Hydrogen recovery from ROG Part 2: membrane separation and compression
Using next-generation separation membranes to recover unused hydrogen
Zach Foss Divigas
R efinery off-gas (ROG) streams will be a crucial source of hydrogen (H2) in refineries as product regulations and crude processing requirements drive increased H2 demands. The need will further increase as energy com- panies look to limit heavy sources of carbon within their operations to meet net zero goals by 2050. As refiners shift from steam methane reformer (SMR)- produced grey H2 to green or blue, costs will rise, increasing the necessity for downstream H2 recovery and purification to remain economically viable. Part 1 in PTQ Gas 2024 previewed sample ROG streams produced from several types of units for their poten- tial separation and purification via Divi-H, a proprietary next-generation H2 separation membrane. It demonstrates separation costs as low at $0.015/kg H₂ separated, with
return on investments (ROIs) exceeding 2,400% over the life of the product when compared to grey H₂ production. Part 2 will analyse its effectiveness in hydrotreaters, hydro- crackers, isomerisation units, and catalytic reformers. Hydrotreaters and hydrocrackers Hydrotreaters and hydrocrackers are similar use cases with a few key variables. ROG pressure can vary between these units depending on the level of reaction severity needed to meet product specifications and the composition of the feedstock. The gasoil hydrotreater, for example, can operate at pressures five times higher than the naphtha hydrotreater. This high-pressure operation makes its ROG ideal for mem- brane separation. There is a significant driving force in the
Stream
Feed
Feed
Permeate
Fibre type
Feed purity
Permeate Recovery
Total
Lifetime separation cost ($/kg)
flow rate pressure pressure
purity
module
(NM 3 /hr)
(bar)
(bar)
cost
GO hydrotreater
20,000
135
63
High throughput
75%
95.31%
93.45%
$800,000
$0.015
95% purity
– single stage
GO hydrotreater
20,000
135
84
High purity
75%
99.00%
93.34% $10,480,000
$0.200
99% purity
– single stage
GO hydrotreater
20,000
135
40
Balanced and high purity – two stage
75%
99.91%
88.94% $18,560,000
$0.371
99.9% purity Hydrocracker 95% purity Hydrocracker 99% purity Hydrocracker 99.9% purity
10,000
120
46
Balanced
50%
95.07%
90.77%
$2,320,000
$0.138
– single stage
10,000
120
36
High purity
50%
99.04%
89.99%
$2,480,000
$0.147
– single stage
10,000
120
20
Balanced and high purity – two stage High throughput
50%
99.90%
85.43%
$5,920,000
$0.370
Diesel hydrotreater
15,000
68
39
80%
95.19%
94.53%
$1,520,000
$0.036
95% purity
– single stage
Diesel hydrotreater
15,000
68
20
Balanced throughput
80%
99.03%
94.48%
$2,720,000
$0.064
99% purity
– single stage
Diesel hydrotreater
15,000
68
23
High throughput and high purity – two stage
80%
99.90%
89.44% $12,880,000
$0.320
99.9% purity
Naphtha hydrotreater 30,000
40
7
High throughput
65%
95.06%
92.34%
$2,160,000
$0.032
95% purity
– single stage
Naphtha hydrotreater 30,000
40
17
High purity
65%
99.06%
92.67% $26,880,000
$0.397
99% purity
– single stage
Naphtha hydrotreater 30,000
40
12
Balanced and high
65%
99.91%
85.36% $38,080,000
$0.592
99.9% purity purity – two stage Table 1 Hydrotreater and hydrocracker analysis – no compression
15
PTQ Q3 2024
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