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(2010) Question 10: What are refiners' experience with respect to unit availability, catalyst performance and product quality when co-processing "renewable" feedstocks in a ULSD unit? Is there a big variation in operability with different sources of renewable feedstocks?

The co-processing of renewable feedstocks in a ULSD unit means introduction of feed components that are completely foreign to a diesel hydrotreater. These oxygenates will react quite readily with hydrogen to form normal paraffins in the diesel range but in doing so consume high amounts of hydrogen and cause high heat release.
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(2010) Question 19: In your experience, what are the effects on ULSD hydrotreaters when FCC operation is adjusted to maximize diesel?

There are a number of approaches to maximize the diesel yield from FCC units, such as catalyst optimization, process modifications, and changing the FCC product cut points. These approaches can be used independently or in combination - the ultimate objective being to maximize the production of light-cycle oil (LCO) from the FCC unit for subsequent conversion to diesel.
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(2010) Question 25: Besides high reactor temperatures and flow maldistribution, what are other causes of high gas and LPG yields in a hydrocracker have you experienced?

Hydrocrackers typically process heavy gas oils into distillate-range material. The gas oils are catalytically cracked at high pressures in the presence of hydrocracking catalyst and hydrogen. The reaction is exothermic and consumes a relatively large quantity of hydrogen. High gas and LPG yields would be generally undesirable in a properly operating hydrocracker.
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(2008) Question 90: What determines the minimum feedrate for a fixed bed reformer? What process indicators would tell you that the feedrate is too low?

Question 90: What determines the minimum feedrate for a fixed bed reformer? What process indicators would tell you that the feedrate is too low? Rick Grubb (Chevron USA) Besides mechanical limitations, such as pump capacities, flowmeter ranges, control valve sizes, etc., the process factors that determine the minimum feed rate of a fixed-bed reformer are: •Flow distribution in the reactors •Heat of reaction dissipation in reactors •Flow distribution in furnaces •Phase separation in exchangers
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(2008) Question 91: In a catalytic reformer with a given pressure, severity, and feed quality (N+2A), what are the major factors that determine the C5+ yield? How do you optimize yield? Have you quantified the impact of pentane and/or hexane content in the feed?

Question 91: In a catalytic reformer with a given pressure, severity, and feed quality (N+2A), what are the major factors that determine the C5+ yield? How do you optimize yield? Have you quantified the impact of pentane and/or hexane content in the feed? Michael Newton (Roddey Engineering) Setting pressure, severity, and feed quality limits you on any significant “knobs to turn” in determining the C5+ yield. If you assume that LHSV is also fixed, there are two factors that can impact C5+ yield. Reactor Inlet Temperature Profile – typically running a “downhill” profile will give you a slightly higher C5+ yield and will lower overall coke make in the unit. Water Chloride balance – having an over-chlorided catalyst will result in more cracking and lower C5+ yields. Under-chlorided – higher deactivation, higher yield, higher temp required.
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(2008) Question 94: In monitoring catalytic reformer operation, how often do you perform a feed/product analysis and what analytical methods do you use? How often do you perform a mass balance and what is the acceptable mass balance closure? What is a typical mass balance closure?

Question 94: In monitoring catalytic reformer operation, how often do you perform a feed/product analysis and what analytical methods do you use? How often do you perform a mass balance and what is the acceptable mass balance closure? What is a typical mass balance closure? Michael Newton (Roddey Engineering) Units were the feed properties are relatively constant need to be monitored much less than those were the properties change often. For material balances during performance evaluation, accuracy should be within +/-1%. For daily monitoring, +/-2% is acceptable. All balances and monitoring require good data from the lab and making sure that meter data is input and calculations performed correctly.
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(2008) Question 98: What metallurgy are you using for mesh pads in reformer compressor suction knockout drums? How often are the mesh pads inspected and how often are they replaced? Are the same criteria used for mesh pads in product separators?

Question 98 What metallurgy are you using for mesh pads in reformer compressor suction knockout drums? How often are the mesh pads inspected and how often are they replaced? Are the same criteria used for mesh pads in product separators? Rick Grubb (Chevron USA) We typically use 304 SS demister pads in the refinery and inspect them every 10 years. In reforming service we have been using Tefzel demister pads and have been replacing them approximately every dump and screen due to separator internal inspections. If we go into the vessel we go ahead and inspect the mesh pad, but assume before opening the vessel that the pad will need replacing. The Tefzel pads have greatly increased the reliability such that we don’t find mesh pad pieces in the compressors anymore. We have been contemplating using co-knit pads (synthetic fiber inter-woven with a SS fiber), but have not done so yet.
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