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ENERGY GENERATION FROM MUNICIPAL SOLID WASTE

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ENERGY  GENERATION FROM MUNICIPAL SOLID WASTE Powered By Docstoc
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                          CONTENTS
1.   Introduction
2.   What is Municipal solid waste
3.   Waste to waste technologies
4.   Physical WTE systems
5.   Thermal WTE systems
          i) Incineration/WTE combustion
         ii) Pyrolisis and Thermal gasification
         iii) Plasma Arc Gasification
6.   Biological WTE systems
7.   Conclusion
8.   References


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               INTRODUCTION
In early days disposal of human and other wastes did not
pose any serious problems, since the population was small
and the amount of land available for accumulation of
waste was large.

 Now the scenario has changed, due to rapid urbanization
and industrialization, which has resulted in tremendous
increase in the migration of public towards urbanized
pockets.

As a result the waste management has now become a
major issue of concern today.                          3
In the modern era, with the advancement of
 technology, attempts are being made to
 explore the potential recovery of energy from
 the city’s Municipal Solid Waste.

Today a new generation of Waste-to-energy
 technologies is emerging, which hold a
 potential to create renewable energy from
 waste matter including Municipal solid wastes,
 industrial wastes and agricultural wastes.

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What is Municipal Solid Waste(MSW)
 MSW is an unavoidable by product of human activities.


 It includes durable goods, non durable goods, containers and
  packing, food wastes, cardboard, rubber, leather, textiles
  wood, paper, glass, plastics etc.

 It includes waste from residential ,commercial, and
  institutional sources , e.g. schools, government offices etc

 However they do not include all forms of solid wastes such as
  construction and demolition debris, industrial process wastes
  and sewage sludge.
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WASTE-TO-ENERGY(WTE)
   TECHNOLOGIES




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PHYSICAL
 Physical WTE technology mechanically process waste to
 produce forms more suitable for use as fuel producing
 refuse-derived fuel(RDF) or solid recovered
 fuel(SRF)

THERMAL
Thermal WTE technology use heat or combustion to treat
waste

BIOLOGICAL
 Biological WTE technologies use microbes and other
 organisms to produce fuel from waste.

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PHYSICAL WTE TECHNOLOGIES.
Waste is processed to produce RDF or SRF.


RDF is a fuel produced by treating it with
 steam pressure in an autoclave. It consists of
 inorganic materials such as plastics and
 wastes.


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THE PROCESS
 The MSW is first processed to remove glass, metals and other
  materials that are not combustible (many of which can be
  recycled).

 Autoclaving (treating with high pressure steam), kills viruses
  and other pathogens, softens and flattens plastics, and
  disintegrates paper and other fibrous materials.

 The volume of wastes is reduced up to 60% and residual
  material can then be compressed into pellets or bricks and
  sold as solid fuel.

 Burning RDF is more clean and efficient but expensive.

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THERMAL WTE TECHNOLOGY

           Incineration


   Pyrolysis
 and Thermal          Plasma Arc
 Gasification         Gasification

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INCINERATION/WTE COMBUSTION
Municipal Solid waste can be   directly combusted
  in WTE incinerators as fuel in a process known as
  mass burn to produce electricity.


Heat from combustion process is used to turn water to
  steam which powers a steam turbine generator

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           HOW IT WORKS

 Incineration involves combustion of typically
      unprepared (raw or residual) MSW



Sufficient quantity of oxygen is required for full
             oxidation to take place.

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Combustion temperature is around 8500C and the waste is
converted to CO2 and H2O


Any non combustible materials(metals, glass, stones)
remain as solid called Incinerator Bottom Ash(IBA),it
contains small amount of residual carbon.


It can however give rise to pollutants emissions in air. Air
emissions include acid gas particulate matter heavy
metals, highly toxic organic compounds and dioxins.
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PYROLYSIS AND THERMAL GASIFICATION

Pyrolysis uses heat to break down organic materials
 in the absence of oxygen,(the molecules break
  down) producing a mixture of combustible gases.


Thermal gasification of waste, in contrast to
  pyrolysis, takes place in the presence of limited
  amounts of oxygen.
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                    PYROLYSIS
                                           • The syngas
                   Products                  produced can be
                                             used for
• Thermal                                   electricity heat
                    • Gaseous mixture
  degradation of                            and fuel
  MSW in the          called
                      syngas(H2+CO) is      production
  absence of
                      produced.
  oxygen                                   • Low net green
                    • Biochar is a           house
• Temperature
  ranges from         useful                 emissions & high
                      byproduct(used as     conversion
  550-1300F                                 effiiency.
                      fertilizer and for
                      CO2 absorbtion)
                                                Power
    Heating                                   generation        18
      THERMAL GASIFICATION
 Gasification is a process that chemically and physically
  changes biomass through the addition of heat in
  an oxygen-starved environment (partial
  oxidation).

 The end products of gasification include solids, ash and
  slag, liquids and synthesis gas, or syngas.



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                HOW IT WORKS
                 Waste fed
                 into primary                   Secondary
                 chamber        Syngas       chamber has a
Has a primary
chamber                         produced     burner(maintai
                 semi                          ns operating
                 pyrolysed                    temperature)
and secondary                   Used as
chamber(exce                    feed stock
ss air                          for          The combined
                 moisture and   secondary
condition)       volatile                      gases are
                                chamber       combusted.
                 components
                 released

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  PLASMA ARC GASIFICATION
WHAT IS PLASMA
 Fourth state of matter


Ionized gas at high temperature capable of
 conducting electrical current.



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   Plasma-Arc-
Gasification is a waste      This arc breaks down waste
 trearment technology that
                             primarily into elemental
uses electrical energy
                              gas and solid waste
        and high
                              (slag) in a device called
temperatures created
                               Plasma converter
 by an electrical arc
       gasifier
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Plasma-Arc Waste-to-Energy Gasification uses Plasma-
  Arc-Torch to produce temperatures as high as 13000F.

 This extreme heat breaks down wastes forming Syngas
  (mixture of H2 & CO) and a rock like solid byproduct
  called Slag (used in construction etc.)

Syngas can be converted into a variety of marketable fuels
  including ethanol, natural gas(methane) and
  hydrogen.

Plasma converters could consume nearly any type
  of waste including concrete steel and toxic chemicals but
  the technology requires large energy inputs.
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COMMERCIAL PLASMA TORCH




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PLASMA TORCH IN OPERATION




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BIOLOGICAL WTE TECHNOLOGY
Use microbes and other organisms to
 produce fuel from waste.

Techniques used: a) Methane capture/Land fill
                  b) Biogas plants
                  c) Fermentation


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METHANE CAPTURE/LAND FILL
Primary method of disposal of municipal solid
 waste


 When left undisturbed the waste produces gaseous
 by products containing CO2 and CH4 called
 Landfill gas or Biogas

This happens due to Anaerobic (O2   free)
 digestion of Organic matter
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Landfill gas can be captured    It consists of series of wells
                                drilled into the land fills and
via a Collection system
                                    connected by Plastic
                                     Piping System
                      HOW IT
                      WORKS
                                  they are used directly in
The gas can be burnt directly
                                 internal combustion
in a boiler as a heat Energy
 source. If biogas is cleaned
                                engines or fuel cells or
by removing water vapor         electricity generation
                                      via gas turbines.
       and SO2 then,                                        32
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              BIOGAS PLANTS
 Wastes and various types of bacteria are placed in an air
  tight container called digester
 The biogas produced is either burnt directly in
  boilers or cleaned and supplied as natural gas.


               FERMENTATION
 Fermentation uses yeast to generate liquid ethanol
   from biomass wastes.
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                   CONCLUSION
 Waste to energy technologies can address two sets of
  environmental issues :

  a) Land use and pollution from landfills
  b) problem of fossil fuels


 How ever they can they an be expensive.


 One of the primary objections against waste incineration is
  that burning releases particulate matter and pollutants like
  nitrogen oxides (NOx)

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 New technologies like Pyrolysis, Thermal incineration,
  plasma arc gasification avoid the pollution concerns
  around thermal incineration

 However these technologies are expensive to install and
  only some can be applied economically today.




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                         REFERENCE
1.   Bryan . F. Staley and Morton . A . Barlaz, Composition of Municipal solid
     Waste in US and the implications for carbon sequestration and methane
     yield, Journal of environmental engineering, Vol:135 ,No:10 October 1,
     2009. ©ASCE,
2.    By Lester B. Lave,1 Chris T. Hendrickson,2 Member, ASCE, Noellette M.
     Conway-Schempf,3 and Francis C. Mc Michael, Municipal Solid Waste
     recycling issues, Journal of Environmental Engineering, Vol . 125, No. 10,
     October, 1999. ASCE,

     Internet sources
1.   1) www.luxresearchinc.com
2.   2) www.altenergymag.com



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