• Energy Research

This paper reviews the advances of enhanced thermo-chemical processes applying H2-selective membrane reactors andin situCO2capture for selective H2production.

Sewage sludge disposal is troublesome because of the presence of microbes, toxins, and heavy metals in it. Co-gasification of sewage sludge with wood is a promising pathway to dispose of sewage sludge and generate usable syngas, simultaneously. By using a sorbent for in situ sorption of CO2, H2 fraction in the generated syngas can be enhanced considerably. An equilibrium model was developed taking wood and sewage sludge as the model compounds and CaO as the sorbent. This evaluation was performed by employing ASPEN PLUS (V 8.8) software. Principle of Gibbs free-energy minimization was adopted to predict the outlet gas composition and gas yield. The impact of reactor temperature (600 to 900 °C) and sludge content (0 to 100 wt % at 700 °C) in the feedstock on syngas yield and constituents were assessed. With 30 wt % sludge, maximum gas yield was observed as 0.526 kg h–1 at 900 °C while minimum CO2 fraction was achieved at 700 °C. At 700 °C, the highest gas yield of 0.251 kg h–1 was recorded at 50 wt % sludge...

Abstract This research focuses on parametric influence on product distribution and syngas production from conventional gasification. Three experimental parameters at three different levels of temperature (700, 800 and 900 °C), sugarcane bagasse loading (2, 3 and 4 g) and residence time (10, 20 and 30 min) were studied using horizontal axis tubular furnace. Response Surface Methodology supported by central composite design was adopted in order to investigate parameters impact on product distribution (i.e., gas, tar and char) and gaseous products (i.e., H2, CO, CO2 and CH4). The highest H2 fraction obtained was 42.88 mol% (36.91 g-H2 kg-biomass−1) at 3 g of sugarcane bagasse loading, 900 °C and 30 min reaction time. The temperature was identified as the most influential parameter followed by reaction time for H2 production and diminishing the bio-tar and char yields. An increase in sugarcane bagasse loading, on other hand, favored the production of bio-tar, CO2 and CH4 production. The statistical analysis verified temperature as most significant (p-value 0.0008) amongst the parameters investigated for sugarcane bagasse biomass gasification.

Cobalt oxide silica membranes were prepared and tested to separate small molecular gases, such as He (dk = 2.6 Å) and H2 (dk = 2.89 Å), from other gases with larger kinetic diameters, such as CO2 (dk = 3.47 Å) and Ar (dk = 3.41 Å). In view of the amorphous nature of silica membranes, pore sizes are generally distributed in the ultra-microporous range. However, it is difficult to determine the pore size of silica derived membranes by conventional characterization methods, such as N2 physisorption-desorption or high-resolution electron microscopy. Therefore, this work endeavors to determine the pore size of the membranes based on transport phenomena and computer modelling. This was carried out by using the oscillator model and correlating with experimental results, such as gas permeance (i.e., normalized pressure flux), apparent activation energy for gas permeation. Based on the oscillator model, He and H2 can diffuse through constrictions narrower than their gas kinetic diameters at high temperatures, and this was possibly due to the high kinetic energy promoted by the increase in external temperature. It was interesting to observe changes in transport phenomena for the cobalt oxide doped membranes exposed to H2 at high temperatures up to 500 °C. This was attributed to the reduction of cobalt oxide, and this redox effect gave different apparent activation energy. The reduced membrane showed lower apparent activation energy and higher gas permeance than the oxidized membrane, due to the enlargement of pores. These results together with effective medium theory (EMT) suggest that the pore size distribution is changed and the peak of the distribution is slightly shifted to a larger value. Hence, this work showed for the first time that the oscillator model with EMT is a potential tool to determine the pore size of silica derived membranes from experimental gas permeation data.

Liquid organic hydrogen carriers (LOHCs), such as methanol and formic acid, offer a reliable solution for the challenges associated with transporting and storing gaseous hydrogen. However, the current industrial LOHCs are costly and in limited supply due to complex synthesis methods involving gasification and Fischer-Tropsch synthesis. An alternative approach utilizing efficient pyrolysis methods can convert biomass into substances that mimic LOHCs, making them a promising avenue for hydrogen storage. Compounds with a high hydrogen content, including glycolaldehyde, acetic acid, and acetol, hold potential as effective LOHCs. This study seeks to assess how the specific properties of biomass impact the resulting products and target molecules, focusing on identifying the primary sources of LOHC compounds. The experimental results indicate that glycolaldehyde primarily originates from cellulose, while acetic acid is mainly derived from hemicellulose. Acetol is produced from both cellulose and hemicellulose. At a pyrolysis temperature of 500 °C and a particle size of 0.38–0.83 mm, corn cob yields a higher quantity of glycolaldehyde, acetic acid, and acetol (107 mg/g) compared to rice husk (85.6 mg/g) and pine (68.9 mg/g) due to its significant cellulose and hemicellulose content. Notably, the primary sources of these hydrogen storage molecules during pyrolysis are the initial biomass pyrolysis products rather than secondary reactions.

Brief introduction of research on rice husk and rice straw torrefaction.

Abstract Torrefaction is an effective pretreatment process of biomass to enhance energy density and reduce moisture and oxygen contents. The kinetics analysis is important to estimate the torrefaction efficiency and understand the thermal degradation characteristics of torrefied biomass. In this study, the pyrolysis kinetics (Flynn–Wall–Ozawa method, Kissinger–Akahira–Sunose​ method, and Starink’s method) of rice husk (RH), rice straw (RS), and their torrefied solid products were investigated under different heating rates. The results demonstrated that the increase of torrefaction temperature decreased the content of hemicellulose and cellulose. TG-FTIR and TG/DTG curves of RH and RS showed a right shift trend after torrefaction. The average activation energy calculated was 149.79 and 161.76 kJ mol −1 for RH and RS pyrolysis. The activation energy of torrefied RH and RS showed an increasing trend with torrefaction temperature. According to the change of activation energy, the pyrolysis model of RH and RS was predicted by Z( α ) master plots and compensation effect, respectively. Torrefaction could convert the First-order reaction model (F1) to nucleation and growth model (An) gradually for RH, and raise the reaction order of the pyrolysis reaction for RS.