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- Alevanau, Aliaksandr, 1965-, et al.
(författare)
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Mechanically assisted low temperature pyrolysis of hydrocarbons
- 2014
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Ingår i: Proceedings of the XVII International Conference Foundations & Advances in Nonlinear Science, September 29 - October 3, Minsk 2014.
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Konferensbidrag (refereegranskat)abstract
- We report experimental setups and conditions leading to pyrolysis (cracking) of such gaseous hydrocarbons as methane, mixed propane and butane, at the temper-atures of the heater below 200oC. The process was mechanically assisted by putting the substances being decomposed into a dynamic interaction with the tin and bismuth alloy. The alloy had periodically changing phase state thus creating fractal interfaces between its surface and the gases. Interaction of the gases with mechanically produced fractal surfaces of the alloy made possible gas decomposition even at lower temperatures of the heater (150oC). At this temperature the heater couldn't melt the alloy in the heated volume with the gas.
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| 2. |
- Alevanau, Aliaksandr, et al.
(författare)
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Study of the effects of gaseous micro-expansion on the efficiency of convective heat transfer during pyrolysis
- 2013
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Ingår i: Fuel processing technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 106, s. 253-261
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of temperature in the proximity of wood pellets (8 mm diameter) and thin wooden stick slices (5 cm diameter and 5 mm thickness) were conducted to estimate the effects of mixing between the evolving volatiles and hot steam (T > 700°C) flowing around the particles. Measurements of mass loss of the slices were conducted to estimate the apparent kinetic parameters of their pyrolysis. A simple kinetic model of the process (type II by Pyle and Zaror (1984) [20]) was investigated. The experiments showed a plateau-like part in the graphs of temperature measured in the proximity to the samples. The existence of this plateau-like part agrees with the general data of calorimetric measurements of pyrolysis, which show extensive energy consumption in the beginning of an active production of volatiles. A hypothesis regarding feedback on the process due to the micro-expansion and mixing of volatiles in the convective boundary layer is discussed.
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| 7. |
- Cuvila, Carlos Alberto, et al.
(författare)
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The Impact of a Mild Sub-Critical Hydrothermal Carbonization of Pretreatment on Umbila Wood : A Mass and Energy Balance Perspective
- 2015
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 8:3, s. 2165-2175
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Tidskriftsartikel (refereegranskat)abstract
- Over the last years, the pretreatment of biomass as a source of energy has become one of the most important steps of biomass conversion. In this work the effect of a mild subcritical hydrothermal carbonization of a tropical woody biomass was studied. Results indicate considerable change in carbon content from 52.78% to 65.1%, reduction of oxygen content from 41.14% to 28.72% and ash slagging and fouling potential. Even though decarboxylation, decarbonylation and dehydration reactions take place, dehydration is the one that prevails. The mass and energy balance was affected by the treatment conditions than the severity of the treatment.
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| 9. |
- Ding, Saiman, et al.
(författare)
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Effects of Porous Structure Development and Ash on the Steam Gasification Reactivity of Biochar Residues from a Commercial Gasifier at Different Temperatures
- 2020
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 13:18
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Tidskriftsartikel (refereegranskat)abstract
- The present study aims at investigating the effects of porous structure development and ash content on the observed reactivity during steam gasification of biochar residues from a commercial gasifier. The experiments were conducted at a temperature range of 700 to 800 °C using biochar, derived from entrained flow gasification of biomass, under isothermal conditions using a thermogravimetric analyzer. The pore size distribution, surface area and morphology of char samples were determined by N2 physiosorption and scanning electron microscopy (SEM). The results showed that the gasification temperature does not affect the porous structure development considerably. The total surface area of char exhibits a threefold increase, while the total pore volume increase ranges between 2.0 and 5.3 times, at all temperatures. Both properties are directly proportional to the observed reactivity, especially at conversions up to 70%. Catalytic effects of the mineral matter of the char (mainly potassium) become predominant at the later stages of conversion (conversion greater than 70%).
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| 10. |
- Ding, Saiman
(författare)
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Gasification of biochars: Evolution of pore structure, effects of alkalis and alkali release
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Renewable energy sources are indispensable to meet the rising demand of energy usage while reducing the negative environmental impact of utilising fossil fuels. Gasification is an efficient technology to convert biogenic waste into valuable gaseous products. The rate of conversion of char, produced in an intermediate step in the conversion, plays an essential role in the conversion of biogenic materials. The conversion of char is significantly affected by properties such as the structure of the char and its alkali content. This thesis presents findings related to the influence of char pore structure development and alkalis content on char gasification, as well as the alkali release during gasification and co-gasification. Experimental results show that the generation of micropores are directly proportional to the observed reactivity up to 70% of char conversion, after which the catalytic effects of potassium become the dominating factor. Furthermore, investigations of the effect of different intrinsic potassium contents on woody char reactivity demonstrate that no alkali surface saturation point is reached, as is the case for high-ash chars. Application of a modified random pore model enabled a successful capture of the later stages of char conversion in comparison to other kinetic models applied. Alkali release and sample mass changes were monitored simultaneously, using a thermogravimetric analyser together with a surface ionization detector (TGA-SID). The studies revealed a significant release of alkali as woody char conversion approaches completion during CO2 gasification. For straw char the release of alkali decreased continuously throughout the conversion process. Similar results were obtained for biochar gasification under steam conditions in a fixed bed reactor. However, in this case the process is more complex, including transfer of alkali between particles inside the fixed bed, which influences char conversion. Co-gasification of different types of biomass can substantially affect char conversion efficiency. In comparison to pure wood, mixing wood and straw had positive effects on the char conversion for rates below 90% of conversion, while exceeding this degree of conversion resulted in negative effects. The most significant positive effect was observed at a gasification temperature of 900 °C, particularly when using a wood-straw blend of 75 wt%:25 wt%. The above findings are important for the understanding of the mechanisms of char conversion and are valuable in the design of gasifiers. The research provides with a deeper understanding of char structure development, alkali release, and migration during gasification of biogenic materials.
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