In industrial metallurgical wastewater, cooling water makes up the majority, accounting for 70% of the wastewater in steel plants. Cooling water can mainly be divided into two types: direct and indirect. This article will explore both direct and indirect cooling water in industrial metallurgical wastewater, as well as the pollutants present in them.
1.Indirect cooling water is used for cooling blast furnace hot stoves, furnace bodies, hot blast valves, etc. After use, the temperature of this water rises, but it remains uncontaminated and can be recycled.
2.Direct cooling water is used for cooling rollers, rolling mill rolls, metal ingots, etc. It comes into direct contact with products, causing its temperature to rise. This water may also contain oil, mill scale, and other substances. If discharged directly, it can lead to water body sedimentation and thermal pollution. Additionally, floating oil poses a threat to the health of aquatic organisms.
The processing of metals such as rolled steel mentioned above also generates pickling wastewater, which primarily includes waste acid and workpiece rinsing water. Pickling wastewater contains free acid and metal ions. In steel pickling wastewater, there are large amounts of iron ions, a small portion of other metal ions (such as zinc, lead, chromium, etc.), and a minor amount of pickling wastewater. At this stage, neutralization treatment can be applied to recover iron and manganese. If the volume is large, methods such as freezing or membrane dialysis can be used to recover acid and iron salts or to separate and recover iron oxide. However, if neutral electrolysis is employed to remove mill scale, no pickling wastewater is generated. Nonetheless, the electrolysis process still requires filtration and magnetic separation treatment to enable recycling.
Additionally, in metallurgical plants, wastewater from blast furnace gas washing and converter flue gas washing contains large amounts of suspended solids. The water quality of such wastewater varies significantly and can also cause temperature increases. It may contain iron ores and oxides, as well as cyanides, phenols, inorganic salts, and some metal ions. Metallurgical plant wastewater often contains high levels of suspended solids and metal ions, requiring filtration and cooling treatment before it can be recycled.
For example, wastewater from heavy metal smelting plants (such as copper, zinc, lead, silver, etc.) contains heavy metals, primarily from washing smelting flue gas and equipment rinsing. In addition to the primary metals extracted from ores, there are often other non-ferrous metals present. As a result, wastewater from non-ferrous metal smelting plants may contain both harmful substances and metal ions.
Regardless of whether the aforementioned wastewater is discharged or recycled, it is essential to monitor the levels of various pollutants in the water to ensure compliance with relevant standards. Online Water Quality Monitoring can be conducted for this purpose. Instruments such as the Hangzhou Modi T8000-Zn Online Zinc Analyzer can be used to monitor specific pollutants like zinc in real time. The monitoring data can then be used to assess the specific condition of the water quality.
