Simple equations to correlate theoretical stages and operating reflux in fractionators

Natural gas is an important source of primary energy. Virtually all gas processing plants producing natural gas liquids require at least one fractionator to produce a liquid product which can meet sales specifications. Fractionation is one of the pivotal unit operations in refineries, gas processing and other industries utilized to separate mixtures into individual products. However, it is capital and energy intensive and, with decreasing relative volatility, the size and energy requirements of a column tend to increase. The primary parameters involved in the design of fractionators are the number of stages and the reflux ratio. The aim of this study is to develop easy-to-use equations, which are simpler than current available models involving a large number of parameters and requiring more complicated and longer computations, for an appropriate prediction the operating reflux ratio for a given number of stages. Alternatively, for a given reflux ratio, number of stages can be determined. The accuracy of the proposed equations was tested and found to be in excellent agreement with the reported data for the wide range of conditions, wherein the average absolute deviation percent of proposed equations being 1.5%. These simple-to-use equations can be of immense practical value for the engineers. In particular, process engineers would find the proposed approach to be user friendly involving no complex expressions with transparent calculations.