Simulation Of A Process Design Model For Anaerobic Digestion Of Municipal Solid Wastes (original) (raw)
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Modelling and Simulation of Anaerobic Digestion of Wastewater Sludge using Mathematica
The increasing demand of energy has led to a chaos among the existing energy sources and the tremendous amount of solid waste generation on a daily basis is making the country a dumping ground. Hence, it becomes an urgent need to address the problem of waste management and energy crisis. Municipal solid waste (MSW) thus serves as an efficient and reliable option for the conversion of waste to energy. The anaerobic digestion of solid waste to produce biogas is gaining importance. The growing need of the process involves increased efforts in reducing biogas plant design cost and optimizing process operation. This could be possibly done through mathematical modelling of the process. This paper particularly highlights the deviation of theoretical method with that obtained during experimentation through simulation results. Simulation is done in Mathematica and the concentration profiles of the substrate, anaerobic microorganisms and methane generation are plotted against various dilution rates and specific growth rate. The results reveal that at lower value of specific growth rate and dilution rate the experimental results fit best with the simulation result. This study can contribute in solving the complex unsteady state modelling equations of anaerobic digestion using Mathematica and pre-simulation of the experimentation results.
Anaerobic Digestion of Organic Fraction of Municipal Solid Wastes: Kinetic Study
Journal of emerging technologies and innovative research, 2018
Energy crisis and waste management is one of the serious issues faced today. Anaerobic digestion is a biological process used for conversion of organic fraction of municipal solid wastes (OFMSW) in to biogas. Thus anaerobic digestion is a promising technology for energy production along with the effective disposal of wastes. In this study batch anaerobic digestion of OFMSW was carried out for 100 days at room temperature (32 oC) for varying substrate concentration (total solid concentration, TS) of 115 g/l , 99 g/l and 83 g/l .The performance of reactors was evaluated by measuring the daily biogas production. Kinetics of anaerobic digestion of OFMSW was described by using, a first order model based on the availability of substrate as the limiting factor. At the end of the 100 days digestion, the biogas yield at TS concentrations of 115 g/l, 99 g/l and 83 g/l were 22.7, 55.9 and 43.1 L /kg VS respectively. The values of kinetic constants (k) obtained were 0.0196, 0.0292 and 0.0319 (d...
International Journal of Renewable Energy Development, 2023
Anaerobic digestion is a complex process whose understanding, optimization, and development require mathematical modeling to simulate digesters' operation under various conditions. Consequently, the present work focuses on developing a new and improved model called "AM2P" derived from the AM2 model. This new model incorporates surface-based kinetics (SBK) into the overall simulation process to transform the system into three stages: hydrolysis, acidogenesis, and methanogenesis. Experimental data from our previous work were used to identify the AM2 and AM2P models' parameters. Simulations showed that the AM2P model satisfactorily represented the effect of the hydrolysis phase on the anaerobic digestion process, since simulated values for acidogenic (X1) and methanogenic (X2) biomass production revealed an increase in their concentration as a function of particle size reduction, with a maximum concentration of the order of 5.5 g/l for X1 and 0.8 g/l for X2 recorded for the case of the smallest particle size of 0.5 cm, thus accurately representing the effect of substrate particle disintegration on biomass production dynamics and enabling the process of anaerobic digestion to be qualitatively reproduced. The AM2P model also provided a more accurate response, with less deviation from the experimental data; this was the case for the evolution of methane production, where the coefficient of determination (R 2) was higher than 0.8, and the root-mean-square error (RMSE) was less than 0.02.
Energy and Environment Research, 2016
The process dynamics of anaerobic digestion of municipal solid waste (MSW) in a batch bioreactor for the production of biogas has been analysed. An anaerobic batch digester was designed for the treatment of MSW in Port Harcourt metropolis, Nigeria, while at the same time generate biogas as a useful by-product. In the course of the design, the biochemical behaviour of the MSW in batch processing was investigated and analysed. Mathematical models were developed to describe the behaviour of the waste using material balance analysis. The models were validated by the formulation of a Microsoft Visual Basic Version 6.0 programme to simulate the digestion process for a fractional conversion of 0.2-0.8 and Total solids (TS) concentration of 4-30%. The results were analysed using Microsoft Chart Editor and showed that the fractional conversion has various levels of effect on other process parameters like the mean cell residence time, substrate and microbial concentrations and the volume of biogas/methane produced.
Waste Management, 2010
A model based on the work of was applied to simulate the anaerobic biodegradation of ruminal contents. In this study, two fractions of solids with different biodegradation rates were considered. A first-order kinetic was used for the easily biodegradable fraction and a kinetic expression that is function of the extracellular enzyme concentration was used for the slowly biodegradable fraction. Batch experiments were performed to obtain an accumulated methane curve that was then used to obtain the model parameters. For this determination, a methodology derived from the ''multiple-shooting" method was successfully used. Monte Carlo simulations allowed a confidence range to be obtained for each parameter. Simulations of a continuous reactor were performed using the optimal set of model parameters. The final steady-states were determined as functions of the operational conditions (solids load and residence time). The simulations showed that methane flow peaked at a flow rate of 0:5-0:8 Nm 3 =d=m 3 reactor at a residence time of 10-20 days. Simulations allow the adequate selection of operating conditions of a continuous reactor.
Process Simulation Model for Anaerobic Digestion
In this study, a novel process simulation model (PSM) was developed for anaerobic digestion using Aspen Plus ® (version 7.3.2). PSM has two parts, one for hydrolysis working based on extent of reaction and the other on kinetics of reactions. A total of 53 reactions were used in the model including inhibitions, rate kinetics, pH, ammonia, volume and HRT. Each reaction set in the kinetic reactor has a FORTRAN program to calculate the kinetics of biogas production. PSM was validated with earlier research studies and industrial experiments in Aspen Plus ® . The P-value after statistical analysis was found to be 0.324, which showed there was no significant difference between different validations, even after a change in process conditions, loading rate, HRT and substrate. The sensitivity analysis with a ±10% change in composition and extent of reaction would result in average 4.56% higher value than the experimental value.
IOP Conference Series: Materials Science and Engineering
Anaerobic digestion was conventionally applied for treating sewage sludge. However, the accumulation of solid waste particularly food waste has reach the critical levels worldwide. In practice, the food waste was dumped into the landfill for ultimate disposal. However, the greenhouse gases produced in the landfill makes this is no longer a preferable option. Anaerobic digestion was seen as an alternative for managing the food waste in a sustainable way. Methane, a renewable energy is potentially in replacing fossil fuel. However, the methane yield from the digestion of food waste inefficient. Therefore, a study of the codigestion of sewage sludge and food waste was conducted to investigate the improvement of the methane yield. This study was conducted by using a mixture of domestic primary sewage sludge and food waste as a co-substrate for the anaerobic digester. The kinetics modified Gompertz modelling was applied to describe the anaerobic digestion process. A series of batch biochemical methane potential (BMP) assay was prepared using Automatic Methane Potential Test System (AMPTS II) to investigate the anaerobic digestibility of the mixture of domestic primary sewage sludge and food waste. The BMP assay showed that the co-digestion improved the ultimate methane yield by 32.6% higher than domestic primary sewage sludge alone, indicated that the co-substrate characteristics influencing the methane yield. Besides that, the greater VS/TS ratio of the substrate also resulted in the greater methane yield. The kinetics parameter from the modelling analysis were slightly lower as compared to the laboratory data.
Validation of a simple kinetic modelling approach for agro-industrial waste anaerobic digesters
Chemical Engineering Journal, 2015
Anaerobic co-digestion of agroindustrial wastes constitutes a promising option for the stabilisation of residues producing biogas. A mixture of bovine ruminal content, tannery carving fat and activated sludge purge was considered for this work. Biodegradability tests for individual wastes and for the mixture of wastes were performed in batch and also in continuous conditions in a completely mixed reactor. The continuous reactor was operated at 30-day average residence times with a load volume of 3.0 g VS/L.d, reaching a VS removal efficiency of 66%, and yielding 0.38 L CH4 /kg VS added and 0.58 L CH4 /kg VS removed. A first order kinetic model with time delay was used to describe the behaviour of the whole process. The determination of parameters was performed in both systems using direct search methods. Monte Carlo methods were used in order to determine the range of parameters. Ultimate methane yield of 90 ± 6% was obtained from batch tests and 88 ± 9% in the continuous reactor. The kinetic rate constant in the reactor (0.205 ± 0.013 d-1) was twice the value obtained in batch conditions (0.089 ± 0.010 d-1), showing that microbial adaptations occurred in the continuous mode.
Modeling of Anaerobic Digestion of Organic Fraction of MSW at industrial scale
2012
The industrial process complexity of biogas production is often a drawback to optimization. Kinetic models allowed the understanding of current phenomenon in reactors making possible the automation and control. To deepen the knowledge of the process, a bibliographic research of the scientific, technological and monitoring state-of-art of the anaerobic digestion process was made, including performance calculations to find parameters best suited for optimization. A mathematical model that describes the general degradation of organic fraction of municipal solid waste (OFMSW) in full scale reactors was then developed. The current study is based on models developed by several authors, where it was included the microbial growth kinetics, each one with their own parameters, found in the bibliography. The kinetic flux was divided into three processes: hydrolysis, acidogenic/acetogenic and methanogenic. The model simulates the decomposition of low biodegradable matter in high biodegradable m...
Research Into Design and Modeling of Anaerobic Digestion Process Applied to Municipal Solid Wastes
Anaerobic digestion (AD) potentially offers a much better option for management of the organic fraction of municipal solid wastes compared with landfill and incineration. AD not only harvests the organic carbon in the form of methane as bioenergy, but also makes it easier to recover and recycle the nutrients contained in the wastes. Additionally, AD system can be constructed near the source of the wastes, thus long distance trucking is eliminated resulting in lower transportation costs of the materials which typically has high water contents. Adoption of AD for municipal waste management however, relies on the development of new technologies that offers required reliability and efficiency at lowest possible costs. This presentation summarizes the research progress made at Washington State University in developing AD technologies with high solids contents aimed at addressing these challenges. Main topics cover (1) concept and test results of a new system design, (2) mixing strategy, ...