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FACULTY OF ENGINEERING AND THE BUILT ENVIRONMENT Department of Chemical, Metallurgical and Materials Engineering Metallurgical Engineering Competition Day 6 May 2016 A MINERAL PROCESSING ADVENTURE: DESIGN AND BUILD A WORKING MODEL OF FROTH FLOTATION PROCESS 1. INTRODUCTION South Africa is a world leader in mining. It has the largest reserves of valuable minerals such as platinum (Pt), manganese (Mn), gold (Au), base metals (copper (Cu), nickel (Ni), zinc (Zn), lead (Pb) and iron (Fe)). Due to this, our country has become a powerhouse for innovation and a pioneer for world-class mineral processing technologies. As a result, there has been a notable interest in the study of various processing techniques which eventually become important tools for a special class of engineers called Metallurgical Engineers. In this science adventure, you will be introduced to basics of a classic process that Metallurgical Engineers use to extract valuable minerals from various ore deposits which is widely known as froth flotation. During flotation, the slurry (water + fine ore particles) is pumped into a flotation cell and mixed with suitable chemicals (known as flotation reagents) as shown in Figure 1a. The added chemicals then cause the valuable minerals to be “repelled” from water while those of less value become “water loving”. What does this mean? What tricks do engineers use to extract these metals when this happens? At this stage, air is pumped into the flotation cell through the center of the agitator (a stirrer) and causes the formation of bubbles. The “water repelled” minerals attach themselves to the bubbles and rise to the upper level of a flotation cell and are then removed as froth ( - just like how soap foam floats on water). Meanwhile, the “water loving” materials then settle at the bottom and are then removed as the tailings. Refer to the Figures 1 and 2 below to better understand this process. a b Figure 1. Illustration of the froth flotation process showing: (a) a cross section of a flotation cell, (b) top view of a flotation cell in the metallurgical plant (picture by www.911metallurgist.com; www.autotec.com). 1 Cleaners Roughers Figure 2. Froth flotation process in a Metallurgical plant (known as a Concentrator) showing flotation cells connected in series (picture by www.e-mj.com ). 2. TEAM ASSIGNMENT In this project, you are required to build a WORKING MODEL that will demonstrate a flotation circuit consisting of FOUR flotation cells. Each cell must produce two streams from the feed stream namely, the froth and tailings as shown on Figure 3a. The flotation circuit will be divided into TWO sections consisting of two flotation cells. In a typical Concentrator plant, these sections are commonly known as the roughers and cleaners which can be connected as illustrated on Figures 2 and 3b. Your model must demonstrate the feed, froth and tailings streams which shall be connected as shown on Figure 3b. The flow of the slurry from one flotation cell to another must occur through GRAVITY i.e. NO ELECTRICAL INSTRUMENTS MUST BE USED. For the construction of the flotation vessels, the team can use any waste material (tins, tape, plastic, glue etc.) to ensure that the model works properly. There are NO RESTRICTIONS on the SIZE but the flotation cells must be similar in SHAPE. 2 a Feed material (slurry) Froth (concentrate, rich in valuable minerals) Tailings bb Roughers ROUGHERS Feed Cleaners CLEANERS Froth Feed Froth R1 R1 C1 Froth C1 Froth Tailings Tailings Froth Tailings R2 Tailings R1 Tailings Froth Froth C2 C1 Tailings Re-Cleaners Tailings Froth Froth RC 1 Froth Tailings Tailings Froth Tailings Froth Figure 3. The prescribed model RC to be 2 constructed by the competing teams. Froth Tailings 3 3. MATERIALS Teams are allowed to make use of any material to construct their model. However, any team that will use vessels that were not handmade will be penalized or disqualified. The teams are only allowed to purchase pipes that can be used for the process streams. Typical materials to use include but not limited to: Glue, cans, plastic bottles, buckets, plastic pipes, slurry (which can be anything the team choses) and other materials of choice. The team is allowed to use any kind of foam forming chemical The team is allowed to use any kind of material which can be used to demonstrate the concept of separation by FLOATING and SINKING. The team is allowed to use any kind of material except paper, cardboard or cloth to make vessels (this is so as to avoid leakages) The teams can put additional cells for the feed, tailings and froth streams to control the flow. VERY IMPORTANT: THE FLOTATION CIRCUIT MUST BE ABLE HANDLE A CONTINUOUS FLOW OF THE FEED MATERIAL. 4. RULES, SPECIFICATIONS AND OUTCOMES Each team shall bring a finished model to TUT. Teams may consist of a minimum of three and maximum of five learners. Schools can enter only one team. Each team will present a report which contains all the sketches, ideas, calculations, test procedures and designs etc. which were used to decide on the final model. The report will contain an indication of what the expected capacity (liters) that the flotation model can treat. TUT will provide two identical chairs or table where the model will be placed during the competition. As for the slurry, TUT will only provide water upon request by the team. The built model will be tested for leakages using water by the TUT competition officials. If there are any water leakages identified, points will be deducted from the team. Lastly, the team will then be allowed to illustrate the froth flotation processes and will be judged on their presentation and functionality of their model. 5. LEARNING OBJECTIVES This project will introduce the learner to the mineral processing fundamentals (in this case, froth flotation), the design principles and operation of a metallurgical plant. The teams will learn the basic calculations and procedures that engineers use when designing, starting and running a metallurgical plant. 4 6. PROCEDURE All teams must plan and build their projects in advance. If the project is transported to TUT in parts, a maximum of 10 minutes will be allowed to set up your project. The place to set up your project will be shown to you by competition officials. 7. TIME There will be a time constriction of ten (10) minutes to set up the project. 8. 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 ACTUAL POINTS CRITERIA MAXIMUM POINTS COMMENTS TEAM Theme 5 Teamwork 5 PRESENTATION Audibility 5 Content 15 Response to questions 10 Report 10 Appearance 10 Capacity 10 Functionality 30 MODEL TOTAL 100 9. CONTACT DETAILS CONTACT PERSON Ms. Lerato Tshabalala Ms. Innocentia Setlhabi TEL (012) 382 4244 (012) 382 4245 E-MAIL [email protected] [email protected] 5