Small-scale District Heating Small-scale District Heating based on Biomassbased on Biomass

Joakim LundgrenJoakim Lundgren

Division of Energy EngineeringDivision of Energy Engineering

Luleå University of TechnologyLuleå University of Technology

BackgroundBackground Nuclear power phase outNuclear power phase out A large amount of electricity is today A large amount of electricity is today

used for heating purposesused for heating purposes Important to reduce the electricity Important to reduce the electricity

demanddemand One measure is to convert to district One measure is to convert to district

heating – an activity in progress heating – an activity in progress

BackgroundBackground

Biomass based district heating for larger Biomass based district heating for larger communities is well established in Swedencommunities is well established in Sweden

Increasing taxes on fuel oil and Increasing taxes on fuel oil and distribution network developments have distribution network developments have made DH interesting also for smaller made DH interesting also for smaller communitiescommunities

Space for at least 10 GW new installed Space for at least 10 GW new installed thermal power in small biomass fired DH thermal power in small biomass fired DH networksnetworks

ProblemsProblems

Studies show that boilers (0.5-10 MW) Studies show that boilers (0.5-10 MW) emits large amounts of hazardous emits large amounts of hazardous products (CO, THC, PAH, VOC) during products (CO, THC, PAH, VOC) during low and varying heat loadslow and varying heat loads

EconomyEconomy

EU project 1998-2001EU project 1998-2001

Develop a boiler concept suitable for Develop a boiler concept suitable for small DH systemssmall DH systems Broad thermal output span (10-100%)Broad thermal output span (10-100%) High fuel moisture contentHigh fuel moisture content Manage heat load fluctuationsManage heat load fluctuations Low emissions of harmful products in Low emissions of harmful products in

the complete thermal output spanthe complete thermal output span

ApplicationsApplications

Public buildingsPublic buildings Small industries and shopping centersSmall industries and shopping centers Small DH networks in villages Small DH networks in villages

……in purpose to change from fossil fuels in purpose to change from fossil fuels in existing boilers or to convert from in existing boilers or to convert from electricityelectricity

Layout of the research plantLayout of the research plant

Cyclones

Furnace Fuel storeFuel

containers

Boiler

Heat store Chimney

To DH network

Module 2

Module 1

Primary combustion Primary combustion chamberchamberGases to the sec. Gases to the sec. zonezone

Fuel feedingFuel feeding

•Partitioned combustion chamberPartitioned combustion chamber

•Drying zoneDrying zone

Secondary zoneSecondary zone

To the boilerTo the boiler

•High gas temperaturesHigh gas temperatures

•Good mixing with combustible Good mixing with combustible gases and secondary airgases and secondary air

•Designed by using CFDDesigned by using CFD

Experimental resultsExperimental results

0

20

40

60

80

100

120

50 60 150 175 200 250 350 500

Thermal output (kW)

CO

and

NO

x (m

g/M

J)

0

0,5

1

1,5

2

2,5

TH

C (m

g/M

J) a

nd e

xces

s ai

r ra

tio

CO NOx THC Excess air

ConclusionsConclusions

Very low emissions of hazardous Very low emissions of hazardous productsproducts

Can manage fuel moisture contents Can manage fuel moisture contents up to 58%up to 58%

Can handle heat load variations with Can handle heat load variations with kept low emissionskept low emissions

Great potential. 10 GW means Great potential. 10 GW means approximately 2000 new boilersapproximately 2000 new boilers

New projectsNew projects Replacing an oil fired boiler in a school Replacing an oil fired boiler in a school

building (Demonstration unit)building (Demonstration unit) BIO-SOL. Biomass based DH in BIO-SOL. Biomass based DH in

combination with solar energycombination with solar energy Combustion of horse manureCombustion of horse manure

BIO-SOLBIO-SOLConventional systemConventional system

BIO-SOLBIO-SOL

ProblemProblem Large heat losses during summer Large heat losses during summer

time, calculated as percentage of the time, calculated as percentage of the generated heat generated heat

Our ideaOur idea Let the customers produce their own Let the customers produce their own

heat during summerheat during summer

Distributed solar collectors and Distributed solar collectors and heat storesheat stores

Combustion of horse Combustion of horse manuremanure

Large costs for depositing waste Large costs for depositing waste materials, up to €100 per tonmaterials, up to €100 per ton

One horse produces 10 tonnes per yearOne horse produces 10 tonnes per year 300 000 horses in Sweden, resulting in 300 000 horses in Sweden, resulting in

a total amount of 3 million tonnes a total amount of 3 million tonnes annuallyannually

Year 2005, there will be a prohibition Year 2005, there will be a prohibition for depositing organic materialsfor depositing organic materials

Very large economical benefits for Very large economical benefits for stable- and trotting course ownersstable- and trotting course owners

Decreasing the demand for fuel oil Decreasing the demand for fuel oil and electricity and electricity

The only condition is that the The only condition is that the combustion process must be combustion process must be environmentally friendly environmentally friendly

Combustion of horse Combustion of horse manuremanure

Experimental resultsExperimental results

0

50

100

150

200

250

300

350

400

Manure Wood-chips

Em

issi

on

s (m

g/n

m3)

CO

NOx