Application of activated process char for gas treatment of biomass gasification producer gases

Application of activated process char for gas treatment of biomass gasification producer gases York Neubauer and Omid-Henrik Elhami Institute of Energy Engineering NWG-TCKON Chicago 03.11.2015

Thermo-chemical gasification gasification product gas: (depending on feed and conditions): gaseous compounds H 2, CO, CH 4, C 2 -C 5, CO 2, H 2 O, (N 2 ) gas contaminants: particulate matter - ash, unreacted carbon condensable organic species tar further contaminants - containing S, N, Cl, 2

Motivation thermo-chemical gasification yields fuel- and synthesis gases for multiple utilization pathways the comparably small to medium sized plants for utilizing biogeneous feedstocks are faced with rather high specific capital and operational expenditures for gas cleanup (dust, tar, N, S, Cl ) No established standard process for process gas cleaning and conditioning available new engineering with each new project and client requirements necessary Either optimized gasifier operation or complex gas aftertreatment Lack of knowledge about the black box gasifier 3

Junior research group TCKON @ TU Berlin Fundamental examinations and selective influencing of heterogeneous reactions in thermochemical conversion of biomass and robust, continuous on-line monitoring of the organic load of the gas phase. Main aims: Targeted influencing of heterogeneous reactions of gas or vapor with the solid surfaces of carbon structures during the conversion process Selective influencing of char properties and utilizing char generated in the process Fluorescence measurements of aromatic multi-component mixtures in hot product gases of thermochemical conversion processes / development of a robust tar -sensor 4

Biomass gasification and its gas quality challenge adapted from: Hofbauer H, Gas production for polygeneration plants. International Conference on Polygeneration Strategies (ICPS), Vienna, Austria (2009) 5

Process char: just an reaction intermediate? Making use of activated carbon within gas producer process chains pyrolysis pyrolysis char process char char activation AC adapted from Hofbauer H, Gas production for polygeneration plants. International Conference on Polygeneration Strategies (ICPS), Vienna, Austria (2009) 6

General approach Objectives: Creating suitable pore structures for tar - species adsorption Investigations on PAH adsorption on activated process char (AC) Study effect of the gasification medium and the gas composition on the pore structure of char intermediates in FB gasification Feasibility of operating the gasifier in a mode generating useful AC for subsequent gas processing 7

Generating char: fixed bed and screw-type pyrolysis unit reaktor d i : 200 mm bed height: 50 cm temperature up to 700 C 8

Generating process-char: bubbling fluidized bed gasifier reactor d i : 114 mm bed height: 60-80 cm temperature 700-900 C gas flow ~6 Nm³/h fuel input 3 kg/h 9

Activating the char reactor d i : 50 or 80 mm bed height: 3-20 cm temperature 700-1000 C T off-gas N 2 CO 2 CO H 2 mass flow controller gas preheater char activation reactor online μ-gc / online GC-FID PAH dosing system Optional for adsorption tests CH 4 evaporator HPLC pump H 2 O 10

PAH adsorption on char in the literature Quantitative study of PAH adsorption on activated carbon from model compounds by Mastral et al.²: total microporosity is the main factor controlling the adsorption process micropore sizes higher than 0.7 nm, where PAH molecules do not find diffusional problems favors the adsorption High development of the mesoporosity not only drive the adsorbate molecules to the micropores but also promote the multilayer interactions increasing the equilibrium adsorption capacity low surface acidity, due to both the hydrophobic nature and the lower humidity adsorption capacity of the PAH Evolution of pore volume per gram of starting char as a function of burn-off (char obtained from olive stones) 3 2 A. M. Mastral et. al. Development of Efficient Adsorbent Materials for PAH Cleaning from AFBC Hot Gas. Energy & Fuels 18, 2004 3 F. Rodriguez-Reinoso et. al. The use of steam and CO 2 as activating agents in the preparation of activated carbons. Carbon Vol. 33, No. 1, 1995 11

starting materials and activated char fluidized bed gasifier char fixed bed pyrolysis char Proximate analysis (dry basis, %) Ultimate analysis (dry & ash free basis, %) samples Fluid.-bed pine char Fixed bed pine char Fixed bed oak-char ( Räuchergold ) reaction temperature volatile matter ash fixed carbon C H N O S 800-820 C 5,0 7,7 87,3 87,65 0,30 0,21 3,89 0,25 600 C 7,6 0,7 91,7 91,02 1,95 0,10 6,22 0,01 600 C 15,1 1,5 83,4 83,05 2,89 0,32 12,06 0,18 12

Characterization of process chars pore size distribution specific surface area (m²/g) pore size distribution (cm³/g) sample reaction temperature S BET micropore < 2 nm mesopore 2 50 nm total < 250 nm fluidized bed gasifier pine chips ~800 C 170 0,038 0,063 0,16 fixed bed - oak chips pyrolysis char 600 C 151 0,088 0,030 0,09 activated pyr.-char 46% burn off (CO 2 ) 850 C 716 0,293 0,032 0,32 53% burn off (CO 2 ) 850 C 766 0,312 0,040 0,34 60% burn off (CO 2 ) 850 C 819 0,334 0,033 0,36 13

Adsorption tests - setup test gas generation adsorber with char sample on-line monitoring N 2 T on-line GC/FID naphthalene SiC SRI GC/FID PAH sublimation device activated carbon sample Alternatives: Single PAH sublimation/evaporation syringe pump + evaporator ethylene pyrolysis on-line GC/FID on-line GC/MS (for process gases) on-line monitoring with LIF 14

PAH adsorption on untreated and activated carbon Adsorption temperature: 150 C mass of activated char sample: 4,0 g bed height: 2,4 (±0,1) cm naphthalene load in gas phase: 1,5 g/nm³ naphthalene c/c 0 1,0 0,8 0,6 0,4 0,2 0,0 SiC Schüttung SiC bed Pyrolysekoks pyrolysis char (0% burn Abbrand) off) Aktivkoks (53% Abbrand) activated char (53% burn off) -0,2 0:00 1:00 2:00 3:00 4:00 5:00 6:00 time (hh:mm) 15

On-line analysis and monitoring of gas-phase PAH by laser- induced fluorescence 1 fluorescence Intensity (standardized) 0,8 0,6 0,4 0,2 0 275 300 325 350 375 400 425 450 475 500 Wavelength [nm] 7 E+04 Peak Area [arb. Units] 6 E+04 5 E+04 4 E+04 3 E+04 2 E+04 1 E+04 0 E+00 00:00:00 00:14:24 00:28:48 00:43:12 00:57:36 Time [hh:mm:ss] 16

Summary and next steps Adsorption of tar species on process-chars and activated processcarbons On-line gas phase analysis and monitoring of PAH by applying online GC/FID and optical fluorescence monitoring devices Characterization and screening of further relevant woody biomass feedstocks (beech, pine, poplar, willow, ) Adsorption of multi-component PAH mixtures Influence of steam in the process on the adsorption results Tests with process gases from BFB gasifier Possibilities for char regeneration and PAH reforming will be examined: partial gasification/reactivation with steam or CO 2 non thermal DBD-Plasma 17

Acknowledgement We want to acknowledge and would like to express our gratitude to the German Federal Ministry of Education and Research for financial support of our current work in the junior research group TCKON (FKZ: 03SF0442) 18

More information on our work Continuous On-Line Tar Monitoring for Process Control by Application of Optical Emission Spectroscopy NON -THERMAL PLASMA application for the enhancement of heterogeneous gasification reactions Poster # 109 Poster # 110 19