US 7,018,529 B2Granted

System for producing ultrapure water

AssigneeKurita Water Industries Ltd.

InventorsYukihiro Furukawa, Masatake Okumura

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Abstract

The ultrapure water producing system produces ultrapure water with high purity and remarkably low content of metals even just after restart of operation thereof. Water sent through the pump 3 or 4 into a line 8 flows through a heat exchanger 10, a line 12, a UV oxidation apparatus 20, a line 22, an ion exchange device 30, a line 32 and a membrane filtering device 40 and is treated in each device in this order to be ultrapure water. The devices 10, 20, 30, 40 have bypass lines 11, 21, 31, 41, respectively. In the sterilizing process, bactericide water is fed only to the membrane filtering device 40 via the bypass lines 11, 21 and 31. In the following sterilizing process of the heat exchanger 10 and the UV oxidation apparatus 20, the bactericide water flows the line 41 bypassing around the membrane filtering device 40.

Claims8

Dependent claims

An ultrapure water producing system comprising:

a subtank for storing primary water;
an ultrapure water producing apparatus for treating primary water to produce ultrapure water comprising at least an ultraviolet oxidization device, an ion exchange device, and a membrane separation device which are arranged in this order;
a supplying line for supplying ultrapure water produced by the ultrapure water producing apparatus to a point of use;
a return line for returning residual ultrapure water passed through the point of use without being used therein to said subtank;
means for passing bactericide water through said membrane separation device with bypassing the devices arranged at the upstream side of said membrane separation device;
means for passing the bactericide water through said device arranged at the upstream side of said ion exchange device, and making the bactericide water flowing out of said device bypass said ion exchange device and said membrane separation device;
means for feeding bactericide to water stored in said subtank to prepare the bactericide water whereby the bactericide water in the subtank is sent therefrom for cleaning the devices;
and
means for substituting the bactericide water in the subtank for primary water.

6 more elements

Dependencies are inferred from the claim text.