Desulfurization wastewater refers to when the limestone-gypsum wet flue gas desulfurization system is running, the concentration of impurities such as salt and suspended solids in the recycling process of absorbent is getting higher and higher, in order to make the impurity concentration not exceed the design upper limit, part of the wastewater needs to be discharged from the system, and this part of the wastewater discharged is called desulfurization wastewater.
The main characteristics of the water quality of desulfurization wastewater are:
1) The wastewater is mainly weakly acidic, and the water quality has high chloride ion and sulfate content, which has a certain corrosiveness to the pipeline
2) Wastewater contains a large number of fine suspended solids, the main components of which are limestone, gypsum particles and silica
3) The concentration of calcium, magnesium ions and silicon ions in wastewater is high, and dirt is easy to form in the pipeline.
The high salt content and high suspended solids concentration of desulfurization wastewater make it difficult to implement in recycling, and the traditional treatment methods of desulfurization wastewater are wet slag removal, coal yard spraying and triple box treatment. Wet slag removal refers to the use of desulfurization wastewater in wet slag removal systems without treatment, but its corrosion and secondary environmental problems caused by slag flushing water make it difficult to truly achieve zero discharge. Coal yard spraying needs to achieve anti-seepage treatment, and the sprayed permeate is easy to cause heavy metal pollution in groundwater, which will also bring secondary environmental problems. Although the triple box method can effectively remove pollutants such as suspended solids and heavy metal ions after simple neutralization, flocculation and precipitation clarification, it is difficult to effectively remove Na+, Cl-, SO42-, Ca2+ and Mg2+ plasma, and the salt content of the effluent is still very high.
Desulfurization wastewater zero discharge is a new wastewater comprehensive treatment technology proposed in recent years, its main meaning is to extract various impurity ion components and suspended solids in the wastewater, the resulting desalinated water for reuse, the concentrate after a series of evaporation crystallization, the ionic dissolved salt to achieve solidification treatment, without any liquid form discharge process. The mature desulfurization wastewater treatment technology route is "pretreatment unit + concentration reduction unit + solidification unit". However, due to the high cost of softening agents and the large amount of energy consumption required for evaporation and crystallization of concentration and curing units, the operation cost is large, so the development of zero-emission technology is restricted.
For specific wastewater treatment process equipment, please consult Cathay Pacific Environment.