power generation using municipal sewage sludge jgermanis
TRANSCRIPT
Power Generation using Municipal Sewage Sludge
Jason Germanis [MScEng]Spha Biyela [BScEng]
Dr Christos Eleftheriades [PhD, MBA, Pr.Eng]
Coal and Waste Utilisation (Pty) Ltd
Presentation for FFF workshop, 16 July 2013
ØKwaMashu WWTWØSludge to agricultureØTreatment optionsØFBR TechnologyØIncineration plant layoutØChallengesØLong term solution
1. Outline
• Sewage sludge: undesirable end product of wastewater treatment?
• An energy resource?• Management options?
How to turn waste into resource?1. Sludge disposal2. Energy production3. Carbon credits
2. Introduction
3. KwaMashu WWTW
• One of the largest treatment works in Durban, eThekwini Municipality, with 45 Ml/day raw inflow
• 2 Primary digesters: production of biogas
• Sludge is de-watered:
– Rota-mat Hubbers: raw sludge, up to 40 tpd, 24-28 % solid (incinerated)
– Belt press: digested and waste activated sludge, 50 tpd, 14-18 % solids (dried to pellets or taken to
agriculture)
Sludge analysis (sludge guidelines).
Continuous monitoring of soil and ground water quality must be carried out, to ensure that metals and microbial limits are not exceeded.
Agricultural land decontamination can take up 10 years.
Rising transport costs with increasing fuel prices
Farming is seasonal and sludge needs to be stockpiled.
Sludge may not be applied more than three times in 5 years period on the same agricultural soil.
Sludge handling and storage is an additional cost.
4. Disadvantages using sludge in Agricultural Applications
5. Treatment Options
• Incineration• Steam production• Power generation
• Drying• Compost pellets for agriculture• Further processing into organic-fertilizer
• Stockpiling / landfill
• Non-agricultural uses• Remediation of mine waste deposits,
contaminated solids
Proposed management
option
6. FBR Technology: Why incineration?
• Reduction of sludge volume by 95 %• Total destruction of pathogens• Stable ash product of inorganics • No odour (due to complete sludge
exposure at 850°C)• Energy recovery options
– Air preheat– Drying facility– Steam or power production
7. Incineration plant layout
Ash
RawSludge
FBR
Air Feed
FeedCoal or Pellet
SBD
850 °C
380 °C
DigestedSludge
RTO
Pellets
Stack
Regenerative Thermal Oxidiser (odour removal)
800 °C
Spouted Bed DryerFluidised Bed
Reactor
LPG Gas
Gas scrubbing
8. Challenges experienced• Sludge pre-treatment
– High inorganics in sludge– Low solids concentration– Varying sludge composition
• Interdependent system– small process disruptions or a mechanical/electrical
breakdown result in shutdown of the entire plant.– Incineration and dryer unit in series
• Starting/stopping operation of the dryer – pellets in the dryer susceptible to auto-ignition– problem experienced in similar dryers worldwide
9. Long term solution, Green Energy
Ash
RawSludge
FBR
Air Feed
Bio Mass
Boiler
850 °C
DigestedSludge
Stack
Gas scrubbing
Steam Turbine
1-2 MWe
