| 1. |
- Hu, Junhao, et al.
(författare)
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Co-gasification of coal and biomass : Synergy, characterization and reactivity of the residual char
- 2017
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 244, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- The synergy effect between coal and biomass in their co-gasification was studied in a vertical fixed bed reactor, and the physic-chemical structural characteristics and gasification reactivity of the residual char obtained from co-gasification were also investigated. The results shows that, conversion of the residual char and tar into gas is enhanced due to the synergy effect between coal and biomass. The physical structure of residual char shows more pore on coal char when more biomass is added in the co-gasification. The migration of inorganic elements between coal and biomass was found, the formation and competitive role of K2SiO3, KAlSiO4, and Ca3Al2(SiO4)(3) is a mechanism behind the synergy. The graphization degree is enhanced but size of graphite crystallite in the residual char decreases with biomass blending ratio increasing. TGA results strongly suggest the big difference in the reactivity of chars derived from coal and biomass in spite of influence from co-gasification.
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| 2. |
- Liu, Huihui, et al.
(författare)
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Conversion of high-ash microalgae through hydrothermal liquefaction
- 2020
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Ingår i: Sustainable Energy & Fuels. - : Royal Society of Chemistry (RSC). - 2398-4902. ; 4:6, s. 2782-2791
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Tidskriftsartikel (refereegranskat)abstract
- Natural microalgae (NM,Scenedesmus) cultivated by utilization of exhaust gas from a municipal solid waste combustion power plant were used for the biofuel production through hydrothermal liquefaction (HTL). The high-ash NM underwent acid-washing to obtain deashing microalgae (DA). HTL experiments were carried out at different temperatures from 260 °C to 340 °C with NM and DA. Products derived from NM and DA were examined by various techniques in order to identify the influence of the ash on the hydrothermal decomposition behavior. The results show that the ash inhibits the transformation of microalgae. The bio-oil yield including heavy oil and light oil is in the range of 17.59-22.09% for NM and 24.30-31.14% for DA, respectively. Calcium carbonate in the ash promotes deamination, resulting in an increase in the relative content of ketones in the NM-derived light oil. The concentration of NH4+in the aqueous phase derived from NM is in the range of 1373-1860 mg L−1, and PO43−is undetected due to the precipitation reaction between phosphorus and calcium ions. The HHV values of NM-derived hydrochars are low, ranging from 8.83 MJ kg−1to 9.88 MJ kg−1, compared with those of DA-derived hydrochars,. For natural microalgae, the deashing pretreatment before HTL is of great significance for improving the biocrude yield and quality, as well as the biomass conversion efficiency, nitrogen utilization and the hydrochar quality.
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| 3. |
- Liu, Huihui, et al.
(författare)
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Hydrothermal carbonization of natural microalgae containing a high ash content
- 2019
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 249, s. 441-448
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Tidskriftsartikel (refereegranskat)abstract
- The potential to convert natural microalgae (Scenedesmus) into solid fuels by hydrothermal carbonization (HTC) was evaluated. The deashing microalgae (DA) were obtained by acid-washing natural microalgae (NM) with HCl. The deashing efficiency was high from 44.66% for NM to 14.45% for DA. HTC carried out at temperature in the range from 180 to 260 degrees C with this two types feedstock (i.e. NM and DA). The results showed that DA-derived hydrochars had good physicochemical and fuel properties compared with that of NM-derived hydrochars. HTC process of DA was mainly based on polymerization, and the hydrolysis process was short. The hydrochars obtained from DA at 220 degrees C (HC-D220) had the highest value of 51.86% with a carbon content and fixed carbon content 1.15 and 1.33 times, respectively, greater than that of DA. The high heating value (HHV) of HC-D220 reached 26.64 MJ/kg which is equivalent to medium-high calorific coal. The thermogravimetric analysis (TG) demonstrated that the hydrochars derived from DA have good combustion properties with stable at high temperature zones. They can easily mix with coal or replace coal in combustion application. The results of this study revealed that natural microalgae can be utilized by hydrothermal carbonization to generate renewable fuel resources.
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| 4. |
- Liu, Huihui, et al.
(författare)
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Hydrothermal Treatment of High Ash Microalgae : Focusing on the Physicochemical and Combustion Properties of Hydrochars
- 2020
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 34:2, s. 1929-1939
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Tidskriftsartikel (refereegranskat)abstract
- Natural microalgae with high ash content are common in water environment. Converting them into biofuels not only meets the energy demands but also improves the aquatic environment. This study aims to explore the physicochemical properties and molecular structural features of hydrochars derived from hydrothermal treatment of natural microalgae. Meanwhile, the combustion behavior and kinetics analysis of hydrochars were also evaluated. The hydrothermal treatment was performed with natural microalgae and its acid-washing microalgae under different temperatures from 260 to 340 °C to reveal the effect of ash on hydrochars properties. The results indicate that the ash significantly influences the functional groups composition and physicochemical property of hydrochars. The yields of hydrochars derived from deashing microalgae are lower than those of hydrochars derived from natural microalgae. However, the relative content of the C-C/C-H/C=C groups representing hydrocarbon carbon in hydrochars derived from deashing microalgae is higher than that of hydrochars derived from natural microalgae. Both natural microalgae and deashing microalgae contain the protein-N and pyrrole-N, and natural microalgae also contain a small amount of inorganic-N. The Brunauer-Emmett-Teller (BET) surface areas of hydrochars derived from natural microalgae and deashing microalgae are in the range of 5.97-10.29 and 21.34-34.74 m2 g-1, respectively. The thermogravimetric analysis results show that hydrochars derived from deashing microalgae have better fuel quality in view of the comprehensive combustibility indexes compared with hydrochars derived from natural microalgae, which is conducive to their application to solid fuels. The acid-washing pretreatment can effectively improve the utilization of natural microalgae.
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| 5. |
- Wu, Tonghua, et al.
(författare)
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Storage, patterns, and environmental controls of soil organic carbon stocks in the permafrost regions of the Northern Hemisphere
- 2022
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 828
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Tidskriftsartikel (refereegranskat)abstract
- Large stocks of soil organic carbon (SOC) accumulated in the Northern Hemisphere permafrost regions may be vulnerable to climatic warming, but global estimates of SOC distribution and magnitude in permafrost regions still have large uncertainties. Based on multiple high-resolution environmental variables and a compiled soil sample dataset (>3000 soil profiles), we used machine-learning methods to estimate the size and spatial distribution of SOC for the top 3 m soils in the Northern Hemisphere permafrost regions. We also identified key environmental predictors of SOC. The results showed that the SOC storage for the top 3 m soil was 1079 ± 174 Pg C across the Northern Hemisphere permafrost regions (20.8 × 106 km2), including 1057 ± 167 Pg C in the northern permafrost regions and 22 ± 7 Pg C in the Third Pole permafrost regions. The mean annual air temperature and NDVI are the main controlling factors for the spatial distribution of SOC stocks in the northern and the Third Pole permafrost regions. Our estimations were more accurate than the existing global SOC stock maps. The results improve our understanding of the regional and global permafrost carbon cycle and their feedback to the climate system.
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| 6. |
- Zhu, Youjian, et al.
(författare)
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Characterization of Hydrochar Pellets from Hydrothermal Carbonization of Agricultural Residues
- 2018
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 32:11, s. 11538-11546
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the effects of operating conditions of hydrothermal carbonization on the hydrochar pelletization and combustion characteristics were investigated. Corn stalk was carbonized under different conditions and then pelletized to obtain the hydrochar pellets. It was found that hydrothermal temperature and residence time greatly affect the pellet quality. When the temperature was raised up to 240 °C with the residence time longer than 60 min, the heating values of hydrochar were close to or even higher than those of lignite. After hydrothermal treatment, 73.71-94.71% K and 91.81-94.32% Cl contained in the feedstock were removed, indicating a low fouling and slagging tendency when the pellets are used in combustion. The compressive strength and durability increased first with increasing temperature and then decreased with further increasing the temperature from 240 to 300 °C. The influence of residence time showed a similar trend, and the compressive strength and durability reached its maximum value at the temperature of 240 °C and residence time of 60 min. The hydrophobicity of the hydrochar pellets increased with increasing the temperature and residence time. Hydrochar pellets obtained at the temperature of 240 °C with residence time of 60 min gives the best performance, which can meet the requirement of industrial fuel pellets. Finally, the combustion characteristics were investigated by thermogravimetric analysis, and the results indicated that hydrochar pellets were combusted in a comparatively mild way with a high thermal efficiency. As a general conclusion, the hydrochar pellets have much better qualities than the raw corn stalk, facilitating the transportation, long-term storage, and combustion application.
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| 7. |
- Zhu, Youjian, et al.
(författare)
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P-Based Additive for Reducing Fine Particulate Matter Emissions during Agricultural Biomass Combustion
- 2019
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 33:11, s. 11274-11284
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Tidskriftsartikel (refereegranskat)abstract
- To understand the influence of P-containing compounds on particulate matter (PM) emissions from the combustion of agricultural residues, the combustion of cornstalk was performed with the addition of a phosphorus-based additive, namely, ammonium dihydrogen phosphate (NH4H2PO4), in a fixed-bed combustion system. Simultaneously the ash samples, including PM collected by a Dekati low-pressure impactor (DLPI) and residual ash, were analyzed with variant analytical techniques. It was found that NH4H2PO4 addition significantly reduced PM0.1 and PM0.1-1 yields but increased PM1-10 yields. The maximum PM0.1 and PM1 reduction efficiency can reach up to 50% at an optimal P/K molar ratio equal to 1. Meanwhile, the addition of NH4H2PO4 to cornstalk changed the chemical composition of PM1 from being dominated by KCl and KOH/K2CO3 with a small amount of K2SO4 to a system dominated by KPO3 and KCl with a small amount of K2SO4. Simultaneously, the possible PM1 reduction mechanism was proposed. In addition, the residual ash after combustion was rich in K- and P-containing species, indicating a potential utilization as a fertilizer. It showed that the addition of NH4H2PO4 is a promising approach to reduce PM1 emissions during the combustion of agricultural biomass.
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