Rejects – a valuable stream of your board making process

Sustainable OCC lines require proper reject handling systems to operate economically. This means minimized process material losses and efficiently recovered resources like fibers, water and energy, as well as minimized waste disposal.

Optimal reject handling systems help you to convert rejects into valuable energy and new raw material sources.

 

Target

Reject

Sludge

     Separate
  • burnable material
  • non-burnable material
  • filtrates
  • burnable material
  • filtrates
     Maximize
  • burnable dryness
  • constant runnability
  • burnable dryness
  • constant runnability
     Minimize
  • ferrite and non-ferrite metal amount of burnable fuel
  • solids in filtrates
  • solids in filtrates
  • retention aid
     Protect
  • boiler
  • effluent system
  • boiler
  • effluent system

 

Coarse reject handling

Valmet’s screw presses are designed for small and large quantities of various coarse rejects for the OCC process, including pulping and coarse screening rejects. These applications require a thickening press with a very rigid design. Valmet’s coarse reject presses are designed for extremely heavy-duty operation and feature a protected safety coupling to avoid screw flight or screen plate damage. This ensures reliable processing with high availability in demanding applications.

 

Sludge handling

A typical sludge handling system is used for fine rejects from screening and cleaning. The system includes a flocculation tank, rotary screen thickener and screw press. Sludge is fed at low consistency into the thickening system from a collection tank. When required, polymer is added to the sludge immediately prior to the flocculation tank. The conditioned sludge flows from the tank to the high consistency rotary screen thickener, where the thickening process begins. The pre-thickened sludge is then fed to the sludge press for final thickening up to a consistency of 50 to 60 percent.