Preparation method and system of ammonia for denitration reaction

Abstract

The invention belongs to the field of industrial gas purification, denitration and environmental protection, and discloses a preparation method and system of ammonia for denitration reaction. The method comprises the following steps: heating liquid ammonia for a denitration reaction through a heat source until the liquid ammonia is gasified to obtain ammonia for the denitration reaction, the heat source is flue gas and / or hot air in a device served by the denitration reaction; a device served by the denitration reaction comprises an industrial furnace, an industrial furnace outlet flue, an air preheater and a smoke exhaust chimney; a device for carrying out the denitration reaction is an SCR (Selective Catalytic Reduction) reactor. On the premise of not additionally adding a heat source, the existing heat source of the device served by the denitration reaction is utilized to heat and gasify the liquid ammonia, so that the ammonia gas required by the denitration reaction is provided.

Description

Technical Field

[0001] The present invention belongs to the field of industrial gas purification, denitration and environmental protection, and more specifically, relates to a method and system for preparing ammonia for denitration reaction. Background Art

[0002] Nitrogen oxides are one of the main sources of air pollution. x There are many types: N2O, NO, NO2, N2O3, N2O4 and N2O5, among which NO and NO2 are important air pollutants. NO is generated in the production process in many industrial fields such as electricity, petrochemicals, and steel. x Its main production mechanism is combustion. Under high temperature combustion conditions, NO x Mainly in the form of NO, the initial emission of NO x NO accounts for about 95% of the total gas. When NO is directly discharged into the atmosphere, a series of reactions will occur, which will eventually affect the environment. First, NO in the atmosphere easily reacts with oxygen in the air to form NO2, which then further reacts with water molecules to form nitric acid (HNO3). In addition, NO x The concentration of NOx can also be increased by the gradual accumulation of exhaust gas emitted by aircraft in the stratosphere. x It then reacts with O3 in the stratosphere, causing the depletion of the O3 layer.

[0003] The two most common denitrification reactions are selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR). SNCR is often used as a supplementary treatment method for low-nitrogen combustion technology because it is affected by industrial furnace temperature and denitrification efficiency. SCR technology is the most mature flue gas denitrification technology. It uses a reducing agent (NH3, urea) to selectively react with NO under the action of a metal catalyst. x A post-furnace denitrification method that reacts to produce N2 and H2O.

[0004] Due to the advantage of easy transportation and storage of NH3 after liquefaction, the ammonia used in SCR technology is usually liquid ammonia. Before the SCR reaction, the liquid ammonia needs to be heated and evaporated again to become gaseous ammonia and passed into the SCR reactor. This process generally requires a heater, an air inlet, a blower and an evaporator to heat and evaporate the liquid ammonia. Since the SCR reaction is a post-furnace reaction, the industrial furnace it serves has many existing heat sources. Therefore, whether the existing heat sources can be used to heat and evaporate the liquid ammonia has become a research focus. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies of the prior art and to provide a method and system for preparing ammonia for denitration reaction. The present invention achieves heating and gasification of liquid ammonia by utilizing the existing heat source of the device served by the denitration reaction without adding an additional heat source, thereby providing ammonia gas required for the denitration reaction.

[0006] In order to achieve the above object, the first aspect of the present invention provides a method for preparing ammonia for denitration reaction, the method comprising heating liquid ammonia for denitration reaction by a heat source until it is gasified to obtain the ammonia for denitration reaction;

[0007] The heat source is flue gas and / or hot air in the device serving the denitration reaction;

[0008] The devices served by the denitration reaction include an industrial furnace, an industrial furnace outlet flue, an air preheater and a smoke exhaust chimney; the device for performing the denitration reaction is an SCR reactor.

[0009] In the present invention, the liquid ammonia can be heated and gasified by one or more existing heat sources according to the temperature of the existing heat source and the required amount of liquid ammonia, such as at least one of the flue gas from an industrial furnace, the flue gas from an industrial furnace outlet flue, the hot air from an air preheater and the flue gas from an exhaust chimney.

[0010] According to the present invention, preferably, the industrial furnace includes a radiation section and a convection section; the air preheater is used to realize heat exchange between cold air and flue gas obtained after denitration reaction, and the air preheater is provided with a hot air outlet, a cold air inlet, a cold flue gas outlet and a denitration reaction flue gas inlet; the hot air outlet is connected to the burner arranged in the radiation section through a hot air duct; the radiation section, the convection section, the industrial furnace outlet flue, the inlet of the SCR reactor, the outlet of the SCR reactor, the denitration reaction flue gas inlet, the cold flue gas outlet, the induced draft fan and the exhaust chimney are connected in sequence;

[0011] The cold air inlet is connected to the cold air suction device through a blower.

[0012] According to the present invention, preferably, the method comprises: arranging a heat exchange coil in at least one of the radiation section, the convection section, the industrial furnace outlet flue, the smoke exhaust chimney and the hot air duct; exchanging heat between the liquid ammonia for denitration reaction and the flue gas in at least one of the radiation section, the convection section, the industrial furnace outlet flue and the smoke exhaust chimney and / or the hot air in the hot air duct, and the liquid ammonia for denitration reaction is heated and gasified to obtain the ammonia for denitration reaction;

[0013] The ammonia used for the denitration reaction and air are mixed in a mixer, and the concentration of the ammonia used for the denitration reaction is diluted by air to obtain gaseous mixed ammonia and send it to the SCR reactor to participate in the denitration reaction.

[0014] According to the present invention, preferably, the concentration of ammonia used for the denitration reaction is diluted to 4-6% by air.

[0015] According to the present invention, preferably, the heat exchange method can be changed according to the temperature of the flue gas and / or hot air in the device served by the denitration reaction and the required amount of liquid ammonia, and tubular countercurrent heat exchange is preferred.

[0016] According to the present invention, preferably, the heat exchange coil is at least one set; preferably, the heat exchange coil is two sets, and an interlocking control device is arranged between the two sets of heat exchange coils; the interlocking control device comprises a pressure gauge, a first temperature gauge, a second temperature gauge and a valve assembly;

[0017] The pressure gauge is used to monitor the pressure of the liquid ammonia for denitration reaction entering the inlet of the first set of heat exchange coils, and then determine the vaporization temperature of the liquid ammonia for denitration reaction;

[0018] The temperature meter 1 and the temperature meter 2 are used to monitor the outlet temperature of the logistics at the outlet of the first set of heat exchange coils and the outlet of the second set of heat exchange coils respectively;

[0019] When the outlet temperature of the logistics at the outlet of the first set of heat exchange coils does not reach the vaporization temperature, the valve assembly can be controlled to allow the logistics at the outlet of the first set of heat exchange coils to enter the second set of heat exchange coils for continued heating.

[0020] According to the present invention, preferably, the method comprises: while allowing the liquid ammonia for denitration reaction to enter the upstream flue of the inlet of the SCR reactor, atomizing the liquid ammonia for denitration reaction to obtain atomized liquid ammonia; allowing the atomized liquid ammonia to absorb the heat of the flue gas in the upstream flue and gasify to obtain the ammonia for denitration reaction and mixing it with the flue gas in the upstream flue to enter the SCR reactor;

[0021] Preferably, the position where the liquid ammonia for denitration reaction enters the upstream flue is not less than 1 meter away from the inlet of the SCR reactor.

[0022] According to the present invention, preferably, the method comprises: the hot air at the hot air outlet is divided into two paths, one path is sent into the burner through a hot air pipe; and the other path is mixed with the liquid ammonia for denitration reaction, so that the liquid ammonia for denitration reaction is diluted and gasified by heat at the same time, to obtain the ammonia for denitration reaction, and sent to the SCR reactor to participate in the denitration reaction.

[0023] A second aspect of the present invention provides a system for preparing ammonia for denitration reaction, the system being used to implement the method described, the system comprising a liquid ammonia storage tank, the SCR reactor, the industrial furnace, the industrial furnace outlet flue, the air preheater and the exhaust chimney;

[0024] The system also includes a heat exchange coil, a mixer and a dilution air delivery device;

[0025] The heat exchange coil is arranged in at least one of the radiation section, the convection section, the industrial furnace outlet flue and the hot air duct; the inlet of the heat exchange coil is connected to the liquid ammonia storage tank, and the outlet of the heat exchange coil and the dilution air conveying device are simultaneously connected to the inlet of the mixer; the outlet of the mixer is connected to the inlet of the SCR reactor;

[0026] Alternatively, the heat exchange coil is arranged in the smoke exhaust chimney; the inlet of the heat exchange coil is connected to the liquid ammonia storage tank through a pressure reducing valve, and the outlet of the heat exchange coil and the dilution air conveying device are simultaneously connected to the inlet of the mixer; the outlet of the mixer is connected to the inlet of the SCR reactor.

[0027] In the present invention, the method and system of the present invention can achieve the effect of heating and gasifying liquid ammonia by introducing heat exchange coils at appropriate positions without changing the basic working principle and function of the original industrial furnace device.

[0028] According to the present invention, preferably, the heat exchange coil is at least one set; preferably, the heat exchange coil is two sets, and an interlocking control device is arranged between the two sets of heat exchange coils; the interlocking control device comprises a pressure gauge, a temperature gauge 1, a temperature gauge 2 and a valve assembly, and the valve assembly comprises a valve 1, a valve 2 and a valve 3;

[0029] The inlet of the first set of heat exchange coils is connected to the liquid ammonia storage tank, and the pressure gauge is arranged at the inlet of the first set of heat exchange coils; the temperature gauge 1 and the temperature gauge 2 are arranged at the outlet of the first set of heat exchange coils and the outlet of the second set of heat exchange coils respectively;

[0030] The outlet of the first set of heat exchange coils is divided into two paths, one path is connected to the inlet of the mixer through the valve one, and the other path is connected to the inlet of the second set of heat exchange coils through the valve two; the outlet of the second set of heat exchange coils is connected to the inlet of the mixer through the valve three.

[0031] In the present invention, if Figure 4As shown, before the liquid ammonia is introduced into the flue at the outlet of the industrial furnace, a pressure gauge 70 is provided to monitor the pressure of the liquid ammonia, thereby determining the vaporization temperature of the liquid ammonia used in the denitration reaction. The first set of heat exchange coils 81 is first heated in the flue at the outlet of the industrial furnace. When the temperature gauge 1 30 at the outlet of the first heating loop 90 has reached the vaporization temperature, the valve 150 is in an open state, and the valves 2 51 and 3 52 are in a closed state, that is, the second heating loop 91 is closed. At this point, the liquid ammonia is transformed from liquid ammonia to gaseous ammonia under the heating of the first heating loop. In the present invention, the area of ​​the heat exchange coil in the flue at the outlet of the industrial furnace should be much larger than the area required for ammonia to be heated to the vaporization temperature. When special circumstances occur, the first and second heating loops can be used to heat together to ensure that the required ammonia is heated to the vaporization temperature. For example, when the temperature detected by the thermometer 1 is lower than the vaporization temperature, the valve 1 50 is in a closed state, and the valves 2 51 and 3 53 are in an open state, so as to ensure that the liquid ammonia continues to enter the second heating loop for heating after being heated by the first heating loop. When the temperature detected by the thermometer 2 40 of the second-stage heating circuit reaches the vaporization temperature, the liquid ammonia has been converted into gaseous ammonia.

[0032] As a preferred solution, in the system of the present invention, the pressure gauge 70, the temperature gauge 1 30, and the temperature gauge 2 40 are interlocked, and the interlocking control is realized: when the temperature gauge 1 of the first stage heating circuit exceeds the vaporization temperature, valve 1 is opened, and valves 2 and 3 are closed. When the temperature gauge 1 of the first stage heating circuit is lower than the vaporization temperature, valve 1 is closed, and valves 2 and 3 are opened; when the temperature gauge 2 of the second stage heating circuit is also lower than the vaporization temperature in extremely special circumstances, valves 1, 2, and 3 are all closed. Since the area of ​​the heat exchange coil far exceeds the required heating area, the interlocking valves 1, 2, and 3 are all closed only when the device served by the denitrification reaction fails.

[0033] The third aspect of the present invention provides a system for preparing ammonia for denitration reaction, the system is used to implement the method, the system comprises a liquid ammonia storage tank, the SCR reactor, the industrial furnace, the industrial furnace outlet flue, the air preheater and the exhaust chimney;

[0034] The system further comprises an atomizing device, the inlet of which is connected to the liquid ammonia storage tank;

[0035] The outlet of the atomizing device is arranged on the flue upstream of the inlet of the SCR reactor. Preferably, the atomizing device is at least one atomizing nozzle;

[0036] Preferably, the outlet of the atomizing device is arranged on the upstream flue of the inlet of the SCR reactor at a distance of not less than 1 meter from the inlet of the SCR reactor.

[0037] A fourth aspect of the present invention provides a system for preparing ammonia for denitration reaction, the system being used to implement the method, the system comprising a liquid ammonia storage tank, the SCR reactor, the industrial furnace, the industrial furnace outlet flue, the air preheater and the exhaust chimney;

[0038] The system also includes a mixer;

[0039] The hot air outlet is divided into two paths, one of which is connected to the inlet of the mixer at the same time as the liquid ammonia storage tank; the outlet of the mixer is connected to the inlet of the SCR reactor.

[0040] The beneficial effects of the technical solution of the present invention are as follows:

[0041] 1. The present invention can save the process and equipment used for liquid ammonia heating, gasification and dilution and mixing in the traditional denitration reaction, thereby further saving the safety valve and ammonia discharge and absorption device, saving investment and land occupation;

[0042] 2. The present invention can realize the heating and gasification of liquid ammonia without adding additional heat sources and devices. On the one hand, it eliminates the supporting devices for heating and evaporating liquid ammonia in the traditional denitration reaction (such as heaters, air inlets, blowers and evaporators), and on the other hand, it further improves the utilization efficiency of thermal energy;

[0043] 3. The present invention can provide an ammonia source for the denitration reaction through simple modification without changing the principle and use effect of the existing device. In addition, the present invention can be widely applied to a variety of devices to meet the ammonia preparation needs under different working conditions;

[0044] 4. The present invention will improve the efficiency of heat utilization in the overall process and avoid waste of heat energy.

[0045] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0047] Figure 1 A schematic diagram of a traditional denitration reaction system provided in Comparative Example 1 of the present invention is shown.

[0048] Figure 2 A schematic diagram of a system for preparing ammonia for denitration reaction provided in Example 1 of the present invention is shown.

[0049] Figure 3A schematic diagram of a system for preparing ammonia for denitration reaction provided in Example 5 of the present invention is shown.

[0050] Figure 4 A schematic diagram showing the interlocking control between two sets of heat exchange coils of an ammonia preparation system for denitration reaction provided by the present invention is shown.

[0051] The following are the descriptions of the reference numerals:

[0052] 1 liquid ammonia storage tank, 2 mixer, 3 SCR reactor, 4 industrial furnace, 5 exhaust chimney, 6 air preheater, 7 blower, 8 cold air suction device, 9 induced draft fan, 10 evaporator, 11 heater, 12 pressure reducing valve, 14 industrial furnace outlet flue, 15 heat exchange coil, 16 hot air outlet, 17 cold air inlet, 18 cold flue gas outlet, 19 denitrification reaction flue gas inlet, 20 hot air duct, 21 dilution air blower, 22 dilution air suction port, 23 heating air blower, 24 heating air suction port, 30 temperature gauge 1, 40 temperature gauge 2, 50 valve 1, 51 valve 2, 52 valve 3, 60 interlock control, 70 pressure gauge, 81 the first set of heat exchange coils, 82 the second set of heat exchange coils, 90 the first stage heating circuit, 91 the second stage heating circuit, 92 gaseous ammonia, 93 liquid ammonia, 94 flue gas. DETAILED DESCRIPTION

[0053] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0054] Example 1

[0055] This embodiment provides a system for preparing ammonia for denitration reaction, such as Figure 2 As shown, the system includes a liquid ammonia storage tank 1, an SCR reactor 3, an industrial furnace 4, an industrial furnace outlet flue 14, an air preheater 6 and a smoke exhaust chimney 5; the system also includes a heat exchange coil 15, a mixer 2 and a dilution air delivery device;

[0056] The industrial furnace 4 includes a radiation section and a convection section; the air preheater 6 is used to realize heat exchange between cold air and the flue gas obtained after the denitration reaction, and the air preheater 6 is provided with a hot air outlet 16, a cold air inlet 17, a cold flue gas outlet 18 and a denitration reaction flue gas inlet 19; the hot air outlet 16 is connected to the burner arranged in the radiation section through a hot air duct 20; the radiation section, the convection section, the industrial furnace outlet flue 14, the inlet of the SCR reactor 3, the outlet of the SCR reactor 3, the denitration reaction flue gas inlet 19, the cold flue gas outlet 18, the induced draft fan 9 and the exhaust chimney 5 are connected in sequence; the cold air inlet 17 is connected to the cold air suction device 8 through the blower 7.

[0057] The heat exchange coil 15 is arranged in the flue 14 at the outlet of the industrial furnace; the inlet of the heat exchange coil 15 is connected to the liquid ammonia storage tank 1, and the outlet of the heat exchange coil 15 and the dilution air delivery device are simultaneously connected to the inlet of the mixer 2; the outlet of the mixer 2 is connected to the inlet of the SCR reactor 3. The dilution air delivery device includes a dilution air blower 21 and a dilution air suction port 22, and the dilution air suction port 22 is connected to the inlet of the mixer 2 through the dilution air blower 21;

[0058] The method for preparing ammonia for denitration reaction using the above system includes: arranging a heat exchange coil 15 in the flue 14 at the outlet of the industrial furnace; performing tubular countercurrent heat exchange between the liquid ammonia for denitration reaction (pressure of 2.16 MPa and temperature of 20° C.) from the liquid ammonia storage tank 1 and the flue gas (420° C.) in the flue 14 at the outlet of the industrial furnace, wherein the liquid ammonia is transported to the heat exchange coil 15 in the flue 14 at the outlet of the industrial furnace by the pressure of the liquid ammonia storage tank 1 itself, the liquid ammonia for denitration reaction is heated (heated to 120° C.) and gasified to form gaseous ammonia to obtain the ammonia for denitration reaction, and the temperature of the flue gas in the flue 14 at the outlet of the industrial furnace is reduced to 410° C.;

[0059] The ammonia used for the denitration reaction and air are mixed in the mixer 2, and the concentration of the ammonia used for the denitration reaction is diluted to 5% by air to obtain gaseous mixed ammonia and send it to the SCR reactor 3 to participate in the denitration reaction.

[0060] Example 2

[0061] This embodiment provides a system for preparing ammonia for denitration reaction. The difference between this embodiment and embodiment 1 is only that:

[0062] The heat exchange coil 15 is disposed in the hot air duct 20 .

[0063] Example 3

[0064] This embodiment provides an ammonia preparation system for denitration reaction, comprising a liquid ammonia storage tank 1, the SCR reactor 3, the industrial furnace 4, the industrial furnace outlet flue 14, the air preheater 6 and the exhaust chimney 5; the system also includes an atomizing device;

[0065] The industrial furnace 4 includes a radiation section and a convection section; the air preheater 6 is used to realize heat exchange between cold air and the flue gas obtained after the denitration reaction, and the air preheater 6 is provided with a hot air outlet 16, a cold air inlet 17, a cold flue gas outlet 18 and a denitration reaction flue gas inlet 19; the hot air outlet 16 is connected to the burner arranged in the radiation section through a hot air duct 20; the radiation section, the convection section, the industrial furnace outlet flue 14, the inlet of the SCR reactor 3, the outlet of the SCR reactor 3, the denitration reaction flue gas inlet 19, the cold flue gas outlet 18, the induced draft fan 9 and the exhaust chimney 5 are connected in sequence; the cold air inlet 17 is connected to the cold air suction device 8 through the blower 7.

[0066] The inlet of the atomizing device is connected to the liquid ammonia storage tank 1;

[0067] The outlet of the atomizing device is arranged on the upstream flue of the inlet of the SCR reactor 3, and the atomizing device is an atomizing nozzle;

[0068] The outlet of the atomizing device is arranged on the upstream flue of the inlet of the SCR reactor 3 at a distance of not less than 1 meter from the inlet of the SCR reactor.

[0069] The method for preparing ammonia for denitration reaction using the above system includes: allowing the liquid ammonia for denitration reaction to enter the upstream flue of the inlet of the SCR reactor and atomizing the liquid ammonia for denitration reaction to obtain atomized liquid ammonia; allowing the atomized liquid ammonia to absorb the heat of the flue gas in the upstream flue and vaporize, further increasing the mixing uniformity, achieving the heating, evaporation and dilution of liquid ammonia, obtaining the ammonia for denitration reaction and mixing it with the flue gas in the upstream flue to enter the SCR reactor 3.

[0070] Example 4

[0071] This embodiment provides an ammonia preparation system for denitration reaction, comprising a liquid ammonia storage tank 1, an SCR reactor 3, an industrial furnace 4, an industrial furnace outlet flue 14, an air preheater 6 and a smoke exhaust chimney 5; and also comprising a mixer 2;

[0072] The industrial furnace 4 includes a radiation section and a convection section; the air preheater 6 is used to realize heat exchange between cold air and the flue gas obtained after the denitration reaction, and the air preheater 6 is provided with a hot air outlet 16, a cold air inlet 17, a cold flue gas outlet 18 and a denitration reaction flue gas inlet 19; the hot air outlet 16 is divided into two paths, one of which is connected to the burner arranged in the radiation section through a hot air duct 20; the radiation section, the convection section, the industrial furnace outlet flue 14, the inlet of the SCR reactor 3, the outlet of the SCR reactor 3, the denitration reaction flue gas inlet 19, the cold flue gas outlet 18, the induced draft fan 9 and the exhaust chimney 5 are connected in sequence; the cold air inlet 17 is connected to the cold air suction device 8 through the blower 7.

[0073] The other route of the hot air outlet 16 and the liquid ammonia storage tank 1 are simultaneously connected to the inlet of the mixer 2 ; the outlet of the mixer 2 is connected to the inlet of the SCR reactor 3 .

[0074] The method for preparing ammonia for denitration reaction using the above system includes: the hot air from the hot air outlet 16 is divided into two paths, one path is sent into the burner through the hot air pipe 20; the other path is mixed with the liquid ammonia for denitration reaction, so that the liquid ammonia for denitration reaction is diluted and gasified by heat, to obtain the ammonia for denitration reaction, and sent to the SCR reactor 3 to participate in the denitration reaction.

[0075] Example 5

[0076] This embodiment provides a system for preparing ammonia for denitration reaction, such as Figure 3 As shown, the difference between this embodiment and embodiment 1 is only that:

[0077] The heat exchange coil 15 is arranged in the smoke exhaust chimney 5 , and the inlet of the heat exchange coil is connected to the liquid ammonia storage tank 1 through a pressure reducing valve 12 .

[0078] The method for preparing ammonia for denitration reaction using the above system includes: arranging a heat exchange coil 15 in the exhaust chimney; reducing the pressure of liquid ammonia for denitration reaction (pressure is 2.16MPa, temperature is 20°C) from the liquid ammonia storage tank 1 to 1MPa through a pressure reducing valve 12, and then performing tubular countercurrent heat exchange with the flue gas in the exhaust chimney 5 (the exhaust flue gas cooled by the air preheater 6, temperature is 110°C), wherein the liquid ammonia for denitration reaction is heated (heated to 60°C) and gasified to form gaseous ammonia to obtain the ammonia for denitration reaction, and the temperature of the flue gas in the exhaust chimney 5 is reduced to 95°C;

[0079] The ammonia used for the denitration reaction and air are mixed in the mixer 2, and the concentration of the ammonia used for the denitration reaction is diluted to 5% by air to obtain gaseous mixed ammonia and send it to the SCR reactor to participate in the denitration reaction.

[0080] Comparative Example 1

[0081] This comparative example provides a conventional denitration reaction system, such as Figure 1 As shown, the system includes a liquid ammonia storage tank 1, a heater 11, an evaporator 10, a mixer 2, a heating air blower 23, a heating air suction port 24, a dilution air blower 21, a dilution air suction port 22, an SCR reactor 3, an industrial furnace 4, an industrial furnace outlet flue 14, an air preheater 6 and a smoke exhaust chimney 5;

[0082] The industrial furnace 4 includes a radiation section and a convection section; the air preheater 6 is used to realize heat exchange between cold air and the flue gas obtained after the denitration reaction, and the air preheater 6 is provided with a hot air outlet 16, a cold air inlet 17, a cold flue gas outlet 18 and a denitration reaction flue gas inlet 19; the hot air outlet 16 is connected to the burner arranged in the radiation section through a hot air duct 20; the radiation section, the convection section, the industrial furnace outlet flue 14, the inlet of the SCR reactor 3, the outlet of the SCR reactor 3, the denitration reaction flue gas inlet 19, the cold flue gas outlet 18, the induced draft fan 9 and the exhaust chimney 5 are connected in sequence; the cold air inlet 17 is connected to the cold air suction device 8 through the blower 7.

[0083] The liquid ammonia storage tank 1 is connected to the evaporator 10. The liquid ammonia exchanges heat with the ambient air heated by the heater in the evaporator 10. The liquid ammonia is heated to the vaporization temperature and vaporized into gaseous ammonia. The gaseous ammonia then enters the mixer 2 and mixes with the ambient air from the dilution air blower 21. Generally, the gaseous ammonia is diluted to a concentration of less than 5% and then enters the SCR reactor 3 for denitration reaction. In the flue gas process, the high-temperature hot flue gas generated by the industrial furnace 4 enters the SCR reactor 3 through the industrial furnace outlet flue 14 and undergoes a denitration reaction with ammonia under the action of a catalyst. The high-temperature hot flue gas after denitration enters the air preheater 6 for heat exchange with the air, and the cold flue gas is discharged through the smoke exhaust chimney 5. The air heated by the high-temperature hot flue gas after denitration enters the industrial furnace 4 through the hot air duct 20 as combustion air.

[0084] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for preparing ammonia for denitration reaction, characterized in that: The method comprises heating liquid ammonia for denitration reaction by a heat source until it is gasified to obtain the ammonia for denitration reaction; The heat source is flue gas and / or hot air in the device serving the denitration reaction; The devices served by the denitration reaction include an industrial furnace, an industrial furnace outlet flue, an air preheater and a smoke exhaust chimney; the device for performing the denitration reaction is an SCR reactor.

2. The method for preparing ammonia for denitration reaction according to claim 1, wherein: The industrial furnace includes a radiation section and a convection section; the air preheater is used to realize heat exchange between cold air and flue gas obtained after denitration reaction, and the air preheater is provided with a hot air outlet, a cold air inlet, a cold flue gas outlet and a denitration reaction flue gas inlet; the hot air outlet is connected to the burner arranged in the radiation section through a hot air duct; the radiation section, the convection section, the industrial furnace outlet flue, the inlet of the SCR reactor, the outlet of the SCR reactor, the denitration reaction flue gas inlet, the cold flue gas outlet, the induced draft fan and the exhaust chimney are connected in sequence; The cold air inlet is connected to the cold air suction device through a blower.

3. The method for preparing ammonia for denitration reaction according to claim 2, wherein: The method comprises: arranging a heat exchange coil in at least one of the radiation section, the convection section, the industrial furnace outlet flue, the smoke exhaust chimney and the hot air duct; exchanging heat between liquid ammonia for denitration reaction and flue gas in at least one of the radiation section, the convection section, the industrial furnace outlet flue and the smoke exhaust chimney and / or hot air in the hot air duct, and the liquid ammonia for denitration reaction is heated and gasified to obtain the ammonia for denitration reaction; The ammonia used for the denitration reaction and air are mixed in a mixer, and the concentration of the ammonia used for the denitration reaction is diluted by air to obtain gaseous mixed ammonia and send it to the SCR reactor to participate in the denitration reaction.

4. The method for preparing ammonia for denitration reaction according to claim 3, wherein: Diluting the concentration of ammonia used for denitration reaction to 4-6% by air; The heat exchange method is tubular countercurrent heat exchange; The heat exchange coil is at least one set; preferably, the heat exchange coil is two sets, and an interlocking control device is arranged between the two sets of heat exchange coils; the interlocking control device includes a pressure gauge, a first temperature gauge, a second temperature gauge and a valve assembly; The pressure gauge is used to monitor the pressure of the liquid ammonia for denitration reaction entering the inlet of the first set of heat exchange coils, and then determine the vaporization temperature of the liquid ammonia for denitration reaction; The temperature meter 1 and the temperature meter 2 are used to monitor the outlet temperature of the logistics at the outlet of the first set of heat exchange coils and the outlet of the second set of heat exchange coils respectively; When the outlet temperature of the logistics at the outlet of the first set of heat exchange coils does not reach the vaporization temperature, the valve assembly can be controlled to allow the logistics at the outlet of the first set of heat exchange coils to enter the second set of heat exchange coils for continued heating.

5. The method for preparing ammonia for denitration reaction according to claim 2, wherein: The method comprises: allowing the liquid ammonia for denitration reaction to enter the upstream flue of the inlet of the SCR reactor and atomizing the liquid ammonia for denitration reaction to obtain atomized liquid ammonia; allowing the atomized liquid ammonia to absorb the heat of the flue gas in the upstream flue and gasify to obtain the ammonia for denitration reaction and mix it with the flue gas in the upstream flue to enter the SCR reactor; Preferably, the position where the liquid ammonia for denitration reaction enters the upstream flue is not less than 1 meter away from the inlet of the SCR reactor.

6. The method for preparing ammonia for denitration reaction according to claim 2, wherein: The method comprises: the hot air at the hot air outlet is divided into two paths, one path is sent into the burner through a hot air pipeline; the other path is mixed with the liquid ammonia for denitration reaction, so that the liquid ammonia for denitration reaction is diluted and gasified by heat, so as to obtain the ammonia for denitration reaction, and the ammonia is sent into the SCR reactor to participate in the denitration reaction.

7. A system for preparing ammonia for denitration reaction, characterized in that: The system is used to implement the method described in any one of claims 1 to 4, and the system comprises a liquid ammonia storage tank, the SCR reactor, the industrial furnace, the industrial furnace outlet flue, the air preheater and the smoke exhaust chimney; The system also includes a heat exchange coil, a mixer and a dilution air delivery device; The heat exchange coil is arranged in at least one of the radiation section, the convection section, the industrial furnace outlet flue and the hot air duct; the inlet of the heat exchange coil is connected to the liquid ammonia storage tank, and the outlet of the heat exchange coil and the dilution air conveying device are simultaneously connected to the inlet of the mixer; the outlet of the mixer is connected to the inlet of the SCR reactor; Alternatively, the heat exchange coil is arranged in the smoke exhaust chimney; the inlet of the heat exchange coil is connected to the liquid ammonia storage tank through a pressure reducing valve, and the outlet of the heat exchange coil and the dilution air conveying device are simultaneously connected to the inlet of the mixer; the outlet of the mixer is connected to the inlet of the SCR reactor.

8. The system for preparing ammonia for denitration reaction according to claim 7, wherein: The heat exchange coil is at least one set; preferably, the heat exchange coil is two sets, and an interlocking control device is arranged between the two sets of heat exchange coils; the interlocking control device comprises a pressure gauge, a temperature gauge 1, a temperature gauge 2 and a valve assembly, and the valve assembly comprises a valve 1, a valve 2 and a valve 3; The inlet of the first set of heat exchange coils is connected to the liquid ammonia storage tank, and the pressure gauge is arranged at the inlet of the first set of heat exchange coils; the temperature gauge 1 and the temperature gauge 2 are arranged at the outlet of the first set of heat exchange coils and the outlet of the second set of heat exchange coils respectively; The outlet of the first set of heat exchange coils is divided into two paths, one path is connected to the inlet of the mixer through the valve one, and the other path is connected to the inlet of the second set of heat exchange coils through the valve two; the outlet of the second set of heat exchange coils is connected to the inlet of the mixer through the valve three.

9. A system for preparing ammonia for denitration reaction, characterized in that: The system is used to implement the method described in claim 1, 2 or 5, and the system comprises a liquid ammonia storage tank, the SCR reactor, the industrial furnace, the industrial furnace outlet flue, the air preheater and the smoke exhaust chimney; The system further comprises an atomizing device, the inlet of which is connected to the liquid ammonia storage tank; The outlet of the atomizing device is arranged on the flue upstream of the inlet of the SCR reactor. Preferably, the atomizing device is at least one atomizing nozzle; Preferably, the outlet of the atomizing device is arranged on the upstream flue of the inlet of the SCR reactor at a distance of not less than 1 meter from the inlet of the SCR reactor.

10. A system for preparing ammonia for denitration reaction, characterized in that: The system is used to implement the method described in claim 1, 2 or 6, and the system comprises a liquid ammonia storage tank, the SCR reactor, the industrial furnace, the industrial furnace outlet flue, the air preheater and the smoke exhaust chimney; The system also includes a mixer; The hot air outlet is divided into two paths, one of which is connected to the inlet of the mixer at the same time as the liquid ammonia storage tank; the outlet of the mixer is connected to the inlet of the SCR reactor.

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