PTQ Q3 2022 Issue

incorporate configurations dedicated to selective produc - tion of a wide range of aromatics, including metaxylene, orthoxylene, benzene, and toluene. Turning challenges into opportunities Keeping units operating as long as possible without com- promising safety and reliability has always affected effi - ciency and utilisation. More importantly, high efficiency also translates to reduced emissions, as discussed in the follow- ing summaries: Improving coker heaters Coker heaters are the most critical heaters in any refinery. They process the heaviest feedstock and are prone to cok- ing from day one. The tube metal temperature starts going up from day one, and the run length is dictated by the tube metal temperature rise per day. According to Ashutog Garg, Vice President at Furnace Improvements in Sugar Land, Texas, “We have analyzed several coker heaters operating data and found that the daily temperature increase ranges from 2 to 8 °F.” He noted that coker heaters require radiant section retubing every 7-10 years. A. Garg also noted that Furnace Improvements has worked on several coker heaters where they have improved the existing radiant and convection section coil designs to improve the run length of the coker heaters. Adding to that, Hemendra Khakhar, Technology BD Director at Wood PLC in Houston, said, “We are hearing from more and more refiners that they are not operating their delayed coker units (DCUs) at design capacity limit.” Khakhar noted that reasons for refiners not operating DCUs at capacity limits include decreased demand for transporta- tion fuels and replacing the portion of asphaltenic vacuum residue feed with shale crude. Khakhar noted that with conventional transportation fuel demand only expected to go down further, demand for synthetic graphite used in battery manufacture is expected to grow. Khakhar emphasised a focus on repurposing an existing fuel-grade coker to produce needle coke, as well as co-processing of recycle waste plastics/rubber. in a DCU to improve operation and increase profitability, with the fol - lowing proposed solutions: •High ROI and low CAPEX revamps for needle coking production • Recycle plastic/rubber and renewable pyrolysis oil pro- cessing in DCUs • Used lubricants re-refining to produce IMO compliant low sulphur fuel oil (LSFO) • Waste plastics mix in SDA asphalt for improved margins • SDA revamps for heavy lube stocks production • Digital solutions and technology support to optimise unit operation. Revamping existing FCC units Long-term projections developed to assist the downstream industry in decision-making in an ever-changing business environment consistently identify aromatics and propylene as healthy growth markets. They also consistently identify conversion of oil residue fractions, which see their outlets

Figure 2 Chemical structure of paraxyxlene molecule (C 8 H 10 )

and tyres). Furthermore, the use of existing and, especially, depreciated units to produce fuels and petrochemicals (such as light olefins and aromatics) facilitates recycling economics. To date, more refiners are exploring the oppor - tunity to operate as waste refineries, whereas some refin - ers are using their current FCC and hydroprocessing units to co-feed alternative fuels. Polymer production According to Prescient Strategic Intelligence, the global polymer market is forecast to reach $838.5 billion by 2030. Most of the demand is attributed to the increasing demand for the product in the packaging, automotive, and electron- ics industries. High-purity olefins building blocks in crude- oil-to-chemicals complexes are imperative for maximum conversion of polymerisation reactions. Polymer demand has accelerated the development of FCC technology able to produce over 25 wt% propylene by converting heavy residue under severe FCC conditions. For example, the Axens HS-FCC process is highly selective to propylene using a down-flow reactor concept. The stand- alone cracking unit operates over a range of severities on VGO and residue feedstock. The process also produces a considerable number of valuable by-products, including butenes feedstock for the lubricants and resins market. Catalysts formulated for specific types of feedstocks and reactor conditions are opening new revenue streams fur- ther downstream (new polymer structures, plastics). FCC propylene provides feedstock for the petrochemical poly- mer market, with an expected annual growth rate of 3-4% CAGR, while the biobased polymer market is expected to grow at almost 20% CAGR. Aromatics production The main entry point to the aromatics block is typically a reforming technology dedicated to the production of aro- matics from heavy naphtha, employing continuous catalyst regeneration. The actual catalyst system should maximise aromatics rings production while retaining operability and reliability. Reforming of heavy naphtha is the first step to high- purity paraxylene (see Figure 2 ), a key intermediate in the value chain in the manufacture of polyethylene terephthal- ate (PET) and fibre-consuming products. It is also important to recover aromatic molecules present in various streams such as pyrolysis gasoline or aromatics- rich cuts from the FCC unit. Ideally, most aromatics ‘blocks’

PTQ Q3 2022