4.3. Quantification of model performance
Since it is necessary to quantify the performance of the HRD model, the simulation results, product distribution, for the reaction step are compared with experimental data by using the root mean square error (RMSE), mean square error (MSE) and absolute fraction of variance (R2). The comparison between the simulation results and experimental results is shown in the following section.
4.4. Economic analysis
Free-on-board (f.o.b.) purchased equipment costs for major equipment in the process were calculated based on mass and energy balance information [31]. The cost of distillation columns was estimated by using Aspen Icarus®. These equipment costs were calculated based on the years 2002 [31] and 2012. The Chemical Engineering Plant Cost Index (CEPCI) was used to update the equipment costs to the year 2013, as in Equation (17)[32]:
equation(17)
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where I is Chemical Engineering cost index (CE index) in the year 2013 (567.6) [35], and I0 is CE index in the year 2002 (394) or 2012 (571.19), as required [35]. Fixed capital investment (FCI), working capital (WC) and total capital investment (TCI) were estimated by using the study estimate and preliminary method based on the delivered-equipment cost [32]. The accuracy of the estimation is in the range of ±20% to ±30%. Key assumptions and variables in the operating cost used to develop the techno-economic analysis are given in Table 8 and Table 9, respectively. From the assumptions stated previously, the profitability of this process was determined based on discounted techniques. Rate of return on investment (ROI) is the yearly profit of an investment divided by the cost of the investment. Payback period (PBP) is the time required to recover the cost of an investment. Net present value (NPV) is used for analyzing the profitability of a project investment with the minimum rate of return (MARR), and it is calculated from the difference of the present value of the net cash inflows and cash outflows.