CHECAL QNA
c. What is the overall conversion with respect to C?
DR. RAy
It is desired to recover NH3 from a gas stream composed of NH3 and N₂ by contacting with an
absorbing solvent. The inlet gas stream contains 10.0 wt% NH3 while the inlet liquid stream is 100%
solvent. Both inlet streams enter at a rate of 1000 kg/h. If 98.0% of the NH3 is absorbed, what are the
flow rates and composition of the two exit streams?
1. In the processing of fruit juices, it is often necessary to evaporate some of the water from the fruit
juice to make it more concentrated before shipping to reduce shipping costs. In a typical orange juice
processing plant, 20,000 kg of fresh juice containing 8.87% solids is being used per day. The processing
plant releases concentrated orange juice containing 45.8% solids.
An absorber is used to remove acetone from a nitrogen carrier gas. The feed, with an acetone weight
fraction of 0.213, enters at a rate of 200 kg/h. The absorbing liquid is water, which enters at a rate of
1000 kg/h. The exit gas stream is 0.800 wt% acetone and 2.90% water vapor. Determine the acetone
mass fraction in the bottom stream.
a. How much water is evaporated per day (in kg)?
The solubility of barium nitrate at 100°C is 34.0 g/100 g H2O and at 0°C is 5.00 g/100 g H2O. If you start
with 100 g of Ba(NO3)2 and make a saturated solution in water at 100°C, how much water is required?
If the saturated solution is cooled to 0°C, how much Ba(NO3)2 is precipitated out of the solution? The
precipitated crystals carry with them on their surface 4.00 g of H2O per 100 g of crystals.
b. How much concentrated juice is produced per day (in kg)?
2. Azolla spp., commonly called water ferns, are an excellent source of protein for poultry (chickens,
ducks, turkeys, etc.). The recommended way of serving Azolla to poultry is sun-drying it first before
feeding to reduce its moisture content. In a farm experiment, 65.8 kg of fresh Azolla with 86.2%
moisture content harvested from a pond was left to dry out in the sun for 4 hours. After drying, the
mass of the Azolla was determined to be 12.5 kg only. Assuming that only water was lost from the
Azolla, determine the following:
a. Amount of water lost during drying (in kg)
b. Final moisture content of the dried Azolla (in % by mass)
3. As an enterprising fellow during the outbreak of COVID-19, you decided to sell disinfecting alcohol
solutions. You are sourcing your raw material as concentrated aqueous ethanol solution (95.00%
ethanol) and diluting it with water to form a 65.00% ethanol solution. If you have a total of 5000 L of
the 95.00% ethanol (density of 0.8160 g/mL) on hand, how many liters of the 65.00% ethanol solution
(density of 0.8810 g/mL) can you produce? If you are packaging your product into 75.00 mL bottles,
how many bottles will you be able to sell?
4. 225 kg/h of a saturated sugar solution at 100°C containing 487.2 g of sucrose per 100 g of water is
cooled to 25°C to allow the formation of sugar crystals. If the sugar crystals are obtained with adhering
5.47 g HO per 100 g sugar crystals, determine the amount of sugar crystals formed (in kg/h) and the
amount of sugar left in the mother liquor after crystallization (in kg/h). The solubility of sucrose in
water at 25°C is 211.4 g/100 g water.
A single effect evaporator is fed with 10,000 kg/h of weak liquor containing 15% caustic by weight and
is concentrated to get thick liquor containing 40% by weight caustic (NaOH). Calculate:
a. kg/h of water evaporated, and;
b. kg/h of thick liquor obtained.
Strawberries contain abt. 15% solids and 85% water. To make strawberry jam crushed strawberries and
sugar are mixed in a 45:55 mass ratio, and the mixture is heated to evaporate water until the residue
contains one-third water.
a. How many kilograms of strawberries are needed to make a kilogram of jam?
b. How much H2O is evaporated in m3?
A triple-effect evaporator is fed with 1,000 lbs of a 5% salt solution to be concentrated to 40% solution.
If the amount of water evaporated from the first effect is 375 lbs and that from the second effect is 1.5
times that from the third effect. Calculate the following:
a. Water removed from the 2nd and 3rd effects.
b. Composition of salt solutions (%wt salt) leaving the 1st and 2nd effects
*4.1.1. You buy 100 kg of cucumbers that contain 99% water. A few days later they are found to be 98%
water. Is it true that the cucumbers now weigh only 50 kg?
*4.1.5 A multiple-stage evaporator concentrates a weak NaOH solution from 3% to 18% and processes
2 tons of feed solution per day. How much product is made per day? How much water is evaporated
per day?
Methanol is synthesized in a catalytic reactor using CO and H2. However, a side reaction is observed to
occur which leads to the formation of formaldehyde, HCHO, The fresh feed to the process contains 30%
mol CO, 60% mol H2, and 10% mol N₂. The combined feed stream to the reactor, containing 22% mol
N₂, consists of 4 mol recycle per mol of fresh feed. In the reactor, 9 moles of CH3OH is produced per
mole of HCHO. The reactor effluent gas goes to the condenser where two streams emerge: a gas
stream containing all CO, H₂, and N₂ and a liquid stream CH3OH and HCHO. The gas stream is split into
two fractions: one stream is purged and the other is combined with the fresh feed to the reactor.
a. What is the fraction of CO in the purge stream?
b. What is the single pass conversion with respect to CO?