Screening (Sieve Shaker)

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ChE Laboratory Exp't, Screening - Final Report

ChE Laboratory Exp't, Screening - Final Report

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  • 1. CEBU INSTITUTE OF TECHNOLOGY N. Bacalso Avenue, Cebu City Chemical Engineeing Department FINAL REPORT ChE Lab 1 Title of Experiment Juphil A. Lamanilao BSChE-5 Engr. Lyda P. Abellanosa Instructor
  • 2. Abstract: Screening is a separation of materials on the basis of size as a means of preparing a product for subsequent operation. The screen size or mesh needed for the computation of particle size must be confirmed, the lowest being the top while the highest at the bottom. It is also a means of analysis, either to control the gage, the effectiveness of another operation or to determine the value of a product for some specific application. Screening in performed using screens equipped with one or two screen surfaces. A single screen provides two products. The product from the top is called the oversize or plus product while the one which passes through the screen is the undersize or minus product. Material passing one screen surface but remaining on the next one in a double deck screen is an intermediate product. During ideal screening, the plus product contains only particles greater than the size of openings of the screen surface while minus product consists of particles smaller than the opening. In real operations the oversized particles are present in the minus product and some undersized particles are in the plus product. It results from adhesion of small particles to large ones and that some particles never get into contact with the screen surface. The presence of large particles in the undersize product may be caused by greater than nominal openings or rupture of the screen surface.
  • 3. Objectives: 1.) To perform the differential and cumulative screen analysis of a given sample 2.) To determine the specific surface, particle population and average particle size of a sample mixture by the use of a screen analysis. Materials & Equipment: Tyler testing sieves; standard with cover and pan, sieve shaker, brush, electronic balance, sand sample Sketch of the Set-up: Procedure: A. The testing sieves were properly arranged according to decreasing aperture and then rested on sieve shaker A weighed amount of sand sample was then placed on the topmost sieve. The sieve shaker motor was turned on and the separation of different fractions was allowed to proceed to completion. The weights and mesh size range of the separated fractions were recorded.
  • 4. Tabulated Data & Result: ITEM TRIAL NUMBER 1 2 3 Feed: Material sand sand sand Quantity, grams 2000 2000 2000 Wt. distribution, grams Through Retained +10 mesh 636.9 976.4 942.9 -10 +20 471.3 474.7 467.4 -20 +30 215.7 243.7 245.9 -40 +60 152 170.8 165.3 -60 +80 82.7 87.9 90.6 -80 +100 21.8 2 24.3 -100 82.2 106.2 77.3 Size Distribution, % +10 mesh 3.185 48.82 47.145 -10 +20 23.57 23.74 23.37 -20 +30 10.79 12.49 12.3 -40 +60 7.6 8.54 8.27 -60 +80 4.135 4.4 4.53 -80 +100 1.09 0.1 1.22 -100 4.11 5.31 3.87 Computations: %PSD = #mesh(thru retained) x 100 quantity TRIAL 1 for +10 mesh: TRIAL 2 %PSD = (636.9/2000) x 100 for -60/+80 mesh: = 31.85% %PSD = (82.7/2000) x 100 for +10 mesh: for -10/+20 mesh: = 4.135% %PSD = (976.4/2000) x 100 %PSD = (471.3/2000) x 100 for -80/+100 mesh: = 48.82% = 23.57% %PSD = (21.8/2000) x 100 for -10/+20 mesh: for -20/+30 mesh: = 1.09% %PSD = (474.7/2000) x 100 %PSD = (215.7/2000) x 100 for -100 mesh: = 23.74% = 10.79% %PSD = (82.2/2000) x 100 for -20/+30 mesh: for -40/+60 mesh: = 4.11% %PSD = (243.7/2000) x 100 %PSD = (152/2000) x 100 = 12.49% = 7.6% for -40/+60 mesh:
  • 5. %PSD = (170.3/2000) x 100 = 5.31% for -40/+60 mesh: = 8.54% %PSD = (165.3/2000) x 100 = 8.27% TRIAL 3 for -60/+80 mesh: for -60/+80 mesh: for +10 mesh: %PSD = (90.6/2000) x 100 %PSD = (87.9/2000) x 100 %PSD = (942.9/2000) x 100 = 4.53% = 4.4% = 47.145% for -80/+100 mesh: for -80/+100 mesh: for -10/+20 mesh: %PSD = (24.3/2000) x 100 %PSD = (2/2000) x 100 %PSD = (467.4/2000) x 100 = 1.22% = 0.1% = 23.37% for -100 mesh: for -100 mesh: for -20/+30 mesh: %PSD = (77.3/2000) x 100 %PSD = (106.2/2000) x 100 %PSD = (245.9/2000) x 100 = 3.87% = 12.32% Data Analysis : The data shows that the size diameter of a particle affects the mean diameter in terms of length, surface & volume. Plotting the data between the sizes of the particle versus the mass fraction of the material retained in the screen, a bell shape curves was generated. It means that this variable is not directly proportional to each other because there’s no linear relationship between them. Eventhough the data gathered show the relationship of some variable; still it shows some inaccurate data. The inaccuracy is due to the insufficient cleanliness of the sieve. Recommendation: In this experiment, there are several precaution we must take to avoid and prevent errors from occur. The screen on the sieves should be clean carefully in order to remove all grain sands. The stack of sieves on the Sieve Shaker must be locked tidily to avoid them from moving away during shaking process. Student should make sure that all the left over sand in each sieve is transferred to the container use in weighing process. We also must clean the area around digital scale balance to get accurate readings and avoid the environmental effects. Student also can use a soft bristle brush to gently wipe the screen. Application to ChE: Gradation is usually specified for chemical engineering application and other engineering disciplines. For example, foundations might only call for coarse aggregates, and therefore an open gradation is needed. Gradation is primarily a concern in pavement mix design. Concrete could call for both coarse and fine particles and a dense graded aggregate would be needed. Asphalt design also calls for a dense graded aggregate. Gradation also applies to subgrades in paving, which is the material that a
  • 6. road is paved on. Gradation, in this case, depends on the type of road (i.e. highway, rural, suburban) that is being paved.