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Ireland Pulp+ dashboard Trouble shooting Refining info

Refining info

Refiner configuration

If not receiving expected properties it’s important to valid.

  • The refiner segments can be worn* and blunt. Regular checking of bars and groves is necessary. At a given spec. refining energy the strength and dewatering properties of the pulp should be the same over a longer period
  • The refiner is too large for the job: high no-load energy =$$. Modified segments can be installed. A recirculation can be the solution
  • The refiner is too small and it’s not possible to reach needed strength and dewatering properties
  • Remember that tensile and tear strength are adverse properties. Either or, but evaluate the best compromise
  • The mechanical status referring to the rotor position and gap clearance have to be valid, especially if the no-load figure has increased.

*Worn

Consequences are:

  • Too low spec. edge load
  • The refiner is too small for the job: too high put-through = inefficient fibre treatment
  • Consistency and hydraulic pressure variations. Oscillation of the “swimming” plate
  • Poor development of strength

Fiber cutting

The fibre length can be controlled by fibre analysis. Control of fibre properties is something Södra Cell has the possibility to support. Fibre cutting is not always wanted and here are some consequences.

  • The tearing strength of the paper will suffer
  • Formation will improve
  •  Amount of fines that inhibit dewatering will increase
  • Bulk of the paper will be better retained than when fibrillating.
  • If not desired, change to fillings with higher bar angle and/or lower specific edge load.

Short plate life = $$

  • Typical spec. edge load for softwood pulp: 1,5 – 2,5 J/m and hardwood pulp: 0,2 – 0,8 J/m. ( Calculations see control strategy)
  • Multi-stage refining develops higher tensile at a given tear
  • Separate refining of NBSK and Hardwood is more flexible
  • In many cases is the difference between separate and mixed refining small. Investment in several refiners and the double no-load gives a too high cost if we compare with the advantages.
  • Too high furnish temperature gives limitations in the development of dry strength.

Control stratergy

  • Consistency control is a must for smallest possible variations. Should be targeted at 5% +/-0,2. Calibration twice a week.
  • Hydraulic pressure control, especially important for a DD-refiner. On both inlets to minimize plate oscillation.
  • Continuous measurement of flow.
  • Measurement of motor power.
  • Control of specific refining energy through closed-loop calculation of consistency, flow and motor power.
  • Control of specific edge load:         PR - PO                                              Bar length x Revs
  • Control of no-load power

Fiber treatment

  • Typical spec. edge load for softwood pulp: 1,5 – 2,5 J/m and hardwood pulp: 0,2 – 0,8 J/m. ( Calculations see control strategy)
  • Multi-stage refining develops higher tensile at a given tear
  • Separate refining of NBSK and Hardwood is more flexible
  • In many cases is the difference between separate and mixed refining small. Investment in several refiners and the double no-load gives a too high cost if we compare with the advantages.
  • Too high furnish temperature gives limitations in the development of dry strength.

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