Mathematical modelling for biogas production
- Authors: Matheri, Anthony Njuguna
- Date: 2016
- Subjects: Sewage - Purification - Anaerobic treatment , Sewage - Purification - Mathematical models , Renewable energy sources , Biomass energy , Biogas
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/213006 , uj:21066
- Description: Abstract: The main focus of this dissertation is the experimental, modelling and simulation of anaerobic digestion processes from pilot bio-digesters. For this purpose, biochemical kinetic models were utilized together with corresponding simulation software; DYNOCHEM. By application of the anaerobic digestion (AD), different parameters have been investigated and simulated including adjustments of the process model and corresponding modifications. To validate the process model, the modelled data was compared with experimental monitored laboratory results. Bio-chemical kinetics modelling was applied as a systematic tool in order to support the process design and optimization of a demonstration of the biogas processes which constitutes the main scientific framework and background of this dissertation. Monitored laboratory-scale biogas production data were used for parameter calibration in order to predict plant performance. The calibration focused on the influent characterization of both substrates and on selection of kinetic of the coefficients in order to generate a uniform set of parameters which are applicable for the simulation of codigestion. In this study, it was observed that the experiment work under laboratory scale using conventional bio-methane potential (BMP) analyzers under mesophilic optimum temperature of 35 oC and 37 oC, and pH of 7 for co-digestion of organic fraction of municipal solid waste (OFMSW) with cow dung and manure with grass clippings. The substrate characterization moisture content ranged from 60-95%, volatile content 55-95%, total solid 10-90% and carbon to nitrogen ratio 16-20 for manure and 5-15 for OFMSW. All trace elements concentration were below the threshold of 32 mg/l that leads to inhibition of micro-organisms activity. The rate of conversion increased with retention time. According to the findings, 54-62% of methane composition was evaluated. The kinetics constant evaluated ranged from 0.009-0.35 d-1 and coefficient of determination (R2) ranged from 0.9989-0.9998. The Michaelis-Menten and Monod models provided goodness of fit of 0.9997 with confidential level of 95%. The simulations confirmed that the rate of conversion increased as temperature increases and conversion of reactants increased with retention time, until an equilibrium state was reached. The AD process modelling using DYNOCHEM was successfully modified and implemented to account for unsteady operation which is generally the case of full-scale reactor by developed methodology. , M.Tech. (Chemical Engineering)
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Green energy (biomethane) production from codigestion of abattoir, market and grass waste as substrates
- Authors: Matheri, Anthony Njuguna , Mwiinga, Masonga Sichibanze , Zelda, Rasmeni Zenzile , Mohamed, Belaid
- Date: 2019
- Subjects: Biogas , Biomethane , Digestion
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/402179 , uj:33645 , Citation: Matheri, A.N. et al. 2019. Green energy (biomethane) production from codigestion of abattoir, market and grass waste as substrates.
- Description: Abstract: South Africa had in the past years been experiencing an increased energy demand. High energy crisis called for research and development in a quest for alternative energy sources (waste to energy) that drive the Nation economy forward in line with Sustainable and National development goals. Utilizing organic waste to produce biogas as a source of energy could significantly help alleviate this problem. Biogas is renewable energy, a mixture primarily consisting of methane (CH4) and carbon dioxide (CO2). The study evaluated mono-digestion of market waste (MW), abattoir waste (AW), and grass (G) and co-digestion of the three mix of substrate by determining their biomethane potential under mesophilic conditions of 37oC. It was found that the mono-digestion of grass produced high methane (1035.3 Nml) after the stipulated 14 days of hydraulic retention time, Abattoir waste, and market waste produced 722.1 Nml and 470.7 Nml of methane respectively, and the co- digestion of all substrates produced 1013.1 Nml of methane after 14 days. Co-digestion of the substrates assisted to regulate the anaerobic digestion condition or variables for biomethane production. Co-digestion of the substrate was recommended for optimality or increase in methane yield.
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