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High pressure reforming: Reducing costs in large ammonia plants

Summary

During the last 50 years, KBR has successfully demonstrated the increase of the front end pressure of reforming from 27 bar(a) in the 1960s to 51 bar(a) in an ammonia plant that was commissioned in India in 2013. A. Malhotra and U. Jain of KBR discuss KBR's experience with high pressure reforming and how it can be incorporated in the design of large capacity ammonia plants to save energy and reduce the plant cost.

Abstract

Natural gas feed stock is usually available at higher pressure and since reforming reactions result in a substantial increase in total volume, reduction in energy consumption per tonne of ammonia and equipment cost can be achieved by increasing the reforming pressure. KBR has been one of the leaders in increasing the reforming pressure, starting at about 27 bar(a) (measured at the inlet of primary reformer tubes) in the KBR designed ammonia plants commissioned in the 1960s rising to 38~39 bar(a) in ammonia plants commissioned in the 1980s, and increasing further to to 43~44 bar(a) in ammonia plants commissioned in the 1990s~2000s. KBR has designed or commissioned more than 25 ammonia plants using such high pressure. In April 2013, KBR successfully commissioned the NFL (National Fertilisers Limited) 950 t/d ammonia plant located at Nangal, Punjab, India. In this plant the pressure was increased to 51 bar(a). Primary reforming reaction The basic reactions in the primary reforming of natural gas (assume methane) are: CH4 + H2O = CO + 3H2 ∆H298 = + 206.3 kJ/mol (1) CO + H2O = CO2 + H2 ∆H298 = -41.2 kJ/mol (2) Keywords: high pressure reforming, large capacity ammonia, front end pressure, KBR, Purifier process, NFL

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Worldwide trends in urea process technologies

Summary

J. Eijkenboom and M. Brouwer of UreaKnowHow.com provide an overview of worldwide trends in urea process technologies including: market share, latest materials of construction, design capacities and final product selection.

Abstract

Urea demand is booming as never before. Since the financial crisis in 2008 the number of new urea plants awarded annually has nearly doubled. The main drivers for urea consumption and new urea plants are: l population growth; l diet change in China; l biofuels in the US, South America and Europe; l AN regulations; l food prices; l monetising on natural gas resources; l change over from gas to coal in China; l shale gas revolution in US; l politics. The most significant drivers having the largest impact are currently: diet change in China, change-over from gas to coal in China and the exploration of shale gas in the US. Diet change in China Economic progress in China has already led to the strong growth of meat consumption in China. However, despite the increase, meat consumption in China is still only 40% of meat consumption in the US (see Figs 1 and 2 for a comparison of meat consumption in China and the US). Keywords: China, coal, US shale gas, urea processes, Stamicarbon, Saipem, TEC, Casale, JX urea technology, urea synthesis, mega urea, multinutrient products, nitrogen efficiency

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Common causes of catalyst failure

Summary

Selecting the right catalyst has a significant impact on a plant's ability to continue operation through an unplanned event, which could be caused by transient conditions such as unusual mechanical forces, rapidly changing temperature, pressures or compositional changes. These challenges can lead to catalyst failures if the catalyst quality does not live up to expectations.

Abstract

Several catalysts are used in the synthesis gas industry, covering the production of ammonia, hydrogen, methanol and other associated products, and the types vary from plant to plant. With the exception of the ammonia synthesis catalyst, catalysts used in syngas plants are mainly fabricated as tablets and extrudates with mechanical properties similar to those of ceramics. Just as ceramics, catalysts used in syngas plants are produced with the objective to obtain a highly porous structure with an optimised pore distribution. Solid catalysts work in a reactive atmosphere, where it is necessary to balance properties for fluid flow, activity, and stability. Good flow distribution and low pressure drop are among the key process requirements for a catalyst, and are achieved by proper design of size and shape of the catalyst pellets. Keywords: poisoning, fouling, sintering, transient conditions, carbon formation, HTS, LTS, MTS, Johnson Matthey, Haldor Topsoe, Clariant

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Plant Manager+ Problem No. 29: Stripper versus decomposer: What is the difference?

Summary

In 1967, Mr Piet Kaasenbrood (picture left) of Stamicarbon invented the CO2 stripper. The CO2 stripper revolutionised the urea process industry as it reduced the synthesis pressure from about 200 bar to 140 bar and reduced the energy consumption of a urea plant by about 50%. The CO2 stripper decomposes the unconverted ammonium carbamate coming from the reactor at the same pressure as that in the reactor. Therefore no water needs to be added to recycle this carbamate to the reactor, which is beneficial for the conversion in the reactor. The phase diagram of the system NH3-CO2-Urea-H2O (see picture) shows that by stripping with CO2 one is able to significantly reduce the ammonia content in the reactor outlet while at the same time reducing the temperature. Minimum temperatures are vital to keep corrosion rates under control and to allow economical materials of construction to be used. A decomposer on the other hand only removes the excess ammonia from the reactor solution until the azeotropic composition is reached. During this process the temperature increases. It is for this reason that in a CO2 stripper with a bottom temperature of 170-175°C 25-22-2 stainless steel can be used, while in a Saipem stripper, with a bottom temperature of 204-212°C, titanium or zirconium needs to be applied to handle the high temperature.

Abstract

Mr Kessla Belkacem of AOA in Algeria initiates the Round Table discussion: I have a question: I would like to know what the difference is between decomposing and stripping? Mr Mark Brouwer of UreaKnowHow.com in the Netherlands replies: These terms are frequently mixed up. Theoretically, stripping is decomposing with the help of a stripping gas. So a CO2 stripper works with CO2 as a stripping agent and is a stripper. An NH3 stripper is in my view more a decomposer than a stripper although one could argue that the decomposed carbamate acts as a kind of stripping agent. Keywords: decomposition, stripping, CO2 stripper, ammonia stripper, carbamate

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The future of Ukraine's nitrogen industry

Summary

An update on how the conflict with Russia could affect Ukraine's gas supplies and its downstream production of ammonia, urea and ammonium nitrate.

Abstract

In addition to the human misery that it has produced, Ukraine’s conflict with pro-Russian separatists – now a year old – raised worries at the time of its outbreak of a shutdown of ammonia and urea supplies out of the Black Sea; the source of about 20% of globally traded ammonia and 5-10% of urea. The worst fears – about the conflict and its affect on fertilizer markets – appear not to have been realised, but the Ukrainian economy in general and the nitrogen industry in particular are nevertheless facing considerable pressures. Keywords: GAS, DF, OSTCHEM, AMMONIA, UREA

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The Chinese ammonia industry

Summary

Cai Zeng of Clariant reviews the ammonia industry in China, with a focus on the technical challenges for both natural gas and coal-based ammonia plants.

Abstract

China is the world’s largest ammonia consumer and producer. With over 80 million t/a of ammonia production capacity, China has almost 40% of the global total. The development of the ammonia industry played a key role in China being able to feed around 20% of the world’s population with only around 8% of the arable land in the world. In order to meet increasing living standards and continued economic development, the ammonia industry is and will continue to be strategically important for China’s 1.35 billion people, especially in terms of food security. Significant efforts and resources were devoted to the development of the ammonia industry over the past several decades. This article aims to review the historical development, current landscape, new regulations and outlook of the ammonia industry. Innovation in ammonia synthesis catalyst development, the vast experience and lessons learned from coal-based ammonia plants are beneficial to the world ammonia industry and will be also reviewed. Keywords: AMMONIUM BICARBONATE, GASIFICATION, CATALYST, FEEDSTOCK, COAL

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