Membrane separation technique

The application of reverse osmosis technology is a kind of membrane separation technology represented by polymer separation membrane, which is a new and efficient fluid separation unit operation technology.

Reverse osmosis technology is primarily used for preparing water for space, pure water, and distilled water; for alcohol production and dilution water; for the preliminary preparation of water in the pharmaceutical and electronics industries; for concentration, separation, purification, and water preparation in chemical processes; for desalination and softening of boiler feedwater; for desalination of seawater and brackish water; and for water use and wastewater treatment in industries such as papermaking.

Application status of reverse osmosis membrane

Among various membrane separation technologies, reverse osmosis has been the most successful, fastest-growing, and most widely adopted in China in recent years. Since 1995, the use of reverse osmosis membranes has increased by an average of 20% annually. According to conservative estimates, in 1999, the market supply of industrial reverse osmosis membrane elements was 6,0008-inch membranes and 26,0004-inch membranes. The market grew even more robustly in 2000 and 2010, with a significant increase in membrane usage each year. It is estimated that the application of reverse osmosis technology has generated an annual output value of over 1 billion RMB in the water treatment industry.

The largest field of domestic reverse osmosis membrane industrial application is still large boiler replenishment water, various industrial pure water, drinking water market scale is second, electronics, semiconductor, pharmaceutical, medical, food, beverage, alcohol, chemical, environmental protection and other industries have also formed a certain scale.

Recent advances in reverse osmosis membranes

Ultra-low pressure membranes have gained increasing application since 1999 due to their advantages, such as reduced material costs and lower pressure levels in mechanical components, which lead to energy savings. This trend is particularly evident in small-scale facilities primarily using 4-inch membranes, and the use of ultra-low pressure membranes is also on the rise in large-scale installations. The largest facility using ultra-low pressure membranes has a water production capacity of 650 tons per hour.

Low pollution membrane fouling is the biggest hazard in reverse osmosis applications. Several low pollution membranes with strong anti-pollution performance, long service life, low cleaning frequency and easy cleaning have been introduced.

The low pressure and ultra-low pressure composite membranes with positive charge are widely used. The material of the low pressure and ultra-low pressure composite membranes is aromatic polyamic acid, and the surface of the membrane is negative charge. Now some membrane manufacturers have developed low pressure composite membranes with positive charge on the surface, which are mainly used in the preparation of high resistivity and high purity water systems.

The positive charge membrane ES10C produced by Japan’s Nittoku Electric has achieved a high-purity water with a resistivity of 10-15 megohms in the tertiary reverse osmosis systems of the semiconductor industry. The combined final water production rate of three plants of South Korea’s Hyundai Electronics is 800 tons per hour, with a resistivity of 8-9 megohms. A 170 tons per hour tertiary reverse osmosis system at a semiconductor plant in Shanghai also meets these standards. Additionally, in several domestic pharmaceutical plants, two-stage reverse osmosis systems with a capacity of 5-20 tons per hour have achieved a resistivity of 1.7-3 megohms for the produced water.

High-temperature resistant, food-grade, and sanitary reverse osmosis membranes are typically used at temperatures ranging from 0 to 45 degrees Celsius. However, for special applications requiring high-temperature sterilization at 90 degrees Celsius, high-temperature resistant and chemical-resistant reverse osmosis membranes can be utilized. Additionally, reverse osmosis membranes with special membrane element structures, designed for food-grade or sanitary use, are also being applied in China.

Application status and latest progress of seawater desalination membrane

There are already reverse osmosis seawater desalination plants abroad with a daily water production capacity of 100,000 tons. The single-unit capacity of large-scale spiral-wound membrane seawater desalination plants currently in operation is 6,000 tons per day. In China, the daily water production capacity of both existing and under-construction reverse osmosis seawater desalination plants ranges from 350 to 1,000 tons per day. The water utilization rate for single-stage reverse osmosis seawater.

Moreover, the reverse osmosis seawater desalination membranes used on domestic fishing boats are mostly small membrane elements with a diameter of 2.5 inches. There are no more than 10 companies in China that produce seawater desalination units in bulk. The ‘Yashuihai’ desalination unit, built in Hebei and capable of producing 18,000 tons of water per day, is the largest reverse osmosis unit in China that uses seawater desalination membranes.

In the future, the application of seawater desalination membrane in China will enter a new period. In the near future, China will also build seawater desalination devices with a daily output of 10,000 tons. In addition, domestic commercial production of seawater desalination reverse osmosis membrane components has begun.