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SULFUR PLANT AND COKING
Publication date:1Q 2014
Sulfur Plant and Coking
The need for on-purpose sulfur production has become non-existent, as byproduct sulfur production from refineries and upstream oil and gas production sites more than meets the current demand for sulfur in the market. Further, major new supplies of byproduct sulfur are expected to be introduced in to market over the coming years due to tightening product specifications for transportation fuels, developing sour gas fields in the Middle East, and increasing oilsands production in Canada.
Typically, refinery sulfur plants consist of an acid gas removal unit, a Claus sulfur recovery unit, a tailgas treatment unit (to achieve sulfur recovery levels >99.99%), and, in some instances, sulfur degasification and finishing processes The amount of sulfur produced by each refinery will differ based on a number of factors including sulfur content in the feed coupled with the final product slate and final product specifications. This section of the Review will focus on the recovery of sulfur in a refinery setting; specifically omitted from the discussion is sulfur recovery technologies that are focused on upstream applications, such as oil and gas production.
Continued sulfur plant technology developments have focused on improving the energy efficiency of the acid gas removal unit, Claus unit, and tailgas treatment unit in order to lower operating costs as sulfur removal is done at a cost to the refiner and offers little back in terms of value, so minimizing costs is necessary to improve margins. Additionally, the utilization of Claus plants that can recover sulfur while mitigating the effects of high levels of ammonia was also discussed as deeper levels of HDS needed to meet more stringent gasoline sulfur requirements tend to increase ammonia production. Also, the use of trilobe and quadralobe tailgas treating catalysts for reducing the pressure drop across the tailgas treater in order to lower coke make on the catalyst has been commercialized by a number of catalyst companies. Finally, processes that can produce sulfuric acid from recovered sulfur may become more popular due to the expected sulfur glut that will occur over the coming years. The sulfur plant section also features the latest trends and technology offerings, including:
Throughout the world, crude and liquid product prices are rising as the global economy continues to recover from widespread demand destruction. Furthermore, there is an increasing presence of heavy crudes on the market; these crudes are typically sold at a discount, but require additional upgrading. As a result, many refiners have been focusing on technology suitable for upgrading these discounted, heavy feedstocks. Coking is a major bottom-of-the-barrel upgrading process whose popularity has risen steadily in response to heavier crude supplies and the dwindling demand for residual fuel oils. This process converts heavy feedstocks such as vacuum residuals, heavy cracked gas oils, and decanted oils into gas, LPG, relatively low-boiling distillates, and solid coke. Furthermore, petroleum coke, a byproduct of coking, is finding use in a variety of markets throughout the industrial sector. Historically, strong gasoline markets and diverse outlets for petroleum coke made delayed coking the most prolific residue upgrading technique; however, some of these market factors are changing as diesel demand is outpacing gasoline and some outlets for petcoke have or will come under scrutiny with new SOX and CO2 regulations. Operational improvements and technical advances must be applied by refiners to support continued growth of coking technology as it is utilized in plants dealing with difficult feedstocks, tight production margins, demanding efficiency standards, and stringent environmental constraints.
As the worldwide crude slate shifts to heavy and extra-heavy refinery feeds, refiners will need to take advantage of various bottoms upgrading techniques to cut deeper into the crude barrel to yield valuable distillate products. Many of these technologies have been around since the 1950s or even earlier and have reached commercial maturity. Some of the more advanced processes have recently evolved as modifications of conventional processes to deal with the increased resid contents of incoming feeds. Finally, the development of highly integrated processing schemes has aided refiners in economically processing resid streams.
Due to the flexibility of the process, coking has emerged as the leading technology in residue upgrading both in the refinery and in upstream heavy oil upgrading plants. Several significant trends have emerged that can be identified by analyzing the current state-of-the-art technology and the recent research work related to coking processes. Strategies to increase efficiency and liquid yield have become prevalent, as have integrated processing options that incorporate delayed coking technology with other refining units. Significant resources have also been invested in efforts to better understand and control coke quality and morphology in delayed coking process. Also, advances in coke drums and feed mechanisms, coker furnace design and use, processes designed for unique/specialized feeds, and improvements in maintenance techniques and equipment have been presented that can extend run length to augment production capacity. Finally, safety issues related to the coking process have emerged as a primary area of focus in the industry. Alternative uses of petroleum coke and handling of coking water have also seen advancements. The coking section also features the latest trends and technology offerings, including:
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Keywords: SRU, acid gas removal, AGR, Claus unit, tailgas treating, TGT, SOX, desulfurization, clean fuels specification, H2S, ultra-low sulfur, ULSD, ULSG, clean fuels, elemental sulfur, direct oxidation, amine scrubbing, amine solvent, advanced process control, acid gas corrosion, foaming, amine loss, fuel gas sweetening, ammonia destruction, sour crude, sub dew-point Claus, sulfur degasification, sulfur finishing, sulfur granulation, analyzers, instrumentation
coking, delayed coking, FLEXICOKING, FLUID COKING, fluidized-bed coking, continuous coking, additives, heavy oil, oilsands, bitumen, opportunity crudes, fuel oil, coker gas oil, integration, bottoms upgrading, bottom-of-the-barrel processing, coker heater, coker furnace, coke drum, coker fractionator, unheading, coke, petcoke, petroleum coke, anode-grade coke, fuel-grade coke, electrode-grade coke, needle coke, sponge coke, coker gas oil, anti-fouling agents, hydrocutting, hydrocyclone