References

J.G. van Bennekom, R.H. Venderbosch, D. Assink, K.P.J. Lemmens, H.J. Heeres, Bench scale demonstration of the Supermethanol concept: The synthesis of methanol from glycerol derived syngas, Chem. Eng. J., 207-208 (2012) 245-253.

Explorative catalyst screening studies on reforming of glycerol in supercritical water, J.G. van Bennekom, V.A. Kirillov, Y.I. Amosov, T. Krieger, R.H. Venderbosch, D. Assink, K.P.J. Lemmens, H.J. Heeres, J. Supercrit. Fluids, 70 (2012) 171-181.

Reforming of methanol and glycerol in supercritical water, J.G. van Bennekoma, R.H. Venderbosch, D. Assink, H.J. Heeres, J. of Supercritical Fluids 58 (2011) 99– 113

Supermethanol: reforming of crude glycerine in supercritical water to produce mehtanol for re-use in biodiesel plants, J.G van Bennekom, J. Vos, R.H. Venderbosch, M.A. Paris Torres, V.A. Kirilov, H.J. Heeres, Z. Knez, M. Bork,J.M.L. Penninger, 17th European biomass conference and exhibition - Hamburg, 29 june – 3 july, 2009

Biomass gasification in near- and super-critical water: status and prospects, Matsumura, Yukihiko and Minowa, Tomoaki and Potic, Biljana and Kersten, Sascha R.A. and Prins, Wolter and Swaaij van, Willibrordus P.M. and Beld van de, Bert and Elliott, Douglas C. and Neuenschwander, Gary G. and Kruse, Andrea and Antal Jr., Michael Jerry (2005) Biomass and Bioenergy, 29 (4). pp. 269-292.

Gasification of biomass in supercritical water, B. Potic, L.van de Beld, D. Assink, W. Prins and W.P.M. van Swaaij, , Amsterdam conference, 2002

SWS process for production of hydrogen integrated with generation of clean energy, J.M.L. Penninger, B.M. Wagenaar, D. Assink, L. van de Beld, 1st European Hydrogen Conference, Grenoble France, September 2003

Biomass and waste conversion in supercritical water for the production of renewable hydrogen, L. van de Beld, B.M. Wagenaar, D. Assink, B. Potic, S. Kersten, W. Prins, W.P.M. van Swaaij, J.M.L. Penninger, 1st European Hydrogen Conference, Grenoble France, September 2003

Exploring new production methods of hydrogen/natural gas blends for mixing into the natural gas network of the Netherlands, L. van de Beld, I. Bouwmans, P.A.M. Claassen, K. Hemmes, H. de Wit, N. Woudstra, Th. Woudstra, J.L. Zachariah, ECOS 2003, Denmark

Production of Biofuels via Hydrothermal Conversion, in: Handbook of Biofuels Production: Process and Technologies, SRA Kersten, D Kneẑeviḉ, RH Venderbosch, 2011, Woodhead Publishing Limited, ISBN 978-1-84569-510-1

Contact

For more information please contact Bert van de Beld.

Contact office@btgworld.com

Contact +31 (0)53 486 1186

Reforming in supercritical water

Reforming in supercritical water

Supercritical water (SCW) exists at pressures higher than 221 bar and temperatures above 374 °C. By treatment of biomass in supercritical water (and in the absence of added oxidants) organics are converted into fuel gases and are easily separated from the water phase by cooling to ambient temperature. The produced high-pressure (HP) gas is rich in hydrogen.

Process Chemistry

Characteristic of the SCW-organics interactions is a gradually changing involvement of water with the temperature. With temperature increasing to 600 °C water becomes a strong oxidant and results in complete disintegration of the substrate structure by transfer of oxygen from water to the carbon atoms of the substrate. As a result of the high density carbon is preferentially oxidized into CO2 but also low concentrations of CO are formed. The hydrogen atoms of water and of the substrate are set free and form H2. A typical overall reaction for glucose can be written as:

2 C6H12O6 + 7 H2O => 9 CO2 + 2 CH4 + CO + 15 H2

Process description

The RSW (Reforming in Supercritical Water) process consists of a number of unit operation as feed pumping & pressurizing, heat exchanging, reactor, gas-liquid separators and if desired product upgrading. The reactor operating temperature is typically between 600 and 650 °C; the operating pressure is around 300 bar. A residence time of up to 2 minutes is required to achieve complete carbon conversion, depending on the feedstock. Heat exchange between the inlet and outlet streams from the reactor is essential for the process to achieve high thermal efficiency. The two-phase product stream is separated in a high-pressure gas-liquid separator (T = 25 - 300 °C), in which a significant part of the CO2 remains dissolved in the water phase.

Reforming in supercritical water

Possible contaminants like H2S, NH3 and HCl are likely captured in the water phase due to their higher solubility, and thus in-situ gas cleaning is obtained. The gas from the HP separator contains mainly the H2, CO and CH4 and part of the CO2. In a low pressure separator a second gas stream is produced containing relative large amounts of CO2, but also some combustibles. This gas can e.g. be used for process heating purposes.

Feedstock

Reforming in supercritical water

The RSW process is in particular suitable for the conversion of wet organic materials (moisture content 70-95%), which can be renewable or non-renewable. The focus of BTG is completely on liquid biomass streams like glycerol or the aqueous phase of pyrolysis oil. In principal, slurries should also be possible, but feeding is extremely difficult and costly.

Application of the product gas

The primary gas produced by the RSW process differs significantly from the syngas that is produced in common thermal biomass gasifiers:

  • Gas is produced at high pressure
  • Hydrogen content is high
  • No dilution by nitrogen

The produced gas is clean (no tar, or other contaminants in high pressure gas even if produced in the process). The gas always contains high amounts of hydrogen; the amounts of CO and CH4 depend on the operating conditions. Based on these process characteristics three main applications of the gas are identified:

  • Hydrogen production (maximise H2)
  • Synthesis gas production (minimise CH4)
  • Substitute natural gas (minimise CO)

SuperHydrogen Project

Reforming in supercritical water

The “SuperHydrogen” project is meant to develop the Supercritical Water (SCW) Gasification process for cost-effective conversion of wet biomass and waste into clean, renewable hydrogen with an energy efficiency to pure hydrogen above 60%.

The RSW process enables the conversion of especially wet biomass (~ 70 – 95 wt% moisture). The product gas is clean, rich in H2 and CH4, and available at high pressure. In a high pressure gas-liquid separator the gases are separated from the water. Due to the high pressure significant part of the CO2 is dissolved in the water phase and will be released in a low pressure gas-liquid separator. The process is now further developed and evaluated to convert aqueous by-products from pyrolysis oil upgrading into an hydrogen rich gas.

SuperMethanol Project

In the GtM (Glycerol to Methanol) concept the production of renewable methanol from glycerol is investigated. Methanol is one of the feedstocks for biodiesel production, while glycerol is a by-product. When glycerol is converted to methanol, the methanol can be re-used in the biodiesel production process. This process makes the biodiesel proces ‘greener’, diminishes the dependency on volatile market prices, secures the supply of methanol and improves biodiesel economics.

Reforming in supercritical water

The GtM concept consists of two processes which are integrated. In the first process glycerol is converted in SCW to H2, CO, CO2, CH4 and higher hydrocarbons. The gas is separated from the water phase and in the second process this gas is converted to methanol in a packed bed reactor. Both processes are operated at a pressure of approximately 250 bar. The methanol is called supermethanol, because the syngas for the methanol is obtained in a reforming process in supercritical water.

The reforming in SCW and methanol synthesis are combined in the GtM process. This is less energy intensive than compressing a gas, which is required in conventional methanol synthesis. High pressures are favourable for both the position of the equilibria and the reaction rates in methanol synthesis. In the GtM concept the conditions for methanol synthesis are such that almost complete conversion of the limiting component is obtained per pass through the reactor allowing the omission of recycle streams of unconverted syngas.

Reforming in supercritical water