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Development of a Mathematical Model for Solid Fuel Gasification and Its Sensitivity Analysis

Within the framework of this study, a brief review of the gasification technology was carried out, the best types of blowing agents and gasification methods used in terms of efficiency and environmental safety were identified, and a mathematical model of a steam–oxygen gasifier was developed in the MS Excel software package. The authors paid special attention to the consideration of the effect of changing the input parameters of the syngas, such as the temperature and relative mass flow rate of steam and oxygen, on the heat of the combustion of the produced syngas. As a result of the research, methods for increasing the heat of the combustion of the syngas and the conditions for using the described methods were formulated. The work also revealed the optimal ratios of the blowing agents and solid fuel supplied for gasification and presented the output parameters of the produced generator gas, including the heat of combustion of the gas, the gas temperature, and the gasification efficiency. Computer simulation models of the gasifier and gasification process were the basis for the analysis of a combined cycle (CC) facility with an integrated solid fuel gasifier. The heat flow thermodynamic analysis shows that the gasification steam bleeding from the turbine is the best solution for the improvement of cycle efficiency

Research and Development of the Combined Cycle Power Plants Working on Supercritical Carbon Dioxide

Today, the use of combined cycle gas turbine (CCGT) plants allows the most efficient conversion of the chemical heat of fossil fuels for generating electric power. In turn, the combined cycle efficiency is largely dependent on the working flow temperature upstream of a gas turbine. Thus, the net electric efficiency of advanced foreign-made CCGT plants can exceed 63%, whereas the net efficiency of domestic combined-cycle power plants is still relatively low. A promising method to increase the heat performance of CCGT plants may be their conversion from a steam heat carrier to a carbon dioxide one. In this paper, we have presented the results of thermodynamic research of a promising combined plant with two carbon dioxide heat recovery circuits based on the GTE-160 gas turbine plant (GTP). We have determined the pressure values that are optimal in terms of the net efficiency upstream and downstream of Brayton cycle turbines using supercritical carbon dioxide with recompression (30 and 8.5 MPa) and base version (38 and 8.0 MPa). The percentage of recompression was 32%. Based on the results of mathematical simulation of heat circuits, we have found out that the use of the solutions suggested allows the increase of the power plant’s net efficiency by 2.4% (up to 51.6%)

Review of Closed SCO₂ and Semi-Closed Oxy–Fuel Combustion Power Cycles for Multi-Scale Power Generation in Terms of Energy, Ecology and Economic Efficiency

Today, with the increases in organic fuel prices and growing legislative restrictions aimed at increasing environmental safety and reducing our carbon footprint, the task of increasing thermal power plant efficiency is becoming more and more topical. Transforming combusting fuel thermal energy into electric power more efficiently will allow the reduction of the fuel cost fraction in the cost structure and decrease harmful emissions, especially greenhouse gases, as less fuel will be consumed. There are traditional ways of improving thermal power plant energy efficiency: increasing turbine inlet temperature and utilizing exhaust heat. An alternative way to improve energy efficiency is the use of supercritical CO2 power cycles, which have a number of advantages over traditional ones due to carbon dioxide’s thermophysical properties. In particular, the use of carbon dioxide allows increasing efficiency by reducing compression and friction losses in the wheel spaces of the turbines; in addition, it is known that CO2 turbomachinery has smaller dimensions compared to traditional steam and gas turbines of similar capacity. Furthermore, semi-closed oxy–fuel combustion power cycles can reduce greenhouse gases emissions by many times; at the same time, they have characteristics of efficiency and specific capital costs comparable with traditional cycles. Given the high volatility of fuel prices, as well as the rising prices of carbon dioxide emission allowances, changes in efficiency, capital costs and specific greenhouse gas emissions can lead to a change in the cost of electricity generation. In this paper, key closed and semi-closed supercritical CO2 combustion power cycles and their promising modifications are considered from the point of view of energy, economic and environmental efficiency; the cycles that are optimal in terms of technical and economic characteristics are identified among those considered

Research and Development of Trinary Power Cycles

The most effective and environmentally safe fossil fuel power production facilities are the combined cycle gas turbine (CCGT) ones. Electric efficiency of advanced facilities is up to 58% in Russia and up to 64% abroad. The further improvement of thermal efficiency by increase of the gas turbine inlet temperature (TIT) is limited by performance of heat resistance alloys that are used for the hot gas path components and the cooling system efficiency. An alternative method for the CCGT efficiency improvement is utilization of low potential heat of the heat recovery steam generator (HRSG) exhaust gas in an additional cycle operating on a low-boiling heat carrier. This paper describes a thermodynamic analysis of the transition from binary cycles to trinary ones by integration of the organic Rankine cycle (ORC). A mathematical model of a cooled gas turbine plant (GT) has been developed to carry out calculations of high-temperature energy complexes. Based on the results of mathematical modeling, recommendations were made for the choice of the structure and parameters of the steam turbine cycle, as well as the ORC, to ensure the achievement of the maximum thermal efficiency of trinary plants. It is shown that the transition from a single pressure CCGT to a trinary plant allows the electric power increase from 213.4 MW to 222.7 MW and the net efficiency increase of 2.14%. The trinary power facility has 0.45% higher efficiency than the dual pressure CCGT

Research and Development of Trinary Power Cycles

The most effective and environmentally safe fossil fuel power production facilities are the combined cycle gas turbine (CCGT) ones. Electric efficiency of advanced facilities is up to 58% in Russia and up to 64% abroad. The further improvement of thermal efficiency by increase of the gas turbine inlet temperature (TIT) is limited by performance of heat resistance alloys that are used for the hot gas path components and the cooling system efficiency. An alternative method for the CCGT efficiency improvement is utilization of low potential heat of the heat recovery steam generator (HRSG) exhaust gas in an additional cycle operating on a low-boiling heat carrier. This paper describes a thermodynamic analysis of the transition from binary cycles to trinary ones by integration of the organic Rankine cycle (ORC). A mathematical model of a cooled gas turbine plant (GT) has been developed to carry out calculations of high-temperature energy complexes. Based on the results of mathematical modeling, recommendations were made for the choice of the structure and parameters of the steam turbine cycle, as well as the ORC, to ensure the achievement of the maximum thermal efficiency of trinary plants. It is shown that the transition from a single pressure CCGT to a trinary plant allows the electric power increase from 213.4 MW to 222.7 MW and the net efficiency increase of 2.14%. The trinary power facility has 0.45% higher efficiency than the dual pressure CCGT

Feasibility Study of the CO₂ Regenerator Parameters for Oxy-Fuel Combustion Power Cycle

The atmosphere carbon dioxide content grows subsequently due to anthropogenic factors. It may be considerably mitigated by the development of thermal power plants with near zero emissions. A promising way is the transition to the semi-closed oxy-fuel combustion power cycles with carbon dioxide and water vapor mixture as a working fluid. However, their wide implementation requires reduction of the metal consumption for the highly efficient regeneration system. This paper discloses the results of feasibility study for the regeneration system of the prospective oxy-fuel combustion power plant. The effect of operating parameters on the cycle energy efficiency, overall dimensions, and the cost of the regenerator was determined. Underheating increase in the regenerator by 1 °C leads to the net efficiency factor drop of the oxy-fuel combustion power cycle by 0.13% at average and increases fuel costs by 0.28%. Increase of pressure drop in the hot channel by 1% leads to efficiency drop by 0.14%. The optimum set of design and operating parameters of the feed heating system has been determined, which ensures the best technical and economic indicators of electrical power generation: the minimum cumulative costs are achieved when underheating in the regenerator is 20 °C and pressure drop in the hot channel is 4%, under the use of S-shaped fins channels

Thermodynamic Analysis of Binary and Trinary Power Cycles Fueled with Methane–Hydrogen Blends

The development of hydrogen energetics is a possible way to reduce emissions of harmful substances into the atmosphere in the production of electricity. Its implementation requires the introduction of energy facilities capable of operating on environmentally safe fuel. At the same time, from a technological point of view, it is easier to implement a gradual shift to the use of hydrogen in power plants by burning methane–hydrogen blends. This paper presents the results of thermodynamic studies of the influence of the chemical composition of the methane–hydrogen blend on the performance of binary and trinary power units. It is shown that an increase in the hydrogen volume fraction in the fuel blend from 0 to 80% leads to a decrease in the Wobbe index by 16% and an increase in the power plant auxiliaries by almost 3.5 times. The use of a trinary CCGT unit with a single-circuit WHB and working fluid water condensation makes it possible to increase the net efficiency by 0.74% compared to a binary CCGT with a double-circuit WHB and a condensate gas heater

Thermodynamic Analysis of Binary and Trinary Power Cycles Fueled with Methane–Hydrogen Blends

The development of hydrogen energetics is a possible way to reduce emissions of harmful substances into the atmosphere in the production of electricity. Its implementation requires the introduction of energy facilities capable of operating on environmentally safe fuel. At the same time, from a technological point of view, it is easier to implement a gradual shift to the use of hydrogen in power plants by burning methane–hydrogen blends. This paper presents the results of thermodynamic studies of the influence of the chemical composition of the methane–hydrogen blend on the performance of binary and trinary power units. It is shown that an increase in the hydrogen volume fraction in the fuel blend from 0 to 80% leads to a decrease in the Wobbe index by 16% and an increase in the power plant auxiliaries by almost 3.5 times. The use of a trinary CCGT unit with a single-circuit WHB and working fluid water condensation makes it possible to increase the net efficiency by 0.74% compared to a binary CCGT with a double-circuit WHB and a condensate gas heater

Research and development of a high-performance oxy-fuel combustion power cycle with coal gasification

Recent climate changes stimulate the search and introduction of solutions for the reduction of the anthropogenic effect upon the environment. Transition to the oxy-fuel combustion power cycles is an advanced method of CO2 emission reduction. In these energy units, the main fuel is natural gas but the cycles may also work on syngas produced by the solid fuel gasification process. This paper discloses a new highly efficient oxy-fuel combustion power cycle with coal gasification, which utilizes the syngas heat in two additional nitrogen gas turbine units. The cycle mathematics simulation and optimization result with the energy unit net efficiency of 40.43%. Parametric studies of the cycle show influence of the parameters upon the energy unit net efficiency. Change of the cycle fuel from natural gas to coal is followed by a nearly twice increase of the carbon dioxide emission from 4.63 to 9.92 gmCO2/kWh