15. Pinch analysis with data extraction (15 points) The process flowsheet for a cellulose acetate fibers process is shown in the figure below. Solvent is removed from the fibers in a dryer by recirculating air. The air is cooled before it enters an absorber where the solvent is absorbed in water. The solvent-water mixture is separated in a distillation column and the water recycled. The process is serviced by saturated steam at 150C, cooling water at 20C and refrigerant at -5C. 80C 100C Air CP= 80 Dryer Steam 20C Water CP= 140 10C 5C 60C CP = 5,000 CW Fan CW, Refrigeration 30C 30C 59C Absorption Column 30C Distillation Column 90C Solvent CP= 5 Refrigeration CW 101C Air/Solvent CP= 100 15C 100C 100C CP= 6,500 CP= kW.K- Steam Water/Solvent CP= 145 (a) Extract the stream data from the flowsheet and present them as hot and cold streams with supply and target temperatures and heat capacity flowrates. Note: a stream passing through multiple heat exchangers in series should be considered as one stream, i.e. the intermediate temperatures can be ignored. For example, the dryer outlet at 80C is first cooled by cooling water to 30C, and then by refrigeration to 15C. This stream is considered as one hot stream with a supply temperature of 80C and target temperature of 15C. (b) Sketch the composite curves for the process for AT min = 20C. (c) Determine the pinch temperature and the minimum cooling and heating utilities. (d) What is the maximum heat recovery (process-to-process heat transfer) that can be achieved at AT min = 20C? (e) Suggest two simple heat integration ideas and calculate how much heat recovery can be achieved by implementing both ideas, with AT min = 20. Sketch the modified process flowsheet. =