Due to its high separation efficiency, energy saving, high efficiency, and no secondary pollution, the membrane is particularly important in today's energy shortage, resource shortage, and ecological environment deterioration. However, the problem of membrane flux decay caused by membrane fouling has become a key problem hindering its industrialization process. In industrial applications, cross-flow filtration is commonly used to reduce membrane fouling and control concentration polarization. However, conventional cross-flow filtration, the first rate is low, and for the treatment of high turbidity water and high viscosity solutions, in order to reduce membrane pollution, it is often necessary to increase the flow rate of the membrane surface to increase the shear force of the membrane surface, but the increase of this shear force is limited, and at the same time, he also needs a high-power reflux pump, which leads to the consumption of a large amount of energy. As a new type of membrane separation technology, the vibrating membrane system can effectively improve the shear speed of the membrane surface, resist membrane fouling, improve the utilization rate, and save a lot of energy.
Comparison of diaphragm and conventional cross-flow filtration.
In cross-flow filtration, the raw material enters the membrane with a certain composition and flows parallel through the membrane surface, and the composition of the raw material gradually changes along different positions of the membrane. The raw material is divided into two strands: permeation logistics and concentration logistics. The higher concentration of retentive material near the membrane surface and the formation of a deposited layer (gel layer) both reduce membrane filtration flux.
The vibrating membrane system effectively prevents the deposition of particulate matter on the membrane surface by generating a sinusoidal shear force wave on the membrane surface, and the strong shear force can make the material deposited on the membrane surface return to the material liquid. There is no deposit on the surface of the vibrating membrane, and the membrane filtration resistance is small, thus maintaining a high filtration flux.
Compared with traditional cross-flow filtration, vibrating membrane filtration has a strong resistance characteristic because of the different flow velocity distribution on their membrane surface. Although the traditional cross-flow filtration can maintain a high flow rate of the membrane surface, the tangential flow rate near the membrane surface is not large due to the existence of viscous force. The tangential velocity of the membrane surface of the overclocked vibrating membrane is determined by the vibration frequency and amplitude of the diaphragm, so that the flow velocity of the membrane surface is large and the intermediate flow velocity is small, so as to obtain a large shear stress.
Diaphragm construction and features.
1 Composition and working principle.
The vibrating membrane can be simply divided into two parts, one is a flat membrane module, and the other is a vibrating device, which can be combined according to needs. The vibrating device can generate 3000 times of vertical vibration per minute, driving the cassette module and the water body to perform small amplitude and high-frequency shear vibration.
2 Advantages of overclocking diaphragm.
1) Strong anti-clogging ability
By introducing a high shear force at the membrane surface, the gel layer is suspended on the membrane surface, which greatly increases the filtration flux and reduces the usable area.
2) High energy utilization
In order to reduce the deposition of particles on the surface of the membrane, conventional filtration generally adopts increasing the flow rate of the membrane surface, and most of its energy is consumed in the membrane, and the energy utilization rate is only 10. The vibrating membrane is capable of generating shear forces in specific areas within the membrane, with an energy utilization of 99 percent.
3) Wide range of applications
The diaphragm system can be used to treat large concentrations of wastewater, and can be used to treat oily wastewater, landfill leachate and other high turbidity and viscosity, which is difficult to treat.
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