Читать книгу Process Intensification and Integration for Sustainable Design - Группа авторов - Страница 48

Figure 2.14 shows NGL prices over time are correlated. Therefore cases where the NGL product prices fluctuated together were considered (Table 2.12). Since for a normal distribution 99.7% of the values lie within 3 standard deviations of the mean, ±3 standard deviations were chosen for the cases (prices were not allowed to be negative). Since the main question is whether the process will be profitable or not, only the deviations in the direction that would make the process less profitable were examined.

Figure 2.14 Price of products over time [34].

Table 2.12 Description of cases for sensitivity analysis.

	Case 4	Case 5	Case 6
Heating value	Average	Average	Average
NGL prices	−1 Standard deviation	−2 Standard deviation	−3 Standard deviation

As can be seen in Figure 2.15, for even a drop of 1 standard deviation in NGL prices, the ROI value will become negative. This occurs because the standard deviations of the product prices are very high. An additional calculation shows that to achieve an ROI of more than 10%, product prices cannot drop more than 16.5%, assuming an average heating value price.

Figure 2.15 Results for Cases 4–6 for the sensitivity analysis.