Chemical Engineering Calculations Flashcards
Air is bubbled through a drum of liquid hexane at a rate of 0.10 kmol /min. The gas stream leaving the drum contains 10 mol% hexane vapor. Air may be considered insoluble in liquid hexane. Use an integral balance to estimate the time required to vaporize 10 m3 of the liquid.
a. 4200 min c. 7700 min
b. 6900 min d. 8100 min
b. 6900 min
An evaporator is fed continuously with 25 MT/h of a solution consisting of 10% NaOH, 10% NaCl, and 80% H2O. During evaporation, water is boiled off, and salt precipitates as crystals, which are settled and removed from the remaining liquor. The concentrated liquor leaving the evaporator contains 50% NaOH, 2% NaCl and 48% H2O.
Calculate the kg of water evaporated per hour.
a. 19300 c. 17600
b. 18500 d. 16200
c. 17600
An evaporator is fed continuously with 25 MT/h of a solution consisting of 10% NaOH, 10% NaCl, and 80% H2O. During evaporation, water is boiled off, and salt precipitates as crystals, which are settled and removed from the remaining liquor. The concentrated liquor leaving the evaporator contains 50% NaOH, 2% NaCl and 48% H2O. Calculate the kg salt precipitated per hour
a. 2400 c. 1100
b. 3500 d. 4700
a. 2400
An evaporator is fed continuously with 25 MT/h of a solution consisting of 10% NaOH, 10% NaCl, and 80% H2O. During evaporation, water is boiled off, and salt precipitates as crystals, which are settled and removed from the remaining liquor. The concentrated liquor leaving the evaporator contains 50% NaOH, 2% NaCl and 48% H2O. Calculate the kg of concentrated liquor produced per hour.
a. 4000 c. 6000
b. 3000 d. 5000
d. 5000
1200 lb of barium nitrate is dissolved in sufficient water to form a saturated solution at 90 deg C. Assuming that 5% of the weight of the original solution is lost through evaporation calculate the crop of crystals obtained when cooled at 20 deg C. Solubility data for barium nitrate at 90 deg C is 30.6% wt and 8.6 wt% at 200C.
a. 952.4 lbs c. 962.4 lbs
b. 970 lbs d. 980 lbs
c. 962.4 lbs
Fresh orange juice contains 12.0 wt% solids and the balance water, and the concentrated orange juice contains 42.0 wt% solids. Initially a single evaporation process was used for the concentration, but volatile constituents of the juice escaped with the water, leaving the concentrate with a flat taste. The current process overcomes this problem by bypassing the evaporator with a fraction of the fresh juice. The juice is concentrated to 58 wt% solids, and the evaporator product stream is mixed with the bypassed fresh juice to achieve the desired final concentration.
Calculate the following:
The amount of product (42% concentrate) produced per 100 kg fresh juice fed to the process.
a. 35.3 c. 28.6
b. 40.5 d. 19.2
c. 28.6
Fresh orange juice contains 12.0 wt% solids and the balance water, and the concentrated orange juice contains 42.0 wt% solids. Initially a single evaporation process was used for the concentration, but volatile constituents of the juice escaped with the water, leaving the concentrate with a flat taste. The current process overcomes this problem by bypassing the evaporator with a fraction of the fresh juice. The juice is concentrated to 58 wt% solids, and the evaporator product stream is mixed with the bypassed fresh juice to achieve the desired final concentration.
Calculate the following:
The fraction of the feed that bypasses the evaporator.
a. 0.032 c. 0.150
b. 0.099 d. 0.250
b. 0.099
A furnace is fired with high volatile A bituminous coal whose ultimate analysis shows 75.2% C, 5.19% H, 8.72% O, 1.5% N, 7.8% ash and 1.6% S. 60% excess air is supplied. Assume CO to CO2 ratio of 0.175. The stack gas leaves at 300 deg C, 740 torrs.
Calculate:
The % water in the complete analysis of the stack gas if air is supplied at 28 deg C, 100 kPa and essentially dry.
a. 2.06% c. 3.12%
b. 5.90% d. 4.47%
d. 4.47%
A furnace is fired with high volatile A bituminous coal whose ultimate analysis shows 75.2% C, 5.19% H, 8.72% O, 1.5% N, 7.8% ash and 1.6% S. 60% excess air is supplied. Assume CO to CO2 ratio of 0.175. The stack gas leaves at 300 deg C, 740 torrs.
Calculate:
The calorific value of the coal.
a. 28 MJ/kg c. 31 MJ/kg
b. 25 MJ/kg d. 39 MJ/kg
c. 31 MJ/kg
A high volatile B bituminous coal analyzing 22% VCM, 64% FC, 4% M, 1.4% N and 1.6% S has a calorific value of 32.5 MJ/kg. It is burned in excess air supplied essentially dry at 280C and 1 atm. The stack gases leave at 250C, 740 mmHg and contain 8.37% CO2, 4.19% CO and 2.51% H2. Calculate:
The % excess O2
a. 38% c. 55%
b. 40% d. 62%
b. 40%
A high volatile B bituminous coal analyzing 22% VCM, 64% FC, 4% M, 1.4% N and 1.6% S has a calorific value of 32.5 MJ/kg. It is burned in excess air supplied essentially dry at 280C and 1 atm. The stack gases leave at 250C, 740 mmHg and contain 8.37% CO2, 4.19% CO and 2.51% H2. Calculate:
The % N2 in the complete Orsat analysis of the stack gas
a. 75% c. 76%
b. 89% d. 80%
c. 76%
A furnace burns coal with the following analysis: M – 4.1%, VCM – 24%, FC – 63.0%, N – 1.20%, S 1.80%, Ash – 8.90%. The refuse analyzed 4.8% VCM, 12.6% FC, 82.6% ash and a calorific value of 32 MJ/kg. Calculate the percentage of gross calorific value lost in the refuse.
a. 1.38% c. 0.90%
b. 2.16% d. 3.05%
b. 2.16%
A pure saturated hydrocarbon is burnt with excess air. Orsat analysis of the stack gas shows 7.9% CO2, 1.18% CO, 0.24% H2, 5.25% O2, and 85.43% N2. Air is substantially dry. The stack gases leave at 750 mmHg pressure. Calculate:
A. The % excess air
B. The formula of the hydrocarbon
A. 25%
B. CH4
The burning of pure butane with excess air gives a stack gas which analyzes 11.55% CO2 on a dry basis. Assuming complete combustion, calculate the % excess air
20%
