Enhanced hydrogen production from thermochemical processes

To alleviate the pressing problem of greenhouse gas emissions, the development and deployment of sustainable energy technologies is necessary. One potentially viable approach for replacing fossil fuels is the development of a H2 economy. Not only can H2 be used to produce heat and electricity, it is also utilised in ammonia synthesis and hydrocracking. H2 is traditionally generated from thermochemical processes such as steam reforming of hydrocarbons and the water-gas-shift (WGS) reaction. However, these processes suffer from low H2 yields owing to their reversible nature. Removing H2 with membranes and/or extracting CO2 with solid sorbents in situ can overcome these issues by shifting the component equilibrium towards enhanced H2 production via Le Chatelier's principle. This can potentially result in reduced energy consumption, smaller reactor sizes and, therefore, lower capital costs. In light of this, a significant amount of work has been conducted over the past few decades to refine these processes through the development of novel materials and complex models. Here, we critically review the most recent developments in these studies, identify possible research gaps, and offer recommendations for future research

Calcium precursors for the production of CaO sorbents for multicycle CO2 capture

A screening of potential calcium precursors for the production of CaO sorbents for CO capture at high temperature was conducted in this work.The precursors studied include microsized calcium carbonate (CC-CaO), calcium hydroxide (CH-CaO), nanosized

Hydrogen production from a victorian brown coal with in situ co2 capture in a 1 kwth dual fluidized-bed gasification reactor

The removal of CO during coal gasification will improve H yield by promoting coal gasification reactions toward the production of H . In this work, coal gasification with in situ CO capture has been investigated in a 1 kWth dual fluidized-bed gasification reactor. A Victorian brown coal was used as the feed stock. Coal gasification tests at 700 °C were performed with silica sands as the heat carrier and synthetic CaO sorbent for comparison. It was found that the addition of the sorbent improved H2 concentration in the outlet of the fuel reactor by nearly 53%. Carbon conversion rate was also increased and a maximum of ̃33% was reported. Calcium aluminate cement was used as a binder for the fabrication of the synthetic CaO sorbent, in an attempt to enhance its mechanical strength and improve its chemical properties

Durability of CaO–CaZrO₃ Sorbents for High-Temperature CO₂ Capture Prepared by a Wet Chemical Method

Powders of CaO sorbent modified with CaZrO have been synthesized by a wet chemical route. For carbonation and calcination conditions relevant to sorbent-enhanced steam reforming applications, a powder of composition 10 wt % CaZrO/90 wt % CaO showed an initial rise in CO uptake capacity in the first 10 carbonation-decarbonation cycles, increasing from 0.31 g of CO/g of sorbent in cycle 1 to 0.37 g of CO/g of sorbent in cycle 10 and stabilizing at this value for the remainder of the 30 cycles tested, with carbonation at 650 C in 15% CO and calcination at 800 C in air. Under more severe conditions of calcination at 950 C in 100% CO, following carbonation at 650 C in 100% CO, the best overall performance was for a sorbent with 30 wt % CaZrO/70 wt % CaO (the highest Zr ratio studied), with an initial uptake of 0.36 g of CO/g of sorbent, decreasing to 0.31 g of CO /g of sorbent at the 30th cycle. Electron microscopy revealed that CaZrO was present in the form of ≤0.5 μm cuboid and 20-80 nm particles dispersed within a porous matrix of CaO/CaCO; the nanoparticles are considered to be the principal reason for promoting multicycle durability