Development and justification of a hydrogen-in-oxygen combustion system using recirculation based on an experimental study

Strategy for energy development of Russia for the period up to 2035 provides for the participation of nuclear power plants with generation 3+ power units in regulating the daily unevenness of the electrical load, which forces the nuclear power plant to operate in an ineffective unloading mode. In order to solve this problem, a combination of nuclear power plants with a hydrogen complex is being considered, when during the hours of supposed unloading of the nuclear power plant due to the electrolysis of water, unclaimed power is converted into hydrogen and oxygen, and during peak load hours, hydrogen is burned in an oxygen environment in order to heat/overheat the working fluid in the steam turbine cycle Nuclear power plants and peak power generation. At the same time, the safety issues of using hydrogen when burned in oxygen are of great importance, which is, first of all, due to the inevitable presence of a certain amount of chemical underburning, which creates the risk of the formation of an explosive hydrogen-oxygen mixture along the working fluid path in the steam turbine cycle of a nuclear power plant. Based on the existing experience of the authors, a method for assessing the underburning of hydrogen and an indicator of the efficiency of recirculation in the proposed scheme using the recycling of unreacted hydrogen have been developed; a theoretical assessment of the underburning of hydrogen has been previously performed. In addition, a small-scale experimental installation has been developed that allows simulating the conditions of combustion of hydrogen in oxygen with recycling of unreacted hydrogen under the conditions of the steam turbine cycle of a nuclear power plant. This work represents a new approach to solving the problem of the safe use of hydrogen. The developed method makes it possible to determine specific concentrations of unreacted hydrogen depending on the flow rate and pressure in the flame tube. Based on the proposed indicator of recycling efficiency, it is shown that the proportion of hydrogen entrainment due to its low solubility in water is very small, which, at the accepted pressure and temperature of recycled unreacted hydrogen, determines a sufficiently high indicator of recycling efficiency. As a preliminary theoretical assessment has shown, the magnitude of the recirculation efficiency depends on the pressure and temperature at which unreacted hydrogen is recycled, which will obviously require further assessments over a wider range of pressures and temperatures. The proposed experimental methodology will make it possible to perform a reasonable assessment of the efficiency of recirculation of unreacted hydrogen for conditions of additional heating of feedwater in the steam turbine cycle of a nuclear power plant.