Development of an Integrated Structure for the Tri-Generation of Power, Liquid Carbon Dioxide, and Medium Pressure Steam Using a Molten Carbonate Fuel Cell, a Dual Pressure Linde-Hampson Liquefaction Plant, and a Heat Recovery Steam Generator

Due to the increase in energy consumption and energy prices, the reduction in fossil fuel resources, and increasing concerns about global warming and environmental issues, it is necessary to develop more efficient energy conversion systems with low environmental impacts. Utilizing fuel cells in the combined process is a method of refrigeration and electricity simultaneous production with a high efficiency and low pollution. In this study, a combined process for the tri-generation of electricity, medium pressure steam, and liquid carbon dioxide by utilizing a molten carbonate fuel cell, a dual pressure Linde-Hampson liquefaction plant and a heat recovery steam generator is developed. This combined process produces 65.53 MW of electricity, 27.8 kg/s of medium pressure steam, and 142.9 kg/s of liquid carbon dioxide. One of the methods of long-term energy storage involves the use of a carbon dioxide liquefaction system. Some of the generated electricity is used in industrial and residential areas and the rest is used for storage as liquid carbon dioxide. Liquid carbon dioxide can be used for peak shavings in buildings. The waste heat from the Linde-Hampson liquefaction plant is used to produce the fuel cell inlet steam. Moreover, the exhaust heat of the fuel cell and gas turbine would be used to produce the medium pressure steam. The total efficiency of this combined process and the coefficient of performance of the refrigeration plant are 82.21% and 1.866, respectively. The exergy analysis of this combined process reveals that the exergy efficiency and the total exergy destruction are 73.18% and 102.7 MW, respectively. The highest rate of exergy destruction in the hybrid process equipment belongs to the fuel cell (37.72%), the HX6 heat exchanger (8.036%), and the HX7 heat exchanger (6.578%). The results of the sensitivity analysis show that an increase in the exit pressure of the V1 valve by 13.33% would result in an increase in the refrigeration energy by 2.151% and a reduction in the refrigeration cycle performance by 9.654%. Moreover, by increasing the inlet fuel to the fuel cell, the thermal efficiency of the whole combined process rises by 18.09%, and the whole exergy efficiency declines by 12.95%.

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.

A generic concept for Helium purification and liquefaction plant

This study describes and evaluates the performance of producing a pure Helium fraction from Helium extraction facility designed for cryogenic natural gas plants. A generic concept for obtaining a Helium pure fraction, which has relatively lower capital and operating costs should be provided. In order to achieve this objective, a new concept for obtaining a Helium pure fraction from a crude Helium fraction, is proposed based on simulations run under diverse process conditions regarding crude Helium gas’ temperature, pressure and composition. This concept is characterized by; reducing the plant safety requirements due to the extensive separation of combustible components, and compact layout of Helium extraction plant. Further re-purification is included in the subsequent Helium liquefaction step through selective adsorption, hence then increasing the purity of the Helium product and reducing the plant energy consumption required for liquefying Helium-rich fraction and the valuable Helium boil-off routed from the storage facility. The Nitrogen-rich fraction is routed to Nitrogen liquefaction installation. Liquid Nitrogen is generated within Helium recovery facility for liquid Helium shielding and container cooling. Surplus gaseous Nitrogen either can be liquefied and used within cryogenic natural gas plant as process coolant or be vented to atmosphere.