Project Background
A 10GW integrated PV cell production base in Chinese Mainland shares one circulating water system for silicon wafer texturing, pure water preparation and cleaning & cooling, with a stable circulating flow rate of 1700m³/h. PV silicon wafer manufacturing requires ultra-high water cleanliness. Suspended silicon powder, colloids and calcium-magnesium precipitates in water will foul reverse osmosis membrane elements, degrade pure water quality, impair silicon wafer etching/texturing appearance and electrical conductivity, and reduce finished PV cell yield. The original pretreatment adopted single-layer quartz sand filters. After three years of operation, insufficient processing capacity and low automation could no longer support expanded production.
The park has strict water reuse assessment targets, yet the old system failed to meet standards. The client needed in-situ replaceable, automatic multi-media filters with layered deep filtration to reduce suspended solids, protect RO membranes, boost reclaimed water ratio and achieve stable output, water conservation and lower maintenance costs.
Core Pain Points
Single filter medium cannot trap fine silicon powder and colloids, causing RO membrane chemical cleaning every 28 days with 8-hour shutdown each time, cutting production and shortening membrane service life with high replacement costs.
All filter tanks must shut down simultaneously for backwashing without independent tank flushing, resulting in soaring water turbidity and damage to precision downstream equipment.
Full manual operation: two staff add/replace quartz sand monthly; manual backwashing consumes massive water, with water reuse rate only 62% (below the 75% standard), incurring extra water intake fees and failing environmental assessments.
No online differential pressure monitoring; fully clogged filter layers lead to sharp pipe pressure spikes, posing risks of pipeline deformation and leakage.
Customized LEFILTER Solution
LEFILTER deployed 4 sets of LF-DM series multi-media filters in parallel for the 1700m³/h working condition, directly replacing old sand tanks via flange connection without large civil reconstruction.
Thickened carbon steel tank with internal & external epoxy anti-corrosion coating resists weak acid & alkali in silicon cleaning water. Three-layer gradient filter media (anthracite, refined quartz sand, garnet) trap large silicon powder, fine colloids and metal precipitates by grading, stabilizing effluent turbidity below 3NTU and SDI＜3 to satisfy RO inlet requirements.
Independent tank air-water combined backwash logic with high-precision differential pressure transmitters. Single tank auto backwash triggers at 0.12MPa while other units keep supplying water; the full 35-second flushing process does not interrupt silicon wafer cleaning circulation.
Independent PLC control cabinet with Modbus interface connects to plant DCS. Operators view real-time differential pressure, backwash times and turbidity remotely, adjust cleaning parameters and receive acousto-optic fault alarms.Full equipment delivery finished within 8 days to match technical transformation schedule.
Operating Effects
Stable operation for 12 months with 93% comprehensive interception of silicon powder and colloids. RO membrane cleaning cycle extended from 28 days to 90 days, cutting annual production loss by 510,000 RMB. Independent auto backwashing eliminates manual filter media replacement; maintenance staff reduced from 2 to 1, saving 230,000 RMB annual labor & media costs. Backwash water consumption reduced by 62%, water reuse rate lifted from 62% to 78%, saving 81,000 tons pure water yearly and passing water-saving assessments. Stable water quality lowers defective silicon wafers, raising PV cell yield by 2.8%. This multi-media filter serves as a benchmark PV water treatment renovation case.
