Pre-combustion packed bed chemical looping (PCCL) technology for efficient H-2-rich gas production processes

摘要

A novel reactor system is presented and investigated for the production of a hydrogen rich gas stream for power or ammonia production, based on pre-combustion chemical looping (PCCL) technology using dynamically operated packed bed reactors. In this process, the oxygen carrier (OC) is alternately oxidized with a gas mixture of air and steam to produce a H-2/N-2 product gas stream combining oxidation by air and water-splitting, and subsequently reduced with syngas producing a concentrated CO2 stream. The process is carried out at elevated pressure, but at intermediate temperature (in the range of 600-900 degrees C), which allows circumventing the extremely high temperatures required in chemical-looping combustion. In addition, the N-2/H-2 gas stream can be produced at the required composition for ammonia production, rendering this process also competitive with the conventional ammonia production. A preliminary experimental study has been carried out in a 2 kW(th) packed bed reactor using an iron-based oxygen carrier. The influence of the operating temperature and the initial solid composition during the oxidation cycle on the H-2-rich gas yield has been investigated. The complete reduction to pure iron reduces the reactivity of the material due to sintering, whereas a controlled reduction to wustite (FeO) allows to maintain a higher stability of the material, although the oxygen capacity is decreased.