Universiti Tunku Abdul RahmanFaculty of Engineering and Green Technology

Petrochemical EngineeringMay 2013 Trimester, Academic Year 2013/2014

UGPA1193 Mass and Energy BalanceTutorial 5

Energy Balance on Non−Reactive Processes

1. Use Hess’s law to calculate the standard heat of the water gas shift reaction CO(g) + H2O (v) −−> CO2(g) + H2(g)

from each of the two sets of data given here.

(a) CO(g) + H2O(l) −−> CO2(g) + H2(g) :

H2O(l) −−> H2O(v) :

(b) CO(g) + ½ O2(g) −−> CO2(g) :

H2(g) + ½ O2(g) −−> H2O(v) :

2. One kg of water at 28oC is left in an open vessel. Calculate how much heat is needed for complete evaporation of the water (at 28oC).

3. Calculate the minimum amount of heat needed to boil 1 kg of the water in an open vessel into steam if the water is initially at 28oC.

4. The gas leaving a combustion chamber has the following composition: Percent (by mole)

CO2 7.8CO 0.6O2 3.4H2O 15.6N2 72.6

Calculate the heat removed if the gas is cooled from 800 to 200oC.

5. Acetone is obtained as the top product stream in a distillation unit. This pure stream of acetone, at a flow rate of 1111 kg/h and 1.0 atm, is condensed from 100oC to 25oC by means of heat exchange with circulating cooling water. The cooling water is available at 25oC and exits the condenser at 65oC. Determine the flowrate(kg/h) of cooling water required.

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6. Three hundred kilograms per hour of air flow through a countercurrent heat exchanger as shown in Figure P24.33. Two hundred thirty kilograms per hour of potassium carbonate solution are heated by the air. Assume that the heat exchanger has negligible heat losses. The terminal temperatures are given in Figure P24.33. Calculate the temperature of the exit potassium carbonate stream. Assume that the heat capacity of the potassium carbonate solution is the same as that of the water in the solution.

7. Determine the enthalpy change when one gram mole of SO2 gas is cooled from 538 oC to −101oC at one atmospheric pressure. Data:

Boiling point : -5oCMelting point : -75.5oCLatent heat of vaporization : 24940 J/gmolLatent heat of fusion : 7401 J/gmolUse the average Cp of liquid SO2 as : 1.28 J/(gmol.oC)Use the average Cp of solid SO2 as : 0.958 J/(gmoloC)Use the Cp of gaseous SO2 from Table B.2.

8. An air stream at 32oC is to be used in a dryer and is first preheated in a steam heater, where it is heated to 70oC. The air flow is 1000 kgmol/h. The steam enters the heater saturated at 150oC, gets condensed and leaves as a liquid at 140oC. Calculate the amount of steam used in kg/h.

9. In a distillation unit, acetone is separated from toluene and obtained as the top product. This gaseous product stream can be assumed as pure acetone at 120oC and 1 atm. It flows at a flow rate of 16100 m3/h into a condenser, in which 80% of the acetone is liquefied. Determine the heat removal rate required of this condenser to achieve the desired cooling.

Tut 51)(a)(i) -41.15 kJ/mol(ii) -41.15 kJ/mol

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127oC300 kg/h air227oC

T=?230 kg/h2.5 % K2CO3

97.5 % H2O

Figure P24.33

Heat Exchanger

27oC

2)2435.4 kJ/kg3)2558 kJ/kg4)20.3492 kJ/mol feed gas5)4346 kg/h6)59 deg C7)-57.8024 kJ8)513.68 kg/h9)787.88 kW

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