CN214390119U - Device for preparing ammonia by hydrolyzing urea at normal temperature under synergistic catalysis of non-thermal plasma - Google Patents
Device for preparing ammonia by hydrolyzing urea at normal temperature under synergistic catalysis of non-thermal plasma Download PDFInfo
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- CN214390119U CN214390119U CN202022511637.0U CN202022511637U CN214390119U CN 214390119 U CN214390119 U CN 214390119U CN 202022511637 U CN202022511637 U CN 202022511637U CN 214390119 U CN214390119 U CN 214390119U
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Abstract
Non-thermal plasma cooperates device of urea system ammonia of hydrolysising at normal temperature, belongs to SCR denitration reductant preparation field. The device comprises a set of urea supply and injection system, a group of non-thermal plasma cooperative catalytic reactors and a set of gas distribution and collection system, wherein urea is suppliedUrea sprayed by the spraying system enters a group of non-thermal plasmas arranged in a matrix form to cooperate with the catalytic reactor, and the non-thermal plasmas and ZrO generated by dielectric barrier discharge are utilized to2、TiO2、Al2O3And the urea is efficiently hydrolyzed to produce ammonia under normal temperature under the synergistic action of the urea decomposition catalysts. The device simple structure, low cost, the normal atmospheric temperature operation opens and stops the convenience, and the potential safety hazard is few, easily popularizes and applies in power station and industrial boiler (especially middle-size and small-size boiler) flue gas SCR denitration.
Description
Technical Field
The utility model relates to a device for producing ammonia by hydrolyzing urea at normal temperature under the synergistic catalysis of non-thermal plasma, in particular to a device for producing ammonia by efficiently hydrolyzing urea at normal temperature under the synergistic action of non-thermal plasma and catalyst, which is used for ammonia selective catalytic reduction (NH)3-SCR) denitration process providing reducing agent (NH)3) The device belongs to the SCR denitration reducing agent preparation field.
Background
Nitrogen Oxides (NO)x) Is one of important atmospheric pollutants, can cause serious environmental problems such as photochemical smog, acid rain and the like, and is a main precursor of nitrate in atmospheric fine particles. The fixed combustion source of the thermal power plant, the industrial kiln and the like is NOxOne of the main emission sources of (1), emitted NOxThe NO content is 90-95%.
By NH3Is a selective catalytic reduction (NH) of a reducing agent3SCR) denitration technology was first developed successfully in japan in the end of the 70 s of the 20 th century, and has become the mainstream process for denitration of flue gas of large industrial boilers worldwide. At NH3Reducing agent NH in SCR denitration technology3Supply of (2) directly affects NOxThe removal effect of (1). The ammonia gas can be directly from liquid ammonia or indirectly prepared by ammonia water or urea. Liquid ammonia and ammonia water have explosiveness, strong corrosivity and larger toxicity, and have larger potential safety hazards in transportation and storage, so in recent years, a fixed source flue gas SCR denitration system represented by a coal-fired power plant starts to try to prepare ammonia by a urea decomposition method.
The urea decomposition for producing ammonia generally includes 2 types of hydrolysis method and pyrolysis method, wherein the hydrolysis method is to decompose urea in the form of aqueous solution under the conditions of low temperature and high pressure (120-180 ℃ and 0.3-0.8 MPa). Removing NH3And CO2In addition, urea hydrolysis also produces highly corrosive substances such as ammonium carbamate and condensates such as biuret that are hardly soluble in water, and is likely to cause hydrolysisCorrosion, leakage and plugging of system piping. In addition, the urea hydrolyzer is a pressure vessel, and certain potential safety hazards exist.
The pyrolysis method is to rapidly heat the atomized urea solution to decompose the urea solution at high temperature and normal pressure (350-650 ℃ and 0.1 MPa). The pyrolysis decomposition of urea requires providing high-temperature flue gas or air as pyrolysis gas flow, and the urea solution sprayed into the pyrolysis gas flow is subjected to moisture evaporation and urea pyrolysis (CO (NH)2)2→NH3+ HNCO, isocyanic acid (HNCO) hydrolysis (HNCO + H)2O→NH3+CO2) Formation of NH by the steps3And CO2. Besides high energy consumption, the pyrolysis method has the defects of low HNCO hydrolysis rate (basically no hydrolysis below 400 ℃), incomplete urea decomposition when the local temperature of the pyrolysis furnace is lower (less than 360 ℃), easy formation of macromolecular intermediate products such as biuret, cyanuric acid, melamine and the like.
The introduction of the catalyst into the pyrolysis furnace is an effective way to lower the decomposition temperature of urea, improve the ammonia production efficiency and reduce the formation of byproducts. Catalysis Science&The studies in Technology 3(2013)942-951 showed that ZrO2、TiO2、Al2O3The catalysts can catalyze the urea pyrolysis and HNCO hydrolysis to produce ammonia at the same time, but the urea pyrolysis process is a quick control step, so that the reaction temperature is required to be higher than 200 ℃ for producing ammonia by completely decomposing urea.
Non-thermal plasma has been attracting attention in recent years because of its properties of initiating various chemical reactions and activating catalysts at low temperatures (room temperature). The non-thermal plasma is combined with the urea decomposition catalyst, and the synergistic effect between the plasma and the catalyst is hopeful to realize the high-efficiency urea hydrolysis to prepare ammonia (total reaction CO (NH)2)2+H2O→2NH3+CO2) Thereby greatly simplifying the process of preparing ammonia by decomposing urea and reducing the energy consumption for preparing ammonia.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to provide a device of urea system ammonia is hydrolysised under non-thermal plasma cooperation catalysis normal atmospheric temperature utilizes the synergism of non-thermal plasma and catalyst to hydrolyze urea system ammonia at the normal atmospheric temperature high efficiency, simplifies urea decomposition system ammonia technology greatly, reduces the system ammonia energy consumption.
The device for producing ammonia by hydrolyzing urea at normal temperature under the synergistic catalysis of non-thermal plasma is characterized by comprising a set of urea supply and injection system, a set of non-thermal plasma synergistic catalytic reactor and a set of gas distribution and collection system;
the urea supply and injection system comprises a urea aqueous solution storage tank (1), a urea aqueous solution distribution system (2) and a urea aqueous solution injection device (3), and the urea injection amount can be adjusted by adjusting the concentration of urea in the urea aqueous solution and the injection flow rate of the injection device;
the group of non-thermal plasma synergistic catalytic reactors comprises a plurality of non-thermal plasma synergistic catalytic single-tube reactors (4) which are arranged in a matrix manner, 5-50 non-thermal plasma synergistic catalytic single-tube reactors are arranged in each row, 5-50 non-thermal plasma synergistic catalytic single-tube reactors in each row share one high-voltage power supply (5), and the interval between every two adjacent non-thermal plasma synergistic catalytic single-tube reactors is 5-10 cm;
the non-thermal plasma synergistic catalysis single-tube reactor (4) is a filling type dielectric barrier discharge reactor and comprises a quartz tube reactor (7), a high-voltage electrode (12), a grounding electrode (9), a catalyst filling layer (8), a quartz sand plate (10), a urea spraying inlet, a carrier gas inlet (6) and an ammonia-containing gas outlet (11), wherein the upper part of the quartz tube reactor is provided with the urea spraying inlet and the carrier gas inlet, and the lower part of the quartz tube reactor is provided with the ammonia-containing gas outlet; the stainless steel bar high-voltage electrode is positioned in the center of the quartz tube reactor and is electrically connected with the high-voltage output end of the high-voltage power supply; the quartz tube reactor is externally coated with a stainless steel mesh, an aluminum foil or a copper foil as a grounding electrode and is electrically connected with the grounding end of a high-voltage power supply; the urea decomposition catalyst is filled in the annular space between the inner wall of the quartz tube reactor and the stainless steel bar high-voltage electrode, is supported by a quartz sand plate arranged in the quartz tube reactor and is completely arranged in a discharge area;
a urea solution injection device (3) is arranged at the urea injection port of each quartz tube reactor (7), and the urea solution storage tank (1) is connected with each urea solution injection device (3) through a urea solution distribution system (2).
The high-voltage power supply (5) adopts an alternating-current or pulse high-voltage power supply, and the discharge power of the non-thermal plasma cooperative catalytic reactor can be adjusted by adjusting the voltage, the frequency and the like output by the high-voltage power supply.
The sizes of the non-thermal plasma and the quartz tube reactor, the high-voltage electrode and the grounding electrode in the catalytic single-tube reactor are adjusted according to the fact that effective discharge can be generated in the reactor, and the discharge power and the catalyst loading amount meet the urea hydrolysis requirement. The non-thermal plasma synergistic catalysis urea decomposition catalyst filled in the single-tube reactor is selected from ZrO2、TiO2、Al2O3And the like have high catalytic urea hydrolysis activity.
In the urea decomposition process, nitrogen or air with a certain flow enters the reactor from carrier gas inlets of the non-thermal plasmas and the catalytic single-tube reactor in cooperation, and urea decomposition products such as ammonia gas flow out of the reactor along with the carrier gas and are collected or used for SCR denitration.
The utility model discloses an above-mentioned technical scheme's beneficial effect as follows:
1. the device can adjust the number of the non-thermal plasma synergistic catalytic single-tube reactors according to the demand of SCR denitration on the reducing agent, so that the ammonia production amount of urea decomposition and the NO removal of SCRxThe amount of the ammonia is matched, and the ammonia escape is reduced while the preset denitration efficiency is achieved.
2. The device has the advantages of simple structure, low cost, normal temperature operation, convenient start and stop, and low energy consumption for preparing ammonia by urea decomposition.
3. The device has less potential safety hazard and is easy to popularize and apply in SCR denitration of flue gas of power stations and industrial boilers (particularly small and medium-sized boilers).
Drawings
FIG. 1 is a schematic view of the device for producing ammonia by hydrolyzing urea at normal temperature under the synergistic action of non-thermal plasma and catalyst.
FIG. 2 is a schematic diagram of a non-thermal plasma co-catalytic single-tube reactor.
In the figure, 1 is a urea aqueous solution storage tank, 2 is a urea aqueous solution distribution system, 3 is a urea aqueous solution injection device, 4 is a non-thermal plasma synergistic catalytic reactor, 5 is a high-voltage power supply, 6 is a carrier gas inlet, 7 is a quartz tube reactor, 8 is a urea decomposition catalyst, 9 is a stainless steel mesh, aluminum foil or copper foil grounding electrode, 10 is a quartz sand plate, 11 is an ammonia-containing gas outlet, and 12 is a stainless steel rod high-voltage electrode.
Detailed Description
In order to make the technical solutions and advantages of the present invention clearer, the following detailed description will be made with reference to the accompanying drawings and specific embodiments.
As shown in figure 1, the urea aqueous solution in the urea aqueous solution storage tank (1) is sprayed into each non-thermal plasma cooperative single-tube reactor (4) through a urea aqueous solution distribution system (2) and a urea aqueous solution spraying device (3), and the urea injection amount can be adjusted by adjusting the concentration of the urea in the urea aqueous solution and the spraying flow rate of the spraying device.
The non-thermal plasma and catalytic single-tube reactors are arranged in a matrix manner, 5-50 non-thermal plasma and catalytic single-tube reactors are arranged in each row, 5-50 non-thermal plasma and catalytic single-tube reactors share one alternating current or pulse high-voltage power supply (5), and the output voltage, frequency and the like of the power supply are set according to requirements; the interval between the adjacent non-thermal plasmas and the single-tube reactor is 5-10 cm.
As shown in fig. 1 and 2, the non-thermal plasma synergistic catalytic single-tube reactor (4) is a filling type dielectric barrier discharge reactor, and comprises a quartz tube reactor (7), a high-voltage electrode (12), a grounding electrode (9), a catalyst filling layer (8), a quartz sand plate (10), a urea spraying inlet, a carrier gas inlet (6) and an ammonia-containing gas outlet (11), wherein the upper part of the quartz tube reactor is provided with the urea spraying inlet and the carrier gas inlet, and the lower part of the quartz tube reactor is provided with the ammonia-containing gas outlet; the stainless steel bar high-voltage electrode is positioned in the center of the quartz tube reactor and is electrically connected with the high-voltage output end of the high-voltage power supply; the quartz tube reactor is externally coated with a stainless steel mesh, an aluminum foil or a copper foil as a grounding electrode and is electrically connected with the grounding end of a high-voltage power supply; the urea decomposition catalyst is filled in the annular space between the inner wall of the quartz tube reactor and the stainless steel bar high-voltage electrode, is supported by a quartz sand plate arranged in the quartz tube reactor and is completely arranged in a discharge area.
The sizes of the non-thermal plasma and the quartz tube reactor, the high-voltage electrode and the grounding electrode in the catalytic single-tube reactor are adjusted according to the fact that effective discharge can be generated in the reactor, and the discharge power and the catalyst loading amount meet the urea hydrolysis requirement. The non-thermal plasma synergistic catalysis urea decomposition catalyst filled in the single-tube reactor is selected from ZrO2、TiO2、Al2O3And the like have high catalytic urea hydrolysis activity.
In the urea decomposition process, nitrogen or air with a certain flow enters the reactor from carrier gas inlets of the non-thermal plasmas and the catalytic single-tube reactor in cooperation, and urea decomposition products such as ammonia gas flow out of the reactor along with the carrier gas and are collected or used for SCR denitration.
Example 1
With ZrO2A quartz tube with an inner diameter of 7.5mm, a wall thickness of 1mm and a length of 50cm was used as a quartz tube reactor, a stainless steel rod with a diameter of 1mm was used as a high-voltage electrode, and an aluminum foil with a length of 4cm was used as a ground electrode. Taking a proper amount of ZrO2Placing in a discharge area, introducing nitrogen with flow of 1L/min as carrier gas into a non-thermal plasma synergistic catalytic single-tube reactor, wherein the concentration of urea aqueous solution is 4 wt%, the injection flow is 16.7 muL/min, the output voltage of an alternating current high-voltage power supply is 22kV, the frequency is 200Hz, the discharge power is 48W, and the obtained NH is3The yield was 90%.
Example 2
With Al2O3A quartz tube with an inner diameter of 28mm, a wall thickness of 1.5mm and a length of 40cm was used as a quartz tube reactor, a stainless steel rod with a diameter of 1.4mm was used as a high-voltage electrode, and an aluminum foil with a length of 5cm was used as a ground electrode. Taking a proper amount of Al2O3Placing in a discharge area, introducing air with flow rate of 1L/min as carrier gas into a non-thermal plasma synergistic catalytic single-tube reactor, wherein the concentration of urea aqueous solution is 25 wt%, the injection flow rate is 20 muL/min, the output voltage of an alternating current high-voltage power supply is 21kV, the frequency is 200Hz, and the discharge power is 44W to obtain NH3The yield was 70%.
The embodiment shows that the urea can be efficiently hydrolyzed to prepare ammonia at normal temperature by virtue of the synergistic effect of the non-thermal plasma and the catalyst, the ammonia preparation process is simple, and the cost is low. The present invention is not limited to the above-described embodiments.
Claims (3)
1. A device for producing ammonia by hydrolyzing urea at normal temperature under the synergistic catalysis of non-thermal plasma is characterized in that: the device comprises a set of urea supply and injection system, a group of non-thermal plasma cooperative catalytic reactors and a set of gas distribution and collection system;
wherein the urea supply and injection system comprises a urea aqueous solution storage tank (1), a urea aqueous solution distribution system (2) and a urea aqueous solution injection device (3);
the group of non-thermal plasma synergistic catalytic reactors comprises a plurality of non-thermal plasma synergistic catalytic single-tube reactors (4) which are arranged in a matrix manner, 5-50 non-thermal plasma synergistic catalytic single-tube reactors are arranged in each row, 5-50 non-thermal plasma synergistic catalytic single-tube reactors in each row share one high-voltage power supply (5), and the interval between every two adjacent non-thermal plasma synergistic catalytic single-tube reactors is 5-10 cm;
the non-thermal plasma synergistic catalysis single-tube reactor (4) is a filling type dielectric barrier discharge reactor and comprises a quartz tube reactor (7), a high-voltage electrode (12), a grounding electrode (9), a catalyst filling layer (8), a quartz sand plate (10), a urea spraying inlet, a carrier gas inlet (6) and an ammonia-containing gas outlet (11), wherein the upper part of the quartz tube reactor is provided with the urea spraying inlet and the carrier gas inlet, and the lower part of the quartz tube reactor is provided with the ammonia-containing gas outlet; the stainless steel bar high-voltage electrode is positioned in the center of the quartz tube reactor and is electrically connected with the high-voltage output end of the high-voltage power supply; the quartz tube reactor is externally coated with a stainless steel mesh, an aluminum foil or a copper foil as a grounding electrode and is electrically connected with the grounding end of a high-voltage power supply; the urea decomposition catalyst is filled in the annular space between the inner wall of the quartz tube reactor and the stainless steel bar high-voltage electrode, is supported by a quartz sand plate arranged in the quartz tube reactor and is completely arranged in a discharge area;
a urea solution injection device (3) is arranged at the urea injection port of each quartz tube reactor (7), and the urea solution storage tank (1) is connected with each urea solution injection device (3) through a urea solution distribution system (2).
2. The device for producing ammonia by hydrolyzing urea at normal temperature under the synergistic catalysis of non-thermal plasma according to claim 1, wherein: the high-voltage power supply (5) is an alternating-current high-voltage power supply or a pulse high-voltage power supply.
3. The device for producing ammonia by hydrolyzing urea at normal temperature under the synergistic catalysis of non-thermal plasma according to claim 1, wherein: the gas distribution and collection system includes a carrier gas supply and distribution system and a reactor outlet ammonia-containing gas collection system.
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