Reliable and Fast Method to Estimate Carryover in Kraft Recovery Boilers

ABSTRACT
A novel method, based on visual imaging, to estimate the amount of carryover in kraft recovery boilers has been
developed. Based on photos (images) taken from a carryover probe, the amount of carryover in different places in the
furnace can be estimated. The data can be used to control the combustion and to tune the boiler operation by adjusting
the air distribution and black liquor spraying according to the carryover results. This will improve recovery boiler
throughput and availability.
In this new approach, images from carryover probe samples are taken either with a mobile phone or with an industrial
camera. Images are analyzed with a special algorithm, which estimates the amount of carryover from spots with
different colors via digital image recognition techniques. The outcome is the number of different spots, which
contribute to the amount of carryover in the sample. The results can be used to estimate the changes in carryover
amount. The objective of the method is to create comparable carryover maps to be able to see the differences and
changes in the combustion and to tune the boiler combustion accordingly.
The system has been extensively tested in a 1200 tds/d recovery boiler, measuring the amount carryover and
confirming the results with chemical analyses. This boiler has suffered from heavy fouling in the superheater area due
to carryover and had to be stopped for water washing twice per year. This has considerably limited the pulp production
at the mill. With the new method, the amount of carryover could be significantly decreased, and water washes have
been eliminated. This paper presents the new carryover estimation method developed with a new smart phone
application.
Keywords
Carryover, visual analysis, recovery boiler 

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