Pulp and Paper

Introduction

Nowadays, bleaching sequences for ECF (Elemental Chlorine Free) or TCF (Totally Chlorine Free) pulps became basic technologies for pulp bleaching stemmed from the chemical crushing of long or short fibers.
 
The production of bleached pulp reached an advanced technological stage and a concern on
sustainability which has motivated researches and system applications on water closing circuits,
minimizing the effluent discharges, placing off course the used water to closed circuits of treatment and reuse. Those processes are being possible due to the combination of hydrogen peroxide and chlorine dioxide in the ECF bleaching processes, and from the combination of hydrogen peroxide with oxygen and ozone in the TCF bleaching sequences.
 
The control of metals and the removal of impurities through more efficient washings favor the stability and the efficiency of Hydrogen peroxide in the bleaching stages, making its application possible in terms of pressure and higher temperature in obtaining products with physical and chemical properties that add value and meet the needs of the countless customers in the bleaching pulp producing industries in several continents.
 
In the bleaching of mechanical pulp the attainment of high productivity, brightness and physical properties, have made the hydrogen peroxide the most efficient feasible bleaching agent to be used. In the important and increasing industry of paper reuse for tissues production, the hydrogen peroxide also adds value and collects properties to the final product, enabling the attainment of high brightness with less need of virgin fibers. 

Bleaching of Chemical Pulp

The bleaching of chemical pulp distinguishes by its multiple stages. Basically, after it had been cooked it results even in two predelignifying oxidative stages, a delignifying stage followed by an oxidative extraction and a bleaching one.
 
The hydrogen peroxide is a versatile product that can be applied in all phases depending only on the control of the application conditions. In alkaline means and in adequate conditions the Hydrogen peroxide releases
the perhydroxyl (HOO-) ion, which is extremely selective and keeps the physical properties of pulp.
 
This way, we present the three most important applications of the Hydrogen peroxide in pulp:

• In the extraction, (Ep) or (Eop), the hydrogen peroxide removes the substances partially oxidized by the delignifying product applied in a previous stage;
• At the end of the bleaching, one stage (P) or (PO) conceives high and steady brightness;
• In the double predelignifying stages, the usage of Hydrogen peroxide enables short stages of bleaching with low discharges of the COD (Chemical Oxygen Demand).

 
In integrated plants, a final alkaline stage with Hydrogen peroxide results in a low use of chemical products and power in the refining.

The advanced technology that makes the high efficiency in cooking feasible, better performance in washing stages with good control of process in the application of the acid lixiviation, improved the alkaline stages with the Hydrogen peroxide. Pressurized stages (PO) or with high consistency (P*) reach excellent results with low use of Hydrogen peroxide when compared with the medium consistency stages, low temperatures and atmospheric conditions.

The field for the application of different technologies enlarged in the use of Hydrogen peroxide with the replacement of chlorine gas and its derivatives, reducing the AOX (absorbable organic halides), the COD, and also the brightness reversion.

For being a liquid product, of easy transportation and handling, the hydrogen peroxide allows production increase without the need of investment in equipment for generation of other oxidizing compounds.

Sequences for bleaching with high brightness values, low reversion grades, productive, of ensured quality and environmental commitment, like: A D PO D; D Eop D P; A Z Q PO; Q Z D PO, that only become possible with the application of hydrogen peroxide.

High Yield Pulp Bleaching

For high brightness, the alkaline bleaching process is indispensable in the production of the mechanical pulp. In the SGW, TGW, TMP, BCTMP, APMP and APP, the process increases the brightness, improves the mechanical properties, reduces brightness reversion and keeps the high yield.

Hydrogen peroxide and the bleaching liquor, composed mainly by caustic soda and a metal chelating, are applied in the paper pulp to guarantee the correct homogenizing and reaction efficiency made during average or high consistency in the bleaching tower, with time e temperature of the process previously determined.

The yields of the physical properties and on bleaching, that can vary from 5 to more than 20 points, depending on the type of mechanical pulp and of the process conditions. 

Bleaching of Paper Scraps

This product is also characterized by one or two steps of bleaching. The pulp to be bleached presents diverse characteristics in function of its achievement, and it might be rich in chemical pulp (white prints), pulps of high yield (newspapers, magazines, cards) and inorganic loads from the alkaline gluing of papers.

The hydrogen peroxide can be used in many steps of the process, aiming to the improving  of fiber properties and bleaching yield. The application points can on pulper, where it can also act as a decontaminating agent; at the disperger step or bleaching tower.

Contact us

PERÓXIDOS DO BRASIL has specialized technicians for the application of hydrogen peroxide in the process of pulp and paper, counting with a laboratory for simulating the complete bleaching sequences and other complimentary analyses.
 
The correct and safe handling of hydrogen peroxide is part of PERÓXIDOS DO BRASIL Responsible Care politic, and as consequence, we put at our clients disposal our services of technical support, evaluation of existing storage tanks; projects and safety training, including lectures and a CD that’s distributed upon request.

Cleaning-in-Place (CIP) 

Considerations:

Due to the nature and dimensions of certain facilities, the manual cleaning of stationary equipment is a job of difficult execution, for being technically insufficient and uneconomic, for the lost time of production line stop in the disassembling and reassembling of the equipment, for the higher maintenance and for the possible breakages and wears of union parts.

Considering these difficulties, an automatic cleaning of stationary equipment (CIP) was devised, which consists of making water, detergent and peracetic acid (disinfectant) circulate in the same circuit of the product.

Based on these aspects, PERÓXIDOS DO BRASIL has developed the PROXITANE® line, consisting of peracetic acid based disinfectant, that’s ideal for use in CIP systems.

Additional benefits of peracetic acid 

• It’s effective against molds, yeasts, bacteria (including spores), viruses and algae. No development of any microbial resistance has been observed.
• It doesn’t produce foam, being ideal for the food industry.
• The absence of peracetic acid residues allows that its use doesn’t alter the chemistry of the taste of the product to be process in the facilities, usually eliminating the rinsing after application.
• Prevents formation of incrustations in the systems in which it is used.
• Under the advised conditions, it doesn’t affect the biological effluent treatment (aerobic or anaerobic), once its decomposition products are totally biocompatible.
• Não produz espuma, sendo ideal para a indústria alimentícia.
• It’s active in a wide range of concentration and temperature.
• Evita a formação de incrustações nos sistemas em que é empregado.
• The concentration of peracetic acid is easily determined through analysis methods provided by PERÓXIDOS DO BRASIL.
• It’s compatible with stainless steel (see product manual).
• It’s a disinfectant of easy application and very quick action.

The constant search for efficiency increase and industrial cost reduction in the paper sector has led to the closing of many whitewater circuits, reducing the loss of fibers, chemical products and industrial water. Besides that, there is the social and legal necessity of reducing the volume and improvement of the quality of liquid effluents.

The water reuse obtained by the closing of the water circuits brings direct economical advantages to the paper industry. However, the presence of fibers, minerals, resins, organic loads (binders, dispersants, etc.), moderately elevated temperature and aeration cause a lot of operational and quality problems. The majority of these products is related to the increase of salinity, odors caused by generation of H2S by sulfate-reducing bacteria, microbiological corrosion and formation of bacterial slime - and cause production interruptions, breakages and paper defects. In most cases, the more closed the system, higher will be its microbial contamination (i.e. recycled paper is potentially more contaminated than virgin cellulose).

The hydrogen peroxide is recognized as a microbicide, being also compatible with the environment. In view of this and with the objective of efficiency increase and cost reduction of whitewater circuits, Peróxidos do Brasil has developed an application of hydrogen peroxide as a microbicide agent for this area.

Its effect is sufficiently powerful, reducing the formation of biological deposits (slime) and number of chemical cleanings required, being able to effectively reduce the bacterial count to the required levels. Corrosion rates caused by sulfate-reducing bacteria are also greatly improved due to increased oxygenation, since they are anaerobic.

Sulfide level reduction is also achieved, eliminating odor in the circuit and reducing need of adding other compounds for H2S control. (See how hydrogen peroxide works for sulfide reduction.

With all these effects, the frequency of paper breakage is reduced and machine speed is increased. Also,  less cellulose is lost by the dumping of whitewater during the paper machine cleaning.

Contact us for helping with the development of this technique on your factory.