(65b) Thermal Cracking Partial Upgrading Product Unstable and Incompatible

Bitumen and extra heavy oil containing asphaltenes are usually blended with condensate, light conventional oil, and, or fully upgraded, hydrotreated synthetic crude oil (SCO) for pipeline transportation and sale to the refinery market.  Research and practice keep the ratio of light oil, condensate or SCO and the bitumen to the portions that will not cause the precipitation and deposition of asphaltenes.  Some dispersants, flow improvers or additives are used in the bitumen blends.  With blending as the most standard, common method of improving viscosity and density, there is little risk to this production transportation method.

     Recently heated rail cars are used to transport bitumen without diluent. As the ratio of asphaltenes to other components such as resin does not change, there is little risk of precipitation of asphaltenes in this production transportation method.  

     During the period of high light crude price, low heavy crude price, high heavy-light crude differential, high diluent and high natural gas cost, partial upgrading schemes were proposed for in-situ down hole and at the wellhead. Typically, the partial upgrader proposals have not provided any flow assurance data that show asphaltenes do not precipitate or deposit in the process heaters, reactors, pipes, vessels, exchangers, downstream, or in storage. 

     Over twenty in-situ down hole methods are in various stages of pilot and testing techniques that might result in some partial upgrading.  Over forty field located partial upgrading schemes have been proposed, none have been build or otherwise commercially proven.  Down hole or above ground, the goal is to produce a lower viscosity material at the well-site, upstream, or midstream, that would require less diluent or natural gas. For example Fluid Catalytic Cracking, FCC, analogues UOP-CCU, Catalytic Crude Upgrading, Viscositor, Ivanhoe Energy IE-HTL, ETX-IYQ, NZ cracking use FCC configurations without hydrotreating the reaction product.  For example, HTL uses high temperature short contact time to thermally crack bitumen vacuum bottoms. 

     Asphaltene deposition and diene gum formation are major flow assurance risks in partial upgrading thermal processing like HTL with high temperature short contact time reactions in an FCC analogue circulating sand.

     The above ground field located partial upgrading methods have no commercial installations to validate performance.  Despite claims of tens and hundreds of runs and commercial readiness, there is very little pilot plant or demonstration unit data on the product properties of the various methods; there is virtually no flow assurance data on the stability or compatibility of the various methods proposed for partial upgrading.  

     One thermal cracking partial upgrading process claims to have stable product, but is unable provide any data to demonstrate stability using any of the sixty possible test methods that have been used to show stability of fuel oils, crude, thermally and, or catalytically cracked products.  On the other hand, problems associated with thermal reaction products are well known from the earliest days of refining with Shukhov, Burton and Dubbs process units.  Unstable thermal reaction products at higher temperatures have been recognized and addressed throughout the long history of delayed, fluid and flexi coking, visbreaking, thermal and catalytic cracking.

     High temperature thermal cracked reactions yield unstable products and with bitumen resid as feed most yield asphaltenes that are self-incompatible, which is completely different than hydrotreated, stable, and compatible SCO. Rather than overstate, confuse, or misrepresent the thermally degraded quality, partial upgraded material should be named differently from SCO, for example, Partially Upgraded Thermal Cracked Unstable Product would have acronym PUTCUP.  PUTCUP with high olefins and dienes, disallowed by some pipelines, could be shipped like raw bitumen in rail cars, or if olefins allowed could be shipped like dilbit in pipelines or rail cars after blending with diluent to gravity or viscosity specification.  PUTCUP includes heavy gum forming dienes in naphtha, jet and distillate fractions, self-incompatible asphaltenes and inorganic feed and produced solids in all fractions. 

     Patents and other open literature sources show short contact, high temperature reaction process products, like FCC, fluidcoker, HTL and pyrolysis naphtha and distillates, are less stable than lower temperature longer contact time products like visbreaker and delayed coker naphtha and distillates.  These facts are in contrast to unsupported marketing claims, like HTL, of stable product due to shorter time. Simple chemistry and physics, it’s about temperature, the higher the reaction temperature the more unstable product is formed, as shown by reaction product gases that have higher dienes including 1,3-butadiene. The higher the short contact reaction temperature, the more 1,3-butadiene in product gas with more liquid dienes throughout the reactor product, and the less stable the product.  Thermal cracking processes with higher mix zone temperatures like HTL produce higher 1,3-butadiene, and corresponding higher C5-C10 dienes leading to high gum formation than process with lower reaction mix zone temperatures.

     Processes, like HTL, with high temperature short contact time of fractions of seconds result in immediate reactor and downstream plugging with unstable self-incompatible asphaltenes reaction product precipitating and depositing with inorganic feed and produced solids and downstream heavy gum formation and deposits caused by dienes in naphtha, jet and distillate fractions. Thermal cracked product gum and residual asphaltenes deposit and plug reactors, transfer lines, quench towers, fractionation towers, downstream filters, catalyst guard beds, hydrotreaters, pumps, pipes and tanks. Self-incompatible PUTCUP is worse than just incompatible with other liquids as PUTCUP has precipitated, condensed and flocculated asphaltenes, semi-solids and solids that are out of solution, toluene insoluble, and cannot be resuspended or dissolved by any dispersant, flow improver, or other additive available. 

     No partial upgraders have been built to prove reliable, long term flow assurance of a year or more continuous operation, rather than a few hours of pilot or demonstration unit run before terminated due to plugging, etc..  Proof of reliable operation with industry standard on-stream factors over 95% uptime is necessary to reduce high risk of a high capital cost, ~ $550 million, investment in an unproven process.  The ~$550 million for a 20,000 bpd partial HTL upgrader is like other partial upgrader estimates that typically don’t include hydrotreating in order to show a significantly lower capital cost compared to full upgraders.  However, partial upgrading reactor product is instantaneously self-incompatible with precipitated or condensed asphaltenes depositing and plugging  in and on reactor walls, transfer lines, quench towers, pipes, and vessels downstream, and is inherently unstable due to dienes that form gums downstream of the reactor. PUTCUP fractions are thermally degraded compared to crude or bitumen.  PUTCUP properties are similar to fluid coker product fractions.  

    Reduced flow assurance risk solutions to these partial upgrading challenges include the common practice of shipping bitumen in heated rail cars, or blending bitumen with diluent without partial upgrading.