A PROCESS FOR RECOVERING H2

Abstract

The present invention relates to processes for recovering H.sub.2 from converting NH.sub.3 in an apparatus, the processes comprising one or more process stages, and an apparatus for these processes.

Claims

1.-18. (canceled)

19. A process for recovering H.sub.2 from converting NH.sub.3 in an apparatus comprising n serially coupled zones Z(i), with i=1 . . . n, with n2, wherein each zone Z(i) contains a conversion reactor CR(i) comprising a catalyst C(i) for converting NH.sub.3 to give H.sub.2, a first membrane unit M1(i) and a second membrane unit M2(i), wherein CR(i) is located upstream of M1(i) and M2(i) is located downstream of M1(i) in Z(i), wherein Z(1) is the most upstream zone and Z(n) is the most downstream zone, the process comprising (a) providing a feed gas stream FS(0) comprising NH.sub.3; (b) n successive process stages S(i), i=1 . . . n, wherein, in each S(i), S(i) comprises a conversion stage SA(i), comprising feeding the feed gas stream FS(i-1) into a conversion reactor CR(i) comprised in Z(i) and bringing said stream FS(i-1) in contact with C(i) in CR(i), obtaining a gas stream G(i) which comprises NH.sub.3, N.sub.2 and H.sub.2, the gas stream G(i) having a molar ratio n(H.sub.2):n(NH.sub.3)=x(G(i)); removing the gas stream G(i) comprising NH.sub.3, N.sub.2 and H.sub.2 from CR(i); passing the gas stream G(i) as a feed gas stream F1(i) through a separation stage SB(i), F1(i) having the same chemical composition as G(i) and the molar ratio x(G(i))=x(F1(i)); a separation stage SB(i), comprising passing the feed gas stream F1(i) through a first membrane unit M1(i), of Z(i), comprising at least one membrane, the at least one membrane having a H.sub.2/NH.sub.3 selectivity of at least 2000, at a pressure ratio greater than 1 across said at least one membrane, calculated as (pressure of feed gas stream F1(i)/pressure of permeate gas stream P1(i)) at constant temperature, obtaining a permeate gas stream P1(i) comprising H.sub.2; and a retentate gas stream R1(i) comprising H.sub.2, N.sub.2 and NH.sub.3, wherein the molar ratio n(H.sub.2):n(NH.sub.3)=x(R1(i)); x(R1(i))<x(F1(i)); passing the retentate gas stream R1(i) as a feed gas stream F2(i), through a separation stage SC(i), F2(i) having the same chemical and physical composition as R1(i) and the molar ratio x(R1(i))=x(F2(i)); a separation stage SC(i), comprising passing the feed gas stream F2(i) through a second membrane unit M2(i) of Z(i) comprising at least one membrane, the at least one membrane having a H.sub.2/NH.sub.3 selectivity of at least 2000, at a pressure ratio of greater than 1 across said at least one membrane, calculated as (pressure of feed gas stream F2(i)/pressure of permeate gas stream P2(i)) at constant temperature, obtaining a permeate gas stream P2(i) comprising H.sub.2; and a retentate gas stream R2(i) comprising H.sub.2, N.sub.2 and NH.sub.3, wherein the molar ratio n(H.sub.2):n(NH.sub.3)=x(R2(i)); x(R2(i))<x(F2(i)); removing the gas stream R2(i) from Z(i); wherein, when i=1 . . . n-1, the gas stream R2(i) is removed from Z(i) as a feed stream FS(i), FS(i) having the same chemical and physical composition as R2(i) and the molar ratio x(R2(i))-x(FS(i)); and wherein, when i=n, the gas stream R2(n) is removed from Z(i) as a product gas stream; wherein the volume flow ratio of FS(i-1) to FS(i) is in the range of from 1.05:1 to 4:1.

20. The process of claim 19, wherein n=2 to 10.

21. The process of claim 19, wherein according to stage S(i), no vacuum apparatus or compressor is operated downstream of the conversion reactor CR(i) according to SA(i) in the obtainment of a permeate gas stream and/or a retentate gas stream.

22. The process of claim 19, wherein according to SA(i) the feed gas stream FS(i-1) is contacted with the conversion catalyst C(i) at a pressure in the range of from 10 to 100 bar (abs); and wherein according to SA(i) the feed gas stream FS(i-1) is preferably contacted with the conversion catalyst C(i) at a temperature in the range of from 50 to 1100 C.

23. The process of claim 19, wherein the conversion catalyst C(i) comprises a transition metal supported on a refractory support material; wherein the transition metal is selected from the group consisting of Fe, Cu, Ni, Co, Ru, Ag, Pd, Rh, Pt, Ir including combinations of two or more thereof.

24. The process of claim 19, wherein the gas stream G(i) has a H.sub.2 to NH.sub.3 molar ratio x(G(i)) (calculated as n(H.sub.2):n(NH.sub.3)=x(G(i)) in the range of from 0.01:1 to 500:1; wherein the gas stream G(i) has a H.sub.2 to N.sub.2 molar ratio y(G(i)) (calculated as n(H.sub.2):n(N.sub.2)=y(G(i))) in the range of from 0.01:1 to 5:1.

25. The process of claim 19, wherein the feed gas stream F1(i), prior to passing through the separation stage SB(i), is passed through a heat exchanger H(i).

26. The process of claim 19, wherein, according to SB(i), the at least one membrane comprised in membrane unit M1(i) is a palladium metal membrane.

27. The process of claim 19, wherein, according to SB(i), the pressure ratio across the at least one membrane comprised in membrane unit M1(i), calculated as (pressure of feed gas stream F1(i)/pressure of permeate gas stream P1(i)) at constant temperature, is in the range of from 1.5:1 to 50:1.

28. The process of claim 19, wherein, according to SC(i), the at least one membrane comprised in membrane unit M2(i) is a palladium metal membrane; wherein according to SC(i), the membrane unit M2(i) comprising at least one membrane has a H.sub.2/NH.sub.3 selectivity of at least 2500; wherein, according to SC(i), the membrane unit M2(i) comprising at least one membrane has a ratio of H.sub.2/N.sub.2 selectivity to H.sub.2/NH.sub.3 selectivity in the range of from 0.8:1 to 5:1.

29. The process of claim 19, wherein according to SC(i), the pressure ratio across the at least one membrane comprised in membrane unit M2(i), calculated as (pressure of feed gas stream F2(i)/pressure of permeate gas stream P2(i)) at constant temperature, is in the range of from 1.5:1 to 50:1.

30. The process of claim 19, wherein according to SC(i), the retentate gas stream R2(i) has a H.sub.2 to NH.sub.3 molar ratio x(R2(i)) (calculated as n(H.sub.2):n(NH.sub.3)=x(R2(i))=x(FS(i)) in the range of from 0.05:1 to 100:1.

31. The process of claim 19, wherein according to SC(n), the retentate gas stream R2(n) has a pressure in the range of from 10 to 100 bar (abs).

32. The process of claim 19, wherein the volume flow ratio of FS(i-1) to (FS(i)) is in the range of from 1.1:1 to 3:1; wherein the ratio of the pressure of permeate gas stream P1(i) to permeate gas stream P2(i) is in the range of from 50:1 to 1.5:1.

33. A process for recovering H.sub.2 from converting NH.sub.3 in an apparatus comprising a zone Z(1) containing a conversion reactor CR(1) comprising a catalyst C(1) for converting NH.sub.3 to give H.sub.2, a first membrane unit M1(1) and a second membrane unit M2(1), wherein CR(1) is located upstream of M1(1) and M2(1) is located downstream of M1(1) in Z(1), the process comprising (a) providing a feed gas stream FS(0) comprising NH.sub.3; (b) a process stage S(1), wherein S(1) comprises a conversion stage SA(1), comprising feeding gas stream FS(0) into a conversion reactor CR(1) comprised in Z(i) and bringing said stream FS(0) in contact with C(1) in CR(1), obtaining a gas stream G(i) which comprises NH.sub.3, N.sub.2 and H.sub.2, the gas stream G(1) having a molar ratio n(H.sub.2):n(NH.sub.3)=x(G(1)); removing the gas stream G(1) comprising NH.sub.3, N.sub.2 and H.sub.2 from CR(1); passing the gas stream G(1) as a feed gas stream F1(1) through a separation stage SB(1), F1(1) having the same chemical and composition as G(1) and the molar ratio x(G(1))=x(F1(1)); a separation stage SB(1), comprising passing the feed gas stream F1(1) through a first membrane unit M1(1), of Z(1), comprising at least one membrane, the at least one membrane having a H.sub.2/NH.sub.3 selectivity of at least 2000, at a pressure ratio greater than 1 across said at least one membrane, calculated as (pressure of feed gas stream F1(i)/pressure of permeate gas stream P1(1)) at constant temperature, obtaining a permeate gas stream P1(1) comprising H.sub.2; and a retentate gas stream R1(1) comprising H.sub.2, N.sub.2 and NH.sub.3, wherein the molar ratio n(H.sub.2):n(NH.sub.3)=x(R1(1)); x(R1(1))<x(F1(1)); passing the retentate gas stream R1(1) as a feed gas stream F2(1), through a separation stage SC(1), F2(1) having the same chemical and physical composition as R1(1) and the molar ratio x(R1(1))=x(F2(1)); a separation stage SC(1), comprising passing the feed gas stream F2(1) through a second membrane unit M2(1) of Z(i) comprising at least one membrane, the at least one membrane having a H.sub.2/NH.sub.3 selectivity of at least 2000, at a pressure ratio of greater than 1 across said at least one membrane, calculated as (pressure of feed gas stream F2(1)/pressure of permeate gas stream P2(1)) at constant temperature, obtaining a permeate gas stream P2(1) comprising H.sub.2; and a retentate gas stream R2(1) comprising H.sub.2, N.sub.2 and NH.sub.3, wherein the molar ratio n(H.sub.2):n(NH.sub.3)=x(R2(1)); x(R2(1))<x(F2(1)); removing the gas stream R2(1) from Z(1); wherein the gas stream R2(1) is removed from Z(1) as a product gas stream; wherein the volume flow ratio of FS(0) to R2(1) is in the range of from 1.05:1 to 4:1.

34. An apparatus for recovering H.sub.2 from converting NH.sub.3 according to the process of claim 19, the apparatus comprising n zones Z(i), with i=1 . . . n, with n>1, wherein, when n>2, the n zones Z(i) are serially coupled and Z(1) is the most upstream zone and Z(n) is the most downstream zone, wherein each zone Z(i) comprises a conversion reactor unit U.CR(i) comprising a supplying means for providing a feed stream FS(i-1) comprising NH.sub.3 to a conversion reactor CR(i); a conversion reactor CR(i) for converting NH.sub.3 to a gas stream G(i) comprising NH.sub.3, N.sub.2 and H.sub.2, the conversion reactor CR(i) comprising a conversion catalyst C(i); an outlet means for removing the gas stream G(i) from CR(i) as a feed gas stream F1(i) to a membrane separation unit U.M1(i); a first membrane separation unit U.M1(i) comprising a means for passing a feed gas stream F1(i) to the first membrane unit M1(i); said membrane unit comprising at least one membrane, the at least one membrane having a H.sub.2/NH.sub.3 selectivity of at least 2000; an outlet means for removing a permeate gas stream P1(i) from the membrane unit M1(i); an outlet means for removing a retentate gas stream R1(i) from the membrane unit M1(i); a second membrane separation unit U.M2(i) comprising a means for passing retentate gas stream R1(i) as a feed gas stream F2(i) to the second membrane unit M2(i); said membrane unit comprising at least one membrane, the at least one membrane having a H.sub.2/NH.sub.3 selectivity of at least 2000; an outlet means for removing a permeate gas stream P2(i) from the membrane unit M2(i); an outlet means for removing a retentate gas stream R2(i) from Z(i); and when n>2 and i/n, a means for passing R2(i) removed from Z(i), as a feed stream FS(i), into Z(i+1); wherein U.CR(i) is located upstream of U.M1(i) and U.M2(i) is located downstream of U.M1(i) in Z(i).

35. The apparatus of claim 34, wherein n=1 to 10; wherein neither a vacuum apparatus nor a compressor is disposed downstream of the conversion reactor CR(i) according to U.CR(i).

36. Use of an apparatus according to claim 34 in a process for recovering H.sub.2 from converting NH.sub.3.

Description

EXAMPLES

Reference Example 1 Simulation Conditions

[0950] The performance of the decomposition reaction and the membrane stages was simulated using MATLAB (version R2020b). The reactor was simulation using an isothermal equilibrium approach. Based on inlet concentration(NH.sub.3, H.sub.2 and N.sub.2), reaction temperature and reaction pressure the equilibrium concentration at the reactor outlet are estimated. The required parameters used for calculation were taken from NIST Chemistry WebBook (NIST Standard Reference Database Number 69.)

[0951] Modelling of the membrane separation stage was conducted using a general equation for the hydrogen permeation through palladium membranes (S. Yun and S. Ted Oyama, Correlations in palladium membranes for hydrogen separation: A review, Journal of Membrane Science, vol. 375, no. 1-2, pp. 28-45, June 2011, doi: 10.1016/j.memsci.2011.03.057.). Hydrogen permeation through palladium membranes follows a solution-diffusion mechanism, described by the following equation:

[00001]$J_i=N_i\left(p_{i,h}^m-p_{i,l}^m\right)$$N_i=\frac{P_i}{L}$${}_{\mathrm{ij}}=\frac{P_i}{P_j}$

[0952] J.sub.i is the flux of component i, N.sub.i is the permeance of component l, P.sub.i is the permeability of component i, L is the thickness of the membrane layer, p.sub.i,h is the partial pressure of component i on the high-pressure side, p.sub.i,l is the partial pressure of component ion the low-pressure side, m is the pressure exponent, typically ranging from 0.5-1.

[0953] In case of hydrogen permeance through a palladium-based membrane, bulk diffusion(4) is the rate controlling step, and m is assumed to be 0.5 for the simulation. For the simulations, the permeance of hydrogen, P.sub.H2/L, was taken from literature and assumed to be 1.510.sup.6 mol s.sup.1 m.sup.2 Pa.

[0954] To obtain matching in units in the above flux equation, the units in which permeance are displayed should be of the form Nm.sup.3/(m.sup.2 h bar{circumflex over ()}n). However, it is common use in literature to simply display the values as Nm.sup.3/(m.sup.2 h bar) (see S. Yun and S. Ted Oyama reference above). Therefore, the skilled person realizes that the units, in particular the exponent of the pressure-unit, of the permeance should be changed accordingly to the value of n that was determined for the particular system.

[0955] Based on the flux equation a CSTR (continuously stirred tank reactor) cascade model was set up, consisting of 1000 unit cells. Following assumptions were made for simulation of the membrane stages: [0956] isothermal conditions (T.sub.in=T.sub.out), [0957] H.sub.2 partial pressure on the permeate side equals the absolute pressure, [0958] retentate pressure loss is small compared to absolute pressure and was neglected, [0959] volume of the gas obtained from reactors was treated as having ideal gas components and the volume flow increased proportional to the increase in gas molecules, [0960] Membranes were treated as ideal and having infinite selectivity [0961] H.sub.2 was isolated as pure hydrogen in the permeates.

[0962] Two different inventive scenarios were calculated, based on the flow diagrams (FIG. 1 and FIG. 2) shown. Each stage according to the invention consists of a reactor CR(i), a high pressure permeate membrane M1(i) and a low pressure permeate membrane M2(i) all connected in series. For the reference example simulations, one stage only consists of a reactor CR(i) and a membrane separation module. Pure, gaseous ammonia (X.sub.NH3=1) was used as feed FS(0) for the first reactor CR(1). For all simulations, a feed stream FS(0) flow of 10000 Nm.sup.3/h was assumed and corresponding volume flow ratios are calculated according to the indicated streams having individual flows values Nm.sup.3/h. Based on these inputs, two different scenarios were calculated: [0963] 1. Reaction and membrane separation at 400 C., 50 bar (a) feed pressure, 3 consecutive stages; [0964] 2. 500 C. reaction temperature and 400 C. membrane separation, 50 bar (a), 2 consecutive stages.

[0965] The identical membrane area and module distribution as for the inventive examples was assumed. For each inventive example there are two reference examples: one at low permeate pressure (1.5 bara) and one at high permeate pressure (10 bara).

[0966] Gas mixtures resultant from reactors were treated as ideal gases and the flow volume increased proportionally to the increase in the number of gas molecules. Therefore, F1 has a larger volume flow than FS(0) proportional to the increased number of gas molecules.

[0967] The results of the different simulations are summarized in the reference examples, examples and associated tables below. With regards to physical implications of the simulations and the results therefrom, it is known to the skilled person that under real word conditions impurities in the permeate are resultant from defects in the Pd membrane, and the membrane itself has a theoretical infinite selectivity according to the solution-diffusion mechanism. The amount of defects is also known to depend on the engineering and size of the membrane module. Therefore although the results of the simulations imply infinite selectivity, the skilled person realizes the selectivity of Pd membranes is limited by said defects under real world conditions. Thus the skilled person would also understand the defects will decrease in proportion to Pd membrane area since there is less edge to membrane surface area which is well known to be the primary source of defects with said membranes.

Comparative Example 1: Two Sequential Stages with Single Membrane Units and Permeates Collected at 10 bar (abs)

[0968] Simulations were carried according to reference example 1 for a system with the individual stages according to FIG. 1. An NH.sub.3 feed stream FS(0) flow of 10000 Nm.sup.3/h was fed into a reactor CR(1) and converted at 773.15 K, obtaining a gas mixture consisting of NH.sub.3, N.sub.2 and H.sub.2 which were passed as a gas stream F(1) at 673.15 K and 50 bara through a membrane stage M1(1) with 400 m.sup.2 membrane area, obtaining a permeate stream P(1) containing pure H.sub.2 at 673.15 K and 10 bara, and obtaining a retentate stream R(1) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. The retentate stream R(1) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 is fed into a reactor CR(2) and converted at 773.15 K, obtaining a gas mixture consisting of NH.sub.3, N.sub.2 and H.sub.2 which were passed as a gas stream F(2) at 673.15 K and 50 bara through a membrane stage M1(2) with 200 m.sup.2 membrane area, obtaining a permeate stream P (2) containing pure H.sub.2 at 673.15 K and 10 bara, and obtaining a retentate stream R (2) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. A total of 94.4% of the ammonia was converted using a total of 600 m.sup.2 Pd membrane surface area and resulting in 72.8% hydrogen recovery, both % conversion and % recovery are determined on a molar basis.

TABLE-US-00001 TABLE 1 Results and flow ratios for Comparative Example 1 Vol. flow Vol. Mol. ratio Mol. ratio Pres. Temp. ratio flow Stream H.sub.2/NH.sub.3 H.sub.2/N.sub.2 (bara) (Kelvin) stream pair ratio FS(0) 0.00 50 773.15 FS(0)/R(2) 1.18 F(1) 12.39 0.06 50 673.15 FS(0)/F(1).sup. 0.53 R(1) 4.86 0.10 50 673.15 F(1)/R(1) 1.75 P(1) 10 673.15 F(1)/P(1).sup. 2.32 F(2) 10.73 0.05 50 673.15 R(1)/F(2) 0.95 R(2) 5.75 0.07 50 673.15 F(2)/R(2) 1.33 P(2) 10 673.15 F(2)/P(2).sup. 4.05 F(1)/R(2) 2.22

Comparative Example 2: Two Sequential Stages with Single Membrane Units and Permeates Collected at 1.5 bar (abs)

[0969] Simulations were carried according to reference example 1 for a system with the individual stages according to FIG. 1. An NH.sub.3 feed stream FS(0) flow of 10000 Nm.sup.3/h was fed into a reactor CR(1) and converted at 773.15 K, obtaining a gas mixture consisting of NH.sub.3, N.sub.2 and H.sub.2 which were passed as a gas stream F(1) at 673.15 K and 50 bara through a membrane stage M1(1) with 400 m.sup.2 membrane area, obtaining a permeate stream P(1) containing pure H.sub.2 at 673.15 K and 1.5 bara, and obtaining a retentate stream R(1) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. The retentate stream R(1) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 is fed into a reactor CR(2) and converted at 773.15 K, obtaining a gas mixture consisting of NH.sub.3, N.sub.2 and H.sub.2 which were passed as a gas stream F(2) at 673.15 K and 50 bara through a membrane stage M1(2) with 200 m.sup.2 membrane area, obtaining a permeate stream P(2) containing pure H.sub.2 at 673.15 K and 1.5 bara, and obtaining a retentate stream R(2) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. A total of 97.8% of the ammonia was converted using a total of 600 m.sup.2 Pd membrane surface area and resulting in 96.7% hydrogen recovery, both % conversion and % recovery are determined on a volume basis assuming ideal gas behavior.

TABLE-US-00002 TABLE 2 Results and flow ratios for Comparative Example 2 Vol. flow Vol. Mol. ratio Mol. ratio Pres. Temp. ratio flow Stream H.sub.2/NH.sub.3 H.sub.2/N.sub.2 (bara) (Kelvin) stream pair ratio FS(0) 0.00 50 773.15 FS(0)/R(2) 1.89 F(1) 12.39 0.06 50 773.15 FS(0)/F(1).sup. 0.53 R(1) 0.88 0.17 50 673.15 F(1)/R(1) 2.92 P(1) 1.5 673.15 F(1)/P(1).sup. 1.52 F(2) 11.19 0.03 50 773.15 R(1)/F(2) 0.88 R(2) 0.93 0.04 50 673.15 F(2)/R(2) 1.39 P(2) 1.5 673.15 F(2)/P(2).sup. 3.55 F(1)/R(2) 3.58

Example 1: Two Sequential Stages with Two Membrane Units Connected in Series

[0970] Simulations were carried according to reference example 1 for a system with the individual stages according to FIG. 2. An NH.sub.3 feed stream FS(0) flow of 10000 Nm.sup.3/h was fed into a reactor CR(1) and converted at 773.15 K, obtaining a gas mixture consisting of NH.sub.3, N.sub.2 and H.sub.2 which were passed as a gas stream F1(1) at 673.15 K and 50 bara through a first membrane stage M1(1) with 200 m.sup.2 membrane area, obtaining a permeate stream P1(1) containing pure H.sub.2 at 673.15 K and 10 bara, and obtaining a retentate stream R1(1) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. The retentate stream R1(1) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 is passed as a feed gas stream F2(1) at 673.15 K and 50 bara through a second membrane stage M2(1) with 200 m.sup.2 membrane area, obtaining a permeate stream P2(1) containing pure H.sub.2 at 673.15 K and 1.5 bara, and obtaining a retentate stream R2(1) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. The retentate stream R2(1) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 is fed into a reactor CR(2) and converted at 773.15 K, obtaining a gas mixture consisting of NH.sub.3, N.sub.2 and H.sub.2 which were passed as a gas stream F1(2) at 673.15 K and 50 bara through a membrane stage M1(2) with 100 m.sup.2 membrane area, obtaining a permeate stream P1(2) containing pure H.sub.2 at 673.15 K and 10 bara, and obtaining a retentate stream R1(2) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. The retentate stream R1(2) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 is passed as a feed gas stream F2(2) at 673.15 K and 50 bara through a second membrane stage M2(2) with 100 m.sup.2 membrane area, obtaining a permeate stream P2(2) containing pure H.sub.2 at 673.15 K and 1.5 bara, and obtaining a retentate stream R2(2) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. A total of 96.6% of the NH.sub.3 was converted using a total of 600 m.sup.2 Pd membrane surface area and resulting in 91.5% H.sub.2 recovery. Concerning the pressure of the hydrogen, 40.1% of the H.sub.2 recovery was isolated at 10 bara calculated as total volume flow of permeate H.sub.2 at 10 bara/sum of the volume flows of permeate H.sub.2 at 10 and 1.5 bara, no correction for the pressure to volume being made in said calculation, both % conversion and % recovery are determined on a volume basis assuming ideal gas behavior.

TABLE-US-00003 TABLE 3 Results and flow ratios for Example 1 Vol. flow Vol. Mol. ratio Mol. ratio Pres. Temp. ratio flow Stream H.sub.2/NH.sub.3 H.sub.2/N.sub.2 (bara) (Kelvin) stream pair ratio FS(0) 0.00 50 773.15 FS(0)/R2(2) 1.68 F1(1) 12.39 0.06 50 773.15 FS(0)/F1(1) 0.53 R1(1) 8.22 0.07 50 673.15 .sup.F1(1)/R1(1) 1.31 P1(1) 10 673.15 F1(1)/P1(1) 4.20 R2(1) 2.34 0.13 50 673.15 R1(1)/R2(1) 1.79 P2(1) 1.5 673.15 R1(1)/P2(1).sup. 2.27 F1(2) 10.64 0.04 50 773.15 R2(1)/F1(2).sup. 0.92 R1(2) 7.70 0.04 50 673.15 .sup.F1(2)/R1(2) 1.13 P1(2) 10 673.15 F1(2)/P1(2) 8.76 R2(2) 2.27 0.06 50 673.15 R1(2)/R2(2) 1.31 P2(2) 1.5 673.15 R1(2)/P2(2).sup. 4.21 .sup.F1(1)/R2(2) 3.18

[0971] Retentate stream R1(1) is equivalent in composition and parameters to feed gas stream F2(1) (F2(1) is not shown in table 3). Also retentate stream R1(2) is equivalent in composition and parameters to feed gas stream F2(2) (F2(2) is also not shown in table 3).

Comparative Example 3: Three Sequential Stages with Single Membrane Units and Permeates Collected at 10 bar (abs)

[0972] Simulations were carried according to reference example 1 for a system with the individual stages according to FIG. 1. An NH.sub.3 feed stream FS(0) flow of 10000 Nm.sup.3/h was fed into a reactor CR(1) and converted at 673.15 K, obtaining a gas mixture consisting of NH.sub.3, N.sub.2 and H.sub.2 which were passed as a gas stream F(1) at 673.15 K and 50 bara through a membrane stage M1(1) with 400 m.sup.2 membrane area, obtaining a permeate stream P(1) containing pure H.sub.2 at 673.15 K and 10 bara, and obtaining a retentate stream R(1) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. The retentate stream R(1) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 is fed into a reactor CR(2) and converted at 673.15 K, obtaining a gas mixture consisting of NH.sub.3, N.sub.2 and H.sub.2 which were passed as a gas stream F(2) at 673.15 K and 50 bara through a membrane stage M1(2) with 200 m.sup.2 membrane area, obtaining a permeate stream P (2) containing pure H.sub.2 at 673.15 K and 10 bara, and obtaining a retentate stream R(2) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. The retentate stream R(2) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 is fed into a reactor CR(3) and converted at 673.15 K, obtaining a gas mixture consisting of NH.sub.3, N.sub.2 and H.sub.2 which were passed as a gas stream F(3) at 673.15 K and 50 bara through a membrane stage M1(3) with 200 m.sup.2 membrane area, obtaining a permeate stream P(3) containing pure H.sub.2 at 673.15 K and 10 bara, and obtaining a retentate stream R(3) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. A total of 88.3% of the ammonia was converted using a total of 800 m.sup.2 Pd membrane surface area and resulting in 73.3% hydrogen recovery, both % conversion and % recovery are determined on a volume basis assuming ideal gas behavior.

TABLE-US-00004 TABLE 4 Results and flow ratios for Comparative Example 3 Mol. ratio Mol. ratio Pres. Vol. flow ratio Vol. Stream H.sub.2/NH.sub.3 H.sub.2/N.sub.2 (bara) stream pair flow ratio FS(0) 0.00 50 FS(0)/R(3) 1.28 F(1) 4.08 0.16 50 FS(0)/F(1).sup. 0.58 R(1) 1.57 0.25 50 F(1)/R(1) 1.64 P(1) 10 F(1)/P(1).sup. 2.57 F(2) 3.52 0.14 50 R(1)/F(2) 0.91 R(2) 1.98 0.18 50 F(2)/R(2) 1.28 P(2) 10 F(2)/P(2).sup. 4.59 F(3) 3.40 0.12 50 R(2)/F(3) 0.95 R(3) 1.92 0.15 50 F(3)/R(3) 1.22 P(3) 10 F(3)/P(3).sup. 5.53 F(1)/R(3) 2.21

Comparative Example 4: Three Sequential Stages with Single Membrane Units and Permeates Collected at 1.5 bar (abs)

[0973] Simulations were carried according to reference example 1 for a system with the individual stages according to FIG. 1. An NH.sub.3 feed stream FS(0) flow of 10000 Nm.sup.3/h was fed into a reactor CR(1) and converted at 673.15 K, obtaining a gas mixture consisting of NH.sub.3, N.sub.2 and H.sub.2 which were passed as a gas stream F(1) at 673.15 K and 50 bara through a membrane stage M1(1) with 400 m.sup.2 membrane area, obtaining a permeate stream P (1) containing pure H.sub.2 at 673.15 K and 1.5 bara, and obtaining a retentate stream R (1) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. The retentate stream R (1) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 is fed into a reactor CR(2) and converted at 673.15 K, obtaining a gas mixture consisting of NH.sub.3, N.sub.2 and H.sub.2 which were passed as a gas stream F(2) at 673.15 K and 50 bara through a membrane stage M1(2) with 200 m.sup.2 membrane area, obtaining a permeate stream P(2) containing pure H.sub.2 at 673.15 K and 1.5 bara, and obtaining a retentate stream R(2) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. The retentate stream R(2) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 is fed into a reactor CR(3) and converted at 673.15 K, obtaining a gas mixture consisting of NH.sub.3, N.sub.2 and H.sub.2 which were passed as a gas stream F(3) at 673.15 K and 50 bara through a membrane stage M1(3) with 200 m.sup.2 membrane area, obtaining a permeate stream P(3) containing pure H.sub.2 at 673.15 K and 1.5 bara, and obtaining a retentate stream R(3) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. A total of 96.8% of the ammonia was converted using a total of 800 m.sup.2 Pd membrane surface area and resulting in 95.7% hydrogen recovery, both % conversion and % recovery are determined on a volume basis assuming ideal gas behavior.

TABLE-US-00005 TABLE 5 Results and flow ratios for reference example 5 Mol. ratio Mol. ratio Pres. Vol. flow ratio Vol. Stream H.sub.2/NH.sub.3 H.sub.2/N.sub.2 (bara) stream pair flow ratio FS(0) 0.00 50 FS(0)/R(3) 1.88 F(1) 4.08 3.00 50 FS(0)/F(1).sup. 0.58 R(1) 0.21 0.16 50 F(1)/R(1) 2.50 P(1) 1.5 F(1)/P(1).sup. 1.67 F(2) 3.40 0.71 50 R(1)/F(2) 0.80 R(2) 0.30 0.06 50 F(2)/R(2) 1.51 P(2) 1.5 F(2)/P(2).sup. 2.98 F(3) 3.40 0.25 50 R(2)/F(3) 0.90 R(3) 0.30 0.03 50 F(3)/R(3) 1.20 P(3) 1.5 F(3)/P(3).sup. 6.02 F(1)/R(3) 3.25

Example 2: Three Sequential Stages with Two Membrane Units Connected in Series

[0974] Simulations were carried according to reference example 1 for a system with the individual stages according to FIG. 2. An NH.sub.3 feed stream FS(0) flow of 10000 Nm.sup.3/h was fed into a reactor CR(1) and converted at 673.15 K, obtaining a gas mixture consisting of NH.sub.3, N.sub.2 and H.sub.2 which were passed as a gas stream F1(1) at 673.15 K and 50 bara through a first membrane stage M1(1) with 200 m.sup.2 membrane area, obtaining a permeate stream P1(1) containing pure H.sub.2 at 673.15 K and 10 bara, and obtaining a retentate stream R1(1) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. The retentate stream R1(1) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 is passed as a feed gas stream F2(1) at 673.15 K and 50 bara through a second membrane stage M2(1) with 200 m.sup.2 membrane area, obtaining a permeate stream P2(1) containing pure H.sub.2 at 673.15 K and 1.5 bara, and obtaining a retentate stream R2(1) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. The retentate stream R2(1) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 is fed into a reactor CR(2) and converted at 673.15 K, obtaining a gas mixture consisting of NH.sub.3, N.sub.2 and H.sub.2 which were passed as a gas stream F1(2) at 673.15 K and 50 bara through a membrane stage M1(2) with 100 m.sup.2 membrane area, obtaining a permeate stream P1(2) containing pure H.sub.2 at 673.15 K and 10 bara, and obtaining a retentate stream R1(2) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. The retentate stream R1(2) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 is passed as a feed gas stream F2(2) at 673.15 K and 50 bara through a second membrane stage M2(2) with 100 m.sup.2 membrane area, obtaining a permeate stream P2(2) containing pure H.sub.2 at 673.15 K and 1.5 bara, and obtaining a retentate stream R2(2) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. The retentate stream R2(2) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 is fed into a reactor CR(3) and converted at 773.15 K, obtaining a gas mixture consisting of NH.sub.3, N.sub.2 and H.sub.2 which were passed as a gas stream F1(3) at 673.15 K and 50 bara through a membrane stage M1(3) with 100 m.sup.2 membrane area, obtaining a permeate stream P1(3) containing pure H.sub.2 at 673.15 K and 10 bara, and obtaining a retentate stream R1(3) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. The retentate stream R1(3) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 is passed as a feed gas stream F2(3) at 673.15 K and 50 bara through a second membrane stage M2(3) with 100 m.sup.2 membrane area, obtaining a permeate stream P2(3) containing pure H.sub.2 at 673.15 K and 1.5 bara, and obtaining a retentate stream R2(3) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2 at 673.15 K and 50 bara. A total of 95.5% of the NH.sub.3 was converted using a total of 800 m.sup.2 Pd membrane surface area and resulting in 91.9% H.sub.2 recovery. Concerning the pressure of the hydrogen, 38% of the H.sub.2 recovery was isolated at 10 bara calculated as total volume flow of permeate H.sub.2 at 10 bara/sum of the volume flows of permeate H.sub.2 at 10 and 1.5 bara, no correction for the pressure to volume being made in said calculation, both % conversion and % recovery are determined on a volume basis assuming ideal gas behavior.

TABLE-US-00006 TABLE 6 Results and flow ratios for example 2 Mol. ratio Mol. ratio Pres. Vol. flow ratio Vol. Stream H.sub.2/NH.sub.3 H.sub.2/N.sub.2 (bara) stream pair flow ratio FS(0) 0.00 50 FS(0)/R2(3) 1.76 F1(1) 4.08 0.16 50 FS(0)/F1(1) 0.58 R1(1) 2.64 0.20 50 .sup.F1(1)/R1(1) 1.29 P1(1) 10 F1(1)/P1(1) 4.47 R2(1) 0.64 0.33 50 R1(1)/R2(1) 1.67 P2(1) 1.5 R1(1)/P2(1).sup. 2.50 F1(2) 3.41 0.12 50 R2(1)/F1(2).sup. 0.84 R1(2) 2.52 0.14 50 .sup.F1(2)/R1(2) 1.12 P1(2) ! 10 F1(2)/P1(2) 9.23 R2(2) 0.85 0.18 50 R1(2)/R2(2) 1.30 P2(2) 1.5 R1(2)/P2(2).sup. 4.36 F1(3) 3.56 0.08 50 R2(2)/F1(3).sup. 0.91 R1(3) 2.97 0.08 50 .sup.F1(3)/R1(3) 1.05 P1(3) 10 F1(3)/P1(3) 22.43 R2(3) 0.73 0.10 50 R1(3)/R2(3) 1.21 P2(3) 1.5 R1(3)/P2(3).sup. 5.67 .sup.F1(1)/R2(3) 3.05

[0975] Retentate stream R1(1) is equivalent in composition and parameters to feed gas stream F2(1) (F2(1) is not shown in table 3). Also retentate stream R1(2) is equivalent in composition and parameters to feed gas stream F2(2) (F2(2) is also not shown in table 3). Finally, retentate stream R1(3) is also equivalent in composition and parameters to feed gas stream F2(3) (F2(3) is also not shown in table 3).

DESCRIPTION OF THE FIGURE(S)

[0976] FIG. 1 depicts a flow diagram according to the prior art for a single stage, wherein a feed source FS(i-1) of NH.sub.3 enters a conversion reactor CR(i), said conversion reactor CR(i) converts the NH.sub.3 to a mixture of NH.sub.3, N.sub.2 and H.sub.2 that is then passed as a feed gas F(i) to a membrane unit M(i) comprising a Pd membrane which then separates the mixture into a permeate gas stream P(i) containing purified H.sub.2 and retentate R(i) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2.

[0977] FIG. 2 depicts a flow diagram according to the invention for a single stage, wherein a feed source FS(i-1) of NH.sub.3 enters a conversion reactor CR(i), said conversion reactor CR(i) converts the NH.sub.3 to a mixture of NH.sub.3, N.sub.2 and H.sub.2 that is then passed as a feed gas F(i) to a membrane unit M(i) comprising a Pd membrane which then separates the mixture into a permeate gas stream P(i) containing purified H.sub.2 and retentate R(i) containing a mixture of NH.sub.3, N.sub.2 and H.sub.2.

[0978] FIG. 3 depicts a flow diagram according to the prior art for a single stage identical to FIG. 1 except showing a means of heat exchange H(i) for adjusting the temperature of F(i) prior to entering membrane unit M1(i).

[0979] FIG. 4 depicts a flow diagram according to the invention for a single stage identical to FIG. 2 except showing a means of heat exchange H(i) for adjusting the temperature of F1(i) prior to entering membrane unit M1(i).

Cited Literature

[0980] Cechetto et. Al. proposes in H.sub.2 production via ammonia decomposition in a catalytic membrane reactor, Fuel Processing Technology(2021), page 106772 [0981] Yun et al reviews in correlations of in palladium membranes for hydrogen separation J. Membrane Sci. (2011) pages 28 to 45 [0982] Schth et al reviews in Ammonia as a possible element in an energy infrastructure: catalysts for ammonia decomposition Energy Eviron. Sci. 2012, page 6278, [0983] Abashar discloses in Ultra-clean hydrogen production by ammonia Decomposition, J. King Saud University-Engineering Sciences (2018) pages 2-11 [0984] Lamb et al. in Ammonia for hydrogen storage; A review of catalytic ammonia decomposition and hydrogen separation and purification, Int. J. of hydrogen energy, 44(2019) 3580 [0985] Murugan et al in Review of purity analysis methods for performing quality assurance of fuel cell hydrogen Int. Journal of Hydrogen Energy (2015) pg 4219 [0986] Pal N. et al, A review on types, fabrication and support material of hydrogen separation membrane, Materials Today: Proceedings, volume 28, part 3, 2020, pages 1386-1391 with regards to acceptable substrate materials for palladium comprising membranes