Tackling Dissipative Components Based on the SPECO Approach: A Cryogenic Heat Exchanger Used in Natural Gas Liquefaction

The cryogenic industry has been experiencing continuous progress in recent years, primarily due to the global development of oil and gas activities. Natural gas liquefaction is a cryogenic process, with the refrigeration system being crucial to the overall process. The objective of the study presented herein is to carry out an exergoeconomic assessment for a dual nitrogen expander process used to liquefy natural gas, employing the SPecific Exergy COsting (SPECO) methodology. The air coolers and throttling valve are dissipative components, which present fictitious unit cost rates that are reallocated to the final product (Liquefied Natural Gas). The liquefaction process has an exergy efficiency of 41.89%, and the specific cost of liquefied natural gas is 292.30 US$/GJ. It was verified that this cost increased along with electricity. The highest exergy destruction rates were obtained for Expander 1 and Air cooler 2. The highest average cost per exergy unit of fuel was obtained for the vertical separator, followed by Air coolers 1 and 2. An assessment of the exergoeconomic factor indicated that both expanders could benefit from a decrease in exergy destruction, improving the exergoeconomic performance of the overall system. Regarding the relative cost difference, all compressors presented high values and can be enhanced with low efforts.

Modification of the cascade methane liquefaction process to improve the efficiency of the system

In recent years, the dynamic development of the LNG industry has been observed. This is largely due to the transition of many countries from coal-based energy to greener energy. Natural gas is regarded as an intermediate fuel. Natural gas can be transported by pipeline, but in many cases it is more economical to transport it in a liquefied form. The liquefaction process is very energy-consuming, which is why many researchers are focused on optimizing this process. This work is an attempt to optimize the operation of the basic cascade natural gas liquefaction system. The proposed modifications contribute to a significant reduction in the costs of the liquefaction process.

ADJUSTMENT OF FUZZY ADAPTIVE REGULATOR OF COMPRESSOR UNIT FOR LIQUEFACTION OF NATURAL GAS

The main properties of the object are studied, as well as the methods by which new parameters can be found for the regulator of the compressor unit for liquefaction of natural gas. The main properties of the adaptive regulator itself are studied, as well as the method by which the work was performed is developed. A comparison was also made with other types of automatic control systems that can be used in this facility. The sequence of construction of the adaptive controller and its interaction with the object is studied. The initial results of the adaptive controller and their comparison with other automatic control systems are investigated. The general properties and rules of construction of the adaptive regulator, the basic subtleties at work with it are studied. New possibilities for regulation of the compressor installation for liquefaction of natural gas are fully considered and the basic rules concerning application of this adaptive regulator are deduced. A study of the effectiveness of the adaptive regulator for this object was conducted and conclusions were made on the work of the regulator and the effectiveness of its results. A special sequence of work was also developed for the construction of an adaptive controller and its application on site. In general, the basic rules for working with such a regulator and its application in a natural gas liquefaction plant are derived. The behavior of the plant is investigated and new settings for the regulation of the natural gas liquefaction plant are derived. The main types of regulation of this object are applied and new rules for finding settings for the main regulator of the compressor unit are derived. The work on comparison of already traditional types of regulation with the adaptive regulator is made and conclusions on application of this or that type of regulation of compressor installation comparing results of regulation are made. The possibility of real use of this regulator on a constant basis in production is investigated, conclusions on the main work of the regulator and also shortcomings which can arise at a choice of regulation with the adaptive regulator are made.