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Plant Manager Plus

Summary

High pressure urea synthesis equipment consists of a carbon steel pressure bearing wall, which is protected by a protective layer. Carbamate can corrode carbon steel with a rate of 1000 mm per year. The protective layer can be a loose liner or weld overlay. Loose liners require an accurate and reliable leak detection system in order identify in time that there is a leak in the liner. Once a leak is confirmed, the only advice is to stop the plant and repair the leak. But how can the leak be located? It is not always easy to find a small leak. There are several methods: helium leak test, air soap test, ammonia leak test, etc, but which method works best for small leaks?

Abstract

Mr Mark Brouwer of UreaKnowHow.com in the Netherlands starts the Round Table discussion: A leak in a liner is identified by a leak detection system. According to your experiences what are the best ways to find the precise location of the leak? Mr Chris Boyda of Agrium Inc. in Canada shares his experiences: We recently experienced a liner leak in our HP stripper. Initially, we tried to use a pressurised ammonia test to locate the leak. This test required putting a small amount of pure ammonia in between the liner and the vessel shell and controlling the pressure to ~5 psig. On the vessel interior we tried to locate the leak by using ammonia sensitive paper (blue print paper), and ammonia sensitive spray. Keywords: leak detection, HP equipment, liner, weep holes, helium test, liner weld, dye penetrant inspection

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Proven ATR technology for methanol plants

Summary

With global demand for methanol continuing its steady rise, the need for improvements in methanol plant capacity is becoming increasingly urgent in order to remain competitive in today's market. Specialised technology is essential in order to achieve world-class production capacities. P.J. Dahl, T.S. Christensen, S. Winter-Madsen and S.M. King of Haldor Topsoe A/S discuss one such example – Topsoe's stand-alone autothermal reforming (ATR) technology for syngas generation.

Abstract

Today, the dominant feedstock for methanol production is natural gas, and this will likely continue to be the case for many years, especially due to the large strides recently made in shale gas production. Production increases and price reductions of natural gas are expected to drive up the demand for new methanol plants based on natural gas. The capacity of methanol plants is also rising, and plans are already underway for plants capable of producing 10,000 t/d, which is twice the capacity of a modern world-scale methanol plant. Such capacities require a significant amount of investment, which presents the incentive to maximise single-line capacity and benefit from economy of scale. The costs associated with large-scale methanol plants are chiefly due to the energy- and capital-intensive processes involved in manufacturing the syngas necessary for methanol production. Estimates suggest that syngas production, including compression and oxygen supply, may account for as much as 60% or more of the investment. One process that greatly benefits from energy and cost optimisation is the reforming process. Keywords: large-scale plants, methanol synthesis, ATR, Topsoe, steam to carbon ratio, syngas, reforming, boiling water reactor, by-product formation

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Optimising ammonia plant operation with APC software

Summary

Unexpected disturbances, fluctuating supply and demand, throughput limitations, changes in equipment and catalyst capability, and basic control limitations result in ammonia plants that do not operate at their optimum state. Increased profitability of ammonia plants is achieved using advanced process control (APC). P. Campo and W. Poe, of Schneider Electric explain how APC reduces variability in the process, allowing the plant to run closer to constraints, maximising throughput, reducing energy consumption and attaining safer, more stable operations.

Abstract

The ammonia industry In 2013 over 150 million tonnes of ammonia were produced worldwide, primarily for the fertilizer industry. The widely adopted Haber-Bosch process for steam reforming relies heavily on natural gas as the source of hydrogen. Ammonia synthesis for the fertilizer industry is a process that demands significant energy to react the chemical species that form NH3. Since nitrogen gas is strongly held together by triple bonded molecules, a large amount of energy is consumed to operate the system at the high temperatures and pressure required. The synthesis of nitrogen and hydrogen is a high energy step in the ammonia production process that only realises a 10 to 20% conversion of gas1, thereby requiring considerable recycle of synthesis gas. Therefore, an ammonia plant generates the highest profitability when natural gas is converted most efficiently. As a result, the most important part of an ammonia plant is maximising the conversion of the inputs. Keywords: advanced process control, DCS, APC, SimSci, proportional controller

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Technical services for nitric acid plants

Summary

In this article, T. Keller and O. Henkes of Heraeus Materials Technology GmbH & Co. KG report on selected case studies of nitric acid plants where technical services provided by Heraeus have been applied to solve problems of mechanical damage and contamination of catalyst gauze systems, and to partially replace gauze packs with inadequate N2O emissions. Possible root causes of unusual low gauze efficiency and high N2O emissions are discussed.

Abstract

The performance of the catalyst gauze system for ammonia oxidation and N2O reduction is highly important for nitric acid plants. In addition, the quality of the technical services provided by the gauze supplier can make a huge difference to nitric acid plant efficiency. High quality technical services are particularly beneficial when applied to plant improvement projects for sustainable better performance or to limit production losses after an unexpected incident. Especially in emergency events, quick and reliable feedback from the supplier is of utmost importance in order to detect and eliminate the root cause of the problem and to quickly bring the plant back to the usual high performance levels. Supplier support is also important during secondary catalyst N2O reduction projects, e.g. during planning, design, manufacturing and installation of catalyst baskets. Keywords: troubleshooting, nitric acid, plant performance, gauze, N2O emissions, secondary catalyst

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ANS process condensate purification

Summary

Technology to purify the process condensate produced by different ANS processes has been developed, installed and operated by Borealis Chimie SAS. The technology is currently in operation in plants ranging in capacity from 250 to 1,800 t/d and has been applied in plants where the neutralisation reaction is carried out at atmospheric pressure and at higher pressure; up to 5 bar. Most of the resulting process condensate can be released with an AN content of below 50 mg/l. J.-B. Peudpiece and J.-F. Granger of Borealis Chimie report on the different process variants that have been developed and implemented.

Abstract

Total world production of ammonium nitrate solution is approximately 40-45 million tonnes. Ammonium nitrate is produced by the direct reaction of nitric acid with ammonia to produce ammonium nitrate solution (ANS). The ANS is used to produce straight N fertilizer such as 33.5% N – 34.8% N; CAN; UAN and compound fertilizers such as NP and NPK. Another use of ANS is the production of technical grades for N20 and the manufacture of explosives. Borealis Chimie SAS developed the pipe reactor technology for ANS production in the 1980s and the process has been continuously improved. The main improvements have focussed on flexibility of operation, the environment and safety. This article focuses on the environmental improvements which have been developed and implemented. Keywords: ammonium nitrate solution, water balance, process condensate, Borealis, filter candles, scrubbing system, Entropie®

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Worth its weight in gold

Summary

Platinum and other precious metal catalysts are a mainstay of the nitric acid industry, but the metals in the gauzes are literally worth their weight in gold. Nitrogen+Syngas looks at the prospects for platinum prices and the effect this is having on nitric acid producers.

Abstract

Nitric acid production relies on the oxidation of ammonia to nitrogen oxide before it is converted further to nitrous oxide and absorbed in water to form nitric acid. The initial ammonia oxidation is carried out at 4-10 atmospheres and 700-950C over a precious metal catalyst gauze, which typically contains up to 90-95% platinum as well as smaller quantities (5-10%) of rhodium and/or palladium. The platinum is slowly oxidised to platinum oxide which is more volatile, and being more volatile it can be lost during an acid production campaign. Over the course of a full production run, anything from 30-60% of the mass of a nitric acid catalyst gauze can be lost, and at a cost of $1,400 per troy ounce – actually higher than the current price of gold – this can represent a significant sum. Keywords: Platnium, Rhodium, Ruthenium, Gauze, Woven, Getter

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The market for low density ammonium nitrate

Summary

Fertilizer use of ammonium nitrate continues to face regulatory pressure due to concerns about misuse of the product in improvised explosive devices and fatal accidents such as the one last year in West, Texas. Conversely, however, the side of the industry concerned with explosives production continues to go from strength to strength, on the back of increasing demand for mining explosives, especially in Asia, South America and Australia.

Abstract

Low density ammonium nitrate (LDAN), also known as industrial grade ammonium nitrate (IGAN), technical ammonium nitrate (TAN) or explosive grade ammonium nitrate (EGAN), as distinct from fertilizer grade ammonium nitrate (FGAN) is a component of most of the world’s widely used commercial explosives. About 98% of low density AN goes towards explosives production, and although there are a wide variety of commercial explosives of varying compositions in use around the world, ammonium nitrate is a key component of most of these. Properties The main difference between fertiliser and explosive grades of AN is, as the name low density ammonium nitrate (LDAN) suggests, in the density of the final product. Low density ammonium nitrate, which is preferred for explosive applications, has a bulk density in the range 0.7-0.8 and is usually made from 96-97% ammonium nitrate solution. By contrast, high density fertiliser grade is usually made from 99.7-99.8% ammonium nitrate solution. The other important characteristic of LDAN as compared to FGAN is its porosity. This is important since the presence of voids enables the prills to absorb and retain fuel oil when they are mixed (as ammonium nitrate/fuel oil, or ANFO) without the mixture becoming unduly wet. These two constituents act as an oxidiser and fuel respectively in the reaction that takes place during detonation. In the past, various other fuel mixes were tried with ammonium nitrate, including anthracite and wood meal, but over the years fuel oil has proved itself to be an ideal component as it has a sufficiently high flashpoint – which means it is safe to use – and because it is readily available at end-user sites, inexpensive and easily combined with ammonium nitrate to produce a uniform mix. Keywords: LDAN, FGAN, EGAN, slurry, emulsion, explosive, fertilizer, mining

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Refinery demand for hydrogen

Summary

Tightening restrictions on fuel quality and increasing use of heavier, sourer crude feeds are helping to boost the refinery market for hydrogen.

Abstract

Syngas production is, in effect, hydrogen production, as it is by and large free hydrogen which is the most desired component. In spite of its extremely low molecular weight, total hydrogen production around the world still reaches around 75 million t/a on a weight basis alone, actually higher than all other industrial chemicals on a molar basis. Its main use has hitherto been in the conversion of nitrogen to ammonia, but converting carbon dioxide to methanol has become a rapidly growing use over the past couple of decades as methanol’s energy and petrochemical uses come to the fore. But the biggest expansion of on-purpose hydrogen generation has come in the refining industry. Eni puts the market for refinery hydrogen at 30 million t/a in 2013, Praxair calculated it at 28 million t/a in 2010. Ammonia production in 2013 was about 170 million tonnes, according to IFA, also representing 30 million tonnes of hydrogen. Methanol production runs some way behind, at about 65 million t/a, according to Methanex, representing about 8 million tonnes of hydrogen. But going back a decade or more, ammonia’s proportion of total use outweighed refining by almost 2:1, and the fact that both industries now require approximately the same volume of hydrogen is indicative of how quickly that side of the business has grown. Keywords: Coal, syngas, fuel cell, captive, merchant

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Maximising uptime in ammonia plants with turbochargers

Summary

Andrea Gains-Germain, Director of New Product Development for Energy Recovery Inc., discusses how using a turbocharger in a CO2 recovery system can help recover pressure energy from the system and increase plant uptime.

Abstract

Over the past century, the practice of energy recycling has been built into industrial processes as a necessary step to minimise what would be otherwise wasted energy. Most are familiar with the concept of waste heat recovery, where heat that would have been dissipated and lost is returned to manufacturing and industrial processes. Waste heat recovery has helped industry optimise efficiencies and seize opportunities to become more profitable. But many industries, including ammonia producers, have yet to broadly apply energy recycling to another form of energy – pressure energy. Much like heat, pressure is often wasted in industrial processes through let-down in valves or other devices. This is squandered energy that increases a plant’s energy consumption and carbon footprint. For ammonia producers, the wasted pressure in the production of synthesis gas, or syngas, costs the industry millions and plagues plants with massive inefficiencies. As margins continue to tighten with ever-higher expectations of efficiency and emissions reduction, such waste can no longer be an option. Keywords: Isoboost, hydraulic, efficiency, turbine

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