Thermal Processes in Biorefineries the Dibanet Example

Transcription

1 Thermal Processes in Biorefineries the Dibanet Example Tony Bridgwater Presented by Daniel Nowakowski Bioenergy Research Group Aston University, Birmingham B4 7ET, UK

2 DIBANET WP4 Tasks Task 4.1 Pyrolysis and gasification of solid residues and biomass and catalyst development ASTON, CERTH, UBA, UFRJ Task 4.2 Upgrading bio-oil to a diesel miscible biofuel and catalyst development and syngas conversion ASTON, CERTH, UBA, UFRJ Task 4.3 Assessment of slow pyrolysis of solid residues as biochars EMB, UL Task 4.4 Evaluation and design of processes ASTON, CERTH, EMB, UL, UBA, UFRJ

3 The DIBANET Biorefinery Feedstock selection Biomass Acid hydrolysis Fast Pyrolysis Furfural Formic acid Levulinic acid Solid residues Bio-oil Valuable co-products Engine, turbine Electricity Combustion Esterification Gasification Upgrading Slow Pyrolysis Biochar Esterification Valuable co-products Synthesis Ammonia Ethyl levulinate Alcohols, H2, etc Hydrocarbons Butyl esters Diesel Miscible Biofuels

4 What is pyrolysis? Biomass is heated in the absence of air or oxygen to decompose or devolatilise the biomass into: Solid char Liquid as bio-oil, tar or pyroligneous liquor Gas Three products are always produced Product yields depend on biomass, vapour and solids residence time, and temperature There are several modes of pyrolysis of which only fast and slow are included in Dibanet. 4

5 Pyrolysis modes Mode Conditions Wt % products Liquid Char Gas Fast Intermediate Slow Torrefaction Gasification ~ 500ºC; very short hot vapour residence time (RT) ~1 s; short solids RT ~ 500ºC; short HVRT ~10-30 s; moderate solids RT ~ 400ºC; long HVRT; very long solids RT ~ 300ºC; long HVRT; long solids RT ~ ºC; short HVRT; short solids RT 75% 12% 13% 50% in 2 phases 25% 25% 35% 35% 30% Vapours 85% solid 1-5% <1% (all burned) 15% vapours 95-99% 5

6 Fast pyrolysis technology Fast pyrolysis aims to maximise liquids. This is achieved with very high heating rates usually requiring very small particle sizes of generally <3mm in size and < 10% moisture Clean wood gives highest liquid yield up to 75 wt.% on dry biomass feed. This is homogenous i.e. single phase, and low viscosity. The charcoal forms about wt.% of the products. It retains virtually all the alkali metals. 6

7 Typical fast pyrolysis reaction system BIOMASS Pyrolysis Char removal Quench GAS Drying Grinding ESP CHAR process heat or export BIO-OIL Gas recycle 7

8 Fast pyrolysis: commercialisation Dynamotive: 200 t/d fluid bed plants in Canada Metso: 100 t/d fluid bed plant in Finland BTG: 50 t/d transported bed in Malaysia. 120 t/d in constructio n Ensyn: 100 t/d transported bed in operation in Canada + 6 others in USA t/d planning 8

9 Fast pyrolysis liquid bio-oil Moisture content 25 % ph 2.5 Specific gravity 1.20 Elemental analysis HHV as made Viscosity (at 40 C) C H O N Ash 56.4 % 6.2 % 37.3 % 0.1 % 0.1 % 17 MJ/kg cp Solids (char) 0.1 % Vacuum distillation residue Max. 50% 9

10 Fast pyrolysis for primary conversion Zeolite cracking Hydrotreating Hydrogen separation Fast pyrolysis Liquid Gasification Chemicals Char Slurry Synthesis Refining Transport fuels Electricity Heat 10

11 Bio-oil for biofuels Indirect production Via gasification of bio-oil followed by hydrocarbon or alcohol synthesis Many technical and economic advantages of gasification of bio-oil rather than solid biomass but with additional costs Direct production Via catalytic upgrading of liquid or vapour Product can be integrated into a conventional refinery 11

12 Direct bio-oil upgrading Bio-oil contains 35-40% oxygen which has to be rejected for production of hydrocarbons Hydro-treatment rejects oxygen as H 2 O Liquid processing with hydrogen and high pressure Projected yield of around 15% naphtha-like product for refining to diesel, using co-produced hydrogen Product fractions can be upgraded Zeolite cracking rejects oxygen as CO 2 Close coupled process for upgrading vapours requiring constant catalyst regeneration. No hydrogen requirement, no pressure Projected yield of around 18% aromatics for refining to gasoline 12

13 Fast pyrolysis for DIBANET (feedstock) Bagasse pellets Bagasse Trash AHR from SCBP

14 Aston FP reactors 100g/h unit 300g/h unit Paste feeder

15 Fast pyrolysis for DIBANET (products) Feedstock Miscanthus Sugarcane bagasse Bagasse pellets Sugarcane trash Feed moisture (wt.%) 9.26% 9.95% 9.62% 11.35% Feed ash (wt.%) 1.87% 1.05% 2.97% 4.44% Char 17.56% 14.84% 17.32% 24.25% Liquid 63.12% 72.96% 73.14% 57.15% Organic yield 39.83% 60.39% 60.45% 42.49% Water content, wt.% 23.28% 12.57% 12.69% 14.67% Gas 23.64% 20.45% 14.01% 24.86% Total product out (g) Total feed in (g) Recovery (%) 94.11% 97.20% 93.83% 93.46%

16 FP bio-oil upgrading via esterification Bio-oil + n-butanol with H 2 SO 4 Bio-oil + n-butanol With WD (bulk) Distillate

17 1.4E E E+07 e c8.0e+06 n a d n u b6.0e+06 A 4.0E+06 FP bio-oil upgrading via esterification with bulk WD HPA propanoic acid 2-hydroxybutyl ester, propanoic acid-4-oxo-butylester, isobutylic acid isobutylester, propanoic acid isobutyl ester 2.0E E Retention time, min. 3.0E E E+06 c e a n d n1.5e+06 u b A 1.0E E+05 with silica WD-SiO2-MTMOS-G propanoic acid butyl ester, propanoic acid 1-methyl ester, 2-butenoic acid butylester, acetic acid diethylene glycoldiester, butanoic acid anhydride 0.0E Retention time, min.

18 Slow pyrolysis Processes include batch kilns and retorts, continuous retorts e.g. Lambiotte and Lurgi Feed size and shape is important Heating can be direct (air addition) or indirect Charcoal is mostly lump with smaller particles and dust Gases, vapours and liquids are seldom collected or processed. Exceptions include Usine Lambiotte (now shut down) and profagus (Chemviron, Degussa) in Germany (still operating) 18

19 Biochar Traditional slow pyrolysis process is used for solid fuel for cooking, leisure and metallurgy e.g. Iron and steel in Brazil and silicon in Australia Recent attention has focussed on use of char for carbon sequestration and soil conditioning - biochar. Char recycles potassium in biomass, provides a microbial base for soil, and improves soil texture. There is much debate on the costs and benefits. Care is needed to manage the non-char products 19

20 Pyrolysis conclusions Pyrolysis is very flexible in the process and products. Fast pyrolysis provides a liquid as an energy carrier The liquid is alkali metal free which has advantages Decentralised pyrolysis plants offer system improvements There is a small cost penalty for using fast pyrolysis for pretreatment Bio-oil can be used for fuel, chemicals or biofuels Fast pyrolysis technology needs to be improved to reduce costs and increase liquid yield and quality Fast pyrolysis liquid upgrading needs to be further developed and demonstrated Biochar is of great interest but questionable economics

21 GASIFICATION What is gasification? Gasification is the substantial or complete conversion of carbonaceous or organic material into a permanent gas, usually containing CO, H 2, CO 2, CH 4 and minor amounts of higher hydrocarbons and trace impurities There are several processes: Thermal or thermochemical and Biological i.e. anaerobic digestion Thermal gasification can be oxidative or anaerobic i.e. pyrolysis

22 Gasification methods Type Gas HV Efficiency Comments Oxidative Air Oxygen Indirect (steam or pyrolytic) Pressure Air Oxygen ~5 MJ/Nm 3 High ~12 MJ/Nm 3 Moderate Simple High cost and high energy use ~17 MJ/Nm 3 Low More complex, Gas needs compression ~5 MJ/Nm 3 High ~10 MJ/Nm 3 Moderate Higher cost, but higher efficiency potential. Needed for biofuel synthesis

23 Commercial gasifiers Guessing Austria 2 MWe indirect (twin bed) Lahti Finland 15 MWe CFB

24 Aston Drop Tube Reactor (DTR) 90 cm

25 Results Drop Tube Reactor (DTR) Higher hydrogen and carbon monoxide concentrations, as well as heating values, were obtained at 900 C Low gas heating value product gas obtained due to high nitrogen flows required for operation

26 Batch gasification system Batch gasification in a stainless steel fixed bed reactor with air Tar collection system with iso-propanol (bottle 1 & 2), silica gel (bottle 3 & 4) and cotton wool (bottle 5) prior to gas measurement and analysis Continuous gas analysis and microgc for cross checking data. Glass collection system Air Sample Furnace Continuous gas analyser and MicroGC Exhaust

27 Gas HHV (wt% dry feed O 2 -free basis) HHV increases with T as product gas concentration in nitrogen increases. On a commercial gasifier with temperatures of around 950 C, the nitrogen content is usually aroun d 50vol.% of product gas for biomass and 65vol.% for charcoal. These results reflect this. HHV of oxygen-free product gas (MJ/Nm 3 ) SCBP AHR Initial reactor temperature ( C)

28 Gasification conclusions Gasification system must be carefully matched to feed characteristics and application For development, large scale thermal gasification and gas cleaning & conditioning needs to be demonstrated For biofuels small scale hydrocarbon synthesis should be developed and demonstrated Develop integrated biorefineries Improve catalysts Robustly compare alternative systems Reduce costs Gasification is complementary to pyrolysis Economy of scale and feed cost dominate bioenergy and biofuel applications so technology and biomass cost are critical

29 Thank you More comprehensive slides on biomass pyrolysis and gasification are on the Dibanet website (E-learning course). Tony Bridgwater will be happy to answer technical questions by Aston s fast pyrolysis facilities are accessible via the BRISK transnational access facilities see BRISK website 29

30 BRISK opens up a wide variety of research infrastructures via Transnational Access, allowing researchers outside and inside the project to conduct experiments. Facility and partner enquiries Visit Transnational Access to European research facilities is open to all researchers