Ultra pure water feed
CO & H
Preheater
Steam /CO superheater
Condenser
Water outlet
Compressor
Sweep air feed
Waste heat or electrical power
Oxygen heat recovery
Top-up heater
Air & oxygen exhaust
Vapouriser
SOE stack + –
Recti er
CO feed
Transformer
AC
Electricity
DC
Figure 4 Solid oxide co-electrolysis process for syngas generation
No. WO/2020/114899 A1, 2020 ). The equipment is similar to classical natural gas-fed POx reactors currently used by industrial gas majors, such as Linde’s POx reactor at La Porte and Singapore. As with the classical POx units, an air separation unit (ASU) or pipeline is used to supply the oxygen. VTT, a Finnish research institute, patented a CPOx process for the RWGS reaction using a rhodium-based catalyst ( International Patent No. W0/2019/175476 A1, 2019 ). This process operates at 800 to 950°C and 20 bar, lower than the range proposed by Shell in its non-catalytic RWGS POx reactor. Generally, the goal is for a catalyst to enable a process to operate at a reduced temperature. USA Patent No. US 2023/0264955 A1, 2023 describes a CPOx process using a nickel-based catalyst. This technology would resemble an autothermal reformer. It proposes to use the oxygen and hydrogen from water electrolysis to feed the RWGS POx reactor. This process integration would reduce or eliminate the need for an air separation unit or pipeline oxygen supply. The syngas processes described herein show we can build carbon circularity into commercially viable chemical processes. As these processes reach meaningful scale, they represent a win-win for more sustainable use of hydrocarbons. VIEW REFERENCES
autothermal reforming, and gas heated reforming for syngas or hydrogen production. It reacts oxygen and methane at high temperature without relying on a catalyst. Air Liquide operates a POx unit at Stade in Germany to supply syngas to the nearby DOW Chemicals facility. During a recent upgrade, Air Liquide enabled CO 2 to be introduced with the oxygen and natural gas to the POx unit to increase the syngas yield. The implication is that captured and recycled CO 2 can be used to produce syngas, making a portion of that syngas circular. This process at Stade still consumes natural gas and emits some CO 2 . However, the upgrade resulted in a 15% increase in energy efficiency, with CO 2 emissions reduced by 15,000 tonnes per year. Every meaningful step towards net zero must be applauded. POx and CPOx for e-syngas POx of green hydrogen, oxygen, and captured, recycled CO 2 produces e-syngas. During this process, hydrogen combines with oxygen and CO 2 to produce water and CO during the RWGS reaction. POx can be enhanced with the use of a catalyst, in which case the term catalytic POx (CPOx) is used. The heat and high temperature required in POx and CPOx RWGS systems are derived from thermal oxidation of green hydrogen with oxygen. Shell has patented a non-catalytic, POx-based RWGS system that operates in the temperature range of 1,000 to 1,500°C ( International Patent
Stephen B. Harrison sbh@sbh4.de
www.decarbonisationtechnology.com
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