Master of Science in Sustainable Process Development
Permanent URI for this collectionhttp://192.248.9.226/handle/123/28
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Browsing Master of Science in Sustainable Process Development by Subject "BIOMASS"
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- item: Thesis-Full-textEffect of particle size on packed bed biomass combustion(2018) Rajapaksha, GDM; Narayana, MIn this thesis, particle size effect on biomass (rubber-wood) combustion in a packed bed reactor was investigated in experimentally. Mass loss rate, bed shrinkage rate, temperature profile at different bed locations and gas compositions in the out-of-bed flue gases were measured at a constant primary air flow rate. In this study used a fixed batch of biomass. An external heat source was used to ignite the biomass initially and after ignited the biomass, removed the external heat source. Rubber-wood cubes were fired with size ranging 25mm, 38mm, 50mm and 63mm. As time pass, the height of the packed bed is decreasing due to shrinkage of the bed and also the weight of biomass is reducing with time. It is found that at the operating condition of the current study, burning rate of biomass particle is higher with smaller fuel size; and also smaller biomass particles are faster to ignite than the large biomass particles and have unique combustion stages; on the other hand, larger biomass particles produced a higher flame temperature. Larger particles also cause the combustion process becoming more transient where the burning rate varies for the most part of the combustion process. And also biomass combustion time (operational time) is increased with increasing biomass particle size. And here calculate the percentage of excess air, when increased the particle size, amount of excess air release is high. Therefore, need to control the amount of primary air supply when increased particle sizes.
- item: Thesis-Full-textKinetic modeling of tar formation in an updraft biomass gasifier(2020) Jayathilake GKM; Gunarathne DAs the depreciation of the fossil fuels in the world, it is obligatory to discover new fuels to the highly industrialized society. With increasing requirements of the energy, it is globally focused on the use of renewable energy. Biomass can be used as an alternative energy source to replace fossil fuels, which contribute to the greenhouse gas emission. Therefore, biomass is a major renewable energy source as of today. Nowadays, converting biomass into biofuel is a major goal. So, the gasification process can be used as such an effective way to convert biomass into syngas. Even if the major goal of the gasification is to produce syngas such as H2, CO, intermittently, many byproducts are generated such as NOx, SO2, fly ash and tar. The formation of tar in the gasifier is a problematic situation. The formation of tar mainly depends on temperature, residence time, type of biomass and gasifying medium. Modeling is an effective method to optimize the gasifier operation. Also, it can be used to determine the relationship between operational parameter limits and explain trends in output products. By using Aspen Plus process simulation tool, a kinetic model was developed to predict the tar formation of updraft gasifier considering the main chemical phenomena biomass pyrolysis, reduction and combustion. The results were compared with the experimental data from the literature to validate the model. According to the developed model, the tar content and the composition could be estimated with respect to the equivalence ratio (ER) and pyrolysis zone bed height. When the ER is increasing the formation of tar is trending to decrease. The pyrolysis zone bed height beyond 1.3 cm does not show a significant impact on the tar content. It is possible to use the developed model to minimize tar content by operating at a suitable temperature (by controlling the ER) and by keeping an applicable residence time (by maintaining a suitable bed height). Further, this model can be used to optimize the tar formation with different biomass types and gasifying mediums when the temperature profile of the gasifier is available.
- item: Thesis-Full-textModeling of biomass gasification with CO₂ enrich air as gasifying agentJayakody, KKR; Narayana, MThe biomass gasification has been carried out using an updraft gasifier. This work focuses on the production of producer gas from biomass (Rubber Wood). Mathematical model for thermo-chemical process of biomass gasification is developed in this research work. ASPEN PLUS simulator and pilot plant gasifier were used to investigate the effect of reactor temperature, equivalence ratio and CO2 to air ratio on composition of producer gas. The gasifier was operated over a temperature range of 500-1000 C, while varying equivalence ratio from 0.2 to 0.36and CO2 to air percentage from 1% to 10% and it was found that the most of trends were similar for both the case. The results showed Carbon monoxide concentration in the product gas increases with increase in temperature and CO2 to biomass ratio but decreases with increasing equivalence ratio.
- item: Thesis-Full-textOne dimensional mathematical model for packed bed biomass combustion using MATLAB(2018) Priyadarshani, U; Narayana, MPacked bed biomass combustion is widely used thermal conversion process which contributes major portion of energy fulfillment around the globe. This process is usually involving higher operation cost due to low efficiency and high emissions. Hence there is a huge room for improvements in the process and needs to be optimized as well as modernized. This thesis presents two-phase one-dimensional mathematical model with MATLAB solver which can be used for diagnosis and optimization of packed bed combustion process under low computing resources and less cost. The mathematical model uses the discretized equations to develop the ordinary differential equations which are solved using implicit method. Free-board region is not taken into account. Only the biomass bed is considered here to solve the combustion system by applying conservation equations into gas and solid phase separately. The main model is consisting with different sub models with subjected to four stages of combustion as drying, pyrolysis, Char oxidization and char combustion. The biomass batch is initially ignited by continuous preheated gas inlet and higher gas flow rate. Radiation heat transfer is assumed to be negligible due to high temperature gas flow at the inlet. Combustion is occurred in batch wise. Particle diameter and bed porosity is considered with a mean value for the simplicity of the model. The developed model is used to find the solid temperature profile and generation of CO2 and CO gases. By using walking column approach, industrial moving grate furnace was represented and required optimum grater length for a particular mass flow rate can be calculated with the fixed bed simulation results.