What is the Importance of ZLD Systems in Power Plants?
Salt-containing wastewater is frequently produced by power plants, including wastewater from wet gas scrubbing, run-off from coal piles, and leachate from gypsum stacks. In a contemporary zero liquid discharge system, evaporation of those liquid wastes yields solid waste, which is appropriate for landfill disposal, as well as, clean water that is recycled back into the plant. As a result, ZLD systems have become a necessity in Power Plants.
Importance of ZLD Systems in Power Plants
The cooling water system is typically a power plant's, biggest source of wastewater production. The method of liquid waste disposal gives a straightforward, but efficient illustration of a zero liquid discharge (ZLD) system.
Use of RO systems
Reverse osmosis (RO) membranes are frequently used to pre-concentrate cooling tower blow-down, before the liquid is concentrated in an evaporator. The remaining liquid is reduced to solids in a crystallizer, because cooling tower blow-down is typically relatively diluted, to less than 10,000 mg/L total dissolved solids (TDS). For instance, the salts found in cooling tower blow-down consists of sodium chloride and sodium sulphate, with trace amounts of calcium, magnesium, sulphate, and bicarbonate. By evaporation, all of these salts can easily form crystals.
Use of clarification technique
Wastewater from integrated gasification combined cycle (IGCC) facilities and wet flue gas desulfurization (wet FGD) systems, contains highly soluble salts including calcium and ammonium chlorides, and certain salts containing heavy metals, which are difficult to crystallize by evaporation.
Therefore, clarification and intensive pretreatment are necessary, for conventional ZLD evaporation-crystallization processes for wet FGD and IGCC waste streams. In order to create a crystalline solid, the wastewater must typically be treated with lime, soda ash, and other chemicals to replace the calcium, magnesium, ammonium, and heavy metal ions, with sodium ions. The ZLD system footprint, capital costs, and maintenance needs are all increased by the pre-treatment machinery and chemicals.
Effect of various chemical species
Sulfur dioxide, hydrochloric acid, hydrofluoric acid, NOx, fly ash, and numerous other chemical species, can all be found in the gas produced while burning, or gasifying coal. Wet FGD systems are employed in coal-fired power plants, to purge such contaminants from the flue gas.
Similar to this, the majority of coal gasification processes include a gas-scrubbing stage. Most employ wet scrubbing, which involves reacting with and removing those toxic components, from the flue gas by the application of an alkaline substance dissolved in water. To prevent the build-up of corrosive salts and suspended particulates, absorbed from the gas stream, wet FGD normally needs a constant blow-down.
Effect of various salts
Wet FGD wastewaters are generally chloride solutions, however their composition varies greatly. Depending on the circumstances of the combustion, there can also be a significant concentration of nitrates.
Similarly, wet FGD and IGCC wastewaters are often solutions of highly soluble salts, like calcium chloride or sodium formate, typically in the range of 5,000 to 40,000 mg/L TDS. Due to the relatively low concentrations of harmful pollutants, such as heavy metals, selenium, boron, and organics, discharge of these wastewaters is typically restricted.
Before the wastewater is released into the environment, it is frequently necessary to treat it through pre-treatment, to decrease, or remove these poisons.
Choose the best ZLD Plant manufacturers in India
Finding a system for your company that is both economical and environmentally friendly can be difficult, particularly in light of the increasingly stringent effluent rules that are limiting your alternatives for discharge. That is why; you must consult experts, like Netsol Water, to manufacture your ZLD Systems.