Analysis of the Efficiency of Hydrogen Production Technology at Mini-CHP Plants Using Local Fuelsby Thermochemical Method

Abstract

Within the framework of the policy of “decarbonization” of the economy, a technology for hydrogen producing from local fuels (LF) and combustible waste of human activity is proposed as a part of the development of the functionality of heating cycles of energy production. The aim of the present study is to evaluate the energy efficiency of a steam-powered mini-CHP plant operating on local fuels with a thermochemical hydrogen production module. A brief literature review of thermochemical cycles of hydrogen production is presented, and it is shown that hybrid copper-chlorine Cu–Cl cycles are recognized as the most promising. In the Aspen Hysys software environment, a mathematical model of a mini-CHP plant with a five-stage hydrogen production cycle was synthesized, which can later be used as a component in the digital twin. According to the results of the analysis of the mathematical model, it was determined that the specific consumption of electric energy per 1 kg of hydrogen for such a scheme will be 9.11 (kW×h)/kg, which is on average more than five times less than in the production of hydrogen by electrolysis, the rest of the required energy is replaced by thermal one, while the maximum fuel utilization factor of mini-CHP with a hydrogen production module using wood waste as fuel amounted to 83.1 %, including a thermal efficiency of 51.5 %, the efficiency of hydrogen production at the lowest calorific value is 31 %, the electrical efficiency for the supply of electricity to the grid is 0.6 %. For comparison, the maximum fuel utilization of a steam-powered mini-CHP of the same electrical capacity reaches 90.9 %. The expansion of mini-CHP options operating on local fuels by introducing a hydrogen production unit by hybrid thermochemical method into its scheme makes it possible to increase the maneuverability of the station, which implies the possibility of organizing the operation of mini-CHP in accordance with the requirements of thermal consumers and electrical graph-reducing the loads of the power system during the hours of maxima and minima of its consumption by changing the electrical power supply to the network or increasing the power consumption of electricity from the external network to the power required for hydrogen production. In conclusion, the possibility of developing the studied scheme of a mini-CHP operating on local fuels towards further utilization of combustion products in order to generate artificial natural gas, which in this case can be called “green”, is indicated.