Online Gas Analysis in Ammonia Plants0 pages

Application Note

Chemical

Online Gas Analysis in Ammonia Plants
Application
Emerson provides Rosemount Analytical gas analyzer technology for
on-line analysis of ammonia plant streams. Strategically placed gas
analyzers improve the process efficiency and the purity of the end
product.

Background
Ammonia is used in the production of a variety of products including
fertilizer, nitric acid, nylon, pharmaceuticals, and refrigerant.
Production of ammonia (NH3) is a two step process. The first step is
to produce hydrogen (H2) by reacting natural gas or methane (CH4)
with steam in a reformer. The second step is to react hydrogen with
nitrogen (N2) in a 3 : 1 ratio over a high-temperature catalyst in the
ammonia synthesis process.

In the process of reforming natural gas or methane to hydrogen,
carbon monoxide (CO) and carbon dioxide (CO2) are formed as
by-products. Even at low concen­ rations, both CO and CO2 cause
t
irreversible problems in the ammonia synthesis process. When the
synthesis gas contains CO, a slow permanent deterioration of the
catalyst occurs. The presence of CO2 in the synthesis gas can result in
the formation of ammonium carbamate, a fine white powder, which
precipitates out and causes plugging of the ammonia converter.
Therefore, to prevent problems in the ammonia synthesis process
and to prolong the life of the expensive catalyst, the removal and
measurement of CO and CO2 on a continuous basis is required.

Gas Analyzer Applications
During the production of ammonia, the gases pass through the steam reformer, high- and low-temperature shift converters, amine scrubber
and methanator before entering the ammonia synthesis process.

Figure 1 - Gas Analyzer Applications
Carbon
Dioxide

3

Air

METHANATOR

ABSORBENT
REGENERATOR

AMINE SCRUBBER

LOW TEMP.
SHIFT CONVERTER

REFORMER

Natural
Gas

HIGH TEMP.
SHIFT CONVERTER

Ammonia

AMMONIA
SYNTHESIS

5

1

1

= Measuring point

2A

2B

4