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LEARN FROM OUR EXPERTS how to increase reliability and profitability in the delayed coking unit with continuous level measurement. Our top minds take you through Berthold's solutions to the challenges faced when measuring level in a coke drum.
 

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Measuring the level and level switch of coke in coke drums

The delayed coker is the only semi-continuous batch process in the refinery, with the feed continuously switched between two drums on a time-based cycle. The fresh feed, usually from the vacuum tower bottoms, is fed to the bottom of the coker fractionation tower to help pre-heat the feed and mix with the bottom hydrocarbons. This mixture is then passed to the heater to add the energy required to thermally crack the large hydrocarbon chains. After that, the heated resid is pumped into a large coke drum to allow for the cracking and expansion of the fluids, whereby the lighter cracked hydrocarbons are taken off the top of the drums to the fractionation tower, due to the high temperature. As the vapours escape the viscous liquid, they tend to create a foam layer. This foam layer can vary depending on many parameters such as operating temperature, pressure of the drum, type of crude, charging rate etc.

Measuring the level of bottom liquids in the fractionator

Monitoring the level of tower bottom liquids in a delayed coker is among the most important measurements in a refinery. Due to the conditions in the coke drum and fractionator, a level measurement is very challenging. Where other measuring technologies tend to fail or end up being extremely unreliable, Berthold‘s radiometric level technology is ideal for monitoring the coke level due to its non-intrusive nature. Since large temperature variations through the whole operational cycle of a coke drum are a known issue to the operators, our patented automatic stabilization technology based on cosmic radiation guarantees a stable and reliable level measurement without the need for recalibration. Separate level alarms provide additional process safety. An advantage of our radiometric solution is that the measurement is unaffected by surface turbulences, product falling down from the trays, different product densities, and scaling/coking.

Customer benefits

  • Reliable level control
  • Improved utilization of drum capacity
  • Efficient use of anti-foam agent
  • Increased throughput, process safety, and reliability
  • Prevents liquid and foam carry-over into the vapor inlets
  • Ensures minimum liquid head for the coker charge pump

Characteristics

  • Non-contacting, non-intrusive level measurement
  • Use of 8 m long TowerSENS detectors (covering up to 32 m when cascaded)
  • High level switch used to compensate continuous level for gas property changes in the coke drum
  • Highest sensitivity due to solid scintillators, leading to significantly lower source activities
  • High repeatability and long-term stability
  • Minimizes NDT interference with internal proprietary algorithms

SIL certification available

The SENSseries LB 480 series offers versions that are certified for use in SIL2 applications. SIL3 is achieved by adding an identical redundant SIL2 detector using the same source for homogenous redundancy. The certificate covers all measurement applications, from high level or low level alarms to continuous level. Thus the safe measurement of critical processes is guaranteed.

More about SIL

 

Long-term stability

A reliable measurement, requiring no recalibration, is vital for the operation of the alky unit, and is our highest priority. Berthold’s detectors offer stability in the face of changes in ambient temperature. Even drastic temperature shifts, e.g. from winter to summer do not cause measurement drift. Our patented method for detector stabilization compensates for temperature changes and aging.

Detector Stability

Gas Property Compensation (GPC)

Gas property fluctuations in large vessels can greatly impact the amount of gamma at the detector, and therefore impact the measured value, if Berthold's gas property compensation is not added. With GPC, a second detector monitors how much the gas properties are effecting gamma transmission. Based on this, the level detector compensates for changes in gas properties, providing a reliable level measurement. 

More about GPC

We help you to optimize your processes

A foam over in a delayed coker unit is a costly event, not only causing loss of production but also requiring a lot of manual labour to clean coke out of the overhead lines and factionation tower. In order to increase throughput of the unit, one of the most important objectives is to safely and reliably fill the drum higher, however, to achieve this, one must have a reliable measurement method for the foam front in the drums.
Due to the conditions in the coke drum, level measurement is a very challenging task. Where other measuring technologies tend to fail or end up being extremely unreliable, Berthold‘s radiometric level technology is ideal for monitoring the coke level due to its non-intrusive nature. Since large temperature variations through the whole operational cycle of a coke drum are a known issue to the operators, our patented automatic stabilization technology based on cosmic radiation guarantees a stable and reliable level measurement without the need for recalibration. Separate level alarms ensure additional process safety, with the upper switch doing double duty feeding gas property information to the continuous level, for gas property compensation. 
In the fractionator, our level gauges are used to monitor the tower bottoms liquid level – an important parameter for the efficient control of the complete coking cycle. As the measurement is unaffected by surface turbulences, product falling down from the trays, changing product density, and scaling/coking, it has a large advantage over other technologies.

DOWNLOADS

Level measurement in delayed coking units Application flyer

English | PDF | 724.9 KB

Measurement solutions for the refining industry Industry brochure

English | PDF | 3.0 MB

Continuous level measurement Product brochure

English | PDF | 4.9 MB

TowerSENS detector for the best solution

TowerSENS Detector

TowerSENS Detector with a maximum length of 8 m, this rod detector is specifically designed to monitor long measuring ranges