Decarbonisation Technology – August 2021

Steam and methane

Catalyst coated tubes surrounded by electrically heated coils

Microwave

Notes: Microwave

plasma would be an alternative to dielectric microwave heating and would allow lower exit gas temperature.

reinventing gas conversion for a cleaner future.” Nu:ionic has developed and validated steam methane reforming based on microwave energy input, a form of electrical reforming. Microwave energy is applied directly into the reforming reactor and penetrates deep into all the catalyst pores. This overcomes one of the issues with traditional reforming where heat and temperature distribution through the catalyst bed is uneven and results in reaction slow spots, meaning that lots of catalyst and a very large reactor are required. Beyond the reduction in methane consumption, the process benefits from a significantly more compact reforming reactor size, simpler materials of construction and an almost instantaneous ramp rate. This means the process is ideal to be combined with variable renewable power such as wind or solar. A traditional SMR takes hours to ramp up due to the heating requirement, and once it is on the flexibility to turn up and down is very limited. “The innovations that we have packed into our process go beyond the microwave,” says Boshoff. “The catalyst must allow the microwave energy to freely flow through it. We do use a nickel-based catalyst because that is a readily available metal, but the trick lies in our choice of catalyst support and the way we have mounted the catalyst on that support.” The process can be fed with low-pressure natural gas or biomethane from the distribution Syngas, ~70% H Notes: 1. Combustion- heated SMR is an alternative to electrical heating. Figure 3 Electrical catalytic steam methane Reforming (eSMR) Syngas, ~70% H

Syngas, ~70% H

Figure 4 Dielectric microwave catalytic steam methane reforming (μSMR)

grid. A compressor boosts the gas up to between 12 and 18 bar in a compact reforming reactor, where the catalyst is directly heated to the reforming temperature by microwave energy. In a conventional steam reformer, a fired heater is required. In that fired heater, combustion superheats the stack gases to 150-300°C above the required process temperature. By directly heating the catalyst with the microwave, energy is efficiently applied in the exact amount required by the reaction. This results in an improvement in overall system efficiency and eliminates the excess heat that is wasted in the reformer stack. After the reformer, a typical chain of shift reactors enriches the hydrogen concentration to around 85%. After those, Nu:ionic has introduced a further innovation: an amine-wash carbon capture system, which removes the carbon dioxide gas prior to hydrogen purification in a traditional PSA system. The PSA tail gas is used to generate the steam that is required to feed the reformer. The carbon capture system effectively removes all the carbon dioxide produced by the process, enabling low-carbon hydrogen production and minimising the size and cost of the PSA equipment.

Jump-starting the hydrogen economy It is hard to imagine what could derail the

development of the emerging hydrogen economy. Positive sentiment and momentum related to the use of hydrogen as a renewable energy vector are