Verbal Modeling

Anchors: Manganese Matt Morabito

Jamie Polan

Process Statement: Vaporized product enters a condenser, is cooled by cooling water, and leaves as a liquid. The liquefied product is stored in a jacketed tank, where refrigerant is used to keep the temperature low, and the product liquefied. The liquid product can be sold for $6/gal. The cooling water is provided by the plant and the exiting water stream is fed to a pond, so cannot exceed 35°C to avoid damage to the habitat. The refrigerant is recycled from another process and can be used again elsewhere. The storage tank has a maximum pressure of 5 atm, and volume limit of 5,000 gal.

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ProductStorage (Liquid)

Cold Cooling Water

Warm Cooling Water

Product (vapor )

Product (liquid)

TC2

Condenser

LC1

TC1

PC1

Cold Refrigerant

Warm Refrigerant

Verbal Modeling Process1) Describe the Process Condense product stream using a condenserStore liquid product in a refrigerated storage tank

2) Identify Process Objectives and Constraints Objective – Obtain liquefied product to sell at $6/galConstraints

Operational – Storage tank volume limitSafety – Storage tank pressure limitEnvironmental – Exiting water stream temperature limit

3) Identify Significant Disturbances Fluctuations of: ambient air temperature, feed temperature, cooling water temperature, refrigerant temperature, flow rates

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Verbal Modeling Process (con’t)

4) Determine Type and Location of Sensors Temperature sensor – exiting water streamTemperature sensor – liquefied product storage tankLevel sensor - liquefied product storage tankPressure sensor - liquefied product storage tank

5) Determine the Location of Control Valves Feed inletCooling water inletRefrigerant inletPressure release on storage tank

6) Perform a Degree of Freedom Analysis Number of manipulated streams – 4Number of control objectives and control restraints - 4DOF = 4 – 4 = 0

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7) Energy Management Cooling water removes the heat from the product streamRefrigerant keeps the temperature of the liquefied product low

8) Control Process Production Rate and Other Operating Parameters Entering product stream valve → product flow rateEntering cooling water stream valve → outlet cooling water temperatureEntering refrigerant stream valve → liquefied product temperatureStorage tank valve → storage tank pressure

9) Handle Disturbances and Process Constraints Ambient air, cooling water, and feed temperature fluctuations

Detected by: temperature sensor on the exiting cooling water streamAffects: valve on the cooling water stream inlet

Refrigerant temperature fluctuationsDetected by: temperature sensor on the storage tankAffects: valve on the refrigerant inlet

Product flow rate fluctuationsDetected by: temperature sensor in the storage tankAffects: valve on the product feed stream

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Verbal Modeling Process (con’t)

Verbal Modeling Process (con’t)

10.) Monitor Component Balances Accumulation and loss of material - neglected

11.) Control Individual Unit Operations The condenser is fully controlled, with the valves on the inlet stream controlling the temperature and flows of products and cooling streams

12.) Optimize the Process DOF = 0 cannot optimize further

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