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Boost from supercharged phosphates markets

Summary

Good news from Istanbul, where the International Fertilizer Industry Association (IFA) – the representative body of the sulphur industry's biggest base of customers – recently held its annual meeting. On the agenda was an analysis of the developments that crucially affect the emerging shape of the demand for sulphur.

Abstract

Global consumption of elemental sulphur is currently forecast to grow at a rate of 4.6% / year between 2007 and 2011, rising to 59.2 million tonnes S in 2011. (Global Fertilizers and Raw Materials Supply and Supply / Demand Balances ­2007-2011. Paper presented by Michel Prud’homme, IFA.) This increase will come from higher consumption of sulphuric acid in the manufacture of phosphoric acid-based fertilizers and its growing use in ore leaching. The international market for phosphoric acid and downstream phosphate fertilizers is currently enjoying a notable boom, with prices reaching unprecedented levels.

At the time of writing, phosphoric acid was being sold at between $475-575/t f.o.b. North Africa, while DAP was available at $438-440/t f.o.b. Tampa, both prices being all-time records. In January 2007, the prevailing market price for phosphoric acid was $400/t f.o.b. North Africa, while DAP was trading at $265/t f.o.b. Tampa. The phosphate fertilizer bull market is expected to sustain its momentum in the months ahead.

IFA forecasts that sulphur and sulphuric acid use for the manufacture of fertilizers will register a compound growth rate of 3.3%/year during the next five years, rising to 123 million tonnes H2SO4 in 2011. Most of this increase will centre on phosphoric acid-based fertilizers, primarily in China and also in western Asia and North Africa.

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Brazil: Driving forces

Summary

Rapid development in the cultivation of soya and sugar cane crops in Brazil is expected to boost local production of phosphate fertilizers and ­­ im­ports of sulphur and sulphuric acid to produce the fertilizers. Sulphur reports on the progress to date. A further boost to Brazil's demand for sulphur may also come from the increased production of base metals.

Abstract

Brazil is by far the largest consumer and importer of sulphur in Latin America, accounting for 75% of sulphur imports in the region. As shown in Table 1, Brazil’s imports of sulphur were stable in 2006, at 1.6 million tonnes, but remained down on the record total of 1.9 million tonnes reported in 2004. This downturn was a reflection of the fortunes of the Brazilian agricultural sector: during 2005, when the combination of lower international crop prices, the weakening of the Brazilian real against the US dollar and a severe drought in the southern Brazilian states led to a collapse in fertilizer applications. In the first half of 2005, fertilizer retail sales to farmers fell by 26% compared with the same period in the previous year, forcing the domestic fertilizer producers to cut back output. The downturn in Brazil’s imports of sulphur was on a par with the fall in fertilizer sales.

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Sulphur in Amsterdam

Summary

The Sulphur Institute's 2007 World Symposium was held from March 26th-28th in Amsterdam. Sulphur eavesdropped on proceedings.

Abstract

Nearly 200 luminaries of the Sulphur industry converged on Amsterdam this March. The US, UK, and Canada were all well-represented, and in Shell’s homeland, many delegates from the Netherlands were also present, but also notable were the number of attendees from the ‘new’ sulphur producers, with 15 from the Middle East, 10 from Kazakhstan alone and five from Russia.

TSI President Bob Morris began with a run-down of the sulphur market as it stands. Phosphoric acid, mainly aimed at the fertilizer sector, remains the key demand driver for sulphur use, with 55% of consumption, although ore leaching in mineral processing is also an important and growing use. There are new uses on the horizon, in sulphur-based fertilizers and construction materials.

In the meantime, 60% of elemental sulphur is now traded internationally, with China a particularly active buyer.

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The long and winding road

Summary

Since the 1990s, lower sulphur prices have returned attention to possible end-uses in construction materials such as asphalt and concrete. However, large-scale adoption of these materials still seems as far away as ever.

Abstract

As permitted sulphur limits in fuels and emissions shrink, so sulphur is increasingly being removed from oil and gas prior to processing. Furthermore, production of sweet gas and crudes is in decline, and the extraction industry is increasingly having to move to sourer gas and oil fields, or the high-sulphur tar sands of northern Canada. All of this is leading inexorably to increasing production of sulphur, and while agriculture is able to absorb some of that demand, there is nevertheless an increasing glut of sulphur on the world markets. What to do with all of this sulphur is a matter which has exercised those in the sulphur industry for some time, although the oil and gas industry itself has occasionally been somewhat of a ‘latecomer to the party’, preferring to treat sulphur as a waste product which must be disposed of rather than a usable product stream from its refineries which can be used to add value.

Nevertheless, minds are gradually turning towards what can be done with sulphur, and although the concept has been around for many years, at the moment incorporation into construction materials is seen as a major po­tential outlet. Sulphur has a number of unique physical and chemical properties which suit it to these kinds of specialist uses, but unfortunately it also carries with it the spectre of hydrogen sulphide emissions, a gas which is (with due apologies) in very bad odour with the environmental lobby at present.

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Waste not, want not

Summary

High energy costs have renewed interest in sulphuric acid plants designed with advanced heat recovery systems. Recovered heat can be used for many purposes, depending on site specific conditions and requirements. Sulphur examines the latest trends in technology and equipment for sulphuric acid heat recovery.

Abstract

Large-scale production of sulphuric acid releases substantial quantities of heat. In a sulphur-burning plant, approximately 98% of the energy input comes from the intrinsic chemical energy of the reactants. The remainder comes from the main blower drive as heat of compression. In the classic process cycle, in which 57% of the total energy is recovered as high-pressure steam, 3% is dissipated with the tail gas via the stack, 0.5% is lost as sensible heat in the product acid, and nearly 40% is available as low level heat in the acid cooling system.

When energy prices are high, this presents sulphuric acid plant operators with significant commercial opportunities if this valuable energy can be recovered efficiently and reliably. Plant operators are therefore increasingly on the lookout for ways to recover as much heat as possible from their sulphuric acid production in order to put this energy to use or, when appropriate, sell it on the open market.

Operators throughout the world now put recovered heat to profitable use for:

  • sale to operators of district heating systems;
  • use as heating media in adjacent processing facilities;
  • pre-heating boiler feed water;
  • generating fresh water;
  • local heating;
  • sale for use in other non-related production activities.

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A hot and tricky process environment

Summary

The thermal combustion stage in sulphur recovery units presents the designer with many challenges. Industrial experiences and solutions to these demanding conditions are presented by Siirtec Nigi and WorleyParsons. Blasch Precision Ceramics reports on its latest developments to its ferrule and checkerwall systems, and the water wall boiler is proposed by Worley­Parsons to overcome the temperature limitations of the conventional refractory-lined reaction furnace.

Abstract

The original Claus process consisted of one catalytic stage operated at 200-350°C. The process was based mainly on the following partial oxidation:

3H2S + 3/2 O2 → 3/xSx + 3H2O ∆H = -49.3 kcal/mol

As indicated, this reaction is exothermic. Because the heat developed by the chemical reaction is proportional to the cube of the reactor diameter (D3), whilst the heat re­moval depends on the square of the reactor diameter (D2), there were difficulties with heat removal when increasing capacity.

The bottleneck was overcome by Farbenindustrie AG in 1938, by achieving the above reaction in two steps:

  1. Oxidation of 1/3 of H2S to SO2.
  2. Reaction of the remaining 2/3 of H2S with SO2 to form water and elemental sulphur.

Therefore, 1/3 of the H2S in the process gas is being burned at a temperature greater then 1,000 °C , without any catalyst, according to the following scheme:

H2S + 3/2 O2 →SO2 + H2O ∆H = -124 kcal/mol

2H2S + SO2 → 1/2S2 + 2H2O ∆H = 5.61 kcal/mol

Overall: 3H2S + 3/2 O2 → 3/2S2 + 3H2O ∆H = -37.6 kcal/mol

The difference in the thermal effect be­tween the original process and the above overall reaction is due to the different operating temperature that determines the prevailing sulphur species in the gas phase: S2 at high temperature and S8 at low temperature.

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