One, reverse osmosis introduction
Reverse osmosis, also known as high filtration (Hyperfiltration) is a membrane separation technology developed in the 1960s. Because it has no phase change of materials, low energy consumption, simple equipment, room temperature operation and adaptability and other characteristics, after more than 40 years of development, has been widely used in various fields of the national economy. From the membrane, components and device development to development, reverse osmosis technology has become a mature membrane separation technology, which is not only applied to the desalination of seawater and brackish water, but also in the field of electronics, petrochemicals, food, health care, environmental engineering and national defense plays an important role.
Reverse osmosis is a pressure difference as the driving force of the membrane separation technology, is currently the most advanced membrane separation technology. Reverse osmosis membrane is under the action of pressure difference as the driving force, only allows the passage of water molecules and block a variety of solutes and solid particles of semi-permeable membranes, our company mainly uses Hyderabad, Dow, Shi Han, Toray and other imported reverse osmosis membrane.
The main factors affecting the desalination rate of reverse osmosis equipment and normal work:
1. Ion valence: the desalination rate with the increase in the number of ionic valence and improve the rate of desalination of divalent, trivalent salt desalination rate higher than the monovalent salt;
2. molecular size: the rate of desalination of the molecular diameter increases and improve;
3. Raw water temperature: the temperature of the raw water rises due to the increase in water viscosity increases;
3. Raw water concentration: when the raw water concentration increases, the desalination rate decreases;
5. Working pressure: when the working pressure increases, the desalination rate increases but not obviously;
6. PH value: although the membrane is not easy to be blocked in acidic conditions, the desalination rate decreases;
7. Dissolved gas: the soluble gas is easy to be permeated in the free state but not in the free state. Free state is easy to permeate and do not remove CO2, SO2, O2, Cl2, H2S, etc.;
8. Hydrogen bonding tendency: for compounds containing strong hydrogen bonding, the removal rate is very low, such as water, phenol and ammonia, etc.; (It is also therefore to achieve the removal of impurities in water and soluble matter to achieve the separation of water and other substances;
9. Organic substances: organic matter in water on the membrane has a Organic matter: organic matter in water has a contaminating effect on the membrane, the more organic matter the performance of the membrane is more prone to deterioration;
10. water hardness: the higher the hardness of the water membrane is easy to block, for high hardness water should be softened to reduce hardness and then into the reverse osmosis;
11. solid particles: solid particles of reverse osmosis membrane is very dangerous, must be pre-treated;
12. microorganisms: microorganisms in the water, Microorganisms: microorganisms and bacteria in the water are harmful to the membrane, and must be pre-treated (the company adopts ultra-rate membrane for treatment, which is at an advanced level in China);
13. oxides: metal oxides can not be removed by themselves when they enter the reverse osmosis, and they should be removed by regular chemical drugs.
Application range
*Desalination of seawater, desalination of brackish water, fluoride reduction of drinking water;
*Pure water for drinking;
*Boiler water softening, deionized water production;
*Pharmaceutical water production;
*Electronic industry, ultra-pure water production;
*Liquid separation, concentration, recovery of valuable objects. Recovery of valuable objects.
Reverse osmosis equipment specifications to be provided by the user according to the quality of raw water, water requirements, water production and the use of reverse osmosis membrane specifications *** with the composition of the company can be provided by the user according to the raw water quality test report (or provide water samples from the company's laboratory), the use of reverse osmosis design software for the design and selection of equipment, according to the unit time of the production of water to determine the equipment Models: 0.5T/H, 1.0T/H, 1.5T/H, 2.0T/H,
3.0T/H, 4.0T/H, 5.0T/H, 10T/H, 15T/H, 20T/H, 30T/H, 40T/H, 50T/H, 60T/H, 100T/H. According to the requirements of users, each model can be designed into a two-stage reverse osmosis to provide users with high quality pure water. The user to provide high-quality pure water.
Two, reverse osmosis principle
According to the principle of osmosis, on both sides of the semi-permeable membrane there exists a "chemical potential" difference, through the permeation process of the solution to compensate for the difference in chemical potential. When the equilibrium is re-established, on both sides of the semi-permeable membrane formed a water level difference that is the net pressure difference, this pressure difference is the osmotic pressure. Osmotic pressure is a property of the solution itself and depends on the concentration of the solution and has nothing to do with the semipermeable membrane. The relationship between osmotic pressure and solute concentration is:
Posm=1.19(T+273)×∑(mi).................. ...............(1)
Equation:Posm......... .................. osmotic pressure (psi);
T...... ........................... temperature (°C);
∑(mi)........................... of all the solutes in the solution Total molar concentration;
In a vessel with a semipermeable membrane, pure water flows through the semipermeable membrane to the brine side, a phenomenon called osmosis, until a new equilibrium is reached and established. The difference in static pressure between the two sides of the membrane is the osmotic pressure, and when an applied pressure is applied to the brine side, the original equilibrium will be affected. The applied pressure will increase the chemical potential of the salt solution on one side, causing the water in the brine to flow through the semi-permeable membrane to the pure water side. This phenomenon is called reverse osmosis. The driving force of the reverse osmosis process is the applied pressure, and the energy required for reverse osmosis separation is directly related to the concentration of the brine. Therefore, the higher the salt concentration, the higher the energy required to reverse osmosis pure water from brine.
■Water transfer
The rate at which water passes through a semipermeable membrane is determined by the following equation:
Qw = (?P-?Posm) × Kw × S/d ............ ...............(2)
Equation: Qw......... ..................... rate of pure water through the membrane;
△P... ........................... pressure difference between the two sides of the membrane;
△Posm........................... osmotic pressure on both sides of the membrane Difference;
Kw........................... ...the pure water permeability coefficient of the membrane;
S..................... ............ membrane area;
d............... .................. membrane thickness.
(2) The equation is usually simplified as:
Qw = A x (NDP)..................... ...........................(3)
Eq: A........................... ...... membrane constant;
NDP.................. ......... total driving pressure or total driving force for water mass transfer across the membrane.