Clean Coal Technologies as an Effective Way in Global Carbon Dioxide Mitigation

1. Introduction

Energy security is a main challenge in today’s economies [1,2]. On the world we use and produce many different types and sources of energy. These sources could be grouped into general categories such as primary and secondary, renewable and nonrenewable, and fossil fuels. The environment benefit of clean coal technologies are obvious. Increase the efficiency of thermochemical coal conversion leads to significant decrease of global warming gases emissions as well as the decrease in SO₂ and NO_X emissions. The pollutants emitted by fossil fuels power plants will be also significantly reduced. All these efforts are the major driving forces in the development of so-called clean coal technologies [3,4]. On the other hand, another alternative in term of reduction of negative effect of increasing energy demand are increasing the share of renewable energy resources in the global energy balance [5,6].

Carbon dioxide is emitted to the atmosphere, and even if it is not the most powerful greenhouse gas, due to the fact that CO₂ is emitted whenever the fossil fuels are burned, it seems to be the main contributor to climate change. The CO₂ could be treated as a very problematic waste [7,8,9]. Within the EU legislation, the legislator defined waste as any substance or object that the holder discards, or intends or is required to discard [10,11]. The EU environmental laws protect the environment and human health by preventing or mitigating the adverse impacts of the generation and management of waste, as well as by reducing the overall impact of resource use and increasing the efficiency of such use [12,13].

In this special issue “The effectiveness of clean coal technologies in global carbon dioxide mitigation”, seven research papers were published as examples of recent developments in widely understand area of clean thermochemical conversion of fossil fuels with maximization of CO₂ emission reduction. Among the clean coal technologies, the new, innovative thermochemical conversion of coal technologies such a (combustion, gasification, pyrolysis, and hydrogenation) and co-gasification with biomass/biowaste/sewage sludge will be discussed. The technologies of fossil fuels thermochemical utilization must be combined with the research concerning CO₂ emission reduction: CCS and CCUS technologies, respectively.

In this Editorial in Section 2 the summary of the published articles in this special issue is presented whereas in Section 3 Editors discuss several topics beyond the coverage of the special issue articles. The Editorial is finalized with short conclusions Section 4.

2. Special Issue Articles

This section summarizes each of the published articles in this SI and tries to emphasis the main aspect of each of them.

The research paper “Investment Model of Agricultural Biogas Plants for Individual Farms in Poland” by Klimek et al. [14] presents the methods which allow assessment of the economic effectiveness of an investment in an agricultural biogas plant. In the paper a financial model was developed. The crucial is fact that the biogas plants operating on organic waste seem to be the future, perspective low-carbon multi-energy systems which will be stable source of heat and electricity generation. Authors prove that the financial analysis of the process gave positive effects throughout the entire period of operation of the biogas plant. Unfortunately, on the Polish market there is a lack of complex and proved technological materials for micro-biogas plants, including the simplest-to-build small-container biogas plants.

Ciuła et al. in the paper entitled “Emission and Neutralization of Methane from a Municipal Landfill-Parametric Analysis” perform a parametric analysis covering the production, emission, and neutralization of CH4 in a real facility [15]. Since methane is serious greenhouse gas the problem of unorganized emission of CH4 from the landfill surface was a serious threat for the environment. Authors applied chemometrics method such as Ward linkage hierarchical clustering analysis as well as the Pearson coefficient calculations to evaluate the distance-based similarity measure and to optimize methods for estimating methane emissions from a landfill. Uncontrolled methane emission and the way of the methane utilization is a crucial part of the effectiveness of clean coal technologies development. The methodological approach proposed in the paper can be used in landfills with similar technical solutions and comparable parameters of CH4 and gas stream, respectively. The proposed procedure can be very useful in the diagnosis of the current state of landfill and forecasting the potential gas production as well as providing recommendations for more effective technical solutions.

Wodołażski et al. in the paper entitled “CFD Modeling of the Catalyst Oil Slurry Hydrodynamics in a High Pressure and Temperature as Potential for Biomass Liquefaction” proposed the model of the catalyst-paraffin oil slurry hydrodynamics under high pressure and temperature in a convex bottom reactor with a Rushton turbine [16]. The modelling was conducted with an application of computational fluid dynamics (CFD) modeling. Authors prove that the hydrodynamics of the catalyst for biomass liquefaction under high pressure and temperature conditions is crucial in the optimization of the biomass liquefaction process in the future and have a significant impact on the process performance. Moreover, in the paper influence of different operating conditions such as solid loading, particle size, and the impeller speed determine the velocity and concentration fields of a suspension on the liquefaction process were also analyzed.

In the fourth paper entitled “Water-Induced Corrosion Damage of Carbon Steel in Sulfolane” written by Kubisztal et al. [17] an analysis of the impact of water concentration in sulfolane on the electrochemical corrosion of AISI 1010 steel is given. The topic is strictly correlated with clean technologies because the sulfolane in contact with water and oxygen forms acidic products that are major factors in accelerating the corrosion of carbon/stainless steel. In the paper Authors studied the corrosion mechanism as well as the corrosion rate using a potentiodynamic technique and scanning Kelvin probe microscopy. The quantification of the corrosion damage of the material surface was performed by application of the fractal analysis using images registered by a scanning electron microscope.

Bielowicz in the paper entitled “Petrographic Characteristics of Coal Gasification and Combustion By-Products from High Volatile Bituminous Coal” showed the benefits of coal gasification in a fluidized bed reactor with CO₂ as a gasifying agent at the temperature 889–980 °C [18]. The gasification is a very attractive way of thermochemical conversion of coal in comparison to classic combustion. Moreover, in the studied process carbon dioxide was used as a gasifying agent what could be treated as an attractive method of chemical utilization of CO₂.

Nikolsky et al. publish an article “A Study of Heat Exchange Processes within the Channels of Disk Pulse Devices” which is focused on specific aspects of clean technologies dealing with mathematical models of the effect of the structural and technological parameters of the channels in the disk pulse device on the heat exchange efficiency [19]. In this paper for the very first time a mathematical model developed, which allowed analysis of gas dynamics processes in the disk gaps of rotor pulse devices. It is a significant progress in comparison with the existing in the literature analytical descriptions of particular cases of the equation of compressible fluid motion in the disk channel.

The paper entitled “Eco-Efficiency Assessment of the Application of Large-Scale Rechargeable Batteries in a Coal-Fired Power Plant” by Krawczyk and Śliwińska presents the eco-efficiency assessment of the application of large-scale rechargeable battery technology in electricity generation from coal [20]. In the paper the eco-efficiency calculation was done for electricity production in the 350 MWe coal-fired power plant. In the cost analysis Authors also proved that the use of the battery to optimize the operation of coal-fired power units will be beneficial from economic point of view.

3. Trends and the Future Development

Besides the research area described in the seven papers published in the special issue devoted to the effectiveness of clean coal technologies in global carbon dioxide mitigation special area is dedicated to the hydrogen, which is new, environment friendly energy carrier [21,22,23]. The aim of the work of scientists in Europe is to achieve climate neutrality in 2050. The development and deployment of hydrogen technologies will make an important contribution to achieving this ambitious goal. This goal is set out in the Green Deal document adopted by the European Commission [24]. Hydrogen is currently classified aa the so-called grey, blue and green hydrogen [25,26]. In the light of the efforts of the European Commission, there is a drive towards zero-emission energy and transport, which can be helped by the so-called green hydrogen produced in the process of water electrolysis with the use of energy from renewable energy sources (wind, solar energy).

It should be noted that currently hydrogen is produced from fossil fuels by methane steam reforming or by gasification of coal. However, this is the so-called grey hydrogen. Production of hydrogen from fossil fuels is associated with high emissivity, therefore it is often said about combining these technologies with technologies of capture, storage or chemical utilization of CO₂. In the light of the climate neutrality of the European Union, in 2050 it is necessary to develop the production technology of the so-called green hydrogen.

4. Conclusions

This special issue is composed of seven research papers with various topics and methodologies in the area of widely understand effectiveness of clean coal technologies in global CO₂ mitigation. In this Editorial the Guest Editors try to briefly summarize the details of all papers focusing the attention on the main conclusions from the presented research. The Guest Editors would like to deeply thank the Authors of the papers as well as all Reviewers whose work allow improving the quality of the works presented in this Special Issue. We hope that further development of clean coal technologies combined with technologies of carbon dioxide capture storage or chemical utilization will be further developed in the near future.