A coupled thermal-mechanical numerical model of underground coal gasification (UCG) including spontaneous coal combustion and its effects

Underground coal gasification (UCG) is a promising option for extracting energy from coal in unworked or hard to access areas of the subsurface. From a geotechnical perspective, UCG involves various complex phenomena resulting from the elevated temperatures induced within the rock surrounding the UCG burn. This paper presents a coupled thermal-mechanical numerical model developed to represent a UCG trial in Wieczorek, Poland. Temperature dependent mechanical properties were assigned according to results obtained from laboratory experiments and data available in the literature. The coal burning process was simulated by modifying the energy balance equation with an additional term related to the calorific value of coal as a source. This source term was described using a time decay function to reflect the fact that the energy release from coal gradually decreases with time. The mechanical degradation of coal due to burning was simulated by removing the burned zone from the calculation after a specific time, which depended on zone size and type of coal. In this study, it was found that the maximum temperature at the burning zone was always less than 1000°C, which agrees with previous research carried out for other UCG trials. The size of the burning zone was predicted to spread about 15m laterally after 20 days of burning. Ground subsidence was evaluated for single and multiple (parallel) panel simulations; subsidence at the top of the numerical mesh, corresponding to a depth of 395m below the surface, ranged from 23mm for a single panel to 85mm for seven panels. The degradation of mechanical properties of the rock surrounding the burned zone due to heating was found to have a marginal effect on the ground subsidence when parallel burning was carried out. The numerical modelling results obtained from this study may provide guidance for the design and operation of UCG processes

Th gme 10: A numerical model to capture the geotechnical response to coal combustion at an underground coal gasification site

A detailed numerical modelling study was carried out to represent geotechnical aspects of the Wieczorek underground coal gasification (UCG) site in Poland. A coupled thermos-mechanical numerical model was created to represent a single coal burning panel. The coal burning proceb was simulated by modifying the energy balance equation with an additional term related to the calorific value of coal as a source. Temperature dependent material properties were abigned to the coupled thermal-mechanical model according to published data. In the model, the burning zone spread about 7.5m laterally after 20 days of burning. Results from the coupled model were used to gauge a worst-case scenario in terms of the potential size of a formed cavity. This data was used within a leb computationally expensive mechanicalonly numerical model in order to evaluate the ground subsidence caused by the worst-case scenario for single and multiple UCG burning panels. The single panel burning resulted in 23mm of ground subsidence at the top of the model after long term coal burning. The ground subsidence measured at the top of the model, at the center point of the gasification arrangement, was approximately 72mm when five panels were burnt with an edge to edge panel distance of 5m; this was increased to 85mm for seven panels. The numerical modelling results have implications to the industrial application of UCG

‘Scarcity amidst plenty’- A rare combination of enterococcal pulmonary valve endocarditis in a young girl: A case report

Isolated pulmonary valve infective endocarditis (IE) with Enterococcus faecalis in a child with an underlying ventricular septal defect (VSD) is rare. A ten year old girl with a VSD with moderate to severe right ventricular mid cavity obstruction presented with fever and loose stools. Examination did not reveal any peripheral stigmata of IE. Five of six blood cultures sent in two sets 12 hours apart, grew E. faecalis sensitive to β-lactams. 2D echocardiography revealed a 7×4 mm vegetation on the pulmonary valve. She was treated with intravenous antibiotics for 6 weeks. Inflammatory markers normalized by 6 weeks and the vegetation cleared by the 7th week. Amongst the aetiological agents, isolation of Enterococcus faecalis is rare in children and drug resistance is an emerging problem. Enterococcus species related native valve IE needs a prolonged course of therapy with penicillin G/ampicillin together with gentamicin for 4-6 weeks. Heart failure and cerebral embolization are the most commonly encountered complications.</p

FracPaQ: A MATLAB™ toolbox for the quantification of fracture patterns

The patterns of fractures in deformed rocks are rarely uniform or random. Fracture orientations, sizes, and spatial distributions often exhibit some kind of order. In detail, relationships may exist among the different fracture attributes, e.g. small fractures dominated by one orientation, larger fractures by another. These relationships are important because the mechanical (e.g. strength, anisotropy) and transport (e.g. fluids, heat) properties of rock depend on these fracture attributes and patterns. This paper describes FracPaQ, a new open source, cross-platform toolbox to quantify fracture patterns, including distributions in fracture attributes and their spatial variation. Software has been developed to quantify fracture patterns from 2-D digital images, such as thin section micrographs, geological maps, outcrop or aerial photographs or satellite images. The toolbox comprises a suite of MATLAB™ scripts based on previously published quantitative methods for the analysis of fracture attributes: orientations, lengths, intensity, density and connectivity.An estimate of permeability in 2-D is made using a parallel plate model. The software provides an objective and consistent methodology for quantifying fracture patterns and their variations in 2-D across a wide range of length scales, rock types and tectonic settings. The implemented methods presented are inherently scale independent, and a key task where applicable is analysing and integrating quantitative fracture pattern data from micro-to macro-scales. The toolbox was developed in MATLAB™ and the source code is publicly available on GitHub™ and the Mathworks™ FileExchange. The code runs on any computer with MATLAB installed, including PCs with Microsoft Windows, Apple Macs with Mac OS X, and machines running different flavours of Linux. The application, source code and sample input files are available in open repositories in the hope that other developers and researchers will optimise and extend the functionality for the benefit of the wider community

Study of the performance of passing and climbing lanes along Colombo - Rathnapura - Wellawaya - Batticolo road

Due to increase of population and rapid economic growth, percentage of heavy and recreational vehicles in the traffic stream from Colombo Capital to Central hills have increased causing severe traffic congestions. Specially all essential supplying services including fuel, food, export goods transport using major highways. Applying climbing lane concept on two-lane highways can be a good recommendation to reduce prevailing extreme conditions. “A climbing lane is, in effect, a passing lane added on an upgrade to allow traffic to pass heavy vehicles whose speeds are reduced”. However, application of Passing Climbing Lanes (PCL) are not a common practice in Sri Lanka. Most of steep upgrades on the major trans mountain highways do not have climbing lanes that cause traffic congestion on major highways. Due to the increasing vehicular traffic along the route, there exists an ongoing construction of Passing climbing lane on Colombo- Rathnapura-Wellawaya- Batticolo (CRWB) road near to Rathnapura. This study evaluates the Impact of Passing and Climbing lane on traffic flow on the particular section at CRWB road considering both travel time and delay time using the existing available data from RDA and new traffic survey data. The collected data at particular location before the construction of PCL and after is expected to show the importance of having PCLs at essential places along CRWB. Further, the impact of selected PCL has been analyzed for various traffic volume by a simulation model which was developed for this study. PCL is low cost improvement method rather than replacing extra lane or providing bypass lane, hence study discusses the economic advantages also

Optimal game theoretic distributed control methodologies in small scale power systems

This dissertation presents the competitive control methodologies for small-scale power system (SSPS). A SSPS is a collection of sources and loads that shares a common network which can be isolated during terrestrial disturbances. Micro-grids, naval ship electric power systems (NSEPS), aircraft power systems and telecommunication system power systems are typical examples of SSPS. The analysis and development of control systems for small-scale power systems (SSPS) lacks a defined slack bus. In addition, a change of a load or source will influence the real time system parameters of the system. Therefore, the control system should provide the required flexibility, to ensure operation as a single aggregated system. In most of the cases of a SSPS the sources and loads must be equipped with power electronic interfaces which can be modeled as a dynamic controllable quantity. The mathematical formulation of the micro-grid is carried out with the help of game theory, optimal control and fundamental theory of electrical power systems. Then the micro-grid can be viewed as a dynamical multi-objective optimization problem with nonlinear objectives and variables. Basically detailed analysis was done with optimal solutions with regards to start up transient modeling, bus selection modeling and level of communication within the micro-grids. In each approach a detail mathematical model is formed to observe the system response. The differential game theoretic approach was also used for modeling and optimization of startup transients. The startup transient controller was implemented with open loop, PI and feedback control methodologies. Then the hardware implementation was carried out to validate the theoretical results. The proposed game theoretic controller shows higher performances over traditional the PI controller during startup. In addition, the optimal transient surface is necessary while implementing the feedback controller for startup transient. Further, the experimental results are in agreement with the theoretical simulation. The bus selection and team communication was modeled with discrete and continuous game theory models. Although players have multiple choices, this controller is capable of choosing the optimum bus. Next the team communication structures are able to optimize the players’ Nash equilibrium point. All mathematical models are based on the local information of the load or source. As a result, these models are the keys to developing accurate distributed controllers

Application of roller compacted concrete for road pavements in Sri Lanka

There is a great need to construct more durable roads such as concrete roads in Sri Lanka since the government is spending a considerable amount of money every year to maintain the national road network which has been constructed using with either conventional asphalt concrete or bituminous paving materials. This research was carried out mainly to explore the possibility of introducing more durable and cost effective Roller Compacted Concrete for road pavements in Sri Lanka. The structural behavior of Roller Compacted Concrete pavement (RCCP), which is a rigid pavement, is completely different from conventional asphalt pavements which are designed as flexible pavements. Since RCCP is not currently used in Sri Lanka there is no local standards available for design and construction of RCCP. An extensive literature review was carried out regarding the design of rigid pavements practiced in other countries. The rigid pavements can be designed using different types of design methods for given conditions. However, out of those methods, American Association of State Highway Traffic Organization method (AASHTO) and Portland Cement Association (PCA) method are popular in the countries where rigid pavements are used. Out of these two methods AASHTO method uses more parameters in designing the pavement thickness. Therefore, parametric study was carried out to investigate the effect of each parameter used in AASHTO method. And also a computer program was developed based on PCA method to carry out the thickness design procedure effectively, as it is more suitable for low volume traffic conditions. An experimental investigation was carried out to formulate a mix design procedure for RCC using local materials. Since the thickness of RCCP depends on the flexural strength of RCC, tests were carried out to investigate the factors affecting the flexural strength of RCC and also other properties such as wet density, compressive strength and drying shrinkage. New test methods were developed to measure these properties specially the flexural strength and wet density incorporating actual conditions of RCC such as actions of static and vibrating rollers. A new apparatus was developed to measure the wet density by modifying the conventional V-B apparatus where vibration as well as known static pressure can be applied to compact concrete. Furthermore, use of chemical and mineral admixtures to improve the properties of RCC was also investigated. Based on the results of experimental investigations a mix design procedure for RCC was proposed

Strategies to overcome barriers in accelerating rural electrification in Sri Lanka

CD ROM IncludedThis report presents a research carried out on rural electrification in Sri Lanka. This research mainly involves surveys and rural electrification policy studies. The analysis was carried out in a selected district in Sri Lanka. The first stage of the project was devoted to gathering the data about present electrification level in Sri Lanka. In this stage, the collected data was organized in a manner that enables comparison between the data components. To identify the barriers for electrification, it was decided to conduct three surveys in un-electrified villages, off grid-electrified villages and un-electrified houses in grid electrified villages. Separate questionnaires were prepared for each survey. The survey in un-electrified villages was carried out in 10 villages in the Ratnapura district. The goal of this survey was to identify the existing barriers in rural electrification. The results of this survey were summarized and nine major barriers for rural electrification were identified. The identified barriers were categorized and ranked using a method developed by the researcher. In this ranking procedure, the opinions of the villagers were taken in to consideration, because those people have experienced these barriers for more than 20 years. The second survey was carried out to observe the existing situation of present off grid projects, specially the micro-hydro power projects, which are functioning properly in Ratnapura district. Five off grid power plants were selected for this survey. Major problems prevailing in the above micro-hydro projects were pin pointed and the contributions that villagers can make- to overcome these problems were identified. IV Third survey was carried out in 5 grid-electrified villages to identify Problems existing in unelectrified houses. Four major barriers were identified in this survey. In these surveys social data too were collected for a better analysis. More than 90% of the villagers in a particular village were interviewed to obtain better survey result. The rural electrification policy study was carried out to identify what improvements could be made to the policies, to have solutions to the survey results. This policy study and possible strategies were analyzed by considering the suitable policy evaluation criteria. Not availability of clear policy for rural electrification in Sri Lanka is a major issue. Identification of areas where nation grid can be extended, policy must support to the rest of the areas of electrification through off grid electrification options. In addition possible strategies were analyzed as solutions to these problems. Integrated rural development, grid extension and isolated power generation, area coverage and intensification can give signification contribution to remove or reduce these barriers. In addition policy improvement also can give significant contribution to solve these barriers.

Game theoretic optimization of DC micro-grids without a communication infrastructure

This paper proposes an algorithm to optimize the steady-state operating point in Small Scale Power Systems (SSPS) without the need for communication channels. The approach follows a game theoretic framework with a modification of objectives inside the SSPS. The players are able to minimize a modified objective which gives a improved cost for their initial local objectives. This modified objective is a function of initial local objectives and augmented non-cooperative game. The new game has multiple Nash equilibriums (NE) and therefore players get the opportunity to shift their operating point to a better one while keeping the game condition non-cooperative and without the need for a communication infrastructure. Further, the modified objective is a simple function of players\u27 initial local objectives. Therefore, this method can be easily implemented in the hardware system even with player higher nonliner objectives

Optimal transient control of microgrids using a game theoretic approach

Small scale power systems (SSPS) are collections of interconnected electrical energy sources and loads. However, the analysis and control of SSPS are different from the more traditional large scale power system techniques because in SSPS the generation has minimal inertia with little if any spinning reserve. A differential game-theoretic framework is helpful in designing the control structures for SSPS for efficient and reliable operation with simultaneous player movement. Defining both loads and sources as players in a SSPS and forming a game between them is the key to modeling in this framework. This paper presents a modeling approach to find the optimum trajectory for the load players to reach a desirable operating point from an arbitrary initial condition given a transient system event. The players follow the optimum trajectory in the movement. In addition, the load modeling is proposed for the power electronic converter end load during transient. Further, this paper defines the suitable modifications needed to drive the optimum trajectory to an unknown static set point. This modification is important while system moves from nominal equilibrium to a new equilibrium due to sudden load or source changes. Example cases are presented with nine bus dc power system with load players