Magazine: Nitrogen+Syngas

Highlights of papers presented at the recent Ammonium Nitrate/Nitric Acid (ANNA) Conference, held in September in Vienna.

EuroChem Group has announced the appointment of Samir Brikho as chairman of the company’s board of directors. Brikho has served on the board since 2018. He has also held senior management positions at Asea and ABB Power Generation between 1983 and 2000, before moving to Alstom, where he served as Chief International Operations Officer and Senior Vice-President, and CEO of Alstom Kraftwerke in Germany. In 2003, he became CEO of ABB Lummus Global and in 2005 he was appointed to the Group Executive Committee of ABB Ltd, and served as Head of the Power Systems Division at ABB Group. From 2006 to 2016 he was CEO of Amec Foster Wheeler. In 2009 and 2016 Brikho was chair of the World Economic Forum’s Engineering and Construction Board.

Cryogenic purge gas recovery units are very tolerant to increased flow from ammonia plant debottlenecking, especially the cryogenic cold box section. However, overload of the dehydration system upstream of the cold box can lead to fouling, loss of hydrogen recovery performance and the need for costly shutdown and thaw. Awareness of key plant parameters and some simple precautions can avoid such problems. A. J. Finn and T. R. Tomlinson of Costain provide some guidance.

BASF has filed a patent application for a greenhouse gas-free method for producing methanol. If successful on a large-scale, the process could eliminate carbon dioxide emissions throughout the entire production process from synthesis gas generation to pure methanol.

A discussion on the effect of vacuum pressure issues on the moisture content of urea prills. As the absolute pressure increases (lower vacuum) the urea melt concentration decreases in concentration (water content % increases). However there are also other causes of high moisture content in the urea melt as mentioned in this discussion.

One of the most important control parameters in urea plant operation is the synthesis pressure and a sharp increase of this pressure is very dangerous for the urea plant. One cause for an increase of the synthesis pressure is oil contamination in the urea process which causes many abnormal variations in many sections of the plant. This problem can be recognised by taking a sample from the ammonia feed and observing the colour change of the urea product. These samples and observations can prevent much confusion in determining the cause of the problem.

Heat exchanger tubes in heaters in a urea plant such as the high pressure stripper and medium pressure and low pressure recirculation heaters typically suffer from process-side fouling. This discussion looks at best ways to clean these heaters.

The main reasons for the installation of high efficiency trays (HET) in a urea reactor are: 1) to improve the redistribution of unreacted carbon dioxide inside the liquid phase rich in free ammonia, 2) to reduce the back mixing phenomena due to the density increase of carbamate and urea solution from the bottom to the top of the reactor and 3) to reduce channelling which has a negative effect on the solution residence time.

Vertical one pass (VOP) heat exchangers are commonly applied in urea plants. As the residence time in these heat exchangers is small, unwanted side reactions like biuret formation and hydrolysis of urea are limited. However, some phenomena can limit or reduce the performance of these heat exchangers e.g. bad distribution of the the inlet liquid/gas mixture over the tubes.

This discussion focuses on nickel content as an indicator of local active corrosion in a urea plant. In order to have an indication of what is going on in the urea plant it is important to look at trends.