JP2011207672A - Ammonia recovery apparatus and recovery method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ammonia recovery apparatus and recovery method which can inexpensively recover ammonia discharged as a mixed gas, so that impurity-free ammonia can be recovered and reused.SOLUTION: The ammonia recovery apparatus 100 for separating and recovering ammonia from a mixed gas includes: a condenser 120 which cools the mixed gas consisting of ammonia and a gas having a lower liquefaction temperature than ammonia discharged from a high temperature and high pressure mixed gas source 110 to an intermediate temperature between the temperature of the mixed gas source and the external temperature to thereby condense ammonia; a back pressure valve V6 which is disposed at the outside of the condenser 120 and applies to the condenser a pressure necessary to condense ammonia determined according to the cooling temperature by the condenser; and storage parts 133, 134 for storing condensed ammonia.

Description

  The present invention relates to an ammonia recovery apparatus and an ammonia recovery method for separating and recovering ammonia from a mixed gas.

  Conventionally, there are known methods for recovering ammonia by cooling it to a liquefaction temperature (−77.7 ° C.) at atmospheric pressure, and methods for recovering by increasing the liquefaction temperature by increasing the pressure of ammonia gas using a compressor. (See, for example, Patent Document 1).

  The ammonia gas recovery device described in Patent Document 1 dissolves ammonia gas in the derived exhaust gas in water, distills the ammonia water in which ammonia is dissolved to separate water and ammonia gas, and separates the ammonia. The gas is liquefied to recover ammonia gas. In the dissolution process, the dissolution step is repeated to increase the ammonia concentration, the ammonia water having a predetermined concentration is stored in the ammonia water tank, the ammonia gas is dehumidified, and then the ammonia gas is pressured at 0.4 MPa, 4 ° C. (277 K) in the refrigerator unit. ) Liquefied by cooling to the extent.

  As an apparatus for removing ammonia gas, an apparatus that adsorbs ammonia to an adsorbent is known (see, for example, Patent Document 2). In the ammonia recovery apparatus described in Patent Document 2, a multi-tube adsorber is filled with an ammonia adsorbent, and the ammonia-containing gas is ventilated while cooling the adsorbent. After the ammonia is adsorbed and collected in this manner, the ammonia is desorbed and recovered under reduced pressure while the multi-tube adsorber is heated with a heat medium.

  On the other hand, research has also been conducted on reactions using liquid ammonia (see, for example, Patent Document 3). In the method for producing a metal amide compound described in Patent Document 3, a metal amide compound is obtained by reacting a metal hydride containing an alkali metal or alkaline earth metal hydride with liquid ammonia.

JP 2008-7378 A JP 2000-317246 A JP 2006-8440 A

  An apparatus for adsorbing ammonia on an adsorbent as described in Patent Document 2 is known, but such a technique is for removing a small amount of ammonia by adsorption, and a large amount of ammonia is used as a solvent. It is not applicable when ammonia is to be recovered and reused.

  On the other hand, Patent Document 3 describes a reaction using a large amount of ammonia as a solvent, but does not disclose specific means for recovering ammonia. In such a case, when attempting to cool the gas in the reaction vessel, it is considered that a normal liquefaction method as described in Patent Document 1 is adopted, and a lot of cooling ripening and electric power are required. In addition, ammonia discharged from the pressure vessel is often at a high temperature, and if it contains a gas at a high temperature other than ammonia, it must be cooled and pressurized together with a gas other than ammonia. It requires a lot of cooling heat and electric power and is inefficient. For example, in order to liquefy ammonia from a high-temperature mixed gas at atmospheric pressure, the ammonia must be cooled to a low temperature of about −77.7 ° C. as shown by the vapor pressure curve of ammonia, which reduces the cost of the equipment. Does not fit. On the other hand, ammonia can be liquefied by compressing it using a compressor, but this method also costs equipment.

  The present invention has been made in view of such circumstances, and provides an ammonia recovery apparatus and an ammonia recovery method that can recover ammonia released as a mixed gas at low cost and recover and reuse ammonia free of impurities. For the purpose.

  (1) In order to achieve the above object, an ammonia recovery device of the present invention is an ammonia recovery device that separates and recovers ammonia from a mixed gas, and is liquefied from ammonia and ammonia released from a high-temperature and high-pressure mixed gas source. A condenser that cools a mixed gas composed of a low gas and condenses ammonia, and a pressure that is provided on the outside of the condenser and that is required to condense the ammonia determined according to the cooling temperature of the condenser And a storage section for storing the condensed ammonia.

  As described above, the ammonia recovery apparatus of the present invention takes out and stores ammonia gas from the mixed gas by applying to the capacitor a pressure required to liquefy ammonia determined by the back pressure valve according to the cooling temperature of the capacitor. . Thereby, ammonia released as a mixed gas can be recovered at low cost, and ammonia free of impurities can be recovered and reused.

  In addition, ammonia can be liquefied without a compressor, and the cost for installing and operating the compressor can be reduced. In order to sufficiently recover ammonia, the scale of the apparatus can be reduced even if it is not necessary to provide a detoxifying device for ammonia discharged together with other gases to the outside.

  (2) Further, in the ammonia recovery apparatus of the present invention, the condenser cools the mixed gas by air cooling or water cooling. Thereby, ammonia can be liquefied by air cooling or water cooling without preparing an expensive facility for cooling.

  (3) Further, in the ammonia recovery device of the present invention, the condenser has a cooling unit that cools the mixed gas and a condensation tank that condenses and temporarily stores the ammonia, and the condensation tank is at the bottom, It has the flow path of ammonia which goes to the storage part. As a result, ammonia is liquefied and stored, and other gases that are not liquefied at that temperature are released through liquid ammonia, and ammonia can be easily separated and extracted.

  (4) Further, in the ammonia recovery device of the present invention, the condenser cools the mixed gas to less than 56 ° C. Thereby, ammonia can be liquefied at the temperature which does not melt the soluble valve which is easy to be used for the cylinder which stores ammonia.

  (5) Further, the ammonia recovery method of the present invention is an ammonia recovery method for separating and recovering ammonia from a mixed gas, and is composed of ammonia released from a high-temperature and high-pressure mixed gas source and a gas having a lower liquefaction temperature than ammonia. Cooling the mixed gas, applying a pressure necessary for liquefying ammonia according to the cooling temperature of the condenser, condensing the ammonia, and storing the condensed ammonia. It is a feature.

  Thereby, ammonia released as a mixed gas can be recovered at low cost, and ammonia free of impurities can be recovered and reused. In addition, ammonia can be liquefied without a compressor, and the cost for installing and operating the compressor can be reduced. In order to sufficiently recover ammonia, it is possible to reduce the scale of the apparatus even if it is not necessary to provide a detoxifying device for ammonia discharged together with other gases.

  According to the present invention, ammonia released as a mixed gas can be recovered at low cost, and ammonia free of impurities can be recovered and reused.

It is a mimetic diagram showing the composition of the ammonia recovery device concerning the present invention. It is a schematic diagram which shows the structure of the capacitor | condenser which concerns on 1st Embodiment. It is a schematic diagram which shows the structure of the capacitor | condenser which concerns on 2nd Embodiment. It is a schematic diagram which shows the structure of the capacitor | condenser which concerns on 3rd Embodiment.

  Next, embodiments of the present invention will be described with reference to the drawings. In order to facilitate understanding of the description, the same reference numerals are given to the same components in the respective drawings, and duplicate descriptions are omitted.

[First Embodiment]
(Configuration of ammonia recovery device)
FIG. 1 is a schematic diagram showing the configuration of the ammonia recovery apparatus 100. The ammonia recovery device 100 separates and recovers ammonia from the mixed gas. As shown in FIG. 1, the ammonia recovery apparatus 100 includes a pressure vessel 110, an introduction valve V1, a flow passage 111, a first back pressure valve V2, a bypass 112, a bypass valve V3, a capacitor 120, a storage path 125, and storage valves V4 and V5. , Reservoirs 131 and 132, weighing scales 133 and 134, a discharge passage 145, and a second back pressure valve V6.

  The pressure vessel 110 is used as a reaction vessel, and controls the internal temperature and pressure to advance the reaction using ammonia. In such a case, the pressure vessel 110 serves as a mixed gas source that discharges a mixed gas composed of ammonia and a gas having a lower liquefaction temperature than ammonia. Ammonia can be introduced into the pressure vessel 110 by opening and closing the introduction valve V1. For example, the thing of a capacity | capacitance of about 10 liters is used, ammonia is used as a solvent inside, and it is made to react with metallic calcium. As a result of such a reaction, a mixed gas of hydrogen and ammonia is generated.

  As described above, the ammonia recovery apparatus 100 is particularly effective when a high pressure of 8 MPa or more is required for the reaction and gas is generated as a secondary. There is no need to increase the pressure again with the compressor, and no power source is required.

  The first back pressure valve V2 is provided between the pressure vessel 110 and the capacitor 120, and maintains the pressure on the pressure vessel 110 side at a predetermined value such as 8 MPa. In that case, the exhaust gas exceeding 8 MPa by the reaction gas flows into the capacitor 120 through the flow passage 111 and the first back pressure valve V2. The bypass 112 is not used while the bypass valve V3 is closed while the first back pressure valve V2 is functioning, and is used when the gas remaining in the pressure vessel 110 is discharged.

  The condenser 120 cools the mixed gas released from the mixed gas source in a high temperature and high pressure state, and condenses the ammonia. The cooling temperature is preferably an intermediate temperature between the temperature of the pressure vessel 110 and the external temperature. By cooling the mixed gas by air cooling with air at room temperature or water cooling with cooling water at room temperature, it can be cooled to a temperature at which ammonia liquefies. In this way, the cooling mechanism can be configured simply and inexpensively. Details of the configuration of the capacitor 120 will be described later.

  The storage path 125 distributes the condensed ammonia from the condenser 120 to the storage units 131 and 132. The reservoir 125 and the reservoirs 131 and 132 are opened and closed by the reservoir valves V4 and V5. The reservoirs 131 and 132 are containers such as cylinders or tanks, respectively, and store condensed ammonia.

  When a cylinder is used, a fusible valve that melts at a predetermined temperature is usually used as the safety valve. This predetermined temperature is determined to be 56 ° C. by the JIS standard, and the mixed gas is cooled at a temperature lower than 56 ° C. by the capacitor 120, and the pressure maintained by the second back pressure valve V6 is set to 3 MPa accordingly. Is preferred.

  Thereby, ammonia can be liquefied at the temperature which does not melt the soluble valve. Since the fusible valve is used in a general-purpose cylinder, the above condition setting is effective for reducing the cost. However, it is possible to use a dedicated storage tank and collect it using an appropriate safety valve.

  The weigh scales 133 and 134 measure the weights of the storage units 131 and 132, respectively. Then, when the weighing unit 133 detects that a predetermined amount or more of the storage unit 131 has been stored, the storage valve V4 is closed and the device is controlled to open the storage valve V5, so that another liquid ammonia is stored. It can flow into the part 132. The discharge path 145 discharges the gas other than ammonia that has not been liquefied through the second back pressure valve V6 when the pressure exceeds 2 MPa. The discharged gas is discharged from the discharge path 145 to the outside, and is sent to, for example, a device for removing the discharged gas. This is effective for separating ammonia from the high-pressure mixed gas discharged from the pressure vessel 110 that performs a reaction process of 2 MPa or more.

  The second back pressure valve V <b> 6 is provided on the outer side of the capacitor 120, and gives the capacitor 120 a pressure necessary to condense ammonia determined according to the cooling temperature of the capacitor 120. Thereby, ammonia released as a mixed gas can be recovered at low cost, and ammonia free of impurities can be recovered and reused. In addition, ammonia can be liquefied without a compressor, and the cost for installing and operating the compressor can be reduced. Further, in order to sufficiently recover ammonia, it is not necessary to provide a detoxifying device for ammonia discharged together with other gases to the outside, and even if it is provided, the device scale can be reduced.

  Therefore, the second back pressure valve V6 cools, liquefies and recovers the gas discharged from the pressure vessel 110 to the normal temperature while maintaining the pressure (25.7 ° C., 1.01 MPa) or higher at the normal temperature. For example, it is possible to control the pressure to liquefy at the temperature of the day. Thereby, the recovery rate can be increased at low cost.

  As described above, the ammonia recovery apparatus 100 can recover the ammonia released to the outside of the pressure vessel at a low cost when a gas containing ammonia is generated in the pressure vessel 110 or when the reaction using ammonia as a solvent is performed.

(Capacitor configuration)
Next, details of the configuration of the capacitor 120 will be described. FIG. 2 is a schematic diagram illustrating the configuration of the capacitor 120. As shown in FIG. 2, the capacitor 120 includes a cooling unit 121 and a condensation tank 123. The cooling unit 121 cools the mixed gas flowing through the flow passage 111 and condenses ammonia. Cooling is preferably performed by air cooling or water cooling. Thereby, ammonia can be liquefied by air cooling or water cooling without preparing an expensive facility for cooling.

  The condensation tank 123 condenses and temporarily stores the cooling unit that cools the mixed gas and ammonia. It is preferable to measure and control the liquid level position. When the liquid level in the condenser 120 rises, liquid ammonia is transferred to the condensation tank 123. The condensed ammonia is introduced into the tank vertically below from the inlet 122 at the bottom of the condensation tank 123.

  The introduced liquid ammonia A is stored in the condensation tank 123. The condensing tank 123 is connected to an ammonia storage path 125 toward the storage units 131 and 133, and the stored ammonia A is transferred from the storage port 124 at the bottom of the vertically lower side to the storage units 131 and 132 via the storage path 125. Inflow. As a result, the ammonia is liquefied and stored, and other gases that are not liquefied unless the temperature is lower than the temperature of the condensing tank 123 are released through the liquid ammonia, and the ammonia can be easily separated and taken out.

  In addition, without providing the cooling unit 121, the condensation tank 123 may be maintained at a low temperature, and the mixed gas may be introduced from vertically below. By introducing from below vertically, ammonia gas is prevented from being discharged as it is without being cooled. On the other hand, the condensing tank 123 has a discharge port 143 connected to the discharge path 145. The discharge port 143 is preferably provided on the vertically upper side of the condensing tank 123. Thereby, a gas having a liquefaction temperature lower than that of ammonia such as hydrogen is discharged from the discharge port 143. By adjusting the liquid level of the condensing tank 123 through the discharge port 143 and leaving the gas in the supernatant, other gas contained in the mixed gas can be released. Since gases other than ammonia are also introduced into the condensing tank 123, the condensing tank 123 has a structure for extracting gas.

(Operation of ammonia recovery device)
Next, an example of the operation of the ammonia recovery apparatus 100 will be described. First, ammonia is introduced into the pressure vessel 110 by opening the introduction valve V1. Then, in the pressure vessel 110, ammonia is used as a solvent and reacted with metallic calcium. As a result, a mixed gas of hydrogen and ammonia is generated. At this time, the first back pressure valve V2 and the bypass valve V3 are closed.

  After completion of the reaction, the pressure vessel 110 is maintained at 50 ° C. In general, since the heat capacity of the pressure vessel 110 is large, control for heat insulation is not necessary. The first back pressure valve V2 sets the pressure on the capacitor side to 2 MPa, and supplies the mixed gas to the capacitor 120 while gradually decreasing the pressure on the pressure vessel 110 side from 8 MPa to 2 MPa.

  The cooling unit 121 of the condenser 120 cools ammonia to about 50 ° C. by air cooling, for example, and condenses it. Then, the storage valves V4 and V5 are opened, and ammonia is recovered as liquid in the storage units 131 and 132. Other gases having a liquefaction temperature lower than that of ammonia, such as hydrogen gas, are not liquefied. Therefore, hydrogen is not mixed with the condensed liquid ammonia. It can also be said that vapor pressure is higher than ammonia instead of liquefaction temperature lower than ammonia.

  Note that the pressure vessel 110 can be efficiently cooled by vaporizing ammonia in the pressure vessel 110. Ammonia is a substance that has the second largest latent heat of evaporation after water and has a high cooling effect. The remaining residual gas is sent to the abatement device.

(Example)
An experiment was conducted using the ammonia recovery apparatus 100 as described above. First, metallic calcium was installed inside the pressure vessel 110, ammonia was introduced, and the system was operated at 100 ° C. and 8 MPa for 2 hours. After the ammonia and metallic calcium are reacted in the pressure vessel 110 in this way, a mixed gas of hydrogen and ammonia is introduced into the capacitor 120, the temperature of the mixed gas is cooled to 56 ° C., and the pressure is changed to the first pressure. The back pressure valve V6 was controlled to 3 MPa. As a result, 71% of the used amount of liquid ammonia could be recovered.

[Second Embodiment]
In the above-described embodiment, the condensed ammonia is introduced into the tank vertically below from the inlet 122 that extends in the vertical direction at the bottom. However, if there is an inlet at the bottom, the ammonia flows vertically upward like a siphon tube. An entrance may be provided. FIG. 3 is a schematic diagram showing a configuration of a capacitor 220 having a siphon tube.

  As shown in FIG. 3, in the capacitor 220, a siphon tube 224 is provided in the condensing tank 123 and is connected to the storage path 125. The inlet of the siphon tube 224 is disposed near the bottom. Thus, if there is an inflow port at the bottom of the condensation tank 123, the form of the inflow port to the storage path 125 is not limited.

[Third Embodiment]
In the above embodiment, the condensing tank 123 is provided separately from the piping of the cooling unit 121, but a configuration in which a part of the piping functions as a condensing tank may be used. FIG. 4 is a schematic diagram showing the configuration of the capacitor 320. As shown in FIG. 4, the condenser 320 has a condensing tank 323 formed in a part of the piping constituting the cooling unit 321. In this way, the piping part that is located at the lowest vertical position of the cooling part 321 is formed thick, and there may be a structure in which ammonia can be condensed and temporarily stored.

100 Ammonia recovery device 110 Pressure vessel (mixed gas source)
111 Flow path 112 Bypass 120 Condenser 121 Cooling part 122 Inlet 123 Condensing tank 124 Reservoir 125 Reservoir 131, 132 Reserving part 133, 134 Weigh scale 145 Discharge path 220 Condenser 224 Siphon tube 320 Condenser 323 Condensing tank A Ammonia V1 Introducing valve V2 Back pressure valve V3 Bypass valve V4, V5 Storage valve V6 Back pressure valve

Claims (5)

An ammonia recovery device for separating and recovering ammonia from a mixed gas,
A condenser for condensing ammonia by cooling a mixed gas composed of ammonia released from a high-temperature and high-pressure mixed gas source and a gas having a lower liquefaction temperature than ammonia;
A back pressure valve that is provided on the outside of the condenser and that provides the condenser with a pressure required to condense ammonia determined according to the cooling temperature of the condenser;
And an accumulator for storing the condensed ammonia.   2. The ammonia recovery apparatus according to claim 1, wherein the condenser cools the mixed gas by air cooling or water cooling. The condenser has a cooling unit that cools the mixed gas and a condensation tank that condenses and temporarily stores ammonia.
3. The ammonia recovery apparatus according to claim 2, wherein the condensation tank has an ammonia flow passage toward the storage section at the bottom.   The ammonia recovery device according to any one of claims 1 to 3, wherein the condenser cools the mixed gas to less than 56 ° C. An ammonia recovery method for separating and recovering ammonia from a mixed gas,
While cooling a mixed gas composed of ammonia released from a high-temperature and high-pressure mixed gas source and a gas having a lower liquefaction temperature than ammonia, a pressure necessary for liquefying ammonia is applied according to the cooling temperature of the condenser, Condensing the ammonia;
Storing the condensed ammonia. A method for recovering ammonia.

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