WP4b Activities M13M24

1
WP4b Activities M13-M24
Partners UNIDO, UVA, TUB, US, LTH,
UCL WP-Leaders Sebastian Engell, Olaf Stursberg
(now TUM)

• Predominantly work on the case studies
• Challenging, industrially relevant problems
• Significant continuous dynamics as well as
  discrete-event control
• Safety-related discrete controls in processing
  plants
• Critical for economic performance and plant
  life-time
• Interaction of discrete logic with continuous
  dynamics
• Not restricted to shutdown logic
• Large transitions involving continuous and
  discrete controls
• No systematic design procedures available
• Degree of automation low, but automation highly
  desirable
• Very complex problems, beyond the state of the art

2
Case Studies Overview

• Reactor-tank example (UCL)
• Derived from PVC plant at Solvay
• Simple dynamics, periodic online scheduling
  problem
• Batch plant (Magdeburg/ Berlin)
• Reactor-filter system derived from color pigment
  production
• Complex kinetics and interactions, batch process
• Evaporator system (Dortmund/ Bayer Tech. Serv.)
• Complex dynamics modeled by hybrid DAE-system
• Ramp-up and safety logic verification problems
• Fuel cell system (Sevilla)
• Complex real laboratory system
• Verification of control logic to prevent
  undesirable states

3
Case Studies Overview (2)

• Sugar Plant Crystallization Section (Valladolid)
• Real complex industrial process
• Full and simplified simulation models available
• Start-up and optimization problem
• Open plate reactor (Lund/ Alfa-Laval)
• System described by nonlinear PDEs
• Startup problem
• Laboratory plant (Valladolid)
• Mixed batch/ continuous process
• Scheduling and level/temperature control
• Refrigeration system (Danfoss) (new)
• Nonlinear model, switched operation
• Feedback control and optimization of the
  operating point

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Discontinuous Plant (TUB)

• 3 products P1, P2, P3 have to be produced in
  given amounts.
• Order of filtering operations matters.
• Each reaction Ai?Pi is accompanied by a parallel
  reaction Ai?Wi
• Concentrations of Wi are constrained.
• First order reaction kinetics
• Discrete control inputs reactor feed rates,
  filter allocations
• Continuous control inputs heating and cooling
  rates
• Safety constraints (bounds for temperatures)
• Goal minimal operating cost (energy, material
  and processing time)

5
Evaporator System
Goal Start up in minimum time and with minimum
steam consumption
Counter-current flow liquid-vapor
3 components mixture A, H2O, Alcohol
?A
Continuous Inputs Vc, V1, V2, V3, V4 and VV2 0
100 Discrete Inputs VVS,1 and VVS,2
0 or 1
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Evaporator Hybrid Process Model

• Discrete dynamics
• 4 locations per evaporator ? complete system 64
  locations
• Combination of the heating and evaporation states
• 2 discretely switched valves
• Continuous dynamics
• Nonlinear DAE-system
• 17 state variables for one evaporator (4
  differential, 13 algebraic)
• Total mass of alcohol in the evaporator
• Flow rate of vapor into a heat exchanger
• 6 continuously actuated valves

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SRDC-CS Discretely Controlled Evaporator

• Only the last evaporator is considered
• The process is close to stationary operation
• Inputs and outputs are held constant
• Discretely switched redundant valve assemblies
• Closed (0 )
• Open (stationary setting)
• Steam pipe PV

0 / 68.1
0 / 14.9
0 / 56.3

• Assumption occurrence of two errors
• Blocking of the valve assemblies in open or
  closed position
• Obstruction of the pipe PV
• Automatic error correction after 130 seconds
  (redundancy)

8
Open Plate Reactor (Lund/ Alfa Laval)
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Open Plate Reactor pilot plants
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Modeling and Start-up Problem Formulation

• Detailed nonlinear pde model from first
  principles
• The plate reactor is described as an ideal
  tubular reactor
• Multiple equilibrium points, rapid transitions
• Discretized to a system of ODEs using finite
  differences
• Operation rules
• Avoid accumulating unreacted chemicals
• Avoid too high temperatures at hot spots

11
Supermarket Refrigeration System (Danfoss)

• Task
• Control the temperature Tair inside each display
  case between 2ºC and 5ºC
• Keep Psuc below 1.7 (1.9) bars during day-time
  (night-time) operation
• Avoid frequent compressor on/off
• Minimize energy consumption
• Control variables Disturbances
• On/off valves - Amount and type of goods
• On/off compressors - Heat transfer from
  surroundings

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Problems with the Current Control Scheme
Synchronization
Large variations of the suction pressure
Many switches in compressor capacity
13
Case Studies Participation

• Reactor-tank example ? 4 contributions
• Batch plant ? 2 contributions
• Evaporator system startup ? 2 contributions
• Evaporator system verification ? 1 contribution
• Fuel cell system ? 1 contribution
• Sugar Plant Crystallization Section ? 1
  contribution
• Open plate reactor ? 2 contributions
• Laboratory plant ? 2 contributions
• Refrigeration system ? 3 contributions

14
Lessons Learned

• Case Studies
• Reasonable set of case studies from simple to
  very complex
• Highlight different aspects of practical control
  problems
• Demanding test-cases for hybrid control
• High industrial relevance, confirmed by advisors
• Separation of concerns (hierarchy) and efficient
  parameterizations enable the (sub-)optimal
  solution of real-world problems.
• All successful solutions of the more complex
  problems are based on engineering insight and
  reduction of the solution space.
• Tool usage
• Modelling and simulation environments
  optimizersEcosimPro / SQP-solver, gPROMS
• MATLAB
• MATLAB-tools under development
• Need for the development of better methods and
  tools!

15
WP4b Meetings and Events in M13-M24
? Periodic WP meeting at the University of
Seville, December 16, 2005 Discussion of the
progress of work, planning for the upcoming
period. ? Session on the activities of WP4b and
overview presentation at the CEmACS/ HYCON
Workshop in Lund, June 1, 2006. ? Special
session on the results obtained within WP4b,
organized for the ADHS conference, Alghero, June
8, 2006. ? Periodic WP meeting during the ADHS
conference Planning of the post-conference
workshop discussion of the decisions required
for M4b.2.3 / M4b.4.2. ? Post-conference workshop
at the PSE/ESCAPE conference in Garmisch,
July 13, 2006. ? Brief WP meeting after the
post-conference workshop Planning of the
activities in M25-M42
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WP4b - Milestones and Deliverables M13-M24
?
?
?
?
submitted in September 2006, since the
solution of the verification tasks turned out to
be significantly more challenging as expected.
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Dissemination

• Workshop in Lund WP 4b session and plenary
  presentation, discussion with industrial advisors
• Invited Session at ADHS 2006
• Post-conference Workshop at ESCAPE 16 / PSE 2006
• Invited session proposal submitted to ACC 2007
• 22 conference papers and contributions to books
  - 3 journal papers