32650 t/h and at the same time there are 1413.19 kmol/h ... if you devide the mass with the mol you get the average molar mass . but how could it be like 23103,758 g/mol

But it don't matter. if you have 1413.19 kmols with the volume of 2046.9m^3 and expand it from 12.8 bar to 5.88bar you get 3706.24m^3 if you have a heat capacity ratio of 4/3 . Then you get the temperature of -87.51°C (wolfram alpha gave me -90°C ) ... ideal gases!!

thanks dude for the effort you done, i really appreciate it

but, i would like to ask you from where you obtain the volume of the stream, did obtain this figure from the relation of mass flow rate and the density??!!, because i tried to calculate it and it was showing 1945.74 m^3. also from where you get the volume of the stream after dropping the pressure to 5.88. and the last question is based on what you are chosing the heat capacity.

i'll be so glad if you answer my question.