Deposit control is used to reduce the need for maintenance stops by controlling deposit and/or scale forming substances in pulping processes. Anti scaling is used in digester and bleaching; chelants are used in O2 delignification and bleaching; dispersing agents are used throughout the entire process.
Anti-scaling agents are chemicals that are used to prevent the build up of or to remove scale and fouling, and are often targeted at specific problems such as limescale, pyrolusite, barite, etc. These chemicals often contain mixes of different chelants and dispersing agents. Anti-scaling agents may be used in the digester or bleaching plant to give longer run times and reduce the need for maintenance and cleaning stops.
Complexing agents used as process chemicals are normally chelants that make multiple bondings with troublesome ions, hence preventing them from reacting with other substances. In pulping, these are used in peroxide bleaching to prevent metal ions from consuming the peroxide.
Dispersing agents are a wide range of surface active chemicals used to keep different substances in suspension. In pulping these are normally used to prevent rosin, pitch or other wood extractives from forming deposits by keeping them finely dispersed.
Felt conditioners are different chemicals that are sprayed on felts to protect the wire from deposits, keeping fine structures open. This increases runnability and reduces the need for washing.