Didem Özçimen

Istanbul Technical University, İstanbul, Istanbul, Turkey

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Publications (7)14.23 Total impact

  • Didem Özçimen, Ayşegül Ersoy-Meriçboyu
    11/2014; 1(1):20-28. DOI:10.15377/2409-983X.2014.01.01.2
  • Didem Özçimen, Ayşegül Ersoy-Meriçboyu
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    ABSTRACT: Activated carbons prepared from hazelnut shells and apricot stones were used as adsorbents for the removal of copper(II) ions from aqueous solution. Adsorption studies were carried out by varying the initial metal ion concentration, the temperature and the pH. The amount of Cu(II) ions adsorbed increased with increasing temperature, pH and initial Cu(II) ion concentration. The equilibrium data were analyzed using the Freundlich and Langmuir isotherms. The parameters of the isotherm models were determined for two activated carbons; it was found that the Freundlich model showed a better fit of the adsorption data than the Langmuir model. The physical and chemical properties of hazelnut shell and apricot stone activated carbons were determined for comparative purposes.
    Adsorption Science and Technology 12/2010; 28(4):327-340. DOI:10.1260/0263-6174.28.4.327 · 0.93 Impact Factor
  • Didem Özçimen, Ayşegül Ersoy-Meriçboyu
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    ABSTRACT: Apricot stone, hazelnut shell, grapeseed and chestnut shell are important biomass residues obtained from the food processing industry in Turkey and they have a great importance as being a source of energy. In this study, the characteristics of bio-oil and biochar samples obtained from the carbonization of apricot stone, hazelnut shell, grapeseed and chestnut shell were investigated. It was found that the biochar products can be characterized as carbon rich, high heating value and relatively pollution-free potential solid biofuels. The bio-oil products were also presented as environmentally friendly green biofuel candidates.
    Renewable Energy 06/2010; DOI:10.1016/j.renene.2009.11.042 · 3.36 Impact Factor
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    Didem Özçimen, Ayşegül Ersoy-Meriçboyu
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    ABSTRACT: Carbonization experiments of grapeseed and chestnut shell samples having the average particle size of 0.657 mm and 0.377 mm, respectively, were performed to determine the effect of temperature, sweep gas flow rate and heating rate on the biochar yield. A statistical design technique was applied by the use of a two-level factorial design matrix to interpret experimental results. Carbonization conditions were selected according to a two-level factorial design matrix considering the following variables: temperature (723 K and 823 K), nitrogen gas flow rate (0 and 1000 cm3/min) and heating rate (5 and 20 K/min). Empirical relations between the biochar yield and the carbonization conditions were developed. To comment on the effect of parameters between the superior and inferior levels and to prove the accuracy of design equations from statistical design technique, biochar yields obtained at different conditions were also presented in the graphical way. It was found that temperature has the strongest effect on the biochar yields in comparison with nitrogen gas flow rate and heating rate. Biochar yields of grapeseed and chestnut shell were decreased with the increasing temperature, heating rate and sweep gas flow rate. A comparison between the fuel properties of waste materials and biochar products was also done.
    Fuel Processing Technology 11/2008; 89(11-89):1041-1046. DOI:10.1016/j.fuproc.2008.04.006 · 3.02 Impact Factor
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    ABSTRACT: Carbonization experiments of hybrid poplar samples were performed in a thermogravimetric (TG) analyzer to investigate the effect of carbonization conditions, such as heating rate, particle size and sweep gas flow rate on the biochar yield. During carbonization, samples were heated from room temperature to the temperature of 723 K in an inert atmosphere. A statistical design technique was applied by using a two-level factorial design matrix to elucidate the experimental results. It was obtained that the biochar yields of samples were changed depending on the carbonization conditions. Empirical relations between the biochar yield and the carbonization conditions were developed. Biochar yields of samples were decreased with the increasing heating rate and sweep gas flow rate and increased with the increasing particle size. Kinetic analysis of the carbonization TG curves was achieved by using three different methods of calculation; also, 19 different model equations of possible solid-state rate controlling mechanisms were considered. A computer program in BASIC which enables regression analysis was used to calculate kinetic parameters from experimental TG data. It was observed that the carbonization conditions and the method of calculation influenced the kinetic results obtained.
    Fuel Processing Technology 09/2008; 89(9):858-863. DOI:10.1016/j.fuproc.2008.02.005 · 3.02 Impact Factor
  • Didem Özçimen, Filiz Karaosmanoğlu
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    ABSTRACT: New and renewable fuels are the major alternatives to conventional fossil fuels. Biomass in the form of agricultural residues is becoming popular among new renewable energy sources, especially given its wide potential and abundant usage. Pyrolysis is the most important process among the thermal conversion processes of biomass. In this study, the production of bio-oil and biochar from rapeseed cake obtained by cold extraction pressing was investigated and the various characteristics of biochar and bio-oil acquired under static atmospheric conditions were identified. The biochar obtained are carbon rich, with high heating value and relatively pollution-free potential solid biofuel. The bio-oil product was presented as an environmentally friendly green biofuel candidate.
    Renewable Energy 04/2004; DOI:10.1016/j.renene.2003.09.006 · 3.36 Impact Factor
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    ABSTRACT: The fixed bed atmospheric pressure pyrolysis and nitrogen swept pyrolysis of the rapeseed cake obtained from cold extraction press have been investigated. Experiments were performed in the Heinze retort at a 7°C min-1 heating rate, with a 500°C final temperature varying sweep gas velocity (50, 100, 150, 200, 250, 300 cm3 min-1) under nitrogen atmosphere. Liquid, gas, and char yields were determined, pyrolysis conversion was calculated, and liquid, char, and gas products were presented as an environmentally friendly fuel candidate.
    Energy Sources 01/2001; 23(10). DOI:10.1080/009083101317071315 · 0.54 Impact Factor