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revamps ptq ptq PETROLEUM TECHNOLOGY QUARTERLY
3 Advancements in retrofits for existing NGL recovery plants
Editor Rene Gonzalez editor@petroleumtechnology.com tel: +1 713 449 5817 Managing Editor Rachel Storry rachel.storry@emap.com Graphics Peter Harper Editorial Assistant Lisa Harrison lisa.harrison@emap.com Business Development Director Paul Mason sales@petroleumtechnology.com tel: +44 7841 699431 Managing Director Richard Watts richard.watts@emap.com Circulation Fran Havard circulation@petroleumtechnology.com
Better plant performance is achieved using proven retrofit techniques to upgrade a gas subcooled process or older plant with more recent retrofit technology Michael Pierce, Scott Miller and John Wilkinson Honeywell UOP Gerry Wooten Mustang Gas Products, LLC Raj Patel Brazos Midstream 11 Increasing efficiency of catalytic reformer unit fired heaters Application of ceramic coating on CRU heater tubing and refractory avoids oxidative scale formation, significantly lowering fuel consumption and CO₂ formation Diyar Kiliç Mert and Alp Zeren Tüpraş Izmit Refinery Anton Korobeynikov and Sergei Merchev Integrated Global Services (IGS) 16 Resolving low slide valve differentials and catalyst circulation problems Troubleshooting catalyst circulation problems that lead to unscheduled shutdowns and reduced income Warren Letzsch Warren Letzsch Consulting PC 23 Technical solutions for hydrotreating Revamps and turnarounds allow time to upgrade hydroprocessing units to make refineries both profitable and sustainable Amy Hearn, Diana Brown, Brian Yeung, Patrick Christensen and Tom Yeung Hydrocarbon Publishing Company 31 Enhancing FCC reliability: The impact of cyclone technology developments How optimising cyclone design and implementing advanced internal hardware enhance operational reliability, illustrated with three real-world examples Mohammad Umer Ansari, Todd Foshee and Robert A Ludolph Shell Catalysts & Technologies 36 Restoring fired heater furnace heat transfer efficiency Convection section cleaning of process heaters at an Egyptian facility achieved more than 90% treating of all tube and surface areas
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Flexibility is profitable
Flexibility Matters
tray vapor loads and internal liquid reflux rates. Keeping the upper pumparounds loaded can also help avoid low pumparound return or tower overhead temperatures that condense water and cause salting or corrosion problems. It may even make sense to turn off a lower pumparound. L ONG - TERM SOLUTIONS inking longer-term, cost-effective revamps can add critical flexibility to allow for wide swings in unit throughput and crude blends while still operating in control. e right process design enables operators to consistently:
In uncertain times, refineries can maximize profit (or at least minimize loss) through flexible operations. Crude units are the first link in the refinery processing chain, and making large changes in crude diet or throughput stresses even the most state-of-the-art unit. S HORT - TERM STRATEGIES Certain operating strategies can maximize reliability, yields, and product qualities. Some practical short- term options include: • K EEP THE BOTTOMS STRIPPING STEAM
At turndown, consider maintaining normal crude tower and vacuum tower bottoms stripping steam rates and lowering heater outlet temperature to control cutpoint. is allows the stripping steam to do the work while heater firing is minimized to protect the heater tubes at low mass velocities. L OWER THE PRESSURE Lowering tower pressures at turndown lowers the density of the vapor, which keeps trays loaded and can avoid weeping and loss of efficiency. Lower pressure also lowers draw temperatures, increasing pumparound rates and hopefully avoiding minimum flow limits for pumps and tower internals. M OVE HEAT UP In multi-pumparound towers, shifting heat to the upper pumparounds at turndown increases
•
Control desalter inlet temperature,
• Control preflash column inlet temperature and naphtha production, • Control pumparound return temperatures and rates independent of pumparound heat removal requirements, and • Precisely control vacuum column top pressure. is advice is, of course, generic. To discuss challenges unique to your own crude/vacuum unit, give us a call. Process Consulting Services believes crude units should have flexibility. We believe that revamp solutions should be flexible too - one size doesn’t fit all. We look forward to working together to find the most cost-effective and reliable solution to your crude processing problems.
•
•
3400 Bissonnet St. Suite 130 Houston, TX 77005, USA
+1 (713) 665-7046 info@revamps.com www.revamps.com
Advancements in retrofits for existing NGL recovery plants
Better plant performance is achieved using proven retrofit techniques to upgrade a gas subcooled process or older plant with more recent retrofit technology
Michael Pierce, Scott Miller, John Wilkinson and S Allen Erickson Honeywell UOP Gerry Wooten Mustang Gas Products, LLC Raj Patel Brazos Midstream
T he processes gas plant owners/operators use to recover hydrocarbon liquids from natural gas streams have undergone continual improvements over many decades. Gas plants today are required to maximise profits by optimising both the recovery of natural gas liquids (NGL) based on market prices and plant throughput to satisfy their delivery contracts. Given recent market volatility, the ability to vary plant operation has become increasingly important. NGL recovery plants designed with built-in flexibility can maximise plant throughput, even above nameplate capac- ity, while maintaining maximum product recovery. This gives them an economic advantage over standard designs. Unfortunately, many standard cryogenic NGL recovery plants were constructed using technologies with limited product recovery capabilities and flexibility. These plants are unable to effectively achieve maximum ethane and pro- pane recovery or adjust operations without losing valuable product, in particular propane, into the residue gas stream. To stay competitive, owners/operators of older plants often need to retrofit their plants. Several new process technologies are available to effec- tively upgrade standard plants. These recent advances can provide higher ethane and propane recoveries, and many offer fully flexible ethane recovery levels, ranging from ultra-high recovery to almost full rejection while maintain- ing high propane recovery. Other technologies include the ability to process higher feed gas flow rates with minimal modifications to existing equipment. Identifying the key performance goals of a proposed retrofit is critical to ensur - ing a successful revamp. The ‘standard’ plant For many years, the ‘standard’ NGL recovery plant included a turboexpander, with the expanded feed gas providing top reflux to a fractionation column. This became known as a ‘simple expander plant’. The integration of the turbo- expander was a significant improvement over the previous standard, the ‘refrigerated J-T plant’, providing higher prod- uct recovery with less compression power. In the 1970s, The Ortloff Corporation improved on the simple expander plant by generating an additional reflux stream to feed the top of the fractionation column. 1 ,2 The
source of the reflux stream was either a portion of the separator vapour or the separator liquids or a combination of the two. The higher product recovery levels and lower power requirements quickly made this the next ‘standard’ process technology, commonly known as the gas sub- cooled process, or GSP (see Figure 1 ). Compared to the simple expander plant, the key fea - ture of GSP was the addition of a reflux stream created by condensing and subcooling a portion of the feed gas. This reflux stream captured more of the valuable ethane and heavier hydrocarbons that were otherwise lost to the res- idue gas stream from the top of the fractionation column. Although the GSP technology required an additional heat exchanger and an additional fractionation section at the top of the column, the product recoveries were significantly improved without requiring more compression power. This allowed operators to recover ethane and heavier hydrocar- bon components as the NGL product while also producing a mostly methane residue gas stream. The process could also be configured to reject the ethane into the residue gas stream while recovering only the propane and heavier components as a liquid product. The latter ‘ethane rejection mode’ of operation was useful in locations without a destina- tion for an ethane product or where market conditions made ethane more valuable for its heating value in the residue gas.
Subcooler
Residue gas
Residue gas compressor
Expander
Inlet gas
Demethaniser
Bottom product
Figure 1 Gas subcooled process (GSP)
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Today’s owners/operators are also frequently faced with the challenge of processing additional gas supply while minimising capital expenditures. A retrofit can provide a relatively inexpensive alternative to building a new plant to achieve higher production targets. Once the goals of a retrofit are identified, a study is rec - ommended to select the best process to achieve the stated goals. This study should include a simulation of the original process design and a simulation of the current plant that may include updates to equipment or possible deficiencies that may or may not be corrected with the retrofit. When an accurate representation of the equipment per- formance has been completed, simulations of various retro- fit alternatives can be developed. These simulations should consider all limitations of the current equipment, such as exchanger performance, rotating equipment capabilities (using available power and performance curves), and rat- ing of separators and columns at the proposed retrofit conditions. Finally, additional external restrictions must be consid - ered. These may include the available plot space and loca- tion for new equipment, time allotted for a plant shutdown to make tie-ins and install equipment, and available fund- ing for the project. A detailed analysis will identify the best technology for the plant retrofit. Retrofit options Retrofitting a cryogenic NGL recovery plant is not a new concept. The procedures applied more than 40 years ago to upgrade simple expander plants to GSP have not changed and are just as applicable to upgrading a standard GSP unit to an enhanced retrofit technology. Several papers have previously covered different retrofit options and the pro - cess of accomplishing retrofits. 4,5 One example is upgrading the GSP unit to the recycle split vapour (RSV) process. For the purposes of this article, we will re-introduce a simple GSP-to-RSV retrofit as a starting point and expand to more recent retrofit technology options specifically developed to upgrade a GSP plant. Recycle split vapour retrofit When increased product recovery is of key importance, converting the standard GSP plant to the RSV process can provide rapid returns with minimal downtime. Figure 2 shows a typical RSV retrofit applied to the gas subcooled process. New equipment and piping are shown in red, with tie-in points indicated by circles. As a means of extending the existing demethaniser with - out any welding or structural concerns, a new absorber column (packed or trayed) is added to improve fractiona- tion. Overhead vapour from the existing demethaniser is routed to the bottom of the absorber. Absorber bottoms pumps transport the bottom liquids to the top of the exist - ing column. The top reflux for the absorber is provided by a recycle stream of lean residue gas that has been compressed. This high-pressure gas is cooled, condensed, and sub- cooled in a new heat exchanger. The high-pressure liquid is then flashed to provide reflux for the top of the absorber,
New heat exchanger
Absorber
Subcooler
Residue gas
Pump
Residue gas compressor
Expander
Inlet gas
Demethaniser
Bottom product
Figure 2 Standard RSV retrofit
The GSP technology was a great improvement and remained the best available NGL recovery technology for many years, but it was not without limitations. In particular, the source of the top reflux stream was still essentially feed gas, containing significant fractions of ethane and propane. In ethane recovery mode, ethane recovery is limited to approx - imately 90-94%, with a propane recovery level of around 99%. Recoveries beyond these levels are technically achiev- able, but the required additional compression is not econom- ically viable. In addition, market conditions in recent years have, at times, made ethane more valuable in the residue gas product for the reasons previously mentioned, forcing operators to switch to ethane rejection mode. Unfortunately, the ‘standard’ GSP process typically loses 5% to 15% of the propane to the residue gas stream when configured for full ethane rejection, i.e., less than 2% ethane recovery. When an accurate representation of the equipment performance has been completed, simulations of various retrofit alternatives can be developed Process retrofit feasibility The limited performance of the ‘standard’ GSP technology provides many opportunities for retrofitting an older facil - ity with an enhanced, more efficient technology, especially given the large number of GSP installations worldwide. The goals for any retrofit will depend on the specifics of each project. As previously mentioned, potential benefits include higher product recoveries, improved operational flexibility, and increased plant throughput. These enhanced retrofit technologies can achieve greater than 99% ethane recovery and 100% propane recovery in ethane recovery mode or maintain greater than 99% propane recovery while rejecting ethane, with equal or only slightly more compression power.
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recovering valuable ethane and propane that exit the top of the existing demethaniser. The resulting RSV retrofit plant can recover as much as 99% of the ethane and 100% of the propane, or it can reject ethane, recovering less than 2% of the ethane while main- taining greater than 99% propane recovery. To achieve these recovery levels, the RSV process usually requires 10-15% more compression power compared to the base GSP plant, which is limited to 90-94% ethane recovery. Therefore, a ret- rofit will typically require either a separate recycle gas com - pressor or additional sales gas compression unless surplus compression power was originally installed. Retro-Flex retrofit The proprietary UOP Retro-Flex technology 6 was co-devel- oped in partnership with SME Products, LP specifically to increase the recoveries of propane and heavier components from GSP plants. It is applicable to both ethane recovery and ethane rejection modes of operation and does not require additional compression. Retro-Flex is considered a ‘bolt-on’ retrofit, with all new equipment located on a skid adjacent to the existing plant. This minimises the number of tie-in points and downtime. Figure 3 shows a Retro-Flex retrofit for a GSP system operating in ethane rejection mode. The cold flashed stream from the GSP subcooler, which normally feeds the top of the column (shown dashed), is instead routed to the cold refluxing module (CRM) for processing. The residue gas stream that normally flows from the column overhead directly to the subcooler (shown dashed) is instead routed to the CRM and then subsequently routed to the subcooler. The resulting condensed liquids are pumped to the top of the existing column as top reflux. For a standard GSP plant, the Retro-Flex installation requires only four tie-in points, shown with circles in Figure 3. By installing appropriate isolation valves, the installation downtime can be minimised, and the CRM module can be easily bypassed if desired, allowing the plant to revert to the original GSP section. Typically, no modifications to the column or other existing equipment are required. The CRM and pumps are mounted on a single module for easy instal- lation, and all equipment is accessible for monitoring and maintenance. In ethane rejection mode, a Retro-Flex retrofitted GSP plant provides a significant propane recovery improvement compared to the original plant performance. Retro-Flex can achieve greater than 99% propane recovery even when rejecting almost all the ethane, whereas the GSP process is typically limited to 85-94% propane recovery while reject- ing ethane. In ethane recovery mode, Retro-Flex achieves nearly 100% propane recovery, while GSP is typically lim- ited to less than 99% propane recovery. It is important to note that the maximum Retro-Flex ethane recovery is gen- erally limited to levels achievable by GSP, i.e., 90-94%. If ultra-high ethane recovery (greater than 98%) is desired, the Retro-Flex Plus technology⁷ should be consid - ered for the retrofit. In this process, a small reflux compres - sor is added to the standard Retro-Flex retrofit package to compress a portion of the column overhead vapour before
CRM
Subcooler
Residue gas
Residue gas compressor
Expander
Inlet gas
Demethaniser
Bottom product
Figure 3 Retro-Flex retrofit
condensing it in the CRM. The additional cooling and rec - tification of this stream allows Retro-Flex Plus to capture more of the unrecovered ethane. In ethane rejection oper- ation, the reflux compressor is shut down, and the retrofit design reverts to the Retro-Flex technology. A Retro-Flex retrofit offers a convenient upgrade option for GSP plant operators who want to improve their propane recovery levels, either in ethane recovery or rejection modes of operation. Moreover, with only four tie-in points, it requires minimal downtime and has small plot space requirements. GSP2 retrofit The standard RSV and Retro-Flex retrofits rely on existing equipment for all the feed gas processing. When through- put greater than nameplate capacity is desired, special con- sideration must be given to processing the additional feed gas without exceeding the existing equipment limitations. One such technology is the proprietary UOP Ortloff GSP2 process⁸ shown in Figure 4 . With GSP2, the feed gas is split into two streams, usually with the existing plant
New heat exchanger
Subcooler
Absorber
Residue gas
Pump
Residue gas compressor
Expander
Inlet gas
Demethaniser
Bottom product
Figure 4 GSP2 retrofit
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5 , combines the concepts of both the GSP2 and RSV ret- rofits previously described, requiring a new heat exchanger and an absorber column with pumps to ‘extend’ the exist- ing column. The absorber bottoms pumps are required to transfer liquids from the bottom of the absorber to the top of the existing demethaniser. As with GSP2, higher feed gas flow rates are possible because the feed gas is split into two streams. The first por- tion flows to the existing equipment at approximately the same design flow rate. The remainder of the feed gas flows to a new heat exchanger, where it is cooled, condensed, and subcooled with cold residue gas. It is then flashed to the existing column through the original top reflux piping. The original separator vapour reflux stream is separately cooled and condensed in the new heat exchanger before feeding the middle of the new absorber. As described in the RSV retrofit, a new reflux stream is provided by recycling a portion of the compressed residue gas stream. This lean gas stream is cooled, completely con- densed, and then subcooled in the new heat exchanger. It is then flashed to the absorber and fed as the top reflux stream. RSV2 is capable of increasing plant throughput by as much as 20% above nameplate capacity by bypassing additional flow around the existing equipment. At the same time, it achieves higher ethane and propane product recov- eries than the original GSP whether operating in ethane recovery or ethane rejection mode. Equipment considerations for retrofits Retrofitting any existing plant to improve performance and/ or throughput requires careful analysis. In addition to com- pleting simulations of the existing process and proposed configuration, the capabilities of the existing equipment must be confirmed. The following shortlist identifies some of the areas to review: • Metallurgy: To improve product recovery in a cryogenic NGL recovery plant, the selected retrofit process may require colder operating temperatures compared to the original design. All existing piping and equipment minimum design temperatures must be checked to ensure safe oper- ation under the new conditions • Design pressures: The selected retrofit process may allow the NGL recovery plant to achieve the desired prod- uct recoveries while operating the low-pressure section of the plant (including the demethaniser) at a higher pressure. The proposed retrofit must be designed with a safe margin from the pressure limitations of the existing equipment • Pumps: Higher product recoveries and certainly increased plant throughput will require greater pumping capacity in the product pumps. Existing pumps may be modified, or additional pumps may be installed to handle the higher liquid flows • Separators: With potentially higher vapour and liquid flow rates, the capability of all separators must be con- firmed at the new conditions • Column capacity: The ability of the existing column must be reviewed for the new conditions. Both the vapour and liquid flow rates and fractionation properties of each stage must be considered, and the column internals may require
New heat exchanger
Subcooler
Absorber
Residue gas
Pump
Residue gas compressor
Expander
Inlet gas
Demethaniser
Bottom product
Figure 5 RSV2 retrofit
continuing to process its design flow rate. The additional flow above nameplate capacity bypasses the existing inlet feed gas-cooling section and is cooled and condensed using cold residue gas in a new multi-pass heat exchanger. This new exchanger, which may either supplement or replace the existing subcooler, provides a similar functionality to the subcooler. The high-pressure, condensed feed gas A Retro-Flex retrofit offers a convenient upgrade option for GSP plant operators who want to improve their propane recovery levels, either in ethane recovery or rejection modes of operation bypass stream is then fed to the original top reflux point in the existing demethaniser. A new absorber column is added to ‘extend’ the existing fractionation column. Absorber bottoms pumps transfer the liquids leaving the bottom of the absorber to the top of the existing demethaniser, and the existing column over- head vapour is routed to the bottom of the new absorber. The top reflux for the absorber is provided by the original separator vapour stream that is cooled and condensed in the new heat exchanger. This provides the leanest possible reflux for the GSP process, which is preferable to using the richer feed gas to reflux the top of the absorber. GSP2 can increase the plant throughput by as much as 20% above nameplate capacity while maintaining or improving the original GSP plant product recoveries. RSV2 retrofit When the retrofit objectives include both higher product recoveries and additional throughput, the proprietary RSV2 process⁹ can be considered. This option, shown in Figure
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replacement with internals better suited for the retrofit operating conditions • Turboexpander: Retrofit operating conditions can be very different from the design point for the expander and should be reviewed by the turboexpander vendor. The expected operating efficiencies must be confirmed and incorporated into the retrofit simulation. In some cases, the expander and/or compressor wheel may need to be replaced for more efficient operation under the new conditions • Heat exchangers: The existing heat exchangers must be re-rated for the new conditions. This includes the heat transfer capability and any change in pressure drops at the new conditions • Bottom reboiler: The bottom reboiler ultimately provides the heat required to meet the liquid product specification. Higher recovery levels will require more heat input, man - dating a review of both the exchanger performance and the heating medium system (steam, hot oil). In cases where the original plant was not designed for ethane rejection but it is now desired, a new bottom reboiler with an external heat source will be required • Residue gas compression: With any increase in plant throughput, additional residue gas compression will likely be required. The same is true when upgrading to a technol - ogy that requires a residue recycle reflux stream. Potential options include a new parallel compressor to handle the higher flow rates, or simply a separate recycle gas com - pressor if plant throughput is not increased • Other units: In cases where increased throughput is desired, the effect on other units must be considered. This includes any inlet treating, such as amine units and dehy - dration, as well as downstream fractionation. These units may require debottlenecking to handle the extra flows. A careful review of existing equipment is as important as designing new equipment in any retrofit and is required to ensure a successful project. Case study 1 The Dover Hennesey Gas Plant, operated by Mustang Gas Products, LLC, was commissioned in 1978. It was designed to process 47 MMSCFD using a simple expander plant pro - cess, with the expander feeding the top of the demethaniser. Although plant performance was low compared to process technologies available today, the plant provided reliable operation for more than 40 years. Prior to the retrofit, the original design recovered 72.0% of the ethane and 98.4% of the propane. Retrofit goals were identified as follows: • Increase processing capacity to 80 MMSCFD • Improve product recoveries, with desired ethane recov - ery greater than 90% • Add the ability to reject ethane, with less than 10% ethane recovery level and maximum propane recovery. Given the desired ethane recovery level, a simple GSP retrofit would have sufficed. However, the requirement to maximise propane recovery while rejecting ethane demanded a different process. The chosen option was to upgrade this plant to GSP technology while also including
Figure 6 Absorber with CRM, left, and existing column, right
a Retro-Flex module to maintain the required propane recoveries. Since the original design only included the ability to recover ethane, the retrofit had to include equipment to accommodate ethane rejection operation. A new bottom reboiler heat exchanger was added to provide this capabil - ity, using hot oil as the heat medium. In addition, problems were identified in several of the existing equipment items, requiring some modifications and replacements: • The gas/gas exchanger was exhibiting very high-pressure
Dover Hennessey retrofit results
Pre-retrofit Retrofit performance Performance Predicted Actual
Ethane recovery mode Ethane recovery, % Propane recovery, % Ethane rejection mode Ethane recovery, % Propane recovery, % Plant capacity, MMSCFD Residue compression, hp
72.0 98.4
92.9
95.0
100.0
100.0
N/A N/A
<10.0 >99.0
<5.0
>99.0
47
80
80
5,400
5,400 1,200
5,400 1,200
C₃ refrigeration, hp
700
Table 1
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Comanche III gas plant retrofit results
Pre-retrofit Retrofit performance Performance Predicted Actual
Ethane recovery mode Ethane recovery, % Propane recovery, % Ethane rejection mode Ethane recovery, % Propane recovery, %
93.0 98.5
99.5
99.9
100.0
100.0
45.0 94.0
57.1 99.9
55.0 99.9
Table 2
shutdown. The upgraded plant was started up in late 2018. Table 1 summarises the performance before the retrofit, the predicted retrofit performance, and the actual perfor- mance after the retrofit. The Dover Hennessey Gas Plant retrofit resulted in significantly higher product recoveries, more flexibility to either recover or reject ethane to adjust to ethane market conditions, and decreased power usage per MMSCFD of gas processed. Case study 2 The Comanche III Gas Processing Plant, owned by Brazos Midstream, was commissioned in January 2018. It was designed as a standard skid-mounted plant using GSP with a design capacity of 200 MMSCFD. At start-up, the recov- ery levels were approximately 93% ethane and slightly less than 99% propane. Although this was a relatively new modular NGL recov- ery plant, Brazos Midstream quickly developed a desire to achieve higher propane recoveries, both in ethane recov - ery and ethane rejection modes of operation. Based on the market needs, the goals of the retrofit were identified as follows: • Improve product recoveries, particularly increasing the propane recovery level to essentially 100% in ethane recov- ery mode and greater than 99.5% while rejecting ethane at a 55% recovery level. Ethane recovery of greater than 99% was also desired • Provide an option to increase plant throughput in the future. To provide the desired ultra-high ethane recovery and essentially 100% propane recovery, a process like RSV was clearly required. However, the RSV2 option was cho- sen because of the potential to process additional gas. It was also attractive because of the ability to connect the new equipment with minimal downtime, requiring only six tie-ins. Given the young age of the original GSP plant and the application of the RSV2 feed gas bypass, the retrofit did not require any modifications to the existing equipment. New equipment for the RSV2 retrofit included the following, along with associated piping and controls: • Absorber column • Absorber bottoms pumps • Recycle gas exchanger/reflux condenser. Figure 7 shows the new equipment during construction. The absorber appears on the left, while the new recycle gas
Figure 7 Absorber, left, and new heat exchanger seen during installation
drops and poor thermal performance. It was replaced as part of the retrofit • The expander/compressor was refurbished and fitted with new expander and compressor wheels to handle the retrofit conditions • The demethaniser internals were replaced to improve packing efficiency and handle higher vapour and liquid flows. New equipment for the GSP/Retro-Flex retrofit included the following, along with associated piping and controls: • Absorber column • Absorber bottoms pumps • Reflux condenser/subcooler • Cold refluxing module (CRM) • Demethaniser hot oil reboiler • Air-cooled product cooler (for ethane rejection mode) • Supplemental refrigeration compression. For this project, the CRM was constructed on top of the absorber, eliminating the need for additional pumps typi- cally required for a Retro-Flex retrofit. The new absorber (with the CRM attached on top) can be seen next to the existing column in Figure 6 . The addition of the new equipment required five tie-in points, which were completed during a planned plant
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QUESTIONS & ANSW
Previous successes: revamping the unit to DMHC mode
exchanger/reflux condenser can be seen prior to connecting the piping and adding insulation. A typical RSV2 retrofit would require extra residue com - pression for the additional recycle gas flow. However, the Comanche III plant already had surplus residue compres - sion that was available. It is also important to note that the ethane recovery level at this facility must be maintained above approximately 55% in ethane rejection mode due to pipeline specifications requiring a minimum amount of ethane in the NGL product. The upgraded plant was started up in November 2021. Table 2 summarises the performance before the retrofit, the predicted retrofit performance, and the actual perfor - mance after the retrofit. The main objective of the Comanche III retrofit was to improve propane recovery in all operating modes. Application of the RSV2 process has always provided essentially 100% propane recovery, maximising product revenue. Although the ability of RSV2 to increase through - put is available, the operator has not yet pursued that option due to capacity limitations in other units. Conclusions Today’s constantly changing market conditions have left many owners/operators seeking ways to provide additional flexibility and improve margins with their existing assets. Process retrofits can provide an attractive option with min - imal downtime and expense. Although selecting the appro - priate retrofit technology requires consideration of several factors, enhanced technologies allow retrofits to improve product recoveries, increase throughput, and provide addi - tional operating flexibility. suboptimal catalyst utilisation and poor vapour–liquid dis- tribution throughout the cracking bed, which would reduce diesel yield and threaten cycle length. Standout performance has been delivered as a result of the new reactor internals and a leading-edge catalyst system. Tüpraş reports enhanced gas–liquid distribution over the catalyst beds. With lower operating temperatures and reduced radial temperature spreads, it has been able to: • Increase throughput by 5% • Process heavier feeds • Extend the cycle length from three to four years. Crucially, increasing the cycle length has enabled the planned distillate hydroprocessing catalyst changeout to fall within a major inspection turnaround, thereby saving Tüpraş the trouble and cost of a catalyst swap outside this period. Ortloff is a registered trademark. Retro-Flex, Retro-Flex Plus, GSP2, RSV, and RSV2 are marks of Honeywell UOP. References 1 Campbell R E, Wilkinson J D, US Patent No. 4,157,904. 2 Campbell R E, Wilkinson J D, US Patent No. 4,278,457. CatCheck is a mark of Shell Catalysts and Technologies. 3 Campbell R E, Wilkinson J D, Hudson H M, US Patent No. 5,568,737. 4 Lynch J T, Wilkinson J D, Hudson H M, Pitman R N, Process Retrofits Maximize the Value of Existing NGL and LPG Recovery Plants, presented at the 82nd Annual Convention of the Gas Processors Association, March 10, 2003, San Antonio, Texas. 5 Pierce M C, Cuellar K T, Lynch J T, Hudson H M, Peyton J A, Miller S A, 5th Generation NGL/LPG Recovery Technologies for Retrofits, presented at the 96th Annual Convention of the Gas Processors Association, April 11, 2017, San Antonio, Texas. 6 Hudson H M, Wilkinson J D, Lynch J T, Miller S A, Cuellar K T, Johnke A F, Lewis W L, US Patent No. 9,637,428. 7 Miller S A, Wilkinson J D, Lynch J T, Hudson H M, Cuellar K T, Johnke A F, Lewis W L, US Patent No. 10,551,119. 8 Anguiano J A, Wilkinson J D, Lynch J T, Hudson H M, US Patent Pending, Appl. No. 14/828,093. 9 Anguiano J A, Wilkinson J D, Lynch J T, Hudson H M, US Patent Pending, Appl. No. 16/815,829. Michael Pierce is Senior Engineering Manager for Ortloff Cryogenic Gas Processing Technologies at Honeywell UOP in Midland, Texas. He has almost 30 years of design experience in cryogenic NGL Enes Cındır is Chief Process Engineer in the hydroprocessing team at Tüpraş Kırıkkale Refinery, where he is responsible for hydrocracking units, hydrogen manufacturing units, sour water stripping, and sulphur recovery units. He has operational experience in refinery operation, dis - tributed control systems, staff management, process products quality monitoring, and catalyst performance monitoring. He holds a bach- elor’s degree in chemical engineering from Ankara University, Turkey. Ersev Dağ is Process Control Superintendent at Tüpraş Kırıkkale Re - finery, where he is responsible for the distributed control system and advanced process control environment. He holds a bachelor’s degree in chemical engineering from Gazi University, Turkey. Elif Kızlap is Process Superintendent at Tüpraş Kırıkkale Refinery and responsible for hydroprocessing units. Her role involves increasing unit profitability, adopting new technologies and optimisation. She holds bachelor’s and master’s degrees in chemical engineering from Hacettepe University, Turkey. She has published an article in the Jour- nal of Materials Science: Materials in Medicine (2019) and authored a Turkish patent related to her master’s degree topic. This is not the first time Tüpraş has demonstrated a will - ingness to think outside the box with this unit. Several years ago, when it was running as a high-pressure distil- late dewaxing unit, Tüpraş revamped it to run as a distil - late mild hydrocracker (DMHC) and became one of only a few refiners worldwide to benefit from this mode of operation. The objective was principally to enable the upgrading of two high-margin streams that are particu- larly challenging, namely the heavy gas oil (HGO) and light vacuum gas oil (LVGO) fractions. In distillate dewaxing service, the unit was process- ing HGO and meeting the T95 ultra-low-sulphur-diesel specification of 360°C. A DMHC can handle much greater quantities of HGO, and LVGO can also be added up to cold-flow property limits. Compared with a conventional distillate dewaxing unit, a DMHC delivers a step change in T90+ shift with benefits to density, cetane, and distil - late recovery. Cracking the heavy tail in a DMHC requires a highly customised catalyst solution that promotes ring
Mbugua Gitau is Senior Technical Service Engineer – Hydroprocessing at Shell Catalysts & Technologies, where he engages with refining cus - tomers, helping to unlock potential from their hydroprocessing units with a focus on value-adding catalyst solutions. He holds a master’s degree in chemical engineering from the University of Bath, UK. Email: mbugua.gitau@shell.com The revamp achieved a significant increase in T95 shift of 16°C, compared to the average of the origi - nal cycle when the unit was just in distillate dewaxing service. Additional benefits included a large density improvement, and therefore volume gain, and high die- sel recovery. opening, an advanced chemical upgrading technique. Such a solution, capturing a substantial margin, does not come off the shelf. To evaluate revamping the unit into a DMHC, Tüpraş worked with Shell Catalysts & Technologies. This work included dedicated pilot plant testing and thermal stabil- ity reviews. The solution they devised was a customised catalyst system. No hardware changes were necessary. It fea- tured a latest-generation, high-activity NiMo catalyst and a zeolite cracking catalyst to crack the heavy tail. As the latter catalyst also had a tendency for dewaxing, the win- ter diesel specifications were also met. John Wilkinson is a Senior Fellow and General Manager for Ortloff Cryogenic Gas Processing Technologies at Honeywell UOP in Midland, Texas. He has more than 48 years of design experience in cryogenic NGL recovery projects and is co-author of more than 80 US patents in hydrocarbon processing. He holds both a BA degree in chemical engineering/chemistry and a Master’s in chemical engineering from Rice University. upgrading process for the oil refining industry, producing vast quantities of transportation fuels. It is also expected that it will gain importance as supplier of propylene worldwide and occasionally ethylene. The FCC process and the products it produces will have to meet strict emission standards. With respect to the processing of residual feedstock in FCC, perhaps the most important change in modern FCC catalyst design is the quantification and subsequent optimisation of catalyst accessibility. Data from about 20 commercial experiences show that when contaminants like iron, vanadium, calcium and sodium increase, cata- lyst accessibility decreases rapidly. When catalysts with high accessibility (as measured by the AAI – Akzo Acces- sibility Index) are used, very marked improvements in activity and selectivity are achieved. recovery projects and is co-author of more than 10 US patents in hydrocarbon processing. He holds degrees in both chemical & petro - leum refining engineering and computer science from the Colorado School of Mines. Scott Miller is a Principal Engineer for Ortloff Cryogenic Gas Processing Technologies at Honeywell UOP in Midland, Texas. He has more than 22 years of experience in oil and gas, of which 15 years are in the design of cryogenic NGL recovery projects. He is co-author of more than 10 US patents in hydrocarbon processing and holds a BS degree in chemical engineering from Texas A&M University. High accessibility and accessibility retention are required the make the processing of even more contam- inated residual feedstock possible. Akzo Nobel has intro- duced the Opal, Sapphire and Coral catalysts line featuring enhanced accessibility. To enhance the production of light olefins, especially propylene, in the FCCU stable narrow pore zeolites, eg ZSM-5, are required. This has to be combined with a host FCC catalyst featuring high propensity to produce olefinic precursors, which are subsequently cracked to light olefins. Increased ability of the FCC catalysts system to make lower sulphur-containing products is necessary for an overall more profitable refining operation. Reduced NO x and SO x emissions from the FCC stack are also required. The introduction of new FCC catalyst additives as Rajnish (Raj) Patel is a Process Engineering Manager at Brazos Midstream. He has more than 12 years of engineering design experi - ence, of which six years are supporting the design of cryogenic NGL recovery projects. He holds an MBA from the University of Texas Dallas and BS degree in chemical engineering from Drexel University. S. Allen Ericksonis a Principal Process Engineer formerly with Honeywell UOP who supported Ortloff Cryogenic Gas Processing Technologies. Gerry Wooten is the Engineering and Projects Manager at Mustang Gas Products. He holds a BS in mechanical engineering with Special Distinction from the University of Oklahoma.
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Increasing efficiency of catalytic reformer unit fired heaters Application of ceramic coating on CRU heater tubing and refractory avoids oxidative scale formation, significantly lowering fuel consumption and CO 2 formation
Diyar Kiliç Mert and Alp Zeren Tüpraş Izmit Refinery Anton Korobeynikov and Sergei Merchev Integrated Global Services (IGS)
C atalytic reforming units (CRUs) are one of the high- est margin but most energy-demanding processes in oil refining. This flexible technology can produce high-octane gasoline components and individual aromatic hydrocarbons (xylene, benzene, toluene), which are raw materials for the petrochemical industry. The reforming process involves converting low-octane naphtha into a reformate at high temperatures and relatively low pressure. Catalytic reforming is typically carried out in a series of four reactors. Before entering each reactor, the feedstock is reheated to a temperature of 520-540°C. This reheating is achieved using high heat flux fired heaters consuming sizeable amounts of energy and emitting greenhouse gases (GHGs). Radiant coils within the catalytic reforming fired heater are made of 9%Cr chromium/molybdenum alloy (ASTM A335P9) and are subject to oxidation scale formation under firebox conditions. This oxidation scale may reach up to 1-2 mm thicknesses, reducing radiant coil thermal conductiv - ity, hindering radiant section efficiency, and significantly impacting the entire plant’s economic performance. Enhancing radiant efficiency A CRU with continuous catalyst regeneration (CCR) experiences a high rate of scale formation, approxi - mately reaching metal loss levels of 0.15-0.25 mm/year. The plant team thoroughly tracked the performance and detected an energy efficiency decrease due to scale for - mation. Every four years, during a major turnaround, the plant carried out activities to clean the external tube sur - faces. Nevertheless, a significant decrease in furnace effi - ciency was observed by the end of the second year after the turnaround. A detailed analysis of furnace operational data revealed the feasibility of high-emissivity ceramic coatings applica- tion to the radiant tube and refractory surfaces. The project was executed during a major turnaround, and the furnace performance analysis was carried out two months later. Post-project analysis showed a radiant efficiency gain of 13%, expected to last over the coating’s service life (8-10 years). Achieved radiant efficiency enhancement may be utilised for reducing fuel consumption along with CO2 emissions or throughput/severity increase under the same firing rat e .
Scale formation Refineries seek ways to find energy optimisation solutions in their processes and prioritises projects that are geared towards reducing fuel gas consumption and cutting GHG emissions. These initiatives align with strong commit - ments to a zero-carbon strategy, sustainability, and opti - mised energy usage, especially for units like the catalytic reformer. While catalytic reforming reactions occur in the stacked set of reactors, scale formation is observed on the external tube heater’s surfaces due to oxidation, fuel gas impuri - ties, and high heat flux. Oxidation scale formation results in the non-uniform heat distribution along the tubes and hotspots formation. Moreover, the radiant efficiency of the heater decreases with the corresponding fuel consumption increase. To prevent oxidation scale formation, the refinery decided to apply ceramic coatings to the furnace tube and refractory surfaces on-site during a turnaround.
A detailed analysis of furnace operational data revealed the feasibility of high-emissivity ceramic coatings application to the radiant tube and refractory surfaces
This case study pertains to the application of Cetek High Emissivity Coatings on both radiant tubes and refractory surfaces within the refinery catalytic reforming heaters. The primary objective was to enhance radiant efficiency and facilitate the sustainable operation of the heater for the next 8-10 years. Ceramic coatings nowadays are approved materials to increase the energy efficiency of fired heaters or debot - tleneck the heaters with various limitations, such as bridgewall temperature (BWT), firing duty or uneven heat flux distribution. Initially developed in the 1970s, coatings have found successful use in all heavy industrial appli- cations, including metals processing, aerospace, glass industry, and fertilisers but became especially beneficial in the oil and gas and petrochemical industries.
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