• 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.

A novel municipal solid waste (MSW)-based power generation system was proposed in this study, which consists of a bubbling fluidized-bed (BFB)-plasma gasification unit, a high-temperature solid oxide fuel cell (SOFC), a chemical looping combustion (CLC) unit and a heat recovery unit. Process simulation was conducted using Aspen PlusTM and validated by literature data. The energetic and exergetic assessment of the proposed system showed that the net electrical efficiency and exergy efficiency reached 40.9 % and 36.1 %, respectively with 99.3 % of carbon dioxide being captured. It was found that the largest exergy destruction took place in the BFB-Plasma gasification unit (476.5 kW) and accounted for 33.6 % of the total exergy destruction, which is followed by the SOFC (219.1 kW) and then CLC (208.6 kW). Moreover, the effects of key variables, such as steam to fuel ratio (STFR), fuel utilization factor (Uf), current density and air reactor operating temperature, etc., on system performance were carried out and revealed that the system efficiency could be optimized under STFR = 0.5, Uf = 0.8 and air reactor operating temperature of 1000 ºC. Furthermore, the proposed process demonstrated more than 14% improvement in net electrical efficiency in comparison with other MSW incineration and/or gasification to power processes.

This work aims to investigate and develop a method to evaluate and predict the combustion behaviour and combustion efficiency of different biomass commonly used in power plants via simple characterisation methods. 11 types of agricultural and industrial wastes were characterised using thermogravimetric analyser to obtain the derivative thermogravimetric (DTG) data and kinetic parameters. For the samples tested, the initiation temperatures were found to be in the range between 224.39 0 C and 260.33 0 C, whilst the local minimum temperatures between 2 peaks were within the range of 360.36 to 382.74 0 C. It was established that there is a clear, direct relationship between the pre-exponential factor and the temperature interval for the first step of combustion. This trend was apparent and recorded for the 2 heating rates tested. © 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 This study investigates the potential of solid fuel blending as an effective approach to manipulate ash melting behaviour to alleviate ash-related problems during gasification, thus improving design, operability and safety. The ash fusion characteristics of Qinghai bituminous coal together with Fushun, Xinghua and Laoheishan oil shales (and their respective blends) were quantified using a novel picture analysis and graphing method, which incorporates conventional ash fusion study, dilatometry and sintering strength test, in a CO/CO2 atmosphere. This image-based characterisation method was used to monitor and quantify the complete melting behaviour of ash samples from room temperature to 1520 °C. The impacts of blending on compositional changes during heating were determined experimentally via X-ray diffraction and validated computationally using FactSage. Results showed that the melting point of Qinghai coal ash to be the lowest at 1116 °C, but would increase up to 1208 °C, 1161 °C and 1160 °C with the addition of 30%–50% of Laoheishan, Fushun, and Xinghua oil shales, respectively. The formation of high-melting anorthite and mullite structures inhibits the formation of low-melting hercynite. However, the sintering point of Qinghai coal ash was seen to decrease from 1005 °C to 855 °C, 834 °C, and 819 °C in the same blends due to the formation of low-melting aluminosilicate. Results also showed that blending directly influences the sintering strength during the various stages of melting. The key finding from this study is that it is possible to mitigate against the severe ash slagging and fouling issue arising from high calcium and iron coals by co-gasification with a high silica-alumina oil shale. Moreover, blending coals with oil shales can also modify the ash melting behaviour of fuels to create the optimal ash chemistry that meets the design specification of the gasifier, without adversely affecting thermal performance.

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.

This research focuses on the non-isothermal CO2 gasification and pyrolysis reactivity via thermogravimetric analysis. It was found that CO2 decreased activation energy of all four types of oil shale (Fushun, Jinzhou, Wulin, Xingsheng). Activation energy of XS oil shale was highly reduced from 59.86 kJ/mol to 9.48 kJ/mol. Reactivity index results showed that WL and XS oil shales were observed to be more dependent on CO2 atmosphere. Alkali metal oxide also contributed to thermal decomposition according to thermogravimetric (TG) and differential thermal analysis (DTG) curves during CO2 gasification process. Overall, CO2 atmosphere can be used to improve oil shale decomposition, especially for alkali- rich shales, while providing an efficient and effective means to convert greenhouse gases into useful fuels. © 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.