ESP Column Information

Q1: What are the default input data currently used with each tray type?

Sieve Tray: Four input parameters

• Column diameter (coldia):

If not entered, ESP calculates diameter using Reference 1.

  su = 0.65d0/dsqrt(denv*0.062428d0)
  calcdiam = dsqrt(av*4.0d0/(pi*su))

where,

  su = Superficial gas velocity, m/sec

  denv = Vapor density, kg/m3

  av = Vapor flow rate, m3/sec

  0.65 = Gas phase kinetic-energy term (F factor), unit-less

  calcdiam = calculated diameter, m

Please note, unit conversions are not shown in the equations.

Reference 1: Perry’s Chemical Engineer’s handbook, 6th Edition, pages 18-6.

• Weir height (hweir):

If not entered, hweir = 1.0 inch.

• Clear liquid height (hl):

If not entered, ESP calculates the clear liquid height or the height of crest over wire (hl) using Reference 2.

  hl = 664.d0*(al/lw)**(0.667)*1.0d-3

where

  al = Liquid flow rate, m3/sec

  lw = Weir length, m

  hl = Clear liquid height, m

The weir length (lw) is calculated from a correlation using Reference 2.

  lw = exp(log(al/6.309d-5)/25)/2.5d0 * 0.3048d0

Reference 2: Perry’s Chemical Engineer’s handbook, 6th Edition, pages 18-10,11.

• Froth height (hf):

If not entered,

  hf = 2.0*hl.

For sieve tray, the weir length information is accounted in our model. Weir height is the only parameter set as default unless it is a user input. Hole diameter and/or arrangements are not required in the currently implemented model, however, current model uses above information plus diffusivity, Schimdt number, porosity of froth and other readily available data to calculate interfacial area per unit froth volume and finally mass transfer coefficients in the gas and liquid phase. More details about OLI’s Sieve tray can be found in Reference 3.

Reference 3: Moniuk, W., Bekassy-Molnar, E., Mustafa, H. and Pohorecki, R., “Absorption of carbon dioxide into sodium hydroxide solutions in a sieve plate column”, Hungarian Journal of Industrial Chemistry, 17 (1989), 93-105.

Valve Tray: Two input parameters

• Column diameter (coldia):

If not entered, ESP calculates diameter using Reference 1 as shown in Item 1 for Sieve Tray.

• Weir height (hweir):

If not entered, hweir = 1.0 inch . No other information is required for the currently implemented model. The valve tray model uses flow rates, Reynolds number, Schimdt number and above two tray hydraulics data to calculate interfacial area and finally mass transfer coefficients. Details of the OLI’s Valve tray model can be found in Reference 4.

Reference 4: Scheffe, R.D. and Weiland, R.H., “Mass-Transfer Characteristics of Valve Trays”, Industrial & Engineering Chemistry Research 26 (1987), 228-236.

Bubble Cap: One input parameter

• Column diameter (coldia):

If not entered, ESP calculates diameter using Reference 1 as shown in Item 1 for Sieve Tray. No other hydraulic information is required for the currently implemented model. The model uses velocity of gas/liquid, density and surface tension to calculate gas holdup using a correlation which is a function of Bond number, Galileo number and Froude number. The model shows that the effect of the diameter of the single gas inlet orifice to the column diameter can be ruled out. The model then calculates interfacial area and mass transfer coefficients using above information and calculated Schimdt number and Sherwood number. Details of the OLI’s bubble column model can be found in Reference 5.

Reference 5: Akita, K. and Yoshida, F., “Gas holdup and volumetric mass transfer coefficient in bubble columns”, Industrial & Engineering Chemistry Process Design & Development, 12(1) (1973), 76-80.

Q2. Output report for trays

Sieve Tray: ESP currently shows the Sieve Tray Report which is accessible through Packed Column Report. It is apparent that accessing Sieve Tray Report through the Packed Column Report may not be a good idea, but we have decided to change the entry name in the column profiles (i.e., Packing/Tray Report). Currently, we report the column diameter at the end of the Sieve Tray Report, however, area can be added too.

Valve Tray: ESP shows the Valve Tray Report which is accessible through Packed Column Report.

Bubble Cap Tray: ESP shows the Bubble Cap Report which is accessible through Packed Column Report. Column diameter is also reported at the end of each report. We can report the area of stage. Let us know what other useful information can be reported.

Q3: Major simulator has the functionality by which calculated pressure

drop is automatically reflected to column pressure drop. Can ESP model have the same? (I think it’s difficult for OLI, though.) Pressure profile is a user input parameter for OLI’s column and is not an estimate. ESP does not recalculate the pressure profile or pressure drop in the column, and apply back to column and converge. ESP only interpolates to match the user provided pressure profiles.