Cost effective energy usage at Himmerfjärdsverket sewage treatment plant

in Sweden.

Malin Tuvesson and Lars GunnarssonSYVAB Himmerfjärdsverket, SE 142 97 Grödinge,

Sweden.

Mats Holmberg and Christian Rosen Industrial Electrical Engineering and Automation (IEA), Lund University, Box 118, SE-221 00 Lund, Sweden.

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Content

• Energy usage: SE, GE

• About SYVAB, Himmerfjärdsverket

• Energy balance

• Simulation tool, scenarios, sensitivity

• Conclusions

• Actions taken

• Results

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Sewage treatment in Sweden

• Total used energy; 930 GWh– Electricity; 630– Other; 300

• 2.5 – 3 kWh electricity / kg BOD

• 90 – 100 kWh electricity / pe / year

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Sewage treatment in Sweden

• Energy production; 3.100 GWh– Biogas; 600– Heat; 2.500

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Sewage treatment in Germany

• Electricity; 45 kWh / pe / year

• Heat; 45 kWh / pe / year

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Sewage treatment in Germany

Electricity 50% of Sweden

and estimate a 30% decrease,

to 30 kWh / pe / year

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Himmerfjädsverket

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Himmerfjärdsverket , WWTP

• 4,500 m3/h• 300,000 p.e.• 7,000 t DS/a• no major industry • N-reduction

– 1984– 1997

• Start up 1974• BOD 15 (8) ppm• COD 70 ppm• tot-N 10 ppm• tot-P 0.5 (0.3) ppm

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50%

41%

Pumping

25%

25%

42%

17%

Aeration

Diffuse

Electrical energyBiogas energySludgedryer

Heatingboilers

Flare

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Himmerfjärden WWTP

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Electricity 2006

• 27 GWh– Inlet pumps 50 %– Aeration 25 %

Electricity cost of operational cost

2006: 21 %

2007: 27%

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Himmerfjärdsverket 2006

• Biogas production; 3.5 MNm3

– 500 Nm3/t DS treated– 1,000 Nm3/t DS reduced

• Oil; 5 m3

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Biogas 2006

• 3,5 mNm3, 23 GWh– Sludge drying 17 %– Heating digesters 28 %– Heating buildings 14 %– Flare 41 %

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Himmerfjärdsverket 2006

• Total energy used: 41GWh– 0.74 kwh/m3 treated water– 1.11 kWh/m3 drinking water sold– 1.9 kWh/COD-red

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Simulation Model

Model input

• Biogas production

• Sludge dryer

• Heating demand

• Electrical energy cost

• Biogas value

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Simulation Model

INPUT VARIABLES

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Model parameters• Biogas engine

– Power, efficiency, etc. • Heat pump

– Size– temperatures

• Heating– Efficiency

• Vehicle fuel production– Volume– price

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Simulation ModelG

AS E

NG

INE

HEAT PUMP

DRYERGAS BURNER

DIGESTERS

BUILDINGS

OIL

VEHIC

LE F

UEL

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Model output

• Energy balance– Biogas– Heating

• Financial results– Revenue– Costs– Total balance

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Simulation Model

GAS BALANCE

HEAT BALANCE

FINANCIA

LS

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Simulation model, scenarios

A - Thickening of sludge to digester

B - Heat pump on reject

C - Gas engine– 500 kW – 300 kW

D - Vehicle fuel production

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Simulation Model

Värmebehov kontra värmetillskott

0 kWh

200 000 kWh

400 000 kWh

600 000 kWh

800 000 kWh

1 000 000 kWh

1 200 000 kWh

Oljepanna

Gaspanna

Värmepump

Gasmotor

Slamtork

Totalt värmebehov

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Conclusions

• Efficiency increase of pumping

• Thickening of sludge to digester

• No heat pump

• No electricity from biogas

• Mechanical energy from biogas engine

• Vehicle fuel production

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Actions

• Modernize inlet pumps

• New centrifuge for sludge thickening

• Gas engine and a new blower

• Contract to provide gas for vehicle fuel

• Introduce deamonification

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Deamonification

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Deamonification

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Results• Inlet pumping efficiency

– decreased energy cost with 5%

• Thickening– 25 % reduction in heating

• Gas engine– Reduction in total electricity demand 10 %– Reduced costs for heating

• Vehicle fuel– Income / Nm3 biogas produced

• Deamonifiction– Reduced cost of N red. with 15 %

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Target

Energy efficiency and Biogas sale

by 2011

to reduce costs equivalent to

2/3 of energy costs 2007

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Summary, SYVAB

• Energy– Energy source– How to utilize– To produce– Legislation

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Summary, SYVAB

• Methodology for investigation – Modelling tool– Scenarios– To understand & communicate

• Cost impact

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Summary, SYVAB

• Actions– Pumps– Heating– Biogas– New process technology

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QUESTIONS ?