Power

What Lessons Can Be Learned From Steam Generation Chemistry Control And Monitoring Failures?

By Brad Buecker

AMINES BOILERS CONDENSATE COOLING TOWERS COOLING WATER CORROSION DEIONIZATION EPRI HEAT RECOVERY STEAM GENERATORS HYDROGEN INSTRUMENTS ION EXCHANGE MONITORING OPERATIONS POWER GENERATION SAFETY STEAM TROUBLESHOOTING WATER CHEMISTRY

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Abstract

During the heyday of coalfired power plant operation, many lessons were learned regarding proper water/steam chemistry control. These messages were and continue to be greatly aided by research from such organizations as the Electric Power Research Institute (EPRI), the International Association of the Properties of Water and Steam (IAPWS), and others.

Now, combined-cycle power plants dominate new plant construction. Unfortunately, many of the previously learned lessons from coal plants are not carried over to the heat recovery steam generators (HRSG) of combined-cycle units; even though these steam generators operate at high temperatures and pressures. A contributing factor to the lack of knowledge transfer is that combined-cycle units are often minimally staffed, with few or no chemistry-trained personnel.

This article uses case histories to outline issues that can arise because of improper chemistry control and monitoring, and examines such issues as waterwall tube failures because of corrosion and hydrogen damage, single-phase and two-phase flow-accelerated corrosion (FAC), steam system damage because of transport of impurities from the boiler, and turbine blade fouling and corrosion, also from the transport of impurities.

Introduction

Research and experience over nearly a century have shown that even trace contamination in high-pressure steam generating systems can cause significantto- severe corrosion, scaling, and fouling. Furthermore, many former solutions to these problems have been demonstrated to be incorrect. Yet, a number of faulty ideas, and/or basic lack of knowledge continue to persist among those who are new to steam generation chemistry or have not had a chance to study modern concepts.

For example, at the many combinedcycle power plants that are replacing coal-fired units, the facilities are minimally staffed with no personnel adequately trained in steam generation chemistry. The same is often true at industrial facilities, where the focus is on process operation, with inadequate attention to water/steam chemistry, even though water and steam are the lifeblood of the plant.

Through case histories from the author’s own direct experience, reinforced by examples related to the author from friends and colleagues in the industry, this article outlines some of the most important issues regarding currentlyaccepted steam generation chemistry control. It will hopefully serve as a guidance document to those power plant and industrial technical professionals who are new to the industry or may be transitioning into new roles.

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