Devices and methods for hydrogen generation via ammonia decomposition
View Patent ↗Systems and methods for hydrogen generation via ammonia decomposition that utilize a fixed bed reactor configured to receive inflows of NH 3 and oxidant and to produce an outflow of high purity H 2 . The fixed bed reactor contains a fixed bed of a NH 3 decomposition catalyst wherewith the NH 3 decomposes to form N 2 and H 2 ; a plurality of ceramic hollows fibers with a high surface to volume ratio disposed in the fixed bed, the hollow fibers having an H 2 selective membrane disposed thereon for extracting H 2 from N 2 and to form a permeate of the high purity H 2 and a retentate of primarily N 2 ; and a catalytic H 2 burner also disposed in the fixed bed, the catalytic H 2 burner for burning a portion of the H 2 with the oxidant to provide thermal energy for the NH 3 decomposition.
1. A system for generating hydrogen via ammonia decomposition, the system comprising:
a fixed bed of a NH 3 decomposition catalyst configured to receive inflows of NH 3 and wherewith the NH 3 decomposes to form a combined stream of N 2 and H 2 ;
a plurality of spaced apart and longitudinally aligned ceramic hollow fibers, each of the plurality of spaced apart and longitudinally aligned ceramic hollow fibers including an H 2 selective membrane disposed thereon for extracting H 2 from the combined stream of N 2 and H 2 and to form a permeate comprising a high purity H 2 and a retentate comprising primarily N 2 ; and
a catalytic H 2 burner extending through the fixed bed, the catalytic H 2 burner comprising a metal tube containing a H 2 oxidizing catalyst therein and configured to receive and burn at least a portion of the retentate to provide thermal energy for the NH 3 decomposition.
2. The system of claim 1 wherein the retentate additionally comprises an amount of H 2 and wherein at least a portion of the retentate and an oxidant inflow are introduced into the catalytic H 2 burner within the fixed bed reactor to provide thermal energy for the NH 3 decomposition.
3. The system of claim 1 , therein the H 2 burner comprises a spiral tube configuration extending through the fixed bed.
4. The system of claim 3 , wherein an outlet end of the H 2 burner metal tube releases N 2 and H 2 O.
5. The system of claim 1 wherein each of the plurality of spaced apart and longitudinally aligned ceramic hollow fibers comprises a porous ceramic material, and additionally comprising a NH 3 cracking catalyst loaded within the porous ceramic material for cracking of residual NH 3 .
6. The system of claim 5 providing a conversion of ammonia to hydrogen and nitrogen in excess of 99%.
7. The system of claim 1 wherein the plurality of spaced apart and longitudinally aligned ceramic hollow fibers are in a parallel alignment.
8. The system of claim 1 , wherein at least a portion of the NH 3 decomposition catalyst is disposed around and in a space between adjacent pairs of the plurality of spaced apart and longitudinally aligned ceramic hollow fibers.
9. The system of claim 1 wherein a maximum NH 3 decomposition reactor temperature of the fixed bed reactor is no more than 450° C.
10. The system of claim 1 wherein the inflow of NH 3 comprises NH 3 vapor at 10-15 bar.
11. The system of claim 1 wherein a conversion of ammonia to hydrogen and nitrogen is in excess of 99%.
12. The system of claim 1 additionally comprising a preheater whereby heat provided by at least one stream selected from the group consisting of a stream of permeated high purity H 2 and a stream of catalytic H 2 combustion exhaust preheats the inflow of NH 3 to the fixed bed reactor.