High-conversion refinery

After World War II most of these alkylation units were subsequently shut down and the process received little attention until the phase out of lead. The alkylation plant then experienced a revival as a source of high-quality, high-octane gasoline. In many of today s high conversion refineries, the FCC unit and the alkylation unit are usually operated hand-in-hand. 

Figure 8 shows a simplified layout for a high-conversion refinery in the United States. The diagram doesn t show product blending and sulfur recovery units, but these are almost always present. Lube-oil processing and hydrogen production units also may be present. 

In short The petroleum refining business is highly capital-intensive and competition is fierce. The predominant cost - purchase of crude oil - is beyond a refiner s control, due to the fact that crude-oil costs are, for the most part, determined by OPEC. Even so, large, well-located, high-conversion refineries can be very profitable, especially during spikes in product prices. In 2005, crack spreads reached all-time highs, exceeding 15 per barrel in most of the United States and > 20 per barrel in California. 

Table 12 shows the sources of solid wastes in a modem oil refinery. These data, provided by the American Petroleum Institute, are based on a typieal 200,000 barrels-per-day high-conversion refinery. A plant this size produces about 50,000 tons per year of solid waste and about 250,000 tons per year of waste water. As discussed above, all waste water must be purified before it leaves the plant. 

Indirect hydration, the traditional route, took advantage of readily available refinery grade propylene and cheap sulfuric acid in a quick two-step to isopropyl alcohol. Persistent catalysis research has now resulted in a direct route involving a small amount of an arcane catalyst, less energy intensity, high conversion rate, and an overall cheaper process. 

HSC [High-conversion Soaker Cracking] A continuous visbreaking process, developed and offered by Toyo Engineering Corporation, Japan. Demonstrated from 1988 to 1989 in the Schwedt oil refinery, Germany. 

The Mizushima Oil Refinery of Japan Energy Corporation first implemented a high conversion operation of vacuum residue, versus a constant desulfurization operation, in the commercial residue hydrodesulfurization unit equipped with fixed-bed reactors, to produce more middle distillates as well as fuel oil with lower viscosity. The catalysts will be replaced when the sulfur content in the product oil reaches the allowable limit. Since we have believed that an increase in the residue conversion decreases the catalyst activity by coke deposition, we have been interested in controlling the coke deactivation to maximize the residue conversion during a scheduled operating period. 

Residual fuel oil is a natural and significant product of crude oil. A yield of 50% residual fuel oil can be derived from typical or average crudes and a yield of 25% remains after mild or moderate petroleum refining. The average residual fuel oil yield in U.S. refineries is 5-6%. The lack of residual fuel oil production in the U.S. is a result of high conversion or severe refinery processing in a complex refinery configura-... 

The Mizushima Oil Refinery of Japan Energy Corporation first implemented an operation of vacuum residue hydrodesulfiirization in the conventional fixed bed reactor system in 1980. We have also conducted a high conversion operation to produce more middle distillates as well as lower the viscosity of the product fuel oil to save valuable gas oil which is used to adjust the viscosity. Vacuum residue hydrodesulfurization in fixed bed reactors mvolves the characteristic problems such as hot spot occurrence and pressure-drop build-up. There has been very little literature available discussing these problems based on commercial results. JafiFe analyzed hot spot phenomena in a gas phase fixed bed reactor mathematically, assuming an existence of the local flow disturbance region [1]. However, no cause of flow disturbance was discussed. To seek for appropriate solutions, we postulated causes ofhot spot occurrence and pressure-drop build-up by conducting process data analysis, chemical analysis of the used catalysts, and cold flow model tests. This paper describes our solutions to these problems, which have been demonstrated in the commercial operations. 

As discussed in Chapter 22, model-predictive control (MPC) and real-time optimization (RTO) can improve the profitability of a major conversion unit by 5 to 10%. Refinery-wide, benefits from MPC and RTO can exceed US 0.40 per barrel, or US30 million per year for a high-conversion 200,000 b/d refinery. 

Figure 1. Layout of a Typical High-Conversion Oil Refinery...

Naphthenic acid corrosion has been a problem ia petroleum-refining operations siace the early 1900s. Naphthenic acid corrosion data have been reported for various materials of constmction (16), and correlations have been found relating corrosion rates to temperature and total acid number (17). Refineries processing highly naphthenic cmdes must use steel alloys 316 stainless steel [11107-04-3] is the material of choice. Conversely, naphthenic acid derivatives find use as corrosion inhibitors ia oil-weU and petroleum refinery appHcations. 

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