Transcript SIMULATION OF PROCESSES FOR THERMAL DISPOSAL OF …

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

Renewable energy sources 
 e.g. Waste-to-Energy
WASTE-TO-ENERGY

Waste-to-energy (WTE) technology =
= thermal processing of wastes including
energy utilization

WTE systems  clean, reliable and
renewable energy

steam
Combustion  generation 
of wastes
of heat
sold electricity
(incineration)
sold
WASTE-TO-ENERGY
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-ENERGY
Reasons for Investment to WTE
Sources of renewable energy for electric generation
Sources
Geothermal
Total in Megawatts
% of Market
2.854
0.37
10.702
1.38
Solar
334
0.04
Wind
1.620
0.21
15.510
2.0
Nonrenewables
763.005
98.0
Total
778.515
100.0
Biomass including waste-to-energy
Total Renewable Energy *
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
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 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
IMPROVED PROCESS AND EQUIPMENT DESIGN
Research domains in improved process and equipment design
IMPROVED PROCESS AND EQUIPMENT DESIGN
(continued)
SOPHISTICATED APPROACH
EXPERIENCE IN
DESIGN AND + (ADVANCED COMPUTATIONAL
OPERATION
METHODS)
=
Improved Process Design
 Process integration (e.g. Pinch Analysis)
 MER design
 Utilities selection
 Total Site Integration
IMPROVED
DESIGN
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
FIND A SOLUTION !
greater
pumping
power
IMPROVED PROCESS AND EQUIPMENT DESIGN
(continued)
Conventional heat
exchanger
(segmental baffles)
Helixchanger
(helical baffles)
Comparison
(crude oil preheating,1 MW, 90t/hr)
Example:
p = 17 kPa
p = 44 kPa
Result:
60% reduction of operating cost
6.3% reduction of total cost
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
THERMAL TREATMENT OF HAZARDOUS
INDUSTRIAL WASTES AND
WASTE-TO-ENERGY SYSTEMS
 Originally:
 disposal
 At
of wastes (treatment of wastes)
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
EXAMPLES
Multi-purpose incinerator for processing solid and liquid wastes
INCINERATION VS. GASIFICATION
- COMPARISON
Rotary kiln vs. gasification reactor
Legend: 1 - screw conveyor
2 - fluidized
rotary kilnbed reactor
3 - cyclone
secondary combustion chamber
4 - secondary
combustion
chamber
heat recovery
steam generator
5 - heat
recovery
steam
turbine steam generator
6 - steam
off-gasturbine
cleaning system
7 -– off-gas
stack cleaning system
8 - stack
4
solid waste
4
5
7
8
3
1
2
3
2
superheated
steam
air
air
flue gas
natural gas
natural gas
6
5
7
6
flue gas
feed water
~
natural gas
Storage waste
feeding
Incineration
Gasification
Combustion
Heat recovery
Off-gas cleaning
INCINERATION VS. GASIFICATION
- COMPARISON

Discussion of comparison in the case of gasification:

Generating gaseous products at the first stage outlet up
to 10 times lower aspects influencing operating and
investment costs

Considerably lower consumption of auxiliary fuel
(natural gas) autothermal regime

Reduced size of the afterburner chamber compared to
that necessary for a comparable oxidation incineration
plant
INCINERATION VS. GASIFICATION
- COMPARISON


Discussion of comparison in the case of gasification:

Lower specific volume of gas produced reduction in
size of flue gas heat utilization and off-gas cleaning
systems 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
INCINERATION VS. GASIFICATION
- COMPARISON
Comparison of the two alternatives
Auxiliary fuel
Auxiliary fuel
Secondary
consumption
consumption
combustion
12 Nm3/hr
602 Nm3/hr
chamber
SCC
Gas output
3 570 Nm3/hr
Gas output
34 250 Nm3/hr
Alternative with a rotary kiln
Alternative with a gasification
reactor
THERMAL PROCESSING OF SLUDGE FROM
PULP PRODUCTION

Incinerator for
thermal treatment
of sludge from
pulp production
COPMLETE RETROFIT
Result: Modern up-to-date plant
RETROFIT: FIRST STAGE
Incinerator capacity vs. dry matter content in
sludge
THERMAL TREATMENT OF HAZARDOUS
INDUSTRIAL WASTES AND
WASTE-TO-ENERGY SYSTEMS - continued
EXAMPLES
Incineration unit of sludge generated in the pulp and paper plant
RETROFIT: THIRD STAGE
ECONOMICS ASPECTS
Payback [yr]
Investment return depending on MG/NG ratio
18
16
14
12
10
8
6
4
2
0
0
0,2
0,4
0,6
0,8
1
Ratio: operational time with MG / total time of operation [ - ]
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
ECONOMICS ASPECTS
Major saving of operational cost
in terms of price of 1MW of energy:
price (MG)
MG – mining gas

2/3 price (NG)
NG – natural gas
Possible saving of cost for fuel
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)
DUAL BURNER
Second stage nozzles
First stage
nozzles
Mining gas nozzle
Swirl generator
Second stage
comb. air
First stage
comb. air
Comb. air
Natural gas
Mining gas
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
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)
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
PERFORMANCE TEST
Alternative fuel
PERFORMANCE TEST
PERFORMANCE TEST
PERFORMANCE TEST
Double-tube
feeder
PERFORMANCE TEST
 Test
evaluation:
Fuel
consumption
Rotary kiln
heat balance
Fuel costs
Achievable
savings
Black oil
Alternative fuel
Heat from black
oil
kg/h
kg/h
GJ/h
%
Baseline
Performance
operation
test
1800
1500
0
500
71.2
59.3
100
83.3
Heat from
alternative fuel
GJ/h
0
11.9
%
0
16.7
Cost of black oil
Cost of
alternative fuel
Total cost
$/h
277.60
231.21
$/h
0
8.60
277.60
0
0
0
239.80
37.81
907.32
15.76
$/h
$/h
Fuel cost savings $/day
%
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
CEMENT FACTORY
 Potential
for savings in a cement factory
with the same alternative fuel:
Optimistic alternative (with cost $8.66 per ton of the alternative fuel)
Heat supplied by alternative fuel: 0 %
5%
10 %
15 %
20 %
TJ / yr 1761.6 1673.52 1585.44 1497.36 1409.28
Heat
Baseline fuel
Weight kt / yr 44.597 42.368 40.138 37.908 35.678
(heavy fuel oil)
M $ / yr
Cost
5.80
5.51
5.22
4.93
4.64
TJ / yr
Heat
0 88.08 176.16 264.24 352.32
Alternative fuel
(mixture of crushed
Weight kt / yr
0
3.67
7.34 11.01 14.68
plastic, textile, paper) Cost
M $ / yr
0
0.03
0,06
0,10
0,13
M $ / yr
0
0.26
0,52
0,77
1,03
Savings
Cost
%
0
4.45
8,90 13,35 17,81
CEMENT FACTORY
 Potential
for savings in a cement factory
with the same alternative fuel:
Pessimistic alternative (with cost $17.33 per ton of the alternative fuel)
Heat supplied by alternative fuel: 0 %
5%
10 %
15 %
20 %
TJ / yr 1761.6 1673.52 1585.44 1497.36 1409.28
Heat
Baseline fuel
Weight kt / yr 44.597 42.368 40.138 37.908 35.678
(heavy fuel oil)
M $ / yr
Cost
5.80
5.51
5.22
4.93
4.64
TJ / yr
Heat
0 88.08 176.16 264.24 352.32
Alternative fuel
(mixture of crushed
Weight kt / yr
0
3.67
7.34 11.01 14.68
plastic, textile, paper) Cost
M $ / yr
0
0.06
0,13
0,19
0,25
M $ / yr
0
0.26
0,52
0,77
1,03
Savings
Cost
%
0
3.9
7,81 11,71 15,61
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)
Air
Natural Gas
Water
Combustion Turbine
Flue/Exhaust
Gas
Gen - set
Heat Recovery
Flue/Exhaust
Gas
Steam Generator
Steam
Power to the Grid
Steam Turbine
Gen - set
Heat Exporting Unit
Steam from
Flue Gas Heat
Recovery Boiler
Exported Heat
Incoming
„Solid“ Waste
Natural Liquid
Gas
Waste
Air
Air
Waste pretreament
Ash
Rotary Kiln & Secondary
Combustion Chamber
Flue Gas
Flue Gas
Water
Steam to
Steam Turbine
Flue Gas Heat
Recovery Boiler
Flue Gas
NaHCO3 Injection Assembly
& Chemical Reactor
Flue Gas
Close Coupled
Gasifier Combustor
Waterwide
Steam
Flue Gas Heat
Recovery Boiler
Ash
Water
Flue Gas
NaHCO3 Injection Assembly
& Chemical Reactor
Flue Gas to Fly
Ash Separation
Flue/Exhaust
Gas
Air
Fly Ash Separation
Fly Ash
Natural
Gas
Fabric Filter
Flue Gas
Separated Fly Ash
Vitrification Unit
Selective Catalytic
Air to Rotary Kiln
& Secondary
Combustion
Chamber
Reduction Facility
Flue/Exhaust
Gas
Flue Gas
Fluidized Bed Sterilizing
- Drying Unit
Fertilizers
Glass Products
Flue / Exhaust
Gas
Air
Concentrated Waste
Water Treatment Sludge
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