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Title: Enhanced Performance Of An Integrated Gas Chromatograph For On-Line Natural Gas Analysis
Author: Teresa J. Lechner-Fish
Source: 1999 International Symposium on Fluid Flow Measurement
Year Published: 1999
Abstract: The physical properties of the gas, the composition of the gas during upset and the operation in hazardous locations can affect the analytical method development and the hardware design. The gas chromatograph must be compatible with the physical properties (e.g., the physical state) of the sample. The sample must be introduced to the gas chromatograph as a single phase. Since on-line gas chromatographs are installed at the pipeline to analyze sample continuously, the system must be designed for fast analyses and low maintenance. The thermal conductivity detector (TCD) has been used extensively in the on-line gas chromatographs due to its simplicity, stability, durability and universal detection. Many analyses require the measurement of fixed gases (H2, O2/Ar, N2, CO and CO2) and light hydrocarbons (C1 - C10) for which the TCD is ideally suited. Optimization of a thermal conductivity detector for on-line gas chromatography inevitably involves improvements in detectability and linearity while minimizing degradation of column performance by the detector itself. To optimize the chromatography, the column module should be warmer than the valves and detectors while minimizing the inter-connecting temperature gradients. With our design (patents pending), the increased thermal mass and improved insulation minimizes the impact of environmental temperature changes. By integrating the valves and detectors into a single structure, the lengths of interconnecting tubing and flow path can be greatly reduced. With this arrangement, the dead volume of the system has been reduced by approximately 60%. In addition, the maintenance process has been greatly simplified. This paper describes the enhanced operating characteristics and performance of a new integrated gas chromatograph. Of particular interest are design improvements, which greatly affect the data quality. In addition, repeatability data for a light hydrocarbon (C1 - C10) application is discussed. This data represents an order of magnitude improvement from data presented in previous publications