JP2634015B2 - Pressure swing separator for ammonia separation and ammonia separation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for separating ammonia by a pressure swing adsorption method (hereinafter referred to as PSA method).

[0002]

BACKGROUND OF THE INVENTION Ammonia is a very important industrial intermediate material, is produced on a large scale, is used in many chemical industries, and there are facilities for separating and concentrating ammonia in various places.

[0003] In recent years, not only as an industrial intermediate material, but also as a reducing agent for flue gas denitration from the viewpoint of environmental protection measures, the demand has been increasing. In this case, unlike ammonia as an industrial intermediate material, high-purity ammonia is not always necessary. However, high-purity ammonia produced as the above-mentioned industrial intermediate material is also used as the ammonia for flue gas denitration as a raw material.

Conventionally, as a method for separating ammonia from a gas containing ammonia, as described below, a cooling separation method or a membrane separation method in which a gas is pressurized and cooled and separated from the gas as liquid ammonia, and a method using water After the ammonia adsorption, there is a water adsorption + distillation method for separating water and ammonia by distillation.

[0005] 1. The cooling separation method is a method for separating ammonia which is usually used in an ammonia synthesis loop of a current ammonia synthesis plant. In the case of an iron catalyst, the composition of the gas supplied to the ammonia synthesis reactor is optimal in terms of the reaction rate when the H ₂ / N ₂ ratio is around the reaction stoichiometric ratio of 3. On the other hand, in the case of a ruthenium catalyst which has recently been developed as a low-pressure high-activity catalyst, it is optimal that the H ₂ / N ₂ ratio deviates from the stoichiometric ratio around 1 due to strong adsorption of hydrogen. Regardless of which catalyst is used, 100% of the raw material nitrogen and hydrogen do not react even when they pass through the ammonia synthesis catalyst reactor, so that the reactor outlet gas contains product ammonia and unreacted gas (nitrogen and nitrogen). After separation into hydrogen, it is necessary to supply the unreacted gas to the ammonia reactor again. The ammonia synthesis reaction is a reversible reaction, and the presence of a chemical equilibrium does not produce ammonia at a certain concentration or higher depending on the reaction conditions. Therefore,
In the synthesis loop, the produced ammonia is separated and removed from the reactor outlet fluid, and the unreacted raw material containing low-concentration ammonia is recycled to the reactor. The gas to be recycled at this time must maintain an optimum gas composition for each catalyst at the reactor inlet. For this purpose, H ₂ before and after separation of ammonia
It is necessary that the / N ₂ ratio be approximately the same. The cooling separation method is an ammonia separation method in which the H ₂ / N ₂ ratio before and after separation is kept almost the same. Ammonia synthesis at 150 bar, 644
When carried out using a conventional iron catalyst at ゜ K (371 ° C.), the ammonia concentration in the reactor outlet gas is usually 13 vol.
% To 18 vol%, and when the cooling separation is performed at, for example, 236 ° K (-37 ° C.), the saturated vapor pressure of ammonia is about 0.8 bar.
Ammonia corresponding to 7 bar to 26.2 bar, ie 96% to 97% of the ammonia in the gas, is liquefied and separated.

[0006] 2. The membrane separation method is disclosed in U.S. Pat.
No. 535 discloses a technique for separating ammonia from nitrogen, hydrogen and hydrogen using a polyvinylammonium thiocyanate film membrane supported on a porous organic polymer. A similar separation method using a perfluorosulfonic membrane supported on Nafion (trade name, DuPont) is described in J. Membrane Science, 68 p43-52 (199).
It is reported in 2).

[0007] 3. The water adsorption + distillation method is a method commonly used for recovering ammonia from ammonia purge gas in an ammonia synthesis loop of a current ammonia synthesis plant.

[0008] 4. Other Ammonia Separation Methods (1) In addition, ammonia recovery from humid air containing ammonia by a temperature swing adsorption method (hereinafter referred to as TSA method) was reported by XC Lu et al.
IChE Annual meeting (November 2
6th, in Miami Beach, Florida). This method is a technique in which a gas to be treated is adsorbed to an adsorbent such as zeolite at normal temperature, and ammonia is desorbed by raising the temperature to 383 ° K (110 ° C). (2) On the other hand, for the separation of ammonia, nitrogen and hydrogen from an ammonia purge gas, a separation method using pressure swing separation and a membrane is proposed in US Pat. No. 4,645,516. In this method, when argon and methane, which are inert substances for ammonia synthesis, are separated from ammonia purge gas, ammonia shortens the life of the membrane.
It is a patent for a system (combination) that separates ammonia by the PSA method upstream of the membrane. However, in this patent, there is no description of an example of ammonia separation by the pressure swing separation method, and no specific technology is disclosed.

[0009]

The above prior arts include:
It has the following problems to be improved.

(1) The cooling separation method is a method in which gaseous ammonia is separated by cooling and liquefying it. At the time of cooling, noncondensable gas which does not need to be cooled must also be cooled. When an iron catalyst is used for the above-mentioned ammonia synthesis, the gas composition at the outlet of the ammonia synthesis catalyst reactor is usually 20% to 2% nitrogen.
5%, hydrogen 60% to 68%, ammonia 13% to 1
8%. Nitrogen 80% or more in the gas phase by cooling, but hydrogen is also cooled, these nitrogen, hydrogen is supplied again to the circulation synthesis reactor. At this time, a temperature suitable for the ammonia synthesis reaction again, for example, at least 423 ° K
(150 ° C.) or higher. Cold separation is such a significant energy consuming process.

(2) When the membrane separation method is applied to the separation of ammonia from off-gas of an ammonia synthesis plant, nitrogen and hydrogen to be circulated are on the passing side, so that a large pressure drop occurring at the time of membrane permeation is compensated, and nitrogen and hydrogen are removed. In order to supply the compound again to the synthesis system, re-pressurization by a compressor is necessary, which is also a remarkable energy-consuming process.

(3) In the water absorption method and the distillation method, if attention is paid to ammonia and water as a solvent, since it is dissolved (bonded) once and heated again to be distilled (separated), considerable energy is required during distillation. Consumed. In addition, nitrogen and hydrogen gas from the water absorption tower contain water vapor, which becomes a poison for the ammonia synthesis catalyst, so these gases need to be dehumidified again by the pressure swing separation method or the cooling separation method. Becomes

(4) The above report on the TSA method does not include hydrogen. Further, the TSA method is an energy-intensive process because the desorption of the adsorbed substance is performed by increasing the temperature.

In addition, a technique for recovering only hydrogen from a mixed gas containing ammonia, nitrogen and hydrogen by a pressure swing separation method (hydrogen recovery PSA method) is known. Since this hydrogen recovery PSA method recovers valuable hydrogen from the ammonia purge gas originally exhausted, only the purity of the recovered hydrogen is a problem, and the hydrogen recovery rate is considered to be a secondary problem and is low. That is, it has been considered that if the purity of the recovered hydrogen is high, it is useful even if the hydrogen concentration in the other waste gas discharged from the hydrogen recovery PSA device is high. However, such techniques were not amenable to ammonia purge gas and could not be applied, for example, to ammonia separation in an ammonia synthesis process.

The present invention divides a gas containing ammonia into ammonia and a gas other than ammonia (nitrogen + hydrogen + other gases). To provide high-purity, high-yield separation of synthetic ammonia into unreacted nitrogen, hydrogen, and other gases with low energy consumption. It is another object of the present invention to provide a technique in which the separated unreacted nitrogen / hydrogen is separated so as to maintain the same ratio as before the separation, and can be directly supplied to an ammonia synthesis reactor. At the same time there is provided a technique for recovering ammonia which can be used for Gasuyo Ri denitrification containing small amounts of ammonia such as ammonia purge gas.

[0016]

SUMMARY OF THE INVENTION The object of the present invention is to provide an apparatus of the present invention, that is, two zeolite or activated carbon particles having a pore size of less than 5 angstroms and having different adsorption characteristics.
Recycle gas separated from each device between adsorption devices
This can be solved by using a pressure swing separator configured as described above , and highly efficient separation of a mixed gas containing ammonia into ammonia and other gases can be performed with low energy consumption.

That is, the present invention provides a mixed gas containing ammonia.
Pressure swing separator for ammonia separation from wastewater
And components (non-adsorbate) other than ammonia (adsorbate component)
Component) Operate to minimize ammonia concentration in gas
Zeolite with pore size less than 5 Å
Or at least one adsorption device filled with activated carbon,
Minimize non-adsorbate component gas concentration in adsorbate component gas
Operated less than 5 angstroms
At least one filled with zeolite or activated carbon
Recycle gas separated from each device with the adsorption device
The separation device is configured to be separated. Also book
The invention is based on a pressure swing from a mixed gas containing ammonia.
In the method of separating ammonia using a separation device,
Components (non-adsorbate components) other than ammonia (adsorbate components)
Is operated to minimize the ammonia concentration in the gas
Zeolite or active material having a pore size of less than 5 Å
At least one adsorption device filled with carbonaceous
Operation to minimize the nonadsorbate component gas concentration in the
Zeola with inverted pore size less than 5 Å
At least one adsorption device filled with site or activated carbon
Recycle gas separated from each device between
The above method is characterized by the following.

The gas containing ammonia to which the method of the present invention is applied includes, in addition to ammonia, nitrogen and hydrogen, methane, argon, nitric oxide, nitrogen dioxide, oxygen dinitride, tetraoxygen dinitride, oxygen, carbon dioxide and the like. However, it is necessary to select an adsorbent whose adsorption power and diffusion rate between these gases and the adsorbent are sufficiently different from those for ammonia. The adsorbent that can be used in the present invention is a molecular size of ammonia (hereinafter, “molecular size” refers to Kinetic D of Lennard-Jones).
iameter; Breck, DW "Zeolite Molecular Sie
ves "P.636 Krieger Publishing (1984)) and the difference in molecular size of the residual gas, an adsorbent satisfying the following relationship between the pore diameter and the adsorbing power is selected.

(1) When the molecular size of all residual gases other than ammonia is larger than the molecular size of ammonia (2.6 angstroms), the pore size of the adsorbent is the same as or larger than the molecular size of ammonia. An adsorbent having an adsorption power for

[0020] (2) Ba含residual gases other than ammonia containing small gas or large gas Ri by molecular size of ammonia, pore size of the adsorbent is smaller than the larger molecular size Ri by ammonia, or equal to the molecular size of ammonia An adsorbent that is large and has an adsorption power for ammonia that is sufficiently larger than the adsorption power for molecules smaller than ammonia. An adsorbent having a sufficiently large adsorption force means that the amount of adsorption of ammonia and a gas other than ammonia to the adsorbent at the pressure to be operated is measured by a normal method for obtaining an adsorption isotherm, and the difference between the adsorption amounts is sufficiently large. Adsorbent.

As described above, the adsorbent has a difference in molecular size between ammonia and residual gas other than ammonia, and has no diffusion resistance (when the pore diameter is sufficiently larger than all the gases to be treated including ammonia). The pore diameter is determined by the difference in the adsorbing power of each adsorbent to each gas.

The present invention can be effectively applied particularly to the separation of the ammonia mixed gas from the ammonia synthesis loop into ammonia and unreacted nitrogen and hydrogen, or the separation of ammonia from the ammonia synthesis plant off-gas. If a natural or synthetic zeolite or activated carbon with a pore size of less than 5 angstroms is used as the adsorbent with selectivity for ammonia, the ammonia will be adsorbed by the adsorbent and the remaining gas will not be adsorbed, or The gas can be separated from each other by utilizing the sufficiently high diffusion rate. Ammonia adsorbed on zeolite or activated carbon can be recovered by desorption by reducing pressure or heating.

Although various zeolites can be used in the present invention, A-type zeolites and pentazyl silicalites are preferred. Furthermore, the KA type zeolite has a particularly high selectivity for ammonia, and is most suitable for the purpose of the present invention. These adsorbents may be used alone or in combination. The optimum one and the optimum amount are selected according to the composition of the gas to be treated.

Further, the pressure swing separators of the present invention can be combined in a plurality of stages, and the gas separated by each pressure swing separator can be recycled to improve the ammonia separation efficiency. The pressure swing separator of the present invention may be combined in plural stages in parallel or in series to continuously separate ammonia and gases other than ammonia.

The present invention, besides applying the above-mentioned ammonia to the separation of ammonia and unreacted nitrogen / hydrogen from the ammonia synthesis loop, can also produce ammonia from a mixture of ammonia and an aliphatic amine or a mixture of ammonia and an aromatic amine. It is also applicable to the separation technique. In this case, the mixed gas is separated into ammonia and amine by using faujasite-based zeolite. In this case, applicable aliphatic and aromatic amines are trimethylamine, triethylamine, tributylamine,
Examples thereof include ethanolamine, diethanolamine, triethanolamine, pyrimidine, morpholine, aniline, and toluidine.

Hereinafter, the present invention will be described in more detail based on one embodiment.

FIG. 1 shows a mixed gas NH ₃ , H ₂ ,
FIG. 1 is a flow chart of a pressure swing separation apparatus (hereinafter, referred to as PSA apparatus) of the present invention for selectively adsorbing NH ₃ from N ₂ , Ar, CH ₄ .

There are four adsorption towers A, B, C, D connected in parallel flow between a manifold 10 for supplying the mixed gas and a manifold 11 for the non-adsorbed product effluent gas. Each adsorption tower is filled with an adsorbent selected from synthetic and natural zeolites having a pore diameter of less than 5 angstroms, activated carbon and the like, alone or in combination. A flow control valve 7 is provided between the adsorbed product outflow manifold 25 and the adsorbed product tank E, and a flow control valve 8 is provided between the non-adsorbed product outflow manifold 26 and the non-adsorbed product tank F. The automatic valves 1A, 1B, 1C, and 1D are valves for supplying a supply gas flow to the adsorption towers A, B, C, and D, respectively. The automatic valves 2A, 2B, 2C, 2D are valves for supplying the non-adsorbed product gas to the manifold 11 from the above-mentioned towers.

The components adsorbed in the adsorption tower are exhaust pump P
It is introduced into the adsorption product tank E by Ri through an exhaust manifold 12 provided at the inlet end of the vacuum in to tower. The adsorption towers A and B are connected at their inlet ends to the exhaust manifold 12 via automatic valves 3A and 3B. Similarly, the adsorption towers C and D have their inlet ends connected to the exhaust manifold 12 via automatic valves 3C and 3D. Adsorption product tank E
Is connected to the inlet ends of the adsorption towers A and B by a conduit 15 having automatic valves 4A and 4B, and the adsorption product gas is returned to the adsorption tower. Similarly, the adsorption towers C and D also have automatic valves 4C and 4
Via D, their inlet ends are connected by a conduit 15 to an adsorbent product tank E so that the adsorbed product gas is recirculated. The non-adsorbed product tank F is connected to the inlet ends of the adsorption towers A and B by a conduit 27 having automatic valves 5A and 5B, and the non-adsorbed product gas is returned to the adsorption tower. Similarly, the inlet ends of the adsorption towers C and D are connected to the non-adsorbed product tank F by the conduit 27 via the automatic valves 5C and 5D, and the non-adsorbed product gas is refluxed.

The automatic valves 6A is is provided with a conduit connecting the gas supply conduit to the adsorption tower B and between the adsorption tower A outlet and the own valve train 2A provided in the adsorption tower A outlet, the adsorption tower A after adsorption operation The gas in the void is returned to the adsorption tower B after the regeneration, and the pressure between the adsorption tower A and the adsorption tower B can be equalized. For the same purpose, automatic valves 6B, 6C and 6D are provided in the conduits connecting the corresponding adsorption towers.

The operation steps for the purpose of increasing the purity and yield of the non -adsorbate PSA non-adsorbed product (hereinafter referred to as non-adsorbate PSA) will be described with reference to Table 1.

Table 1 shows that one cycle from the adsorption step to the return to the adsorption step through the regeneration step from the adsorption step is defined as one cycle, and that one cycle is divided into 12 steps to operate each adsorption tower corresponding to each step. It shows the state. Time required indicated in each step is an illustration of the example. The adsorption towers A, B, C, and D repeat the above cycle at the same period with a predetermined time difference. That is, for example, the adsorption step time in the adsorption tower C, the pressure equalization step time in the tower, the pressure equalization step between the columns, the regeneration step time, and the non-adsorbed product gas reflux step are respectively the adsorption step time (θ21) in the adsorption tower A, the tower Internal pressure equalization process time (θ2
2), equalizing the column pressure equalization step time (θ13, θ23), the regeneration step time (θ11), and the non-adsorbed product gas reflux step (θ12). In step 12 before step 1, the adsorption tower A is in the adsorption step (opening the automatic valves 1A and 2A to flow the mixed gas from the supply gas manifold to adsorb NH ₃ in the mixed gas), The adsorption tower B is in a regeneration step (opening the automatic valve 3B and discharging the adsorbed NH ₃ under reduced pressure by the exhaust pump P). After completing these steps, the process proceeds to step 1 where the adsorption tower A is operated by the automatic valve 1
A, 2A, 3A, 4A, 5A, 6A, and 6B are closed and the pressure equalization step in the column is performed (in order to sufficiently perform the adsorption because the adsorption speed of the adsorbate NH ₃ in the column is not sufficiently high), B
Closes the automatic valve 2B and opens 5B to recirculate the non-adsorbed product gas from the non-adsorbed product tank through the conduit 27 (a small amount of NH ₃ remaining in the non-adsorbed product gas is further adsorbed by the regenerated adsorption tower). It is in.

In step 2, the automatic valve 6A between the adsorption tower A and the adsorption tower B is opened, and the adsorption tower A and the adsorption tower B enter a step of equalizing the pressure between the two adsorption towers. . In this inter-column equalizing step, the adsorption tower B has undergone a (reduced pressure) regeneration (step 9 to step 12) and a reflux step (step 1).
Column, among others pressure equalization step adsorption column A by Ri pressure via (Step 1) is low. Therefore, the gas flows from the adsorption tower A to the adsorption tower B.
The adsorption tower C is in the regeneration step from step 12, and this state is continued until step 3, and the adsorption tower D is in the adsorption step from step 12 to step 3.

[0034]

[Table 1]

Adsorbate PSA On the other hand, the operation steps for the purpose of increasing the purity and yield of the adsorbed product (hereinafter referred to as adsorbate PSA) will be described with reference to Table 2. As in Table 1, one cycle of returning from the adsorption step to the adsorption step through the regeneration step is divided into 12 steps, and shows the operation state of each adsorption tower corresponding to each step. The time required for each step is an example. Like non-adsorbate PSA,
For example, the adsorption step time in the adsorption tower C, the adsorption product gas reflux step, the inter-column pressure equalization step time, and the regeneration step time are respectively the adsorption step time (θ21) in the adsorption tower A, the adsorption product gas reflux step (θ12, θ22). , The equalization step time between columns (θ13, θ23) and the regeneration step time (θ11).

[0036]

[Table 2]

The difference between the operation steps of the adsorbate PSA and the non-adsorbate PSA is a product gas reflux step. As shown in Table 1, in Step 1 of the non-adsorbate PSA, when the adsorption tower A is performing the pressure equalization step in the tower, the non-adsorbed product gas is refluxed in the adsorption tower B. As shown in Table 2, in Step 1, the adsorbed product gas is continuously refluxed to the adsorption tower B through the adsorption tower A. That is, step 1
At 2, the adsorption tower A is in the adsorption step, and the adsorption tower B is in the regeneration step. After these steps are completed, the process proceeds to step 1 and the automatic valves 4A and 6A are opened from the adsorbed product tank E through the conduit 15 to open the adsorbed product gas to the adsorber A and the adsorber B in a reflux step ( the gap portion rich in non adsorbate of the adsorption tower a was replaced with adsorbed product gas, fine amount of residual NH ₃ in the gas directed gas rich in non adsorbate of the void portion in the adsorption tower B after regeneration simultaneously Is further adsorbed in the adsorption tower B). Other steps are the same as those described for the non-adsorbate PSA.

In the present invention, pressure swings having different adsorption characteristics are used.
Combination of multiple stages for each pressure swing separator
By recycling more separated gas,
Ammonia separation much higher than with existing PSA units
Performance can be achieved.

FIG. 2 shows an example in which the PSA apparatus described in FIG. 1 is combined and the separated gas is recycled. NH
_{3, H 2, N 2,} Ar, and supplies the mixed gas of CH ₄ · · · in required pressure Ri good conduit 51. The PSA1 in the figure optimizes the required time (hereinafter referred to as θ) of each step described in Tables 1 and 2 and the gas passage speed in the adsorption tower, etc., and optimizes the gas components other than NH ₃ (hereinafter referred to as non-adsorbate). N) in gas
A PSA device operated to minimize the H ₃ concentration, ie, a non-adsorbate PSA device. The gas components other than NH ₃ separated from the mixed gas are separated and recovered from the conduit 52. PSA1 is the NH in the non-adsorbate component gas.
_{(3) Since the} operation is performed so as to minimize the concentration, a slight but unacceptable amount of non-adsorbate component gas is contained in the conduit 53 from which NH ₃ (hereinafter referred to as adsorbate component) gas is discharged.

The PSA 2 is a PSA device that is operated so as to minimize the non-adsorbate component gas concentration in the adsorbate component gas by optimizing θ, the gas passing speed in the adsorption tower, etc., that is, an adsorbate PSA device. is there. The adsorbate component gas from PSA1 is supplied to PSA2 via conduit 53 . In PSA1, regeneration of the adsorption tower is performed by a decompression pump. At this time, the pressure of the decompression pump can be increased to an optimum pressure as a supply pressure to PSA2 by adjusting the adjustment valve 7 in FIG. Is unnecessary. This means that each PS
The A device also holds. When the amount of the non-adsorbate component contained in the adsorbate component gas separated by the PSA 2 is allowable, the conduit 55 is a separation / recovery conduit for the concentrated and separated NH ₃ gas. In this case, the PSA 3 in FIG. 2 is unnecessary.
Non adsorbate component gas from PSA2 is directed to conduit 54 but, PSA2 is because it is operated so as to minimize non-adsorptive component gas concentration of adsorbate component in the gas conduit 5
The non-adsorbate component gas of No. 4 contains an unacceptable amount of adsorbate components. To separate the adsorbate and non-adsorbate components, the gas in conduit 54 is recycled to PSA 1 and
The non-adsorbate component containing almost no adsorbate component is separated in A1, and is recovered from the conduit 52 as the gas component other than the separated NH ₃ .

[0041] When the separated adsorbate component gas in PSA2 is Nde contains a non adsorbate component gas amount but is unacceptable slightly, and supplies it to PSA3 the conduit 5 5. P
SA3 is an adsorbate PSA device like PSA2.
In the PSA 3, an adsorbate component gas containing almost no non-adsorbate components is separated and recovered from the conduit 58. In PSA3, but are amounts adsorbate component unacceptable non adsorbate component in the gas in the same manner as PSA2, which is next to the conduit 57 merges with a conduit 54 by a conduit 56, through the compressor PS
It is recycled to A1. As shown in Table 10, the pressure increase required here may be very slight, and is 1/10 or less of the membrane separation method which requires a large pressure increase due to a large pressure loss in principle.

[0042]

The present invention is not limited to the following examples.

[0043] Example 1 First, an example of a non-adsorptive PSA.

Synthetic zeolite having a pore size of 3 Å (Bay 1 SG SG-232, 1.6 mm)
PSA with a stainless steel adsorption column packed with spheres)
FIG. 3 shows the configuration of the unit. Ammonia as raw <br/> material gas Ri good conduit 61 in the apparatus, nitrogen, flowing a mixed gas of hydrogen, nonadsorbed product gas from the conduit 63, to obtain an adsorption product gas from the conduit 62, the amount thereof gases, the composition It was measured. The composition was determined by gas chromatography. Tables 3, 4, and 5 show the valve operating state, operating conditions, and operating results, respectively.

The N ₂ / H ₂ ratio in the raw material mixed gas is about 1,
This ratio was substantially maintained in the conduits 2 and 3, and most of the ammonia in the mixed gas was obtained from the conduit 2, and a gas containing almost no ammonia was obtained from the conduit 3.

[0046]

[Table 3] Each valve is operated as shown in the valve operation table corresponding to each cycle (θ). When there is an indication of “○” in the valve operation table, the corresponding valve is opened. It is closed when there is no display.

[0047]

[Table 4]

[0048]

[Table 5]

Next, an example of the adsorbate PSA will be described.

With the same filler and the same equipment as described above , the valve operation was changed as shown in Table 6, and the operating conditions were changed as shown in Table 7, and the operation was carried out. Others were performed similarly to the case of non-adsorbate PSA . Table 8 shows the results.

The N ₂ / H ₂ ratio in the raw material mixed gas is about 1,
This ratio was substantially maintained in the conduits 2 and 3, and most of the ammonia in the mixed gas was obtained from the conduit 2, and a gas containing almost no ammonia was obtained from the conduit 3.

[0052]

[Table 6]

[0053]

[Table 7]

[0054]

[Table 8]

Synthetic zeolite (Baylith SG-
FIG. 2 shows an apparatus combined with a PSA apparatus using a stainless steel adsorption column filled with 232, 1.6 mm spheres). PSA1 was operated under the operating conditions in Table 1 according to the valve operation table of PSA unit (1) in Table 3. PSA2, PS
A3 was operated under the operating conditions in Table 9 according to the valve operation table of PSA unit (2) in Table 6. A mixed gas of ammonia, nitrogen, and hydrogen as a raw material is passed through a conduit 51 shown in FIG.
2 and a non-adsorbed product gas was obtained from the conduit 58, and an adsorbed product gas was obtained from the conduit 58, and their gas amounts and compositions were measured. The composition was determined by gas chromatography. Table 10 shows the operation results.

[0056]

[Table 9]

[0057]

[Table 10] The mixed gas containing 3.6 v% ammonia was concentrated to 97.0 v% as shown in Table 10. Further, the ammonia concentration in the non-adsorbed product gas was reduced to 0.2 v%. The mixed gas was almost completely separated from ammonia and the residual gas (nitrogen + hydrogen).

Comparative Example 1 A synthetic zeolite having a pore size of 5 angstroms (Baylith KE-G25) was used in the same apparatus as in Example 1.
Except for changing the 2,1.6mm sphere) was performed in a manner similar to. The operating conditions are shown in Table 11 and the results are shown in Table 12. N ₂ / H ₂ ratio contained in the raw material mixed gas is about 1 but the ratio is conduit 62,
At 63, it was greatly broken. Ammonia could not be separated from the mixed gas while maintaining the N ₂ / H ₂ ratio at about 1 . The N ₂ / H ₂ ratio in conduit 62 is fairly large, indicating that the nitrogen has been significantly adsorbed on the adsorbent along with the ammonia in the adsorption step;
It turns out that this synthetic zeolite is not suitable for the present invention.

[0059]

[Table 11]

[0060]

[Table 12]

The chemical compositions of the adsorbent used in this comparative example and the adsorbent used in the examples are the same. Adsorption force for the nitrogen of the adsorbent, is small Ri by the suction force to ammonia, a large amount that can not be ignored compared to the adsorption force with respect to hydrogen. Therefore, in this comparative example using an adsorbent having a pore size of 5 Å, all of ammonia, hydrogen, and nitrogen gases can pass through the pores and reach the adsorption site (locus), and are divided according to the difference in the adsorption power. Can be Since only hydrogen is hardly adsorbed, only hydrogen is concentrated, and the H ₂ / N ₂ ratio before and after the separation greatly changes. In contrast, in the example, the adsorbent having a pore size of 3 angstroms was used, and therefore, the present adsorbent originally has an adsorbing power that cannot be ignored even for nitrogen. And cannot reach the adsorption site (locus), so neither nitrogen nor hydrogen is adsorbed.

[0062]

As described above, the present invention comprises a zeolite or activated carbon having a specific pore diameter for selectively adsorbing only ammonia as an adsorbent and having different adsorption characteristics.
Due to the configuration by combining a plurality of pressure swing device that provides the following advantages with respect to the separation of ammonia. (1) ammonia and nitrogen from a gas mixture from the synthesis loop of ammonia synthesis, the energy required for the separation operation of the hydrogen significantly be reduced. (2) The energy required for the operation of separating ammonia, nitrogen and hydrogen from the off-gas of ammonia synthesis can be significantly reduced. (3) Since the ratio of nitrogen / hydrogen separated by the above operation is not different from the ratio of nitrogen / hydrogen in the mixed gas before separation, it can be returned to the synthesis system as it is. (4) Ammonia gas can be easily obtained as an extremely high-purity product. (5) Ammonia that can be used for denitration can be separated from the diluted ammonia mixed gas. (6) The operation of dehumidifying the separated nitrogen and hydrogen is unnecessary.

[Brief description of the drawings]

FIG. 1 is a flowchart for continuously implementing the present invention.

FIG. 2 is a diagram showing an example in which a PSA device of the present invention is used in combination.

FIG. 3 is a diagram showing a configuration of a PSA unit used in an embodiment of the present invention.

[Explanation of symbols]

A, B, C, D Adsorption tower E Adsorption product tank F Non-adsorption product tank P Exhaust pump 1A, 1B, 1C, 1D Automatic valve 2A, 2B, 2C, 2D Automatic valve 3A, 3B, 3C, 3D Automatic valve 4A, 4B, 4C, 4D automatic valve 5A, 5B, 5C, 5D automatic valve 6A, 6B, 6C, 6D automatic valve V1, V2, V3, V4, V5, V6, V7, V8, V
9 automatic valve FN, RN, PN flow adjustment valves 7 and 8 the flow adjustment valve 10 a mixed gas supply manifold 11 nonadsorbed product outlet gas manifold 12 exhaust manifold 15, 27 conduit 25 adsorption product outlet manifold 26 nonadsorbed product Outflow manifold 51, 52, 53, 54, 55, 56, 57, 58 Conduit 61, 62, 63 Conduit

Claims (2)

(57) [Claims] 1. Ammonia from a mixed gas containing ammonia
In a pressure swing separator for near separation, ammonia
A) In components (non-adsorbate components) other than (adsorbate components) gas
Pore size operated to minimize ammonia concentration
Uses less than 5 angstroms of zeolite or activated carbon
At least one filled adsorption device and adsorbate component gas
Is operated to minimize the concentration of non-adsorbate component gas in
Zeolite with pore size less than 5 Å
Or at least one adsorption device filled with activated carbon
Configured to recycle gas separated from each device
The separation device as described above. 2. A pressure switch from a mixed gas containing ammonia.
Method for separating ammonia using a separating device
Components other than ammonia (adsorbate component)
Min) Operate to minimize the ammonia concentration in the gas
Zeolite with pore size less than 5 Å
Or at least one adsorption device filled with activated carbon.
Minimize the concentration of non-adsorbate component gas in the component gas
The pore size is less than 5 angstroms
At least one filter filled with zeolite or activated carbon
Recycle gas separated from each device to and from the landing device
The method as described above.