Help: Solving the problem of the wastewater from power plant desulfurization turning into a paste after Mg(OH)2 precipitation
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Currently, the desulfurization wastewater from power plants is generally treated using the traditional three-tank process: neutralization, flocculation, and sedimentation. Desulfurization wastewater mainly contains Ca2+, Mg2+ and other heavy metal ions, while the anions mainly include SO42-, Cl-, NO3-, HSO32- and so on. The neutralization step adjusts the pH to around 11; thereafter, the addition of Na2CO3, organic sulfur, flocculants, and similar substances enables the precipitation of calcium and magnesium ions. The problem is that Mg(OH)2 can be flocculated, but it is difficult to settle; as a result, it turns into a paste and cannot become a solid like CaCO3. The cost of adding this substance amounts to around 50–60 yuan per ton of wastewater. This issue becomes particularly severe when the magnesium ions in the wastewater are high (6000–10,000 mg/L) while the calcium ions are low (for example, 200 mg/L). Are there any effective solutions to recover all the Mg2+ resources or to enable effective precipitation of Mg2+ while reducing the costs associated with adding this substance? Thank you!
There’s basically nothing that can be done about it. The precipitate of magnesium hydroxide has very fine particles, and due to its excellent water affinity, it is in a paste-like state. This is its physical nature.
High-concentration magnesium ions can be attempted to be recovered by forming struvite using the MAP method.
That would require the introduction of phosphate ions and ammonium ions; what is lost is replaced by more, which isn’t very practical. Regarding desulfurization wastewater from power plants, if traditional pretreatment methods are still used, it’s impossible to reduce the costs. I’m wondering if there are any new technologies that could help lower these costs. I’ve heard of electrocoagulation; I’m not sure about its effectiveness. Are there any other solutions? I hope everyone can offer some suggestions
The magnesium ammonium phosphate method can be used for phosphorus removal, but not for magnesium removal; the requirements for total phosphorus in water are more stringent.
Adopt MVR evaporation crystallization technology; new power plants in Europe and the United States are required to use this technology. Due to the low concentration, the operating costs are not high, and it is a zero-emission technology. Evaporation treatment of FGD flushing water makes wastewater desulfurization easier http://bbs.hcbbs.com/thread-1221791-1-1.html (Source: Haichuan Chemical Industry Forum)
:victory::victory::victory::victory::victory: