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Improving reformer pigtail reliability

Summary

Previously reformer outlet pigtails were considered standalone components with a nominal 100,000 hour lifespan. With improvements in reformer tube metallurgy and manufacture, pigtails are now seen as a weak link and often require replacement before the reformer tubes and manifolds. There is a strong incentive to improve pigtail reliability and lifespan, taking into account all the key factors, from design to material selection, metallurgy, grain size distribution, quality control or inspection techniques, and all the major focal points during the life cycle of these components.

Abstract

The steam methane reformer (SMR) is a major and critical piece of equipment in oil refineries, hydrogen plants, methanol plants and ammonia plants. Much attention is paid to the reliability and inspection of the catalyst tubes in SMRs, but equally important in ensuring the reliability and safe operation of a SMR is the outlet system. In most SMR designs, the relative thermal expansion between the catalyst tubes and the outlet manifolds is accommodated by tubes known as pigtails or hairpins, due to their often convoluted geometry. Pigtails carry the reformed gas from the catalyst tubes to the collection manifold. Failure of these outlet pigtails represents a common cause of plant downtime and potential risk to plant personnel. The current industry standard material for steam reformer pigtails is Alloy 800H/HT (UNS 08810/08811) or proprietary equivalents, e.g. 800AT, Sanicro 31HT, Nicrofer 3220H/HP. These are iron-nickel-chromium alloys with additions of aluminium and titanium. Based on Alloy 800, the H and HT grades have tighter compositional limits on carbon, aluminium and titanium, plus a requirement for the grain size to be ASTM 5 or coarser. Other proprietary versions (e.g. Nicrofer 3220HP and Sanicro 31HT) may have slightly different compositional and grain size limits, but are still within the UNS N08810 and UNS N08811 specifications. Table 1 shows the variations in chemical composition and grain sizes between common 800H/HT variants1. Keywords:Alloy 800, outlet manifold, reformer design, piglet geometry, grain size, failure mechanisms, creep, inspection

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Urea plant instruments and tools

Summary

A wide variety of tools and instrumentation is available for urea plants to ensure reliable and safe operations, reduce emissions to the environment, prolong equipment life, as well as increase process control and provide operator training. In this article Stamicarbon, Saipem and NIIK report on the services, instrumentation and tools they offer.

Abstract

Stamicarbon services Stamicarbon has an extensive service and product portfolio for existing plants. Stamicarbon services are offered from the sales and service department and its products and services are an integral part of its full life cycle support. After the launch of a new plant, Stamicarbon offers advanced products and services relating to: support and training, plant maintenance, plant optimisation, product quality, as well as safety and environmental improvements. In order to evolve the plant to the next stage Stamicarbon also offers revamp technologies. These services in relation to the life cycle of the plant are depicted in Fig. 1. Stamicarbon offers 35 advanced products and services for urea melt plants and urea granulation plants, of which 11 products and services were developed in the last ten years. Within the next five years Stamicarbon plans to launch a further 11 new and improved services. Several of the products offered are standard technologies for new grass root plants and are made available to older generation plants. It is not within the scope of this article to review all 35 services and products of Stamicarbon but some of the new and popular products and services are mentioned. Keywords: training, Advance Coat, relining, equipment replacement, level control, simulator, leak detection, advanced process control, OTS

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Understanding process problems before taking action

Summary

When a plant experiences problems and exhibits unexpected behaviour, many plants lack adequate instrumentation to completely diagnose the cause of the problem. Johnson Matthey is able to provide unique process diagnostics support through its Tracerco business. In this article, Dave Ferguson of Tracerco illustrates the importance of understanding process problems before taking action by looking at two case studies in ammonia plants.

Abstract

When a piece of process equipment starts experiencing problems and producing off-spec product, every engineer’s reaction is to make a change to “fix” the problem and get it back on-spec. Yet, many plants lack adequate instrumentation to completely diagnose the cause of the poor performance. Without a more complete understanding of the root cause of the problem, “corrective action” could have little effect or make the problem worse. Gathering supplemental data can sharpen the “image” of the problem and lead to the appropriate action. In the following case studies, seeking additional information allowed more informed and effective decision making. Case study 1 High differential pressure in an H2S absorber Keywords: differential pressure, H2S absorber, gamma scan, ammonia converter, radiation detector, leak test

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Strength in unity

Summary

As of May 27, 2014, Ammonia Casale, Urea Casale, Methanol Casale and Casale Chemicals have merged into a single entity, which will trade under the name of Casale SA. By simplifying the company structure, Casale wishes to co-ordinate and integrate its services, talents and creativity more closely, thus strengthening its market presence and becoming even more competitive. The merger of the previous companies should enable the new Casale SA to take on larger world-scale projects.

Abstract

The following sections trace Casale’s history from its early beginnings, when Ammonia Casale was founded in 1921, through the foundation of the other Casale companies to the present day with the merging of the Casale companies. Ammonia Casale Luigi Casale and his wife, Maria Sacchi, also a talented chemist, lacked personal finances but in 1919 convinced Idros, a company in Terni Italy, to build a pilot plant for the synthesis of ammonia with a capacity of 100 kg/day, based on their patents. Terni was an ideal place because of its availability of hydrogen, produced via water electrolysis, and the presence of a steel factory. Keywords: Ammonia Casale, Urea Casale, Methanol Casale, melamine

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Plant Manager+ Problem No. 25 High temperature in top of HP scrubber

Summary

Sometimes, when a process condition changes in a urea plant, for example, an operating temperature, the cause is not clear. Such a situation happened at Kermanshah Petrochemical Company in Iran. Mr Reza Keyhani started a discussion in the UreaKnowHow.com Round Tables to aid his troubleshooting. The following discussion helped Reza to find the root cause of the problem much more quickly. Mr Keyhani experienced a high temperature in the top of the high pressure (HP) scrubber. The function of a HP scrubber is to reduce the ammonia content in the inert stream coming from the high pressure synthesis section by washing the inert stream with the recycle carbamate and cooling it against cooling water.

Abstract

Mr Reza Keyhani of Kermanshah Petrochemical Company in Iran initiated the following ­discussion: The normal temperature at the top of the HP scrubber in our Stamicarbon pool condenser urea process is about 112-115°C and the O2 required in the outlet of the hydrogen converter is 0.59 vol-%. If the temperature in the top of the HP scrubber increases to 145°C but the overflow temperature of the scrubber is normal (166°C) what is the cause? Is it due to inerts or is there another explanation? Keywords: N/C ratio, HP scrubber, inert valve

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Nitrogen use efficiency

Summary

While for the second half of the 20th century the focus of the nitrogen fertilizer industry was on encouraging greater take-up of fertilizers in the developing world, as agricultural markets mature there is an increasing focus on the more efficient use of fertilizer.

Abstract

As our article elsewhere in this issue indicates, nitrogen fertilizer is the destination for more than 80% of all synthetic ammonia production in the world. The chemical fixation of nitrogen has allowed agriculture to keep pace with population growth over the past century. From 1900 to 1960 the world’s population doubled from 1.7 billion to 3.5 billion, and over the subsequent half century global population doubled again, from 3.5 billion people in 1961 to over 7 billion today. Land under cultivation, however, has increased by only 12% over the past 50 years, from 1.37 billion hectares to 1.53 billion hectares. And yet, in spite of this, agricultural production has managed to increase faster than population over that period, more than doubling for cereal crops, tripling for fruit and vegetables, and quadrupling for oilseeds. Overall agricultural production has roughly tripled over the same 50-year period that global population has doubled, and the fact that agricultural production has risen faster than global population has actually allowed the real price of food to fall over the past century, as figures from the US Department of Agriculture (USDA) show in Figure 1. While wars, depressions and oil crises have led to the decrease being a very uneven one, as can be seen in the spikiness of the graph of prices, the general trend has been downwards by on average 1% per year, so that at the turn of the 21st century people were paying in constant dollar terms only one quarter of what they did in 1900 for their food, allowing millions in Asia and South America to escape the risk of starvation, and even leading to the epidemic of obesity in the developed world, in defiance of Malthusian population doomsayers, some of whom, like Paul Erlich were predicting disaster as recently as the 1960s. Keywords: TOTAL; FACTOR; PRODUCTIVITY; TFP; NUTRIENT STEWARDSHIP; GREEN; REVOLUTION;

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Factors shaping the global ammonia industry

Summary

On both the supply and demand sides of the equation, political factors can loom as large as economic ones in determining the location and profitability of new ammonia capacity.

Abstract

Ammonia is the second largest industrial chemical in terms of tonnage produced in the world, after sulphuric acid. According to IFA, in 2013 a total of 172 million tonnes of ammonia was produced, representing 141 million tonnes of nitrogen. Its popularity resides on the fact that it is the only industrial way of fixing nitrogen from the air for chemical purposes, and its uses, while widespread, are very much geared towards agriculture. It is reckoned that just under 80% of all ammonia produced in 2013 ended up in nitrogenous fertilizers. Table 1 summarises these end uses. These figures do not include conversion into nitric acid, which is a key intermediary in a number of processes, particularly ammonium nitrate production. Where nitric acid is used as an intermediate in industrial production, the figures have been allocated to ammonia instead. Several industrial processes, most notably caprolactam production, but also leaching of some metal-bearing ores, lead to ammonium sulphate production as a by-product, but these are also subsumed into the ‘industrial’ figure for ammonia, and the ammonium sulphate (AS) figure given below only concerns direct ‘on purpose’ conversion of ammonia into AS. Keywords: TECHNICAL; ADBLUE; SCR; DEF; CAPROLACTAM; FEEDSTOCK; COAL; GAS; PRICING

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The human element

Summary

During the previous construction boom, many projects faced shortages of engineers and skilled personnel in critical areas. With a generation of engineers facing retirement and project activity continuing to increase, is the chemical industry facing a skills crunch?

Abstract

It is one of those frequently repeated adages that a company- especially one working in a technological field – depends more on its human capital than it does on any other resource. Human resources can be one of the most limiting of factors in project development, compared to capital equipment and finance, as scale-up is not always as easy – people can only work so many hours in the day. During boom times, companies can end up chasing a small pool of workers, and availability of key engineers or contractors can cause delays and cost increases. Keywords: EDUCATION; TRAINING; MODULAR; COMMUNICATION; SKILLS; CONTRACTOR

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