Faculty of Engineering, Chemical & Process Engineering

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item: Thesis-Abstract
A Study of natural rubber latex - filler interaction
Peris, CN; Gunapala, O; Gunapala, PY
An attempt has been made to evaluate natural rubber latex - filler interaction. 1800- peel test of flexible to rigid joints was performed to determine the peel strength of natural rubber latex -kaolin joints in order to evaluate the interaction of natural rubber latex with standard rubber grade kaolin and activated one by ion exchange reaction with amino -functional derivatives. Experimented natural rubber latex compounds were pre vulcanized with sulphur and ionization radiation. Radiation vulcanization was performed using 60 Co source irradiator, originally designed for sterilization of medical products, with reduced gamma rays dose rate. Its suitability for radiation vulcanization of locally produced natural rubber latex was confirmed experimentally. Obtained results showed that the peel off test device was acceptable for evaluation of natural rubber latex -filler interaction irrespective of the vulcanization system used with latex compound. Peel test results displayed the influence of modified fillers on the peel strength values of tested laminates. Increased peel strength values of the samples containing modified kaolin were attributed to better interaction of the filler with rubber polymer. It was investigated, that facilitated interaction observed with natural rubber latex and modified kaolin resulted in improved properties of filled natural rubber latex compounds of both vulcanization system, and irradiated one was more susceptible within the experiment performed. Preference in mechanical stability time, viscosity factor and tensile was given to radiation vulcanization natural rubber latex (RVNRL). Reinforcing effect of modified filers in natural rubber latex compounds was lower of that observed earlier with dry rubber compounds. The reason for it could be associated with partial deactivation of the active centres initially brought by modification the phenomenon that have to be studied and overcome in the future. However, it is hoped that carried out research positively contributes to the understanding the mechanism of reinforcement of rubber polymers with fillers and development of the technologies upgrading cheap local mineral resources to use them more beneficially in natural rubber formulation technology. Another aspect covered by research related to development of radiation vulcanization technology that gives a definite support for introduction to local latex based manufacturing industries.
item: Thesis-Full-text
A Study on the effect of aeration on mechanical stability of concentrated natural rubber latex upon maturation
Roshanie, LKS
ABSTRACT The ever innovation of rubber products in diversified fields have made it necessary to find suitable quality latex rubberfordifferentproducts.Because,manufacturesofrubberproductsareinsistingoncertain range of mechanical stability ( usually in the range of 500 -1000 seconds), there is a continuous research going on to find suitable test method to asses a such quality of latex It is been found that volatile fatty acid number (VFA No:), Alkalinity and Mechanical Stability Time (MST) test for quality control test proved to be a sui tabl e methods for making quality products. The objective of this research to simply give a alternative mclhod to develop mechanical stability without adding soap because previous studies shows that when soap level is high the quality of the latex was low. Current studies consist of analyzing the MST variation of centrifuged latex with aeration level and maturation. And also analyze the variation of other properties such as Alkalinity, VF A No:, Viscosity , to nductivity and pH. The latex used for this study were obtained from a centrifuged plant, accordingly a special request was made to them to supply latex with minimum addition of soap. Aeration was supplied in different levels to different sample. Following properties was investigated at intervals: MST, Alkalinity, VFA No:, Viscosity, pH and Conductivity Out of the whole investigated properties; response to the aeration level was remarkable in MST, with maturation results suggest that MST is increases with higher the aeration level. Other properties such as a VF A, Alkalinity are not much effect with the air quantity. Therefore supply of air is not destroying the quality of the latex. VF A increment is not much significant. Viscosity is decreases up to some significant level with air quality. pH of the samples show some storage patterns not a trend pattern. Variation in MST is due to the air supplied to the sample; promote hydrolysis of proteins and phospholipids in the latex. Finally former fatty acids anions, phosphate anions are observed at the ... particle interface and enhance the stability of latex Further more results show that the highest aeration level is not the optimum aeration level . so • further studies should be carried out to find an optimum aeration level and how minimize the space of vessel which is required for aeration.
item: Thesis-Abstract
Abatement of odour from tobacco process emissions by condensation, scrubbing and biofiltration
Wijayawardhana, AJ; Amarasinghe, ADUS
A study was conducted to evaluate the removal efficiency of NH3 and Hydrogen Sulfide emitted from tobacco process emissions by infiltration. The experiments were based on testing the removal efficiency of the contaminants on four types of packing material, namely: coconut fiber/tobacco compost, peat/wood chips, garden waste compost/wood chips and inert plastic media/garden waste compost. Results indicate that maximum removal efficiencies of ammonia and hydrogen sulfide ( 100% and 100% respectively) can be achieved for coconut fiber/tobacco compost mixture while similar removal efficiencies was obtained by peat/wood chips mixture. The maximum elimination capacities for ammonia for the respective packing materials were 5.59, 7.74, 4.58 and 1.98 gm3h-1 . Hydrogen sulfide maximum elimination capacities for the same packing materials were 6.99, 9.91, 6.04 and 2.96 gm3h-1 . The study was conducted as a preliminary evaluation for selecting the most suitable packing material relevant for application in an industrial scale biofilter for the treatment of the same waste gas stream.An industrial biofilter of 23 m3 in volume, packed with a coconut fiber filter medium inoculated with tobacco compost (20% by weight) was operated for a period of 45 days. The biofilter was supplied with a humidified gas stream from. Tobacco processing with main components being ammonia and hydrogen sulfide. The flow rate of the gas stream was varied from 1160 m3h-1 to 2100 m3h-1 . Results indicated that hydrogen sulfide and ammonia were effectively removed 100% and 95% under an empty bed retention time (EBRT) of 36s and 100% and 90% under an EBRT of 20s respectively. Maximum elimination capacities of 5.9 gm-3h-1 and 27.6 gm-3h-1 were reached for an inlet loading of 1.8 gm-3h-1 and 3.8 gm-3h-1 for ammonia and hydrogen sulfide respectivelyAn industrial scale odour abatement system was designed and constructed, consisting of three units namely: condenser, scrubber and biofilter, the latter acting as the major unit of the system. The gas passes initially through a shell and tube heat exchanger giving moderate pollutant removal (7% ammonia). The gas stream is then directed to a packed column scrubber where average removal of 85% ammonia and greater than 19% hydrogen sulfide was achieved. The two layer biofilter unit (24m3 in total volume) was packed only in a single layer (11.65 m3 in volume) with a mixture of coconut fiber and tobacco compost (90/1 0 (w/w)) and was used to polish off remaining hydrogen sulfide completely while more than 95% of ammonia removal overall was achieved, resulting in a non odourous gas stream emitting to the atmosphere at ambient temperature. To our knowledge, this is the first waste gas treatment system employing the tricombination of condensation, scrubbing and biofiltration for the removal of odourous contaminants from tobacco waste gas.
item: Thesis-Abstract
Abatement of odour from tobacco process emissions by condensation, scrubbing and biofiltration
Wijayawardhana, AJ; Amarasinghe, ADUS
A study was conducted to evaluate the removal efficiency of NH3 and Hydrogen Sulfide emitted from tobacco process emissions by biofiltration. The experiments were based on testing the removal efficiency of the contaminants on four types of packing material, namely: coconut fiber/tobacco compost, peat/wood chips, garden waste compost/wood chips and inert plastic media/garden waste compost. Results indicate that maximum removal efficiencies of ammonia and hydrogen sulfide (100% and 100% respectively) can be achieved for coconut fiber/tobacco compost mixture while similar removal efficiencies was obtained by peat/wood chips mixture. The maximum elimination capacities for ammonia for the respective packing materials were 5.59, 7.74, 4.58 and 1.98 gm3h-1. Hydrogen sulfide maximum elimination capacities for the same packing materials were 6.99, 9.91, 6.04 and 2.96 gm3h-1 . The study was conducted as a preliminary evaluation for selecting the most suitable packing material relevant for application in an industrial scale biofilter for the treatment of the same waste gas stream. An industrial biofilter of 23 m3 in volume, packed with a coconut fiber filter medium inoculated with tobacco compost (20% by weight) was operated for a period of 45 days. The biofilter was supplied with a humidified gas stream from tobacco processing with main components being ammonia and hydrogen sulfide. The flow rate of the gas stream was varied from 1160 m3h-1 to 2100 m3h-1 . Results indicated that hydrogen sulfide and ammonia were effectively removed 100% and 95% under an empty bed retention time (EBRT) of 36s and 100% and 90% under an EBRT of 20s respectively. Maximum elimination capacities of 5.9 gm-3h-1and 27.6 gm-3h-1 were reached for an inlet loading of 1'-·8gm-3h-1and 3.8"gm-3h-1 for ammonia and hydrogen sulfide respectively. An industrial scale odour abatement system was designed and constructed, consisting of three units namely: condenser, scrubber and biofilter, the latter acting as the major unit of the system. The gas passes initially through a shell and tube heat exchanger giving moderate pollutant removal (7% ammonia). The gas stream is then directed to a packed column scrubber where average removal of 85% ammonia and qreater Jhan 19% "hydrogen sulfide was achieved. The two layer biofilter unit (24 m3 in total volume) was packed only in a single layer (11.65 m3 in volume) with a mixture of coconut fiber and tobacco compost (90/10 (w/w)) and was used to polish' off remaining hydrogen sulfide completely while more than 95% of ammonia removal overall was achieved, resulting in a non odourous gas stream emitting to the atmosphere at ambient temperature. To our knowledge, this is the first waste gas treatment system employing the tri combination of condensation, scrubbing and biofiltration for the removal of odourous contaminants from tobacco waste gas
item: Thesis-Full-text
Analysis and optimization of cyclone separators by using rans
De silva, MSM; Narayana, M
Many types of particulate matter collectors are used in the industry to separate particulate matter from the gaseous streams. Among various type of particulate collectors, cyclone separators are one of the most extensively used gas cleaning equipment because ofthey are inexpensive; easier to fabricate, and could be designed to stand under harsh operating conditions. Due to this extensive usage in the industry, many theoretical and experimental studies have been carried out and empirical models were developed to predict cyclone separator’s most important operational parameters. These models have many limitations of illustrating flow behavior properly due to the complex nature of the cyclone gas-solid flow behavior. Computational Fluid Dynamic (CFD) simulation could be useful to predict cyclone performance as an alternative approach. This work represents a CFD simulation of a Lapple cyclone separator using OpenFOAM software. Cyclone simulations have been carried out using turbulence models associated with the Reynolds Average Navier Stokes (RANS) equations. Multiphase Particle in Cell (MPPIC) method was used for the particle modeling, in which particle interactions with other particles were represented by models. The perditions of simulations have been compared both mutually and to literature in terms of cyclone pressure drop, gas-solid flow pattern and collection efficiency. RANS model fairly predict the gas-solid flow pattern of the cyclone. Pressure drop and collection efficiency of cyclone well fitted to the experimental results in the literature. Optimum values for inlet gas-solid velocity and particulate loading rate for the Lapple cyclone were obtained by RANS analysis. Pressure drop variation with gassolid inlet velocity which has been obtained by this analysis could be useful to minimize the energy requirement while maintaining the required collection efficiency.
item: Thesis-Full-text
Analysis of wood chip combustion system for hot air generation in the industrial drying process
(2015-10-19) Rajika, JKAT; Narayana, M
A two-dimensional steady state packed bed CFD model is developed for the combustion of wood chip in a moving grate.The model is validated using an industrial moving bed hot air generator used in Tea industry.Various empirical models have used for thermophysical property modeling.For this purpose free-board region of the hot air generator is also simulated including volatile reactions and turbulent combustion.Modeling and simulation carried out using open source CFD software OpenFOAM.Radiation heat incident on the packed bed is unknown and it is assumed in the first packed bed simulation.Therefore, CFD simulation involves number of iterative runs of the packed bed model and free board model to obtain the radiation temperature incident on packed bed due to free board heat.According to the validation results the developed packed bed model can be used to predict temperature of the packed bed wood chip combustion of thermally thin wood particles. The gas compositions could not be validated using the model.Further improvements to the model have suggested.
item: Thesis-Full-text
Application of nanoclay on polyester fabrics as a bio-inspired approach to improve moisture management
(2018) Abeywardena, SBY; Walpalage, S; Perera, WPSK; Somararatne, MCW
Bio-inspired and biomimetic surface modifications are identified as one of the fascinating areas of research. In this study, nature’s way of cooling elephants’ body temperature using mud bathing was mimicked to create moisture management in polyester fabric. For that, bentonite nanoclay (BNC) was covalently grafted on polyester fabric using (3-aminopropyl) triethoxysilane (APTES) as a coupling agent. The novel modification method was proved qualitatively and quantitatively using characterization techniques such as X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FTIR), X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission electron microscope (TEM), Xray fluorescence (XRF) and Thermo gravimetric analysis (TGA). Moisture management tests, and physical and mechanical properties of modified polyester fabric were used to analyse the accomplishment of the modification. Hydroxyl groups on edges of BNC played a vital role in grafting with APTES. Primary amine group in APTES reacted with ester groups in polyester fibres, while silanols reacted with BNC. XRD analysis confirmed grafting of APTES on the surface of BNC without intercalation. XPS and FTIR spectroscopies confirmed the new secondary amide bond formation, while surface morphology was observed from SEM images. The significant enhancement in wettability, absorptive capacity, drying rate and wicking length proved moisture management property of polyester fabric. This fabric coating strongly withstood more than 10 cycles of laundry and against 5000 abrasion cycles. Physical and mechanical properties of modified fabrics remained unchanged, while tensile strength and elongation showed a slight improvement due to fibre preserving aminolysis reaction between APTES and ester groups in polyester fabrics. It is expected that this bio-inspired BNC modified polyester fabric may break the barrier of using polyester in various hydrophilic textile applications.
item: Thesis-Abstract
Application of polyethylene terephthalate scraps for the manufacturing long oil alkyd resin
(2012-12) Darshana, LAP; Gunapala, O; Premarathna, T
A new aspect of work that covers Polyethylene terephthalate (PET) waste recycling and application in coating industry is presented through this report. It was shown that chemical recycled PET can be used in the manufacturing long oil alkyd resin. In Sri Lanka alone, about 6.5 million polyethylene terephthalate bottles (water bottles, food and other liquid containers, etc) are used monthly. Then large amount of Polyethylene terephthalate scraps are discharged in to the environment. The development of effective recycling technology was based on chemical de-polymerization of post-consumer PET bottles in order to use manufacturing alkyd resin based paint. The depolymerization of PET can be carried out in many ways such as glycolysis, hydrolysis, aminolysis, methanolysis and simultaneous hydrolysis and glycolysis. The useful material terephthalic salt can be synthesis through the hydrolysis process of PET. That could be used to derive terephthalic acid. This terephtalic acid can be used for alkyd resin process. Alkyd resins were any of a large group of thermoplastic resins that were essentially polyester made by heating polyhydric alcohol with polybasic acids or their anhydride and used chiefly in making protective coatings. Originally, alkyd resins were merely the reaction products of phthalic anhydride and glycerine. But these products were too brittle to make satisfactory coatings. The use of oils or unsaturated fatty acids in combination with the brittle alkyds resulted in the air-drying coatings which revolutionized the chemical coating industry. The properties of Terephthalic acid have far same to the phthalic acid. Phthalic anhydride was used as a main material in esterification reaction of alkyd resin process. Then pththalic anhydride could be replaced by Terephthalic acid. This process has been done in two stages. At the first stage, reaction between PET waste and sodium hydroxide were used to produce terepththalic acid. At the second stage, application of terepththalic acid was done in the manufacturing process of long oil alkyd resin. That could be used in industrially. Terephthalic salt could be produced successfully by hydrolysis process using Ethylglycol and sodium hydroxide at the higher temperature (180°C). The reacting mixture was neutralized using strong Acid to take Terephthalic acid. Then terephthalic acid could be applied in alkyd resin process without filtering. This new application of the recycled PET in synthesis of alkyd resin had provided same properties of normal alkyd resins. This method was cost saving method by reducing Rs. 3.00 per one kilogram of resin. As well as this can be used as environmental friendly method to give a better solution for the environment pollution due to plastic waste.
item: Thesis-Full-text
Assessment of environmental impact for accidental release of heavy gas
Gunawardena, YN; Gunasekera, MY; Narayan, M
An air dispersion model can be used to mathematically simulate air pollutants dispersion in the ambient atmosphere. These dispersion results can be used to predict their environmental impact, concentrations and movement. Such predicted data of hazardous gases released after a chemical accident are valuable since it can be used to provide timely information to emergency response providers as well as to make decisions on siting chemical plants at safe distances from settlements during plant development stages. Dense gas dispersion is the focus of this research as several pressurized dense gas release accidents have happened during the last few years in this country. These gases form clouds heavier than air when released to the atmospheric environment. In this study a mathematical model for the dispersion of heavy gas due to an accidental release is presented in order to determine the environmental impact. The heavy gas model was then used to simulate the dispersion of negatively buoyant and highly toxic chlorine gas to illustrate the use of heavy gas dispersion modeling in hazard analysis. A worst case scenario study with stability class A, was used for an accidental release of 900kg of chlorine from a location in Kaluthara district in Sri Lanka. To determine the impact of the release probit analysis, safe distance and hazardous time period calculations were done. From the model results, for a 900kg chlorine release, safe Immediately Dangerous to Life or Health (IDLH) distance was above 490m. Within this hazardous zone the safe time period starts after 5.44 minutes from the release. Further, this model can be used to predict information, such as concentration variation of the substance released with time and, cloud dimensions such as height and radius. For validation, experimental data in literature were collected and a sensitivity analysis was done to identify the best values for the model parameters.
item: Thesis-Full-text
Assessment of the feasibility of co-production of fucoxanthin, omega-3 fatty acids and bioethanol from marine microalgae
(2021) Premarathne R G M M; Ariyadasa TU; Attalage R A
The marine microalga Tisochrysis lutea is renowned for its ability to synthesize fucoxanthin and docosahexaenoic acid (DHA), which are nutritionally valuable high- value compounds. Although numerous studies in literature have assessed fucoxanthin and DHA production by T. lutea, very few have evaluated the feasibility of comprehensively utilizing biomass for co-production of these metabolites within the framework of biorefineries. To this end, the current study focused on the synthesis of fucoxanthin and DHA by cultivation of T. lutea under two different initial nitrate concentrations (1x: 882 μM, 3x: 2,646 μM) and three different illuminance levels (LL: 3,750 lux; ML: 7,500 lux; HL: 11,250 lux). The maximum fucoxanthin yield of 8.80 ± 0.30 mg/L (14.43 ± 0.52 mg/g) and DHA yield of 7.08 ± 0.02 mg/L (11.90 ± 0.14 mg/g) were achieved in the 3x HL culture at the end of 16 days of cultivation. Thereafter, a biphasic solvent extraction procedure using ethanol/n-hexane/water (10:9:1 v/v/v) was utilized for co-extraction of 97.96 ± 0.54% fucoxanthin and 74.11 ± 1.49% DHA from 3x HL biomass, and products were separated into two fractions. Fermentation of the residual biomass obtained from co- extraction resulted in a bioethanol yield of 48.49 ± 0.58 mg/g. Thus, results showcase the efficacy of the developed co-extraction procedure and the biorefinery potential of T. lutea.
item: Thesis-Abstract
Bacterial cellulose production by acetobacter xylinum in aerated, agitated and attached system
(2016-02-20) Dissanayake, DMSC; Ismail, M
Cellulose is the most common biopolymer on earth and has been identified as a major building material of all plants. It is common not only in the higher order plants, but also in microorganisms. Plant Cellulose formed to be structural materials for higher order cell, while bacterial cellulose (BC) plays a protective action in its cell. Most common genera which produce BC are Acetobacter, Rizobium, Agrobacterium and Sarcina. It was found that Acetobacter xylinum has the highest capability to produce cellulose rather than other species performed in the same condition. BC could play a very important role as a versatile biomaterial in modern industries as it has high purity, high mechanical strength, high water holding capacity and high crystalline ability compared to plant cellulose. Most of the BC studies have been carried out with Static Fermentation (SF) techniques. However static systems have the drawback when it comes to an industrial usage, due to the reduction of dissolved oxygen (DO) and pH of the media with the increase of cell mass increment and cellulose production. Therefore agitated and aerated systems were developed to overcome the limitations of the SF. Rotating Biological Fermentor (RBF) could be considered as both an agitated and aerated system. This was developed to overcome problems which hindered BC production in SF system. In this research, lab scale RBF was designed and fabricated to operate in three different agitator speeds. Substrate media was prepared using sterilized coconut water inoculated with Acetobacter xylinum. pH and DO variations in RBF and in SF were recorded for 7 to 8 days. Yield of cellulose production and the cell mass was also investigated during the fermentation period for different agitator speeds on both systems. Initial pH of the SF and RBF was 5.3 and with time it reached a steady value of 3.4 whereas in SF the pH decreased further. In the case of DO, the initial value was 1.47 mg/l. There was a continuous drop of DO in SF while in RBF it fluctuated within the range of 0.25 to 0 .43 mg/l. Cellulose production was 0.889×10-10 g CFU-1 ml-1 for SF and 1.92x10-10 g CFU-1 ml-1 for RBF respectively after 8 days. These investigations indicate that the RBF system could supply air to the culture medium in a continuous manner and was able to regulate DO when compared to a SF system. Further pH variation was also minimized in RBF compared to SF favoring the growth of cell mass and thereby yield of cellulose. A mathematical model for the synthesis of BC in a RBF system was also developed. The growth of cellulose is considered as a cellulose film from a mono culture. Glucose depletion, cellulose production and microbial growth in the fermentation medium were explained using the developed models. It was shown that the simulated and experimental results were in close agreement. In addition, the model was successful in predicting yield of cellulose at different rotational speeds of the RBF unit. On conclusion it could be said that RBF is a better system to generate cellulose when compared to SF and the developed model could explain the cell mass and cellulose growth profiles which could be useful in mass scale production.
item: Thesis-Abstract
Bio methanation and composting for managing sugar processing waste
Ariyaratne, WKH; De Alwis, A; Gunasekera, M; Hettiarchchi, M
In Sri Lanka, two integrated sugar cane based sugar plants cum distilleries are running with satisfying around 12% sugar requirement of the country. As the other countries, we are also facing the waste disposal problem of sugar and distillery waste. At present, few of the wastes generated in the plant are being used by the factory it self as material or energy source, but still some wastes are released to the environment with out any proper treatment. The major objective of this research is to find out the potential of in vessel high rate composting of sugar press mud along with maximum contribution of spent wash and other wastes generated in an integrated sugar plant cum distillery. The major draw back of high rate composting is high energy requirement and it is expected to satisfy through biomethanation of spent wash. A series of experiments were carried out in a 210 L compost unit to determine possible feedstock composition for in vessel composting. By in-vessel high-rate method, the compo sting period could be dramatically brought down to about 12 Press mud: spent wash ratio of 18:1 (spent wash added initially) appeared to be best composition for in vessel high rate composting. However, 9: 1 ratio could be achieved if spent wash is applied after reaching the highest temperature in the However 183 T of annual nitrogen supply could be achieved through production compost. Also a senes of experiments were carried out to observe biornefhanation potential of distillery spent wash. All the experiments were carried out in specially designed laboratory scale apparatus. It was calculated that energy .needed to achieve above rates of composting could be easily achieved by simple, single-stage batch type bio-rnethanation without mixing. 65-70% COD reduction and 9.4 m3/m3 feed to specific gas production could be obtained, by this method with optimum conditions
item: Thesis-Full-text
Biological removal of sulfurous pollutants in skim latex wastewater
(2020) Samarathunga IR; Rathnasiri PG
Skim Latex Wastewater (SLW) contains high concentrations of sulfate, together with organic matter and nitrogenous compounds such as Ammonia and protein. High concentrated sulfuric acid is added in coagulation process to recover rubber particles and ammonia is used for preservation of rubber latex. Under anaerobic digestion, sulfate breakdown into hydrogen sulfide which is one of the highly toxic, corrosive and odorous gas which causes severe threat to the environment and health Nevertheless, it degrades the commercial value of biogas as a renewable energy source causing severe corrosion in connected components of equipment. Conventional biological process to treat sulfate rich wastewater consists of two processes, sulfate reduction to sulfide by Sulfate Reducing Bacteria (SRB) and Sulfide oxidation to elemental sulfur by Sulfide Oxidation Bacteria (SOB) in separate reactors. Major objectives of this research study are to investigate the effect of ammonia rich SLW on sulfate reduction and Hydrogen sulfide emission reduction under anaerobic condition and develop strategies for enhancement of sulfate reduction for subsequent elementary sulfur formation under different micro-aeration techniques. Optimum conditions for both sulfate reduction as well as elementary sulfur formation are also investigated. In previous studies, various reactor configurations have been developed by integrating both the SRB and SOB into a single reactor. In this study SRB and SOB integrated suspended growth reactor for SLW which is not only rich in sulfate, but also ammonia and protein which ultimately breakdown to produce more ammonia is introduced. This new reactor is termed as Single-stage Sulfate-removal Micro-aerated Anaerobic Digester (SSMAD). It is hypothesized that this SRB and SOB integrated micro-aerated anaerobic reactor approach can be applied to enhance removal of sulfurous pollutants from SLW. To achieve the research objectives, seven experiments were conducted. All experiments were conducted semi batch wise using 3 litres airtight completely mixed anaerobic reactors which were maintained at 35 ±1 ̊C. From the results, it can be concluded that, Single-stage Sulfate-removal Micro-aerated Anaerobic Digester (SSMAD) simultaneously reduced high concentrated influent sulfate of SLW, while hydrogen sulfide been transformed to reusable elemental sulfur. To achieve the optimum sulfate reduction as well as maximum elemental sulfur yield, bulk liquid of the SSMAD was micro-aerated with air at rate of 1.6 ml/hr for two hours following half an hour of feeding SLW. It was found that yield and the stability of the generated elemental sulfur improved at O2/S ratio 1.0-1.2, after 18-24 hours of feeding. At this range, specific H2S formation was less than 0.2 mmol/mmol while the sulfate reduction was 95.8%. The COD/SO4-2 ratio of SLW was nearly 3 and it was increased to 5 adding an external electron donor for efficient sulfate reduction but further increased up to 10, reduced the sulfate reduction as Methanogens dominate than SRB. Although ethanol enhances the sulfate reduction than acetate, excess ethanol adversely affected on the micro-aerobic systems degrading generated elemental sulfur back to gaseous H2S faster. Thus, the elemental sulfur yield reduced by 69% when the COD/SO4-2 ratio was increased from 5 to 10. However, sufficient precautions were taken to increase the C/N ratio from 3.8 to 6.9, by maintaining pH of the reactor at 7.5-8.0 and volumetric loading at 50 l/m3.d to minimize ammonia inhibition in the reactor. Developed novel approach through Single-stage Sulfate-removal Micro-aerated Anaerobic Digester (SSMAD) can be successively used to recover sulfurous pollutants from SLW
item: Thesis-Full-text
CFD modeling of a centrifuge for oil - water separation
Thilakarathna, HGSM; Narayana, M
Centrifugation is an efficient, economical and environmentally friendly method to remove un-desirable water content from oil and water mixtures and separate out the desired oil content.Moreover, the disc stack centrifuges are widely used for separating liquids of different densi-ties and applied in industrial coconut oil clarification as well.The main focus of this research work is to model the fluid flow inside the Westfalia discstack centrifuge using Ansys Fluent and identify the flow behavior. With the availability of thelimited computer hardware facility, the model has been run without the discs to avoid com-plexities. In the developed 3 dimensional model, the fluid dynamic behavior of the multiphaseflow has been considered and modeled using the VOF multiphase model available in fluent.The step by step procedure of the model development has been discussed such as the veryfirst stage of geometry selection, drawing and importing to the fluent, mesh generation, allsolution set ups and even the two stage simulation procedure.The simulation results of this research work provides an out line of the resulted flow param-eters of velocity and pressure profiles, turbulent effects such as turbulence intensity, turbulentkinetic energy, and specific dissipation rate and also the phase volume fractions which havebeen saved in every critical stage of the simulation process. Despite the phase volume fractionwhich has been experimentally validated, all other results were theoretically validated.CFD modeling of flow behavior inside the centrifuges is not a popular topic among theresearchers due to the complex flow patterns and the requirement of advanced computer hard-ware facility. However this research work provides a platform to model the similar flow be-haviors and even to model the same case including the discs.
item: Thesis-Abstract
Characterization and evaluation of starch xanthide encased powdered natural rubber
Maduwage, S; Amarasinghe, ADUS; Subramaniam, K
Rubber as a free-flowing powder, is essential in order to stream line the manufacturing processes of rubber goods. The previous works noted the importance of using powdered rubber as a competitive raw material for continuous processing in rubber industry. However, in most of these works, the study was continued to the synthetic rubbers and only a few had been reported on the natural rubber. Sri Lanka which is an agricultural based country, has a bulk quantity of natural rubber field latex at a low price. Hence, it is worthwhile to produce a value-added product like powdered rubber using field latex. Encapsulation is a common process in preparing powdered natural rubber. In this process, starch xanthate, SX, which acts as a diluent/reinforcing filler, behaves as an encapsulating agent for latex particles. The level of encapsulation as well as the properties of the resulting powder is highly dependent on the strength and the amount of the SX solution. The present work investigates these effects with varying strength of SX by changing the degrees of substitution, DS, of the SX solution and also the loading of the SX. The lower and the upper limits of DS of SX examined were 0.07 and 0.35 and the results suggested that the intermediate DS levels were more promising. The physical properties of the final vulcanizates were found to be satisfactory and were comparable with the rubbers available in the market. Study on drying techniques established the necessity of water washing step for natural rubber powders to remove non-rubber substances and the applicltion of an anti-cake agent to prevent agglomeration during drying. The effect of different anti-cake agents such as zinc stearate, talc powder and whiting was examined and zinc stearate was found to be the best out of the anti-cake agents used. Highly friable crumbs that ground readily to give powders were obtained with oven drying rather than with sun drying.
item: Thesis-Full-text
Characterization of calcium carbonate filled natural rubber - low density polyethylene blends prepared with a titanate coupling agent
(2019) Sampath WDM; Egodage SM; Edirisinghe DG
The aim of this study was to develop reactive blends from natural rubber (NR) and low density polyethylene (LDPE) with acceptable physico-mechanical properties. NR and LDPE blends at different blend ratios were produced in a Brabender Plasticorder by melt mixing at a temperature of 150 oC, and rotor speed of 60 rpm. 20 parts per hundred parts of polymer (pphp) calcium carbonate was added as an inorganic filler. Physico-mechanical and chemical properties of the blends and composites were determined according to international standards. Thermal properties were determined using a differential scanning calorimeter. Morphology and structural characteristics were examined by a scanning electron microscope and fourier transform infrared analyzer, respectively. 50/50 NR/LDPE blends were prepared using three vulcanizing systems: sulphur, peroxide and mixture of sulphur and peroxide. NR/LDPE blend prepared with the mixed vulcanizing system showed the highest physicomechanical, chemical, and ageing properties with a fine morphology. A series of simple blends was formulated by varying the LDPE loading from 10 to 90 pphp at 20 pphp intervals. The tensile strength, tear strength, and hardness increased with the increase of LDPE loading, while elongation at break decreased. The continuous phase of blends changed from NR to LDPE above 30 pphp LDPE loading. The optimum tensile and ageing properties were obtained for the composite prepared with 20 pphp calcium carbonate with or without titanate coupling agent (titanate CA) at 30 pphp LDPE loading. Further, 70/30 NR/LDPE composite prepared with 0.7 pphp titanate CA presented the highest physicomechanical, chemical and ageing properties. Furthermore, the performance of the 70/30 NR/LDPE blends produced with 0.3 pphp peroxide was greater than that of the composites prepared without the peroxide and with a high amount of peroxide. Nevertheless, tensile properties, stress and strain of the 70/30 NR/LDPE composite improved with partial replacement of LDPE with recycled LDPE (rLDPE). The composite with 20 pphp rLDPE indicated the best improvement in all physico-mechanical properties.
item: Thesis-Abstract
Chemical leasing and nanotechnology for agriculture sector
Edrisinghe, LGLM; De Alwis, A; Bandara, JMRS
During recent years the service-oriented business approach of Chemical Leasing has been researched and implemented at various companies of different industry sectors around the globe. The novel business model promotes sustainable use of chemicals through linking the supplier’s sales income to chemical performance. Experiences show that key elements of a successful application of chemical leasing are know-how exchange and process optimization. Excessive use of chemicals in the agriculture sector emphasizes the potential in application of chemical leasing in the country. Nanotechnology is a major emerging technology, which can revolutionize the agriculture sector by employing special nanoscale properties of matter. It can be applied to agrochemicals and fertilizer in order to improve quality and safety, as well as reduce environmental and health effects. Sri Lanka as a country based on an agricultural economy has the potential to use these new technologies for its socio- economical development. Global need of ecologically sustainable farming system, increasing global nano food market, growing demand for safe and healthy food, threat from changing weather conditions and increasing risk of diseases to plants highlight the opportunities. The proposed model performs as a national frame work for management of agrochemicals in the country. The research “chemical leasing & nanotechnology in agriculture sector” introduces the use of Blue Ocean strategy to enter the sustainable farming system.
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Chemical modification of rubber waste and characterization of their blends with natural rubber
(2014-05-31) Edirisinghe, DG; Premachandra, JK
Ground rubber tyre (GRT) produced by recycling of tyre waste or rejects is used as a filler in the manufacture of tyre components, mainly to reduce the cost. Rubber matrix-GRT compositions generally exhibit poor mechanical properties due to poor matrix-filler adhesion and lack of reactive sites on GRT particle surfaces. Therefore, GRT is modified by employing various types of reclamation processes to enhance mechanical properties. The modified GRT known as reclaimed rubber is widely used as a component in rubber blends in many applications, especially in tyre manufacturing. This study is focused on developing a cost effective, environmental friendly mechano-chemical reclamation process for GRT to produce reclaim rubber using a readily available amino compound. Initially, influence of the amino compound on rubber compound properties was evaluated and results indicate that it acts as an activator for sulphur vulcanization. Properties of GRT modified with the amino compound indicate that the amino compound acts as a reclaiming agent as well. Comparison of properties of natural rubber (NR) / novel reclaimed rubber blend compounds and revulcanisates with those of the controls reveal that the former can be used as alternatives to the latter in the manufacture of tyre treads. Replacement of 30% of virgin NR in the vulcanisates with the novel reclaimed rubber retains about 65-85% of strength properties, elongation at break and resilience. Abrasion volume loss is at an acceptable level and ageing properties are comparable to those of the 100% virgin NR vulcanisate. Further, most of the properties of the virgin NR / novel reclaimed rubber composites are comparable to those of the corresponding composites prepared by blending NR with commercially available reclaimed rubbers. Accordingly, the novel reclaimed rubber could be a suitable component to blend with virgin NR in the manufacture of tyre treads with required properties.
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Chemical process route selection based on assessment of inherent environmental hazard, occupational health and safety
(2015-03-01) Warnasooriya, S; Gunasekera, MY
Chemical process route selection is one of the main design decisions that needs to be taken during the preliminary stages of chemical plant design and development. A chemical process route is considered as the raw materials and the sequence of reaction steps that converts them in to desired products. Previously, the most important factor considered in selecting the chemical process route was plant economics. However, now other issues such as safety, environment and occupational health have also become important considerations. Therefore, at early stages of chemical process plant design and development it is necessary to apply methodologies to identify and assess environmental, occupational health and safety hazards involved in the process routes. This work proposes a methodology for assessing chemical process routes to manufacture a chemical based on inherent environmental, occupational health and safety hazards. The method developed in this work can be used during early design stages of a chemical process plant. The process route selection is done based on impacts due to emissions from the ongoing operational conditions of the plant. It considers the potential toxicological impacts on the environment, potential impacts on the occupational health due to fugitive emissions and the potential chemical and process safety impacts within the plant. As the outcome of the methodology, an integrated index called “Inherent Chemical Process Route Index” (ICPRI) is proposed which can be used for the selection of the ‘best’ chemical process route for a chemical process plant, based on inherent environmental hazard, occupational health and safety (IEHS). The lower the ICPRI the more inherently environmentally friendly, inherently occupational healthier and inherently safer the route is. The methodology developed in this work can also rank alternative chemical process routes based on inherent environmental hazard or occupational health hazard and or safety hazard separately. The method was applied on four possible process routes to produce acetone. The propene oxidation route showed the lowest ICPRI value indicating potentially the ‘best’ chemical process route for acetone manufacturing process based on the IEHS assessment. Keywords: Inherent Environmental hazard, occupational health, Inherent Safety, Chemical process route
item: Thesis-Full-text
Climate change impact on the spatial distribution of droughts in Kirindi oya and Maduru oya dry zone river basins in Sri Lanka
(2023) Wijekoon, WMRTY; Rajapakse RLHL
Drought, a consequence of prolonged precipitation deficiencies, is a significant hazard exacerbated by climate change. Sri Lanka, highly susceptible to extreme climatic events, faces drought as its most prominent hazard, necessitating a comprehensive assessment of its impact. This study focuses on the escalating impact of drought intensified by climate change on the Maduru Oya and Kirindi Oya dry zone basins, crucial due to their vulnerability to altered hydroclimatic dynamics. With the substantial contribution of the dry zone to the paddy cultivation of the country, early detection of agricultural droughts is crucial for effective water allocation planning. Recognizing the importance of meteorological droughts as precursors to physical droughts, proactive monitoring and forecasting are essential for planning against subsequent agricultural droughts, while monitoring hydrological droughts is imperative for ensuring a reliable water supply for irrigation and other purposes. Thus, this research primarily focuses on evaluating meteorological and hydrological droughts. The research employs the Standardized Precipitation Index (SPI) and the Streamflow Drought Index (SDI) for the monitoring of meteorological and hydrological droughts, respectively. It considers six CMIP6 (sixth Phase of the Coupled Model Inter Comparison Project) Global Climate Models (GCMs), and the CNRM-HR-1 model was selected as the preferred model. The two future projection scenarios, SSP1-2.6 and SSP5-8.5, were selected for the analysis. In the meteorological drought assessment, maps illustrating the spatial distribution of meteorological droughts were generated for both current and future climate scenarios. In order to generate maps, a future gridded rainfall dataset was developed by developing statistical relationships with the Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS) set and observed precipitation data. For the hydrological drought assessment, machine learning methods, including Recurrent Neural Network and Random Forest Algorithm, were used to predict future streamflow at specific gauging stations, with the Random Forest model selected for its superior performance. Additionally, the climatic indices formulated by the Expert Team on Climate Change Detection and Indices (ETCCDI) were used in this study to monitor the occurrence of climate extremes of precipitation in the past. The meteorological and hydrological drought assessments reveal significant insights into the anticipated impacts of climate change. In the Maduru Oya basin, meteorological droughts exhibit varying percentage increases under SSP1-2.6 and SSP5-8.5 scenarios. Extreme and severe droughts experience increases of 18%, and 16%, respectively, under SSP1-2.6, and 31%, and 2%, under SSP5-8.5. Conversely, the Kirindi Oya basin displays significant susceptibility to extreme meteorological droughts, with increases of 49% under SSP1-2.6 and 37% under SSP5-8.5, particularly with extreme droughts surging by over 35% under both scenarios. Furthermore, the hydrological drought assessment highlights the heightened vulnerability of the Padiyathalawa sub-basin in the Maduru Oya basin, indicating a significant increase in the occurrence of moderate hydrological droughts at the 12-month timescale under both future scenarios. Conversely, the Wellawaya sub-basin in the Kirindi Oya basin also shows susceptibility to frequent moderate hydrological droughts along with an 80% increase in the occurrence of severe hydrological droughts under the SSP5-8.5 scenario at the 12-month scale. Therefore, both basins are expected to face water scarcity in the future, emphasizing the importance of implementing measures to ensure a reliable water supply for irrigation and domestic purposes, given the substantial impact of climate change on watershed hydrology. Keywords: Climate-driven water stress, CMIP6 GCM projections, Drought resilience in water resources, Drought vulnerabilit