Title: SOME ASPECTS CONTRIBUTING TO WASTETOENERGY AND ENVIRONMENTAL PROTECTION
1SOME ASPECTS CONTRIBUTING TO WASTE-TO-ENERGY AND
ENVIRONMENTAL PROTECTION
Petr Stehlik Technical University of Brno,
Czech Republic
2INTRODUCTION
- Present situation
- Energy saving and pollution
prevention priorities - Sustainability concepts complex problem
- Renewable energy sources ? ? e.g.
Waste-to-Energy
3WASTE-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
4WASTE-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
5WASTE-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
8PROCESS, WASTE AND ENERGY
9IMPROVED PROCESS AND EQUIPMENT DESIGN
Research domains in improved process and
equipment design
10IMPROVED 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
11IMPROVED 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 !
12IMPROVED 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
13IMPROVED 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
14THERMAL 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)
15THERMAL TREATMENT OF HAZARDOUS INDUSTRIAL WASTES
AND WASTE-TO-ENERGY SYSTEMS - continued
EXAMPLES Multi-purpose incinerator for
processing solid and liquid wastes
16INCINERATION 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
17INCINERATION 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
18INCINERATION 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
19INCINERATION 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
20THERMAL PROCESSING OF SLUDGE FROM PULP PRODUCTION
- Incinerator for thermal treatment of sludge from
pulp production
21COPMLETE RETROFIT
Result Modern up-to-date plant
22RETROFIT FIRST STAGE
- Incinerator capacity vs. dry matter content in
sludge
23THERMAL TREATMENT OF HAZARDOUS INDUSTRIAL WASTES
AND WASTE-TO-ENERGY SYSTEMS - continued
EXAMPLES Incineration unit of sludge
generated in the pulp and paper plant
24RETROFIT 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
25RETROFIT 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
26DUAL 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)
27DUAL 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
29PERFORMANCE 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)
30PERFORMANCE 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
31PERFORMANCE TEST
Alternative fuel
32PERFORMANCE TEST
33PERFORMANCE TEST
34PERFORMANCE TEST
Double-tube feeder
35PERFORMANCE TEST
36PERFORMANCE 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
37CEMENT FACTORY
- Potential for savings in a cement factory with
the same alternative fuel
38CEMENT FACTORY
- Potential for savings in a cement factory with
the same alternative fuel
39THERMAL 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)
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41Flue Gas
Steam
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43CONCLUSION
- 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