Making the invisible visible

In FCC Units (Fluidised Catalyst Cracking Units) the atmospheric residue from the distillation is cracked to LPG, naptha and other components. This sometimes leads to “invisible” deposits inside the Riser. This article features Tracerco’s ThruVision™ scans to illustrate how the technology helped the refinery to identify these deposits at an early stage.

Bayernoil operates two FCC Units to convert heavy hydrocarbons. In the FCC Unit the feed is injected through nozzles with lifting steam into the hot catalyst flow (about 700°C) from the Regenerator. Inside the riser the hydrocarbons are cracked into smaller compounds. At the top of the riser, catalyst and vapourised hydrocarbons are separated. The catalyst flows to the regenerator where the coke is burned and the hydrocarbons go to the main fractionator column. (Figure 1).

Some of the coke generated will remain in the riser as deposits on the inner wall. If these deposits build-up and become too thick, this can cause problems. The throughput will be reduced and the FCC Unit must be shut down for cleaning operations. 

Most of the coke deposits are found above the feed nozzles. Caused by turbulent flow, the material hits the hot inner walls and coke builds up over time. This process is influenced by the catalyst throughput, the condition of the feed nozzles and the lifting steam rates.

To detect coking in the riser at an early stage and to start actions to prevent the build-up, the Bayernoil FCCUs are regularly investigated by ThruVision™ measurements performed by Tracerco.

A ThruVision™ study is performed at a fixed elevation to generate a detailed cross-sectional density profile. Several measurements are taken at selected positions. For this study, a radiation source is placed in the first of nine positions, which are evenly spaced around the circumference of the riser. A measurement is taken with a detector positioned opposite the source. Then, the detector is moved to four more positions to the right and to four positions to the left of the first detector position, creating an arc of nine readings from the one source position. The source is then moved to the second position and nine more readings are collected. A total of 81 readings are collected. (Figure 2)

The gathered data from the ThruVision™ scan is used to generate a tomographic picture showing different densities which directly refer to the deposits inside the riser. (Figure 3) The riser of the Bayernoil Vohburg site was replaced during a turnaround in 2013. To get a better understanding of the interpretation of the ThruVision™ scans this riser was investigated by Tracerco to compare the picture with the real deposits. Figure 4 shows the correlation of the red and yellow areas in the ThruVision™ results with the coke deposits in the riser segment.

The new riser was scanned to obtain baseline reference data. (Figure 5) These ThruVision™ scans are repeated regularly to monitor the unit and to help develop the best plan for it’s performance and shutdowns for cleaning.


View More

  • Optimise your alkylation process and take control with the Profiler™ TGA

    The Challenge. Alkylation processes present some of the more challenging applications for interface measurement and control in refinery operations. It is important for the operator to have confidence in the process to optimise alkylate production, while ensuring safe operation and environmental compliance. In ...

  • Profiler™ TGA

    The Profiler™ TGA provides extremely reliable liquid level and interface measurements for alkylation units and other harsh service environments. The Profiler™ TGA is specifically designed to measure the vertical distribution of multiple interfaces in real time and at high resolution. Key features • ...

  • Tracerco™ Level System

    Bulk level measurement. Developed to comply with the latest functional safety standards, the SIL2 certified TracercoTM level system delivers extremely reliable bulk level measurements, regardless of process conditions. Its external modular design, with no moving parts, provides measurement redundancy, ...

  • Profiler™ GPS

    Level, interface and multiphase measurement. The Profiler™ GPS provides a ‘window’ into the vessel to enable the operator to improve production throughput, reduce the number of unscheduled shutdowns and achieve significant cost savings. The Profiler™ GPS has no moving parts and is installed in ...

  • Optimus™

    Bulk level and interface measurement. Optimus™ is designed for liquid level, interface and solids monitoring in upstream and downstream vessels. Optimus™ is suitable for bulk level measurement in the most challenging oil, chemical and petrochemical industry applications, including those with the ...

  • Hyperion™

    Bulk level and density measurement. Designed using innovative scintillator-based technology, Hyperion™ is a non-contact, no moving parts measurement solution that provides accurate and extremely reliable bulk level and density measurements. This enables operators in the oil, gas, petrochemical, refining, ...

  • FCC stripper - distribution studies

    A Tracerco Diagnostics™ Distribution study can be performed to identify catalyst and vapor distribution in the stripper. Uniform distribution of catalyst and steam in the stripper is critical to achieve high stripping efficiency (less carry-down of the hydrocarbon products from reactor to regenerator). ...

  • Exchanger leak testing - chemical tracers

    Tracerco has been at the forefront of the development of online leak detection for the last 40 years. The method allows the detection of leaks as small as 0.5%. However, customer demands to measure smaller leaks affecting product quality, has prompted extensive research to develop alternative online ...

  • Tracerco Diagnostics™

    Providing real time measurement technologies to assist with critical decision making. Tracerco Scanning Services TRU-SCAN® Application. Do you have problems with the operation of your stripper/absorber or fractionation tower? Is this limiting production? Do you want to reduce your operating costs? ...

  • Tracerco Diagnostics™ FCCU Study

    The Fluidized Catalytic Cracking Unit (FCCU) is the economic heart of a modern refinery. Even small increases in its yield can bring about significant overall gains in productivity and revenue. Tracerco is a world leading industrial technology company providing unique and specialized detection, diagnostic ...

  • Responsive image FCC catalysts & additives
  • Responsive image FluegasExact 2700 effective combustion analysis
  • Responsive image ITW technologies online cleaning
  • Responsive image Process catalysts
  • Responsive image Process flares
  • Responsive image OpX® Digital
  • Responsive image Catalyst portfolio
  • Responsive image Use your catalyst buying power
  • Responsive image The sulphur processing expert
  • Responsive image Optimize everything plant-wide