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SOME ASPECTS CONTRIBUTING TO WASTETOENERGY AND ENVIRONMENTAL PROTECTION

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Title: SOME ASPECTS CONTRIBUTING TO WASTETOENERGY AND ENVIRONMENTAL PROTECTION


1
SOME ASPECTS CONTRIBUTING TO WASTE-TO-ENERGY AND
ENVIRONMENTAL PROTECTION
Petr Stehlik Technical University of Brno,
Czech Republic
2
INTRODUCTION
  • Present situation
  • Energy saving and pollution
    prevention priorities
  • Sustainability concepts complex problem
  • Renewable energy sources ? ? e.g.
    Waste-to-Energy

3
WASTE-TO-ENERGY
  • Waste-to-energy (WTE) technology
    thermal processing of wastes including
    energy utilization
  • WTE systems ? clean, reliable
    and renewable energy

Combustion of wastes (incineration)
generation of heat
steam
?
?
sold
electricity
sold
4
WASTE-TO-ENERGY
  • Environmental Benefit
  • WTE prevents the release of greenh
    ouse gases (CH4, CO2, NOX, VOC)
  • Dual benefit clean source of electricity and
    clean waste disposal
  • Economic Benefit
  • Renewable energy
  • Reduction of need to landfill municipal
    waste

5
WASTE-TO-ENERGY
Reasons for Investment to WTE Sources of
renewable energy for electric generation
Note Source - Renewable Energy Annual 1998 -
U.S. Department of Energy, Energy
Information Administration
6
SUSTAINABLE DEVELOPMENT, EFFICIENT DESIGN AND
RENEWABLE ENERGY SOURCES IN THE PROCESS INDUSTRY
  • The following criteria can play a decisive role
  • economic and efficient process design
  • global heat transfer intensification
    (design of heat exchanger network
    for maximum energy recovery)
  • efficient selection of utilities including
    combined heat and power systems
    (co-generation) wherever possible
  • using waste-to-energy systems and/or their
    combination with conventional ones as
    much as possible

7
SUSTAINABLE DEVELOPMENT, EFFICIENT DESIGN AND
RENEWABLE ENERGY SOURCES IN THE PROCESS INDUSTRY
  • Criteria (continued)
  • design of efficient equipment
    (reactors, separators, heat
    exchangers, utility systems etc.)
  • local heat transfer intensification
    (selection and design of individual
    heat exchangers including heat transfer
    enhancement)
  • and various other criteria

8
PROCESS, WASTE AND ENERGY
9
IMPROVED PROCESS AND EQUIPMENT DESIGN
Research domains in improved process and
equipment design
10
IMPROVED PROCESS AND EQUIPMENT DESIGN (continued)
EXPERIENCE IN DESIGN AND OPERATION
SOPHISTICATED APPROACH (ADVANCED COMPUTATIONAL
METHODS)
IMPROVED DESIGN

  • Improved Process Design
  • Process integration (e.g. Pinch Analysis)
  • MER design
  • Utilities selection
  • Total Site Integration

11
IMPROVED PROCESS AND EQUIPMENT DESIGN (continued)
Improved Equipment Design
Examples
New type of Shell-and-Tube Heat Exchanger
Retrofit of an industrial process
adding a few more heat exchangers
energy saving
increased pressure losses
greater pumping power
FIND A SOLUTION !
12
IMPROVED PROCESS AND EQUIPMENT DESIGN (continued)
Conventional heat exchanger (segmental baffles)
Helixchanger (helical baffles)
Comparison
Example ?p 44 kPa
(crude oil preheating,1 MW, 90t/hr) ?p 17 kPa
Result 60 reduction of operating cost 6.3
reduction of total cost
13
IMPROVED PROCESS AND EQUIPMENT DESIGN (continued)
Optimization of Plate Type Heat Exchanger
  • Minimization of total cost
  • (utilizing relation ?p - h.t.c.)
  • Obtaining optimum dimensions
  • Example
  • Industrial unit for the thermal
  • treatment of polluting hydrocarbons
  • of synthetic solvents contained
  • in air (4.52 MW)
  • Result up to 14 reduction of annual
  • total cost can be achieved

14
THERMAL TREATMENT OF HAZARDOUS INDUSTRIAL WASTES
AND WASTE-TO-ENERGY SYSTEMS
  • Originally
  • disposal of wastes (treatment of wastes)
  • At present
  • waste processing (waste-to-energy systems)
  • recovering heat (generating steam electricity
  • preheating purposes (reduced fuel demand)
  • processing of residues (vitrification)

15
THERMAL TREATMENT OF HAZARDOUS INDUSTRIAL WASTES
AND WASTE-TO-ENERGY SYSTEMS - continued
EXAMPLES Multi-purpose incinerator for
processing solid and liquid wastes
16
INCINERATION VS. GASIFICATION - COMPARISON
Rotary kiln vs. gasification reactor
flue gas
solid waste
flue gas
superheated steam
feed water
air
air
natural gas
Storage waste feeding
Heat recovery
Off-gas cleaning
17
INCINERATION VS. GASIFICATION - COMPARISON
  • Discussion of comparison Þ in the case of
    gasification
  • Generating gaseous products at the first stage
    outlet up to 10 times lower Þ aspects influencing
    operating and investment costs
  • Considerably lower consumption of auxiliary fuel
    (natural gas) Þ autothermal regime
  • Reduced size of the afterburner chamber compared
    to that necessary for a comparable oxidation
    incineration plant

18
INCINERATION VS. GASIFICATION - COMPARISON
  • Discussion of comparison Þ in the case of
    gasification
  • Lower specific volume of gas produced Þ reduction
    in size of flue gas heat utilization and off-gas
    cleaning systems Þ reduction of investment and
    operating costs of the flue gas blower
  • Lower production of steam (proportional to the
    volume of flue gas produced)
  • Disadvantage of gasification technology
  • Treatment of wastes by crushing/shredding and by
    homogenization before feeding into the reactor

19
INCINERATION VS. GASIFICATION - COMPARISON
Comparison of the two alternatives
SCC
Auxiliary fuel consumption 12 Nm3/hr
Secondary combustion chamber
Auxiliary fuel consumption 602 Nm3/hr
Alternative with a rotary kiln
Alternative with a gasification reactor
20
THERMAL PROCESSING OF SLUDGE FROM PULP PRODUCTION
  • Incinerator for thermal treatment of sludge from
    pulp production

21
COPMLETE RETROFIT
Result Modern up-to-date plant
22
RETROFIT FIRST STAGE
  • Incinerator capacity vs. dry matter content in
    sludge

23
THERMAL TREATMENT OF HAZARDOUS INDUSTRIAL WASTES
AND WASTE-TO-ENERGY SYSTEMS - continued
EXAMPLES Incineration unit of sludge
generated in the pulp and paper plant
24
RETROFIT THIRD STAGE
ECONOMICS ASPECTS Investment return depending on
MG/NG ratio
  • The curve is valid for
  • considering depreciation, loan interest,
    inflation etc.
  • annual operation 7000 hours
  • nominal burners duty 6.4 MW (2.4 MW for fluidized
    bed combustion chamber and 4.0 MW for secondary
    combustion chamber)
  • investment of 250,000

25
RETROFIT THIRD STAGE
ECONOMICS ASPECTS Major saving of operational
cost in terms of price of 1MW of energy price
(MG) ? 2/3 price (NG) MG mining gas NG
natural gas Possible saving of cost for fuel
26
DUAL BURNER
  • ORIGINAL DESIGN
  • One fuel
  • Two stages of fuel and two stages of combustion
    air
  • LATER
  • Dual burner mining gas natural gas
    (primary fuel) (auxiliary fuel)
  • INTERESTING APPLICATION
  • Secondary combustion chamber in the incineration
    plant for thermal treatment of sludge from pulp
    production (see above)

27
DUAL BURNER
28
Utilisation of Alternative Fuels in Cement and
Lime Making Industries
  • Current situation
  • alternative fuels (wastes) used mainly in cement
    kilns
  • use of alternative fuels in lime production is
    less applied due to potential impact on product
    quality
  • practical issues of the application include waste
    specification, way of feeding, product quality,
    and emission levels

29
PERFORMANCE TEST
  • Feeding of alternative fuel
  • composition mixture of crushed plastic, textile,
    paper
  • pneumatic conveying into the kiln by special
    nozzle beside main burner
  • heating value 24 GJ/t (compared to 39.5 GJ/t of
    the baseline fuel)

30
PERFORMANCE TEST
  • Test site
  • limekiln, production capacity 370 t/d
  • rotary kiln
  • baseline feed black oil (1.8 t/h)
  • goal to feed 0.5 t/h of waste and validate
    product quality, emission levels, and the
    potential for savings

31
PERFORMANCE TEST
Alternative fuel
32
PERFORMANCE TEST
33
PERFORMANCE TEST
34
PERFORMANCE TEST
Double-tube feeder
35
PERFORMANCE TEST
  • Test evaluation

36
PERFORMANCE TEST
  • Conclusions
  • Substitution of a part of the conventional fuel
    to cover partially heat supply demands of cement
    factories
  • It is possible to achieve 10 to 20 of the
    overall energy demand of the rotary kilns
  • In the case of limekilns (where substitution of
    the noble fuels is often hindered by higher
    requirements on the final product quality) up to
    17 of the primary fuel without notable impact on
    the lime quality was achieved

37
CEMENT FACTORY
  • Potential for savings in a cement factory with
    the same alternative fuel

38
CEMENT FACTORY
  • Potential for savings in a cement factory with
    the same alternative fuel

39
THERMAL TREATMENT OF HAZARDOUS INDUSTRIAL WASTES
AND WASTE-TO-ENERGY SYSTEMS - continued
  • Waste-to-Energy Plant Structure
  • Processing of wastes of wide spectrum
  • WTE Plant Structure
  • (mutual interconnection of main units )
  • WTE utility heat output - for various purposes
  • (e.g. servicing district heating system, air
    conditioning, chilled
  • water production, exporting steam to an
    industrial plant)

40
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41
Flue Gas
Steam
42
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43
CONCLUSION
  • It has been shown how various aspects of a
    process and
  • equipment design can contribute to improving
    economic
  • and environmental design.
  • WTE systems provides us with clean, reliable and
  • renewable energy.
  • WTE systems up-to-date technology experience
  • (know-how) theoretical background
  • Examples
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