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Kinetic modelling of the hydrothermal carbonization of compost derived from municipal solid waste

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Resumo:Nowadays, municipal solid waste (MSW) management commonly includes a mechanical and biological treatment process (MBT). The solid stream from the anaerobic digestion of the organic fraction can be processed to obtain a compost, which can be used as fertilizer. However, compost production is higher than the existing demand, and the expected developments on up-coming directives ruling “End-of-waste” criteria are leading to barriers on the use of MSW-derived fertilizers [1]. Thus, the development of new alternatives for the treatment of organic wastes and compost valorization are necessary. This work deals with the valorization of compost from MBT, through the production of catalysts by Hydrothermal Carbonization (HTC) [2]. HTC of the compost was carried out in a Teflon vessel inserted in a stainless-steel body at different operating conditions (150-230 ºC,1-5 h, 1-4 g of compost, 30 mL). A Doehlert Matrix was considered to plan the experiments. The carbon balance and the kinetic equations were evaluated from experimental data reporting the carbon content in the liquid (estimated by TOC analysis) and solid phases (estimated by elemental analysis). A lumped kinetic model based on the elemental carbon content is proposed (Fig. 1), anticipating that the compost (C) undergoes reactions that originate liquid intermediates (L), reaction 1, and sequentially results in hydrochar (HC) and gases (G), reactions 2 and 3, respectively. In addition, it was assumed that HC and G were also produced from the compost directly, reactions 4 and 5, respectively. The highest kinetic constant at 190 ºC (8.3·10-4 min-1) was found for the formation of the liquid soluble intermediates from compost (reaction 1), whereas the production of hydrochar from the liquid intermediates (reaction 2) shows the lowest kinetic constant (3.1·10-4 min-1). The lowest activation energy was estimated for reaction 1 (23 kJ·mol-1), while reactions 2 and 4, related to the formation of hydrochar, resulted in the highest values (85 and 195 kJ·mol-1, respectively), meaning that the production of hydrochar strongly depends on the temperature.
Autores principais:Roman, Fernanda
Outros Autores:Díaz de Tuesta, Jose Luis; Praça, Paulo; Silva, Adrián; Faria, Joaquim; Gomes, Helder
Ano:2019
País:Portugal
Tipo de documento:documento de conferência
Tipo de acesso:acesso aberto
Instituição associada:Instituto Politécnico de Bragança
Idioma:inglês
Origem:Biblioteca Digital do IPB

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