For each of the 5 filtration pressures ranging from 10 to 60 kPa shown in Fig。 7, an optimized cycle time and a minimized dewater- ing cost can be determined。 Plotting these minimized dewatering costs and the optimized cycle times with respect to the corre- sponding filtration pressure helps identify the optimum operating conditions and the minimum dewatering cost。 As shown in Fig。 8, the minimum dewatering cost of 0。93 US$/h can be achieved by operating the filter at the filtration pressure of 20 kPa, and at the rotation cycle of 40 s。
A contours plot for dewatering cost levels covering a wide range of the operating conditions and the major range of the simulated dewatering cost from 0。93 to 1。30 US$/h are shown in Fig。 9。
Two cost-sensitive areas A and B were found in the domain of operating conditions。 Operating the filter in area A comes with great energy expense from the greater rotational resistance experi- enced by the filter。 While operating the filter in area B, with a low filtration driving force, much more capital investment for the pro- cessing is required, rendering the dewatering process less cost- effective。 In view of these considerations, the filter should operate with at least 10 kPa of filtration pressure, and with a rotation cycle upwards of 20 s。
This identified cost-sensitivity is also valuable for offering bet- ter control over the operating variables。 For such dewatering pro- cesses, it is very difficult to maintain the operating conditions such as the vacuum pressure completely constant。 Normally, the pressure would fluctuate in the process within control tolerance。 Fig。 9。 suggests that a positive deviation relative to the optimum operating conditions (p > popt。 in the pressure, and T > Topt。 in the cycle time) would incur less increase in dewatering cost。 A more favorable control scheme can be formulated with this cost- sensitivity understanding。
Table 3
A report of process techno-economics。
Item Amount Unit
Feed 100 m3/d
Algae conc。 20 w/w%
Capital investment 54。73 kUS$
Equipment 23。69 kUS$
Installation 14。21 kUS$
Infrastructure 11。85 kUS$
Project life-span 20 yr
Capital depreciation 2。74 kUS$/yr
Power 5。59 kW
Energy consumption 176。3 GJ/yr
Energy cost 2。45 kUS$/yr
Labor 3。0 kUS$/yr
Maintenance 0。25 kUS$/yr
Annual dewatering cost 8。23 kUS$/yr
5。6。 Techno-economics of the algae-dewatering
The list of optimal parameters arrived at through techno-eco- nomic evaluation of the algae-dewatering process are summarized in Table 3。 For processing 100 m3 of algae feed daily, the total cap- ital investment for the project is 54。73 kUS$ with a process life- span of 20 years, and the annual capital depreciation is 转鼓真空过滤机英文文献和中文翻译(10):http://www.youerw.com/fanyi/lunwen_83220.html