Due to its high separation efficiency, energy saving, high efficiency, and no secondary pollution, membranes are particularly important in today's energy supply shortage, increasing resource scarcity, and deteriorating ecological environment. However, the problem of membrane flux attenuation caused by membrane fouling has become a key obstacle to its industrialization process. In industrial applications, cross flow filtration is generally used to reduce membrane fouling and control concentration polarization. However, conventional cross flow filtration has a low recovery rate, and for treating high turbidity water and high viscosity solutions, in order to reduce membrane fouling, it is often necessary to increase the membrane surface flow rate to increase the shear force on the membrane surface. However, this increase in shear force is limited, and it also requires a high-power reflux pump, which consumes a lot of energy
. As a new membrane separation technology, the vibrating membrane system can effectively improve the shear velocity of the membrane surface, resist membrane fouling, improve recycling efficiency, and save a lot of energy.
Comparison between vibrating membrane and conventional cross flow filtration
In cross flow filtration, the raw materials enter the membrane with a certain composition and flow parallel to the membrane surface. Along different positions of the membrane, the composition of the raw materials gradually changes. The raw material liquid is divided into two streams: permeate stream and concentrate stream. The concentration of retention near the membrane surface of the filter membrane is high, and a deposition layer (gel layer) is generated, both of which reduce the membrane filtration flux.
The vibrating membrane system effectively prevents the deposition of particulate matter on the membrane surface by generating sinusoidal shear waves on the membrane surface, and strong shear forces can cause the deposited material on the membrane surface to return to the feed solution. The surface of the vibrating membrane is free of sediment, and the membrane filtration resistance is low, thus maintaining a high filtration flux.
Compared to traditional cross flow filtration, vibrating membrane filtration has strong resistance characteristics due to the different flow velocity distribution on the membrane surface. Although traditional cross flow filtration can maintain a high membrane surface flow velocity, the presence of viscous forces results in a low tangential flow velocity near the membrane surface. The tangential velocity of the membrane surface of the overclocking diaphragm is determined by the vibration frequency and amplitude of the diaphragm, resulting in a high membrane surface velocity and a low intermediate velocity, thereby obtaining a larger shear stress.
Structure and characteristics of vibrating membrane
1 Composition and working principle
The vibrating membrane can be simply divided into two parts, one is the flat membrane component, and the other is the vibration device, which can be combined in various ways according to needs. The vibration device can generate 3000 vertical vibrations per minute to drive the membrane module and water body to undergo small amplitude high-frequency shear vibration.
Advantages of overclocking diaphragm
(1) Strong anti blocking ability
By introducing a high shear force on the membrane surface, the gel layer is suspended on the membrane surface, greatly improving the filtration flux and reducing the use area.
(2) High energy utilization efficiency
Conventional filtration is generally achieved by increasing the membrane surface flow rate to reduce particle deposition on the membrane surface. Most of the energy is consumed within the membrane, and the energy utilization rate is only 10%. The vibrating membrane can generate shear forces in specific areas within the membrane, with an energy utilization rate of 99%.
(3) Wide application range
The vibrating membrane system can be used to treat high concentration wastewater, including oily wastewater, leachate from garbage, and other high turbidity and viscous materials that are difficult to treat.
