Solar Hydrogen by Thermal Decarbonization of Fossil Fuels

Funding source: external pageBfE - Swiss Federal Office of Energy, ETH-Project Nr. TH-29'/99-4

Background – Hybrid solar/fossil endothermic processes, in which fossil fuels are used exclusively as the chemical source for H2 production, and solar energy as the source of high-temperature process heat, offer viable and efficient routes for fossil fuel decarbonization and CO2 mitigation. The advantages of the solar-driven process are three-folded: 1) the discharge of pollutants is avoided; 2) the gaseous products are not contaminated; and 3) the calorific value of the fuel is upgraded.

Objective – Two decarbonization routes for H2 production from fossil fuels are investigated (see adjacent diagram): 

(a)    thermal cracking:     CnHm = nC(gr) + (m/2)H2

(b)    thermal gasification/reforming:     CnHm + nH2O = nCO + (m/2+n)H2

Both routes proceed endothermically at T > 1500 K.

Milestones – The project encompasses:

1st phase)    Establish the chemical boundary conditions for the solar reactor design and a base for evaluating the process efficiency.

2nd phase)    Formulate solar reactor modeling and use it as a tool for pre-design and optimization.

3rd phase)    Design, fabricate, and test a reactor prototype; determine its energy conversion efficiency; validate solar reactor modeling.

Collaboration – NREL (USA), University of Colorado (USA), Weizmann Institute of Science (IL)

Scientific and technological challenges

  • Modeling radiation heat exchange in a gas-particle flow undergoing a heterogeneous chemical transformation, in which optical properties, species composition, and phases vary as the chemical reaction progresses. The gas-particle suspension is modeled as a non-gray non-isothermal absorbing-emitting-scattering media. Such modeling finds application in several other fields (e.g., combustion phenomena).
  • Design of a high-temperature chemical reactor based on the direct high-flux irradiation of reactants. Reactor concept for route (a): vortex flow of natural gas laden with C(gr)-particles that serve as radiant absorbers and nucleation sites. Reactor concept for route (b): vortex-flow of steam laden with coal particles that serve as radiant absorbers and chemical reactants.

Project-related Publications

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