The biogas is passing a dryer cooler with separator to avoid liquid water entering the compressor (CO2 and H2S is not aggressive as long as liquid is not present). The gas is compressed by a screw compressor up to 10 bar(g), cooled down and water is separated in the after cooler. Residue water of the ongoing flow is removed by two stage pre-filters. Two stage filters are mounted for extended maintenance interval.
The next step is removing H2S from the gas in a tower filled with the adsorbent SULABEAD®. This adsorbent adsorbs H2S at ambient temperature. The other tower is regenerated by heating the system above 100°C and gas is purged into a collector from which gas is blown into an U tube and burned up to 900° C on the end of which we inject water where H2SO3/4 is created. The injected water is collected from different drain points upstream of the process.
Because of the presence of heavy hydrocarbons as siloxane a guard tower is mounted before gas floods into the membranes.
Now CO2 removal starts in two stage membranes. In the first stage gas is upgraded to the next stage and a mixture of CO2/CH4 is permeated and led back into to the inlet of the compressor, in the second stage green gas is produced with customer required Wobbe index (44-55 mJ/Nm3).
The permeate produced by the first stage is CO2 gas suitable for green house growing.
Other solutions are remove the methane in an incinerator.
For CO2 removal several methods are available:
Growing trees: Most successful and sustainable is growing trees.
Injection in green houses
The permeate gas from the first stage membrane is compressed up to 55 bar(g) and led in to the condenser with liquefies the CO2 gas at 11° C. The liquid CO2 is boosted up to a pressure of 150 bar(g) for the bottle distribution station.
Both packages are chilled water cooled for creating a high efficiency of all apparatus in the process line from compressor reverser up to membranes. This system creates hot water for district heating through a heat pump water chiller.
The actual heating capacity is more than might be expected for the absorbed power due to the condensation heat in the gas dryer and the condenser in the CO2 circuit due to this recovery more energy is recovered, than used.
We have two stage membranes CO2 for upgrading of CH4. In the first stage the CH4 content is increased from 55/65% up to 62/72% depending on inlet percentage. In the second stage final percentage will be reached according to Wobbe index requirement by controlling the CO2 value around between 2 and 10, whatever is required.
Are you interested in useful deployment of your biomass? Do not hesitate to contact us to evaluate all the possibilities.
This project was made possible by a contribution from the European Regional Development Fund as part of OP-South.