| 1. |
- He, Qing, et al.
(författare)
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Co-pyrolysis Behavior and Char Structure Evolution of Raw/Torrefied Rice Straw and Coal Blends
- 2018
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Ingår i: Energy & Fuels. - Washington : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 32:12, s. 12469-12476
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Tidskriftsartikel (refereegranskat)abstract
- Combination of biomass and coal for energy production is conducive to the sustainable development of society and a clean-energy future. This study investigates co-pyrolysis behavior of raw/torrefied rice straw and coal blends. Mild torrefaction (250 degrees C) and severe torrefaction (300 degrees C) were taken into consideration. Samples of five mixing ratios were tested by thermogravimetric analyzer, and the resulting chars were characterized by Raman spectroscopy and SEM-EDS. The results show that co-pyrolysis had little effect on char yields. Decomposition rate curves showed two distinct peaks for raw/mildtorrefied rice straw and coal blends, and the reaction rate was enhanced below 380 degrees C. However, only one peak appeared for severely torrefied rice straw blended with coal. During co-pyrolysis, the secondary pyrolysis of coal around 700 degrees C was inhibited, and the graphitization degree of biomass char increased, while the crystalline structure of coal char was poorly organized. The activation energy of mixtures also changed in different pyrolysis stages.
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| 2. |
- Wei, Juntao, et al.
(författare)
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A mechanism investigation of synergy behaviour variations during blended char co-gasification of biomass and different rank coals
- 2018
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Ingår i: Renewable energy. - : Elsevier. - 0960-1481 .- 1879-0682. ; 131, s. 597-605
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Tidskriftsartikel (refereegranskat)abstract
- Co-gasification reactivity of rice straw and bituminous coal/anthracite blended chars under CO2 atmosphere was evaluated using thermogravimetric analysis, and the influences of coal type and gasification temperature on synergy behaviour variations on co-gasification reactivity as carbon conversions increased were quantitatively studied. Furthermore, the chemical forms and concentrations of AAEM species at different co-gasification conversions were quantitatively analyzed for revealing co-gasification synergy mechanism. The results demonstrate that as conversions increased, synergy behaviour on co-gasification reactivity of rice straw-bituminous coal blends was shown as the weakened inhibition effect firstly and then the enhanced synergistic effect. Moreover, the inhibition effect on co-gasification reactivity of rice straw-bituminous coal blends was sustained up to higher conversion with the increment of gasification temperature. Differing from rice straw-bituminous coal blends, synergistic effect on co-gasification reactivity of rice straw-anthracite blends was obviously enhanced at early stage of co-gasification and started to slowly weaken after reaching the most significant synergistic effect at middle stage of co-gasification. Additionally, it was revealed that synergy behaviour variations on co-gasification reactivity of rice straw-bituminous coal blends were mainly attributed to the combination effects of active K and Ca transformation during co-gasification, while those of rice straw-anthracite blends indicated a good correlation with active K transformation during co-gasification.
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| 3. |
- Wei, Juntao, et al.
(författare)
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Influence of Biomass Ash Additive on Reactivity Characteristics and Structure Evolution of Coal Char–CO2 Gasification
- 2018
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 32:10, s. 10428-10436
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the influence of biomass ash (rice straw ash, RSA) additive on char gasification reactivity of different rank coals (Shenfu bituminous coal and Zunyi anthracite) was investigated using thermogravimetric analysis. Moreover, the structure characteristics (i.e., the chemical forms and concentrations of AAEM species and the order degree of carbon structure) of gasified semichars were quantitatively studied to evaluate the effect of RSA additive on coal char structure evolution during gasification. Specific reactivity index was proposed as a quantitative index and showed that RSA additive facilitated coal char gasification, especially at lower gasification temperature and for high-rank coal char. In addition, the results from the active AAEM concentrations and the Raman band area ratios of gasified semichars indicate that the RSA additive was conducive to the increase of active AAEM concentrations in coal char and the decrease of the degree of graphitization of coal char carbon structure during gasification, which were more significant at lower temperature and for high-rank coal char. It could be concluded from these results that the function mechanism of the RSA additive on coal char gasification reactivity had a close relationship with char structure evolution during gasification. Kinetics analysis using isoconversional method demonstrated that the gasification activation energy of Shenfu and Zunyi coal char with RSA additive were respectively lower than those of the corresponding coal chars by 8.33 and 22.32 kJ mol-1, indicating that the RSA additive was favorable for activation energy reduction of coal char gasification, especially for high-rank coal char. This work verified the possibility of promoting coal gasification using biomass ash as a natural catalyst and revealed the function mechanism of biomass ash additive on coal char gasification.
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