Computer program for leaching

There are usually two types of leaching calculations---the required number of separation stages may be found for a given set of input conditions and process specifications or the number of steps may be specified and their effects can be calculated. The stage balances are calculated by assuming equilibrium or a stage efficiency. Input/output material streams must equal the output/input material streams of the next stage. Stage one is the stage in which the solid feed stream enters the system. For each set of stagewise calculations, the amount of solute leaving in the raffinate stream is compared to the solute leaving in the total system raffinate stream. The computer calculations finish when the former is less than or equal to the later.

For the second type of calculations, the number of stages is specified. In this case the value of the solvent rate is adjusted upwards or downwards by increments until the number of calculated stages matches the specification. The Newton Method is used for iterating on the solvent rate.

Our program LEACH.BAS runs with any version of BASIC. It is part of the compressed collection that can be downloaded from our archive (see page for Dept. of Chemical Engr). The calculation portion was derived from a FORTRAN program written by Harry G. Folster. Our version has a built-in example, and it is easy to replace these numbers with those for an actual problem. Some demonstration data and results are shown below with comments added to the table printed by the program. 

    VALUES USED IN PROGRAM 

 

BASIS IS 1 UNIT WEIGHT OF SOLIDS 'older version asks for amount

FRESH SOLVENT FEED   5      ' This is merely a starting guess, the program keeps adjusting 

MASS FRACT. SOLUTE IN FEED .1  ' This + next 2 numbers must add up to 1 

MASS FRACT. SOLVENT IN FEED .8  

MASS FRACT. SOLID IN FEED 9.999996E-02  ' computerese  

MASS FRACT SOLUTE IN FRESH SOLVENT 0  

MF SOLVENT IN FRESH FEED 1  

FRACT. SOLUTE IN SOLVENT EXTRACT .05 ' used when you ask how many stages 

FRACT. SOLUTE IN FEED RECOVERED .9  

WT. RATIO OF SOLVENT TO INERT SOLID 10 'based on inerts only 

NO. OF AVAILABLE STAGES 9 ' specify zero to get no. of stages 

 

           STAGE CALCULATIONS FOR LEACHING 

                  MATERIAL BALANCE 

       RAFFINATE                              EXTRACT 

STAGE INPUT   FRAC   OUTPUT   FRAC     INPUT   FRAC   OUTPUT   FR 

       T/D    SOLUTE  T/D    SOLUTE     T/D   SOLUTE   T/D   SOLUTE 

 0      1     .1      1.11   .009009  1.022808  0   .9128084  9.859681E-02

A good way to get familiar with the program is to check the overall material balance using pencil and paper.

Several students have improved the program over the years. One term paper had text explanations that have been merged with our HTML files. The programers are: Maria CARO, William CHAN, H. BUNGAY, John Ecker and Lynn Culotta. BASED ON A FORTRAN PROGRAM BY H. G. FOLSTER

14-March-96