Sludge Drying & Incineration

[arj00]

We have an existing STP with belt press (4 units) handling 63 mgd, the solids conentration after the belt press is 20%. We desire to incinerate the sludge:
1- Can we incinerate the sludge directly after the belt press or we have to dry it first & what are the recommended methods for drying & incineration?
2- Can we by-pass the belt press process, so we go directly from the anaerobic digestors then drying then incineration?

 

[oxilume]

Dear ARJ00,

Keep in mind that to dry your sludge you need 1000 BTUs for every pound of water vapor removed. If you recover the heat, by condensing the water vapor and preheating the sludge, then you can be very efficient.

Why go through the process of heating the sludge then incinerating it.

Simply, thermally oxidize underwater as it is pumped from from the digester. The Plasma Whirl ArcLight has demonstrated this. A full scale unit is currently being tested. see:

http://www.oxilume.com

Todd

http://www.oxilume.com

 

[bimr]

It depends on the type of incinerator. If you go with a multiple-hearth incinerator, you need 15% dry solids in the feed sludge. If you go with a fluidized bed incinerator, then you can probably skip the belt press.

 

[ch81pc]

From some research I did on some fluidised bed incinerators, I found that a dry solids content of >30% was needed to achieve autothermal conditions.

Digested sludges have had most of the available volatile carbons ect broken down, so consequently have a much much lower energy output when burned.

Increasing the proportion of secondary sludge in the mix will also decrease the energy output and will no doubt cause you more problems with dewatering too.
The plant I worked at used separate thickening streams for primary and secondary sludges (picket fence and aquabelt respectively) before being combined and dewatered in plate presses.

Hope this helps

Paul