Solutions Manual Fundamentals Of Modern Manufacturing; Materials, Processes, And Systems (5th Edition)Full description
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Full description
SOLUTIONS TO CHAPTER 13: SIZE ENLARGEMENT EXERCISE 13.1: In the pharmaceutical industry, any batch that deviates from the set parameters is designated as an “atypical” batch and must be investigated before the product can be released. You are a pharmaceutical process engineer, responsible for granulating a pharmaceutical product in a 600L mixer containing 150kg of dry powders. It was noticed while manufacturing a new batch that the liquid delivery stage ended earlier than usual and the batch contained larger granules than normal. During normal production, the impeller speed is set to 90rpm and water is added at a flowrate of 2L/minute through a nozzle producing an average drop size of 400 μm. Due to an incorrect setting, the actual flowrate used in the atypical batch was 3.5L/min and the actual drop size was estimated at 250 μm. The spray width and powder surface velocity were unaffected and remained r emained constant at 40cm and a nd 60cm/s respectively. Calculate the dimensionless dimensionless spray flux for the normal case and the atypical batch, and explain why this would have created larger granules. EXERCISE 13.1 SOLUTION: Using Text-Equation 13.5 and ensuring consistent units, the calculations are summarised in the table below. Parameter
Normal batch
Atypical batch
2
3.5
Drop size (um)
400
250
Spray width (m)
0.4
0.4
Powder Velocity (m/s)
0.6
0.6
Spray flux
0.52
1.46
Flowrate (kg/min)
a
The larger granules were formed because the incorrect settings resulted in a spray flux almost 3 times larger than the normal conditions. This means high spray density f wet wet and high overlap of the drops, forming larger granules than usual, since the number of nuclei formed by a single drop f 1 will be reduced, but the number of nuclei formed from multiple drops ( f 2, 2, f 3, 3, f 4 etc.) will increase dramatically. EXERCISE 13.2: Calculate the fraction or percentage of nuclei formed from one drop, two drops and three drops, etc at spray flux values of of (i) 0.05 (ii) 0.3 (iii) 0.8. What fraction of the powder surface will be wetted by the spray? EXERCISE 13.2 SOLUTION: Using a spreadsheet and Text-Equation 13.7 with n=1, 2, 3, 4, the fraction of nuclei formed from 1-5 1-5 drops for cases (i) to (iii) are shown below. below. The f wet wet values from equation (13.6) are (i) 0.05 (ii) 0.26 and (iii) 0.55. Number of drops n
