(45g) Pure Hydrogen and Pure Carbon Dioxide From Gaseous Hydrocarbons Via Chemical Looping Reforming

In chemical looping reforming a metal oxide is circulated between two fluidized bed reactors. In the so-called fuel reactor, a hydrocarbon fuel is partly oxidized by oxygen emitted from the solid oxygen carrier particles. In the so-called air reactor, the oxygen carrier is re-oxidized by air. The amount of air provided limits the available oxygen in the process and determines the final product composition. A dual circulating fluidized bed pilot plant was operated in chemical looping reforming conditions at a scale of 140 kW fuel power with natural gas as fuel. A nickel based oxygen carrier was used as bed material. The results show that the oxygen in the air reactor can be completely absorbed by the solids and that the fuel reactor exhaust gas is a syngas in thermodynamic equilibrium with no methane left at atmospheric pressure. Even though no steam was added to the natural gas feed no carbon formation was found for global excess air ratios larger than 0.4. A process configuration is proposed for production of pure H2 and CO2 from chemical looping reforming. Two separation steps where the pure gases can be obtained are arranged consecutively and the final off gas is largely recycled into the CLR fuel reactor. The performance of the system will depend on the necessary amount of steam to prevent carbon deposition on the particles at low global air/fuel ratios.