Economics annual variable costs

The scope of the economic evaluation includes estimation of capital cost figures for a nitric add plant producing 280 tonnes/day of a 60% product. Following this capital cost estimation the total annual operating costs are estimated, both variable and fixed components being considered. Also considered is the cost of providing finance for the initial capital outlay at 25% interest per annum. 

Power plants to burn scrap tires involve large capital investments and annual operating expenses. However, plants located near large supplies of tires can be feasible. A key variable in determining economic feasibility for these plants is the buy-back rate granted by the utility. In areas of the country where the rate is high, such as California and the northeast, power plants are feasible. The buy-back rate is the rate the utilities pay for electricity generated from alternative fuel, and reflects the fuel and other costs avoided by the utility. 

The basis and various parameters for the economic analysis are given in Table II. The overall column efficiency used was obtained from a plot of efficiency vs. the product of relative volatility and liquid viscosity (9), corrected to match predicted (10) data for the propane-propylene system. The value from the plot (9) was increased by a factor required to make the efficiency of the propane-propylene binary distillation equal to 100%. Costs were calculated by the Venture Analysis method (II), because this method yields the appropriate weighting factors for the fixed and operating costs in order to calculate the total costs. Results are expressed as annual costs, before taxes. The important process variables are discussed below. 

As with many therapeutic decisions, economic cost both to the individual and to society mnst be considered. Currently, the annual cost of the new potentially disease-modifying therapies is considerable. The cost to the pharmacist of glatiramer and both currently available interferons is between 10,000 and 17,000 per patient per year. Given this expense, it must be remembered that these therapies are not curative and that individual patients may experience variable results. Future investigations evaluating these therapeutic modahties clearly will need to address not only chnical but also economic and humanistic outcomes. 

The economic optimal process flowsheet was obtained by minimization of the total annual cost (TAG) with five design variables IPA distillate composition (XD2) in the recovery column, total number of stages for the heterogeneous azeotropic column and the recovery column (Ni and N2), and the two feed stages (Api and Apa). The product specification of IPA is set to be ultrapure (99.9999 mol%) to be used in the semi-conductor industry. The product specification of water is set to be 99.9 mol%. In each simulation run, the IPA product specification is achieved by varying the reboiler duty of the heterogeneous azeotropic column, and the water product specification is achieved by varying the reboiler duty of the recovery column. The entrainer makeup flowrate will be very small to balance the entrainer loss from the two bottom streams. 

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