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Recent Publications by Uhde on Fertilizer-Related Topics

First application of Uhde’s dual pressure ammonia process for revamping of the Duslo ammonia plant


Duslo operates an Uhde ammonia plant at Šal'a, Slovak Republic. In 2004 Duslo decided to increase the ammonia production capacity and optimise the energy consumption for the total ammonia production at Šal'a. Uhde provided the basic engineering for the capacity upgrade of the ammonia plant by applying their dual pressure ammonia process.

The front end of the plant will be upgraded by Uhde’s latest reformer technology using reformer tubes with increased diameter with state of the art metallurgy and Uhde’s latest secondary reformer design.

Process air compressor will be upgraded by a turbine driven parallel machine. CO2 removal system capacity will be increased using UOP ‘s Benfield ACT-1 process.

Synthesis gas compression is upgraded for the first 3 stages of the existing compressor by a parallel turbo compressor. Synthesis gas drying will be applied downstream the 3rd stage of the compressor.

The dual pressure ammonia process features Uhde’s OT-Synthesis operating at approx. 135 bar and the original Uhde High pressure Synthesis which Duslo operates successfully since 1973. A 2 bed radial ammonia converter will be applied in the OT-Synthesis. Synthesis gas from the OT-Synthesis is fed to the suction of the 4th stage of the existing synthesis gas compressor and subsequently fed to the existing high pressure loop. Thus the changes to existing H. P. equipment are minimised.

The revamp measures for the front end have been started in the annual Shutdown in 2005 and will be continued throughout 2006. Independently from the operation of the existing plant the OT-Synthesis will be installed and commissioning is scheduled for 2007.


Fred Kessler

Dirk Hoberg

Stefan Hrubý

Uhde GmbH, Germany

Duslo, a.s., Šal'a, Slovakia

Presented at:

Nitrogen 2006 Conference & Exhibition, Vienna, Austria, March 12-15, 2006

The Uhde Dual Pressure Process - Reliability issues and scale up considerations


With aiming at improved economics the capacity of new ammonia plants increased continuously over the decades. While the first Uhde ammonia plant built in 1928 had a capacity of 100 MTPD distributed on four reactors, nowadays single train plants are typically around 2,000 MTPD and projects for 3,000 MTPD or beyond are promoted.

As early as 1971 Uhde commissioned a 1,400 MTPD plant at a loop pressure of 225 bar. In 1991 the next generation of Uhde ammonia plants started with the BASF Antwerp plant having a nameplate capacity of 1,800 MTPD (now operating at 2,060 MTPD). For this plant design a second ammonia converter was introduced into the loop, the scale up experiences from this project led to design considerations taken into account for the next capacity generation at 3,300 MTPD and beyond.

When targeting larger capacities it is not sufficient just to consider what technically can be built or realised, also the risk of the scale up has to be considered for the overall economics of a project, especially when a step change in production capacity is foreseen.

It is the objective of this paper to give an assessment of these risks and to show measures for reducing these. At very large capacities the demand for plant reliability is even more important due to the large amount of capital involved and the significant production losses during any shutdown which will be difficult to compensate for with ammonia from the market.


J. S. Larsen

D. Lippmann

Uhde GmbH, Germany

Presented at:

The 47th Annual Safety in Ammonia Plants and Related Facilities Symposium, San Diego, California, USA, September 16-19, 2002

Uhde dual-pressure process for large-scale ammonia plants


There is a clear trend toward the use of larger plants for more cost-effective production of ammonia, which is key to the manufacture of fertilizers. However, significant capacity increases are restricted by the manufacturing limits of certain equipment and the reference situation for critical compressors. Uhde's dual-pressure process, in which a "once-through synthesis" is implemented to produce ammonia upstream of the conventional synthesis loop, can boost the capacity of a single-train plant using current equipment by 65% while reducing energy consumption by 4%.


Dennis Lippmann

John Larsen

Uhde GmbH, Germany

Published in:

thyssenkrupp techforum, July 2004

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