DESIGN OF BATCH PROCESSES. USING PINCH TECHNOLOGY

Abstract

Both the academic and industrial communities are urged to deliver cleaner, more energy efficient solutions which are ecologically and economically sound and therefore, have the potential to contribute to sustainability of our societies. In this scenario the challenge faced by every process engineer is to maximize the process to process heat recovery and to minimize the utility (energy) requirements. Energy saving in process plant design has essentially been a trial-and-error procedure between changes in structure and its outcome until satisfactory reductions are achieved. As far as continuous process is concerned, maximum energy recovery between two processes stream can be achieved without a great deal of difficulty. But problem lies in batch process due to time factor complexity as in this case (batch) streams are not coinciding in a particular time interval. In this study an attempt is being made to meet the goal of maximum energy recovery or minimum energy requirement for batch process through the application of a modem tool known as pinch technology. Here, this methodology is applied for batch process to calculate the heat utility for each stream separately with considering the time effect through four different approaches i.e. Time Average Model (TAM), Time Slice Model (TSM) and Time- Temperature Cascade approach with heat storage both in single and repeated batch. The result obtained from various approach can be summarized as: No single approach can be adopted for the design of hatch process for all circumstances as all the four proposed approaches have their own pros and cons. TAM gives best-case idealized targets with the maximum possible heat recovery, but the approach is overoptimistic due to pseudo continuous nature. From the results obtained, it can be envisaged that in terms of quantity of heat recovery, Time- Temperature Cascade with heat storage in repeated batch should be the best option available next to TAM for designing purpose. But many more research investigations are needed in the field for developing heat storage units before transforming the approach economically feasible for industrial purpose. These in turns left only two options i.e. TSM and Time- Temperature Cascade approach with heat storage in single batch to identifying the opportunity for ii energy saving in batch process. From the discussion, it has been found that, a significant amount of energy saving can be achieved with the TSM approach by rescheduling the streams without compromising the plant flexibility. As far as Time- Temperature Cascade approach with heat storage in single batch is concerned, it should be considered only next to TSM and that's when the capital gain from energy saving is more than the investment on heat storage units. In addition, as the calculation part deal with various approaches are too lengthy and error prone, computer aided program has been developed on MATLAB platform to analyze complicated industrial batch purpose. The complete approach i.e. batch process design through pinch technology method has been demonstrated with the help of three sample problems (includes one solved problem and two unsolved) and two industrial case studies. iii