Industry News
Our analysis of three large seawater desalination technologies
From:admin Date:2013-04-23

Intro: seawater desalination using seawater desalination producing fresh water. It is the  open source incremental technique of water resource utilization, which can increase the total freshwater, and is not influenced by the time and climate impact, good water quality, prices are becoming reasonable, also can protect the coastal residents drinking water and industrial boiler stable water supply. Obtained from the seawater freshwater, it   processes the seawater  esalination. Now that the use of seawater desalination method of seawater freezing method, distillation, electro dialysis, reverse osmosis, the application of reverse osmosis membrane reverse osmosis method with the advantages of simple equipment, easy maintenance and equipment modular and quickly occupied the market, instead of distillation gradually become the most widely used method of pan. Reverse osmosis is my company(Qinhuangdao Yuwang Environment Engineering Co. Ltd.) in the mainstream technology of water treatment engineering application, is now with the famous foreign reverse osmosis membrane manufacturers in the United States HYDRANAUTICS (Hyde)established good long-term cooperative relationship.

  In sixteenth Century, people began to try in the seawater freshwater, seawater is heated at first will produce water vapor, cooling condensation can be pure water, this is the beginning of seawater desalination technology. At present, there are mainly three kinds of mainstream technology of large-scale seawater desalination, respectively, multi effect evaporation (MED), multi-stage flash (MSF) and reverse osmosis (SWRO).

Multi effect evaporation (MED)
  Multi effect evaporation desalination methods are one of the oldest, before birth is one of the leading multi-stage flash desalination markets. Multi effect distillation system is composed of single effect evaporation. Two steams will before the introduction of the next generated by an evaporator as the heating steam, and the effective evaporator in condensed into distilled water.
  The advantages and disadvantages are listed as follows, low temperature multi effect distillation technology is mature and reliable, cost is low, not high on the original water quality requirements; per ton desalination of water required to power 1.2 KWH, tons of water consumption of low pressure steam 0.1 tons, one-time equipment investment is slightly higher, but the operating maintenance costs are low.
The multi-stage flash (MSF)

   Flash is the sudden evaporation occurring pressure saturated steam refers to a certain temperature in the environment of water pressure is lower than the temperature corresponding to the. After the flash evaporation water temperature is reduced to make the saturated vapor pressure and environmental pressure balance. MSF is the use of this principle, the container heated to a certain temperature saline reduced successively in a series of pressure in the process of flash vaporization, fresh water steam condensation.

  The advantages and disadvantages: the multi-stage flash technologies mature and reliable, cost is moderate, suitable for large-scale desalination of sea water, desalinated water per ton needs electricity of 4 KWH to 5 KWH, 0.14 tons of low-pressure steam consumption. Disposable equipment investment is slightly higher, but running repair cost is low; is not high on the original water quality requirements.

Reverse osmosis (SWRO)

  Reverse osmosis seawater and freshwater is separated by using a special semi permeable membrane material, membrane material is only allowed through, do not allow the solvent solute permeation. Typically, a low concentration of fresh water through a semi permeable membrane diffusion to the high concentration of the sea side, so that  the level of the sea side of the gradually increased, until a certain height to stop, this process is penetration. At this point, the water column pressure higher than the seawater side called osmotic pressure. If a is greater than the sea water osmotic pressure of the external pressure on the sea side, so pure water reverse osmosis in seawater to fresh water, fresh water process which is reverse osmosis.
  The advantages and disadvantages: one-time equipment investment relative thermal process is a bit small, but the film to replace the high operation cost, per ton desalination water need of electricity consumption is about 6 KWH, high requirements on raw water quality, and the need to maintain more personnel. In addition, even if the two membrane effluent index is still below the thermal water indicators, if the acquisition and heat the same quality, the increased level of membrane or other desalination facilities. 

In the Chinese market the reverse osmosis process greater market space.
  Multi effect distillation, multi-stage flash all belong to the typical thermal desalination process, the one-time equipment investment cost is higher, the main use ofequipment is the main evaporator and heat exchanger, heat compressor, vacuum pumping device, auxiliary steam temperature and pressure reducing device, seawater corrosion resistant pumps, valves, the materials used mainly has: alloy tube heat exchanger, such as titanium alloy tubes, copper alloy pipe, stainless steel plate, sheet, carbon steel and the steel and other materials.
  We believe that there is no correct process in seawater desalination market, only more suitable technology. In the selection process, the final target analysis of local energy prices and desalinated water product requirements weigh much. For example, the price of energy in the Middle East is low, although the one-time investment is higher, lower prices of steam and later operation and maintenance costs have strong advantage. In contrast, in the Chinese market the reverse osmosis process greater market space, because of low pressure steam in the actual production of 100 pieces of buy, only about 9 tons of sea water desalination, operation cost is very high, so in addition to get low pressure steam power plant outside, the desalination process better economic benefit by membrane method. Yuwang Environment Engineering Co Ltd. will seize the opportunity in the water treatment industry development.

Qinhuangdao Yuwang Environment Engineering Co.,Ltd