Application of the fractal theory for evaluating effects of coal comminution by waterjet

© 2014, The Author(s).Comminution of coal to ultrafine sizes by high-pressure waterjet provides a novel method for preparation of coal-water fuels for next generation, near-zero emission electric power generation. The particle size distribution (PSD) of ground coal is a key parameter in the preparation of slurries as it determines the settling behavior of the particles and viscosity of the coal-water mixture. There are several methods available for representation and evaluation of particle size analysis data. However, fractal theory provides a means by which the entire PSD of comminuted materials can be quantified by using of a specific and exact value. In this paper, a volume-based fractal model was deduced to characterize the PSD of the coal which is ground in a specially designed comminution cell. During the size reduction process, the inlet pressures up to 276 MPa were used

Enhanced Production of Geothermal Heat through the Reaming of Underground Wells in the Production Zone [abstract]

Only abstract of poster available.Track I: Power GenerationIn order to extract heat from the high temperature rocks that lie relatively close to the surface in different parts of the world, wells must first be drilled down into those rocks. Once the wells are established then either natural fissures or artificially induced fractures are generated to create an underground network of channels in the hot rock. Either existing steam in the rock, or injected water is then pumped through this network as a way of extracting the heat, turning it into steam, and bringing it to the surface. At the surface the steam, depending on temperature, can be used to drive generators, and/or to provide district heating. The rocks through which the wells must be drilled are generally igneous, and thus of a high strength, tough and very hot, and conventional methods of drilling are difficult and slow. The use of high-pressure fluid jets to drill the wells has been shown to be faster than conventional drilling, and since the jets cut away from the bit, there are not the wear problems that are associated with conventional drilling tools. Further the jets have the potential to be re-oriented in the production zone to ream out the well from a radius of 4.5 inches to some 36 inches. This increases the productivity of individual wells, and reduces the number that may need to be drilled. Abrasive can also be introduced into the water-jet stream as it is pumped down the borehole, and it is also possible to create a cutting jet that can notch the walls of the borehole so that, under controlled pressurization, cracks can be grown out in preferred directions, and the process of heat extraction simplified

Enhanced Oil Recovery from Shallow Depths Through the Use of Tight Radius Lateral Drilling [abstract]

Only abstract of poster available.Track I: Power GenerationThere are many heavy oil fields in the world where the oil does not easily flow to the well and conventional production is thereby limited, or currently not economically viable. Missouri alone has billions of barrels of oil along its western edge, that lie just too deep for conventional surface mining (similar to that of the tar sands of Alberta) and yet have an oil that is too heavy to be easily recovered by normal oil well production. Where this oil can be extracted it will add significantly to the reserves of the country. Missouri S&T pioneered the use of high-pressure waterjets as a means of drilling long horizontal holes underground - a technology validated in field tests with Sandia National Laboratories. The technique allows the turning of a drill from an existing vertical well in a radius of less than 9 inches, whereas conventional tools require 20 ft. Once the turn has been made, the drill can then penetrate out horizontally. Once the horizontal wells have been established then one of two different approaches can be taken. The wells may be hydrofraced, as is conventionally done, for example in shale gas recovery, or the sand might be mined. Once the well has been drilled to the edge of a defined area, the drilling head can be reconfigured into a reaming mode in which the jets cut into and mine the oil bearing rock (which in Missouri is up to 30 ft thick). By disintegrating the rock and pumping it to the surface, (in the same way as in Alberta) using a hot water solution, the oil can be removed from the sand, which can then be mixed with a small amount of a binder and re-pumped back into the reamed cavity to provide support for adjacent mining of the material so that all the rock can be mined, and all the oil is recovered. In this way the oil can be recovered without the environmental impacts of the open pit tar sand operations

High Speed Production of Large Coal to Facilitate Easier and More Effective Cleaning

Track I: Power GenerationIncludes audio file (14 min.)Due to technical difficulties, the audio portion of this presentation is joined in progress.Most modern mining equipment extracts coal through grinding it from the solid using a set of rotating picks. This produces coal that is quite small in average size and generates a lot of dust in the process. The coal is also more expensive to collect and process to remove contained undesirable components. The use of high-pressure water jets as a cutting tool has been shown to provide a product that is larger in size, while con-commitantly eliminating the generation of dust (which carries with it the risk of ignition and explosion) and reducing the energy required for the mining process. Two different mining machines are described, one for use on longwall faces and one in room and pillar mines, and the potential for their development is discussed

Applying Cfd Model Studies to Determine Zones at Risk of Methane Explosion and Spontaneous Combustion of Coal in Goaves

Underground mining operations are subject to a number of natural hazards. Events resulting from these hazards are difficult to predict, and if they occur, they disrupt the entire mining process and pose a great danger to the crew. Some of the most dangerous include ventilation hazards involving methane explosions and fires caused by the spontaneous combustion of coal. The complex state of the underground environment means that these hazards oftentimes occur simultaneously, making mining conditions even worse. The following paper addresses this issue by developing the methodology for determining areas endangered by methane explosions and spontaneous coal combustion in goaves. The reference to goaves results from the fact that this particular area is most frequently affected by spontaneous coal combustion and the accumulation of dangerous amounts of methane. The developed methodology was based on model tests with the use of the CFD method and data necessary to develop a numerical model. The research encompassed a real longwall in one of the hard coal mines, ventilated with the Y system during its exploitation, which is beneficial in the case of the methane hazard but worsens the safety in terms of the self-ignition of coal. As a result of the conducted research, for the exploitation conditions, dangerous zones were specified due to the potential possibility of methane explosion and self-heating of coal. The basis for determining dangerous zones was the criteria of occurrence of the examined phenomena. In this study, the zones were identified for each of the investigated hazards separately and for their simultaneous occurrence. Thus, the aim of the study, which involved the determination of potentially hazardous zones by applying modern methods of modelling in the mining area, was achieved. The results are an immensely important source of information for activities aimed at improving safety in the studied area in relation to the studied threats

Method and Apparatus for Jet-Assisted Drilling or Cutting

An abrasive cutting or drilling system, apparatus and method, which includes an upstream supercritical fluid and/or liquid carrier fluid, abrasive particles, a nozzle and a gaseous or low-density supercritical fluid exhaust abrasive stream. The nozzle includes a throat section and, optionally, a converging inlet section, a divergent discharge section, and a feed section

Development of a Waterjet System for Direct Delivery of Granular Iron and Activated Carbon to Remediate Contaminated Aqueous Sediments

While the Techniques and Technologies Associated with Contaminated Sediment Remediation Are Relatively Mature, There Are Several Issues Associated with These Practices that Make Them Unattractive. the Inability of Currently Used Mechanical Mixing Implements to Place Amendments in Aqueous Environments and their Intrusive Behavior toward Benthic Communities Are Just Two Examples of a Necessity for an Improved Delivery Method. Waterjets May Be a Viable Option for Placement of Particulate Remediation Amendments, Such as Activated Carbon and Granular Iron, at Depth. a Custom Waterjet Nozzle and Injection System Has Been Fabricated by the Authors to Examine This Delivery Concept. the Developed Injection System\u27s Performance Was Tested by Characterizing the Waterjet-Delivered Amendment (Activated Carbon and Granular Iron) Distributions in a Surrogate Sediment. the Delivered Amendment Distributions Followed Similar Patterns for a Range of Injection Times and a Variety of Amendments. the Injection Depths, However, Were Dependent Upon the Type of Amendment Being Injected. These Findings Have Led to a Better Understanding of What Occurs during an Amendment Injection, Which Can Be Used for a More Controlled Placement of Remediation Amendments using This Technique in the Future. the Laboratory Results Indicate that the Subject Waterjet System May Have the Potential for Field-Scale Applications, Especially for Granular Iron Delivery, as the Authors Were Able to Place between 60 and 70 Wt Percent into a Surrogate Sediment Bed Along the Path of Injection. © 2011 Wiley Periodicals, Inc

Hydroabrasive Cutting Head-Energy Transfer Efficiency

The ability of an abrasive waterjet to cut materials traditionally considered difficult to machine is unmatched by alternative mechanical or thermal cutting techniques - the problems of material delamination and thermal deformation along the cutting path being eliminated. The effectiveness of hydroabrasive jets in such cutting applications depends on the energy which can be imparted to the abrasive particles. Many existing cutting head designs are based on the concept of entraining the abrasive grains in either single or multiple water jets within the head. Both the abrasive particle milling effect and the transfer of energy that take place between the water nozzle exit and the slurry nozzle inlet are introduced as criteria that can be applied in the evaluation of the effectiveness of the hydroabrasive cutting head design. This paper presents the results and general conclusions drawn from a test program designed to investigate both of these effects

Method of Trepanate Drilling of Deep and Large Diameter Holes in Hard Rocks

Existing methods for the tunneling and deep drilling of hard rock rely on blasting techniques to separate the material and produce cavities. As a result of this process microcracks are introduced into the surface of the rock material. For special applications high quality large diameter holes are required that are free from such microcracking. Since high pressure abrasive waterjet cutting was introduced five years ago it has become possible to concentrate the energy of cutting on much smaller surface areas. This material removal method is based both on the microchipping action of the abrasives and the formation of hydraulic wedges within the rock structure. Together, these mechanisms minimize the risk of crack propagation to the outer surfaces of the hole being drilled. The total thrust exerted on the material is also significantly reduced. The presence of abrasives in the jet ensures that stubborn pieces of aggregate in the parent rock can also be cut away. This technique can be applied successfully in the drilling of large deep diameter holes. Test results for the cutting of granite samples by abrasive waterjet, over the pressure range of 70 to 280 MPa, are presented in this paper. These results are used in the compilation of a technological data base for the proposed trepanate method of high efficiency, microcrack free drilling of hard rocks