Technological Solutions in the Field of Production and Use of Hydrogen Fuel to Increase the Thermal Efficiency of Steam Turbine TPPs

Abstract

The paper discusses technological solutions in the field of production and use of hydrogen fuel, the combustion of which, in a steam-oxygen environment, can significantly increase the initial parameters of the steam turbine cycle and, thus, increase the thermal efficiency of traditional steam turbine thermal power plants. A study of technologies for the industrial production of hydrogen has been carried out. An analysis of the technical and economic features of hydrogen production technologies for use in the electric power industry showed that the most promising method is electrolysis, which makes it possible to obtain inexpensive hydrogen during hours of low demand for electricity or cogeneration of heat and electricity when electricity is a by-product. It is shown that in order to increase the power and efficiency of steam turbine TPPs, it is important to use external steam superheating from an external source of thermal energy, thus providing intermediate overheating of the working fluid by connecting an additional cycle with a higher equivalent initial temperature to the main steam turbine cycle. We have established that if we use hydrogen as a thermal energy source, the absolute efficiency of the steam turbine cycle can be increased up to 54%, taking into account the regenerative heating of feed water. In this case, at an overheating temperature equal to tnn = 760 °C, the absolute efficiency of the cycle is virtually equal to that of a CCGT unit operating at the initial gas temperature t0 = 1350 °C. At the same time, while maintaining the boiler performance, the rated capacity of the steam turbine power unit is increased by 12%. In addition, the study pays attention to the problem of increasing the power consumption of TPPs for the auxiliaries, as required to compress hydrogen and oxygen up to a pressure higher than that in the steam pipeline where the combustion chamber is installed. Our calculations have allowed us to conclude that, for the case of installing the combustion chamber in live steam, the share of additional power spent for auxiliaries should be 7%, whereas the main share of power is consumed for compressing hydrogen—94%. Despite the identified shortcomings, an economic analysis of the process of hydrogen production at TPP by electrolysis and its further use for intermediate overheating in steam turbines in order to increase their efficiency showed the effectiveness of this solution.