BC Insight - Nitrogen+Syngas, Sulphur, Fertilizer International
Login
BCInsight Ltd
China Works
Black Prince Road
London, SE1 7SJ
United Kingdom
Tel: +44 (0)20 7793 2567
Fax: +44 (0)20 7793 2577

Publication > Issue > Articles

North African phosphates

Summary

Most of the new investment in phosphate capacity over the next few years will take place in the Middle East and North Africa. Although Jordan and Saudi Arabia have large projects under development, so does Tunisia, while the largest slice of new capacity is slated for Morocco, bringing additional requirements for sulphur and sulphuric acid, but Algeria also has considerable reserves and the potential for new production.

Abstract

The world’s phosphate reserves are not evenly distributed. In 2010 the International Center for Fertilizer Development (IFDC) presented the results of a major review of global phosphate reserves, and concluded that out of a world total of 67 billion tonnes P2O5, almost 80% were in North Africa, with Morocco accounting for the vast bulk of this total. The US Geological Survey has also upgraded its estimate of phosphate reserves in the past few years, from 16 billion tonnes to 65 billion tonnes, ending some of the fears about ‘Peak Phosphate’ that had been circulating, and again indicating that Morocco was the major reserve holder. The three North African nations of Morocco, Algeria and Tunisia are all major phosphate rock producers, representing 20% of global production between them, although they represent only 12% of processed phosphate production; Algeria does not currently process phosphates and instead exports beneficiated rock, and Tunisia only has limited processing capacity. Nevertheless, as there is limited refining and sulphur recovery within these countries, they have to import large quantities of sulphur in order to run their phosphoric acid production, and all three countries have major plans to expand both rock phosphate production and phosphate processing, particularly Morocco. Keywords: MAP, DAP, AMMONIUM, TIFERT, JORF LASFAR, SONATRACH, OCP, CPG, GCT

Add to basket


Captrolactam and ammonium sulphate

Summary

One of sulphuric acid's prominent chemical uses is in the production of caprolactam, with ammonium sulphate generated as a by-product. The switch of global fibre production to China has led to a major increase in caprolactam production there, and concomitant demand for sulphuric acid, but may also displace production elsewhere in the world.

Abstract

Caprolactam is a cyclic amide whose main use is as an intermediate in the production of polyamides, specifically nylon-6 (aka polyamide-6 or PA6), which is in effect polycaprolactam, and it is produced by opening the caprolactam ring and joining it end on end. The resulting polymer is extremely similar to nylon-6,6, and was developed by IG Farben in the 1950s to produce artificial fibres without violating DuPont’s trademark on nylon-6,6. Almost all (about 95%) of caprolactam is produced by reacting cyclohexanone (made from cyclohexane or phenol) with ammonia and sulphuric acid (Figure 1). Cyclohexanone oxime is converted to caprolactam via a process known as the Beckmann rearrangement, which occurs at 100C in the presence of sulphuric acid. The oxime rearranges to become the lactam sulphate, which is then neutralised with ammonia, releasing the caprolactam with co-production of ammonium sulphate. One disadvantage of the process is the amount of ammonium sulphate generated by the process, which could be up to 4.5 tonnes per tonne of caprolactam produced. DSM (amongst others) have made great strides in reducing this via their HPO process, and have managed to get this figure down to 1.5-1.8 tonnes of AS per tonne of caprolactam. Keywords: HPO, AMMOXIMATION, ASIA, NYLON, RENTECH, CYCLOHEXANE

Add to basket


Gearing up for lower emissions

Summary

As sulphuric acid plants face increasing pressure to reduce SO2 emissions, not only during normal operation but also during start-up, Sulphur reports on proven, well established technologies as well as new and emerging technologies that can be applied to meet current and future environmental objectives.

Abstract

There are environmental pressures around the world to reduce sulphur dioxide (SO2) emissions from sulphuric acid plants. In the USA, the US Environmental Protection Agency (USEPA) is charged with protecting the environment and insuring best available control technology (BACT) is used to minimise SO2 emissions from sulphuric acid plants. For over 41 years best available control technology for sulphuric acid plants was considered by EPA to be the double absorption process with a sulphur dioxide emission level of 4 lb SO2/ton of acid produced. In recent years, however, EPA has established the 4 lb SO2/ton level as a maximum emission limit, and used all methods at its disposal to drive the acceptable SO2 emission level to 1-2 lb SO2/ton and even as low as 0.1-0.2 lb SO2/ton. EPA has been driving existing plants with double absorption systems to add tail gas scrubbing to reduce SO2 emissions to well below the 1.0 lb SO2/ton level. To date, EPA efforts have been directed at fertilizer companies with multiple double absorption plants. Keywords: Debottlenecking, SO2 emissions, sulphuric acid mist, sulphur trioxide, cold start-up, VK-701 LEAP™, tail gas scrubbing, TurboScrubber, Cansolv, SolvR™

Add to basket


New processing schemes for challenging feed gas compositions

Summary

Rameshni & Associated Technology & Engineering (RATE) has developed new processing schemes for a grass roots SRU designed to handle lean gas with a wide range of H2S concentrations and impurities as part of sour gas field development project in Asia. The special proprietary schemes and features are designed to handle a wide range of operating cases and to maintain stable operation while meeting the required performance.

Abstract

RATE was recently awarded a contract to license a new grass roots sulphur recovery project for a sour gas field development (SGFD) in Asia. The contract included the design of the units for acid gas removal, sulphur recovery, tail gas treating, water dew point control, thermal oxidation (incineration system) and liquid sulphur degassing. The challenge in this project was to design a plant that could deal with the wide range of feed gas compositions and impurities, achieving stable operation and meeting the performance guarantees and environmental regulations. According to the gas analysis from more than 100 wells, the feed gas composition to the acid gas removal unit (AGRU) varies significantly, consisting of 2.3% to 5% H2S, 3% to 6% CO2, 40 to 90 ppmv benzene, 45 to 220 ppmv toluene, 20 150 ppmv xylene, 25 to 70 ppmv COS, 15 to 50 ppmv mercaptans, plus heavy hydrocarbons up to C50+ and many pseudo components, The H2S concentration to the sulphur recovery unit varies from 30% to 47% and CO2 ranges varies from 58% to 43% respectively. The gas pressure was around 100 barg at 50°C. Keywords: Acid gas removal, AGE, solvent, lean gas, S-MAX

Add to basket


SRU over-pressure protection and sulphur sealing trends

Summary

There is a recent industry trend to replace in-ground sulphur seal legs with above-ground sulphur traps. However, this does not address the risks during potential SRU over-pressure. This article considers how to best protect the SRU from over-pressure conditions and introduces recent advances in sulphur trap designs.

Abstract

Early Claus sulphur recovery units (SRUs) were designed for only about 100 kPa (ga) (15 psig). However, SRUs did not have any tail gas treating units (TGTUs) until environmental regulations increased the required sulphur recovery efficiencies. Without a TGTU, there is clearly an open path for process gas flow through the SRU out of the incinerator stack to the atmosphere. Based on the argument of an open path to the atmosphere, there were no provisions for pressure relief devices on the process gas flow path for early SRUs. In-ground sulphur seal legs were included in the design of most SRUs for drainage of liquid elemental sulphur. It was found that the SRU pressure could sometimes exceed the pressure needed to blow process gas through the sulphur seal legs (approaching 100 kPa (ga)), and it was noticed that the SRU equipment was not ruptured during these overpressure scenarios. Thus, a habit developed of considering the sulphur seal legs as a quasi relief device or at least an alternative relief flow path. Keywords: In-ground sealing, above-ground sealing, reaction furnace deflagration, waste heat boilere tube leaks, SxSeal™, Sultrap.

Add to basket