© Vattenfall AB

BFB furnace bottom modification in Idbäcken CHP

Demo in NextGenBioWaste WP1.2Christer Forsberg

Vattenfall Heat Nordic

© Vattenfall AB 2

Idbäcken CHP in Nyköping

1994, Bubbling Fluidised Bed: 70 MWheat 35 MWel

Steam data: 140 bar/540°CNGBW targets:

Double the lifetime of heat exchanger components at existing steam temperatures

Increase the electrical efficiency for biomass combustion plants from 33 to 35%, while making the systems more cost-effective by the use of more low-grade fuels

Lower the fuel cost at least 1 mill. €/year for a 100 MWth biomass combustion plant while mainting the two former subtargets (2 and 3)

© Vattenfall AB 3

Demolition waste wood

© Vattenfall AB 4

Forest residues

© Vattenfall AB 5

Fuel mixture

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Waste wood MWhVirgin wood MWhOil MWhCoal MWhPower sold MWhHeat sold MWh

© Vattenfall AB 6

Need for new bed bottom

• 50% waste wood => stop every month for bed cleaning

• Target: 100% waste wood!

© Vattenfall AB 7

Tested nozzlesAnkfotsdysa Hög dysaOriginaldysa

Trappstegsinsats

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Pilot scale test – nail transport

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Original nozzles

© Vattenfall AB 10

Step grid

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New bed bottom design

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Installation summer 2007

© Vattenfall AB 13

The problem to drain sand from all shutes…

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4:1 scale sand drain tests

Original design- empty hopper ‘Kinesiska hatten’ ver. 4 in hopper

Unfortunately, the sand don´t behave the same in the full scale hopper…

© Vattenfall AB 15

Steam production BFB 2007-08IDBACKEN.P3.CQI4039

(Eff ånga e ÖH)

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S S SN NN

N= nozzle cleaningS= sintering

© Vattenfall AB 16

Main bed bottom problems 2007-08

Primary reasons for unavailability:• (Partial) defluidisation of bed (3 stops)• Pluggning of nozzles (3 stops)

Other problems/malfunctions:• Bed sand drained only from 25% of the bottom ash chutes • Extensive wear and high temperature in bottom ash chain conveyor

© Vattenfall AB 17

Status March 2008

• Bed bottom not yet taken over by Vattenfall.• Development and adjustments still made by the supplier.• Neither test run period nor performance test has been

possible to initiate.• The boiler availability still lower than expected (~92%)• Capacity still limited to 80 MWth

© Vattenfall AB 18

Modifications summer 2008

• New bottom ash hopper design installed in all 8 hoppers• All nozzles replaced by new design with 9 mm holes• All furnaces walls replaced (due to corrosion)• Two water washing robots installed in furnace

© Vattenfall AB 19

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09-01-08 00:00:00 10-21-08 00:00:00 12-10-08 00:00:00 01-29-09 00:00:00 03-20-09 00:00:00 05-09-09 00:00:00 06-28-09 00:00:00

BFB steam production Sept 08 – June 09Planned shut-down Bed sintering

© Vattenfall AB 20

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BFB operation 2008-09 – nozzle pressure drop

Nozzle cleaning

© Vattenfall AB 21

Inspection at summer overhaul 2009About 2x2 m totally plugged area outside all fuel feeding chutes

© Vattenfall AB 22

Inspection at summer overhaul 2009About 2x2 m totally plugged area outside all fuel feeding chutesEdge of plugged area – nozzles outlet still above layer

© Vattenfall AB 23

Inspection at summer overhaulAbout 2x2 m totally plugged area outside all fuel feeding chutesEdge of plugged area – nozzles outlet still above layerPartially plugged nozzle holes

© Vattenfall AB 24

Summary operation season 2008-09

• Modifications performed summer 2008 made significant improvements to the bed bottom operation.

• Only one unscheduled shut-down (16-20 Jan).• Two nozzle cleanings needed. • Nozzle pressure drop increase ~ 1 kPa/month (compare to ~6

kPa/month 2007-08)• Performance tests and test run approved, delivery taken over by

Vattenfall.• Operation at 90 MWth proven possible.• Washing robots in furnace important additional measure.• Corrosion on furnace walls worse than expected, next

challenge..

© Vattenfall AB

Thank you!