Biomass Combustion With State Of The Art Bubbling Bed Steam Generators€¦ · · 2009-08-181999-12-15 · Biomass Combustion With State Of The Art Bubbling Bed Steam Generators

Power-Gen Europe 2003

Biomass Combustion

With State Of The Art Bubbling Bed

Steam Generators

Ingo Tschanun

Martin Mineur

AUSTRIAN ENERGY & ENVIRONMENT

VERA - Hamburg

Austria

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1. Preamble

Austrian Energy & Environment AG (AE&E) is Austria’s largest systems supplier for thermal

energy production and environmental engineering. AE&E is the concentrate of 150 years in

successful tradition of the two predecessor companies Simmering-Graz-Pauker and Waagner-

Biro. The ATB Beteiligungs GmbH Wien, a holding company of private entrepreneurs, owns

the company.

The Business Unit Biomass, located at Vienna, is the centre of competence for future-oriented

green power solutions in the field of the thermal utilization of renewable fuels by means of

biomass-fired power stations, and has been able to assure a technological top position.

The company was and is a worldwide supplier of fluidised bed technology. The reference list

comprises plants with steam generating capacities from 9 t/h to 290 t/h and a fuel range from

coal, biomass, sludges, RDF to various industrial wastes.

Biomass fuel exists in various forms, traditionally as wood, bark, harvesting residues and

organic waste resulting from agricultural industry. In the new type of biomass the carbon

content for incineration is contained in the so-called “renewable energy sources” – residual

material and residues like industrial waste, tailings, sewage sludge and RDF.

Our main combustion technology for these biomass fuels is the bubbling fluidised bed

combustion named “EcoFluid” with our special design features.

We would like to present some examples of biomass-fired plants with different fuels and

plants under different stages of construction or operation. This will comprise of operating

results, experience made during initial operation, and plants under construction as well as in

start up condition and a preview of market development.

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2. VERA – Plant in Hamburg / Germany

In April 1994, the city of Hamburg awarded the consortium of German Babcock,

Steinmueller and Austrian Energy with the contract for the installation of combustion plant

for sewage sludge in the area of the wastewater treatment plant Koelbrandhoeft. As a partner

in this consortium, AE&E supplied the three steam generators with the integrated bubbling

bed combustion as well as the accessory systems.

The steam generated in the fluidised bed plants is utilised together with the steam from a gas

turbine heat recovery boiler in a steam turbine for the production of electric power. The gas

turbine operates with digester gas from the wastewater treatment plant.

The sludge from the wastewater treatment plant is mechanically dewatered and dried in a

steam drying plant to a content of app. 42% dry matter.

The combustion and flue gas cleaning plant is built in three parallel lines, where one of the

three is in stand by.

The overall concept of the plant is disposal of the sludge, generating of electric power and

steam supply for the sludge drying plant with high availability. Please contact the official

website www.verahamburg.de for more detailed information about the overall plant concept.

The contract date for AE&E was in May 1995 and the provisional acceptance certificate was

signed in December 1997. Final acceptance date was the 15th December 1999.

Basis for the Design of the Fluidised Bed Combustion at VERA

As the sewage sludge has a low heating value and AE&E has gained very positive operation

experience with plants firing paper sludge, also bubbling fluidised bed combustion was

chosen. The thermal combustion capacity of the three lines is 8,2 MW each burning a mixture

of the following fuels:

Fuel NCV [MJ/kg] Dry Matter [%] Sewage sludge 3,2 – 5,3 39 – 46 Screenings 4,8 26 Used Sorbalit from the flue gas cleaning 14,6 98 Sewage gas (start up & support fuel) 23,0 -- Diesel oil (Spare fuel for sewage gas) 42 --

The plant is approved according to the 17th BImSchV, a very strong German decree for waste

combustion, which sets emission limits as well as operating conditions. The most important

operation conditions that are required are 6% minimum oxygen content in the dry flue gas and

2 seconds residence time above 850°C for the flue gas in the post combustion chamber.

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The air distributor in open design of AE&E enables the drain of bed material with impurities

over the whole bed cross-section during operation.

To keep the bed- and post-combustion chamber temperature with these low heating values in

the required range for the operation conditions, a marked staging of the combustion air is

foreseen. This air staging enables the control of the heat release in a distinct area and sets the

dimensions of the bed and the post combustion chamber.

The customer tightened up the already strong emission limits of the 17th BImSchV decree.

For example, the reference O2-content for the emission limits in the flue gas was lowered

from 11% to 6%. The residence time at 850°C was increased from two to three seconds.

The emission values for CO, NO2 and organic matter have to be obtained with the fluidised

bed combustion without secondary measures.

Plant description

The design figures of the steam generator are listed in the table below:

Live Steam Flow 8,6 t/h

Live Steam Pressure 40 bar

Live Steam Temperature 400°C

Boiler Efficiency (average operation value) 87%

The steam generator is a bottom supported 4-pass type with natural circulation, where three

passes are integrated in the evaporator waterwalls. The fluidised bed is situated in the lower

part of the boiler. Due to erosion protection and thermal reasons, the waterwalls in the

fluidised bed and post-combustion chamber are covered with refractory material. The primary

air enters the bed via the open type air distributor and bubble caps.

The temperature of the fluidised bed is controlled in the range between 750°C and 800°C.

This temperature can be supported with the hot gas generator when the heating value is very

low.

The secondary air is distributed over the cross-section of the post-combustion chamber inlet.

This results in a staged combustion and a temperature increase to 870°C up to 950°C at the

maximum. This temperature can be limited with the installed flue gas recirculation. In the

opposite case, the freeboard burner ensures the minimum temperature of 850°C.

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The third pass contains two superheaters and one evaporator bundle. To avoid high

temperature corrosion, the final superheater is arranged in parallel flow. The fourth pass, built

as carbon steel casing, contains the flue gas air heater and the economizer, which cools the

flue gases down to 180°C.

As the flue gas contains acid gases, the feedwater is preheated to 130°C in a heat exchanger in

the steam drum.

VERA Plant Hamburg

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Solid Fuel System

Belt conveyors transport the dried sewage sludge to three big day silos in the boiler house.

The shredded screenings are added to this belt conveyor. Push rods discharge the sludge from

the silos into small metering bins. Speed controlled double screws carry out the metering of

the fuel mixture. A screw conveys the fuel to the spreader, which distributes the sludge into

the fluidised bed. The contaminated sorbalit is added to this screw.

Combustion Air System and Burners

Effluent air from the sludge drying is mixed to the combustion air in front of the FD fan.

Downstream of the steam air preheater the air for the start up and freeboard burners branches

off. Before the air is divided into primary and secondary air, the tubular air heater increases

the air temperature to 320°C to 360°C. The primary air passes the hot gas generator and enters

the air distributor via an air plenum. The secondary air nozzles are situated in the boiler

sidewalls at the elevation of the spreader.

Start up of the fluidised bed boiler is carried out with a hot gas generator, heating the bed

material to the ignition temperature of the sludge via the primary air system. In addition, the

freeboard burners support the heating up of the boiler. The burners are designed for sewage

gas and diesel oil as back-up fuel.

Bed Material and Ash Handling

The bed material together with the impurities is drained as required from the furnace hopper

with water-cooled screws. The coarse parts are separated in a drum screen; the fine material is

conveyed either to the bed-material silo or to the ash silo.

The ash from the boiler passes is collected with water-cooled screws with drum-screens.

These screens separate the steel balls from the shot cleaning of the heating surfaces. The fly

ash is conveyed to the ash silo.

Denoxing of the Flue Gases

To keep the NOx Emissions below the limit, a selective non-catalytic reduction system

(SNCR) was installed. Urea can be injected into the post-combustion chamber at a suitable

place. Due to the optimised combustion process, the operation of this system could be

avoided.

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Flue Gas Cleaning

L&C Steinmueller GmbH supplied the flue gas cleaning plant. An electrostatic precipitator

removes the dust from the flue gas leaving the boiler. Then the flue gases pass through a 2-

stage wet scrubber. Sorbalit is injected into the flue gas after re-heating to adsorb dioxins,

furans and mercury. A baghouse filter collects this sorbalit. The sorbalit is circulating, new

material is added and a part is continuously drained and burned.

Commissioning and Initial Operation

The design of the fluidised bed combustion was confirmed during start up and the following

commercial operation by the achieved operation data. Most of the emission values are far

below the guaranteed limits.

The limit for self-sustaining combustion could also be lowered to 3,0 MJ/kg, what is

remarkable lower then the contractual guarantee.

A test operation with lowered O2–content in the flue gas showed that the low emission levels

could also be kept. Based on the good results the authorities approved an exception from the

decree for this plant and gave the permit to operate at >4% O2–content instead of >6% in dry

flue gas. This results in a higher efficiency of the steam generator. Also for the combustion

chamber temperature of 850°C VERA could get an exception to operate down to 810°C, what

increases the operation range and reduces the energy demand for support firing.

During the commercial operation of the last years, the owner of the plant carried out several

improvements, especially by optimising the operation conditions and parameters.

Operating Results of the VERA – Plant from the Years 1998 to 2002:

The following charts show the trend of the operation results from the year 1998 to 2002.

The first three diagrams show the development of the fuel input. The amount of sludge was

increasing because the wastewater treatment plant accepted additional foreign sludge and

residues.

The portion of screenings decreased because of optimising the dewatering equipment.

The volume of digester gas increased due to the additional organic residues in the wastewater

treatment plant, improved digesting process and a raised takeover capacity of the VERA

plant.

.

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0

20.000

40.000

60.000

80.000

100.000

120.000

98 99 00 01 02

Slud

ge-Q

uant

ity [t

]

0

1.000

2.000

3.000

4.000

5.000

6.000

7.000

98 99 00 01 02

Scre

enin

gs [t

]

The delivered electric power increased according to the chart below because of the raised

amount of sludge and gas. An additional reason is the increase of plant efficiency caused by

other improvements like the lowered oxygen content in the fluidised bed combustion.

0

5

10

15

20

25

30

35

98 99 00 01 02

Dig

este

r Gas

[Mio

m³]

0

10.000

20.000

30.000

40.000

50.000

60.000

98 99 00 01 02

Del

iver

ed e

lect

r. Po

wer

[MW

h]

The consumption of utilities for the operation of the fluidised bed could also be lowered in

this operating period.

In a test program the temperature profile in the furnace, that is bed area, freeboard and post

combustion chamber was varied and the NOx emissions were tracked to find the optimal

conditions regarding NOx formation.

These test showed as a result, that temperatures around 900°C in the freeboard and post

combustion chamber in a combination with bed temperatures lower than 800°C showed the

best result in relation to the NOx emissions. These temperatures together with the lowered

excess air (5,5% Oxygen in dry flue gas) leads to average NOx emission values of 30 to

40 mg/sm3. It has to be pointed out, that these results were achieved without employing the

SNCR system.

The flow of the flue gas recirculation takes control of the temperatures above the bed.

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As there is no flue gas recirculation into the fluidising air installed, the control of the bed

temperatures is more complicated. The solution is a combination of a minimum fluidising

airflow, variation of the heating value of the sludge (possible in this special case) and a water

injection into the bed that serves as a temperature limiter.

These measures resulted in a remarkable cutback in the consumption of denoxing agent as

shown in the chart below. Today the SNCR is only in operation during a failure of other

components like e.g. the FGR – fan.

0

200

400

600

800

1000

1200

98 99 00 01 02

Sand

[t]

0

10000

20000

30000

40000

50000

60000

70000

80000

90000

98 99 00 01 02

DEN

OX

Age

nt [

l]

Another result of these improvements is that the make up sand consumption is minimised to

refills after shut downs for revision. At higher temperatures around 900°C the bed material

and the ash tend to build up agglomerations. These agglomerations in a size range up to a fist

had to be drained with the bed material and were separated in a drum screen from the fine bed

material. This leads to a loss of bed material that has to be replaced with make up sand.

The improved bed temperature control avoids this effect. At present, the bed drain is only in

service if the bed pressure increases due to the sand contained in the sludge.

0

2.000

4.000

6.000

8.000

10.000

12.000

14.000

16.000

18.000

20.000

98 99 00 01 02

Ash

Qua

ntity

[t]

9/20


The avoidance of the adding of make up sand has two positive impacts to the operating cost

of the plant. One is the direct costs for the sand supply and the other one is the reduction of

ash disposal costs for the drained bed material.

The successful combination of a well-designed plant and a highly dedicated operator showed

these remarkable results that will be ended with a chart showing the favourable trend of the

emissions of the plant.

NOxDust

Sum CSO2

CO

Average 2002Average 2001


Average 1998Operation Licence

17. BImSchV

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

HgHCl

HFPCDD/PCDF Cd,TI

Sb..Sn



Average 1998Operation Licence

17. BImSchV

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

VERA Emissions, continuously and discontinuously measured, yearly average

10/20


3. Westfield Plant in FIFE/Scotland

The Westfield plant is an excellent example for the thermal utilization of the new kind of

biomass. The plant is designed to burn poultry litter coming from the chicken farms in the

surrounding area. This fuel is a mixture of chicken excrements with sawdust, fine wood

wastes and sometimes straw.

The plant was realized for EPR-SCOTLAND. Abengoa SA of Seville/Spain acted as general

contractor and AE&E as a subcontractor.

In summer 1998 Austrian Energy was awarded with the contract for the fluidised bed boiler

including related fuel supply, combustion air with start up burners and flue gas cleaning.

The condensing turbine and the generator with a capacity of 11,8 MW was also awarded to

Austrian Energy.

The plant is feeding the generated electric power into the utility grid and EPR is paid a green

price according to the SRO regulations in Scotland.

Basis for the Design of the fluidised bed combustion

Considering the fuel properties and the range of the heating values, the decision was made to

use an EcoFluid bubbling bed with substoichiometric combustion in the bed and a staged air

supply for the post combustion chamber. This staged air supply with bed temperature control

was developed by Austrian Energy to fire a wider range of heating values with this system.

Maximum fuel heat rate 40,5 MW Lower heating Value 7,5 ÷ 13,6 MJ/kg Moisture 20 ÷ 45 % (w) Ash content 11 - 17 % (dry matter) Fuel flow 10,7 - 18,1 t/h Control range 70 ÷ 100 %

The plant is approved according to the SEPA (Scottish Environmental Protection Agency), a

special regulation in Scotland, which sets emission limits for renewable fuels.

The emissions relate to 11 % O2 content in dry flue gas and are half hour mean values.

Pollutants according regulations Emission limit

Carbon monoxide CO 200 mg/m3n

Sulphur dioxide SO2 300 mg/m3n

Nitrogen oxides NOx as NO2 300 mg/m3n

Unburned organic carbon Corg 20 mg/m3n

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Dust 25 mg/m3n

Hydro chloride HCl 150 mg/m3n

Dioxins and Furans PCDD/F 0,5 ng/m3n

Unburned matter in bed ash < 5 % (w)

Unburned matter in fly ash < 5 % (w)

The emission values for CO, NO2, SO2, unburned and organic matter have to be obtained

with the fluidised bed combustion.

Plant description





Boiler Efficiency (actual average operation value) 89,5%

The steam generator is a bottom supported 4-pass type with natural circulation, where three

passes are integrated in the evaporator waterwalls. The bubbling fluidised bed and the post-

combustion chamber are the first pass. The waterwalls in the fluidised bed and a part of the

post-combustion chamber are covered with refractory material due to erosion protection and

thermal reasons. The second pass is a radiation chamber to cool down the flue gas before

entering the convection surfaces. The third pass contains the superheater bundles.

The fourth pass, built as carbon steel casing, contains the economizer, which cools the flue

gases down to 160°C.

The process characteristics of the EcoFluid bubbling bed are a substoichiometric air supply

through the air distributor to control the bed temperature. A proper designed secondary air

system feeds the balance of the required combustion air above the fluidised bed and results in

a good burnout in the post-combustion chamber. In addition, a flue-gas recirculation system

mixes flue-gas into the post combustion chamber as well as into the primary air. This enables

very good temperature control in the furnace according to legal and process requirements and

leads to lowest emissions.

12/20


The requirements regarding the combustion, at the minimum 850°C for two seconds and a

minimum O2 content of 6% (vol) in the dry flue gas, as well as the ash properties regarding

agglomeration tendencies require these good temperature control possibilities.

The secondary air, which is the bigger part of the combustion air, is taken from the fuel

storage house. This avoids smell harassment in the surrounding area and the contaminated air

is disposed according to the regulations.

Together with the fuel, incombustible parts like stones, glass and metals come as tramp

material to the fluidised bed, where they collect and hinder the fluidization. To prevent this,

an open type air distributor in AE&E – design is built in and the bed material is consciously

drained and cleaned.

Start-up of the plant is carried out with two burners firing fuel oil No.2. They are not used

above minimum load of the boiler.

Westfield Plant FIFE Scotland

13/20


Solid Fuel System

The fuel is collected from several chicken farms and therefore the composition can vary

depending on the feeding of the chicken and the binding material for the excrements.

Trucks dump the litter into a pit, from where a pocket crane takes it out and transports it into

the big storage pit. The pocket crane mixes and feeds the fuel to two bunkers in the storage

building. From these bunkers two trough chain conveyors elevate the fuel up into the day silos

in the boiler house. The day silo is unloaded into the metering screws by two push rod

systems. Each screw supplies one feeding point in the boiler sidewalls. Two air supplied

feeding chutes distribute the poultry litter across the fluidised bed.

Flue Gas Cleaning

A bag filter removes the fly ash from the flue gas. A hydrated limestone injection into the flue

gas in front of the bag filter reduces the SO2 and HCl emissions.

As an additional benefit, the owner of the plant has the target to sell the fly ash with its high

content of potassium and phosphor as a fertilizer. For this reason, "impurities" like sand and

Ca(OH)2 from the flue gas cleaning have to be minimized.

Commissioning and Initial Operation

The hot commissioning started in March 2000 and the plant was handed over to the client

after successful trial run in October 2000.

Some problems occurred with the conveying equipment for the fuel. Due to the fuel

properties, the friction forces of pressed litter were very high and required higher driving

forces.

Some serious problems were arising out of the ash properties. During the design, the expected

fouling tendencies of the ash were already considered. However, during continuous operation

fouling of heating surfaces turned out to be worse than expected.

Some agglomerations appeared in and above the fluidised bed region. The solution for this

problem was lowering the bed operation temperature to minimise the sintering.

The fouling in the furnace and radiation pass was higher than calculated. This caused higher

temperatures at the inlet of the convection surfaces and fouling there.

The initially installed soot blowers were not sufficient to clean the tube bundles. Therefore,

soot blowers with stronger cleaning power were installed. In the post combustion chamber

and the radiation pass wall soot blowers were refitted.

14/20


An unexpected fouling of the economizer heating surfaces in low temperature regions

occurred and resulted in an unacceptable increase of the flue gas exit temperature.

A layer of phosphorpentoxide and calciumoxide caused the fouling. It appeared as a strongly

insulating and sticky layer of very fine powder that was very resistant to the soot blowing.

The solution was also increasing of the power of the soot blowers in the Economizer.

After these improvements and some optimisation in the operating conditions of the

combustion, the plant is now in successful commercial operation.

In addition, the achieved ash quality is sufficient for use as a fertilizer and gives additional

profit to the owner.

A clear evidence of the successful handling of this difficult fuel in the Westfield plant can be

seen in the fact that the same client has chosen AE&E for a follow up contract for a chicken

litter fired power plant in the Netherlands in a consortium with Siemens. This plant will burn

chicken litter with a lower heating value of 6 to 10 MJ/kg. Feathers and meat meal are

optional fuels for mixing.

The generating capacity of the boiler will be 130 t/h with 66 barg and 478°C. The Plant will

deliver 31, 5 MW of green electric power to the grid.

The project will start after reaching the purchase agreement for the electric power and the

financial closing.

4. Langerbrugge Plant for Stora Enso in Belgium

The Langerbrugge EcoFluid boiler plant is an example for the consistent development of the

AE&E bubbling fluidised bed boilers for the Pulp & Paper industry.

In November 2001, Austrian Energy was awarded with the contract for the fluidised bed

boiler including related equipment. The plant is located in the paper mill of Stora Enso in

Langerbrugge near Gent.

The plant will burn a mixture of deinking sludge, effluent sludge and fines without rejects of

the deinking plant for a new paper machine as the guarantee fuel. Wood waste can serve as

additional fuel.

The generated steam will be utilised in a backpressure turbine for generating electric power

and as low-pressure steam supply for the paper mill.

15/20



As the sludge has a minimum lower heating value of 2,9 MJ/kg, support firing of natural gas

will be necessary with these conditions of the solid fuel. Depending on the required steam

flow, the heating value of the mixture can go up to 8,1 MJ/kg. Considering this range of the

heating value, the EcoFluid bubbling bed is designed for traditional and substoichiometric

combustion in the bed and a staged air supply for the freeboard and post combustion chamber.

The flue gas recirculation system is equipped with a low and high-pressure fan to supply flue

gas into the freeboard and post combustion chamber as well as into the bed. Natural gas will

serve for start up and support fuel at low heating values of the solid fuel.

Maximum fuel heat rate 56,0 MW Lower heating Value of fuel mix (sludge, waste and gas) 3,6 ÷ 8,1 MJ/kg Moisture of the sludges 38 – 50 % Ash content 50 – 62 % (in dry matter)Fuel flow (sludge) 18,0 - 40,0 t/h Control range 55 ÷ 100 %

A flue gas air heater for the primary air is installed to minimise the support firing at the very

low heating values. In addition, a natural gas fired hot gas generator is installed to support the

bed temperature if required.

Plant description





Boiler Efficiency (average operation value) 87,5%

The steam generator is of the standard EcoFluid design. The final superheater has due to the

high live steam temperature a protection against chlorine corrosion. This protection is a thin

layer of refractory on the five platen - type superheaters in the radiation pass. This protection

is a standard design in municipal waste burning boilers.

16/20


Langerbrugge EcoFluid Boiler

The plant is in final erection status and commissioning will take place in April and May 2003.

17/20


5. Niklasdorf Plant in Austria

The plant is located in the Mur valley in Styria close to a paper mill. It is built and operated

by ENAGES, a special purpose company mainly owned by the styrian utility ESTAG.

The focus for the design of the entire waste to energy plant is the continuous thermal

treatment of residues with varying calorific values with a minimised impact to the

environment.

It is a part of the styrian waste concept and burns fractions from waste treatment plants.

The general contractor for the plant is SIEMENS AG AUSTRIA. AE&E supplies the fuel

handling and preparation, the fluidised bed boiler with associated equipment and the flue gas

cleaning. The power plant will replace the existing gas fired boiler of the paper mill and will

help to substitute fossil fuels for heat and power production.

Due to the fuel mix, the steam parameters are the traditional values for waste burning plants.

Even though all preventive measures for high availability have been taken, the risk of heat

surface fouling in a plant with this fuel mix is evident. The extremely high availability

required for the steam supply of the paper mill caused the installation of a 100% fluidised bed

boiler and three 50% gas fired steam blocks for stand by.

The plant is designed to burn a mixture of residues from waste paper treatment, waste woods

from construction and demolition, packaging materials, anaerobe stabilised sludge and light

fraction from municipal waste and various industrial wastes.

The generated steam will be utilised in an extraction/condensation turbine for generating

electric power and low-pressure steam for a nearby paper mill.


Considering the wide variety of fuels and the range of the heating values, the EcoFluid

bubbling bed is designed for substoichiometric combustion in the bed and a flue gas

recirculation into the bed and into freeboard. In addition, there is a flue gas recirculation into

the second pass to keep superheating temperatures in part load.

Maximum fuel heat rate 40,0 MW Lower heating Value 8,0 ÷ 18,0 MJ/kg Moisture 10 ÷ 40 % (w) Ash content 10 - 35 % (w) Fuel flow 8,0 - 16,0 t/h Control range 60 ÷ 100 % Bed temperature 750 ÷ 850 °C Freeboard temperature 850 ÷ 950 °C

18/20


The emission limits affected by the fluidised bed combustion relate to 11 % O2 content in dry

flue gas and are half hour mean values.

Pollutants according regulations Emission limit

Carbon monoxide CO 50 mg/m3n

Unburned organic carbon Corg 8 mg/m3n

The flue gas cleaning plant has to fulfil very strong emission limits. Therefore, it consists of a

bag filter with hydrated lime and activated carbon injection, 2- stage wet scrubber and a SCR

and is in the scope of AE&E too.

Plant description


Live Steam Flow operation 25 – 51,7 t/h

Live Steam Pressure 43 barg


The steam generator has some special design features. It is a bottom supported 5-pass type

with natural circulation. The evaporator waterwalls contain three passes. The fluidised bed is

in the first pass. The second pass is a radiation chamber to cool down the flue gases before

entering the convection surfaces. At the entrance of the third pass, an evaporator bank serves

as a cooling trap in front of the superheaters. The last superheater in the third pass can be

bypassed on the steam side to keep the required temperatures in the cyclone that is situated

between the third and fourth pass. The cyclone separates fly ash at high temperature to reduce

reformation of dioxins and the portion of contaminated ash.

The fourth and fifth passes are built as carbon steel casing. The fourth pass contains two

superheaters and two economiser bundles. The fifth pass contains three economiser bundles,

which cool the flue gases down to 170°C.

As the fuel preparation and supply is essential for a plant firing this kind of fuel mix, much

attention is given to the design of this part of the plant.

Trucks will dump the already processed fuel into a bunker and a grapple crane will bring it to

a vibrating screen and a shredder. As the fuel preparation and the mixing are essential for

good combustion conditions, the storage bunker is sized for 4 days full load capacity. Another

grapple crane will mix the fuel and supplies it to the metering system for the combustion.

19/20


EcoFluid boiler Niklasdorf Austria

The plant is under construction and commissioning will take place in autumn of 2003.

6. Standard Biomass Power Plant for 20 MW

Based on the EEG decree in Germany AE&E designed a standardised biomass power plant

with the EcoFluid bubbling bed as combustion process. It comprises a turnkey plant for a

generating capacity of 20 MW electric Power. The plant consists mainly of the fuel handling,

EcoFluid boiler, Turbine, air condenser and the required electric equipment. The flue gas

cleaning is carried out in a conventional dry cleaning or with the TURBOSORP process

developed by AE&E. The choice depends on the wood used as fuel. The basic concept is for

already chipped wood. Several Projects in Germany are under negotiation.

7. Market Development

The business unit Biomass concentrates on the projects arising of the EU directives

2000/76/EC Incineration of waste and 2001/77/EC on the promotion of electricity produced

from renewable energy sources in the internal electricity market. These directives result in

various national guidelines creating a market for biomass and waste burning power plants.

With the EcoFluid combustion system, AE&E is well prepared to fulfil the requirements for

these plants in the EC an the candidate countries

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Documents

Biomass Combustion With State Of The Art Bubbling Bed Steam Generators€¦ · · 2009-08-181999-12-15 · Biomass Combustion With State Of The Art Bubbling Bed Steam Generators