WP2. Fuel Characterization

Transcription

1 GREEN Center for Power Generation and Renewable Energy WP2. Fuel Characterization 3. October Steering Group meeting DTU Chemical Engineering Peter Arendt Jensen

2 Background Compared to coal: large non spherical particles, high volatile content, Objectives To make an adequate geometric particle description To develop a model of single biomass particles of ignition, pyrolysis and char combustion that can be implemented in CFD Present activities Ph.D. Student Joakim Myung Johansen: Experiments with pyrolysis of small biomass particles at Stanford. Ph.D. Student Anna Trubetskaya: Biomass particle size and form characterization leads on to particle conversion modeling Ph.D. Student Anna Trubetskaya: Grid heater / Entrained flow reactor biomass fuel conversion (Pyrolysis) Master project: Mallak Stella Aweis large single particle combustion experiments 2 DTU Chemical Engineering,

3 Project status Ph.D. Student Joakim Myung Johansen: Experiments with pyrolysis of small biomass particles at Stanford. Conducted at Riginal Mitchells group at Stanford Reactor: Temp K K (adiabatic), residence time ms Fuels: Pine wood, Miscanthus, leached Mischantus, Wood + KCl Ashe contents: 0.2 wt%, 3.4 wt% Particle sizes: µm, µm 3 DTU Chemical Engineering,

4 Flow reactor with flat flame burner Determination of biomass conversion: Using the ash as tracer: Total yield dependent on deposits in tubes Total ash: Release and leached K, Cl, S Si very low content Ca will probably be used (Small samples) CO T=cold He T=hot H 2 O N 2 Q T=1655 K Exhaust CH 4 +H 2 O 2 Nonpremixed N 2 + Solid fuel CH 4 +H 2 O 2 Nonpremixed 4 DTU Chemical Engineering,

5 Project status Ph.D. Student Anna Trubetskaya: Biomass particle size and form characterization leads on to particle conversion modeling Samples were used: Poplar from Germany (cutting mill, up to 4mm), 0-180µm and µm Wheat straw (cutting mill, up to 4mm), µm Dong Energy pellets (Loesche roller mill, 0-2mm), pinewood, µm Grid heater / Entrained flow reactor biomass fuel conversion (Pyrolysis) 5 DTU Chemical Engineering,

6 Objective: Particle characterization To relate biomass type and milling to morphology of particles To verify appropriate use of particle size to obtain a adequate geometric description of particles To make an adequate choice of particle description used for modeling: (slip velocity, mass transport and heat transfer) Analysis of particle size and shape 1. Sieving 2. Malvern (Laser Diffraction) 3. Camsizer + microscope Retsch manual for Camsizer, DTU Chemical Engineering,

7 Camsizer characterization 1. x c_min is the shortest chord of maximal chords 2. x Fe_min is a distance between two minimal tangents directed parallel to each other 3. x Fe_max is a distance between two maximal tangents directed parallel to each other 4. x Ma_min 2* (shortest distance from the center point to the particle surface) 7 DTU Chemical Engineering,

8 Particle characterization some results Biomass particle Particles appear as flakes with three distinct dimensions: L, W, T. Verification of measurements by use of particles with well known shapes Measurements of Vp/Ap [m] were done correctly Limitation of Camsizer measurements based on a 2D image Appropriate for elongated biomass particles: L: X fe,max * cos(45º) (to compensate for 2D measurement) W: X Ma,min T: *2/3 (adequate for wood particles determined by microscopy) Further work: Reporting particle geometrical model representation for combustion modeling 8 DTU Chemical Engineering,

9 Particle characterization An example Camsizer measurement on the polar sample 3. Symmetry r 2 r 1 C 9 DTU Chemical Engineering,

10 Project status Ph.D. Student Anna Trubetskaya: Grid heater / Entrained flow reactor biomass fuel conversion (Pyrolysis) Grid heater study (TUM Germany): Fuels: wheat straw / washed wheat straw / washed wheat straw +KCl -- DCC pellets/washed DCC pellets beech wood, cut willow. Operation conditions: Temperature: 700ºC, 1100ºC. Particle feeder Heating rates: 10 K/s, 1000 K/s. Gas Preheater Entrained flow reactor Pyrolysis November repair December and January Electrically heated reactor 10 DTU Chemical Engineering, Particle and gas sampling

11 SPC-setup Single particle combustion setup new version Master project: Comparison: Wood pelletized wood torrified wood Setup description Fuel is held by platinum wire High temperature gas flow Observation with camera, and IR camera Gas analysis just above combusting particle Heat generated flat diffusion flame burner 11 DTU Chemical Engineering,