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Publication > Issue > Articles

North American Syngas: boom or bubble?

Summary

Has the global fall in oil and hence petrochemical product prices tempered the enthusiasm for people to develop new gas-based chemical projects in North America?

Abstract

High gas prices closed down domestic US syngas-based chemicals production, and now the US is a major importer of both nitrogen fertilizer and methanol. The slump in domestic US gas prices caused by shale gas drilling has therefore led to a plethora of re-starts of mothballed facilities and new project announcements to try and use shale gas to produce downstream products to substitute for these imports. However, the first wave of new capacity is now either already on-stream or well under construction, while the number of new projects still under development has not yet significantly diminished. Is there a bubble about to burst for US gas-based production? Keywords: METHANOL, MTBE, CTL, GTL, MTO, MTG, COAL

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African nitrogen demand

Summary

Sub-Saharan Africa has the lowest rates of fertilizer application in the world, and hence some see it as having the greatest potential for new nitrogen demand in the years to come. But difficult issues surrounding infrastructure and rural poverty may cloud the rosy forecast.

Abstract

In the January/February issue of Nitrogen+Syngas we looked at the supply-side prospects for gas-based ammonia and downstream production in sub-Saharan Africa, some of it based on new gas discoveries in places such as Tanzania and Mozambique. However, almost all of the proposed new capacity is of necessity focused towards the export of urea to places like India, because there is insufficient demand domestically to justify investment. Africa has 13% of the world’s arable land and 12% of the world’s population, but consumes only 3% of the world’s fertilizer, and when North Africa and the Republic of South Africa are removed from that, the figure falls to only 1%. Keywords: IFA, MALABO, FAO

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Issues in ammonia handling

Summary

The US Chemical Safety Board's final report on an ammonia accident at a refrigeration plant highlights issues with process control and emergency response.

Abstract

In January this year the US Chemical Safety and Hazard Investigation Board issued its final report on an anhydrous ammonia release at Millard Refrigerated Services, Inc., which took place in Theodore, Alabama on August 23rd 2010. Although there were no fatalities, several people were seriously affected by ammonia inhalation and the CSB took the incident as offering insights into ammonia handling, especially as regards refrigeration systems. The CSB notes in its report that, in addition to health and safety risks from ammonia exposure, these types of large-scale releases can result in deflagration if an ignition source is present with concentrations of ammonia in the flammable range. In 2007, hydraulic shock caused a similar ammonia release incident that resulted in an explosion at another cold storage company. Keywords: HYDRAULIC, CONTROL, HEALTH, SAFETY, HSE

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Combatting corrosion in urea plants

Summary

Ammonium carbamate produced in the synthesis section of urea plants is highly corrosive. Although corrosion cannot be fully avoided, the risk of corrosion damage causing leakages or plant shutdowns can be minimised by proper material selection, quality control on fabrication, inspection and maintenance of equipment.

Abstract

In general, all urea processes fit the following description. Urea is formed together with carbamate from CO2 and ammonia in the high-pressure urea synthesis section. This section is the most critical from a metallurgical and mechanical point of view on account of the high pressure, medium temperature and the corrosive character of the fluids treated. The urea solution, still containing unreacted NH3 and CO2 in the form of carbamate, is sent to single or multiple decomposition/condensation stages, where generally unreacted NH3 and CO2 are recovered in the form of a carbamate solution. Key words: urea synthesis, corrosion control, ammonium carbamate, leakage, material selection, inspection, maintenance, leak detection, support ring, seat ring, weep hole system

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Added value with steam reformer solutions

Summary

K. Svennerberg of Haldor Topsoe discusses steam reformer solutions that add significant value throughout the whole operating cycle, providing industry examples where Topsoe's solutions have enabled customers to improve feedstock utilisation, increase synthesis gas production, prolong operating cycles and save valuable days during shut-down due to innovative loading methods and services.

Abstract

Successful plants can’t afford to underperform”. This quote comes from the technical director at a large ammonia plant in Southeast Asia. And he is right, in today’s competitive market a successful plant cannot afford to underperform in any area. With the steam reformer being right at the heart of ammonia plants, it has a strong impact on the overall plant performance and ultimately, the bottom line. Steam reforming Reforming reactions are typically carried out in a heated furnace over a nickel catalyst. The Topsoe furnace consists of a box-type radiant section with side wall burners and a convection section to recover the waste heat contained in the flue gases (Fig. 1). Key words: Haldor Topsoe, primary reforming, catalyst, carbon formation, alkali catalyst, catalyst loading, prereduced catalyst, SpiraLoad, Gold Cup, reformer assessment

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Improving flue gas tunnel reliability

Summary

J. Quintiliani and W. Russell of Blasch Precision Ceramics discuss how the reliability of primary reformer flue gas tunnels can be improved through the application of engineering design and improved material selection.

Abstract

Steam methane reforming is one of the most prevalent routes for the conversion of methane (CH4) to petrochemicals. The process produces a mixture of hydrogen and carbon monoxide referred to as “synthesis gas” or “syngas”. In the most common configuration, methane is put through a primary reformer which is essentially a large refractory lined furnace with centrifugally cast chrome-nickel tubes mounted vertically in the furnace. The process gas and steam are fed downward over a catalyst which is heated by burners mounted in the side or top of the furnace. Along the bottom of this unit are refractory tunnels that function to distribute exhaust discharge uniformly from the furnace, optimising process efficiency and tube reliability. These tunnels have always suffered from reliability issues which can lead to unexpected shutdowns, losses in efficiency, or at the very least high turnaround costs. Key words: steam methane reforming, primary reformer, flue gas tunnel, thermal stress, thermal expansion, FEA

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Plant Manager+ Problem No. 31: Insulation of high-pressure flanges in a urea plant

Summary

The intermediate product in the production of urea from carbon dioxide and ammonia is ammonium carbamate. Ammonium carbamate is very corrosive under the synthesis conditions in a urea plant. It is good practice to minimise the number of flange connections in the high pressure urea synthesis section. However some flange connections will be unavoidable. Typically two types of flange connections are applied in the high pressure urea synthesis section: ring type joints and lens ring joints. Once a flange connection leaks it is almost impossible to stop the leak by re-tightening the bolts. Due to the leak a crevice is created in which the oxygen dissolved in the carbamate containing liquid will be depleted and passive corrosion will become active corrosion. Active corrosion rates of stainless steel can be >50 mm per year and this means that in the case of a leaking flange connection one has to stop the plant immediately and service the leaking flange connection. This raises the question whether the flange connection should be insulated.

Abstract

Mr Easa Norozipour of Khorasan Petrochemical Company in Iran starts up the round table discussion: What do people recommend as regards insulating the high pressure flanges in the high pressure section in a urea plant? Keywords: high pressure flanges, insulation, leakage, corrosion, titanium gaskets, manholes, lens ring, urea synthesis section

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Avoiding tube failures in ammonia condensers

Summary

Carbon steel is the most commonly used material for tubes in heat exchangers, yet more than 50% of the yearly maintenance replacements are in this grade. Operators require a replacement material that enables superior erosion corrosion resistance and reduced maintenance costs. Marcelo Senatore, Sandvik Global technical marketing specialist, explains the benefits that duplex stainless steel have to offer.

Abstract

Year after year, large amounts of money are spent on replacing materials that have corroded to the point of failure in the ammonia units of fertilizer plants. Heat exchangers are especially vital in the ammonia production processes, and are dependent on the efficient transfer of energy from one point to another. Tubing must be versatile in order to be relied upon in a variety of applications such as waste heat recovery boilers, shift conversion heat exchangers, lean amine coolers, carbon dioxide stripper overhead condensers, sync gas compression coolers, ammonia condensers and convertor effluent coolers. The physical properties of steel grades selected for these demanding applications should offer design advantages, with ease of fabrication and good toughness and good weldability. Keywords:

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