Reclamation of Process Water and Silicon Fines

Shaping of silicon ingots prior to wafering comprises several cutting and grinding operations.  

Large quantities of water must be used to cool tools and silicon surfaces, to act as a lubricant and to remove the resultant silicon fines. The spent process water leaves the tools highly contaminated by silicon particles.

Pall introduces a new generation of fully automated separation systems for the reclamation of water and silicon sludge from the spent grinding/sawing water. (Read the related Application Bulletin here.) The systems enable PV wafer manufacturers to:

  • Re-use up to 95 % of spent process water as high quality water.
  • Reduce wastewater discharge volumes.
  • Improve sawing/grinding performance by controlling process water specifications.
  • Reduce machine fouling and uncontrolled. sedimentation in pipes, tanks and sinks.
  • Reduce chemical hazards due to silicon-water. interaction by controlled pre-treatment of spent process water.
  • Collect de-watered silicon debris having very little chemical contamination, as feedstock for silicon re-use.

The heart of such a reclaim system (see diagram below) is a dynamic membrane filtration (MF) unit combined with physico-chemical treatment of the concentrated silicon.

The systems clarify the contaminated process water. Typically 90 to 95 % of the contaminated process water is perfectly clarified ready for re-use. The remaining concentrate may be discharged, mixed with other wastewater streams, or subjected to additional treatment to meet discharge regulations or to de-water the silicon debris. Other options are available on request. 

 

Photovoltaics Overview
Photovoltaics - Applications
Photovoltaics - Polysilicon Purification and Processing
Photovoltaics - Crystal Growing
Photovoltaics - Silicon and Process Water Reclamation
Photovoltaics - Crystalline Silicon Cell Processing
Photovoltaics - Thin Film Module Manufacturing
Photovoltaics - Products

Pall has over 20 systems, treating 3 to 33 m³/h (13-145 GPM) silicon containing wastewater, operating successfully throughout the world.   The photograph below shows a dynamic filtration unit designed for 30 m³/h (132 GPM) silicon grinding/sawing wastewater. It provides 2 x 75 % architecture for safe process water supply.

Reclaim of Spent Grinding/Sawing Water

Reclaim of Spent Grinding/Sawing Water

Automated Microfiltration System for PV Silicon Grinding/Sawing Water Reclaim

Automated Microfiltration System for PV Silicon Grinding/Sawing Water Reclaim