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Economics of ammonia production from off-gases

Summary

VK Arora of Kinetics Process Improvements, Inc. examines various process options to produce ammonia from off-gases along with case study economics for the US Gulf Coast and Middle East for different sourcing and process options.

Abstract

Ammonia production using hydrogen rich off-gases has been well known for a long time but practiced only in a handful of plants. The dynamics of a new feedstock trend in the petrochemicals industry coupled with several new process options provide opportunities to source larger volumes of hydrogen rich off-gas streams to produce low cost ammonia. The new sources of hydrogen rich off-gases are large enough to integrate and support a typical world scale ammonia plant to provide an economy of scale even in smaller sizes with an added environmental benefit. However, sourcing those off-gas streams will pose its own challenges. Feedstock dynamics The abundant supplies of ethane from the shale gas boom has positioned the US as the most competitive, low-cost ethylene producer, resulting in increased investments in ethane recovery, pipelines and ethane crackers. Figures 1a and 1b are indicative of the excess ethane availability along with its demand growth for the crackers in the US. Keywords: ethylene, ethane crackers, PDH, PSA, nitrogen wash, secondary reforming, GHR

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Methanol purge gas for ammonia production

Summary

Johnson Matthey and ThyssenKrupp Industrial Solutions discuss how the use of methanol purge gas to generate ammonia in a dedicated ammonia synthesis loop can be an effective way of unlocking value in a high efficiency process which does not compromise operability and reliability and which demonstrates favourable plant economics.

Abstract

The concept of making methanol and ammonia from the same synthesis gas generation capacity has a long history2. Prior to the development of pressure steam reforming, low temperature shift conversion and modern CO2 removal processes, methanol production was a useful carbon oxide removal step in an ammonia flowsheet. Early ammonia production capacity was based upon coal and ICI were leaders in the field with factories at both Billingham and Heysham in the United Kingdom. When compared to dedicated ammonia and methanol plants, co-production schemes can suffer from a degree of compromise because the incorporation of both methanol and ammonia into a single flowsheet means that the process conditions for both can deviate from the ideal conditions. When present, these compromises can affect efficiency and can increase risks to product quality. Keywords: PSA, nitrogen wash, ammonia coproduction, purge gas hydrogen recovery

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Safe reduction of LTS catalysts

Summary

Reduction of copper catalysts is an infrequent but essential activity in ammonia plants. Improper reduction procedures can lead to serious damage of both the catalyst and the reactor. The risk of uncontrollable hazards can be significantly minimised by adhering to a careful procedure that includes initial inspection and constant monitoring of gas compositions and catalyst bed temperatures.

Abstract

Low temperature shift (LTS) catalysts are used in ammonia and hydrogen plants. The LTS is the last step in the process to make additional hydrogen from the process gas by the water-gas shift reaction, which converts CO to CO2 while generating hydrogen and heat. CO + H2O = CO2 + H2 + heat (1) The low temperature shift catalyst is typically operated at pressures between atmospheric and 40 barg (600 psig). Normal reactor inlet operating temperatures range from start-of-run values as low as 195°C (385°F) up to 225°C (440°F ) as the catalyst becomes deactivated. Because the CO shift reaction generates heat, a temperature rise will be observed through the bed of catalyst. Besides standard LTS catalyst, some plants require a “low methanol” version, meaning that the by-product formation of methanol during operation is suppressed by a special catalyst formulation. This enhanced selectivity also increases hydrogen production at this reactor. The formation of byproduct methanol can cause problems in downstream units, add costs for extra purification of condensates, and might exceed the allowed concentration in waste water limited by environmental standards. Keywords: low temperature shift, catalyst reduction, hydrogen test, carrier gas, partial bed reduction

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Plant Manager+ : Problem No. 24 Why is the minimum urea plant load 60%?

Summary

It is commonly known that any urea plant has a certain minimum plant load, typically 60% of its design capacity. But why is this so critical for urea plants? Several equipment items and valves in urea plants could have limitations when operating at a minimum load and there is always the risk of active corrosion.

Abstract

Mr Omid Fayezifar of Pardis Petrochamical Company in Iran initiates the discussion: We operate a urea plant of Stamicarbon design with a pool condenser and a design capacity of 3,250 t/d. I have a question about our start-up procedure. We always start our plant at 60% of total capacity (according to our licensor’s recommendation). What is the background for this recommendation, is it due to plant process reasons or corrosion? Keywords: corrosion, N/C ratio, start-up procedure, stripper tubes

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Is North American nitrogen investment as attractive as advertised?

Summary

Alistair Wallace, Senior Consultant at CRU Analysis, and Anders Isberg, Research Analyst, look at the economic rationale for investment in US nitrogen capacity.

Abstract

It is hard to avoid the word ‘revolution’ when referring to the development of shale gas reserves in the United States. Over the last decade the production of shale gas has not only altered the business environment of many natural gas end-users, it has fundamentally changed how the USA looks at its national energy balance. Shale gas production is revitalising the US economy, providing much needed energy security. It has also stimulated investment in downstream chemical processes, especially the nitrogen industry, where existing producers are planning to take advantage of a ‘perfect storm’ of lower input costs and premium Midwest nitrogen prices by investing in brownfield expansions to greatly expand domestic nitrogen capacity. These factors, coupled with the stable US investment environment and comparatively low cost of capital, have also attracted interest in new greenfield capacity additions from domestic and foreign investors new to the North American nitrogen market. Keywords: UAN, YARA, CF INDUSTRIES, UREA, AMMONIA

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Unconventional feedstocks for syngas production

Summary

While natural gas remains the dominant feedstock for syngas production, and coal a significant minority use, there are niches for a variety of less conventional feedstocks, from coke oven gas, petroleum coke and naphtha to gasified municipal waste and biomass.

Abstract

Natural gas is the feedstock for about two thirds of ammonia and methanol production. The primacy of natural gas as a feedstock for syngas production is because it is already in a gaseous form and so can be fed to a reformer with a minimum of pre-processing. Using solid, liquid or slurry feeds requires converting them to gaseous form, and this tends to mean use of gasification technology. However, the proportion of ammonia and methanol generated from natural gas actually peaked around the turn of the 20th/21st century, and has in fact been steadily dropping since then. In 2000, about 95% of all methanol and nearly 80% of ammonia was made from natural gas, and in many ways the past decade and a half has been the story of the return of gasification, once the main route for syngas production. Rising natural gas costs, especially in Asian markets, has been the main driver for this, with China in particular seeking to monetise its coal resources, but various environmental concerns have forced a new look at a variety of alternative feedstocks in Europe and North America, many of them solid or liquid and hence requiring a gasification front end, and new developments in gasification technology aimed at coal feedstock have found application for other feedstocks. Gasified coal now represents 30% of global methanol production and this continues to rise rapidly as China uses it as a fuel or a fuel or olefin intermediate. Keywords: IGCC, SNG, UCG, PETCOKE, GASIFIER, REFINERY, BIOMASS, METHANATION, RENEWABLE, MTO, MTG, CTL

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