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1

Comparison of the burial rate estimation methods of organic and inorganic carbon and quantification of carbon burial in two high Arctic fjords

Koziorowska K., Kuliński K., Pempkowiak J.

Oceanologia

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2018

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No. 60 (3)

405--418

EN

Quantifying the burial of organic carbon (OC) and inorganic carbon (IC) species in marine sediments contribute to a better understanding of carbon cycle. This is especially important in the Arctic, where carbon deposition is relatively high and expected to change with climate warming. This study aimed to quantify the burial rates of OC and IC in the sediments of two high-latitude fjords – Hornsund and Kongsfjorden (European Arctic). Comparison of the results from three methods quantifying carbon burial in marine sediments was carried out. Sediment cores, pore water, and over-bottom water samples were analyzed for OC and IC. The burial rates were established by considering: carbon deposition to sediments minus carbon return flux, carbon deposited to sediments 80-100 years ago and carbon deposited to sediments recently. The radiolead method was employed for sediment dating. Carbon return flux was obtained using dissolved carbon species concentrations in pore water and over-bottom water. Sediment linear and mass accumulation rates in the fjords were 0.12-0.20 cm y−1 and 1160-2330 g m−2y−1. The OC burial rates were 19.3-30.3 g OC m−2 y−1 in Hornsund and 5.7-10.0 g OC m−2y−1 in Kongsfjorden. IC burial was taken as equal to IC deposition and ranged from 10.7 to 20.8 g IC m−2 y−1 in Hornsund and 19.4-45.7 g IC m−2 y−1 in Kongsfjorden. The “return flux” model seems most appropriate for carbon burial rate studies. The data demonstrated that OC burial dominates in Hornsund, while in Kongsfjorden, IC burial is more important.

2

Effects of gas velocity on formation of carbon deposits on AS-SOFC fuel electrodes

Motylinski K., Skrzypkiewicz M., Naumovich Y., Wierzbicki M., Kupecki J.

Journal of Power Technologies

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2018

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Vol. 98, nr 4

322--328

EN

The elevated operating temperatures of solid oxide fuel cells (SOFC) create favorable kinetics for the oxidation of carboncontaining gas mixtures, which may include carbon monoxide and light organic compounds. The presence of carbon-based components in the fuel might result in the formation and deposition of soot on the surface of the anode in a fuel cell. This process depends on and is driven by the prevailing thermodynamic, kinetic and electrochemical conditions. The present study was premised on the following: in addition to the aforementioned parameters providing for the operating conditions, gas velocity also affects the formation of deposits on the anode. The role of fuel gas velocity in the process was studied experimentally using 5 cm x 5 cm anode supported solid oxide fuel cells (AS-SOFC) at 750°C at velocities in the range 0.1 to 0.9 m/s. It was found that carbon deposition was clearly observable approximately 24 hours after the necessary conditions were attained. An intense stage of performance degradation typically lasts for a period of up to 60 hours. An increase in fuel flow velocity leads to an acceleration in the carbon deposition process. The correlation between velocity and cell degradation due to this phenomenon was determined and the corresponding function was proposed.

3

Controlled fluoridation of amorphous carbon films deposited at reactive plasma conditions

Yoffe A., Zon I., Feldman Y., Shelukhin V.

Materials Science Poland

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2015

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Vol. 33, No. 3

606--611

EN

A study of the correlations between plasma parameters, gas ratios, and deposited amorphous carbon film properties is presented. The injection of a C4F8/Ar/N2 mixture of gases was successfully used in an inductively coupled plasma system for the preparation of amorphous carbon films with different fluoride doping at room-temperature, using silicon as a substrate. This coating was formed at low-pressure and low-energy using an inductively coupled plasma process. A strong dependence between the ratios of gases during deposition and the composition of the substrate compounds was shown. The values of ratios between Ar (or Ar+ N2) and C4F8 - 1:1 and between N2 and Ar - 1:2 in the N2/Ar/C4F8 mixture were found as the best for low fluoridated coatings. In addition, an example of improving the etch-passivation in the Bosch procedure was described. Scanning electron microscopy with energy dispersive spectroscopy options, X-ray diffraction, and X-ray reflectivity were used for quantitative analysis of the deposited films.

4

An experimental and theoretical approach for the carbon deposition problem during steam reforming of model biogas

Brus G., Nowak R., Szmyd J., S., Komatsu Y., Kimijima S.

Journal of Theoretical and Applied Mechanics

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2015

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Vol. 53 nr 2

273--284

EN

The conversion of biogas to electricity presents an attractive niche application for solid oxide fuel cells (SOFCs). A number of attempts have been made to use biogas as a fuel for high temperature fuel cell systems such as SOFCs. Biogas can be converted to a hydrogen-rich fuel in a reforming process which can use steam or carbon dioxide as the reforming agent. Conventionally, the reforming process is conducted at around 850◦C using several different catalysts depending on application. Biogas naturally contains the reforming agent, carbon dioxide, however, for typical biogas the content of carbon dioxide is insufficient to conduct the reforming process safely. Fore those cases, steam is added to prevent carbon deposition. Carbon formation occurs between the catalyst and the metal support, creating fibers which damage the catalytic property of the reactor. A number of papers have dealt with the problem of carbon deposition during both methane steam reforming and dry reforming. However, from the standpoint of solid oxide fuel cells, not every carbon-free condition is optimal for its operation. This paper treats this subject, explaining the mechanism of carbon formation during the steam reforming of biogas and using a numerical analysis to determine efficient and carbon-free working conditions.

5

Model Approach of Carbon Deposition Phenomenon in Steam and Dry Methane Reforming Process

Kaczmarczyk R., Gurgul S.

Archives of Metallurgy and Materials

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2014

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Vol. 59, iss. 1

145--148

EN

This paper presents thermodynamic conditions for carbon deposition in steam and dry methane reforming process. Ranges of substrate concentrations and temperatures for creating carbon deposition were specified in an analytical form. In the description of the conversion of methane CH4-H2O and CH4-CO2 parametric equations were used, which allowed to define equilibrium composition of the process. The article formulates the basic assumptions of parametric equations models and their use to describe the course of the homogeneous reactions. The results may provide a model basis for the description of properties of the mixed reforming process CH4-H2O-CO2.

PL

W prezentowanej pracy przedstawiono termodynamiczny warunek wytracania wegla w procesie parowego i suchego reformingu metanu. Określono zakresy stężenia substratów i temperatury tworzenia depozytów węglowych w postaci analitycznej. Opis konwersji metanu CH4-H2O i CH4-CO2 zrealizowano z wykorzystaniem formalizmu równań parametrycznych, pozwalającego na określenie składu równowagowego zachodzącego procesu. Przedstawiono podstawowe założenia modelu równań parametrycznych oraz ich wykorzystanie do opisu przebiegu reakcji homogenicznych. Uzyskane wyniki mogą stanowić bazę modelowa do opisu własności procesu reformingu mieszanego CH4-H2O-CO2.

6

Model Approach of Carbon Deposition Phenomenon in Mixed H2O/Co2 Methane Reforming Process

Kaczmarczyk R., Gurgul S.

Archives of Metallurgy and Materials

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2014

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Vol. 59, iss. 4

1379--1383

EN

This paper presents thermodynamic conditions for carbon deposition in methane reforming process by gas phase H2O/CO2. Ranges of substrate concentrations and temperatures for creating carbon deposition were specified in an analytical form. In the description of the conversion of methane CH4-(H2O/CO2) parametric equations were used, which allowed to define equilibrium composition of the process. The article formulates the basic assumptions of parametric equations models and their use to describe the course of the homogeneous reactions. The results may provide a model basis for the description of properties of the mixed reforming process CH4 - (H2O/CO2).

PL

W prezentowanej pracy przedstawiono termodynamiczny warunek wytrącania węgla w procesie reformingu metanu faza gazowa H2O/CO2). Określono zakresy stężenia substratów i temperatury tworzenia depozytów węglowych w postaci analitycznej. Opis konwersji metanu CH4-(H2O/CO2) zrealizowano z wykorzystaniem formalizmu równań parametrycznych, pozwalającego na określenie składu równowagowego zachodzacego procesu. Przedstawiono podstawowe założenia modelu równań parametrycznych oraz ich wykorzystanie do opisu przebiegu reakcji homogenicznych. Uzyskane wyniki mogą stanowić bazę modelowa do opisu własności tzw. procesu reformingu mieszanego CH4-(H2O/CO2).

7

Proces grafityzacji obmurza komór koksowniczych, jako jedno z potencjalnych źródeł jego degradacji

Rejdak M., Nowicki G., Mytych J.

Karbo

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2012

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Nr 1

44--53

PL

Formowanie się struktur grafitowych na obmurzach komór koksowniczych ma bardzo istotne znaczenie z punktu widzenia eksploatacji baterii koksowniczych. Cienka warstwa grafitu wpływa pozytywnie na gazoszczelność masywu ceramicznego i zapobiega przedostawaniu się surowego gazu koksowniczego z komory koksowniczej do kanałów grzewczych, a także nadmiar grafitu przyczynia się do przedwczesnego zużycia elementów masywu, co w konsekwencji prowadzi do skrócenia żywotności baterii koksowniczych. W niniejszym artykule skupiono się na przedstawieniu procesu powstawania depozytów węglowych, a także opisano eksploatacyjne aspekty ich występowania na obmurzach komór koksowniczych oraz metody ich usuwania.

EN

Formation of graphite structure on coke oven ceramic brickwork is important from the perspective of coke oven battery operation. On the one hand thin layer of graphite has positive influence on gas-tightness of ceramic brickwork and prevents leakage of raw gas from chamber to heating flue, on the other hand excess graphite contributes to premature wear of brickwork which consequently leads to reduction of coke oven' lifetime. This paper presents process of carbon deposits formation, aspect of its presence on ceramic brickwork and methods of its removal.

8

Badanie depozytu węglowego na katalizatorach Co/SiO2 oraz Fe-Co/SiO2 powstającego w reakcji Fischera-Tropscha

Kwintal P., Michalak A., Jóźwiak W. K.

Chemik

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2009

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Vol. 62, nr 9

320-322

PL

Głównym celem niniejszej pracy było zbadanie depozytu węglowego, powstającego na katalizatorach Co/SiO2 oraz Fe-Co/SiO2 w reakcji FTS. Badane układy charakteryzowały się odmiennymi właściwościami katalitycznymi. Do temperatury ok. 360°C dla katalizatorów bimetalicznych Fe-Co stopień konwersji był na poziomie kilku procent, powyżej tej temperatury wzrastał do ok. 80%. W przypadku katalizatora mono-metalicznego Co/SiO2 stopień konwersji już w temperaturze 280°C był bliski 100%. W przypadku układu Fe-Co problem stanowił węgiel, który odkładał się na katalizatorze po osiągnięciu tak wysokiej aktywności. W celu oceny depozytu węglowego jego ilości i formy oraz przyczyny dezaktywacji katalizatorów Co zostały wykonane następujące badania: TPSR-MS, TG-DTA-MS.

EN

The main aim of this paper was investigation of carbon deposition created on Co/SiO2 and Fe-Co/SiO2 catalysts in Fischer-Tropsch synthesis. Examined samples showed a different catalytic properties. For bimetallic Fe-Co catalyst obtained conversion was below 10% up to 360°C. Above this temperature conversion increase dramatically to 80%. In the case of monometallic catalyst Co/SiO2 degree of conversion was close to 100% in 280°C. For Fe-Co catalyst carbon, which deposited on the surface of catalyst was a problem. For estimate of carbon deposition and the reasons of deactivation of Co catalyst the research of TPSR-MS and TG-DTA-MS was carried out.