Decarbonisation Technology – August 2021

CO 2 capture and natural gas savings in SMR process Study of the efficiency optimisation of an H 2 production plant through natural gas reforming and its contribution to preserving the environment

Marcelo Tagliabue Air Liquide Argentina S.A.

S ixty-six per cent of the world’s hydrogen production, estimated at 70 million tonnes, is used as an input in refining oil, the production of ammonia, methanol and, in recent years, in the development of engines that run on hydrogen (H 2 ). At the start of 2021, 70% of the world’s economy has made ambitious commitments on carbon neutrality, and H 2 will play a fundamental role in reducing emissions. Currently, the best-known and most developed production methods are: • Electrolysis of water : currently limited to 4% of H 2 production, it is achieved by dissociating the water molecule into its components (hydrogen and oxygen) using electricity. It is known as green H 2 . • Steam reformed from

availability of H 2 has become a critical point in modern refineries. This article looks at the efficiency optimisation of an H 2 production plant through natural gas reforming and its contribution to preserving the environment. One of our business units consists of an SMR, mainly to satisfy the H 2 needs of a refinery. Additionally, part of the CO 2 generated is captured, purified and sold to the local market with food grade. In a modern, natural gas-fired steam reforming H 2 plant, up to approximately 60% of the total CO 2 produced is contained in the syngas produced (and then in the tail gas pressure swing absorption, PSA). The remaining 40% is the product of the combustion of the additional

Flue gas to atm.

mol %

natural gas (SMR ): it accounts for 96% of current production worldwide. It is a

Q = Heat removed DE-S = Desulphurisation PSA = Pressure swing absorption HTS = High temperature shift unit

N O

60.88

1.20

mol %

CO 19.83 HO 17.37

H N

75.64

0.35

thermochemical process that requires high temperatures and a subsequent purification of the final stream, obtaining the so-called grey H 2 . If you capture the CO 2 produced in this process, you are in the presence of so-called blue H 2 . To achieve the highest possible conversion of crude oil into gasoline, gas oil or middle distillates, the

15.43

Methane 3.26 CO 5.04

STM

SMR

DE-S

HTS

mol %

H N

27.16

Make-up fuel

PSA

1.01

46.17

Methane 9.75 CO 15.07

PSA purge gas

Figure 1 Typical H 2 plant