Desorption method for nitrogen oxide adsorbent

Abstract

A desorption method for a nitrogen oxide adsorbent, relating to the technical field of atmospheric pollution control and environmental protection. The method comprises two processes, i.e., desorption of an adsorbent and treatment of a mixed gas obtained by desorption, wherein the desorption process comprises using at least one of steam, ammonia or carbon dioxide as a desorption and regeneration gas to desorb and regenerate the adsorbent that has reached saturation, and a mixed gas stream obtained by desorption flowing through a treatment system of said mixed gas to remove moisture, ammonia, or carbon dioxide and gas contained in the gas stream, so as to obtain high-concentration nitric oxide. The present invention realizes regeneration of the absorbent and recovery of a nitrogen oxide gas.

Description

Desorption method of nitrogen oxide adsorbent TECHNICAL FIELD

[0001] The present application relates to a desorption method of nitrogen oxide adsorbent, belonging to the technical field of atmospheric pollution control and environmental protection. BACKGROUND

[0002] The nitrogen oxide harmful gas (NO x ) produced by fuel combustion mainly includes NO and NO2, and the concentration is about several hundred to several thousand ppm, of which more than 95% is nitric oxide. Nitrogen oxides are toxic to the human body, and a large amount of nitrogen oxide emission is also one of the main causes of atmospheric photochemical haze and acid rain.

[0003] At present, the selective catalytic reduction method (SCR) is the main means for treating NOx in fossil fuel flue gas or tail gas, but the catalyst has strict requirements on operating conditions, and needs reducing agents such as ammonia or urea. The influence of sulfides, chlorides and dust in the gas flow on the catalyst is great, especially the treatment of nitrogen oxides in the tail gas using an internal combustion engine as a power source is difficult and expensive.

[0004] The adsorption method is one of the effective methods for removing NO x in the gas flow. Chinese patent (CN101326004) discloses a NOx adsorbent composed of an oxide carrier containing Co, Fe, Cu, Ce or Mn and a metal catalyst containing Co, Cu, Ag or Pd loaded on the carrier. U.S. patent (US5362463) discloses an adsorbent mainly composed of a mixture of manganese oxide and aluminum oxide and loaded with potassium carbonate. The desorption regeneration method of these adsorbents is to release the adsorbed NO x by heating the saturated adsorbent to a higher temperature, and at the same time, a reducing agent such as hydrogen or ammonia is introduced to reduce it to nitrogen, so as to achieve the purpose of adsorbent regeneration. TECHNICAL PROBLEM

[0005] The present application discloses a solid adsorbent for adsorbing and treating NO xThe regeneration method of the adsorbent can use desorption in a nitrogen or air or other inert gas stream, or hydrogen, methane, formaldehyde, ammonia or carbon monoxide gas as a reducing agent added to the inert gas to reduce the adsorbed nitrogen oxides to nitrogen. The inventors found that the above reduction reaction needs to be carried out at a temperature greater than 600°C, and at a temperature lower than 600°C, the reducing agent other than ammonia has little effect on the desorption and reduction of the adsorbent, and the presence of ammonia can promote the desorption of the adsorbed nitrogen oxides, which is not the reduction effect. Based on this discovery, the present application provides a desorption and regeneration method of the solid adsorbent of nitrogen oxides, which realizes the desorption and recovery of the adsorbed nitrogen oxide (or nitric oxide) gas. Technical solution

[0006] The technical solution adopted by the present application is a desorption and regeneration method of a nitrogen oxide adsorbent, the nitrogen oxide being a mixture of nitric oxide and nitrogen dioxide (mainly nitric oxide) or a nitric oxide gas, characterized in that the method comprises two processes of desorption and regeneration of the adsorbent after adsorption saturation and treatment of the mixed gas after desorption, wherein the desorption process uses at least one of water vapor, ammonia or carbon dioxide gas as a desorption gas to desorb the adsorbent after adsorption saturation, and the mixed gas after desorption is treated to remove water, ammonia or carbon dioxide gas in the gas stream, thereby obtaining high-concentration nitric oxide gas, thereby realizing the desorption of the adsorbent and the recovery of the nitrogen oxide gas, and the water vapor, ammonia and carbon dioxide can be recycled.

[0007] The main principle of the desorption and regeneration of the present application is to find and utilize these gases, especially the ability of ammonia to replace the adsorbed nitrogen oxides in the adsorbent, that is, these gases have a greater adsorption capacity than nitrogen oxides under certain conditions, thereby replacing the nitric oxide in the adsorbent and realizing the desorption of the adsorbent, among which ammonia is the best, followed by carbon dioxide. This is significantly different from the principle of using nitrogen or other inert gases as a desorption gas stream or vacuum (or reduced pressure) desorption, thereby greatly reducing the regeneration temperature of the adsorbent, and these desorption gases are also easy to separate from the desorbed nitrogen oxides.

[0008] The treatment system of the mixed gas after desorption of the present application uses condensation (or freezing), solid adsorbent adsorption and other methods to remove water in the gas stream; uses condensation (or freezing), solid adsorbent adsorption, water or acid solution absorption and other methods to remove ammonia in the gas stream; for carbon dioxide gas in the gas stream, condensation (or freezing), water or alkaline solution or solid adsorbent adsorption and other methods can be used to remove it. The above-mentioned methods can be used alone or in combination. The solid adsorbent includes molecular sieve, alumina and silica gel and other general adsorbents.

[0009] The desorption temperature of the nitrogen oxide adsorbent described in the present application is 60°C or higher and 600°C or lower, preferably 200-400°C, and varies depending on the desorption gas and the composition of the adsorbent, and the gas pressure, and can be lower under negative pressure, with the lowest being ammonia gas (including pure ammonia and ammonia-containing mixed gas stream), followed by carbon dioxide (including pure carbon dioxide and carbon dioxide-containing mixed gas stream), and the highest being water vapor.

[0010] A desorption regeneration method for a nitrogen oxide adsorbent using water vapor as the desorption gas, which process is to introduce the adsorbent to be desorbed and regenerated into a regeneration reactor (or switch the adsorber to the regeneration mode, which has the same effect, as follows), remove other gases in the reactor by vacuum pumping or water vapor gas displacement, and then introduce water vapor into the reactor and heat it to a predetermined desorption temperature to bring out the nitrogen oxide gas adsorbed by the adsorbent, and then cool and condense the desorbed mixed gas to remove the water in the gas stream, and then further dehydrate and dry the gas using a solid adsorbent such as molecular sieve, and the dry gas is high-concentration nitric oxide gas, and the condensed water can be recycled. The desorption temperature when using water vapor as the desorption gas is 300°C or higher at normal pressure, and is preferably 450-550°C.

[0011] A desorption regeneration method for a nitrogen oxide adsorbent using ammonia or ammonia water as the desorption gas, which process is to introduce the adsorbent to be desorbed and regenerated into a regeneration reactor, remove other gases in the reactor by vacuum pumping or ammonia or ammonia water vapor mixed gas displacement, and then introduce pure ammonia gas or ammonia water vapor into the reactor and heat it to a predetermined desorption temperature to bring out the nitrogen oxide gas adsorbed by the adsorbent, and then cool and condense the desorbed mixed gas to remove the ammonia in the gas stream, and then further dehydrate and dry the gas using a solid adsorbent such as molecular sieve or calcium chloride, and the dry gas is high-concentration nitric oxide gas. The liquid ammonia recovered by freezing can be used as the desorption gas, and the ammonia water or ammonia salt solution obtained by absorption with water or acidic solution can also be recycled. Among them, the ammonia water after absorption can be directly heated and evaporated for use as the desorption regeneration gas, and the ammonium salt solution can be neutralized by adding alkali and then heated and volatilized to obtain ammonia water mixed gas, which can also be recycled. The desorption temperature when using ammonia or ammonia water as the desorption gas is 60°C or higher at normal pressure, and is preferably 150-250°C, which is much lower than when using water vapor alone. When using ammonia water mixed gas as the regeneration gas, the proportion of each component in the gas stream can be adjusted at will, and there is no special requirement for the ammonia concentration, which is generally 0.5% or higher, and is preferably 5-15%, and the specific value can be determined by testing according to the properties of the specific adsorbent and the desorption requirements. Considering storage and use safety, ammonia water is commonly used instead of pure ammonia gas.

[0012] A method for desorption and regeneration of a nitrogen oxide adsorbent using carbon dioxide gas as a desorption gas, which process is to introduce the adsorbent to be regenerated into a regeneration reactor, then remove other gases in the reactor by vacuum or carbon dioxide gas displacement, and then introduce carbon dioxide gas into the reactor and heat it to a predetermined desorption temperature to bring out the nitrogen oxide gas adsorbed by the adsorbent, and then cool the desorbed mixed gas, absorb it with water or an alkaline solution, or pressurize and freeze it to remove carbon dioxide in the gas stream, and then dry the gas by a drying process using a solid adsorbent such as molecular sieve, and the dry gas is high-concentration nitric oxide gas. The carbon dioxide obtained by absorption with water or an alkaline solution or freezing can be recycled, wherein the carbon dioxide gasified by freezing recovery can be used as a desorption gas, and the carbonate obtained by absorption with an alkaline solution can be neutralized by adding acid and then volatilized to obtain carbon dioxide gas, which can also be recycled. When carbon dioxide is used as a desorption gas, the desorption temperature of the adsorbent is generally above 250°C, and preferably 400-500°C.

[0013] A method for desorption and regeneration of a nitrogen oxide adsorbent using a mixed gas of water vapor, ammonia gas, and carbon dioxide as a desorption gas, which process is basically the same as the above, and the proportions of the components are not particularly required, and the desorption temperature is substantially the same as that using ammonia gas or ammonia water, and in the process for removing the mixed gas after desorption, water, carbon dioxide gas, and ammonia removal processes need to be separately provided.

[0014] The adsorbent after removal of nitrogen oxide can be further subjected to vacuum, or heated in air or inert gas, to remove the desorption gas remaining in the adsorbent during desorption and regeneration, and at the same time, the adsorbent can be activated. The heating temperature is generally about 20-50°C higher than the desorption temperature.

[0015] The method for desorption and regeneration of nitrogen oxide according to the present application can add a certain proportion of inert gas such as nitrogen, argon, or helium to the regeneration gas stream according to the required concentration of nitric oxide product, and the content of the inert gas can be adjusted as required, and there is no particular requirement. The added inert gas has no effect on the regeneration process of the adsorbent. An oxidizing agent such as oxygen can also be added to the desorption gas stream to oxidize nitric oxide to nitrogen dioxide, and then ammonium nitrate solution is obtained by absorption, and the specific product can be selected according to the requirements.

[0016] In the method for desorption and regeneration of a nitrogen oxide adsorbent according to the present application, the dehumidification or drying of the gas stream can be carried out by one or a combination of several common dehumidification methods such as condensation or freezing dehydration, solid dehumidifier adsorption dehydration, pressure swing dehydration, or other common dehumidification methods, and the relevant parameters can be referred to the relevant chemical equipment manual. The absorption device can use common chemical gas-liquid reaction absorption devices such as bubble column, sieve tray column, spray tower, and fluidized bed, and one or more stages can be provided according to the requirements to ensure complete absorption.

[0017] In the desorption regeneration method of the nitrogen oxide adsorbent, the removal of ammonia gas can be achieved by water or acidic solution absorption, water absorption and multi-stage absorption or pressurized absorption method, and the acidic solution absorption can be achieved by dilute sulfuric acid or dilute hydrochloric acid solution absorption. The relevant parameters can be referred to the relevant chemical equipment manual. The ammonia water obtained after water absorption can be directly heated and evaporated for use as a regenerated gas, and the ammonium salt obtained after dilute acid absorption can be neutralized by sodium hydroxide or calcium oxide or other alkali or alkaline substances, and then the ammonia water mixed gas obtained by volatilization can also be recycled. The ammonia gas solid adsorbent can also use calcium chloride or other chemical adsorbents as adsorbents, which can be regenerated and recycled by heating.

[0018] In the desorption method of the nitrogen oxide adsorbent, the removal of carbon dioxide in the desorption gas stream can be achieved by using calcium hydroxide or sodium hydroxide solution or slurry as the absorbent, and calcium carbonate or sodium carbonate (or sodium bicarbonate) can be obtained at the same time. The carbon dioxide gas can be regenerated and recycled by adding acid. The carbon dioxide solid adsorbent can use alkaline earth metal oxides such as calcium oxide or calcium hydroxide as adsorbents.

[0019] The cooling temperature of the mixed gas after desorption is lower, which is beneficial to the subsequent process, and is generally below 60°C. Part of the condensed water can be removed at the same time, and then introduced into the subsequent treatment system. The condensation or freezing can also use multi-stage condensation or freezing method to save energy. In the desorption method of the nitrogen oxide adsorbent, the carbon dioxide and ammonia in the gas stream can also be obtained in liquid state by freezing, and separated from the nitric oxide gas. The related technology can be referred to the relevant chemical equipment manual.

[0020] In the desorption method of the nitrogen oxide adsorbent, a small amount of nitrogen dioxide and other acidic gases in the desorbed gas stream can be removed by the alkali absorption process.

[0021] The nitrogen oxide adsorbent contains at least one element of components iron, cobalt, manganese or copper, at least one element of components sodium, potassium, lithium, calcium, barium or magnesium, and at least one component of components sulfate, chloride or carbonate. The specific preparation method, adsorption and operation parameters are described in detail in the aforementioned documents disclosed by the inventor, and will not be described here.

[0022] The nitrogen oxide adsorbent can also be an adsorbent containing at least one active component of metal iron, cobalt, manganese, copper, cerium or zirconium oxide, and using alumina and kaolin as the base and calcium carbonate as the auxiliary agent, and the regeneration effect is generally comparable to the aforementioned adsorbent. The preparation method is generally as follows: a metal nitrate solution of the oxide and the related base and auxiliary agent (taking alumina and calcium carbonate as examples) are mixed in a certain proportion, and then granulated, dried (at about 60-95°C) and activated (at about 500-700°C) to obtain the granular adsorbent. The content of the active component metal oxide is generally not higher than 90%, and the content of the base and auxiliary agent is generally not less than 10%.

[0023] The adsorption amount of the nitrogen oxide adsorbent of the present application is about 0.1% to 1% of the mass of the adsorbent, and can be determined by a simulation adsorption experiment.

[0024] The desorption and regeneration temperature of the nitrogen oxide adsorbent of the present application is different depending on the composition of the adsorbent. The regeneration temperature of the adsorbent with iron and cobalt as the main components can be higher, and the regeneration temperature of the adsorbent with manganese and copper as the main components can be lower. The residence time of the desorption gas in the adsorber is generally more than 0.5s, and preferably 2-5s.

[0025] The desorption and regeneration method of the nitrogen oxide adsorbent of the present application is used for the regeneration of the adsorbent for nitrogen oxides with nitrogen monoxide as the main component in the gas stream. The gas stream mainly includes combustion tail gas of various industrial processes, including combustion tail gas of various internal combustion engines (including mobile sources such as vehicles and ships), and other industrial processes, including fossil fuel combustion or other high-temperature processes to produce nitrogen oxide-containing gas streams. Advantages

[0026] Compared with the prior art, the present application has the advantages that at least one of water vapor, ammonia gas or carbon dioxide gas is used as the regeneration gas of the nitrogen oxide adsorbent, which takes advantage of the fact that the binding capacity of ammonia to the adsorbent is greater than that of nitrogen oxide, which is beneficial to the desorption and regeneration of the nitrogen oxide adsorbent at a lower temperature, reduces energy consumption, and is also beneficial to the separation of the mixed gas after desorption and the recovery of nitrogen monoxide gas. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a schematic diagram of the regeneration reactor structure of the desorption method of the nitrogen oxide adsorbent used in the embodiment of the present application.

[0028] Figure 2 is a schematic diagram of the mixed gas treatment system after the desorption and regeneration of the nitrogen oxide adsorbent used in the embodiment of the present application.

[0029] In the figure: 1 regenerating gas inlet; 2 gas flow distributor; 3 adsorbent; 4 regenerating reactor; 5 regenerating gas outlet; 6 adsorbent inlet; 7 adsorbent outlet; 8 maintenance opening; 101 condenser; 102 first absorber; 103 second absorber; 104 dehumidifier; 9 condenser gas inlet; 10 refrigerant inlet; 11 first connecting pipe; 12 absorption liquid inlet; 13 second connecting pipe; 14 absorption liquid inlet; 15 third connecting pipe; 16 dehumidifier inlet; 17 dry gas outlet; 18 dehumidifier outlet; 19 absorption liquid outlet; 20 absorption liquid outlet; 21 refrigerant outlet. Best mode of the invention

[0030] The best mode of the invention is described in Example 1. Embodiment of the invention

[0031] The invention is described in further detail below in connection with the accompanying drawings and examples.

[0032] A regenerating reactor and a post-regeneration mixed gas treatment system of a nitrogen oxide adsorbent desorption method are shown in Figures 1 and 2, respectively. The regenerating reactor (4) is provided with a regenerating gas inlet (1), a gas flow distributor (2), a regenerating gas outlet (5), an adsorbent inlet (6), an adsorbent outlet (7), and a maintenance opening (8), and the adsorbent (3) to be regenerated is placed above the gas flow distributor (2). The post-regeneration mixed gas treatment system is composed of a condenser (101), a first absorber (102), a second absorber (103), and a dehumidifier (104), wherein the condenser (101) has a condenser gas inlet (9), a refrigerant inlet (10), and a refrigerant outlet (21), the first absorber (102) has an absorption liquid inlet (12) and an absorption liquid outlet (20), the second absorber (103) has an absorption liquid inlet (14) and an absorption liquid outlet (19), the dehumidifier (104) has a dehumidifier inlet (16), a dehumidifier outlet (18), and a dry gas outlet (17), the regenerating gas outlet (5) of the regenerating reactor (4) is connected to the condenser (101) through the condenser gas inlet (9), the condenser (101) is connected to the first absorber (102) through the first connecting pipe (11), the first absorber (102) is connected to the second absorber (103) through the second connecting pipe (13), and the second absorber (103) is connected to the dehumidifier (104) through the third connecting pipe (15).

[0033] The treatment process is that the adsorbent (3) to be regenerated is added to the upper part of the gas distributor (2) in the regeneration reactor (4) through the adsorbent adding port (6), then the gas in the reactor is removed or replaced by gas, and then the desorption regeneration gas is introduced through the regeneration gas inlet (1) to contact the filled adsorbent (3) through the gas distributor (2), so that the nitrogen oxide gas adsorbed by the adsorbent is carried out, and then the mixed gas after desorption is introduced into the desorption mixed gas treatment system through the regeneration gas outlet (5) arranged at the upper part of the regeneration reactor.

[0034] The mixed gas containing nitrogen oxide and at least one of water vapor, ammonia and carbon dioxide gas discharged through the regeneration gas outlet (5) is sequentially introduced into the condenser (101) through the condenser gas inlet (9) to be cooled and preliminarily dehydrated, and then introduced into the first absorber (102) through the first connecting pipe (11), the ammonia gas in the gas stream is absorbed by the absorbing liquid added from the absorbing liquid adding port (12) at the upper part of the first absorber (102), the absorbing liquid after absorbing ammonia is discharged from the absorbing liquid discharge port (20), the gas after removing ammonia is introduced into the second absorber (103) through the second connecting pipe (13), the carbon dioxide gas in the gas stream is absorbed by the absorbing liquid added from the absorbing liquid adding port (14) at the upper part of the second absorber (103), the absorbing liquid after absorbing carbon dioxide is discharged from the absorbing liquid discharge port (19), the gas after removing ammonia and carbon dioxide is introduced into the dehumidifier (104) through the third connecting pipe (15) to be dehumidified and dehydrated, the water in the gas stream is absorbed by the dehumidifier added from the dehumidifier adding port (14) at the upper part of the dehumidifier (104), the dehumidifier after absorbing water is periodically discharged from the dehumidifier discharge port (18), and the dried nitric oxide gas product is finally discharged from the dry gas discharge port (17) to obtain high-concentration nitric oxide gas, which can be up to 99.9% or more.

[0035] The various adsorbents used for desorption and regeneration in the present application are all taken as examples of particles with a particle size of about 3-5mm, and the adsorbent saturated with nitrogen oxides in simulated boiler combustion flue gas is regenerated, and the adsorption amount of nitrogen oxides is about 0.1%-1% of the mass of the adsorbent. The preparation and adsorption operation parameters can refer to the aforementioned documents disclosed by the inventor.

[0036] According to the above-mentioned mixed gas treatment system after regeneration, if there is no carbon dioxide in the gas stream, the related operation unit can be omitted, and if there is no water vapor or ammonia, the related operation unit can also be omitted. The water, ammonia and carbon dioxide gas in the mixed gas stream after regeneration can also be separated by using a refrigeration liquefaction separation operation unit instead of the above-mentioned related absorption operation unit. The absorption of ammonia and carbon dioxide can also use multi-stage absorption or pressurized absorption.

[0037] The regeneration reactor of the nitrogen oxide adsorbent desorption regeneration method of Example 1 is shown in Fig. 1, and the mixed gas treatment system after desorption is shown in Fig. 2. The regeneration reactor has a size of Φ300 mm x 600 mm, is externally insulated and can be heated, the reactor is made of carbon steel, the condenser is a Φ150 mm coil type glass condenser, the condenser cooling water inlet temperature is about 35°C, the condenser outlet desorption gas flow temperature is about 60°C or lower, the first and second absorbers and the dehumidifier are all Φ150 mm x 1500 mm packed towers, the carbon dioxide absorption uses a sodium hydroxide solution with a concentration of about 5%, the ammonia absorption uses a clear water solution, the absorption liquid spray amount is about 15 L / min, and the dehumidifier uses calcium chloride solid particle adsorbent. The original main component of the adsorbent is the product after mixing and reacting of ferrous sulfate and calcium oxide (about 1:2, molar ratio, same below), and the particle adsorbent is prepared by drying and activating (about 600-750°C). (For details, see the above-mentioned related documents disclosed by the inventor, same below), and the adsorption working temperature is about 400°C.

[0038] The treatment process is to first add about 30 kg of adsorbent to be regenerated to the upper part of the gas distributor (2) in the regeneration reactor (4) through the adsorbent adding port (6), then remove the gas in the regeneration reactor, and then introduce the mixed regeneration gas of carbon dioxide and ammonia water vapor into the reactor through the regeneration gas adding port (3), wherein CO2 is about 30%, H2O is about 65%, and NH3 is about 5% (by volume), and the gas flow is about 2 L / min. The temperature in the regeneration reactor is maintained at 100, 250, 350, 450, and 550°C, respectively, the desorbed gas is discharged through the regeneration gas discharge port (6) at the upper part of the regeneration reactor (4), and then passes through the condenser, the first absorber, the second absorber, and the dehumidifier in turn to obtain high-concentration nitric oxide gas. When the temperature in the regeneration reactor is 100, 250, 350, 450, and 550°C, respectively, the regeneration time of the adsorbent completely desorbed (about ≥98%, same below) is about 360 min, 240 min, 120 min, 75 min, and 40 min, respectively. After desorption, the adsorbent is activated in an atmosphere with an air flow of about 2 L / min and a temperature of 550°C for 60 min, and the regeneration process is completed. The carbon dioxide and ammonia absorption liquid can be recycled.

[0039] Example 2: Granular adsorbents were prepared by mixing the raw materials of ferrous sulfate, cobalt sulfate, manganese sulfate and copper sulfate with sodium hydroxide and calcium carbonate (about 1:1:3) and adding water (if necessary), drying and activating (about 500-600°C). The adsorption temperature was about 350°C. The regeneration reactor temperature was about 150, 250, 350 and 450°C, respectively, and other conditions were the same as in Example 1. The regeneration time required for complete desorption of the adsorbents was about 200, 150, 100 and 80 min, respectively, for ferrous sulfate (raw material, hereinafter the same), 220, 170, 120 and 90 min for cobalt sulfate, 150, 120, 80 and 60 min for manganese sulfate, and 150, 120, 70 and 45 min for copper sulfate. After desorption, the adsorbents were activated at an air flow rate of about 2 L / min and a temperature of 450°C for about 60 min to complete the regeneration process.

[0040] Example 3: Granular adsorbents were prepared by mixing the raw materials of iron oxide, cobalt oxide, manganese oxide, copper oxide, cerium oxide and zirconium oxide with aluminum hydroxide and calcium carbonate in a ratio of about 1:3:2 (molar ratio) by mixing the metal nitrate solution of the oxides (about 50% by mass, converted to the amount of the corresponding metal oxide) with the corresponding proportion of aluminum hydroxide and calcium carbonate powder, granulating, drying (about 60-95°C) and activating (about 500°C). The regeneration reactor temperature was about 200, 300 and 400°C, respectively, and other conditions were the same as in Example 1. The regeneration time required for complete desorption of the adsorbents was about 280, 220 and 180 min, respectively, for iron oxide (main component, hereinafter the same), 250, 190 and 150 min for cobalt oxide, 200, 150 and 120 min for manganese oxide, 160, 120 and 90 min for copper oxide, 150, 100 and 60 min for cerium oxide, and 150, 90 and 60 min for zirconium oxide. After desorption, the adsorbents were activated at an air flow rate of about 2 L / min and a temperature of 400°C for about 60 min to complete the regeneration process.

[0041] Example 4: Granular adsorbents were prepared by mixing the raw materials of ferrous carbonate, manganese carbonate and basic copper carbonate with calcium hydroxide, sodium sulfate and water in a ratio of about 1:2:1:6, drying (about 60-95°C) and activating (about 500-600°C). The adsorption temperature was about 250-300°C. The regeneration reactor temperature was about 100, 200 and 350°C, respectively, and other conditions were the same as in Example 1. The regeneration time required for complete desorption of the adsorbents was about 180, 120 and 90 min, respectively, for ferrous carbonate, 160, 100 and 60 min for manganese carbonate, and 150, 90 and 45 min for basic copper carbonate. After desorption, the adsorbents were activated at an air flow rate of about 2 L / min and the same temperature for about 60 min to complete the regeneration process.

[0042] Example 5: Granular adsorbents were prepared by mixing the raw materials of iron chloride, cobalt chloride, manganese chloride and copper chloride with sodium hydroxide and calcium carbonate in the ratio of about 1:2:2, respectively, drying (about 60-95°C) and activating (about 450°C). The adsorption temperature was about 250°C. The regeneration reactor temperature was about 100, 250 and 350°C, respectively. The other conditions were the same as in Example 1. The regeneration time required for complete desorption of the adsorbents was about 220, 150 and 120 min for iron chloride, 220, 150 and 120 min for cobalt chloride, 150, 100 and 70 min for manganese chloride, and 120, 80 and 50 min for copper chloride, respectively. After complete desorption, the adsorbents were activated in air at a flow rate of about 2 L / min and a temperature of about 350°C for about 60 min, and the regeneration process was completed.

[0043] Example 6: Granular adsorbents were prepared by mixing the raw materials of ferrous carbonate, manganese carbonate and basic copper carbonate with potassium hydroxide, calcium carbonate and water in the ratio of about 1:2:2:6, respectively, drying (about 60-95°C) and activating (about 550°C). The adsorption temperature was about 250-300°C. The regeneration reactor temperature was about 60, 150 and 300°C, respectively. A mixture of ammonia and nitrogen was used as the regeneration gas, with about 90% nitrogen and about 10% ammonia (by volume). The treatment system for the mixed gas containing ammonia and nitrogen oxides after regeneration did not require a carbon dioxide removal process. The other conditions were the same as in Example 1. The regeneration time required for complete desorption of the adsorbents was about 280, 200 and 90 min for ferrous carbonate, 250, 180 and 80 min for manganese carbonate, and 250, 180 and 80 min for basic copper carbonate, respectively, at different temperatures. After complete desorption, the adsorbents were activated in air at a flow rate of about 2 L / min and a temperature of about 350°C for about 60 min, and the regeneration process was completed.

[0044] Example 7: The adsorbents used in Example 1 were used. Water vapor was used for regeneration. The regeneration reactor temperature was about 500, 550 and 600°C, respectively. The treatment system for the mixed gas of water vapor and nitrogen oxides after regeneration did not require a carbon dioxide removal and ammonia removal unit. The other conditions were the same as in Example 1. The regeneration time required for complete desorption of the adsorbents was about 350, 260 and 180 min, respectively, at different temperatures.

[0045] Example 8: The absorbent of Example 4 was used as the main component, carbon dioxide gas was used for regeneration, the temperature of the regeneration reactor was 350, 450 and 550°C respectively, the treatment system of the regenerated carbon dioxide and nitrogen oxide mixed gas did not need a deamination operation unit, the de-carbon dioxide was replaced by refrigeration instead of alkali liquid absorption, water was removed by cooling or condensation, the carbon dioxide was removed by pressurized refrigeration and molecular sieve adsorption, and the other conditions were the same as those of Example 5. The results showed that the regeneration time required for complete desorption of the absorbent at different temperatures was about 300, 210 and 120 min respectively.

[0046] Example 9: The absorbents of Examples 4 and 6 were used respectively with manganese carbonate as the main component, the temperature of the regeneration reactor was 300°C, ammonia water evaporation gas was used as the regeneration gas, the water content was about 90% and the ammonia content was about 10% (volume), the treatment system of the desorbed mixed gas containing water vapor, ammonia and nitrogen oxide did not need a de-carbon dioxide process, the deamination was replaced by pressurized refrigeration instead of dilute acid solution absorption, water was removed by cooling or condensation, the ammonia was removed by pressurized refrigeration and the moisture was removed by calcium chloride solid adsorbent, and the other conditions were the same as those of Examples 4 and 6 respectively. The results showed that the regeneration time required for complete desorption of the absorbent was about 70 min.

[0047] Example 10: The absorbent prepared by using manganese carbonate as the main raw component in Example 6 was desorbed at different temperatures (room temperature to 700°C) by using a mixed gas of nitrogen and reducing agents hydrogen, methane, formaldehyde, ammonia and carbon monoxide respectively to investigate the influence on the reduction and desorption of nitrogen oxides (the effects of using the absorbents of other examples were basically the same). The content of the reducing agent in the gas stream was about 5% (the effects of using different reducing agent contents were basically the same), and the experimental results are shown in Tables 1 and 2 below. The experimental results of using water vapor or carbon dioxide instead of nitrogen were basically the same except that the desorption temperature was reduced.

[0048] Table 1 Effect of different desorption temperatures on the reduction of nitrogen monoxide

[0049] Desorption gas composition Temperature (°C) Effect on the reduction of NO N2 Any temperature No N2+ NH3 ≤600 No N2+ CH4 ≤650 No N2+ H2 ≤600 No N2+ CO ≤650 No N2+ HCHO ≤600 No

[0050] Table 2 Effect of different desorption temperatures on the desorption of nitrogen monoxide

[0051] Desorption gas composition Temperature (°C) Effect on the desorption of NO N2 ≤450 No N2+ NH3 100 ≤600 Yes N2+ CH4 ≤650 Same as N2 atmosphere N2+ H2 ≤600 Same as N2 atmosphere N2+ CO ≤650 Same as N2 atmosphere N2+ HCHO ≤600 Same as N2 atmosphere Industrial applicability

[0052] The desorption regeneration method of the nitrogen oxide adsorbent described in the present application is used for the regeneration of the adsorbent of nitrogen oxides with the main component of nitric oxide in the gas stream, and the gas stream is mainly the combustion tail gas of various industrial processes, including the combustion tail gas of various internal combustion engines (including mobile sources such as vehicles, ships, etc.), and also including the related gas streams generated by other industrial processes, including the nitrogen oxide-containing gas streams generated by the combustion of fossil fuels or other high-temperature processes in power generation, building materials, smelting, etc. Free content of the sequence listing

[0053] (None).

Claims

1. A method for desorbing nitrogen oxide adsorbents, characterized in that... The method comprises two processes: desorption of the adsorbent and treatment of the desorbed mixed gas. The desorption process uses at least one gas selected from water vapor, ammonia, or carbon dioxide as the desorption gas to regenerate the adsorbent after it has become saturated with nitrogen oxides. The gas stream containing nitrogen oxides after desorption passes through a desorption mixed gas treatment system to remove moisture, ammonia, and carbon dioxide, resulting in a high-concentration nitric oxide gas. This achieves both the desorption of the adsorbent and the recovery of the nitrogen oxide gas. The nitrogen oxide adsorbent is a solid compound or a mixture of components containing at least one element of iron, cobalt, manganese, or copper; at least one element of sodium, potassium, lithium, calcium, barium, or magnesium; and at least one component of sulfate, chloride, or carbonate.

2. The desorption method according to claim 1, characterized in that... The desorption temperature is above 60℃ and below 600℃.

3. The desorption method according to claim 1, characterized in that... The desorption temperature is 200–400℃.

4. The desorption method according to claim 1, characterized in that... The desorbed mixed gas treatment system removes moisture from the gas stream using one or more of the following methods: condensation or freezing, and adsorption with a solid adsorbent; removes ammonia from the gas stream using one or more of the following methods: condensation or freezing, adsorption with a solid adsorbent, and absorption with water or an acidic solution; and removes carbon dioxide from the gas stream using one or more of the following methods: condensation or freezing, adsorption with a solid adsorbent, and absorption with water or an alkaline solution.

5. The desorption method according to claim 1, characterized in that... The adsorbent desorption and regeneration method uses water vapor as the desorption gas. The adsorbent to be desorbed and regenerated is introduced into the regeneration reactor. Then, after vacuuming or water vapor replacement to remove other gases in the reactor, water vapor is introduced into the reactor to carry out the nitrogen oxide gas adsorbed by the adsorbent. The desorption temperature of nitrogen oxides in the regeneration reactor is above 300°C. After desorption, the mixed gas is cooled and condensed to remove moisture from the gas flow. After further drying with a solid adsorbent, high-concentration nitric oxide gas is obtained.

6. The desorption method according to claim 1, characterized in that... The adsorbent desorption and regeneration method uses ammonia or ammonia water as the desorption gas. The adsorbent to be desorbed and regenerated is introduced into the regeneration reactor. After vacuuming or replacing with ammonia and water vapor to remove other gases in the reactor, ammonia or ammonia water mixed gas is introduced into the reactor to carry out the adsorbed nitrogen oxide gas. The desorption temperature of the regeneration reactor is above 60°C. After desorption, the mixed gas is cooled down, absorbed by water or acidic solution, or pressurized and frozen to remove ammonia from the gas flow. After further drying with a solid adsorbent, high-concentration nitric oxide gas is obtained.

7. The desorption method according to claim 1, characterized in that... The desorption and regeneration method uses carbon dioxide gas as the desorption gas. The adsorbent to be desorbed and regenerated is introduced into the regeneration reactor. After vacuuming or replacing the other gases in the reactor with carbon dioxide gas, carbon dioxide gas is introduced into the reactor to carry out the adsorbed nitrogen oxide gas. The desorption temperature of the regeneration reactor is 250°C or above. After desorption, the mixed gas is cooled, absorbed by water or alkaline solution, or pressurized and frozen to remove the carbon dioxide gas. After drying with a solid adsorbent, high-concentration nitric oxide gas is obtained.

8. The desorption and regeneration method according to claim 1, 4, 5, or 6, characterized in that... The adsorbent after nitrogen oxide removal is activated by heating in air or an inert gas, wherein the heating activation temperature is 20 to 50°C higher than the desorption temperature.

9. The desorption method according to claim 1, characterized in that... The nitrogen oxide adsorbent is an adsorbent containing at least one compound of oxides of metallic iron, cobalt, manganese, copper, cerium or zirconium as its active ingredient.

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