Experimental Study On Vacuum Membrane Distillation Seawater Desalination Device With Rotating Solar Collector

As is known to all, freshwater resources are one of the basic materials for human survival and development. However, with the continuous development of social economy and modern industry, the shortage of freshwater resources has become a worldwide problem. So, as an important means to solve the shortage of fresh water resources, the sea water desalination has been paid attention to by many countries. Conventional seawater desalination is a high energy consumption industry, but in today’s increasingly depleted oil resources, human beings have to seek a sustainable development path of green and sustainable development. Therefore, the combination of renewable energy(such as solar energy) to achieve the sea water desalination is bound to become an important research direction to solve the water crisis. Membrane distillation(MD) is a new membrane separation technology which combines membrane technology with thermal distillation process. Because the MD does not need to heat the liquid to be heated above the boiling point, the operating temperature is lower. It is a new hot spot in the research of membrane distillation desalination which MD coupled with the solar heat collection technology, and the low grade heat source is used as the energy source of membrane distillation. This is expected to be an efficient and cheap desalination technology.In this paper, we use the constant temperature electric heating water tank as the heat source, 3.5%NaCl solution was used to simulate seawater, and the vacuum membrane distillation experiment was carried out with hydrophobic polypropylene(PP) hollow fiber membrane, The effects of different feed liquid temperature, cold side vacuum degree, feed liquid flow rate and feed liquid concentration on membrane flux, rejection rate, fresh water conductivity were studied, So as to determine the best reaction conditions affecting the experimental system. The experimental results show that the feed liquid temperature and the cold side vacuum degree are the main factors affecting the performance of the system, The optimal reaction conditions are as follows: 70 degreesC, the vacuum degree is 0.095MPa; The maximum membrane flux reached 10.31kg/(m2 h). Polypropylene(PP) hydrophobic membrane showed a good membrane separation function, the rejection rate was greater than 99.9%, and the conductivity of fresh water up to 10μs/cm.Secondly, based on the experiment on vacuum membrane distillation,a new type of rotating solar energy heat collection vacuum membrane distillation desalination system was designed and constructed, Based on the investigation of the thermal stability of the rotating solar collector, the feasibility of its application in the membrane distillation experiment was determined.Finally, do the experiments of the real Seawater Pretreatment in the installation of solar membrane distillation, effects of solar desalination unit in a working day working state, And analysis the device of seawater desalination process,to summarize the defects and deficiencies in the operation process, in order to provide some reference and basis for the construction of solar desalination pilot system in the future.