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Ammonia synthesis converter design and safety

Summary

Materials selection is a critical aspect in the design of ammonia synthesis converters. Due to the aggressive operating conditions, ammonia converters can experience different types of metal deterioration phenomena, especially hydrogen attack and nitriding. The safety, efficiency and reliability of ammonia synthesis converters is highly important as they must typically run for between 10 and 15 years between catalyst changes, without the need for repairs and inspections. In this article Casale, Haldor Topsøe and KBR discuss the design and safety features of ammonia synthesis converters.

Abstract

The ammonia synthesis converter is a key item in ammonia plants and its reliability is essential. It is the reactor with the longest run between catalyst changes (typically 10-15 years). It is important that ammonia catalyst, once reduced, does not come in contact with oxygen since it is highly pyrophoric. Therefore converters should operate between catalyst changes without repairs or inspections.1,2 The performance of the converter also has a significant impact on the overall energy consumption so it is important that it operates efficiently.
In order to achieve this without any impact on the safety and reliability of the plant, several aspects have to be considered as converters have a complicated mechanical design with multiple catalyst beds and are subject to different metallurgical deterioration phenomena. From a safety point of view, catalyst replacements and inspections are also critical.

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KRES-ES™ makes more ammonia by energy substitution

Summary

KBR now offers low cost KRES-ESTM technology for revamping ammonia plants by energy substitution. Ammonia plants having either expensive or uncertain supply of natural gas may find this technology of benefit if an alternative source of energy is available. The revamped ammonia plant requires oxygen and steam imports. Steam import can be met by either using existing capacity or an alternative source of energy such as coal. Total natural gas consumption is reduced to <6.35 Gcal/tonne of ammonia by adding a new reforming exchanger to the existing primary and secondary reformers. Shashi Singh and Joe Price of KBR illustrate application of this technology by presenting three examples of KRES-ES based revamps including technical and economic analysis.

Abstract

KRES™ – KBR Reforming Exchanger System – that replaces conventional primary and secondary reformers in an ammonia plant – has been in successful commercial operation1,2 in the ammonia plants in Methanex, Canada, since 1994 and in Liaohe, China, since 2003. A reforming exchanger is the heart of the KRES technology. It uses high temperature process heat exiting the secondary reformer (or exiting an auto-thermal reformer) to produce syngas by reforming an additional flow of natural gas and steam. As described in a previous paper3, KRES has been offered as two process schemes until now. One of these schemes is what is used at Methanex and Liaohe. The other scheme is used in the KRES unit in the Chambal Fertilisers and Chemicals Ltd (CFCL) plant in India. CFCL commissioned their KRES based revamp project in their ammonia plant 1, which has been in successful operation since April 2009.
KBR is now offering KRES – Energy Substitution (KRES-ES™) technology (patent pending) as another application of KRES for revamping ammonia plants. This technology provides a low cost revamp solution to any existing ammonia plant that has either an expensive, curtailed and/or uncertain supply of natural gas but has an alternative source of energy available. The revamped ammonia plant requires oxygen and steam imports. Steam import can be met by either using existing or new capacity. The source of energy for steam could be fossil fuel (e.g. coal) or another non-fossil energy source.

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World record on-stream time for urea strippers

Summary

SKW Piesteritz has achieved a world record on-stream time for the strippers in their CO2 stripping urea plants. The record currently stands at 35 years for a HP CO2 stripper with Sandvik 2RE69 tubes, but is likely to be 36 years when the stripper is scheduled to be replaced in 2011. This outstanding performance can be attributed to many factors including high quality tubing and great care in the fabrication and operation of the plant. Mark Brouwer of UreaKnowHow.com reports.

Abstract

SKW Piesteriz
SKW Piesteritz is the largest ammonia and urea producer in Germany and one of the most innovative fertilizer producers in Europe. The plant is located in Lutherstadt Wittenberg, in a largely agricultural region of Saxony-Anhalt in eastern Germany. The roots of the fertilizer production located there can be traced back to the year 1915. Today SKW Piesteritz is part of the Czech Agrofert Holding. Around 770 employees at sites in Piesteritz and Cunnersdorf produce a broad range of agrochemical and industrial chemical products, around three million tonnes of products every year. Around half of SKW Piesteritz’ turnover is derived from industrial chemicals, such as ammonia, urea or nitric acid. SKW Piesteritz’ agricultural products have been closely oriented to the changing requirements of both crop producers and the environment. The product portfolio ranges from traditional nitrogen based fertilizers to stabilised nitrogen fertilizers and different fertilizers with sulphur. These modern products for plant nutrition were developed in the company’s own research and development centre near Leipzig. Therefore comprehensive application engineering studies are being carried out on more than 4,500 test plots. In 2005, an Agrochemical Institute was also founded by SKW Piesteritz and the University of Halle-Wittenberg where scientific know-how and modern, technical equipment are being combined with industrial product management and the infrastructure of a chemical site. In order to expand the range of specialist products, numerous new facilities and additional modern logistics areas have recently been built. SKW Piesteritz also benefits from its ideal geographic location. Lutherstadt Wittenberg is situated at the interface between eastern and western Europe. Major national highways and the most important railway lines between eastern and central Germany intersect the city. It is also located right next to the river Elbe which provides access to the German and European waterway network. Furthermore, SKW Piesteritz is actively involved in the commercialisation of the Agro-chemical Park Piesteritz as an attractive industrial location. The Agro-chemical Park is unique in Germany. Set over 30 hectares, the park is already home to 1,500 employees, with a full industrial infrastructure available for future investors.

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China still sets the pace

Summary

CMAI's 2010 World Methanol Conference was held from November 10-11 at the Hilton Diagonal Mar in Barcelona.

Abstract

The global methanol industry met in the pleasant late autumn warmth of Barcelona in November, and considered where the industry stood and where it might be going. The past few years have been a time of tremendous change, with the development of China’s fuel-based and coal-based methanol market turning things on their head. However, chemical uses for methanol and remote gas-based capacity also remain key drivers.
CMAI Europe’s managing director John Bonarius began with an overview of the global economic outlook and its impact on petrochemicals. In spite of the overhang of debt burden in western economies, and fears of a ‘double-dip’ recession, the outlook from emerging markets such as China and India remains very positive, and will drive global expansion through 2011, according to John, with global GDP growth gradually rising back towards its long-term average of 3%. Consumer confidence and retail sales are also beginning to pick up in the US, although unemployment remains high and the housing market subdued, while Europe continues to struggle.

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Process simulators for safety and efficiency

Summary

Dr Vladimir Brusov, head of optimal control systems department for the R&D Institute of Urea (NIIK) in Russia discusses the role of computer process simulators in enhancing the safety and efficiency of industrial facilities.

Abstract

Recent years have seen an increase in industrial- and technology-related accidents. This seems to be symptomatic of a serious imbalance between the growth of emergency-producing conditions and the countermeasures taken for their elimination. The increase in the number and significance of such accidents has both an objective and subjective cause. The need to increase competitiveness requires the construction and operation of more large-scale facilities. In order to reduce unit production cost, these plants also have to be operated under modes close to critical or upset conditions. A corresponding increase in operation time for equipment between turnarounds also contributes towards a significant increase in operational danger for industrial units. These are the objective factors leading to the rise in emergency situations. As for the subjective ones, the human factor plays a significant role in this respect, as the cost of mistakes is high in present-day facilities.
With the implementation of distributed control systems (DCS) at the majority of industrial plants, the number of process start-ups and shutdowns has been reduced, as has the degree of direct interaction between operational personnel and the technical processes. Consequently, operational staff have less practical working experience both in normal operational conditions and in upset and emergency situations. Global statistics shows that the number of emergency situations caused by operational personnel, particularly in the hydrocarbon industry, is up to 80% of the total.

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WS tail gas saturated nitric acid plant concept

Summary

Weel & Sandvig has developed a tail gas saturated nitric acid concept for energy efficiency enhancement. The concept provides new opportunities for optimisation of the heat and power recovery network. The concept is applicable to all nitric acid processes (high/low pressure mono pressure plants and dual pressure plants). To gain maximum power, the tail gas saturated concept requires a moderate to high tail gas turbine inlet temperature. Jan Sandvig Nielsen of Weel & Sandvig reports on the new concept.

Abstract

Basic principles
The tail gas saturated nitric acid process is a new concept based on a simple yet important modification of the conventional process. The modification is to humidify the tail gas at elevated temperature before it enters the tail gas turbine and to systematically optimise the operating parameters. This allows an improved matching between heat release and heat absorption especially at high temperature.
To match the heat flow from ammonia combustion and partial NO oxidation with the tail gas heating (with less flow than the nitrous gas stream) it is proposed to modify the process concept by increasing the tail gas flow rate. This is realised using a saturation column, where heated water is fed to the top and the tail gas is fed to the bottom. With this modification it is possible to increase the mass flow rate of the tail gas by up to 50%. In the saturator, a simultaneous heat and mass transfer takes place (Fig. 1). With this concept low temperature heat can be used for tail gas flow rate enhancement and more power can be recovered in the tail gas turbine.

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Profile: Toyo Engineering Corporation

Summary

Toyo Engineering Corporation (TOYO) has been in the forefront of developing chemical technologies since its foundation in 1961, and continues to innovate in areas such as floating production units.

Abstract

TOYO was established in 1961 when the engineering and construction section of Toyo Koatsu, Inc. was spun off as a separate company. The remainder of TOYO Koatsu, Inc. merged with Mitsui Chemical Industries in 1968 (Mitsui Toatsu Chemicals, Inc.) and with Mitsui Petrochemical in 1997 to become Mitsui Chemicals, Inc. TOYO’s major shareholders are Mitsui & Co. Ltd. and Mitsui Chemicals, Inc., each of which owns 23% and 13% respectively.
TOYO’s experience runs the gamut from oil and gas exploration, production and treatment, through gas processing and refineries, to downstream chemicals, including aromatics, petrochemicals, polymers, fertilizers and other syngas-based chemicals.

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The rise and rise of urea

Summary

Urea prices have been rising steadily over the past two years, backed by surging agricultural demand.

Abstract

Urea is an easily transportable and applied bulk solid, and is not subject to the same shipping, handling and storage regulations which have hamstrung AN use as a fertilizer. And it has a high nitrogen content – at 46% the highest of any nitrogenous fertilizer. These properties have made it the nitrogen fertilizer of choice in industrialising countries, which now dominate use of the compound.
Urea consumption
Because 78% of urea consumption is by farmers, particularly for growing staple nitrogen-hungry cereal crops such as wheat, maize and rice, farm economics have a major impact on urea demand. And at the moment, it looks as though agricultural markets are moving back into the kind of commodity bubble last seen two years ago, as severe weather in some of the major producing regions, such as Australia, has hit supply. Floods also hit the planting season in Canada last year, and drought and fire devastated wheat and other grain production in Russia, prompting the country to ban exports. Even though this year’s wheat harvest will be the third largest on record globally, production has not kept pace with increasing demand, and stocks are falling.

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