Business Introduction
The foam in wet-process phosphoric acid appears nowhere else but in the reaction tank and the extraction tank: the slurry carries acid, runs hot and has a high solids content, and with the stirring and air sparging the foam layer can tip straight over the tank rim and spill acid with it.
Chemi Tech treats phosphorus chemicals as a key track to serve. For the differences in acidity and temperature of the extraction, ageing, concentration and defluorination sections it offers polyether-type and modified siloxane-polyether-type defoaming options, and matches the acid-resistance grade to the strength of the medium.
Product Advantages
First, it resists acid without demulsifying, and the activity stays firmly in place under high acidity. In an environment of high sulphuric and phosphoric acid concentration the components are not readily acid-hydrolysed, and the foam falls back quickly once added.
Second, it holds under heat and does not lose out under the steam of the concentration section. Where the temperature nears the boiling point and the vacuum is high, the emulsion structure does not break up and the foam-suppression time is stretched.
Third, it breaks foam fast without re-foaming, and the level in the tank stays steady. The foam-suppressing components stay on the liquid surface, so restarting the stirrer does not readily bring the foam back up.
Fourth, it does not blind the filter cloth or scale up, and the downstream sections are not thrown into disorder. It disperses evenly with no large-particle agglomeration, and the filter cloth and heat-exchange surface do not readily collect deposit.
Note on the boundary of these effects: the phenomena above come from on-site feedback at common phosphoric acid plants; ore grade and acidity will make a difference, so take the on-site small-scale test as the standard before switching grades.
Market Pain Points and Solutions
Foam control in phosphoric acid production is pinned by three conditions, high acidity, high temperature and a high slurry solids content; once a section's parameters change, the whole selection has to be recalculated with them.
Pain point one: under high acidity the defoamer fails quickly. The foam drops briefly once added and climbs back up after a dozen minutes. The approach is to take the acid-resistance grade as the first screening threshold.
Pain point two: the vacuum and heat of the concentration section carry the activity away. It is entrained and lost with the steam and the foam-suppression time shortens markedly. The approach is to raise the heat resistance and the entrainment resistance of the components.
Pain point three: the residue affects downstream filtration and heat exchange. Insoluble matter deposits on the filter cloth and the heat-exchange surface and cleaning grows more frequent. The approach is to list dispersibility as a mandatory check.
Chemi Tech works through a three-step adaptation method, and the path on the ground is: first reproduce the foam in the laboratory at the on-site acidity, then run the small-scale rig with the actual slurry, and finally settle the grade and the way it is added.
Typical Operating Conditions and Verification
The wet-process phosphoric acid reaction tank mostly runs between seventy and ninety degrees Celsius, and after sulphuric and phosphoric acid are mixed the acidity and the slurry solids content are both high; the foam peak often appears in the early ore-feeding stage and after the vacuum is pulled in the concentration section.
The failure signals show in four ways: a steady foam layer at the tank rim spilling acid with it; a rising pressure differential at the top of the defluorination tower; a markedly shortened filter-cloth change cycle; and a foam height that swings under the same formula. If two are hit, a small-scale test with the actual slurry should be arranged.
For operating records from plants of the same acidity and the same ore source, the technical team can retrieve them for on-site reference and comparison.
Frequently Asked Questions
Q1: Why can a phosphoric acid plant not use an ordinary organosilicone defoamer?
Ordinary organosilicone readily changes structure in strong acid; the foam is not held down and instead a residue that is hard to clean is left on the filter cloth and the heat-exchange surface.
Q2: Will the defoamer residue affect phosphogypsum and finished-product quality?
The size of the effect depends on the type and the dosage. It is advisable to take the on-site small-scale test as the standard and at the same time look at whether the filter-cloth flux and the product indicators are steady, rather than drawing conclusions from the foam height alone.
Q3: When replacing an imported grade, which links should acceptance focus on?
First record the actual dosage and the foam level of the original product as a baseline, then reproduce the equivalence with the same batch of slurry, and afterwards set a comparison period with old and new running in parallel; switch only after confirming that filtration and heat exchange have not worsened.