Basic Formulas.

The following short calculations can be helpful in understanding your evaporator operation. These calculations are for informational purposes only. We assume no responsibility regarding the accuracy of the values presented. For a detailed look at evaporator performance a complex heat and material balance must be completed. Feel free to contact us if you have any questions regarding the calculations shown or if questions regarding your specific analysis.


Evaporator Evaporation Rate (lb/hr)

Input: (do not use commas)

(A) Black Liquor Feed Flow (gpm)
(B) Black Liquor Feed Solids (%)
(T) Black Liquor Feed Liquor Temperature (deg F)
(C) Black Liquor Product Solids (%)

Output:

Evaporation Rate (lb/hr)
Formula
Specific Gravity: SG=0.9982*0.006*B-0.0003*T
Evaporation Rate: EVAP=((100/FS)-(100/PS))*A*500*SG*(B/100)

Black Liquor Solids Processed by Evaporator

Input: (do not use commas)

(A) Black Liquor Flow (gpm)
(B) Black Liquor Solids (%)
(T) Black Liquor Liquor Temperature (deg F)

Output

Dry Black Liquor Solids Processed (lb/hr)

Estimated Steam Economy

Note the value calculated is only an approximation. A heat and material must be completed for an accurate determination.

Input: (do not use commas)

(A) Number of Effects in Evaporator

Output:

Estimated Steam Economy
Formula
Steam Economy: ECON=A*0.8

Conversion of Steam Flow (lb/hr) to Condensate Flow (gpm)

Input: (do not use commas)

Steam or Vapor Flow (lb/hr)

Output:

Condensate Flow (gpm)

Liquor Level in Effect Down Leg

With this equation recognize the elevation being calculated is from the elevation of the bottom measurement point to the top liquid level. Any restrictions in the line between measurement points may yield an inaccurate result. Calculation is based on measurements taken near sea level.

Input: (do not use commas)

For measurements under vacuum enter a value with a negative sign (e.g. -18). For measurements under positive pressure enter a positive value (e.g. 30).

(PVAP) Vapor Dome Pressure (psig/in Hg)
(PLIQ) Liquor Line Pressure (psig/in Hg)
(S) Black Liquor Solids in Down Leg (%)
(T) Black Liquor Liquor Temperature (deg F)

Output:

PVAP in psia
PLIQ in psia
Liquor Level in Down Leg (ft)

Conversion of Liquor Flow: lb/hr to gpm

Input: (do not use commas)

(A) Black Liquor Flow (lb/hr)
(B) Black Liquor Solids (%)
(T) Black Liquor Liquor Temperature (deg F)

Output:

Black Liquor Flow (gpm)
Formula
Specific Gravity: SG=0.9982+0.006*B-0.0003*T
Black Liquor Flow (gpm): GPM=A/(500*SG)

Liquor Flow Velocity (f/s)

Note the value calculated is only an approximation. A heat and material must be completed for an accurate determination. This formula calculates the liquor flow velocity in a pipe.

Input: (do not use commas)

(A) Black Liquor Flow (gpm)
(d) Inside Pipe Diameter (inches)

Output:

Liquor Flow Velocity (ft/sec)
Formula
Liquor Flow Velocity: V=0.4085*A/d2
Note: An excessively high fluid velocity can cause an array of operational issues.