Handling of dewatered sewage sludge

[MartinLe]

We need to handle (dose into AD system) sewage sludge at ~17%TS - I assume it's dewatered to a degree.
I expect that it will leach water when heaped high, so for dosing we will need some sort of through with an auger. We use them for some waste projects, but I'm interested if there are alternatives.

My questions: What can we expcet the material to behave like mechanically, and what equipment is there to store, dose and convey the sludge?

 

[MartinLe]

forgot to add: we deal with approx. 100 t/d, we will need to store about 100m³ and dose automatically out of this storage.

 

[bimr]

The 17% dry solids concentration is basically dewatered. There should be minimum water drainage. This is normally considered to have a cake like consistency.

It is possible to pump this material with a positive displacement pump, but this will require expensive pumping equipment and it is not recommended.

This material is usually handled with a conveyor belt or a screw conveyor. Conveyor belts can be used, but the material will stick to the belt and solids may fall off on the bottom return side of the belt. Because of this, the conveyor belt will have more cleaning required and will also generate odors from the exposed material.

The screw conveyor is your best option. The screw conveyor can be covered to minimize spillage and odors. The shaftless screw conveyor is also a good choice.

This material will probably not flow well inside of a storage bin. Your best option is to store the material on a concrete floor and pick the material up with a front end loader. You can then deposit the material in a receiving hopper with a live bottom.

 

[MartinLe]

Thanks. We were practically set on a hopper with augers. But we'll need a large hopper, so I'm thinking about alternatives.

Normally we'd use a large hopper with a conveyor belt as the floor, this would be the wrong technology here because of the stickiness of the substrate, also with a heap 2-3m high I'd still expect some leaching.

Do you (or anyone else) know of an installation were walking floors are used, for sludge like this? I'm sceptical wether there's enough friction within the heap to move the mass with a pull floor system.

 

[bimr]

I have never seen a live floor used for something like this.

I am not sure what your overall layout is, but the best option will be a screw conveyor bottom. Note that the screw conveyors can be fabricated with very long lengths.

 

[Subystud]

Got a simple process flow diagram? A sketch would suffice.

For transfer, a shaftless screw conveyor works. "Cake pump" could be an option, too. A seepex progressive screw pump with an open hopper feed will transfer the biosolids, but I wouldn't recommend pumping over 300' with this setup.

 

[QualityTime]

At 17% it will be a wet sticky cake. As with any dewaterd product where polymer was used it will eventually release some water. So make sure everything is sealed tight. I have built four (170 m3 each ?) large live bottom hoppers for 25-30% dewatered aerobically dewatered sludge. The upper portion of the hopper was full height rectangular and the lower half of the hopper had 60 degree slope. They had a double screw conveyor under each hopper. They have been in operation since 1992. Dewatering centrifuges were located about the hoppers and the sludge dropped in by gravity.

 

[ch81pc]

We have used a live floor loading hopper taking 2x 30 tonne tippers at a time, which feeds into a twin covered auger. We do get some leaching from the belt, so be sure to have adequate draiange and wash down facilites.
We dose quick lime into the twin augers and then pass into a plough shere mixer. I have found that if product (undosed) is passed back through the system for a second time, the added mechanical mixing makes the cake much more plasticised, going from a friable materials to what ressembles elephant dung. The feeder we use is manafuactured by

http://www.samson-mh.com/

 

[MartinLe]

Thanks ch81pc & Quality time