Master of Science in Sustainable Process Development
http://dl.lib.uom.lk/handle/123/28
2024-03-29T09:12:11ZProcess parameter optimization of urban biowaste carbonization
http://dl.lib.uom.lk/handle/123/16197
Process parameter optimization of urban biowaste carbonization
Perera SMHD
About 75% of Municipal solid waste (MSW) collected around the country is organic biomass which mainly includes food waste, wood, paper, saw dust and paddy husk. Urban councils in Colombo city and nearby suburbs collect biowaste separately which has created a huge potential in converting urban biowaste into value-added component like biochar, thus resolving the problems associated with MSW management and mitigating socio-economic and environmental issues related to MSW. In this study, torrefaction is identified as the most viable technology available for the conversion of organic MSW into biochar and the study mainly focuses on developing a three dimensional computational fluid dynamics (CFD) model of a continuous packed-bed torrefaction reactor for organic MSW and then optimizing the process variables and the geometry. A mathematical model including all heat, mass and energy transfers, and heterogeneous & homogeneous reactions is firstly developed and then converted to a numerical model and simulated using OpenFOAM for an insulated cylindrical reactor in which hot gas at elevated temperatures (473 – 623K) is provided from the bottom while solid at ambient conditions is fed from the top. The torrefaction reactor is optimized for gas inlet temperature and residence time and then the geometry of the reactor is optimized for the optimum gas inlet temperature and residence time. Four reaction zones are identified in the reactor domain; i.e. drying, softening & depolymerization, limited devolatilization & carbonization and extensive devolatilization and carbonization. The optimum inlet gas temperature, residence time and D/L ratio are 573K, 13000s and 0.24 respectively. For the optimum conditions, biochar yield is 55.7% while ash content is 19.1%. Further In dry basis, 95.9% of biomass is decomposed and the total weight loss based on the initial wet biomass is 86.6%.
2020-01-01T00:00:00ZEffect of particle size and secondary air for particulate biomass combustion in a bubbling fluidized bed reactor
http://dl.lib.uom.lk/handle/123/16198
Effect of particle size and secondary air for particulate biomass combustion in a bubbling fluidized bed reactor
Silva GGSN
Biomass combustion is used as basic technology to generate heat by humans for millennia. With the incremental needs of modern man, biomass combustion still plays a major role in heat and power generation. In Sri Lankan context, biomass combustion is extensively used in manufacturing industries for boilers, furnaces, dryers, etc. Even though biomass is abundantly available as an energy source in Sri Lanka, industrial biomass combustion systems are operating under very low efficiencies. Operating these industrial combustion systems in an optimum manner will help in numerous ways to industries, environment and society.
In this study, particulate biomass combustion in a bubbling fluidized bed combustor model is used to evaluate optimum secondary air flow rate rates and particle sizes. First Proximity of particulate biomass (saw dust) was conducted to find out moisture and volatile content, then sieve analysis was conducted to segregate and name the particle sizes. Different particle sizes were fluidized using measured primary air flow and combusted under varied secondary air flow rates and obtained maximum temperature achievement in three distinct locations (top, middle and bottom) in the fluidized bed reactor by using installed temperature transducers. Secondary air flow rates and temperature results were tabulated for each particle sizes to analyze temperature variation. Matlab CFTool feature was used to generate surface fits for all three location (top, middle and bottom) temperature variation against particle size and secondary air flow rates. After evaluation results and surface fits, Optimum operating secondary air flow rates and particles sizes were identified for used lab scale bubbling fluidized bed combustor. Recommendations were suggested for industrial scale particulate biomass combustion systems such as boilers, furnaces, etc. for optimum operation based on lab scale system results.
2020-01-01T00:00:00ZInvestigation of multicomponent heavy metals adsorption capability using raw coir dust and processed coir pith
http://dl.lib.uom.lk/handle/123/16213
Investigation of multicomponent heavy metals adsorption capability using raw coir dust and processed coir pith
Amarasinghe AMPC
Water is the most vital natural resource that sustains all living organisms on the earth and access to safe and clean water has become a crisis due to intense water pollution by anthropogenic activities, over-pumping of groundwater for irrigation purposes, limited water availability due to climate changes, regional conflicts over common water resources, etc. Wastewaters that contain various heavy metals, such as arsenic, chromium, manganese, nickel, lead, cadmium, zinc, and copper are being discharged into natural water bodies annually by many industries. Industrial processes that generate wastewater with significantly high levels of heavy metals use various techniques, such as chemical coagulation, chemical precipitation, membrane separation, extraction, electrodeposition, ion-exchange, and electrochemical techniques in order to remove the heavy metal contents. Nevertheless, most of these techniques use expensive chemicals and require considerable time, and some of them are proven to be less effective and less efficient, especially in removing trace amounts of metals. Besides above methods, adsorption technique is one of the most widely used technique to remove heavy metals from water and studies have revealed that it is much effective in removing heavy metals with high solute loading and even at minute concentrations. In the past decade, significant number of studies have been conducted worldwide on the removal of heavy metals from aqueous solutions by non-living and biologically inactive biomass. This approach of wastewater treatment is known as biosorption, and the non-living biomass used there is defined as bio sorbent. Use of bio sorbents to remove heavy metals from wastewater is a novel and developing technology in the water treatment field. Coir pith is a waste-derived material that can be utilized as a biosorbent for heavy metals removal from wastewater. In this study, directly obtained raw coir dust from coconut husks and processed coir pith were tested for their removal efficiencies of 8 heavy metals, i.e., As, Cd, Cu, Cr, Mn, Ni, Pb, and Zn. Standard heavy metal solutions were prepared for each metal and heavy metal content of standard solutions, coir pith, and coir dust were first measured using the Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES) method. A multicomponent batch adsorption experimental procedure was conducted to determine the removal efficiencies of each metal by both coir dust and coir pith. In experimental procedures, respectively, 1g, 2g, 3g, 4g, and 5g of coir pith and coir dust were added to equal volumes of each metal solution and allow adsorption for 2 hours. Then filtered samples were tested for the heavy metal concentrations using
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the ICP-OES method. Multicomponent heavy metal removal efficiencies of coir pith were tested by varying the adsorption temperatures and the contact time between the heavy metal solution and the coir pith sample. Analytical results show that both raw coir dust and coir pith act as suitable bio sorbents for removal of As, Cd, Cr, Ni, and Pb, and the optimum solid/liquid ratio is 0.1 g/ml at room temperature for 2 hours if contact time for all these five heavy metals. According to the results comparison between the of raw coir dust and processed coir pith, raw coir dust shows higher heavy metals removal capacities Coir pith is the most suitable biosorbent for Cu removal while coir dust is most suitable biosorbent for Mn removal. For raw coir dust metals and bio sorbents 0.08g/ml at room temperature for 2 hours contact period is the optimum solid/liquid ratio. For processed coir pith metals and bio sorbents 0.1g/ml at room temperature for 2 hours contact period is the optimum solid/liquid ratio Anyway both coir pith and coir dust are not suitable for Zn removal from aqueous solutions. For all metals except Zn, contact period of 30 minutes and temperature of 30 °C are the optimum operating conditions.
In this experimental we have used multi component heavy metal sample as a result of it both materials adsorption and desorption are happening in the same sample. When we consider heavy metal adsorption with the temperature from 30-70 °C heavy metals adsorption capacity has decreased the reason for this with the increasing of temperature kinetic energy of the metal has increased then desorption is happened inside the sample. As a result of it with increasing of temperature heavy metals adsorption capacity will decrease.
When we consider contact time of the heavy metals sample with the absorbent, For Cr, Cu and Pb show similar results. From 30 min to 2 hr material adsorption efficiency has decreased but 2 hr to 4 hr adsorption efficiency has increased the reason is for this, from 30 min to 2 hr desorption appeared in the sample but with the increasing of the contact time from 2 hr to 4 hr again heavy metals adsorption is happened in the sample. But all other heavy metals are showing decreasing trend of heavy metals adsorption capacity with the increasing of contact time.
2020-01-01T00:00:00ZInvestigation of CO2 sequestration possibility via aqueous phase mineral carbonation using industrial waste materials
http://dl.lib.uom.lk/handle/123/16214
Investigation of CO2 sequestration possibility via aqueous phase mineral carbonation using industrial waste materials
Nanayakkara SG
Carbon dioxide (CO2) as the most vital greenhouse gas in the earth’s atmosphere plays a major role in maintaining the global temperature. Higher concentrations of CO2 in the atmosphere, increases amounts of heat entrapped in the atmosphere. Thus, the environmental temperature increases when the CO2 concertation increases and results in global warming. The global CO2 emission was approximately 35.3 billion metric tonnes in 2018 and, it is predicted to be increasing up to 43.08 billion metric tonnes by 2050 as per the prevailing trends in statistical analysis. Therefore, maintaining an acceptable concentration of atmospheric CO2 is required. In this situation, anthropogenic CO2 capture and storage technologies have emerged to reduce the atmospheric CO2 concentration. Among the carbon capture methods, post-combustion CO2 capture technologies are the most common as there is the advantage of ability to retrofitting to existing plants.
Mineral carbonation is considered as a natural and exothermic process among available post combustion CO2 capture technologies, which gives promising results in CO2 sequestration by storing as mineral carbonates. Suitable materials for mineralization are natural minerals like silicate rocks, serpentine, olivine minerals or else industrial wastes like oil shale ash, steel slag, paper mill waste, fly ash or mine tailing, etc.
In this study, the existing literature on CO2 sequestration capabilities through aqueous phase mineral carbonation of industrial waste materials were reviewed and analyzed. Industrial waste materials, such as coal fly ash and steel slag have significant capture capacities and coal fly ash consumes significantly lesser energy and costs to capture one tonne of CO2. In addition, calcium extraction from Lakvijaya Coal Fired Power Plant fly ash was experimentally investigated to identify the potential for indirect carbonation, to sequestrate CO2 from coal flue gas. A maximum calcium extraction efficiency of 9.65% was obtained for coal fly ash obtained from Lakvijaya Coal Fired Power Plant.
2020-01-01T00:00:00Z