Energy and exergy analyses of sewage sludge thermochemical treatment

Abstract

The aim of this research was to provide a methodology for calculating the energy and exergy balances for the thermochemical treatment of sewage sludge. The results of the balances were assessed and compared for three different scenarios (torrefaction, pyrolysis and pyrolysis combined with catalytic post-treatment of the vapors). The balances were calculated based on previously published experimental data and evaluated under different conditions. The results indicated that the endothermicity decreased with the severity of the process. The energy recovery from the products favored the exothermicity of the processes. The three-step process (pyrolysis of torrefied sewage sludge combined with catalytic post-treatment of the hot vapors) was the least exergy efficient scenario.

Exergy analysis of cavitation pretreatment of sludge

“…The results of the analysis are related to the specific system for which the average values of numerical parameters describing the amount and properties of sewage sludge were taken [11], [12], [14], [21], [27], [33]. Thus, the results of the analysis present a general assessment of the modified method of sewage sludge treatment, however, these may not be the same for a system with other parameters and sewage sludge with different properties than those assumed in the analysis presented in the article.…”

Sanitary and environmental aspects of sewage sludge management

“…Generally, pyrolysis and similar processes of combustion of sewage sludge are regarded as endothermic. Nevertheless, Atienza-Martínez et al (2018) have shown lately that the necessity of pretreatment of this substrate (dehydration) moves it more to the exothermic processes, although it is still the most cost-consuming throughout the scenario. Thus, improvement of the steps allowing water removal is crucial for the future potential of the process.…”

Pyrolysis of cashew nutshells: Characterization of products and energy balance

“…Two approaches were taken for performing an energy balance, using data from the experiments made at the intermediate temperature of 500 ºC. First, an energy balance considering the products (char, AP, OP, CNSL and gases) and reactant (CNS) at the standard temperature of 25 ºC was made by subtracting the standard enthalpies of formation of each one of them, which were calculated from their HHVs and the enthalpies of the corresponding combustion products, as detailed elsewhere [41,42]. The resulting value, Q py 0 , represents the standard heat for pyrolysis, i.e., without considering the sensible and latent heat of all the obtained products.…”