Attention of humanity is being increasingly focused on prevention of anthropogenic emissions of greenhouse gases, including CO2 [1]. One of the main contributions to CO2 emissions is associated with the production of electric and thermal energy. Despite great efforts, aimed at developing renewable energy technologies, fossil fuels will dominate in this area of human activity for a very long time. Therefore, the capture of CO2, formed during the combustion of fossil fuels, is of particular importance. If air is used as a fuel oxidizer, the combustion products consist of more than 70% nitrogen. It is very difficult and expensive to separate carbon dioxide from this nitrogen. Promising solutions for carbon capture are associated with air separation and fuel combustion in pure oxygen. Recently, considerable attention has been paid to such cycles [2-4]. The gases temperature of a combustor chamber exit is regulated by the supply of CO2 and H2O to a combustion zone. In this case, a spent working fluid is almost entirely composed of a mixture of carbon dioxide and water vapor, which is easily divided into water and pure carbon dioxide. One of the options for such solutions involves a pressure increase for all components of the working fluid before injection them into a combustion chamber in a liquid phase by pumping equipment [5]. Thermodynamic cycles, in which a pressure of the working fluid is increased in the liquid phase by pumping equipment (without a compressor), can be called compressorless.

Nowadays, thermodynamic cycles are actively studied, in which pure oxygen and fuel are fed into a combustion chamber, and a temperature of a working fluid is regulated by the supply of carbon dioxide and/or water vapor. These cycles are called “oxygen-fuel”. They allow easy to separate CO2, resulting from a fuel combustion, from the working fluid and remove it from the cycle in its pure form. In addition, it has already been shown that an efficiency of electric power generation of such cycles is approaching the best known technologies. However, the efficiency of cogeneration of electricity and heat is more important for many energy systems, especially for Russian, in comparison with the efficiency of electricity generation. The main goal of the study was to analyze the thermal efficiency for cogeneration of electricity and heat of one of the options for the implementation of oxygen-fuel cycles - compressorless combined cycle gas turbine (CCGT) units. A mathematical model of the compressorless CCGT units was developed, which allows to study the thermal performance in a wide range of operating modes. It is conventionally accepted that the system requires a maximum power for power supply of 300 MW, and a maximum power for heat supply of 600 MW. It is assumed that 300 MW of electricity is constantly supplied to the network. In addition, the heat load is provided according to the standard schedule depending on the ambient temperature, and at the same time an averaged data on the temperature of atmospheric air for central Russia over a tenyear period is accepted. The comparison is made with a steam turbine CHP plant and a CCGTCHP plant. The results of the comparison showed a significant advantage of the compressorless CCGT unit.

In this article, problems of effectiveness increasing in complex power supply are considered. Disadvantages of centralized power engineering and advantages of power engineering capabilities organization in immediate consumer proximity are presented. Consumer needs satisfaction in electricity, heat supply and cold supply are offered to be realized by conversion of district and quarter boiler houses to trigeneration stations, which are based on gas turbine plants units. In this research, solutions of problem related to lack of fuel gas pressure for gas turbine engine power, which is included in gas turbine plant of trigeneration stations, are suggested. As a result, after considering possible variants of fuel gas pressure increasing, it was decided that there is a perspective of using fuel gas intracyclic compression attachment. Its operating principle involves organization of main steam extraction in heat cycle for booster compressor drive, which compresses fuel gas before its transfer to combustor of gas turbine plant. Results of gas compressor and drive steam turbine design are presented. These parts are included in fuel gas intracyclic compression attachment in specific unit of gas turbine plant. Also, general recommendations about new compressor and turbine stages design for any other units of gas turbine plant are pointed. Further, in the article, two variants of thermal circuit, based on gas turbine plant, are suggested. The first one is a circuit with hot water boiler, where exhaust gas recuperation after turbine is carried out for producing steam, related to fuel gas intracyclic compression attachment demands, and heat system water heating for consumer heat supply system. The second variant involves development of typical gas turbine plant unit in power station with exhaust boiler. There fuel gas intracyclic compression attachment is activated by steam work after exhaust boiler. Then, variants of diagram are compared between each other. Also advantages and disadvantages each of them are considered.