Our purpose

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Strategic Waste Management Planning in SEE,
Middle East and Mediterranean Region
Bio-drying Municipal Solid Waste in a rotary Drum
Reactor. The effect of Biomass Temperature and
Inoculation
Novi Sad 10th and 11th December, 2009
Kyriakos Hapeshis
Cyprus Research Promotion Foundation
University of Cyprus
Vassilico Cement Works
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Introduction
Increase of MSW
European Landfill Directive
540
400
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Introduction

• What is biodrying?
• Biodrying is the utilization of heat released
  during the aerobic decomposition of biodegradable
  solid waste in order to reduce the moisture
  content and partially stabilize the waste

• Limited information about control and
  optimization of biodrying of MSW
• Only Few studies are referred in the literature
  and these were conducted at laboratory scale
  using static systems
• Our study was performed in a continuously
  agitated semi-industrial scale rotary drum
  reactor

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Rotary Vs Static biodrying

• Rotary biodrying is an alternative approach to
  static methods with significant advantages
• Increases microbial activity and heat generation
  at low moisture content
• Reduces process retention time
• Improves particle size reduction
• Improves homogeneity of the end product

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Materials and Methods

• Semi industrial rotary drum with 1.2m diameter
  and 5 m length
• Paddles to increase the contact time
• between air entering and feedstock.
• enhance moisture removal
• PLC controls the process and records data

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Materials and Methods

• Shell with a 40 mm insulation of glass wool to
  reduce heat losses and improve the efficiency of
  biodrying process
• Two fans to provide airflows
• equivalent to 30m³/h and 100m³/h
• Motor with frequency controller gear
• to provide rotation speed 0.05 -0.1 rpm
• integral load cell system

Glass wool 40 mm
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Experimental Design
Rotation speed 0.1 rpm
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Fundamental conditions applied during the
experimental trials
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Temperature profiles
RESULTS

• Biomass temperature was more stable in trials
  with temperature control within the mesophilic
  range (35-40C )
• Instability observed at high process control
  temperature (1B, 2B , 1C, 2C)
• In trials with thermophilic temperature control
  and 0-10 product recycling temperature declined
  below the set point value, 1-2 days after
  starting the trials (indicating process
  inhibition related to acidification)

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pH profiles
RESULTS

• pH initially declined in all trials
• Acidification became more severe with increasing
  biomass temperature and decreasing product
  recycling
• The minimum pH values occurred in trial 1C with
  temperature control at 60C and no product
  recycling
• Acidification was less severe at all temperatures
  with increasing product recycling

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Moisture reduction (BDR)
RESULTS

• Biodrying rate increased with decreasing
  temperature and increasing product recycling
• The highest BDR occurred at 50C and 20 product
  recycling (Trial 3B)
• The lowest BDR occurred at 60C and 0 product
  recycling (Trial 1C)

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Dry solid decomposition rates profiles (DSDR)
RESULTS

• Similarly, DSDR increased with decreasing
  biomass temperature and increasing product
  recycling
• The highest DSDR occurred at 50C and 20 product
  recycling (Trial 3B)
• The lowest DSDR occurred at 60C and 0 product
  recycling (Trial 1C)

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Effect of thermal process control regime and
product recycling rate on BDR and DSDR

• BDR moisture reduction per hour
• BDR and DSDR increased with decreasing biomass
  temperature and increasing product recycling
• The highest BDR was 0.44 moisture reduction per
  hour
• The highest DSDR was 44g kg-1 d-1

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Chemical characteristics and calorific value of
SRF

• Screened material less than 30mm accounted for
  about 60-65 of the biodried output
• Volatile solid ranged from 83-87.1
• Ash content ranged from 12.5 15
• Calorific Value ranged from 10.1 16.1 MJ/kg

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DISCUSSION AND CONCLUSIONS

• Optimum temperature for biodrying shifts to
  higher values with increasing product recycling
• Rotary biodrying process can operate efficiently
  at higher temperature when adequate biodried
  product is recycled.
  .
  Lower energy consumption
• Severe acidification and acid inhibition occurred
  at thermophilic biomass temperatures and no
  product recycling
• Acidification became less severe with increasing
  product recycling and temperature control within
  the mesophilic range
• Due to presence of NH3 released from protein
  decomposition
• DSDR and BDR increased with increasing product
  recycling irrespective of the biomass temperature
  because
• increased bio-available nitrogen
• increased microbial concentration
• reduced the initial moisture content

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Thank for your attention !!