Investigations on Slags under Gasification Process Conditions

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Jerome Sullivan
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Radebeul TU Bergakademie Freiberg - Institute of Energy Process Engineering and Chemical Engineering - 09596

1 Zentrum für Innovationskompetenz: Virtual High Temperature Conversion Investigations on Slags under Gasification Process Conditions Daniel Schwitalla, Arne Bronsch, Stefan Guhl 6th International Freiberg Conference, Dresden Radebeul TU Bergakademie Freiberg - Institute of Energy Process Engineering and Chemical Engineering Freiberg - Germany-Tel Fax [email protected] - Web

2 Outline 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

3 Motivation Virtual High Temperature Conversion - Strategy Substance Properties Experimental Acquisition Database Extraction Equilibrium Calculations Process Data & Experimental Measurement Data Validation Virtualization Process model Mathematical Models Example Presentation Subgrid model for slag behaviour at entrained flow gasifier walls VTC IPP Group 3

Experimental Measurement Data Validation Virtualization Process model Mathematical

4 Properties relevant for modelling slag behavior Viscosity Rotational Viscosimeter (searle-type) (Baehr HTviscometer) Rotational Viscosimeter (searle-type) (AntonPaar MCR 302) Surface Tension Sessile Drop (Fraunhofer ISC Tommiplus, TOM-AC) Maximum Bubble Pressure (Fraunhofer ISC Tommiplus+ MBP-Module) Density Diffusivity Heat Capacity Measurement of Hydrostatic Pressure (Fraunhofer ISC Tommiplus + MBP-Module) Laser Flash (Department of Thermal Engineering TU Freiberg) Differential Scanning Calorimetry (Setaram MHTC 96) 4

Pressure (Fraunhofer ISC Tommiplus+ MBP-Module) Density Diffusivity Heat Capacity Measurement of Hydrostatic Pressure (Fraunhofer

5 Heat Conductivity [W/(m*K) Heat Conductivity Laser Flash + Calorimetry + MBP Determine Diffusivity (Laser Flash) 2,5 2 1,5 Density (Lange et al*) λ = a ρ c p 1 0,5 Heat Capacity (Mills et al**) T [ C] Measurements of the institute of thermal engineering and the applied models yield realistic values*** * Lange: Densities of Na2O-K2O-CaO-MgO-FeO-Fe2O3-Al2O3-TiO2-SiO2 liquids: New measurements and derived partial molar properties ** Mills: Estimation of Physicochemical Properties of Coal Slags and Ashes, from ACS symposium series 301: Mineral Matter in Coal an Ash, 1984 ***Slag Atlas 2nd ed. (2008); SCI Glass Database 5

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

6 Viscosity Bähr Viscometer Anton Paar MCR 302 Type Rotating (searle) Rotating (searle) Material PtRh (80/20) PtRh (80/20) T-Range C C p O2 Range bar bar Temperature Mesurement Type B Accuracy: +/- 1,5 4,25 C Type B Accuracy: +/- 1,5 4,25 C* + Inductivity compensation Atmosphere CO:CO 2 / Air/ N 2 CO:CO 2 / Air/ N 2 Heater High Frequency Inductive Heater Separated MoSi 2 Resistive Heater Calibration Standard Oil, Standard Glass Standard Oil Torque 1 50 mnm mnm 6

21 bar Temperature Mesurement Type B Accuracy: +/- 1,5 4,25 C Type B Accuracy: +/- 1,5 4,25 C* + Inductivity compensation

7 Viscosity Measurement Principle n, M 1. Ash and slag coal 2. Mill to below 63 µm for homogeinity and XRF 3. Calculate p o2 for maximum FeO-Content using FACTSage 4. Create gas-atmosphere for calculated p o2 (to simulate gasification atmosphere) 5. Continuously measure torque and turn speed to calculate viscosity 6. Repeat measurement with different shear rates τ = r i 2 2π l cyl 1,1 M C* γ = 2π 2r a 2 r a 2 r i 2 n η = τ γ 7 * Calibration Coefficient determined from Standard Glass and Silicon Oil; additional validation of viscosity measurements was achieved in ring-test

Continuously measure torque and turn speed to calculate viscosity 6.

8 Viscosity [Pas] Viscosity Measurement Validation Temperature [ C] VTC_a VTC_b VTC_c Siemens_a Siemens_b Siemens_c Siemens_d IEST_a IEST_b IEST_c IEST_d 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 Maximum Deviation is 20 % within accepted Limit** * Gas atmosphere was reducing (CO:CO 2 ; Ar:H 2 ) ** Slag Atlas 2nd ed. (2008) 8

Siemens Gasification Test Center Institute of Iron and Steel Freiberg Test conditions: Reducing atmosphere* Different shear

9 Viscosity Slag Viscosity Toolbox* 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: 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 9 * Duchesne MA, Bronsch AM, Hughes RW, Masset PJ. Slag viscosity modeling toolbox. Fuel 2013.

prediction of h(t) for a given slag composition: Input: slag composition, T-range search for referenced slag system in Database test of implemented models with

10 Viscosity Modeling approach - Example Classical Model Fails for non-newtonian slag behavior Corundum, Anortite, Tridymite/Christobalite systems were selected for model development Calculate Solid Volume Fraction with FACTSage Classical Model + ER Model Classical Model + Modified ER Model Improved Applicability for nonnewtonian region Einstein-Roscoe-Equation* η = η liq 1 a f 2,5 a = f(shear rate; species) 10 * Roscoe R: The viscosity of suspensions of rigid spheres 1952

Classical Model + ER Model Classical Model + Modified ER Model Improved Applicability for nonnewtonian region

11 AALE Viscosity Modeling approach Model development I. Select Particle-Slag-System from the Slag Viscosity Toolbox* II. Perform viscosity measurements on selected slag systems and shear rates III. Comparison of modeled and measured viscosity data by the Slag Viscosity Toolbox* IV. Select best fitting classical viscosity model and apply ER V. Adjust a-factor to model-selected particle system VI. Validation of adjusted a-factors with referenced systems. AALE = 1 n n i=1 log 10 η pi log 10 η mi AALE Average Absolute Logarithmic Error n number of data records η pi predicted viscosity value for T i η mi measured viscosity value for T i 11 * Duchesne MA, Bronsch AM, Hughes RW, Masset PJ. Slag viscosity modeling toolbox. Fuel 2012.

Select best fitting classical viscosity model and apply ER V. Adjust a-factor to model-selected particle system VI. Validation of adjusted a-factors with referenced systems.

12 Viscosity in Pa s Viscosity in Pa s Sol. Vol. Frac. f Viscosity Modeling approach - Example , , , , , , T in C SR=20.2 1/s Streeter T in C Streeter SR=20.2 +RE, SR=20.2 1/s a = /s Streeter Streeter Streeter Solid +RE, Vol-fract a = 1.2 Streeter Solid Vol-fract +RE, a = 1.35 Solid Vol-fract SR=6.7 1/s SR=13.5 1/s SR=20.2 1/S * currently modelled for solid fractions of anortite, corundum, christobalite/tridymite Classical Model Calculate Solid Volume Fraction with FACTSage * Classical Model + ER Model Classical Model + modified ER model Einstein-Roscoe-Equation** η = η liq 1 a f 2,5 a = f(shear rate; species) 12 ** Roscoe R: The viscosity of suspensions of rigid spheres 1952

$2 1/s Streeter T in C Streeter SR=20.2 +RE, SR=20.2 1/s a = 1.35 1/s Streeter Streeter Streeter Solid +RE, Vol-fract a = 1.2 Streeter Solid Vol-fract +RE, a = 1.35 Solid Vol-fract SR=6.7 1/s SR=13.$

13 Surface Tension TOMAC TOMMI T-Range C C Temperature Mesurement Type B Thermocouple Accuracy: +/- 1,5 4,25 C Type B Thermocouple Accuracy: +/- 1,5 4,25 C Atmosphere N 2 ; Ar; Ar/H 2 (95/5) Air Heater Graphite Electrodes Separated MoSi 2 Resistive Heater Measurement Principle Sessile Drop Maximum Bubble Pressure 13

4,25 C Atmosphere N 2 ; Ar; Ar/H 2 (95/5) Air Heater Graphite Electrodes Separated

14 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 ACSF1 - Composition 0 Al2O3 CaO Fe2O3 SiO2 14

Adjust gas flow and immersion depth accordingly 4. Detect surface inside crucible 5.

15 Maximum Bubble Pressure [Pa] Surface Tension Maximum Bubble pressure Method Determine Maximum pressure Derive density from different depths of immersion ACSF1_MBP ACSF1_5mm ACSF1_10mm ACSF1_15mm Calculate Maximum bubble pressure ρ 5 10mm = MP 10mm MP 5mm g 0,01m 0,005m p σ = MP ρgh immersion 3395 kg m 3 * Apply Schrödingers Correction/assume hemispherical bubble Hemisphere Schrödinger σ = p σ r cap 2 σ = p σ r cap r cap ρ g p σ 1 6 r cap ρ g p σ 2 0,4783 J m 2 ** 0,8455 J m 2 *within 20% of slag atlas & Lange et al; **validated with sessile drop method 15

0,005m p σ = MP ρgh immersion 3395 kg m 3 * Apply Schrödingers Correction/assume hemispherical bubble Hemisphere Schrödinger σ = p σ r cap 2 σ = p σ

16 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 16

Volume Fraction Evaluate possible supercooling effects inside gasifiers through viscosity measurement at

17 Acknowledgment This research has been funded by the Federal Ministry of Education and Research of Germany in the framework of Virtuhcon (Project Number 03Z2FN12). TU Bergakademie Freiberg Institute of Energy Process Engineering and Chemical Engineering Freiberg - Germany Tel Fax [email protected] Web 17

TU Bergakademie Freiberg Institute of Energy Process Engineering and Chemical Engineering 09596

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