Engineering

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A consecutive reaction model and kinetics of cr2o3 reduction from slag by carbon dissolved in molten iron
(2011-01-12) Simukanga, Stephen
A first-order, consecutive, two-stage reaction model for the reduction of cr2o3 from slag was developed. The model was applied to the results obtained by studying the effect of various parameters on the rate of reduction of cr2o3 from a CaO-SiO2-Al2o3 slag, by carbon dissolved in molten iron, at temperatures 1400-1550 degrees celcius.The parameters studied were: varying the furnace atmosphere; cr2o3 concertration in slag; metal chromium content; the experimental temperature; slag and metal volume;the presence of the surface-active elements, S or Se and adding FeO and CaF2 to the slag. The progress of the reactions was monitored by taking slag samples at predetermined time intervals, and analyzing them for the relevant species. The results showed that the reduction of cr2o3 from slag takes place primarily at the slag/metal interface, and follows a first-order, consecutive, reversible, two-stage reaction scheme in which (cr2+)is the intermediary product. The rate of (cr3+) reduction remained the same in an argon or carbon monoxide atmosphere whilst an argon atmosphere increased the rate of (cr2+) reduction by a factor of about 1.4,compared to a carbon monoxide atmosphere. The rate of reduction of the chronium species increased with increase in temperature and activation energies obtained were 54.16,27.15 and 81.33 kcal/mol for (cr3+),(cr2+) and cr2o3 reduction. Addition of S or Se to the system markedly increased the attendant increase in the Feo content of the slag. Metal emulsification, which is a consequence of reduced surface-tension of the metal,is thought to be responsible for the increase in the rate of cr2o2 reduction. Addition of FeO to slag decreased the reduction rates of all the chromium species whilst CaF2 addition increased the rate of reduction of the chronium species.The reduction in slag viscosity due to CaF2 addition is thought to be responsible for the increased rates of reduction.
Process Design study for the beneficiation of Kaluwe Phosphate Ore
(2011-01-12) Simukanga, Stephen
Kaluwe phosphate ore constitutes calcite(74.4 wt %)as the major mineral with minor amounts of apatite(5.9 wt %),opaques(13.5 wt%),which are predominantly iron minerals,quart/feldspar(5.7) and traces of biotite(o.5 wt %).The chemical composition of the ore averaged 2.2% p2o5,47.7% Cao,1.6%mgo,1.2% Al2o3,3.3% Fe2o3 and 4.7% Sio2.Beneficiation studies were performed to investigate methods of concertrating the phosphate values.Preliminary studies involved detailed identification of mineralogical and chemical properties of the constituent minerals which could form the basis of selective seperation of apatite from the gangue.The results of these studies showed that liberation of apatite ocurred below 425um.On the basis of the identified mineralogical and chemical properties of the minerals,tabling,magnetic concertration and flotation techniques were applied in the beneficiation tests.The results indicated that these techniques could not be individually applied to produce a final phosphate concertrate because of the poor grade of ore.Encouraging concertrate grades were obtained after combining these techniques.A treatment flowsheet has been proposed on the obtained results.The multiplicity of processing steps in the flowsheet implies increased capital and operating costs.This is unavoidable due to low grade nature of the ore.
Estimation of Rotational Degrees of Freedom Using Spline Functions
(2011-01-25) Ng'andu, Namasamu Alvert
Structural Dynamics Modification work often requires the inclusion of rational degrees of freedom in the modal data. These are not usually directly measurable because suitable transducers are not yet readily available. This work investigates the estimation of rotations from computed or measured translational data using spline functions for curve and surface fitting.The estimation accuracy is found to depend on a number of factors including the spatial distribution of data points, the level of error in the original data and the degree of smoothing applied. Analysis on beam and plate structures show that an interpolating spline gives the best results on error-free data, but that some degree of smoothing is required when dealing with noisy data. It is shown that structural boundary conditions provide a useful basis for judging the level of smoothing required. For clamped structures, the approximation which minimises the slope at the clamped boundary is found to be acceptable . For free boundaries, the approximation which minimises the second derivative of the fit function there gives the best overral results. The accuracy of the rotation estimates is found to depend on the general level of error in the origainal data but is influenced to a much lesser extent by the distribution of error between data points. The error in the rotation from data with a maximum error of 1% of the largest modal translation are shown to be generally below 10% provided there are atleast two maesurement points between modal lines for the highest mode of interest.As the consequence of errors in the rotations, the errors in the structural dynamics modification predictions are found to be broadly less than 5% when rotational errors are of the order of 10%. Further, it is shown that estimates of rotations which are within 20% of the correct value yield frequency prediction errors which are under 10%. Thus it is concluded that the proposed method is a quick ,simple, versatile and effective tool for estimating rotations yielding comparable performance with existing methods on similar structures. An addition benefit is that there is no requirement for performing finite element analyses of the structure.
Private sector participation in the water and sanitation industry in Zambia : opportunities and constraints
(2011-06-30) BANDA, IAN; NZALI
Adoption of new mechanisms through which water supply and sanitation services may be provided to communities in Zambia has been undergoing continuous transformations over the last decade.Policy makers and other key stakeholders have been trying to find the most appropriate and self sustaining service delivery mechanism, through which good quality services can be provided to consumers throughout the country. In 1993 the Government of Zambia embarked on a reform process primarily aimed at addressing the many problems associated with water supply and sanitation to communities.Notable outputs of the reform process were; passing of a new National Water Policy, enactment of new legislation, establishment of new institutions and the strengthening of the regulatory framework.Private Sector Participation (PSP) has prominently emerged as one of the probable ways through which service delivery can be improved in Zambia. This assertion emanates from the widely held notion that, "the private sector can enhance operational efficiency due to their strong adherence to sound commercial principles and good management practices ".The main objective of this study therefore was to, "investigate the appropriateness of PSP service delivery arrangements as a means through which water supply and sanitation services may be rendered in Zambia (the City of Lusaka being the test case) and to identify the associated opportunities and constraints". The main approach centered on evaluating the experiences gained from PSP contracts in water supply and sanitation that are already in existence and using the findings to help formulate a PSP option for Lusaka, Zambia. Three PSP cases were evaluated in this study namely, Kampala-Uganda, Dar Es Salaam-Tanzania and the Copperbelt Province-Zambia (this contract was confined to only the ex-mining areas of the Copperbelt Province).The main findings revealed that the main problematic issues in Zambia's urban water supply and sanitation service arena are; failure to access capital required for infrastructure rehabilitation in order to stem the many network losses, inadequate capital for network expansion, poor commercial management leading to low revenue collections, overstating, financing for effecting improvements to the poor and political interference.In this study it was determined that these issues were to a large extent addressed in the PSP contract in Uganda and to a lesser extent in the newly incepted PSP contract in Tanzania. Based on the attributes of the many PSP contracts in use world wide, it has been established that initially, a 2 to 3 years duration Performance Based Management Contract, followed by a 7 to 10 years duration Lease Contract (upon successful completion of Management Contract) as the most suitable PSP proposition for Lusaka.However,haphazard adoption and subsequent implementation of PSP in any form will not bring about the expected results. What is cardinal is that prior to adoption of PSP for any given service area, a well focused, detailed and thoroughly laid out due diligence study ought to be undertaken to establish the merits and or demerits of using PSP. This stems from the position that not all of the problems outlined above are prevalent in all the service areas implying that the solution will vary on a case by case basis. Therefore it can be asserted that PSP is not necessarily a panacea for Zambia's water supply and sanitation sector.
Design and evaluate a cellular manufacturing facility for selected copper products in Zambia
(2011-06-30) Hamweendo, Agripa
The economic advancement of any country depends on its ability to add value (through manufacturing) to its available local raw material resources. Zambia for a long time has been exporting copper as a raw material and importing finished copper products. This economic situation deprives Zambia of more foreign exchange earning which is necessary for national development. It is therefore important that researches on viability of adding value to locally available raw material resources (such as copper) are encouraged to promote value addition before export. This research aims to address the problem of exporting copper as raw material without adding value to it. The research focuses on designing and evaluating a cellular manufacturing facility for adding value to selected copper products. Cellular manufacturing was chosen in this research because it has become a popular manufacturing system for medium demand and medium variety products. In addition, cellular manufacturing facilitates job design, job flow, capacity planning, utilization, machinery arrangement and modernization. The products selected in this research included: cable lugs, contact terminals, earth rods, neutral blocks, copper washers, copper connectors, top plugs and sockets.A market survey was conducted to identify and select the copper products. The parts from the selected copper products were grouped into part families using poly-code classification system. Production Flow Analysis was applied to identify the process engineering and the required machinery. To design the cells (to form the Part-Machine Clusters), simultaneous part family formation and machine grouping solution strategy i.e. the Ranking Order Clustering Algorithm was used. Cellular layout and evaluation processes followed the cell design stage. Cell evaluation involved cell balancing, cost, and benefit analysis. To balance the cells, the Killbridge and Wester method was used.Two (2) linked cells were formed and designed. The cell balance efficiencies were 94.2% and 88.3% indicating good capacity utilization. The cost benefit analysis was done to appraise the facility. The calculated amount of copper cathodes required per week was 3.9591 tonnes which cost US$ 7,773.74. If copper was to be supplied in ready-madeform,the cost per week would be US$ 85,083. This implies that a tonne of copper when processed to primary product would cost US$ 21,490.09 (330% of value of copper cathode). When a tonne of copper undergoes secondary processing, the value increases to US$ 27,390.20 (420% of the copper cathode value). The total revenue per week from the sales of the selected copper products was US$ 113,488.37.The total cost of production was estimated at US$98,408.17 giving a gross Profit US$15,080.20 (13.3% profit margin). In conclusion, this research has brought out important synoptic issues indicating the urgency of considering adding value to copper to earn more foreign exchange necessary for national development. It is therefore encouraged that investors and the government invest into research and development of primary and secondary copper processing industries. Continuing to export raw copper as cathode is not a good economic setup.
Redesign and manufacture of a centrifugal pump
(2011-07-13) Nyirenda, Paulos
Pumps, of varying designs, have historically been vital in fluid flow. In Zambia, typical applications could be found in domestic water supplies and industrial applications. Complete pumping units have been designed and manufactured elsewhere. The manufacture of pumps in Zambia has generally involved the production of simpler parts such as volutes and covers while complex parts such as the impeller and diffuser casings are imported. This research work was initiated in the School of Engineering at the University of Zambia (UNZA) to carry out product re-engineering on a widely used pump in Zambia. The objective was to re-design the centrifugal pump, submersible type, which could be produced locally while maintaining its current performance characteristics.Concurrent engineering and CAD-CAM software (MasterCam and SolidWorks) were used'in the design process. The final pump design had fewer parts and the production process has been optimised. The Computer Numerical Control (CNC) technology was used to produce permanent moulds for casting the diffuser casings, impeller and bearing housing.
Digital control of an Encryptic broad-band radar application
(2011-07-13) Raghavan, Vijaya Srinivasa
This project describes the digital control of a radar that is ideally insensitive to alien disturbance signals. The key factor in this project comprises the design and realisation of a wide range of digital techniques combined into one digital controller consisting of several elements.The project is divided into three major parts, namely,Transmitter, Channel and Receiver.Transmitter: A radar control circuitry that generates binary noise with hidden codes has been developed. A modulo-2 feedback shift register generates a pseudo-random sequence. This sequence constitutes the binary noise. The codes [called Complementary Semi- Barker codes] are generated by cascading 16-1 multiplexers. Control signals were developed to establish a switch. The output of this switch transmits a signal consisting of the noise and the codes. The codes are known only to the sender. This makes it difficult for an intelligent target to distinguish between the codes and the binary noise.Consequently, this radar system is hard to influence. Receiver: The codes are matched using auto-correlation technique. In order to retrieve the matched codes, they have to appear in an adder simultaneously. This calls for the introduction of a delay in the signal. A threshold voltage is set to clip off the undesired part of the retrieved signal. This resembles a traditional radar signal. Channel: A channel is introduced in the final stage to intrude on the output of the transmitter. Disturbances in the form of additional pulses are introduced in order to investigate the sensitivity and robustness of the encryption technique.
Modification of a vertical machining centre to include turning operations : an investigation
(2011-07-14) Mwanza, Sichingwenje Moffat
There has been an accelerated use of Computer Numerical Control machine tools by developed countries over the past decade resulting in manufacturing companies becoming more competitive on the world market. However, the initial cost of these machines is prohibitive to many companies in the third world countries such as Zambia. Therefore,methods of adapting these machines to do much more than initially designed for would make the investment much more attractive. Various CNC machine builders have developed latest designs of combined turning and milling centres. This has been made possible through construction of more than three axes of rotation. None of the three-axis machining facilities convert a machining centre to a turning centre. It was the goal of this research to investigate the possibility of modifying a 3-axes CNC Vertical Machining Centre (VMC) to include CNC turning operations. This report outlines the research activity in the Department of Mechanical Engineering - School of Engineering at University of Zambia, exploring the methodology for widening the capability of a VMC to operate as a Turning Centre as well. The main objective was to add a modification to the existing Supermax 65A Vertical Machine Centre, so that turning operations could be performed within the designed parameters and programming software.During the research, fixtures for tool and workpiece holding were designed and produced.These were designed in line with the requirement for turning operations, original machine tool designed features and parameters. The use of Mastercam Mill software (Direct Numerical Control) and manual programming (Manual Data Input) were demonstrated as options for carrying out numerical control turning operations. Three samples of typical turned profiles were produced using designed fixtures. An estimation of force and power consumed during these operations was carried out. Although the study had certain limitations as regards the size and weight of turned jobs, it enhanced the number of part profiles that could be produced on the CNC Supermax 65A. The results proved that CNC machine tools could be improved for adaptability and productivity at minimum cost to a company.
Accessing applications from multiple file servers in a novell Computer Network
(2011-07-14) Isaac, John Sherrin
This research focused on solving the problems of application access from multiple file servers in a Novell network that caters for a large user community. The application access technique discussed in this dissertation is a step towards creating a computer network system, called a Virtual Machine (VM), with the following characteristics: it is simple to implement, scalable, easy to manage, transparent to the user and suitable for the conditions prevailing in a university-type environment. The VM has some of the features of a distributed system, but is not as complex and is built around a very popular commercial network operating system called NetWare.This dissertation presents the motivation, requirements, design considerations and performance of the developed VM.
The potential for the use of roughing-slow sand filtration systems in Zambia
(2011-07-14) Mwiinga, Godfrey
There is growing concern in most developing countries regarding the use of technologies that are inappropriate to local conditions. In the area of treating surface water to drinking water quality, consideration of alternative treatment methods is receiving great attention particularly with regard to small and medium community water supplies. In Zambia, surface water treatment to potable water is mainly by conventional methods. A recent evaluation of these methods revealed that operation and maintenance problems associated with the chemical pretreatment stage were rampant, particularly in small and medium community water supplies.To date, there have been hardly any studies on alternative methods. The current trend in the water sector is largely inclined towards addressing the rehabilitation of water supply systems so that private sector participation is facilitated. One of the sector principles, however, is to consider alternative treatment methods to alleviate current problems.The combination of roughing and slow sand filtration systems has emerged to be an appropriate alternative to conventional methods in most small and medium community water supplies. Roughing filtration as a pre-treatment method neither requires expert supervision nor chemicals. However, current studies elsewhere reveal that adequate design guidelines for roughing filters are not yet fully established. Slow sand filtration, as the main and final filtration stage, is excellent in producing potable water. However, new applications of slow sand filtration require pilot testing to ascertain their suitability. Operation and maintenance needs of roughing and slow sand filtration systems are reported to be simpler and economical compared to conventional systems. Nevertheless, for new applications, and where local experience is lacking, this can only be ascertained through pilot studies. The principal objective of the study was to evaluate the potential of a combination of roughing filtration and slow sand filtration systems for small and medium community water supplies in Zambia (using local materials) as alternatives to conventional systems. A pilot plant encompassing up-flow roughing filtration in layers and slow sand filtration processes was designed, constructed and investigated. Local filter media were used for the filtration processes. The pilot plant treated Kafue River water and high turbidity simulated raw water.The use of simulated raw water was inevitable since the investigation period did not cover the rain season when high turbidity raw water is common. The characteristics of the actual Kafue iver water during the period of investigation were: daily average turbidity < 5 NTU, total suspended solids < 5 mg/1, faecal coliforms < 200 FC/100 ml. Those of the simulated raw water were: daily average turbidity < 300 NTU, total suspended solids < 2000 mg/L and faecal coliforms < 4000 FC/100 ml. The performance of the pilot plant was evaluated by analyzing the quality of the filtrates. Roughing filters were operated at filtration rates ranging from 0.4 to 1.25 m/h, while slow sand filters were run at an average filtration rate of 0.24 m/h. Up-flow roughing filters in layers managed to pre-treat raw water to quality suitable for slow sand filtration, by significantly reducing the levels of turbidity, total suspended solids and faecal coliforms. There was no significant difference in performance, with respect to turbidity and suspended solids removal, of the roughing filters by varying filtration rates from 0.4 to 1.25 m/h. However, the removal of faecal coliforms was slightly lower at 1.25 m/h. The final slow sand filtrates showed acceptable turbidity levels (<1 NTU). However, faecal coliform levels occasionally exceeded the less than 1 FC/100 ml recommendation by the World Health Organization. Hence, slow sand filtrates may still require disinfection to guarantee potable water supply. Because of the sufficient pre-treatment provided by roughing filtration, slow sand filters were characterized by longer filter-runs than those reported for slow sand filters applied in Zambia, and elsewhere where chemical pre-treatment methods are used. The operation and maintenance of the pilot plant was easy, simpler and economical, managed by a local, compared to reported operation and maintenance requirements of conventional systems. It was therefore concluded that the use of roughing and slow sand filtration systems has great potential for small and medium communities in Zambia. Local materials can readily be utilized to construct these systems. The systems are able to treat raw water of high turbidity to potable water without the use of pre-treatment chemicals. Operation and maintenance procedures are relatively easy and can even be met at community level management. The results of the study provide the first basis for designing roughing and slow sand filtration systems in Zambia based on local practical investigations.
An investigation into the selection process of consultants and contractors in the public construction sector in Zambia
(2011-07-14) Mukumbwa, Brian Brown Makumba
Procurement of consultants and contractors in the public construction sector is regulated in most countries. In Zambia, all public procurement is regulated by the Zambia National Tender Board Act No. 30 of 1982. Various procurement methods are used for the selection of consultants and contractors in the public sector. In Zambia, the Quality and Cost Based Selection method (QCBS), Quality Based Selection method (QBS), Fixed Budget Selection method (FBS), and Least Cost Selection method (LCS) are the traditional methods used in the selection of consultants. The National Competitive Bidding (NCB) and the International Competitive Bidding (ICB) are the two methods used for formal tendering for selection of contractors. Informal tenders are used for the selection of both consultants and contractors for tenders below some prescribed threshold. The European Union (EU) and the Government of Japan also use the competitive traditional method of procurement. However, in Japan, cost was established to be the main factor considered in the selection of consultants and contractors.Good procedures for selection of contractors and consultants are critical to the successful implementation of construction projects. The Auditor General's reports, for the period 2000 to 2004, highlighted some anomalies in the procurement of construction projects. The reports also indicated poor workmanship, uncompleted and abandoned works as a result of non compliance to procedures. This study of the selection process of consultants and contractors sought to investigate and address problems in the procurement of consultancy and construction services in the public construction sector in Zambia. The aim of the study was therefore to develop best practice models for the selection of consultants and contractors. The research was undertaken through literature review, data collection using research instruments, analysis of results and case studies and report preparation. Through the analysis of results and case studies, a best practice model was developed and validated. Conclusions and recommendations were then drawn from the analysis of results, case studies and the validation process for the best practice model.Three research instruments, a questionnaire, case studies and in-depth direct interviews were used. It was established that the traditional method of procurement was still the most popular method of procurement for the selection of consultants and contractors in the public sector in Zambia. The following elements, in ranked order, were considered important in the selection of consultants: understanding the assignment; level of education of professional staff, experience in relevant works; experience in relevant tasks,methodology; and the work plan. In the appointment of consultants, pre-contract negotiation was favoured. On the other hand, the following, in ranked order, were determined as important factors in the selection of contractors: qualified technical personnel; financial capacity; experience in relevant works; and availability of construction equipment. Post contract assessment of consultants and contractors was also favoured upon completion of all projects.It was established that both project partnering and Public Private Partnerships (PPPs)were not commonly used procurement methods for construction projects in Zambia.However, they recognized for improving productivity in construction projects. To fully achieve the benefits of project partnering in Zambia, it was recommended that a clearly defined policy and legal frameworks for partnering be put in place. The major hindrance to the effective use of PPPs as a procurement method for construction projects in Zambia was the lack of political will to enact the legal framework for its implementation. Eprocurement was also not a commonly used method of procurement in Zambia, however,it was acknowledged that it could quicken the procurement process and improve on efficiency.An e-procurement model (Figure 6.1) was developed and validated as a best practice model in line with the aim of this study. It was established that this e-procurement model could bring about efficiencies in the selection of consultants and contractors in the public construction sector in Zambia and was also user friendly. The major limitation to this study was the failure by the researcher to access records for projects undertaken by other institutions other than National Assembly of Zambia and the Zambia Revenue Authority for use in the case study.
Industrial waste management in Zambia:Case study of a Lusaka slaughterhouse
(2011-07-14) Mangule, Mambwe Ronald
In Zambia, like in many other countries, industrialisation has brought with it the problem of environmental pollution associated with industrial waste waters. The discharge of industrial waste water into public sewers may deteriorate sewer structures, increase maintenance costs, add problems in sewage treatment and contribute to stream pollution.Direct discharge into streams may harm aquatic life and deem the water unfit for its intended use. It is therefore necessary to reduce the volumes and strengths of wastes by a combination of measures. Realising that some work has already been done with regard to the legal, policy and administrative frameworks, this study sought to clarify the situation with regard to industrial wastewater management. The study covered three main areas,each of which had its own objectives. These were: a) Industrial waste water management in Zambia (i)To analyse the effectiveness, relevance and currency of the relevant legal, policy and administrative frameworks with regard to industrial waste water management in Zambia (ii)To assess the perspectives and awareness of local industry regarding the relevant legislative and other frameworks and the resulting responses b) Case study of a Lusaka slaughterhouse (i) To evaluate the installed industrial technology (ii)To establish water use patterns and conservation measures (iii) To assess awareness of effluent regulations and compliance requirements (iv) To evaluate the status of pretreatment technology (v)To establish the availability of analytical facilities for water quality testing c) Pilot plant investigations on treatability of slaughterhouse wastewater by trickling filtration (i)To assess treatability of slaughterhouse wastewater by trickling filters (ii)To assess the potential for reducing pollution loads so as to meet discharge standards (iii)To provide a basis for the design of a full scale trickling filter treatment plant Assessment of industrial wastewater management was carried out by way of an extensive literature review of the relevant legislation and local publications. This was backed by interviews and discussions with personnel from industry, relevant government departments and local authorities. The awareness and perspectives of local industries to environmental legislation and related issues was further ascertained by conducting industrial site surveys coupled with questionnaires. The situation was further clarified by a case study of a slaughterhouse in Lusaka involving water and wastewater management. The industrial technology, water supply and consumption situation, wastewater production and treatment and attitude towards environmental protection were established by working in close cooperation with personnel in various sections of the plant. Pilot plant investigations were carried out on a rock media fixed distributor trickling filter on the treatability of slaughterhouse wastewater. Treatability studies were based on COD removal efficiency of composite samples. It has been found that there are a lot of duplications and overlaps in responsibilities among various government departments characterised by lack of implementation and enforcement. Of all the relevant Acts, only the Environmental Protection and Pollution Control Act was being implemented though with some drawbacks. Dissemination of the necessary information to the target group had not been effective which prompted industries to advocate for regular seminars and workshops on the relevant legislation and aspects of pollution control. The case study further revealed the non-enforcement of regulations and lack of environmental awareness from industry. Pilot plant treatability studies gave results that showed average COD removal efficiencies of 37.8 and 23.9 percent at hydraulic loading rates of 0.34 m3/m2h and 0.49 mVm2h, respectively. Generally, the legal and institutional frameworks need to be reformulated to eliminate duplications and overlaps of authority. It is important that only one body is charged with the responsibility of pollution prevention and control. There is also need to strengthen the enforcement procedures and to launch an awareness drive to enlighten industries and local authorities on the relevant legislation and aspects of pollution control. It has been recommended that emphasis should shift from an approach based on discharge licences and permits to one which promotes a preventive approach. The case study established the need to address the aspect of enforcement and environmental awareness. For the pilot plant investigation, the effluent COD values were mostly higher than the stipulated value (1800 mg/1) for discharge into public sewers. This has been attributed to high fluctuations in influent COD that gave rise to inconsistent treatment performance. It has been recommended that the research be continued incorporating proper primary treatment (screening, equalization and settling) and an effective final clarification step
Bioprocessing for renewable energy production from Municipal and industrial wet wastes in Zambia
(2011-07-14) Siwale, Lennox Zumbe
The poor management of wastewater causes loss of environmental quality. Biomethanation, a biogas-producing technique, as an attractive solution to the problem, was investigated. Biogas, a greenhouse gas, is a mixture of methane and carbon dioxide. While carbon dioxide is returned into the environment in the carbon cycle, methane can be burned as a fuel in existing types of power conversion technology namely, Internal combustion engines or microturbines to produce electric power and heat. This technique has the added incentive of accessing the carbon credit facility of the Kyoto Protocol's Clean Development Mechanism, COM.Laplace transformation was used to develop a mathematical model to predict process behavior applicable for municipal and industrial waste water produced, by way of example, respectively,Lusaka Water and Sewerage Company at Manchinchi treatment plant and Kembe Meat Products Limited, at their bovine meat processing plant. Experiments were used to both investigate biodegradability of the wastewater and validate the model developed. Characterizing the waste included determination of Biochemical Oxygen Demand, (BOD),Total Solid (TS), Volatile Solids (VS), biogas yield and determination of n coefficient in the model calibration. Apparatus used to determine biogas production included a 5-litre mild steel bioreactor where gas was collected by water displacement.Computing the energy content in the biogas, where 62 percent was methane, the potential of the available power from the wastewater was determined. By using Homer micro-power simulation software, a 350 kW micro turbine was suitable for Manchinchi. This would meet the operating load for in-house energy saving. Where commercialization was considered, a power output of 1 MW with grid sales would be available using gas generator and ancillary equipment. For Kembe, 40 to 60 kW Power can be accessed with a sound waste management system in place.Due to the smaller footprint, biomethanation is recommended to support financially strapped organizations in their waste management matters. Besides the economic investigations of the application of biogas in energy supply, estimation of the carbon credits of the Kyoto protocol's Clean Development Mechanism, (COM) represents a key incentive for organizations to adopt Anaerobic Digestion, (AD), where applicable, and therefore address the current global environmental concerns with benefits. Selecting a gas engine generator and 3x 3,500m3anaerobic digesters, gas handling and storage equipment and exhaust heat recovery facility for process heating, can produce a revenue-generating plant adding benefits to the core business. The operating load at Manchinchi during this investigation was valued at 55kW.In monetary terms, supposing that the carbon trade facility or the CDM arrangement was accessed, a value of US$ 107,489.5 could be realized annually over seven years. In meeting the demands for emission reduction, it was estimated that 26,872.37 tons of carbon dioxide would fall for mitigation by implementing the energy recovery scheme. The carbon dioxide content measured by a Dansensor gas detector was 37 percent. The remaining 1 percent was other trace gases including hydrogen sulfide. Economic and financial appraisal showed that the NPV was US$ 484,939.89 and IRR 23 percent in the case that the plant was equipped with biogas recovery and energy conversion technology to produce heat and power with the renovation of existing anaerobic digestion tanks.
Intelligent Control of the inverted pendulum
(2011-07-14) Ng'oma, Anthony
Artificial Intelligence (AI) based control techniques are becoming more popular for their applicability to complex control systems. In this research, an Intelligent Controller is designed for a non-linear process with complex dynamics - the Inverted Pendulum. The controller is designed to interact with other controllers in the process. That is, the Intelligent Controller is designed to control the Inverted Pendulum for part of the state space and afterwards transfers control to other existing controllers. This arrangement is referred to as Operation-Space (OS) based control. The Intelligent Controller is designed to steer the Inverted Pendulum from the downward resting position or state, to a state controllable by an existing OS based controller. Control knowledge for this swing up operation is generated by applying a multi-stage decision process called Differential Dynamic Programming (DDP). A DDP algorithm is developed by solving a set of partial differential equations. The Inverted Pendulum is represented as a discretised fourth order process model. The discretised model is based on the corrected van Luenen continuous time model. The van Luenen model has an error which I discovered using step response simulations. After a series of trials, two cost objective functions J, and J2 were chosen for the DDP algorithm. This was the most difficult part of the design process. The DDP equations were implemented in a computer algorithm to compute optimal control data in the form of process states and control signals. The downward resting position was the initial state , x(0) while the final state x ( N ) , was a state controllable by the OS based controller. The resulting two sets of control data constituted the training data for the Neural Network (N-Net) structure. An N-Net structure was designed and trained on the generated control data. Its simulation results showed excellent performance. Sensitivity analysis to variations of model parameters was performed. The N-Net was then implemented as a controller on the laboratory setup. Hardware constraints on the laboratory setup and the transputer system, made it difficult to test the controller's full capabilities. However, results obtained indicated that the N-Net controller was able to reproduce the control trajectories in real time.In addition to the design of the N-Net controller, an integrated PD swing up controller was designed and implemented on the laboratory setup. The PD controllers, assisted by saturation effects, successfully steer the Inverted Pendulum from the downward resting position to join the OS based control cycle. The controller demonstrates compatibility with the existing OS based controller, which the N-Net was designed to have. An N-Net structure was designed and trained on the generated control data. Its simulation results showed excellent performance. Sensitivity analysis to variations of model parameters was performed. The N-Net was then implemented as a controller on the laboratory setup. Hardware constraints on the laboratory setup and the transputer system, made it difficult to test the controller's full capabilities. However, results obtained indicated that the N-Net controller was able to reproduce the control trajectories in real time. In addition to the design of the N-Net controller, an integrated PD swing up controller was designed and implemented on the laboratory setup. The PD controllers, assisted by saturation effects, successfully steer the Inverted Pendulum from the downward resting position to join the OS based control cycle. The controller demonstrates compatibility with the existing OS based controller, which the N-Net was designed to have.
Combustion efficiency improvement in a rotary furnance using a post combustion chamber
(2011-07-14) Luwaya, Edwin
Combustion Efficiency Improvement in a Rotary Furnace using a Post Combustion Chamber. Luwaya Edwin. Department of Mechanical Engineering, University of Zambia.Geometric parameters, of a rotary furnace, necessary for the improvement of combustion efficiency are analysed using Computational Fluid Dynamics (CFD). The simulation is based on a real Rotary Furnace at Kabwe Power and Metals Limited in Kabwe. A Post Combustor Chamber (PCC) was incorporated in the numerical model at the exit of the combustor and the results compared with the case where no post combustor was used. Performance optimisation of the furnace was done by varying the fuel-air ratio and the size of the PCC. The flow characteristic results obtained, for the case of PCC and no PCC incorporated were contrasted. Flow characteristics were looked at in the wake of combustion,focusing on convection, temperature distribution, conduction, and radiative heat transfer. The k-e model is used for turbulence flow prediction. Combustion of premixed fuel is simulated by the Simple Chemical Reacting Scheme (SCRS). The eddy break-up (EBU) model is used to determine the rate of the reaction. The six-flux model is used for the radiative heat transfer without turbulence-radiation interaction i.e. only the products of combustion are participating in radiative heat transfer. The SIMPLEST algorithm is employed to solve the transport equations of momentum and other scalar variables. Radiation field is determined using a modification of the SIMPLEST scheme. The computation has shown that improvement of the thermal performance of the Rotary Furnace can be done using the post combustion chamber. The PCC improves the thermal performance of the furnace by increasing the intensity of recirculation and mixing of hot vitiated products with fresh charge in the primary combustion zone thus increasing residence time of combusting materials in the furnace space. This reduces the exhaust gas loss therefore increasing the useful heat value in the combustor. The heat flux to the sink is equally increased. The combustion efficiency improved by 0.53 percent. For the rotary furnace at Kabwe the PCC should be optimised as demonstrated in this study
Tool design for the production of a collimator on a 3-axes vertical milling centre
(2011-07-14) Malama, Terence
The continuous quest for modernization and industrialization has brought a great challenge upon the third world countries such as Zambia in that these countries have to keep on importing production machinery whose spares cannot be obtained locally but from outside. This problem has been compounded by these countries' lack of funds to acquire machinery that could produce the much-needed spares. However, the high cost of initial investment of Computer Numeric Control (CNC) machines is a huge obstacle to many companies. It is, therefore, imperative that avenues of adapting these machines to perform a variety of operations than what they were initially designed for are sought and thereby make the investment much more cost effective. A cobalt refinery plant at Chambishi Metals Pic running at normal capacity consumes about one collimator in every three to four weeks. The cost of replacement of each collimator is approximately US$3800 from Mitutoyo and Fowyer in America. Chambishi Metals Pic notes that it is spending thousands of dollars in importing the component and is looking for means to have local manufacturers to produce it locally since this would be cheaper and readily available. However, local companies have so far failed to achieve the required tolerances using conventional machining and have very little or no capacity in ordering CNC machine tools.The collimator assembly is a water-cooled frontal electrode, used on the plasma arc torch. This torch is used in the reheating of the alloy prior to atomizing. A collimator is an assembly made up of two separate components whose metallurgical composition is 90 to 99 percent copper. In order to accommodate plasma gas flow, process thermodynamics and to prevent coolant leakages, collimator components are normally produced by precision machining, a process that is best performed on CNC lathe machine tools. It is for this reason that it was identified as a test piece for production. In 2001, Mwanza S. M.,University of Zambia, successfully adapted a Supermax 65A, 3-axes CNC Vertical Milling Centre (VMC) to include turning operations'. Later, in 2002, Daka B., University of Zambia, looked at turning tools that could produce various profiles using the adaptations made on the same machine tool. After having done the modifications, it was imperative that a specific commercial product was produced to test the applicability of the adaptations. In addition, this was to answer and reduce on queries and shortcomings that were unanswered in the previous two studies. These included improvement in dimensional tolerances and surface texture of the products, use of CAD/CAM software and DNC to accommodate complex products. Thus, this research started by designing the production process and production tools which involved coming up with turning, threading and boring tools and also the workpiece and tool holding mechanisms. The designed production process, tools and fixtures were further used in the configuration of the 3-axes CNC VMC machine tool. Since no software capable of generating NC part programs for turning and compatible with VMC machine tools exists, it was imperative that less time consuming methodologies of generating such programs were developed. Thus, Mastercam Lathe V9, an advanced CAD/CAM software, was modified to generate turning NC part programs to run on the VMC machine tool with the application of a unique remote operation of direct numeric control (DNC). Hence, with these techniques, the coilimator assembly was produced and examined for dimensional accuracy and surface finish. An analysis of generated forces was also done to avoid overloading the machine tool. After costing, the total cost of producing one collimator came out to be ZMK 9,9 75,686.00. The produced collimator assembly was inspected and tested on a plasma arc torch-testing rig found at Chambihsi Metals Pic, Ultra-modern Smelter Plant, and it was found to conform to ISO 9001 standards.
Risk management in the procurement of Community-Based construction projects in Zambia
(2011-07-14) Manelele, Inambao
The need to improve the socio-economic well being of the citizenry has placed huge challenges on the provision of better social infrastructure in developing countries like Zambia. To help with meeting the challenges, inputs from local communities have been incorporated in infrastructure development in Zambia. This arrangement minimizes construction costs compared to conventional construction modes and also instills a sense of responsibility in the community. However, the involvement of local communities in construction introduces a number of risks during the execution of the projects as the community may not be conversant with construction and the procedures involved in the procurement process. The consequences of not assessing and managing construction risks are that projects may experience time and cost overruns and lead to poor quality structures. This research sought to propose improvements in the management of community-based projects by identifying the risks involved at every stage in the procurement of the projects, analyzing them and developing a risk management model that would improve the implementation of the projects.The methodology employed in this research included desk study, which involved literature review of studies and works done in the field of construction risk management. Group brainstorming sessions with PMCs were conducted to identify potential risks. A questionnaire survey that sought to validate the findings from the brainstorming sessions and also to collect data relating to probability and impact of the identified risks on project objectives was carried out. The risks identified in the study were classified in six categories namely: project initiation; community contribution and participation; budget and finance; skilled labour; materials procurement; and technical supervision and quality control. A risk management model that could be used in the implementation of community-based projects was developed at the end of the study and validated. The main limitation of the study was that data from other types of construction other than school infrastructure could not be collected.
A variable-speed drive for local manufacture
(2011-07-15) Rajamani, Haile-Selassie
Recent developments in the design of variable-speed drives have been aimed at the control of a standard squirrel cage induction motor because of its many attractive features including robustness, reliability and low maintenance requirements. This dissertation demonstrates the design of a drive package that meets specified requirements, while being sufficiently simple and economic to be attractive to local industry. The drive is designed for applications that do not require very precise speed control and fast dynamic response, such as water pumping and food processing.In Chapter 1 an overview of variable speed drives is given.Chapter 2 describes the open loop control strategy used.Constant torque capability and acceleration of the motor are studied, illustrating the advantage of variable speed drive. A review of Pulse Width Modulation (PWM) techniques and their implementation is given in Chapter 3. Chapter 4 presents a study of asynchronous PWM technique using a high carrier frequency with particular reference to voltage utilization and harmonic distortion. An optimum waveform is suggested that ideally provides a pure sinusoidal output current. The effect of dead-time and harmonic losses are also considered. Chapter 5 describes the inverter circuit built with MOSFET's. The following chapter describes the implementation of the control technique using a specialized integrated circuit, the MAS 18, and a computer. In Chapter 7 the implementation and testing of the drive system is detailed and the results presented.The optimum waveform suggested is shown to give good utilization of rail voltage. The current distortion is also shown to be low. In Chapter 8, the practicability of the simple design is discussed.The final drive unit is shown to be very simple consisting of the inverter circuit, the MAS 18, a micro-controller chip and a low voltage power supply. The inverter circuit is also a simple design that avoids the use of transformers and opto-couplers.Possible modifications and suggestions for future work are given.
Modelling of the effects of potholes on motor vehicle structures
(2011-07-19) Matsika, Emmanuel
The objective of this work was to investigate the effects of the impulses induced by potholes on motor vehicle structures. MATLAB computer package was used to develop a computer program to carry out the tasks. This was done with a view to make recommendations in the nature and frequency of maintenance or replacement of vulnerable parts of the vehicle structure. Further, recommendations were made that vehicle manufacturers should consider in the design of vehicles intended for areas where potholes exist. Mathematical models of the vehicle suspension systems were used to predict the dynamic forces induced. Stress analysis was performed on selected most susceptible parts of the vehicle. These included wheel bearings, linkage pins and associated bushings, springs and shock absorbers and related fastenings. The parts were chosen following verbal interviews with auto-mechanics in garages and indeed from the experience of the author while working in the transport section of a company. This study only considered stress analysis. In order to practically determine the vibration responses (acceleration and displacement) of the vehicle and the waveform that best approximates the exciting and excited motion when a wheel hits a pothole, on-vehicle vibration tests were carried out using a two-axle Toyota Corolla 1.5 GL saloon car. The experimental results were found to be lower than the simulated ones.Simulated results showed that for the car used as a case study, each wheel could be treated separately as a quarter car. The investigation on potholes showed that the pothole length determines the vehicle velocity at which resonance occurs while the magnitude of the induced force is influenced strongly by the pothole depth. In addition and to some extent, the velocity affects the force as it determines the value of the dynamic load factor. For the saloon car used, it was shown that the critical speed (resonance velocity) for both the sprung and unsprung masses fell within 4 to 10 km/h and 40 to 55 km/h for the sprung and unsprung masses, respectively. Since most driving is up to a maximum of 50 km/h around towns and residential areas, the issue of potholes has to be seriously addressed.The load on the unsprung mass was found to be much higher than that on the sprung mass.Therefore, in the design of suspension parts, emphasis should be put on the unsprung mass components. For the vehicle user, more frequent replacements of suspension parts was recommended, while for the manufacturer, redesigning of some suspension components was recommended.The results also showed that the suspension geometry, load path characteristics and components materials' mechanical properties dictate the failure mechanism of the vulnerable parts.
Developing Small-Scale Mining in Malawi
(2011-07-21) Chipili, Evance E.M.
Malawi is endowed with a variety of mineral resources. Predominant among these are gemstones, industrial minerals, construction mineral materials and fuel minerals such as coal. However, most of these are small deposits, amenable by small-scale mining (SSM). Therefore, the promotion and development of SSM can be considered an important option for exploiting these mineral resources of the country. Once developed, SSM has the potential to contribute significantly to the economy of the country. Efforts by government institutions to assist the mining and minerals sector have not brought the expected level of development in the sector. Consequently, most of the minerals remain unexploited.The principal objective of this study is to identify sectoral constraints associated with technical,administrative, financial and legal factors, which directly and indirectly affect investment and development of SSM. A review is made of the status of the mining sector and mineral development potential. The study further suggests promotional strategies required for the successful development of the SSM sector in Malawi.Recommendations are given which emphasise on a vigorous approach and commitment by Government and other key players in the sector in implementing the strategies for the development of SSM in Malawi.

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