Section: CRUNS Plant Manager+

Rohit Khurana and Umesh Jainker of KBR presented a technical paper on this topic during the 2013 Asian Nitrogen + Syngas Conference. It can be found in the UreaKnowHow.com E-Library with the title: ”Replacing ammonia plant catalyst with maximum efficiency and lowest cost”. The paper addresses the importance of de-dusting catalyst beds before commissioning and the serious impacts on the plant if not performed thoroughly. Many ammonia plants have faced problems related to the plugging of exchangers, pipe choking, pressure drop increase of the downstream catalyst beds and separators or foaming in the CO 2 removal section which could be caused by the presence of catalyst dust. Most of these problems have led to either decrease in the efficiency of the plant or operation at lower throughputs. The paper presents the critical steps and procedures for proper dedusting of the catalyst beds before commissioning. In addition, the foaming problem in the CO 2 removal section associated with catalyst dust is discussed signifying the importance of cleaning the CO 2 removal system and solution. The role of filters in the CO 2 removal section was also emphasised.

Avoiding chloride contamination is critical in urea plants, not only from the process and utility side but also from the atmospheric side. The applied stainless steels in urea plants are susceptible to detrimental failure modes when chlorides and moisture are present. This UreaKnowHow.com Round Table discussion provides several examples of failures and important prevention measures relating to chloride stress corrosion cracking risks in urea plants.

In 1967 Stamicarbon revolutionised the urea process by the invention of the high-pressure CO2  stripper by Petrus J. C. Kaasenbrood. The high-pressure CO2  stripper led to following benefits:

Storing urea under hot and humid ambient conditions can be a chall enge. Several quality parameters of the urea product itself like moisture, temperature and particle size distribution are critical. Fluctuations of these parameters over time are also important and can lead to caking issues and complaints by clients. Off-spec product means big losses in revenue and results in a troublesome stream that has to be handled separately. Learning from each other’s experiences is vital to minimise and avoid these problems. n

This UreaKnowHow.com round table discusses the process upset condition of a high urea concentration in the ammonium carbamate recycle. It is commonly known that the urea formation reaction from ammonia and carbon dioxide via ammonium carbamate is an equilibrium reaction and that the urea conversion in any urea plant is limited. That is why downstream of the urea synthesis section the urea is separated from the ammonium carbamate in a recirculation section. Ammonium carbamate is dissociated into ammonia and carbon dioxide gases by means of low pressure and the addition of heat. The ammonia and carbon dioxide gases are dissolved in water and recycled back to the urea synthesis section. The urea content should be minimal as urea in the ammonium carbamate recycle leads to lower efficiencies. What are the causes and remedies for a high urea concentration in the ammonium carbamate recycle? n

Leaks in the high-pressure synthesis section of a urea plant may lead to catastrophic consequences. UreaKnowHow.com started to collect incidents in an incident database and in 2017 AmmoniaKnowHow.com and UreaKnowHow.com introduced FIORDA, the Fertilizer Industry Operational Risk Database, a global open source risk register for ammonia and urea plants.

Leaks in the high-pressure synthesis section of a urea plant can have catastrophic consequences. UreaKnowHow.com started to collect incidents in an incident database and in 2017 AmmoniaKnowHow.com and UreaKnowHow.com introduced FIORDA, the Fertilizer Industry Operational Risk Database, a global open source risk register for ammonia and urea plants.

Leaks in the high-pressure synthesis section of a urea plant may lead to catastrophic consequences. In 2017, building on an incident database set up by UreaKnowHow.com, AmmoniaKnowHow.com and UreaKnowHow.com introduced FIORDA, the Fertilizer Industry Operational Risk Database, a global open source risk register for ammonia and urea plants.

This case study refers to the carbamate condensers and separators in the urea recirculation and hydrolyser desorber section of a urea plant, operating under normal operation at 0.3 MPa and 75°C. After 48,000 hours of operation, during the turnaround of the urea plant, the diaphragm type instruments were sent to the original equipment manufacturer for inspection and refurbishment. In addition to damage of the diaphragm, crevice corrosion was found in the gasket area (see picture) posing a health and safety risk .

A proper leak detection system for loose liners of high-pressure urea equipment is the number one safeguard for any urea plant, as has been proven by detailed safety studies and incidents investigations. However, leak detection systems easily choke especially when urea is present in the leaking solution. When no urea is present, the ammonium carbamate will dissociate above 60°C when flashing to atmospheric pressure in the leak detection system. But, when urea is present, it can solidify and at higher temperatures polymerise into biuret and triuret, which have even higher crystallisation temperatures. An early and reliable leak detection system is therefore very important. UreaKnowHow.com has developed such a system: the state-of-the-art AMMO LASER Leak Detection System.