who are we? - heat management · • abs formation in aph on coal fired boilers with scr ... hot...

Who are we?

Andreas Aspell

Among the oldest

Service Engieer

and sales

Klas Lindahl

Among the youngest

Experienced Sales Manager

• Fuels

• Type of boilers - Technologies. Pros/cons

• Typical problems

• Our solutions

• Support material

• Case results

• ABS Formation in APH on Coal fired boilers with SCR

Power boilers – Biomass and coal

Available fuel sets the conditions when deciding boiler type.

E.g. fast growing biomass (crops, straw, eucalyptus etc.) has

high alkali content → difficult application

Available Fuels

Fuel consideration

Co

st o

f fu

el [

$/M

Wh]

Difficulty

Fossil fuels

• Coal Forest fuels

• Wood chips

• Pellets

• Fiber sludge

• Residue Other forest fuel

• Eucalyptus

• Fast growingAgriculture fuels

• Straw

• Sunflower seeds

• Etc.

Biomass boilers

sweetspot

Waste

• Alkali content (fouls high temp areas)

– Sodium sinters in furnace

– Potassium fouls back pass

• Chlorine content

– In combination with alkali, it hardens and causes corrosion

• Moist content

These parameters in large sets the conditions for the choice of

the boiler.

Key challenges biomass

Coal

Anthracite: The highest rank of coal. It is a hard, brittle, and black lustrous

coal, often referred to as hard coal, containing a high percentage

of fixed carbon and a low percentage of volatile matter.

Bituminous: Bituminous coal is a middle rank coal between subbituminous

and anthracite. Bituminous usually has a high heating (Btu) value

and is the most common type of coal used in electricity

generation in the United States. Bituminous coal appears shiny

and smooth when you first see it, but look closer and you may

see it has layers.

Subbituminous: Subbituminous coal is black in color and dull (not shiny), and has

a higher heating value than lignite.

Lignite: Lignite coal, aka brown coal, is the lowest grade coal with the

least concentration of carbon.

Future for Biomass? Who knows!

• Everyone wants to use it

– Bio-oil

• Bioplastic

• High grade fuel

– P&P

• Paper, carboard

• Textile

• Tall oil

• Fuels



• Our solutions


• Case results


Power boilers

• Fluidized

– Bubbling

– Circulating

• Grate

– Vibrating

– Moving grate

Boiler typs

• Bubbling Fluidized Bed– Fluidizing velocity 1,2 m/s

• Pros:

– Low OPEX

– Lower combustion temp

• Cons:

– Units < 100 MW

– Higher CAPEX

• Circulating Fluidized Bed– Fluidizing velocity 4,5 – 6,5 m/s

• Pros:

– Low OPEX

– Allows for larger boiler

• Cons:

– Higher CAPEX

Fluidized

Fresh fuel and combustible matter <3 % by weight of the

hot solids in the bed.

• Primary air fluidizes

• Combustion temp, below forming of NOx.

BFB

Furnace

SH

EKO/APH/SCR

ESP/gas cleaning

CFB

Furnace

Super heater

ECO

APH

SCR area

Cyclone

• Some has SCR

• Most has NSCR

• Often finned tube ECO → good for infra

• Tube Air Pre Heaters, sometimes rotary on larger boilers.

Typical designs features

• Fuel is combusted while traveling down the grate

– Units < 100 MW

• Pros:

– Favourable in handling different types of fuel

– Low CAPEX

• Cons:

– Moving parts → high OPEX

– Requires large space

– Worse emissions compared to fluidized

– Uneven combustion → more unburned fuel

Grate

Grate

Fuel feed

Grate

SHEmpty passECO/SCR/APH

ESP/gas cleaning

• Heat Managements solutions can be applicable for all

types.

Infra normally only below 450-550°C. For easy fuels, such

as peat and coal, infra have effect in SH.

• More difficult fuels → more steam soot blowing → HISS

is favourable

Heat Management solutions


• Available fuels


• Our solutions


• Case results


Power boilers

• Fluidized beds:

– Hard to burn high alkali fuels due to bed sintering

• Grate (mostly biomass):

– High furnace temp makes control of NOx and SOx emissions

difficult → additional emission control systems needed

Typical problems

Common for both types

• High temp fouling in:

– Furnace walls,

– Super heater → HISS

• Lower temp fouling:

– Economizer → HISS/infra

– Air pre heater → HISS/infra

– Rotary APH → infra

– SCR → infra

Fouling


• Available fuels


• Our solutions


• Case results


Our solutions

Infrasound cleaning

Economizers

SCR (catalyst)

Air pre-heaters

ESP (electrofilter)

Ducts

~550 °C > T > 140 ° C

100 systems on

power plants

&

300 systems on

vessels (cruise

and cargo)

~900 °C > T > 140 ° C

SH

HISS INFRA

Possibility’s:

– Burning cheaper fuels → more fouling → need for best cleaning

– Increase availability, prolong time between revision

– Increase thermal efficiency, lower d-Temp increases steam quality

– Avoid negative effects from steam soot blowing

• Erosion

• Corrosion

• Reduced load

– Better control of steam soot blowing

• Maintenance

• Ensure function

• Early warnings

• A way to identify needs and savings

– Low risk investment

– High accuracy

Can tell things about the customer process that they aren’t aware of,

such as:

- Malfunctioning soot blowers,

- Unnecessary long sequences

Pre-studys


• Available fuels


• Our solutions


• Case results


Power boilers

• Questionnaire

• Reference list

• Case studies

• White papers

• Presentation

Support material

• Nice to know:

– Boiler make, year, soot blower make

• Need to know:

– Size & production (electricity, heat, process steam, hours annually)

– Type (CFB, BFB, grate etc)

– Boiler design and layout (ECO, SCR, RAPH)

• Temperature in different areas

– Fuel

– Current soot cleaning and how its used

• No of soot blower, operation, consumption, steam data

– Effects from fouling

• All can be found on our website

Questionnaire


• Available fuels


• Our solutions


• Case results


Power boilers

Finland CFB 50MWth

Fuel: Peat 70%, wood chips 30%

Boiler make: Foster Wheeler

Infrasound cleaner: APX7000 commissioning 2013

Cleaning area: SH, ECO and APH

Before: Steam soot blowing once a day. The customer needed

to replace/major repair the soot blower so they were looking

for other solution and a general cleaner boiler.

Result:

• Eliminated need for steam soot blowing in ECO & APH

• Reduced need in SH. Now operated once a week.

• Stable flue gas temperature.

• Increased efficiency of 5% → lower fuel cost.

Vattenfall Idebäcksverket

Boiler type: 97 MWth BFB

Steam: 540 oC, 140 bar

Infrasound cleaner: 2 x APX7000

Cleaning area: Vertical upstream fine tube ECO, APH

Fuel design: Wood chips, peat and coal

Fuel today: >90% waste wood, <10 % wood chips

Performance:

• Steam soot blowing eliminated in ECO and APH.

Previously used 3 times/day

• The differential pressure is now on a lower level

than with steam soot blowing operating 3

times/day.

Tiefstack, SCR catalyst

Situation prior installation

- The catalyst had to be manually cleaned every 3 months, due to increased differential pressure over

the catalyst layers

- Boiler load had to be decreased to not overload the flue gas fan

- Each time the boiler was stopped, 5 days went into cleaning over 800 000 orifices in the catalyst

Infra sound cleaner: 2 x AP2000

Cleaning area: SCR – Catalyst

Fuel: Ruhr and Colombian coal

Result

• The catalyst layers are kept clean the entire season, no need for manual cleaning.

• Differential pressure is kept on a low and stable level

• Since the catalyst was so much cleaner, 25 % of the catalyst could be removed without affecting

the emission levels, reducing the stress on the flue gas fan

German references


• Available fuels


• Our solutions


• Case results


Power boilers

Background RAPH

• Between 5% to 10% of the boilers efficiency

• Critical for reducing fuel cost

• 3 major challenges

– Corrosion

– Plugging

– Leakage

Before installation of SCR

• Sulfur in coal burns and generates SO2 (sulfur dioxide)

• Some SO2 converts to SO3 (sulfur trioxide)

• SO3 (together with flue gas moisture forms sulfuric acid

vapor)

• Sulfuric acid vapor has a dew point between 140 C to 160 C

(higher SO3 (level = higher dew point))

• Sulfuric acid vapor creates corrosion in the cold end layer

• Together with fly ashes it creates plugging in cold end layer

• Plugging could be resolved by soot blowing and water wash

With SCR

• Ammonia is injected to convert Nox to nitrogen and water

• With high efficient SCR, all ammonia used for Nox reduction

• When efficiency of SCR decrease, ammonia slip occurs

• Ammonia slip together with SO3 forms ammonium sulfate

and bisulfate (ABS)

• ABS together with fly ash forms sticky deposits

• ABS sticks on surfaces between 150 C to 230C, in the

intermediate layer, difficult to reach with soot blowing

• Variation in moisture and sulfur in the fuel may increase

plugging

Possible Results

• Corrosion of both cold and intermediate layer

• Plugging in both layer

• Reduced load due to high pressure drop

• Increased air leakage due to dP between hot and cold

sections

• More stops due to maintanence

• Less effiecient RAPH

Cold fact

• Sulfur in fuel is converted to SO2 or SO3 (1-2% to SO3)

• SCR can convert 1-3% more of the SO2 to SO3

• SO3 varies between 10 – 120 ppm

• SO3 varies with type of boiler, sulfur and moisture content of

fuel, temperature and flue gas

• Less efficient SCR will create more ammonium slip

• Load and temperature of SCR is important to prevent

blocking

Potential solutions

• Coating with higher corrosion resistance and ”non-sticky”

surface

• Different configurations of temperature layers

• Improved soot blowers

• Removing ammonia slip before APH

• Spraying alkaline sorbents

• New generation SCR

• De-accelerate formation of ABS by keeping surfaces free from

fly ash with Infrasound

• Use Infrasound to keep SCR high efficient longer

who are we? - heat management · • abs formation in aph on coal fired boilers with scr ... hot...

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