SNCR (selective non-catalytic reduction) and SCR (selective catalytic reduction) combined denitration co-processing device and method

Abstract

The invention relates to the technical field of synthesis ammonia and flue gas denitration, in particular to an SNCR (selective non-catalytic reduction) and SCR (selective catalytic reduction) combined denitration co-processing device and method. Comprising an ice maker compressor, a condensation mechanism, a liquid ammonia storage tank, an ammonia evaporator, a flue and an SCR catalytic reactor. The section III exhaust gas of the ice maker compressor is communicated with the condensation mechanism, the condensation mechanism is communicated with the liquid ammonia storage tank, and the liquid ammonia storage tank is respectively communicated with the boiler hearth and the vent gas recovery device through the vent gas boiler pipeline; and III-section exhaust gas of the ice maker compressor is communicated with the ammonia evaporator through an ammonia gas boiler pipeline, and the ammonia evaporator is communicated with the SCR catalytic reactor through a flue. The SNCR and SCR combined denitration co-processing device provided by the invention is reasonable in design, simple in structure, safe and reliable, convenient to use and capable of effectively improving the utilization rate of ammonia gas.

Description

Technical Field

[0001] The present invention relates to the technical fields of synthetic ammonia and flue gas denitrification, and particularly to a combined SNCR and SCR denitrification collaborative treatment device and method. Background Art

[0002] Currently, the non-condensable gas of the ice machine in the synthetic ammonia plant is discharged to the flare after being washed by the tail gas recovery device. The H2 content in this part of the discharged gas is ≥ 30%, and direct discharge to the flare is relatively wasteful.

[0003] Both SCR and SNCR are effective technologies for reducing NO x emissions. Selective catalytic reduction (SCR) denitrification usually uses 20% concentrated ammonia water as the denitrification reducing agent. Cold air enters the hot air heating pipe in the boiler rising flue through a dilution fan, and the cold air is heated to the temperature required for ammonia evaporation (about 280 °C) to evaporate the ammonia water. This process has a long heating time and high energy consumption. Normally, a set of ammonia water atomization evaporation and air mixing system is required for the mixing of the atomized ammonia evaporation and air after the ammonia water is atomized in the SCR reactor. The mixed gas then enters the main pipe and is sprayed into the rising flue through the nozzles of the ammonia injection grid, so that the mixture of ammonia, air, etc. is uniform after being sprayed out by the ammonia injection grid. However, the ammonia consumption of ammonia water denitrification is relatively high. Moreover, due to the large amount of water in the ammonia water, the humidity of the flue gas increases after entering the flue, which increases the possibility of ash plugging and corrosion at the end, and is not conducive to the long-term stable operation of the boiler. Summary of the Invention

[0004] The object of the present invention is to provide a combined SNCR and SCR denitrification collaborative treatment device and method.

[0005] To achieve the above object, the present invention provides a combined SNCR and SCR denitrification collaborative treatment device, including an ice machine compressor, a condensation mechanism, a liquid ammonia storage tank, an ammonia evaporator, a flue and an SCR catalytic reactor;

[0006] The third-stage exhaust of the ice machine compressor is connected to the condensation mechanism, the condensation mechanism is connected to the liquid ammonia storage tank, and the liquid ammonia storage tank is respectively connected to the boiler furnace and the air release recovery device through the air release boiler pipeline;

[0007] The third-stage exhaust of the ice machine compressor is connected to the ammonia evaporator through the ammonia gas to boiler pipeline, and the ammonia evaporator is connected to the SCR catalytic reactor through the flue.

[0008] Preferably, the condensation mechanism includes a third-stage cooler, a final cooler and a condenser. The third-stage exhaust of the ice machine compressor is connected to the third-stage cooler, and the condenser is connected to the fourth-stage exhaust of the ice machine compressor through the final cooler.

[0009] Preferably, the above SNCR and SCR combined denitration and co-disposal device further includes a concentrated ammonia water tank, and the concentrated ammonia water tank is connected to an ammonia evaporator through an ammonia water pump.

[0010] Preferably, gas online analyzers are respectively arranged at the air inlet of the flue and the outlet of the SCR catalytic reactor.

[0011] Preferably, the flue includes heat exchange pipes, and the air in the dilution fan enters the ammonia evaporator through the heat exchange pipes.

[0012] The present invention also provides a denitration method for the above SNCR and SCR combined denitration and co-disposal device, which includes the following steps:

[0013] The exhaust gas of the third stage of the ice machine compressor is condensed into liquid ammonia by a condensing mechanism and stored in a liquid ammonia storage tank, and the uncondensed exhaust gas is sent to the boiler furnace through the air release boiler pipeline for SNCR denitration reaction;

[0014] The exhaust gas of the third stage of the ice machine compressor enters the ammonia evaporator through the ammonia gas to boiler pipeline, the dilution fan compresses the air and passes it into the ammonia evaporator, enters the flue together with the exhaust gas of the third stage, mixes with the flue gas, and the mixed gas enters the SCR catalytic reactor for SCR catalytic reaction.

[0015] Preferably, the exhaust gas of the third stage of the ice machine compressor sequentially passes through a condensing mechanism and an air release recovery device and enters the flare.

[0016] Preferably, the ammonia water in the concentrated ammonia water tank enters the ammonia evaporator through an ammonia water pump, evaporates to obtain ammonia gas, and then enters the SCR catalytic reactor through the flue for SCR denitration reaction.

[0017] The present invention has the following beneficial effects:

[0018] In the SNCR and SCR combined denitration and co-disposal device provided by the present invention, when operating normally, ammonia gas (exhaust gas of the third stage) is used instead of ammonia water for SCR denitration. In this way, the concentrated ammonia water tank can be closed, power consumption can be saved, and gaseous ammonia can improve the ammonia utilization rate, saving about 20% of ammonia consumption. Moreover, using ammonia gas for denitration can reduce the moisture brought into the flue, thereby reducing the risk of blockage of the boiler air preheater and improving the economic efficiency of boiler operation.

[0019] By controlling the exhaust gas of the third stage of the ice machine compressor, the present invention reasonably distributes the exhaust gas of the third stage to the third stage cooler and the ammonia evaporator, which can reduce the load of the fourth stage compression of the ice machine.

[0020] The uncondensed gas in the liquid ammonia storage tank of the present invention can be directly sent into the boiler furnace for combustion. On the one hand, the combustible gas in the uncondensed gas is fully utilized, reducing the steam consumption when the uncondensed gas passes through the recovery device. On the other hand, ammonia in the uncondensed gas will undergo SNCR denitrification at an appropriate temperature, which can preliminarily denitrify the boiler flue gas.

[0021] The SNCR and SCR combined denitrification collaborative treatment device of the present invention is reasonably designed, simple in structure, safe and reliable, and convenient to use, and has good popularization and application value.

[0022] The technical solution of the present invention will be further described in detail below through the accompanying drawings and embodiments. Description of the Drawings

[0023] Figure 1 is a schematic diagram of a collaborative treatment device for SNCR and SCR combined denitrification of the present invention.

[0024] Reference Signs:

[0025] 1. Ice machine compressor; 2. Condensing mechanism; 201. III-stage cooler; 202. Final cooler; 203. Condenser; 3. Liquid ammonia storage tank; 4. Pipeline for discharging air to the boiler; 5. Air discharge recovery device; 6. Pipeline for ammonia gas to the boiler; 7. Control valve; 8. Ammonia evaporator; 9. Flue; 10. SCR catalytic reactor; 11. Dilution fan; 12. Heat exchange pipeline; 13. Concentrated ammonia water tank; 14. Ammonia water pump; 15. On-line gas analysis. Detailed Embodiments

[0026] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. Unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meaning understood by those of ordinary skill in the field to which the present invention belongs. The above-mentioned features mentioned in the present invention or the features mentioned in the specific examples can be combined arbitrarily. These specific embodiments are only used to illustrate the present invention and do not limit the scope of the present invention.

[0027] Embodiment 1

[0028] As Figure 1 shown, the present invention provides a collaborative treatment device for SNCR and SCR combined denitrification, including an ice machine compressor 1, a condensing mechanism 2, a liquid ammonia storage tank 4, an ammonia evaporator 8, a flue 9 and an SCR catalytic reactor 10. Among them, the condensing mechanism includes a III-stage cooler 201, a final cooler 202 and a condenser 203. Through the multi-stage cooling setting, the stable operation of the ice machine compressor 1 is ensured, and it is ensured that the temperature of the exhaust gas does not exceed the threshold value of 130 °C before entering the fourth-stage compression, avoiding local temperature runaway and realizing the step-by-step control of the temperature of the compressed gas.

[0029] The ice machine compressor 1 is connected to the ice machine. After the intake air of the third stage discharged from the ice machine is compressed by the third stage of the ice machine compressor 1, the pressure is raised to 0.74 MPa and the temperature is about 118 °C. As the exhaust gas of the third stage of the ice machine compressor 1, the exhaust gas of the third stage of the ice machine compressor 1 is connected to the third stage cooler 201. At the same time, the exhaust gas of the third stage of the ice machine compressor 1 is connected to the ammonia evaporator 8 through the ammonia pipeline to the boiler 6. Among them, the conditions of the exhaust gas of the third stage of the ice machine compressor 1 are a pressure of 0.74 MPa and a temperature of 118 °C. The exhaust gas of the third stage of the ice machine compressor 1 is respectively introduced into the third stage cooler 201 and the ammonia evaporator 8. On the one hand, it can reduce the load of the fourth stage of the ice machine. On the other hand, the ammonia gas pressure in this section is moderate and the temperature is also relatively high. After being decompressed by the regulating valve 7, it will not cause frosting of the pipeline and valves, which is beneficial to the safe operation of the device.

[0030] The exhaust gas of the third stage of the ice machine compressor 1 is connected to the third stage cooler 201. The exhaust gas of the third stage cooler 201 is connected to the intake air of the fourth stage of the ice machine compressor 1. The exhaust gas of the fourth stage of the ice machine compressor 1 passes through the final cooler 202 and is connected to the condenser 203. The condenser 203 is connected to the liquid ammonia storage tank 3. The liquid ammonia storage tank 3 is respectively connected to the boiler furnace and the air release recovery device 4 through the air release boiler pipeline 4. The non-condensable gas of the liquid ammonia storage tank 3 is sent to the air release recovery device 5 through the air release boiler pipeline 4. The air release recovery device 5 is connected to the spraying mechanism, the pressure reducing mechanism and the ammonia water tank. The air release recovery device 5 can change the ammonia gas in the air release into liquid ammonia and store it in the ammonia water tank, and the remaining air release is discharged into the torch for combustion, improving the utilization rate of the air release and reducing the coal consumption of the boiler.

[0031] When the air release recovery device 4 is closed, the non-condensable gas of the liquid ammonia storage tank 3 is sent to the boiler furnace through the air release boiler pipeline 4, and the SCNR denitration reaction is carried out in the boiler furnace. On the one hand, the combustible gas in the air release is fully utilized, reducing the steam consumption of the air release recovery device 5. On the other hand, ammonia gas will undergo SNCR denitration at an appropriate temperature, which can preliminarily denitrate the boiler flue gas.

[0032] The concentrated ammonia water tank 13 is connected to the ammonia evaporator 8 through the ammonia water pump 14. When the concentrated ammonia water tank 13 is closed, the exhaust gas of the third stage of the ice machine compressor 1 is connected to the ammonia evaporator 8 through the ammonia pipeline to the boiler 6. The ammonia evaporator 8 is connected to the SCR catalytic reactor 10 through the flue 9. The flue 9 includes a heat exchange pipeline 12. The air in the dilution fan 11 enters the ammonia evaporator 8 through the heat exchange pipeline 12. Using ammonia gas instead of ammonia water for SCR denitration can stop the ammonia water pump, save power consumption, and the utilization rate of ammonia is improved compared with liquid ammonia water, saving about 20% of ammonia consumption. And directly using ammonia gas for SCR denitration can reduce the moisture brought into the flue 9, thereby reducing the risk of air preheater blockage and improving the economic efficiency of boiler operation.

[0033] When the concentrated ammonia water tank 13 is opened, the concentrated ammonia water tank 13 is connected to the ammonia evaporator 8 through the ammonia water pump 14. The ammonia evaporator 8 evaporates the ammonia water into ammonia gas, which enters the flue 9 through the exhaust pipe of the ammonia evaporator 8 and is mixed with the flue gas in the flue 9 and then introduced into the SCR catalytic reactor 10.

[0034] Gas online analyzers 15 are respectively installed at the inlet of the flue 9 and the outlet of the SCR catalytic reactor 10 to measure NO x and oxygen content in real time.

[0035] Example 2

[0036] A denitrification method for the SNCR and SCR combined denitrification and co-disposal device in Example 1 includes the following steps:

[0037] During normal operation, after the exhaust gas from the III section of the ice machine compressor 1 is compressed, most of it is discharged into the III section cooler 201. After the initial cooling in the III section cooler 201, it enters the ice machine compressor 1 through the IV section inlet of the ice machine compressor 1, and then enters the final cooler 202 through the IV section exhaust of the ice machine compressor 1 for further cooling, and then is discharged into the condenser 203 for condensation. The condensed liquid ammonia flows into the liquid ammonia storage tank 3 through the drain pipe at the bottom of the condenser 203. The uncondensed gas enters the liquid ammonia storage tank 3 through the upper drain pipe and then enters the boiler furnace for the SCNR denitrification reaction.

[0038] When the air release recovery device 5 is opened, the gas that cannot be condensed by the condenser 203 passes through the liquid ammonia storage tank 3 and then is discharged into the air release recovery device 5 through the air release to boiler pipeline 4. The ammonia in the non-condensable gas is recovered by spraying desalted water, and the produced ammonia water with a mass concentration of 8% goes to the ammonia water tank, and the remaining air release is sent to the torch for flaring.

[0039] After the exhaust gas from the III section of the ice machine compressor 1 is compressed, a small part of the ammonia gas passes through the regulating valve 7 on the ammonia gas to boiler pipeline 6 to be decompressed and then sent to the hot air pipeline at the inlet of the ammonia evaporator 8. The air is compressed by the dilution fan 11, first exchanges heat in the flue 9 through the heat exchange pipeline 12, and then is sent to the hot air pipeline at the inlet of the ammonia evaporator 8. After the ammonia gas and the air are mixed to a certain proportion, they enter the ammonia evaporator 8, and then are discharged into the flue 9 together and mixed with the flue gas in the flue 9. The mixed gas is introduced into the SCR catalytic reactor 10 through the upper exhaust of the flue 9 for the denitrification reaction.

[0040] When the concentrated ammonia water tank 13 is opened, the ammonia water with a mass concentration of 20% in the concentrated ammonia water tank 13 enters the ammonia evaporator 8 through the ammonia water pump 14, and after evaporation in the ammonia evaporator 8, it becomes ammonia gas and enters the flue 9 together with the air in the ammonia evaporator 8 to be mixed with the flue gas. The mixed gas is introduced into the SCR catalytic reactor 10 through the upper exhaust of the flue 9 for the denitrification reaction.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A SNCR and SCR combined denitrification coordinated treatment device, characterized in that: It includes ice machine compressor, condensing mechanism, liquid ammonia storage tank, ammonia evaporator, flue and SCR catalytic reactor; The exhaust gas of the stage III of the ice machine compressor is connected to the condensing mechanism, the condensing mechanism is connected to the liquid ammonia storage tank, and the liquid ammonia storage tank is connected to the boiler furnace and the vent air recovery device through the vent air boiler pipeline; The exhaust gas of the III section of the ice machine compressor is connected to the ammonia evaporator through the ammonia to boiler pipeline, and the ammonia evaporator is connected to the SCR catalytic reactor through the flue.

2. The SNCR and SCR combined denitrification coordinated treatment device according to claim 1 is characterized in that: The condensing mechanism comprises a stage III cooler, a final cooler and a condenser. The stage III exhaust of the ice machine compressor is connected to the stage III cooler, and the condenser is connected to the stage IV exhaust of the ice machine compressor through the final cooler.

3. The SNCR and SCR combined denitrification coordinated treatment device according to claim 1 is characterized in that: The device also comprises a concentrated ammonia water tank, which is connected with the ammonia evaporator through an ammonia water pump.

4. The SNCR and SCR combined denitrification coordinated treatment device according to claim 1, characterized in that: The air inlet of the flue and the outlet of the SCR catalytic reactor are respectively provided with a gas online analyzer.

5. The SNCR and SCR combined denitrification coordinated treatment device according to claim 1, characterized in that: The flue includes a heat exchange pipe, and the air in the dilution fan enters the ammonia evaporator through the heat exchange pipe.

6. A denitration method for a SNCR and SCR combined denitration coordinated treatment device according to any one of claims 1 to 5, characterized in that: It includes the following steps: The exhaust gas of the III section of the ice machine compressor is condensed into liquid ammonia through the condensing mechanism and stored in the liquid ammonia storage tank. The uncondensed exhaust gas is sent to the boiler furnace through the venting boiler pipeline for SNCR denitration reaction; The exhaust gas of section III of the ice machine compressor enters the ammonia evaporator through the ammonia to boiler pipeline. The dilution fan compresses the air and passes it into the ammonia evaporator. It enters the flue together with the exhaust gas of section III and mixes with the flue gas. The mixed gas is passed into the SCR catalytic reactor for SCR catalytic reaction.

7. The denitration method of the SNCR and SCR combined denitration coordinated treatment device according to claim 6, characterized in that: The exhaust gas of stage III of the ice machine compressor passes through the condensing mechanism and the air recovery device in turn and enters the flare.

8. The denitration method of the SNCR and SCR combined denitration coordinated treatment device according to claim 6, characterized in that: The ammonia water in the concentrated ammonia water tank enters the ammonia evaporator through the ammonia water pump, evaporates to obtain ammonia gas, and then enters the SCR catalytic reactor through the flue to carry out SCR denitrification reaction.

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