A Method for
energy
optimization and
product quality
improvement in
manufacturing
processes
Presented by: B. ABOU KHALIL
With M. BERHTOU, D. CLODIC
Summer study, June 2007
1
Centre Energétique et Procédés
Contents
1. Context
2. Energy optimization methods
3. The Process Energy Analysis (PEA)
4. Conclusion and future working program
2
1
Context
3
1
Context
I.
Environmental and political context
•
•
•
II.
Flow
Billion barrels
per year
•
•
Estimated by 2015
Decrease in productivity by 2%
per year
Increase in demand by
1.6 % per year
 Availability decreasing by
3.6% per year
Production
Peak
Depletion
1st half
“easy”
exploitation
Oil production peak
•
•
4
Earth temperature increased by
0.6 K during the 20th century
Human activities contribute
significantly to greenhouse gas
emissions
Kyoto Protocol aims at
decreasing GHG emissions by
5% referred to the 1990 level
1859
2015
2nd half
“difficult”
exploitation
2150
Years
2
An overview on existing energy
optimization methods in industry
5
2.1 Process Integration by Pinch analysis
I.
•
II.
Goal
Improvement of energy efficiency in industrial
processes in order to minimize total cost (operating
and investment costs)
Determine cost optimal process pinch
•
Analyze heat exchange between heat flows in
processes
PINCH
ΔTmin
Overall vision of the process
•
Economic optimization of heat recovery and heat
exchange within the process
H
T
Qext losses
Pinch analysis limitations
•
Batch processes imply time differences
•
Spatial discontinuity of heat flows
•
Technological difficulties with respect to some
materials
•
Transformation process “taken as granted”
•
Heavy and expensive tool
Qext losses
Qf Geographical
losses
6
Cold composite
curve
Advantages
•
IV.
Hot composite
curve
Composite curves
•
III.
T
Temporal
disparity
losses
Qch
ΔH
2.2 The Kissock “inside-out” approach and the
Frazier method
7
Primary
Energy
Conversion
equipment
I.
Kissock “inside-out” approach
•
Basic criteria : process requirement
•
Exergy-based analysis of equipment
•
Identification of the best suited energy source
for the process
Inside-out analysis sequence
for reducing energy
•
Limitations: transformation process “taken as
granted”
Schematic representation of the inside-out approach
[Kissock et Hallinan, U.DAYTON]
II.
The Frazier method
•
Basic requirements: Minimum Required
Energy
•
Process energy flow mapping
•
Minimum Required Energy : Value added
energy
•
Losses: Non value added energy
•
Technical energy management method
leading to incremental improvements
•
Limitations: transformation process “taken as
granted”
Ein
Energy
Distribution
system
Manufacturing
Process and
Equipment
[Frazier, Oklahoma State University]
2.3 Key issues from literature review
I.
The existing methods do not allow comparison of alternative
processes to the current one
II.
The existing methods consider the actual process as “granted”,
so the potential radical improvements are out of the scope
III. An analysis method has to be developed focused on the product
itself in order to define the most efficient transformation
processes
8
3
The Process Energy Analysis (PEA)
9
3.1 The 3 steps of PEA
3 steps
The 3 steps
•
Process analysis
•
•
Molecular and energy analyses of
transformation process
•
MRE based on product quality and plant
productivity
•
Best transformation process and BAT
Manufacturing plant synopsis and energy consumption
inventories
Process Analysis
Energy assessment
and result evaluation
•
•
Process mapping (process transformation
operations)
•
Inventories of energy and mass fluxes
•
Plant energy exchange model
Energy assessment and results evaluation
Plant synopsis
Energy consumption
inventory
•
•
•
10
Analysis of energy losses
Incremental improvements
Radical improvements
Analysis results
MRE
Maximum efficiency
Process efficiency
Energy losses
Ideal efficiency
Exergy efficiency
Plant efficiency
Incremental improvements
Radical improvements
3.2 Process analysis
I.
Molecular analysis
•
Basic criteria: Product quality and plant
productivity
•
Determine Minimum Required Energy
II.
Energy and Exergy analyses
•
Determine best suited transformation
process
•
Determine the energy sources at the
highest temperatures
•
Determine maximum energy efficiency
11
Product quality
Productivity
Molecular analysis
Minimum Required Energy
Energy and Exergy Analyses
of the transformation
process
Best Transformation process
Best available technology
12
Energy consumption
g)
yin
s
ve
se
on
los
,c
d
re
ui
eq
•
R
•
•
gy
er
•
Energy needed for ancillary needs
linked with the actual process
Mould heating, conveyor
heating…etc.
Irreversibility losses
Elimination of fatal losses requires
changing the actual process
Radical energy improvements
um
•
En
Fatal losses
im
•
in
•
M
•
Losses related to system
malfunction
Elimination of non fatal losses does
not affect the actual process
Incremental energy improvements
tal
•
lds
Non fatal losses
Fa
•
ou
Energy Losses
(m
I.
Non-fatal losses
(Transport, walls…)
3.3 Analyzing data
3.4 Example step 1 (milk pasteurization for cheese
production)
I.
Molecular analysis
Eliminate harmful pathogenic bacteria
Development of bacteria is limited at low temperatures
Storage up to 1 week possible without pasteurization
Pasteurization must then be followed by cooling to 35°C
MRE: Energy to heat milk from 5 to 35°C
Temperature
Temperature (°C)
(°C)
•
•
•
•
•
100
100
90
90
80
80
ΔT=30 K
70
70
60
60
Coldfroid
milk
Lait
50
50
Lait
chaud
Hot milk
40
40
30
30
20
20
10
10
00
Δh (kJ/kgmilk)
Δh (kJ/kglait)
23,7 kJ/kgmilk
13
23,7 kJ/kgmilk
High température
hot utility
II.
Energy and exergy analyses
Composite curve analysis
Temperature (°C)
3.4 Example step 1 (milk pasteurization for cheese
production)
ΔT ≤30 K  Constant heating
needs
•
ΔTmin ↑  QHT ↑
•
ΔTmin ↓  QHT ↓
Best available techniques and energy ratios
80
ΔT=30 K
70
60
Cold Milk
Hot Milk
40
30
20
10
0
Δh (kJ/kglait)
High temperature
hot utility
a) Milk composite curves with 30 K pinch
Temperature (°C)
•
Minimize the high temperature
need
Air-to-water heat pump. Heat
production at 35/37°C
90
50
•
•
100
100
90
80
70
60
ΔT=2 K
Cold milk
50
Hot milk
40
•
COPPASTO =
MRE MRE QHP
=
!
= " HX ! COPHP
Wcomp
QHP Wcomp
30
20
10
0
ΔTminLow
=2 Temperature
K
hot utility
Heat recovery
∆h (kJ/kg_milk)
High Temperature
hot utility
b) Milk composite curves with 2 K pinch
14
4
Conclusions and future working program
15
4.1 Conclusions
•
PEA application determines energy saving opportunities that
cannot be identified by classic energy analysis methods
•
Transformation process analysis leads to define accessible MRE
•
In most industries, it is common to take the transformation
process as “established forever”. The PEA method allows
comparing several processes for producing a defined product with
similar quality in order to define the lowest achievable energy
expense
16
4.2 The future working program
•
Reference PEA for each industrial process: similar exhaustive
approach as IPPC (Integrated Pollution Prevention and Control)
•
Best transformation process and Best Available Technologies for a
given product
•
Processes have to be studied under dynamic simulation in order to
take into account energy losses along the time
•
The MRE has to be defined for each and every process taking into
account the mass flow rates of raw materials, by-products,
effluents, and product itself
•
GHG and pollutant emissions have to be integrated into the PEA
17