TABLE OF CONTENTS In assessing the economics of a mass exchanger, two types of cost must be considered: fixed and operating. The fixed cost (investment) refers to the cost of the mass exchanger (e.g., shell, trays, etc.), ancillary devices (e.g., pump, compressor), installation, insulation, instrumentation, electric work, piping, engineering work, and construction. Fixed capital investments are characterized by the fact that they have to be replaced after a number of years commonly referred to as service life or useful life period because of wear and tear or by virtue of becoming obsolete or inefficient. Therefore, it is useful to evaluate an annual cost associated with the capital investment of the mass exchanger, referred to as the annualized fixed cost AFC . A simplified method for evaluating AFC is to consider the initial fixed cost of the equipment (FC o) and its salvage value (FC s) after n years of useful life period. Using an annual depreciation scheme, we get
In addition to the fixed capital investment needed to purchase and install the mass exchange system and auxiliaries, there is a continuous expenditure referred to as operating cost which is needed to operate the mass exchanger. The operating cost includes mass separating agents (makeup, regeneration, etc.) and utilities (heating, cooling, etc.).
By combining the fixed and operating costs, we get the total annualized cost (TAC) of a mass exchange system:
In order to minimize TAC, it is necessary to trade off the fixed...
