Section outline

  • Material balance calculations to chemical processes involving no chemical reaction - blending, mixing to get the required composition, humidification - relative humidity, drying, evaporation, crystallization, unsteady mass balance.

    • Checklist
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    • Questions - Material Balance without Reaction Book
    • Short Questions - Material Balance without Reaction Book
    • Blending of Two Liquid Streams Page
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    • Weight Loss due to Breathing Page
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    • Preparation of Mixed Acid Page
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      For carrying out a nitration reaction, it is desired to have a mixed acid containing 39% HNO3, 42% H2SO4 and 19% H2O (by weight). Nitric acid of 68.3% (weight) is readily available (azeotropic composition). Calculate: (a) the required strength of sulphuric acid to obtain the above mixed acid, and (b) the weight ratio of nitric acid to sulphuric acid to be mixed. 

    • Mixed Fertilizer Formulation Page
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    • Preparation of Sulfuric Acid Solution Page
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    • Removal of Water by Bubbling Air Page
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    • Removal of Hexane from Gas by Condensation Page

      A gas mixture containing 85.0 mole% N and the balance -hexane flows through a pipe at a rate of 100.0 m3/h. The pressure is 2.00 atm absolute and the temperature is 100oC. 

      1. What is the molar flow rate of the gas in kmol/h?
      2. Is the gas saturated? If not, to what temperature (oC) would it have to be cooled at constant pressure in order to begin condensing hexane?
      3. To what temperature (oC) would the gas have to be cooled at constant pressure in order to condense 80% of the hexane?

      For hexane, vapor pressure (\(P^{\text{sat}}\)) is given by \[ \log_{10}P^{\text{sat}} = 6.88555 - \frac{1175.817}{T+224.867}\] where \(P^{\text{sat}}\) is in mm Hg; and, \(T\) in oC.

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    • Loss of Octane due to Vaporization Page

      A storage tank for liquid n-octane has a diameter of 30 ft and a height of 20 ft. During a typical 24-h period the level of liquid octane falls from 18 ft to 8 ft, after which fresh octane is pumped into the tank to return the level to 18 ft. As the level in the tank falls, nitrogen is fed into the free space to maintain the pressure at 16 psia; when the tank is being filled, the pressure is maintained at 16 psia by discharging gas from the vapor space to the environment. The nitrogen in the tank may be considered saturated with octane vapor at all times. The average temperature is 90oF. Density of liquid octane is 703 kg/m3. Vapor pressure of octane at 90oF = 20.74 mm Hg.

      1. What is the daily rate, in m3 and lb at which which octane is used? ______ m3 (round off to 1 decimal place); ______ lb (round off to 1 decimal place)

      2. What is the variation in absolute pressure at the bottom of the tank in inches of mercury? _______ (round off to 1 decimal place)

      3. How much octane, in kg is lost to the environment during a 24-h period? ______ (round off to 1 decimal place)

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    • Drying of CaCO3 Slurry Page
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    • Condensation of Moisture from Compressed Air Page
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    • Condensation of Moisture in Air-Conditioning Process Page
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      On a hot summer day the temperature is 35oC, barometric pressure is 103 kPa, and the relative humidity is 90%. An air conditioner draws in outside air, cools it to 20oC, and delivers it at a rate of 12,500 L/h. Calculate the rate of moisture condensation ________ kg/h (round off to 3 decimal places), and the volumetric flow rate of the air drawn from the outside ________ L/h (round off to the nearest integer).
      Vapor pressure of water at 20oC = 17.535 mm Hg; at 35oC = 42.175 mm Hg

    • Adsorber for Moisture Removal Page

      Wet air containing 4.0 mol% water vapor is passed through a column of calcium chloride pellets. The pellets adsorb 97.0% of the water and none of the other constituents of the air. The column packing was initially dry and had a mass of 3.40 kg. Following 5 hours of operation, the pellets are reweighed and found to have a mass of 3.54 kg. Calculate the molar flow rate (mol/h) of the feed gas, and the mole percentage of water vapor in the product gas.

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    • Bypass for RO Page
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    • Evaporation of Spent Lye Page

      A spent lye sample obtained from soap-making unit contains 9.6% glycerol and 10.3% salt (NaCl). It is concentrated at the rate of 5000 kg/h in a double-effect evaporator until the final solution contains 80% glycerol and 6% salt. Assume that about 4.5% glycerol is lost by entrainment. Find: (a) the amount of water vaporized _____ kg/h , and (b) the amount of salt crystallized in the salt box of the evaporator _____ kg/h. All percentages are by weight.

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    • Capacity of Evaporator Page
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    • Solute Dissolution in Solvent Page
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    • Preparation of Saturated MnSO4 Solution Page
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    • Crystallization of Na2SO4 Page
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    • Unsteady Mass Balance - Salt Dissolution Page
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