Iron fouling

Iron fouling is caused by both forms of iron ions the insoluble form will coat the resin bead surface and the soluble form can exchange and attach to exchange sites on the resin bead. These exchanged ions can be oxidized by subsequent cycles and precipitate ferric oxide within the bead interior. 

Reduced operating capacity due to iron fouling of the resin, which occurs because soluble iron (in the form of ferrous bicarbon-... 

In many smaller manufacturing or factory processes in which live steam is directly employed (such as in a bakery, laundry, etc.), there often is little returning condensate (perhaps only 15-20%). Here, the MU requirement is correspondingly high and the FW may be relatively cool (and therefore partially oxygenated). Under these circumstances, it is not uncommon to observe the transport of ferrous bicarbonate [Fe(HC03)2]) into the boiler and the subsequent development of iron fouling. 

The condition of an exhausted resin bed is an ionically banded bed, with the most strongly held ions on the top of the bed. Iron is more strongly held than calcium, which may lead to iron fouling problems. Some practical considerations for a RW softener are ... 

Phosphonates exhibit all the properties of polyphosphates, such as threshold effect, crystal distortion, and sequestration, but are superior in their effectiveness. They provide good chelates for calcium, magnesium, iron, and copper and are commonly used where iron fouling is a problem. Their sequestering properties are generally superior to other common chelants, such as EDTA and NTA. 

A full bed-depth, core sample should be taken of ion-exchange resin and checked for cracked and broken beads, iron fouling, and loss of capacity. The bed should be checked for loss of volume. 

DVE does not destroy contaminants it must be used in conjunction with another remediation technology. DVE cannot remove heavy chlorinated compounds or hydrocarbons heavier than the middiesel range. DVE cannot recover pesticides or polychlorinated biphenyls (PCBs). Generally, the deeper the contaminant, the more complex extraction becomes. Problems with iron fouling have been reported at DVE sites. 

Such adjuncts may be required to deal with, for example, the risk of iron fouling or high sulfate. Or, perhaps, they may provide supplementary dispersion or additional corrosion protection to the main inhibitor. 

Excess acid feed and pH correction Iron fouling, then cleanup, and tube damage resulting in permanent increased heat-transfer resistance. 

Figure 14.13 Iron-fouled resin beads on membrane surface.

As stated above, intermittent operation can cause varying concentrations of iron in the condensate system. Heavily iron-fouled condensate should be dumped if its use in the feedwater would be detrimental to good boiler operation. The criteria should be the ASME Guidelines and past plant history. Some form of condensate polishing may be worth considering if the condition is severe or continuous. 

Iron Fouling 1.0% sodium hydrosulfate, pH 5,30oC 1.0% sodium hydrosulfate, pH 11.5,35oC... 

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