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Publication > Issue > Articles
Mitigating corrosion in sulphuric acid production
Summary
A number of highly corrosion resistant materials are available today for use in the production of concentrated sulphuric acid. Provided they are properly selected for the operating conditions, these alloys provide the benefits of long operating life under harsh operating conditions, extended periods of uninterrupted production cycle and a lower incidence of catastrophic equipment failure. Lisa Connock reports.Abstract
Modern sulphuric acid plants handle acid strengths normally in the range 93% to 99.5% and, in some plants various concentrations of oleum. The corrosion resistance of alloys within this relatively small concentration range can vary widely and can be difficult to predict.
The corrosiveness of sulphuric acid depends upon many factors, particularly temperature and concentration. However, whereas increases in temperature generally give a corresponding increase in corrosion rate, increasing the acid concentration can increase or decrease the corrosion rate depending upon the actual concentration. This effect is attributed to the fact that the hydrogen ion concentration in sulphuric acid increases with concentration, but at higher levels decreases again (Fig. 1). The hydrogen ion concentration directly affects the rate of the cathodic reaction and thereby the rate of anodic dissolution.
Additionally, corrosion rates can also be critically affected by other variables. The presence of oxidising or reducing impurities, the presence of chlorides, velocity effects and galvanic effects may alter the serviceability of a particular material of construction. These influences can make predicting actual corrosion rates for a given material problematic.
A review of solid sulphur technology - Part 1
Summary
Solid sulphur presents several technical, logistic and safety challenges in its handling, transportation and utilisation. In this article, Peter Clark, Director of Research, Alberta Sulphur Research Ltd, reviews existing data on these topics and presents new results from its laboratories which may assist the industry in fine-tuning practices for handling this important industrial commodity.Abstract
Elemental sulphur has now become one of the World’s cheapest raw materials because of its increased production in association with oil and gas use.1 It is somewhat ironic that a commodity, which is now so inexpensive, plays, in fact, a pivotal role in any industrialised society. Without sulphur a large portion of the World’s population would starve and without the sulphuric acid, which is made from it, all-important sectors of an economy, including the transportation and high-tech sectors, would collapse. And yet, sulphur is still seen by many oil and gas producers as a nuisance product on which as little as possible should be spent. In some cases, sulphur cargoes end up at the port of destination in a dusty and contaminated state quite unnecessarily. In fact, most, if not all of the technology required to safely and cleanly ship sulphur from the point of production to the customer is well known and available. Nevertheless, new or, perhaps, forgotten aspects of the chemistry of sulphur could improve this situation. The purpose of this article is to discuss some of the salient features of solid sulphur chemistry with the hope that this knowledge will facilitate the handling and use of solid sulphur. Much of the work reported herein has been developed in Canada, which, through implementation of new technology, has lead the World in the export of high-quality solid sulphur. In addition to the discussion on solid sulphur, a few aspects of the remelt of sulphur for use in sulphuric acid plants will be discussed.
A legal block for Venezuelan sulphur
Summary
Just as Venezuela seemed set to swamp the world with sulphur, its government seems to have less encouraging news for processors of heavy sour crude. Chris Cunningham reports.Abstract
The current year has proved to be seminal for the world’s synthetic crude oil industry. The last of the Canadian oil sands leases was allocated and cash was approved for billions of dollars-worth of processing operations. In Venezuela, the first of four bitumen production/upgrading ventures started up, closely followed by the second and with a third upgrader site due into production before the year’s end.
Whether or not they are Saudi-scale operations in terms of recoverable reserves of hydrocarbons, as local estimates occasionally claim, the sour bitumen operations of Canada and Venezuela are certainly Saudi-like in their potential to add sulphur to the world’s markets.
Whilst refiners in the US have been rubbing their hands at the prospect of liberal new supplies of high quality syncrude, sulphur marketers have been flinching in expectation of massive new flows of brimstone.
Maybe it’s a little early to worry about a world awash with sulphur – at least in the western hemisphere. Unfavourable logistics, not to mention market conditions, have yet to favour large scale movement of sulphur extracted from northern Albertan bitumen.
Believing in technology
Summary
Siirtec Nigi covers the whole gamut of hydrocarbon and fuel gas treatment processes, with a special emphasis on sulphur. With decades of accumulated experience, its own revolutionary HCR sulphur recovery process, reciprocal licensing arrangements with a carefully selected list of leading sulphur process developers and its own equipment fabrication capability, this smallish company has a very strong position in the field of gas purification.Abstract
Continuously based in Milan since its inception, the company known today as Siirtec Nigi was first established in 1934 as a designer of town gas plants based on coal gasification. The original company, Il Gas Integrale (IGI), was part of a family-owned group of three companies, the other members of which were Integral, based in Austria, and Le Gaz Integral, of France. Though historical ties remain with these former partners, they are no longer under common ownership. For a short time in the 1970s IGI was owned by the Babcock group before being returned to private ownership under a new name that reflected its changed market orientation but retained the same familiar IGI initials: Impianti Gas Internazionali. When the company came under the same ownership as Siirtec – an equipment fabricator founded in 1960 – the name changed again, to Nuova IGI. Finally, in about 1983, the two companies were amalgamated under the present name, Siirtec Nigi SpA.