TOC Determination in Brine Samples Coming from Desalting Process of Crude Oil Application Note · multi N/C 2100S, multi N/C 3100

Introduction

Crude oil always contains salt, either dissolved in water droplets or in form of crystalline salt. Since salt contents can cause problems by forming precipitates, accelerating corrosion processes or catalyst degradation during the refining process, crude oil is undergoing a desalting process. By-product of this process is water of high salt concentrations up to 26 % of mostly NaCl (smaller amounts of CaCL2 and MgCL2), so-called brine. Brine, as a product of petrochemical industry, is a starting material in other industries, e.g. as refrigerating fluid, in water purification or de-icing processes. One of the quality criteria for the further use of brine is its TOC content. Analysis of brine for TOC content is an important, however challenging task. Quartz components of the TOC analyzer as well as the expensive platinum catalyst are exposed to the destructive influence of this heavily salt loaded water sample. The common TOC analysis technique uses an oxidation process at 800 °C. At this temperature the melting of NaCl takes place. Salt deposits inside the combustion tube lead to a devitrification of quartz, a fast consumption of the platinum catalyst and gas flow blockages, thus causing high maintenance costs.

To overcome these difficulties the common technique and method have been improved. An optimized construction of the combustion tube, the use of a special catalyst filling and a reduced combustion temperature (750 °C) proved to deliver reliable analysis results, improve long-term stability and prolong the lifetime of the components.