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Bimetallic tubes for nitric acid applications

Summary

Corrosion problems in nitric acid plants often occur where there are alternating wet and dry zones e.g. the nitric acid cooler/condenser. A heat exchanger with tubes built entirely of zirconium would solve the problem but would be very expensive. A novel alternative solution has been developed by Sandvik, a bimetallic tube consisting of an outer component in stainless steel mechanically bonded to an inner component of zirconium. D. Gullberg, J. Wallin, and M. Senatore of Sandvik Materials Technology give a detailed description of the bimetallic tube and all its potential benefits.

Abstract

Nitric acid is one of the strong acids and is a powerful oxidising agent which has great importance in the production of fertilizers. Stainless steels are commonly used for the construction of nitric acid plants. Low carbon austenitic stainless steels such as AISI 304L and AISI 310L, are particularly well suited for most nitric acid equipment1. The stainless steels are protected by a thin chromium oxide layer (Cr2O3) which spontaneously forms in air, however it also forms when suspended in moderately concentrated nitric acid due to the oxidising character of the acid. As long as the corrosion potential remains in the passive domain the chromium oxide will be renewed at least at the same rate as it is dissolved ensuring passive corrosion1-3. Corrosion resistance of an austenitic stainless steel in nitric acid is very much dependent upon the chromium content, which will reduce the corrosion rate and increase the limits of use with respect to temperature and concentration. It is also important with low impurity levels such as carbon, sulphur, and phosphorus to ensure good performance. Keywords: corrosion, nitric acid, cooler condenser, Sandvik, bimetallic tube, zirconium, welding, material of construction.

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Colourless start-up and shutdown of a nitric acid plant

Summary

J. Dammeier, A. Anheyer, P. Kern, C. Perbandt and C. Renk of thyssenkrupp Industrial Solutions (tkIS) propose plant modifications to reduce emissions during the start-up and shutdown of nitric acid plants. The options presented are linked to available utilities and will allow operating companies to custom design or revamp their plant to meet emission targets.

Abstract

Worldwide the limits for gas emissions are becoming stricter. With nitric acid plants generating nitrogen oxides (NOx) and nitrous oxide (N2O), a high efficiency gas cleaning system is required. The EnviNOx® system provided by tkIS enables the producer to meet the requested emissions in normal operation. In many countries however the emission limits also include start-up, shutdown and even malfunction. For example, in the US an emission maximum can be defined by a moving average over the period of 30 days. Additionally many operating companies request invisible start-up and shutdowns as local communities are irritated by orange/brownish clouds from the stack. The estimated value for a colourless NOx emission is below 50 ppmv. Keywords: thyssenkrupp Industrial Solutions, emissions, start-up, shutdown, nitric acid, expander, ammonium nitrate, nitrogen oxides, nitrous oxide, EnviNOx plants.

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Improving yields with secondary N2O abatement

Summary

Over the past decades, significant developments have been made to reduce the emission of nitrogen oxides and nitrous oxide from nitric acid plants. Typically, one or more types of catalytic abatement technology are installed, each with their ability to efficiently and effectively remove these harmful emissions. Recently, however, Clariant's EnviCat® N2O-S secondary catalyst was found to not only reduce N2O emissions, but to also help improve nitric acid yield.

Abstract

Three main types of emission control measures exist for nitric acid plants. These are: primary, secondary and tertiary abatement. While not new, secondary abatement technology is an area that has received much recent focus. Keywords: Clariant, EnviCat, N2O-S secondary catalyst, N2O emissions, nitric acid, abatement technology, Huayangdier.

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Small-scale production of ammonia

Summary

B. Keil, and K. Noelker of thyssenkrupp Industrial Solutions and J. Pach of Johnson Matthey propose small-scale ammonia plants as a measure to minimise transport risk and cost of ammonia. The process of small-scale ammonia production is different to the usual ammonia process. Key equipment are described, advantages of this process are highlighted and reference plants are shown.

Abstract

Eighty percent of anhydrous ammonia is used as fertilizer, either by direct injection to the soil or in the form of nitrogen fertilizers such as urea. Other direct consumers of anhydrous ammonia are phosphate fertilizer plants, nitric acid and ammonium nitrate plants, nylon intermediate manufacturers, some waste water treatment facilities, refrigeration plants and power plant pollution control systems. Many of these have a relatively small consumption and import their ammonia feedstock by railcar or truck. In 2007, 3.9 million tons of ammonia was shipped by railcar in the United States. Keywords: thyssenkrupp Industrial Solutions, Johnson Matthey, small-scale ammonia, transport, ammonia, compressor, gas heated reformer, isothermal shift reactor.

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Syra 4: A nitric acid project overview

Summary

Casale and Chemoproject Nitrogen (CHPN) have been awarded a contract by Yara for the construction of a new nitric acid plant in Köping, Sweden. The Yara contract is based on state‐of‐the‐art technology, improving energy efficiency and further reducing greenhouse gas emissions in the Köping plant. I Cerea of Casale discusses the project under execution, the roles of the companies involved and the technology applied.

Abstract

In 2014, Casale made two important acquisitions, namely the Czech contractor Chemoproject Nitrogen (CHPN) and, from Borealis, the complete process technology portfolio related to nitric acid/nitrates and phosphates, formerly owned by GPN. In 2015, CHPN was awarded the contract as EPC contractor to build a new 685 t/d 58 wt-% nitric acid plant based on Casale technology for Yara’s Syra complex in Sweden. Keywords: Casale, nitric acid, Yara, Syra 4, Chemoproject Nitrogen, dual pressure, MHI, compressor, burner hood, cooler condenser, DeNox.

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Plant Manager+ Problem No. 38: Flares in urea plants

Summary

Flares in urea plants are designed to improve the site's safety performance by capturing and burning ammonia emissions from safety release points. This will prevent/reduce ammonia emissions from entering the environment and in turn reduce ammonia risks. Flares are becoming more common in new urea plants, but are they the optimum solution to improve safety and reduce environmental risks?

Abstract

João Amilton from Petrobras, Brazil initiates this round table: Recently I read about flare stacks to reduce ammonia emissions in Profertil, Argentina. Our manager wants to know more about flares to handle the discharge of pressure safety relief valves of the high pressure synthesis section because he is considering installing one in our plant. Is this kind of flare available and is it a good idea? Keywords: flare system, safety valve, urea , relief valve, vent stack, blowdown.

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The outlook for Indian's natural gas and fertilizer sectors

Summary

Nelly Mikhaiel, Senior Consultant, and Priyanka Khemka, Consultant with Nexant Inc look at how recent and future changes to India's natural gas industry may impact upon future nitrogen fertilizer production.

Abstract

India’s gas industry is in a state of transition. The country faces a broadening gap between indigenous supply and demand. Thanks to India’s rising population and the ongoing quest to provide a better standard of living for its people, the country’s outlook for energy demand growth is robust. The role of gas in the country’s energy mix, however, is hard to determine. Today, gas occupies less than 7% of India’s primary energy mix. Because the ability of end-users’ to pay high prices for gas-fired power generation and/or gas as a fuel or feedstock is limited, India’s future demand growth is contingent on several factors. These include, but are by no means limited to: government backing for indigenous gas production and equitable pricing for upstream producers; New Delhi’s continued support for gas allocations to the fertilizer sector; and (in light of the country’s growing import dependency), the price of India’s broadening portfolio of imported liquefied natural gas (LNG). Keywords: FEEDSTOCK, LNG, RELIANCE, FACT, COAL, CIL, GAIL, SNG, CTP, CHAMBAL, CTL

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The future of ammonium nitrate

Summary

Ammonium nitrate's storage and use continues to face scrutiny on two fronts – one related to safety, the other to security.

Abstract

As we noted in last issue’s Editorial (Nitrogen+Syngas 342, Jul/Aug 2016, p4), ammonium nitrate faces continuing regulatory pressure around the world due to concerns about its potential for accidental detonation or deliberate misuse. Turkey has recently joined the list of countries which have banned the sale of AN as a fertilizer, including the Philippines, Afghanistan, China and Colombia. Other countries ban the sale of ‘pure’ AN, such as Pakistan, Germany, Ireland, the UK and Australia, and India has reclassified it as an explosive, severely tightening the regulations on its storage and handling. While most of these have been security related, the accidental explosions at West, Texas in the US in 2013 and Tianjin in China in 2015 have shown that poorly enforced regulations on storage and handling still have the potential to lead to catastrophic loss of life. Keywords: CSB, FGAN, OSHA, EPA, FIRE, EXPLOSION, RISK, TRAINING, SAFETY, STORAGE, HANDLING, DHS, HOMELAND SECURITY, ATF

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