pulp and paper

Pulp & Paper

Chemical pulping is used to break down/dissolve the lignin “glue” which binds the wood cells (often referred to as fibers, cellulose or carbohydrates) together by use of chemicals. Caustic calcined magnesia (or calcined magnesium oxide) is typically used in the Magnefite process, as a raw material for the on-site production of magnesium sulfite liquors which are subsequently used for pulping. MgO is also used as alkali in the bleaching process, especially for mechanical pulps, with the potential to replace caustic soda (NaOH) and/or magnesium sulfate protector/stabilizer. Grecian Magnesite’s high reactive magnesium oxide products with very low iron and manganese levels, can offer peroxide savings and reduce chelation costs compared to conventional MgOs in the market. The following table summarizes the potential utilization of MgO in P&P related processes:

 

Application Role of MgO Benefits
Pulping

Raw material for
production of
magnesium bisulfite
used in the pulping
liquor.

Magnefite Process
requires MgO use.

Peroxide Bleaching
of Mechanical Pulps
 

Potential for total NaOH
replacement as the alkali
for peroxide decomposition.

Lower charging levels
compared to NaOH,
constant pH without swings,
cost reductions for the treatment
of water effluents, reduction in
the use of sodium silicate,
replacement of MgSO4 as cellulose protector. MgO is non-hazardous.

Extraction stage 
(Eop or Ep) 
Bleaching and Oxygen 
Delignification 
Partial NaOH replacement
as extraction alkali and/or
replacement of MgSO
as cellulose protector.
0,5 kg of MgO can replace 1 kg
of NaOH. Elimination of MgSO4
if previously used, will be an added benefit. 
pulp and paper
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AK98 HR

AK98® HR is a natural, high purity, calcined magnesium oxide, extremely low in impurities (low-acid insoluble) and undesirable substances. It is processed under carefully controlled conditions to give a finely divided white powder with a high and uniform reactivity index.

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