 1 As shown in the figure, this utility model embodiment provides a hydrogen-fired boiler exhaust gas treatment device, including a hydrogen-fired steam boiler and an SCR denitrification system. A burner is installed at the bottom of the hydrogen-fired steam boiler. The SCR denitrification system includes a denitrification tower, an exhaust gas pipe, a urea dissolving tank, a pyrolyzer, and a metering pump. The inlet of the denitrification tower is connected to the flue of the hydrogen-fired steam boiler, and an economizer is installed on the flue. The outlet of the denitrification tower is connected to the exhaust gas pipe. The urea dissolving tank is connected to the inlet of the pyrolyzer through the metering pump, and the outlet of the pyrolyzer is connected to the denitrification tower. The denitrification tower is internally equipped with multiple layers of honeycomb catalyst, with a total packing volume of 1.3m³. The honeycomb catalyst has an interlayer height of 2.65m, a single-layer resistance of 180Pa, a total resistance of 600Pa, a long-term tolerance temperature of 400℃, a short-term tolerance temperature of 420℃, and a chemical lifetime of more than 40,000 hours.

[0036] The urea dissolving tank is equipped with an external steam heating jacket and an internal stirring assembly, and is used to prepare a 20% concentration urea solution.

[0037] Understandably, both the steam heating jacket and the stirring assembly are existing technologies; the steam heating jacket heats the urea dissolving tank through steam heat exchange; the stirring assembly includes a stirring motor, a stirring shaft connected to the stirring motor drive, and a stirring rod mounted on the stirring shaft, used to stir urea, pure water, and steam in the urea dissolving tank.

[0038] The hydrogen-fired steam boiler is connected to a steam pipeline, and a steam-water separator and a steam distribution platform are installed sequentially on the steam pipeline.

[0039] The hydrogen-fired steam boiler is connected to a drainage pipeline, which is equipped with a steam trap, a cooling sewage pool, and a rainwater ditch in sequence.

[0040] In addition, the exhaust gas treatment device for the hydrogen-fired boiler is also equipped with a combustion air pipeline and a hydrogen pipeline. The combustion air pipeline is equipped with a combustion air fan and a first automatic regulator, which are connected in sequence to one inlet of the burner. The hydrogen pipeline is equipped with a precooler, a cooler, a filter, and a second automatic regulator, which are connected in sequence to the other inlet of the burner.

[0041] The working principle of this utility model is as follows: Hydrogen gas output from the hydrogen treatment process distribution station enters the precooler, cooler, and filter through pipelines for pretreatment. The treated hydrogen gas is then sent to the burner inlet at the bottom of the hydrogen-fired steam boiler through a flame arrester for combustion. The heat generated heats the deoxygenated water in the boiler tubes (the deoxygenated water is pressurized by a feed water pump and sent to the preheater at the top of the boiler, where it is preheated using the heat of the flue gas before entering the boiler tubes). The resulting qualified steam passes through the external steam-water separator at the top of the boiler and enters the distribution station, where it is distributed to the plant's low-pressure steam network for use in chlor-alkali production, insulation, and living areas. Subsequently, the flue gas discharged from the hydrogen-fired steam boiler enters the denitrification tower through the flue. Simultaneously, a 20% concentration urea solution prepared in the urea dissolving tank is sent to the pyrolyzer via a metering pump, where it is pyrolyzed into ammonia gas, which is then introduced into the denitrification tower. Under the action of a honeycomb catalyst, the ammonia gas reacts with nitrogen oxides in the flue gas to generate nitrogen gas and water. The treated tail gas is then discharged through the tail gas vent pipe.

[0042] The exhaust emission indicators before treatment are shown in Table 1 below:

[0043] Table 1 The exhaust emission indicators after treatment using this method are shown in Table 2 below:

[0044] Table 2 A comparison of the two tables above shows that the concentration of nitrogen oxides in the exhaust gas treated by this method is controlled at <30 mg / Nm³. Ammonia slip < 8 ppm, dust content < 10 mg / Nm³ It fully meets the latest environmental standards.

[0045] The embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A hydrogen-fueled boiler exhaust gas treatment device comprising a hydrogen-fueled steam boiler and an SCR denitration system, characterized by: The bottom of the hydrogen-fueled steam boiler is provided with a burner, and the SCR denitration system comprises a denitration tower, an exhaust gas exhaust pipe, a urea dissolving tank, a thermal decomposer and a metering pump, the inlet of the denitration tower is connected with the flue of the hydrogen-fueled steam boiler, a coal economizer is arranged on the flue, the outlet of the denitration tower is connected with the exhaust gas exhaust pipe, the urea dissolving tank is connected with the inlet of the thermal decomposer through the metering pump, and the outlet of the thermal decomposer is connected with the denitration tower.

2. The hydrogen-fueled boiler exhaust gas treatment device according to claim 1, characterized by: The inside of the denitration tower is provided with multiple layers of honeycomb catalysts, and the total loading amount of the honeycomb catalysts is 1.3m The interlayer height of the honeycomb catalysts is 2.65m, the single-layer resistance is 180Pa, the total resistance is 600Pa, the long-term tolerance temperature is 400℃, the short-term tolerance temperature is 420℃, and the chemical life is greater than 40000 hours.

3. The hydrogen-fueled boiler exhaust gas treatment device according to claim 1, characterized by: The urea dissolving tank is externally provided with a steam heating jacket and internally provided with a stirring assembly, and is used for preparing a 20% concentration urea solution.

4. The hydrogen-fueled boiler exhaust gas treatment device according to claim 1, characterized by: The hydrogen-fueled steam boiler is connected with a steam pipeline, and a steam-water separator and a steam distribution table are sequentially arranged on the steam pipeline.

5. The hydrogen-fueled boiler exhaust treatment device according to claim 1, characterized by: The hydrogen-fueled steam boiler is connected with a drainage pipeline, and a trap, a cooling and sewage pool and a rainwater ditch are sequentially arranged on the drainage pipeline.

6. The hydrogen-fueled boiler exhaust gas treatment device according to claim 1, characterized by: A combustion-supporting air pipeline and a hydrogen pipeline are further arranged, the combustion-supporting air pipeline is provided with a combustion-supporting air fan and a first automatic regulator, and the combustion-supporting air fan and the first automatic regulator are sequentially connected to one inlet of the burner, the hydrogen pipeline is provided with a pre-cooler, a cooler, a filter and a second automatic regulator, and the pre-cooler, the cooler, the filter and the second automatic regulator are sequentially connected to another inlet of the burner.

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