Enhanced hydrogen production process from coal integrated with CO ₂ separation using dual chemical looping

An advanced hydrogen production system with CO₂ separation is introduced in this paper, which is based on HyPr-RING and enhanced by dual chemical looping. The first chemical looping is for CO₂ separation using lithium ortho-silicate (Li₄SiO₄) as a solid CO ₂ sorbent which can absorb CO₂ around 650 °C with an exothermic reaction and regenerate around 800 °C. Another chemical looping by red-ox reaction of a metal oxide is applied to oxygen carrier in the gasification reactor and heat source to regenerate the sorbent. Copper oxide (CuO) is one of the suitable materials for oxygen carrier because reduction of CuO by carbon is exothermic reaction which benefits energy balance, while reduction of nickel oxide or hematite by carbon is endothermic reaction. Dry mixtures of copper oxide and graphite in various ratio and sieve mesh size were dropped into the reactor preheated at various temperatures and each component of product gas was quantified by gas meter and GC/TCD. Hydrogen production from graphite was confirmed even at around temperature of CO₂ absorption, but in any test conditions, a simple mixture of CuO and graphite mainly produced CO₂ by complete oxidation.