# How do you calculate the unburnt char or carbon-in-ash from each burner in a CFX coal combustion calculation?

 In CFX-Post:1) Edit the "Res PT for HC Fuel" object, select Reduction Factor of 1, switch on "Filter" and select the start and end regions to be the burner inlet and the outlet. Press "Apply";2) In the "Variables" tab, right-click to create two new variables:(i) steps = step((x-xmin)/1[m])*step((xmax-x)/1[m])*step((y-ymin)/1[m])*step((xmax-y)/1[m])*step((z-zmin)/1[m])*step((zmax-z)/1[m])where xmin < x < xmax, ymin < y < ymax zmin < z < zmax bound a region close to the outlet (within about 0.1m).and(ii) averageCharOut = HC Fuel.Total Particle Mass*HC Fuel.Char.Mass Fraction*HC Fuel.Particle Number Rate*steps3) In Tools > Function Calculator, evaluate:(i) count on Res PT for HC Fuel(ii) lengthInt on Res PT for HC Fuel of steps(iii) lengthInt on Res PT for HC Fuel of averageCharOut4) Calculate Char Mass Flow = count(Res PT)*lengthInt(averageCharOut)/lengthInt(steps). This is the unburnt char flow rate.5) For C-in-ash or LOI: From the inlet coal flow rate for the burner multiplied by the (as received) ash mass fraction, given in the proximate coal analysis, calculate the Ash Mass Flow. The Char Mass Flow / Ash Mass Flowis the C-in-ash or LOI.6) For HHV or GCV loss is the Char Mass Flow* Heating Value of Char (32.87 MJ/kg) / (Total Coal Flow * HHV of the coal (as received basis))To obtain unburnt char for other burners, repeat Steps 1, 3, 4 and 5.If Step 2 is recorded as a session file, then it can be repeated for other res files by simply playing the session file again.