Modelling and Simulation of a Diaspore Tubular Digestion Process (original) (raw)

Mathematical modelling of autothermal thermophilic aerobic digesters

Water Research, 2007

Calibration Energy model Influent characterization Modelling Specific heat yield a b s t r a c t This paper presents a new mathematical model for Autothermal Thermophilic Aerobic Digesters. The reactor has been modelled as two completely mixed volumes to separately predict the behaviour of the liquid and gaseous phases as well as the interrelation between them. The model includes biochemical transformations based on the standard Activated Sludge Models of IWA, as well as physico-chemical transformations associated with the chemical equilibria and the mass transfer between the liquid and the gaseous phases similar to those proposed in the ADM1 of IWA. An energy balance has also been included in the model in order to predict the temperature of the system. This thermal balance takes into account all those biochemical and physico-chemical transformations that entail the most relevant heat interchanges. Reactor performance has been explored by simulation in two different scenarios: in the first where it acts as the initial stage in a Dual system, and in the second where it acts as a single-stage treatment. Each scenario enabled the identification of the relevance of the different parameters.

Solid Digestate—Mathematical Modeling of Combustion Process

Energies

The combustion of waste biomass is becoming a key challenge for the energy sector, especially in times of growing energy demand and increasing environmental awareness of society. Processing such fuels is usually demanding. Mathematical modeling makes it possible to adapt the course of the process. The best option is to use appropriate fuel mixtures. The aim of this work was to develop a simple model that would allow the pre-selection of the mixture of two types of digestate. Residues from methane fermentation of maize and apple pomace were used in the study. The paper presents both a mathematical model and laboratory tests. The practical part was to check the validity of the model estimates. The model works on the basic data from physicochemical analysis. Laboratory tests included combustion of the samples of different mixtures. We used image analysis of thermograms to determine changes during combustion, which allowed us to determine when and where the main combustion occurs. Resul...

Mathematical Modelling, Finite Element Simulation and Experimental Validation of Biogas-digester Slurry Temperature

International Journal of Energy and Power Engineering, 2013

The present describes and simulates the temperature distribution of slurry by using the heat equation and appropriate boundary conditions and their numerical simulations with the Finite Element Method. This method is suitable to describe the temperature profile in Bio-digester and Bio-rectors for optimum biogas production. The Mathematical modeling of bio-digester helps us to understand the change in digester temperature with the change in the ambient temperature, internal heat generation, thermal conductivity and other physical and thermo-dynamical processes that govern the thermal system. Mathematical modeling can also be used to predict and estimate the physical and chemical parameters affecting the biogas production. The internal heat generation was estimated to be 1.2 W/m 3 .The Finite Element linear, quadratic solutions and exact solution was compared for the profile of temperature of the bio-digester slurry. The average temperature of bio-digester slurry was found to be 33.12 °C at its center. The thermal conductivity we have also found to be 0.69 W/ m °C. By using the finite element method to solve the mathematical modeling, the maximum slurry temperature was found to be 33.13 °C at its center. Furthermore, we have calculated the thermal conductivity in the biogas chamber from our measurement data. This thermal conductivity (k) 0.69 W/m °C was used in the exact solution of the physical model equation, linear and quadratic finite elements solutions. The temperature profiles of these three solutions virtually collapse to a single parabolic profile, which in term agreed very well with our measured data of the temperature profile.

Thermodynamic analysis and optimization of the integrated system of pyrolysis and anaerobic digestion

Chemical Engineering Research & Design, 2022

In this paper, the performance of an integrated Rankine power cycle with parabolic trough solar system and a thermal storage system is simulated based on four different nano-fluids in the solar collector system, namely CuO, SiO 2 , TiO 2 and Al 2 O 3. The effects of solar intensity, dead state temperature, and volume fraction of different nano-particles on the performance of the integrated cycle are studied using second law of thermodynamics. Also, the genetic algorithm is applied to optimize the net output power of the solar Rankine cycle. The solar thermal energy is stored in a two-tank system to improve the overall performance of the system when sunlight is not available. The concept of Finite Time Thermodynamics is applied for analyzing the performance of the solar collector and thermal energy storage system. This study reveals that by increasing the volume fraction of nano-particles, the exergy efficiency of the system increases. At higher dead state temperatures, the overall exergy efficiency is increased, and higher solar irradiation leads to considerable increase of the output power of the system. It is shown that among the selected nano-fluids, CuO/oil has the best performance from exergy perspective.

Solid Digestate—Physicochemical and Thermal Study

Energies

Biogas production is an important component of sustainable energy management. In addition to energy-rich biogas, this process also generates solid waste in the form of digestate. The management of this stream has been problematic for many years. One promising method of utilizing this fraction seems to be incineration under controlled conditions. This paper presents an analysis of mixtures of different digestates to assess their suitability for incineration. Four digestates based on corn silage CS and apple pomace AP were used as test fuel. The ultimate and proximate analysis showed that this fuel deviates from the standards accepted for pure biomass, but was found in other fuels, especially those treated as waste. This materials can be a valuable source of energy, but combustion needs be undertaken in special units. Moisture content of investigated digestate-type ranges from 11.9–12.2% and ash content ranges from 8.2% to 11.6%. This could lead to ash sintering and slugging problems,...

An analysis of bio-digester substrate heating methods: A review

Renewable and Sustainable Energy Reviews, 2021

This review paper studied substrate heating methods currently used in Bio-digesters with a view to assess their effectiveness in establishing and maintaining a stable temperature in a bio-digester. Stable temperature is known to enhance biogas productivity and process stability. Four heating approaches, on-vessel; floor heating; in-vessel and ex-vessel, were critically analyzed. The analysis focused on their potential to distribute heat and temperature uniformly in the whole volume of digester slurry, the ultimate effect on the methane content and quantity of the biogas produced and applicability to small scale household digesters. The study revealed that the In-vessel heating approach has the best heat and temperature distribution and that since the microbial activities responsible for methane production are sensitive to temperature fluctuations, has the highest potential to produce high quantity and quality biogas. The heating approach can also be easily applied to household biodigesters. It was also revealed that both insulation and substrate heating are necessary for digester temperature stability. The limiting factor in substrate heating in biodigesters is the heating cost. This can be minimized by using heat recovered from CHP plants and solar radiation, in case of non-electricity generating plants. Water, because of its high specific heat capacity, was recommended as a better medium of heat transfer than air in case of indirect heating. To enhance efficiency in biogas production, even household digesters should be designed with some insulation and heating facility regardless of the intended use of the produced gas.

Thermal-hydraulic digester model using a higher order numerical method

2001

Abstract This paper presents a detailed fundamental model of a continuous pulp digester developed for simulation and control. Most modeling efforts in the past have either emphasized on reaction kinetics and energy transfer assuming a prescribed flow behavior, or modeled digester hydraulics with simplified reaction kinetics.

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.