Determining the reduction rate of a recovery boiler

Patent metadata

Field	Value
Publication number	US-12134859-B2
Application number	US-202017612191-A
Country	US
Kind code	B2
Filing date	May 15, 2020
Priority date	May 17, 2019
Publication date	Nov 5, 2024
Grant date	Nov 5, 2024

Abstract

A method to determine a reduction rate of a recovery boiler using optical information from a chemical smelt sample. A processor is used to read a digital frame at least part of which represents the chemical smelt sample of the recovery boiler. An area of interest is determined from the digital frame read comprising at least part of the area in the digital frame representing the chemical smelt sample. Of the pixel values of the area of interest, one or more spectral characteristic values correlating with the change of reduction rate are determined. The reduction rate of the recovery boiler is determined using a reduction rate function of one or more of the determined spectral characteristic values weighted at predetermined weights.

First claim

The invention claimed is:

1. A method for determining a reduction rate of a recovery boiler comprising:
obtaining a chemical smelt sample from smelt that flows from the recovery boiler;
capturing a digital frame of an image of the chemical smelt sample;
reading with a processor the digital frame including an area within the image which represents the chemical smelt sample of the recovery boiler;
determining from the digital frame an area of interest within the image comprising at least part of the area in the digital frame representing the chemical smelt sample;
determining with the processor and from pixel values of the area of interest one or more spectral characteristic values;
determining with the processor a reduction rate of the recovery boiler based on the one or more spectral characteristic values and using a reduction rate function to correlate the one or more of the spectral characteristic values to corresponding predetermined weights used to determine the reduction rate, and
controlling the recovery boiler using the reduction rate.

2. The method according to claim 1 , wherein the reduction rate function correlates the one or more spectral characteristic values to a corresponding weight, and the method further comprising determining the predetermining weights by:
determining with a laboratory measurement of a chemical smelt sample of the recovery boiler to determine a reduction rate of the recovery boiler to be used as a target value;
producing a digital calibration frame representing said chemical smelt sample of the recovery boiler and determining said one or more spectral characteristic values; and
fitting the one or more spectral characteristic values and the target value together.

3. The method according to claim 2 , wherein the fitting is performed using a linear least squares method or a neural network calculation.

4. The method according to claim 1 , wherein the determining the area of interest comprises removal, by the processor, of at least one of: one or more edge zones of the digital frame, one or more crack zones of the digital frame, or one or more carbon particle zones of the digital frame.

5. The method according to claim 1 , wherein each of the one or more spectral characteristic value comprises at least one of:
a redness in the area of the area of interest in relation to an overall intensity in the area of interest,
a blueness in the area of interest in relation to the overall intensity,
a yellowness in the area of interest in relation to the overall intensity,
a standard deviation of the redness,
an average gradient of the redness, the blueness or the yellowness, or
an average hue in the region of interest.

6. The method according to claim 1 , wherein the reading of the digital frame involves sampling information comprising at least one of: an identification of a sampling point of the chemical smelt sample represented in the digital frame, or a sampling time of the chemical smelt sample represented in the digital frame.

7. A method to control a recovery boiler comprising:
obtaining a chemical smelt sample from smelt that flows from the recovery boiler;
capturing a digital frame of an image of the chemical smelt sample;
identifying an area of interest within the digital frame comprising at least part of an area in the digital frame representing the chemical smelt sample;
analyzing in the area of interest to determine a spectral characteristic value of the chemical smelt sample shown in the area of interest;
calculating a reduction rate of the chemical smelt sample by using the spectral characteristic and a reduction rate function that correlates spectral characteristic values or data representing spectral characteristic values to reduction rates of chemical smelt, and
controlling the recovery boiler based on the reduction rate.

8. The method according to claim 7 , wherein the reduction rate function correlates each of the spectral characteristic values to a corresponding weight, and the method further comprises:
determining the weights corresponding to the spectral characteristic values by:
performing a laboratory measurement of a chemical smelt test sample taken from the recovery boiler to determine a target value reduction rate of the recovery boiler;
capturing a digital calibration frame of an image of the chemical smelt test sample;
identifying at least one of the one or more spectral characteristic values from the digital calibration frame; and
correlating the one or more spectral characteristic values identified in the digital calibration frame to the target value to determine the weight.

9. The method according to claim 8 , wherein the correlating includes using a linear least squares method or a neural network calculation.

10. The method according to claim 7 , wherein the determining the area of interest includes removing at least one of one or more edge zones of the digital frame, one or more crack zones of the digital frame, or one or more carbon particle zones of the digital frame.

11. The method according to claim 7 , wherein the spectral characteristic value comprises at least one of:
a redness in the area of the area of interest in relation to an overall intensity in the area of interest,
a blueness in the area of interest in relation to the overall intensity,
a yellowness in the area of interest in relation to the overall intensity,
a standard deviation of the redness,
an average gradient of the redness, the blueness or the yellowness, or
an average hue in the area of interest.

12. The method according to claim 7 , wherein the reading of the digital frame involves sampling information comprising at least one of: an identification of a sampling point of the chemical smelt sample represented in the digital frame, or a sampling time of the chemical smelt sample represented in the digital frame.

Assignees

• Andritz Oy

Inventors

• Lappalainen Heikki
• Nurmi Juho
• Rissanen Sauli
• Vihavainen Esa

Classifications

• G01N2201/1296

  using neural networks · CPC title

• G01N2021/1776

  Colour camera · CPC title

• G01N21/27

  using photo-electric detection (G01N21/31 takes precedence){; circuits for computing concentration (logarithmic circuits G06G7/24; photometric circuits in general G01J)} · CPC title

• G01N21/251 Primary

  Colorimeters; Construction thereof · CPC title

• F23N5/082

  using electronic means · CPC title