Greatly increase FCC residue processing through simple steps of additive control (ERTC)
With oncoming challenges of IMO and further gaseous emissions control regulations, it is becoming a challenge for refiners in the European area to stay profitable.
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It is the expectation that refineries that cannot adapt will close. Although there is a cost to increasing complexity to stay competitive, that cost does not always have to be high. Low-cost, low-risk and highly flexible approaches exist for the refiner to deploy rapidly, with the additional opportunity to test the benefits in a trial manner before any long-term commitments are made.
The most profitable fluid catalytic cracking (FCC) units are pushed constantly against their limits of operation. In many cases, this means maximising the processing of low-value feedstocks, such as residue. Without a viable future outlet for residue, refineries will struggle to sell these unwanted products on a market that will become quickly saturated following IMO. The FCC unit has long been a home to these distressed feeds, and the focus of many refiners is to determine how these heavy feeds can be best accommodated. The problem then distils down to: how to extend the coke handling capacity of your FCC unit?
The common limitations in FCC are, to different extents, all affected by delta coke. The limits we refer to are the normally encountered ones of maximum regenerator temperature, wet gas compressor volumetric throughput and air blower capacity. The fundamental challenge of delta coke has meant that catalyst suppliers focus on producing lower and lower delta coke catalysts for the FCC process. Incremental improvements in FCC catalyst technology have allowed refiners to process more heavy feed than they could 10 years ago, but the developments seen in catalyst technology are slow and may eventually reach a plateau once the methods deployed to this aim have all been exhausted.
At Johnson Matthey, we have taken a significant step in changing forever the terrain of dynamic delta coke management with our new additive, LO-COKER™. Even in catalyst systems that have already been optimised for minimum ultra-low catalytic coke, it will be possible to achieve a further reduction in delta coke of 10-12%. Thus, FCC operators that operate against the typical constraints can now extend the operation of the unit further at a vastly improved profitability.
Regardless of FCC unit type, catalyst platform or supplier, type of feed processed or operating mode, delta coke reductions in the range of 10% can be achieved with LO-COKER. Any refiner that is limited by maximum regenerator temperature now has the opportunity to take advantage of the delta coke reduction benefits through the use of a straightforward, non-hazardous additive. Reduction in delta coke allows conversion to be increased, higher feed rates and processing of more refractory feeds. The reduction of feedstock value through increased residue processing provides a large economic benefit to the refiner.
The built-in metal trapping functionality of LO-COKER typically affords equal or improved conversion at higher metals levels. Critically, this means poorer quality feeds can be processed without loss of yield value. A side effect of LO-COKER is adsorption of SOx from the FCC (in full burn or partial burn). This is important if you are limited on sour feed processing due to SOx emissions regulations as LO-COKER will reduce and possibly even eliminate any additional SOx mitigation method you use. This side benefit of reducing SOx can be seen as an additional cost saving.
LO-COKER is likely to be more cost-effective than any other way of increasing coke handling in the FCC. One common example of a method to increase the coke handling ability of a FCC is a catalyst cooler. Installing a catalyst cooler, either as part of the new build of a FCC or a retrofit project, is a high cost when compared to LO-COKER giving similar benefits at a fraction of the cost. In addition to the upfront capital cost of the equipment, it should be remembered that a catalyst cooler will generate steam from FCC feed via an increase in coke yield. This is likely to be a very costly way to raise steam. Ten per cent delta coke reduction with LO-COKER in a 90 Kbpd residue FCC is the equivalent of adding a catalyst cooler with a duty of 27 MW. A catalyst cooler of this size is a multimillion-dollar investment with a payback of many years. In comparison, LO-COKER will be almost instantly profitable with virtually no upfront cost required.
As well as 10% reduction in delta coke and 40-60% SOx reduction (in full burn), LO-COKER users witness dry gas reductions. This is mainly through a reduction in hydrogen make. Alleviating the wet gas compressor constraint by reducing low molecular weight species in the gas stream will allow an increase in feed rate, to target higher conversion, increase LPG make with higher ZSM-5 addition, or increase feed concarbon by increasing the residue proportion. This method of rebalancing the FCC unit through an effective manipulation of operating variables will increase unit profitability when LO-COKER is in use.
Understanding how LO-COKER gives these substantial reductions in delta coke and dry gas requires a deep knowledge of FCC operation and catalysis. Although a significant factor is metals trapping, thus allowing the main FCC catalyst to operate more effectively, this is not the only mechanism and does not fully explain the benefits seen. Other elements to consider include a synergistic effect with the FCC catalyst matrix to improve pre-cracking of refractory molecules, enhanced porosity for improved stripping, and the ability to improve the transfer of energy through the FCC process.
The data shown here is a result of extensive laboratory work carried out by Johnson Matthey to optimise the formulation of this new and revolutionary FCC additive. ACE pilot plant studies use a fresh catalyst formulated for moderate residue operation as a base case. Both sets of fresh catalyst and the 90/10 blend of fresh catalyst and LO-COKER additive are deactivated following the standard deactivation procedure: metal deposition on 11 cracking/regeneration cycles targeting 2750 ppm of vanadium and 1650 ppm of nickel, and steam deactivated at 788°C for 10 hours with 70% steam.
This short article originally appeared in the 2018 ERTC Newspaper, produced by PTQ / DigitalRefining.
For more information contact: Ventham@matthey.com
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