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What is the BIVIS Paper process ? |
Simply defined, a BIVIS machine is: a processing machine consisting of two identical co-rotating intermeshing self-wiping screw profiles operating within a closed barrel
Clextral developed pulping process jointly with Research Instituts and leading paper companies, applying proven twin screw extrusion technology used in the plastics, chemical, food and feed industries since the mid 1950’s.
BIVIS Machine for paper pulp processing
Clextral BIVIS machines provide continuous, automated processing for:
Wood Chips Defibering or Fiber Cutting
Chemical Impregnation
Bleaching
Washing
 
Wood chips defibering in Clextral BIVIS machine Active part of the BIVIS pulping machine
Wood Defibering / Fiber Cutting
The BIVIS or TSM (Twin Screw Machine) process is completely different compared to conventional defibering processes.
Fibres separation or fibres cutting are achieved by compression and shearing forces thanks to reverse threads screw components called reverse sections.
Several shearing modules are required for an efficient fibres separation.
Using a combination of reverse screw sections with varying geometries, the BIVIS machine efficiently processes wood chips, non wood fibres, textile fibres, recycled fibres, virtually any cellulose raw material, to achieve optimum fibre separation or fibre cutting depending on the raw materials.The highly efficient BIVIS system uses a fraction of the energy required by traditional processing equipment.
Chemical impregnation Various chemical treatments may be performed by TSM machine. Cooking, Chemical Treatment and Chlorine Free Bleaching Treatment of cellulosic material with chemicals and bleaching agents is easily and efficiently accomplished by the BIVIS machine. The high consistency of the material, plus the combined actions of temperature and pressure, accelerate the chemical reactions.Liquids or gases may be injected into the barrel at specific areas. The highly efficient BIVIS process greatly reduces the volume of chemicals required and dramatically lowers the volume of effluent to be treated. Bleaching to attain maximum brightness is accomplished without the use of chloric agents; sodium hydrosulfite and hydrogen peroxide achieve optimum results.Efficient and Thorough Pulp Washing Pulp washing operations consists of drawing out dissolved organic and mineral matters which remain after chemical treatment. For Chemi-Mechanical or Semi-Chemical pulps, the BIVIS machine enables to perform both washing and defibering simultaneously thanks to filters adequately located along high pressure zones. TSM can be supplied with several washing sections depending on pulp washing efficiency required. Owing to high pressure developed and efficient mixing by the screws, highly efficient washing is possible giving substantial savings in washing water and much less effluents to be processed.
Pulp bleaching
Pulp bleaching is a chemical treatment of the fibres, and pulp brightness depends on the end use of the pulp.
One or two pulp bleaching stages can be easily achieved with BIVIS process.
Main advantages of the process are:
. speeding up of the bleaching reaction
. high consistency bleaching
. high efficiency bleaching
. savings of bleaching agents and other chemicals.
BIVIS process is a Total Chlorine Free (TCF) process.
Sodium hydrosulfite and hydrogen peroxide are the main bleaching agents used.
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