• "good testing costs money, bad costs even more"
• K numbers are archaic, non-linear, introduces error, use Kappa
• "Doin’ it in the Dig" - focus process control first in digester
• digester rate change biggest impact on fibre line control
• changed O-stage algorithm using kappa rather than K number, resulted in kappa number down from 19 to 16, but with standard deviation drop from 3 to 1
• Four principles for improved delignification

1. level out alkali concentration
1. keep SH- concentration high (especially at start)
1. keep dissolved lignin low (especially at end)
1. keep temperature low (especially at start and end)

• Low solids cooking (LSC) showed a step change up in tear at tensile
• Brownstock testing
• don’t do soda testing, but COD testing, because it’s the organic portion that consumes bleaching chemicals, not the sodium
• COD also has a detrimental impact on fibre strength
• defoamer re-entrains COD back on the fibre (minimize defoamer with DCS control - 2.2 kg/ADt to 0.8 kg/ADt)
• Do brightness and ClO₂ usage correlate well with brownstock COD carryover on fibre, but poorly with inlet Kappa number
• to decrease COD losses from post O2 washer increase caustic charge
• water hardness contributes to ionic bonding of COD within fibre pore structure
• Mill trials show that brightness is a poor way to control D0 stage - should use kappa factor
• Acidify brownstock to 3 pH before ClO₂ addition

Tim Evans, National Silicates (no paper in minutes)

• 2.1 Literature search - no one seems to know exactly what MgSO₄ actually does, contradictory mechanisms, even in same papers!
• stabilizes radicals? consumes caustic? scavenger depressing catalytic effects of copper? promotes formation of cellulose salts? lignin intensifies the effect of transition metals? reduced cellulose degradation? form coordination compounds?
• even removing all metals, still get benefit from MgSO₄
• direct interaction of Mg with carbohydrate to stabilize?
• scavenging superoxide anion radicals (1986 PhD study)
• some authors note that Mg and Mn can synergistically protect
• 2.2 Lab experiments
• 0.1 - 0.3% can save protect viscosity
• adding MgSO4 can accelarate or decellarate delignification
• adding too much MgSO₄ can actually increase delignification
• TCF Western SW Kraft mill OQEopP1P2 found 7% to 15% prevention of strength loss with MgSO₄, higher with silicates

• see notes in Appendix 3 and Dupont paper in Appendix 4
• significant problem currently is nickel-base molybdenum bearing alloys above pH 3 (reduce pH, reduce corrosion), eg. Hastelloys
• giveaway is if it is shiny when inspected - indicates corrosion, thickness loss
• be careful when specifying FRP for ClO₂ - eg. brominated resins may be better and pay attention to curing
• switching between P and D in a single tower could result in silica and grout dissolving
• everybody should now know that titanium can dissolve in alkaline peroxide (around pH 11 - see Paprican report)
• 7% to 8% Mo now available (Super Austenitic) but have same welding problems as 6% Mo alloys (Ni-base filler can thin in ClO₂)
• lots of failures recently in ClO₂ generator boiler tubes - grade 7 titanium tubes now standard but close to the limit of crevice corrosion protection. SCC is possible in acidified CH₃OH (palladium instead of nickel for crevice corrosion protection)
• many instances of continuous digester corrosion recently, especially for those who have changed methods of operation
• general or pitting corrosion, not cracking, inspection critical
• weld overlay, anodic protection, or thermal spray coatings
• Any corrosion concerns with O2 delig? yes, 2 mills in U.S. experienced vessel cracking from the outside due to moisture and chloride accumulation under vessel insulation. Make sure all vessels are painted with appropriate coating in advance of lagging
• Derakane 510N resin common in D2 stages? yes, seems to last longer, but can get longer life if you write purchase orders that carefully specify the curing
• pH around 3 in Do stage, what temperature to run to avoid corrosion? lower than temp to bleach pulp (Celgar 55 - 60 C, rebuilt mixer)

• if objective is to meet environmental regulations, then partial closure may be adequate
• key question - how to encourage continual progress and future innovation within the boundaries of existing mill processes and markets
• TEF does not require elimination of ClO₂, so conversion to TCF is a very costly and unnecessary intermediate step
• Eka Nobel study showed that dioxins from sources other than bleaching can actually be degraded by ClO₂ treatment
• ECF and TCF are equal with respect to environmental performance, but receiving waters may still be impacted by resin acids and other wood constituents, so focus is moving towards TEF processes
• partnership of Jaakko Poyry and Eka Nobel in the Stora Billerud Gruvon mill for ECF closure (about 800 tpd, 10 m³/t water consumption)
• Concept: bleach plant filtrates can be treated separately from the recovery system, eg. dissolving of NPEs such as Si, Al, Mg, K

1. water volume reduction (to 10-15 m³/ADt)
1. bleach plant filtrate evaporation (plastic, vapour recompression)
1. purification of evaporator conensate (may contain VOCs)
1. electrodialysis to purge chlorides and inorganics

• Costs for 1000 Adtpd bleached SW kraft mill
• Capital costs US$35 million
• Operating costs US$15/ton
• additional costs may include new recovery boiler and oxygen delignification at a cost of US$120 million
• 1995 will have a 6 month continuous operation of the evaporation, concentration, electrodialysis and oxidation on the Do effluent from the Billerud mill

• target water consumption? <15 m³ /t, only one in NA that he knows of
• oxygen delignification necessary? it will help becaus it will reduce the amount of chemicals in the bleach plant
• Electrodialysis scaling? tried a lot of membranes, don’t know what hapens to NPEs, but suspect will come out in process, some going to recovery boiler
• burning the combined bleach filtrate? one option for ECF
• how much brine produced in electrodialysis unit? don’t know, but hope it is clean enough to use in chlorate plant

• 5.1 Background:
• Great lakes Forest Products "Effluent Free Mill"
• Union Camp "C-free"
• Champion "BFR"
• 5 years of intensive research
• 1994 pilot scale studies
• late 1995 Canton, NC demonstration facility starting
• 5.2 BFR Equipment
• BL evaporators additions (evaporators)
• chloride removal processs (precipitator catch)
• metals removal process (Do stage)
• 5.3 Bleach Filtrate Issues
• 5.3.1. high chloride content
• O₂ delignification
• 100% ClO₂ substitution
• H₂O₂
• Chloride removal process - forced circulation crystallizer preferentially crystallizes saltcake which is sent to recovery boiler, while chloride is purged to effluent treatment
• 5.3.2. increased evap requirement
• low chloride input
• 5.3.3. high bleach consumption (BFR will cause increase)
• low kappa pulp to bleach plant
• highly oxidized dissolved organics
• selectivity of chlorine dioxide
• 5.3.4. buildup of non process elements (NPEs)
• potassium removal by chloride removal process (CRP)
• highly oxidized bleach sequence
• metal removal process (MRP)
• current mills: 80% NPEs are removed in Do filtrate, pass through Eop stage, removed in final D stages, so strategy is to focus on Do filtrate
• Options: acid wash, chelation, or remove from Do filtrate
• Technologies:
• carbonate precipitation - 90% removal, but dissolved organics were problem
• Ion exchange - 95% removal, no fouling (chosen)
• 5.4 Effluent benefits:
• BOD down 70%
• COD down 85%
• AOX below 0.1 kg/t
• water usage down 10%
  
• What kind of resin? not zeolite, will regenerate with brine or other sodium source,
• impact of increased chloride concentration back through digester? chloride level will be watched carefully in canton plant, wexpect 3 gpl up to 4.5 gpl. Corrosion is not such an issue in these alkaline conditions
• WL metals concentration go up? no, being removed in the bleaching sequence, the only NPE in the recovery process will be K, which will be higher in the WL, will be looking at this
• metal removal result in enrichment of some metals in the WL? mostly in the BL, particularly Mg and Mn, some trace elements, will be looked at in Canton
• ratio of carbonate and sulphonate in ash? will both be recovered, carbonate lost in brine, but loss should not be significant (sodium makeup 1/10 of what mills have now)
• what will this do to sulphidity? HASimons - should not change