Another cost to be considered is the substitution of the MEA in the traditional plant and the catalyst in the CLC one, even if this was evaluated not to have such a great impact in the final balance.
In order to calculate the cost for MEA substitution, it was necessary to extract the molar flow from ASPEN and suppose a residence time τ of about 180 seconds, in order to obtain the total quantity of MEA in the plant. Then, it was found in literature a reference price for MEA (1760 $/ton) [41], so it was easy to calculate the final cost for MEA, that resulted to be around 0,042 M$/year with the assumption that all the MEA in the plant is substituted each 3 months.
As far as catalyst substitution in CLC plant is concerned, the calculation is easier; as a matter of fact, ASPEN provides directly the total quantity of solid catalyst present in both CLC reactors. Thus, it was sufficient to multiply that value by the cost of NiO found in literature (15400 $/ton) [41], in order to obtain the final cost for catalyst substitution (4,27 M$/year), with the same assumption that all the material is replaced one time each three months.
After that, the cost of labour (CL) should be evaluated. The estimation is based on some general assumptions taken by Vergis [63], presented in table 23.
Working weeks per year per operator 49 N. of operating shifts per week per operator 5
N. of operating shifts per year per operator 245 N. of shifts per year 1095 Table 23: Starting assumption for CL calculation
At this point, the number of operating shifhts per shift NOLhas to be calculated by means of Alkhayat and Gerrard correlation [78], reported below:
NOL=p
6.29 + 31.7P2+ 0.23NM P (75)
where P is the number of steps that comprise handling, distribution and trasportation, solid matter control and removal, while NM P is the number of processing steps that comprise heating, cooling, compression, mixing and reaction, found in literature for SMR [63] and re-adapted for CLC. Once having this value, it is sufficient to multiply it for the number of total yearly shifts to obtain the total number of operating shifts per year. It is now sufficient to divide this last result for the number of operating shifts per year per operator, to obtain the number of operators yearly needed. Supposing an average yearly salary of 40000 $/operator, it it possible to calculate the cost of operating labour CL. All the results for both plants are summarized in table 24.
5.2 OPEX
TRAD CLC
P 4 5
NM P 6 6
N. of operating shifts per shift 23 28 N. of operating shifts per year 25185 30660
N. of operators per year 103 125 Average annual salary per operator ($/year) 40000 40000
Labour cost CL (M$/year) 4,1 5
Table 24: Final CL calculation
Moreover, there are several other parts that form the direct manufacturing costs, evaluated just as percentages of the labour or investment cost. The estimations were made by referring to Vergis [63], and involved the calculation of:
• Direct supervisory and clerical labour, that is the cost for engineering and amministrative support, and stands for about 18 % of CL;
• Maintenance and repair, that is the cost for maintenance labour, and stands for about 6 % of total cost of investment excluding the cost of land (FCIL);
• Operating supplies, that is the cost for additional staff required by operators (lubrificants, protective equipmente etc.), and stands for about 0.9 % of total cost of investment excluding the cost of land (FCIL);
• Operating supplies, that is the cost for additional staff required by operators (lubrificants, protective equipmente etc.), and stands for about 0.9 % of total cost of investment excluding the cost of land (FCIL);
• Laboratory Charges, that is the cost for continuous technological testing in lab-oratory, and stands for about 15 % of total cost of investment excluding the cost of land (FCIL);
• Patens, that is the cost for the use of patented inventions or technologies, and stands for about 3 % of total direct manufacturing costs.
So, in the end the direct manufacturing costs accounts for 140 M$/year for the tradi-tional plant and 187,5 M$/year for the CLC one. Details of their different contributions can be found in Appendix B, table 32.
On the other hand, manufacturing costs have also a fixed component that should be evaluated. This can be easily summarized in two main contributions:
• Plant overhead costs, that comprise all those operative costs associated with internal and external facilities, and stand for about 70,8 % of the CL plus 3,6 % of FCIL;
• Local taxes and insurance, that stand for about 3,2 % of FCIL.
88
So, the fixed manufacturing costs amount to 7,7 M$/year for the traditional plant and textbf11 M$/year for the CLC one.
Finally, the last contribution to the OPEX is represented by the so called “General Ex-penses”, that comprise the costs for:
• Administration, that stand for about 17,7 % of the CL plus 0,9 % of FCIL;
• Distribution and selling, that stand for about 1,1 % of total direct manufacturing costs;
• Research and development, that stand for about 5 % of total direct manufac-turing costs.
The general expenses result thus to be equal to 11 M$/year for the traditional plant and 14,9 M$/year for the CLC one.
Each contribution of fixed manufacturing costs and general expenses, for both plants, is reported in Appendix B, tables 33 and 34.
In last analysis, it was considered also the presence of the carbon tax, in an European location, for the traditional plant that is the only one that emits CO2 in the atmosphere.
Considering the data and the trends of the energy perspectives of IEA in 2016 [4], it was possible to extract an average value of carbon tax to be applied to the traditional plant, equal to 32,8 $/ton. Thus, by simply extracting the flowrate of CO2 leaving the plant and multiplying it for the annual operation hours, the total quantity of CO2 emitted can be calculated, and consequently the costs associated to carbon tax (6,93 M$/year).
In the end, the final OPEX was estimated to amount to 165,5 M$/year for the tradi-tional plant and 213,4 M$/year for the CLC one.