Liquid nitrogen washing tail gas graded oxygen regulation explosion-proof and resource utilization system and method

Abstract

The present invention provides a liquid nitrogen-washed tail gas graded oxygen regulation explosion-proof and resource utilization system and method, which relates to the field of environmental protection and energy utilization technology. The system provided by the present invention includes: a multi-stage catalytic burner, the multi-stage catalytic burner is divided into a first-stage catalytic combustion zone, a second-stage catalytic combustion zone and a third-stage catalytic combustion zone, the first-stage catalytic combustion zone and the second-stage catalytic combustion zone are filled with multiple layers of catalysts arranged at intervals, and an air guide tube is arranged above each layer of catalyst; a first-stage heat exchanger connected to the first-stage catalytic combustion zone; a second-stage heat exchanger connected to the second-stage catalytic combustion zone; a coal grinding and drying section connected to the second-stage heat exchanger; and a boiler section connected to the third-stage catalytic combustion zone. The present invention improves the circulation and oxygen intake mode of flue gas, which can not only more efficiently utilize and recover heat, greatly improve the heat utilization rate, but also avoid the uneven mixing of liquid nitrogen-washed tail gas with air to prevent explosion; and can avoid the risk of spontaneous combustion of dry coal powder.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental protection and energy utilization, and in particular to a liquid nitrogen washing tail gas graded oxygen regulation explosion-proof and resource utilization system and method. Background Art

[0002] The process of using pulverized coal gasification to produce synthetic ammonia accounts for an increasing proportion in coal-to-synthetic ammonia. However, in the process of removing CO from the syngas after the shift, liquid nitrogen is used as an absorbent to wash the shift gas. CO and CH4 in the shift gas will be absorbed by liquid nitrogen, and the gas discharged in gaseous form after cold recovery is called liquid nitrogen washed tail gas. The liquid nitrogen washed tail gas contains CH4, CO, H2 and N2, and the gas composition is clean. The composition of the liquid nitrogen washed tail gas is shown in Table 1.

[0003] Table 1 Liquid nitrogen washing tail gas composition

[0004] <![CDATA[H2 content Vol%]]> <![CDATA[Volume percentage of N2]]> CO content Vol% <![CDATA[CH4 content Vol%]]> 1.6～1.9 80～85 3～8 0～0.4

[0005] From Table 1, we can see that the liquid nitrogen washing tail gas contains three kinds of combustible gases: H2, CH4 and CO, with a calorific value of 1200-2250 kJ / m 3 .

[0006] Liquid nitrogen washing tail gas cannot be used directly because of its low calorific value. In order to meet environmental protection requirements, a few companies send liquid nitrogen washing tail gas into thermal power boilers for mixing and burning. However, the temperature of liquid nitrogen washing tail gas is much lower than that of the boiler. Directly introducing it into the boiler will take away the heat of the boiler and increase the power consumption of the fan. Not only is the heat not recovered, but the thermal efficiency of the boiler is also reduced. Therefore, most companies directly discharge liquid nitrogen washing tail gas, which not only pollutes the environment, but also wastes energy. In addition, in the pulverized coal gasification process, coal needs to undergo grinding, pulverizing and inert drying processes before gasification. Companies mainly use the high-temperature gas after the combustion of synthesis gas to mix with nitrogen and send it into the coal mill as a drying heat source. The consumption of synthesis gas is large and the process operation cost is high. To address this problem, the patent (CN201810666089.3) discloses a method and device for treating liquid nitrogen tail gas, which divides air into three sections (upper section, middle section and lower section), and mixes them with liquid nitrogen washing tail gas for catalytic combustion to produce low-pressure steam, thereby realizing resource utilization of waste gas; however, it has been found through practice that this method of treating liquid nitrogen washing tail gas has great safety risks, because of the high temperature and large amount of air introduced, there is a great potential explosion hazard; and the patent can only produce low-pressure steam using the flue gas in the middle section, the economic value is too low, and the value of heat cannot be highlighted; the temperature of the flue gas at the outlet of the three sections of the patent is between 400 and 420°C, and there is a great safety hazard for use in coal grinding and drying, and the coal powder is in danger of spontaneous combustion. Summary of the invention

[0007] In view of this, the purpose of the present invention is to provide a liquid nitrogen washing tail gas graded oxygen regulation explosion prevention and resource recovery system and method. The system provided by the present invention can not only fully utilize and recycle the heat, greatly improving the heat utilization rate; it can also avoid the uneven mixing of liquid nitrogen washing tail gas with air to prevent explosion; and it can avoid the risk of spontaneous combustion of dry coal powder.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0009] The present invention provides a liquid nitrogen washing tail gas graded oxygen regulation explosion-proof and resource recovery system, comprising:

[0010] A multi-stage catalytic burner 1; the multi-stage catalytic burner 1 comprises a first catalytic combustion zone 1-1, a second catalytic combustion zone 1-2 and a third catalytic combustion zone 1-3 arranged from top to bottom; the first catalytic combustion zone 1-1 and the second catalytic combustion zone 1-2 are respectively filled with multiple layers of catalyst, the number of layers of the multiple layers of catalyst is ≥3 layers, and the multiple layers of catalyst are respectively arranged at intervals, and an air guide tube 6 is arranged above each layer of catalyst; the third catalytic combustion zone 1-3 is filled with a layer of catalyst, and an air guide tube 6 is arranged above the catalyst of the third catalytic combustion zone 1-3;

[0011] A heat exchanger 2 having a hot outlet 2-2 connected to the top inlet 1-1-1 of the first stage catalytic combustion zone 1-1; a cold inlet 2-1 of the first stage heat exchanger 2 is a liquid nitrogen tail gas inlet, and a hot inlet 2-3 of the first stage heat exchanger 2 is connected to the bottom outlet 1-1-2 of the first stage catalytic combustion zone 1-1; a cold outlet 2-4 of the first stage heat exchanger 2 is connected to the top inlet 1-2-1 of the second stage catalytic combustion zone 1-2;

[0012] A second-stage heat exchanger 3 whose hot inlet 3-3 is connected to the bottom outlet 1-2-2 of the second-stage catalytic combustion zone 1-2; a cold outlet 3-4 of the second-stage heat exchanger 3 is connected to the top inlet 1-3-1 of the third-stage catalytic combustion zone 1-3;

[0013] The low-temperature flue gas outlet 4-1 is connected to the cold inlet 3-1 of the second-stage heat exchanger 3, and a flue gas outlet 4-3 is provided between the low-temperature flue gas outlet 4-1 and the cold inlet 3-1; the hot flue gas inlet 4-2 of the coal-grinding drying section 4 is connected to the hot outlet 3-2 of the second-stage heat exchanger 3;

[0014] The boiler section 5 is connected with the bottom outlet 1-3-2 of the three-stage catalytic combustion zone 1-3 through the heating gas inlet 5-1-1, and the boiler section 5 includes a boiler 5-1 and a steam drum 5-2 connected with the boiler 5-1; the heating gas outlet 5-1-2 of the boiler 5-1 is connected with the hot flue gas inlet 4-2 of the coal grinding and drying section 4; the steam drum 5-2 is also provided with a soft water inlet 5-2-1 and a steam outlet 5-2-2.

[0015] Preferably, the bottom outlet 1 - 3 - 2 of the three-stage catalytic combustion zone 1 - 3 is also connected to the hot flue gas inlet 4 - 2 of the coal grinding and drying section 4 .

[0016] The present invention provides a liquid nitrogen washing tail gas graded oxygen regulation explosion-proof and resource recovery method, comprising the following steps:

[0017] (a) Liquid nitrogen-washed tail gas enters a heat exchanger 2 from a cold inlet 2-1, and exchanges heat with a section of high-temperature flue gas from a bottom outlet 1-1-2 of a catalytic combustion zone 1-1. After heat exchange, the liquid nitrogen-washed tail gas enters a top inlet 1-1-1 of a catalytic combustion zone 1-1 from a hot outlet 2-2, and performs a catalytic reaction layer by layer on the multi-layer catalysts arranged at intervals in the catalytic combustion zone 1-1, thereby obtaining a section of high-temperature flue gas. During the process of performing the catalytic reaction layer by layer, the liquid nitrogen-washed tail gas is respectively mixed with air from an air guide pipe 6 above each layer of catalyst, and the catalytic reaction is an oxygen-deficient reaction.

[0018] (b) The first stage high-temperature flue gas is discharged from the bottom outlet 1-1-2 of the first stage catalytic combustion zone 1-1, enters the first stage heat exchanger 2 through the hot inlet 2-3 for heat exchange, and after heat exchange, the first stage high-temperature flue gas enters the top inlet 1-2-1 of the second stage catalytic combustion zone 1-2 through the cold outlet 2-4 of the first stage heat exchanger 2, and performs a second stage catalytic reaction layer by layer on the multi-layer catalysts arranged at intervals in the second stage catalytic combustion zone 1-2 to obtain a second stage high-temperature flue gas; during the process of performing the second stage catalytic reaction layer by layer, the first stage high-temperature flue gas is respectively mixed with the air from the air guide pipe 6 above each layer of catalyst, and the second stage catalytic reaction is an oxygen-deficient reaction;

[0019] (c) The second stage high temperature flue gas is discharged from the bottom outlet 1-2-2 of the second stage catalytic combustion zone 1-2, enters the second stage heat exchanger 3 from the hot inlet 3-3, and exchanges heat with the low temperature flue gas discharged from the low temperature flue gas outlet 4-1 of the pulverized coal drying section 4 in the second stage heat exchanger 3. After heat exchange, the low temperature flue gas is discharged from the hot outlet 3-2 of the second stage heat exchanger 3 and enters the pulverized coal drying section 4 through the hot flue gas inlet 4-2. The low temperature flue gas is also partially discharged through the flue gas external outlet 4-3; after heat exchange, the second stage high temperature flue gas is discharged from the cold outlet 3-4 of the second stage heat exchanger 3 and enters the top inlet 1-3-1 of the third stage catalytic combustion zone 1-3, and performs a three-stage catalytic reaction on the catalyst of the third stage catalytic combustion zone 1-3 to obtain a three-stage high temperature flue gas; during the three-stage catalytic reaction, the second stage high temperature flue gas is mixed with the air from the air guide pipe 6 above the catalyst of the third stage catalytic combustion zone 1-3, and the three-stage catalytic reaction is an oxygen-enriched reaction;

[0020] (d) The three-stage high-temperature flue gas is discharged from the bottom outlet 1-3-2 of the three-stage catalytic combustion zone 1-3, enters the boiler 5-1 through the heating gas inlet 5-1-1, and transfers heat to the soft water in the steam drum 5-2 through the boiler 5-1, and the soft water is converted into medium-pressure steam for external use; after transferring heat, the three-stage high-temperature flue gas is discharged from the heating gas outlet 5-1-2 of the boiler 5-1, and enters the coal grinding and drying section 4 through the hot flue gas inlet 4-2.

[0021] Preferably, the three-stage high-temperature flue gas is discharged from the bottom outlet 1-3-2 of the three-stage catalytic combustion zone 1-3, and then enters the coal grinding and drying section 4 through the hot flue gas inlet 4-2.

[0022] Preferably, the volume content of O2 in the first stage catalytic reaction and the second stage catalytic reaction is independently 0.4-0.9%.

[0023] Preferably, the temperature of the high-temperature flue gas in step (a) is 450-480°C, and the temperature of the liquid nitrogen washed tail gas rises to 230-240°C after heat exchange.

[0024] Preferably, in step (b), the temperature of the first stage high-temperature flue gas after heat exchange is reduced to 220-240°C; the temperature of the second stage high-temperature flue gas is 450-480°C.

[0025] Preferably, in step (c), the temperature of the low-temperature flue gas is 90-100°C, and the temperature of the low-temperature flue gas after heat exchange rises to 150-180°C; the temperature of the second-stage high-temperature flue gas after heat exchange drops to 300-350°C; the temperature of the third-stage high-temperature flue gas is 550-650°C; the volume content of O2 in the three-stage catalytic reaction is 3-4%.

[0026] Preferably, in step (d), the temperature of the three sections of high-temperature flue gas drops to 250-300° C. after transferring heat.

[0027] Preferably, in the steps (c) and (d), the oxygen content in the coal grinding and drying section (4) is ≤3%, and the total content of CO and H2 is <200 ppm.

[0028] The present invention provides a liquid nitrogen washing tail gas staged oxygen regulation explosion-proof and resource utilization system. The system provided by the present invention is divided into a heat exchange part, a catalytic combustion part and a resource utilization part. The heat exchange part mainly preheats the liquid nitrogen washing tail gas in a first heat exchanger and the coal grinding and drying section gas in a second heat exchanger to increase the temperature; the catalytic combustion part is a multi-stage catalytic burner part, which can make the liquid nitrogen washing tail gas and the multi-stage air perform multi-stage catalytic combustion by splitting the air into multiple stages, thereby avoiding the situation that the liquid nitrogen washing tail gas is mixed with the air to produce unevenness and avoid the risk of explosion; the resource utilization part mainly utilizes the heat generated by each catalytic combustion zone through heat exchange, especially the high-temperature flue gas generated by the three-stage catalytic combustion zone can enter the boiler to transfer the heat to soft water to generate medium-pressure steam with high utilization value, and the flue gas after heat transfer can also enter the coal grinding and drying section to dry the coal powder, and the flue gas temperature after heat transfer is reduced, which can meet the requirements of coal powder drying and avoid the risk of coal powder spontaneous combustion when the high-temperature flue gas is drying the coal powder. The system provided by the present invention improves the circulation and oxygen intake of flue gas. The system is used to perform liquid nitrogen washing tail gas graded oxygen regulation explosion prevention and resource utilization, which can not only more efficiently utilize and recycle heat, greatly improve the heat utilization rate, but also avoid the situation where liquid nitrogen washing tail gas is mixed with air to produce unevenness, prevent explosion; and avoid the risk of spontaneous combustion of dry coal powder. The present invention turns liquid nitrogen washing tail gas into treasure, protects the environment, and achieves the effect of energy saving and emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of the liquid nitrogen washing tail gas graded oxygen regulation explosion-proof and resource utilization system provided by the present invention; Figure 1In the embodiment, 1-multi-stage catalytic burner, 1-1-one-stage catalytic combustion zone, 1-1-1-top inlet of one-stage catalytic combustion zone, 1-1-2-bottom outlet of one-stage catalytic combustion zone, 1-2-two-stage catalytic combustion zone, 1-2-1-top inlet of two-stage catalytic combustion zone, 1-2-2-bottom outlet of two-stage catalytic combustion zone, 1-3-three-stage catalytic combustion zone, 1-3-1-top inlet of three-stage catalytic combustion zone, 1-3-2-bottom outlet of three-stage catalytic combustion zone, 2-one-stage heat exchanger, 2-1-cold inlet of one-stage heat exchanger, 2-2-hot outlet of one-stage heat exchanger, 2-3-hot inlet of one-stage heat exchanger, 2-4 -cold outlet of the first stage heat exchanger, 3-second stage heat exchanger, 3-1-cold inlet of the second stage heat exchanger, 3-2-hot outlet of the second stage heat exchanger, 3-3-hot inlet of the second stage heat exchanger, 3-4-cold outlet of the second stage heat exchanger, 4-coal grinding and drying section, 4-1-low temperature flue gas outlet of the coal grinding and drying section, 4-2-hot flue gas inlet of the coal grinding and drying section, 4-3-flue gas outlet, 5-boiler section, 5-1-boiler, 5-1-1-heating gas inlet of the boiler section, 5-1-2-heating gas outlet of the boiler, 5-2-steam drum, 5-2-1-soft water inlet, 5-2-2-steam outlet, 6-air guide pipe, 7-flue gas guide plate. DETAILED DESCRIPTION

[0030] The present invention provides a liquid nitrogen washing tail gas graded oxygen regulation explosion-proof and resource recovery system, comprising:

[0031] A multi-stage catalytic burner 1; the multi-stage catalytic burner 1 comprises a first catalytic combustion zone 1-1, a second catalytic combustion zone 1-2 and a third catalytic combustion zone 1-3 arranged from top to bottom; the first catalytic combustion zone 1-1 and the second catalytic combustion zone 1-2 are both filled with multiple layers of catalyst, the number of layers of the multiple layers of catalyst is ≥3 layers, and the multiple layers of catalyst are arranged at intervals, and an air guide tube 6 is arranged above each layer of catalyst; the third catalytic combustion zone 1-3 is filled with a layer of catalyst, and an air guide tube 6 is arranged above the catalyst of the third catalytic combustion zone 1-3;

[0032] A heat exchanger 2 having a hot outlet 2-2 connected to the top inlet 1-1-1 of the first stage catalytic combustion zone 1-1; a cold inlet 2-1 of the first stage heat exchanger 2 is a liquid nitrogen tail gas inlet, and a hot inlet 2-3 of the first stage heat exchanger 2 is connected to the bottom outlet 1-1-2 of the first stage catalytic combustion zone 1-1; a cold outlet 2-4 of the first stage heat exchanger 2 is connected to the top inlet 1-2-1 of the second stage catalytic combustion zone 1-2;

[0033] A second-stage heat exchanger 3 whose hot inlet 3-3 is connected to the bottom outlet 1-2-2 of the second-stage catalytic combustion zone 1-2; a cold outlet 3-4 of the second-stage heat exchanger 3 is connected to the top inlet 1-3-1 of the third-stage catalytic combustion zone 1-3;

[0034] The low-temperature flue gas outlet 4-1 is connected to the cold inlet 3-1 of the second-stage heat exchanger 3, and a flue gas outlet 4-3 is provided between the low-temperature flue gas outlet 4-1 and the cold inlet 3-1; the hot flue gas inlet 4-2 of the coal-grinding drying section 4 is connected to the hot outlet 3-2 of the second-stage heat exchanger 3;

[0035] The boiler section 5 is connected with the bottom outlet 1-3-2 of the three-stage catalytic combustion zone 1-3 through the heating gas inlet 5-1-1, and the boiler section 5 includes a boiler 5-1 and a steam drum 5-2 connected with the boiler 5-1; the heating gas outlet 5-1-2 of the boiler 5-1 is connected with the hot flue gas inlet 4-2 of the coal grinding and drying section 4; the steam drum 5-2 is also provided with a soft water inlet 5-2-1 and a steam outlet 5-2-2.

[0036] The liquid nitrogen washing tail gas graded oxygen regulation explosion-proof and resource recovery system provided by the present invention is as follows Figure 1 shown.

[0037] The liquid nitrogen-washed tail gas graded oxygen regulation explosion-proof and resource utilization system provided by the present invention includes a multi-stage catalytic burner 1, and the multi-stage catalytic burner 1 includes a first-stage catalytic combustion zone 1-1, a second-stage catalytic combustion zone 1-2 and a third-stage catalytic combustion zone 1-3 arranged from top to bottom. In the present invention, the first-stage catalytic combustion zone 1-1 and the second-stage catalytic combustion zone 1-2 are respectively filled with multi-layer catalysts, the number of layers of the multi-layer catalysts is ≥3 layers, and the multi-layer catalysts are respectively arranged at intervals, and an air guide tube 6 is arranged above each layer of catalyst. In the present invention, the multi-layer catalysts in the first-stage catalytic combustion zone 1-1 and the second-stage catalytic combustion zone 1-2 are respectively selected from the catalysts described in patent CN201610705294.7. In the present invention, the tower wall of the multi-stage catalytic burner 1 is preferably made of heat-resistant stainless steel plate, and the structure of each layer of catalyst in the first catalytic combustion zone 1-1 and the second catalytic combustion zone 1-2 is composed of a refractory support, a high-aluminum refractory grid screen, a refractory ball (60 mm thick, 20-30 mm in diameter), a stainless steel wire mesh and a catalyst from bottom to top; a flue gas guide plate (see Figure 17), the flue gas guide plate is preferably located below the air guide tube 6. The present invention arranges multiple layers of catalysts in the first catalytic combustion zone 1-1 and the second catalytic combustion zone 1-2, and an air guide tube is arranged above each layer of catalyst. By controlling the different air amounts of each layer of catalyst, the degree of catalytic combustion of each layer can be different, and the catalyst layer can be gradually heated up to avoid sintering of the catalyst or reducing the life of the catalyst due to excessive temperature. It can also avoid uneven mixing of air and prevent explosions. In the present invention, the specific number of layers of the multiple layers of catalyst in the first catalytic combustion zone 1-1 and the second catalytic combustion zone 1-2 is determined by the calorific value of the liquid nitrogen washed tail gas. In an embodiment of the present invention, three layers of catalyst are arranged in the first catalytic combustion zone 1-1 and the second catalytic combustion zone 1-2.

[0038] In the present invention, a layer of catalyst is filled in the three-stage catalytic combustion zone 1-3, and an air guide pipe 6 is arranged above the catalyst in the three-stage catalytic combustion zone 1-3. In the present invention, the three-stage catalytic combustion zone 1-3 is a high-temperature area, and the catalyst of the three-stage catalytic combustion zone 1-3 is selected from the catalyst described in patent CN201910457896.9; the structural structure of the catalyst in the three-stage catalytic combustion zone 1-3 is the same as the above-mentioned scheme, which will not be repeated here; unlike the one-stage catalytic combustion zone 1-1 and the two-stage catalytic combustion zone 1-2, the inner wall of the three-stage catalytic combustion zone 1-3 is preferably provided with an asbestos board layer, a clay refractory brick layer, a high-alumina refractory brick layer and a clay refractory brick in sequence, and the thickness of the asbestos board layer, the clay refractory brick layer, the high-alumina refractory brick layer and the clay refractory brick are preferably 10mm, 150mm, 150mm and 150mm respectively; the outer wall of the three-stage catalytic combustion zone 1-3 is preferably provided with an insulation layer, the thickness of the insulation layer is preferably 140-150mm, and the material of the insulation layer is preferably expanded perlite.

[0039] In the present invention, each air guide tube 6 is connected to an air duct. In the present invention, the air duct provides air required for catalytic combustion to each layer of catalyst through each air guide tube 6; an air valve is preferably provided between the air duct and each air guide tube 6; the air valve is conducive to adjusting the amount of air entering each layer of catalyst.

[0040] In the present invention, the multi-stage catalytic burner 1 splits the air into multiple stages, so that the liquid nitrogen-washed tail gas and the multi-stage air can be subjected to multi-stage catalytic combustion, thereby avoiding the uneven mixing of the liquid nitrogen-washed tail gas with the air and avoiding the risk of explosion.

[0041] The liquid nitrogen washing tail gas staged oxygen regulation explosion-proof and resource utilization system provided by the present invention comprises a heat exchanger 2 whose heat outlet 2-2 is connected to the top inlet 1-1-1 of the first stage catalytic combustion zone 1-1. In the present invention, the function of the first stage heat exchanger 2 is to preheat and raise the temperature of the liquid nitrogen washing tail gas by using the high-temperature flue gas generated by the catalytic combustion of the liquid nitrogen washing tail gas in the first stage catalytic combustion zone 1-1, thereby making full use of the heat generated by the first stage catalytic combustion zone 1-1.

[0042] The liquid nitrogen washing tail gas graded oxygen regulation explosion-proof and resource utilization system provided by the present invention comprises a two-stage heat exchanger 3 whose heat inlet 3-3 is connected to the bottom outlet 1-2-2 of the second-stage catalytic combustion zone 1-2. In the present invention, the function of the two-stage heat exchanger 3 is to use the heat generated by the catalytic combustion in the second-stage catalytic combustion zone 1-2 to preheat and raise the temperature of the low-temperature flue gas discharged from the pulverized coal drying section, and make full use of the heat of the second-stage catalytic combustion zone 1-2.

[0043] The liquid nitrogen washing tail gas graded oxygen regulation explosion-proof and resource utilization system provided by the present invention includes a coal grinding and drying section 4 whose low-temperature flue gas outlet 4-1 is connected to the cold inlet 3-1 of the second-stage heat exchanger 3. The present invention has no special requirements for the structure of the coal grinding and drying section 4, and the corresponding structure familiar to those skilled in the art can be adopted. The present invention connects the hot flue gas inlet 4-2 of the coal grinding and drying section 4 with the hot outlet 3-2 of the second-stage heat exchanger 3, and can resupply the low-temperature gas discharged from the coal grinding and drying section 4 to the coal grinding and drying section after the temperature is increased by the second-stage heat exchanger 3 for recycling.

[0044] The liquid nitrogen washing tail gas graded oxygen regulation explosion-proof and resource utilization system provided by the present invention also includes a boiler section 5 whose heating gas inlet 5-1-1 is connected to the bottom outlet 1-3-2 of the three-stage catalytic combustion zone 1-3. In the present invention, the boiler section 5 includes a boiler 5-1 and a steam drum 5-2 connected to the boiler 5-1; the present invention has no special requirements for the connection method of the boiler 5-1 and the steam drum 5-2, and a connection method familiar to those skilled in the art can be used. In the present invention, the function of the boiler section 5 is to transfer the heat of the high-temperature flue gas generated by the three-stage catalytic combustion zone 1-3 to soft water to generate medium-pressure steam with higher utilization value. The flue gas after heat transfer can also enter the coal grinding and drying section for coal powder drying. The flue gas temperature after heat transfer is reduced, which can meet the requirements of coal powder drying while avoiding the risk of coal powder spontaneous combustion during high-temperature flue gas drying. In the present invention, when the inlet flue gas temperature of the coal grinding and drying section needs to be further increased, the bottom outlet 1-3-2 of the three-stage catalytic combustion zone 1-3 is preferably connected to the hot flue gas inlet 4-2 of the coal grinding and drying section 4, so as to fully utilize the heat of the three-stage catalytic combustion zone 1-3.

[0045] The system provided by the present invention improves the circulation and oxygen intake of flue gas, which can not only more efficiently utilize and recover heat and greatly improve the heat utilization rate, but also avoid the uneven mixing of liquid nitrogen-washed tail gas with air to prevent explosion; and avoid the risk of spontaneous combustion of dry coal powder.

[0046] The present invention provides a liquid nitrogen washing tail gas graded oxygen regulation explosion-proof and resource recovery method, comprising the following steps:

[0047] (a) Liquid nitrogen-washed tail gas enters a heat exchanger 2 from a cold inlet 2-1, and exchanges heat with a section of high-temperature flue gas from a bottom outlet 1-1-2 of a catalytic combustion zone 1-1. After heat exchange, the liquid nitrogen-washed tail gas enters a top inlet 1-1-1 of a catalytic combustion zone 1-1 from a hot outlet 2-2, and performs a catalytic reaction layer by layer on the multi-layer catalysts arranged at intervals in the catalytic combustion zone 1-1, thereby obtaining a section of high-temperature flue gas. During the process of performing the catalytic reaction layer by layer, the liquid nitrogen-washed tail gas is respectively mixed with air from an air guide pipe 6 above each layer of catalyst, and the catalytic reaction is an oxygen-deficient reaction.

[0048] (b) The first stage high-temperature flue gas is discharged from the bottom outlet 1-1-2 of the first stage catalytic combustion zone 1-1, enters the first stage heat exchanger 2 through the hot inlet 2-3 for heat exchange, and after heat exchange, the first stage high-temperature flue gas enters the top inlet 1-2-1 of the second stage catalytic combustion zone 1-2 through the cold outlet 2-4 of the first stage heat exchanger 2, and performs a second stage catalytic reaction layer by layer on the multi-layer catalysts arranged at intervals in the second stage catalytic combustion zone 1-2 to obtain a second stage high-temperature flue gas; during the process of performing the second stage catalytic reaction layer by layer, the first stage high-temperature flue gas is respectively mixed with the air from the air guide pipe 6 above each layer of catalyst, and the second stage catalytic reaction is an oxygen-deficient reaction;

[0049] (c) The second stage high temperature flue gas is discharged from the bottom outlet 1-2-2 of the second stage catalytic combustion zone 1-2, enters the second stage heat exchanger 3 from the hot inlet 3-3, and exchanges heat with the low temperature flue gas discharged from the low temperature flue gas outlet 4-1 of the pulverized coal drying section 4 in the second stage heat exchanger 3. After heat exchange, the low temperature flue gas is discharged from the hot outlet 3-2 of the second stage heat exchanger 3 and enters the pulverized coal drying section 4 through the hot flue gas inlet 4-2. The low temperature flue gas is also partially discharged through the flue gas external outlet 4-3; after heat exchange, the second stage high temperature flue gas is discharged from the cold outlet 3-4 of the second stage heat exchanger 3 and enters the top inlet 1-3-1 of the third stage catalytic combustion zone 1-3, and performs a three-stage catalytic reaction on the catalyst of the third stage catalytic combustion zone 1-3 to obtain a three-stage high temperature flue gas; during the three-stage catalytic reaction, the second stage high temperature flue gas is mixed with the air from the air guide pipe 6 above the catalyst of the third stage catalytic combustion zone 1-3, and the three-stage catalytic reaction is an oxygen-enriched reaction;

[0050] (d) The three-stage high-temperature flue gas is discharged from the bottom outlet 1-3-2 of the three-stage catalytic combustion zone 1-3, enters the boiler 5-1 through the heating gas inlet 5-1-1, and transfers heat to the soft water in the steam drum 5-2 through the boiler 5-1, and the soft water is converted into medium-pressure steam for external use; after transferring heat, the three-stage high-temperature flue gas is discharged from the heating gas outlet 5-1-2 of the boiler 5-1, and enters the coal grinding and drying section 4 through the hot flue gas inlet 4-2.

[0051] In the present invention, the liquid nitrogen-washed tail gas enters a heat exchanger 2 from a cold inlet 2-1, and exchanges heat with a section of high-temperature flue gas from a bottom outlet 1-1-2 of a catalytic combustion zone 1-1. After heat exchange, the liquid nitrogen-washed tail gas enters the top inlet 1-1-1 of a catalytic combustion zone 1-1 from the hot outlet 2-2, and performs a catalytic reaction layer by layer on the multi-layer catalysts arranged at intervals in the catalytic combustion zone 1-1 to obtain a section of high-temperature flue gas. In the present invention, the temperature of the section of high-temperature flue gas is preferably 450-480°C, and the temperature of the liquid nitrogen-washed tail gas after heat exchange is preferably increased from room temperature to 230-240°C. In the present invention, during the process of performing a catalytic reaction layer by layer, the liquid nitrogen-washed tail gas is mixed with the air from the air guide pipe 6 above each layer of catalyst. In an embodiment of the present invention, three layers of catalysts are arranged at intervals in the first stage catalytic combustion zone 1-1, so the first stage catalytic reaction includes a first stage catalytic reaction, a second stage catalytic reaction and a third stage catalytic reaction performed in sequence; the specific process of the first stage catalytic reaction, the second stage catalytic reaction and the third stage catalytic reaction is preferably: the liquid nitrogen washed tail gas enters the top inlet 1-1-1 of the first stage catalytic combustion zone 1-1 after heat exchange, mixes with the primary air entering the first layer of catalyst in the first stage catalytic combustion zone 1-1 through the air guide pipe, and performs a first stage catalytic reaction at the first layer of catalyst to obtain a primary reaction gas; the primary reaction gas is then mixed with the secondary air entering the second layer of catalyst in the first stage catalytic combustion zone 1-1 through the air guide pipe, enters the second layer of catalyst through the flue gas guide plate to perform a second stage catalytic reaction, and obtains a secondary reaction gas; the secondary reaction gas is then mixed with the tertiary air entering the third layer of catalyst in the first stage catalytic combustion zone 1-1 through the air guide pipe, enters the third layer of catalyst through the flue gas guide plate to perform a third stage catalytic reaction, and obtains a section of high-temperature flue gas. In the present invention, the one-stage catalytic reaction is an oxygen-deficient reaction, and the O2 volume content of the one-stage catalytic reaction is preferably 0.4-0.9%; in an embodiment of the present invention, the O2 volume content of the first-stage catalytic reaction, the second-stage catalytic reaction and the third-stage catalytic reaction in the one-stage catalytic reaction is further preferably 0.4-0.5%, 0.6-0.7% and 0.8-0.9%, respectively; the temperatures of the first-stage catalytic reaction, the second-stage catalytic reaction and the third-stage catalytic reaction in the one-stage catalytic reaction are preferably 200-230°C, 340-360°C and 450-480°C, respectively.

[0052] After obtaining a section of high-temperature flue gas, the present invention discharges the section of high-temperature flue gas from the bottom outlet 1-1-2 of the first catalytic combustion zone 1-1, enters the first heat exchanger 2 from the hot inlet 2-3 for heat exchange, and after heat exchange, the section of high-temperature flue gas enters the top inlet 1-2-1 of the second catalytic combustion zone 1-2 from the cold outlet 2-4 of the first heat exchanger 2, and performs a second-stage catalytic reaction layer by layer on the multi-layer catalysts arranged at intervals in the second catalytic combustion zone 1-2 to obtain a second section of high-temperature flue gas. In the present invention, the temperature of the section of high-temperature flue gas after heat exchange is preferably reduced to 220-240°C; the temperature of the second section of high-temperature flue gas is 450-480°C. In the present invention, during the process of performing the second-stage catalytic reaction layer by layer, the section of high-temperature flue gas is respectively mixed with the air from the air guide pipe 6 above each layer of catalyst. In an embodiment of the present invention, three layers of catalyst are arranged at intervals in the second-stage catalytic combustion zone 1-2, so the second-stage catalytic reaction includes a fourth-stage catalytic reaction, a fifth-stage catalytic reaction and a sixth-stage catalytic reaction carried out in sequence; the specific reaction forms of the fourth-stage catalytic reaction, the fifth-stage catalytic reaction and the sixth-stage catalytic reaction are the same as the specific reaction forms of the first-stage catalytic reaction, the second-stage catalytic reaction and the third-stage catalytic reaction mentioned above, and are not repeated here. In the present invention, the second-stage catalytic reaction is an oxygen-deficient reaction, and the O2 volume content of the second-stage catalytic reaction is preferably 0.4-0.9%; in an embodiment of the present invention, the O2 volume content of the fourth-stage catalytic reaction, the fifth-stage catalytic reaction and the sixth-stage catalytic reaction in the second-stage catalytic reaction is further preferably 0.4-0.5%, 0.6-0.7% and 0.8-0.9% respectively; the temperatures of the fourth-stage catalytic reaction, the fifth-stage catalytic reaction and the sixth-stage catalytic reaction in the second-stage catalytic reaction are preferably 200-230°C, 340-360°C and 450-480°C respectively.

[0053] The present invention first performs an oxygen-deficient reaction in the first-stage catalytic combustion zone 1-1 and the second-stage catalytic combustion zone 1-2 to avoid releasing a large amount of heat at the beginning of the reaction, which may burn out the catalytic burner due to excessive temperature, and to avoid direct mixing of liquid nitrogen-washed tail gas with a large amount of oxygen, which may easily cause uneven mixing and explosion.

[0054] After obtaining the second-stage high-temperature flue gas, the present invention discharges the second-stage high-temperature flue gas from the bottom outlet 1-2-2 of the second-stage catalytic combustion zone 1-2, enters the second-stage heat exchanger 3 from the hot inlet 3-3, and exchanges heat with the low-temperature flue gas discharged from the low-temperature flue gas outlet 4-1 of the pulverized coal drying section 4 in the second-stage heat exchanger 3. After heat exchange, the low-temperature flue gas is discharged from the hot outlet 3-2 of the second-stage heat exchanger 3 and enters the pulverized coal drying section 4 through the hot flue gas inlet 4-2. The low-temperature flue gas is also partially discharged through the flue gas external outlet 4-3; after heat exchange, the second-stage high-temperature flue gas is discharged from the cold outlet 3-4 of the second-stage heat exchanger 3, enters the top inlet 1-3-1 of the third-stage catalytic combustion zone 1-3, and performs a three-stage catalytic reaction on the catalyst in the third-stage catalytic combustion zone 1-3 to obtain the three-stage high-temperature flue gas. In the present invention, the temperature of the low-temperature flue gas is preferably 90-100°C, and the temperature of the low-temperature flue gas after heat exchange is preferably increased to 150-180°C; the temperature of the second-stage high-temperature flue gas after heat exchange is preferably reduced to 300-350°C. In the present invention, during the three-stage catalytic reaction, the second-stage high-temperature flue gas is mixed with the air from the air guide pipe 6 above the three-stage catalytic combustion zone 1-3. Since a layer of catalyst is loaded in the three-stage catalytic combustion zone, the three-stage catalytic reaction is a first-stage catalytic reaction. In the embodiment of the present invention, it is specifically a seventh-stage catalytic reaction. In the present invention, the three-stage catalytic reaction is an oxygen-enriched reaction; the O2 volume content of the three-stage catalytic reaction is preferably 3-4% (the volume ratio of liquid nitrogen washing tail gas to air is 1:0.16-0.2); the temperature of the three-stage high-temperature flue gas is preferably 550-650°C.

[0055] After obtaining the three-stage high-temperature flue gas, the present invention discharges the three-stage high-temperature flue gas from the bottom outlet 1-3-2 of the three-stage catalytic combustion zone 1-3, enters the boiler 5-1 from the heating gas inlet 5-1-1, transfers heat to the soft water in the drum 5-2 through the boiler 5-1, and converts the soft water into medium-pressure steam for external use; after transferring heat, the three-stage high-temperature flue gas is discharged from the heating gas outlet 5-1-2 of the boiler 5-1, and enters the coal grinding drying section 4 from the hot flue gas inlet 4-2. In the present invention, every 10,000 m 3Washing tail gas with liquid nitrogen can produce 1400-1500kg of medium-pressure steam of 1.6MPa (according to HG / T 20521-1992 "Design Regulations for Chemical Steam Systems": low-pressure steam is generally below 1.57MPa; medium-pressure steam is 1.58-3.82MPa), which has significant economic benefits. In the present invention, the temperature of the three-stage high-temperature flue gas is preferably reduced to 250-300°C after transferring heat. The flue gas at this temperature supplies heat source for the pulverized coal drying section 4, which can meet the working condition requirements of the pulverized coal drying section, and can also avoid the risk of spontaneous combustion of pulverized coal due to excessive flue gas temperature. In the present invention, when the inlet flue gas temperature of the pulverized coal drying section 4 needs to be further increased, the three-stage high-temperature flue gas is discharged from the bottom outlet 1-3-2 of the three-stage catalytic combustion zone 1-3, and preferably enters the pulverized coal drying section 4 from the hot flue gas inlet 4-2.

[0056] In the present invention, the oxygen content in the coal grinding and drying section 4 is preferably ≤3%, and the total content of CO and H2 is preferably <200 ppm to prevent explosion.

[0057] The following is a detailed description of the liquid nitrogen washing tail gas graded oxygen regulation explosion-proof and resource utilization system and method provided by the present invention in conjunction with the embodiments, but they should not be understood as limiting the protection scope of the present invention.

[0058] Example 1

[0059] A liquid nitrogen washing tail gas graded oxygen regulation explosion-proof and resource recovery system, such as Figure 1 As shown, it includes a multi-stage catalytic burner 1, a first-stage heat exchanger 2, a second-stage heat exchanger 3, a pulverized coal drying section 4, and a boiler section 5, wherein the multi-stage catalytic burner 1 is divided into a first-stage catalytic combustion zone 1-1, a second-stage catalytic combustion zone 1-2, and a third-stage catalytic combustion zone 1-3. The first-stage catalytic combustion zone 1-1 and the second-stage catalytic combustion zone 1-2 are filled with three layers of catalysts (selected from the catalyst prepared in Example 1 of patent CN201610705294.7) arranged at intervals, and an air guide tube is arranged above each layer of catalyst; the third-stage catalytic combustion zone 1-3 is filled with a layer of catalyst (selected from the catalyst prepared in Example 1 of patent CN201910457896.9), and an air guide tube is arranged above the catalyst of the third-stage catalytic combustion zone 1-3.

[0060] Liquid nitrogen washing tail gas components to be treated (Vol%): H21.8%, CO 7%, N284.82%; Liquid nitrogen washing tail gas treatment capacity: 30000Nm 3 / h.

[0061] use Figure 1 The system shown treats the liquid nitrogen washing tail gas, and the process is as follows:

[0062] 30000Nm 3 / h of liquid nitrogen washed tail gas enters the first stage heat exchanger 2 from the cold inlet 2-1, and exchanges heat with a section of high-temperature flue gas with a temperature of 450-480°C from the bottom outlet 1-1-2 of the first stage catalytic combustion zone 1-1. After the heat exchange, the temperature of the liquid nitrogen washed tail gas rises from room temperature to 230-240°C, and then enters the top inlet 1-1-1 of the first stage catalytic combustion zone 1-1 from the hot outlet 2-2. The first stage catalytic reaction, the second stage catalytic reaction and the third stage catalytic reaction are sequentially carried out on the three layers of catalysts arranged at intervals in the first stage catalytic combustion zone 1-1 to obtain a section of high-temperature flue gas. Specifically, the air flow rate of the multi-stage catalytic burner is adjusted by controlling the air valve, and the liquid nitrogen washed tail gas with a temperature of 230-240°C after heat exchange and the liquid nitrogen washed tail gas with a flow rate of 714m / s entering the first layer of catalyst in the first stage catalytic combustion zone 1-1 from the air guide pipe. 3 / h of the first-stage air is evenly mixed, and the first-stage catalytic reaction is carried out at the first-layer catalyst position, and the reaction temperature is 200-230°C to obtain the first-stage reaction gas; the first-stage reaction gas is then mixed with the air flow rate of 1000m above the second-layer catalyst in the first-stage catalytic combustion zone 1-1 through the air guide pipe. 3 / h of secondary air is evenly mixed and enters the second layer of catalyst position through the flue gas guide plate for second-stage catalytic reaction. The reaction temperature is 340-360°C to obtain secondary reaction gas; the secondary reaction gas then enters the third layer of catalyst above the first catalytic combustion zone 1-1 through the air guide pipe with a flow rate of 1286m 3 / h of three-stage air is evenly mixed and enters the third layer of catalyst position through the flue gas guide plate for the third-stage catalytic reaction to obtain a section of high-temperature flue gas with a temperature of 450-480℃.

[0063] After the first partial combustion, a section of high-temperature flue gas is discharged from the bottom outlet 1-1-2 of the first catalytic combustion zone 1-1, and enters the first heat exchanger 2 through the hot inlet 2-3 for heat exchange. After the heat exchange, the temperature of the section of high-temperature flue gas drops to 220-230°C, and enters the top inlet 1-2-1 of the second catalytic combustion zone 1-2 through the cold outlet 2-4 of the first heat exchanger 2. The fourth-stage catalytic reaction, the fifth-stage catalytic reaction and the sixth-stage catalytic reaction are sequentially carried out on the three-layer catalyst arranged at intervals in the second catalytic combustion zone 1-2 to obtain the second section of high-temperature flue gas. Specifically, the section of high-temperature flue gas with a temperature of 220-230°C after heat exchange enters the second catalytic combustion zone 1-2 above the first layer of catalyst through the air guide pipe, and the flow rate is 714m 3 / h of the four-stage air is evenly mixed and enters the first layer of catalyst position through the flue gas guide plate for the fourth-stage catalytic reaction. The reaction temperature is 200-230°C to obtain the fourth-stage reaction gas; the fourth-stage reaction gas is then mixed with the air flow rate of 1000m / s above the second layer of catalyst entering the second-stage catalytic combustion zone 1-2 through the air guide pipe. 3 / h of five-stage air is evenly mixed and enters the second-layer catalyst position through the flue gas guide plate for the fifth-stage catalytic reaction. The reaction temperature is 340-360°C to obtain the five-stage reaction gas; the five-stage reaction gas then enters the second-stage catalytic combustion zone 1-2 above the third layer of catalyst through the air guide pipe with a flow rate of 1286m 3 / h of six-stage air is evenly mixed and enters the third layer catalyst position through the flue gas guide plate for the sixth-stage catalytic reaction to obtain the second-stage high-temperature flue gas with a temperature of 450-480℃.

[0064] The second stage high temperature flue gas after the second partial combustion is discharged from the bottom outlet 1-2-2 of the second stage catalytic combustion zone 1-2, and enters the second stage heat exchanger 3 through the hot inlet 3-3 for heat exchange. The temperature of the second stage high temperature flue gas after heat exchange drops to 300-330°C, and is discharged from the cold outlet 3-4 of the second stage heat exchanger 3, and enters the top inlet 1-3-1 of the third stage catalytic combustion zone 1-3, and enters the catalyst above the third stage catalytic combustion zone 1-3 through the air guide pipe, with a flow rate of 4286m 3 / h of air is evenly mixed and enters the catalyst position through the flue gas guide plate for the seventh stage catalytic reaction to obtain three sections of high-temperature flue gas with a temperature of 550-650℃.

[0065] The three-stage high-temperature flue gas with a temperature of 550-650℃ is discharged from the bottom outlet 1-3-2 of the three-stage catalytic combustion zone 1-3, enters the boiler 5-1 through the heating gas inlet 5-1-1, and transfers heat to the soft water in the drum 5-2 through the boiler 5-1, generating 1680-1800kg / h of medium-pressure steam for external use; the temperature of the three-stage high-temperature flue gas after heat transfer drops to 250-300℃, and is discharged from the heating gas outlet 5-1-2 of the boiler 5-1, and enters the pulverized coal drying section 4 through the hot flue gas inlet 4-2 for drying coal powder; the outlet flue gas temperature of the pulverized coal drying section 4 is 90℃, and the flue gas volume is 100,000Nm 3 / h; including 30,000 Nm 3 / h of flue gas exhaust, 70,000 Nm 3 The flue gas of / h enters the second-stage heat exchanger 3 and is heat-exchanged to 160°C. Then, together with the third-stage high-temperature flue gas whose temperature is reduced to 250-300°C after heat transfer, it enters the coal grinding and drying section 4 through the hot flue gas inlet 4-2 for recycling.

[0066] Example 2

[0067] A liquid nitrogen washing tail gas graded oxygen regulation explosion-proof and resource recovery system, such as Figure 1As shown, it includes a multi-stage catalytic burner 1, a first-stage heat exchanger 2, a second-stage heat exchanger 3, a pulverized coal drying section 4, and a boiler section 5, wherein the multi-stage catalytic burner 1 is divided into a first-stage catalytic combustion zone 1-1, a second-stage catalytic combustion zone 1-2, and a third-stage catalytic combustion zone 1-3. The first-stage catalytic combustion zone 1-1 and the second-stage catalytic combustion zone 1-2 are filled with three layers of catalysts (the catalysts are the same as those in Example 1) arranged at intervals, and an air guide tube is arranged above each layer of catalyst. The third-stage catalytic combustion zone 1-3 is filled with a layer of catalyst (the catalyst is the same as that in Example 1), and an air guide tube is arranged above the catalyst of the three-stage catalytic combustion zone 1-3.

[0068] Liquid nitrogen washing tail gas components to be treated (Vol%): H21.7%, CO 6%, N292.3%; Liquid nitrogen washing tail gas treatment capacity: 90000Nm 3 / h.

[0069] use Figure 1 The system shown treats the liquid nitrogen washing tail gas, and the process is as follows:

[0070] 90000Nm 3 / h of liquid nitrogen washed tail gas enters the first stage heat exchanger 2 from the cold inlet 2-1, and exchanges heat with a section of high-temperature flue gas with a temperature of 450-460°C from the bottom outlet 1-1-2 of the first stage catalytic combustion zone 1-1. After the heat exchange, the temperature of the liquid nitrogen washed tail gas rises from room temperature to 230-240°C, and then enters the top inlet 1-1-1 of the first stage catalytic combustion zone 1-1 from the hot outlet 2-2. The first stage catalytic reaction, the second stage catalytic reaction and the third stage catalytic reaction are sequentially carried out on the three layers of catalysts arranged at intervals in the first stage catalytic combustion zone 1-1 to obtain a section of high-temperature flue gas. Specifically, the air flow rate of the multi-stage catalytic burner is adjusted by controlling the air valve, and the liquid nitrogen washed tail gas with a temperature of 230-240°C after heat exchange and the liquid nitrogen washed tail gas with a flow rate of 2143m 3 / h of the first-stage air is evenly mixed, and the first-stage catalytic reaction is carried out at the first-layer catalyst position, and the reaction temperature is 200-220°C to obtain the first-stage reaction gas; the first-stage reaction gas is then mixed with the air flow rate of 3000m above the second-layer catalyst in the first-stage catalytic combustion zone 1-1 through the air guide pipe. 3 / h of secondary air is evenly mixed and enters the second layer of catalyst position through the flue gas guide plate for second-stage catalytic reaction. The reaction temperature is 340-350°C to obtain secondary reaction gas; the secondary reaction gas then enters the third layer of catalyst above the first catalytic combustion zone 1-1 through the air guide pipe with a flow rate of 3857m 3 / h of three-stage air is evenly mixed and enters the third layer of catalyst position through the flue gas guide plate for third-stage catalytic reaction to obtain a section of high-temperature flue gas with a temperature of 450-460℃.

[0071] After the first partial combustion, a section of high-temperature flue gas is discharged from the bottom outlet 1-1-2 of the first catalytic combustion zone 1-1, and enters the first heat exchanger 2 through the hot inlet 2-3 for heat exchange. After the heat exchange, the temperature of the section of high-temperature flue gas drops to 220-240°C, and enters the top inlet 1-2-1 of the second catalytic combustion zone 1-2 through the cold outlet 2-4 of the first heat exchanger 2. The fourth-stage catalytic reaction, the fifth-stage catalytic reaction and the sixth-stage catalytic reaction are sequentially carried out on the three-layer catalysts arranged at intervals in the second catalytic combustion zone 1-2 to obtain the second section of high-temperature flue gas. Specifically, the section of high-temperature flue gas with a temperature of 220-240°C after heat exchange enters the second catalytic combustion zone 1-2 above the first layer of catalyst through the air guide pipe, and the flow rate is 2143m 3 / h of the four-stage air is evenly mixed and enters the first layer of catalyst position through the flue gas guide plate for the fourth-stage catalytic reaction. The reaction temperature is 200-220°C to obtain the fourth-stage reaction gas; the fourth-stage reaction gas is then mixed with the air flow rate of 3000m / s above the second layer of catalyst entering the second-stage catalytic combustion zone 1-2 through the air guide pipe. 3 / h of five-stage air is evenly mixed and enters the second-layer catalyst position through the flue gas guide plate for the fifth-stage catalytic reaction. The reaction temperature is 340-350°C to obtain the five-stage reaction gas; the five-stage reaction gas then enters the second-stage catalytic combustion zone 1-2 above the third layer of catalyst through the air guide pipe with a flow rate of 3857m 3 / h of six-stage air is evenly mixed and enters the third layer catalyst position through the flue gas guide plate for the sixth-stage catalytic reaction to obtain the second-stage high-temperature flue gas with a temperature of 450-460℃.

[0072] The second stage high temperature flue gas after the second partial combustion is discharged from the bottom outlet 1-2-2 of the second stage catalytic combustion zone 1-2, and enters the second stage heat exchanger 3 through the hot inlet 3-3 for heat exchange. The temperature of the second stage high temperature flue gas after heat exchange drops to 300-350°C, and is discharged from the cold outlet 3-4 of the second stage heat exchanger 3, and enters the top inlet 1-3-1 of the third stage catalytic combustion zone 1-3, and enters the catalyst above the third stage catalytic combustion zone 1-3 through the air guide pipe, with a flow rate of 12857m 3 / h of air is evenly mixed and enters the catalyst position through the flue gas guide plate for the seventh stage catalytic reaction to obtain three sections of high-temperature flue gas with a temperature of 550-650℃.

[0073] The three-stage high-temperature flue gas with a temperature of 550-650°C is discharged from the bottom outlet 1-3-2 of the three-stage catalytic combustion zone 1-3. 70% of the three-stage high-temperature flue gas enters the boiler 5-1 through the heating gas inlet 5-1-1, and transfers heat to the soft water in the drum 5-2 through the boiler 5-1, generating 2646-2835 kg / h of medium-pressure steam for external use; the temperature of this part of the three-stage high-temperature flue gas after heat transfer drops to 250-300°C, and is discharged from the heating gas outlet 5-1-2 of the boiler 5-1, and enters the pulverized coal drying section 4 through the hot flue gas inlet 4-2 for drying coal powder; the other 30% of the three-stage high-temperature flue gas enters the pulverized coal drying section through the hot flue gas inlet 4-2; the outlet flue gas temperature of the pulverized coal drying section 4 is 90°C, and the flue gas volume is 300,000 Nm 3 / h; including 30,000 Nm 3 / h of flue gas exhaust, 270,000 Nm 3 / h flue gas enters the second stage heat exchanger 3 and is heat exchanged to 180℃, and then enters the coal grinding and drying section 4 for recycling through the hot flue gas inlet 4-2 together with the third stage high temperature flue gas whose temperature drops to 250-300℃ after heat transfer and 30% of the third stage high temperature flue gas.

[0074] It can be seen from the above embodiments that the present invention improves the circulation and oxygen intake of flue gas, which can not only fully utilize and recycle the heat and greatly improve the heat utilization rate, but also avoid the risk of liquid nitrogen washing exhaust gas mixing with air to produce unevenness and cause explosion.

[0075] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A liquid nitrogen washing tail gas graded oxygen regulation explosion-proof and resource recovery method, characterized in that: A liquid nitrogen washing tail gas grading oxygen regulation explosion-proof and resource recovery system is adopted, and the liquid nitrogen washing tail gas grading oxygen regulation explosion-proof and resource recovery system includes: A multi-stage catalytic burner (1); the multi-stage catalytic burner (1) comprises a first stage catalytic combustion zone (1-1), a second stage catalytic combustion zone (1-2) and a third stage catalytic combustion zone (1-3) arranged from top to bottom; the first stage catalytic combustion zone (1-1) and the second stage catalytic combustion zone (1-2) are respectively filled with multiple layers of catalyst, the number of layers of the multiple layers of catalyst is ≥3 layers, and the multiple layers of catalyst are respectively arranged at intervals, and an air guide tube (6) is arranged above each layer of catalyst; the third stage catalytic combustion zone (1-3) is filled with a layer of catalyst, and an air guide tube (6) is arranged above the catalyst of the third stage catalytic combustion zone (1-3); A first stage heat exchanger (2) having a hot outlet (2-2) connected to a top inlet (1-1-1) of the first stage catalytic combustion zone (1-1); a cold inlet (2-1) of the first stage heat exchanger (2) being a liquid nitrogen-washed tail gas inlet; a hot inlet (2-3) of the first stage heat exchanger (2) being connected to a bottom outlet (1-1-2) of the first stage catalytic combustion zone (1-1); and a cold outlet (2-4) of the first stage heat exchanger (2) being connected to a top inlet (1-2-1) of the second stage catalytic combustion zone (1-2); A second-stage heat exchanger (3) whose hot inlet (3-3) is connected to the bottom outlet (1-2-2) of the second-stage catalytic combustion zone (1-2); and whose cold outlet (3-4) is connected to the top inlet (1-3-1) of the third-stage catalytic combustion zone (1-3); A coal grinding and drying section (4) having a low-temperature flue gas outlet (4-1) connected to a cold inlet (3-1) of the second-stage heat exchanger (3), wherein a flue gas outlet (4-3) is provided between the low-temperature flue gas outlet (4-1) and the cold inlet (3-1); a hot flue gas inlet (4-2) of the coal grinding and drying section (4) is connected to a hot outlet (3-2) of the second-stage heat exchanger (3); A boiler section (5) having a heating gas inlet (5-1-1) connected to a bottom outlet (1-3-2) of the three-stage catalytic combustion zone (1-3), the boiler section (5) comprising a boiler (5-1) and a steam drum (5-2) connected to the boiler (5-1); the heating gas outlet (5-1-2) of the boiler (5-1) is connected to a hot flue gas inlet (4-2) of the pulverized coal drying section (4); the steam drum (5-2) is also provided with a soft water inlet (5-2-1) and a steam outlet (5-2-2); The following steps are involved: (a) Liquid nitrogen-washed tail gas enters a heat exchanger (2) from a cold inlet (2-1) and exchanges heat with a section of high-temperature flue gas from a bottom outlet (1-1-2) of a section of catalytic combustion zone (1-1). After heat exchange, the liquid nitrogen-washed tail gas enters a top inlet (1-1-1) of a section of catalytic combustion zone (1-1) from a hot outlet (2-2) and performs a catalytic reaction layer by layer on multiple layers of catalysts arranged at intervals in the section of catalytic combustion zone (1-1) to obtain a section of high-temperature flue gas. During the process of performing the catalytic reaction layer by layer, the liquid nitrogen-washed tail gas is respectively mixed with air from an air guide pipe (6) above each layer of catalyst. The one-stage catalytic reaction is an oxygen-deficient reaction; the one-stage catalytic reaction includes a first-stage catalytic reaction, a second-stage catalytic reaction and a third-stage catalytic reaction performed in sequence, and the volume contents of O2 in the first-stage catalytic reaction, the second-stage catalytic reaction and the third-stage catalytic reaction in the one-stage catalytic reaction are 0.4-0.5%, 0.6-0.7% and 0.8-0.9% respectively; the temperatures of the first-stage catalytic reaction, the second-stage catalytic reaction and the third-stage catalytic reaction in the one-stage catalytic reaction are 200-230° C., 340-360° C. and 450-480° C. respectively, and the temperature of the one-stage high-temperature flue gas is 450-480° C.; (b) The first stage high-temperature flue gas is discharged from the bottom outlet (1-1-2) of the first stage catalytic combustion zone (1-1), enters the first stage heat exchanger (2) through the hot inlet (2-3) for heat exchange, and after heat exchange, the first stage high-temperature flue gas enters the top inlet (1-2-1) of the second stage catalytic combustion zone (1-2) through the cold outlet (2-4) of the first stage heat exchanger (2), and performs a second stage catalytic reaction layer by layer on the multiple layers of catalysts arranged at intervals in the second stage catalytic combustion zone (1-2), thereby obtaining a second stage high-temperature flue gas; during the process of performing the second stage catalytic reaction layer by layer, the first stage high-temperature flue gas is respectively mixed with the air from the air guide pipe (6) above each layer of catalyst. , the second stage catalytic reaction is an oxygen-deficient reaction; the second stage catalytic reaction includes a fourth stage catalytic reaction, a fifth stage catalytic reaction and a sixth stage catalytic reaction carried out in sequence, and the volume contents of O2 in the fourth stage catalytic reaction, the fifth stage catalytic reaction and the sixth stage catalytic reaction in the second stage catalytic reaction are 0.4-0.5%, 0.6-0.7% and 0.8-0.9% respectively; the temperatures of the fourth stage catalytic reaction, the fifth stage catalytic reaction and the sixth stage catalytic reaction in the second stage catalytic reaction are 200-230°C, 340-360°C and 450-480°C respectively, and the temperature of the second stage high temperature flue gas is 450-480°C; (c) The second stage high-temperature flue gas is discharged from the bottom outlet (1-2-2) of the second stage catalytic combustion zone (1-2), enters the second stage heat exchanger (3) through the hot inlet (3-3), and exchanges heat with the low-temperature flue gas discharged from the low-temperature flue gas outlet (4-1) of the pulverized coal drying section (4) in the second stage heat exchanger (3). After the heat exchange, the low-temperature flue gas is discharged from the hot outlet (3-2) of the second stage heat exchanger (3) and enters the pulverized coal drying section (4) through the hot flue gas inlet (4-2). The low-temperature flue gas is also partially discharged through the flue gas external outlet (4-3); after the heat exchange, the second stage high-temperature flue gas is discharged from the second stage heat exchanger (3) through the hot flue gas inlet (4-2). The flue gas is discharged from the cold outlet (3-4) of the stage heat exchanger (3) and enters the top inlet (1-3-1) of the three-stage catalytic combustion zone (1-3), and undergoes a three-stage catalytic reaction on the catalyst of the three-stage catalytic combustion zone (1-3) to obtain three-stage high-temperature flue gas; during the three-stage catalytic reaction, the second-stage high-temperature flue gas is mixed with the air from the air guide pipe (6) above the catalyst of the three-stage catalytic combustion zone (1-3), and the three-stage catalytic reaction is an oxygen-enriched reaction; the volume content of O2 in the three-stage catalytic reaction is 3-4%, and the temperature of the three-stage high-temperature flue gas is 550-650°C; (d) The three-stage high-temperature flue gas is discharged from the bottom outlet (1-3-2) of the three-stage catalytic combustion zone (1-3), enters the boiler (5-1) through the heating gas inlet (5-1-1), and transfers heat to the soft water in the steam drum (5-2) through the boiler (5-1), and the soft water is converted into medium-pressure steam for external use; after transferring heat, the three-stage high-temperature flue gas is discharged from the heating gas outlet (5-1-2) of the boiler (5-1), and enters the coal grinding drying section (4) through the hot flue gas inlet (4-2).

2. The method according to claim 1, characterized in that The bottom outlet (1-3-2) of the three-stage catalytic combustion zone (1-3) is also connected to the hot flue gas inlet (4-2) of the coal grinding and drying section (4).

3. The method according to claim 1, characterized in that After being discharged from the bottom outlet (1-3-2) of the three-stage catalytic combustion zone (1-3), the three-stage high-temperature flue gas also enters the coal grinding and drying section (4) through the hot flue gas inlet (4-2).

4. The method according to claim 1, characterized in that In the step (a), the temperature of the tail gas washed with liquid nitrogen rises to 230-240° C. after heat exchange.

5. The method according to claim 1, characterized in that In the step (b), the temperature of a section of high-temperature flue gas is reduced to 220-240° C. after heat exchange.

6. The method according to claim 1, characterized in that In the step (c), the temperature of the low-temperature flue gas is 90-100°C, and the temperature of the low-temperature flue gas after heat exchange rises to 150-180°C; the temperature of the second-stage high-temperature flue gas after heat exchange drops to 300-350°C.

7. The method according to claim 1, characterized in that In the step (d), the temperature of the three sections of high-temperature flue gas drops to 250-300° C. after transferring heat.

8. The method according to claim 1, characterized in that In the steps (c) and (d), the oxygen content in the coal grinding and drying section (4) is ≤3%, and the total content of CO and H2 is <200 ppm.

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