The study included bituminous coal seams (30 samples coal from the Bogdanka and Chełm deposits)
of the Lublin Formation, the most coal-bearing strata in the best developed and recognized in
terms of mining parts of the Lublin Coal Basin in Poland. High phosphorus concentrations in coal of
the Lublin Formation were found (1375 g/Mg) as well as P2O5 in coal ash (2.267 wt%). The phosphorus
contents in coal and coal ash from the 385 and 391 coal seams in the area of the Lubelski Coal Bogdanka
Mine and in the area of its SE neighbor is the highest (max. 2.644 wt. % in coal and 6.055 wt. %
of P2O5 in coal ash). It has been shown that mineral matter effectively affects phosphorus contents
in coal and coal ash. At the same time, phosphate minerals (probably apatite and crandallite) present
in kaolinite aggregates of tonsteins contain the most of phosphorus and have the greatest impact on
the average P content in the 382, 385, 387, and 391. The secondary source of phosphorus in these
coal seams and main source of phosphorus in these coal deposits that do not contain mineral matter
of pyroclastic origin (378, 389, 394) may be clay minerals, which absorbed phosphorus compounds
derived from organic matter released during coalification. Phosphorus-rich ash from the combustion
of the Lublin Formation coal tend to be environmentally beneficial to the environment and also useful
for improving the soil quality. Due to the low degree of coalification and high content of phosphorus
in coal, this coals of little use for coking.
In Poland, the economic use of methane from coal seams has been recognized as one of the objectives of the „Energy Policy of Poland until 2030“. In Poland at the Upper Silesian Coal Basin, reconnaissance operations were initiated to collect methane from coal seams using drilling wells and hydraulic fracturing operations.
During these operations, noise emission can have a significant impact on the environment. In order to limit the negative impact of noise, well pads are usually located in undeveloped areas. However, in the European Union, the majority of hard coal deposits from which methane can be extracted are located in areas with a high population density.
This article presents the results of noise measurements carried out during hydraulic fracturing operations of coal seams and the results of calculations of the equivalent sound level during the daytime. Based on the analysis of noise emission, some recommendations are given regarding the location of planned new well pads in highly urbanized areas in order to meet the applicable standards of noise protection.
The technology for gob-side entry retaining in steep coal seams is still in the development stage. The
analysis results of the caving structure of main roof, low influence of gateway’s stability because of long
filling distance and weak dynamic effect of the gateway, and the low stress redistribution environment
indicate that using this technology in steep coal seams has significant advantages. Moreover, to reinforce
the waste rock and the soft floor and to better guard against the impact of the waste rock during natural
filling, a rock blocking device and grouting reinforcement method were invented, and theoretical calculations
result show that the blocking device has high safety factor. In addition, we also developed a set of
hydraulic support devices for use in the strengthening support zone. Furthermore, because the retaining
gateway was a systematic project, the selection of the size and shape of the gateway cross section and its
support method during the initial driving stage is a key step. Thus, first, a section the size of bottom width
and roof height of a new gateway was determined to meet any related requirements. Then, according
to the cross sections of 75 statistical gateways and the support technique, it chosen a trapezoidal cross
section when the dip of the coal seam is 35° < α ≤ 45°, a special and an inclined arch cross section when
45° < α ≤ 55°. Eventually, a support system of bolts and cables combined with steel mesh and steel belts
was provided. The support system used optimized material and improved parameters, can enhanced the
self-bearing ability of the surrounding coal and rock masses.
Mining the lower seams in a sequence of shallow, closely spaced coal seams causes serious air leakage in the upper goaf; this can easily aggravate spontaneous combustion in abandoned coal. Understanding the redevelopment of fractures and the changes in permeability is of great significance for controlling coal spontaneous combustion in the upper goaf. Based on actual conditions at the 22307 working face in the Bulianta coal mine, Particle Flow Code (PFC) and a corresponding physical experiment were used to study the redevelopment of fractures and changes in permeability during lower coal seam mining. The results show that after mining the lower coal seam, the upper and lower goafs become connected and form a new composite goaf. The permeability and the number of fractures in each area of the overlying strata show a pattern of „stability-rapid increase-stability“ as the lower coal seam is mined and the working face advances. Above the central area of goaf, the permeability has changed slightly, while in the open-cut and stop line areas are significant, which formed the main air leakage passage in the composite goaf.
As one of the key techniques in the fully mechanized mining process, equipment selection and matching has a great effect on security, production and efficiency. The selection and matching of fully mechanized mining equipment in thin coal seam are restricted by many factors. In fully mechanized mining (FMM) faced in thin coal seams (TCS), to counter the problems existing in equipment selection, such as many the parameters concerned and low automation, an expert system (ES) of equipment selection for fully mechanized mining longwall face was established. A database for the equipment selection and matching expert system in thin coal seam, fully mechanized mining face has been established. Meanwhile, a decision-making software matching the ES was developed. Based on several real world examples, the reliability and technical risks of the results from the ES was discussed. Compared with the field applications, the shearer selection from the ES is reliable. However, some small deviations existed in the hydraulic support and scraper conveyor selection. Then, the ES was further improved. As a result, equipment selection in fully mechanized mining longwall face called 4301 in the Liangshuijing coal mine was carried out by the improved ES. Equipment selection results of the interface in the improved ES is consistent with the design proposal of the 4301 FMM working face. The reliability of the improved ES can meet the requirements of the engineering. It promotes the intelligent and efficient mining of coal resources in China.