Problem Summary

Deposition in the wet end of a Newsprint machine is typically composed of microorganisms, organic and inorganic contaminants. This is especially true when running 100% recycled fiber. The microbiological content of such deposits can be composed by aerobic or anaerobic unicellular bacteria, fungi and fresh water microorganisms, such as filamentous bacteria (normally associated with pink slime formation around showers etc.).  These microorganisms entrap fillers, fibers, and naturally occurring inorganic contaminants, forming deposits. When these deposits slough off they can cause a variety of production and quality problems such as holes, spots, and breaks and can increase the frequency of required boilouts and wash-ups.

In addition, many Newsprint Mills utilising recycled fiber as a fiber source, have a negative redox contributing to the growth of anaerobic bacteria which are normally associated with corrosion and pungent smells (rotten eggs).
Microbiological deposition has traditionally been controlled on a Newsprint machine through the addition of organic biocides such as MBT, DBNPA, BDNP (Bronopol) and various blends.

Oxidizing biocides, such hypobromous acid (formed from hydantoin) and sodium hypochlorite are also used in certain cases, at least in shower water. However, Newsprint short loops contain many substances that consume oxidizers (e.g. fiber and starch). Therefore, to achieve effective microbiological control, the oxidizer must be overdosed to overcome the effect of these substances. When dosed in this manner, the oxidizer can cause many unwanted reactions and adverse side effects, including consumption of costly wet end additives such as retention aid and dyes, increased corrosion rates, and reduced felt life.

Recommended Solution

Spectrum® Ammonium Bromide Technology is a new, patented biocide that effectively controls microorganisms in alkaline papermaking systems without the adverse side effects associated with strong oxidizing biocides. The biocide, which is produced onsite by blending ammonium bromide, sodium hypochlorite, and mill fresh water, can be applied in a continuous or intermittent fashion, depending on the specific system. Because the biocide does not react with fiber, it can be added not only to white water systems but also to thick stock, such as broke and recycled fiber.  It is highly effective in reducing microbiological levels thus reducing contamination that can impact the efficiency of other wet end additives such as fixatives, retention aids, strength aids etc.

Key benefits recorded from practical applications of Spectrum® Ammonium Bromide Technology include:

Reduced sheet breaks and defects
Increased time between boilouts
Reduced washups
Reduced corrosion rates
Reduced consumption of costly wet end additives such as fixative, dyes, retention aids
No negative effect on activated sludge plants
Reduced environmental impact