US 7,066,008 B2 · Method for measuring concentration of solid or liquid particulate matter in a gaseous carrier medium

Abstract

A method of measuring concentration of solid or liquid particulate matter in a gaseous carrier medium, particularly suitable for measuring concentration and flow rate of pulverized fuel pneumatically transported in a duct to power station boiler burners. The method includes generating a radio frequency electromagnetic wave within a duct, measuring wave parameters within a range of frequencies, including a cut-off frequency, determining the cut-off frequency from changes in wave parameters, calculating dielectric permittivity of a two-phase flow duct load, and ascribing to this value a corresponding concentration value. The measured parameter is the rate of change of phase shift against frequency at two arbitrary points on a wave transmission path, whereas the waveguide cut-off frequency value is determined at a point where the rate of change of phase shift against frequency reaches a maximum.

Claims11

Dependent claims

A method of measuring the concentration of particulate matter suspended in a gaseous carrier medium whilst transported via a duct made of electrically conductive material, said method comprising the steps:

(a) generating a radio frequency electromagnetic wave within the duct,
(b) measuring wave parameters across a range of frequencies, including a wave cut-off frequency, at two arbitrary points on a wave transmission path the two arbitrary points lying in a plane that intersects both a duct axis and a wave generation point,
(c) determining the wave cut-off frequency, based on changes in wave parameters, and
(d) calculating a value of dielectric permittivity of a two-phase flow of a carrier gas and a particulate matter with which the duct is loaded and ascribing to this value of dielectric permittivity a corresponding value of a particulate matter concentration in actual flow conditions,
wherein measured wave parameters include a rate of change of phase shift in two points along a wave propagation (d(Δφ1)/df), and
wherein a value of a waveguide cut-off frequency (fg1) is determined as a value at which the rate of change of phase shift against frequency (d(Δφ1)df) reaches a maximum, and the value of dielectric permittivity (∈1) is derived from a dielectric permittivity formula
ɛ
1
=
(
1
⁢
,
⁢
81118
⁢
c
2
⁢
π
⁢
⁢
rf
g1
)
2
⁢
1
μ
1
.

28 more elements

(a) generating an electromagnetic wave within the duct,
(b) measuring wave parameters across a range of frequencies including the cut-off frequency at two arbitrary points on the wave transmission path which lie in a plane intersecting both the duct axis and the wave generation point,
(c) based on changes in wave parameters, determining a cut-off frequency shift for flow conditions of a particulate material of known concentration and for actual flow conditions, and
(d) deriving a value of dielectric permittivity ∈1 from a dielectric permittivity equation ∈1=1/μ1(1−Δfg/fgo)2, and ascribing to thus calculated dielectric permittivity (∈1), a corresponding concentration value of the particulate matter,
wherein a parameter determining the difference between cut-off frequency values (Δfg) is a value of the phase shift against frequency, represented by (S0, S1) section, of a selected S0 point on a phase shift curve (Δφ0), measured in two points of a wave propagation (k1) and (k2);
the shift being caused by a change in a concentration value from a known concentration value to an actual concentration value.

3 more elements

Dependencies are inferred from the claim text.

Method for measuring concentration of solid or liquid particulate matter in a gaseous carrier medium

Life of this patent

Method for measuring concentration of solid or liquid particulate matter in a gaseous carrier medium

Life of this patent

Abstract

Claims11