About effects of flocculants during drying -1 / Sludge drying, Recycling drying

About effects of flocculants during drying

1) What is flocculants?
Flocculant is a chemical to assemble scattered particles about the cloudy water in water treatment plant etc. and to makes clusters, then the clusters are settled out of water. The cluster made by assembled particles are called aggregates or flocs. By settling down the particles, it becomes easier to separate flocs from water. In the water treatment process, it is used in settling tank or during dewatering.

2) Effects for organic sludge during drying.
Sludge is kind of solid cake which is discharged after condensing and dewatering process of water treatment and it has strong stickiness and adhesiveness. It is a solid cake which is separated from water by effect of flocculants and is holding a lot of water inside. Moisture contents are 80% W.B. or more in average. This sludge is containing flocculant and the flocculant affects in drying process.
There are two types of sludge which are organic sludge and inorganic sludge, and the effects of flocculants in drying process is more conspicuous especially in organic sludge.
When organic sludge is dried by dryer, it becomes granular as it is dried. In case the size of the granular is large after drying process, it is often seen that water comes out from inside by smashing them or only surface is dried even inside of them are not dried. As size of the granular become small, inner part can be dried better. Because of effects of flocculants, dried materials become granular easily during drying process. Organic sludge always become granular after drying.
Important points for drying process of organic sludge containing flocculants are the following.
1）To prevent the material to be dried from clogging inside the dryer since it has strong stickiness and adhesiveness.
2）To agitate and crush the material repeatedly as much as possible and make the granular of the material into small pieces during drying process.
In the drying of organic sludge, materials to be dried becomes very small grains when they are dried to around 5%W.B. The grains are small and cannot be smashed with fingers. It will never be powdery, so there is no need for dust prevention.
However, the dried materials become powdery easily in case of drying of inorganic sludge since effects of flocculants is small, so that dust prevention will be necessary if the materials are dried until low moisture contents. In case of drying of inorganic sludge, it is recommended to make moisture contents after drying 30% W.B or more.

3）About drying of flocculant itself.
Flocculant of poly aluminum chloride (PAC) is dried by KENKI DRYER. It was liquid before drying but becomes granular after drying. The followings are movie during drying and photos.