Minutes of Meeting

We add 50% sulphuric acid to the Do feed pump. When the acid is on, the nuclear consistency meter signal gets very noisy. Why?

• Northwood - some problem with BTG consistency meter, lived with it, but mill process changes have now reduced need for acid.
  
• Owen - localized high concentrations of acid may react with carbonates to produce C0₂ or some other gas which will cause noise on the nuclear consistency meter.

Does anyone have any experience with fibre recovery from MC pump degas pump?

• Harmac and Grande Prairie - put back into chute.
  
• Prince Albert - use internal degas pump.
  

Is anyone using roll wrap to wrap pulp bales?

• Canfor - is running a trial in November, 1997 to make roll wrap (160 gm basis weight papers) on their sack machine.
  
• Gilles St. Jean has seen roll-wrapped bales in Europe. Good fold appearance but lots of problem with damage to wrapper tearing.
  

How many mills still running cylinder moulds?

• Irving, Espanola, Terrace Bay, Marathon, Miramichi, and Powell River.
  

Do these mills sewer their fines or recover?

• Miramichi does not sewer.

Started up after spring shutdown. Now have foam in the Bleach Plant. Why?

• Weyerhaeuser - suggests looking at amount of pitch dispersant used.
  
• Number of mills use defoamers, but usually in only 1 stage.
  

Recent vat inspections of D1 and D2 tile lined vats now show the tile to be very soft. Why?

• Unknown
  

We have to adjust pH probe every week in our bleach plant. Why?

• It's normal, as other mills are doing it that way. Most mills have one dedicated person. Jack Histed has a solution without pH
• probe.
  

Medium consistency controller. Successful operation on how to correct problems.

• Domtar, Windsor - MCS - Microwave Consistency Analyzer.
  
• Domtar - Norkraft - Steve Frechette.
  

How many people are testing residual peroxide in their Eop filtrate? By what method?
We are using titration method and it doesn't give good results.

• Titration method with thiosulphate.
  Titanium indicator - with colour wheel. Use polprox.

Are there any mills using any advanced controls on their R8-R10 generators?

• Northwood, Prince George - some success with recent neural network, to be used as soft sensors, not control.
  
• Fletcher, Mackenzie - model was developed but strike has curtailed further testing.
  
• Dennis Owen - several mills in the U.S. have old line acidity measuring devices.

How to add a steam mixer when the reactor pressure exceeds steam pressure by 20 psig?

• Lower the reactor pressure, since the reactor pressure only compensates for poor mixing. Also, minimize pressure drop in all steam
• lines.
  

Like to know how other pulp mills purge their S0₂ railcar and trucks and where it purges to?

• Canfor - purge to tall gas scrubber in Chem. plant (watch for H₂S formation).
  
• Harmac - purge S0₂ to a bucket. Car is pad with N2.
  
• Weyerhaeuser, Grande Prairie - purge S0₂ to D2 stage seal chest.
  

What kind of liquid pH sample system is available for bleach towers?

• Repap - extractor (developed by Boise Cascade).
  
• Crofton - has one.
  
• Grande Prairie - has Kajaani sampler.
  

"Summer Sickness" - a loss of pulp strength (tear/tensile) each year in April/May until September/October. Approximately 10% (in CSP). Perfectly correlated with drop in chip moisture.

• Relationship to log diameter (NTC work?) VS. fibre length.
  
• As moisture drops, chip becomes brittle (pre-steam).
  
• Chlorine becoming mono-chloride.
  

Has anyone done work on vacuum assist bleach washing?

• Canfor - successfully trialed and still happy (Canron washers).
  

Residual and brightness probes after B.S. storage not seeming to respond since gone ECF. Time from chemical added to tower about 30 seconds. Would like to develop a Kappa factor type control to gas addition. Suggestions on how to get system back up and running.

• Murray Walters - separate two probes. Put brightness at 5 seconds. Residual (35 seconds - as late as can) after chemical added. Check temperature range of probes to make sure of proper zone.
  
• Northwood - Run by-pass line to make up time.

In by-pass of E2 stage - still need caustic?

• Yes. Aim for pH > 10.5.

Effect on Cl0₂?

• May need more. May require acid to get target pH. Strength should be OK.
  

Of the mills (if any) that have moved from 3% Do to medium consistency Do, have any of them seen Cl0₂ usage improvements related to the higher concentration effect?

• Harmac and Thurso saw 10% savings. Norm Liebergott reported 2 mills in the U.S. have claimed savings of 15%.

Has anyone studied or observed Cl0₂ usage effects or quality effects associated with Do filtrate recycle?

• Norm Liebergott said that at normal Kappa factors, there should be only a positive effect with recycle, but at low Kappa factors there may be increased Cl0₂ usages. Do an on/off trial to confirm.

"H" type flakt dryers and steam condensate systems.

• Contact Jim Collins.

Can anyone show how they have justified a bleach plant DCS replacement project.

• Contact Pierre Jean at Donohue St. Felicien.
  

What are people doing with vents of the standpipes of MC pumps?

• Bleach side - U.S. mills going directly to Scrubber. Mackenzie, Marathon, Harmac, Irving and Malette Kraft. Brown Stock side -
• standpipe vent is going to washer hood.

High caustic usage in D1 pH control. Up close to 9 kg/tonne. Caustic is added before Cl0₂ addition.

• Check the acidity of the Cl0₂ solution, the addition of caustic amount may be normal.
  
• Change the pH target lower so that less caustic is needed.

Is anyone not air sweeping Cl0₂ storage tank?

• No. Everyone sweeps their Cl0₂ storage tanks.
  

Are mills using Papritection for protection of washer vats and drums? Are people switching to different metallurgy?

• Marathon - Irving - still have Papritection. Most other mills have changed metallurgy and/or residuals to ensure that corrosion is
• not likely to happen.