title: A new model to predict diffusive self-heating during composting incorporating the reaction engineering approach (REA) framework.
abstract: During composting, self-heating may occur due to the exothermicities of the chemical and biological reactions. An accurate model for predicting maximum temperature is useful in predicting whether the phenomena would occur and to what extent it would have undergone. Elevated temperatures would lead to undesirable situations such as the release of large amount of toxic gases or sometimes would even lead to spontaneous combustion. In this paper, we report a new model for predicting the profiles of temperature, concentration of oxygen, moisture content and concentration of water vapor during composting. The model, which consists of a set of equations of conservation of heat and mass transfer as well as biological heating term, employs the reaction engineering approach (REA) framework to describe the local evaporation/condensation rate quantitatively. A good agreement between the predicted and experimental data of temperature during composting of sewage sludge is observed. The modeling indicates that the maximum temperature is achieved after some 46weeks of composting. Following this period, the temperature decreases in line with a significant decrease in moisture content and a tremendous increase in concentration of water vapor, indicating the massive cooling effect due to water evaporation. The spatial profiles indicate that the maximum temperature is approximately located at the middle-bottom of the compost piles. Towards the upper surface of the piles, the moisture content and concentration of water vapor decreases due to the moisture transfer to the surrounding. The newly proposed model can be used as reliable simulation tool to explore several geometry configurations and operating conditions for avoiding elevated temperature build-up and self-heating during industrial composting.
authors.affiliation: School of Chemistry and Chemical Engineering, Queen's University Belfast, David Keir Building, Stranmillis Road, Belfast BT9 5AG, UK; School of Chemical and Environmental Engineering, College of Chemical Engineering, Chemistry and Material Science, Soochow University, Suzhou, Jiangsu Province, PR China.
authors.forename: Aditya
authors.initials: A
authors.lastname: Putranto
authors.affiliation: School of Chemical and Environmental Engineering, College of Chemical Engineering, Chemistry and Material Science, Soochow University, Suzhou, Jiangsu Province, PR China. Electronic address: xdchen@mail.suda.edu.cn.
authors.forename: Xiao Dong
authors.initials: XD
authors.lastname: Chen
mesh_terms: D057005:Bioengineering / Q000379:methods*; D004058:Diffusion; D005740:Gases / Q000737:chemistry; D006358:Hot Temperature; D008962:Models, Theoretical; D010100:Oxygen / Q000737:chemistry; D012722:Sewage / Q000737:chemistry; D012987:Soil / Q000737:chemistry*; D013227:Steam; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D005740:Gases; D012722:Sewage; D012987:Soil; D013227:Steam; D014867:Water; D010100:Oxygen
keywords: Composting; Evaporation/condensation; Model; Reaction engineering approach (REA); Self-heating