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Snamprogetti's ammonia stripping technology is well suited for revamping total recycle urea plants - an attractive alternative to complete replacement under the volatile conditions of today's urea markets.
Urea plant revamping - by which is understood any or all of debottlenecking, upgrading, retrofitting, rehabilitation, refurbishment and modernization -- has been a regular topic in Nitrogen & Methanol over the years.
Because a urea plant is quite complex and therefore costly to build, there is an economic incentive to repair and modify existing hardware, as long as it is still serviceable, rather than to rebuild from scratch, even when the plant is basically outdated. It is not uncommon for a urea plant to be revamped more than once in its lifetime to take advantage of process improvements, better and more reliable machinery, and (in the more critical areas) new, more durable materials of construction, as and when they become available.
Previous articles in Nitrogen and Methanol have looked in detail at the revamping philosophies of Stamicarbon, Urea Casale, Toyo Engineering Corp. and UTI (now Monsanto). Some years ago Snamprogetti - a major force in urea plant design and construction -- licensed Siirtec Nigi to handle revamp projects using Snamprogetti technology. This article presents Siirtec-Nigi's viewpoint on urea plant revamping.
The operator's dilemma
In recent years the world urea market has been rather unstable and is likely to remain so. Twice the price of urea has fallen to values dangerously near to the production cost (Fig. 1), though this fact has not always been as much of a brake on new plant construction as it might have been: even when the price of urea has been at its most depressed, large grassroots projects have still been going ahead in low-- cost areas.
These price troughs are certainly a serious challenge for established producers operating older, less efficient plants, whose operations are in the greatest danger of actually becoming uneconomic. For such operators, revamping can be an attractive and altogether safer choice than investing in replacement facilities. It allows them to increase their capacity (if they wish to do so) and reduce specific production costs at a fraction of the investment cost for a new plant, so the pay-out time is much lower.
In some cases...