FCC Unit Regenerator Temperature Troubleshooting

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Questions and Answers

What happens to the regenerator temperature when the feed temperature is lowered?

It remains constant at all feed temperatures.

It always increases regardless of feed viscosity.

It may increase until a certain viscosity level is reached. (correct)

It consistently decreases, improving efficiency.

How does the nitrogen content in the feed affect the catalyst's performance?

It enhances the catalyst's selectivity.

It increases the catalyst's regeneration capability.

It has no effect on the performance of the catalyst.

It forms strong bonds with acidic sites, reducing activity. (correct)

What determines the increase in delta coke when the feed contains vacuum resid?

The entire Conradson Carbon converts to coke.

The viscosity of the feed prevents coke formation.

Only a portion of the Conradson Carbon contributes to coke. (correct)

The amount of Conradson Carbon is irrelevant.

What is the effect of increasing the stripping steam on the regenerator temperature?

It lowers the regenerator temperature by reducing hydrogen in coke. Signup and view all the answers

What is the relationship between residue composition and delta coke?

Mostly aromatic residues increase delta coke based on Concarbon. Signup and view all the answers

What does a darker color of gasoil typically indicate about the FCC feed?

It has more coke precursors. Signup and view all the answers

What common practice is followed when adjusting the stripping steam rate?

Decrease the steam rate until the regenerator temperature rises. Signup and view all the answers

What indicates the coking tendencies of the feed?

The Conradson Carbon test results. Signup and view all the answers

Which range of temperature corresponds to diesel molecules in the feed stream?

430-650ºF Signup and view all the answers

What happens to coke formation if the vacuum tower operation deteriorates?

Coke formation tendencies may increase. Signup and view all the answers

What is the primary purpose of using dispersion steam in the feed vaporization process?

To reduce the hydrocarbon partial pressure. Signup and view all the answers

What impact does recycling light cycle oil (LCO) have on coke-making tendencies?

It lowers coke-making tendencies. Signup and view all the answers

What happens if larger oil droplets are present during the vaporization process?

They cause problems by not vaporizing. Signup and view all the answers

Why is catalytic cracking considered a vapor-solid reaction scheme?

Because a liquid-solid system would inhibit conversion. Signup and view all the answers

How does high pressure affect the vaporization of absorbed hydrocarbons?

It inhibits vaporization. Signup and view all the answers

What is the role of decant oil in the catalytic cracking process?

To help increase the regenerator temperature. Signup and view all the answers

What effect does low regenerator temperature have on the FCC unit's operation?

It may impede conversion and product yields. Signup and view all the answers

How does higher regenerator temperatures affect catalyst deactivation?

It leads to excessive catalyst deactivation. Signup and view all the answers

What is the relationship between delta coke and regenerator temperature?

Delta coke influences regenerator temperature. Signup and view all the answers

What is the proportionality of coke burned to the delta temperature between the regenerator and reactor?

Coke burned is proportional to delta T. Signup and view all the answers

What is the potential consequence of operating at high regenerator temperatures?

Increased equipment damage. Signup and view all the answers

If the coke burning rate is too low, what impact does it have on catalyst circulation rates?

It may limit catalyst circulation rates. Signup and view all the answers

In a full CO burn regenerator, how much does the temperature rise for every 0.1 wt% increase in delta?

40ºF Signup and view all the answers

What type of operation experiences a temperature difference of about 30-32ºF?

Partial burn regenerator operation Signup and view all the answers

What phenomenon is observed with the vapor flow in a riser?

Vapor flows parabolically with varying velocities. Signup and view all the answers

What effect does increased catalyst residence time have on pressure drop?

It increases the pressure drop. Signup and view all the answers

Which riser design is preferred for better catalyst performance?

A straight vertical riser. Signup and view all the answers

How does increased active site density on a catalyst affect coke production?

It increases the amount of coke produced. Signup and view all the answers

What should be considered when comparing catalysts for cracking?

Both catalysts should have the same feed and conversion. Signup and view all the answers

How does spacing of active sites on a catalyst influence coking reactions?

Closer spacing reduces coking tendency. Signup and view all the answers

What is the impact of increasing dispersion steam on delta coke production?

It reduces delta coke by decreasing residence time. Signup and view all the answers

Which catalyst activity characteristic is crucial for its performance?

The initial activity and deactivation rate. Signup and view all the answers

What is one factor that can increase deactivation rates in a catalyst?

Temperature of the regenerator Signup and view all the answers

Which metals can cause problems with catalyst performance?

Ni, V, and Fe Signup and view all the answers

What is the preferred method to minimize catalyst deactivation when certain compounds are present in the feed?

Use dry gas instead of steam Signup and view all the answers

What effect do alkali metals have on catalysts?

They compound damage to catalysts Signup and view all the answers

How can the layout of equipment influence operations in a refinery?

It can impact the delta coke production Signup and view all the answers

What happens to delta P if the pressure drop between the regenerator and reactor increases?

Delta P will decline Signup and view all the answers

What is one effect of adding reactor internals to FCC units?

Reduction of residence time Signup and view all the answers

What can be an important consideration when evaluating the revamp of equipment?

Paybacks can take a year or less Signup and view all the answers

Study Notes

Regenerator Temperature Management

Fluid catalytic cracking (FCC) units require regenerator temperatures to be within specific limits for optimal performance.
Low regenerator temperatures can reduce coke burning rates, leading to increased coke on regenerated catalyst, negatively affecting conversion and product yields.
High regenerator temperatures may cause equipment damage, low conversions, and excessive catalyst deactivation.

Factors Influencing Regenerator Temperatures

Temperature difference between the regenerator and reactor affects heat transfer and catalyst circulation rates.
For full CO burn regenerators, a 0.1 wt% increase in delta coke results in a temperature rise of approximately 40°F; partial burns show a difference of 30-32°F.
The relationship between coke make on feed and coke burned in the regenerator (delta coke) heavily influences temperature variations.

Feed Composition and Coke Production

The boiling range of feeds can affect delta coke significantly; presence of vacuum resid may lead to more coke formation.
Increasing nitrogen content in the feed can hinder desorption from acid sites, further increasing delta coke levels.
Conradson Carbon (Concarbon) tests are used to measure the potential for coking; primarily influenced by the catalyst-to-oil ratio.

Operational Adjustments

Adjusting stripping steam rates can lower the regenerator temperature by modifying hydrogen levels in coke.
Increasing the stripping steam may reduce regenerator temperatures; however, caution is needed as excessive steam adjustments can lead to operational issues.

Catalyst Behavior and Feed Interactions

All cracking catalysts produce coke, with higher activity catalysts leading to increased coke production and higher regenerator temperatures.
Delta coke can vary significantly with different catalysts, impacting overall performance and temperatures.

Catalyst and Equipment Configuration

Equipment layout can impact delta coke generation; optimal riser design enhances reaction efficiency by minimizing residence time.
Steam injection positions should be carefully established to maximize operational safety and effectiveness.

Importance of Monitoring and Adjustment

Continuously monitor feed properties and operating conditions to maintain optimal catalyst performance and prevent excessive coke formation.
Collaboration with catalyst suppliers is essential in managing feed contaminants that negatively impact catalyst performance.

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Description

This quiz focuses on troubleshooting low or high temperatures in fluid catalytic cracking (FCC) units. It covers various resources, technologies, and expertise needed to quickly identify operational problems within the regenerator, emphasizing thermal and catalytic effects.