JP6477487B2 - Method and apparatus for measuring the number of fine particles in ultrapure water - Google Patents

Description

  The present invention relates to a method and apparatus for measuring the number of fine particles in ultrapure water, and more particularly to a method and apparatus for measuring the number of fine particles so as to reduce errors due to noise.

  As a device for measuring (counting) the number of fine particles in ultrapure water online, a fine particle meter (particle counter) using laser scattering is used (Patent Document 1).

  It is known that particle detectors using laser scattering are prone to photodetection errors due to the effects of vibration, cosmic rays, self-noise, etc. It is necessary to distinguish whether a particle meter using laser scattering actually detects particles due to noise due to cell contamination or the like, or causes false detection due to noise. When trend management is performed by a particle meter using laser scattering, it is necessary to determine whether or not the sudden rise or hunting of particles is affected by the noise of the particle meter.

  In Patent Document 2, it is assumed that particles in the air traverse the light beam, scattered light is detected by two photodiodes, and when any of the photodiodes detects particles, the particles are detected. Only the method of dealing with noise when detecting particles is described. FIG. 4 is an explanatory diagram of the method disclosed in Patent Document 2. The air is discharged from the inflow nozzle 41, passes through the light beam, is sucked by the discharge nozzle 42 and discharged. The scattered light scattered by the particles in the air is collected and detected by the first photodiode 51 or the second photodiode 52 via the condenser lens 50.

  At time t, the particles are located near the inflow side nozzle in the light beam, and the scattered light at this time is focused on the first photodiode 51. When the time advances by Δt and becomes time t + Δt, the particles have progressed to the discharge nozzle 42 side in the light beam, and the scattered light at this time is focused on the second photodiode 52.

  It is assumed that particles are detected when the first photodiode 51 detects particles in a predetermined time zone including time t and the second photodiode 52 detects particles in a predetermined time zone including time t + Δt. When only one of the photodiodes 51 and 52 detects particles, it is handled as noise.

JP2008-241584 JP-A-5-149866

  The method disclosed in Patent Document 2 is for detecting particles in the air. Even if this method is applied to the detection of particles in ultrapure water, the particles cannot be detected with high accuracy. That is, both the air and water particles perform Brownian motion, but in water, the Brownian motion speed of the particles is significantly higher than in air, and the particles present in the light beam at time t in FIG. Even so, it does not necessarily proceed to the discharge nozzle 42 side at time t + Δt. Therefore, even though there are actually fine particles in ultrapure water, only the first photodiode 51 may detect the fine particles, and the second photodiode 52 may not detect the fine particles. Becomes larger.

  The present invention solves such problems, and a method and apparatus for measuring the number of fine particles in ultrapure water capable of accurately detecting the number of fine particles in ultrapure water, and an ultrapure water production apparatus equipped with this measurement apparatus. The purpose is to provide.

  The method for measuring the number of fine particles in the ultrapure water of the present invention comprises the steps of separately passing ultrapure water through two or more fine particle number measuring means and measuring the number of fine particles per unit time or unit volume, And adopting the lowest value of each measured value as the number of fine particles in ultrapure water.

  As a means for measuring the number of fine particles, an apparatus for measuring the number of fine particles by a laser light scattering method is preferable.

  The apparatus for measuring the number of fine particles in ultrapure water according to the present invention comprises two or more measuring means for measuring the number of fine particles in ultrapure water, ultrapure water flow means for flowing ultrapure water to each measurement means, Comparing means for comparing the number of fine particles per unit time or unit volume detected by each measuring means and outputting the lowest value.

  An apparatus for measuring the number of fine particles in ultrapure water according to another aspect of the present invention comprises a measuring means for measuring the number of fine particles of 2 or more and an ultrapure water flow means for flowing ultrapure water separately to each measuring means.

  The ultrapure water production facility of the present invention includes such a fine particle number measuring device as water quality monitoring means.

  According to the method and apparatus for measuring the number of fine particles in ultrapure water of the present invention, the number of fine particles per unit time or unit volume is measured by passing ultrapure water through a plurality of fine particle number measuring means. Since the smallest one is adopted as the number of fine particles of the ultrapure water, it is possible to obtain fine particle number data having no or almost no influence of noise. Therefore, the water quality of the ultrapure water production facility can be managed with high accuracy, and the water quality trend can be managed with high accuracy.

It is a chart which shows the result of an Example. It is a flowchart of an ultrapure water manufacturing system. It is a block diagram of the particulate measuring device concerning an embodiment. It is explanatory drawing of a prior art example.

  Hereinafter, embodiments will be described.

  The present invention relates to a method and apparatus for measuring the number of fine particles in ultrapure water (the number of fine particles in a unit volume or the number of fine particles counted per unit time). In the present invention, the fine particles preferably have a particle size measured by a laser light scattering type fine particle meter of 0.2 μm or less and a detection lower limit value or more of the fine particle meter.

  In the present invention, ultrapure water is water having an electrical conductivity of 18.2 MΩ or more. The present invention is suitable for measuring the number of fine particles of ultrapure water having a fine particle number of 5000 / L or less.

  FIG. 2 is a flowchart showing an example of the ultrapure water production apparatus. As shown in the figure, ultrapure water is raw water (industrial water, city water, wells) in an ultrapure water production facility composed of a pretreatment device 1, a primary pure water production device 2, and an ultrapure water production device (subsystem) 3. Manufactured by treating water, etc.).

  The pretreatment device 1 including agglomeration, pressurized flotation (precipitation), filtration (membrane filtration) device, etc. removes suspended substances and colloidal substances in raw water. In this process, it is also possible to remove high molecular organic substances, hydrophobic organic substances, and the like.

  In the primary pure water production apparatus 2 equipped with a reverse osmosis membrane separation device, a deaeration device, and an ion exchange device (such as a mixed bed type or a 4-bed 5-tower type), ions and organic components in raw water are removed. The reverse osmosis membrane separation apparatus removes salts and ionic and colloidal TOC. The ion exchange apparatus removes salts and removes the TOC component adsorbed or ion exchanged by the ion exchange resin. In the deaerator, inorganic carbon (IC) and dissolved oxygen are removed.

The primary pure water from the primary pure water production apparatus 2 is passed from the tank 11 to the heat exchanger 13 by the pump 12 in the ultrapure water production apparatus 3, and then the ultraviolet (UV) irradiation apparatus (low-pressure UV oxidation in FIG. 2). Device) 14, ion exchange device 15 and ultrafiltration (UF) membrane separation device 16 to produce ultrapure water. In the low-pressure UV oxidizer 14, TOC is decomposed to an organic acid and further to CO ₂ by 185 nm UV emitted from a UV lamp. Organic substances and CO ₂ produced by the decomposition are removed by the ion exchange device 15 at the subsequent stage. In the UF membrane separation device 16, the fine particles are removed, and the outflow particles of the ion exchange resin are also removed.

  The ultrapure water obtained in this way is supplied to the use point 4 through the pipe 17, and surplus ultrapure water is returned to the tank 11 through the pipe 18.

  The use point 4 indicates a place where ultrapure water is used, and may include pipes, nozzles, and the like as appropriate in addition to a cleaning device for cleaning an object (for example, a semiconductor). Note that the ultrapure water used at the use point 4 is appropriately collected as drainage.

  Part of the ultrapure water from the UF membrane separation device 16 is supplied to the first particle counter 31 and the particle counter 32 via a pipe 20 branched from the pipe 17 and pipes 21 and 22 further branched from the pipe 20, respectively. Supply separately and measure the number of fine particles. Hereinafter, the first fine particle meter 31 is referred to as a fine particle meter A, and the second fine particle meter 32 is referred to as a fine particle meter B.

  Although illustration is omitted, a flow meter is provided on the downstream side of the particle meters A and B, respectively. The inner surfaces of the pipes 20, 21, and 22 are lined with fluororesin.

  In this embodiment, it is necessary to use the same model for the particle counters A and B. The fine particle meters A and B are preferably of a laser light scattering type. As the laser beam, one having a wavelength selected from a range of 532 to 808 nm is preferable. As the particle counter, Ultra DI20 (UDI-20) and Ultra DI50 (UDI-50) manufactured by Particle Measuring Systems, Inc., located in United States 5475 Airport Blvd Boulder, CO 80301 can be used, but are not limited thereto.

  The fine particle meters A and B are configured to flow the sample water so as to cross the light beam of the laser light, and detect the light scattered by the fine particles with a photodiode to detect the fine particles. The detection circuit of the particle counter generates a pulse signal every time one particle is detected. In this embodiment, the fine particle meter outputs the number of pulses per unit time, but the number of pulses per unit time is divided by the flow rate per unit time to obtain an ultrapure water per unit volume (for example, 1 L). The number of fine particles may be calculated and output. The unit time is preferably a time selected from 5 to 600 seconds, and 60 seconds (1 minute) is adopted in the examples described later.

  The particle count data signals detected by these particle meters A and B are respectively input to the comparison circuit as shown in FIG. 3, and the smaller number of particles per unit time is output as the number of particles to control the water quality of the ultrapure water production facility. Data.

  Thus, by setting the smaller number of detected particles of the two particle meters A and B as the number of particles, it is possible to obtain particle number data that is not affected by noise, and trend management of the ultrapure water production apparatus. Can be performed with high accuracy.

  In FIG. 2, two particle meters A and B are provided, but three or more particle meters are provided, and the minimum number of particles detected from the three or more particle meters is output from the particle comparison circuit. You may do it. In FIG. 2, the pipes 21 and 22 connected to the particle analyzers A and B are connected to the pipe 20 branched from the pipe 17, but the pipes 21 and 22 may be directly connected to the pipe 17. .

  An apparatus for measuring the number of fine particles in ultrapure water according to an aspect of the present invention includes a measuring means for measuring the number of fine particles of 2 or more, and ultrapure water flow means for flowing ultrapure water separately to each measuring means. .

  When a particle measuring device having the same (same model) particle size range is used as this measuring device, the measurement results are compared to determine whether the measuring device is abnormal or faulty. For example, when one measuring device counts many fine particles but the other one does not count, it can be determined that one of them is abnormal. In this case, by separately measuring the number of fine particles in ultrapure water using a highly reliable method such as a microscopic method, it is possible to determine which measuring device has an abnormality / failure and to determine whether there is an abnormality / failure. It is possible to replace the measuring device.

  Particle measurement devices with different particle size ranges (measurement ranges) (for example, when using Particle Measuring Systems particle counters UDI-50 and UDI-20, the number of fine particles present in each particle size range is known. When an increase in fine particles is recognized, it is possible to use and analyze this information to search for the cause and plan a solution.

In the ultrapure water production facility shown in FIG. 2, ultrapure water was produced at 15 m ³ / hr. A part of the ultrapure water from the UF membrane separation device 16 was passed through the pipes 20, 21, 22 to the particle counters A and B, respectively, and the number of particles was measured. The particle counters A and B are of a laser beam scattering system with a wavelength of 808 nm, and are of the same model (lower limit of measurement particle size 0.05 μm) of a domestic manufacturer.

  A time chart of the fine particle detection pulses of the fine particle meters A and B is shown in FIG. It should be noted that the number of pulses after 107 minutes of the particle counter A is considerably larger than that of the particle counter B, and the data after 107 minutes of the particle counter A of FIG. Table 1 shows the number of detected particles per minute between 100 and 139 minutes of the particle counters A and B.

  As shown in Table 1 and FIG. 1, between 0 and 107 minutes, the fine particle detection pulse per minute is 0 or 1 for both fine particle meters A and B, and the comparison circuit is 1 / min (both A and B). 1 / min.) Or 0 / min. (Other cases) is output as the particle count data. During the period of 107 to 250 minutes, the number of fine particles detected by the fine particle meter A is often significantly higher than that of the fine particle meter B. This is probably due to noise. During this time, the comparison circuit outputs the number of detected particles of the particle counter B as particle number data.

  As a result, the influence of noise was eliminated, and the quality of ultrapure water could be managed correctly. The average number of fine particles was 1/20 min, and 0.05 / min per minute. Since the amount of water passing through the particle meters A and B was 0.00375 L / min (3.75 ml / min), the number of particles per liter of ultrapure water was 13 particles / L.

Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.
This application is based on the JP Patent application 2013-226926 for which it applied on October 31, 2013, The whole is used by reference.

Claims (7)

A method for measuring the number of fine particles in ultrapure water,
A step of circulating ultrapure water separately to each means for measuring the number of fine particles of 2 or more and measuring the number of fine particles per unit time or unit volume,
A method of measuring the number of fine particles, comprising adopting the lowest value of each measured value as the number of fine particles in ultrapure water.   2. The method for measuring the number of fine particles according to claim 1, wherein said means for measuring the number of fine particles is a laser light scattering type fine particle number measuring device.   3. The method for measuring the number of fine particles according to claim 1, wherein the unit time is a time selected from 5 to 600 seconds. Two or more measuring means for measuring the number of fine particles in ultrapure water;
Ultrapure water distribution means for distributing ultrapure water to each measurement means,
An apparatus for measuring the number of fine particles in ultrapure water, comprising comparison means for comparing the number of fine particles per unit time or volume detected by each measuring means and outputting the lowest value.   5. The particle number measuring apparatus according to claim 4, wherein the particle number measuring means is a laser light scattering type particle number measuring apparatus.   6. The apparatus for measuring the number of fine particles according to claim 4, wherein the unit time is a time selected from 5 to 600 seconds. An ultrapure water production facility comprising the fine particle count measuring device according to any one of claims 4 to 6 as water quality monitoring means.

Images