SCR (Selective Catalytic Reduction) denitration system for flue gas of oil-gas co-combustion boiler

Abstract

The utility model relates to the technical field of flue gas treatment, in particular to an SCR (Selective Catalytic Reduction) denitration system for flue gas of an oil-gas co-combustion boiler. The system comprises a boiler flue, and further comprises a denitration reactor and an ammonia-air mixing device, and a flue gas inlet of the denitration reactor is communicated with a flue gas outlet of the boiler flue; at least one catalyst bed layer is mounted in the denitration reactor, and a steam soot blower assembly and a sound wave soot blower assembly are arranged in the air inlet direction of each catalyst bed layer; the ammonia-air mixing device comprises an ammonia-air mixer, and an air outlet of the ammonia-air mixer is communicated with the boiler flue. The system can perform effective soot blowing on a catalyst bed layer, and prevents viscous substances carried in flue gas of an oil-gas co-combustion boiler from being attached to the surface of a catalyst to affect the activity of the catalyst; the ammonia-air mixing device is communicated with the boiler flue, so that flue gas can be mixed with ammonia gas and air before entering the reactor, and the denitration efficiency is improved.

Description

Technical Field

[0001] This utility model relates to the field of flue gas treatment technology, and more specifically, to an SCR denitrification system for flue gas from oil-gas co-firing boilers. Background Technology

[0002] Currently, industrial boilers in my country primarily use coal, specifically unwashed raw coal. The combustion conditions of raw coal within the boiler are poor, and the varying coal quality makes it difficult for boilers to operate exactly as designed, resulting in very low thermal efficiency. Furthermore, coal-fired boilers contain a large amount of ash, causing severe equipment blockage and wear problems when the flue gas passes through the SCR catalyst bed or downstream air preheater. With the adjustment of my country's energy structure and the vigorous promotion of coal-to-gas, coal-to-oil, and new energy development, oil and gas-fired boilers will inevitably become the trend. Oil and gas-fired boilers have advantages such as high efficiency and low environmental pollution, making them highly favored.

[0003] Controlling the concentration and emission of nitrogen oxides (NOx) in boiler flue gas can reduce its pollution to the atmosphere. NOx control technologies include various techniques such as low-NOx combustion, fuel staging, and flue gas reburning, all aimed at minimizing NOx generation at the source. However, these methods fall far short of achieving ultra-clean emission requirements.

[0004] Currently, denitrification technology is widely used in coal-fired boilers. For denitrification of already generated nitrogen oxides, the main technologies include selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR), and a hybrid method (SCR / SNCR). The most widely used is selective catalytic reduction (SCR), which has high denitrification efficiency and low ammonia slip. SCR denitrification involves injecting a reducing agent into the flue gas under the action of a catalyst. Conventional medium-temperature catalysts at temperatures of 300-420℃ undergo a selective catalytic reduction reaction with the nitrogen oxides in the flue gas, generating harmless nitrogen and water vapor, thereby achieving the purpose of removing nitrogen oxides.

[0005] SCR denitrification technology is widely used in coal-fired boilers in thermal power plants, and its denitrification efficiency is relatively high. However, there are few successful cases of SCR denitrification projects applied to flue gas of oil and gas co-fired boilers in China. In particular, under the condition of 100% heavy oil combustion, VOCs may be generated in the flue gas, which become liquid at low temperature and adhere to the catalyst surface. If the soot blowing effect is not good, long-term operation will block the catalyst, thus affecting the denitrification efficiency. Utility Model Content

[0006] The technical problem to be solved by this invention is to provide an SCR denitrification system for flue gas from oil and gas co-firing boilers, so as to solve the problems of liquid VOCs sticking to and clogging catalysts in the prior art.

[0007] The technical solution of this utility model to solve the above-mentioned technical problems is as follows:

[0008] This utility model provides an SCR denitrification system for flue gas from an oil-gas co-firing boiler, including a boiler flue, a denitrification reactor, and an ammonia-air mixing device, wherein the flue gas inlet of the denitrification reactor is connected to the flue gas outlet of the boiler flue.

[0009] The denitrification reactor is equipped with at least one catalyst bed. Along the flow direction of the flue gas, a steam soot blower assembly and an acoustic soot blower assembly are arranged upstream of each catalyst bed. The steam soot blower assembly and the acoustic soot blower assembly are installed on the inner wall of the denitrification reactor.

[0010] The ammonia-air mixing device includes an ammonia-air mixer, the outlet of which is connected to the boiler flue.

[0011] The beneficial effects of this invention are as follows: by setting up a steam soot blower assembly and an acoustic soot blower assembly on the catalyst bed, the catalyst bed can be effectively soot blown, preventing sticky substances carried in the flue gas of the oil-gas co-firing boiler from adhering to the catalyst surface and affecting the catalyst activity; by connecting the ammonia-air mixing device to the boiler flue, the flue gas can be mixed with ammonia and air before entering the reactor, thereby improving the denitrification efficiency.

[0012] Based on the above technical solution, the present invention can be further improved as follows.

[0013] Furthermore, the steam sootblower assembly includes at least one steam sootblower, and the acoustic sootblower assembly includes at least one acoustic sootblower.

[0014] The beneficial effect of adopting the above-mentioned further technical solution is that it can improve the dust removal effect of the catalyst bed and ensure that the activity of the catalyst is not affected.

[0015] Furthermore, the catalyst bed includes multiple catalyst modules, each catalyst module having 22 or 25 pores.

[0016] The beneficial effect of adopting the above-mentioned further technical solution is that it can effectively reduce the catalyst blockage problem caused by VOCs liquid substances.

[0017] Furthermore, an ammonia injection grille is also installed inside the boiler flue, the ammonia injection grille is connected to the ammonia-air mixer, and the injection direction of the ammonia injection grille is towards the flue gas outlet of the boiler flue.

[0018] The beneficial effect of adopting the above-mentioned further technical solution is that it enables the ammonia-air mixture to be mixed more evenly with the flue gas.

[0019] Furthermore, the ammonia-air mixing device also includes an ammonia buffer tank and a dilution fan assembly, wherein the outlet of the ammonia buffer tank and the outlet of the dilution fan assembly are respectively connected to the inlet of the ammonia-air mixer.

[0020] The beneficial effect of adopting the above-mentioned further technical solution is that the ammonia content can be adjusted in real time.

[0021] Furthermore, it also includes a liquid ammonia evaporation device, the outlet of which is connected to the ammonia buffer tank; the liquid ammonia evaporation device is also connected to a liquid ammonia storage device and a low-pressure steam pipeline.

[0022] The beneficial effect of adopting the above-mentioned further technical solution is that ammonia gas can be generated by using a liquid ammonia evaporation device.

[0023] Furthermore, it also includes an ammonia recovery main pipe, the inlet of which is connected to the liquid ammonia storage device and the liquid ammonia evaporation device. The ammonia recovery main pipe includes a first outlet and a second outlet, the first outlet being connected to an ammonia dilution tank and the second outlet being connected to the boiler flue.

[0024] The beneficial effect of adopting the above-mentioned further technical solution is that by setting the ammonia recovery main pipe into two branches, a portion of the ammonia can be recovered and reused, thus avoiding the waste of ammonia.

[0025] The system of this invention performs SCR denitrification treatment on flue gas from oil-gas co-firing boilers, including the following steps:

[0026] The ammonia-air mixing device inputs ammonia-air mixed gas into the boiler flue and mixes it with the flue gas from the oil-gas co-firing boiler. The mixed flue gas enters the denitrification reactor and undergoes a denitrification reaction through the catalyst bed. The opening or closing of the steam soot blower assembly and the acoustic soot blower assembly is controlled according to the temperature in the denitrification reactor and the pressure drop of the catalyst bed.

[0027] This invention's system effectively improves denitrification efficiency by using steam and sonic soot blowing to prevent catalyst blockage in the liquid VOCs contained in the flue gas of oil-gas co-fired boilers. The method features a reasonable process design and equipment selection, a compact equipment layout, and a small footprint. It makes efficient use of limited on-site space, adapting to local conditions by arranging relevant devices within the spare space of the oil-gas co-fired boiler structure, and considering the space and facilities required for maintenance.

[0028] The SCR denitrification system involved in this utility model will effectively solve the problems encountered in the flue gas treatment of oil and gas co-fired boilers and provide technical support for the stable operation of SCR denitrification in oil and gas co-fired boilers.

[0029] Furthermore, the temperature of the mixed flue gas is 280℃~430℃, and the volume percentage of ammonia in the ammonia-air mixture is less than 5%. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the SCR denitrification system for flue gas from an oil-gas co-firing boiler, including the denitrification reactor, boiler flue, and ammonia-air mixing device.

[0031] Figure 2 This is a cross-sectional view of the catalyst bed, steam soot blower, and acoustic soot blower of the SCR denitrification system for flue gas from an oil-gas co-firing boiler according to this utility model.

[0032] Figure 3 This is a schematic diagram of the structure of the SCR denitrification system for flue gas from an oil-gas co-firing boiler, including the liquid ammonia evaporation device and the liquid ammonia storage device.

[0033] Figure 4 This is a schematic diagram of the structure of the SCR denitrification system for flue gas from an oil-gas co-firing boiler, including the ammonia dilution tank and the wastewater pool.

[0034] Figure 5 This is a schematic diagram of an embodiment of the SCR denitrification system for flue gas from a co-fired oil and gas boiler according to the present invention.

[0035] The attached diagram lists the components represented by each number as follows:

[0036] 1. Denitrification reactor; 101. Catalyst bed; 1011. Catalyst spare layer; 102. Steam soot blower; 103. Acoustic soot blower; 104. Ammonia injection grid;

[0037] 2. Ammonia-air mixing unit; 201. Ammonia buffer tank; 202. Dilution fan; 203. Ammonia-air mixer;

[0038] 3. Liquid ammonia evaporation device; 301. Liquid ammonia evaporation tank;

[0039] 4. Liquid ammonia storage device; 401. Liquid ammonia storage tank;

[0040] 5. Ammonia dilution tank; 6. Wastewater pool; 7. Boiler flue; 8. Ammonia recovery main pipe. Detailed Implementation

[0041] The principles and features of this utility model are described below with reference to the accompanying drawings. The examples given are only for explaining this utility model and are not intended to limit the scope of this utility model.

[0042] like Figures 1-5As shown, the SCR denitrification system for flue gas from a co-fired oil and gas boiler of this utility model includes a boiler flue 7, a denitrification reactor 1, and an ammonia-air mixing device 2. The flue gas inlet of the denitrification reactor 1 is connected to the flue gas outlet of the boiler flue 7. At least one catalyst bed 101 is installed in the denitrification reactor 1, and a steam soot blower assembly is arranged in the air inlet direction of each catalyst bed 101. An acoustic soot blower assembly is also arranged in the air inlet direction of each catalyst bed 101. The ammonia-air mixing device 2 includes an ammonia-air mixer 203, and the outlet of the ammonia-air mixer 203 is connected to the boiler flue 7.

[0043] This invention relates to an SCR denitrification system for flue gas from a co-fired oil and gas boiler. The ammonia-air mixing device 2 supplies a mixture of ammonia and air to the boiler flue duct 7, mixing it with the flue gas in the denitrification reactor 1. The mixture then enters the denitrification reactor 1 and passes through the catalyst bed 101, achieving denitrification treatment of the flue gas. At each location of the catalyst bed 101, steam soot blowing components and acoustic soot blowing components are combined, effectively solving the problem of VOCs in the flue gas from co-fired oil and gas boilers clogging the pores of the catalyst at low temperatures. Therefore, this invention's system is particularly suitable for co-fired oil and gas boilers.

[0044] Preferably, the steam sootblower assembly includes at least one steam sootblower 102; the acoustic sootblower assembly includes at least one acoustic sootblower 103; this can make steam sootblowing and acoustic sootblowing more efficient.

[0045] As attached Figure 3 As shown, the arrangement of the steam sootblower assembly and the acoustic sootblower assembly is adjusted according to the cross-sectional dimensions of the denitrification reactor 1. The steam sootblower 102 is a rake-type sootblower, which is generally installed on the short side of the denitrification reactor 1 due to its structural limitations, while the acoustic sootblower 103 is installed on the long side of the denitrification reactor 1. The spacing between the acoustic sootblower 103 is generally 2~2.5m.

[0046] Preferably, the catalyst bed 101 includes multiple catalysts, each catalyst having 22 or 25 pores; compared to ordinary boiler flue gas SCR denitrification systems, the present invention uses catalysts with more pores, thereby reducing the number of pores that may be blocked.

[0047] Monitoring the pressure drop of the catalyst bed 101 can be done using conventional methods in the art. In one embodiment of this invention, preferably, multiple pressure monitoring devices are also installed in the denitrification reactor 1. Each pressure monitoring device is generally installed upstream of the catalyst bed 101, and the difference between two pressure monitoring devices can be used to monitor the pressure drop of a single catalyst bed 101.

[0048] Preferably, a temperature monitoring device is also installed at the flue gas inlet of the denitrification reactor 1.

[0049] It should be noted that the catalyst of this invention is a commercially available catalyst capable of denitrification. To make it more effective against flue gas from oil-gas co-fired boilers, it is preferable to include substances such as Mo that resist metal poisoning, in order to reduce and avoid catalyst poisoning problems caused by the potential inclusion of alkali metals, arsenic, etc., in the flue gas.

[0050] Preferably, the denitrification reactor 1 is also equipped with an ammonia injection grid 104, which is connected to the ammonia-air mixer 203. The injection direction of the ammonia injection grid 104 is towards the catalyst bed 101. By setting the ammonia injection grid 104, the ammonia-air mixture can be mixed more evenly with the flue gas.

[0051] Preferably, the ammonia-air mixing device 2 further includes an ammonia buffer tank 201 and a dilution fan assembly, wherein the outlet of the ammonia buffer tank 201 and the outlet of the dilution fan assembly are respectively connected to the inlet of the ammonia-air mixer 203.

[0052] The system of this invention also includes an ammonia zone, in which a series of devices can store, evaporate, transport and recycle liquid ammonia, thereby effectively providing ammonia gas.

[0053] The ammonia zone-related equipment specifically includes a liquid ammonia evaporation unit 3 and a liquid ammonia storage unit 4.

[0054] The liquid ammonia storage device 4 includes at least one liquid ammonia storage tank 401, and each liquid ammonia storage tank 401 is equipped with a liquid ammonia transfer pump on its liquid phase outlet pipeline. Liquid ammonia can be unloaded into the liquid ammonia storage tank 401 via tank trucks and a discharge compressor, or it can be transported to the liquid ammonia storage tank 401 from other tank areas over long distances via liquid ammonia pipelines. The liquid phase outlet of the liquid ammonia storage tank 401 is located at the bottom of the tank, so that liquid ammonia can enter the liquid ammonia evaporation device 3 by its own pressure or by the liquid ammonia transfer pump.

[0055] Preferably, the liquid ammonia storage tank 401 has a design pressure of not less than 2.2 MPa, an operating pressure controlled below 1.5 MPa, is made of low alloy steel, and has a volume factor of not more than 0.9.

[0056] Preferably, the liquid ammonia storage tank 401 is equipped with at least three pressure gauges for remote pressure control, and two different types of liquid level detection instruments for liquid level control.

[0057] Preferably, a cooling spray system is installed above the liquid ammonia storage tank 401 to prevent excessively high temperatures in summer from causing overpressure risk in the liquid ammonia storage tank 401.

[0058] The liquid ammonia evaporation device 3 includes at least one liquid ammonia evaporation tank 301. Liquid ammonia is fed into the liquid ammonia evaporation tank 301 and evaporates into ammonia gas. The liquid ammonia evaporation tank 301 and the ammonia gas buffer tank 201 allow the ammonia gas to be mixed with dilution air after passing through the ammonia gas buffer tank 201. This allows for certain control over the pressure and flow rate of the ammonia gas through the ammonia gas buffer tank 201, making the ammonia-air mixing more suitable and easier to control.

[0059] In addition, the liquid ammonia evaporation device 3 is also connected to a low-pressure steam pipeline, and the low-pressure steam can be used to evaporate the liquid ammonia.

[0060] Preferably, the liquid ammonia evaporation tank 301 is equipped with a low-pressure steam U-shaped pipe and a liquid ammonia coil. After the steam heats the hot water, the condensate (hydrophobic liquid) is discharged into the hydrophobic collection header through the hydrophobic valve on the pipeline, and then transported to the hydrophobic tank (not shown in the figure).

[0061] For the liquid ammonia evaporation tank 301, the commonly used heating methods are water bath type or steam U-shaped coil type. The difference between the two methods is that the water bath type directly introduces steam into the heat medium water to heat the hot water, and then evaporates the liquid ammonia in the tube side; the steam U-shaped coil type introduces steam into the heating coil at the bottom of the evaporation tank, and after indirect heat exchange with the heat medium water, it is discharged into the pit or condensate tank.

[0062] Compared with traditional water bath liquid ammonia evaporators, the liquid ammonia evaporation tank 301 of this invention avoids the phenomenon of a large amount of hot mist being emitted into the air, and also avoids the risk of burns to operators during operation.

[0063] Preferably, the liquid ammonia evaporation tank 301 is designed to handle the maximum ammonia consumption of all units under maximum operating conditions, with the operating temperature controlled between 50 and 70°C. The ammonia buffer tank 201 can accommodate ammonia for a residence time of 0.5 to 1 minute, with the pressure controlled between 0.15 and 0.4 MPa.

[0064] It also includes an ammonia recovery main pipe 8, whose inlet is connected to the liquid ammonia storage device 4 and the liquid ammonia evaporation device 3. The ammonia recovery main pipe 8 includes a first outlet and a second outlet. The first outlet is connected to the ammonia dilution tank 5, and the second outlet is connected to the boiler flue 7. In this way, the ammonia gas that is urgently discharged or emptied from the liquid ammonia storage device 4 and the liquid ammonia evaporation device 3 can be collected in a main ammonia recovery main pipe 8, and then split into two paths. The first path is discharged into the ammonia dilution tank 5, where it is absorbed by water to form dilute ammonia water. The ammonia water in the ammonia dilution tank 5 is then discharged into the wastewater pool 6 and pumped to the sewage treatment system. The second path enters the boiler flue 7 and reacts with NO. x The reaction is complete. Through the above setup, a portion of the ammonia gas can be recovered and reused, preventing a large amount of ammonia from being wasted.

[0065] Specifically, the second branch of the ammonia recovery main pipe 8 can be connected to the ammonia outlet main pipe of the ammonia buffer tank 201, and enter the boiler flue 7 together with the ammonia output from the ammonia buffer tank 201.

[0066] Preferably, the ammonia recovery main pipe 8 is connected to the bottom of the ammonia dilution tank 5. To avoid siphoning, a vacuum release valve needs to be installed on this pipe. In addition, a spray water main pipe is installed at the top of the ammonia dilution tank 5. Several small holes are opened on the main pipe to increase the atomization effect and coverage area of ​​the water spray, effectively improving the absorption rate of waste ammonia.

[0067] It should be noted that in the system of this utility model, in order to flexibly and effectively control the flow of liquid and gas phases, valves and pumps can be installed on any connected pipeline as needed. The valves can be ordinary valves, pneumatic regulating valves, or valve groups composed of pneumatic regulating valves and control valves.

[0068] The present invention discloses an SCR denitrification method for flue gas from oil-gas co-firing boilers, which employs the system described above to perform SCR denitrification treatment on the flue gas from oil-gas co-firing boilers.

[0069] The method specifically includes the following steps:

[0070] The ammonia-air mixing device 2 inputs ammonia-air mixed gas into the boiler flue 7 and mixes it with the flue gas from the oil-gas co-firing boiler. The mixed flue gas enters the denitrification reactor 1 and undergoes a denitrification reaction through the catalyst bed 101. The opening or closing of the steam soot blower assembly and the acoustic soot blower assembly is controlled according to the temperature in the denitrification reactor 1 and the pressure drop of the catalyst bed 101.

[0071] Preferably, before flue gas treatment, the temperature of the flue gas needs to be measured. The flue gas temperature measurement point is located at the flue gas inlet of the denitrification reactor 1, that is, the temperature of the flue gas after mixing with ammonia and air is measured. When this temperature is outside the allowable ammonia injection range, the temperature signal will automatically close the quick-cut-off valve for ammonia entering the ammonia-air mixing device 2. The ammonia from the ammonia zone and the air delivered by the dilution fan assembly are fully mixed in the ammonia-air mixing device 2. The concentration of ammonia in the mixed gas is controlled to be less than 5% by the ammonia flow regulating valve group, and then injected into the boiler flue 7. After the injected ammonia-air mixed gas is evenly mixed with the flue gas, it enters the denitrification reactor 1, where a redox reaction occurs in the catalyst bed 101. The catalyst bed 101 in the denitrification reactor 1 is generally determined according to the denitrification efficiency and the inlet NO. x Values ​​can be set to one or two layers, with an additional layer added as a backup.

[0072] Regarding the control of the opening and closing of the steam sootblower assembly and the sonic sootblower assembly, specifically, when the boiler load is high, the flue gas temperature of the denitrification reactor 1 is high, and the VOCs that may be mixed in the boiler flue gas are in the gas phase and will not clog the catalyst. Under this condition, the sootblower assembly can be activated independently for sonic sootblowing of the catalyst bed 101. If the boiler operates at a low load for a long period of time, or the pressure drop of the catalyst bed 101 is large, the steam sootblower assembly can be activated independently for steam sootblowing. At this time, the pressure drop of the catalyst bed 101 is monitored simultaneously. If there is no significant decrease or the pressure drop cannot be restored to the original level, the sonic sootblower assembly can be activated simultaneously to improve the sootblowing effect of the catalyst bed and ensure the performance of the catalyst.

[0073] Preferably, the temperature of the mixed flue gas is 280℃~430℃, and the volume percentage of ammonia in the ammonia-air mixture is less than 5%.

[0074] The present invention will be specifically described below through specific embodiments.

[0075] Example

[0076] like Figure 1 , 2 As shown in Figure 5, this embodiment uses the system of this invention to perform SCR denitrification treatment on flue gas from a co-fired oil and gas boiler. The catalyst bed 101 in the denitrification reactor 1 consists of two layers arranged at intervals. Each catalyst bed 101 is equipped with a steam sootblower assembly and an acoustic sootblower assembly. The steam sootblower assembly includes two steam sootblowers 102, arranged at equal intervals; the acoustic sootblower assembly includes three acoustic sootblowers 103, arranged at equal intervals.

[0077] As attached Figure 3 As shown, the arrangement of the soot blowers is adjusted according to the cross-sectional dimensions of the denitrification reactor 1. The steam soot blower 102 adopts a rake-type soot blower. Due to its structural limitations, the steam soot blower 102 is generally set on the short side of the reactor, and the sonic soot blower 103 is set on the long side. The interval between the sonic soot blowers 103 is generally 2~2.5m.

[0078] In this embodiment, a 25-pore honeycomb catalyst was selected. The ash concentration in the flue gas of oil-gas co-firing boilers is generally low, at the milligram level. However, considering the possibility of entrained viscous substances in the flue gas, a honeycomb catalyst with a denser pore count could not be selected. When formulating the catalyst, anti-poisoning components were added to increase the catalyst's tolerance. Additionally, sufficient margin was considered in the catalyst design to increase the stability of the denitrification system.

[0079] In addition, in this embodiment, a catalyst reserve layer 1011 is also installed inside the denitrification reactor 1, which is closest to the flue gas inlet of the denitrification reactor 1.

[0080] In order to effectively monitor the pressure drop of each catalyst bed 101 and the catalyst spare bed 1011, a pressure gauge is installed at the corresponding position on the upper side of each layer inside the denitrification reactor 1.

[0081] In this embodiment, the dilution fan assembly includes two dilution fans 202, both of which are connected to the ammonia-air mixer 203. An ammonia regulating valve assembly is installed on the pipeline connecting the ammonia buffer tank 201 and the ammonia-air mixer 203 to control the ammonia flow rate. A second branch of the ammonia recovery main pipe 8 is connected to the pipeline between the ammonia buffer tank 201 and the ammonia-air mixer 203, allowing some ammonia to be recovered and reused. A pressure gauge and a thermometer are installed inside the ammonia buffer tank 201 to measure the ammonia pressure and temperature within it.

[0082] In this embodiment, the liquid ammonia storage device 4 includes two liquid ammonia storage tanks 401, one for use and one for standby. The capacity of the liquid ammonia storage tank 401 meets the storage requirements for the number of days required for the liquid ammonia consumption under the BMCR operating conditions of all units. The storage days are determined by the method of liquid ammonia transportation. If the liquid ammonia is transported by pipeline, a storage capacity of 5 days is generally set; if it is transported by tank truck, a storage capacity of 7 days is generally set.

[0083] The liquid ammonia evaporation unit 3 includes two liquid ammonia evaporation tanks 301. A pneumatic regulating valve is installed on the pipeline before each liquid ammonia evaporation tank 301. The liquid ammonia evaporation tank 301 is a steam U-shaped coil type for heating the heat transfer medium water. A regulating valve is installed on the steam pipeline, which is interlocked with the temperature of the heat transfer medium water for control. The heated heat transfer medium water is maintained at 50~70℃ and the pressure is maintained at 0.25~0.4MPa. The liquid ammonia evaporation tank 301 vaporizes the liquid ammonia in the tube side into ammonia gas, which then enters the ammonia buffer tank 201.

[0084] The system operation process in this embodiment is as follows:

[0085] Liquid ammonia supplied by pipeline enters liquid ammonia storage tank 401 for storage. The liquid ammonia in storage tank 401 is then transported to liquid ammonia evaporation tank 301 by the tank's own pressure (or via a liquid ammonia transfer pump in winter when ambient temperatures are low). A U-shaped steam coil is installed at the bottom of liquid ammonia evaporation tank 301 to heat the shell-side heat transfer medium water. Liquid ammonia is then introduced into the tube side, evaporating into gaseous ammonia, which then enters ammonia buffer tank 201. The amount of liquid ammonia entering liquid ammonia evaporation tank 301 is controlled by a pneumatic regulating valve before entering the tank to maintain a constant operating pressure in ammonia buffer tank 201.

[0086] Ammonia gas enters the ammonia-air mixer 203 through the regulating valve group. After being fully mixed with the dilution air from the dilution fan 202, the ammonia gas is diluted to a concentration below 5% and then injected into the boiler flue duct 7 through the ammonia injection grille 104. The ammonia-air mixture entering the boiler flue duct 7 mixes with the boiler flue gas and then enters the denitrification reactor 1. The temperature of the denitrification reactor 1 is generally controlled between 300 and 420°C, with a minimum ammonia injection temperature of 280°C. The flue gas undergoes a redox reaction in the catalyst bed 101, generating N2 and H2O, thereby removing NO from the flue gas. x To achieve standard emissions for boiler flue gas.

[0087] Three temperature transmitters are installed at the inlet of the denitrification reactor 1 to monitor the flue gas temperature. The pneumatic valves in the ammonia regulating valve group are interlocked with these thermometers, ensuring that ammonia is injected only after the minimum ammonia injection temperature is reached. Additionally, the regulating valves in the ammonia regulating valve group are connected to the inlet and outlet NO... x The concentration and flue gas volume are interlocked and controlled by DCS to ensure that the NO concentration at the flue gas outlet is controlled. x The concentration meets environmental protection requirements.

[0088] Waste liquid and waste gas discharged from liquid ammonia storage tank 401 and liquid ammonia evaporation tank 301 are collected in ammonia recovery main pipe 8. Ammonia recovery main pipe 8 is connected to the ammonia dilution tank 5 at a certain distance below the liquid level. An ammonia leak alarm is installed at the top of the ammonia dilution tank 5. The ammonia leak alarm signal is interlocked with the dilution spray water pneumatic valve. When ammonia escapes from the top of the ammonia dilution tank 5, the alarm will be triggered, and then the spray water replenishment valve will be opened to absorb the volatilized waste ammonia gas. Finally, the gas enters the wastewater pool 6 through the bottom drain port of the ammonia dilution tank 5.

[0089] In a co-fired boiler using 100% PFO, 90% PGO, and 100% natural gas, the NO in the flue gas at the inlet of the denitrification reactor... x Content (maximum) ≤250mg / Nm 3 In the case of the SCR denitrification method of this utility model embodiment, the NO in the flue gas outlet of the denitrification reactor is reduced. x Content ≤25 mg / Nm 3 (Dry basis, O2, 3%); The ammonia slip rate at the outlet of the denitrification reactor is 3 ppm (dry basis, 3% O2), which meets the environmental emission requirements.

[0090] In the description of this utility model, it should be noted that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0091] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this utility model, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0092] In this utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0093] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0094] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0095] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An SCR denitrification system for flue gas from a co-fired oil and gas boiler, comprising a boiler flue (7) characterized in that, It also includes a denitrification reactor (1) and an ammonia-air mixing device (2), wherein the flue gas inlet of the denitrification reactor (1) is connected to the flue gas outlet of the boiler flue (7); At least one catalyst bed (101) is installed inside the denitrification reactor (1). Along the flow direction of the flue gas, a steam soot blower assembly and an acoustic soot blower assembly are arranged upstream of each catalyst bed (101); the steam soot blower assembly and the acoustic soot blower assembly are installed on the inner wall of the denitrification reactor (1). The ammonia-air mixing device (2) includes an ammonia-air mixer (203), the outlet of which is connected to the boiler flue (7); The ammonia-air mixing device (2) further includes an ammonia buffer tank (201) and a dilution fan assembly. The outlet of the ammonia buffer tank (201) and the outlet of the dilution fan assembly are respectively connected to the inlet of the ammonia-air mixer (203). It also includes a liquid ammonia evaporation device (3), the outlet of which is connected to the ammonia buffer tank (201); the liquid ammonia evaporation device (3) is also connected to the liquid ammonia storage device (4) and the low-pressure steam pipeline respectively; It also includes an ammonia recovery main pipe (8), the inlet of which is connected to the liquid ammonia storage device (4) and the liquid ammonia evaporation device (3). The ammonia recovery main pipe (8) includes a first outlet and a second outlet. The first outlet is connected to the ammonia dilution tank (5), and the second outlet is connected to the boiler flue (7).

2. The SCR denitrification system for flue gas from a co-fired oil and gas boiler according to claim 1, characterized in that, The steam soot blower assembly includes at least one steam soot blower (102).

3. The SCR denitrification system for flue gas from a co-fired oil and gas boiler according to claim 1, characterized in that, The acoustic soot blower assembly includes at least one acoustic soot blower (103).

4. An SCR denitrification system for flue gas from a co-fired oil and gas boiler according to any one of claims 1 to 3, characterized in that, The catalyst bed (101) includes multiple catalyst modules, each catalyst module having 22 or 25 pores.

5. An SCR denitrification system for flue gas from a co-fired oil and gas boiler according to any one of claims 1 to 3, characterized in that, An ammonia injection grille (104) is also installed in the boiler flue (7). The ammonia injection grille (104) is connected to the ammonia-air mixer (203). The injection direction of the ammonia injection grille (104) is towards the flue gas outlet of the boiler flue (7).

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