Process Eng Design Pressure Vessel

First the total volume of gas that is to be stored needs to be calculated. From the mass balance it is known that 30.92 kmol of methane can be expected every hour. This correlates to 742.0 kmol/day. The ideal gas law will be used, with a compressibility factor, Z, to account for departure for un-idealality. An operating temperature of 50 ℃ will be assumed, as this is the highest feasible ambient temperature that can be expected. Also assume that the pump or compressor used to transport the methane from the flash vessel will not cause the methane to rise above this design temperature.

The expected surge pressure from of the 15 atm storage pressure is 16.5 atm. This will be taken as the operating pressure throughout the design. As Pop=∆P the actual pressure inside the vessel will be

PD=16.5 atm=1.67 MPaPOP=PD+1 atm=17.5 atm=1.77 MPa

The compressibility factor, Z, for methane at 17.5 atm and 50 ℃ is 0.979 from SOURCE.

The total volume of the daily quantity of methane at the specified conditions is calculated below.

V=ZnRTP

n=742.08 kmol

T=50 ℃=323 K

P=17.5 atm=1773.19 kPa

V24 hours methane=1100.25 m3

However the vessels must not fall below 0 gauge pressure inside, there must be at least one atm absolute pressure inside each vessel otherwise they will fail due to the difference in pressure. So total amount of storage needs to account for this. Assuming a linear relationship exists between pressure and volume at constant temperature 1 atm would correlate to one fifteenth of the volume, such that total volume required.

Vtotal=V24 hours methane+V24 hours methane15=1173.60 m3

Allowances for extra volume in=case of train delays etc will be made later in the design.

CHOICE OF END CAP

To avoid designing a shell and then having to make adjustments such that it fit a specific end cap the end cap was chosen first and the shell designed around it.

Sem-Ellipsoidal end caps were chosen as the operating pressure exceeds 15 bar (p28). Hot pressed caps will be...