Performance Evaluation of Refrigeration Units in Natural Gas Liquid Extraction Plant

This paper has applied thermodynamics principles to evaluate the reliability of 390？m3/hr natural gas processing plant. The thermodynamics equations were utilized in the evaluation, characterization, and numerical simulation of key process parameters in natural gas liquid extraction plant. The results obtained show the comparison of the coefficient of performance, compression ratio, isentropic work, actual work, electrical power requirements, cooling water consumption in intercoolers, compressor power output, compressor capacity, and isentropic, volumetric, and mechanical efficiency of the two-stage refrigeration unit with a flash gas economizer and these were compared with the designed specifications. The second law of thermodynamics was applied in analyzing the refrigeration unit and the result shows that exergetic losses or lost work due to irreversibility falls within operating limit that is less than 1.0%. Similarly, the performance of expansion turbine (expander) parameters was monitored and the results indicate a considerable decrease in turbine efficiencies as the inlet gas pressure increases resulting in an increased power output of the turbine leading to a higher liquefaction rate. 1. Introduction The production and availability of natural gas liquid depend largely on the supply of raw natural gas from production wellhead and the operating conditions of the process unit that make up the extraction plant. Most gas processing plants are faced with problems ranging from inadequate supply, poor facility performance, and human factors. These problems can lead to low productivity of natural gas liquids and reduction in gas quality which could result in shutting down of the plant. Poor facilities such as inadequate electricity supply and processed water supply used in process equipment also lead to intermittent operations and malfunction of process equipment such as pumps, compressors, and valves if they are not adequately checked. Human factors may also result from the inability of gas plant operators to monitor thermodynamics parameters such as the pressure, flow rates, and temperature on process equipment which could result in loss of data in control room and unintended activation or deactivation of process devices and reduce the plant efficiency. In spite of the fact that these thermodynamics parameters are monitored daily in a gas plant, there are problems of low gas feed inlet pressure and insufficient gas flow rate. These have resulted in low volume of natural gas liquids produced, the extracted natural gas liquids not attaining the expected