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Publication > Issue > Articles

The surplus that never came

Summary

For the past several years, there have been predictions of a large glut of recovered sulphur which has failed to materialise. We look at the sulphur market and why it has stayed in balance, and what the prospects are for the next few years.

Abstract

One of the oddities of the sulphur market over the past few years is that, even though production is largely involuntary and demand is cyclical, the market has managed to stay roughly in balance. Both oil and gas production and fertilizer and other industrial production are roughly related to global GDP, and so there is of necessity a degree of parallel movement, but for the past few years the market has been balanced or even tight in spite of dire predictions that a wave of new sulphur production from refineries and sour gas processing would swamp sulphur markets in similar manner to that which occurred in the late 1990s, when sulphur prices were at very low levels.

Production

Production of sulphur in all forms reached approximately 80 million t/a in 2011. Elemental sulphur (‘brimstone’) production continues to represent the lion’s share of this, at just under two thirds (about 52 million t/a in 2011). Roughly half of this comes from oil refining and half from natural gas processing, with mining just 1%, mainly from Poland. Of the remainder of sulphur in all forms, most (22 million tonnes in 2011) is represented by metallurgical sulphuric acid production from smelter off-gases, and 6.5 million t/a comes from pyrite roasting, almost all of it in China. Pyrite roasting is the only section of sulphur production which tends to show much sensitivity to prevailing sulphur prices, and so represents the only real ‘swing’ capacity in the sulphur industry. However, since its use is almost all (>90%) consumed within China, it is sensitive only to Chinese domestic market conditions and not global sulphur prices. Nevertheless, during 2008, when global commodity demand crashed, pyrite production showed a major contraction, and it has bounced back again as sulphur prices have recovered during 2010 and 2011.

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SOGAT 2012

Summary

The Sour Oil and Gas Advanced Technologies (SOGAT) 2012 conference brought together operators and licensors from the sour gas industry in the Hilton Hotel, Abu Dhabi in April.

Abstract

Sour gas developments continue to make progress, both in the Gulf region and surrounds. Oman is currently developing a gas/condensate field in the south of the country containing 3% H2S and 16% CO2 and another field 300km from Muscat with 3% H2S and 6% CO2. Qatar continues its dominating presence in LNG and has recently signed a 30-year production sharing agreement in its North Field, the world’s largest gas reservoir. Kuwait is studying the challenges of developing sour gas fields and Saudi Aramco is aiming to produce 2.5 billion cfd of sulphur-rich non-associated gas to be processed at Wasit. There is further potential from the Kidan field and the offshore Karan Field with 450 MMcf/d of sour gas expected to yield 67% sales gas. Iran is also addressing its sour field issues, having just announced that the 12th phase of the South Pars when operational in 2012 will produce 84 million cubic meters of sour gas per day.

But perhaps most important of all is Abu Dhabi’s own major project, at Shah, critical for infrastructure development in Abu Dhabi’s Economic Vision 2030 plan. When operational, the Shah gas plant will process well fluids containing 23% H2S and 10% CO2, making the project a new benchmark for the world’s gas processing and treating industry.

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Sulphur forming plant listing

Summary

Sulphur's regular update of recent and scheduled projects worldwide to supply equipment for the manufacture of formed product.

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Digging for victory – Morocco's phosphate fertilizer boom

Summary

Office Cherefien des Phosphates (OCP), Morocco's state-owned phosphate business, is already the world's largest owner of phosphate reserves and one of the largest producers of phosphates. Now, however, it has launched a 10-year, $13 billion investment programme to more than triple its downstream phosphate fertilizer production, with major implications for the sulphur industry

Abstract

Since launching its ambitious plans to massively increase both its mining and its downstream phosphates capacity in 2010, Morocco has moved ahead rapidly with project development. The country is in search of greater export earnings capacity; last year its current account deficit reached its highest level since the 1980s, due to higher energy and food bills and growing competition for Morocco’s non-phosphate exports. With phosphates one of Morocco’s key exports, the strategic decision has been taken to achieve a greater monetisation by increased production, particularly of downstream DAP.

Company background

OCP on its own represents a major segment of the Moroccan economy. It is the largest company in the country, employing 18,000 people, and accounts for one quarter of Morocco’s exports and about 3.5% of its GDP. Earnings in 2010 were $5.2 billion. It also has the largest phosphate reserves in the world. A recent revision to global phosphate estimates by a geologist working for the International Fertilizer Development Centre (IFDC) put Morocco’s total reserve at an astonishing 51 billion tonnes of rock, representing just over 80% of all known phosphate reserves.

The group is also the world’s largest producer of phosphates, with 30% of the market for rock phosphate and 40% of that for phosphoric acid. However, the company has a market share of only 15% in processed phosphates, and has announced that it intends to become as larger player in the downstream sector as it is upstream, adding value to its phosphate products. The company also aims to develop technical expertise in speciality fertilizers to innovate in fields such as micronutrients and other high tech fertilizer areas.

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Deployment of Flexsorb® SE

Summary

Designers tend to consider Flexsorb solvent when they are faced with technically challenging operations, but may not typically consider it for less demanding applications, due to its perceived higher up-front license fees and solvent costs. However, a recent study has established that Flexsorb's lifecycle cost advantage over MDEA makes it a contender for typical conventional gas plant and refinery sulphur facilities too.

Abstract

Sulphur plant designers have various options for the treatment of acid gas streams. Multiple technologies and/or process configurations will successfully achieve the primary objective of converting acid gas sulphur species to elemental sulphur product. The commercially available sulphur recovery technologies that are capable of achieving operational performance objectives are well known; yet, the most economically attractive option is not always apparent without an in-depth study comparing capital, operating and maintenance costs of the technologies under consideration. A specific example case study can be used to illustrate this point.

The industry is well aware of the primary technical advantages of ExxonMobil Research & Engineering Company’s (EMRE’s) proprietary Flexsorb solvent; high H2S selectivity and high CO2 slip. Thus, when a particular sulphur recovery application calls for ultra-high removal efficiency (99.9%+), especially at high amine temperature (45-55°C), Flexsorb tail gas treating technology is almost always a consideration. Likewise, large train size (1,000 t/d+), and/or lean acid gas applications often prompt the consideration of Flexsorb technology for acid gas enrichment units (AGEU) and/or tail gas treating units (TGTU) due to its ability to slip CO2, thus reducing the size of the sulphur plant. When these operational performance requirements do not exist, however, Flexsorb technology may not enter the designer’s mind as an option because the solvent cost is known to be greater that that of MDEA. However, solvent cost alone cannot be used as the basis of comparison in a commercial evaluation of gas treating technologies. All factors affecting capital, operating and maintenance expenditures must be considered in the assessment of facility lifecycle cost. A study has been carried out by WorleyParsons and EMRE to explore the technical and commercial performance of Flexsorb solvent versus MDEA over a range of design conditions in order to demonstrate that Flexsorb should not only be considered in technically challenging applications, but also in conventional applications that do not have unusually stringent performance requirements. Thus, it was very important to set performance specifications that could be readily achieved by generic MDEA, in order to assess those applications in which Flexsorb’s superior performance merits would not be required, and thus its employment may not ordinarily be considered.

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Spent sulphuric acid plants and services

Summary

Sulphuric acid regeneration technology has matured into a well established and reliable route to the recovery and reuse of spent sulphuric acid from many sources. In this article we report on the key design features of SAR plants designed by MECS, Inc. and the field services offered to sulphuric acid users by Rhodia Eco Services, including the inherently safe, patented tank cleaning technology that avoids the need for people to work inside the tank.

Abstract

Several chemical processes utilise concentrated sulphuric acid as a catalyst or dehydrating agent, in which the acid becomes "spent", i.e., weakened and/or contaminated. In a few cases, this spent acid may be safely disposed of or used in other processes, but usually, it must be regenerated back to relatively pure and concentrated acid for reuse in the main process, over and over again. The major processes include alkylation to produce high octane gasoline, nitration to produce explosives and pesticides, and the acrylonitrile (AN) and methyl methacrylate (MMA) processes. The sulphuric acid regeneration (SAR) plant processes for all of these feeds are essentially the same, with consideration given to the organic and inorganic contaminants, overall water balance, and the desired product specifications. These plants may be readily designed to produce fresh sulphuric acid in concentrations from 93% acid to 40% oleum, with 99.2% H2SO4 typical for alkylation use.

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Design challenges for large gas plants

Summary

The design of the acid gas treatment for a sour gas field development, is a challenging task requiring considerable expertise and a holistic approach to the design in order to co-ordinate the units of the SRU in a cost effective manner. Maximum possible flexibility is required to process a wide range of feedstocks and to allow the smooth and reliable operation of the tail gas treating unit. L. Micucci of Siirtec Nigi SpA describes Siirtec Nigi's approach to tackling some of these technical challenges in connection with the design and operation of difficult field gas development projects.

Abstract

The variability of contaminants content of natural gas and the broad variations of plant throughput often required to handle different feedstocks from different production areas, makes the design and operations of the sour gas processing facility an intriguing challenge. It requires proper selection of the technologies for the the various parts of the sulphur recovery unit (SRU) in a holistic approach taking into consideration the mutual interactions of these units.

Each process has its advantages and disadvantages so the technology selection is a trade off of a number of variables such as the gas pressure, temperature and composition, quantity of sulphur species (H2S, COS and CS2 and RSH), carbon dioxide to be removed, economic framework and last, but not least, the location of the gas field.

In cases where the acid gas from the natural gas sweetening unit is lean (i.e. 0.5 to approx. 20 vol-%), an acid gas enrichment (AGE) unit is needed at the front end of the SRU to raise the H2S concentration in the acid gas so that it can be handled by the Claus unit.

Technology options

In cases of rich sour natural gases, the acid gas from the sweetening unit is rich enough to be handled directly in the Claus reaction furnace without any particular issues. For lean gases, the Claus feed may be so dilute that it cannot be treated in the reactor furnace without major modification of the Claus thermal stage.

Furthermore, the need to reduce the environmental impact due to the release to the atmosphere of sulphur oxides often requires the integration of the Claus unit with a tail gas treatment unit based on the catalytic reduction of the sulphur species contained in the Claus off gases which allows an overall sulphur recovery efficiency of 99.8+%.

In these cases hydrogen or a reducing agent is needed to carry out such a process. However, because the gas fields are typically located in remote areas where industrial infrastructures do not exist, hydrogen is not necessarily available. Thus it must be produced inside the plant battery limits.

The use of pure oxygen or oxygen enriched air as the oxidant for the Claus process theoretically may be a route to process lean acid gas in a SRU unit because less nitrogen (an inert gas relative to the Claus process) enters into the chemical system compensating the inert gas influx of the lean acid gas.

For large plants, as is often the case for the SRU for natural gas field development projects, this option would not make economic sense due to the need to install a costly air separation unit.

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Puguang gas plant sets the benchmark in China

Summary

The Puguang gas plant, with its capacity to process more than 10 billion m3, is the first world-scale sour gas treating/sulphur recovery project to be built in China. The extremely sour gas of Puguang required innovation in the process design to ensure that an economical, safe and reliable facility could be built. The design of the facility considered the logistical challenges for building such a facility in the mountainous regions of the Sichuan province.

Abstract

The Sichuan to eastern China gas transmission project is regarded as one of the most technically challenging in China’s history. It included exploration and development of the Puguang gas field, sour gas processing, and the transmission of sales gas via a pipeline across eight provinces to Shanghai. The annual purified natural gas transmission capacity is 12 billion m3, with a total sulphur production rate of 8,600 t/d.

The Puguang gas field was discovered in the northeast Sichuan province in 2003 as a result of innovative exploration technology by Sinopec. The total gas field area covers 1,118 km2 and has proven gas reserves estimated at 500-550 billion m3 in the year 2008. The gas field is one of five in China with reserves of more than 200 billion m3.

The gas field has an H2S content of approximately 15 vol-% and a high CO2 content in excess of 8 vol-%.

The Puguang gas plant was built in Puguang, Xuanhan County, Sichuan province of China. It is the major gas supply source for the Sichuan gas to eastern China transmission line, which delivers natural gas from western China, Sichuan province to eastern China. The pipeline covers Sichuan, Chongqing, Hubei, Anhui, Jiangsu, Zhejiang, Jiangxi, with the final destination being the Shanghai area (Fig. 1).

Sinopec Zhongyuan Oil Field is responsible for the operation of the gas gathering facilities as well as the purification plant at Puguang. The gas purification plant processes 36,000,000 Nm3/day of sour gas in 12 identical processing units. This gas purification plant is currently the largest sulphur producer in the world with an installed capacity of 2.4 million t/a byproduct sulphur.

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