Soft Sensors for Pulp Freeness and Outlet Consistency Estimation in the Alkaline Peroxide Mechanical Pulping (APMP) High-Consistency Refining Process

The largest mechanical pulp production units are high-consistency refiners. In the high-consistency refiners, in-situ measurements of pulp quality are rare. Temperature profile is one of the measurements that is industrially applicable to estimate pulp quality. It measures the steam temperature in the refining area – but how it can detect deteriorated pulp quality will be shown. This paper analyzed the high-consistency refiner plate temperature and its correlation to pulp quality in a 1.34 MW pilot-scale Sunds RGP-44 variable speed refiner in a variety of operating conditions and particularly at production rates close to maximum refiner capacity. The study showed that there was a narrow band of optimal refining conditions at the maximum refiner production level just before pulp quality drastically decreased. When the refiner was pushed above this optimal point of operation, the plate temperature rapidly increased above normal refining temperature, causing reduction of fiber length and consequently lower pulp strength and quality. Thus, refiner plate temperature measurement was found to be a quick way and an effective tool for preventing low-quality pulp production through overloading the refiner.

Section: Discussionmentioning

confidence: 99%

Maximizing pulp output and quality through measurement of plate gap temperature in high-consistency refining

Fredrikson¹,

Paltakari

2020

“…If this scenario is present, a soft sensor can potentially be used to calculate quantities based on interaction from multiple signals. Zhang et al (2016) developed a soft sensor for estimating freeness and outlet consistency according to a case-based reasoning method based on operating conditions and pulp quality data. One of the conclusions in the study was that real-time soft sensors estimating freeness and outlet consistency can support reducing the electricity consumption and maintain uniform pulp quality.…”

Section: Previous Studies On Mechanical Pulp Modellingmentioning

confidence: 99%

Time series analysis of refining conditions and estimated pulp properties in a chemi-thermomechanical pulp process

Ekbåge

Nilsson

Håkansson

2019

Frequently sampled process data from a conical disc refiner and infrequently sampled pulp data from a full scale chemi-thermomechanical pulp (CTMP) mill were evaluated to study autocovariance with aspects of potential dynamic modelling applicability. Two trial measurements with an online pulp analyzer at decreased sampling intervals were performed. For variability analysis, time-series containing up to one day of operational data were used. At the chip refiner, the clearest significant autocovariance was identified for the specific electricity consumption, based on the longer sequences. Most of the estimated pulp properties indicated low or non-significant autocovariance, limiting applicability of a specific dynamic model. A mill trial was conducted to investigate the impact from an increase in the conical disc gap on the specific electricity consumption and the resulting freeness. The response time from the gap change in the refiner to measured change in freeness was estimated at 19 min, which was approximately the hydraulic residence time in the latency chest. The relevance of this study lies in applicability of mill-data-driven modelling to capture the dynamics of a specific refining process. Through mill trials the sampling speed of pulp properties was more than doubled to gain insights into short term systematic variations by applying time-series-analysis.

“…And then I thought about an article that we recently published: Zhang et al (2016) showed that it is possible to gain an improved understanding of the functional relationship between different process variables just by looking at routine process data, without any "mill trial" activity at all. Often there is enough random variation in such data to be able to train an artificial intelligence algorithm.…”

Section: Roots Of Our Curiositymentioning

confidence: 99%

My Production Facility, My Laboratory of Discovery

Hubbe

2016

By exercising of one's curiosity, in combination with a lot of persistence, it is possible to solve some seemingly intractable problems. Many readers of this journal will have spent much, if not all of their careers, in university laboratories. In such settings there is an understandable emphasis on understanding underlying reasons. In other words, one is expected to focus on "why things happen" rather than just getting results. But if such an approach works well at the university, how about applying it at the production facility? This editorial features the stories of a man who was brave enough to spend his career asking "why" questions while working to improve the operations of paper mills.