1.0 Status of US EPA Cluster Rules, Phil Pagoria, Weyerhauser Technology Center, Tacoma, WA (see Appendix)

• "Cluster" = EPA’s first attempt at clustering a group of environmental regulations, for both effluent and air
• "Proposed", but not yet law
• effluent - regulations for bleached papergrade kraft and sulphite to be out mid-1996, all rest of effluent regulations 8 months later
• air - anybody’s guess when air regulations come out
• "Subcategories" for types of mills exist for effluent, none for air

• Effluent Technology basis - defines regulatory limits based on performance of best pollutant control or process technologies
• "BPT" = best practical technology = secondary treatment
• "BCT" = best conventional technology = secondary treatment
• "BAT" = proposed best available technology = O₂ delignification or extended delignification + 100% ClO₂ substitution
• "BMP" = best management practice = spill prevention and control

• Key Finding Since Proposal - industry can meet the EPA requirements for bleached kraft with 100% ClO₂ alone, so the requirements for O₂ delignification and extended delignification will be dropped for existing mills (but not for new mills)

• "Beyond BAT" = incentives program - Install technology better than "best available", in return for incentives like longer permit terms, less monitoring, shows EPA is realizing that regulation is not the only way to reduce industrial pollutants - most companies are behind this program.

• "MACT I" = maximum achievable control technology for hazardous air pollutants
• "MACT II" = combustion sources - regulations not yet proposed

• AOX will be regulated, but after secondary treatment
• specific pollutants regulated at bleach plant

1.5 "Best Guess" - Effluent Regulations

• BOD, TSS - not as tough as proposed
• AOX - 0.5-0.6 kg/t
• COD - consistent with 100 % ClO₂ substitution
• colour - no Federal limit; site specific regulations

• Final BAT for COD, chloroform, other toxics
• assessment of COD, toxics from complex mills
• revised limits for BOD, TSS

• installed two stage oxygen delignification system and new EMCC digester, but did not get increased tear strength that they were expecting
• lab trials at Econotech showed that lab:mill strength ratio was 73% as brownstock, 78% as final product
• the trials showed that the strength problems were due to the oxygen delignification area

2.2 Optimization

• performed mill factorial experiments by varying:
• MgSO₄
• COD (= shower water - strength was lower using fresh water)
• caustic applied
• oxygen applied
• temperature
• variables that affected strength - temperature first, then caustic and oxygen

• mill kappa range to oxygen delignification 23 to 33 kappa over 10 days shown in example (typical standard deviation = 2.5)
• decided to minimize temperature, but still retain kappa by moving temperature around and compensating with chemicals, found good strength control AND good kappa control with SD under 1.

• temperature has most significant effect on strength
• pulp brightness is not strongly dependent on temperature or chemical application
• COD had little impact on performance
• recycle of free caustic has major impact on % delignification

• Dennis Owen - 0.33 kappa?
• normally use temp to drive reaction - do you have to slow down? Answer - we crank up temperature when incoming kappa is high to allow faster reaction when needed.
• Norm Leibergott
• cool down pulp before blowing out of O2 reactor
• maintain caustic charge gets up to 60%
• Chris Kanters
• increased oxygen, total chemical higher? Answer - yes extra oxygen, no extra caustic
• Mill uses caustic, not oxidized white liquor
• mill averages 35% delignification, can achieve 50%, but not normally so bp sees steady kappa of 20

• End-of-pipe treatment is not the best way to meet EPA regulations, need to make process changes in mill

• operating cost savings
• don’t have to expand ClO2 generator
• reuse of existing equipment
• AOX < 0.14 kg.t, 50% less COD, BOD, less odour
• lower capital, process costs, can be applied in stages

• orange (polysulphide) liquor to digesters (= Sx) in place of white liquor
• brownstock rerouted to E2 which has been converted to oxygen delignification ahead of first bleach stage, 30% delignification target, no need for additional washer, use E2 tower as a blow tank, 90 psig, 10-12% consistency, 1.2% oxygen
• first bleaching stage = lignin activation (Ad), acidification with H₂SO₄ to static mixer, ClO₂ to dynamic mixer, kappa factor 0.05-1.15 (or could use other chemicals at this stage), 3.5-12% consistency, existing pressure, 0.2-0.4% ClO2, ????? % H2SO4
• add oxygen reactor to E1 stage for oygen bleaching, use E1 tower for blow tank, no need for additional washer, peroxide may be added after reactor, 90 psig, 10-12% consistency, 0.8% oxygen, 1% caustic (depending on ClO2 charge), same kappa number target as before
• DnD, same chemical applications as normal

• polysulphide stabilizes reducing end groups, so assume yield increase of 1.5% (literature says up to 5%), use PAPRICAN in-situ process for orange liquor manufacture

• see table in Appendix for savings based on stepwise conversion of mill:
• mini-O2

• Super O₂ Process presents operational, environmenatal and tchnical advantages

• HASimons - filtrate recycle for Ad? No, only recycle first oxygen stage, because we use ClO2 in first bleach stage, and it is also the only purge for NPEs.
• HASimons - a softwood mill with OAO could not do interstage activation with ClO2 in the middle because could not use enough acid due to organic buffering (good news - they got their 65% delig with strength retention anyway)
• Liebergott - good news - AOX levels were too high in paper because of combining, can’t just add them up; bad news - you require much more acid unless the pulp was washed better before bleach plant, also would use less ClO2, so lower AOX too
• Tom - use oxidized white liquor? Yes, not caustic
• Gerry - strength properties? not yet done, will be available in a month
• Gerry Pageau - Howe Sound found a lot of strength loss in the Eop stage, needed chelation

4.0 Bleaching with Bicarbonate: The Secret of Dimethyldioxirane, Jean Bouchard, Paprican, Pointe Claire, PQ (no paper available - Paprican report will come out next month)

• acetone + peroxymonosulphate (Px) -------> dimethyldioxirane (DMD) (at pH 7-8) which is an excellent bleaching agent, but too costly
• DMD has both a delignification reaction and a decomposition reaction, so Paprican started working on designing a selective bleaching raction

• pH increase results in reduced Px stability
• similarly, for DMD the stability decreases as pH increases, but adding Mg⁺² increases the half life of DMD
• Why should we then bleach at 7.5pH here both are unstable? Set up experiment which showed:
• using phosphate buffer increase pH, got linear increase in delignification, 35% delig at 7.5 pH
• BUT using bicarbonate buffer got 50% delig at pH 7.5, but carbonate buffer at pH 9.5 dropped delig back to 40%
• this means that only when using bicarbonate are you actually bleaching with both Px and DMD, without bicarbonate you are mainly doing Px bleaching.
• results of the experiment shows that bicarbonate participates in the reaction. How?
• (lots of organic chemistry stuff at this point)
• proposed mechanism is that bicarbonate tends to drive off CO2, resulting in shifting of the reaction towards generation of DMD

• (get copies of Jean’s 2 conclusion slides)

• increased selectivity and better understanding of organic peroxide chemistry
• could lead to a DMD-like process without the use of non-desirable chemical like acetone

Vancouver, BC (see Appendix for paper and overheads)

• HASimons Research - with Paprican, BC Science Council, PAPRO, etc, 20 plus papers
• HASimons Applications
• Champion BFR process
• Chloride removal process in conventional mill (confidential)
• LP Samoa TCF closed cycle

• BCTMP - four, 2 in Canada, 1 in Brazil, 1 in Australia
• recycle - state of the art for all new recycle mills
• sulphite - two for sure (Modo Domsjo, PWA Manheim, Lenzing partly closed cycle)
• kraft - none yet

• Sweden has generally backed off on closed cycle until the next downturn when they will again start pushing closed cycle for product differentiation
• Champion soon to have OD₁₀₀ in all nine of there mills
• many companies are quietly laying the groundwork for closed cycle by doing water reduction studies, etc. (especially in Europe)

• (summarize 3 mill case studies from 9 overheads here)

• (get copy of this slide - looked good)

• many mills are on the path to closed loop bleaching
• water reduction studies
• Eo recycle
• acid effluent treatement and recycle
• closed cycle retrofits capital costs high
• both TCF and ECF closed cycle possible

• Liebergott - strength of TEF pulps? no improvement, tear typically 5% lower than TCF equivalent
• Pageau - delivery cost on overhead? typical pulp delivery cost to market compared to Europe to market
• Liebergott - cost for "manning" should be cost for "peopling"