Scientists from the Joint Institute for High Temperatures of the Russian Academy of Sciences (JIHT RAS) have developed an environmentally friendly combined heat and power plant (CHPP) operating on a new thermodynamic cycle with oxygen combustion of natural gas. The proposed technology makes it possible to generate electricity and heat at the same time while virtually eliminating CO₂ emissions. In an environment where fossil fuels will continue to play a key role in the energy mix for a long time as emissions reduction requirements become more and more stringent, this design is being considered a possible way to modernize conventional power generation.
The new solution, dubbed as the JIHT RAS cycle, eliminates the use of air for fuel combustion. The combustion chamber is supplied with pure oxygen, while a mixture of carbon dioxide and water vapor serves as the working fluid that rotates the turbine. This fundamentally changes the composition of the combustion products and the configuration of the entire power plant. In a conventional CHPP, flue gases contain only a few percent of CO₂, which means that its extraction requires complex and energy-intensive systems. In the new design, carbon dioxide is part of the working fluid initially; after water condensation, it gets removed from the cycle in liquid form, which is convenient for transportation, storage or industrial uses. In addition, working fluid components are compressed by pumps in the liquid state, rather than by compressors in the gaseous state, which reduces energy consumption and makes it possible to achieve high pressures upstream of the turbine.
According to the developers’ calculations, the CHPP’s specific fuel consumption for useful energy production is less than 130 g of fuel equivalent per kWh year on year in integral terms. This provides fuel savings of over 30% compared to modern cogeneration plants of similar capacity. Also notable is the fact that the plant can flexibly regulate the ratio of thermal to electrical power, eliminating the need for peak-load boilers. This capability is especially important for Russian cities with well-developed centralized heating systems, where the thermal load often exceeds the electrical load.
The environmental benefit is primarily linked to the specifics of the combustion process. Since air is not used, there is virtually no nitrogen in the combustion zone, which means that the formation of nitrogen oxides is kept to a minimum. Carbon dioxide does not get emitted through the chimney; it condenses and gets discharged as a liquid. For a plant with a capacity of about 300 MW, this represents over 550 tons of CO₂ per day, which can be used for industrial purposes, such as the production of fertilizers and chemicals or injection into oil reservoirs. At the same time, water vapor gets fully condensed, which includes the so-called fuel water formed during the combustion of hydrogen in methane. This represents some 1 million tons of water per year, which is suitable for industrial purposes. The air separation unit, which is required for oxygen production, additionally produces more than 5 million tons of nitrogen per year for a 300-MW plant. This product is sought after in the metallurgical, oil-and-gas and food industries.
It is proposed to create a testing site at a 60-MW power plant for practical testing of the technology. This facility will allow the developers to address design and technological challenges, check equipment operation in various modes and assess economic parameters before scaling up to plants with a capacity of 100–600 MW or more. The project envisages the participation of Russian power engineering enterprises.
