Opportunities for conversion of biomass and waste using hydrothermal Carbonisation

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1 Opportunities for conversion of biomass and waste using hydrothermal Carbonisation Dr Andy Ross School of Chemical and Process Engineering

2 Hydrothermal processing Hydrothermal processing converts organic material in hot compressed liquid water Increasing interest in treatment of waste streams such as biosolids and MSW by hydrothermal processing; Hydrothermal carbonisation (HTC) Mainly CO2 Soluble organics and inorganics 20% solids Higher HHV ( 25 MJ/kg), friable, coal like o C, bar 2

3 Feedstocks Any feedstock can be processed by HTC Advantages for wet feedstocks Pumping and feeding an important consideration Integration with AD can be difficult with some feedstocks Need to understand potential for different feedstocks, blended feedstocks and different integration strategies 5

4 Hydrothermal carbonisation (HTC) Processing High pressure batch reactors (80ml to 2 L) Process variables (temp, time, loading) Conventional vs microwave heating Characterisation of products BioCoal/Hydrochar characterisation Fuel properties, agronomic, environmental Analysis and treatment of process water 2L reactor 500 ml reactor Feedstocks Variable levels of lignin, protein, lipid, ash 6

5 Energy densification by HTC Low moisture High moisture Processed at 10 % solids * 1. Smith AM; Singh S; Ross AB (2016) Fate of inorganic material during hydrothermal carbonisation of biomass: Influence of feedstock on combustion behaviour of hydrochar. Fuel, 169, pp Smith AM; Ross AB (2016) Production of bio-coal, bio-methane and fertilizer from seaweed via hydrothermal carbonisation. Algal Research, 16, pp

6 Bio-Coal properties Deoxygentation results in: Increased Energy Density More coal like fuel Influence of Temperature: Higher HHV Reduced O/C Effects demineralisation 8

7 Demineralisation HTC leads to significant demineralisation Big reduction in fouling Reduces fuel slagging and fouling propensity Improved properties for combustion and gasification Potential for recovery of extracted minerals from water Some extraction of NH 4+ and PO 4 3- Extraction is highly feedstock dependent! 9

8 Slagging, fouling and corrosion Ash = metal oxides in fuel Can be problematic Slagging = melting and fusion of ash in furnace low temp = high temp (1500 ) = K + Na lower melting temperature Ca + Mg increase melting temperature Fouling = formation of corrosive alkali chlorides on heat exchangers K + Na + Cl + S problematic 10

9 Ash fusion tests Ash fusion test using an ash fusion oven Original sample Shrinkage Deformation Hemisphere Flow Other indexes include Slagging index (SI), fouling index (FI) and slag viscosity index SVI) 11

10 Slagging and fouling AI-alkali index, BAI- bed agglomeration index, R b/a Acid base ratio, SI slagging index, FI fouling index, SVI slag viscosity index. 12

11 Ash fusion test example 13

12 Rate of Combustion Burning profiles Coal vs Biomass 0.02 Miscathus Raw Coal Volatile burn Fixed carbon burn Temperature (⁰C) Biomass = two stage; Coal = continuous burn Different burning profiles can make co-firing challenging. 14

13 Rate of Combustion Burning profile of BioCoal 0.02 Miscathus Raw HTC 250 Coal HTC 250 = continuous burn Temperature (⁰C) HTC reduces two stage profile becoming largely single stage at HTC 250 Production of high quality bio-coal from early harvested Miscanthus by hydrothermal carbonisation Smith A, Whittaker C, Shield I, Ross AB submitted to FUEL and under review. 15

14 Grindability Coal: Lignocellulosics: 0-15 Torrefaction: Grinding Resistance (HGI) Alkali Index Fuel Chlorine wt%(db) Miscanthus Raw Miscanthus HTC Miscanthus HTC HGI index assesses resistance to crushing - energy requirement in grinding PF coal combustion requires 70% fuel below 75µm for 100% combustion Production of high quality bio-coal from early harvested Miscanthus by hydrothermal carbonisation Smith A, Whittaker C, Shield I, Ross AB submitted to FUEL and under review. 16

15 % Moisture Moisture retention profiles of HTC bio-coal Samples dried then rehydrated at 100% RH Moisture retention profiles measured at 70% RH RAW BIOMASS Moisture content reduces rapidly for HTC bio-coals Moisture retention linked to oxygen functionality Linked to reduction in hydroxyl and carbonyl groups HTC BIOCOAL 0 Hours 24 Hours 48 Hours 72 Hours HTC Bio-Coal are hydrophobic! 17

16 Bio-Coal yields from HTC Low moisture High moisture Processed at 10 % solids 1. Smith AM; Singh S; Ross AB (2016) Fate of inorganic material during hydrothermal carbonisation of biomass: Influence of feedstock on combustion behaviour of hydrochar. Fuel, 169, pp Smith AM; Ross AB (2016) Production of bio-coal, bio-methane and fertilizer from seaweed via hydrothermal carbonisation. Algal Research, 16, pp

17 Aqueous Co-product Potential Uses % original organic matter Complex mixture of sugars, organic acids, phenols and inorganic salts Recovery of C essential Efficiency Waste disposal a) Extract chemicals? b) Anaerobically digest? CH 4 c) Recycle waters? Chemicals Feed HTC HTC Coal AD HTC Coal Coal 19

18 Typical composition of process waters ph range from TOC range from 10,000 20,000 mg/l C/N ratio from 8-14 Ammonium mg/l Phosphate mg/l Process water typically contains around 15% mineral matter and 85% VM Typical components in process water Sugars VFA Other Glucose Acetic acid Furfural xylose Formic acid 4-HMF Org-N Lactic acid phenols PO 4 3- Citric acid NH 4 + Increasing temperature 20

19 Integration with AD HTC 200 o C # Considerable potential for enhanced energy recovery from process water by AD Inhibition and biodegradability of process water is under investigation HTC 250 o C Inhibition is highly feedstock and temperature dependent. # based on theoretical bio-methane potential of process water 21

20 Experimental Bio-methane potential BMP of process waters Lower temp HTC shows higher BD Less inhibition 10g/L inoculum: 1.5g COD substrate Evaluation and comparison of product yields and bio-methane potential in Sewage digestate following hydrothermal treatment. C. Aragon-Briceno, A. B. Ross and M. A. Camargo-Valero, under review 22

21 Conclusions HTC = potential pre-treatment for biomass and waste Significant improvement in Combustion and gasification behaviour Significant opportunity for Integration with AD Biomass Low bulk density High moisture Low calorific value Hydrophilic Difficult to mill Slagging and Fouling propensity HTC Bio-Coal Higher bulk density? low moisture High calorific value Hydrophobic Easily friable No Slagging and Fouling 25

22 Acknowledgements: EPSRC CDT in low carbon technologies EP/G036608/1 EPSRC CDT for Bioenergy EP/L Supergen Bioenergy Hub grant EF/J Petroleum Institute Scholarships Mexican Government Scholarship Scheme Thank you for your attention. Andy Ross: 26

23 Hydrothermal Research Group - Leeds Aidan Smith Dr Ugo Ekpo Aaron Brown Kiran Palmer Christian Aragon Briceno Iram Razaq Gillian Finnerty James Hammerton Dr Andy Ross Dr Miller Camargo- Valero 27