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In the commercial production of sugar (sucrose), the product crystals are washed and
Chapter 4, Problem 4.28(choose chapter or problem)
In the commercial production of sugar (sucrose), the product crystals are washed and centrifuged to partial dryness. The crystals are then sent through a rotary dryer where they are contacted with a hot stream of air that reduces the moisture content from 1:0 wt% to 0:1 wt%. The ratio of wet sugar to inlet air fed to the dryer is 3.3 kg wet sugar/kg inlet air. The inlet air contains 1.5 mole% water. (a) Draw and label the flowchart and do the degree-of-freedom analysis. (b) Taking a basis of 100 kg of wet sugar fed to the dryer, calculate the mass of water and its mole fraction in the air leaving the dryer. (c) If 1000 tons/day of dried sugar is to be produced, at what rate (lbm/h) is water evaporated from the sugar? (d) Determine the current price of sugar and estimate in $/year the current income (not the same as profit) from operation in Part (c). (e) Samples of the product crystals are analyzed routinely for water content. The mass fractions of water in the samples on successive days of operation are shown in the following table. Day 1 2 3 4 5 6 7 8 9 10 xW 0.00102 0.00097 0.00099 0.00101 0.00107 0.00099 0.00102 0.00094 0.000101 0.00098 The quality of the product during these days of operation has been graded acceptable, and it is decided that the process will be shut down for maintenance when the value of measured value of xW is more than three standard deviations from the mean of this series of runs. What are the maximum and minimum values of xW?
Questions & Answers
QUESTION:
In the commercial production of sugar (sucrose), the product crystals are washed and centrifuged to partial dryness. The crystals are then sent through a rotary dryer where they are contacted with a hot stream of air that reduces the moisture content from 1:0 wt% to 0:1 wt%. The ratio of wet sugar to inlet air fed to the dryer is 3.3 kg wet sugar/kg inlet air. The inlet air contains 1.5 mole% water. (a) Draw and label the flowchart and do the degree-of-freedom analysis. (b) Taking a basis of 100 kg of wet sugar fed to the dryer, calculate the mass of water and its mole fraction in the air leaving the dryer. (c) If 1000 tons/day of dried sugar is to be produced, at what rate (lbm/h) is water evaporated from the sugar? (d) Determine the current price of sugar and estimate in $/year the current income (not the same as profit) from operation in Part (c). (e) Samples of the product crystals are analyzed routinely for water content. The mass fractions of water in the samples on successive days of operation are shown in the following table. Day 1 2 3 4 5 6 7 8 9 10 xW 0.00102 0.00097 0.00099 0.00101 0.00107 0.00099 0.00102 0.00094 0.000101 0.00098 The quality of the product during these days of operation has been graded acceptable, and it is decided that the process will be shut down for maintenance when the value of measured value of xW is more than three standard deviations from the mean of this series of runs. What are the maximum and minimum values of xW?
ANSWER:Step 1 of 6
The given data says 3.3 kg wet sugar/ 1 kg inlet air is the wet sugar fed ratio to the dryer, i.e., 3.3 kg wet sugar= 1kg inlet air.
Now, for 100 kg wet air = 100/3.3 kg or 30.3 kg inlet air.