JP2016101537A - Urea hydrolyzer and catalyst regeneration method for urea hydrolyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method enabling a hydrolysis catalyst to be easily regenerated without taking out the catalyst from a reactor and enabling deterioration of the hydrolysis catalyst and a timing of the catalyst regeneration to become clear.SOLUTION: There is provided an urea hydrolyzer which brings urea water U into contact with a hydrolysis catalyst 1 in a heating environment to produce ammonia A, blows the ammonia A into combustion exhaust gas in a furnace 10 or a flue to reduce nitrogen oxide. The urea hydrolyzer comprises: a reactor 2 having a hydrolysis catalyst layer 1 inside; an urea water supply line 3; an urea water spray nozzle 6 which sprays urea water; a heated air supply line 7 which supplies heated air a' into the reactor 2; an ammonia supply line 11; an ammonia spray nozzle 12; an urea water bypass line 14; and a second urea water spray nozzle 15 which sprays the urea water U into the furnace 10 or the flue. When the catalyst is regenerated, the urea water supply line 3 is intercepted to stop the supply of the urea water U, only the heated air a' is supplied into the reactor 2 by the heated air supply line 7 to cause gas to pass through the hydrolysis catalyst layer 1, so that the catalyst is regenerated.SELECTED DRAWING: Figure 1

Description

  The present invention is mainly attached to a waste incinerator, a boiler facility, etc., contacting urea water with a hydrolysis catalyst in a heated atmosphere, generating ammonia by hydrolysis of urea, and generating the generated ammonia in the furnace The present invention relates to a urea hydrolysis apparatus for reducing nitrogen oxides in combustion exhaust gas by being blown into the combustion exhaust gas in an inner or flue, and a catalyst regeneration method for the urea hydrolysis apparatus.

  Conventionally, as a method of reducing nitrogen oxides in combustion exhaust gas generated from waste incinerators, etc., non-catalytic denitration that decomposes nitrogen oxides in combustion exhaust gas by blowing ammonia water or urea water into the furnace or flue Methods and catalytic denitration methods that decompose nitrogen oxides in combustion exhaust gas into nitrogen gas in the presence of ammonia on the catalyst surface are known (see, for example, Patent Documents 1 to 5).

  In these denitration methods, as an example, urea water is hydrolyzed to produce ammonia, and the produced ammonia is blown into the flue gas in the furnace or flue to reduce nitrogen oxides in the flue gas. A cracker is used.

  As the urea hydrolysis apparatus, for example, one having a structure disclosed in Japanese Patent No. 4599998 (see Patent Document 6) is known.

  That is, as shown in FIG. 3, the urea hydrolysis apparatus includes a urea hydrolysis reactor 31 in which a hydrolysis catalyst 30 is loaded, and urea water pumped from a urea water tank 32 by a pump 33. A urea nozzle 34 for spraying the air, an air supply port 37 for supplying the air pressure-fed from the compressor 35 through the valve 36 into the urea hydrolysis reactor 31, and an electric heater 38 for keeping the urea hydrolysis reactor 31 at a constant temperature. And an ammonia conduit 40 extending from the urea hydrolysis reactor 31 into the exhaust gas line 39, an ammonia nozzle 41 for blowing ammonia into the exhaust gas line 39, and a control unit 42 for controlling the pump 33 and the valve 36.

  Thus, in the urea hydrolysis apparatus having the above configuration, the urea water pumped by the pump 33 is sprayed from the urea nozzle 34 toward the hydrolysis catalyst 30 in the urea hydrolysis reactor 31, and the sprayed urea is sprayed. Water is made into mist form by pressurized air supplied from the compressor 35 through the valve 36, the urea mist is brought into contact with the hydrolysis catalyst 30, and urea is hydrolyzed in a heating atmosphere by the electric heater 38 to generate ammonia. . The produced ammonia is sprayed to the denitration catalyst 43 loaded in the exhaust gas line 39 from the ammonia nozzle 41 at the tip thereof through the ammonia conduit 40 and used for the denitration reaction.

  By the way, in the urea hydrolysis apparatus, when a by-product such as cyanuric acid or biuret adheres to the hydrolysis catalyst 30 during operation of the apparatus, the catalyst performance is deteriorated, so that the catalyst is regenerated. . As this catalyst regeneration method, for example, there is a method in which the urea hydrolysis catalyst 30 is once taken out from the urea hydrolysis reactor 31 and a by-product attached to the urea hydrolysis catalyst 30 is removed.

  However, in the above method, the urea hydrolysis catalyst 30 is taken out from the urea hydrolysis reactor 31, the urea hydrolysis catalyst 30 is transported to the regeneration site, and the urea hydrolysis catalyst 30 is regenerated by the regeneration facility. Therefore, the urea hydrolysis catalyst 30 must be taken out, transported, regenerated, etc., and there has been a problem that the catalyst regeneration is very troublesome and the cost is increased.

  In the urea hydrolysis apparatus, the urea hydrolysis catalyst 30 in the urea hydrolysis reactor 31 is heated, and in this state, only air is supplied from the air supply port 31 into the urea hydrolysis reactor 31. By passing the gas through the hydrolysis catalyst 30, the by-product fixed to the urea hydrolysis catalyst 30 can be thermally decomposed. However, the by-product is fixed to the urea hydrolysis catalyst 30 and the urea hydrolysis catalyst 30 is In reality, the catalyst regeneration cannot be performed in a state where the deterioration or the timing of catalyst regeneration is not known at all and the urea hydrolysis catalyst 30 is still loaded in the urea hydrolysis reactor 31.

JP-A-53-62772 JP-A-6-269634 JP 2009-103381 A JP 2010-48456 A JP 2010-99603 A Japanese Patent No. 4599898

  The present invention has been made in view of such problems. The object of the present invention is to easily and easily regenerate the catalyst without taking out the hydrolysis catalyst from the reactor, as well as degradation of the hydrolysis catalyst and catalyst. It is an object of the present invention to provide a urea hydrolysis apparatus and a catalyst regeneration method for the urea hydrolysis apparatus in which the regeneration timing can be surely determined.

  In order to achieve the above object, according to a first aspect of the present invention, urea water is brought into contact with a hydrolysis catalyst in a heated atmosphere to generate ammonia by hydrolysis of urea, and the generated ammonia is burned in a furnace or a flue. In a urea hydrolysis apparatus that reduces nitrogen oxides in combustion exhaust gas by blowing into exhaust gas, the urea hydrolysis apparatus supplies a reactor having a hydrolysis catalyst layer formed therein, and urea water into the reactor. A urea water supply line, a urea water spray nozzle connected to the downstream end of the urea water supply line and spraying urea water toward the surface of the hydrolysis catalyst layer in the reactor, and heated air into the reactor A heated air supply line to be supplied, an ammonia supply line for introducing ammonia generated in the reactor into the furnace or the flue, and an ammonia supply line connected to the downstream end of the ammonia supply line. An urea spray nozzle connected to the downstream end of the urea water bypass line, an ammonia spray nozzle that blows into the flue, a urea water bypass line that branches a part of the urea water from the urea water supply line and leads to the furnace or the flue A second urea water spray nozzle that sprays water into the furnace or flue, shuts off the urea water supply line at the time of catalyst regeneration and stops the supply of urea water, and only the heated air through the heated air supply line It is characterized in that it is configured to be supplied into the gas and passed through the hydrolysis catalyst layer.

According to a second aspect of the present invention, in the first aspect, the urea hydrolyzing device includes a blower for supplying air connected to an upstream end of the heated air supply line, and heating provided in the heated air supply line. A first temperature detector for detecting the surface temperature of the hydrolysis catalyst layer, a second temperature detector and a third temperature detector for detecting the inlet temperature and the outlet temperature of the reactor, respectively. One or more of a differential pressure gauge that measures the pressure difference between the inlet and outlet of the reactor, and a CO ₂ concentration meter that detects the concentration of carbon dioxide in the gas flowing through the ammonia supply line, Based on one or more detection results or measurement results of the first temperature detector, the second temperature detector, the third temperature detector, the differential pressure gauge, and the CO ₂ concentration meter, the air volume of the blower and the heater for the heated air One or both of the outputs It is characterized in that the Gosuru configuration.

  According to a third aspect of the present invention, in the first aspect of the present invention, an on-off valve is provided in a downstream portion of the urea water supply line where the urea water bypass line is connected. It is characterized by the interposition.

  According to a fourth aspect of the present invention, in the first aspect, the second urea water spray nozzle is disposed near the ammonia spray nozzle so as to spray the urea water onto the ammonia gas diffusion portion from the ammonia spray nozzle. It is characterized by being.

  A fifth invention of the present invention is the catalyst regeneration method for a urea hydrolysis apparatus according to the first invention, the second invention, the third invention or the fourth invention, wherein the urea water supply line is shut off. Then, the supply of urea water is stopped, and only the heated air is supplied into the reactor through the heated air supply line and gas is passed to the hydrolysis catalyst layer, and the by-product fixed to the hydrolysis catalyst is removed by the heated air. The catalyst is regenerated by thermal decomposition, and the generated ammonia is blown into the furnace or flue for denitration reaction.

  According to a sixth aspect of the present invention, in the fifth aspect, the heated air is passed through the hydrolysis catalyst layer so that the surface temperature of the hydrolysis catalyst layer is 250 ° C. to 450 ° C. during catalyst regeneration. There is a special feature.

  According to a seventh aspect of the present invention, in the fifth aspect, when the ammonia generated at the time of catalyst regeneration is less than the required amount for the denitration reaction, the elemental water is guided to the furnace or flue by the urea water bypass line. Along with the ammonia spray nozzle, urea water is sprayed from the second urea water spray nozzle into the furnace or flue to compensate for the amount of ammonia required for the denitration reaction.

  The eighth invention of the present invention is characterized in that, in the seventh invention, the branched urea water is sprayed to the ammonia gas diffusion portion from the ammonia spray nozzle by the second urea water spray nozzle.

  According to a ninth aspect of the present invention, in the fifth aspect, the sixth aspect, the seventh aspect or the eighth aspect, the surface temperature of the hydrolysis catalyst layer, the temperature difference between the inlet temperature and the outlet temperature of the reactor. Detecting or measuring any one or more of the pressure difference between the inlet and outlet of the reactor and the carbon dioxide concentration in the gas flowing through the ammonia supply line, and upstream of the heated air supply line based on the detection result or the measurement result It is characterized in that either one or both of the air volume of the blower connected to the side end and the output of the heater for heating air provided in the heating air supply line are controlled.

  According to the present invention, the urea water supply line is shut off at the time of catalyst regeneration, and only heated air is supplied into the reactor through the heated air supply line so as to pass gas to the hydrolysis catalyst layer, and cyanurium fixed to the hydrolysis catalyst. Since by-products such as acid and biuret are thermally decomposed by the heated air, the hydrolysis catalyst can be regenerated without being removed from the reactor, and catalyst regeneration can be performed easily and easily. The cost can be reduced.

  Further, according to the present invention, the heated air is passed through the hydrolysis catalyst layer so that the surface temperature of the hydrolysis catalyst layer is 250 ° C. to 450 ° C. during catalyst regeneration. The product can be thermally decomposed reliably and satisfactorily, and the ammonia generated by the thermal decomposition of the by-product can be prevented from being ignited.

Furthermore, according to the present invention, a first temperature detector that detects the surface temperature of the hydrolysis catalyst layer, a second temperature detector and a third temperature detector that respectively detect the inlet temperature and the outlet temperature of the reactor, Hydrolysis catalyst because it has one or more of a differential pressure gauge that measures the pressure difference between the inlet and outlet of the reactor and a CO ₂ concentration meter that detects the carbon dioxide concentration in the gas flowing through the ammonia supply line By-products are firmly attached to the hydrolysis catalyst and the hydrolysis catalyst is deteriorated, and the regeneration timing of the hydrolysis catalyst is surely known.

  Further, according to the present invention, the surface temperature of the hydrolysis catalyst layer, the temperature difference between the inlet temperature and the outlet temperature of the reactor, the pressure difference between the inlet and outlet of the reactor, the carbon dioxide concentration in the gas flowing through the ammonia supply line Any one or more of these are detected or measured, and based on the detection result or the measurement result, the air volume of the blower connected to the upstream end of the heated air supply line and the heated air heater installed in the heated air supply line Since one or both of the outputs are controlled, the surface temperature of the hydrolysis catalyst layer can be maintained at a temperature suitable for catalyst regeneration.

Further, according to the present invention, when the ammonia generated during catalyst regeneration is less than the required amount for the denitration reaction, the urea water is led to the furnace or the flue through the urea water bypass line, and is combined with the ammonia spray nozzle. Since urea water is sprayed into the furnace or flue from the second urea water spray nozzle to compensate for the amount of ammonia required for the denitration reaction, denitration treatment is performed in the furnace or flue even during catalyst regeneration. be able to.
At this time, since the branched urea water is sprayed to the ammonia gas diffusion portion from the ammonia spray nozzle by the second urea water spray nozzle, the second urea water spray nozzle is utilized by using the discharge pressure from the ammonia spray nozzle. The urea water sprayed from the water can be diffused reliably, and the denitration reaction is favorably performed in the furnace or the flue.

1 is a schematic system diagram of a urea hydrolysis apparatus according to an embodiment of the present invention. It is a schematic longitudinal cross-sectional view of the reactor of a urea hydrolysis apparatus. It is a schematic longitudinal cross-sectional view of the conventional urea hydrolysis apparatus.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a urea hydrolysis apparatus according to an embodiment of the present invention. The urea hydrolysis apparatus is attached to, for example, a waste incinerator or a boiler facility, and a urea catalyst is used as a hydrolysis catalyst in a heated atmosphere. Contact is made to produce ammonia by hydrolysis of urea, and the produced ammonia is blown into the combustion exhaust gas in the furnace or flue to reduce nitrogen oxides in the combustion exhaust gas.

  That is, as shown in FIG. 1, the urea hydrolysis apparatus includes a reactor 2 in which a hydrolysis catalyst layer 1 is formed, a urea water supply line 3 for supplying urea water U to the reactor 2, and a urea water U. A urea water storage tank 4 for storing water, a urea water supply pump 5 interposed in the urea water supply line 3, and a urea water spray nozzle for spraying urea water U toward the surface of the hydrolysis catalyst layer 1 in the reactor 2. 6, a heated air supply line 7 for supplying heated air a ′ into the reactor 2, a blower 8 for supplying air connected to an upstream end of the heated air supply line 7, and a heated air supply line 7. Heated air heater 9 provided, ammonia supply line 11 for introducing ammonia A generated in reactor 2 into furnace 10 (or flue), and ammonia for blowing ammonia A into furnace 10 (or flue) Spray nozzle 12 and heated air supply line 7 The air bypass line 13 that branches a part of the air a, the urea water bypass line 14 that branches a part of the urea water U from the urea water supply line 3, and the urea water U into the furnace 10 (or in the flue). And a second urea water spray nozzle 15 for spraying.

  As shown in FIGS. 1 and 2, the reactor 2 is loaded into a cylindrical metal casing 2c having a truncated conical ceiling wall 2a and a bottom wall 2b, and the metal casing 2c is sprayed. And a hydrolysis catalyst layer 1 for hydrolyzing the urea water U. The hydrolysis catalyst layer 1 is formed by laminating granular alumina.

  In the above embodiment, granular alumina is used as the urea decomposition catalyst. However, in other embodiments, silica, titania, zeolite, magnesia, calcia, or the like may be used as the urea decomposition catalyst. These urea decomposition catalysts may be used alone or in combination of two or more.

  In the above embodiment, the metal casing 2c is formed in a cylindrical shape, and the ceiling wall 2a and the bottom wall 2b of the metal casing 2c are formed in a truncated cone shape. Although not shown, the metal casing 2c may be formed in a columnar shape having a flat ceiling wall 2a and a bottom wall 2b, and although not shown, the metal casing 2c is formed in a rectangular tube shape, The ceiling wall 2a and the bottom wall 2b of the casing 2c may be formed in a truncated quadrangular pyramid shape.

  The urea water supply line 3 supplies urea water U to the reactor 2, and a urea water storage tank 4 that stores the urea water U is connected to an upstream end of the urea water supply line 3. At the same time, a urea water supply pump 5 and an opening / closing valve 16 are interposed in the middle of the urea water supply line 3.

  The urea water supply pump 5 includes a variable speed control mechanism 5a and is controlled at a variable speed based on the NOx concentration in the exhaust gas discharged from the chimney. That is, the urea water supply pump 5 detects the NOx concentration in the exhaust gas discharged from the chimney with a NOx concentration detector (not shown), and when the NOx concentration in the exhaust gas discharged from the chimney is high, the urea water Control is performed to send out a small amount of urea water U when a large amount of U is sent out and the NOx concentration in the exhaust gas is low.

  The urea water spray nozzle 6 is connected to the downstream end of the urea water supply line 3 and is inserted and supported at the center of the ceiling wall 2a of the reactor 2 (the axial position of the reactor 2). The urea water U is sprayed toward the surface of the hydrolysis catalyst layer 1.

  The urea water spray nozzle 6 uses a two-fluid nozzle that jets a liquid (urea water U) into a fine mist by mixing it with a gas (compressed air a ″). The urea water U is supplied from the urea water supply line 3, and the compressed air a ″ is supplied from the compressor (not shown) by the compressed air supply line 18 provided with the control valve 17.

  The heated air supply line 7 supplies heated air a ′ (heated air a ′ of 400 ° C. to 450 ° C.) into the reactor 2 to supply the reactor 2, the hydrolysis catalyst layer 1 and the sprayed urea water U. A blower 8 capable of supplying a large volume of air a is connected to an upstream end of the heated air supply line 7 and heated air is supplied in the middle of the heated air supply line 7. A heater 9 for heating air for heating the air a flowing in the line 7 is interposed.

  Further, at the downstream end of the heated air supply line 7, the heated air a ′ can be supplied into the reactor 2 so that the rectifying effect of the heated air a ′ can be obtained in the reactor 2, and the heated air a A heated air supply unit that can heat a portion of ′ by spraying the urea water spray nozzle 6 to heat the urea water spray nozzle 6 is provided at the axial position of the reactor 2. Yes.

  As shown in FIGS. 1 and 2, the heated air supply unit has an upward end of the urea water spray nozzle 6 inserted in a vertical posture so that the heated air a ′ flows upward and flows along the urea water spray nozzle 6. An upper opening 7a and a downward lower opening 7b through which the tip end side of the urea water spray nozzle 6 is inserted in a vertical posture to flow the heated air a ′ downward and along the urea water spray nozzle 6 are provided.

  The ammonia supply line 11 guides ammonia A generated by hydrolysis of urea in the reactor 2 to the furnace 10 (or flue). The ammonia supply line 11 has ammonia at the downstream end. An ammonia spray nozzle 12 that blows A into the furnace 10 (or the flue) is connected.

  The air bypass line 13 branches a part of the air a from the heated air supply line 7 upstream of the heater 9 for heated air and supplies it to the ammonia supply line 11 upstream of the ammonia spray nozzle 12. The bypass line 13 is provided with a control valve 19 for controlling the amount of branched air. The air bypass line 13 controls the discharge gas amount (ammonia gas amount) from the ammonia spray nozzle 12 to be constant.

  The urea water bypass line 14 branches a part of the urea water U from the urea water supply line 3 and leads it into the furnace 10 (or the flue). 20 is established, and a second urea water spray nozzle 15 that sprays urea water U into the furnace 10 (or the flue) is connected to the downstream end of the urea water bypass line 14.

  The urea water bypass line 14 and the second urea water spray nozzle 15 are used when the hydrolysis catalyst in the reactor 2 is regenerated. Ammonia A generated during the regeneration of the hydrolysis catalyst is reduced to a necessary amount for the denitration reaction. When it is not satisfied, the urea water U is supplied into the furnace 10 (or the flue).

  Further, the second urea water spray nozzle 15 uses the discharge pressure of the ammonia spray nozzle 12 for the purpose of diffusing the urea water U in the furnace 10 (or in the flue) and diffuses the ammonia gas from the ammonia spray nozzle 12. It arrange | positions in the vicinity position of the ammonia spray nozzle 12 so that urea water U may be sprayed to a part (near nozzle front-end | tip).

  In the urea hydrolysis apparatus described above, the air flow rate of the blower 8 and the surface temperature of the hydrolysis catalyst layer 1 in the reactor 2 are 200 ° C. or higher (preferably 220 ° C. or higher) when urea is hydrolyzed. Either one or both of the outputs of the heater 9 for heated air are controlled. This is because when the surface temperature of the hydrolysis catalyst layer 1 falls below 200 ° C., by-products such as cyanuric acid and biuret are deposited, which adheres to the hydrolysis catalyst and deteriorates the catalyst performance.

  In this embodiment, either or both of the air volume of the blower 8 and the output of the heater 9 for heated air are controlled so that the surface temperature of the hydrolysis catalyst layer 1 is 200 ° C. to 250 ° C.

  The blower 8 and the heated air heater 9 detect the surface temperature of the hydrolysis catalyst layer 1 with the first temperature detector 21, and based on the detection signal from the first temperature detector 21, The surface temperature is controlled to be the above temperature (200 ° C. to 250 ° C.).

  Further, in the urea hydrolysis apparatus described above, the hydrolysis catalyst layer 1 is controlled by controlling either one or both of the air volume of the blower 8 and the output of the heater 9 for heated air by an output signal from the urea water supply pump 5. Is kept at the above set value (200 ° C. to 250 ° C.). This is to prevent a rapid decrease in the surface temperature of the hydrolysis catalyst layer 1 due to excessive supply of urea water U.

Furthermore, in the above-described urea hydrolysis apparatus, when the surface temperature of the hydrolysis catalyst layer 1 rapidly decreases, it is necessary to quickly increase the surface temperature of the hydrolysis catalyst layer 1.
As a measure therefor, a method of increasing the amount of heated air a ′ to the reactor 2 is conceivable. At that time, the amount of gas discharged from the ammonia spray nozzle 12 (ammonia gas amount) is increased by increasing the amount of heated air a ′. There is a possibility that the diffusion state of ammonia A in the furnace 10 (or in the flue) changes.

  Therefore, in the urea hydrolysis apparatus described above, the heated air supply line upstream of the heated air heater 9 by the air bypass line 13 so that the discharge gas amount (ammonia gas amount) from the ammonia spray nozzle 12 is constant. 7, a part of the air a is branched and supplied to the ammonia supply line 11 on the upstream side of the ammonia spray nozzle 12, whereby the discharge gas amount (ammonia gas amount) from the ammonia spray nozzle 12 is controlled to be constant. ing.

  In this embodiment, the amount of heated air a ′ to the reactor 2 is set so that the ammonia concentration sprayed from the ammonia spray nozzle 12 is 3% or less. Excess air a is supplied from the air bypass line 13 to the ammonia supply line 11 upstream of the ammonia spray nozzle 12 by controlling the control valve 19.

  According to the method, the excess air a bypassed by the air bypass line 13 is not heated by the heater 9 for heated air, and the discharge gas amount (ammonia gas amount) from the ammonia spray nozzle 12 can be kept constant. There is. Further, since excess air a is not heated by the heater 9 for heated air, energy loss can be reduced.

  Further, in the above-described urea hydrolysis apparatus, when a by-product such as cyanuric acid or biuret adheres to the hydrolysis catalyst, the catalyst performance is deteriorated, so that the catalyst is regenerated. Catalyst regeneration is performed by thermally decomposing by-products fixed on the surface of the hydrolysis catalyst into ammonia A or the like with heated air a ′.

  That is, at the time of catalyst regeneration, the urea hydrolysis apparatus closes the opening / closing valve 16 provided in the urea water supply line 3 to stop the supply of the urea water U to the reactor 2, and the air volume and heating of the blower 8. One or both of the outputs of the air heater 9 are controlled, and only the heated air a ′ is passed through the hydrolysis catalyst layer 1 in the reactor 2 to regenerate the catalyst.

  During the regeneration of the catalyst, heated air a ′ is passed through the hydrolysis catalyst layer 1 in the reactor 2 so that the surface temperature of the hydrolysis catalyst layer 1 is 250 ° C. or higher (preferably 300 ° C. or higher).

  In this embodiment, either or both of the air volume of the blower 8 and the output of the heater 9 for heated air are controlled so that the surface temperature of the hydrolysis catalyst layer 1 is 250 ° C. to 450 ° C. This is because if the temperature is raised too much, ammonia A will ignite, and if the temperature is lowered too much, by-products such as cyanuric acid cannot be thermally decomposed.

  Ammonia A generated by passing heated air a ′ through the hydrolysis catalyst layer 1 in the reactor 2 (generated by thermal decomposition of by-products such as cyanuric acid fixed to the catalyst) is sprayed with ammonia. It sprays in the furnace 10 (or flue) from the nozzle 12, and is used for denitration reaction.

  If the ammonia A generated during catalyst regeneration is less than the required amount for the denitration reaction, the opening / closing valve 20 of the urea water bypass line 14 is opened, and the second urea water spray nozzle 15 along with the ammonia spray nozzle 12 is opened. Then, urea water U is sprayed into the furnace 10 (or in the flue) to supplement the amount of reducing agent (ammonia amount) necessary for the denitration reaction.

  The catalyst regeneration timing is as follows: (1) temperature at the inlet and outlet of the reactor 2, (2) surface temperature of the hydrolysis catalyst layer 1, (3) pressure loss of the hydrolysis catalyst layer 1, and (4) reactor. Any one or a combination of two or more carbon dioxide concentrations in the gas at the outlet side of the two is detected, and the detection is performed based on these detection results.

  In the catalyst regeneration timing according to the above (1), the inlet temperature and the outlet temperature of the reactor 2 are detected by the second temperature detector 22 and the third temperature detector 23, respectively, and the temperature difference reaches a set value. Therefore, it is determined that the catalyst has deteriorated, and the regeneration process is performed. This is because if the exothermic reaction does not proceed in the thermal decomposition reaction of urea, a by-product such as cyanuric acid is fixed on the catalyst, and a temperature difference occurs between the inlet and the outlet of the reactor 2, This is because the temperature on the outlet side decreases.

  At the timing of catalyst regeneration according to the above (2), the surface temperature of the hydrolysis catalyst layer 1 is detected by the first temperature detector 21 composed of a thermocouple or the like disposed on the surface of the hydrolysis catalyst layer 1, and the hydrolysis catalyst layer 1 When the temperature at the center of the surface of the catalyst is lower than the ambient temperature, it is determined that the catalyst has deteriorated, and the regeneration process is performed. The reason why the temperature at the center of the surface of the hydrolysis catalyst layer 1 is detected is that a by-product tends to precipitate at the center, and if the by-product is precipitated, no exothermic reaction occurs.

  At the catalyst regeneration timing according to the above (3), the pressure difference between the inlet and the outlet of the reactor 2 is measured by the differential pressure gauge 24, and when the pressure difference reaches the set value, it is judged that the catalyst has deteriorated, and regeneration is performed. Switch to the process. That is, a pressure increase when a by-product is fixed to the catalyst is detected.

At the timing of catalyst regeneration according to the above (4), the CO ₂ concentration in the gas flowing in the ammonia supply line 11 is detected by the CO ₂ concentration meter 25 and calculated from the detected CO ₂ concentration and the supplied amount of urea water U. When the estimated difference in CO ₂ concentration exceeds a predetermined value, it is determined that the catalyst has deteriorated, and the process is switched to the regeneration process.

In this embodiment, when the temperature difference between the inlet temperature and the outlet temperature of the reactor 2 reaches 10 ° C. to 20 ° C., the temperature at the center of the surface of the hydrolysis catalyst layer 1 is 5 ° C. to 10 ° C. than the ambient temperature. ℃ when lowered, the pressure difference between the inlet and outlet reactor 2 (pressure loss) upon reaching 100MmAq～200mmAq, was calculated from the feed amount of the detected CO ₂ concentration and the urea water U by CO ₂ concentration meter 25 estimates When the difference in CO ₂ concentration reaches 10% to 20%, it is determined that the catalyst has deteriorated, and the regeneration process is switched.

In addition, in each calculation part of each of the temperature detectors 21 to 23, the differential pressure gauge 24, and the CO ₂ concentration meter 25, the set value of the temperature difference between the inlet temperature and the outlet temperature of the reactor 2 described above, the hydrolysis catalyst layer 1 The set value of the surface temperature, the set value of the pressure difference between the inlet and outlet of the reactor 2, and the set value of the difference between the detected CO ₂ concentration and the estimated CO ₂ concentration calculated from the supply amount of the urea water U are stored in advance. Yes.

  Thus, in the above-described urea hydrolysis apparatus, the urea water U in the urea water storage tank 4 is supplied to the urea water spray nozzle 6 having the two-fluid nozzle structure via the urea water supply line 3 by the urea water supply pump 5. At the same time, the compressed air a ″ from the compressor is supplied to the urea water spray nozzle 6 through the compressed air supply line 18, and urea water is directed from the urea water spray nozzle 6 toward the surface of the hydrolysis catalyst layer 1 in the reactor 2. At this time, since the two-fluid nozzle is used as the urea water spray nozzle 6, the sprayed urea water U has a fine particle diameter.

  Further, the air a for heating the reactor 2 (including the hydrolysis catalyst layer 1) is supplied to the heater 9 for heating air by the blower 8 and heated, and the heating air a ′ is downstream end of the heating air supply line 7. The reactor 2, the hydrolysis catalyst layer 1, and the sprayed urea water U are heated by being supplied into the reactor 2 from the heated air supply section provided in the section.

  At the time of hydrolysis of urea in the reactor 2, either or both of the air volume of the blower 8 and the output of the heater 9 for heated air are controlled so that the surface temperature of the hydrolysis catalyst layer 1 becomes 200 ° C. to 250 ° C. Has been. That is, the surface temperature of the hydrolysis catalyst layer 1 is detected by the first temperature detector 21, and the surface temperature of the hydrolysis catalyst layer 1 becomes 200 ° C. to 250 ° C. based on the detection signal from the first temperature detector 21. Thus, one or both of the blower 8 and the heater 9 for heated air are controlled by the first temperature detector 21.

  Further, the surface temperature of the hydrolysis catalyst layer 1 can be set to 200 ° C. to 250 ° C. by controlling either one or both of the air volume of the blower 8 and the output of the heater 9 for heating air by the output signal from the urea water supply pump 5. Keep it at ℃. That is, the surface temperature of the hydrolysis catalyst layer 1 is set to 200 ° C. to 250 ° C. when the urea water U is excessively supplied from the urea water supply pump 5 accompanying the increase in the NOx concentration in the exhaust gas discharged from the chimney. Either or both of the blower 8 and the heater 9 for heated air are controlled by an output signal from the urea water supply pump 5. Thereby, the rapid fall of the surface temperature of the hydrolysis catalyst accompanying the excessive supply of urea water U can be prevented.

  In this way, by keeping the surface temperature of the hydrolysis catalyst layer 1 at 200 ° C. to 250 ° C., it is possible to prevent the precipitation of by-products such as cyanuric acid and biuret and the fixation of the by-products to the hydrolysis catalyst. it can.

  Further, during the hydrolysis of urea in the reactor 2, the heated air a ′ supplied into the reactor 2 from the heated air supply section provided at the downstream end of the heated air supply line 7 is converted into the reactor 2 by the rectification effect. Since the heating air a ′ uniformly heats the hydrolysis catalyst layer 1, the urea water U sprayed from the urea water spray nozzle 6 is also supplied to the heating air a ′ in the reactor 2. Due to the rectifying effect, the inside of the reactor 2 flows evenly toward the hydrolysis catalyst layer 1 and comes into contact with the entire area of the hydrolysis catalyst layer 1, so that urea can be efficiently decomposed. However, the heated air a ′ not only heats the reactor 2, the hydrolysis catalyst layer 1 and the sprayed urea water U, but also blows ammonia A generated in the hydrolysis of urea into the furnace 10 or the flue. Can be used as a carrier gas.

  Further, since the urea water spray nozzle 6 is heated by the heated air a ′ supplied from the heated air supply unit, urea adheres to the surface of the urea water spray nozzle 6 and the injection port, and cyanuric acid, biuret, etc. By-product sticking can be suppressed, and the continuous operation can be performed by preventing the urea water spray nozzle 6 from being blocked or clogged with piping.

  In particular, the heated air supply unit includes an upward upper opening 7a through which the distal end side of the urea water spray nozzle 6 is inserted in a vertical posture so that the heated air a 'flows upward and along the urea water spray nozzle 6, and urea water spray. Since the tip end side of the nozzle 6 is inserted in a vertical posture and has a downward lower opening 7b that flows the heated air a 'downward and flows along the urea water spray nozzle 6, heating that has flowed upward from the upper opening 7a The air a ′ is inverted at the ceiling wall 2a of the reactor 2 and flows toward the hydrolysis catalyst layer 1, so that a higher rectification effect is obtained, and the heated air a ′ flowing from the upper opening 7a and the lower opening 7b The entire urea water spray nozzle 6 can be heated reliably and satisfactorily, and sticking of byproducts such as cyanuric acid and biuret can be further suppressed.

  Then, the urea sprayed onto the hydrolysis catalyst layer 1 in the reactor 2 comes into contact with the heated hydrolysis catalyst and is hydrolyzed to produce ammonia A. The generated ammonia A is sprayed from the ammonia spray nozzle 12 into the furnace 10 (or the flue) through the ammonia supply line 11 and used for the denitration reaction.

In addition, reaction which produces | generates ammonia A from urea is as the following (1) Formula, and is what is called a hydrolysis reaction.
(NH ₂ ) ₂ CO + H ₂ O → 2NH ₃ + CO ₂ (1) Formula

The reaction performed in the space above the hydrolysis catalyst layer 1 in the reactor 2 is an endothermic reaction of the following formula (2), and the reaction performed in the hydrolysis catalyst layer 1 in the reactor 2 is as follows. (3) exothermic reaction.
(NH ₂ ) ₂ CO → HNCO + NH ₃ (2) Formula HNCO + H ₂ O → NH ₃ + CO ₂ (3) Formula

  By the way, in the urea hydrolysis apparatus described above, when a by-product such as cyanuric acid or biuret adheres to the hydrolysis catalyst during operation of the apparatus, the catalyst performance is deteriorated, so that the catalyst is regenerated. .

  At the time of catalyst regeneration, the on-off valve 16 provided in the urea water supply line 3 is closed to stop the supply of the urea water U to the reactor 2, and either one or both of the blower 8 and the heater 9 for heated air are used. And only the heated air a ′ is passed through the hydrolysis catalyst layer 1 in the reactor 2 to regenerate the catalyst, and the surface temperature of the hydrolysis catalyst layer 1 becomes 250 ° C. to 450 ° C. As described above, either or both of the air volume of the blower 8 and the output of the heater 9 for heated air are controlled.

  The timing of catalyst regeneration is as follows: (1) Inlet temperature and outlet temperature of reactor 2, (2) Surface temperature of hydrolysis catalyst layer 1, (3) Pressure loss of hydrolysis catalyst layer 1, (4) Reactor Any one or a combination of two or more carbon dioxide concentrations in the gas at the outlet side of the two are detected or measured, and the detection results or measurement results are used.

  That is, at the catalyst regeneration timing according to the above (1), the inlet temperature and the outlet temperature of the reactor 2 are detected by the second temperature detector 22 and the third temperature detector 23, respectively, and the temperature difference is a set value (10 ° C. ˜20 ° C.), the on-off valve 16 provided in the urea water supply line 3 is closed to stop the supply of the urea water U to the reactor 2, and the second temperature detector 22 and the third temperature detection One or both of the blower 8 and the heated air heater 9 are controlled based on the detection signal from the reactor 23, and only the heated air a ′ is passed through the hydrolysis catalyst layer 1 in the reactor 2.

  At this time, since either or both of the air volume of the blower 8 and the output of the heater 9 for heated air are controlled so that the surface temperature of the hydrolysis catalyst layer 1 is 250 ° C. to 450 ° C., the hydrolysis catalyst By-products such as cyanuric acid and biuret adhered to the catalyst are thermally decomposed to regenerate the catalyst, and the surface temperature of the hydrolysis catalyst layer 1 can be maintained at a temperature suitable for catalyst regeneration. However, the hydrolysis catalyst can be regenerated without taking it out of the reactor 2, and the catalyst regeneration can be performed easily and easily, and the cost is not excessive and the cost can be reduced.

  In addition, ammonia A or the like is generated in the reactor 2 due to thermal decomposition of the by-product, and this ammonia A is sprayed from the ammonia spray nozzle 12 into the furnace 10 (or in the flue) through the ammonia supply line 11. Used for denitration reaction. Therefore, it is not necessary to stop the operation of a waste incinerator or the like during catalyst regeneration.

  When the ammonia A generated at the time of catalyst regeneration is less than the necessary amount for the denitration reaction, the opening / closing valve 20 of the urea water bypass line 14 is opened, and the second urea water spray nozzle 15 along with the ammonia spray nozzle 12 is opened. The urea water U is sprayed into the furnace 10 (or in the flue) to supplement the amount of reducing agent (ammonia amount) necessary for the denitration reaction.

  At this time, since the branched urea water U is sprayed to the ammonia gas diffusion portion from the ammonia spray nozzle 12 by the second urea water spray nozzle 15, the second pressure using the discharge pressure from the ammonia spray nozzle 12 is used. The urea water U sprayed from the urea water spray nozzle 15 can be reliably diffused, and the denitration reaction is favorably performed in the furnace 10 (or in the flue).

  At the timing of catalyst regeneration according to the above (2), the surface temperature of the hydrolysis catalyst layer 1 is detected by the first temperature detector 21, and the temperature at the center of the surface of the hydrolysis catalyst layer 1 is 5 ° C. higher than the ambient temperature. When the temperature decreases by -10 ° C., the opening / closing valve 16 provided in the urea water supply line 3 is closed to stop the supply of the urea water U to the reactor 2 and based on the detection signal from the first temperature detector 21. Either or both of the blower 8 and the heater 9 for heated air are controlled so that only the heated air a ′ is passed through the hydrolysis catalyst layer 1 in the reactor 2.

  At this time, either or both of the air volume of the blower 8 and the output of the heater 9 for heated air are controlled so that the surface temperature of the hydrolysis catalyst layer 1 is 250 ° C. to 450 ° C. Similarly to the catalyst regeneration according to 1), thermal decomposition of by-products, catalyst regeneration, generation of ammonia A, spraying of ammonia A into the furnace 10 (or in the flue), and spraying of urea water U are performed.

  At the timing of catalyst regeneration according to (3) above, when the pressure difference between the inlet and outlet of the reactor 2 is measured by the differential pressure gauge 24 and the pressure difference (pressure loss) reaches a set value (100 mmAq to 200 mmAq), urea The on-off valve 16 provided in the water supply line 3 is closed to stop the supply of the urea water U to the reactor 2, and any one of the blower 8 and the heated air heater 9 based on the detection signal from the differential pressure gauge 24. Either or both are controlled, and only the heated air a ′ is passed through the hydrolysis catalyst layer 1 in the reactor 2.

  At this time, either or both of the air volume of the blower 8 and the output of the heater 9 for heated air are controlled so that the surface temperature of the hydrolysis catalyst layer 1 is 250 ° C. to 450 ° C. Similarly to the catalyst regeneration according to 1), thermal decomposition of by-products, catalyst regeneration, generation of ammonia A, spraying of ammonia A into the furnace 10 (or in the flue), and spraying of urea water U are performed.

At the catalyst regeneration timing according to the above (4), the CO ₂ concentration meter 25 detects the concentration of CO _{2 in} the gas flowing in the ammonia supply line 11 and calculates from the detected CO ₂ concentration and the supplied amount of urea water U. When the difference in estimated CO ₂ concentration exceeds the set value (10% to 20%), the open / close valve 16 provided in the urea water supply line 3 is closed to stop the supply of the urea water U to the reactor 2. At the same time, either or both of the blower 8 and the heater 9 for heated air are controlled based on the detection signal from the CO ₂ concentration meter 25, and only the heated air a ′ is passed to the hydrolysis catalyst layer 1 in the reactor 2. Gas.

  At this time, either or both of the air volume of the blower 8 and the output of the heater 9 for heated air are controlled so that the surface temperature of the hydrolysis catalyst layer 1 is 250 ° C. to 450 ° C. Similarly to the catalyst regeneration according to 1), thermal decomposition of by-products, catalyst regeneration, generation of ammonia A, spraying of ammonia A into the furnace 10 (or in the flue), and spraying of urea water U are performed.

  In the above embodiment, the ammonia A produced by the urea hydrolysis apparatus is blown into the furnace 10. However, in another embodiment, the ammonia A produced by the urea hydrolysis apparatus is flue gas. You may make it blow in (illustration omitted).

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

1 is a hydrolysis catalyst layer, 1a is a lower catalyst layer, 1b is an upper catalyst layer, 2 is a reactor, 2a is a ceiling wall, 2b is a bottom wall, 2c is a metal casing, 3 is a urea water supply line, 4 is urea Water storage tank, 5 is urea water supply pump, 5a is variable speed control mechanism, 6 is urea water spray nozzle, 7 is heating air supply line, 7a is upper opening, 7b is lower opening, 8 is blower, 9 is for heating air Heater, 10 in furnace, 11 ammonia supply line, 12 ammonia spray nozzle, 13 air bypass line, 14 urea water bypass line, 15 second urea water spray nozzle, 16 open / close valve of urea water supply line , 17 is a control valve for the compressed air supply line, 18 is a compressed air supply line, 19 is a control valve for the air bypass line, 20 is an open / close valve for the urea water bypass line, 21 is a first temperature detector, 22 The second temperature detector, the third temperature detector 23, the differential pressure gauge 24, 25 CO ₂ concentration meter, A is ammonia, a is the air, a 'is heated air, a "compressed air, U is the urea water .

Claims (9)

  Urea in which urea water is brought into contact with a hydrolysis catalyst in a heated atmosphere to generate ammonia by hydrolysis of urea, and the generated ammonia is blown into the combustion exhaust gas in the furnace or flue to reduce nitrogen oxides in the combustion exhaust gas In the hydrolysis apparatus, the urea hydrolysis apparatus includes a reactor having a hydrolysis catalyst layer formed therein, a urea water supply line for supplying urea water into the reactor, and a downstream end of the urea water supply line. A urea water spray nozzle that is connected to spray urea water toward the surface of the hydrolysis catalyst layer in the reactor, a heated air supply line that supplies heated air into the reactor, and ammonia generated in the reactor An ammonia supply line that leads to the furnace or flue, an ammonia spray nozzle that is connected to the downstream end of the ammonia supply line and blows ammonia into the furnace or flue, and urea A urea water bypass line that branches a part of the urea water from the supply line and leads to the furnace or the flue, and is connected to the downstream end of the urea water bypass line to spray the urea water into the furnace or the flue. 2 The urea water spray nozzle is provided, the urea water supply line is shut off during catalyst regeneration to stop the urea water supply, and only the heated air is supplied into the reactor through the heated air supply line and passed to the hydrolysis catalyst layer. A urea hydrolysis apparatus characterized in that it is configured to gas. The urea hydrolysis apparatus includes a blower for supplying air connected to an upstream end of the heated air supply line, a heater for heated air interposed in the heated air supply line, and a surface temperature of the hydrolysis catalyst layer. A first temperature detector for detecting the temperature, a second temperature detector and a third temperature detector for detecting an inlet temperature and an outlet temperature of the reactor, respectively, and a differential pressure gauge for measuring a pressure difference between the inlet and the outlet of the reactor Any one or more of CO ₂ concentration meters for detecting the carbon dioxide concentration in the gas flowing through the ammonia supply line, the first temperature detector, the second temperature detector, and the third temperature detector. The air volume of the blower and / or the output of the heater for heated air are controlled based on one or a plurality of detection results or measurement results of a pressure gauge, a differential pressure gauge, and a CO ₂ concentration meter. As described in claim 1 Urea hydrolysis apparatus.   2. The urea according to claim 1, wherein an on-off valve is provided in a portion downstream of the urea water supply line connected to the urea water bypass line, and an on-off valve is provided in the urea water bypass line. Hydrolysis equipment.   2. The urea water spray nozzle according to claim 1, wherein the second urea water spray nozzle is disposed in the vicinity of the ammonia spray nozzle so as to spray the urea water onto the ammonia gas diffusion portion from the ammonia spray nozzle. Disassembly equipment.   5. The catalyst regeneration method for a urea hydrolysis apparatus according to claim 1, 2, 3, or 4, wherein the urea water supply line is shut off to stop the supply of urea water, and the heated air supply is performed. Only heated air is supplied into the reactor through the line and gas is passed to the hydrolysis catalyst layer. By-products fixed to the hydrolysis catalyst are thermally decomposed by the heated air to regenerate the catalyst, and the generated ammonia is supplied to the furnace. A catalyst regeneration method for a urea hydrolyzing apparatus, wherein the catalyst is blown into a flue for denitration reaction.   6. The urea hydrolysis apparatus according to claim 5, wherein heated air is passed through the hydrolysis catalyst layer so that the surface temperature of the hydrolysis catalyst layer is 250 ° C. to 450 ° C. during catalyst regeneration. Catalyst regeneration method.   When ammonia generated during catalyst regeneration is less than the required amount for denitration reaction, element water is guided to the furnace or flue through the urea water bypass line, and urea is discharged from the second urea water spray nozzle in parallel with the ammonia spray nozzle. 6. The catalyst regeneration method for a urea hydrolysis apparatus according to claim 5, wherein water is sprayed into the furnace or flue to compensate for the amount of ammonia required for the denitration reaction.   8. The catalyst regeneration method for a urea hydrolysis apparatus according to claim 7, wherein the branched urea water is sprayed to the ammonia gas diffusion portion from the ammonia spray nozzle by the second urea water spray nozzle.   Detects one or more of surface temperature of hydrolysis catalyst layer, temperature difference between reactor inlet temperature and outlet temperature, pressure difference between reactor inlet and outlet, and carbon dioxide concentration in gas flowing through ammonia supply line Or, based on the detection result or the measurement result, measure either or both of the air volume of the blower connected to the upstream end of the heated air supply line and the output of the heated air heater installed in the heated air supply line 9. The method for regenerating a catalyst of a urea hydrolysis apparatus according to claim 5, wherein the catalyst is regenerated.

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