Ural Federal University Scientists Turn Coal-Fired Combustion Clean, Waste-Free

13:30, July 29, 2020

A unique technology was illustrated in 'Fuel' scientific journal

A team of scientists from the Ural Federal University and the Institute of Thermophysics of the Siberian Branch of the Russian Academy of Sciences (IT SB RAS, Novosibirsk), under the leadership of Alexander Ryzhkov, Professor at the Department of Thermal Power Plants of the Ural Federal University, has created a unique technology. It helps turn coal-fired power generation into a waste-free, cleaner and more cost-effective production.

An article with the research results was published in the highly rated magazine Fuel. As the authors note, these results are one of the stages of more than ten years of searching for solutions to reduce greenhouse gas emissions by the energy sector of the economy. Suffice it to say that the technology proposed by scientists from the Ural Federal University and the IT SB RAS and including a solid fuel power plant and a system for capturing, storing and utilizing technogenic carbon reduces CO2 emissions by 90–99%.

The article is devoted to solving the problem of intensifying the process of gasification (conversion) of coal. In existing technologies, this result is achieved by enriching the blast air with oxygen, which is supplied to the first stage of traditional two-stage air gasifiers: an increase in oxygen concentration leads to an acceleration of coal conversion. Theoretically, the same result is achieved by additional heating of the blast air in an air boiler to a high temperature, of the order of 1200 °C, however, due to the technological complexity, this method is not yet applicable in real production. Ural and Siberian scientists offer a more economical and simpler solution.

“The air gasifier we are developing resembles an hourglass: it consists of two stages connected by a confuser-diffuser bridge. The first, lower, stage is supplied with coal and an oxidizer - air, which is more accessible and cheaper than oxygen. The volume of air supplied is less than required for complete combustion of coal. Coal is fed into the second stage with the help of nitrogen, which, reacting with the conversion products from the first stage, is gasified with the formation of fuel synthesis gas - a mixture of combustible CO, H2 and non-combustible CO2, H2O, N2", - explains Nikolai Abaimov, associate professor of the Department of Thermal Power Plants at UrFU.

A distinctive feature of the coal gasification technology developed at Ural Federal University is that micronized coal is fed into the gasifier; its particle diameter - 30–40 microns - is significantly less than the diameter of standard-ground coal particles, which is about 100 microns. Due to the micronization of coal, the specific area of ​​its reaction becomes larger, the access of the oxidizer to coal is easier, therefore, the process of coal combustion and its gasification is faster. The synthesis gas obtained in this way is combusted in the combustion chamber of a gas turbine with the formation of carbon dioxide and water vapor with the presence of nitrogen and some impurities, for example, sulfur and nitrogen oxides.

“In Russia, coal conversion is usually understood as its combustion in power boilers of thermal power plants based on a steam power cycle, the so-called Rankine cycle. The efficiency of such stations is 35–40%, which is significantly lower than that of our proposed cycle based on a combined cycle plant (Brighton-Rankine cycle) with intracycle gasification, its efficiency can reach 50–55%. Our proposed capture and utilization technology involves the purification and compression of CO2 syngas from combustion. As a result, we get liquid CO2, which is much more convenient to deposit, that is, pump it underground,” continues Nikolai Abaimov.

However, according to the scientist, "storage" of gas is the most primitive solution. At the same time, for example, injection of liquefied carbon dioxide into oil-bearing strata significantly increases their recovery. CO2 has many other useful uses - in the food industry, in the plastics industry, in fire extinguishing systems, and so on.

“Moreover, we see an opportunity directly at thermal power plants to establish production of carbon dioxide of different characteristics - pressure, temperature, purity, depending on the needs of certain consumers. Thus, they will be relieved of the need to “bring” CO2 to meet their own needs. The remaining impurities - sulfur, nitric oxide - can also be sold, for example, in agriculture, medicine, the automotive industry, and so on,” adds Nikolay Abaimov.

UrFU is developing a concept and key technological solutions for a promising installation that will provide low-cost transmission of carbon dioxide to industrial consumers. The use of mineralization technology - the reaction of CO2 with rocks or industrial wastes with the formation of carbonates - opens up the possibility of obtaining new products by utilizing carbon dioxide, as well as ash, slag, and construction industry waste.

Artificial materials are most suitable for use in CO2 utilization schemes. If, as a rule, high pressures and temperatures are required for the carbonization of rocks, then the carbonization of artificial materials can be carried out at low, including atmospheric, pressure and low temperature. At the same time, the end product of carbonation is much more stable than in other technological solutions for the utilization of carbon dioxide, and finds many industrial applications, including within the framework of a housing renovation campaign.

About Ryzhkov's Team

The group of scientists led by Alexander Ryzhkov sees its goal as the transformation of waste from thermal power plants into a useful product, a commodity, and coal power generation into a waste-free, environmentally friendly and at the same time economically profitable production, equipped with modern, high-tech systems for capturing and utilizing carbon dioxide. Separate stages of work were supported by grants from the Russian Science Foundation, the Russian Foundation for Basic Research, the Federal Target Program "Research and Development in Priority Areas of Development of the Scientific and Technical Complex of Russia for 2007-2013"