The main advantages of Coal-to-SNG systems are their unique abilities for backing up the increasing content of fluctuating renewable energies (i.e. wind, photovoltaics (pv)) in the European electricity grid. As an alternative for water electrolysis and subsequent methanation, energy from coal as Substitute Natural Gas (SNG) can be continuously stored in the existing natural gas grid infrastructure in order to provide energy to flexible gas turbines which combine ideally with wind and pv.
The state-of-the-art for Coal-to-SNG systems comprises large scale systems with entrained flow or oxygen-blown fixed bed gasifiers including an extensive cleaning of the syngas. Cold gas cleaning by means of Rectisol process implies scrubbing of the gas at temperatures of - 40°C to -70°C with significant efficiency losses and an extraordinary high technical effort and again large-scale systems.
However grid injection requires usually medium-scale systems in order to use existing grid infrastructure due to locally limited gas injection capacities. The first CO2freeSNG project proved the feasibility of such medium-scale systems (50- 500 MW) combined with gas cleaning and scrubber systems at elevated pressures and temperatures. The proposed continuation of the project focuses on a pre- pilot scale demonstration (150 kW) of the complete process chain developed within the former project in order to enhance the technological basis for a demonstration in the pilot scale (i.e. 5-10 MW).
The main challenge of this approach is the CO2 removal in this scale and a simplified integration of sulphur capture. Thus the CO2freeSNG2.0 project will focus on a simplified system to remove CO2 , H2S, organic sulphur and excess steam by means of a specially adapted pressurized water/carbonate scrubbing process as simulations in the preceding project indicated that such systems may capture CO2 and sulphur components most effectively at reduced costs.
So the main objectives of the project are
1. the integrated process optimization and economic feasibility of medium-scale SNG plants based on process simulations (Work package 1)
2. extensive lab-scale testing of the integrated CO2 removal and catalytic methanation (Work packages 2 and 3)
3. testing of the complete process chain at a pre-pilot scale plant with all integrated technologies (Work packages 4 and 5)