Online monitoring device and method for fouling and slagging based on capacitance principle differential measurement

Patent metadata

Field	Value
Publication number	US-12092599-B2
Application number	US-202017433150-A
Country	US
Kind code	B2
Filing date	Aug 10, 2020
Priority date	Sep 16, 2019
Publication date	Sep 17, 2024
Grant date	Sep 17, 2024

Abstract

An online monitoring device for fouling and slagging based on capacitance principle differential measurement includes multiple measuring devices arranged at the same height of the boiler heating surface. Each measuring device includes a fixed sleeve and a sensor, one end of the fixed sleeve is fixed on the boiler heating surface, the sensor is connected with the fixed sleeve through screw threads, the end of the sensor near the boiler is equipped with a measuring probe. When measuring the thickness of ash residue on the monitoring surface, three sets of the measuring devices are at the same height of the monitoring surface. Each sensor is adjusted at a different position in the corresponding fixed sleeve to realize the differential measuring on ash residue thickness. Thus, the thickness of ash residue on the monitoring surface can be calculated based on the measured capacitance by applying the capacitance formula of planar capacitor.

First claim

The invention claimed is:

1. An online monitoring device for fouling and slagging based on capacitance principle differential measurement, comprising three measuring devices being arranged at the same height of a boiler heating surface of a boiler, wherein
each measuring device among the three measuring devices includes a fixed sleeve and a sensor, one end of the fixed sleeve is fixed on the boiler heating surface, the sensor is nested in the fixed sleeve and connected with the fixed sleeve through screw threads, the end of the sensor near the boiler is equipped with a measuring probe;
the measuring probe includes a central electrode, a ring electrode, a insulating ceramic and a thermometric element, the central electrode has a circular cross section, the ring electrode is arranged around the central electrode, the insulating ceramic is arranged on the outside of the ring electrode and also between the ring electrode and the central electrode, the thermometric element is arranged in the insulating ceramic to measure the temperature of the measuring probe; and
the distances between the end of sensor and the end of fixed sleeve are different for each measuring device.

2. The online monitoring device according to claim 1 , wherein
the fixed sleeve comprises a sleeve and a fixed flange, and an inner wall of the sleeve is arranged with an internal thread; and
the sensor comprises a measuring rod and a meter case, the measuring rod is provided with a external thread which is matched with the internal thread of the sleeve, the meter case is connected with one end of the measuring rod, the measuring probe is arranged in the other end of the measuring rod, the measuring probe is connected with a electrocircuit in the meter case by a lead wire through the measuring rod, the periphery of the measuring rod is connected with a threaded flange and a lock nut through screw threads, the threaded flange is used to connect the fixed flange and the lock nut is used to lock the threaded flange.

3. The online monitoring device according to claim 2 , wherein the sleeve is made of a refractory metal.

4. An online monitoring method for fouling and slagging based on capacitance principle differential measurement, using an online monitoring device comprising multiple measuring devices being arranged at the same height of a boiler heating surface of a boiler, wherein
each measuring device among the multiple measuring devices includes a fixed sleeve and a sensor, one end of the fixed sleeve is fixed on the boiler heating surface, the sensor is nested in the fixed sleeve and connected with the fixed sleeve through screw threads, the end of the sensor near the boiler is equipped with a measuring probe,
the measuring probe includes a central electrode, a ring electrode, a insulating ceramic and a thermometric element, the central electrode has a circular cross section, the ring electrode is arranged around the central electrode, the insulating ceramic is arranged on the outside of the ring electrode and also between the ring electrode and the central electrode, the thermometric element is arranged in the insulating ceramic to measure the temperature of the measuring probe, the method comprising:
adjusting a distance between the end of measuring probe and the end of fixed sleeve so that the distances for each measuring device are different, and recording each distance value;
installing the measuring devices on the monitoring surface of the boiler, with the end of fixed sleeve being flush with the monitoring surface, and filling the high thermal conductivity material between the fixed sleeve and the monitoring surface; and
recording a capacitance value C of each sensor, substituting the capacitance value C and the corresponding distance value into the calculation formulas of ring capacitance, and then obtaining a thickness of ash residue δ, calculation formulas are as follows:

C
=

π
⁡

(

ɛ
1

+

ɛ
2

)

1
a

⁢
ln
⁢

2
a

+

1
b

⁢
ln
⁢

2
b

-

ɛ
1

-

ɛ
2

ɛ
1

+

ɛ
2

⁢
A

;

A
=

2
⁢
δ

a
2

-

a
2

+

(

2
⁢
δ

)

2

a
2

+

1
a

⁢
ln
⁢

2
⁢
δ

a
+

a
2

Assignees

• Univ Taiyuan Technology

Inventors

• Zhang Jiajie
• Zhang Jiansheng
• Chen Yanwei
• Ma Suxia
• Bi Dapeng

Classifications

• G01K7/00

  Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat (giving results other than momentary value of temperature G01K3/00) {; Power supply therefor, e.g. using thermoelectric elements} · CPC title

• F23J1/00

  Removing ash, clinker, or slag from combustion chambers ({removing flyash from flue gas F23J15/022;} devices for removal of material from the bed of fluidised bed combustion apparatus F23C10/24) · CPC title

• F23G2900/55005

  Sensing ash or slag properties · CPC title

• F23J2700/00

  Ash removal, handling and treatment means; Ash and slag handling in pulverulent fuel furnaces; Ash removal means for incinerators · CPC title

• G01N27/22 Primary

  by investigating capacitance · CPC title