Question
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What are the most attractive long-term options for incorporating autothermal reforming (ATR) and/or partial oxidation (POX) to produce blue hydrogen at near-zero CO2 emissions? Or can CO2 emissions from SMR units be further reduced?
Mar-2023
Answers
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Andrew Layton, KBC (A Yokogawa Company), andew.layton@kbc.global
CO2 emissions from SMRs can be reduced by maximising design efficiency. Compared to units from the 1980s, modern units are typically at least 10% more efficient because they use a PSA to purify hydrogen instead of CO2 scrubbing. In addition, enhancing the design and, to a lesser extent, the catalysts has also improved SMR efficiency. While the efficiency of an existing SMR can be improved to a limited extent, older and less efficient units are replaced rather than upgraded. Reconfiguring or upgrading the SMR furnace is very expensive because the steam generation, process, and flue gas heat recovery system are integrated. Furthermore, it is often necessary to generate more hydrogen and, therefore, build a larger unit.
New SMR units tend to be designed to export less steam or even no steam at all. This leads to substantial reductions of CO2 emissions in the SMR, at least part of which is likely to be offset by steam generation elsewhere unless green electricity can generate steam.
With pre-combustion carbon capture, at least 30% of the CO2 generated will still be released. An SMR equipped with pre-combustion capture will still emit the CO2 from the fuel fired. Furthermore, the carbon in the feed that is not converted to CO2 in the reaction section but downstream in the PSA will not be captured. It will still leave the unit as CO2 from the furnace stack. Thus, higher capture rates require post-combustion capture, which is more expensive in terms of capital expenditures and operating costs.
Finally, ATR and POX do not use separate furnace firing as SMRs do. Therefore, pre-combustion capture allows a larger percentage of CO2 to be captured. As a result, ATR/POX units may be preferred over greenfield SMRs for producing blue hydrogen on a large scale.
Mar-2023
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