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        Last update : September 05, 2003
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  Logo EFPG     IX - Existing pulping alternatives to improve yield and benefits
Economics of Yield Increase (slides 9-17)


M. Sundar, M. Muguet, M. Epiney et G. Homer (Air Liquide)
 
     
 
9 - Every Mill Manager's Goal
  Optimize mill as a whole
  Maximize profits/cash by:
    lowering fiber cost
  lowering manufacturing cost
The cost structure of a 500K tons/year softwood chemical
pulp mill at full production is as follows:
Cost Percent
Production related/variable costs 50
Time related/fixed costs 13
Capital costs 36
Data from: Economics of the pulp and paper industry,
Tappi papermaking & technology series - 1
 
10 - Cost structure
In production related/variable costs, wood accounts for
31%, OMS (Operating Materials & Services) for 11%,
chemicals for 7% and energy for 1%, as shown by the
following figure.
Data from: Economics of the pulp and paper industry,
Tappi papermaking & technology series - 1
 
     
 
11 - Conventional Wisdom
Incremental production is extremely profitable, and
incentive is always there to improve productivity, as shown
by the following diagram:
Why are mills reluctant to practice new yield technologies?
Data from: Alkaline pulping, Tappi pulp and paper manufacture - 5
   
12 - Mills reluctant to practice new
yield technologies?
Major challenges:
      can incremental pulp be produced with existing
bottlenecks in the mill
  incremental pulp or save on wood
Desired strategy
  validate yield improvment at the mill
  ROI/Payback/Profit
Of course, the main challenge is fiber quality.
 
 
13 - Back to the basic: the kraft process
Let us start from basic, and have a look on the kraft process flow sheet:
 
 
14 - Technology options in various zones of the kraft process
Let us examine the various technology options in the four zones of the kraft process:
Zone Stage Options
1 Tree Improvement in forestry management as a whole
2 Wood Uniform chip size and improved screening
3 Digestion   Cooking additives: surfactants, AQ, polysulfides...
  Cooking process: batch, continuous, super batch, lo-solids and low temp for hardwoods, process control...
  Cooking conditions: increasing kappa to go up on the cooking curve in combination with 1 or 2 O2 delig stages, avoiding kappa fluctuations...
  black liquor gasification
4 Bleaching   Minimize bleach plant shrinkage
 
 
15 - Available preferences
Let us examine the various available preferences based on funds available:
Option Preferences Cost
Little to spend Optimize what currently exists in the mill. Example: minimize kappa variations  
Operating funds Chemical additives. Example: AQ, surfactants (exception of polysulfides) < 3-4 MÄ
Capital funds Polysulfide, minor wood yard modifications... > 3-4 MÄ
Modified/improved delignification opportunities. Example: super batch, two-stage oxygen...  
New risk technologies Wait & see. Example: black liquor gasification, wood genetics, cloning  
 
     
 
16 - Additional scenarios
Additional scenarios requiring yield improvement:
    production limited by recovery bloiler, or
    integrated mills with pulp demanding machines, or
  expensive wood cost
Some low cost options are:
  higher UB kappa
  AQ cooking (1% yield improvement)
   
17 - Air Liquide vision of pulp industry
ROI/Payback/Profit Validate yield improvement at the mill
Polysulfide Yield model
with or without combination of ozone & chlorine dioxide developed by Air Liquide
 
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