been successfully deployed under various operational conditions in over 100 oxygen enrichment pro- jects worldwide. Multiple reference projects also attest to the safety, effi - ciency and climate mitigation bene- fits of enrichment technology in the petrochemical industry. Case study: toluene to benzoic acid A leading global specialty chemi- cals company uses oxygen enrich- ment technology from Linde for the oxidation of toluene to benzoic acid. Linde’s technology has helped to increase the throughput and improve the quality of the prod- uct by increasing selectivity (more of the feed is reacted to the desired product). Linde initially presented lab results to the customer as proof- of-concept. Linde went on to offer a full-scale test at one of the two production lines to validate the lab results in an operating environment. Prior to testing, Linde supported a HAZOP study to demonstrate that the safety concept it presented was robust. During a regular shutdown of the plant, the Oxymix Injector was installed. The injector was connected to a mobile trailer with an evaporator and a test Oxymix Flowtrain oxygen control unit (see Figure 4 ).
Signals to DCS
O
Gas injector (O xymix I njector)
as fuel oil diluent. But in some refineries, this stream can be used to produce black carbon. Light cycle oil (LCO) has a distillation range close to diesel, and this stream is generally directed to treatment in severe hydrotreating units (due to the high aromaticity) before sending to the refinery diesel pool. These process steps shed light on opportunities that a portion of the recycling of plastic materials could also be done through FCC units at different injection points, mixed with FCC feed, or hydrotreated (pretreating) before feeding to the FCC. Heavy cracked naphtha is usually directed to the refinery gasoline pool. However, in scenarios where the objective is to raise the production of middle distillates, this stream can be sent to hydrotreating units for further diesel production. Refiners focused on producing high-quality needle coke tend to operate their FCC units optimised to maximise the decanted oil (DO) due to high aromaticity. This is the less common operating mode in FCC units, where the main objective is to maximise DO yield and achieve aromatic res- idue quality requirements. The aromatic residue is normally applied to produce black carbon, which is in high demand in some markets. The main difficulty in complying with the aromatic residue specification is DO ash content. This parameter is strictly related to cyclone efficiency in the catalyst regeneration section. To achieve this objective, some refiners apply addi- tives to promote de-ash decantation in the final tanks or specific filtration systems, requiring more capital spending. Another key quality parameter to meet aromatic residue specification is the BMCI (Bureau of Mines Correlation Index) related to DO aromaticity. To achieve the current specifica- tions of black carbon, it is necessary to achieve a minimum BMCI higher than 120. The BMCI is calculated based on the viscosity of the decanted oil at the temperature of 210°F. DO metals content also needs to be controlled, especially sodium, aluminium, and silicon. Going forwards, we can visualise an FCC unit without CO₂ emissions or with significant CO₂ reduction and trans - formed to new products – perhaps with regenerator heat- ing with renewable electricity. In addition, new catalysts can be designed to produce less coke (i.e., lower loss of feed to coke formation) while maintaining the energy balance. In addition to better control of regenerator temperature and cat/oil ratio with a double riser or a proprietary down flow- type FCC reactor, other value-adding chemistry includes new zeolites, matrix technology incorporating new meso- pore distribution, and more active or selectivity catalyst. Other initiatives are directed towards connecting regen- erator emissions to the transformation of CO₂ into new products that employ green hydrogen. Another pathway to reducing energy intensity is the use of membrane separa- tion technology as a gas component separation. These bespoke schemes involving the integration of 690ºC, and the coke content on the regenerated catalyst was burned and reduced to about 0.05 wt% before return- ing to the reactor. Air Those factors will continue to propel new variations of future FCC configurations. Without a doubt, environmental drivers have prompted evolutionary changes where we see actual and future advances in FCC technology coming from many sources that tend to ‘act’ synergistically. Transformation successfully deployed in various petrochemical plants, upstream petrochemical processes such as FCC, and in Claus units. Key safety requirements include a flow control valve enabling rapid, even mix- ing of the oxygen feed upstream of the reactor; a flow control cab - inet ensuring the oxygen content remains under the MOC; various safety features such as block-and- bleed valves to cut off the gas sup - ply in the event of an emergency; piping temperature control to make sure that cold oxygen does not enter the air duct; and complete discon- nection of the gas supply from the processing plant during shutdowns (with gas creep safeguards). Industrial gas specialists such as Linde Gas have developed robust safety concepts addressing all of these concerns and issues. With extensive experience in the design and delivery of oxygen enrichment applications and a proven track LOX tank Evaporator O xymix Flowtrain Figure 4 Arrangement for the installation of an Oxymix Injector
The operating severity in maximum aromatic residue mode tends to be high with high TRX, high catalyst/oil ratio, and high catalyst activity. An observed side effect is higher octane number in cracked naphtha due to the incorporation of aromatics compounds in this intermediate. In maximum aromatic residue operating mode, the main restrictions are the temperature of the bottom section in the main fractionator, leading to coke formation, metallur- gic limitations in the hot sections, as well as the capacity of blowers and cold area compressors. The use of FCCDO as a needle precursor in a DCU is determined by a multitude of factors: • The relatively high temperature (approximately 700°C) of the FCC reaction promotes aromaticity (although not to the same degree as HT-CTP). Thus, long chain alkyl functions may persist on the aromatic ring structure, leading to ste- ric hindrance during polycondensation and a reduction in microstructural order during delayed coking • As a carbon rejection conversion process, FCC is dehydro- genative. While this favours aromatisation, it may addition- ally lead to the production of olefins or conjugated dienes, which are known to promote crosslinking during delayed coking, leading to microstructural defects and a higher coke CTE. However, olefin formation is usually associated with lighter distillates, and its effect on heavier residual mol- ecules may not be so profound • The reference to vanadium (V) and nickel (Ni) impurities in Table 1 would (based on an initial assessment) seem out of place. However, it holds considerable value as both Ni and V are bound as organo-metallics (and not inorgani- cally as with other metallic contaminants). Thus, Ni and V pyphorins cannot be extracted using traditional filtration Maria Nieves Alvarez is a senior advisor in oil refining/petrochemical technology at MERYT Catalysts & Innovation. She has over 38 years’ experience in the refining and petrochemical industries, specialising in the analysis of refining schemes and new products to the development of rigorous and non-rigorous models. She graduated as a chemical engi- neer from the Central University of Venezuela and holds various patents. renewable energy result in a much more sustainable pro- cess. Recycling/treatment of limited resources (water, hydrogen) and integration of more intelligent control sys- tems should also be considered to reduce both environ- mental impact and operating costs. FCC adapts to new industry needs, including the impera- tive for demonstrating environmental stewardship, and remains one of the most flexible catalytic processes in an era with higher expectations for premium petrochemicals in a cyclic economy. This new era of ‘reuse’ and transitioning to safer energies for the environment also leads to recycled and extended life span of existing facility assets and processes. Renewable energies backed by emergency energy accumulators open a world of possibilities in controlling future energy costs while improving the environment. References 1 Mohammed A. Alabdullah et al . 2 F P C Guedes, Avaliaç˜ao, 2015. 3 J H Gary, G E Handwerk, M J Kaiser, Petroleum Refining , CRC Press, 2007. 4 E Vogt, B M Weckhuysen, 2015. 5 A R Pinho, M B B Almeida, F L Mendes, L C Casavechia, M S Talmadge, C Kinchin, HL Chum, 2015-2021. Enriched air to oxidation reactor
record in the safe handling and metering of oxygen across different supply modes, the company spe- cialises in fail-safe oxygen injection technologies tailored to safety-crit- ical applications, and in reliable measuring and control equipment. In addition to its Oxymix Injector and Oxymix Flowtrain gas control cabinet, both designed for precise, even and rapid metering and mix- ing of the oxygen within a short distance to avoid hotspots and run- away reactions, the company offers extensive feasibility assessments and field trials, project execution services, plus maintenance and gas supply services to ensure all-round peace of mind. Oxygen enrichment in action Drawing on its experience in low, mid and high level oxygen enrich- ment applications, Linde supplies a low risk, low investment and short payback solution for debottlenecking
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