Pulp Paper & Logistics
ABB 11
felt-marked papers and boards, embossed papers, wet-strength papers, bulky boards, security papers and converting products. The mill had been experiencing quality problems that were shown as colour, ash and moisture variations that were caused by the difference in feedstock and because of variations from batch to batch, particularly in the case of coloured paper. It had also been having problems with dryline control with watermarked papers. Following a meeting between the mill’s managers and L&W and ABB experts last October to detail the needs of the operations it was decided to go ahead with the project. A key component of the system
was the implementation of the control loop in normal running conditions, followed earlier this by later refining of the control loop during batch changes. The Rossano Veneto mill’s stock
flow is a batch process, each batch taking 45 minutes with production runs being between two and ten batches.
During a visit to the mill by
PPL’s publishing manager Vince Maynard, Favini’s assistant production manager Giovanni Pruscini explained the issues that were addressed. “Moisture was a key area, as for every 45-minute machine run, which involved four tons of stock, we were getting a
Refined material coming into the machine chest
variance of plus and minus three per cent,” said Pruscini. “Due to the refiner being on-line, as the level in the chest dropped the refining rate and moisture content was going down.” The installation of a new refiner some two years earlier, aimed at increasing quality and production capacity plus widening the range of papers that the line could produce including watermarked paper, had highlighted these errors by means of the QCS system that was already in place. “After the meeting to discuss the
problems and the decision to go ahead, L&W installed the sensor on 1 November on a trial basis so that the mill could evaluate its performance during production,” said Pruscini. “The sensor was being used manually rather than
fully integrated onto the machine. “It took only until December for the sensor to prove its capabilities, and as an additional result also highlighted an oscillation in the vacuum boxes. Production on the paper machine has a target moisture content of 5.5 per cent, with a tolerance of plus or minus one per cent, for optimum results and the full integration of the sensor, with a direct control loop on the refiner developed by ABB, has yielded some great results. “Previous jumps in moisture
content that had a range of between four and seven per cent have now dropped dramatically to a plus or minus one per cent variance that is well within the production parameters. “In real terms, and prior to the sensor’s integration on the
The Forming Sensor Drainage system installed under the wire
average 45-minute run, the moisture spike and drops would last 20 minutes at 4 per cent moisture and the next 20 minutes would be at 7 per cent moisture, leaving only 5 minutes at the optimum moisture level of 5.5 per cent.
“Since the installation of the
FSD sensor the variance has been reduced to a low of 5 per cent and a high of 6.2 per cent but for a total period of 7 minutes, leaving 38 minutes of quality production as opposed to only 5 minutes.” Pruscini said that savings had also been made in energy consumption in the refiner. “This was running at a constant 600 kilowatt-hours which has now been halved to 300KWh,” he said. “It will spike no higher than 630KWh, but this spike is only for
4
The Forming Sensor Drainage hardware
Control panel for the Forming Sensor Drainage system May 2013
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