Background of the research

The process of reforming in supercritical water (RSW) has the earliest literature references dating back to 1985. Still, the technology is not well developed. Unit operations well established for operation at atmospheric pressure are rarely applicable to supercritical conditions (water becomes supercritical at t=374 °C and P=22 MPa). Reactor concepts are to be developed, while effects of process parameters on dedicated feedstocks are still to be established. Heat recovery appears to be essential for the supercritical water reforming process to be energetically viable (RSW Process).

The work in this project expands on expertise of the project partners on the reforming of biomass in supercritical water generated in earlier research projects, including SUPERHYDROGEN. In the SUPERHYDROGEN project, which ran from December 2001 until November 2005, a large number of biomass types were tested for their suitability as feedstock for reforming. Glycerine was identified as the ideal feedstock for this technology.

Next, the technical and economic potential to substitute fossil fuel based methanol with “renewable” methanol, produced through supercritical reforming of crude glycerine, was explored. The exploration study showed the glycerine-to-methanol (GtM) process to be very promising.

A simplified diagram of the proposed system, integrated in a biodiesel production plant and with global mass balances, is shown above/below. Through GtM more than 50% of the required methanol may be produced, while some combustible gases (mainly CH4 and C2+) are returned to the biodiesel production plant. Water is required as a feed, while the ash in the crude glycerine is the main by-product together with CO2.

Simplified diagram of a biodiesel production unit coupled with the GtM process.