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Options to reduce methanol emissions from ammonia plants

Summary

Regulators are starting to pay more attention to methanol emissions from ammonia plants since they are considered to contribute to ground level ozone. Several technical options exist to reduce these emissions including low methanol LTS catalysts, improved process condensate treatment, modifying the CO2 removal process and end-of-pipe solutions.

Abstract

Methanol, like other volatile organic compounds (VOC), contributes to the formation of photochemical smog which consists mostly of ozone (O3). Since ozone adversely affects human health, ozone limits are set in many parts of the world. Consequently, in many places in the world, e.g. the USA, targets and regulations exist to reduce VOC emissions. Methanol emissions from ammonia plants are considered to contribute to ground-level ozone. Regulators are starting to pay more attention to VOC emissions from ammonia plants and this trend is likely to increase. In some areas, increasing environmental focus has led to strict local methanol emission regulations. Keywords: methanol formation; LTS catalyst; process condensate treatment; catalytic oxidation; MP stripping; saturator.

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Replacing aging bayonet type boilers

Summary

Ammonia plants built prior to the mid 1980s need to compete with newer ones, and upgrading their boiler technology will enhance plant on-stream factor significantly. KBR has developed a cost effective solution and numerous plants with bayonet boilers are either implementing or considering this solution. M. Gandhi, S. Singh, and R. Burlingame of KBR discuss reliability issues associated with reformed gas boilers, compare different technologies and describe the retrofit execution.

Abstract

More than 150 ammonia plants worldwide use reformed gas waste heat boilers featuring bayonet style tube bundles. Legacy Kellogg (KBR) plants built from the 1960s to the 1980s typically have three shells numbered as 101-CA, 101-CB & 102-C. 101-CA/CB are bayonet, water tube boilers and 102-C is a fixed tube sheet, fired tube boiler. Although the bayonet technology was highly successful and credible in that timeline, it has become obsolete. KBR has been offering single shell one pass floating head technology since the mid-eighties, which has been highly successful in numerous ammonia plants. A review of on-stream factors of plants having bayonet boilers reveals that such aging boilers may contribute significantly to loss of production. Severe process conditions and inevitable transient operations lead to failure of these boilers. Smooth and reliable performance of these boilers is a pre-requisite for profitable operation of ammonia plants. Keywords: Kellogg waste heat boiler; bayonet exchangers; floating head exchanger; water tube boiler.

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Enhanced urea synthesis

Summary

NIIK has demonstrated the benefits of installing its vortex mixer in urea reactor revamps to improve the energy efficiency of the urea synthesis section and to provide enhanced capacity of the urea unit. The NIIK revamping concept is described with results of the latest urea reactor revamp project.

Abstract

NIIK (Research and Design Institute of Urea) has 60 years of experience in the design of new urea plants and the revamping of old urea plants. Based on this accumulated experience NIIK can offer a number of activities aimed at increasing urea unit capacity and improving energy efficiency. One of the key activities in the NIIK revamping concept is the modernisation of the synthesis section. Efficiency enhancement of the synthesis section not only improves process parameters, but also increases final product output. Efficient operation of synthesis section greatly depends on the amount of ammonia and CO2 recycle. Any change of this amount results in changes in energy consumption. In a synthesis reactor it is very important to achieve the maximum conversion of original feedstock into the final product under the required process conditions. Keywords: vortex mixer; NIIK; NFCL; urea reactor, revamping

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Plant Manager+ Problem No. 27: How do you clean the scraper in a prilling tower?

Summary

A scraper rotates above the floor of the prilling tower and moves the prills from the bottom of the prilling tower to the conveyor belt. At higher plant loads and/or under summer conditions the prills are not completely solidified and are still soft when reaching the bottom of the prilling tower. These soft prills clog up the scraper forming a hard layer of solid urea. This kind of fouling can also build up on the walls and ceiling of the prilling tower and at regular intervals cleaning becomes necessary. But how can this be done safely? This Round Table discussion starts with a description of a related safety incident as reported in UreaKnowHow.com's urea incident database.

Abstract

Mr Mark Brouwer of UreaKnowHow.com in the Netherlands starts the Round Table discussion: The incident: During 2010 overhaul activity employees were in a prilling tower for cleaning to remove lumps on the scraper’s arms. A steel structure with a wooden platform on top was used for safety of the employees. A big lump fell down onto the steel structure breaking the wooden platform. The shoulder of one employee was crushed without major injuries. Keywords: Cone cleaning; beam washing; prilling tower; scraper cleaning; cake formation; urea lump.

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Methanol as an energy carrier

Summary

While the traditional chemical markets for methanol are largely mature, large-scale growth in methanol consumption is still coming from two areas; as a petrochemical feedstock (so-called methanol to olefins/propylene or MTO/MTP), and as a liquid fuel, either in its own right or as a precursor for a variety of other downstream fuels.

Abstract

In a time of high oil prices but relatively lower prices for coal and natural gas, methanol has also become an ideal bridging compound for translating the benefits of one to the other. As a liquid at room temperature it is readily transportable, and it can be made from a variety of feedstocks, mainly coal and natural gas. While methanol pricing for energy uses is largely tied to global oil prices, this can allow producers to take advantage of cost differentials between oil and gas or coal. Methanol must compete with liquefied natural gas (LNG) as a way for gas producers to monetise natural gas on the world market, but LNG tends to require large scale liquefaction and regasification installations and the commitment of large volumes of natural gas, as well as extremely deep pockets – typically several billion dollars. Methanol is beginning to develop a niche as an energy carrier in China, where shortages of gas have led to widespread use of coal as a feedstock, and China’s experience with methanol fuels is now beginning to see interest in other regions. Keywords: DME, MTBE, BIODIESEL, MTG, GASOLINE, MARITIME

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Small-scale syngas production

Summary

While many technology developers and producers have geared their syngas-based plants towards large-scale production in order to take advantage of economies of scale, there is also a new generation of smaller scale offerings for more flexible, localised production.

Abstract

The issue with large scale chemical production is that it requires large scale gas or other feedstock production locally to supply it, and this reduces the scope for commercialisation. There are far more small scale gas production wells around the world than there are large fields with multiple wellheads, while for floating production vessels or unconventional feedstocks like biomass, municipal waste etc the quantities of feedstock available are generally not enough to feed a conventional world-scale syngas plant. Oil fields often have associated gas which many jurisdictions do not allow to be flared, and so the gas must be collected and somehow used economically, and this can be a barrier to exploitation of that field. Small scale chemical production offers a potential way of not only monetising the stranded gas but also unlocking the oil field development itself. Keywords: VELOCYS, COMPACTGTL, CARBON SCIENCE, MAVERICK, OASIS

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