Calciner Technology in AF Firing

8/10/2019 Calciner Technology in AF Firing

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Calciner Technology for improved alternative

fuel firing


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Calciner Presentation Agenda

Comparison of several HeidelbergCement calciners which

are firing high percentage of calciner alternative fuels

Desirable features which maximize the ability of burning

alternative fuels in the calciner

Conclusion


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Comparison of several HeidelbergCement calciners which are

firing high percentage of calciner alternative fuels

Antoing (CLE Onoda type calciner)

Slite (CLE Onoda type calciner)

Brevik (KHD Low Nox calciner)

Important features and principles for enhancing secondary

fuel firing in a calciner

1. Gas retention time

2. Geometry: particle retention time gas mixing

3. Hot core combustion

4. Kiln riser restrictor5. Chlorine bypass system

6. Pressure drop across calciner system


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Geometry of Antoing Calciner (CLE Onoda type)

A

B

C

D

E

F

G

Preheatedmeal

Tertiary air

Tertiary air Tertiary air

Petcoke Waste fuel

Preheated meal

To lowercyclone stage

Kiln gas

MIXINGCHAMBER

SWIRL

CALCINER

LOOPDUCT

Calciner downcomer

Inclined Duct


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Geometry of Slite Calciner (CLE Onoda type)

Tertiaryair

Tertiary

air

Calciner

coal

Shredded

car tyres

Preheated

meal

Bypass

gas

Kiln gas

To lower

cyclone stage

Diaphragm

8

97

11

1

5

6

13

Mixing ChamberInclined Duct


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Samples and measurements Brevik

(KHD Low-NOx calciner)

To lower

cyclone

stage,

string 1

To lowercyclone

stage,

string 2

Preheated

meal,

string 1

Preheated

meal,

string 2

Solid

hazardous

wasteSecondary

coal

Tertiary airKiln

gas

A

F

K

M

8

13

X5

X10

Loop Duct

Inclined Duct

Square Duct to Circular

Transition


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1. Residence time in investigated AS calciners of HeidelbergCement

(note retention times calculated on a common set of data)

The calculated residence times are from the calciner fuel inlet to thelower cyclone stage. Residence times calculated using a common set of data

Avg = 3.6 seconds

Max = 6.4 seconds (Edmonton)

Min = 1.9 seconds (Canakkale)

Union Bridge = 6 seconds @ 5500 MTPDclk and 5 seconds at 6500 MTPDclkPadeswood and Lixhe similar to UB

Plant Calculated gasresidence time

[s]

Antoing 2.9Brevik 3.5

Bykcekmece 3.7

Canakkale 1.9

Edmonton 6.4

Kjoepsvik 3.3

Mason City 3.1Slite 3.7

Tehachapi 4.4

Vac 3.2

This data along with

following table makesclear that retention time

isnt the only pre-

requisite for burning

secondary alternative

fuels


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Calciner Testing Data

Antoing Slite Brevik

Calculated gas retention

time seconds 2,9 3,7 3,5

CO concentration -

bottom cyclone exit ppmv ol 130 700 1000Oxygen concentration -

bottom cyclone exit %v ol 3,8 4,6 3,5

Temperature - bottom

cyclone exit C 964 895 890

Antoing

Bottom CycloneConditions

1100 ppmvol CO

130 ppmvol CO

Calculated gas retention time for bottom

Cyclone is 0,75 seconds assuming that

50% of the cyclone body is active. This means

that the required gas retention time for fuel burnout

is at least 3,7 seconds with good calcinergeometry (as will be discussed in the next

section). It is therefore recommended to have as a

minimum about 3 seconds to top of loop duct, then

deflection chamber, then 1 2 seconds gas

retention time before entering bottom cyclone

Antoing Data


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2. Good calciner geometry: higher particle retention time and gas mixing

To lower

cyclonestage,

string 1

To lower

cyclone

stage,string 2

Preheated

meal,

string 1

Preheated

meal,string 2

Solid

hazardous

wasteSecondary

coal

Tertiary airKiln

gas

A

F

K

M

8

13

X5

X10

Tube type calciner Not a

good design for increasing

particle retention time and gas

mixing

Calciner design which enhances

particle retention time and gasmixing

Turbulant flow increasesmixing which is generated

by the geometric design

and the way the various

flows are introduced intothe calciner. Low

velocities and turbulance

increase particle retention

time

Brevik - When

RDF and SHW

are supplied at >

40% of calcinerfuel, CO in main

stack gases goes

high (> 0,3% CO)

Geometry of the Antoing calciner system is good to promote


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Geometry of the Antoing calciner system is good to promote

gas mixing, turbulance and particle retention time

A

B

C

D

E

F

G

Preheated

mealQuaternary air


Petcoke Waste fuel

Preheated meal


Kiln gas

MIXINGCHAMBER

SWIRL

CALCINER

LOOPDUCT

Calciner downcomer

Inclined Duct


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Interesting to compare geometry and gas velocities

of both Antoing and Slite

Preheatedmeal

Quaternary air


Petcoke Waste fuel

Preheated meal


Kiln gas

MIXING

CHAMBER

SWIRLCALCINER

LOOP

DUCT

Tertiaryair

Quaternaryair

Secondarycoal

Shreddedcar tyres

Preheated

meal

Bypassgas

Kiln gas


Diaphragm

11 m/s

15 m/s

29 m/s

13 m/s

25 m/s

Retention time = 2,9 sec.

Average Velocity = 17 m/sec

12 m/s

25 m/s

14 m/s

12 m/s

Retention time = 3,7 sec.Ave. Velocity = 10 m/sec


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Union Bridge design based on computer modeling and

pilot plant testing

Deflection Chamber

Deflection chamber

Inlet Duct

Deflection Chamber

Outlet Duct

Feed Pipe

Deflection Chamber Model

CO Injection

Manual CO

Measuring Ports

Mixing efficiency, build up and plugging tendencies are

important topics


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3. Hot core - promotes combustion with a flame and reduces

tendency of flameless combustion or delayed combustion


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Both Slite and Antoing are feeding alternative fuels to the hot core in

the combustion hat of the swirl calciner

A

B

C

D

E

F

G

Preheated

mealQuaternary air


Petcoke Waste fuel

Preheated meal

To lower

cyclone stage

Kiln gas

MIXING

CHAMBER

SWIRL

CALCINER

LOOP

DUCT

Tertiary

air

Quaternary

air

Secondary

coal

Shredded

car tyres

Preheated

meal

Bypass

gas

Kiln gas

To lower

cyclone stage

Diaphragm

8

97

11

1

5

6

13

4. Kiln riser restriction - (high riser duct velocity) important to


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4. Kiln riser restriction (high riser duct velocity) important to

assure solid alternative fuels do not fall into the kiln and burn in

the feed bed of the kiln leading to increase in volatile cycles.

Tertiary

air

Quaternary

air

Secondary

coal

Shredded

car tyres

Preheatedmeal

Bypass

gas

Kiln gas

To lower

cyclone stage

Diaphragm

8

97

11

1

5

6

13

28 32 m/sec Good design number

Slite gas velocity is about 40 m/sec, but the pressure drop

is also high. Pressure measured above the restriction is >

15 mbar, during tire firing.


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5. Chlorine bypass system

Alternative fuels are typically high in chlorine.

Animal meal 0,7 1,0 % Cl

Plastics 1,0 % ClRefuse derived fuel 0,5 2,0 % Cl

Resofuel (impregnated saw dust) 0,3 % Cl

Solid hazardous waste 0,5 % Cl

Small chlorine bypass systems significantly increase the

ability of a kiln system to utilize alternative fuels. Slite and

Antoing operating with about 6% kiln bypass.


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6. Calciner system pressure drop

Pressure drop across different calciner systems are in

general in the range of 8 15 mbar (~80 150 mmwg)

verified by a pressure drop across Antoing calciner of

about 11 mbar (110 mmwg).


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Conclusions

CLE-Onoda type SLC-S calciner promotes alternative fuel firing in

the calciner verified by the success these types of calcinershave in the HeidelbergCement group burning hard to burn fuels(solid alternative fuels)

Geometry has an important influence on overall calciner

performance verified by testing done by HTC in 2000.

Antoing geometry is best for particle retention time and mixing,but retention time should be more verified by testing done byHTC in 2000 and internal HTC standards

Calciner with good geometry requires a gas retention time ofabout 5 seconds to assure good burnout of solid alternative fuels Verified by Antoing data and supported by design of new

installations

Gas mixing and particle retention time are important parametersthat we as a group could learn a lot from with regards tooptimizing calciner designs for alternative fuel firing


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Conclusions

The effectiveness of a loop duct creating good mixingbehavior is limited, therefore a mixing chamber (deflection)in top of loop duct is important. Investigations andreporting on UB deflection chamber results will be

important, including build-up tendencies.

A great deal could be learned from computer modeling ofcalciner systems. Purpose of modeling is to thoroughlyinvestigate geometry with the target of finding an optimizedcombination of gas mixing, particle retention time and lowbuild-up tendencies.

Small scale modeling (water bead and acid / alkalimodeling), might in particular be useful to investigateexisting calciner designs/problems. FCT-Combustionsupplies this type of service to the cement industry.


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Documents

Calciner Technology in AF Firing