H2 production with CO2 capture by sorption enhanced chemical-looping reforming using NiO as oxygen carrier and CaO as CO2 sorbent

A novel process for conversion of hydrocarbons to H2 has been examined. The process, sorption enhanced chemical-looping reforming, involves three interconnected reactor vessels. In the reforming reactor, hydrocarbon fuel is partially oxidized with oxygen provided via a solid oxygen carrier such as NiO. Resulting CO is shifted instantly to CO2 via sorption enhanced water–gas shift, facilitated by the capturing of CO2 with a solid CO2 sorbent such as CaO. Ni and CaCO3, are regenerated downstream in separate reactors. The process produces H2, CO2 and N2 of reasonable purity in separate streams, without need for additional gas separation equipment. The characteristics of the process have been examined by thermodynamic calculations and by process modeling. At 1 bar it could produce > 2.8 mol H2 with a purity of > 98 vol.% for each mol CH4 added as fuel, while capturing > 95% of added carbon as CO2. Increasing the pressure reduces the performance due to lower conversion of CH4. Involved reactions have also been examined in a fluidized-bed reactor at 600–750 °C, with particles of NiO and CaO as bed material and CH4 mixed with steam as fuel. The CH4 conversion was incomplete but the results fitted with theory and gas with a H2/(H2 + CO + CO2) ratio of more than 98% was produced at 600 °C.

► A novel method to convert hydrocarbon fuels to H2 with inherent CO2 capture has been examined. ► The process is a hybrid between chemical-looping reforming and sorption enhanced reforming. ► Hydrocarbons are oxidized with solid NiO and steam and CO2 is captured by carbonation of CaO. ► Both reactions take place in one single reactor vessel at 600–750 °C. ► The process has been examined by modeling as well as by experiments in a fluidized bed reactor.