Investigations on Slags under Gasification Process Conditions

Zentrum für Innovationskompetenz:

Virtual High Temperature Conversion

Investigations on Slags under Gasification

Process Conditions

Daniel Schwitalla, Arne Bronsch, Stefan Guhl

TU Bergakademie Freiberg - Institute of Energy Process Engineering and Chemical

Engineering - 09596 Freiberg - Germany-Tel. +49 3731 394206- Fax +49 3731 394555

Email [email protected] - Web www.iec.tu-freiberg.de

6th International Freiberg Conference, Dresden Radebeul

http://www.iec.tu-freiberg.de/



1. Motivation

2. Relevant Properties for Modeling Slag Behavior

3. Heat Conductivity

4. Viscosity

1. Experimental Setup

2. Calibration and Validation of Measurements

3. Extended Modeling approach

5. Surface Tension

1. Experimental Setup

2. Measurement Evaluation

6. Outlook

2

Outline

TU Bergakademie Freiberg · ZIK VIRTUHCON (Virtual High Temperature Conversion) · Reiche Zeche · Fuchsmühlenweg 9 · 09599 Freiberg

Telefon: 03731 39-2693 · Fax: 03731 39-4555 · Internet: www.virtuhcon.de

Motivation

Virtual High Temperature Conversion - Strategy

3 TU Bergakademie Freiberg · ZIK VIRTUHCON (Virtual High Temperature Conversion) · Reiche Zeche · Fuchsmühlenweg 9 · 09599 Freiberg


Substance

Properties • Experimental

Acquisition

• Database Extraction

• Equilibrium

Calculations

Process Data &

Experimental

Measurement Data

Mathematical Models

Virtualization Process model

Validation

Example Presentation

Subgrid model for slag behaviour at

entrained flow gasifier walls

VTC IPP Group

Properties relevant for modelling slag behavior



Viscosity Surface

Tension

Density Diffusivity Heat

Capacity

Rotational

Viscosimeter

(searle-type)

(Baehr HT-

viscometer)

Sessile Drop

(Fraunhofer

ISC

Tommiplus,

TOM-AC)

Measurement

of Hydrostatic

Pressure

(Fraunhofer

ISC

Tommiplus +

MBP-Module)

Laser Flash

(Department

of Thermal

Engineering –

TU Freiberg)

Differential

Scanning

Calorimetry

(Setaram

MHTC 96)

Rotational

Viscosimeter

(searle-type)

(AntonPaar

MCR 302)

Maximum

Bubble

Pressure

(Fraunhofer

ISC

Tommiplus+

MBP-Module)

Heat Conductivity

Laser Flash + Calorimetry + MBP

5

Determine

Diffusivity

(Laser Flash)

Density

(Lange et al*)

Heat Capacity

(Mills et al**)

Measurements of the institute of thermal engineering and the applied

models yield realistic values***

** Mills: Estimation of Physicochemical Properties of Coal Slags and Ashes, from ACS symposium series 301: Mineral Matter in Coal an Ash, 1984

* Lange: Densities of Na2O-K2O-CaO-MgO-FeO-Fe2O3-Al2O3-TiO2-SiO2 liquids: New measurements and derived partial molar properties

***Slag Atlas 2nd ed. (2008); SCI Glass Database

𝜆 = 𝑎 ∙ 𝜌 ∙ 𝑐𝑝

0

0,5

1

1,5

2

2,5

0 500 1000

Hea

t C

on

du

ctivity [

W/(

m*K

)

T [°C]

Viscosity

6

Bähr

Viscometer

Anton Paar

MCR 302

Type Rotating (searle) Rotating (searle)

Material PtRh (80/20) PtRh (80/20)

T-Range 400 – 1700 °C 400 – 1800 °C

pO2 – Range 10-22 – 0.21 bar 10-22 – 0.21 bar

Temperature

Mesurement

Type B

Accuracy:

+/- 1,5…4,25 °C

Type B

Accuracy:

+/- 1,5…4,25°C*

+ Inductivity

compensation

Atmosphere CO:CO2/ Air/ N2 CO:CO2/ Air/ N2

Heater High Frequency

Inductive Heater

Separated MoSi2

Resistive Heater

Calibration Standard Oil,

Standard Glass

Standard Oil

Torque 1…50 mNm 10-5…200 mNm

Viscosity

Measurement Principle



𝜏 =𝑟𝑖2

2𝜋∙𝑙𝑐𝑦𝑙∙1,1∙ 𝑀 ∙ 𝐶*

𝛾 = 2𝜋2𝑟𝑎

2

𝑟𝑎2 − 𝑟𝑖

2 ∙ 𝑛

𝑛,𝑀

𝜂 =𝜏

𝛾

* Calibration Coefficient determined from Standard Glass and Silicon Oil; additional validation of viscosity measurements was achieved in ring-test

1. Ash and slag coal

2. Mill to below 63 µm for homogeinity and XRF

3. Calculate po2 for maximum FeO-Content using

FACTSage™

4. Create gas-atmosphere for calculated po2 (to

simulate gasification atmosphere)

5. Continuously measure torque and turn speed to

calculate viscosity

6. Repeat measurement with different shear rates

Viscosity

Measurement Validation



Maximum Deviation is 20 %

within accepted Limit**

** Slag Atlas 2nd ed. (2008)

0

10

20

30

40

50

60

70

80

90

100

1300 1400 1500 1600

Vis

co

sit

y [

Pas

]

Temperature [°C]

VTC_a

VTC_b

VTC_c

Siemens_a

Siemens_b

Siemens_c

Siemens_d

IEST_a

IEST_b

IEST_c

IEST_d

* Gas atmosphere was reducing (CO:CO2; Ar:H2)

A ring-test was performed* at:

• CIC Virtuhcon

• Siemens Gasification Test

Center

• Institute of Iron and Steel

Freiberg

Test conditions:

• Reducing atmosphere*

• Different shear rates

Viscosity

• Database with measurements of 770 slags and h(T), 4550 data points from literature

• Own measurements included:

• 38 samples

• 186 measurements (various shear rates, atmospheres)

• 12 slag viscosity models and Einstein-Roscoe Equation, link to FactSage for Solid

Volume Fraction

• Application for prediction of h(T) for a given slag composition:

Slag Viscosity Toolbox*



Input: slag composition, T-range

search for “referenced slag system” in Database

test of implemented models with reference slag system

Output: prediction of slag viscosity with recommended model

* Duchesne MA, Bronsch AM, Hughes RW, Masset PJ. Slag viscosity modeling toolbox. Fuel 2013.

Viscosity

Modeling approach - Example



Classical Model

Classical Model

+ ER Model

Classical Model

+ Modified ER

Model

𝜂 = 𝜂𝑙𝑖𝑞 ∙ 1 − 𝑎 ∙ 𝑓 −2,5

𝑎 = 𝑓(𝑠ℎ𝑒𝑎𝑟 𝑟𝑎𝑡𝑒; 𝑠𝑝𝑒𝑐𝑖𝑒𝑠)

Einstein-Roscoe-Equation*

Calculate Solid

Volume Fraction

with FACTSage™

Corundum, Anortite,

Tridymite/Christobalite

systems were selected for

model development

Fails for non-newtonian slag

behavior

Improved Applicability for non-

newtonian region

* Roscoe R: The viscosity of suspensions of rigid spheres 1952

Viscosity

Modeling approach – Model development



I. Select Particle-Slag-System from the Slag Viscosity Toolbox*

III. Comparison of modeled and measured viscosity data by the Slag Viscosity Toolbox*

II. Perform viscosity measurements on selected slag systems and shear rates

V. Adjust a-factor to model-selected particle system

VI. Validation of adjusted a-factors with referenced systems.

AA

LE

𝐴𝐴𝐿𝐸 =1

𝑛 𝑙𝑜𝑔10 𝜂𝑝𝑖 − 𝑙𝑜𝑔10 𝜂𝑚𝑖

𝑛

𝑖=1

AALE – Average Absolute Logarithmic Error

n – number of data records

𝜂𝑝𝑖 – predicted viscosity value for Ti

𝜂𝑚𝑖 – measured viscosity value for Ti

* Duchesne MA, Bronsch AM, Hughes RW, Masset PJ. Slag viscosity modeling toolbox. Fuel 2012.

IV. Select best fitting classical viscosity model and apply ER

0

10

20

30

40

50

60

70

80

90

100

1300 1350 1400 1450 1500 1550

Vis

co

sit

y i

n P

a s

T in °C

SR=6.7 1/s SR=13.5 1/s SR=20.2 1/S

0

20

40

60

80

100

1300 1350 1400 1450 1500 1550

Vis

co

sit

y i

n P

a s

T in °C

SR=20.2 1/s Streeter

Viscosity

Modeling approach - Example

12

Classical Model

Classical Model

+ ER Model

Classical Model

+ modified ER

model

𝜂 = 𝜂𝑙𝑖𝑞 ∙ 1 − 𝑎 ∙ 𝑓 −2,5

𝑎 = 𝑓(𝒔𝒉𝒆𝒂𝒓 𝒓𝒂𝒕𝒆; 𝒔𝒑𝒆𝒄𝒊𝒆𝒔)

Einstein-Roscoe-Equation**

Calculate Solid

Volume Fraction

with FACTSage™*

0,0

0,1

0,2

0,3

0,4

0,5

0

20

40

60

80

100

1300 1350 1400 1450 1500 1550

So

l. V

ol. F

rac

. f

Vis

co

sit

y i

n P

a s

T in °C

SR=20.2 1/s Streeter Solid Vol-fract

0,0

0,1

0,2

0,3

0,4

0,5

0

20

40

60

80

100

1300 1350 1400 1450 1500 1550

So

l. V

ol. F

rac

. f

Vis

co

sit

y i

n P

a s

T in °C


Streeter +RE, a = 1.35 Solid Vol-fract

0,0

0,1

0,2

0,3

0,4

0,5

0

20

40

60

80

100

1300 1350 1400 1450 1500 1550

So

l. V

ol. F

rac

. f

Vis

co

sit

y i

n P

a s

T in °C


Streeter +RE, a = 1.35 Streeter +RE, a = 1.2

Solid Vol-fract

* currently modelled for solid fractions of anortite, corundum, christobalite/tridymite

** Roscoe R: The viscosity of suspensions of rigid spheres 1952

Surface Tension

13

TOMAC TOMMI

T-Range 400 – 2000 °C 400 – 1700 °C

Temperature

Mesurement

Type B

Thermocouple

Accuracy:

+/- 1,5…4,25 °C

Type B

Thermocouple

Accuracy:

+/- 1,5…4,25°C

Atmosphere N2; Ar; Ar/H2

(95/5)

Air

Heater Graphite

Electrodes

Separated MoSi2

Resistive Heater

Measurement

Principle

Sessile Drop Maximum Bubble

Pressure

Surface Tension

Maximum Bubble Pressure



1. Ash and slag the coal

2. Calculate liquid volume in the crucible

according to Lange et al

3. Adjust gas flow and immersion depth

accordingly

4. Detect surface inside crucible

5. Continuously measure pressure necessary

for gas flow at 3 immersion depths

6. Derive density and surface tension from

measured pressure curves

0

10

20

30

40

Al2O3 CaO Fe2O3 SiO2

ACSF1 - Composition

Surface Tension

Maximum Bubble pressure – Method



𝑝𝜎 = 𝑀𝑃 − 𝜌𝑔ℎ𝑖𝑚𝑚𝑒𝑟𝑠𝑖𝑜𝑛

𝜎 =𝑝𝜎∙𝑟𝑐𝑎𝑝

2 1−23

𝑟𝑐𝑎𝑝∙𝜌∙𝑔

𝑝𝜎−16

𝑟𝑐𝑎𝑝∙𝜌∙𝑔

𝑝𝜎

2

0

200

400

600

800

1000

1200

Ma

xim

um

Bu

bb

le

Pre

ss

ure

[P

a]

ACSF1_MBP

ACSF1_5mm

ACSF1_10mm

ACSF1_15mm

Determine Maximum

pressure

Calculate Maximum

bubble pressure

Apply Schrödingers

Correction/assume

hemispherical bubble 0,8455 𝐽

𝑚2

0,4783 𝐽

𝑚2** Hemisphere

Schrödinger

*within 20% of slag atlas & Lange et al; **validated with sessile drop method

𝜎 =𝑝𝜎 ∙ 𝑟𝑐𝑎𝑝

2

Derive density from

different depths of

immersion

𝜌5−10𝑚𝑚 = 𝑀𝑃10𝑚𝑚−𝑀𝑃5𝑚𝑚𝑔 0,01𝑚−0,005𝑚

3395 𝑘𝑔𝑚3*

Outlook

• Expand viscosity measurement database to improve viscosity model

• Validate Viscosity Model for Leucite particles

• Perform High Temperature XRD to confirm FactSage™ results used

in the calculation of the Solid Volume Fraction

• Evaluate possible supercooling effects inside gasifiers through

viscosity measurement at different cooling rates

• Improve MBP measurement system to improve dependability of

derived values for coal ash slags



TU Bergakademie Freiberg

Institute of Energy Process Engineering and Chemical Engineering

09596 Freiberg - Germany

Tel. +493731-39 4206

Fax +493731-39 4555

Email [email protected]

Web www.iec.tu-freiberg.de

This research has been funded by the Federal Ministry of Education and

Research of Germany in the framework of Virtuhcon (Project Number

03Z2FN12).

Acknowledgment

17

Investigations on Slags under Gasification Process Conditions

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