Download Amine Acid and Sour Gas Plant Experiences

Thank you.

Hello! Every one.

We have assigned sour water stripping system as our design project and we are compelled to show manual calculations at each and every step.

For material balance on the entire process scheme we need flash calculations on the 3_phase separator to find the composition and flow rates of the outlet streams and before flash calculations a basic conditions must be satisfied  that is the existing pressure must be between dew point and bubble point pressure. (Mathematically Pdew < P< Pbubble ) but in our case the given pressure (ie: 5 psig = 19.7 psia) lies above both the dew point and bubble point pressures. We  have followed three books to find the solution namely Coulson and Richardson's Chemical Engineering volume 6, Introduction to chemical Engineering Thermodynamics by J.M. Smith and Introduction to Distillation operations by Pradheep Desh Pandey, we have also calculated activity coefficients and fugacity coefficients to compensate for the limitations  of real mixture but still unsuccessful. The dew point and bubble points were also calculated on HYSYS and thermosolver and they were again found to be below the given pressure. On the other hand HYSYS simulation is clearly showing the occurrence  of flashing (both vapor and liquid streams have considerable amounts of the feed components). Please guide us how to justify this awkward situation. I have added some screen shots and simulation files  in the attachments please have a look at those files for better understanding of this problem.
The equilibrium ratio ( Ki) values were obtained from De Preister charts while for H2S , NH3 and H2O these values are calculated by the formula

(K_i = (γ_{i *}P_i^sat)  /(Φ_i*P)

where,

Φi = Fugacity coefficient of component i

γ_{i =   Activity coefficient of component i}

P_i^{sat  = Saturation pressure of component i at given temperature by Antoine's equation.}

For flash calculations two conditions must be satisfied which are

1.  ∑ K_i Z_i  > 1

2. ∑ (Z_i/_Ki)  >1

The second condition was easily satisfied but the first one is has become almost impossible. In other words the given pressure  is greater then dew point but not less than bubble point while it should be between them.

Please review the simulation files also.