Question 35: What is the importance of sodium to reliability in the coker? What are some of the potential sources of the sodium in coker feed? In light of IMO how should sodium be managed in purchased coker feed?
DENNIS HAYNES (Nalco Champion, an Ecolab company)
Sodium in the coker feed can be introduced via sodium content of the salts in crude, caustic addition at the crude unit for corrosion control purposes, as a contaminant in recovered oil material in the refinery, sodium content of other purchased feedstocks (as mentioned in the question) among others. Elevated sodium levels in the feeds will increase fouling of the Coker furnace. Potential solutions are enhanced dehydration of slops, crudes, or feedstocks where possible in tankage, improved reliability and optimization of crude unit caustic feed rates via addition of caustic blend tanks for improved control of strength and also automation of overhead chloride analysis tied to caustic feed pumps, optimization of the crude unit desalting process, and addition of heavy oil desalting for imported feeds.
Question 37: With higher anticipated charge rates at the coker due to IMO, what are your best practices around defoamer application to minimize impact on hydrotreater catalyst life?
STEVE WILLIAMS (Marathon Petroleum Corporation)
- As equipment ages and reaches end of useful life, the opportunity arises with necessary replacement to include enhancements or upgrades at little additional cost.
- Since the only cost associated with an upgrade, in these cases, would be any incremental cost of the upgraded components, the associated capital cost is significantly reduced and makes for a prime opportunity to obtain performance enhancement.
- However, the key to successfully identifying and capitalizing on these opportunities is an integrated, multi-functional team-based approach to work scope identification and planning to ensure that upcoming opportunities are realized far enough in advance to allow for the engineering and procurement associated with the upgrade scope.
- Failures to capitalize on equipment replacement activities as opportunities to affect performance enhancements, resulting in simple replacement in kind, are typically the result of late realization of the planned work.
- Typical project economics and justification, such as increased throughput or product recovery, are suitable, and can typically be applied to the incremental capital costs of the upgraded components only.
- Presentation will include specific examples where this approach has been successful.
Question 88: What options exist for the disposition of FCC equilibrium catalyst and fines? For refineries processing residual feedstocks, what are the limitations on the contaminate levels for the various disposal options?
![](/sites/default/files/inline-images/question%2088%2C%20figure%201.jpg)
A review of all ecats BASF receives shows the following distribution of Vanadium,
![](/sites/default/files/inline-images/question%2088%2C%20figure%202.jpg)
A review of all ecats BASF receives shows the following distribution of Nickel,
![](/sites/default/files/inline-images/question%2088%2C%20figure%203.jpg)
Shown below is generalized envelope for Re-sell / Re-use. This chart suggests a significant portion of ecats are recycled for use in another FCC.
![](/sites/default/files/inline-images/question%2088%2C%20figure%204.jpg)
Emerson Domingo (Sunoco)
E-cat and ESP hopper fines are either send to a cement kiln or land filled. Fines captured by the Wet Gas Scrubber are also land filled. Metals limits are normally for leachable metals as measured by the TCLP (Toxicity Characteristic Leaching Procedure) testing, as opposed to total metals in the catalyst.
Stuart Kipnis (Grace Davison)
There are generally three disposition options for FCC equilibrium catalyst (E-cat) and fines. 1.Selling of E-cat is an option if the quality is deemed suitable for reuse. With GRACE’s ENCORE™ program the catalyst technology is appropriately matched to another refinery’s needs. Resale of E-cat fines, normally limited to refineries in need of improved circulation is much less common.
2.Recycling of E-cat and fines through cement kilns is a common practice for material coming from residual feedstock operations where metals contamination is much higher. In most cases the material must be classified as a non-hazardous waste. [There are select kilns that are permitted for handling hazardous materials.] Claude Kennard from Metaloy states that in order to dispose of E-cat and fines at a cement kiln, the material must be non-pyrophoric. As such, most kilns will require a full TCLP analysis before accepting E-cat. Levels of nickel and vanadium are not necessarily the limiting factors for determining acceptance of E-cat for a cement kiln. As raw material requirements change, contaminants like sodium can become important. Each kiln will have unique requirements – larger units will have less constraints since the E-cat and fines are a very small percentage of raw material input.
3.The last option is to dispose of E-cat and fines at a landfill. This becomes a viable alternative when a local cement kiln is perhaps too small to accept the volume of E-cat or if there is no local kiln.
Question 42: What are your best practices to minimize catalyst carry over to the main column on start up?
MICHAEL FEDERSPIEL (W. R. Grace & Co.)
Catalyst loss events experienced while bringing the FCC online after a shutdown are troublesome as they can add significant cost and delay to the startup. Because the main air blower is run close to design conditions throughout the startup, losses are more frequently observed from the reactor side.
Prior to feed-in, it’s difficult to maintain sufficient velocity in the reactor cyclones for effective retention of the catalyst. However, some steam must be kept flowing to the distributors on the reactor side to keep them clear of catalyst, provide a steam purge through the reactor system and to circulate the catalyst during the reactor heat-up phase. These steam flows are generally minimized to reduce the amount of catalyst carried to the cyclones, which will typically not be efficient until after feed-in.
Developing a steam plan for use during startup can help mitigate problems. For each steam distributor, the exit velocity and nozzle delta P are calculated to ensure they are within design conditions. Additionally, riser, stripper and cyclone velocities are also calculated. These calculations are done for each of several conditions during the startup, and adjustments are made as the unit heats up. It’s a good idea to consider the starting conditions, the status of the wet gas compressor, the removal of the main column blind, the presence of catalyst in the system, the heat up phase of the reactor and the increase in charge rate as you move from feed-in to a design condition hold (typically 60% of the design feed rate).
During the startup, some small amount of catalyst is circulated between the regenerator and reactor to heat up the reactor in a controlled fashion. This can be done continuously or via a batch method, depending on unit configuration. The catalyst flow rate required to heat the reactor is much less than typically seen on an operating FCC, and as such, the flux of catalyst in the cyclone diplegs, stripper and standpipes is much lower than normal. The lower flux rate can cause local de-fluidization of catalyst. This can go unnoticed until after feed-in when the circulation rate increases dramatically. Monitoring temperature profile in the reactor, stripper and if available, cyclones is a good way to catch de-fluidization before feed-in. Stopping circulation, lowering the reactor level to minimum, then restarting circulation and re-inventorying the reactor immediately prior to feed-in can help give the cyclone diplegs time to drain and the stripper a chance to re-fluidize.
Many times, during startup, while the level instrumentation is not yet operating properly, catalyst is being loaded to the system and moved between vessels. As a result, it’s difficult to monitor the exact catalyst inventory. If you suspect you may have a loss problem, pause the start-up until you’ve identified the trouble area. Continuing with feed-in can make a small problem into a much bigger issue.
Working closely with experienced operations staff, technical services and your process licensor to develop startup procedures that address your specific unit, along with incorporating lessons learned from previous startup attempts will help prevent catalyst losses and other unit upsets during startup.