Numerical simulations of coal gasification process inside a generic 2-stage entrainedflow gasifier are carried out using the commercial CFD solver ANSYS/FLUENT. The 3-D Navier-Stokes equations and eight species transport equations are solved with three heterogeneous global reactions, three homogeneous reactions, and one thermal cracking equation of volatiles. Finite rates are used for the heterogeneous solid-gas reactions. Both finite rate and eddy-breakup combustion models are calculated for each homogeneous gas-gas reaction, and the smaller of the two rates is used. Lagrangian-Eulerian method is employed. The Eulerian method calculates the continuous phase while the Lagrangian method tracks each coal particle. Fundamental study is carried out to investigate effects of five turbulence models (standard k-ε, k-ω, RSM, k-ω SST, and k-ε RNG) and four devolatilization models (Kobayashi, single rate, constant rate, and CPD) on gasification simulation. A study is also conducted to investigate the effects of different operation parameters on gasification process including coal mixture (dry vs. slurry), oxidant (oxygen-blown vs. air-blown), and different coal distributions between two stages. Finite-rate model and instantaneous gasification model are compared. It is revealed that the instantaneous gasification approach can provide an overall evaluation of relative changes of gasifier performance in terms of temperature, heating value, and gasification efficiency corresponding to parametric variations, but not adequately capture the local gasification process predicted by the finite rate model in most part of the gasifier. Simulations are performed to help with design modifications of a small industrial demonstration entrained-flow gasifier. It is discovered that the benefit of opening the slag tap on the quench-type gasifier wider by allowing slag to move successfully without clogging is compromised by increased heat losses, reduced gasification performance, downgraded syngas heating value, and increased unburned volatiles. The investigation of heat transfer on fuel injectors shows that blunt tip fuel injector is less likely to fail compared to conical tip fuel injector because the maximum high temperature on the injector is scattered. Two concentric fuel/oxidant injections provide better fuel-oxidant mixing and higher syngas heating value than four separate fuel and oxidant injections.

A mild gasification method has been developed to provide an innovative clean coal technology. The objectives of this study are to (a) incorporate a fixed rate devolatilization model into the existing 2D multiphase reaction model, (b) expand the 2D model to 3D and (c) utilize the improved model to investigate the mild-gasification process and guide modification of the mild-gasifier design. The Eulerain-Eulerian method is employed to calculate both the primary phase (air) and secondary phase (coal particles). The improved 3D simulation model, incorporated with a devolatilization model, has been successfully developed and employed to determine the appropriate draft tube dimensions, entrained flow residence time, The simulations also help determine the appropriate operating fluidization velocity range to sustain the fluidized bed depth without depleting the chars or blowing the char away. The results are informative, but require future experimental data for verification.

M. Tech. (Engineering: Electrical, Department Electronic Engineering, Faculty of Engineering and Technology), Vaal University of Technology, / “If we think oil is a problem now, just wait 20 years. It’ll be a nightmare.” — Jeremy Rifkin, Foundation of Economic Trends, Washington, D.C., August 2003. This statement harmonises with the reality that human civilisation faces today. As a result, humankind has been forced to look for alternatives to fossil fuels. Among possible solutions, fuel cell (FC) technology has received a lot of attention because of its potential to generate clean energy. Fuel cells have the advantage that they can be used in remote telecommunication sites with no grid connectivity as the majority of telecommunication equipment operates from a DC voltage supply. Power plants based on phosphoric acid fuel cell (PAFC) have been installed worldwide supplying urban areas, shopping centres and medical facilities with electricity, heat and hot water. Although these are facts regarding large scale power plants for on-site use, portable units have been explored as well. Like any other fuel cell, the PAFC output power is highly unregulated leading to a drastic drop in the output voltage with changing load value. Therefore, various DC–DC converter topologies with a wide range of input voltages can be used to regulate the fuel cell voltage to a required DC load. An interleaved synchronous buck converter intended for efficiently stepping down the energy generated by a PAFC was designed and developed. The design is based on the National Semiconductor LM5119 IC. A LM5119 evaluation board was redesigned to meet the requirements for the application. The measurements were performed and it was found that the converter achieved the expectations. The results showed that the converter efficiently stepped down a wide range of input voltages (22 to 46 V) to a regulated 13.8 V while achieving a 93 percent efficiency. The conclusions reached and recommendations for future research are presented. / Telkom Centre of Excellence, TFMC, M-Tech, THRIP.

With a growing population but scarce primary phosphorus sources, recycling of the vital element has become an important research area throughout the last decades. Several streams in society are potential resources for recirculation but municipal sewage is considered one of the most available materials. With current technologies in wastewater treatment, over 95 % of the influent phosphorus is captured in the sludge along with a variety of other nutrients. However, due to increasing fractions of pharmaceutical residues and heavy metals also following the sludge, direct use as fertiliser is being phased out in most European countries in favour of extraction methods. Extraction of nutrients from the sludge is problematic mainly because of dewaterability difficulties. Thus, pretreatment of the material is required to access the desired components at a reasonable cost and energy consumption. Hydrothermal carbonisation (HTC) is a technology showing high potential for treatment of wet carbonaceous material without necessity of prior drying. The resulting product is hygenised, essentially free from pharmaceuticals and easily dewatered. In this Master’s thesis principal conditions for release of phosphorus from HTC converted digested sludge under acid leaching have been experimentally investigated. Dependence of time, temperature, dry solids (DS) content of HTC sludge and pH have been studied. Also, differences arising from acid type have been considered by comparing acidulation with sulphuric acid and hydrochloric acid. A short investigation of the recovery of the dissolved phosphorus from leachate by precipitation was also performed where calcium ions were added to both sulphuric and hydrochloric acid leachates. Extraction of phosphorus from HTC converted sludge has shown to be easier than from pure metal phosphates under comparable leaching conditions and pH values. Also, the dissolved phosphorus concentrations obtained in the presence of HTC converted sludge was higher than for theoretical equilibrium concentrations where all phosphorus is in the form of iron(III) or aluminium(III) phosphate. A maximum leachate phosphorus concentration was around 2500 mg/L, recorded in leaching experiments performed at a dry HTC product concentration of 10 % (w/w) in an extraction solution of water acidified with sulphuric acid. Leaching procedures performed at pH values between 2 and 1 with 1 and 5 % DS HTC product resulted in dissolution of 90 % of ingoing phosphorus at an acid charge of 0.5 kg H2SO4/kg DS HTC product. At this chemical charge, release of phosphorus from converted sludge is fast. Similar amounts of dissolved phosphorus were recorded after 15 min as after 16 h retention time. Possibly, time dependence becomes relevant at lower charges. The dissolution of phosphorus is negatively affected by temperature increases at moderate acid loads, and by possibly by hydrochloric acid at pH values below 2. Addition of calcium gave a dissolved phosphorus reduction of 99.9 % in both the sulphuric acid and hydrochloric acid leachates. Gypsum, CaSO4, also precipitates from the sulphuric acid leachate resulting in 67 % more dry mass. Due to high release of metals during acidulation, the precipitate was also contaminated with large fractions of metals in addition to calcium. In summary, this investigation has demonstrated that up to 90 % of the phosphorus content of the HTC converted sludge can be released by acid leaching, and almost 100 % of the phosphorus can be recovered from the leachate by precipitation with calcium ions.

Student Number : 0104363F - MSc research report - School of Architecture and Planning - Faculty of Engineering and the Built Environment / South Africa is a constitutional state. The constitution is the supreme law of the country (RSA, 1996). Any of the state laws, policies and programmes that are inconsistent with the constitution are invalid, thus they have no legitimate standing. In the preamble of its constitution, the post apartheid South Africa sworn itself as a country recognising the past injustices, hence planning for the society based on social justices, in order to improving the quality of life of all citizens and free the potential of each person. The Bill of Rights is a cornerstone of democracy in South Africa, as it encompasses all human rights, especially socioeconomic rights, whose fulfilment will contribute towards realisation of equal and united society based on social justice. However, the post apartheid South African government adopted a Free Basic Water policy as a way of adhering to the constitutional requirements of ensuring that everyone has the right to sufficient water. Access to clean sufficient water has been identified as a crucial requirement for Care and Prevention to the HIV/AIDS affected households. In the midst of socioeconomic inequalities, scarce water resources and high HIV/AIDS prevalence confronting the post apartheid South Africa today, the Free Basic Water policy guarantees every household of eight; irrespective of its socioeconomic status and health concerns, 6kl/6000 litres of water every month free. The local government has been blamed for not being responsive these special water needs of the poor HIV/AIDS households, especially in townships areas, where water is mostly provided on cost-recovery. However, little attention has been paid on the difficulty faced by the local government authorities in this regard. The report argue for a need of collaboration between planners and others major stakeholders, to come up with group-conscious water policy that will guide for planning of a society based on social justice. However, the research recommends that this policy should not only be guided by / concerned with justice and fairness in the distribution of basic needs of the society with special needs. More important, this new policy should be fair, thus account for the sustainability of the water resources, since South Africa is regarded as water-scarce country.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2015. / Over 60% of the Swazi population resides in rural areas and rely on woodfuel for their daily cooking needs. Cooking with woodfuel on open fires is inefficient and unhealthy, leading to millions of deaths of women and children each year while also contributing to environmental degradation. This has necessitated the implementation of Government’s clean cookstoves programme in Swaziland. This study focused on household stove users in six chiefdoms in the Lower Usuthu Sustainable Land Management (LUSLM) Project area in Siphofaneni Swaziland. A survey conducted through the dissemination of a questionnaire was used to investigate how rural perceptions impact on the adoption of clean cookstove technologies as an alternative household energy technology contributing towards sustainable development in rural Swaziland. Results from this study indicate that although cooking on an open fire was the least desired cooking technology, only 2% of households in the project area own clean cookstoves and less than half of the households had knowledge of cookstoves. The study further revealed that over 80% of the households in the survey area would prefer using a clean cookstoves to reduce the labour intensive task of collecting firewood as well as reducing exposure to smoke. The households found to have some knowledge of the benefits of clean cookstoves indicated the willingness to pay for a clean cookstove; however, a third of the respondents indicated a preference of obtaining a free clean cookstove. The price and availability of the clean cookstove in rural areas were two main barriers to increased uptake of the stoves, coupled with the need to purchase new pots. Despite the general lack of awareness of these technologies, challenges such as danger of the stoves to children and stove durability were also cited. The results indicate the need for the ongoing clean cookstove programme being implemented by the Government of Swaziland to improve on its strategy, to focus on incorporation of perceptions of rural stove users in development of appropriate cookstove designs, distribution models, and the design and implementation of a cookstove quality control programme.

A necessidade mundial de mitigação dos gases de efeito estufa (GEE) e a mobilização internacional para atingir os objetivos de redução estabelecidos pela Convenção-Quadro das Nações Unidas para Mudanças Climáticas (CQNUMC) deram abertura para que finalmente as energias renováveis pudessem ser utilizadas e aumentassem sua parcela na matriz energética mundial. No Brasil, a sólida indústria sucroalcooleira atualmente desenvolve projetos de redução de emissões de carbono no âmbito do Mecanismo de Desenvolvimento Limpo (MDL) do Protocolo de Quioto, por meio de 18 projetos baseados na geração de energia elétrica renovável excedente através da cogeração, com exportação para a rede elétrica nacional, deslocando energia marginal termelétrica de origem fóssil, em apenas 20 unidades produtoras paulistas. Neste trabalho foi projetado um cenário ideal de reduções de emissões, que considerou a adesão total de 151 usinas paulistas para a safra de 2006/2007, para cinco cenários patamares tecnológicos de cogeração, com queima de bagaco e também aproveitamento da palha. Foi utilizando os parâmetros tecnológicos elaborados pela Comissão Especial de Bioenergia do Governo do Estado de São Paulo e o fator de linha de base de 0,268 tCO2e/MWh adotado pelos projetos de MDL em operação no Estado de São Paulo. No cenário tecnológico mais conservador as emissões evitadas somariam 1.404.593 tCO2e/ano. Para o cenário ideal as emissões evitadas somam 12.199.443 tCO2e/ano. Para composição do cenário ideal também foram calculadas as emissões referentes à queima da palha da cana-de-açúcar. / The world-wide necessity of Greenhouse Gases (GHG) mitigation and the intergovernmental mobilization to reach the objectives established by the United Nations Framework on Climate Change (UNFCCC) has opened space for the renewable energy increase in the worlds energy matrix. In Brazil, the solid sugarcane industry currently develops business in the scope of the Clean Development Mechanism (CDM) under the Kyotos Protocol, by means of 18 biomass-based projects, with renewable energy generation through bagasse cogeneration at 20 São Paulo States sugarcane production units. The projects activitys consists of increasing the efficiency in the bagasse cogeneration facilities, qualifying the units to sell surplus electricity to the national grid, avoiding the dispatch of same amount of energy produced by fossil-fuelled thermal plants to that grid. The reduced emissions are measured in carbon equivalent and can be converted into negotiable credits. The objective of this dissertation was to build a state of art scenario, calculating the potential emissions reduction through CDM projects for the sugarcane sector of São Paulo State, in which we consider the adherence of all the production units of the State to the CDM projects. The technological parameters used to elaborate the scenario were provided by the São Paulo State Government Bioenergy Special Commission and the baseline factor used of 0,268 tCO2e/MWh was that adopted by the CDM projects in operation in the State. The sugarcane database for the calculations was the production ranking provided by UNICA for the 2006/2007 season. In the most conservative scenario 131 units could avoid the emission of 1.404.593 tCO2e/year. For state of art scenario, the units could avoid 12.199.443 tCO2e/year. Also have been calculated the sugarcane straw burning emission for the sugarcane harvested in 2006/2007 season.

O presente trabalho tem o objetivo de identificar fatores intervenientes na adoção de energias limpas nos principais setores industriais do Estado de São Paulo. Para tanto, apresenta a fundamentação teórica sobre os diversos temas pertinentes a pesquisa, tais como: o atual cenário energético brasileiro e o desenvolvimento sustentável, bem como o estudo dos métodos aplicados. A análise dos dados realizada teve caráter qualitativo e quantitativo, por meio, respectivamente, da Técnica do Incidente Crítico e da Análise Conjunta. A aplicação da Técnica do Incidente Crítico forneceu os atributos que as empresas consideram importantes no processo de escolha. Já a Análise Conjunta, técnica estatística multivariada de análise de dados, foi utilizada para determinar a utilidade e importância relativa dos atributos relevantes na escolha das empresas. Com os resultados da pesquisa acredita-se que as empresas usuárias e não usuárias de energias limpas poderão ter conhecimentos sobre a opinião de seus pares com relação às vantagens e desvantagens do uso destes energéticos nos processos produtivos, assim como ao governo estabelecer estratégias adequadas para orientar e estimular a adoção de energias que promovem baixo impacto ao meio ambiente. / The scope of the present work is to identify intervening factors in the adoption of clean energy resources in the main industrial sectors of the São Paulo state. In order to perform such evaluation, a theoretical reasoning on the various relevant issues related to the research shall be displayed, such as: the current brazilian energy context and sustainable development, as well as the study of applied methods. The data analysis was realized guided on a qualitative and quantitative basis, by means, respectively, of the Critical Incident Technique and the Conjoint Analysis. The application of the Critical Incident Technique has imputed capabilities that companies regard as pivotal in the selection process. The Conjoint Analysis, on its hand, multivariate statistics technique on data analysis, was used in order to determine the utility and relative importance of the capabilities relevant to the companies\' selection. Based on the results inferred from the research it may be conjectured that companies that adopt and do not adopt clean energy resources may acquire acknowledge about the opinion of its couples in what it concerns the advantages and disadvantages of the use of these energetic in these productive processes, as well the government may set to establish adequate strategies in order to instruct and encourage the adoption of energy resources that promote a lesser impact to the environment.

Although the general principles of biomass gasification are broadly understood, at a larger scale of operation (e.g. > 200 kg/h) there is a lack of confidence in the translation of the basic scientific concepts into a financially viable operation that satisfies regulatory requirements. Looking in particular at the operation of a down-draft type of gasifier, a number of challenges were identified and studied in greater detail. Gasification experiments were performed on wood and straw pellets in a small scale, 21 mm i.d. quartz-tube reactor. These provided useful insight into what was occurring inside the gasifier, and the complexity and roles of the various reaction zones. In order to perform on-line gas analysis measurements in real time, a method was developed which enabled a quadrupole mass spectrometer (QMS) to be used. This was tested in a laboratory environment, and then used on a commercial pilot-plant gasifier (150 to 250 kg/h). This enabled the composition of the gas to be monitored while the plant was started up, and then operated at various levels of gas flow through the plant. In general the concentrations measured during a stable operation were as follows: CO = 16.0 vol.%, H2 = 11.9 vol.%, CO2 = 15.8 vol.%, N2 = 54.1 vol.%, CH4 = 1.9 vol.%, O2 = 0.3 vol.%. Measurements of O2 concentrations in the gas stream on start-up provide useful information on conditions when a flammable atmosphere could exist in the lines/vessels. To help with the development of suitable gas clean-up strategies, the presence of two key sulphur species, H2S and carbonyl sulphide (COS), was studied in more detail. Experimental measurements were taken on the laboratory reactor (e.g. H2S = 286 ppmv, COS = 28 ppmv for gasification of refuse-derived fuel (RDF) pellets), and the commercial pilot-scale gasifier (e.g. H2S = 332 ppmv, COS = 12 ppmv). This data was also compared with theoretical thermodynamic predictions. The steam gasification of char was also studied in a laboratory 9.5 mm i.d. reactor, and kinetic expressions were determined for RDF-derived char. It was shown that high concentrations of H2 (20 vol.%) and CO (15 vol.%) can be achieved, and the temperature at which reactions were initiated was > 700 ºC, and significant at 900 ºC. Interestingly, the RDF-derived char (at carbon conversion from 10 to 70 %) appears to be more reactive than other biochars reported in the literature. However, at high conversion (> 50 %), its apparent reactivity decreases with carbon conversion, behaving in a similar manner to coal chars.

This project analyzes the validity of theoretical models used to predict the duration (hold time) for which a halon-replacement suppression agent will remain within a protected enclosure. Two current models and one new formulation are investigated; the sharp descending interface model (as applied in NFPA 2001, Annex C), the wide descending interface model (implemented in ISO 14520.1, Annex E), and the thick descending interface model (introduced herein). The thick interface model develops the characteristic thickness as an additional input parameter. Experimental data from 34 full-scale tests designed to characterize the discharge and draining dynamics of seven clean extinguishing agents (CEA) is used to assess model validity. For purposes of model validation the characteristic thickness is regressed from the experimental data although further work may be required to establish the independence of this parameter to other system design and environmental variables. Results show that the wide and sharp interface models' validity is highly sensitive to the threshold of agent concentration decay being modeled; whereas the thick interface prediction method demonstrates increased robustness at any modeled threshold. When the hold time is defined as a 15% decay in agent concentration, experimentally obtained hold time values are roughly 10% shorter than sharp interface predictions, 60% longer than wide interface predictions, and 30% longer than the thick interface model predicts.