by EF Lozano · 2020 — The Bucket Wheel Excavator, also known as BWE, is a mechanical excavation machine used in open pit mines, widely implemented in open pit coal mines. BWE.
130 pages

95 KB – 130 Pages

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Microwave irradiation treatment in the improvement P age 1 of the performance of a BWE I wo uld like to thank my adviser Mr. Dipl. – Ing. Dr. M ont Philipp Hartlieb, for the advice and suggestions during the time I was involved in this topic. I also want to thank FL – Smidth for the help they provided me. Especialmente, a mis padres y mi hermano, por su apoyo incondicional incluso en los peores momentos. No habría llegado hasta aquí sin vosotros.

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Microwave irradiation treatment in the improvement P age 2 of the performance of a BWE Der Schaufelradbagger, ist eine mechanische Baggermaschine für den Tagebau. Der Schaufelradbagg er kann kontinuierlich arbeiten: Er gräbt, lä dt und transportiert das Material gleichzeitig. Das Material, das ein Schaufelradbagger extrahieren kann, ist durch seine FestigKeit begrenzt. In der Regel können nur lose oder weiche Gesteinsarten wirtschaftlic h verladen werden. Härtere Gesteine werden of t durch Sprengen vor dem Aushub mit einem Schaufelradbagger vorbehandelt. Ziel dieser Arbeit ist es, zu zeigen, dass die Bandbreite des Materials, das ein Schaufelradbagger graben kann, durch eine Vorbehandlung des Materials mit Mikrowellenbestrahlung erwe itert werden kann, um dessen mechanische FestigKeit zu reduzieren. Die Demonstrationen bestehen im direkten Vergleich beider Situationen: behandeltes und unbehandeltes Material. Zuerst werden die Simulationen in einer hypothetischen Situation durchgeführt, wobei ein breites Spektrum von Materialeigenschaften basierend auf dem Gebirgsklassifikationssystem verwendet wird. Im zweiten Schritt beinhaltet die Simulationen reale Daten, die von Sensoren gewonnen werden, die auf einem Schaufelradbagger installiert sind. Zusätzlich wird die Energieverbrauchsbilanz berechnet, einschließlich der Daten der Maschinensensoren sowie der Daten aus Labortests zur Mikrowellenbehandlung – durchgeführt in früheren Untersuchungen zur Mi krowellenbestrahlung von Gesteinen. Die Ergeb nisse zeigen, dass nach der Mikrowellenbehandlung an einem bestimmten Material die auf das Schaufelrad ausgeübten Kräfte durch die Verringerung des Schnittwiderstands des Materials reduziert werden. Dadurch wird auch eine konsequente proportionale Reduzier ung des Energieverbrauchs erreicht, was bestätigt, dass die Leistung der Schaufelradbagger Extraktion verbessert wird.

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Microwave irradiation treatment in the improvement P age 3 of the performance of a BWE The Bucket Wheel Excavator, also known as BWE , is a mechanical excavation machine used in open pit mines, widely implemented in open pit coal mines. BWE can continuously work a regime: it digs, loads and hauls the material simultaneously. The material that a BWE can extract is limited by its strength . Normally, only loose or soft rock types can be loaded economically. Harder rocks are often preconditioned by blasting prior to excavation with a BWE . This research is demonstrating that the range of the material that a BWE is able to dig can be widened b y pretreating the material with microwave irradiation, in order to reduce its rock The demonstrations consist of the direct comparison of both situations: treated and non – treated material. At first, the simulations are run in a hypot hetical situation, using a wide range of material properties based on the Rock Mas s Rating system. In the second step, the simulations include real data obtained by sensors installed on a BWE . Additionally, the energy consumption balance is calculated, inc luding the data from the machine sensors as well as the data obtained in laborator y tests regarding the microwave treatment performed in previous research regarding microwave irradiation tests on rocks. The results show that after the microwave treatment o n a specific material, the forces applied to the bucket wheel are reduced, due to the decrease of the cutting resistance of the material. Therefore, as a consequence, a proportional reduction in energy consumption will be also achieved, which confirms that the performance of the BWE

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Microwave irradiation treatment in the improvement P age 4 of the performance of a BWE PREFACE, DEDICATION, ACKNOWLEDGEMENT .. . 1 ZUSAMMENFASSUNG .. .. .. 2 ABSTRACT .. .. .. . 3 TABLE OF CONTENTS .. .. .. . 4 1 INTRODUCTION: THE BUCKET WHEEL EXCAVATOR .. 5 1.1 Applicabili ty .. .. .. . 6 1.2 BWE operation .. .. .. 8 1.3 Problematic areas during extraction .. .. . 12 1.4 Excavate ro ck with a BWE .. .. 14 1.5 Benefits of microwave irradiation .. .. .. 15 2 MECHANICAL EXCAVATION AND INFLUENCE OF ROCK PARAME TERS .. 17 2.1 Cutting resistance .. .. . 17 2.2 Workin g regime of a BWE and its relation with the Ke .. .. 20 2.3 Rock mass classifications .. .. . 27 2.4 Relation between the RMR and Ke .. .. .. 30 3 REDUCTION OF RMR BY INDU CING FRACTURES .. 37 3.1 Definition of microwaves and applicability .. 37 3.2 Rock fracturing using microwave irradiation .. 43 3.3 Fractures patterns on laboratory tests .. .. . 44 4 CALCULATIONS PROCEDURE .. .. 55 4.1 Input parameters .. .. .. . 55 4.2 Machine regime and comparison .. .. .. 59 4.3 Calculation code .. .. .. . 60 5 RESULTS ON THE BWE WORKING REGIME .. 71 5.1 Data provided .. .. .. .. 71 5.2 Relation between Ke reduced values and the fracture patterns 86 CONCLUSIONS .. .. .. . 92 BIBLIOGRAPHY .. .. .. . 93 LIST OF FIG URES .. .. .. 96 LIST OF T ABLES .. .. .. 100 LIST OF ABBREVIATIONS .. .. 101 ANNEX I: INPUT DATA OF THE MACHINES .. .. . I ANNEX II: MATLAB CODE .. .. IV

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Microwave irradiation treatment in the improvement P age 6 of the performance of a BWE The first sketches and designs of a BWE belong to Leonardo Da Vinci and appeared in a publication of excavating machines. However, the first implementation of this type of excavator took place in Germany, by Peltier. Unti l 1834 the steam engine was not ass embled on the shovel. From 1863 until 1868, primitive bucket wheel owever the basic layout of a BWE as are known now was unrecognizable until 1936, when a co mpany settled in Leipzig patented i t (U.S Department of Energy 1 979; Rasper 1975) . 1.1 Applicability The applicability of the bucket wheel excavator is basically determined by the amount of material that must be extracted, which m ust be reasonably large to be feasible. As an example, in the United States, in the Illino is coal basin, these machines are extensively used due to the large dimensions of the mineralization. Additionally, it must be highlighted that several studies took p lace in these coal mines such as Bucket Wheel Excavator Study, (U.S Departmen t of Energy 1979) . Generally, the topography is rather flat, which enhances the performance and the exposure of the deposit once the overburden is removed. Furthermore, the bucket wheel excavators need large surfaces o f land in order to maneuver due to the large dimensions o f their design. Those are the reasons why BWE s are limited to open pit mines as well as big construction site s, which normally are related to motorways, canals or dams. Bucket wheel excavators can di g out easily loose material and soft rocks and up to now the applicability has been reduced to those situations. However, the ground is never ideal and as it happens in Europe, the soft layers of coal are located among boulders or layers of other harder ro cks such as sandstone. Harder and abrasive rocks like san dstone may cause delays in the production or stops due to the incapability of the BWE to excavate those occur rences. The changes in the rock properties are also a large struggle for these machines a s they have not been designed for that propose. On the oth er hand, the diggable material range enlargement has been a point for long time. The larger the range of mate rials regarding abrasiveness and strength a BWE can get extracted the more efficient and more applicable will become. The

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Microwave irradiation treatment in the improvement P age 7 of the performance of a BWE following chapters 1.1.1 and 1.1.2 list all t he items regarding the advantages and disadvantages related to the BWE operation and extra ction, which define the applicability of this machine and its feasibility. 1.1.1 Advantages of BWE Among others, the literature describes these as the main advan tages again st other type s of excavator s : – Bucket wheel excavators are the best solution for large tonn age of material; draglines and other type of excavators must be larger than BWE for the same payload. – The working regime is continuous, not cyclic as dragl ines or reg ular excavators. – Energy consumption per produced unit is approximately 65% of cable excava tors. – The dumping radius is larger. – BWE works above and below the crawler tracks level, and the material extracted can be delivered at different levels. – It can work i n with different bench heights – The material, which has been dug out and after hauled, can be dumped in several types of further h aulage. – stable. – Selective method. 1.1.2 Disadvantages of BW E – High maintenance costs. – Problems related to adverse weather conditions, such as snow or low temperatures. – The material will be difficult to haul by the conveyor belt when the moisture content is rather high. – BWE s are not flexible due to reduced maneuvera bility. – High initial investment.

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Microwave irradiation treatment in the improvement P age 8 of the performance of a BWE – The material that can be extracted is limited in terms of abrasiveness and strength. – The infrast ructure of the machine will suffer when the lithology changes dramatically or when there are lenses of hard material – Depending on the size, the machine will not be able to transport boulders or load them. 1.2 BWE operatio n The applicability of the machine is a lso defined by the type of operation , the movements and the dimensions of the main parts of the machine, such as the BW and the boom. The basic operation can be split into two main movements: Wheel rotation Slewing of the arm During operation the machine performs both movements at the same time, leaving a helical curve behind. A bucket cuts a slice of material from the front face , which width changes as the bucket moves. The literature defines the final movement that the machine describes as an el lipse, whose formula is described as follows: [ 1 ] Where, – = diameter of the BW – = dimen – = slewed angle In the Figure 2 of the slewing , nt to the end of the working face.

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Microwave irradiation treatment in the improvement P age 9 of the performance of a BWE Figure 2 Sickle scheme (Bucket Wheel Excavat or, 1988) 1.2.1 Full block operation Full block method is the most economical mode when operating with a BWE , and basically consists in the total extraction of a block. Once the block is dug out, the BWE continues extracting the following block. The most critic al issues is the haulage of the material, if the transportation of the mined out material fails, t he operation must stop. in equation [ 2 ] : [ 2 ] Where, – = height of the block (m) – = block width (m) – = block length (m) 1.2.2 Types of operation The selection of the type of operation depends on the selectivity needed as well as the geometric constrains o f the design. In case of high selectivity, it could be possible to perform a mixed operation between terrace cut and drop cut.

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