Norrigin’s R&D team broke through the key technologies of quantitative coating of PVDF microfiltration layers and successfully developed innovative products by independently designing the support and composite equipment with wave crest coated. How to optimize the operating process in a targeted manner, explore the best operating conditions, and reduce operating energy consumption and maintenance costs is one of the difficult problems that the R&D team needs to overcome.
The water production channels of the corrugated flat membrane are arranged horizontally to ensure that the gas and water channels are connected up and down, so that the filter membrane surface and the gas and water channels are interspersed and fully contacted. Through simulation calculation and optimization through fluid mechanics modeling, the aeration system of the corrugated flat membrane module is designed to not only meet the uniform distribution of bubbles in all membrane gaps, but also provide cross-flow shear stress to effectively suppress membrane fouling.
Membrane Module Design
Operational stability: With the corrugated flow channel structure on the membrane surface, the corrugated flat membrane module forms a local vortex during the rising process of the air-water two-phase flow, and spins back under the action of aeration. Compared with the flat structure, The scrubbing ability of this structure is significantly enhanced. At the same time, the bubbles are evenly distributed, which greatly reduces the aeration dead zone in the flow field and avoids the anaerobic state of local activated sludge.
Anti-pollution: After the bubbles rise to the top of the membrane, they enter the external descending zone and circulate with the low-concentration mixed liquid to achieve effective back-mixing of the high-concentration mixed liquid, forming a good hydraulic circulation flow inside and outside the membrane module. field to avoid membrane surface pollution caused by local sludge concentration and provide good biochemical conditions and anti-pollution capabilities for the operation of the unit .
Central airlift internal circulation reaction model
Packing density: Corrugated flat membrane not only has the advantages of high flux, stable operation, and long service life of traditional flat membranes , but also greatly improves the packing density of the membrane module , which is more than twice that of traditional flat membranes. The string-pattern flat membrane module can achieve multi-layer module stacking , which is extremely flexible and effectively reduces the cost of space. The energy consumption per ton of water is much less than that of traditional membrane modules .
Packing density (㎡/㎡) | design flux ( LMH ) | Design projected aeration intensity (m³/㎡·h) | Membrane surface aeration intensity ( L /㎡·min) |
5 75 | 2 0-25 | 9 0-105 | 1.8 _ |
Membrane Process Operation Mode
Intermittent water production: Corrugated flat membrane modules usually adopt a built-in operation mode with constant flow of intermittent water production. The water is pumped for 7 minutes and air-exposed for 1 minute . This operation mode can avoid local sludge accumulation on the surface of the reaction tank membrane during the continuous suction process , causing serious concentration polarization and increasing filtration resistance. The intermittent water discharge method can effectively alleviate membrane pollution and facilitate long-term stable operation of the unit .
Physical cleaning: The corrugated flat membrane module uses a unique high-aeration cleaning process to perform short-term high-intensity scouring on the membrane surface. Combined with the flexibility of the membrane's own structure, it can form high-frequency vibrations during the aeration process. The evenly distributed bubbles in the aeration system can effectively remove the mud cake layer on the membrane surface, laying the foundation for in-situ cleaning of the corrugated flat membrane and ensuring the subsequent chemical cleaning effect.
Chemical cleaning: The corrugated flat membrane module uses acid /alkali agents for compound online chemical cleaning. During the cleaning process, the chemical cleaning pump provides a certain flushing pressure (≤35KPa), injects chemicals into the membrane module in reverse direction , and then overflows evenly from the membrane surface through the membrane holes. The cleaning flux (12-15LMH) and cleaning time (15-20min) are determined through calculation and experiment of resistance and flux distribution in the flow channel. This cleaning method can effectively remove organic and inorganic pollution and inhibit the growth of microorganisms in the membrane pores.