FACULTY OF ENGINEERING AND THE BUILT ENVIRONMENT. Department of Chemical, Metallurgical and Materials Engineering Metallurgical Engineering

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1 FACULTY OF ENGINEERING AND THE BUILT ENVIRONMENT Department of Chemical, Metallurgical and Materials Engineering Metallurgical Engineering Particle size reduction using simple Comminution Plant Prototype Design Competition Day: 8 August INTRODUCTION Metallurgy is a scientific field of study that entails detailed metals property studies as well as their extraction from the earth s crust. Their production, properties and nature are studied through strategic sound established metallurgical principles. Metals in the earth s crust originate as minerals which are compounds collectively called ore-body. Ore-body in its simple explanation is any natural occurring compound which can have economical value when extracted or separated. Ore-bodies are usually associated with non-valuable minerals which are called gangue, and require to be separated to produce the required metal content. Metallurgy is branched into different sectors or fields of, namely physical metallurgy, powder metallurgy, pyrometallurgy, hydrometallurgy and mineral processing. Mineral processing is usually the primary step in metals production because this is where the value-bearing minerals are prepared and concentrated through a series or sometimes parallel stages to separate them from non-value-bearing minerals or compounds. Physical metallurgy deals with the study of properties of the metals such as their crystallographic characteristics, physical property like tensile strength, hardness, etc. Powder metallurgy and pyrometallurgy utilises high temperature melting point to produce metals either in powder form or ingot or wrought form. Hydrometallurgy involves production of metals in aqueous form through dissolution in acid medium or base medium depending on the metals to be extracted.

2 The aim of this design is focused on the primary stages in mineral processing, namely comminution. Comminution is the reduction of solid materials from large unmanageable particle size to manageable smaller particle size. It is the first stage in mineral processing and involves the crushing, grinding, and screening of ore. Comminution is an important process in mineral processing because it liberates valuable minerals from matrix materials in which they are embedded and concentrate minerals (Agba D. Salman, 2007), increasing the particle surface area as well as assisting in improved ore transportation. Comminution requires different types of processing and transportation equipment depending on the type of ores or materials to be produced, the following equipment are mostly used in comminution: Crushers (Jaw, Cone and Hammer) Ball/Rod mill Belt Conveyor Vibrating screens The purpose of this design project is focused on fabricating the above-mentioned equipment for comminution stage in mineral processing. Basically, a comminution plant must be designed by the learners to simulate a comminution plant either operating in batch mode or continuous flow process. The idea is not really the sequential steps but to create a working model that can produce the desired outcomes. Since comminution is a reduction process, the learners design will be tested on whether it can be able to reduce size from a larger given particle size to a finer particle size. 2. Premature Literature Review of the Project Equipment 2.1 Jaw Crusher Figure 1 shows a typical Jaw Crusher designed to reduce large rocks into smaller rocks so that minerals of different compositions can be liberated.

Figure 1: Jaw Crusher (https://www.911metallurgist.com/blog/wp-content/uploads/2016/02/singletoggle-jaw-crusher.gif) There are different types of Jaw Crushers available in the industry.

3 Figure 1: Jaw Crusher ( There are different types of Jaw Crushers available in the industry. A generalised principle of operation is that the large size rocks or ore are placed into compression between a fixed jaw and a moving jaw. This is mounted in a "V" type alignment whereby the movable jaw exerts force on the rock by forcing it against the stationary plate to result in its breakage. The space at the bottom of the "V" aligned jaw blades is the crusher product size gap, or the size of the crushed product from the jaw crusher. The rock remains in the jaws until it is small enough to pass through the gap at the bottom of the jaws. 2.2 Ball mill Ball mill is used to grind and blend materials for use in mineral processing as shown in Figure 2.

Figure 2: Ball mill (http://www.everysingletopic.com/wp-content/uploads/2014/10/ball-mill.

4 Figure 2: Ball mill ( It comprises of balls filled at calculated amounts in a cylindrical vessel where the material to be grinded is introduced. The grinding balls are normally called grinding medium make of steel or any hard material. It operates on the principle of rotating the cylindrical vessel mixed with the material to be grinded which are in turn lifted on the rising side of the shell and cascade down from near the top of the shell. In doing so, the solid particles in between the balls and ground are reduced in size by impact. 2.3 Vibratory Screen A vibratory screen is equipment that can easily be described as a single deck positioned in an incline frame that is used to separate feed material according to the required screen size after the material has been crushed; separation of the material is promoted through a vibrating motion. Feed material consisting of coarse and fine materials are fed to a vibrating screen, the vibrating motion causes the separation on the wire meshes, the coarse will flow at the top of the mesh while fine percolate through the meshes.

Figure 3: Vibrating Screen (https://image.slidesharecdn.

4 Conveyor Belt Conveyor belts are mediums used to carry materials consisting of two or more pulleys with endless

5 Figure 3: Vibrating Screen ( /95/vibrating-screen-manufacturers) 2.4 Conveyor Belt Conveyor belts are mediums used to carry materials consisting of two or more pulleys with endless loop of carrying medium. They are considered as labour saving systems that allow large volumes to move rapidly through a process. Figure 4: Conveyor Belt (

6 3. TEAM ASSIGNMENT A team will constitute of 6 people, each team is required to build a working a model of a comminution plant consisting of the following equipment: a jaw crusher that is able to crush a given material, followed with a screen that will be separating the material into two streams (coarse and fine), whereby the coarse particles will be fed to a mill as the final stage of the circuit. The screen aperture size to be used can be anything in the range of 1mm to 5mm opening. The plant can either be presented complete or mounted on-site before the competition. Kindly note that electricity or any type of power source will not be provided by TUT. If the team requires a source of power they are welcomed to bring their own. The only material to be provided by TUT will be the material to be milled and crushed. The model will be evaluated based on the particle size of the product and efficiency of their size reduction plant, meaning at least 70% of the product (fine product of the crusher and product from the mill) must pass through a 340 µm sieve. 4. RECOMMENDED BUILDING MATERIALS 4.1. Ball mill Transparent and strong bottle as a mill. Motor for rotational motion of the mill. Sticks, tubes or pipes as supporting structures for the mill to rotate on or any form of supporting structure. Mill stands. Marbles or any other form of balls to be used as grinding medium Jaw crusher Cardboard Motor Sticks or any form of material for the stationery blades.

7 4.3. Screen Sieve Mesh Any vibrating component, to create vibrating motion in your screen 4.4. Conveyer belt Motor Wheels (rollers) Rubber belt or a thin box which will serve as your belt (NB: the belt should be able to transport the material) 4.5. General Batteries Glue Tape Switches Foundation base for your plant Paints/Spray Paints or assorted colours of markers for decorating the model. Note: Old toys or small equipment motors can be used. Boxes can also be used to build the model structure. 5. RULES AND SPECIFICATIONS Only one team is allowed to represent each school Only the prescribed materials (as indicated) are allowed No electricity will be provided Learners need to construct the plant themselves using the indicated materials. No Ball mill, crusher, screen, conveyor etc. may be purchased and used in the plant. The learners must assemble their plant before judging takes place or learners may bring their readily assembled plant.

8 Each team will only have 10 min to demonstrate their plant. No water may be used in the plant. The plant must be between 0.4m(L)x0.2m(B) to 1m(L)x1m(B)x0.5m(H). The process can either be continuous or run in batches. The sequential steps of the process depend on the teams however; the choice made would also determine the outcome of the results. It is up to each team to determine the steps to follow and direct the facilitator of where to take the material. 6. DAY PLAN This competition day will occur as follows: Each team will be given a maximum of 10 minutes for their demonstration. If there is a need for the assembling of the model, the team must make sure that their prototype is assembled before the completion starts. The place to display the prototype will be allocated to each team by competition officials. There will be a facilitator or competition official at each station for evaluation. The teams will be graded and there will be awards at the end of the competition.

9 7. EVALUATION All teams will be judged based on the categories displayed in Table 1. Table 1: The assessment criteria to be used for all the competing teams CRITERIA MAXIMUM POINTS TEAM Theme 5 Teamwork 5 PRESENTATION Audibility 5 Content 15 Response to question 10 Report 10 MODEL Appearance 10 Capacity 10 Functionality 30 TOTAL CONTACT DETAILS CONTACT PERSON TELEPHONE Ms Innocentia Setlhabi (012) / 4245 setlhabibi@tut.ac.za

Crushing. Comminution

Crushing. Comminution Comminution In order to separate the minerals from gangue (the waste minerals), it is necessary to crush and grind the rock to unlock, or liberate, valuable minerals so that they are partially or fully