• Energy Research

Oil shale, as an unconventional fossil fuel, exhibits unique properties compared with coal and other petroleum. Due to the nature of sedimentary rock, large amounts of inorganic mineral impurities in rock matrix reduce the grade of oil shale, whilst increase the grinding resistance. This investigation presents the effects of microwave-enhanced pretreatment on the nature of oil shale and compared with conventional preheating process. Two Chinese oil shale from Fushun and Xingsheng Deposits were grounded and sieved into a size fraction (1-1.18mm) and were cut into eighteen cube-shaped specimens respectively. The prepared samples were processed accordingly to investigate how the grindability changed, in comparison to that of raw samples, and how the fundamental chemical properties of oil shale were altered after pretreatment. Quantitive data were used to assess the effects of different pretreatment methods on oil shale milling performance in a lab-scale pulverizer along with the impacts on moisture content, chemical properties. The uniaxial compressive strength (σmax) of Fushun oil shale was reduced 63.1% and the breakage rate increased 44.9% by short exposure to microwave irradiation. In conclusion, microwave-enhanced pretreatment presents significant improvement in oil shale milling performance compared to conventional preheating process in terms of breakage rate (Si) and uniaxial compressive strength (σmax) which showed negligible alterations. © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of ICAE2018 - The 10th International Conference on Applied Energy.

Abstract In-situ monitoring of the impacts of biomass blending and temperature on the morphology of coal ash was conducted by using a scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS) coupled with a heating stage and an ash fusion analyser. It is found that the interactions between ash originated from different parent fuels affected the morphology of the ash samples derived from the blends and promoted the rapid disintegration and melting of the ash particles. This helps reveal the deformation mechanism and the decrease in ash fusion temperatures of the fuel blends. Results showed that slagging propensity was mitigated as a result of blending the coal with the AAEMs-rich biomass, which is illustrated by the ash fusibility index. Subsequently, a new prediction method based on the mineral composition of the coal and biomass was formulated to elucidate the trends observed in fusion temperature of the fuel blends. This method can be used as a tool to guide the selection of biomass to adjust fusion characteristics of fuel blends.

The increasing volume of sewage sludge from wastewater treatment facilities is becoming a prominent concern globally. The disposal of this sludge is particularly challenging and poses severe environmental hazards due to the high content of organic, toxic and heavy metal pollutants among its constituents. This study presents a simple review of four sewage to energy recovery routes (anaerobic digestion, combustion, pyrolysis and gasification) with emphasis on recent developments in research, as well as benefits and limitations of the technology for ensuring cost and environmentally viable sewage to energy pathway. This study focusses on the review of various commercially viable sludge conversion processes and technologies used for energy recovery from sewage sludge. This was done via in-depth process descriptions gathered from literatures and simplified schematic depiction of such energy recovery processes when utilised for sludge. Specifically, the impact of fuel properties and its effect on the recovery process were discussed to indicate the current challenges and recent scientific research undertaken to resolve these challenges and improve the operational, environmental and cost competitiveness of these technologies.

In this study, synergistic interaction between coal and biomass and its intensity were investigated systematically using a low rank coal and its blends with different biomass samples at various blending ratios. The catalytic effects of minerals originated from biomass were also studied. It was found that some of the minerals existing in the ash derived from oat straw catalysed the combustions process and contributed to synergistic interactions. However, for the coal and rice husk blends, minimal improvements were recorded even when the biomass and coal blending ratio was as high as 30 wt%. Biomass volatile also influenced the overall combustion performance of the blends and contributed to synergistic interactions between the two fuels in the blends. Based on these findings, a novel index was formulated to quantify the degree of synergistic interactions. This index was also validated using data extracted from literature and showed satisfactory correlation coefficients. It was found that at a blending ratio of 30 wt% oat straw in the blend, the degree of synergistic interaction between coal and oat straw showed an additional SF value of 0.25 with non-catalytic and catalytic synergistic effect contributing 0.16 (64%) and 0.09 (36%) respectively. This index could be used in the selection of proper biomass and proper blending ratio for co-firing at coal-fired power stations aiming at improving the combustion performance of poor quality coals via enhancing synergistic interactions during co-processing.

Abstract Historically, pyrolysis technologies occupied a niche, producing materials with useful chemical functionality from wood, by the continuous application of heat. In the 21st century pyrolysis is promoted as an "advanced" technology for the extraction of heat from municipal refuse, at the same time as claiming "sustainable" and "efficient" credentials. This paper examines the concept of pyrolysis, and the potential for a phenomenon which demands energy to be considered as something which can be engineered to provide energy. Using literature review and case study methods, along with civil permit applications and experimental results, it shows that a pyrolysis plant for self-sustaining Energy from Waste is thermodynamically unproven, practically implausible, and environmentally unsound. A linkage between widespread commercial failures and a lack of focus on thermodynamic fundamentals is also identified, along with an environment of indifference or ignorance towards energy balances and sustainability when these technologies are presented, assessed and financed. Though proposals to build machines which violate physical laws is not new, in a modern context this phenomenon is found to be stimulated by competitive financial rewards. The situation presents a high risk to investors and has the potential to adversely impact on societal transitions to a more sustainable future.

The influences of biomass constituents, such as lignocellulosic components and minerals, on the combustion of coal/biomass blends are of significant importance in co-firing due to its potential impacts on ignition, flame stability and burnout. In this research, combustion characteristics of pure lignocellulosic elements, Rosewood, Mengxi coal and their blends were studied in detail. The effect of minerals in Rosewood on combustion of biomass/Mengxi coal blends was investigated which revealed reductions in the ignition (≤20 °C), peak (≤12 °C)and burnout temperatures (≤6 °C). The results also demonstrate the existence of interactions between lignocellulosic constituents in the model biomass, which is dominated by the interactions of cellulose-derived products with xylan and lignin respectively which led to ∼8% reduction in char oxidation temperature. The minerals in biomass showed different impacts at different stages of the combustion process, such as inhibition effect during the devolatilization stage, and promotive synergy (mainly due to calcium)on ignition and char oxidation. © 2019 Elsevier Ltd

The importance of biomass in the emerging low carbon economy remains quite crucial especially relating to the co-firing of coal and biomass due to the improvements in thermal properties and its influence on reactivity, burnout and flame stability. In this research, the combustion profile of coal and biomass blends, coal and low temperature biomass ash blends and coal and demineralized biomass blends were studied using thermogravimetric analysis. The results established the presence of both mechanism of synergy in the fuel blends during co-firing. This was substantiated by significant decrease in peak, burnout temperature as well as reduction in activation energy, demonstrating non-additive interaction between the biomass and coal sample. Further deductions reveal a degree of overlap in the function of catalytic and non-catalytic synergy mechanisms in the biomass blends due to competitive reactions among the catalyzing AAEMs and the hydrogen contributing organic constituents of biomass with coal. Finally, this study further establishes a higher degree of catalytic synergy in potassium rich oat straw in comparison to calcium rich gumwood. © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of ICAE2018 - The 10th International Conference on Applied Energy.