Amine Analysis and Monitoring – A Practical Approach

ABSTRACT

Amines are used for three different purposes in a water/steam cycle (WSC): as reducing agents (reducing amines (RA)), to adjust the pH in the WSC (alkalising amines (AA)), and to protect the inner surfaces of the WSC by the formation of an adsorptive film on the metal surfaces (film forming amines (FFA)). Monitoring and control have to be chosen according to the purpose of use. The chemistry and selected properties that are important for the application and control of the amine groups are presented.

This article discusses the different approaches for monitoring and control of the three groups of amines together with the common methods of analysis. For the monitoring of RA and AA, standardised methods of analysis are available.

For FFA monitoring, two main methods are available, which are primarily applied for grab samples. They are well established; however, there is a limit of detection so that in some cases free residual FFA cannot be detected in the whole WSC, and, thus, the completeness of film formation is not proven.

A process for the upgrading of FFA to improve the limit of detection is presented which is suitable for on-site application. Furthermore, several approaches for indirect analysis of FFA in water are presented in which test specimens are introduced into the WSC. Either the FFA adsorbed on the surface is measured or, alternatively, the FFA presence is proven via the change in surface properties due to the effect of FFA adsorption. In this way the completeness of film formation in the WSC can be demonstrated.

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