A new approach to feedwater corrosion control: A detailed @T ORP~(?) study at a paper mill

摘要

The protection of paper mill boiler system assets and life extension should be primary drivers for water chemistry control in these hot water/steam systems. The dynamics of the pulp and paper making process puts a lot of demands and strain on the boiler steam generating system. It is not surprising that the unwanted ingress of dissolved oxygen into the feedwater and the resulting corrosion attack and damage to the boiler system, is a problem in these plants. Most feedwater REDOX (reduction/oxidation) stress events are not predictable. As a consequence, the majority of REDOX stress events go undetected, unnoticed and thus go uncorrected. Therefore, controlling the REDOX stress in boiler feedwater (FW) is essential to maintaining the integrity of Boiler systems. To address the need for improved monitoring and control of boiler FW REDOX stress events, Nalco Company in 1992 began a research effort to develop a technology that could measure the actual FW REDOX stress at the temperatures and pressures of the operating boiler systems. The outcome of this 15 year extensive R&D effort is the development of an innovative @T ORP? sensor technology that measures the net oxidation-reduction potential (ORP) of the water at actual boiler FW system temperatures and pressures. Nalco @T ORP? provides a quantum improvement (and paradigm shift) in FW REDOX stress management by greatly improving pre-boiler corrosion control with continuous, real-time monitoring and diagnostics by measuring, and reacting to, the changing corrosivity of the system at actual operating conditions. @T ORP technology automatically feeds chemicals on demand based on true at-temperature and pressure REDOX changes. Monitoring and controlling the feedwater oxidation-reduction potential in-situ, at system temperature and pressure, has been successfully demonstrated for the past 3 years in boiler systems operating at low pressures to electric power utility boilers operating above 2500 psig. The primary focus of this paper is to introduce the reader to the concept of @T ORP and cover the application of the technology to paper mill boiler systems.