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1

Catalysis and compensation effect of K2CO3 in low-rank coal - CO2 gasification

100%

Skodras G.

Open Chemistry

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2013

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tom 11

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nr 7

1187-1200

EN

The CO2 gasification of a low rank coal catalysed by K2CO3 was studied, at 700–950°C and 1 atm. A two level full factorial design revealed that the gasification reaction was sensitive to the solid residence time, reaction temperature, CO2 partial pressure and catalyst load. K2CO3 was an efficient catalyst at all temperatures studied, particularly during the second stage when the Boudouard reaction dominates. The gasification rate was increased continuously with increasing catalyst load up to a load of ∼20% w/w K2CO3 concentration, following a sigmoid curve. Above this point, limited catalytic effect was observed, possibly due to the saturation of the lignite surface by K+. A correlation was found to exist between the catalytic gasification rate and the Alkali Index, which increased with the impregnation of the inorganic K2CO3 salt. When K2CO3 load increased, the Arrhenius parameters, E and k 0, increased simultaneously exhibiting a compensation effect. The isokinetic temperature was found about 600 to 650°C corresponding to the minimum temperature required for the formation of catalytic active intermediates. At temperatures studied, the catalytic active intermediates seemed to be always present and the catalysis progresses unhindered due to the redox cycle, resulting in high rates and conversion. [...]

2

Research and development of a high-performance oxy-fuel combustion power cycle with coal gasification

88%

Kindra V. , Rogalev A. , Zlyvko O. , Sokolov V. , Milukov I.

Archives of Thermodynamics

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2021

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tom Vol. 42, no 4

155--168

EN

Recent climate changes stimulate the search and introduction of solutions for the reduction of the anthropogenic effect upon the environment. Transition to the oxy-fuel combustion power cycles is an advanced method of CO2 emission reduction. In these energy units, the main fuel is natural gas but the cycles may also work on syngas produced by the solid fuel gasification process. This paper discloses a new highly efficient oxy-fuel combustion power cycle with coal gasification, which utilizes the syngas heat in two additional nitrogen gas turbine units. The cycle mathematics simulation and optimization result with the energy unit net efficiency of 40.43%. Parametric studies of the cycle show influence of the parameters upon the energy unit net efficiency. Change of the cycle fuel from natural gas to coal is followed by a nearly twice increase of the carbon dioxide emission from 4.63 to 9.92 gmCO2/kWh.

3

Cation exchange capability and reactivity of low-rank coal and chars

88%

Skodras G. , Kokorotsikos P. , Serafidou M.

Open Chemistry

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2014

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tom 12

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nr 1

33-43

EN

In this work the C.E.C. and its effect on the reactivity of low rank coal and chars were investigated. The C.E.C. was measured by potentiometric titration and was correlated with the solution pH, the carbonization extent and the oxygen content. Coal and chars presented permanent C.E.C. primarily derived from inorganic sites and was independent of solution pH, and variable C.E.C. derived from organic matter and was increased continuously, and reversibly, as the solution pH increased. The latter is due to the complete dissociation of the carboxylic groups of the organic matter of the coal and, thus, the C.E.C. is directly related with the oxygen content. The C.E.C. of chars decreased with the carbonization extents and its variation was described by a modified cumulative distribution function of the Weibull probability density function. A linear correlation was identified between the C.E.C. and the elemental oxygen conversion, justifying further the direct relation between the C.E.C. and the oxygen functional groups. Following the decrease of the C.E.C., the potassium chemisorption capacity of the chars also decreased. Chars of decreased C.E.C. were less reactive during CO2 gasification and reduced maximum weight loss and CO formation rates were obtained, also shifted at higher temperatures. [...]

4

Thermocatalytic Conversion of Sugarcane Bagasse (SCB) for Bioethanol Production: A Review

75%

Akinkuade K. A. , Olasesan I. P. , Fakayode O. A. , Odesanmi A. A. , Ajibade O. A.

World News of Natural Sciences

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2022

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tom 45

117-142

EN

An estimated 1.6 billion metric tons of sugarcane are produced worldwide each year, producing 279 million tons in metric of sugarcane bagasse (SCB) [1]. In terms of sugarcane production, Brazil leads the world with an annual output of about 739,300 metric tons, followed by India, China, Thailand, Pakistan, Mexico, Colombia, Indonesia, the Philippines, and the United States [2]. Sugarcane production produces waste and, if neglected, will have a serious negative impact on the environment. Alcohols, furfurals, organic acids, butanol, hydrogen, methane, ethanol, and other value-added products have all seen a major increase in output during the past few years [3], [4], [5]. The sustainable bio economy should be expanded via bio-based methods. An economic transformation from linear to circular will occur if the bio economy is more circular and sustainable. In view of the requirement for energy and environmental sustainability, a great deal of research has been done on the various SCB applications. Due to its successful application in the production of bioethanol, SCB is an acceptable source of sustainable feedstock for biofuel production. The SCB's bio products and enzymes demonstrate their economic value. Due to the higher reserve price than the current market price, the feasibility and industrial scale economics of biodiesel with sugar cane bagasse have revealed adverse net present values.