Ammonia Production How to increase Ammonia Plant Capacity

This paper investigates the technical and economical feasibility of several concepts for a 30 % capacity increase of an old ammonia plant. It shows an interesting way to overcome the limitations in the two most critical plant units: Reforming capacity is increased by a newly added autothermal reformer, while capacity is added to the ammonia synthesis by the Uhde Dual Pressure Process.

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Using experience from reference projects, this process concept is compared to other technical options and is discussed on the basis of investment and operating cost.

One of the factors making this concept competitive is the fact that by installation of parallel equipment with few tie-ins only, the shutdown time for its implementation is very short. Another interesting feature is that the ATR concept offers more CO2 as a pure stream to be used in a urea plant compared to the other concepts. This provides the possibility to easily combine it with a larger urea plant.

Introduction

A capacity increase of an ammonia plant can be a successful way to increase its economic viability. Also, a revamp involves considerably less risk than the erection of a new plant since the overall investment is moderate and project implementation takes less time.

A capacity enlargement up to about 10 to 15 % can usually be realized with moderate modifications by mobilizing the reserves which are already present in the majority of the process units. Only some equipment items are acting as bottlenecks and require modifications or re-placement.

Larger capacity increases tend to require more substantial measures and bigger changes in the process. As this makes the capacity increase considerably more expensive, it is of key importance to select the most cost effective solution.

Scope of the Study

Basis for the investigation is an existing ammo-nia plant in Russia. Its actual capacity at the time of preparing the study was 1680 mtpd. An expansion target of 30 % extra capacity was chosen. The plant had already undergone several capacity enlargements and modifications. Its current production capacity is considerably larger than its original nameplate capacity. Therefore, no significant potential for additional capacity is available in the existing plant equipment.

Three different revamp concepts are presented, with their main difference being within the reforming section. To compare their economic viability, capital and operating cost have been determined and evaluated for each revamp concept [1], [2].

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