Optimization & Fleshing Out the Design Optimizing for capital and/or operating costs More detailed look at specific equipment

Three Tasks as Examples Use an economic analysis to select number of trays in acetone column Do a detailed design of a heat exchanger to cool the product Look for opportunities to save energy Use model in “Costing Version.inp” on web

Documentation in “Optimization” Refining the Model Optimization of Distillation Column Design of Heat Exchangers Energy Minimization

Column Optimization Many trays but low reflux (steam) has a high capital cost but a low operating cost Few trays but high reflux has a low capital cost but a high operating cost We want to minimize capital cost + 3 times annual operating cost

Method 1. Select a number of trays 2. Determine optimum feed tray location 3. Collect data for that case 4. Repeat 1-3 by varying the number of trays, covering the range from minimum trays to minimum reflux 5. Cost 6 – 8 cases

Factors to Consider in Cost Only significant factors which change from case to case Equipment: column, condenser, reboiler Utilities: steam, cooling water

Sources of Information Text (e.g. steam costs) Rules of thumb in “Design & Costing => Rules of Thumb” or chapter 9 (e.g. heat transfer coefficient estimates) Documents in “Optimization” Equipment cost estimating program

Equipment Cost Estimator See “Tools and Concepts=>Equipment Costing Programs=>Estimator” Program is on CD and web (requires unzipping)

Starting the Task Trace the flow of information backwards What data does Estimator need? How can we calculate those parameters? What data is available from PRO/II? See Tray Hydraulics section of Column What else is needed? (Rules of Thumb)

Gilliland Correlation

Product Cooler Cool the product stream to 40°C, heat the cooling water to 40 to 45 °C Model as a separate piece of the flowsheet Use “Rigorous HX”, not “Simple HX” Change thermodynamics to estimate transport properties

PRO/II Input

Energy Reduction Identify streams that require heating Identify streams that require cooling Look for opportunities to reduce steam and cooling water consumption by using the two streams to heat and cool each other This can introduce operating or startup/shutdown problems

Saving Energy A B A B Water Steam A is hot, B is cold

Submission Put material in folder “Optimize” within your group folder by 2:15 PM on Nov 5 Include model(s) and spreadsheets Also a summary of what you did, why, any unusual findings (include data sheets for heat exchanger)

Contents of Report The engineer from our client is returning to review our progress since we did the preliminary model Our supervisor has asked us to prepare a summary of: What we have accomplished since then What we learned in working out the design Any issues of concern that have arisen

Contents of Report continued Our visitor has 10 minutes to read and digest the report before discussing it with us