The Rapid and Continuous Production of Hydrothermally Carbonized Biomass and Chemicals by Reactive, Twin-Screw Extrusion

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1 1 The Rapid and Continuous Production of Hydrothermally Carbonized Biomass and Chemicals by Reactive, Twin-Screw Extrusion Larry G. Felix, William E. Farthing Gas Technology Institute, Des Plaines, IL USA S. Kent Hoekman, Amber Broch Desert Research Institute, Reno, NV USA

2 2 What has this got to do with Pyrolysis? HTC wood is a solid, black, friable material that looks much like, well, charcoal or torrefied wood, so much so that the HTC process has been called Wet Torrefaction. However, looks are deceiving. HTC Wood Torrefied Wood

3 3 Outline Presently, the production of hydrothermally carbonized (HTC) biomass to make solid, energy-dense hydrochar, mixture of valuable chemicals (sugars, acids, furfural, 5-HMF),* and gas requires lengthy, capital-intensive, batch-based processing. HTC biomass is an excellent, waterproof binder for pelletizing biomass, torrefied biomass, and coal. In the continuous Fast-HTC or FHTC process, a smooth slurry of fine solids, value-added liquids, and gas is produced by reactive, twin-screw extrusion (R-TSE) in ~30s or less. HTC and FHTC processing produces chemically similar but physically very different products. An example of this difference is a new, cross-linkable polymer (Lignaplast ) derived from the FHTC biomass slurry. FHTC biomass is easily pelletized. Economics, Summary and Conclusions * Not necessarily a valuable mixture of chemicals

4 4 Conventional HTC Batch Processing* Raw biomass is treated in liquid water Feedstocks can be wet Typical temperatures: C Typical reaction times: 5-30 min (at temperature). Products include: A solid, friable hydrochar Gaseous products (mainly CO 2 ) Water-soluble organics (sugars, acids, furfurals, etc.) Hydrochar is hydrophobic and is readily pelletized DRI 2 Chamber reactor: 1-2 g DRI 2-L reactor: 100 g DRI PDU reactor: 2-3 kg 4 *DOI: /s , DOI: /s y

5 5 Pelletized Hydrochar Resists Water Immersion and Tumbling* Raw wood pellets completely disintegrate upon water immersion Torrefied wood pellets swell considerably upon water immersion, but disintegrate when tumbled Hydrochar pellets maintain their integrity after water immersion and tumbling *DOI: /

6 6 Blending of Wood and Hydrochar with Coal* Pulverized Galatia coal with either raw ground loblolly pine or hydrochar Pelletized blends of coal and raw biomass disintegrate when immersed in water for 1 hour Pelletized coal disintegrates when immersed in water for 1 hour and tumbled Pelletized blends of hydrochar with coal withstand water immersion for 1 hour, followed by tumbling *US DOE, Contract No. DE-FE , R&D to Prepare and Characterize Robust Coal/Biomass Mixtures for Direct Co-feeding Into Gasification Systems

7 7 Primary Reaction Sequences Leading to HTC Biomass The degree of completion for each step depends on mixing, particle size, temperature, and reaction time

8 8 Energy Content of HTC Biomass as a Function of Reaction Severity Factor* HTC Severity is a function of reaction temperature (T) and hold time (t) R 0 = t * e [(T-100)/14.75] Severity Factor = log(r 0 ) Coal Biomass *DOI /s y

9 9 Fast HTC Biomass via Twin-Screw Extrusion Barrel Clextral BC-21 Reactive, Twin-Screw Extruder

10 10 A Continuous, Fast HTC Process - 1 Reactive, twin-screw extrusion (R-TSE) is an ideal platform for carrying out the fast hydrothermal carbonization (FHTC) of biomass. This is because the intense grinding and mixing that occurs within a TSE provides the mixing and particle size reduction (surface area) necessary to accelerate HTC reactions. However, these reactions impose three important operational and mechanical requirements when a R-TSE is employed to create FHTC biomass in a continuous process.

11 11 A Continuous, Fast HTC Process - 2 An instrumented, but otherwise standard, Clextral BC-21, 9- barrel R-TSE configured to feed biomass was used as a reactor to produce a FHTC product in less than 30 seconds A novel High Pressure, High Temperature (HPHT) water heater (not shown) supplies liquid water to the BC-21 TSE at up to 295 C The FHTC product is exhausted through a novel pressure-reducing valve to a downstream product reservoir (the Generation-1 valve is shown)

12 12 A Continuous, Fast HTC Process - 3 First, to define a reactor space within a R-TSE, a first pressure boundary is created by feeding raw biomass (~50% water) at atmospheric pressure into the R-TSE where it is masticated, ground, compacted, and recirculated to form a dynamic, stationary, pressure-resisting plug and then discharged out of the plug into the FHTC reactor. This plug resists reaction pressures > 27 MPa (270 bar) on the downstream side.

13 13 Forming the First Pressure Boundary RECIRCULATION

14 14 A Continuous, Fast HTC Process - 4 Second, in the FHTC process, lignocellulosic biomass is converted to a paste-like slurry of fine solids, liquids, and gases as the FHTC reactions proceed, and the end of the FHTC reactor cannot be defined by a recirculation zone. So, a novel, pressure-sustaining valve was invented to define the end/exit of the FHTC reactor and permit the FHTC product to be discharged in a constant, controlled manner while a more or less constant pressure is maintained within the reaction space. Two early versions of this valve are shown below: Gen. 1 Manually Loaded Spring Valve Gen. 2 Pneumatically Loaded Valve

15 15 A Continuous, Fast HTC Process - 5 High pressure, high temperature (HPHT) water is extremely effective for carrying out hydrolysis and, therefore the FHTC of biomass. At ~250 C, liquid water exhibits strong acidity, increased chemical activity, and is a strong solvent. This makes water preferable to a strong acid for hydrolysis. Third, the requirement for very hot water to initiate and sustain the hydrolysis reactions of FHTC led to the invention of a novel, compact, on-demand, HPHT water heater. This HPHT water heater can continuously deliver liquid water at up to 295 C, up to 200 bar, and up to 19 L/m to the FHTC reactor space within the R-TSE. Within a R-TSE, FHTC reactions proceed quickly and require ~30 s or less to process and exhaust a slurry of finely-divided FHTC biomass solids, value-added chemicals (sugars, acids, furfural, 5-HMF), and CO 2. U.S. Patent Application 14/216,028 and other patent filings protect the innovations required to practice this technology.

16 16 GTI Fast-HTC Reactor Operation Typical operating conditions: Biomass (wet wood) feed rate 7.5 kg/h Hot water feed rate 8.3 kg/h Reactor temperature C Reactor pressure bar ( MPa) Reaction time sec Rotational speed 220 rpm Hot products exiting the R-TSE are flashed by controlled decompression FHTC biomass is a thick slurry/paste Condensable liquids are collected Non-condensable gases are scrubbed and vented FHTC Slurry/Paste FHTC Liquid Modified Clextral BC-21 R-TSE

17 Energy Content 17 Energy Content of Hydrochar as a Function of Reaction Severity Factor Energy Content by Severity Energy Content Tahoe Mix (2-L) Loblolly (2-L Loblolly (PDU) Loblolly (2-Chamber) Pinyon/ Juniper (2-L) FHTC- February, 2013 FHTC-July, Severity Severity Factor Circled areas represent experiments with FHTC reactor

18 18 Mass Balance of FHTC Experiments with Loblolly Pine Feedstock Six tests were conducted in July, Samples and data from these tests were analyzed. Excellent mass balances obtained. Produced water was not included in the mass balances because it is very difficult to quantify, however, at a severity factor of 5.3 to 5.5, it is known to add ~10%. Compared to Parr reactor results, FHTC experiments were similar, with slightly greater production of solid product (Char) and non-volatile liquids and slightly smaller production of volatiles and gases. Water Water

19 19 Sugars Analyses from FHTC Experiments with Loblolly Pine Feedstock FHTC sugar profiles differ from Parr reactor results. However, in this range of operation, yields for either technology were ~6-8% of starting dry mass. FHTC sugars include much lower amounts of furfurals, larger amounts of simple primary sugars, and less secondary products. This suggests a R-TSEbased FHTC process may be better suited for deriving simple sugars from lignocellulosic biomass than batch-based HTC technologies. Short reaction times in the R-TSE could involve kinetic effects that favor the production of simple sugars over furfurals. Sugar profiles at reaction severity ~5.3

20 20 Organic Acids Analyses from FHTC Experiments with Loblolly Pine Feedstock Total yields of organic acids in this range of operation were 3-5% for both FHTC and Parr reactor-based technologies. FHTC acid product profiles do not significantly differ from Parr reactor results and are dominated by slightly lesser amounts of acetic acid and slightly greater amounts of lactic acid and methane sulfonic acid (MSA). Short reaction times in the R-TSE do not significantly influence acid production. Acid profiles at reaction severity ~5.3

21 21 Continuous, Fast HTC Technology Utilize Reactive Twin-Screw Extrusion Technology to produce FHTC biomass A continuous process is more likely to be economically viable. Various techno-economic analyses (TEA) have been conducted. Combine FHTC formation with coal/biomass blending in a single process Produce bio-coal products in the form of briquettes.* Biomass Coal Feeder FHTC Product On-Line Blender/Mixer Coal/FHTC Mix For Briquetting *US DOE, Contract No. DE-FE

22 22 Production of Briquettes from Blends of FHTC Biomass and Pulverized Coal* 70% Coal 30% Biomass Briquette Analysis Results Description Wt. %, As Received Residual Moisture Volatile Matter Ash Fixed C (by diff.) Wt. %, Dry Basis Heating Value Grindability C H N Komarek BC-100 Briquetter Oxygen (by diff.) S Cl MJ/kg, Dry Basis % of Coal Hardgrove Index 100% GALATIA COAL /30 COAL/BIOMASS /10 COAL/BIOMASS *US DOE, Contract No. DE-FE

23 23 FHTC Biomass is Lignaplast Lignaplast is produced in a hydrothermal FHTC process and is a stable, hydrophobic material. When dried, the resulting fine powder appears to have an indefinite shelf life, with no propensity to absorb water. Lignaplast is a thermally cross-linkable polymer that when molded and cured at up to 200 C, possesses an operating range up to C (the glass transition temperature). Flexural strength and modulus tests show that cured (cross-linked) Lignaplast polymer is similar in strength to polypropylene, but is much tougher, more like an ABS-glass fiber composite. Dynamic Mechanical Analysis carried out on thin wafers of compressed Lignaplast polymer during cyclical twisting and curing at up to 200 C suggests that higher cure temperatures result in more elastic polymers. Although composite materials have yet to be tested, it is expected that the addition of appropriate composites to molded Lignaplast polymer will provide a significant increase in strength and performance. 4

24 24 Economics 1. A Lifecycle Analysis based on an Aspen Plus -based techno-economic analysis of the production of briquettes composed of coal fines bound with FHTC biomass is presented in our tcbiomass 2015 poster entitled: Life Cycle Analysis of Co-Formed Coal Fines and Hydrochar Produced in Twin-Screw Extruder (TSE), by Vivian Liu, S. Kent Hoekman, Bill Farthing, & Larry Felix 2. An updated Aspen Plus -based techno-economic analysis of the production of Lignaplast has been carried out employing an improved FHTC production scheme with the same base TSE capital and operating costs and biomass costs as above. This updated TEA predicts the maximum cost for producing dry powdered Lignaplast will be less than $0.10/lb. (< $220/tonne), for production rates as low as 120 tonne/day (highest relative capital cost) and biomass feedstock costs of $40/tonne (highest cost for loblolly pine), in 2014 dollars. At these estimated costs, if Lignaplast can perform as well as a cheaper thermosetting polymer (~ $1/lb.), it will enjoy a significant cost advantage in the marketplace. 4

25 25 Conclusions Thermochemical conversion (by torrefaction, HTC, or FHTC) is effective in increasing the energy density of woody biomass and creating a homogeneous, renewable feedstock suitable for cofiring with coal. The FHTC process has been demonstrated to produce a renewable biomass hydrochar in a rapid and continuous fashion. R-TSE-based FHTC biomass processing results in superior product which when pelletized or briquetted provides robust handling characteristics and water resistance. FHTC biomass properties vary with processing severity, with maximum energy densification at severity factors of 5-6 (demonstrated in a pilot-scale R-TSE). Lignaplast is a new renewable product; it is a biomass-derived, thermally cross-linkable polymer that when molded and then cured at up to 200 C, possesses an operating range up to C. 4

26 26 Acknowledgements Portions of this presentation are based upon work supported by the U.S. Department of Energy, under award numbers DE- FE , DE-FG36-01GO11082, DE-FG36-02GO12011 and DE-EE Our former colleagues, Mr. James Irvin and Mr. Todd Snyder, now at Southern Research, and Dr. Wei Yan now at BASF, are co-inventors of this technology. The assistance and expertise of Mr. Mike Rhinehart and Mr. Hal Zoock of Clextral USA are gratefully acknowledged for their efforts directed to preparation, setting up, and configuring the Clextral BC-21 extruder used in this work at GTI s laboratory in Birmingham, AL, USA. The important assistance of Mr. Grady Coble of Parker Towing Company is also gratefully acknowledged. 4

27 27 Thank You! Questions? Loblolly Pine Pulpwood Forest 4