arvi getting most out of the thermal drying of sewage sludge, deviatkin
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Getting most out of the thermaldrying of sewage sludgeto stay within the planetaryboundaries for the nitrogen cycle
16.01.2016
Ivan DeviatkinDoctoral student, Department of Sustainability Science, School of Energy Systems, Lappeenranta University of Technology
Planetary boundaries
1.0-2.5 mg N/L – limit to prevent eutrophication.
To keep it such, the planetary nitrogen fixationboundary is set to 62-82 Mt N/year.
Currently, the fixation rate is 121 Mt N/year, where82 Mt N comes from synthetic fertilizers.
Therefore, 20-26 Mt N from synthetic fertilizersshould be avoided.
Where to get N, if not a synthetic one?
Stream N content, mg/LLiquid manure fractions ≈ 3,500
Digested manure ≈ 3,500
Organic waste ≈ 1,200
Reject water from WWTP ≈ 750
Industrial waste streams *
Condensate from sludge drying *
N-fertilizer
N-food
N-wastewaterN-sludge
N-NO3
N2
N-Anam
mox
N-A
nam
mox
Shor
t circ
uit
N-H
aber
-Bos
ch
van Eekert, M., Weijma, J., Verdoes, N., de Buisonje, F., Reitsma, B., van den Bulk, J., van Gastel, J., 2012. Explorative research on innovative nitrogen recovery.
Great attention was drawn to N recovery from liquidflows neglecting direct recovery from gaseous flows!
Research idea (!) and questions (?)
(!) sludge drying and incineration is a commonpractice, so nitrogen recovery during thermal dryingof sludge (and similar streams) was seen favorable.
(?) how much N is released from sewage sludge, digestate, and biosludge from a pulp and paper mill
(?) what is the impact of T on the N release
(?) which recovery methods could be practiced
(?) intensifying N release through condensatestripping
Legend
N-NH3
Sewage sludge
(1)
(2)
(4)
(3)
Nitrogen fertilizer
Hot air/steam
Fumes for treatment
Energy
Ash for recycling
Solid flowLiquid flowGas flowEnergy flow
(1)(2)(3)(4)
- sludge bunker;- drier;- incineration plant;- absorber/adsorber.
drier
bunker recovery
Incineration plant
Nitrogen release during batch drying 1
Experimental setup on the Figure→
Sewage sludge Toikansuo WWTP, LPRDigestate Kouvolan Vesi Oy, KouvolaBiosludge UPM Kymmene, LPR
b a cd
e
fg
Legend:a – vessel with sludgeb – inlet pipec – outlet piped – electric ovene – thermometerf – praparation unitg – Gasmet analyzer
Nitrogen species Digestate Exhaust fumes Condensate
Total nitrogen (𝑁"#") Modified Kjeldahl test
n.d. Nitrogen (total) cell test
Soluble nitrogen (𝑁$#%) WE + Nitrogen (total) cell test
n.a. n.d.
Ammonium (𝑁𝐻'() WE + Ion chromatography
n.a. Ion chromatography
Ammonia gas (𝑁𝐻)) n.a. FTIR n.a.
Nitrogen release during batch drying 2
100°C 130°C 160°C
70°C 100°C 130°C 160°C
130°C 180°C 210°C
Sewage sludge
Digestate
Biosludge
0
10 000
20 000
30 000
40 000
50 000
60 000
Sewage sludge Digestate Biosludge
Total Nitrogen Soluble Nitrogen N-NH470°C 100°C 130°C160°C 180°C 210°C
19%
58%
7%
mg/
kg T
S
Nitrogen release during batch drying 3
100°C 130°C 160°C
70°C 100°C 130°C 160°C
130°C 180°C 210°C
Sewage sludge
Digestate
Biosludge
0
5 000
10 000
15 000
20 000
Sewage sludge Digestate Biosludge
Total Nitrogen Soluble Nitrogen N-NH470°C 100°C 130°C160°C 180°C 210°C
mg/
kg T
S
55%
4900 −6200
9000 −9900
1300 −1700
50%65%
Nitrogen release during continuous drying 1
Experimental setup on the Figure →
Two (+1) tests. Feeding at 1.38±0.17 kg/h.MC of raw sludge was 83.7±0.1% and of driedsludge – 31.1±0.1%.Each experiment lasted for 8 hours.
Ammonia measurement at 2h, 4h, 5h, 6h, 7h, 8h.Acid traps for NH3 capture. Ion chromatography.
Biochar was used for ammonia capture
Nitrogen release during continuous drying 2
0
400
800
1 200
1 600
2 000
0.00
0.30
1.00
1.30
2.00
2.30
3.00
3.30
4.00
4.30
5.00C
umul
ativ
e m
ass o
f dry
slu
dge,
g Test I Test II Test III
100
200
300
400
500
1h 2h 3h 4h 5h 6h
Drie
d sl
udge
out
put,
g·h-1
Test I Test II Test III
- calculated driedsludge output (280±10 g/h)
R² = 0,99413
R² = 0,99861
0,0
200,0
400,0
600,0
800,0
1000,0
1200,0
1400,0
0 1 2 3 4 5 6 7 8 9
Cum
ulat
ive
N in
exh
aust
fum
es, m
g
Time, h
So we get:
0.53±0.01 mg N/g dried sludge
0.21±0.01 g dried sludge/g wet sludge.
Therefore, we can get:
110±6 g N/t wet sludge.
Adsorption on biochar: organic materials doped with N
Absorption:• ammonium sulphate solution,• ammonium nitrate solution,• ammonium chloride solution,• etc.
Aqua ammonia
General recovery methods
Packed adsorption Packed absorption
Sprayed absorption Droplet absorption
Thus, there is the need to release 30% Nback for recovery!
Intensifying ammonia release
100%90%
TEST IITEST I
30% in condensate
70% goesfor recovery
Let us strip it!
14ºC 31ºC
Sludge is a reliable source of nitrogen as its amount is ever-growing worldwide.
When we incinerate sludge, we have a good possibility to recover nitrogen.
50-65% of soluble nitrogen is release as ammonia duringthe drying process.
Nitrogen released could be recovered by ad/absorption.
Moreover, great possibilities for symbiosis exist. The process could be retrofitted to:• a sludge incineration plant to get nitrogen released;• a WWTP for nitrogen stripping from condensate.
What do we get after all?
Legend
N-NH3
Sewage sludge
(1)
(2)
(4)
(3)
Nitrogen fertilizer
Hot air/steam
Fumes for treatment
Energy
Ash for recycling
Solid flowLiquid flowGas flowEnergy flow
(1)(2)(3)(4)
- sludge bunker;- drier;- incineration plant;- absorber/adsorber.
drier
bunker recovery
Incineration plant
1. Technical study on recovery possibilities
2. Economical analysis
3. Environmental impact assessment
Future research needs
Socialacceptance
Environmental impact
Economicconditions
SYSTEM ANALYSIS
Thank you for your attention!
Questions?
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