Ozone and pulp bleaching

The bleaching of chlorine-free pulp combines in sequenced operations, ozone: Z / oxygenated water: P / xylanases: E.

The bleaching processes developed and exploitable industrially, can radically eliminate pollution by chlorine and its derivatives, they will inevitably replace in the short and medium term.

The bleaching operations are studied at different consistencies. Remarkable results have been obtained with ZP, ZZP, ZE, ZEP sequences where pH control plays a decisive role.

The experience gained in this field makes it possible today to propose optimal bleaching sequences, according to the raw material in question, and the desired degree of whiteness under economic conditions equivalent to chlorine for the same final quality of dough. The bleaching of annual vegetable pasta with ozone, starting from these results, becomes an industrial reality.

The elimination of the organic acids generated by the bleaching sequences in the aqueous effluents by recovery on ion exchange resins or liquid-liquid extraction or removed by a biological treatment stage makes these technologies perfectly non-polluting.

Xylanases by hydrolyzing the hemicellulose structure of paper pulps promote their bleaching.
A selection of specific xylanases of the bacillus type was performed. The microorganisms were then tested in TCF (total chlorine free) bleaching sequence.

The effect of the xylanases decreases the kappa of the processed pasta, increasing very significantly the degree of whiteness, their conditions of production and recycling are studied.

The saving in ozone can reach 20 to 30%. The electron microscopic analyzes show a modification of fibers without the physicochemical properties of the pasta being substantially degraded.

Ozone and water treatment

The destructuring action of ozone has been studied for a long time. The results obtained have already made it possible to propose industrial installations for the depollution of heavily loaded organic effluents with a hard COD (Chemical Oxygen Demand).

A new reactor design combining anaerobic biological treatment with the oxidative reactivity of ozone has recently been developed. The process applied to the treatment of paper pulp from Kraft units gives excellent results in terms of discoloration and destruction of the hard COD

Another type of reactor, with the original hydrodynamics, called multi-impact current has also been developed. The remarkable performance of this new reactor in terms of gas retention and material transfer makes it currently being developed on a pilot scale on a drinking water production line.