Q1. Sodium sulphate decahydrate crystals (NazS04.10H2O), DH are produced in a continuous vacuum crystallizer. Concentrated sodium sulphate solution from an evaporation system with a flow rate of 2000 kg/h at 80°C and 1 atm is mixed with 4000 kg/h of a saturated aqueous recycle filtrate of sodium sulphate solution at 20°C and 1 atm. The mixture is sent to the vacuum crystallizer, operating at 20°C and 50 mmHg, to produce water vapor and magma of 25 wt% crystals and 75 wt% saturated solution. The magma is then sent to a filter, from which filtrate is recycled. a) Draw a block diagram of the process. b) Define the streams and units in the block diagram. c) Mark the streams on temperature versus concentration diagram and enthalpy concentration diagram. Determine:

Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
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Q1. Sodium sulphate decahydrate crystals (NażSO4.10H2O), DH are produced in a
continuous vacuum crystallizer. Concentrated sodium sulphate solution from an evaporation
system with a flow rate of 2000 kg/h at 80°C and 1 atm is mixed with 4000 kg/h of a saturated
aqueous recycle filtrate of sodium sulphate solution at 20°C and 1 atm. The mixture is sent to
the vacuum crystallizer, operating at 20°C and 50 mmHg, to produce water vapor and magma
of 25 wt% crystals and 75 wt% saturated solution. The magma is then sent to a filter, from
which filtrate is recycled.
a) Draw a block diagram of the process.
b) Define the streams and units in the block diagram.
c) Mark the streams on temperature versus concentration diagram and enthalpy
concentration diagram.
Determine:
d) crystal production rate (on a dry basis).
e) evaporation rate of water in vacuum crystallizer.
f) the energy required in vacuum crystallizer.
120
100
80
60
Na, so, + solution
solution
40
20
Na, so, 10H,O + solution
4
-20
0.1
0.2
0.3
0.4
0.5
0.6
Concentration of Na, SO,, kg Na,SO /kg solution
4"
Figure Q1-a. Solubility curve of sodium
sulfate in water.
Temperature, °c
Transcribed Image Text:QUESTIONS Q1. Sodium sulphate decahydrate crystals (NażSO4.10H2O), DH are produced in a continuous vacuum crystallizer. Concentrated sodium sulphate solution from an evaporation system with a flow rate of 2000 kg/h at 80°C and 1 atm is mixed with 4000 kg/h of a saturated aqueous recycle filtrate of sodium sulphate solution at 20°C and 1 atm. The mixture is sent to the vacuum crystallizer, operating at 20°C and 50 mmHg, to produce water vapor and magma of 25 wt% crystals and 75 wt% saturated solution. The magma is then sent to a filter, from which filtrate is recycled. a) Draw a block diagram of the process. b) Define the streams and units in the block diagram. c) Mark the streams on temperature versus concentration diagram and enthalpy concentration diagram. Determine: d) crystal production rate (on a dry basis). e) evaporation rate of water in vacuum crystallizer. f) the energy required in vacuum crystallizer. 120 100 80 60 Na, so, + solution solution 40 20 Na, so, 10H,O + solution 4 -20 0.1 0.2 0.3 0.4 0.5 0.6 Concentration of Na, SO,, kg Na,SO /kg solution 4" Figure Q1-a. Solubility curve of sodium sulfate in water. Temperature, °c
400
100°C
90
101.7°C
100
101.7
30070
80
50 solution
200
60 NazSO4 + solution
30
40
100-20
10
32.4°C
Na2 SOa 10 H20
solution
Na2 S04
+
25°C
Naz So4-1OH20
15
+
-100
-1.2°C
solution
Naz SO4 IOH20
+
-200
solution
+
ice
-300H
03H01.*os?ON
Naz SO¿IOH20 Noz sO4
ice
Na,so; 10H,0
-400!
0.2
0.3
0.4
0.5
0.6
Concentration-weight fraction of Na,SO,
Figure Q1-b. Enthalpy concentration diagram of sodium sulfate in water.
Enthalpy, kJ/kg of solution
Transcribed Image Text:400 100°C 90 101.7°C 100 101.7 30070 80 50 solution 200 60 NazSO4 + solution 30 40 100-20 10 32.4°C Na2 SOa 10 H20 solution Na2 S04 + 25°C Naz So4-1OH20 15 + -100 -1.2°C solution Naz SO4 IOH20 + -200 solution + ice -300H 03H01.*os?ON Naz SO¿IOH20 Noz sO4 ice Na,so; 10H,0 -400! 0.2 0.3 0.4 0.5 0.6 Concentration-weight fraction of Na,SO, Figure Q1-b. Enthalpy concentration diagram of sodium sulfate in water. Enthalpy, kJ/kg of solution
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