Hydrothermal Treatment Of Solid Waste

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HYDROTHERMAL TREATMENT OF SOLID WASTE

By: ketan wadodkarM.Tech. Environment EngineeringEnrollment No. 105190131st yr.Under guidance of Dr. Renu Bhargava

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What is hydrothermal process?

It employs the combination of heat and water as a media to convert unutilized resources in various shapes and characteristics into uniform product.

It is a functional way to active reactions via dissolution.

It involves heating of raw slurry at 300-350˚C in at pressure to maintain water phase.

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It comes under chemical conversion of solid waste before MSW is sent to landfill.

It is a thermo chemical conversion technology. The other processes for recovery of solid fuel s

from MSW are: RDF (refuse-derived fuel) carboniztion

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Various uses of Hydrothermal Treatment in MSW

For solid fuel recovery method from MSW. Decomposition and oxidation of municipal

waste products. Extraction of metals from MSWI fly ash. Retention of Cs(I), Cd(II), Pb(II) and Cr(III) Liquid fertilizer production from

hydrothermally treated sewage sludge (the liquid residue obtained has possibility to be used as liquid fertilizer).

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Introduction:

About 90% solid waste produced in china is disposed in landfills.

Which caused adverse effect on land. Hence introducing this process results in

reduction in volume and thermal destruction of toxic organic components.

Hydrothermal process converts different kinds of MSW into powdered products and improving there combustion performance.

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Process:

Loading the raw material into reactor. Injecting saturated stream of about 374˚C at

22.1MPa below critical point in the reactor. Then the it is mixed with the help of stirrer

while maintaining same temperature and pressure.

After this wet uniform product is obtained and can be easily dried up to obtain solid.

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Fig: Hydrothermal Treatment

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Fig: Commercial hydrothermal treatment plant in Hokkaido, Japan

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Does not require moisture removal unlike other thermal treatment.

The moisture content of MSW can be used as heating medium to decompose MSW.

In this experiment, two saturated streams were examined: 233.9˚C and 3 MPa (LT) and 295˚C and 8 MPa (HT).

more than 85% of carbon in raw material was recovered as char, condensed liquid, and gas.

more than 80% of the recovered carbon was in the char regardless of LT and HT conditions.

Variation in yield and composition of char depending on temperature and holding time.

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Fig: experimental apparatus

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Heating value of char The high heating value (HHV):

HHV [kJ/kg] = 33,940×(C-3/8×O)+23,880×3/8×O+14,3510×(H-O/16)+9,430×S

where C, H, N, S, and O are the respective weight ratios of carbon, hydrogen, nitrogen, sulfur, and oxygen. O [–] is calculated with a mass balance.

the recovery ratio of the HHV of char produced from raw material was determined as follows:

Recovery ratio of HHV [%] = (HHVchar [kJ/kg]×char yield [%]) / HHVraw material [kJ/kg]

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The organic chlorine in high combustion temperature will be released to the atmosphere as dioxin which cause corrosion and clogging in exhaust gas lines.

The washing process is then needed to separate the inorganic (water-soluble) chlorine from the product in the form of salt, so that a chlorine-free solid fuel product from MSW.

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Fig: MSW before and after Hydrothermal Treatment

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Site: Army base camp

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Bouldin corp. technology for Hydrothermal treatment

The system includes: two shredders, a grinder, a hydrothermal process (hydrolyzer), dryer, and particle screens.

The shredded waste is then augured through the hydrolyser where it is exposed to high-pressure steam.

The process causes cellulose fibers in the paper, cardboard, food, etc. to expand, creating a soft, gray, end product appropriately named “fluff”

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Fig: Fluff

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Various hypothesis involved in this treatment Cellulose matrix is expanded by sudden

pressure release. Migration and coalescing of liquid lignin

could enhance cellulose expansion in wood and improve the reuse value of fluff.

The rapid expansion of cellulose fibers can occur at temperatures lower than currently used by Bouldin.

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Cost comparison:

Cost to landfill all the waste: $4.6million Cost to process entire waste stream by Bouldin

process: $2.339million Cost to process entire waste stream by Bouldin

process using waste wood as fuel: $1.734million

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Advantages of Bouldin techniques:

Results showed the screened fluff had excellent soil amendment properties.

Chemical analysis of the fluff confirmed the processed waste was not a characterized hazardous waste.

Analysis of air samples for particulate matter and volatile organic compounds showed that the Bouldin system generated no air pollutants of concern.

It was concluded that extruded fluff had good potential for use as a construction material, though it would be limited to specific types of use.

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Results and conclusion:

Min processing temp. lies between 120-150 ˚C. The expansion of shredded wood into a fluff-like

material was not successful. Processed waste containing a large fraction of

shredded wood is not offensive in appearance and can be used as a soil amendment without concern regarding aesthetics.

Further research into innovative base camp applications for the system is also recommended.

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References:

Google http://yk.wtert.jp/index.php?option=com_content&view=article&i

d=107&Itemid=161&lang=en Hydrothermal conversion of municipal organic waste into

resources Motonobu Goto a,*, Ryusaku Obuchi a, Tsutomu Hirose a, Tsuyoshi Sakaki b,Masao Shibata b Bioresource Technology 93 (2004) 279–284

Hydrothermal Processing of Base Camp Solid Wastes To Allow Onsite Recycling Gary L. Gerdes, Deborah Curtin, and Christopher Gutkowski September 2008 ERDC/CERL TR-08-13

RECOVERY OF SOLID FUEL FROM MUNICIPAL SOLID WASTE USING HYDROTHERMAL TREATMENT I.-H. HWANG, T. MATSUTO, H. AOYAMA, T. NAKAGISHI AND T.MATSUO Venice 2010, Third International Symposium on Energy from Biomass and Waste

L. Kacimi et al. / Journal of Hazardous Materials 181 (2010) 593–601

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