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This thesis is concerned with a study of the effect of The Acid Rain Provision of the 1990 Clean Air Act on the investment, production, and distribution operations in the coal industry, with a concentration on the development of new mines, shutting down of inefficient strips of existing mines, and on blending and distribution problems. The problem here is to determine which new mines to open and when, and what decisions and schedules to make for the shipment of coal from mines to silos, cleaning and blending operations at silos, and the subsequent shipment of coal to customers over a multi-period time horizon, so as to satisfy the demand at a minimum total operational cost. To meet this objective, a long-term strategic model is developed, and is coordinated with a modification of a short-term tactical model developed by Sherali and Puri (1991). The final product is a computer-based decision tool which will serve as a mechanism for implementing cost effective decisions in light of complex variations in the production levels of existing and potential mines, ore quality, and demand and quality requirements. The strategic model will play a useful role in planning future growth and in making capital investment decisions, and the tactical model will help in making better operational decisions. The models can also be used to study the effect of various policies, by testing the sensitivity, feasibility, and the cost of system operations under different perturbations of system configuration, data, and demand specifications. Real operational data and future projections from the Westmoreland Coal Company are used for testing purposes. / Master of Science

Södra Cell Mönsterås (SCMS) är en betydande producent av pappersmassa som årligen producerar runt 750 000 ton. Vid produktion av pappersmassa så blir bark en biprodukt. Barken barkas av i renseriet och transporteras upp till barkpannan och rökgastorken via transportörsband. SCMS står inför betydande problem med dammbildning när barken byter transportband, särskilt med en höjdskillnad på 5–6 meter. Ett övertryck bildas i kanalen under övergången och alla små partiklar trycks ut och det resulterar i en dammfylld miljö.Syftet med examensarbetet är således att förklara hur dammbildning uppstår och vad det finns för risker med det. Men huvudmålet är att hitta den bästa lösningen för att minska dammbildningen runt transportörerna. Denna undersökning kommer att vara relevant för mer än bara SCMS då detta är ett problem som är vanligt förekommande i olika industrier. Med hjälp av vår forskning så kommer SCMS få en bra överblick över vad det finns för relevanta lösningar och vad det skulle kosta. Uppgiftsbeställningen kan ses i bilaga 1.Både i miljö och arbetssyfte är detta ett problem som måste lösas. Att andas in barkdamm är hälsofarligt och kan även vara cancerframkallande vid vissa trädslag. Mestadels av trädamm som vi andas in kan vår näsa stoppa, men är det nog små dammpartiklar kan de leta sig ner i lungorna.Under forskningen kontaktades relevanta industrier som har eller haft liknande problem. Studenterna kontaktade även kunnigt folk inom detta område och diskuterade olika lösningar på problemet. Resultatet av dessa kontakter var att det finns många som stött på liknande problem men inte exakt likadana, vilket gör att det inte fanns en universell lösning innan undersökningen var slutförd.Undersökningen visade att det finns många olika lösningar för att hantera dammbildningen vid omlastningsstationen på SCMS under barktransportens bandbyte. Många av dessa lösningar hade dock betydande nackdelar, såsom höga tekniska krav, höga kostnader eller för stor potentiell påverkan på processen.Slutligen kom studenterna fram till att den bästa lösningen var att leda bort dammet med en ventilationskanal till en behållare, där vattendysor sprayar ner dammet i avloppet. Denna metod påverkar barken minimalt medan den effektivt avlägsnar dammet. Dessutom var kostnaden för denna lösning rimlig, vilket gör den både säker och ekonomiskt fördelaktig. Slutkommentar från SCMS visas i bilaga 2, denna visar att studenterna har löst uppgiften på ett bra sätt. / Södra Cell Mönsterås (SCMS) is a significant producer of pulp, annually producing around 750,000 tons. In the production of pulp, bark becomes a residual product. The bark is stripped off in the cleaning plant and transported up to the bark boiler and the bark furnace via conveyor belts. SCMS faces significant problems with dust formation when the bark changes conveyor belts, especially with a height difference of 5-6 meters. An overpressure is formed in the channel during the transition, and all small particles are pushed out, resulting in a dusty environment.The purpose of the thesis is thus to explain how dust formation occurs and what risks are associated with it. However, the main goal is to find the best solution to reduce dust formation around the conveyor. This study will be relevant to more than just SCMS as this is a fairly common problem. With the help of our research, SCMS will get a good overview of relevant solutions and their costs.Both environmentally and from a work perspective, this is a problem that must be solved. Inhaling wood dust is hazardous to health and can even be carcinogenic for certain tree species. Most of the wood dust we inhale can be stopped by our nose, but if the dust particles are small enough, they can penetrate into the lungs.During the research, relevant industries that have or have had similar problems were contacted. The students also contacted knowledgeable people in this field and discussed various solutions to the problem. The result of these contacts was that many had encountered similar problems but not exactly the same, which meant that there was no universal solution until the investigation was completed.The investigation resulted in finding many different solutions for managing dust formation at SCMS during bark transport belt changes. However, many of them were found to have significant drawbacks, such as technical requirements, high costs, or too much potential impact on the process.Finally, the students concluded to use the solution where the dust is directed away through a ventilation duct to a container, where water nozzles have been installed to spray the dust down the drain. This solution was one of the solutions that affected the dust the least and effectively removed the dust. It was also reasonably priced for a safe and efficient solution.

Ph.D. (Geography) / The focus of Aeolian research has mainly been on wind-blown dust from desert and arid areas. Numerous dust emission schemes have been developed over the years aimed at accurately estimating dust emission rates from various soil types and land use surfaces. Limited research has been done on wind-blown dust from smaller area sources – such as mine tailings and ash storage facilities. Lately, the concern about the environmental and health impacts, caused by dust from mine tailings storage facilities and ash disposal sites, has become more prominent, calling for better methods in determining dust emissions and their related impacts. This thesis established a practical approach for wind-blown dust emissions estimation and dispersion modelling from mine waste and ash storage facilities for the purpose of legal compliance assessment. Extensive research on the physics of wind erosion has been done over the past decade, compelling the re-evaluation of previously applied techniques. The latest and most widely applied dust emission schemes are evaluated to determine, through systematic testing of parameterisation and validation, using empirical mine waste and coal ash data, a best-practice prescription for quantifying wind-blown dust emissions and determining effects on a local scale using commercially available dispersion models. The applicability of two dust-flux schemes, (one developed by Marticorena and Bergametti (1995) and the simplified Shao 2004 scheme, as reported in 2011) for the quantification of wind-blown dust emissions, were tested using site specific particle size distribution data, bulk density and moisture content from six gold- and one platinum- tailings storage facilities and from two ash storage facilities. The availability of the required input parameters and the uncertainty associated with these parameters, were tested. The dependency of the Shao et al. (2011) model on plastic pressure (P) and the coefficient cy, both of which are not easily determined, added to the uncertainty of the emission rates. In this study, P and cy were both interpolated using the range limits provided by Shao (2004) for natural soils. By calculating P, using the salt and calcium carbonate content, similar values were obtained. The minimally disturbed dust fraction, as required by the Shao et al. (2011) scheme were derived from particle size distribution analysis but found to be more representative of the fully disturbed particle size faction (𝜂fi) and therefore needed to be corrected to represent the minimally disturbed particle size faction (𝜂mi) through the application of a correction factor, CF𝜂mi. Specific attention was given to the quantification of the threshold friction velocity (u*t) and the threshold velocities (u*), and how these two parameters relate to each under variable wind speed and time durations. This was tested using sub-hourly averaged meteorological data, one set reflected 5-minute intervals and the other 10-minute intervals. Dependent on the frequency and strength of the sub-hourly wind gusts, the resulting dust-flux rates were found to vary significantly when based on hourly averaged wind data in comparison with 5- and 10-minute wind data. Dispersion models are useful tools in air quality management. Whereas ambient monitoring provides actual ambient concentrations for specific pollutants at set locations, atmospheric dispersion models can be used to simulate any number of pollutants and determine the impacts at any location within the modelling domain. These dust-flux schemes of Marticorena and Bergametti (1995) and Shao et al. (2011) have been coupled with the US EPA regulatory Gaussian plume AERMOD dispersion model for the simulation of ground level concentrations resulting from wind-blown dust from mine tailings facilities. For this study, two Case Studies were evaluated; one included two of the gold mine tailings and the second focused on the platinum tailings. Simulated ambient near surface concentrations were validated with ambient monitored data for the same period as used in the model. For the Marticorena and Bergametti (1995) dust-flux scheme, only z0 had to be adjusted to provide a good fit with measured data – whereas the Shao et al. (2011) scheme resulted in significantly higher concentrations, resulting in an over-prediction of the measured data. By applying the correction factor, CF𝜂mi, to the minimally disturbed dust fraction, the predicted concentrations improved considerably. The coupling of the dust-flux schemes with a regulatory Gaussian plume model provided simulated ground level PM10 concentrations in good agreement with measured data. The best correlation was found under conditions of high wind speeds when the prevailing wind was from the direction of the tailings storage facility. This thesis demonstrates that simulated impacts from complex source groups can be performed, within an acceptable range of certainty, using widely applied dust-flux schemes. These dust-flux schemes, developed primarily for large-scale desert and arid areas, have been demonstrated to be applicable also to small-scale sources, of the order of 1 km2, and can be coupled to regularly available dispersion models for impact evaluations of wind-blown dust. The value of this improved approach to the mining and mineral processing industries are substantial, allowing for more accurate health risks and adverse environmental assessments from wind-blown dust from large material storage piles, a source category that has hitherto been difficult to quantify.

Dust is a detrimental, but unavoidable, consequence of any mining process. It is particularly problematic in underground coal mining, where respirable coal dust poses the potential health risk of coal workers’ pneumoconiosis (CWP). Float dust, if not adequately diluted with rock dust, also creates the potential for a dust explosion initiated by a methane ignition. Furthermore, recently promulgated dust regulations for lowering a miner’s exposure to respirable coal dust will soon call for dramatic improvements in dust suppression and capture. Computational fluid dynamics (CFD) results are presented for a research project with the primary goal of applying a flooded-bed dust scrubber, with high capture and cleaning efficiencies, to a Joy 7LS longwall shearer operating in a 7-ft (2.1 m) coal seam. CFD software, Cradle is used to analyze and evaluate airflow patterns and dust concentrations, under various arrangements and conditions, around the active mining zone of the shearer for maximizing the capture efficiency of the scrubber.

Dust is ubiquitous in underground mine activities. Continuous inhalation of dust could lead to irreversible occupational diseases. Dust particles of size lower than 75.0 µm, also known as float coal dust, can trigger a coal dust explosion following a methane ignition. Ventilation air carries the float coal dust from the point of production to some distance before it’s deposited on the surfaces of underground coal mine. Sources of dust are widely studied, but study of dust transportation has been mainly based on experimental data and simplified models. An understanding of dust transportation in the mine airways is instrumental in the implementation of local dust control strategies. This thesis presents techniques for sampling float coal dust, computational fluid dynamics (CFD) analysis, and mathematical modeling to estimate average dust deposition in an underground coal mine. Dust samples were taken from roof, ribs, and floor at multiple areas along single air splits from longwall and room and pillar mines. Thermogravimetric analysis of these samples showed no conclusive trends in float coal dust deposition rate with location and origin of dust source within the mine network. CFD models were developed using the Lagrangian particle tracking approach to model dust transportation in reduced scale model of mine. Three dimensional CFD analysis showed random deposition pattern of particle on the mine model floor. A pseudo 2D model was generated to approximate the distance dust particles travel when released from a 7 ft. high coal seam. The models showed that lighter particles released in a high airflow field travel farthest. NIOSH developed MFIRE software was adopted to simulate dust transportation in a mine airway analogous to fume migration. The simulations from MFIRE can be calibrated using the dust sampling results to estimate dust transportation in the ventilation network.

Even minimal improvements in particle collection efficiency of electrostatic precipitators significantly reduce dust emission from fossil-fuelled power stations and reduce pollution. Yet current designs rely on the Deutsch collection theory, which was developed for tubular precipitators and has been applied to wire-plate precipitators on the assumption that the inter-electrode electric fields at the same discharge distance in both were similar. Differences in geometry and associated collector electric fields and current density non-uniformity have not been taken into account, although the collector electric field and current density of the wire-plate precipitator are not uniform. And observations show that precipitated dust patterns and the distribution of collector current density are interrelated. Investigations revealed a simple square law relationship between the collector electric field and the collector current density in the space charge dominated coronas. Applying this relationship to the Deutsch collection theory led to a current-density-based collection formula that takes into account the non-uniform collector current density distribution. The current-density-based collection formula is then used to assess the impact of collector current density on collection efficiency, the results closely following published measurements. Applying the current-density-based collection formula to estimate the dust accumulation shows that most of the dust accumulates at collector locations facing the corona wires. The effect of the non-uniform precipitated dust layer on collection performance is assessed using the distributed corona impedance - the ratio of the inter-electrode voltage and the non-uniform collector current. Re-distribution of the collector current profile as dust builds up is also compatible with published measurements. Finally this is applied to optimize the wire-plate precipitator collection performance. This shows that optimal collection performance is obtained with the wire-wire spacing less than the wire-plate distance, once again confirming published experimental results. This is the first analytical approach to show better collection performance can be achieved at the ratio of wire-wire spacing/wire-plate distance not equal to unity, which has been the standard industry practice since 1960.