With so many names, you may recognize this common refinery unit under a different name. The Fluid Catalytic Cracking Unit also goes by fluid catalytic cracker, cat cracker, cat unit, FCCU, CCU or Houdry. Why a whole article dedicated to Fluid Catalytic Cracking Units you ask? Well, in today’s world, gasoline and diesel fuel are essential to daily life.
Gas allows us to access so many of our basic needs. To make money, the majority of us need to drive to our job offices. To feed ourselves, we need gas to fuel our automobiles so we can go to the grocery store. Before we reach the gas station to pump our cars with fuel, many processes have to happen to supply us with gasoline. Cracking is one of these essential processes needed to commercially produce gas and diesel fuel. Cracking is the most important process for the generation of gas and diesel. In this article, we will discuss what FCCU is, why it is used, what potential repairs and maintenance issues this unit may have and how to repair and maintain them properly so refineries avoid unexpected shutdowns!
What is a Fluid Catalytic Cracking Unit?
If fluid catalytic cracking had not been commercialized all the way back in 1942 for petroleum refining, we would not have the well established foundation of petroleum refinement that we see today (Britannica). The cracking that occurs in petroleum refining is known as the process where heavy hydrocarbon molecules are separated into lighter molecules through the use of heat and pressures, occasionally catalysts.
The cracking of petroleum creates light oils that correspond to gasoline, middle-range oils utilized in diesel fuels, left over heavy oils, a carbonaceous product known as coke, and gases likes methane, ethane, ethylene, propane, propylene and butylene. Based on the desired end product, the oils may be sent to fuel blending or they undergo more cracking reactions/refining processes until the final product is the appropriate weight.
An interesting fun fact even though we are talking about cracking in oil and gas refineries is that the gas products mentioned previously are important raw materials for petrochemical plants. In petrochemical plants gases like methane, ethane, ethylene, propane etc. are made into end products that range from rubber, plastic or chemicals for agriculture.
How Do Cat Units Operate?
First, before even talking about how catalyst units even work, we need to know what the FCC inputs are! Heavy gasoils are fed to the FCCU that would otherwise be blended to generate residual fuel oil. Feeds usually include VGO which is a heavy cut from the vacuum distillation unit and is the largest input given to the cat cracker. To reduce the sulfur content before being fed to the FCC, the VGO is processed through a gasoil hydrotreater. The other input into the FCCU is the coker gasoil. Oil and gas refineries that have a coker know that it is a major feedstock for the FCC as it is a VGO range material.
Now that we’ve discussed the main inputs for a catalyst cracker, we can continue on with how the whole process works. According to Energy Insights, the heated inputs are mixed with a heated catalyst which is then injected into a reactor. Once inside the reactor, the catalyst can mix with the feed uninhibited as a fluid. The feed then is cracked and while this occurs, the coke is deposited on the catalyst leading to the deactivation of the catalyst. The cracked product is extracted from the top of the reactor and sent to a regenerator where the coke is burned off through heat and air. The cleaned/regenerated catalyst can be sent back to the reactor so the cycle can repeat.
The cat cracker catalyst is moved around the reactor and regenerator circuits in seconds at high velocities. This means that the surfaces inside the catalyst circuit need to be protected with ceramic coatings to prevent erosion. The heat created from burning the coke from the catalyst allows for the majority of the heat needed for the separation of reactions that take place in the reactor. The coke that is burned off the catalyst creates a mix of CO and CO2. These gases pass through a series of processes that are later evacuated into the atmosphere. This makes the FCC the largest emitter of CO2 in oil and gas refineries.
Quickly, the final products generated from a houdry are FCC gasoline, cycle oils, FCC slurry and FCC gas...now you know!
Why Do Refineries Use Cat Crackers?
FCCUs are particularly important in oil and gas refineries that are making an effort to maximize gasoline production instead of residual fuel oil. Fluid Catalyst Crackers generate decent quality gasoline in high volumes, this means there is high octane concentrations and low vapor pressure. Alternatively, the volume yield of diesel is low and of low quality (low cetane), due to the fact that is it made up of cracked material which typically has low cetane (Energy Insights).
Many times a refinery will have a cat cracker and a hydrocracker to produce a high yield of light products with a balance between gasoline and diesel. You can think this of this relationship between the two units as a complimentary duo. The houdry takes the unconverted feed from the hydrocracker and the hydrocracker consumes the heavier cracked products from the FCCU.
What CCU Repair & Maintenance Issues Can Arise?
We know that the profitability of a refinery depends highly on the CCU which is why so much has been done to ensure the reliability of the process. In a journal article written by Warren Letzsch titled “Fluid Catalytic Cracking in Petroleum Refining,” it was cited that the cost of a single day of downtime of a large FCCU can range from $1-2 million!
Unexpected shutdowns can be a horror for oil and gas refineries. The average houdry had a turnaround every 2 years back in the 1960’s and by 1990 it was 3 years (Letzsch, 2014). Fast forward to 2013 and the average cat cracker runs approximately 5 years in between scheduled shutdowns. According to a survey conducted on U.S. refiners, most of unexpected shutdowns are due to issues with: slide valves, power failures, expansion joints, wet gas compressors, main air blowers, refractory, catalyst losses or interlock trips.
Most frequently, problems arise after start-up or after an outage like a power failure. Refiners typically capture data from the unit under a distressed condition and compare it to data documented when there is normal operation. Oftentimes there refiners do not take enough measurements of data on equipment when everything is normal making the localization of problems more challenging.
How to Properly Repair & Maintain a Fluid Catalytic Cracker?
We at Phoenix specialize in oil and gas refinery repair and maintenance. We know that unexpected outages can cost a facility MILLIONS each day that its units are offline. That is why we pride ourselves in performing high temperature repair and maintenance in immediately dangerous to life or health (IDLH) environments thanks to our proprietary safety suits that can withstand temperatures exceeding 400 degrees. This eliminates waiting for units to cool down enough to repair and minimizes lost production therefore increasing oil and gas refinery uptime. Phoenix specifically targets fluid catalytic cracker unit repairs and maintenance, as we are experts in the field of oil and gas refinery repair and maintenance of any kind!
Should your oil and gas refinery want to take preventive measures to avoid a shutdown, call us. Should your facility have an emergency involving a fluid cat cracker, call us.
In the meantime, here are some tips for maintaining your houdry up and running! When troubleshooting and monitoring FCCU performance some techniques are: leak detection, pilot plant testing, reaction mix sampling, infrared scans, feedstock analyses, process tomography, catalyst analyses, single-gauge pressure surveys, radioactive tracers, computational fluid dynamics, gamma scans and cold-flow modeling.
Other factors that lead to longer run lengths include better equipment inspections, continuous monitoring of unit components, better equipment designs and better instrumentation (Letzsch, 2014). Acquiring smart equipment would include the large rotating units needed as well as pumps. Extensive temperature and pressure measurements would allow for the identification of fouling therefore making action to correct a potential failure quicker.
For information, contact Phoenix by visiting our website: https://hightemprepair.com/
