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SOME ASPECTS CONTRIBUTING TO WASTE-TO-ENERGY AND ENVIRONMENTAL PROTECTION. Petr Stehlik Technical University of Brno, Czech Republic. INTRODUCTION. Present situation: Energy saving and pollution prevention = priorities Sustainability concepts = complex problem

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Some aspects contributing to waste to energy and environmental protection

SOME ASPECTS CONTRIBUTING TO WASTE-TO-ENERGY AND ENVIRONMENTAL PROTECTION

Petr StehlikTechnical University of Brno, Czech Republic


Introduction
INTRODUCTION ENVIRONMENTAL PROTECTION

Present situation:

  • Energy saving and pollution prevention = priorities

  • Sustainability concepts = complex problem

  • Renewable energy sources   e.g. Waste-to-Energy


Waste to energy
WASTE-TO-ENERGY ENVIRONMENTAL PROTECTION

  • Waste-to-energy (WTE) technology = = thermal processing of wastesincluding energy utilization

  • WTE systems  clean, reliable and renewable energy

Combustion of wastes (incineration)

generation of heat

steam

sold

electricity

sold


Waste to energy1
WASTE-TO-ENERGY ENVIRONMENTAL PROTECTION

Environmental Benefit:

  • WTE prevents the release of greenhouse 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


Waste to energy2
WASTE-TO-ENERGY ENVIRONMENTAL PROTECTION

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


Sustainable development efficient design and renewable energy sources in the process industry
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


Sustainable development efficient design and renewable energy sources in the process industry1
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


Process waste and energy
PROCESS, WASTE AND ENERGY ENERGY SOURCES IN THE PROCESS INDUSTRY


Improved process and equipment design
IMPROVED PROCESS AND EQUIPMENT DESIGN ENERGY SOURCES IN THE PROCESS INDUSTRY

Research domains in improved process and equipment design


Improved process and equipment design continued
IMPROVED PROCESS AND EQUIPMENT DESIGN ENERGY SOURCES IN THE PROCESS INDUSTRY(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


IMPROVED PROCESS AND EQUIPMENT DESIGN ENERGY SOURCES IN THE PROCESS INDUSTRY(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 !


IMPROVED PROCESS AND EQUIPMENT DESIGN ENERGY SOURCES IN THE PROCESS INDUSTRY(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


IMPROVED PROCESS AND EQUIPMENT DESIGN ENERGY SOURCES IN THE PROCESS INDUSTRY(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


Thermal treatment of hazardous industrial wastes and waste to energy systems
THERMAL TREATMENT OF HAZARDOUS INDUSTRIAL WASTES AND ENERGY SOURCES IN THE PROCESS INDUSTRYWASTE-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)


Thermal treatment of hazardous industrial wastes and waste to energy systems continued
THERMAL TREATMENT OF HAZARDOUS INDUSTRIAL WASTES AND ENERGY SOURCES IN THE PROCESS INDUSTRYWASTE-TO-ENERGY SYSTEMS - continued

EXAMPLES

Multi-purpose incinerator for processing solid and liquid wastes


Legend: 1 - screw conveyor 4 - secondary combustion chamber 2 - fluidized bed reactor 5 - heat recovery steam generator

3 - cyclone 6 - steam turbine 7 - off-gas cleaning system

8 - stack

Legend: 1 - screw conveyor 4 - heat recovery steam generator

2 - rotary kiln 5 - steam turbine

3 - secondary combustion chamber 6 - off-gas cleaning system

7 – stack

4

4

5

7

8

3

1

2

3

7

6

2

6

5

natural gas

natural gas

Incineration

Gasification

Combustion

~

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


INCINERATION VS. GASIFICATION - COMPARISON chamber

  • Discussion of comparisonÞ 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


INCINERATION VS. GASIFICATION - COMPARISON chamber

  • Discussion of comparisonÞ 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


Gas output chamber

34 250 Nm3/hr

Gas output

3 570 Nm3/hr

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


THERMAL chamberPROCESSING OF SLUDGE FROM PULP PRODUCTION

Incinerator for thermal treatment of sludge from pulp production


COPMLETE RETROFIT chamber

Result: Modern up-to-date plant


Retrofit first stage
RETROFIT: FIRST STAGE chamber

Incinerator capacity vs. dry matter content in sludge


Thermal treatment of hazardous industrial wastes and waste to energy systems continued1
THERMAL TREATMENT OF HAZARDOUS INDUSTRIAL WASTES AND chamberWASTE-TO-ENERGY SYSTEMS - continued

EXAMPLES

Incineration unit of sludge generated in the pulp and paper plant


RETROFIT: THIRD STAGE chamber

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


RETROFIT: THIRD STAGE chamber

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


DUAL BURNER chamber

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)


DUAL BURNER chamber


Utilisation of Alternative Fuels chamberin 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


PERFORMANCE TEST chamber

  • 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)


PERFORMANCE TEST chamber

  • 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


PERFORMANCE TEST chamber

Alternative fuel




PERFORMANCE TEST chamber

Double-tube

feeder


PERFORMANCE TEST chamber

  • Test evaluation:


PERFORMANCE TEST chamber

  • 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


CEMENT FACTORY chamber

  • Potential for savings in a cement factory with the same alternative fuel:


CEMENT FACTORY chamber

  • Potential for savings in a cement factory with the same alternative fuel:


Thermal treatment of hazardous industrial wastes and waste to energy systems continued2
THERMAL TREATMENT OF HAZARDOUS INDUSTRIAL WASTES AND chamberWASTE-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)


Air chamber

Natural Gas

Water

Flue/Exhaust

Gas

Flue/Exhaust

Gas

Combustion Turbine

Gen - set

Heat Recovery

Steam Generator

Steam

Power to the Grid

Steam Turbine

Gen - set

Heat Exporting Unit

Steam from

Flue Gas Heat

Recovery Boiler

Exported Heat


Incoming chamber

„Solid“ Waste

Natural

Gas

Liquid

Waste

Air

Air

Close Coupled

Gasifier Combustor

Waterwide

Flue Gas Heat

Recovery Boiler

Flue Gas Heat

Recovery Boiler

NaHCO3 Injection Assembly

& Chemical Reactor

NaHCO3 Injection Assembly

& Chemical Reactor

Ash

Waste pretreament

Rotary Kiln & Secondary

Combustion Chamber

Ash

Flue Gas

Water

Water

Steam to

Steam Turbine

Flue Gas

Flue Gas

Flue Gas to Fly

Ash Separation

Flue Gas

Flue Gas

Steam


Flue/Exhaust chamber

Gas

Natural

Gas

Air

Fly Ash

Fly Ash Separation

Fabric Filter

Flue Gas

Glass Products

Flue/Exhaust

Gas

Air to Rotary Kiln

& Secondary

Combustion

Chamber

Fluidized Bed Sterilizing

- Drying Unit

Separated Fly Ash

Vitrification Unit

Selective Catalytic

Reduction Facility

Flue Gas

Air

Concentrated Waste

Water Treatment Sludge

Fertilizers

Flue / Exhaust

Gas


Conclusion
CONCLUSION chamber

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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