Biogas Upgrading

The objective of the gas line of the ULISES Project is to achieve a more efficient use of biogas at the WWTP. A new concept biogas scrubber will convert biogas into biomethane (composition above 85% of CH4), removing sulphur and other undesirable compounds from biogas and producing a biofuel for natural gas cars. About 2/5 of the biogas produced at the plant is currently used in boilers to heat the digesters and the rest is disposed of in a flare, where CH4 is transformed into CO2 and liberated to the atmosphere without use. LIFE ULISES project proposes an efficient valorization of this gas by application of an up-grading technique as an automotive biofuel.

Upgrading plant design, developed by Aqualia, took into account its previous experience in biogas upgrading plants based on ABAD Bioenergy® technology, patented by Aqualia. References such as the upgrading plants of Guadalete WWTP (Jerez de la Frontera, Cadiz, Spain), La Gavia WWTP (Madrid, Spain), El Torno WWTP (Chiclana de la Frontera, Cadiz, Spain) or Lleida WWTP, endorse Aqualia with the required experience to deal with the design and construction of this Demo plant.

The biogas upgrading process using ABAD Bioenergy® technology consists of two processes:

  • A first absorption process, where biogas flows in countercurrent against settled wastewater in order to remove CO2 and most of the H2S using two absorption columns connected in series.
  • A second adsorption process called refining, where the rest of the minority compounds such as hydrogen sulfide, and siloxanes, as well as moisture, are removed.

After verifying the optimum quality of the biomethane produced with an online monitoring system, the gas is stored in high pressure bottles, for the latter refueling of several natural gas vehicles. In this project, at least one car from Aqualia service will be powered with biomethane, to which periodical checks of the engine and mileage follow up will be carried out. Once the biomethane quality will be validated, a wider vehicle fleet from Aqualia or the Council of Almería would be considered to be fueled with biomethane.

The reactor will operate with a treatment capacity up to 15 Nm3/h of biomethane, using raw wastewater as scrubbing liquid, simplifying the operation of the plant. Main operating variables are controlled by a PLC, integrating several PID and on-off controllers. A robust instrumentation, control, and automation (ICA) system are implemented in a SCADA, enabling its optimization.

With the contribution of the European Union

LIFE programme LIFE18 ENV/ES/000165

 

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