Effect of Operating Decisions on the Design and Energy Consumption of Inverted Batch Distillation Column
Systematic methods and tools for managing the complexity
Process Simulation and Optimization (T4-9P)
Keywords: Inverted Batch Distillation, Design and Operation, Fixed Product Demand, Utility and Energy cost, Profitability
In inverted batch distillation column, the feed is introduced into the condenser and the product is collected from the bottom in increasing order of relative volatility. The light component remains in the condenser at the end of the process. This type of column is usually employed when the heavier components are thermally sensitive and cannot be exposed to high temperatures for a long period
In this paper, the effect of operating decisions on the design and energy consumption for inverted batch distillation is considered. In distillation utility cost is a function of column vapour load (V). We present a different type (as compared to what is available in the existing literature) of optimisation problem formulation and show that for a fixed market demand scenario minimisation of V for a given N will not only minimise the utility cost (cooling water + energy cost) and the capital cost but will also maximise the profitability of the operation. Also, with several examples of binary separation, it is shown that the decision of operating policy (such as constant reboil ratio, time dependent reboil ratio, etc.) at the design stage can have a significant impact on the capital and utility cost and overall profitability. This will in turn have significant effect on global warming as savings in utility cost reflects savings in energy cost. For difficult separations, which are capital and energy intensive, 40% savings in capital cost, 60% savings in utility and 70% improvement in profitability are possible if operating decisions are taken at the design stage.
