Comparison of Seawater Desalination Technologies Distillation and Reverse Osmosis

2022-05-10


There are many technologies for seawater desalination. Among the technologies of seawater desalination system, Reverse Osmosis Seawater Desalination is developing rapidly, and large-scale seawater desalination equipment with a daily output of 10,000 tons has appeared. However, at present, the proportion of distillation used in seawater desalination is still high in the world.

Comparison between distillation and reverse osmosis:

1.Energy consumption:

From the direct energy consumption of desalination, reverse osmosis is obviously better than single-purpose distillation, but not obviously better than binocular distillation. Moreover, due to the short life of reverse osmosis membrane and the high cost of membrane replacement, the membrane itself reflects the energy consumption. For distillation method, the direct energy consumption of the process varies greatly from region to region, so it needs to be determined by technical and economic comparison.

2. The total cost of seawater desalination.

Due to the limitation of membrane life and membrane equipment, membrane method is still at a disadvantage in large-scale seawater treatment. Because the water production cost of reverse osmosis method is affected by the adverse effects of membrane life and device scale, which exceeds the benefits of low energy consumption, it is generally believed that binocular distillation method is more economical than reverse osmosis method when the capacity of seawater desalination device exceeds 6000t tons of fresh water per day.

3. Pretreatment of seawater:

The seawater entering the distillation unit does not need to be pretreated, but only a seawater filter screen is required. However, the seawater entering the Seawater Reverse Osmosis System needs to be pretreated by flocculation, clarification, filtration and chlorination. Moreover, due to the low water utilization rate of reverse osmosis, the pretreatment system is huge, the investment is high, and the occupied area is large.

4. Other supporting facilities:

Distillation method requires start-up steam, so the capacity of start-up boiler should be considered to meet the needs of desalination facilities, and a separate water treatment facility should be considered for start-up of make-up water of start-up boiler.

In addition, because there is no spare equipment, fresh water is needed as a spare water source for industrial water. However, the membrane method does not need to start steam. When the unit starts, the feed water temperature is low, which slightly affects the output of desalination equipment, does not affect the start-up water of the unit, and does not need to consider additional start-up facilities. SWRO Desalination Equipment is considered to have enough spare output, which can meet the need of water for equipment maintenance.