model-based operator support for improved energy efficiency in … · 2018-12-07 · 3 na 2 so 4...
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Model-based operator support for improved energy efficiency in viscose production
Christian Jasch, LENZING Group
Frankfurt, 18.10.2018
Results from the CoPro Lenzing use case
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- World market leader in man made cellulose fibers
- Sales: EUR 2.26 bn
- Fiber sales volumes: 1 Mio tons
- Employees: 6488
The Lenzing Group 2017
Digitized Operations Workshop Frankfurt 2018
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Na2SO4
Spinning
Recovery
Heat Recovery
Bottom tank Degassing
Filter Evaporation
ZnSO4
CS2
H2S
H2SO4
H2O
Calcination Na2SO4*10H2O
H2O
Fiber Viscose (NaOH+CS2+Cell)
Crystallization
To maintain a certain spinbath composition and to extract the co-product Na2SO4
Digitized Operations Workshop Frankfurt 2018
The Spinbath Recovery Cycle
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The challenge with the evaporator network
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A single evaporator at Lenzing
Digitized Operations Workshop Frankfurt 2018
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EV2 EV1 EV4 EV3
Cycle 1
Cycle 2
Target output
20
42 Cycle 3
15
EV6 EV5
t/h
t/h
t/h
Evaporators
⁞
… EV5
The Lenzing evaporator network
- 29 different evaporators
- 9 different product cycles
- Target evaporation output per cycle is fixed
Digitized Operations Workshop Frankfurt 2018
The challenge with the evaporator network
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EV2 EV1 EV4 EV3
Cycle 1
Cycle 2
Target output
20
42 Cycle 3
15
EV6 EV5
t/h
t/h
t/h
Evaporators
… EV5
Production constraints
- Only specific combinations are possible
- Each evaporator can only serve one cycle per time
- Cleaning and maintenance reduce the network availability
Cleaning / Maintenance
Digitized Operations Workshop Frankfurt 2018
The challenge with the evaporator network
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EV2 EV1 EV4 EV3
Cycle 1
Cycle 2
Target output
20
42 Cycle 3
15
EV6 EV5
t/h
t/h
t/h
Evaporators
… EV5
Optimization potential
- Manual load allocation by operator based on experience is complicated and time consuming
- Not shifting load to more efficient evaporators can cost energy
- Hundreds of various combinations possible
Goal: operation at minimum overall energy consumption
Cleaning / Maintenance
Digitized Operations Workshop Frankfurt 2018
The challenge with the evaporator network
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For our operators in the control room to find the most energy efficient load allocation for our evaporator network
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The Solution: Model-based Decision Support System (DSS)
DSS Key Features:
1. Multiple data-based evaporator regression models
2. Optimization algorithm with live connection to process data in matlab
3. HMI for Visualization and settings in OSIsoft PI
Digitized Operations Workshop Frankfurt 2018
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Evaporator modelling
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Capacity and efficiency depends on: - Cycle flowrate F
- Flow temperature T
- Condenser temperature TK
- Fouling
multi-stage evaporator
T
F
Spin bath TK
Fouling
Concentrate
Data-based modelling approach
- Evaporation capacity
𝐸𝐶 = 𝑎1𝑇 + 𝑎2𝐹 + 𝑎3𝑇𝑚𝑘 + 𝑓𝑓𝑜𝑢𝑙𝑖𝑛𝑔,1
- Specific steam consumption
𝑆𝐶 = 𝑏1𝑇 + 𝑏2𝐹 + 𝑏3𝑇𝑚𝑘 + 𝑓𝑓𝑜𝑢𝑙𝑖𝑛𝑔,2
- Absolute steam consumption
A𝐶 = 𝐸𝐶 ⋅ 𝑆𝐶
Digitized Operations Workshop Frankfurt 2018
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Optimization task and constraints
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Simplified formulation as MIQP:
Information and constraints from live process data
- Target EC
- State of every evaporator
Current load and allocation
Fouling and steady state
Max. EC
Digitized Operations Workshop Frankfurt 2018
min 𝐸𝐶𝑖,𝑒 ⋅ 𝑆𝐶𝑖,𝑒
𝑖𝑒
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Modelling and network optimization
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Data historian/ Process data
Decision Support Interface
Data treatment
Process information
Least-Squares Optimization
Model structure
Plant state
Optimization
Results
Model parameters
Fouling state
Constraints
Single run
Online analysis
Digitized Operations Workshop Frankfurt 2018
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HMI for the operators in control
Digitized Operations Workshop Frankfurt 2018
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Results so far
Advanced DSS implemented in control room August 2018
1.8 % more efficient operation
Steam savings around 1200 t/month
≈250.000 €/year savings
v2.0 update with semi automatic control currently under development
Digitized Operations Workshop Frankfurt 2018
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Thanks for your attention
Digitized Operations Workshop Frankfurt 2018
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The projects leading to this application have received funding from the European Union’s Horizon 2020 research and innovation program
Christian Jasch
CoPro – LENZING Group
www.copro-project.eu
www.lenzing.com