Cheng Heng Pang

Hg0 Capture over CoMoS/γ-Al2O3 with MoS2 Nanosheets at Low Temperatures

CoMoS/γ-Al2O3 sorbent was prepared via incipient wetness impregnation (IWI) and sulfur-chemical vapor reaction (S-CVR) methods and tested in terms of its potential for Hg(0) capture. It was observed that the CoMoO/γ-Al2O3 showed a Hg(0) capture efficiency around 75% at a temperature between 175 and 325 °C while CoMoS/γ-Al2O3 achieved almost 100% Hg(0) removal efficiency at 50 °C. The high removal efficiency for CoMoS/γ-Al2O3 remained unchanged for 2000 min in the test. Its theoretical capacity for Hg(0) capture was found to be 18.95 mg/g based on the Elovich model. The ability of this material for Hg(0) capture is atributed to the MoS2 nanosheets coated on surface of the maro- and meso-pores of γ-Al2O3. These MoS2 are two-dimensional transition-metal dichalcogenide (2D TMDC) assembled with unsulfided cobalt atoms at the edges. It is believed that these MoS2 nanosheets provided dense active sites for Hg(0) capture. The removal of Hg(0) at low temperatures was achieved via the combination of Hg(0) with the chalcogen (S) atoms on the entire basal plane of the MoS2 nanosheets with coordinative unsaturated sites (CUS) to form a stable compound, HgS.

Morphology and reactivity characteristics of char biomass particles

In this work, 10 different biomasses were selected which included directly grown energy crops, industrial waste material and different wood types. Each biomass was sieved into six different size fractions and pyrolysed in a fixed bed furnace preheated to 1000 °C to produce a char residue. Intrinsic reactivity during burnout was measured using a non-isothermal thermogravimetric method. Scanning electron microscopy and oil immersion microscopy were used to characterise the morphology of the products. Char morphology was summarised in terms of degree of deformation, internal particle structure and wall thickness. Intrinsic reactivity corresponded directly with these morphology groupings showing a significant correlation between char morphotypes, char reactivity and the initial biomass material.

Relationship between thermal behaviour of lignocellulosic components and properties of biomass.

Five different biomass samples were selected for this study, including miscanthus, distillers dried grain (DDG), wheat shorts, wheat straw and UK wood. These samples were thermochemically treated to alter the lignin, cellulose and hemicellulose composition. Thermogravimetric tests were carried out on these samples to determine thermal behaviours of biomass and its individual lignocellulosic components. The relationship between thermal behaviour of biomass and its corresponding lignocellulosic composition was revealed. The reliability of this relationship was proved by thermogravimetric analysis of samples of artificial biomass prepared by mixing commercially obtained lignin, cellulose and hemicellulose at various blending ratios. It is shown that actual biomass profiles can be predicted with some degree of accuracy based on the lignocellulosic composition.

Microwave-enhanced pyrolysis of macroalgae and microalgae for syngas production

In this study, three different marine biomasses, i.e., microalgae-spirulina, chlorella and macroalgae-porphyra, were pyrolyzed in a laboratory-scale multimode-microwave cavity at 400, 550 and 700°C. Ovalbumin and cellulose were also chosen as model compounds to simulate algae. The influence of heating rate on pyrolysis and the βi curves of different samples under different temperatures were studied in detail. The porphyra was found to be the most reactive and produced the largest gaseous fraction (87.1wt%) amongst the three algae, which comprised of 73.3vol% of syngas. It was found that nitrogenated compounds in bio-oil were derived from protein in algae while carbohydrate led to the formation of PAHs. For the production of bio-oil, protein-rich microalgae is favorable compared with porphyra due to their lower amount of PAHs, while porphyra is more suitable for the production of H2+CO rich gas product, which is comparable with that of conventional gasification processes.