COAL BLENDING MODEL Theory and Application of the Model by EDWIN
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COAL BLENDING MODEL Theory and Application of the Model by EDWIN ALOIS BAUER B.A.Sc., The University of British Columbia, 19 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OF GRADUATE STUDIES Mining and Mineral Process Engineering University of British Columbia We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA December 1988 (c)Edwin Alois Bauer, 1988 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of ft\'in\rt^ + M; A<*f»\ Prated gnj. The University of British Columbia Vancouver, Canada Date kprfl 1 L A 1 DE-6 (2/88) Pg ii ABSTRACT Over the past decade, most Western Canadian coal mines have been forced to mine deposits containing multiple seams of coal, with varying coal qualities. This change in mining practice has caused considerable challenges for coal washery personnel. Blending or homogenization of these multiple seams has been the standard approach in attempting to minimize the disruption to washery operations. The purpose of this research was to develop a method of quantifying the effects of a controlled blending program on preparation plant yield, thus providing a way to optimize the blending program within the constraints of the mining program, the processing unit operations, and the final product quality constraints. A yield-based objective function called the Coal Blending Coefficient was developed to evaluate the effects of blending on preparation plant yield. This formula can be described as the difference in yield between blending and batching of the same coals. The Coal Blending Coefficient was then incorporated into a collection of existing computer programs called the CANMET Coal Data Manipulation Programs, and after some modifications, the Coal Blending Model was produced. The Coal Plant Simulation program, which is included in the CANMET program, is the heart of the model, while the Pg iii Coal Blending Coefficient values allow the model to rank the blends. To date, approximately twenty runs of the Coal Blending Model have been tried on coals from three British Columbia coal deposits. The results range from zero benefit of blending for similar quality seams, to potential gains of over five percent increase in yield for highly varied seam qualities. Most runs produced Coal Blending Coefficient values in excess of one, which represent a potential gain in profits of over ten million dollars for the Western Canadian coal industry. Though these initial trials have been successful, further improvements must be made to the Coal Blending Model, and actual field testing performed before this model would be available for use within the industry. Pg iv TABLE OF CONTENTS PAGE NO. ABSTRACT ii LIST OF TABLES vi LIST OF FIGURES vii ACKNOWLEDGEMENTS viii I. INTRODUCTION General 1 Statement of the Problem 1 Scope of the Study 3 II. LITERATURE REVIEW Introduction to Gravity Separation 5 Float-And-Sink Analysis 10 Method of Analysis 13 Plant and/or Equipment Efficiency 17 Effect of the Raw Coal 18 Effect of the Cleaning Unit 19 Methods of Raw Coal Blending: 25 No Blending 26 Batching 27 Homogenization 29 Blending Prior To Treatment 30 In-Pit Blending 31 Summary 32 Preparation Plant Computer Simulation Modeling.... 33 III. DEVELOPMENT OF THE COAL BLENDING MODEL Introduction 35 Development of the Coal Blending Coefficient 36 Coal Blending Model Description 41 Model Input 45 Model Output 51 Summary 57 IV. COAL BLENDING MODEL APPLICATION 59 Example Problems and Data Evaluation: 61 Example Problem One: Two Seam Blend 62 Example Problem Two: Three Seam Blend "1" 68 Example Problem Three: Three Seam Blend "2".... 75 Pg v TABLE OF CONTENTS (continued...) PAGE NO. V. SUMMARY AND REMARKS 81 VI. REFERENCES 84 VII. APPENDICES: 87 A. Coal Blending Model Program Listings.... 88 B. Washability Data Used For Example Problems 92 C. Coal Blending Model Results: Example Problem One.. 101 D. Coal Blending Model Results: Example Problem Two 107 E. Coal Blending Model Results: Example Problem Three 123 Pg vi LIST OF TABLES PAGE NO. I. Classification of Coals by Rank 7 II. Cumulative Float Data 39 III. List of Required Input Information 47 IV. Sample Model Inputs 52 V. Sample Batching Results 55 VI. Sample Coal Blending Model Results 56 VII. Coal Production For Example One 66 VIII. Coal Production For Example Two 74 IX. Coal Production For Example Three 76 Pg vii LIST OF FIGURES PAGE NO. 1. Sample Washability Graph. 11 2. Distribution Curve of a Perfect Separation at 1.50 Specific Gravity 20 3. Illustration of Probable Error (EPM) of a Separation at 1.50 Specific Gravity 21 4. Imperfection as a Function of Probable Error and Specific Gravity of Separation: United States Bureau of Mines 24 5. Benefits of Raw Coal Homogenization 28 6. Coal Blending Model Flowsheet 42 7. Two Seam Blend Model Results: Example One 63 8. Three Seam Blend Model Results: Example Two Coal Blending Coefficient Contours No. 1 70 9. Three Seam Blend Model Results: Example Two Coal Blending Coefficient Contours No. 2 71 10. Three Seam Blend Model Results: Example Two Coal Blending Coefficient Contours No. 3 72 11. Three Seam Blend Model Results: Example Three Coal Blending Coefficient Contours 77 12. Three Seam Blend Model Results: Example Three Blending Feasibility Zones 78 Pg viii ACKNOWLEDGEMENTS I wish to acknowledge and thank the following people and organizations for their support and encouragement: Professor Allan Hall; University of British Columbia Dr. David Osborne and Tony Walters; Kilborn Engineering Tom Milner; Quinsam Coal Limited Ian Parsons; CANMET Coal Research Laboratory Ross Leeder; Denison Mines Ltd. I also wish to thank my wife, Maureen, for her help, understanding, and support, for without her encouragement, this thesis may never have been completed. 1 I.INTRODUCTION GENERAL The coal mining industry is of significant economic importance to Canada. In 1984, there were 12 operating coal preparation plants in Western Canada, as well as one in Eastern Canada, all processing coal for export (Duncan) (1). The plants ranged in capacity from approximately 400 to 2000 tonnes per hour. Total capacity is over 10,500 tonnes per hour of treatment capacity, which is in excess of 50 million tonnes of clean coal per year. STATEMENT OF THE PROBLEM Ten years ago, the majority of Western Canadian coal mines worked deposits consisting of one or two economical seams. Since then, the changes in operating and economic conditions have necessitated multiple seam mining, and some mines currently work up to ten separate seams in a single pit. Even though Rocky Mountain coals have a similar rank to the carboniferous coals of Western Europe and the Eastern United States, their seam structure is very different from coking coal The Coal Blending Model Pg 2 deposits elsewhere (Butcher)(2). The development of the mountain coal seams was accompanied by severe geological disturbances which caused most of the coal seams to be sheared and the strata to become highly inclined, closely folded and repeated by overthrusts. Mining these multiple seams requires coping with these complex physical conditions, including: variable seam pitch and thickness; rugged, diverse topography; sundry roof and floor strata; as well as the most important variable to the coal preparation process-- variable coal qualities. Multiple seam mining, with its added complexities, was significant in the lower than expected yields experienced by several Western coal washeries recently. The cost associated with low yields has been calculated by Picard (3), who determined in 1985 that, for each 1% improvement in recovery that could be achieved without loss of quality, the Canadian coal mining industry as a whole would gain $11-13 million per year at the current prices and production rates. Plant yield is affected by a large variation in feed quality that commonly occurs in multiseam mining operations. This variation in coal quality can have diverse effects on the different unit operations in the plant, resulting in a decrease of overall The Coal Blending Model Pg 3 plant yields. Blending or homogenization methods have been proven to help minimize the variations in plant feed, thus improving the overall production yield. In Western Canadian coal mines, most multiple seam mines practice some form of blending, but few of these coal mines have determined how blending affects their washery yield. The rest have developed arbitrary criteria for blending which may or may not optimize washery yield. Coal mines require a reliable method which can be used to establish a blending strategy for the life of the mine, thus optimizing the clean coal yield. SCOPE OF THE STUDY The main objective of this research was to develop a method of evaluating the effects of controlled blending on preparation plant efficiency. A criterion for evaluation of the relative plant efficiency due to controlled blending of multiple seams was developed and is called the Coal Blending Coefficient. Once the Coal Blending Coefficient's formula was determined, the next stage of the study was data collection. The data collection had to be done in one of three ways: using a pilot plant, an operating mine, or a reliable preparation plant simulation model. Unfortunately, the first two options were not available due to the time and financial constraints of these procedures. A computer simulation model was the most The Coal Blending Model Pg 4 appropriate alternative.