WtH (Waste-to-Hydrogen) with CCUS

The process is made up of the following steps:

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Advanced Biofuel Solutions Ltd (ABSL), owns a process where fluidised bed gasifier, plasma furnace and Giammarco-Vetrocoke CO2 capture technologies are utilised to produce hydrogen from RDF or wood.

Powerhouse Energy Group PLC, is one of the world’s first proven, distributed, modular, WtH process. The Powerhouse process can 1 tonne of road-fuel quality hydrogen or 58 MWh of exportable electricity per day from 25 tonnes of plastic.

RWE is investing on a process where torrefaction, entrained flow gasifier and Air Liquid WGS and Rectisol technologies are utilised to produce hydrogen from SRF and dried sewage sludge.

As per gasification of MSW and water-gas shift reaction of CO (shown below), WtH technologies similar to WtE technologies produce the maximum CO2 compared to the other WtV technologies.

C + 0.5 O2 —> CO

CO + H2O —> CO2 + H2

CO2 can be captured at high pressures within WtH technologies; therefore, CCUS cost of the WtH technologies is lower than WtE technologies and is higher than other WtV technologies.

There are two demonstrated types of WtH technology, namely Fluidised Bed (FB) and Entrained Flow (EF).

1. WtH-FB

In the FB technology, fluidised bed gasifier operates at atmospheric pressures and generated crude syngas is then heated and exposed to oxygen free radicals within a plasma furnace to catalyse the reformation of tar.

The tar free syngas is cooled in a waste heat boiler with boiler feed water and the produced steam is taken to be used elsewhere in the process. The gas is filtered to remove particulates and scrubbed to remove acid and alkali contaminants. At this point cool, clean, chemical grade syngas is available.

The process is summarised in Figure 8.

Figure 8: WtH-FB schematic flow diagram

2. WtH-EF

In the EF technology, entrained flow gasifier operates at high pressures (up to 40-50 barg) and generated crude syngas with minimum tar content due to its higher operating temperature compared to fluidised bed gasifier. The tar free syngas is cooled and saturated with water in a direct cooling scrubber coupled with the gasifier and a black water treatment system. To operate the entrained flow gasifiers, it is required to have a fairly uniform feedstock, namely torrefied and milled feedstock. Figure 9 present schematic flow diagram of the gasification process for a WtH-EF technology.

Figure 9: WtH-EF gasification schematic flow diagram