Stable and efficient denitration system of biomass boiler
By combining the biomass boiler denitrification system with high-temperature SNCR and low-temperature SCR, the problems of low denitrification efficiency of biomass boiler flue gas and frequent catalyst poisoning are solved, and efficient and stable flue gas denitrification effect is achieved, reducing operating costs.
Patent Information
- Application Number
- CN202511024859.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-24
- Publication Date
- 2025-09-02
AI Technical Summary
The flue gas denitrition technology of biomass boilers has the problem of frequent catalyst poisoning and low denitrification efficiency. Conventional SNCR and SCR methods are unstable in application on biomass boilers and have high operating costs.
The system consisting of energy conversion unit, heat recovery unit, dust removal and desulfurization unit, SNCR treatment unit, low-temperature denitrification unit and detection control unit is adopted. Through the combination of high-temperature SNCR and low-temperature SCR, combined with flue gas temperature and NOx concentration detection, the switching of multiple denitrification functions is achieved, reducing the probability of catalyst poisoning and improving denitrification efficiency.
The flue gas denitrification efficiency has been achieved to reach more than 90%, the system is stable, the catalyst replacement frequency is reduced, the operating costs are reduced, and the boiler load changes is adapted to the problem of flue gas denitrition of biomass boiler is solved.
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Figure CN120571391A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of flue gas denitration, and in particular to a stable and efficient denitration system for a biomass boiler. Background Art
[0002] The stable and efficient flue gas denitrification technology of biomass boilers has always been a difficult point. Currently, there is no more effective and reliable denitrification method to solve this problem. This is mainly because the flue gas of biomass boilers has the following characteristics: 1. The furnace temperature varies greatly. Biomass boilers mainly include grate furnaces and circulating fluidized bed furnaces. The furnace temperature of each type of furnace is 700-760℃ and 880-950℃ respectively; 2. The hydrogen content in biomass is relatively high, and the water content in the flue gas is also high, which can reach 15%-30% or even higher; 3. The smoke contains a high mass fraction of alkali metals such as K, Na, and Ca, which can reach more than 8%; 4. The concentrations of sulfur dioxide and nitrogen oxides are low and fluctuate greatly. When burning pure biomass, the concentrations of sulfur dioxide and nitrogen oxides are between 120 and 250 mg / m 3 Fluctuations, such as the presence of templates, wood, or bark in the fuel, and the concentration of sulfur dioxide and nitrogen oxides in the flue gas ranging from 250 to 600 mg / m 3 Fluctuations. Due to the aforementioned characteristics of biomass boilers, conventional SNCR and SCR denitrification methods present various challenges in their application. Conventional SNCR denitrification has low efficiency, leading to issues such as excessive nitrogen oxide emissions. SCR denitrification, due to the high water content and alkali metal content of flue gas, and the wide fluctuations in sulfur dioxide and nitrogen oxide concentrations, can lead to catalyst poisoning after a short period of use, requiring frequent catalyst replacement, resulting in high operating costs and unstable operation. Therefore, a solution is urgently needed. Summary of the Invention The technical problem to be solved by the present invention is to provide a stable and efficient denitrification system for biomass boilers. The system greatly reduces the possibility of catalyst poisoning, not only solving the problem of frequent catalyst poisoning in conventional SCR denitrification, but also the method has high denitrification efficiency and a stable system, solving the problem of biomass boiler flue gas denitrification.
[0003] To achieve the above-mentioned purpose, the technical solution of the present invention is implemented as follows: a stable and efficient denitrification system for a biomass boiler, comprising: an energy conversion unit, connected to the biomass boiler, for converting heat energy generated by the biomass boiler into electrical energy; A heat recovery unit is connected to the biomass boiler and is used to recover heat from the flue gas generated by the biomass boiler; The dust removal and desulfurization unit is connected to the heat recovery unit and is used to perform secondary dust removal and desulfurization on the flue gas treated by the heat recovery unit; A chimney, connected to the dust removal and desulfurization unit, for discharging the flue gas treated by the dust removal and desulfurization unit; The SNCR treatment unit is installed between the heat recovery unit and the biomass boiler to perform high-temperature denitrification on the flue gas generated by the biomass boiler; The low-temperature denitrification unit is arranged between the chimney and the dust removal and desulfurization unit, and is connected to both the energy conversion unit and the heat recovery unit, and is used to perform low-temperature denitrification on the flue gas treated by the dust removal and desulfurization unit; Detection control unit, used to detect the flue gas temperature generated by the biomass boiler and the NO in the flue gas in the dust removal and desulfurization unit X The concentration of NO X The concentration controls the operation of the SNCR treatment unit and / or the low-temperature denitrification unit.
[0004] Preferably, the dust removal and desulfurization unit includes a cyclone dust collector, a dry desulfurization device and a bag dust collector; the cyclone dust collector is connected to the heat recovery unit to remove large particles of smoke from the flue gas; the bag dust collector is connected to the low-temperature denitrification unit; the dry desulfurization device is arranged between the cyclone dust collector and the bag dust collector to remove sulfides from the flue gas.
[0005] Preferably, the low-temperature denitrification unit includes a heater, a low-temperature denitrification device and a waste heat recovery device; the heater is connected to both the energy conversion unit and the bag-type dust collector, and is used to use the heat energy of the energy conversion unit to heat the flue gas treated by the bag-type dust collector; the low-temperature denitrification device is connected to the heater, and performs low-temperature SCR denitrification on the flue gas heated by the heater; the waste heat recovery device is connected to the heat energy recovery unit, and recovers heat from the flue gas treated by the low-temperature denitrification device, and transfers the recovered heat to the heat energy recovery unit.
[0006] Preferably, it also includes an induced draft fan; the induced draft fan is connected to the waste heat recovery device and sends the flue gas into the chimney.
[0007] Preferably, the heater heats the flue gas to 180°C to 220°C.
[0008] Preferably, the detection control unit includes a controller, a temperature sensor and an online monitor for nitrogen oxide concentration; the controller is electrically connected to the SNCR treatment unit, the low-temperature denitrification device, the temperature sensor and the online monitor for nitrogen oxide concentration; there are at least two temperature sensors, which are respectively arranged at the connection between the SNCR treatment unit and the biomass boiler and in the heater; the online monitor for nitrogen oxide concentration is arranged in the cyclone dust collector.
[0009] Preferably, the energy conversion unit includes a steam turbine and a generator; the steam turbine is connected to the biomass boiler and converts the thermal energy provided by the biomass boiler into kinetic energy; the generator is connected to the steam turbine and converts the kinetic energy of the steam turbine into electrical energy; and the heater is connected to the steam turbine.
[0010] Preferably, the heat recovery unit includes an economizer and an air preheater; the economizer is connected to the SNCR processing unit; the air preheater is connected to the economizer; and the cyclone dust collector is connected to the air preheater.
[0011] Preferably, the SNCR treatment unit performs high-temperature SNCR denitrification on the flue gas.
[0012] The beneficial effects of the present invention are embodied in: (1) The low-temperature denitrification device in the system provided by the present invention denitrates flue gas at a temperature of 180°C to 220°C. At this operating temperature, the catalyst activity in the low-temperature denitrification device is relatively good, and the denitrification efficiency can reach over 90%. Moreover, since it is used on clean flue gas after dust removal and desulfurization, the possibility of catalyst poisoning is greatly reduced, solving the problem of frequent catalyst poisoning in conventional SCR denitrification. In addition, the system provided by the present invention has high denitrification efficiency and system stability, which is of great significance to the development of biomass boiler flue gas denitrification technology and solves the problem of biomass boiler flue gas denitrification.
[0013] (2) The system provided by the present invention can basically meet the requirements of nitrogen oxide emission concentration when the biomass boiler is under high load, and SCR does not participate in the reaction; or when the biomass boiler fuel changes greatly, NO x When emission concentrations exceed the efficiency of a single SNCR denitrification system, a low-temperature SCR denitrification system can be used as a supplement to meet nitrogen oxide emission requirements. When denitrification efficiency is not met, supplementing the SCR system significantly improves denitrification efficiency. When the boiler is operating at low load, the furnace temperature is low, and SNCR denitrification fails, so consider using SCR low-temperature denitrification entirely. Because SCR low-temperature denitrification is performed on clean flue gas after desulfurization and dust removal, the probability of catalyst poisoning is greatly reduced, and the service life is greatly extended, reaching 3 to 5 years or even longer. This reduces the need for frequent replacement of low-temperature catalysts, saves operating costs, and achieves flue gas denitrification efficiency exceeding 90%. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 It is a framework diagram of the system of the present invention. DETAILED DESCRIPTION
[0015] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.
[0016] like Figure 1 As shown, the present invention provides a stable and efficient denitrification system for a biomass boiler.
[0017] Example 1 When the biomass boiler is running at high load: The SNCR treatment unit performs high-temperature SNCR denitrification on the flue gas generated by the biomass boiler, which can basically meet the flue gas denitrification requirements of the biomass boiler.
[0018] The flue gas after denitrification is transported to the heat recovery unit. After the heat of the flue gas is recovered in turn through the economizer and air preheater, the flue gas is transported to the dust removal and desulfurization unit. The flue gas undergoes secondary dust removal and desulfurization treatment through the cyclone dust collector, dry desulfurization device and bag dust collector of the dust removal and desulfurization unit respectively.
[0019] At this time, the flue gas of the biomass boiler has been subjected to cyclone dust removal, semi-dry desulfurization and bag dust removal, and the flue gas temperature is about 110 ° C, and the dust content of the flue gas is relatively low (generally less than 10 mg / Nm 3 ), and the sulfur dioxide content is also low (generally less than 50mg / Nm 3 ) to meet emission requirements. Therefore, the heater and low-temperature denitrification device of the low-temperature denitrification unit do not need to be turned on.
[0020] In specific applications, heat exchange is generally achieved by exchanging desalted water with the outside of the flue gas transmission pipeline to absorb its heat, and the recovered heat is transferred to the economizer of the heat recovery unit through the circulation of desalted water, thereby increasing the feed water temperature, improving the thermal efficiency of the boiler, reducing energy consumption, and extending the life of the boiler.
[0021] When the fuel of the biomass boiler changes greatly, and the nitrogen oxide concentration online monitor of the detection control unit detects NO xWhen the emission concentration exceeds the single SNCR denitrification efficiency, the controller activates the low-temperature denitrification unit's heater and the low-temperature denitrification device. The heater uses steam from the energy conversion unit's steam turbine as a heat source to heat the flue gas until the temperature sensor at the heater detects that the flue gas temperature exceeds 180°C. The flue gas then enters the low-temperature denitrification device, which performs low-temperature SCR denitrification on the flue gas heated by the heater. The flue gas after low-temperature SCR denitrification passes through the low-temperature denitrification unit's waste heat recovery device for heat recovery, and the recovered heat is transferred to the heat energy recovery unit. The induced draft fan delivers the denitrified flue gas into the chimney, through which the flue gas is discharged.
[0022] In this way, the low-temperature denitrification unit can be used as a supplement to the SNCR treatment unit for flue gas denitrification, which can not only meet the nitrogen oxide emission requirements, but also greatly improve the denitrification efficiency of the flue gas when the SNCR treatment unit fails to achieve the denitrification efficiency.
[0023] Example 2 When the boiler is under low load: When the biomass boiler is running at low load, due to the decrease in flue gas temperature, the temperature sensor at the connection between the SNCR treatment unit and the biomass boiler detects that the flue gas temperature is lower than the temperature of the SNCR reaction zone of the SNCR treatment unit. At this time, the SNCR fails, and the controller turns on the heater and low-temperature denitrification device of the low-temperature denitrification unit, and uses low-temperature SCR denitrification to denitrify the flue gas.
[0024] The flue gas generated by the biomass boiler is transported to the dust removal and desulfurization unit after heat recovery through the economizer and air preheater in sequence; the flue gas undergoes secondary dust removal and desulfurization treatment through the cyclone dust collector, dry desulfurization device and bag dust collector of the dust removal and desulfurization unit respectively.
[0025] At this time, after the flue gas from the biomass boiler has undergone cyclone dust removal, semi-dry desulfurization and bag dust removal, the flue gas temperature is about 110°C. The heater uses the steam from the turbine of the energy conversion unit as a heating source to heat the flue gas until the temperature sensor at the heater detects that the flue gas temperature exceeds 180°C. The flue gas then enters the low-temperature denitrification device, which performs low-temperature SCR denitrification on the flue gas heated by the heater. The flue gas after low-temperature SCR denitrification is subjected to heat recovery by the waste heat recovery device of the low-temperature denitrification unit, and the recovered heat is transferred to the heat energy recovery unit. The induced draft fan sends the flue gas that has completed the denitrification treatment into the chimney, and the flue gas is discharged through the chimney. The waste heat recovery device generally adopts the desalted water heat exchange principle.
[0026] In actual use, the low-temperature denitration device is equipped with a honeycomb-shaped denitration catalyst layer. The catalyst is applied to the surface of the denitration catalyst layer to increase the contact area between the flue gas and the catalyst, thereby improving the denitration efficiency. The catalyst is generally selected from conventional flue gas denitration catalysts on the market, such as manganese-based catalysts.
[0027] Testing of flue gas emitted from chimneys shows that activity is highest at flue gas temperatures around 180°C, with denitrification efficiencies exceeding 90%. Compared to the high dust and sulfur content flue gas environments encountered by medium- and high-temperature catalysts, low-temperature catalysts operate in clean flue gas environments, making them less likely to clog, extending their service life and significantly reducing operating costs. Because the flue gas temperature is lower than the catalyst's reaction temperature, this portion of the flue gas must be heated before entering the low-temperature denitrification system, requiring additional steam or other heating methods.
[0028] It can be seen from Examples 1 and 2 that, compared with independent SNCR denitrification, the system provided by the present invention has the ability to switch between multiple denitrification functions, which not only has a higher denitrification efficiency for flue gas, but is also more adaptable to changes in boiler load.
[0029] Because the low-temperature denitration system is used when nitrogen oxide concentrations are high and SNCR denitration alone cannot meet emission requirements, it is continuously in use compared to independent SCR. The service life of the low-temperature SCR catalyst is greatly extended, thereby reducing the frequency of low-temperature catalyst replacement. Furthermore, because the low-temperature denitration system is used on clean flue gas after dust removal and desulfurization, the possibility of catalyst poisoning is greatly reduced. Therefore, when the system provided by the present invention is actually in operation, the operating costs of the hybrid denitration system are reduced.
[0030] In addition, since the low-temperature denitrification device performs low-temperature SCR denitrification on the flue gas and only operates in a low-temperature environment, the possibility of catalyst poisoning is greatly reduced, solving the problem of frequent catalyst poisoning in conventional SCR denitrification. The service life of the catalyst will be greatly extended, thereby reducing the frequency of replacing the low-temperature catalyst and saving operating costs.
[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A stable and efficient denitrification system for a biomass boiler, characterized in that: include: an energy conversion unit, connected to the biomass boiler, for converting heat energy generated by the biomass boiler into electrical energy; A heat recovery unit is connected to the biomass boiler and is used to recover heat from the flue gas generated by the biomass boiler; The dust removal and desulfurization unit is connected to the heat recovery unit and is used to perform secondary dust removal and desulfurization on the flue gas treated by the heat recovery unit; A chimney, connected to the dust removal and desulfurization unit, for discharging the flue gas treated by the dust removal and desulfurization unit; The SNCR treatment unit is installed between the heat recovery unit and the biomass boiler to perform high-temperature denitrification on the flue gas generated by the biomass boiler; The low-temperature denitrification unit is arranged between the chimney and the dust removal and desulfurization unit, and is connected to both the energy conversion unit and the heat recovery unit, and is used to perform low-temperature denitrification on the flue gas treated by the dust removal and desulfurization unit; Detection control unit, used to detect the flue gas temperature generated by the biomass boiler and the NO in the flue gas in the dust removal and desulfurization unit X The concentration of NO X The concentration controls the operation of the SNCR treatment unit and / or the low-temperature denitrification unit.
2. A stable and efficient denitrification system for a biomass boiler according to claim 1, characterized in that: The dust removal and desulfurization unit includes a cyclone dust collector, a dry desulfurization device and a bag dust collector; the cyclone dust collector is connected to the heat recovery unit to remove large particles of smoke from the flue gas; the bag dust collector is connected to the low-temperature denitrification unit; the dry desulfurization device is arranged between the cyclone dust collector and the bag dust collector to remove sulfides from the flue gas.
3. A stable and efficient denitrification system for a biomass boiler according to claim 2, characterized in that: The low-temperature denitrification unit includes a heater, a low-temperature denitrification device and a waste heat recovery device; the heater is connected to both the energy conversion unit and the bag-type dust collector, and is used to use the heat energy of the energy conversion unit to heat the flue gas treated by the bag-type dust collector; the low-temperature denitrification device is connected to the heater, and performs low-temperature SCR denitrification on the flue gas heated by the heater; the waste heat recovery device is connected to the heat energy recovery unit, and recovers heat from the flue gas treated by the low-temperature denitrification device, and transfers the recovered heat to the heat energy recovery unit.
4. A stable and efficient denitrification system for a biomass boiler according to claim 3, characterized in that: It also includes an induced draft fan; the induced draft fan is connected to the waste heat recovery device and sends the flue gas into the chimney.
5. A stable and efficient denitrification system for a biomass boiler according to claim 3 or 4, characterized in that: The heater heats the flue gas to 180°C to 220°C.
6. A stable and efficient denitrification system for a biomass boiler according to claim 3 or 4, characterized in that: The detection and control unit includes a controller, a temperature sensor and an online monitor for nitrogen oxide concentration; the controller is electrically connected to the SNCR treatment unit, the low-temperature denitrification device, the temperature sensor and the online monitor for nitrogen oxide concentration; there are at least two temperature sensors, which are respectively arranged at the connection between the SNCR treatment unit and the biomass boiler and in the heater; the online monitor for nitrogen oxide concentration is arranged in the cyclone dust collector.
7. The stable and efficient denitrification system for a biomass boiler according to claim 4, characterized in that: The energy conversion unit includes a steam turbine and a generator; the steam turbine is connected to the biomass boiler and converts the thermal energy provided by the biomass boiler into kinetic energy; the generator is connected to the steam turbine and converts the kinetic energy of the steam turbine into electrical energy; the heater is connected to the steam turbine.
8. The stable and efficient denitrification system for a biomass boiler according to claim 4, characterized in that: The heat energy recovery unit includes an economizer and an air preheater; the economizer is connected to the SNCR processing unit; the air preheater is connected to the economizer; and the cyclone dust collector is connected to the air preheater.
9. The stable and efficient denitrification system for a biomass boiler according to claim 4, characterized in that: The SNCR treatment unit performs SNCR denitrification on the flue gas.