Liquid nitrogen washing tail gas resource utilization system and method

Abstract

The application provides a liquid nitrogen washing tail gas resource utilization system and method, and belongs to the technical field of tail gas treatment and energy recovery. The application uses a heat exchanger (1) to heat exchange the liquid nitrogen washing tail gas, so that the liquid nitrogen washing tail gas is combusted at a suitable working temperature of a first catalyst (3). In the application, the first catalytic combustion tower (2) is communicated with a constant temperature device, so that the temperature of the first catalytic combustion tower (2) is stably kept at 250-320 DEG C, the safety hidden danger caused by violent reaction is eliminated, and the catalyst cost is significantly reduced. Meanwhile, the steam generated after the constant temperature device is cooled can be used for enterprise heating and heating, and economic benefits are created. The application uses a second catalytic combustion tower (4) to fully catalytically oxidize the combustible gas in the first flue gas, and the generated second flue gas is partly used for heat exchange of the heat exchanger (1), and the gas after heat exchange and the other part of the second flue gas are used for heat supply of a coal mill (6), so that the heat is fully recycled and utilized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tail gas treatment and energy recovery, in particular to a liquid nitrogen washing tail gas resource utilization system and method. BACKGROUND

[0002] The synthetic ammonia industry is the basis of global chemical industry, and in China, coal is mainly used as raw material for synthetic ammonia production. The coal powder gasification process has a high gasification efficiency, small environmental pollution, and high carbon conversion rate, and thus its proportion in the coal-to-synthetic ammonia industry is increasing. The coal powder gasification process for synthetic ammonia production mainly includes the following steps: gasification, dust removal, desulfurization, shift conversion, decarburization, fine CO removal, and ammonia synthesis. In large-scale coal-to-synthetic ammonia industries, the low-temperature methanol washing process is mainly used for decarburization to remove CO2, H2S, and other impurities. The low-temperature crude hydrogen gas obtained through the low-temperature methanol washing process is generally matched with a low-temperature liquid nitrogen washing process to remove trace amounts of harmful impurities such as CH4, CO, Ar, and CO2 in the crude hydrogen gas to obtain clean H2, which is then used for ammonia synthesis. The liquid rich in harmful impurities after the liquid nitrogen washing process is discharged after cold energy recovery, and the liquid nitrogen washing tail gas contains CH4 (1-2%), CO (6-10%), H2 (2-3%), N2 (85-90%), and CO2. The liquid nitrogen washing tail gas has a low heat value (about 1200-2000 kJ / m 3 ), and cannot be directly combusted and purified.

[0003] At present, the utilization rate of the liquid nitrogen washing tail gas in the synthetic ammonia industry is very low. The domestic enterprises mainly use two methods to treat the low-heat-value liquid nitrogen washing tail gas, i.e., hot blast stove mixed synthesis gas combustion and flare venting combustion. Due to the low heat value of the liquid nitrogen washing tail gas, in the hot blast stove mixed combustion process, a large amount of synthesis gas and a small amount of liquid nitrogen washing tail gas are mixed and then sent to the hot blast stove for combustion in order to increase the heat value. This not only increases the power consumption of the boiler induced draft fan, but also mainly causes a large amount of heat to be taken away by the induced draft fan, which not only fails to recover the heat, but also reduces the thermal efficiency of the boiler. Therefore, in most cases, most of the liquid nitrogen washing tail gas can only be sent to the flare venting combustion, which greatly wastes energy. SUMMARY

[0004] In view of the above, the present application aims to provide a liquid nitrogen washing tail gas resource utilization system and method. The system and method provided by the present application can recover the heat in the liquid nitrogen washing tail gas, thereby bringing economic benefits.

[0005] In order to achieve the above-mentioned purpose of the present application, the present application provides the following technical solutions:

[0006] The present application provides a liquid nitrogen washing tail gas resource utilization system, which comprises a heat exchanger 1, wherein the heat exchanger 1 is provided with a liquid nitrogen washing tail gas inlet, a liquid nitrogen washing tail gas outlet, a heat exchange gas inlet, and a heat exchange gas outlet.

[0007] A first catalytic combustion tower 2 is connected to the outlet of the heat exchanger 1, and the first catalytic combustion tower 2 is connected to a constant temperature device, which is provided with a water inlet and a steam outlet; a first catalyst 3 is arranged in the first catalytic combustion tower 2; a first air inlet is arranged between the first catalytic combustion tower 2 and the pipeline connected to the outlet of the heat exchanger 1; and the first catalytic combustion tower 2 is provided with a first flue gas outlet;

[0008] A second catalytic combustion tower 4 is connected to the first flue gas outlet of the low-temperature catalytic combustion tower, and the second catalytic combustion tower 4 is provided with a second catalyst 5; a second air inlet is arranged between the second catalytic combustion tower 4 and the pipeline connected to the first flue gas outlet of the low-temperature catalytic combustion tower; the second catalytic combustion tower 4 is provided with a second flue gas outlet; and the second flue gas outlet is connected to the heat exchange gas inlet of the heat exchanger 1;

[0009] A coal mill 6 is provided with a gas inlet and a gas outlet, and the gas inlet is connected to the heat exchange gas outlet of the heat exchanger 1 and the second flue gas outlet of the second catalytic combustion tower 4.

[0010] Preferably, the constant temperature device of the first catalytic combustion tower 2 is a water curtain constant temperature device.

[0011] The water curtain constant temperature device comprises an expansion tank 7 arranged outside the first catalytic combustion tower 2, and the expansion tank 7 is provided with a water inlet, a water outlet, a steam inlet and a steam outlet.

[0012] A water storage chamber 8 is connected to the water outlet of the expansion tank 7, and the water storage chamber 8 is arranged inside the first catalytic combustion tower 2.

[0013] A steam storage chamber 9 is arranged inside the first catalytic combustion tower 2, and the outlet of the steam storage chamber 9 is connected to the steam inlet of the expansion tank 7; and the steam storage chamber 9 is not connected to the water storage chamber 8.

[0014] A heat exchange sleeve is arranged inside the first catalyst 3; the heat exchange sleeve comprises a heat exchange inner sleeve 10-1 and a heat exchange outer sleeve 10-2 nested outside the heat exchange inner sleeve 10-1; the bottom of the heat exchange inner sleeve 10-1 is connected to the heat exchange outer sleeve 10-2; the heat exchange inner sleeve 10-1 is connected to the water storage chamber 8, and the heat exchange outer sleeve 10-2 is connected to the steam storage chamber 9.

[0015] Preferably, the first catalyst 3 comprises a composite oxide composed of MnO2, CeO2 and ZrO2.

[0016] Preferably, the active component of the second catalyst 5 is Pt and / or Ag.

[0017] Preferably, the gas outlet of the coal mill 6 is connected to the gas inlet.

[0018] The application provides a method for resource utilization of liquid nitrogen washing tail gas by using the liquid nitrogen washing tail gas resource utilization system.

[0019] (1) The liquid nitrogen washing tail gas enters the heat exchanger 1 to be heated, and the obtained hot liquid nitrogen washing tail gas is mixed with air entering the first air inlet and then enters the first catalytic combustion tower 2 to be subjected to first catalytic combustion, so as to obtain first flue gas; during the first catalytic combustion, water enters the constant temperature device to reduce the temperature of the first catalytic combustion tower 2 to 250-320 DEG C, and steam is generated;

[0020] (2) The first flue gas is mixed with air entering the second air inlet and then enters the second catalytic combustion tower (4) to be subjected to second catalytic combustion, so as to obtain second flue gas;

[0021] (3) Part of the second flue gas enters the heat exchanger 1 to be subjected to heat exchange, so as to obtain cooled second flue gas, and the cooled second flue gas and the remaining second flue gas enter the coal mill 6, and the obtained cooled gas is discharged through the gas outlet.

[0022] Preferably, the temperature of the hot liquid nitrogen washing tail gas is 220-300 DEG C, and the volume ratio of the hot liquid nitrogen washing tail gas to air is 100:10-19.5.

[0023] Preferably, the temperature of the first flue gas is 250-320 DEG C, and the volume ratio of the liquid nitrogen washing tail gas to air entering the second air inlet is 100:15-19.5.

[0024] Preferably, the temperature of the second flue gas is 450-550 DEG C.

[0025] Preferably, the volume ratio of the cooled second flue gas to the remaining second flue gas is 1:0.71-0.81.

[0026] The application provides a liquid nitrogen washing tail gas resource utilization system, which comprises a heat exchanger 1, a first catalytic combustion tower 2, a second catalytic combustion tower 4 and a coal mill 6. The liquid nitrogen washing tail gas is subjected to heat exchange by the heat exchanger 1, so that the temperature of the liquid nitrogen washing tail gas can be increased, and the liquid nitrogen washing tail gas can be combusted at a suitable working temperature of the first catalyst 3. The heat for heat exchange is obtained from the second flue gas generated by combustion of the second catalytic combustion tower 4. The liquid nitrogen washing tail gas is subjected to first catalytic combustion by the first catalytic combustion tower 2, so that the CO in the liquid nitrogen washing tail gas can be combusted. In the application, the first catalytic combustion tower 2 is communicated with a constant temperature device, so that the temperature of the first catalytic combustion tower 2 can be ensured to be 250-320 DEG C, and the safety hidden danger of explosion of the first catalytic combustion tower caused by violent reaction can be avoided. Meanwhile, the constant temperature device is used for cooling by water, and the steam generated after cooling can be used for enterprise heating and heating, so that economic benefits can be created. The combustible gas in the first flue gas is fully combusted by the second catalytic combustion tower 4, and the second flue gas generated is used for heat exchange of the heat exchanger 1, and the gas after heat exchange and the other part of the second flue gas are used for heat supply of the coal mill 6, so that the heat can be fully recycled, the carbon deposition problem of high-temperature anoxic reaction can be avoided, and the equipment loss caused by excessive pressure can be reduced.

[0027] Meanwhile, the liquid nitrogen washing tail gas resource utilization system provided by the application can realize purification of the liquid nitrogen washing tail gas, the content of CO and CH4 in the second flue gas is ≤200 mg / Nm 3 , and the harm of CO to the environment can be avoided. The liquid nitrogen washing tail gas resource utilization system provided by the application has simple device structure, low investment cost and low operation cost. The application adopts the design of double-tower combination of the first catalytic combustion tower 2 and the second catalytic combustion tower 4, compared with the same amount of processing device, the safety performance is improved, and the cost is reduced by about 50-60%.

[0028] The application realizes the following four breakthroughs: 1, the carbon deposition problem of high-temperature anoxic reaction is avoided; 2, the equipment loss caused by excessive heat pressure is reduced; 3, the reaction conditions are optimized, and the service life of the catalyst is prolonged; 4, the reaction temperature is reduced, and the safety is improved; the problem of frequent cracking of the equipment under the action of continuous high-temperature thermal stress is solved, and the investment and operation cost is reduced. 5, the first catalyst can use non-noble metal catalyst, the catalyst cost is reduced by 70%, and the investment and operation cost is greatly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a schematic diagram of the liquid nitrogen washing tail gas resource utilization system, wherein 1 is a heat exchanger, 2 is a first catalytic combustion tower, 3 is a first catalyst, 4 is a second catalytic combustion tower, 5 is a second catalyst, 6 is a coal mill, 7 is an expansion tank, 8 is a water storage chamber, 9 is a steam storage chamber, 10-1 is a heat exchange inner sleeve, 10-2 is a heat exchange outer sleeve, and 11 is a gas storage chamber. DETAILED DESCRIPTION

[0030] The application provides a liquid nitrogen washing tail gas resource utilization system, which comprises a heat exchanger 1, wherein the heat exchanger 1 is provided with a liquid nitrogen washing tail gas inlet, a liquid nitrogen washing tail gas outlet, a heat exchange gas inlet and a heat exchange gas outlet.

[0031] A first catalytic combustion tower 2 in communication with the liquid nitrogen washing tail gas outlet of the heat exchanger 1 is arranged at the inlet, the first catalytic combustion tower 2 is in communication with a constant temperature device, the constant temperature device is provided with a water inlet and a steam outlet, a first catalyst 3 is arranged in the first catalytic combustion tower 2, a first air inlet is arranged between the first catalytic combustion tower 2 and a pipeline in communication with the liquid nitrogen washing tail gas outlet of the heat exchanger 1, and the first catalytic combustion tower 2 is provided with a first flue gas outlet.

[0032] A second catalytic combustion tower 4 in communication with the first flue gas outlet of the low-temperature catalytic combustion tower is arranged at the inlet, the second catalytic combustion tower 4 is provided with a second catalyst 5, a second air inlet is arranged between the second catalytic combustion tower 4 and a pipeline in communication with the first flue gas outlet of the low-temperature catalytic combustion tower, the second catalytic combustion tower 4 is provided with a second flue gas outlet, and the second flue gas outlet is in communication with the heat exchange gas inlet of the heat exchanger 1.

[0033] A coal mill 6 is arranged at the inlet, the coal mill 6 is provided with a gas inlet and a gas outlet, and the gas inlet is in communication with the heat exchange gas outlet of the heat exchanger 1 and the second flue gas outlet of the second catalytic combustion tower 4.

[0034] The liquid nitrogen washing tail gas resource utilization system provided by the application comprises a heat exchanger 1. The application does not have special requirements for the type of the heat exchanger 1, and the type of the heat exchanger 1 known to those skilled in the art can be used. In the application, the pipeline between the liquid nitrogen washing tail gas inlet and the liquid nitrogen washing tail gas outlet in the heat exchanger 1 is not in communication with the pipeline between the heat exchange gas inlet and the heat exchange gas outlet.

[0035] The liquid nitrogen washing tail gas resource utilization system provided by the application comprises a first catalytic combustion tower 2 in communication with the liquid nitrogen washing tail gas outlet of the heat exchanger 1 at the inlet, the first catalytic combustion tower 2 is in communication with a constant temperature device, the constant temperature device is provided with a water inlet and a steam outlet, a first catalyst 3 is arranged in the first catalytic combustion tower 2, a first air inlet is arranged between the first catalytic combustion tower 2 and a pipeline in communication with the liquid nitrogen washing tail gas outlet of the heat exchanger 1, and the first catalytic combustion tower 2 is provided with a first flue gas outlet.

[0036] In the application, the composition of the first catalyst 3 comprises a composite oxide composed of MnO2, CeO2 and ZrO2. x In the composite oxide composed of MnO2, CeO2 and ZrO2, MnO2 accounts for 20% to 30%, CeO2 accounts for 30% to 40%, and ZrO2 accounts for 30% to 40%. xThe mass percentage of MnO is 15-20%, the mass percentage of CeO2 is 32-34%, and the mass percentage of ZrO2 is 48-51%. In the present application, the first catalyst preferably further comprises a promoter component, which is one or more of BaO, La2O3 and Y2O3; in the present application, the mass of the promoter component is 3-6% of the total mass of the first catalyst 3.

[0037] As a specific embodiment of the present application, the preparation method of the first catalyst 3 comprises the following steps:

[0038] 1) mixing manganese nitrate, cerium nitrate, zirconium nitrate, a second metal nitrate compound and water, and performing a precipitation reaction on the obtained second mixture under the action of a buffer to obtain a precipitate;

[0039] 2) drying and calcining the precipitate to obtain a high-temperature catalytic combustion catalyst; the second metal nitrate compound comprises one or more of barium nitrate, lanthanum nitrate, zirconium nitrate and yttrium nitrate.

[0040] Preferably, the temperature of the first calcination is 450-550°C, and the time is 2.5-3.5h.

[0041] Preferably, the buffer in step 1) is a mixture of saturated sodium carbonate and concentrated ammonia water, and the volume ratio of the saturated sodium carbonate to the concentrated ammonia water is 1:1.

[0042] Preferably, the temperature of the second calcination is 500-700°C, and the time is 4-6h.

[0043] In the present application, the constant-temperature device is preferably a water curtain constant-temperature device; the water curtain constant-temperature device comprises an expansion pool 7 located outside the first catalytic combustion tower 2, and the expansion pool 7 is provided with a water inlet, a water outlet, a steam inlet and a steam outlet;

[0044] A water storage chamber 8 in communication with the water outlet of the expansion pool 7, the water storage chamber 8 being located inside the first catalytic combustion tower 2;

[0045] A steam storage chamber 9 located inside the first catalytic combustion tower 2, the outlet of the steam storage chamber 9 being in communication with the steam inlet of the expansion pool 7; the steam storage chamber 9 is not in communication with the water storage chamber 8;

[0046] A heat exchange sleeve 10 located inside the first catalyst 3; the heat exchange sleeve 10 comprises a heat exchange inner sleeve 10-1 and a heat exchange outer sleeve 10-2 nested outside the heat exchange inner sleeve 10-1, the bottom of the heat exchange inner sleeve 10-1 being in communication with the heat exchange outer sleeve 10-2; the heat exchange inner sleeve 10-1 is in communication with the water storage chamber 8, and the heat exchange outer sleeve 10-2 is in communication with the steam storage chamber 9.

[0047] The present application does not have special requirements for the kind of the expansion tank 7, and the expansion tank 7 known by those skilled in the art can be used. In the present application, the water outlet is preferably arranged at the bottom of the expansion tank 7, and the steam outlet is preferably arranged at the top of the expansion tank 7.

[0048] In the present application, the water storage chamber 8 is preferably arranged at the top of the first catalytic combustion tower 2, and the steam storage chamber 9 is arranged below the water storage chamber 8.

[0049] The present application does not have special requirements for the specific size and specification of the heat exchange inner sleeve 10-1 and the heat exchange outer sleeve 10-2, and corresponding design can be made according to the actual situation. In the present application, the outer wall of the heat exchange sleeve 10 is preferably coated with high-temperature corrosion-resistant paint.

[0050] In the present application, the cooling water of the water curtain type constant temperature device is preferably soft water. In the present application, the cooling method of the water curtain type constant temperature device is as follows: water enters the expansion tank 7, passes through the water outlet of the expansion tank 7 to enter the water storage chamber 8, and then enters the heat exchange inner sleeve 10-1; the water in the heat exchange inner sleeve 10-1 enters the heat exchange outer sleeve 10-2 through the opening at the bottom, the outer wall of the heat exchange outer sleeve 10-2 contacts the first catalyst 3 to cool the first catalyst 3, the water in the heat exchange outer sleeve 10-2 is heated to become a steam-water mixture, enters the steam storage chamber 9, and is then transported to the expansion tank 7 through a pipeline, a part of the gas is sent out in the form of low-pressure steam, and the other part is mixed with the cooling water in the expansion tank 7 to continue to participate in the circulation.

[0051] In the present application, the first catalytic combustion tower 2 is preferably provided with a gas storage chamber 11, which is preferably arranged below the steam storage chamber 9 and communicates with the first catalyst 3. In the present application, the gas storage chamber communicates with the inlet of the first catalytic combustion tower 2.

[0052] In the present application, the inlet of the first catalytic combustion tower 2 is preferably arranged at the sidewall above the tower, and the outlet of the first catalytic combustion tower 2 is preferably arranged at the bottom of the tower.

[0053] The liquid nitrogen washing tail gas resource utilization system provided by the application comprises a second catalytic combustion tower 4 in communication with the first flue gas outlet of the low-temperature catalytic combustion tower through an inlet, and a second catalyst 5 is arranged in the second catalytic combustion tower 4; a second air inlet is arranged between the second catalytic combustion tower 4 and the pipeline in communication with the first flue gas outlet of the low-temperature catalytic combustion tower; the second catalytic combustion tower 4 is provided with a second flue gas outlet; and the second flue gas outlet is in communication with the heat exchange gas inlet of the heat exchanger 1. In the application, the active component of the second catalyst 5 is preferably one or more of Ag and Pt. In the application, the second catalyst 5 comprises a carrier, an active component and a catalyst promoter, the carrier component is preferably a CeO2-ZrO2-Al2O3 mesoporous carrier, the content of CeO2 in the CeO2-ZrO2-Al2O3 mesoporous carrier is 15-25%, the content of ZrO2 is 15-25%, and the content of Al2O3 is 50-70%; the catalyst promoter is one or more of La, Y, K, Sr and Ba metal oxides; in the application, the active component accounts for 0.05-0.8% of the total mass of the catalyst in terms of noble metal elements; and the catalyst promoter accounts for 3-20% of the total mass of the catalyst in terms of metal oxides. The preparation method of the second catalyst 5 refers to the method in CN110152660A.

[0054] The liquid nitrogen washing tail gas resource utilization system provided by the application comprises a coal mill 6, the coal mill 6 is provided with a gas inlet and a gas outlet, and the gas inlet is in communication with the heat exchange gas outlet of the heat exchanger 1 and the second flue gas outlet of the second catalytic combustion tower 4. In the application, the gas outlet of the coal mill 6 is preferably in communication with the gas inlet, so that the gas containing residual heat discharged from the gas outlet reenters the steam as a heat source, thereby achieving full utilization of heat.

[0055] A schematic diagram of the liquid nitrogen washing tail gas resource utilization system provided by the application is shown in Figure 1 , wherein 1 is a heat exchanger, 2 is a first catalytic combustion tower, 3 is a first catalyst, 4 is a second catalytic combustion tower, 5 is a second catalyst, 6 is a coal mill, 7 is an expansion tank, 8 is a water storage chamber, 9 is a steam storage chamber, 10-1 is a heat exchange inner sleeve, 10-2 is a heat exchange outer sleeve, and 11 is a gas storage chamber.

[0056] The application provides a method for resource utilization of liquid nitrogen washing tail gas based on the above-mentioned liquid nitrogen washing tail gas resource utilization system, which comprises the following steps:

[0057] (1) The liquid nitrogen washing tail gas enters the heat exchanger 1 to be heated, and the obtained hot liquid nitrogen washing tail gas is mixed with air entering the first air inlet and then enters the first catalytic combustion tower 2 to be subjected to first catalytic combustion, so as to obtain first flue gas; during the first catalytic combustion, water enters a constant-temperature device to cool the first catalytic combustion tower 2 to 270-320 DEG C and generate steam;

[0058] (2) the first flue gas mixes with the air entering the second air inlet, and then enters the second catalytic combustion tower 4 to perform second catalytic combustion, thereby obtaining a second flue gas;

[0059] (3) a part of the second flue gas enters the heat exchanger 1 to perform heat exchange, thereby obtaining a cooled second flue gas, and the cooled second flue gas and the remaining second flue gas enter the coal mill 6, and the obtained cooled gas is discharged through the gas outlet.

[0060] In the present application, the liquid nitrogen washing tail gas enters the heat exchanger 1 to be heated, and the obtained hot liquid nitrogen washing tail gas mixes with the air entering the first air inlet, and then enters the first catalytic combustion tower 2 to perform first catalytic combustion, thereby obtaining a first flue gas; during the first catalytic combustion, water enters the thermostat device to cool the first catalytic combustion tower 2 to 250-320℃, and steam is generated. The present application does not have special requirements for the type of the liquid nitrogen washing tail gas, and the liquid nitrogen washing tail gas known to those skilled in the art can be used. As a specific embodiment of the present application, the composition of the liquid nitrogen washing tail gas includes CH4 1-2%, CO 6-10%, H2 2-3%, N2 85-90% and the balance of CO2, in terms of volume percentage.

[0061] In the present application, the temperature of the hot liquid nitrogen washing tail gas is preferably 220-300℃, and more preferably 240-280℃; the volume ratio of the hot liquid nitrogen washing tail gas to air is preferably 100:10-19.5, and more preferably 100:14.5-15.5. In the present application, the temperature of the hot liquid nitrogen washing tail gas is higher than the activation temperature of the first catalyst for catalyzing CO combustion, and the first catalytic combustion can be spontaneously performed without external heat source.

[0062] In the present application, the flow rate of the liquid nitrogen washing tail gas is preferably 10000-60000 Nm 3 / h, and preferably 30000-50000 Nm 3 / h.

[0063] In the present application, during the first catalytic combustion, water enters the thermostat device to cool the first catalytic combustion tower 2 to 270-320℃, and steam is generated. The present application does not have special requirements for the flow rate of the water, which can only ensure that the temperature of the first catalytic combustion tower 2 reaches the requirement. Through the first catalytic combustion, the present application can preliminarily reduce the content of CO in the liquid nitrogen washing tail gas.

[0064] After the first flue gas is obtained, the first flue gas is mixed with air entering the second air inlet, and then enters the second catalytic combustion tower 4 to perform the second catalytic combustion, so as to obtain the second flue gas. In the present application, the temperature of the first flue gas is preferably 250-320°C, and more preferably 280-300°C; the volume ratio of the liquid nitrogen washing tail gas to the air entering the second air inlet is preferably 100:15-19.5, and more preferably 100:16-18. In the present application, the temperature of the second flue gas is preferably 450-550°C, and more preferably 480-520°C. In the present application, the temperature of the first flue gas is higher than the activation temperature of the second catalyst for catalyzing CO combustion, and after the CO is combusted, the temperature of the obtained flue gas is 450-480°C, which is higher than the activation temperature of the second catalyst for catalyzing CH4 combustion, so that the second catalytic combustion can be spontaneously performed without external heat source.

[0065] After the second flue gas is obtained, a part of the second flue gas enters the heat exchanger 1 to perform heat exchange, so as to obtain the cooled second flue gas, and the cooled second flue gas and the remaining second flue gas enter the coal mill 6, and the obtained cooled gas is discharged through the gas outlet. In the present application, the inlet gas temperature of the device using steam as a heat source is preferably 250-300°C, and more preferably 260-280°C; and the outlet gas temperature is 70-90°C, and more preferably 80°C.

[0066] In the present application, the volume ratio of the cooled second flue gas to the remaining second flue gas is preferably 1:0.71-0.81, and more preferably 1:0.74-0.78.

[0067] In the present application, when the gas outlet of the coal mill 6 is communicated with the gas inlet, the volume ratio of the cooled second flue gas, the remaining second flue gas and the device outlet return gas is 1:0.71-0.81:0.71-0.8, and more preferably 1:0.74-0.78:0.74-0.78.

[0068] The liquid nitrogen washing tail gas resource utilization system and method provided by the present application will be described in detail below in combination with examples, but they should not be understood as limiting the scope of protection of the present application.

[0069] Example 1

[0070] Use Figure 1 The liquid nitrogen washing tail gas resource utilization system shown is used for resource utilization of liquid nitrogen washing tail gas, wherein the first catalyst 3 is a CeO2-MnO2-ZrO2-based catalyst, and the second catalyst 5 is a Pt / CeO2-ZrO2-Al2O3 catalyst.

[0071] The liquid nitrogen washing tail gas treatment capacity is 40000 Nm 3 / h;

[0072] By volume percentage, the liquid nitrogen washing components are: H2: 1.52%; CO: 9.00%; N2: 88.28%; CH4: 1.20%.

[0073] The specific method is as follows:

[0074] (1) The liquid nitrogen scrubbing exhaust gas enters heat exchanger 1 and mixes with the second flue gas from the second catalytic combustion tower 4 at a temperature of 550°C. The flue gas temperature rises from 90°C to 280°C, and then mixes with air (Q = 5000m). 3 The mixture (at a rate of 1 h) enters the first catalytic combustion tower 2 for combustion. Since the flue gas temperature is 280℃, higher than the activation temperature of the first catalyst 3 (180℃), the first catalyst 3 is activated, and the temperature inside the tower rises to 500℃. Therefore, the first catalytic combustion can spontaneously occur without an external heating source, producing the first flue gas. Simultaneously, circulating water cools the gas, ensuring the tower and flue gas temperatures remain between 270 and 320℃, preventing violent reactions that could lead to an explosion in the combustion tower. The first flue gas temperature is 260℃, and the CO content decreases to 4%.

[0075] (2) Flue gas and air (Q=2500m) 3 After mixing ( / h), the mixture enters the second catalytic combustion tower 4. Since the temperature of the first flue gas is 260℃, which is higher than the activation temperature of the second catalyst 5 (180℃) for CO combustion, CO combustion occurs, and the temperature inside the tower rises to 450℃, which is higher than the activation temperature of CH4 (400℃), causing CH4 combustion. At this point, the temperature inside the tower rises to 520℃. Therefore, the second catalytic combustion reaction can proceed spontaneously without an external heating source, producing a second flue gas with a temperature of 500℃. The CO and CH4 content in the second flue gas is reduced to 150 mg / Nm³. 3 At this point, part of the second flue gas enters heat exchanger 1 to heat the liquid nitrogen washing tail gas, and the rest is used to dry the pulverized coal in the coal mill.

[0076] Calculations show that the system provided by this invention can reduce exhaust gas treatment costs to 1.33 yuan / kNm³. 3 .

[0077] Example 2

[0078] use Figure 1 The liquid nitrogen scrubbing tail gas resource utilization system shown above utilizes the liquid nitrogen scrubbing tail gas for resource utilization. The first catalyst 3 is a CeO2-MnO2-ZrO2-based catalyst, and the second catalyst 5 is a Pt / CeO2-ZrO2-Al2O3 catalyst.

[0079] Liquid nitrogen scrubbing exhaust gas treatment capacity: 60000 Nm³ 3 / h;

[0080] By volume percentage, the liquid nitrogen washing components are: H2: 1.62%; CO: 9.00%; N2: 88.20%; CH4: 1.18%.

[0081] The specific method is as follows:

[0082] (1) The liquid nitrogen scrubbing exhaust gas enters heat exchanger 1 and mixes and exchanges heat with the second flue gas from the second catalytic combustion tower 4 at a temperature of 550℃. The flue gas temperature rises from 90℃ to 280℃, and then it mixes with air (Q = 6500m). 3 The mixture ( / h) enters the first catalytic combustion tower 2 for combustion. At this point, the flue gas temperature is 280℃, 180℃ higher than the activation temperature of the first catalyst 3. The catalyst is activated, and the CO in the tail gas is burned by liquid nitrogen scrubbing. The temperature inside the tower rises to 460℃, generating the first flue gas, ensuring the reaction can proceed spontaneously without an external heating source. Simultaneously, circulating water cools the gas, ensuring the tower and flue gas temperatures remain between 270 and 320℃, preventing a violent reaction that could lead to an explosion in the combustion tower. The temperature of the first flue gas is 280℃, and the CO content decreases to 3%.

[0083] (2) First flue gas and air (Q = 3300m) 3 After mixing ( / h), the mixture enters the second catalytic combustion tower 4. Since the flue gas temperature is 280℃, higher than the activation temperature of the second catalyst 5 (180℃) for CO combustion, the first flue gas undergoes low-temperature combustion. The temperature inside the tower rises to 460℃, higher than the activation temperature of the second catalyst 5 (400℃) for CH4 combustion. CH4 then combusts, and the temperature inside the tower rises to 520℃. Therefore, the reaction can also proceed spontaneously without an external heating source. The resulting second flue gas is at 480℃, at which point the CO and CH4 content decreases to 200 mg / Nm³. 3 At this point, part of the second flue gas enters heat exchanger 1 to heat the liquid nitrogen washing tail gas, and the rest is used to dry the pulverized coal in the coal mill.

[0084] Example 3

[0085] use Figure 1 The liquid nitrogen scrubbing tail gas resource utilization system shown above utilizes the liquid nitrogen scrubbing tail gas. The first catalyst 3 is a CeO2-MnO2-ZrO2-based catalyst, and the second catalyst 5 is a Pt / CeO2-ZrO2-Al2O3 catalyst disclosed.

[0086] Liquid nitrogen scrubbing exhaust gas treatment capacity: 40000 Nm 3 / h;

[0087] By volume percentage, the liquid nitrogen washing components are: H2: 1.62%; CO: 8.50%; N2: 88.58%; CH4: 1.30%.

[0088] The specific method is as follows:

[0089] (1) The liquid nitrogen scrubbing exhaust gas enters heat exchanger 1 and mixes with the second flue gas from the second catalytic combustion tower 4 at a temperature of 550℃. After the temperature rises from 90℃ to 280℃, it mixes with air (Q = 4000m). 3 After mixing ( / h), the mixture enters the first catalytic combustion tower 2 for combustion. At this point, the flue gas temperature is 270℃, which is 180℃ higher than the activation temperature of the first catalyst 3. The catalyst is activated, and the tail gas is washed with liquid nitrogen for low-temperature combustion, raising the temperature inside the tower to 450-480℃, generating the first flue gas. This ensures that the reaction can proceed spontaneously without an external heating source. Simultaneously, circulating water is used for cooling, ensuring that the tower body and flue gas temperature are maintained between 270-320℃ to prevent violent reactions that could lead to an explosion of the combustion tower. The temperature of the first flue gas is 270℃, and the CO content decreases to 3%.

[0090] (2) First flue gas and air (Q = 2500m) 3 After mixing ( / h), the mixture enters the second catalytic combustion tower 4. Since the flue gas temperature is 270℃, higher than the activation temperature of the second catalyst 5 (180℃) for CO combustion, the first flue gas undergoes low-temperature combustion. The temperature inside the tower rises to 480℃, higher than the activation temperature of the second catalyst 5 (400℃) for CH4 combustion. CH4 combustion occurs, and the temperature inside the tower rises to 530℃. Therefore, the reaction can also proceed spontaneously without an external heating source. The resulting second flue gas has a temperature of 510℃, at which point the CO and CH4 content decreases to 150 mg / Nm³. 3 At this point, part of the second flue gas enters heat exchanger 1 to heat the liquid nitrogen washing tail gas, and the rest is used to dry the pulverized coal in the coal mill.

[0091] Example 4

[0092] use Figure 1 The liquid nitrogen scrubbing tail gas resource utilization system shown above utilizes the liquid nitrogen scrubbing tail gas for resource utilization. The first catalyst 3 is a CeO2-MnO2-ZrO2-based catalyst, and the second catalyst 5 is an Ag / CeO2-ZrO2-Al2O3 catalyst.

[0093] Liquid nitrogen scrubbing exhaust gas treatment capacity: 10000 Nm³ 3 / h;

[0094] By volume percentage, the liquid nitrogen washing components are: H2: 1.62%; CO: 7.50%; N2: 89.08%; CH4: 1.80%.

[0095] The specific method is as follows:

[0096] (1) The liquid nitrogen scrubbing exhaust gas enters heat exchanger 1 and mixes with the second flue gas from the second catalytic combustion tower 4 at a temperature of 550℃. The flue gas temperature rises from 90℃ to 280℃ and then mixes with air (Q=1000m). 3h) mixed and burned in the first catalytic combustion tower 2. At this time, the flue gas temperature is 280℃, which is higher than the activation temperature of the first catalyst 3, 180℃, and the catalyst is activated. The tail gas is washed with liquid nitrogen, and the temperature in the tower is raised to 450℃, generating the first flue gas, which ensures that the reaction can proceed spontaneously without external heat source. At the same time, the circulating water is cooled to ensure that the tower body and flue gas temperature is 270-320℃, and to prevent the reaction from being too violent to cause the combustion tower to explode. The temperature of the first flue gas is 280℃, and the CO content is reduced to 3%.

[0097] (2) The first flue gas is mixed with air (Q=800m 3 h) mixed and burned in the second catalytic combustion tower 4. Since the flue gas temperature is 280℃, which is higher than the activation temperature of the second catalyst 5, 180℃, the first flue gas is burned at low temperature, and the temperature in the tower is raised to 480℃, which is higher than the activation temperature of the second catalyst 5, 400℃, for burning CH4. At this time, the temperature in the tower is raised to 500℃, so the reaction can also proceed spontaneously without external heat source. The second flue gas obtained is 450℃, and at this time, the CO and CH4 contents are reduced to 100mg / Nm 3 At this time, part of the second flue gas enters the heat exchanger 1 to warm up the liquid nitrogen tail gas, and the rest is used for drying the coal powder in the coal mill.

[0098] The above is only a preferred embodiment of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which should also be considered as the protection scope of the present application.

Claims

1. A method for utilizing liquid nitrogen scrubbing tail gas based on a liquid nitrogen scrubbing tail gas resource utilization system, comprising the following steps: Step 1: The liquid nitrogen wash tail gas enters the heat exchanger (1) for heating. The resulting hot liquid nitrogen wash tail gas is mixed with the air entering the first air inlet and then enters the first catalytic combustion tower (2) for first catalytic combustion to obtain the first flue gas. During the first catalytic combustion, water enters the constant temperature device to cool the first catalytic combustion tower (2) to 250~320℃ and generate steam. Step 2: The first flue gas is mixed with the air entering through the second air inlet and then enters the second catalytic combustion tower (4) for second catalytic combustion to obtain the second flue gas; Step 3: A portion of the second flue gas enters the heat exchanger (1) for heat exchange to obtain cooled second flue gas. The cooled second flue gas and the remaining second flue gas enter the coal mill (6), and the resulting cooled gas is discharged through the gas outlet. The liquid nitrogen washing tail gas resource utilization system includes a heat exchanger (1), which is provided with a liquid nitrogen washing tail gas inlet, a liquid nitrogen washing tail gas outlet, a heat exchange gas inlet and a heat exchange gas outlet. A first catalytic combustion tower (2) is connected to the liquid nitrogen wash tail gas outlet of the heat exchanger (1) via an inlet. The first catalytic combustion tower (2) is connected to a constant temperature device, which has a water inlet and a steam outlet. A first catalyst (3) is provided inside the first catalytic combustion tower (2). A first air inlet is provided between the pipeline connecting the first catalytic combustion tower (2) and the liquid nitrogen wash tail gas outlet of the heat exchanger (1). The first catalytic combustion tower (2) has a first flue gas outlet. A second catalytic combustion tower (4) is connected to the first flue gas outlet of the first catalytic combustion tower (2) at its inlet, and a second catalyst (5) is provided inside the second catalytic combustion tower (4); a second air inlet is provided between the pipeline connecting the second catalytic combustion tower (4) and the first flue gas outlet of the first catalytic combustion tower (2); the second catalytic combustion tower (4) is provided with a second flue gas outlet; the second flue gas outlet is connected to the heat exchange gas inlet of the heat exchanger (1); The coal mill (6) is provided with a gas inlet and a gas outlet. The gas inlet is connected to the heat exchange gas outlet of the heat exchanger (1) and the second flue gas outlet of the second catalytic combustion tower (4). The temperature control device of the first catalytic combustion tower (2) is a water curtain type temperature control device; The water curtain constant temperature device includes an expansion tank (7) located outside the first catalytic combustion tower (2), and the expansion tank (7) is provided with a water inlet, a water outlet, a steam inlet and a steam outlet; A water storage chamber (8) with its inlet connected to the water outlet of the expansion tank (7) is located inside the first catalytic combustion tower (2); The steam storage chamber (9) is located inside the first catalytic combustion tower (2), and the outlet of the steam storage chamber (9) is connected to the steam inlet of the expansion tank (7); the steam storage chamber (9) is not connected to the water storage chamber (8); A heat exchange sleeve located inside the first catalyst (3); the heat exchange sleeve includes an inner heat exchange sleeve (10-1) and an outer heat exchange sleeve (10-2) nested outside the inner heat exchange sleeve (10-1), the bottom of the inner heat exchange sleeve (10-1) is connected to the outer heat exchange sleeve (10-2); the inner heat exchange sleeve (10-1) is connected to the water storage chamber (8), and the outer heat exchange sleeve (10-2) is connected to the steam storage chamber (9).

2. The method according to claim 1, characterized in that, The first catalyst (3) consists of a composite oxide composed of MnO2, CeO2 and ZrO2.

3. The method according to claim 1, characterized in that, The active components of the second catalyst (5) are Pt and / or Ag.

4. The method according to claim 1, characterized in that, The gas outlet of the coal mill (6) is connected to the gas inlet.

5. The method according to claim 1, characterized in that, The temperature of the hydrothermal nitrogen scrubbing tail gas is 220~300℃, and the volume ratio of the hydrothermal nitrogen scrubbing tail gas to air is 100:10~19.

5.

6. The method according to claim 1, characterized in that, The temperature of the first flue gas is 250~320℃, and the volume ratio of the liquid nitrogen scrubbing tail gas to the air entering through the second air inlet is 100:15~19.

5.

7. The method according to claim 1, characterized in that, The temperature of the second flue gas is 450~550℃.

8. The method according to claim 1, characterized in that, The volume ratio of the cooled second flue gas to the remaining second flue gas is 1:0.71~0.81.

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