Liquid purification or separation – Processes – Utilizing electrical or wave energy directly applied to...
Reexamination Certificate
1999-04-20
2001-07-03
Drodge, Joseph W. (Department: 1723)
Liquid purification or separation
Processes
Utilizing electrical or wave energy directly applied to...
C095S058000, C095S068000, C095S069000, C210S634000, C210S785000, C209S001000, C436S010000, C073S001020, C073S038000
Reexamination Certificate
active
06254787
ABSTRACT:
This application claims priority under 35 U.S.C. §§119 and/or 365 to 121505/1998 filed in Japan on Apr. 30, 1998; the entire content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for preparing a fluid containing size-controlled particles, thereby establishing a fluid flow of size-controlled particles in a dispersed state. This type of fluid can be used for the particle size calibration (scale adjustment or correction) of particle measurement instruments and for testing the particle collection performance of filters.
2. Description of the Related Art
Light-scattering particle measurement instruments for measuring microparticles in a gas or liquid must be subjected to a particle size calibration prior to use. Fluids that contain size-controlled particles in a dispersed state are used as the standard fluids in these calibrations, and monodispersed particles whose size distribution essentially presents a single peak are used as the size-controlled particles in these standard fluids.
The standard fluids used for the calibration of light-scattering instruments for measuring the particles in a gas typically consist of inert gases containing monodispersed particles of polystyrene latex (PSL). More specifically, standard fluids of this type typically comprise gaseous fluids prepared by spraying a commercially available liquid containing monodispersed PSL particles into an inert gas flow at around atmospheric pressure. Water containing dispersed PSL monodispersed particles is generally employed as the standard fluid for calibrating light-scattering instruments for measuring particles in a liquid.
The particle collection performance of particle-removing filters is tested by passing a standard fluid—in this case a gas containing size-controlled particles in a dispersed state—through the filter. The size-controlled particles used in tests of this type take the form of polydispersed particles whose size distribution essentially presents a plural number of peaks. The use of polydispersed particles and the measurement of the number of particles exiting the filter enables calculation of the collection efficiency at various particle sizes in a single procedure.
The standard fluid (gas) employed in the testing of the particle collection performance of filters typically consists of polydispersed particles of, for example, dioctyl phthalate (DOP) or triphenyl phosphate (TPP), dispersed in N
2
gas. Standard fluids of this type are prepared by spraying an aqueous solution containing the DOP or TPP into a flow of N
2
gas at around atmospheric pressure.
In order to achieve higher measurement accuracies with light-scattering particle measurement instruments, the calibration must be run under conditions approximating actual conditions using the target fluid (i.e., the fluid that will ultimately be subjected to measurement) as the matrix fluid of the calibrating standard fluid. When, for example, the target fluid is a gas such as HCl, HBr, SiH
4
, PH
3
, or B
2
H
6
, one is dealing with reactive gases whose pressure during measurement is typically substantially higher than atmospheric pressure. When the target fluid is a liquid such as H
2
O
2
, NH
4
OH, trichloroethylene, or xylene, one is dealing with liquids whose refractive index is different from that of water, which prevents accurate particle size measurement when water is used for calibration. Similarly, in the case of particle-removing filters, in order to obtain agreement between the performance data acquired by testing and the performance data during actual use, the testing must be run under conditions approximating actual conditions using the target fluid (i.e., the fluid that will ultimately be filtered) as the matrix fluid of the standard fluid used for particle collection performance testing.
The use of the target fluid as the matrix fluid under conditions approximating actual conditions causes the following problems for the procedures heretofore used to prepare a fluid containing size-controlled particles. When the target fluid is a reactive fluid, the size-controlled particles can react with the reactive matrix fluid, which can lead to changes in the particle sizes and to the admixture of reaction products into the matrix fluid. In addition, the admixture/dispersion of size-controlled particles into the fluid by spraying results in the admixture of the spray gas into the matrix fluid and hence in a shift in composition. Moreover, this admixture/dispersion method cannot be used when the target fluid is a compressed gas.
The present invention was developed in view of the aforedescribed problems of the prior art. The object of the present invention is to provide a method for establishing a fluid containing size-controlled particles that has been optimized with respect to use of the target fluid as the matrix fluid under conditions approximating actual conditions.
SUMMARY OF THE INVENTION
In a first aspect of the present invention, there is provided a method for preparing or establishing a fluid containing size-controlled particles. Also provided is a method for establishing a fluid flow of size-controlled particles and its use in calibration applications. The method for preparing the fluid comprises
a predispersion process in which starting particles having various sizes and comprising a material inert to the matrix fluid are mixed and dispersed into a high-purity carrier gas that is inert with respect to said starting particles,
a fractionation process in which size-controlled particles are obtained by fractionating said starting particles by passing a flow of the starting particle-loaded carrier gas through a dry-process fractionator,
a collection process in which a flow of the carrier gas loaded with the now size-controlled particles is passed through a porous member in order to collect said size-controlled particles on said porous member, with said porous member comprising a material inert with respect to the matrix fluid, and effecting an electrostatic particle collection, and
a main dispersion process in which said size-controlled particles are released from the porous member and mixed and dispersed into the matrix fluid by passing a flow of said matrix fluid through the porous member loaded with the size-controlled particles while at the same time applying ultrasonic vibrations to said porous member.
A second aspect of the present invention is characterized by using the aforesaid fractionator in the method of the first aspect to carry out an electrostatic fractionation of the starting particles.
A third aspect of the present invention is characterized by the porous member in the methods of the first and second aspects being a filter with a pore size that is substantially larger than the size-controlled particles.
A fourth aspect of the present invention is characterized by the use of spraying to mix and disperse the starting particles into the carrier gas in the predispersion process of any of the methods according to the first to third aspects.
A fifth aspect of the present invention is characterized by the application of the ultrasonic waves as pulses with a width of 1 msec. to 10 seconds and an interval of 100 msec. to 100 seconds in any of the methods according to the first to fourth aspects.
A sixth aspect of the present invention is characterized by the matrix fluid in any of the methods according to the first to fifth aspects being a reactive gas selected from the group consisting of SiH
4
, PH
3
, B
2
H
6
, AsH
3
, SiCL
2
H
2
, H
2
, HCl, Cl
2
, HF, F
2
, HBr, Br
2
, HI, NH
3
, CH
4
, C
2
H
2
, C
2
H
4
, C
2
H
6
, C
3
H
8
, C
4
H
10
, NO, NO
2
, N
2
O, CO, and O
2.
A seventh aspect of the present invention is characterized by the pressure of the aforesaid reactive gas matrix fluid in the method of the sixth aspect being higher than atmospheric pressure.
An eighth aspect of the present invention is characterized by the use of a liquid selected from the group consisting of water, hydrochloric acid, nitric acid, hydrogen fluoride,
Kimura Masao
Suzuki Itsuko
Tarutani Kohei
Burns Doane Swecker & Mathis L.L.P.
Drodge Joseph W.
L'Air Liquide, Societe Anonyme pour l'Etude et l'
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