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The desalination process's energy consumption depends on the water's salinity. Brackish water desalination requires less energy than seawater desalination. [82] The energy intensity of seawater desalination has improved: It is now about 3 kWh/m 3 (in 2018), down by a factor of 10 from 20-30 kWh/m 3 in 1970.
The process goes through the following steps: When the plant is operating in steady state, feed water at the cold inlet temperature flows, or is pumped, through the heat exchangers in the stages and warms up. When it reaches the brine heater it already has nearly the maximum temperature. In the heater, an amount of additional heat is added.
The first and last stages need external heating and cooling respectively. The amount of heat removed from the last stage must nearly equal the amount of heat supplied to the first stage. For sea water desalination, even the first and warmest stage is typically operated at a temperature below 70-75 °C, to avoid scale formation. [3]
Sea-water RO (SWRO) desalination requires around 3 kWh/m 3, much higher than those required for other forms of water supply, including RO treatment of wastewater, at 0.1 to 1 kWh/m 3. Up to 50% of the seawater input can be recovered as fresh water, though lower recovery rates may reduce membrane fouling and energy consumption.
Low temperature distillation (LTD) is a thermal distillation process in several stages, powered by temperature differences between heat and cooling sources of at least 5 K per stage. Two separate volume flows, a hot evaporator flow and a cool condenser flow, with different temperatures and vapor pressures, are sprayed in a combined pressure ...
Vapor-compression desalination (VC) refers to a distillation process where the evaporation of sea or saline water is obtained by the application of heat delivered by compressed vapor. Overview [ edit ]
The flow of water can be reversed if a pressure larger than the osmotic pressure is applied on the higher concentration side. In Reverse osmosis desalination systems, seawater pressure is raised above the natural osmotic pressure, forcing pure water through membrane pores to the fresh water side. Reverse osmosis (RO) is the most common ...
The solar humidification–dehumidification method (HDH) is a thermal water desalination method. It is based on evaporation of sea water or brackish water and subsequent condensation of the generated humid air, mostly at ambient pressure. This process mimics the natural water cycle, but over a much shorter time frame.