ERTC 2023
Transforming a refinery unit into a key component of end-of-life plastic circularity
Nicolas MENET, Ana-Isabel PACO and Thomas MALLET AXENS
Every year, in Europe alone, roughly 30 million tonnes of plastic waste is col- lected. However, more than 80% of that resource is not recycled into new prod- ucts because the majority of it is still incinerated, exported, or dumped in land- fills. This is a waste of precious resources that could be used as secondary raw materials in place of fossil feedstock in addition to being a source of CO₂ emis- sions. A rapid scale-up of mechanical and chemical recycling capability is required to further increase plastic recycling and support Europe in meeting its recycled content targets. Plastic production pathways Generally, today, the economics of a cir- cular, sustainable plastics economy remain challenging in terms of profitabil- ity. Strengthening the links in the plastics value chain and implementing a solid pol- icy framework will be key. However, effi- cient, innovative solutions will need to be implemented to improve the economics of the different recycling pathways (see Figure 1 ). The pyrolysis pathway will play an impor- tant role in addressing the difficult-to- recycle end-of-life plastic while meeting the production objectives of virgin-qual- ity food-grade plastics. When consider- ing it, we see that an economically viable and efficient way of scaling up that route is to integrate it into existing refineries or petrochemical sites. The efficiency will not only come from utilities sharing, process synergies, and overall yield optimisation but also from opportunities to reduce pro- jects’ Capex, repurposing existing hydro- processing units for the purification and upgrading of the recycled oil prior to pro- cessing in the steam cracker. REWIND ® MIX: A UNIQUE SOLUTION TO PURIFY PYROLYSIS OILS AND MEET STRINGENT STEAM CRACKER SPECIFICATIONS Pyrolysis of mix plastic waste is today considered the unique industrially avail- able route to permit a true closed-loop recycling of polyolefin, meeting quality requirements and regulatory objectives. That route, however, relies on the ability to properly purify the pyrolysis oil (pyoil) for reprocessing in an existing petrochemical plant. That purification step is not a trivial refin- ing kind of processing as pyrolysis oil usu- ally combines multiple contaminants and unstable molecules that, if not removed and stabilised, would jeopardise the safe operation and performance of the petro- chemical plant steam cracker. Repsol, Axens, and IFP Energies nou- velles (IFPEN), fully committed to playing a major role in the chemical recycling indus- try, have joined their efforts to unlock the recovery of plastic waste that would oth- erwise remain in the landfills or be incin- erated so that it could be turned into
Great candidates for retrofit into Rewind Mix • HCK • Diesel and kero hydrotreatment • Naphtha hydrotreatment
Mechanical recycling
Recycled plastics Recycled plastics
Waste collection and sorting
Recycling dissolution
Dissolution
Depolymerisation
Recycled monomer
Chemical recycling
Pyrolysis
Recycled plastics
Gasi cation
Recycled feedstock (Syngas pyrolysis oil)
• Pygaz hydrotreatment • VGO hydrotreatment • Lube hydrotreatment
Plastic production (Polymerisation)
Bio-based and Bio-attributed plastics Carbon-captured plastics Fossil-based plastics
Bio - based feedstock
first stage. The check-run is carried out by Axens technical experts who are special- ised in units’ start-up, follow-up, trouble- shooting, and operating excellence. CASE STUDY: REVAMPING AN EXISTING EUROPEAN DHT UNIT INTO REWIND MIX Rewind Mix process scheme has been developed relying on Axens’ proven expe- rience in hydrotreatment and, therefore, uses similar codes as conventional hydro- treatment units typically found in refinery and petrochemical complexes. Retrofitting existing or idle units into Rewind Mix is therefore feasible, and hydrocracking and hydrotreatment units are great candidates. Axens has already performed several studies of retrofitting hydrotreatment units into Rewind Mix, demonstrating that the conversion of idle units allow signifi- cant investment cost reduction compared to a grassroots unit. As an example, Axens has been working on the possibility of revamping an existing European DHT unit into Rewind Mix. After a preliminary assessment of the existing unit, consisting of gathering all relevant information (equipment as-built documen- tation, operation history) to identify the main bottlenecks, Axens has elaborated several revamping options focusing on dif- ferent drivers the client was interested in: u Identify the maximum pyrolysis oil treatment capacity while reusing most of the existing equipment. v Maximise the pyrolysis oil throughput while minimising the capital investment; for example, reusing main equipment such as reactors, heaters, and compressors. After agreeing with the client on the most profitable scenario, Axens developed a detailed study of the selected option with the objective to provide more accu- rate economics and LCA information. The results of the study revealed that the DHT unit is a good candidate for being retrofit- ted into Rewind Mix. Indeed, the unit ret- rofit cost has been estimated to be up to 65% lower than a grassroots Rewind Mix with the same capacity and performance. Each above technology is a great candidate for revamping into Rewind Mix, offering advantages and limits that, case by case, can be studied and optimised by Axens.
Carbon-captured feedstock
Circular feedstocks
Fossil feedstock
Figure 1 Plastic production pathways
key factor in success. Indeed, pyoil prod- ucts concentrate a large proportion of mul- tiple contaminants, making it difficult to analyse them through conventional analy- sis methods. As pyrolysis oil qualities also vary sub- stantially, depending on the nature of the feedstock to the pyrolysis plant, the Rewind Mix process has a unique flexibil- ity to cope with those quality changes. It is able to continually guarantee the produc- tion of on-specification products suitable for direct undiluted processing on a naph- tha steam cracker. In addition to its capacity to process a full range of pyrolysis oil to maximise closed-loop production of polyolefin circu- lar polymer, Rewind Mix can also embed a hydrocracking function that will turn heav- ier products back into virgin equivalent recycled naphtha. AXENS: A CASE-BY-CASE PRAGMATIC APPROACH TO ENHANCE REVAMP CAPABILITIES Axens, through its Process Licensing Department, is able to conduct feasibility studies for identifying all technical solu- tions to overcome pyrolysis oil processing impacts on existing hydrotreatment units: catalyst poisoning, reactor pressure drop, exotherm, corrosion, hydrogen partial pres- sure, hydrogen consumption, unit turndown, unbalanced stripping, and fractionation. Axens proposes a case-by-case prag- matic approach to select the best revamp solution. This approach consists of succes- sive phases performed before the beginning of the detailed engineering design to opti- mise available resources: a scoping study, a process study, and then a process design package could be proposed (see Figure 2 ). To better optimise the existing process and to check the possible bottlenecks on the existing unit, a site check-run survey of the unit is highly recommended as a
high-quality, virgin-like circular polyole- fins and other chemical products through pyrolysis. How? By solving the issue of purification/decontamination of those pyrolysis oils. Those efforts resulted in the development and commercialisation of the Rewind Mix technology. The Rewind Mix process removes impu- rities such as silicon, chlorine, di-olefins, and other metals from the plastics pyroly- sis oils produced, allowing direct and undi-
did you know? Retrofitting existing or idle units into Rewind Mix is feasible, and hydrocracking and hydrotreatment units are great candidates
luted feed to the steam cracker. Proper purification is key, as contaminants could jeopardise the operation of the petrochem- ical steam cracker. Besides, contaminants can also flow on downstream units and ulti- mately end up in final polymers products. The successful commercialisation of that purification technology would not have been possible without the exper- tise IFPEN, Axens, and Repsol have built throughout the last decades on the hydro- processing of various polluted petrochemi- cals streams. Moreover, the development of new anal- ysis methods by IFPEN to properly assess the different qualities of pyoil has been a
Axens’ scope of work
Scoping study
Detailed engineering
Feasibil i ty study
Process study
Process design package
Rewind Mix is a trademark of Axens.
Contact: Nicolas.MENET@axens.net
Figure 2 Typical approach to select best revamp strategy
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