Heat Exchanger Network

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Heat Exchanger Network Design for the Cumene Process|
C.A.K.E. Because We’re Just that Delicious Iowa State University Ames IA, 50010| Crego, Courtney LHines, KirkMonterrubio, AmyToohey, Erin|

Abstract

Often a major consideration of a chemical process plant is the high cost of utilities used for heating and cooling of process streams. Heat integration of process streams is an effective way to reduce the cost of these utilities, and this process is often referred to as a MUMNE (minimum utility, and minimum number of exchangers) network. In this report three separate heat exchange designs were examined to find the best design in terms of cost. Each design used a different amount of heat integration for the same process streams. Case A used no integration, Case B used all the streams for integration, and Case C only used cold streams 1 and 2, and hot streams 1, 2, 3, and 5 to obtain the same end temperatures for each of the streams given. The specified minimum approach temperature was 15°C. For each of the three cases, a heat exchange network was designed according to the criteria given in the specified case. Case A included no heat integration and the sizing parameters and cost analysis were done only using utilities. For Case B and Case C, a pinch analysis was performed to properly integrate the process streams. Once the pinch analysis was completed, temperature interval diagrams were drawn on Excel spreadsheets in order to map out the MUMNE network. A HENSAD simulation was a possible computer oriented approach to the design, but the team opted to use other resources instead. The cost analysis of the three cases was done using the Excel CAPCOST program. This program gave totals for the total capital cost, and total annual utilities cost for each of the three cases. These costs were used to calculate the EAOC (equivalent annual operation cost) using i =5%, and n = 7 years. The EAOC results were Case A ($2,976,213 per year), Case B ($1,194,728 per year), and Case C ($1,561,503 per year). If the only consideration is cost, the Case B would be the recommended design. However, other considerations such as controllability should be taken into account, which results in a recommendation of Case C.

Table of Contents
Abstract1
Introduction3
Calculations4
Pinch Theory4
Pinch Methodology4
1.Choose a Minimum Approach Temperature5
2.Construct a Temperature Interval Diagram5
3.Construct a Cascade Diagram6
4.Calculate the Minimum Number of Heat Exchangers Above/Below6
5.Construct the Heat-exchanger Network7
Heuristics8
Heat Exchanger Sizing9
Area Calculation9
Shell Calculation10
HENSAD Simulation11
Material of Construction11
Cost Analysis12
Sample Calculations12
Results14
Zone Analysis14
Case Specifications15
Case A15
Case B17
Case C18
MUMNE Networks19
Utility Summary20
Economic Analysis21
Discussion21
Cost Comparison21
Controllability22
Quality and Safety Considerations22
Conclusions and Recommendations23
References24
Appendix A- Temperature Interval Diagrams25

Introduction
As oil prices continue to climb, energy conservation is one of the main focuses in many process industries. Companies look for ways to reduce operation costs that do not hurt profit margins or compromise the quality of the product. Rising utility costs are one of the main costs that affect profit margins. As utilities rise, implementing energy efficient solutions becomes increasingly important [1]. Heat integration is one of the main areas where costs can be cut. All streams involved in a process that have a heating or cooling aspect to them require some energy duty. When the required energy duty is not fulfilled by other streams, utilities must be put in place in order to achieve the desired temperatures. Heat integration focuses on cascading the energy down through the system in order to decrease the quantity of...
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