In the vacuum evaporation water treatment stage, the foam problem is often underestimated. As the system vacuum level increases, the bubble stabilization time is prolonged, resulting in foam layer accumulation, liquid level misjudgment, vapor carrying liquid droplets and even equipment corrosion. Conventional defoamers fail quickly under high-temperature, high-shear and vacuum environments, requiring frequent replenishment, which increases costs and interferes with continuous operation.
We have observed that the core triggers of foam include: residual surfactants in the feed water, saponified substances formed by alkaline water quality, and the aggregation of microbubbles released from gas during evaporation. For such scenarios, Chemi Tech has developed a defoamer dedicated to vacuum evaporation, solving three key pain points: defoaming speed, durability and high-temperature tolerance.
The specific solution is carried out in four steps. Step one: system diagnosis. Install online foam monitoring probes at the evaporator feed inlet and circulation pipeline, continuously record foam height and density changes for 72 hours, and locate the peak foam outbreak period. Step two: agent selection. Based on the water quality analysis report (such as conductivity and surface tension values), match a defoamer product with the corresponding HLB value to avoid emulsion demulsification or over-dispersion. Step three: precise dosing. Use a metering pump to inject continuously in trace amounts at the outlet of the feed pump; the initial dosage is 50-200 ppm and is adjusted to a steady state according to foam layer feedback. Step four: effect verification. After one week of operation, compare the data on evaporation efficiency, condensate turbidity and equipment inspection cycle.
The application case comes from a chemical intermediate manufacturer in East China. The plant's MVR evaporation system treats wastewater containing anionic surfactants, with the vacuum level maintained at -80 kPa. It originally used an ordinary silicone defoamer, needing manual replenishment every 2 hours, with the foam layer thickness staying at 10-15 cm and the heat exchanger cleaned every 3 days. After switching to Chemi Tech's defoamer dedicated to vacuum evaporation, the foam layer dropped to below 3 cm after the first dosing, stabilized within 1 cm after 48 hours of operation, the replenishment interval was extended to 24 hours, and the heat exchanger cleaning cycle was extended to 14 days. Evaporation efficiency increased by 12% year on year and steam consumption decreased by 8%.
This solution has been verified to be effective in vacuum evaporation scenarios such as petroleum refining, printing and dyeing wastewater, and papermaking black liquor concentration. The key lies in matching the system vacuum level with the agent's surface-active structure rather than blindly increasing the dosage. If you need a specific selection parameter table or optimization plan, you can contact our technical team directly for operating recommendations.