Sugar Production Control

  • Sugar production control

  • A case study for large scale industrial control

  • outline

  • Desciption of the sugar plant

  • Description of the evaporation process

  • Control problems in the evaporation process

Exercise

Make a contol concept for the evaporation process

  • Sugar production

  • Extraction of sugar from sugar beets

  • Filtration of sugar juice

  • Concentration of the sugar juice through a multiple-effect evaporator’

  • Crystallization through boiling and graining

  • Separation of sugar crystals and molasses by centrifugation

  • The evaporation process

  • Energy consumption

  • Juice flow in 133 kg/sec

  • Juice flow out 28 kg/sec

  • Juice brix in 15.5

  • Juice brix out 72

  • Control problems in the evaporation process

  • The output brix of the syrup must be high as the cheapest evaporation is carried out in the evaporation process

  • To avoid spontanous crystallization in the pipes the output brix must be stable

  • A adequate steam pressure for the crystallization process must be secured

  • There must be a minimization of the energy consumption

  • The plant must be robust to flow variations

  • Control characteristics in sugar production

  • Sugar production is a combination of continous and batch process

  • The sub-systems are strongly coupled by the flow of sugar juice and the flow of heating energy.

  • In each sub-system there are several inputs, outputs and disturbances

  • Control characteristics in sugar production

  • A large number of parameters and variables correlates to some extent determining the dynamics of the plant

  • The correlation of parametersand variables makes it difficult to survey the important links in the process

  • It can be difficult to distinguish inputs, outputs and disturbances according to the control strategy

  • Demands for the control system development concept

  • it must be able to handle MIMO systems

  • It may rely on a hierarchic decomposition ot the control goals

  • The modelling method must be able to describe the functionality of the plant

  • It must be possibel to identify relevant control loops without deveolpment of an entire matematical model

  • It must be possibel to connect the goal description and the functional description

  • Modelling for control system design

  • Modelling by a mathematical description of the static and dynamic relations according to system apparatus

  • Modelling by a functional description of the plant

  • Hierarchic goal oriented functional description

  • The goals due to plant functionallity, production rate, safety aspects and economy must be identified

  • The goals must be arranged hierarchic due to the internal supporting relations

  • the plant functionality must be described due to the flow of material, energy and information

  • The low level goals in the hierarchy must be related to plant functionallity

  • Idiomatic control

  • The basic idea is to setarate the system into a number of independent subsystems each controllable using well suited method

  • Basic idioms are:

  • Feedback, feedforward, ratio control, cascades, decoupling etc

  • Exercise

  • Design a control system for the evaporation process.

  • You can use the described hierachic structure and elements from the fist mm


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