Experimental and modelling studies on viscosity of typical Australian brown coal ashes Alexander Ilyushechkin, Daniel Roberts, and David Harris 7 th International Freiberg Conference on IGCC & XtL Technologies, Coal Conversion and Syngas, 7-11 June 2015, Hohhot, Inner Mongolia, China CSIRO ENERGY FLAGSHIP
Gasification research opportunity for lignite Driving force for research: Increasing interest in the use of low rank coals as feed stocks for the production of liquid fuels and chemicals via gasification-based processes; Oxygen-blown gasifiers are well suited to these applications; The most common oxygen-blown gasification technology is entrained-flow gasification; Very few studies of lignite behavior under entrained flow gasification conditions.
Slagging in entrained flow gasifier Slag formation AFT (reducing) has to be < operating temperatures (<1600 C) Slag Viscosity Newtonian flow behaviour for continuous flow 25 Pa s is the accepted maximum viscosity at the slag tap for successful operation (@ 1400-1500 C) Flux addition required if viscosity is too high Temperature of Critical Viscosity Slag becomes heterogeneous Trouble-free tapping of slag is not possible
Mineral matter assessment Non-slagging gasifier: AFT(high) Phase compositions Impact of: alkalies and volatiles sulphur and chlorine Laboratory: Modelling: Pilot-scale: Assessment tools: Ash analysis Heating and quenching AFT Thermodynamic modelling Pilot-tests Slagging gasifier: AFT (low) Phase compositions Viscosity 5-25 Pa s (typical for black coals) Suggesting15-40 Pa s (for low ash coals) Tcv (<T operating) Viscosity measurements Viscosity modelling Presentation title Presenter name Page 4
Slag characteristics: experimental and modelling tools
Slag characteristics: viscosity Slag preparation, viscosity measurements & quenching at 1200-1600 C Melt Tube furnace Rotating bob Mo/graphite crucible Thermocouple N 2 Application: slag viscosity data for coal ashes; evaluate fluxing requirements; estimate effect of coal blending on slagging behaviour; evaluation of trace elements in slags. Data analysis & presentation: Viscosity-Temperature curves Viscosity contours in phase diagram Tcv contours in phase diagram Viscosity as function of S/A (silica/alumina), CaO, FeO and other componets
Slag characteristics: phase composition Materials exposure at temperatures up to 1500 C in controlled atmospheres, with possible quenching and followed SEM/EDS/XRD analysis Drop tube furnace rig Mo/Pt wire Thermocouple Samples in Pt/Mo envelope Gas out Tube cold end flanges Gas in Plastic film, attached to flange Iced water Application: Slag preparation; Slag refractory interaction; Ash/slags phase equilibria studies;
Viscosity modelling Viscosity models for Australian black coal ashes, Viscalc, (1996-2012): synthetic mixtures model with 0, 5, 10 and 15wt.% FeO, Real slag models 0-16% FeO Most of the models - anorthite region (to high viscosity for mulite region) High iron model 16-21 % FeO, includes anorthite and mulite region Tool for fluxing and blending selection Weymann model (extension of Arrhenius model): linking viscosity with temperature modified Urbain type: linking composition with viscosity Ln(ɳ) = a o +a 1 y + a 2 y 2 + a 3 x + a 4 xy+ a 5 xy 2 + a 6 x 2 +a 7 x 2 y +a 8 x 2 y 2 +a 9 x 3 +a 10 x 3 y + a 11 x 3 y 2 m s - SiO 2 wt.%; m a - Al 2 O 3 wt.%; m c - CaO wt.%; m f - FeO wt.%. There are number of models available for Newtonian flow slags
Slag flow behaviour: Australian brown coals
Focus of present work: Groups of typical brown coal ashes Identify compositions with Newtonian flow: basic criteria Viscosity versus temperature trends for typical coal ashes Evaluation of the existing models: Viscosity; Phase compositions
Black and Brown coal characteristics Australian Brown coals Australian Black coals Proximate analysis Moisture %, ar 50-60 1-15 Ash, % db 1.5-4 5-15 VM, % db 48-50 25-44 FC, % db 46-49 42-80 Ash analysis Yallourn Morwell Loy Yang SiO 2 1-15 2-14 5-75 28-80 Al 2 O 3 2-6 1.5-4 13-28 8-48 Fe 2 O 3 34-49 10-30 4-14 0.1-32 CaO 6-12 15-35 1-8 0.1-28 MgO 14-36 9-24 3-15 0.1-3 Na 2 O 3-13 3-5 2-20 0.1-2 K 2 O 0.1-1.0 0.1-0.4 0.3-1.2 0.1-4 SO 3 10-20 17-26 3-22 0.2-6 Major for black coals Specific for brown coals Presentation title Presenter name Page 11
Typical coal ashes Category High Fe, Mg High Ca, Fe High Si, Al Ash ID FM CF LSA SA1 SA2 HSA SiO 2 13.0 13.9 21.2 56.5 41.6 76.7 Al 2 O 3 4.2 3.6 26.71 20.5 13.1 10.3 Fe 2 O 3 34.0 15.4 5.5 4.6 7.5 3.6 TiO 2 0.46 0.34 0.75 1.5 1.1 0.95 K 2 O 0.28 0.35 0.21 1.3 0.5 0.4 MgO 23.52 9.1 9.3 3.6 8 2.2 Na 2 O 3.3 2.5 9.5 4.7 6.1 1.8 CaO 8.51 20.5 5.0 1.6 6.3 1.06 SO 3 11.8 24.3 21.8 5.0 12.6 2.8 S/A 3.05 3.87 0.79 2.76 3.18 7.45 S+A(slag) 19.7 26.7 61.4 81.7 65 89.7
Phase content, wt.% Viscosity, Pa s High Fe and Mg slags 160 140 120 80 60 40 20 0 1200 1300 1400 1500 1600 Temperature, C 90 Olivine 80 Fe(Mg)3O4-x 70 Liquid 60 50 40 30 20 10 0 1200 1225 1250 1275 1300 1350 1400 1450 1500 1550 1600 Temperature, C FM slag Non-Newtonian viscosity: Very low at T>1500 C High solids content (30-60wt.%) Can be used only with other coal blends (as fluxing agent)
Viscosity, Pa s Phase content, wt.% High Ca and Fe slags 25 CF slag 20 15 10 5 0 1200 1300 1400 1500 1600 Temperature, C 90 Merwinite 80 Fe(Mg)O4 70 60 Liquid 50 40 30 20 10 0 1200 1225 1250 1275 1300 1350 1400 1450 1500 1550 1600 Temperature, C Non-Newtonian viscosity: Very low at T>1450 C Solids content: 7-42wt.% (1200-1600 C) Can be used only with other coal blends (as fluxing agent)
Viscosity, Pa s Viscosity, Pa s Silica-alumina slags: Low S/A 200 180 160 140 120 80 60 40 20 0 1200 1250 1300 1350 1400 1450 1500 1550 1600 Temperature, C LSA slag 80 60 40 20 0 1200 1250 1300 1350 1400 1450 1500 1550 1600 Temperature, C olivine spinel liquid Non-Newtonian viscosity: at T<1550 C Solids content: 11-38 wt.% (1200-1600 C) Very narrow operational range (~1500 C)
1200 1225 1250 1275 1300 1325 1350 1375 1400 1425 1450 1475 1500 1550 1600 1200 1225 1250 1275 1300 1350 1400 1450 1500 1550 1600 Phase content, wt.% Phase content, wt.% Viscosity, Pa s Silica-alumina slags: moderate S/A 200 150 50 SA slags SA1 SA2 Newtonian flow: SA1: high viscosity: only 1550-1600 C operational temperatures SA2: good viscosity: wide temperature range 1270-1450 C operational temperatures Solids: low content at T<~1300-but not observed by SEM 0 1200 1300 1400 1500 1600 Temperature, C 80 60 40 SA1 cordierite liquid 80 60 40 SA2 Olivine Liquid 20 20 0 0 Temperature, C Temperature, C
Viscosity., Pa s Viscosity models 0 SA1 10 Urbain Mod. Urbain Kalm-Frank Watt-Fereday Lakatos Wall FactSage Experimental 1 1200 1250 1300 1350 1400 1450 Temperature, C 1500 1550 1600 No perfect fit: Best fit- Watt-Fereday, and Wall models
Viscosity, Pa s Viscosity models 0 SA2 10 1 Urbain Mod. Urbain Kalm-Frank Watt-Fereday Lakatos Wall FactSage Viscalc Experimental 0.1 1200 1250 1300 1350 1400 1450 1500 1550 1600 Good fit: Viscalc; Temperature, C Modified Urbain
Phase content, wt.% Viscosity, Pa s High S/A slags 0 800 600 400 HSA slag 00 0 HSA 200 25 Pa s 0 1560 1610 1660 Temperature, C HSA 80 cordierite quartz 60 liquid 40 20 0 1200 1250 1300 1350 1400 1450 1500 1600 Temperature, C 10 1 1540 1560 1580 1600 1620 1640 1660 Urbain Mod. Urbain Kalm-Frank Watt-Fereday Lakatos Wall FactSage Experimental Newtonian viscosity, but: Very high viscosity Need fluxing and alumina No model to predict
Summary Slagging behaviour: Brown coals have a wide range of compositions - screening proper compositions for specific gasification application is important; Thermodynamic modelling can be used for preliminary evaluation of slag/ash phase composition 3 Groups of slags were identified: high Fe&Mg, high Ca& Fe and high Si&Al All slags with Non-Newtonian flow have significant amounts of solids and S/A<1; and/or Low SiO 2 content;
Summary Slag viscosity: High Fe&Mg, high Ca& Fe: have to be blended with silica-rich coal ashes/ or with sand; Si&Al slags: Low S/A: narrow range need more Si or less Al; moderate S/A: can be used with or without fluxing; Viscosity models: Only some models fit well with experimental data; And only for specific compositional range; have to be developed for extended brown coal compositional range.
Thank you Alexander Ilyushechkin Senior research scientist Energy Flagship, CSIRO t +61 7 3327 4187 e alex.ilyushechkin@csiro.au w www.csiro.au/energy ENERGY FLAGSHIP