Slimicide or antislime agent is a substance which is used as antimicrobial agents to kill slime-producing microorganisms in the papermaking process such as bacteria, slime, fungi and algae. It helps reducing production costs due to occasional breaks and shuts which save energy and time. Since paper can be manufactured under acidic or alkaline conditions, a slimicide should ideally be able to function over a wide pH range and compatible with common papermaking additives. Some slimicides are effective only for alkaline system and some are equally effective for Acidic and Alkaline media.
Slimicides or antislime agent has anti action on slime. Slimicides can be liquid or powder. The chemical types of anti-slime agents are organic sulfur, bromium and quaternary ammonium compounds, as well as aldehydes.
Why slime is developing
In a paper mill industry water is used mostly in re-circulation process. Moreover different water-based chemicals and materials are added in this papermaking process to increase productivity and improve the quality of the finished paper. The environmental condition (temperature, pH etc) of this recirculating water is ideal for growth of many undesirable microorganisms such as bacteria, slime, fungi, algae, yeast and mold. Sometimes spots of aluminum hydroxide gel or other inorganic matter are mistakenly judged as slime spots.
Effects of slime on paper/paper machine
The growth of microorganisms in the papermaking process creates a number of process and paper quality problems. For example –
- Slime lumps create holes, spots and breaks in paper web. Hence decreases paper machine runnability. To improve paper machine runnability need to be system cleaning. As a result increase downtime and energy loss.
- Clogged piping
- spray nozzle blockages
- Reduction of drainage, thermal transfer efficiency and flow.
- Sticking of valves and fittings causing operational troubles.
- corrosion of equipment
- Offensive odors
- Quality deviation out of discoloration of finished paper sheet.
- Above all reduce paper quality and increase cost of production.
Benefits of slimicides/anti slime agent
- Check of bacteria, slime, fungi, algae, yeast and mold growth and fibre degradation.
- Decrease paper web breaks and improve paper machine runnability.
- Prevents clogged piping, blockages, corrosion of equipment.
- Improves drainage, thermal transfer efficiency and flow.
- Slimicides can be act as a biocide and strong oxidizer and remove unwanted smell.
- Improve paper quality and increase productivity.
Slimicide ought to be added to a paper making process where mixing is uniform such as broke chest, beaters, drop chest, head box, and especially in wire pit. For a good result from a slimicide correct dosage is also very important. A continuous addition is necessary with very dilute solution in the chest.