MFA Control and Optimization
of Distillation Columns
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| • Tightly controls key process variables
during various feed rate changes, operating conditions,
and plant upsets. |
• Process stability, smoother operations,
and higher yield are achieved. |
| • Decouples loop interactions and minimizes
chain reactions among the columns. |
• Avoids potential vicious cycles, plant
upsets, and accidents. |
| • Improves feed throughput and achieves
higher product quality. |
• Return on investment within a few months. |
CyboSoft's
Distillation Column MFA Control and Optimization Solution
Process: Distillation
column chains are used to separate a liquid or vapor
mixture of two or more substances into component fractions
of desired purity. A reboiler brings the liquid at the
bottom to the boiling point where the component with
a lower boiling point will evaporate. Trays or plates
inside the column shell enhance the separation. A condenser
cools and condenses the vapor leaving the top. A reflux
drum holds the condensed vapor and sends a portion back
for recycling and improving the material and energy
balance.
Goals: Distillation columns consume
so much energy that it contributes to more than 50%
of plant operating costs. It is desirable to tightly
control bottom and tray temperatures to optimize separation,
avoid flooding, minimize steam consumption, and maximize
yield.
Challenges: Since it is a multiphase
and multivariable process with complex operating conditions,
control of critical temperature, pressure, and level
loops can be very difficult.
Solution: CyboSoft offers effective
Model-Free Adaptive (MFA) control solutions for controlling
critical process variables without the need to build
column process models and retune controller parameters.
Column Level Control: Use a Robust
MFA controller to smoothly control the
level and minimize outlet flow variation to reduce potential
vicious cycles in the column chains. User-selectable
higher and lower bounds on level PV protect the level
from running too high or too low during plant upsets.
Column Temperatures: Use a Multivariable
MFA controller to manipulate the boiler
flow and reflux flow setpoints to control the bottom
and tray temperatures. Interactions between the bottom
and tray temperatures are decoupled.
Anti delay MFA
features may be enabled to handle the large time delays
in these loops.
Application Story: Lanzhou Petrochemical
Complex of PetroChina has deployed MFA controllers on
4 distillation columns in its MTBE production processes
and achieved great results:
• Bottom and tray temperatures are controlled
within +/- 3 °C;
• Reduced reflux flow to achieve higher yield;
• Much smoother level control and plant operations;
• Improved production safety, separation efficiency,
and productivity.
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