Hydrothermal carbonization for biochar production Vidar Grönberg, Hanne Wikberg VTT Technical Research Centre of Finland

Transcription

1 Place for a photo (no lines around photo) Hydrothermal carbonization for biochar production Vidar Grönberg, Hanne Wikberg VTT Technical Research Centre of Finland

2 The history of hydrothermal carbonization Hydrothermal Carbonization - Revival of an old technology Bergius (1913): Conversion of biomass to coal to be used as liquid fuel HTC at VTT: Dewatering of peat for energy ~1980 Conversion of biomass to advanced applications > Carbon-nanofibers made from glucose by hydrothermal carbonization (Qian et al. 2006) Bergius process: Ruin of a coal-to-liquid production plant (1940s) 27/03/2015 2

3 Hydrothermal processes 27/03/2015 3

4 Hydrothermal carbonization (HTC) + Heating Raw material suspending and mixing HTC reaction - Gas phase Filtering / sentrifuging Drying + H 2 O (+ additives) - Cooling Liquid phase Solid HTC carbon Typical temperature range C, self-generated pressures ~20-50 bars. Reactions in water (no drying stage before the treatment). Dry matter ~5-30%, even higher. All kind of biomass and organic waste materials can be used as feedstock. Residence time a few hours. The ph value normally below 7. Catalyst, for example citric acid, can be used. Reaction is exothermic. Water can be recirculated in the process. 27/03/2015 4

5 HTC products of biomass Solid HTC coal represents an agglomeration of different chemical substances several potential applications Liquid phase has a high load of inorganics and organics (as well as solid particles which cannot be recovered marked as total organic carbon, TOC) potentially valuable chemicals The proportion of gas is very small, mainly carbon dioxide and small amounts of other gases such as methane, ethane, propene and butane. Products of hydrothermal carbonisation of biomass, separated according to their state of aggregation (Funke and Ziegler 2010) 27/03/2015 5

6 HTC reaction mechanisms 6

7 HTC raw materials 1/2 Wood polymers Lignin: + Inexpensive + Attractive among customers - Hard to carbonize in HTC - Contains impurities (e.g. S, Na) which are unwanted in some applications Cellulose + Very potential in producing high value added solid and liquid products - Price? Hemicellulose + Very potential in producing high value added solid and liquid products - Availability - Price Wood residues (e.g. woodchips, bark, leaves, etc.) + Inexpensive + General interest in renewable bioresources - Raw material variations - Might need pretreatment prior to HTC (e.g. grinding) Glucose Birch bark Lignin Black liquor 27/03/2015 7

8 HTC raw materials 2/2 Agricultural residues (e.g. straw, grasses, BSG, bagasse, animal manure, etc.) + Inexpensive + Large global markets - Collection infra is missing/patchy Municipal sewage sludge Algae + Inexpensive waste (gate fees) + Includes nutrients - Large (seasonal) variations of the raw material - For low value products mainly (e.g. energy, landfill) + Inexpensive - Low concentrations in the feed Forest industry side streams (e.g. black liquor, dissolving pulp side stream, deinking water, biosludge, etc.) Black liquor + Inexpensive + Availability - Contains impurities which are unwanted in some applications Prehydrolysate from kraft dissolving pulp process + Very potential in producing high value added solid and liquid products - Availability 27/03/2015 8

9 HTC carbon properties Property Carbon content Carbon type Particle size Particle shape Impurities Heating value Description Maximum carbon content in HTC ~70% (e.g. glucose originally from 40% to 70% in HTC; lignin originally from 65% to 70% in HTC). Other elements mainly oxygen ~20% + hydrogen+impurities. Further activation can be used to increase the carbon content >90%. Amorphous carbon-rich material. Porosity depend on the raw material (e.g. glucose more porous than lignin). HTC carbon materials have inhomogeneous particle size distribution depending much on the raw material (e.g. number average particle size for lignin nm and volume average 10-50microns). Most of the particles are in nanoscale (or a few microns) but larger aggregates/agglomerates exist. Distribution can be affected by the raw material feed form and posttreatments, such as fluidization or fractionation. Depend on the raw material (e.g. glucose spherical, lignin irregular, hard and cubical). Depend on the raw material, migration of the impurities can be affected during the HTC-process. References from the literature ~25-30MJ/kg 27/03/2015 9

10 Current status of the potential applications 1/5 Carbon black: Carbon black is a form of amorphous carbon having dimensions in nanometer scale. Surface areas are in the range of ~ m 2 /g. Carbon black is in the top 50 industrial chemicals manufactured worldwide, based on annual tonnage. The current worldwide production is about 18 billion pounds per year (8.1 million metric tons). In 2010, the demand for carbon black was estimated to reach 11.6 Mt in 2013 increasing to13.8 Mt in Approximately 90% of carbon black is used in rubber applications, 9% as a pigment, and the remaining 1% as an essential ingredient in hundreds of diverse applications. Price depends on the purity and varies from ~500 /t 3300 /t? Activated carbon: Activated carbon is a micro-porous carbon with large surface area ranging from ~ m 2 /g being a good adsorbent material for purification and separation. Wood and coal are currently the most common raw materials used for production. Since a large share of activated carbons are already produced from bio-based raw materials, the bio-based content may not be a very strong selling point. The global demand for activated carbons has increased in the last decade from t to (2001) to t (2011) annual growth rate being 8,9%. The average price in 2012 according to the import and export statistics in Europe for selected countries (India, China, USA, Japan) was 1,8 /kg, but the average price of the imported activated carbon from Japan was 8,4 /kg. The price of activated carbon is highly dependent on the purity, product properties, etc. 27/03/

11 Current status of the possible applications 2/5 Electrode carbon: Quality parameters in the applications are purity, chemical and physical stability and conductivity of electricity and heat. The global market is around 20 Mt per year. Price for the electrodes ranges ~ /t. Electrodes in batteries Electrodes in supercapacitors: Porous carbon materials (e.g. activated carbon) are the main candidate for supercapacitors in terms of cost, availability, large surface area, versatility in porosity and surface chemistry, good conductivity and lack of negative environmental impact. Total markets in 2010 was about 345 M, forecast for 2015 about 876 M. Pigment: Carbon black has a higher tinting strength compared to iron black or organic pigments, and it is widely used in newspaper inks, printing inks, India inks, and paints. It is also thermally stable, and therefore suitable for coloring resins and films that are heatformed. Carbon black is also used as black pigment for inkjet ink or toners. A few of these special pigment grades have carbon contents below 90%. Catalyst carrier: Porous carbon materials are ideal candidates as supports for various nanoparticles. Depending on the functional groups present on the carbon and its porosity, the size and the shape of the nanoparticles can be controlled leading to size-selective and reusable heterogeneous catalysts. 27/03/

12 Current status of the possible applications 3/5 Nanocomposite/hybrid material: Coating of preformed nanostructures in HTC to form nanocomposites for many applications, such as catalysis, fuel cells, drug delivery and bioimaging is one of the most academically studied reserach area related to HTC. HTC carbons have also different functional groups on the surface (e.g. hydroxyl, aldehyde, carboxyl groups) which can be utilized for further modification. Tribology: Green lubrication and low friction surface solutions are major development topics for machinery used in e.g. food processing and cosmetics. Soft carbon particles are a natural match as additives for such solutions due to suitable physical properties and chemical compatibility. HTC produces spherical soft particles that can be used in special purposes as additives in lubricants and low friction surfaces. There is also a market pull for green lubricant solutions which do not exist at the moment and a need for energy savings in machinery by reduction of friction. Additives in lubricants and carbon coatings are fossil-based at the moment and are relatively expensive. There are markets for environmentally friendly solutions, especially with reduction in material costs (e.g. with water-based lubricants, with low-wear coatings). Mineral oil-based lubricant formulations are the largest product segment and volume (96.8% of the overall consumption in 2011). Lubricating oils consist of ~93% base oil and 7% additives. In 2011, approx. 37 million tons of lubricants were consumed worldwide, and the consumption is expected to reach 42 million tons by In 2011, the global markets were worth 32 billion euros. Metallurgical carbon: Carbon as a reductant, additive or filler is an essential element in the processing of metallic ores and the manufacture of iron and steel in the metallurgical industry. In most cases, the element carbon is derived from coal and its carbon derivatives. The properties of carbon required for the different processes in each metallurgical sector vary significantly. 27/03/

13 Current status of the possible applications 4/5 Chemicals / nutrients: HTC liquid phase contains high loads of inorganics and organics such as organic acids, aromatics and furanic compounds (e.g. HMF), as well as inorganic ions and metals, many of which might be potentially valuable substances for chemical industry as valuable chemicals/intermediates. This liquid phase is not, however, well studied and utilized at the moment. Soil amendment / fertilizer Waste stream conversion to value-added products via HTC is attractive way to utilize cheap raw materials. However, waste materials contains often unwanted substances, such as toxic materials and e.g. metals which are not desired for certain valueadded products. HTC biochar from waste could be used as an adsorbent in environmental remediation applications or soil amendment, even solid fertilizer. Land application of biochar can increase the carbon content of the soil and improving its fertility. In addition, the potentially harmful compounds that currently pose significant environmental concerns in landfills, such as pharmaceuticals, are thermally degraded during carbonization. The research is, however, in its infancy even though most companies interested in HTC keep an eye on research in the soil application area in order to support evaluation of biochar potential for increasing soil fertility and/or carbon sequestration. Cement / asphalt additive Carbon blacks having lower carbon content have been used to produce a carbon-rich powder with semi-reinforcing characteristics used in modified asphalts as a compatible additive for road constructions. 27/03/

14 Current status of the possible applications 5/5 Energy HTC-carbon can be used as a source of fuel. However, the emissions of particulate matter, sulphur compounds, nitric oxides, hydrocarbons, and other gases resulting from the combustion of fuel is regulated. HTC carbon would probably need pelletizing in this application. The European companies active in HTC process development are particularly concentrating on converting wet organic waste to biochar for energy recovery. The economic viability at the moment is mainly based on renewable energy source regulations and subsidies. 27/03/

15 HTC is being introduced for waste treatment 27/03/

16 Why HTC? The process converts wet input material into carbonaceous solids Materials with low dry content (5-30 wt-%) can be processed. HTC requires less solids processing and treatment, such as chemical or mechanical dewatering of bio-solids. Basically, all kind of biomass materials can be used: Traditional: wood, cellulose, lignin, plant tissue, resin, peat.. Nontraditional: wet animal manures, human waste, sewage sludge, municipal solid waste, algae.. The process takes only hours, instead of the days or months required for biological processes. High process temperatures will destroy pathogens and potentially organic contaminants such as pharmaceutically active compounds potentially toxic materials can be processed. Useful solid, liquid and gaseous end-products can be produced. The structure of the product can be controlled by process parameters several possible applications depending on the structure. The mass yield is rather high (~35-70 %). The process is exothermic. Some of this energy can power the process. The process is carbon neutral and is therefore more environmental friendly than conventional carbon conversion routes. 27/03/

17 Evolution of carbon know-how Know-how level - research input Low value products Energy applications Soil amendment Environmental applications Added value by technology excellence Medium value products Structured carbon - carbon black - activated carbon Catalyst carriers Electrode carbon Evolutionary progress High value products Graphenes Fullerenes Nanostructures Small volumes, high price * Carbon chemistry efforts required Necessary for progress into sophisticated products *Hewitt J, Researchers successfully grow defect-free graphene, commercial uses now in sight, /03/

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