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Publication > Issue > Articles

Analysers and next generation SRU control

Summary

Acid gas analysis has arrived and tail gas analysers are now coming into the third generation. S. Simmonds and R. Hauer of AMETEK discuss current trends in SRU process analysers and A. Henning of Jacobs reports on experience to date with Advanced Burner Control+ (ABC+) which now includes sour water acid gas (SWAG) control.

Abstract

The history of on-line process analytics is a relatively short one. Development was driven by the need for process control of high value hydrocarbon-based products. The first on-line analyser applications came during the second war. Rapid development came in the 1970s with the advent of the microprocessor and resultant chemometric techniques. Led by Phillips Petroleum, Union Carbide and Dupont Chemical, amongst others, these initiatives were the antecedents of today’s Siemens Applied Automation, ABB Analytics and AMETEK Process Instruments. Whether or not sulphur can be considered a high value product, in most cases the driving force for process measurement and control of the SRU is largely environmental. The US EPA Clean Air Act of 1970 and the ground-breaking study by Alberta Environment on the capability of the modified Claus process coincided with the first attempts to control the modified Claus process using an on-line analyser and closed loop control. Keywords: AMETEK, tail gas analyser, feed gas analyser, emissions monitoring analyser, pit gas analyser, SRU control, Jacobs, ABC+, feed forward control, start-up, shutdown, sour water stripper, SWAG

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A better picture of working catalysts

Summary

From nano-scale studies of working sulphuric acid catalysts using new advanced in situ techniques, to improved industrial-scale sulphuric acid production, K. Christensen, F. Cavalca, P. Beato and S. Helveg of Haldor Topsoe present unprecedented new insight into the mechanisms of sulphuric acid catalysts.

Abstract

The main purpose of a catalyst is to increase the rate of chemical reactions without being consumed. This is also the main function of the V2O5-based sulphuric acid catalyst, which has been used for more than 50 years for SO2 oxidation in sulphuric acid production: SO2 + ˝ O2 = SO3 + heat (1) In general, however, a catalyst is also a dynamic system for which the detailed chemical composition and nano-scale structure depend on the composition, temperature and pressure of the surrounding gas. As a consequence, catalyst nature and structure are different in the individual beds of a sulphuric acid converter, even if the same catalyst type were loaded in all beds. One implication of this is the different colours of the operating catalyst that may also sometimes be observed after a shutdown depending on the shutdown procedure. Another effect of the dynamic nature of the catalyst is that after a change of feed gas composition, plant load or bed temperatures, the catalyst will adjust to the new local conditions on a time scale from minutes to a couple of days depending primarily on the temperature. Keywords: Topsoe, sulphuric acid catalysts, in situ TEM, active phase, liquid loading, dust protection, operando Raman

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Selection of sulphuric acid catalysts grows

Summary

MECS and Clariant have recently announced new additions to their sulphuric acid catalyst portfolios. The latest catalyst enhancements provide an even greater choice of options to tailor catalyst requirements according to sulphuric acid plant requirements. Benefits of the new catalyst developments include increased converter performance while limiting SO2 emissions and the ability to operate at lower bed inlet temperatures.

Abstract

New MECS® catalyst developments Driving innovation in the sulphuric acid market since the 1920s, MECS, Inc. (MECS) remains an industry leader in technology, engineering and equipment dedicated to sulphuric acid producer’s needs. As energy savings and environmental concerns create new operational and design challenges for sulphuric acid plants, innovations in catalyst technology provide the solution. Over the past 90 years, the dedicated Research and Development team at MECS has evolved catalyst from pellets to energy-saving rings to low-emission cesium-promoted catalyst. In 2015 MECS commemorates its rich history of catalyst developments with a year-long 90th anniversary celebration. Keywords: MECS, Clariant, GEAR®, cesium catalyst, dust, low inlet temperature, SO2 emissions, SulfoMax®, activity, conversion

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Timely furnace replacement at Burnside

Summary

J. Bolebruch of Blasch Precision Ceramics, B. Lamb of MECS and M.D. Harris of J.T. Thorpe & Son, report on the successful recent spent acid furnace upgrade in which HexWall™ ceramic furnace internals enabled DuPont Burnside to conduct a complete furnace replacement in a matter of days.

Abstract

The DuPont sulphuric acid plant in Burnside, Louisiana, in the USA is a large and versatile facility with a history of pioneering technology and world-class maintenance and operational practices. It is a 2,300 t/d plant capable of producing everything from standard industrial grades of acid to more specialised products like alkylation grade sulphuric acid, oleum and liquid SO3. Not only is its size and product slate impressive, but the site also has access to shipment via boat, rail and truck, making it a site of high strategic importance to DuPont. Keywords: Blasch, HexWall™, DuPont, MECS, JT Thorpe & Son, ferrule, ceramic internals, spent acid, baffle, furnace, pressure drop

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The return of SSP

Summary

For years the most popular phosphorus-based fertilizer, SSP has been eclipsed during the past few decades by the rise of higher analysis fertilizers like mono- and di-ammonium phosphate. However, in the past couple of years the trend of long-term decline seems to have reversed.

Abstract

Single superphosphate (SSP) is the most simple form of phosphate fertilizer. In essence its production consists only of crushing phosphate rock and treating it with sulphuric acid, as shown in reaction 1. Ca3(PO4)2 + 2 H2SO4 → [rock phosphate] [sulphuric acid] Ca(H2PO4)2 + 2 CaSO4 (1) [monocalcium phosphate] [gypsum] Production of SSP via this method was first used in 1842, and for many years SSP was in effect the only phosphate fertilizer in existence. In the 1870s it was joined by triple superphosphate (TSP), formed by the action of phosphoric acid on phosphate rock, but the ease of production of sulphuric acid as compared to phosphoric acid meant that SSP continued to predominate. It was not until the 1940s that mono- and di-ammonium phosphates (MAP/DAP) was first produced on a commercial scale, and it did not begin to make serious inroads into the market for SSP until the 1960s. Keywords: INDIA, BRAZIL, EGYPT, CHINA, SUBSIDY, DEMAND, SUPPLY

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Mind the gap

Summary

For 40 years now the gold standard for formed sulphur has been the Canadian SUDIC Premium Product specification. However, questions have been raised about its very low specification for moisture content, and whether this is necessary, realistic, or even prudent. Friability meanwhile, although vital for sulphur quality and tightly regulated in the SUDIC specification, is conversely often overlooked in sulphur purchase requirements, leading to a gap between buyer and seller in terms of standards and expectations.

Abstract

The Sulphur Development Institute of Canada (SUDIC) was a Canadian non-profit corporation based in Calgary, Alberta from 1973-1994, whose objectives included; “promoting and developing new uses for sulphur; encouraging, coordinating, supervising and assisting with research and development of testing work; furthering use and consumption of sulphur; and furthering ideas, inventions and patents”. SUDIC did not maintain research facilities, but functioned as a project management group via external resources. In 1977, SUDIC, via the Canadian Industry Sulphur Forming Committee, developed the Standard and Premium Product Specifications (see Table 1)1. The impetus behind this was a dual concern with safety on the one hand and marketing on the other. A lot of sulphur was (and is) shipped as a molten liquid, but Canada did not have the facilities for doing this at Vancouver port, nor did many client countries have terminals suitable for handling molten product. Sulphur was therefore exported as a bulk solid, often chipped from sulphur blocks in large lumps. This product was extremely dusty, which produced both a safety and environmental hazard in storage and transport, and eventually in 1972 the shipping of crushed bulk sulphur was banned by the Vancouver port authorities3. The first attempt to ameliorate the problem was via the production of ‘slate’ sulphur on a continuous, water-cooled moving belt, but by the mid-1970s other forming technologies were becoming available, including pelletising, wet prilling, and dry or air prilling. The SUDIC standards were designed as a way of encouraging the use of these new forming techniques, in order to produce what could be described and marketed as a ‘premium product’, differentiating it from crushed bulk/lump production elsewhere. Keywords: DEVCO, SANDVIK, ROTOFORM, ENERSUL, MOISTURE, CORROSION, FRIABILITY, DUST

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Sulphur – a refiner's view

Summary

The squeeze between regulation, changing product slates and higher sulphur feeds continues to force refiners to invest in new coking and desulphurisation capacity.

Abstract

The refining industry exists at a unique juncture between the oil industry and both the petrochemical industry and downstream consumers, industrial and individual. It must eke a margin between the cost of oil feedstock and the price of end products, while facing a continual push by governments and regulatory agencies to not only improve product quality, especially in terms of levels of sulphur, aromatics, oxygenates and renewables, but also in terms of refinery emissions of sulphur dioxide, carbon dioxide, etc. To begin with, refiners must cope with changing demand for products. In the past decade or so, this has come in the form of a move from gasoline towards diesel, a move from OECD to non-OECD countries, and a decline in demand for heavy fuel oil, to name just three of the major trends in the industry. Some of this is down to government intervention in markets, and regulatory issues continue to loom large for refiners. In particular, regulatory limits on sulphur content of fuels are a continually evolving area and represent a major challenge. Keywords: LEGISLATION, REGULATIONS, EMISSIONS, FEEDSTOCK, CRUDE OIL, FCC, CRACKER

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