Category: Equipment

Most urea plants operate a two-stage evaporator section. Both stages operate under vacuum pressure conditions and both pressures and temperatures are critical to achieve the right urea product quality. It is not always easy to determine the exact cause of non-optimum values for certain process parameters like, for example, low vacuum pressure in the second stage evaporator. Many factors can influence this vacuum pressure as discussed below.

The CO2 compressor of the urea plant is an expensive piece of critical rotating equipment installed without any spare posi­tion. Its reliability is therefore of prime importance. Sometimes reverse rotation occurs which can damage the internals of the compressor. What are the causes and what are the remedies to avoid reverse rotation of the CO2 compressor? There is a lot of misunderstanding around this subject. Here we share the experiences of various end users.

There is a lot of misunderstanding about the purpose and functioning of the seal systems (stuffing box) of the high pressure (HP) ammonia and HP carbamate reciprocating pumps. Some believe that lubrication is the main purpose, while others feel it is all about sealing. Both views are partly true. This article features experiences from various end users.

A discussion about CO2 coolers in the inter stages of CO2 compressors and the problems that can occur after the third stage when cooling water is on the shell side and the CO2 is on the tubes side.

In the case of a failure in a urea plant, when the problem is expected to be solved within a short period, the high pressure synthesis section is typically blocked in (referred to in this article as reactor hold up). All input and output streams are closed and the synthesis section remains partly filled with a solution consisting of ammonia, CO2, water, ammonium carbamate and of course urea. Several risks can occur during this blocked in situation.

A discussion about the high-pressure CO2 stripper and how to solve the problem of a high temperature in the bottom of the stripper.

Dust formation in the granulator can adversely affect stream time. There are several reasons for increased dust in the fluid bed granulator. No formaldehyde or less formaldehyde injection, lower bed level in the granulator, lower concentration of urea melt to the granulator, a higher pressure in atomisation (sprayer) air and a higher pressure in the urea melt header are all factors which can play a role. This article discusses increased dust level and its causes.

Among the many problems that threaten the daily operation of a urea plant, fluid leakage is perhaps the most common, especially the leaking of high pressure flanges in the urea synthesis section. A high-velocity jet emerging from a flange due to a failed gasket, a pinhole in an elbow, corroded threads of a level transmitter, etc., are familiar scenes that the maintenance crew encounters and must rectify.

Control of the process conditions of the MP absorber is one of the key control parameters in a Saipem urea plant. CO2 carryover to the ammonia receiver is not permitted in the process as it will create corrosion problems and upset conditions in the ammonia recovery and pumping system. This round table discussion considers the problems and solutions in this process section.

Preservation covers the method of protection and preventative maintenance carried out on equipment and systems before and after they are put into use. In power plants, fertilizer units and refineries, expensive equipment like turbines, chillers, power generators, boilers, condensers, panels etc. begin to rust and corrode when in storage or during shutdown or even when in operation due to the presence of excess moisture in the air. Proper downtime procedures are extremely important. In this discussion, preservation and its importance is discussed by urea plant experts.