Design Options for Recovery of Acetic Acid from Aqueous Solution
The project involves the comparison of two methods for recovery of acetic acid from an aqueous solution. Your client is planning to add additional acetic acid production capacity of 2500 kg/h acetic acid (based on unpurified reactor product). The raw product from the reactor will be 80%wt acetic acid and 20%wt water. You will analyze two purification process options to recover 95% of the raw acetic acid at a purity of 97%wt.
The first option to be explored for recovery of purified acetic acid will be a simple binary distillation process. You should consider a staged column for this operation. You should first determine the required number of ideal stages and the feed stage location by using the McCabe Thiele diagram approach. You should assume that your feed of composition 80%wt acetic acid and 20%wt water enters the column as a saturated liquid. Since the acetic acid - water system does not meet the criteria for constant molar overflow; there will be significant error in this approach. Table 1 provides VLE data for the acetic acid - water system. After evaluating this option using the McCabe Thiele approach, you should develop a CHEMCAD simulation for the same separation.
The second option is to use liquid - liquid extraction with isopropyl ether to separate the acetic acid from the water followed by distillation to recover the purified acetic acid product. This process is likely to require multiple distillation columns. You should first determine the required number of ideal extraction stages by using the McCabe Thiele diagram approach for extraction. LLE data for the acetic acid - water - isopropyl ether system is provided in Table 2. Since both streams exiting the extraction column will contain three components it is not practical to analyze the distillation using the McCabe Thiele diagram approach. Therefore you should develop a second CHEMCAD simulation to analyze the combined extraction plus distillation process.
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Table 1
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Table 2
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Water-Acetic Acid VLE
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Acetic Acid - Water - Isopropyl Ether System
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At 760 mmHg pressure
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Liquid - Liquid Equilibria at 293 K (20 OC)
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xW
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yW
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Acetic
Acid
(raffinate)
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Water
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Isopropyl
Ether
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Acetic
Acid
(extracted)
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Water
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Isopropyl
Ether
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0.053
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0.1333
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0.125
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0.24
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0
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98.8
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1.2
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0
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0.6
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99.4
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0.206
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0.338
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0.69
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98.1
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1.2
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0.18
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0.5
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99.3
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0.297
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0.437
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1.41
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97.1
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1.5
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0.37
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0.7
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98.9
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0.394
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0.533
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2.89
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95.5
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1.6
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0.79
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0.8
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98.4
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0.51
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0.63
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6.42
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91.7
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1.9
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1.93
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1
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97.1
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0.649
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0.751
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13.3
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84.4
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2.3
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4.82
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1.9
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93.3
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0.803
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0.866
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25.5
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71.1
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3.4
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11.4
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3.9
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84.7
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0.9594
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0.9725
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36.7
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58.9
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4.4
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21.6
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6.9
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71.5
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44.3
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45.1
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10.6
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31.1
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10.8
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58.1
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46.4
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37.1
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16.5
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36.2
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15.1
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48.7
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This should include a memo discussing the results and how they were obtained along with paper copies of relevant calculations, spreadsheet pages, and CHEMCAD simulations.
Your report should include a written comparison of the two alternatives for purification of the acetic acid. Consider if the added complexity of the extraction plus distillation alternative is offset by other factors. You should also consider cost, energy usage, safety and environmental factors.