Patent ID: 9592471
Date: 2017-03-14
CPC Classifications: B01D,B24B,C02F

Claim:
1. A recycling method for recycling fresh slurry-containing wastewater from a chemical-mechanical semiconductor polishing process, the recycling method comprising: continuously feeding, in a filtration step, the fresh slurry-containing wastewater into a circulation vessel, while continuously removing mixed wastewater from the circulation vessel, continuously passing the removed mixed wastewater through an ultrafilter device which removes permeate from the mixed wastewater to obtain concentrated wastewater, and continuously passing the concentrated wastewater back into the circulation vessel to mix with the fresh slurry-containing wastewater in the circulation vessel in order to obtain the mixed wastewater; adding, in a concentration step which follows the filtration step in time, an agglomeration inhibitor and shutting off the feed of the fresh slurry-containing wastewater into the circulation vessel, while maintaining the continuously removing the mixed wastewater from the circulation vessel, the continuously passing the removed mixed wastewater through the ultrafilter device to produce the concentrated wastewater, and the continuously passing the concentrated wastewater back into the circulation vessel; and removing, in a step which follows the concentration step in time, the mixed wastewater from the circulation vessel as recycling slurry, wherein the filtration step further comprises determining a first solids concentration in the circulation vessel, and the filtration step is performed until the first solids concentration exceeds a first-concentration threshold value, and after the first solids concentration exceeds the first-concentration threshold value, the concentration step is performed, and wherein the concentration step further comprises determining a second solids concentration in the circulation vessel, and the concentration step is performed until the second solids concentration exceeds a second-concentration threshold value, and after the second solids concentration exceeds the second-concentration threshold value, the step of removing the mixed wastewater as recycling slurry is performed.