Method of utilizing optical path difference in two-phase flow for analytical calculation of particle size gradation and solid content
A method utilizing optical path difference in two-phase flow for analytical calculation of particle size gradation and solid content comprises: changing a width of measurement area of a laser particle size analyzer, and collecting extinction values at two different optical path lengths and a scattered light intensity signal on each detector during monitoring; utilizing the scattered light intensity signal with a long optical path to subtract the scattered light intensity signal with a short optical path on each detector to obtain a set of new scattered light intensity signals with background subtracted; processing particle size distribution inversion calculations for the set of scattered light intensity signals with background subtracted to obtain gradation data of solid particles; processing subtraction of the logarithm of the extinction value of the short optical path from the logarithm of the extinction value of the long optical path to obtain new extinction value; calculating the solid content based on the new extinction value related data and the gradation data obtained. Neither the measured scattered light intensity signal of particle gradation nor the extinction value signal of measured solid content is affected by window lens contamination. A pure scattered light intensity signal can be obtained without measuring the background signal in the pure medium state. The long-term real-time underwater or atmospheric monitoring is realized.
1 . A method of solid content measurement utilizing optical path difference in two-phase flow, characterized in that, said method, carried out through a laser particle size analyzer comprises the following steps:
step 1: providing the laser particle size analyzer with a plurality of detectors, changing a width of measurement area of the laser particle size analyzer, and monitoring and collecting extinction values from direct source at two different optical path lengths and a scattered light intensity signal on each detector at two different optical path lengths, wherein the two different optical path lengths are defined as a long optical path length and a short optical path length, and the long optical path length is greater than the short optical path length;
step 2: utilizing the scattered light intensity signal at the long optical path length to subtract the scattered light intensity signal at the short optical path length on each detector to obtain a set of new scattered light intensity signals with background subtracted;
step 3: processing particle size distribution inversion calculations for the set of scattered light intensity signals with background subtracted to obtain gradation data of solid particles;
step 4: processing subtraction of the logarithm of the extinction value of the short optical path from the logarithm of the extinction value of the long optical path to obtain new extinction value related data;
step 5: processing calculation of the solid content based on the new extinction value related data and the gradation data obtained.
2 . The method of solid content measurement utilizing optical path difference in two-phase flow according to claim 1 , characterized in that: in step 2, the new scattered light intensity signals on each detector is calculated by the followings:
S
=
A
1
-
A
2
=
(
S
1
+
B
)
-
(
S
2
+
B
)
=
S
1
-
S
2
wherein A 1 refers to a scattered light intensity signal with long optical path and background on the detector, A 2 refers to a scattered light intensity signal with short optical path and background on the detector, B refers to the background signal, S 1 refers to a scattered light intensity signal with long optical path after the background is subtracted, S 2 refers to a scattered light intensity signal with short optical path after the background is subtracted, S refers to a scattered light intensity signal difference for different optical paths, that is, the new scattered light intensity signal; the new scattered light intensity signal on each detector constitutes a new set of scattered light intensity signals.
3 . The method of solid content measurement utilizing optical path difference in two-phase flow according to claim 1 , characterized in that: in step 4,
the new extinction value is:
-
3
C
v
K
ext
2
D
(
L
1
-
L
2
)
and a specific calculation of the new extinction value is:
ln
(
I
1
I
0
)
=
-
3
C
v
L
1
K
e
x
t
2
D
ln
(
I
2
I
0
)
=
-
3
C
v
L
2
K
e
x
t
2
D
ln
(
I
1
I
0
)
-
ln
(
I
2
I
0
)
=
-
3
C
v
L
1
K
e
x
t
2
D
+
3
C
v
L
2
K
e
x
t
2
D
=
-
3
C
v
K
e
x
t
2
D
(
L
1
-
L
2
)
wherein I 1 refers to transmitted signal for long optical path, I 2 refers to transmitted signal for short optical path, I 0 refers to the initial light intensity signal, D refers to the surface area mean diameter of the solid particles calculated by the scattered light intensity inversion in step 3, and Kext refers to the extinction coefficient, L 1 refers to a length of the long optical path, L 2 refers to a length of the short optical path, Cv refers to a volume concentration of solid particles.
4 . The method of solid content measurement utilizing optical path difference in two-phase flow according to claim 3 , characterized in that: in step 5, the solid content H is calculated according to the following formula:
H
=
C
v
×
ρ
=
-
[
ln
(
I
1
I
0
)
-
ln
(
I
2
I
0
)
]
2
D
3
K
e
x
t
(
L
1
-
L
2
)
×
ρ
wherein ρ refers to a density of solid particle.
5 . The method of solid content measurement utilizing optical path difference in two-phase flow according to claim 2 , characterized in that: in step 4,
the new extinction value is:
-
3
C
v
K
ext
2
D
(
L
1
-
L
2
)
and a specific calculation of the new extinction value is:
ln
(
I
1
I
0
)
=
-
3
C
v
L
1
K
e
x
t
2
D
ln
(
I
2
I
0
)
=
-
3
C
v
L
2
K
e
x
t
2
D
ln
(
I
1
I
0
)
-
ln
(
I
2
I
0
)
=
-
3
C
v
L
1
K
e
x
t
2
D
+
3
C
v
L
2
K
e
x
t
2
D
=
-
3
C
v
K
e
x
t
2
D
(
L
1
-
L
2
)
wherein I 1 refers to transmitted signal for long optical path, I 2 refers to transmitted signal for short optical path, I 0 refers to the initial light intensity signal, D refers to the surface area mean diameter of the solid particles calculated by the scattered light intensity inversion in step 3, and Kext refers to the extinction coefficient, L 1 refers to a length of the long optical path, L 2 refers to a length of the short optical path, Cv refers to a volume concentration of solid particles.
6 . The method of solid content measurement utilizing optical path difference in two-phase flow according to claim 5 , characterized in that: in step 5, the solid content H is calculated according to the following formula:
H
=
C
v
×
ρ
=
-
[
ln
(
I
1
I
0
)
-
ln
(
I
2
I
0
)
]
2
D
3
K
e
x
t
(
L
1
-
L
2
)
×
ρ
wherein ρ refers to a density of solid particle.
7 . The method of solid content measurement utilizing optical path difference in two-phase flow according to claim 1 , wherein the processing particle size distribution inversion calculations is based on Mie scattering theory, which comprises the steps of:
calculating characteristic values comprising volume mean diameter, surface area mean diameter, length mean diameter, number mean diameter, peak particle size diameter, specific surface area, and span.
8 . The method of solid content measurement utilizing optical path difference in two-phase flow according to claim 2 , wherein the processing particle size distribution inversion calculations is based on Mie scattering theory, which comprises the steps of:
calculating characteristic values comprising volume mean diameter, surface area mean diameter, length mean diameter, number mean diameter, peak particle size diameter, specific surface area, and span.
9 . The method of solid content measurement utilizing optical path difference in two-phase flow according to claim 6 , wherein the processing particle size distribution inversion calculations is based on Mie scattering theory, which comprises the steps of:
calculating characteristic values comprising volume mean diameter, surface area mean diameter, length mean diameter, number mean diameter, peak particle size diameter, specific surface area, and span.