model-based operator support for improved energy efficiency in … · 2018-12-07 · 3 na 2 so 4...

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

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

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

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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

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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

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min 𝐸𝐶𝑖,𝑒 ⋅ 𝑆𝐶𝑖,𝑒

𝑖𝑒

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

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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

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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