JPH081029Y2 - Ultrapure water production equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an apparatus for producing ultrapure water used in the electronic industry such as the semiconductor industry.

(Prior Art and Problems to be Solved) Ultrapure water used in the electronic industry is required to have, for example, the water quality shown in Table 1 below.

 An example of a conventional ultrapure water production system is shown in FIG.

The manufacturing apparatus (51) is composed of a primary pure water system (52) and a secondary pure water system (53), and the primary pure water system (52) includes a filtration device (54), a reverse osmosis device (55), and a deionizer. It mainly consists of a gas device (56) and an ion exchange device (57), and the secondary pure water system (53) is an ultraviolet sterilizer (58) and a demineralizer (5).
9) and reverse osmosis device (60). However, in the secondary pure water system having such a configuration, the configuration of the device is complicated and operation monitoring is complicated, and since the ion exchange device and the reverse osmosis device are used, regeneration of the ion exchange resin is performed. There was a drawback that the replacement cost of the reverse osmosis membrane was high.

Further, there is an example in which a multi-effect evaporation device is partially used in a pure water producing device for pharmaceuticals, but this device could not produce ultrapure water for the electronic industry due to the following reasons. That is, as the method of finishing the inner surface of the evaporator of this apparatus, the average roughness is 0.8 μm or more by mechanical polishing (buff # 400 finishing), or the average roughness is 0.7 after performing electrolytic polishing on the mechanical polishing. The method of finishing to more than μm was adopted. However, with this level of surface finish, as shown in FIGS. 3 and 4, there are numerous irregularities with severe undulations on the inner surface of the evaporator, so the fine particles adhering to these recesses cannot be removed by washing. ,
During the operation of the equipment, the outflow of fine particles would continue in the pure water produced. In addition, if there are undulating irregularities on the inner surface of the evaporator, the surface becomes active and metal ions are easily eluted, and the metal ion concentration in the product water is 0.01%.
Could not be less than ppb.

An object of the present invention is to provide an apparatus for producing ultrapure water that can solve all the problems of the above-mentioned conventional techniques.

(Means for Solving the Problem) This invention was made based on the finding that the above object can be achieved by mirror-finishing the surface of a required portion of the secondary pure water system to a required average surface roughness.

That is, the ultrapure water producing apparatus according to the present invention is a multiple-effect evaporator that evaporates primary pure water from a primary pure water apparatus to obtain secondary pure water. The surface of the contact point between the vapor generated by the evaporation of the primary pure water concentrate and the secondary pure water generated by the condensation of the generated vapor was mirror-polished to an average roughness of 0.6 μm or less. It is characterized by.

The mirror-finished portions are, for example, the outer surface of the heat transfer tube, the inner surface of the still body, and the outer surface of the condenser, which are in contact with pure steam and ultrapure water in which the steam is condensed.

The mirror finishing is performed by subjecting the material surface to, for example, an electrolytic composite polishing method.

The reason for limiting the average roughness to 0.6 μm or less is that if the average roughness exceeds 0.6 μm, numerous irregularities with severe undulations exist on the machined surface, and the fine particles adhering to these recesses cannot be removed even by washing, resulting in a pure production. If it mixes in water forever and if there are undulations on the machined surface, the surface will be in an active state and metal ions will easily elute, reducing the metal ion concentration in the product water to 0.01 ppb or less. Because you cannot do it.

(Function) By mirror-finishing the surface of the required portion of the secondary pure water system to an average roughness of 0.6 μm or less, it is possible to prevent fine particles from adhering to the surface, and the adhered fine particles are easily removed by washing. It Furthermore, because the surface is smooth,
The elution of metal ions is greatly reduced, and the concentration of eluted metal ions in production water is 0.01 ppb or less.

(Embodiment) An example of this invention will be specifically described with reference to FIG.

The ultrapure water production system consists of a multi-effect distillation system, including a multi-effect distiller (1), multiple effect pumps (5),
It is mainly composed of an ultrapure water pump (9) and a vacuum device (6). The steam generated in each effect stage becomes mist removed as it passes through the demister (4) to become pure water steam, which is then formed on the outer surfaces of the vertical heat transfer tubes (7) and the preheater (2). It is condensed and becomes secondary pure water, that is, ultrapure water. The outer surface of the heat transfer tube (7) and the inner surface of the still body, which are in contact with the pure steam in the still and the ultrapure water generated by the condensation of the steam, respectively, have a surface of 0.6
It is mirror-finished to an average roughness of less than μm.

The pure water obtained at each effect stage flows into the pure water reservoir of the next stage, merges, and flows into the pure water reservoir (8) of the final stage. The steam generated in the n-th effect stage is mist-removed by the mist separator (4), then condensed on the outer surface of the preheater and the outer surface of the heat transfer tube of the condenser (3) to become ultrapure water, and the pure water reservoir ( Enter 8),
The ultrapure water pump (9) delivers water to the point of use.

The outer surface of the condenser (3) is also mirror-finished to 0.6.
The average roughness is less than μm.

In the above embodiment, the heat transfer tube (7) is the pleated heat transfer tube used in the pure water producing apparatus for medicine.

FIG. 6 shows a modified example of the heat transfer tube used in the above-mentioned multi-effect distiller (1). This heat transfer tube (10) is called a pleated heat transfer tube, and has a spiral fold (11) perpendicular to the heat transfer tube axis.
Is provided. If the outer surface of the pleated heat transfer tube is mirror-finished to an average roughness of 0.6 μm or less, droplet condensation is likely to occur and the overall heat transfer coefficient increases. Fig. 7 shows the flow rate inside the fluted heat transfer tube, the foldless heat transfer tube without mirror finishing, and the pleated heat transfer tube with mirror finishing, and the sum of the flow rate inside each tube when the diameter is 2 inches. A graph showing the relationship with the heat transfer coefficient is shown. From this graph, the heat transfer tubes with pleats are 2-3 of the heat transfer tubes without pleats.
It has double the overall heat transfer coefficient, and when the pleated heat transfer tube is subjected to mirror surface processing, it is 10% more than that without mirror surface processing.
It can be seen that the overall heat transfer coefficient increases by about%. Therefore, the use of a pleated heat transfer tube having a mirror finish as the heat transfer tube (7) has an advantage that the device can be made smaller than when a foldless heat transfer tube is used.

Table 2 shows the results of water quality surveys for the case of using the pleated heat transfer tube with no mirror finish and the case of using the pleated heat transfer tube with mirror finish. From this table, it can be seen that the iron ion concentration can be made extremely small by using the heat transfer tube with a fold that is mirror-finished.

The pleats of the pleated heat transfer tube may be, for example, a disc fold other than the spiral pleats, or a pleated attached parallel to the heat transfer tube axis.

(Effect of the Invention) According to the pure water production system of the present invention, since the surface of the required portion of the secondary pure water system is mirror-finished to an average roughness of 0.6 μm or less, fine particles will adhere to the surface. Can be effectively prevented, and the adhered fine particles can be easily removed by washing. Furthermore, since the surface is smooth, the elution of metal ions can be reduced as much as possible, and the concentration of eluted metal ions in product water can be suppressed to 0.01 ppb or less.

Further, according to this system, operation monitoring can be greatly simplified as compared with the system shown in FIG. 2, and since no ion exchange resin is used, resin replacement / regeneration costs are unnecessary, and a reverse osmosis device is also available. Since it is not used, there is no need to replace the reverse osmosis membrane.

[Brief description of drawings]

FIG. 1 is a flow sheet of a pure water production system showing an embodiment of the present invention, FIG. 2 is a flow sheet of a pure water production system showing a conventional example, and FIG. 3 is a graph showing surface roughness by conventional mechanical polishing. , Fig. 4 is a graph showing the surface roughness by the conventional mechanical polishing and electrolytic polishing, Fig. 5 is a graph showing the surface roughness by the mirror surface processing of this invention, and Fig. 6 is the heat transfer tube used in this invention. And FIG. 7 is a graph showing an example of the overall heat transfer coefficient of the heat transfer tube. (1) ... Multi-effect distiller, (2) ... Preheater, (3)
… Condenser, (4) …… Demister, (5) …… Pump, (6) …… Vacuum device, (7) …… Heat transfer tube, (8)…
... Pure water reservoir, (9) ... Ultra pure water pump.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Shiro Inoue 5-3 28 Nishikujo, Konohana-ku, Osaka City, Osaka Prefecture Hitachi Shipbuilding Co., Ltd. (72) Hideo Suematsu 5-9, Nishikujo, Konohana-ku, Osaka City, Osaka Prefecture Hitachi Shipbuilding Co., Ltd. 3-28 (72) Inventor Kazunori Kiba 5-3-28 Nishikujo, Konohana-ku, Osaka City, Osaka Prefecture Hitachi Shipbuilding Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. A multiple-effect evaporator for evaporating primary pure water from a primary pure water apparatus to obtain secondary pure water, wherein a primary pure water or a primary pure water concentrate is obtained at a required evaporation effecting stage. The average roughness is 0.6 μm on the surfaces of the steam generated by evaporation and the secondary pure water generated by condensation of the generated steam.
A pure water producing apparatus characterized by being mirror-polished as follows.