By : M.B Mwaba
Eindhoven Technische Universiteit Eindhoven
An example of a process industry where scaling leads to high economic penalties is the manufacture of sugar from cane sugar. In this thesis, the problem of scaling of heat exchangers in the cane sugar industry is studied. A cane sugar factory in Zambia is used as an example. Deposit samples taken from juice and syrup heaters are analysed so as to identify the scale causing components. From samples investigated it is found that CaSO4 is the main scale causing component Further particles are found in both the deposit samples and the process. This leads to the conclusion that crystallization of CaSO4 is the main cause for scaling in syrup heaters. Because particles are also present it is concluded that particulate fouling also contributes to deposit formation.
Experiments are conducted in order to study how the various operational parameters affect the scaling process The focus is on the velocity and on the species concentration. No influence is found at low Reynolds numbers. At higher Reynolds numbers. however the rate of scaling decreases Since CaSO4 crystallization is reaction controlled the findings at low Reynolds numbers are not unusual. It is therefor concluded that the decrease observed at higher Reynolds numbers is due to removal effects.
The influence of particles is studied by performing experiments with different particle materials and particle sizes. When added at the start of the experiments they are all seen to reduce the induction period. With Fe2O3 there is totally no induction period leading to the conclusion that Fe2O3 is compatible with CaSO4. To test the influence of the particle size Al2O3 particles in two sizes are used. It is observed that in general smaller particles tend to decrease the rate of scaling while larger particles increase the scaling rate. It is concluded that larger particles are relatively more difficult to remove once they have attached to the wall. Consequently crystal growth takes place around themleading to a scale layer that is compact and adheres strongly to the wall.
Misheck Gift Mwaba
It’s vary nice article.Is there any other compound or component present in cane juice or molasses which can cause scaling.
most of scaling in sugar cane evaporation process is caused by silica and oxalic. another components are fosfat, carbonat, sesquioksid, organic compounds and organic acid.