Call number: LD2668 .T4 1986 C56 / Master of Science / Biological and Agricultural Engineering

published_or_final_version / abstract / Mechanical Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

Surplus sugarcane bagasse, estimated at a maximum of 0,9x106 tons/year, represents an annual renewable resource which is readily available at the mill site and is a suitable potential source of alternative fuels and chemical feedstocks. This work contains an extensive literature survey which covers the production of C5- and C6- sugars from lignocelluloses by chemical hydrolysis and the pretreatment of cellulosic materials for enzymatic hydrolysis of the cellulose fraction. This survey was then used to determine the final direction of this research into the utilisation of bagasse for the production of fermentable sugars. It was decided that research should be directed at the dilute acid hydrolysis of the bagasse hemicellulose fraction to determine whether this fraction could be selectively hydrolysed from the complex lignocellulose structure and to obtain xylose yields under different hydrolysis conditions. Acids, especially acetic acid, are liberated from bagasse by steaming at elevated temperatures. In this acid medium the hemicelluloses are hydrolysed and become soluble. Autohydrolysis tests on whole bagasse indicate that hemicellulose hydrolysis becomes significant at temperatures above 140°C. However, the autohydrolysis liquor would still require dilute mineral acid hydrolysis to convert the pentose oligomers to their monomeric forms. Dilute sulphuric and batch hydrolysis of whole bagasse hemicellulose has thus been investigated at a solid to liquid ratio of 1:15 over the following temperature and acid concentrations ranges : 80° to 150°C and 3 to 40 g/l acid. Xylose, glucose, furfural and acetic acid formation and sulphuric acid consumption were monitored during these hydrolyses. Hemicellulose hydrolysis to produce mainly xylose is readily achieved over the entire range of acid hydrolysis conditions tested with little removal of the other bagasse components (lignin and cellulose). At the upper end of the temperature range acid concentrations below 20 g/l are sufficient for hemicellulose hydrolysis due to the effect of temperature on reaction rate. The bagasse hemicellulose consists of two fractions, an easily hydrolysable portion containing 165 mg of potential xylose/g bagasse and a resistant fraction containing 105 mg of potential xylose/g bagasse. A first order reaction model has been developed using the batch acid hydrolysis results. It is based on two hemicellulose fractions reacting simultaneously to give a common product (xylose) and predicts total xylose yield as a function of hydrolysis time for a given set of hydrolysis conditions. The encouraging xylose yields obtained during the batch hydrolyses led to the design of a continuous hydrolysis reactor to process bagasse at low liquid to solid ratios to determine whether xylose yields similar to the batch hydrolysis yields could be obtained at the same hydrolysis conditions. The continuous hydrolyses showed that for the conditions tested the xylose yields are unaffected by the decrease in liquid to solid ratio (down to 3,6:1) and it would appear that reactor performance is still controlled by reaction kinetics. A number of reactor configurations for the industrial production of pentoses from bagasse hemicelluloses are also proposed. / Thesis (M.Sc.)-University of Natal. Durban, 1982.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science. April, 2015 / Microbial fuel cell (MFC) technology presents great potential for use as a dual system for industrial waste water remediation and electricity generation. The hurdle in up-scaling this technology has been identified as MFC-bioreactor architecture, both with regards to bioremediation and carbon source to electricity conversion rates. In addition to the latter’s limitations, the use of expensive mediators and membrane to enhance MFC performance renders the technology uneconomic to employ industrially. A 60mm high double chamber membrane and mediator-less MFC-bioreactor was designed, and constructed. The novel MFC-bioreactor made of transparent polyacrylic plastic had a total working volume of 8 litres with the anode chamber situated at the bottom and the cathode chamber at the top separated by a 10cm deep artificial membrane made up of glass wool, glass beads and marble balls. The MFC was operated under various operating parameters including; feeding modes (batch and continuous), with different substrate concentration at a range of external resistance (100-9000Ω) .The voltage produced during MFC operation was monitored and used to estimate the power density output of the MFC. The pseudo membrane was able to sufficiently separate the anode and cathode chambers allowing the development of potential difference and hence generation of current. The MFC demonstrated the potential for sustainable operation by producing and maintaining a stable power density of 2000mW/m2 when operated with an external resistance of 1000Ω. This power density was accompanied by a 73% remediation efficiency of the synthetic wastewater. It was concluded that the results of this research show proof of concept for a membrane-less MFC that can produce electrical energy in the absence of an electron shuffling mediator.

Thesis (Master of Engineering in Chemical Engineering)--Cape Peninsula University of Technology, 2018. / Renewable energy security for the future and better use of natural resources are key challenges that can be concurrently managed by a practical anaerobic co-digestion approach in the production of methane. For this study, co-digestion of cassava and winery waste was investigated for the production of biogas. Cassava biomass is a good substrate for biogas production due to its high carbohydrate yield per hectare (4.742 kg/carb) than most plants. Winery wastes constitute a lot of challenge in South Africa due to high amounts currently being dumped at landfills. Due to the chemical properties of the two substrates, it is envisaged that their co-digestion will produce more biogas than use of a single substrate. Biomethane potential (BMP) tests were carried out in a batch, mesophilic (37 °C±0.5) reactor using cassava and winery waste singly and in combination at a ratio of 1:1 and ran for 30 days. Biogas optimization was also evaluated. The optimal conditions for methane production from anaerobic co-digestion of cassava biomass and winery solid waste using response surface methodology (RSM). The effects of temperature, pH and co-substrate ratios on the methane yield were explored. A central composite design technique was used to set-up the anaerobic co-digestion experiment was determined. Once the optimized values were established, biogas production from co-digestion of cassava biomass with winery waste was investigated using a single-stage 5 L mesophilic batch digester and the microbial dynamics inside the digester during co-digestion of cassava and winery waste in the single-stage 5 L mesophilic batch digester. The samples were collected on days 1, 15 and 30 of the anaerobic digestion period and DNA extracted from them while 16sRNA bacterial sequencing was performed. The results for the BMP tests showed that cumulative methane yield for cassava, winery waste and in combination were 42, 21 and 38 mLCH4 respectively. It was concluded that biogas production from anaerobic digestion was dependent on many factors such as pH, substrate properties and the ratio of different feedstocks used during co-digestion. The results from the optimization study were pH 7, temperature of 35 °C±0.5 and co-digestion ratio of 70:30 cassava to winery waste. The maximum methane yield of 346.28 mLCH4/gVSadded was predicted by the quadratic model at the optimal temperature of 35 oC±0.5, pH of 7 and 70:30 ratio of cassava biomass to winery solid waste. Experimental results showed a close fit but higher methane yield (396 mLCH4/gVSadded) than predicted values as indicated by the coefficient of determination (R2) value of 0.9521. The response surface model proved successful in the optimization process of methane yield. The single-stage 5L mesophilic batch digester with a co-substrate ratio of 70:30 cassava to winery waste produced a total of 819.54 mL/gVS biogas with a 62 % methane content. The study of microbial community dynamics showed the presence of the bacteria that is responsible for each stage of anaerobic digestion. The study concluded that both winery waste and cassava substrates were favourable for biogas production and most underprivileged people in the rural areas with no access to electricity can produce & utilise it.

Wong Yiu Kwong Kenji. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 189-204). / Abstracts in English and Chinese. / Acknowledgement --- p.i / Abstract --- p.ii / 摘要 --- p.iv / Contents --- p.vi / List of Figure --- p.xii / List of Table --- p.xvi / Introduction --- p.1 / Chapter 1.1. --- Vegetable oil production and their refining --- p.1 / Chapter 1.1.1. --- Vegetable oil production and consumption --- p.1 / Chapter 1.1.2. --- Vegetable oil refining steps --- p.2 / Chapter 1.2. --- Chemical refining vs. Physical refining --- p.3 / Chapter 1.2.1. --- Differences between chemical and physical refining --- p.3 / Chapter 1.2.2. --- Pros and Cons of the two refining practices --- p.4 / Chapter 1.2.3. --- Adoption criteria and popularity of refining methods --- p.6 / Chapter 1.3. --- Deodorizer distillate (DODc vs. DODp) --- p.7 / Chapter 1.3.1. --- Compositions of DODc and DODp --- p.7 / Chapter 1.3.1.1. --- Squalene --- p.9 / Chapter 1.3.1.2. --- Tocopherols --- p.10 / Chapter 1.3.1.3. --- Phytosterols --- p.12 / Chapter 1.3.2. --- Usages of DODc and DODp and purification of phytochemicals --- p.14 / Chapter 1.3.2.1. --- Concentration of tocopherols and phytosterols --- p.15 / Chapter 1.3.2.2. --- Purification of tocopherols and phytosterols --- p.18 / Chapter 1.3.3. --- Alternative usage of DODp --- p.20 / Chapter 1.4. --- Usages of fatty acid mono-alkyl esters --- p.20 / Chapter 1.4.1. --- As intermediate for Bio-surfactants --- p.21 / Chapter 1.4.2. --- Bio-lubricants --- p.21 / Chapter 1.4.3. --- Biodiesel --- p.22 / Chapter 1.5. --- Production of biodiesel and its advantages and disadvantages --- p.23 / Chapter 1.5.1. --- Production of biodiesel --- p.23 / Chapter 1.5.1.1. --- Use of catalyst --- p.25 / Chapter 1.5.1.2. --- "Molar ratios between methanol, sample and catalyst" --- p.26 / Chapter 1.5.1.3. --- Temperature and pressure --- p.27 / Chapter 1.5.1.4. --- Biodiesel purification --- p.27 / Chapter 1.5.2. --- Pros and Cons of using biodiesel --- p.27 / Chapter 1.5.3. --- Sources of Biodiesel production --- p.29 / Chapter 1.6. --- Proposed strategy --- p.33 / Chapter 1.6.1. --- Summary of the literatures reviewed --- p.33 / Chapter 1.6.2. --- Hypothesis making --- p.34 / Chapter 1.6.3. --- Aim and objectives --- p.34 / Chapter 1.6.4. --- Significance of study --- p.34 / Chapter 1.6.5. --- Study scheme --- p.35 / Chapter 2. --- Methodology --- p.36 / Chapter 2.1. --- Characterization of physically refined Deodorizer Distillate (DODp) --- p.36 / Chapter 2.1.1. --- Collection & storage of DODp --- p.36 / Chapter 2.1.2. --- Determination of fatty acids composition --- p.36 / Chapter 2.1.3. --- Determination of acid number (ASTM D 664) --- p.37 / Chapter 2.1.4. --- Determination of free fatty acid contents --- p.38 / Chapter 2.1.5. --- Determination of unsaponifiable matter content --- p.38 / Chapter 2.1.6. --- "Determination of squalene, tocopherol and phytosterol contents." --- p.39 / Chapter 2.1.7. --- Deduction of natural glyceride contents --- p.40 / Chapter 2.1.8. --- "Other physical, chemical and biological analyses" --- p.40 / Chapter 2.1.8.1. --- Elemental analysis --- p.40 / Chapter 2.1.8.2. --- Nitrogen --- p.41 / Chapter 2.1.8.3. --- Water and volatile matter content --- p.41 / Chapter 2.1.8.4. --- Melting point and specific gravity --- p.41 / Chapter 2.1.8.5. --- Microbial counts --- p.42 / Chapter 2.2. --- Production of fatty acid methyl esters (FAMEs) - Protocol A --- p.42 / Chapter 2.2.1. --- Optimization of Esterification --- p.42 / Chapter 2.2.1.1. --- Molar ratio of methanol: DODp --- p.43 / Chapter 2.2.1.2. --- Molar ratio of DODp: sulfuric acid --- p.43 / Chapter 2.2.1.3. --- Reaction temperature --- p.44 / Chapter 2.2.2. --- Optimization of Molecular Distillation --- p.44 / Chapter 2.2.2.1. --- Feed rate --- p.45 / Chapter 2.2.2.2. --- Distillation temperature --- p.45 / Chapter 2.2.2.3. --- Speed of rotary blade --- p.45 / Chapter 2.2.3. --- Crystallization --- p.46 / Chapter 2.3. --- Production of fatty acid methyl esters (FAMEs) - Protocol B --- p.46 / Chapter 2.3.1. --- Optimization of Saponification --- p.47 / Chapter 2.3.1.1. --- Saponification number --- p.47 / Chapter 2.3.1.2. --- Saponification --- p.47 / Chapter 2.3.2. --- Extraction of unsaponifiable matter --- p.48 / Chapter 2.3.3. --- Acidification --- p.49 / Chapter 2.3.4. --- Esterification --- p.49 / Chapter 2.3.5. --- Hot water washing --- p.49 / Chapter 2.3.6. --- Crystallization --- p.49 / Chapter 2.4. --- Quantity and quality assessments of FAMEs --- p.50 / Chapter 2.4.1. --- Determination of purity and yield of FAMEs --- p.50 / Chapter 2.4.2. --- Quality of FAMEs: Biodiesel Specifications in USA --- p.50 / Chapter 2.4.2.1. --- Sulfated Ash (ASTM D 874) --- p.50 / Chapter 2.4.2.2. --- Copper strip corrosion test (ASTM D 130) --- p.51 / Chapter 2.4.2.3. --- Water and Sediment (ASTM D 2709) --- p.52 / Chapter 2.4.2.4. --- Conradson Carbon Residue of Petroleum Products (ASTM D 189) --- p.52 / Chapter 2.4.2.5. --- Determination of Free and Total Glycerine in B-100 Biodiesel Methyl Esters By Gas Chromatography (ASTM D 6584) --- p.53 / Chapter 2.4.2.6. --- Flash point (modified from ASTM D 93) --- p.54 / Chapter 2.4.2.7. --- Determination of Additive Elements in Lubricating Oils by Inductively Coupled Plasma Atomic Emission Spectrometry (ASTM D 4951) --- p.54 / Chapter 2.4.2.8. --- Kinematic Viscosity --- p.55 / Chapter 2.4.2.9. --- "Cetane index, Cloud Point and Distillation Temperature (ASTM D 613, ASTM D 2500 and ASTM D 90)" --- p.55 / Chapter 2.4.3. --- Toxicity assays of FAMEs --- p.55 / Chapter 2.4.3.1. --- Acute toxicity to mice --- p.56 / Chapter 2.4.3.2. --- Seed germination test --- p.56 / Chapter 2.4.3.3. --- Acute toxicity to aquatic invertebrate --- p.56 / Chapter 2.5. --- Quantity and quality assessments of phytochemical products --- p.57 / Chapter 2.5.1. --- Determination of purity and yield of phytochemicals in phytosterol and desterolized fractions --- p.57 / Chapter 2.5.2. --- Antioxidants activity of desterolized fraction --- p.58 / Chapter 2.5.2.1. --- ABTS scavenging activity --- p.58 / Chapter 2.5.2.2. --- Free radical scavenging activity --- p.58 / Chapter 2.5.3. --- Anti-proliferative effect on cancer cells of phytosterols --- p.59 / Chapter 2.5.3.1. --- Cell culture --- p.59 / Chapter 2.5.3.2. --- Determination of optimal cell density for antiproliferative assays --- p.59 / Chapter 2.5.3.3. --- Anti-proliferative effect of phytosterols on H1299 and Hep G2. --- p.60 / Chapter 2.5.3.4. --- Detection of action mechanism(s) of the anti-proliferative effects of β-sitosterol on H1299 and Hep G2 cancer cells --- p.61 / Chapter 3. --- Result --- p.70 / Chapter 3.1. --- Characterization of Physically Refined Deodorizer Distillate (DODp) --- p.70 / Chapter 3.1.1. --- Free fatty acids composition --- p.70 / Chapter 3.1.2. --- Acid number --- p.75 / Chapter 3.1.3. --- "Free fatty acids, natural glyceride and unsaponifiable matter contents" --- p.75 / Chapter 3.1.4. --- "Squalene, tocopherol and phytosterol contents" --- p.77 / Chapter 3.1.5. --- Other physicochemical and biological analyses --- p.81 / Chapter 3.2. --- Production of fatty acid methyl esters (FAMEs) - Protocol A --- p.83 / Chapter 3.2.1. --- Optimization of Esterification --- p.83 / Chapter 3.2.1.1. --- Methanol to DODp molar ratio --- p.83 / Chapter 3.2.1.2. --- DODp to sulfuric acid molar ratio --- p.85 / Chapter 3.2.1.3. --- Reaction temperature --- p.87 / Chapter 3.2.1.4. --- Calculation of esterification efficiency --- p.87 / Chapter 3.2.2. --- Optimization of Molecular Distillation --- p.89 / Chapter 3.2.2.1. --- Feed rate --- p.89 / Chapter 3.2.2.2. --- Distillation temperature --- p.91 / Chapter 3.2.2.3. --- Rotating blade speed --- p.93 / Chapter 3.2.3. --- Crystallization --- p.97 / Chapter 3.2.3.1. --- Phytosterol preparations --- p.97 / Chapter 3.2.3.2. --- Desterolized fractions --- p.97 / Chapter 3.3. --- Production of fatty acid methyl esters (FAMEs) 一 Protocol B --- p.99 / Chapter 3.3.1. --- Optimization of Saponification --- p.99 / Chapter 3.3.1.1. --- Saponification number --- p.99 / Chapter 3.3.1.2. --- Saponification --- p.99 / Chapter 3.3.2. --- Extraction of unsaponifiable matter --- p.101 / Chapter 3.3.3. --- FAMEs product after esterification --- p.101 / Chapter 3.3.4. --- Crystallization --- p.104 / Chapter 3.3.4.1. --- Phytosterol preparations --- p.104 / Chapter 3.3.4.2. --- Desterolized fractions --- p.104 / Chapter 3.4. --- Quantity and Quality assessments of FAMEs --- p.106 / Chapter 3.4.1. --- "FAMEs yield, purity and appearance" --- p.106 / Chapter 3.4.2. --- Specifications for Biodiesel in U.S.A --- p.106 / Chapter 3.4.3. --- Acute Toxicity assays of FAMEs --- p.109 / Chapter 3.4.3.1. --- Acute toxicity to mice --- p.109 / Chapter 3.4.3.2. --- Seed germination test --- p.109 / Chapter 3.4.3.3. --- Acute toxicity to aquatic invertebrate --- p.109 / Chapter 3.5. --- Quantity and Quality assessments of phytochemicals --- p.113 / Chapter 3.5.1. --- Phytochemicals recoveries and compositions in phytosterol preparations and desterolized fractions --- p.113 / Chapter 3.5.1.1. --- Phytosterols recoveries and compositions in phytosterol preparations --- p.113 / Chapter 3.5.1.2. --- Squalene and tocopherols recoveries and compositions in desterolized fraction --- p.115 / Chapter 3.5.2. --- Antioxidant activities of desterolized fractions --- p.118 / Chapter 3.5.2.1. --- ABTS scavenging activity --- p.118 / Chapter 3.5.2.2. --- Scavenging Activities of DPPH radicals --- p.120 / Chapter 3.5.3. --- Anti-proliferative effect of phytosterols on cancer cells --- p.123 / Chapter 3.5.3.1. --- Determination of optimal cell density for antiproliferative assays --- p.123 / Chapter 3.5.3.2. --- Anti-proliferative effect of phytosterols on H1299 --- p.126 / Chapter 3.5.3.3. --- Anti-proliferative effect of phytosterols on Hep G2 --- p.132 / Chapter 3.5.3.4. --- Further investigation of anti-proliferative mechanism of β-sitosterol --- p.138 / Chapter 4. --- Discussion --- p.149 / Chapter 4.1. --- Characteristics of Physically Refined Deodorizer Distillate (DODp) --- p.149 / Chapter 4.1.1. --- Fatty acid contents and compositions --- p.149 / Chapter 4.1.2. --- "Squalene, tocopherol and phytosterol contents" --- p.153 / Chapter 4.1.3. --- Other physical and chemical analyses --- p.155 / Chapter 4.2. --- Production of fatty acid methyl esters (FAMEs) 一 Protocol A --- p.156 / Chapter 4.2.1. --- Optimization of Esterification --- p.156 / Chapter 4.2.2. --- Optimization of Molecular Distillation --- p.158 / Chapter 4.3. --- Production of fatty acid methyl esters (FAMEs) 一 Protocol B --- p.159 / Chapter 4.3.1. --- Optimization of Saponification --- p.159 / Chapter 4.3.2. --- Extraction of unsaponifiable matter --- p.160 / Chapter 4.3.3. --- Production of FAMEs --- p.161 / Chapter 4.4. --- Purification of phytosterols --- p.162 / Chapter 4.4.1. --- Purity and recovery of phytosterols --- p.162 / Chapter 4.4.2. --- Purity and recovery of squalene and tocopherols in desterolized fractions --- p.163 / Chapter 4.5. --- Quantification of the Loss of Valuable products during Processing --- p.165 / Chapter 4.6. --- Quality assessment of FAMEs and phytochemicals --- p.170 / Chapter 4.6.1. --- Specifications for Biodiesel in USA --- p.170 / Chapter 4.6.2. --- Acute toxicities of FAMEs --- p.171 / Chapter 4.6.3. --- Antioxidant activities of desterolized fractions --- p.172 / Chapter 4.6.4. --- Anti-proliferative effects of phytosterols on cancer cells --- p.173 / Chapter 4.7. --- Comparisons of the two protocols --- p.182 / Chapter 4.7.1. --- Products from protocol A and B --- p.182 / Chapter 4.7.2. --- Characteristics of protocol A and B --- p.183 / Chapter 4.7.3. --- Sustainable recycling technology --- p.184 / Chapter 4.7.4. --- Life cycle analysis --- p.185 / Chapter 4.8. --- Further investigation --- p.186 / Chapter 5. --- Conclusion --- p.187 / Chapter 6. --- Reference --- p.189

Waste-to-energy (WTE) is the environmentally preferred method of managing post-recycling wastes. In this process, municipal solid waste is combusted under controlled conditions to generate steam and electricity. Waste is by nature heterogeneous and has a substantially high composition of chlorine (0.47-0.72 wt%) as compared to other solid fuels used for power production. During combustion, chlorine is converted to hydrogen chloride and metal chlorides, which can accelerate the high temperature corrosion of boiler surfaces, especially superheater tubes. This corrosion can significantly affect plant efficiency and profitability by causing unplanned shutdowns or preemptively forcing operators to limit steam temperatures. The following work focuses on the role of chlorine compounds on boiler tube corrosion and investigates approaches for minimizing its effects. The corrosion behavior was studied by conducting laboratory furnace tests on alloys of current and future interest to the WTE industry. Test specimens were coupons machined from boiler tubes to a nominal area of 3.2 cm² (0.5 in²). An chemical environment was introduced in an electrical furnace that replicates the fireside of superheater tube. This included a mixed gas stream with O₂, CO₂, H₂O, HCl, SO₂, and N₂, and temperatures ranging between 400-550°C (752-1022°F). For some experiments, a salt layer was applied to the coupons with a loading of 4.0 ±10% mg/ cm² to understand the behavior of the effects of metal chlorides. Following each experiment, the corrosion rate was determined by taking the mass loss as specified in an American Standard Testing Method (ASTM) protocol, G1-09. Additional insights were obtained by characterizing the coupons via scanning electron microscopy (SEM) and elemental dispersive spectroscopy (EDS). Additionally, the corrosion scale and salt layer were characterized via powder X-ray diffraction (XRD). The addition of 800 ppm of hydrogen chloride (HCl) gas to a mixed gas oxidizing environment accelerated the corrosion rate of SA178A (Fe-0.1C) at 500°C (932°F) as determined by the change in the parabolic rate constant over a period of 72 hours, from 0.18 to 1.7 μm²/h (3.0 E-03 to 2.5 E-02 mil²/h). The findings from the EDS and XRD scale analyses were compared to other literature and thermodynamic calculations that showed that effect that HCl accelerates corrosion via an active oxidation mechanism. A parametric study was performed on the effect of hydrogen chloride on three alloys, SA178A, SA 213-T22 (2.5 Cr-1 Mo-Fe) and NSSER-4 (Fe-17Cr-13Ni). Varying the concentration from 400 ppm to 800 ppm at 500°C increased the mean mass loss by 17.5%, as compared to the 60% increase from 0 to 400 ppm. For each alloy, the mass loss increased sharply with temperature between 450, 500, and 500°C, with corresponding apparent activation energies of Ea NSSER- 4 53 kJ/mol, Ea SA213 T22 110 kJ/mol, and Ea SA178A 111 kJ/mol. The lower apparent activation energy for NSSER-4 demonstrates that effect of hydrogen chloride is mitigated with austenitic alloys versus carbon steel or low alloyed steel. In a comparative study between isothermal and temperature gradient tests, it was also shown that the corrosion of SA178A was not impacted by a temperature gradient up to 250 °C. Another important chlorine compound in WTE boilers are metal chlorides, which are readily contained in fly ash and boiler deposits. Using sodium chloride as a surrogate compound, the corrosion behavior under chloride salts was investigated by applying a salt layer (4.0 mg/cm²) on coupon surfaces. Corrosion under the chloride layer was much more severe than below the HCl-containing atmospheres alone. The mass loss for the commercial steels was increased by more than an order of magnitude. Based on SEM and XRD coupon and corrosion product characterization, this behavior was the result of a second active oxidation mechanism in which sodium chloride reacts with and depletes protective oxides such as chromium (II) oxide. The WTE furnace tests with the sodium chloride layer were executed for six different Ni-Cr coatings, including Inconel 625 (Ni-Cr-Mo), SW1600, SW1641 (Ni-Cr-Mo-B-Si) and Colmonoy 88 and SP 99 (Ni-Cr-B-W). The primary corrosion attack observed was pitting located under the original salt layer. Colmonoy 88, showed superior corrosion resistance with mass losses between 0.3-3.1 mg/cm2 between 450-550°C as compared to the Ni-Cr-Mo, and Ni-Cr-B-So coatings which has mass losses between 10-30 mg/cm². The enhanced corrosion performance of Colmonoy 88 and SP 99 was attributed to the alloying addition of tungsten, which had been previously shown in literature to also improve the pitting resistance for Ni-Cr in aqueous environments. The corrosion behavior under metal chlorides was compared with metal sulfates, which are also prominent in WTE fly ash and boiler deposits. The application of sulfate salts on coupon surfaces was shown to semi-protective on WTE boiler tube surfaces up to temperatures of 550°C. The mass loss for carbon steel and Fe-17Cr-13Ni (NSSER-4) below sodium sulfate was an order of magnitude lower than under sodium chloride. These results motivated experiments aimed at sulfating chloride boiler deposits by increases the sulfur/chlorine gas ratio (SO₂/HCl) in WTE fuel gas. The SO₂/HCl ratio was modified between 0.3 to 0.6 and 1.0 respectively. By increasing the SO₂/HCl ratio, the sodium chloride layer applied on the coupon surface was converted from a chloride rich salt to a sulfate rich and was shown to dramatically reduce the corrosion of tube alloys up to 500°C. The impact of sulfating the alloy was most prominent with alloys with high mass loss under the sodium chloride layer. Tests showed a reduction in the corrosion rates of SA213 T22 (37%), Inconel 625 (23%), and NSSER-4 (27%). At 550 °C, there was no trend with respect to increases of the ratio, which suggests that other corrosion reactions are faster than the rate of sulfation. Finally, the annualized cost factor was defined and proposed as a method for replacing current superheater alloys with alternative materials, such as those tested in this thesis. From this discussion it was calculated that the installation of a colmonoy 88 protected superheater can cost approximately 1.4 times the cost of an Inconel 625 cladded replacement, or as much as 4.3 times the cost of a T22 superheater tube and remain a cost effective option.

Thesis (Doctor of Engineering in Chemical Engineering)--Cape Peninsula University of Technology, 2017. / The search for alternatives to fossil fuel is necessary with a view to reducing the negative environmental impact of fossil fuel and most importantly, to exploit an affordable and secured fuel source. This study investigated the viability of municipal solid waste gasification for a fuel cell system. Potential solid fuels obtained from the study in the form of refuse-derived fuel (RDF) had high heating value (HHV) between 18.17 MJ/Kg - 28.91 MJ/Kg with energy density increased from 4142.07 MJ/m3 to 10735.80 MJ/m3. The molecular formulas of RDF derived from Ladies Smith drop-off site, Woodstock drop-off site and an average molecular formula of all thirteen municipal solid waste (MSW) disposal facilities were CH1.43O1.02, CH1.49O1.19, and CH1.50O0.86 respectively. The comparative ratios of C/H were in the range of 7.11 to 8.90. The Thermo Gravimetric Analysis showed that the dehydration, thermal decompositions, char combustions were involved in the production of gaseous products but flaming pyrolysis stage was when most tar was converted to syngas mixture. The simulation of RDF gasification allowed a prediction of the RDF gasification behaviour under various operating parameters in an air-blown downdraft gasifier. Optimum SFR (steam flowrate) values for RDF1, RDF2 and RDF3 were determined to be within these values 2.80, 2.50 and 3.50 and Optimum ER values for RDF1, RDF2 and RDF3 were also determined to be within these values 0.15, 0.04 and 0.08. These conditions produced the desired high molar ratio of H2/CO yield in the syngas mixture in the product stream. The molar ratios of H2/CO yield in the syngas mixture in the product stream for all the RDFs were between 18.81 and 20.16. The values of H2/CO satisfy the requirement for fuel cell application. The highest concentration of heavy metal was observed for Al, Fe, Zn and Cr, namely 16627.77 mg/Kg at Coastal Park (CP), 17232.37 mg/Kg at Killarney (KL), 235.01 mg/Kg at Tygerdal (TG), and 564.87 mg/Kg at Kraaifontein (KF) respectively. The results of quantitative economic evaluation measurements were a net return (NR) of $0.20 million, a rate of return on investment (ROI) of 27.88 %, payback time (PBP) of 2.30 years, a net present value (NPV) of $1.11 million and a discounted cash flow rate of return (DCFROR) of 24.80 % and 28.20 % respectively. The results of the economic evaluations revealed that some findings of the economic benefits of this system would be viable if costs of handling MSW were further quantified into the costs analysis. The viability of the costs could depend on government responsibility to accept costs of handling MSW.

Thesis (Master of Engineering in Electrical Engineering)--Cape Peninsula University of Technology, 2018. / In Sub-Saharan Africa (SSA), there are several challenges that hinder development. One of these challenges is access to electricity. There are numerous benefits to having access to reliable electricity. These include less time spent fetching water from rivers and dams, as water purification systems for households could be used in villages; children in villages would be able to spend more time doing their schoolwork and not fetching wood for fire; and automated irrigation systems could be used for villagers to farm and make an income. Finding alternative ways to generate electricity would enable access to electricity for regions that currently do not have the electricity. This means that large organisations need to find alternative ways of generating electricity, as they have the means to do so. With the current renewable energy technologies available, there are now more ways in which electricity could be generated. The use of biomass is no exception to this. With constant developments in the renewable energy sector, waste-to-energy (WtE) is proving to be a viable method to generate electricity. The main aim of this research was to determine if a commercial food retailing organisation could use their food waste for generating electricity for their own use to reduce their demand from the central grid. A way of determining the viability of this type of technology is using a software that simulates renewable energy projects. In this research, an organisation was contacted for waste data. Systems for two of the stores will be simulated and results will be discussed. The organisation will remain anonymous. The software used in this research is System Advisor Model (SAM), which was developed by the National Renewable Energy Laboratory (NREL) in the United States. In the results, three results were discussed. These are the monthly energy, monthly heat rate and the monthly boiler efficiency for each of the stores for Store 1, the annual energy simulated was 138,509 kWh and 131,677 kWh for Store 2. Monthly energy averages for each store were 11,542 kWh for Store 1 and 10,973 kWh for Store 2, respectively. There are several opportunities for research based on the findings. These include researching other food sectors in the study; conducting a financial analysis of small-scale WtE systems; constructing a prototype of the system; and using three different softwares to simulate a system for the same project.