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The cost of compliance

Summary

As the deadline approaches for US refineries to produce low sulphur fuels, the industry's leading association gathered to consider the costs and practical problems arising from this latest challenge. Chris Cunningham reports from the National Petrochemical & Refiners Association's centennial Annual Meeting in San Antonio. On page 25 Lisa Connock reviews the latest approaches to desulphurisation raised at the meeting

Abstract

The National Petrochemical & Refiners Asscoiation (NPRA) regularly chooses San Antonio, Texas, home of the Alamo, as the venue for its principal conference. Perhaps folk memories of a famous siege sit well with the mood of a refining industry under almost constant federal pressure to rein back the environmental impact of its products – never more so than under current legislation to cut sulphur in fuels.

The taking of the Alamo proved to be a Pyrrhic victory.Texas maintained its independence and certainly thrived. As for the NPRA, the celebration of the association’s 100th Annual Meeting in March is evidence alone of an industry’s ability to survive.

Nonetheless, there was the matter to consider of how to manage, finance – and still survive – the technological response to Tier II regulations on sulphur in gasoline and the concurrent arrival of ultra-low sulphur diesel, not to mention the looming ban on methyl t-butyl ether (MTBE) and an emerging mandate to include more ethanol in gasoline.

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Operation Low Sulphur

Summary

At the recent NPRA Annual Meeting, plenty of catalyst and technology providers were at hand to present the numerous options available to refiners to meet pending clean fuels specifications. Lisa Connock reports.

Abstract

In order to meet evolving transportation fuel specifications, refiners must continuously evaluate their current operations and equipment. The permissible sulphur levels in gasoline in the United States and Europe are being reduced to 30 ppm and 10 ppm respectively, while allowable diesel fuel levels are being reduced to 15 ppm and 10 ppm (Figs. 1 and 2). In order to meet these sulphur specifications at the pump, refiners will need to produce even lower sulphur levels at the refinery gate. Therefore, refiners will need to invest significantly during the next few years.

Numerous mature hydroprocessing technologies are available for complying with new clean fuels regulations. Great strides have been made in catalyst technology, reactor design and process configurations. However, even with incremental changes, the conventional technologies are limited by their chemistry and, as the specifications for clean fuels grow tighter, the real costs of compliance using conventional technologies increase.

At the recent NPRA Annual Meeting in San Antonio, 17-19 March, a multitude of catalyst and technology companies were in attendance to present refiners with potential solutions to the challenges that they are facing. Changes in feed and product requirements can often be met by selecting the correct catalyst. However, by combining the right catalyst, innovative technologies and process application expertise, refiners can handle difficult feeds, expand capacity, produce cleaner fuels and maximise the value of existing assets while keeping capital investments and operating expenses to a minimum.

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A review of solid sulphur technology - Part 2

Summary

In this concluding instalment, Peter Clark, Director of Research, Alberta Research Ltd continues his review of the technical, logistic and safety challenges in handling solid sulphur. Control of acidity in solid sulphur, control of corrosion during handling and transportation, particle sizes for pelletised sulphur and the remelt of solid sulphur are discussed.

Abstract

According to the previous discussion in part 1 of this article (Sulphur No. 277) it is clear that, in tandem with the development of efficient pelletising technologies, solid sulphur can be formed containing only minimal quantities of H2S and with little propensity for dust formation, given careful physical handling of the product. However, without precautions to protect the pelletised product, downstream problems may arise through bacterial acidification and from corrosion of carbon steel by the sulphur.

It is well known that naturally occurring bacteria, thiobacilli oxidans, which form part of the natural sulphur cycle, attack stockpiled sulphur and cause acidification by excretion of sulphuric acid.6,7 These bacteria are present throughout the World and will, if given the chance, populate any area which stores or handles elemental sulphur. These aerobic bacteria thrive at 20-35°C and, if allowed to grow unchecked, can acidify sulphur to a level that severely complicates remelt and use by the customer. Corrosion of carbon steel by sulphur is also very well known. The basic corrosion mechanism (Fig. 6) requires direct contact between the steel and the sulphur along with a film of water to complete the chemical couple between these elements. Since both acidity development and iron/sulphur corrosion have been discussed in numerous other articles,8,9,10 only aspects of how these problems can be overcome in commercial settings are discussed in this article.

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Stop welding on my valve

Summary

In this article Henry Gaines, P.E. of Controls Southeast, Inc. discusses the importance of keeping valves hot in applications such as sulphur recovery and molten sulphur transport. With proper thermal maintenance to keep sulphur flowing, failures can be eliminated and thousands of dollars saved.

Abstract

Recently I saw a butterfly valve that had “torqued itself to death”. Besides shutting down a sulphur recovery unit for days and endangering refinery output at a Taiwan refinery, the failure cost thousands of dollars in labour and replacement costs.

The root cause was a poorly designed weld-on jacket that did not provide adequate heat to the bearing housing area and the adjacent process flanges. Sulphur condensed and froze because of the heat loss through those critical areas.Weld-induced distortion in the bearing housing area exacerbated the problem. When the valve actuator received the “GO” signal and applied power to move the stem, the disc would not budge. The result was inevitable.

What could have been done? At a minimum the jacket design should incorporate coverage on the bonnet, bearing housing area, and adjacent process flanges. Supplemental bolt-on jackets for these critical areas provided adequate solution for this application. Such failures are, unfortunately, all too common and usually require replacement of the equipment.

As specialists in thermal maintenance solutions for difficult heated processes since 1971, we hear about many incidents every year. Overtorquing a frozen valve is just one of many possible failure modes. Casting defects exposed when external pressure is applied during hydro test or by the heating medium is fairly commonplace, as is weld failure in the heataffected zone. Pancaking (concaving) of flanges, resulting from too much welding heat can cause bolt-up problems during valve installation. Many fabricators of weld-on valve jackets fail to apply good design practices, because there are no industry standards in place governing this specialty fabrication. And this absence of industry- wide standards exposes plant management to severe and unnecessary risks in process integrity, plant investment, and capital return. Further, most corporate engineering specifications for jacketed valves are old, very broad, and do not specify any design or fabrication standard.

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The value of hydrogen sulphide

Summary

Despite being the primary cause of a huge oversupply of elemental sulphur, hydrogen sulphide is not entirely without its merits. In fact, it needn't be the bane that it has been allowed to become, as J. B. Hyne of Hyjay R&D points out.

Abstract

It’s highly toxic, very corrosive, dangerous to store and present as a “contaminant” in ever greater amount in natural gas that comes from deeper and hotter sour natural gas fields. If it were not for the ever increasing demand for “clean” methane fuel nobody would even bother with the stuff. But the “cleaning” of sour gas produces huge amounts of hydrogen sulphide per annum which is converted to elemental sulphur by recovery processes such as the well established Modified Claus methodology.

The problem is that this elemental sulphur is now in such excess supply over demand (about 5 million tonnes per year out of balance worldwide) that it has become a worthless glut on the market.“Worthless” because hauling it from where it is produced to where it is consumed often costs more than the stuff is worth.

The gas drillers’ fondest dream is that it won’t be found in the hole they are digging.

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