hydrothermal carbonization (htc) for solid recovery of...

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Hydrothermal Carbonization (HTC) for Solid Recovery of Organic Fractions in Municipal Solid Waste (OFMSW) Zhang Junting, Li Guangming*, He Wenzhi, Huang Juwen, Zhu Haochen Corresponding author: Li Guangming, [email protected], 2017-06-23 Tongji University, Shanghai, China College of Environmental Science & Technology 5 th International Conference on Sustainable Solid Waste Management

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Page 1: Hydrothermal Carbonization (HTC) for Solid Recovery of ...uest.ntua.gr/athens2017/proceedings/presentations/... · Solid Recovery of Organic Fractions in Municipal Solid Waste (OFMSW)

Hydrothermal Carbonization (HTC) forSolid Recovery of Organic Fractions inMunicipal Solid Waste (OFMSW)

Zhang Junting, Li Guangming*, He Wenzhi, Huang Juwen, Zhu Haochen

Corresponding author: Li Guangming, [email protected], 2017-06-23

Tongji University, Shanghai, ChinaCollege of Environmental Science & Technology

5th International Conference onSustainable Solid Waste Management

Page 2: Hydrothermal Carbonization (HTC) for Solid Recovery of ...uest.ntua.gr/athens2017/proceedings/presentations/... · Solid Recovery of Organic Fractions in Municipal Solid Waste (OFMSW)

• The organic fractions in MSW (OFMSW) accounts for 47%-62% of MSW in developing countries (Figure 1) ;

• These kinds of waste mainly consist of organic matter along with high content of moisture since generation.

• Sludge• Garden waste• Food waste

(High content of moisture, carbohydrates, lipid, salts and pathogens)

• Other package waste

Increasing Amount of OFMSW

01Figure 1. Composition of MSW in developing countries by region

Page 3: Hydrothermal Carbonization (HTC) for Solid Recovery of ...uest.ntua.gr/athens2017/proceedings/presentations/... · Solid Recovery of Organic Fractions in Municipal Solid Waste (OFMSW)

5th International Conference on Sustainable Solid Waste Management 02

• Lowers average heating value (HV) of MSW;

• Unexpected interactions during waste collection, transportation, and disposal.

Conventional treatments• Generally time consuming

and have strict requirements for precursors;

• High content of moisture, lipid, salts and pathogens are unfavorable.

Bioconversion methods• A series of thermochemical

approaches including gasification, pyrolysis and hydrothermal carbonization (HTC) method

Thermochemical Recovery

Organic waste treatments

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Table 1. Comparison of gasification, pyrolysis and hydrothermal carbonization(HTC)

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Char-deriving Treatments

Table 1 compared process conditions and products between gasification, pyrolysis and hydrothermal carbonization. During these methods, energy is maintained within solid product known as ‘biochar’ or ‘hydrochar’to obtain higher HV and maximize the added value of recovery products after treatment.

HTC has been recognized as wet process that operates with moisture as heating medium on the country to pyrolysis and gasification. Hydrothermal methods are a sort of novel thermal conversion process, with wet, moisture as heating medium;relatively low temperature; autogenouspressure. Less requirement of feedstock drying process suggested HTC favorable for treating wet OFMSW like FW.

5th International Conference on Sustainable Solid Waste Management

Page 5: Hydrothermal Carbonization (HTC) for Solid Recovery of ...uest.ntua.gr/athens2017/proceedings/presentations/... · Solid Recovery of Organic Fractions in Municipal Solid Waste (OFMSW)

Decomposition route of celluloseassumed by M. Sevilla et.al

HTC of OFMSW - Feedstocks

Figure 2. Elemental composition and bromatological analysis of OFMSW

• The bromatological analysis of OFMSW shows various recyclable compounds, where carbohydrates as the most abundant components account for more than 40% in terms of dry basis (Figure 2).

• The composition of the OFMSW produced hydrocharsuggests both dehydration and decarboxylation occur during carbonization.

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Table 2. Comparison of hydrochar generated from different organic feedstock 06

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HTC of OFMSW – Conditions

Temperature• Typical range of 15–60% dry-weight will decrease in

the solid residue;• Accelerates not only dissolution of feedstock but

also decomposition;• Organic N compounds of OFMSW were reported to

hydrolysis and dissolution.

•Residence Time• Less significant impacts comparing with

temperature;• Though residence time varies from hours to days,

most reactions take place in the first hour.

Existing ions in process water• Acid: accelerating cellulose dissolution;• Alkali: decreasing dissolution of cellulose;• Salt ions: Chlorine ions disrupt hydrogen bonding of

cellulose and promotes dissolution.

Hydrochar properties• No significant high yield while specific structures like

aromatic rings are formed;• Restrain more thermal stable compounds within solid

residues owing to the decrease in the amount of volatile compounds and thermo-sensitive molecules;

• Lower H/C and O/C atomic ratios indicating enhanced decarboxylation and dehydration reactions.

• No obvious evidence that solids yields increase with increases in residence time;

• Longer reaction time may correlate to greater energy, which can be recovered from the gas-phase.

• Presence of ferric ions also shows impacts on morphologies of generated spheres

Optimization

075th International Conference on Sustainable Solid Waste Management

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Carbon enriched char for co-combustion as energy supplement

The combustion behaviors of hydrochar are controlled by the substances in majority of OFMSW feedstock. Most hydrocharspresented good dewatering and drying properties. Thus the net calorific value of hydrochar is often higher than that first has to be dewatered or dried.Co-combustion of lignite and hydrochargenerated from coconut fibers and eucalyptus leaves proved that both two kinds of hydrochar addition improved energy conversion by increasing the burnout, tensile strengths and shortened the combustion range of the blends.

Energy balances associated with: (a) hydrothermal carbonization and (b) incineration,calculated by Liang Li et.al

5th International Conference on Sustainable Solid Waste Management

Feasible use of hydrochar I

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Highly functional carbon material as soil amendment for carbon storage

Small clusters of microspheres are found in pure carbohydrates-generated hydrochars in previous research with core and shell structures. The morphologies of the hybrid carbon materials derived from KW presented similar structure with those made by pure saccharides. Interesting products such as peat or humus can be gained for soil improvement.Approximately less than 10% of the carbon is released as gas (mainly carbon dioxide) after HTC Of OFMSW accordingly. Therefore, if using hydrochar as soil amendment for carbon storage, the total gas produced during HTC results in fewer emissions.

SEM picture of hydrochars generated from (a) cellulose and (b) kitchen waste,Presented by M. Sevilla and Fushen Zhang et.al

Structure of hydrochar particles from cellulose by M. Sevilla et.al

5th International Conference on Sustainable Solid Waste Management

Feasible use of hydrochar II

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Industrial application of HTC

Table 3. In-used industrial HTC plant5th International Conference on Sustainable Solid Waste Management

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Pending problems during industrial application of HTC

Uncertainty of aqueous phase utilization1

2 Significant energy consumption during heating process

Industrial application of HTC

The aqueous phase from HTC is one of the main drawbacks:• Reused to heat up the reactor or introduced for reaction optimization;• Extraction of valuable in aqueous phase and recirculation is favorable.

The significant energy consumption during heating process need more efficiency and less environmental impacts:• A local biorefinery concept to exploit solar energy into combustion

energy employing wet organic waste as energy carrier;• Application of microwave irradiation results in shorten of reaction time.Ingelia’s HTC pilot plant by Martin Hitzl et.al

5th International Conference on Sustainable Solid Waste Management

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This work summarized recent research progress of HTC using OFMSW as feedstocks and concludes as below:

• The high content of carbohydrates in OFMSW is quite promising for carbon enrichment during HTC treatment. The carbon content of recovered solid products (hydrochar) can be predicted with chemical properties of feedstock. Thus, OFMSW with high initial carbon content, such as food waste, is commonly favorable for energy-rich hydrochar generation.

• Besides initial properties of OFMSW, reaction conditions also have significant effects on hydrochar properties. To properly increase the reaction temperature and extent reaction time are both desirable for carbon recovery.

• Combustion of HTC-generated hydrocharas alternative fuel is the main industrial application for OFMSW treatment. Two main obstacles for HTC industrial application are the uncertainty of aqueous phase utilization and significant energy consumption during heating process. TheHTC treatment can be improved with microwave assisted heating system and utilization of process water for future industrial application.

• Feasible use of hydrochar generated from OFMSW includes energy supplement and soil amendment. Co-combustion of lignite and hydrochar shows promising result.The application of hydrochars as soil amendment turns to has least environmental impact with limited gas emissions.

Conclusion

5th International Conference on Sustainable Solid Waste Management

Page 13: Hydrothermal Carbonization (HTC) for Solid Recovery of ...uest.ntua.gr/athens2017/proceedings/presentations/... · Solid Recovery of Organic Fractions in Municipal Solid Waste (OFMSW)

Thanks foryour attention!

College of EnvitonmentalScience & Engineering

For more info please contact us:

Tongji University, Shanghai, ChinaEmail: [email protected]

Corresponding author: Li Guangming, [email protected], 2017-06-23

5th International Conference onSustainable Solid Waste Management