How does non-woven fabric become reverse osmosis membrane

Hangzhou Water Treatment Technology Research and Development Center, this company hidden on Yile Road in the west of Hangzhou City does not seem to be very conspicuous, but it is the country's largest seawater desalination engineering service provider with the largest market share. The center is currently a leading company in the field of domestic desalination, with a current market share of more than 60%. How does sea water turn salty into lighter? Our reporter went deep into the production workshop to uncover the mysterious hijab of desalination.　　The secret of turning seawater into rain is a membrane. 　　Reverse osmosis is currently the most commonly used seawater desalination technology in the world. It is favored by coastal water-scarce cities due to its relatively low cost, relatively convenient process and almost no pollution.　　'The working principle of reverse osmosis membrane is to reject sodium chloride molecules in seawater from the membrane through high pressure, leaving only pure fresh water. Said Wang Shougen, deputy director of Hangzhou Water Treatment Technology Research and Development Center. To put it simply, this membrane is the core of making sea water salty.　　So, how did this magic film come out? The secret is hidden in the workshops of Beidouxing Membrane Products Co., Ltd. in Shiqiao, a subsidiary of Hangzhou Water Treatment Center. It is hard to imagine that such a high-tech membrane base material turned out to be a non-woven fabric. However, this is not an ordinary non-woven fabric, currently all rely on imports. In a relatively closed workshop, the white non-woven fabric is gradually unfolded. After pre-treatment, it has to go through three coatings. The first layer is polysulfone, the second layer is amine, and the third layer is chlorine. This process After that, the non-woven fabric achieved the effect of pinholes. 'The final formed film has a very high precision. 'On-site staff made a demonstration: under a high-precision microscope, a hole cannot be seen on the surface of the membrane, and a cross section is cut, and no hole is visible at all.　　 How does water pass through such a dense membrane? Wang Shougen said:'The membrane is selectively adsorbed, and a 20-micron water layer is formed on the surface. It is similar to that water molecules penetrate this membrane under the action of capillaries, but other ions and molecules cannot pass, so that the effect of seawater desalination is achieved. The key technology of'　　' reverse osmosis membrane is the membrane production process and formula. The staff said that there are 50 or 60 kinds of originals for the production of reverse osmosis membranes, and there are more than 50 kinds of processes. After completion, these membranes are rolled by the machine into a spiral finished product (membrane element), the cross section is like tree rings, very regular. This film is also very'squeaky'. After the finished product is completed, they are put in a'plastic wrap' and sealed for storage. 'They are not afraid of oxygen, but are afraid of the evaporation of the protective liquid, so they are all disassembled and installed on the spot, which has very high technical requirements. 'Generally a set of membrane can be used for 3 to 5 years.　　 Since the second half of last year, after years of technical reserves, Beidouxing membrane seawater reverse osmosis membrane has been officially produced on a large scale, with an annual output of 200,000 square meters. At present, the product has been applied to three projects including the 100,000-ton level in Zhoushan Liuheng and the 10,000-ton level in Shengsi, the largest seawater desalination project in China, and all of them have been operating normally for more than half a year. 'The scale of the national seawater membrane market is between 80 million yuan and 100 million yuan, with a rapid growth rate of 20% every year, and the market space is huge. '　　The precision splicing game in the complete workshop　　After the reverse osmosis membrane is released, to make it play the role of seawater desalination, many follow-up sophisticated assembly processes are required. In the complete workshop of Hangzhou Water Treatment Center.　　 Assembler Lang Minghua first took out an iron circular end plate, the diameter of which was equivalent to that of a steel pipe. I saw him carefully pushing the end plate into the nozzle, and then used a hammer to force each area of u200bu200bthe end plate. 'There is a lot of attention here. 'Lang Minghua told reporters that the steel pipe is the core of the entire system, which contains reverse osmosis membrane elements, and there are generally 7 reverse osmosis membranes inside. Sea water is transformed into fresh water through this pipe.　　'The tightness requirements of the end plate are very high, and the error will be accurate to micrometers. 'He said that the whole procedure looks simple, but every link is very demanding. Taking paint as an example, because the pipe is eroded by sea wind more, every small corner cannot be sloppy. Generally, only one set of desalination equipment can be installed a week.　　 In these three workshops, the project is only half completed. Generally, a complete set of reverse osmosis seawater desalination production line with a stand-alone scale of 10,000 tons/day requires 114 pipes as large as the above, and each pipe requires 7 reverse osmosis membrane products. The reverse osmosis membrane elements need to be installed on the construction site. . At the same time, many pipes and connections were installed in the complete workshop, and then the paint was removed, and it was finally installed in place after several iterations. It takes at least half a year for a set of equipment from design to final completion.　　'In layman's terms, we are like a jigsaw puzzle, placing each part in the correct position so that we can achieve synergy. 'Lang Minghua has been in this position for 10 years, and he has assembled dozens of hundreds of sets of equipment. The desalinated seawater eventually flows into millions of households through these well-connected pipelines.