Economic Analysis
An economic analysis of the optimized case was done focusing on the utilities cost as well as equipment cost. In the optimized case only the heat exchangers were manipulated leaving the rest of the plant unchanged with respect to equipment cost. The key factors in the pricing of heat exchangers are there areas, materials of construction and type of heat exchanger. A choice of carbon steel as the material of construction was made because the process is relatively free of corrosive materials. Floating head heat exchangers were used in the optimized case because phase changes occurred in all of the exchangers except for one. Through heat integration the total area of heat exchange was increased by the addition of one heat exchanger in the process. This one addition lead to increased equipment cost of $49, 000 over the base case as seen in the table below.
Base Case Bare Module Cost
Optimized Case Bare Module Cost
E-401
$17,452
$17,039
E-402
$21,869
$25,419
E-403
$17,305
$16,021
E-404
$23,017
$23,017
E-405
$25,535
$16,021
E-406
$26,284
$26,284
E-407
$37,088
$34,122
E-408
$2,117
$16,021
E-extra
-
$46,021
Total
$170,667
$219,965
Even though equipment cost were increased a significant decrease was achieved with respect to utilities cost. The use of heat integration allowed for the reduction of heat duties in several of the exchangers as well as the elimination for the need of process water and steam in some exchangers. Heat integration also enabled the duties of the exchangers requiring outside utilities to be lowered significantly. A utilities cost comparison of the base case and optimized case is displayed below.
Base Case Utilities (/yr)
Optimized Case Utilities (/yr)
E-401
$144,628
$122,038
E-402
$2,614
$1,428
E-403
$119,040
$14,786
E-404
$677,120
$677,120
E-405
$105,371
-
E-406
$2,899
$2,899
E-407
$72,124
-
E-408
$152
-
Total
$1,123,948
$818,271
Net Savings
$305,677
As seen in the above table net savings of $305, 000 were found for the optimized case over the base case. This turns into savings of $3.2 million over a plant life of twenty years. For a detailed cost listing of the base case and optimized case refer to the Appendix.
