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a) A feed stream entering into a flash vessel at 50C and 10 bar contains 17.3wt% propane, 22.7wt% iso-butane, 38.5wt% propylene and 21.5wt% benzene. The mass flow rate of the feed is 833.0kg/hr. Inside the flash vessel the pressure suddenly drops causing the liquid to separate into two streams, a vapour and liquid stream. The liquid stream has a composition of 14.8wt% propane, 25.2wt% iso-butane, 30.8wt% propylene and 29.2wt% benzene. While the composition of the vapour stream is not fully known, it is known that the stream contains 24.1 wt\% propane. Note: Assume i) there is no accumulation of material within the flash vessel; ii) no chemical reactions occur within the flash vessel. (i) Is the process continuous or batch? Justify your reaoning. [2 marks] (ii) Draw a block flow diagram of the described process and label all known streams. [6 marks] (iii) Using the known stream values, calculate the complete composition of the vapour stream. [12 marks] (iv) Redraw the block flow diagram (as in (ii)) as a process flow diagram (PFD) and include two feedback loops to control the liquid level and pressure in the flash vessel