The purpose of the article was to characterize the international steam coal market based on the latest available data. The information goes back to the first half of 2018. The article focuses on the description of the three largest exporters and importers of steam coal. Representatives in these categories were selected using the latest global statistics on 2017. In 2017, global production of steam coal amounted to 5.68 billion tons and exceeded production in 2016 by 4%. For several years, invariably the world’s leading exporters of steam coal are: Indonesia, Australia and Russia. In total, these three countries in 2017 supplied 73% of steam coal to the international market. However, for the 46% of global steam coal imports (data for 2017), three Asian countries are responsible: China, India and Japan. For each of the six listed countries (i.e. for: three major global exporters and three major global importers), the paper presents volumes related to coal production, export or import. The directions of deliveries or major coal exporters to a given country were also included. At the end of the article, the price situation was presented, as it appeared in the first half of 2018 on the European and Asian markets.

The article presents an analysis of Russia’s participation in international steam coal trade, which has been its important participant for years. The research covered the years 2014–2018. The geographical location on two continents and the availability of coal deposits, favors its presence on both the Pacific and Atlantic markets. The article also discusses the main coal producers in Russia and the prices of Russian steam coal directed to the spot market. Due to the significant share of coal exports for the Russian economy, the focus was also on analyzing Russian seaports.

In recent years, Asian exports have dominated in Russian steam coal exports. The share of export to this market in the years 2014–2018 was in the range of 49–57% (60–87 million tons). Currently, three countries play an important role among Asian countries: South Korea, China and J apan. They purchased a total of 38–52 million tons of Russian coal. Although in the years under analysis Russia exported 52–67 million tons of steam coal to the European market, the share of this market dropped from almost half to around 40%. T he slow departure from coal energy contributes to reducing the share of recipients from this direction. Among European countries, in 2014 the main direction of export was Great Britain with 19% (24 million tons) of total export share. In 2018, exports fell to 9 million tons (5%).

Among European destinations for Russian coal, Poland’s share is growing in importance. In the years 2014–2018, steam coal exports to Poland varied in the range of 5.6–16.2 million tons. In the years 2014–2018 it changed in the range of 5.6–16.2 million tons. The dynamic growth achieved in the last three years is noteworthy. In relation to 2016, imports increased by 10.0 million tons and in 2018 amounted to as much as 16.1 million tons. The article also discusses the geographical structure of coal imports to Poland by railway border crossings and seaports.

The article presents current state of the structure of hard coal enrichment plants in Poland, taking the capacity, the range of grain enrichment and the type of equipment used into account. This data were presented in a tabular format for each Polish Coal Company operating on the Polish market. The article was also present simplified: flow sheet of the steam and coking coal enrichment system. Based on the presented data, the planned needs and trends were described in terms of increasing production efficiency, minimizing water consumption and safety of work. A list of research and development works which must be undertaken were also presented as well as factors determining the technological development of the processing plants.

The paper presents selected issues related to the development of international coal markets. World consumption of coal dropped for the second year in a row in 2016, primarily due to lower demand from China and the U S. The share of coal in global primary energy consumption decreased to 28%. World coal production accounted to 3.66 billion toe and it was lower by 6.2% when compared to the previous year. More than 60% of this decline took place in China. The decline in global production was more than four times higher than the decrease in consumption. The sufficiency of world resources of coal are estimated at 153 years – that is three times more than the sufficiency of oil and gas resources. After several years of decline, coal prices increased by 77% in 2016. The current spot prices are at the level of $80/t and are close to the 2014 prices. In the European market, after the first half of the year, coal prices reached the level of around 66% higher than in the same period of the last year. The average price in the first half amounted to PLN 12.6/GJ, which is close to the 2012 prices. The share of spot trade in the total purchase amount accounted to approx. 20%. Prices in futures contracts can be estimated on the basis of the Japan-Australia contracts prices and prices in supplies to power plants located in Germany. On average, the prices in supplies to these power plants were higher by approximately 9% in the years 2010–2016 and prices in Australia – Japan contracts were 12% higher than CIF ARA prices in 2017. Global energy coal trade reached about 1.012 billion tonnes in 2016. In 2019, a decline by 4.8% is expected primarily due to the expected reduction in the demand in major importing countries in Asia.

Turbine stages can be divided into two types: impulse stages and reaction stages. The advantages of one type over the second one are generally known based on the basic physics of turbine stage. In this paper these differences between mentioned two types of turbines were indicated on the example of single stage turbines dedicated to work in organic Rankine cycle (ORC) power systems. The turbines for two ORC cases were analysed: the plant generating up to 30 kW and up to 300 kW of net electric power, respectively. Mentioned ORC systems operate with different working fluids: DMC (dimethyl carbonate) for the 30 kW power plant and MM (hexamethyldisiloxane) for the 300 kW power plant. The turbines were compared according to three major issues: thermodynamic and aerodynamic performance, mechanical and manufacturing aspects. The analysis was performed by means of the 0D turbomachinery theory and 3D computational aerodynamic calculations. As a result of this analysis, the paper indicates conclusions which type of turbine is a recommended choice to use in ORC systems taking into account the features of these systems.

Consumption of energy is one of the important indicators in developing countries, but a lot of companies from the energy sector have to cope with three key challenges, namely how to reduce their impact on the environment, how to ensure the low cost of the energy production and how to improve the system overall performance? For Polish energy market, the number of challenges is greater. The growing demand for electricity and contemporary development of nuclear power technology allow today’s design, implement new solutions for high energy conversion system low unit cost for energy and fuel production. In the present paper, numerical analysis of modular high-temperature nuclear reactor coupled with the steam cycle for electricity production has been presented. The analysed system consists of three independent cycles. The first two are high-temperature nuclear reactor cycles which are equipped with two high-temperature nuclear reactors, heat exchangers, blowers, steam generators. The third cycle is a Rankine cycle which is equipped with up to four steam turbines, that operate in the heat recovery system. The analysis of such a system shows that is possible to achieve significantly greater efficiency than offered by traditional nuclear reactor technology.

This paper presents the origins of marine steam turbine application on liquefied natural gas carriers. An analysis of alternative propulsion plant trends has been made. The more efficient ones with marine diesel engines gradually began to replace the less efficient plants. However, because of many advantages of the steam turbine, further development research is in progress in order to achieve comparable thermal efficiency. Research has been carried out in order to achieve higher thermal efficiency throughout increasing operational parameters of superheated steam before the turbine unit; improving its efficiency to bring it nearer to the ideal Carnot cycle by applying a reheating system of steam and multi stage regenerative boiler feed water heating. Furthermore, heat losses of the system are reduced by: improving the design of turbine blades, application of turbine casing and bearing cooling, as well as reduction in steam flow resistance in pipe work and maneuvering valves. The article identifies waste energy sources using the energy balance of a steam turbine propulsion plant applied on the liquefied natural gas carrier which was made out basing on results of a passive operation experiment, using the measured and calculated values from behavioral equations for the zero-dimensional model. Thermodynamic functions of state of waste heat fluxes have been identified in terms of their capability to be converted into usable energy fluxes. Thus, new ways of increasing the efficiency of energy conversion of a steam turbine propulsion plant have been addressed.

An important operational task for thermal turbines during run-up and run-down is to keep the stresses in the structural elements at a right level. This applies not only to their instantaneous values, but also to the impact of them on the engine lifetime. The turbine shaft is a particularly important element. The distribution of stresses depends on geometric characteristics of the shaft and its specific locations. This means a groove manufactured for fixing the rotor blades. The extreme stresses in this place occur during the start-up and the shaft heating to normal operating temperature. The process needs optimisation. Optimization tasks are multidisciplinary issues and can be carried out using different methods. In recent years, particular attention in optimisation has been paid to the use of artificial intelligence methods. Among them, a special role is assigned to genetic algorithms. The paper presents a genetic algorithm method to optimise the steam turbine shaft heating process during its start-up phase. The presented optimization task of this algorithm is to carry out the process of the shaft heating as soon as possible at the conditions of not exceeding the stresses at critical locations at any heating phase.

Recently, significant progress has been made in experimental studies on the flow of wet steam, measuring techniques based on recording the phenomenon of extinction of light and ultrasound have been elaborated or improved. The basic value experimentally determined in the final stage was the content of the liquid phase defined as the wetness fraction. The methodology of tests and experimental investigations was presented, as well as the applied and developed measurement systems. Next, some developed designs of new ultrasonic and light extinction measuring probe and their modifications are described. The article presents also some examples of applications of the developed measurement techniques in application to experimental research conducted on wet steam. Examples of comparison between experimental and numerical tests for the extinction method are also provided.

This paper presents a comparison of three surface condenser connection setups on the cooling water side. Four connections were considered, namely serial, mixed and two parallel ones. The analysis was conducted based on the calculated heat balances of proposed power unit for nominal and not nominal parameters for tested connections. Thermodynamic justification for the use of more complex configuration was verified. The exhaust steam pressure calculation was presented. Three methods of computing the heat transfer coefficient based on characteristic numbers, namely the Heat Exchange Institute (HEI) method, and the American Society of Mechanical Engineers (ASME) standard, were used. Calculation results were validated with the real data. The most accurate model was indicated and used in heat balance calculations. The assumptions and simplifications for the calculations are discussed. Examples of the calculation results are presented.

Reactive powder concrete (RPC), due to its characteristic composition with reduced water quantity, often below a stoichiometric ratio, the addition of pozzolana usually close to or above 20% of the weight of cement and a significantly reduced inclusion rate compared to normal or high performance concrete, has a different nature of the interfacial transition zone between the micro aggregate grains and the binder matrix. Due to the significant influence of RPC curing conditions on the morphology of the interfacial transition zone, the analysis included composites cured in water of Tmax=20°C, subject to low-pressure steam curing Tmax=90°C and autoclaved at Tmax=250°C. The paper presents a qualitative assessment of the interfacial transition zone in reactive powder concretes with the use of a scanning microscope with the use of linear EDS and quantitative analysis by means of stereological analysis of the image obtained with the use of a BSE detector. The results of the study unequivocally confirm the lack of portlandite crystallisation at the phase interface and the different phase composition in the interfacial transition zone in relation to the mean mass composition.

The paper investigates the competitiveness of the Polish hard coal mining sector as a fuel source for heat and power generation. The main objective of the study is to make a quantitative assessment of the impact of the price relationship between domestic and imported steam coal on the consumption of domestic fine coal in the Polish heat and power generation sector. For this purpose, a long-term mathematical model of the Polish steam coal market is employed and scenarios that mimic the relationship between domestic and imported steam coal prices is developed. The following results are analysed:

- the volume of total domestic steam coal consumption under the scenarios analysed,

- the absolute difference in domestic steam coal consumption under the scenarios analysed in comparison with the scenario 0%,

- the total imported and domestic steam coal consumption in the period analysed.

In addition, the results were depicted in cartograms in order to present the distribution of domestic and imported coal consumption in the various regions of Poland.

The results of the study indicate that the supply of steam coal in Poland can be completely covered by domestic mines when the price of domestic coal is from –40% to –20% lower than that of imported coal. For the remaining scenarios, the consumption of imported coal increases and reaches its highest value in the scenario +40%, in which imported coal covered of 71% of total steam coal consumption in Poland over the period.

The conclusions presented in this paper provide valuable findings and policy insights into the competitiveness of domestic mines and management of domestic production both in Poland and other countries in which power generation systems are mostly dominated by coal.

The paper presents selected issues related to the development of international coal markets. World consumption of coal dropped for the second year in a row in 2016, primarily due to the lower demand from China and the US. The share of coal in global primary energy consumption decreased to 28%. World coal production accounted to 3.66 billion toe and it was lower by 6.2% when compared to the previous year. More than 60% of this decline took place in China. The decline in global production was more than four times higher than the decrease in consumption. The sufficiency of the world resources of coal are estimated at 153 years – that is three times more than the sufficiency of oil and gas resources. After several years of decline, coal prices increased by 77% in 2016. The current spot prices are at the level of $80/ton and are close to the 2014 prices. In the European market, after the first half of the year, coal prices reached the level of around 66% higher than in the same period of the last year. The average price in the first half amounted to PLN 12.6/GJ, which is close to the 2012 prices. The share of spot trade in the total purchase amount accounted to approx. 20%. Prices in futures contracts can be estimated on the basis of the Japan-Australia contracts prices and prices in supplies to power plants located in Germany. On average, the prices in supplies to these power plants were higher by approximately 9% in the years 2010 – 2016 and prices in Australia – Japan contracts were 12% higher than CIF ARA prices in 2017. Global energy coal trade reached about 1.012 billion tons in 2016. A decline by 4.8% is expected in 2019 primarily due to the expected reduction in demand in major importing countries in Asia.