化学工艺最优化方法.ppt

3.3 Measure of Profitability PBP (Payback years): Take an integrated view of profits over a period of several years. The PBP is one criterion and defined as: Note that no weighting of earlier cash flows and later cash flows; No consideration of project earning after the initial investment has been recovered. No assumptions regarding equipment life. 3.3 Measure of Profitability ROI（return on investment，投资回报率）: relative profit criterion divided the investment NPV (net present value，净现值) Ignore taxes and computer a before-tax cash flow 3.3 Measure of Profitability Fj: each year cash flow; i: the stated interest rate for capital; I0: the initial investment. Let NPV=0, solve the above equation to find i, which is IRR内部收益率. 3.3 Measure of Profitability Example 3.5 Payout period of A=100,000/20,000=5year Payout period of B=100,000/15,000=6.67year Example 3.5 Applying Eq.(3.12) for NPV=0 and n=10, we find that the IRR for A is 10%, B is 8%. For i=0.1,NPV of A is -$640, NPA of B is -$7840. 3.4 Opt. Profitability（盈利能力最优化） In order to do the job, you first need to determine the independent variables which influence: （1）Capital investment; （2）Income; （3）Operating costs; （4）Cash flow Assuming there are p independent variables, denote (1) as I(x1,x2,….xp) and the cash flow F(x1,x2,….xp) is obtain from (1),(2),(3) 3.4 Opt. Profitability Define the specific profitability measure, such as payback time PBP, return on investment ROI (投资回报率）, net present value NPV, or internal rate of return IRR (内部收益率）. The first three objective functions are explicit functions（显函数） of F and I; while IRR is an implicit functions （隐函数） of F and I; once F and I are specified, an iterative solution must be used to find i. In order to maximize the IRR, you must vary the independent unknowns and computer I and F for each trial set of (x1,x2,….xp). Next solve equation for i and continue the procedure until you find the value of x which maximizes the IRR. 3.4 Opt. Profitability 3.4 Opt. Profitabilit