Biochar washing to improve the fuel quality of agro-industrial waste biomass

Low energy density and low ash melting temperatures of agro-industrial waste biomass are bottlenecks for their sustainable use in combustion utilities. Torrefaction at low temperature (350 °C for 30 min) for energy density enhancement followed by very simple aqua-washing technique to remove soluble mineral matters from biochar (BC) samples have been employed in this research work to investigate possible improvement of combustion performance of tobacco stalk (TS), sugarcane bagasse (SB), and poultry litter (PL) biomasses (BM). Though the energy density of the BC was significantly higher than their respective BM, the propensity for slagging was also higher, particularly in TS-BC and PL-BC. On char washing, ash content as well as the slagging and fouling tendencies were estimated to be decreased. Energy densification ratio (as compared to biomass) as well as GCV were further increased in washed biochar (WBC). As per the DSC-TGA investigations, combustion reactivity of BC was improved by washing. The significant advantages of BC washing were observed in TS-BC and PL-BC due to the removal of a large amount of soluble materials from respective BCs. As the water extracted material from SB-BC is insignificant, unwashed SB-BC having sufficiently high GCV (20.6 MJ/kg), energy densification ratio (1.5), carbon content (66.7%) can be directly used without washing. Water washing of BC is highly beneficial for TS and PL in respect of combustion performance and a valuable potassium-rich fertilizer material was obtained on evaporation of the leachate depicting unique value-addition of entire process

Investigation on the combustion characteristics of different plant parts of Cassia siamea by DSC-TGA

Plant parts like root, wood, twig and leaf of Cassia siamea, a fast-growing tree in the abandoned mines of Jharkhand, India, have been considered here as a possible fuel source for decentralized power generation. This is a low greenhouse gas emission pathway to cater the electricity need of the adjoining locality. Seasonal availability of the plant parts originated interests of studying the basic combustion characteristics of the plant parts separately. Finding out the roles of cellulose and lignin to regulate the combustion behavior of plant parts was another objective. Cellulose and lignin were extracted from each plant part, and their burning performances were evaluated against those of respective plant parts with the help of DSC-TGA. Cellulose and lignin were found to influence the combustion processes of plant parts differently. Lignin in case of leaf combustion and cellulose for wood combustion regulated the combustion process. Both lignin and cellulose were competitive in regulating the combustion of twig and root. Burning characteristics of cellulose or lignin extracted from different plant parts varied. Higher heating value (HHV) was low for celluloses (~ 16.8 ± 1 MJ kg−1) as compared to lignin (HHV ~ 23.0 ± 1 MJ kg−1). Leaf having substantial lignin and extractives showed the highest HHV around 23.5 MJ kg−1, while the lowest HHV (16.0 MJ kg−1) was observed for wood. Results are interesting for considering each plant part as a single fuel or as a potential component of coal–biomass blended fuel, where locally available low-grade high ash coal may be the other component

Mercury in coal from south eastern coalfeld and mercury partitioning at sub‑critical coal‑fred power plant

India is considered as one of the major mercury emitters of the world. Coal combustion in power plants is the foremost source of mercury emissions. Coal samples from South Eastern Coalfeld (SECL) region, India were assessed for mercury content and its partition in a 500 MW boiler unit of a coal-fred power plant. Hg content in the runof mine coal samples varied from 0.011 to 0.188 mg/kg. The Hg content in coal was positively correlated with ash and sulfur. In the power plant, about 65% of the Hg present in the feed coal was emitted through stack, whereas the rest were associated with the fne fy ash (33%), bottom ash (1.9%), and mill rejects (0.1%).The concentration of total Hg in the stack gas varied from 8.5 to 13.7 μg/Nm3, wherein Hg0 (74–81%) was much higher than Hg2+ (19–26%). The estimated mercury emission factor was 1.0–3.2 mg/GJ, which is comparatively higher due to the use of high ash coal and the lack of fue gas desulphurisation system. Hg portion�ing along the fue gas hoppers were also investigated which indicates relationship between Hg adsorption and carbon/sulfur content of the fy ash