The Pitfalls of Process TOC Analysis and How To Avoid Them

Since the introduction of Total Organic Carbon (TOC) Analyzers by Dow, Union Carbide and Automated Environmental Systems in the1960's, they have proven to be an invaluable tool in the environmental and process monitoring fields. While technologies have advanced since then, certain performance characteristics required for true process control have been notably absent. The purpose of this paper is to discuss those limitations as evidenced by field experience, maintenance requirements and other practical considerations. Failure mode and effect analyses are summarized for critical components, as well as suggested corrective design, operation, and maintenance approaches, with a view toward minimizing cost of ownership. Generally, all TOC Analyzers employ the same basic technique as depicted in figure 1. A liquid sample is initially introduced to an Inorganic Carbon (IC) removal stage, where acid is added to the sample, dropping its pH to approximately 2.0. At this point, the IC is converted to carbon dioxide (CO2) gas, which is stripped out of the liquid by a sparge carrier gas. The remaining inorganic carbon-free sample is then delivered to the Oxidation Chamber.