Chemical Process Technology: Level and Flow Solutions

The chemical industry continues to be a crucial component of the world economy. The high demand and essential nature of chemicals to modern life increases the need for efficiency in chemical process technology. Concerns about safety and environmental impact also create a need to prevent leakage or spilling of potentially harmful substances. In addition, many governments are imposing new regulations on chemical production. Today’s chemical processors need to be productive, creative and efficient to stay competitive in their market.

Level measurement plays a critical role in improving efficiency in chemical processing. In this post and others in a short series of blogs from Magnetrol, we will explore the ways that chemical process technology can benefit from level control instrumentation. This post will focus on various level measurement applications for the distilling process.

Distillation Tower

Screen Shot 2015-02-04 at 2.04.17 PMApplication: Selecting a separation technology from among 20 leading varieties depends upon a chemical’s nature, the number of phases, and the capacity, speed and efficiency required. Distillation—separating substances based on differences in volatilities—is the most widely used separation and purification method. Today, approximately 40,000 distillation towers are operating in U.S. chemical plants.

Challenges: Level measurement at the bottom of a distillation tower controls the “bottoms” product rate. Poor level control could allow liquid to back up over the stripping trays causing damage and reduced yields. Too low level may cause pump cavitation. In related extraction towers, interface level control provides optimal separation from associated substances.

Level Technologies:
– Series 3 Float-Actuated External Cage Level Switch for point level
– Eclipse® Model 705 Guided Wave Radar or E3 Modulevel® Displacer-Actuated Transmitter for continuous level
– Orion® Instruments Atlas™ or Aurora® Magnetic Level Indicators for visual indication

Reboiler

Application: Reboilers, or vaporizers, are heat exchangers that provide heat to the bottom of a distillation tower. They boil the bottom liquid to generate vapors which are returned to the tower to drive the distillation separation process. The reboiler mayScreen Shot 2015-02-04 at 2.04.26 PM partially or completely vaporize the stream it receives from the bottom of the tower.

Challenges: Excess reboiler liquids (bottoms or blow-down) overflow a baffle where level is controlled by means of a level controller. If the reboiler level becomes too low, it will affect the maximum flow rate of bottoms product that can be drawn off. Inaccurate reboiler level can also degrade composition control for material balance control configurations.

Level Technologies:
Series 3 Float-Actuated External Cage Level Switch or Tuffy® II Float-Actuated Switch for point level
-ECLIPSE Model 705 Guided Wave Radar or E3 MODULEVEL Displacer-Actuated Transmitter for continuous level
-ORION Instruments ATLAS or AURORA Magnetic Level Indicators for visual indication

Condenser

chemical_process_technology_3Application: A heat transfer process that changes a gas or vapor to a liquid, condensation is employed in the reflux process to improve the efficiency of distillation. Condensation can also be employed for producing saturated liquid products, for sub-cooling, or to serve an environmental or vapor recovery function. Condensation is carried out in a variety of configurations.

Challenges: In the distillation process, tower vapors are condensed prior to entering an accumulator. The condenser’s level can be used to control tower pressure where the liquid level set point serves as the manipulated variable (MV) for the pressure controller. Adjusting liquid level in the condenser changes the effective heat-transfer area.

Level Technologies:
– Series 3 Float-Actuated External Cage Level Switch for point level
– ECLIPSE Model 705 Guided Wave Radar Transmitter for continuous level
– ORION Instruments ATLAS or AURORA Magnetic Level Indicators for visual indication

Reflux Drum

Application: Large-scale distillation towers use a reflux system to achieve a more complete product separation. Reflux is that portion of a tower’s condensed overhead liquid product that is cycled back to the top of the tower where it flows downward to provide chemical_process_engineering_4cooling and condensation of the upflowing vapors.

Challenges: The reflux drum, or accumulator, is the piece of chemical process technology that serves as a distribution point for reflux and distillate. Condensed liquid leaves the reflux drum under level control. Drum level control is critical to ensure that the proper amount of reflux will return to the distillation tower. Poor liquid level indication can cause expensive operating problems and product degradation.

Level Technologies:
– Series 3 Float-Actuated External Cage Level Switch for point level
– ECLIPSE Model 705 Guided Wave Radar Transmitter or E3 MODULEVEL Displacer-Actuated Transmitter for continuous level
– ORION Instruments ATLAS or AURORA Magnetic Level Indicators for visual indication

Be sure to follow our blog in the coming weeks as we discuss level control for many chemical processing applications, including liquid extraction and separation, mixing and blending, chemical reactors, and scrubber vessels.

CTA-MAG-Banner_Feb15_ChemInds_v2

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One Response to Chemical Process Technology: Level and Flow Solutions

  1. Pingback: Level and Flow Solutions for Chemical Process Equipment | Heidi Mao

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