CO2 Adsorption–Desorption Kinetics from the Plane Sheet of Hard Coal and Associated Shrinkage of the Material

The paper presents the results of studies on sorption and CO2 desorptions from coals from two Polish mines that differed in petrographic and structural properties. The tests were carried out on spherical and plane sheet samples. On the basis of the sorption tests, the effective diffusion coefficient was calculated on the plane sheet samples based on a proper model. Similar tests were performed on the spherical samples. Mathematical model results for plane sheet samples were compared with the most frequently chosen model for spherical samples. The kinetics of CO2 desorption from plane sheet samples were compared with the kinetics of sample shrinkage. In both samples, the shrinkage was about 0.35%. The size change kinetics and CO2 desorption kinetics significantly differed between the samples. In both samples, the determined shrinkage kinetics was clearly faster than CO2 kinetics

Analyzing the Parameters of the Coal—Gas System Using a Low-Cost Device Based on a Flowmeter

Investigations of the coal—gas system—in particular, those concerning the amount of the gas adsorbed and the kinetics of its release—are extremely important in the analysis of hazards associated with the presence of methane and outbursts of gas and rocks. Such an investigation is also useful for analyzing the adsorbent parameters. Adsorption analyzers that are available on the market fall into two types: gravimetric and volumetric. Gravimetric analyzers are very complex, stationary devices. Their biggest drawback is the problem pertaining to a sudden pressure change, which initiates the processes of gas adsorption and transportation. This is associated with a higher degree of measurement uncertainty with regard to the determination of the diffusion coefficient. By contrast, volumetric analyzers are usually far cheaper and are capable of processing sudden pressure changes. However, in this case, the measurement is seldom isobaric in nature, which makes it difficult to use for determination of the diffusion coefficient on the basis of the unipore model. The author of this paper intends to show a simple device based on a gas flowmeter, which makes use of a phenomenon known as ‘barbotage’. The cost of constructing such a device is several dozen times cheaper than the cost of gravimetric and volumetric analyzers available on the market. A sudden pressure change is allowed, and the release of methane is measured under quasi-isobaric conditions. The paper discusses the concept of the device and provides an analysis of the results that it generated. These results were juxtaposed with those obtained using a gravimetric reference device

The Repeatability of Sorption Processes Occurring in the Coal-Methane System during Multiple Measurement Series

The aim of this paper was to investigate the repeatability of sorption processes occurring in the coal-methane system during multiple measurement series. For research purposes, three granular samples of coal sorbent were used. The samples were subjected to a series of three measurements, each time performed under the same conditions. During each series of measurements, the following stages took place: outgassing the sample in a vacuum, and then saturating it with methane under the pressure of 1, 3, and 10 bar. Sorption capacities and the values of effective diffusion coefficients were compared. The studies into the repeatability of measurements of sorption capacities, conducted by means of the IGA-001 (Intelligent Gravimetric Analyzer) gravimetric instrument for three measurement cycles, showed that the obtained measurement discrepancies in relation to the mean value did not exceed 1.23%. The discrepancies in question approximated the measurement uncertainty of the IGA-001 device. The evaluation of the recurrence of determining the values of effective diffusion coefficients showed that the obtained discrepancies were no larger than 10%, which might have resulted from problems with fulfilling most of the assumptions of the applied unipore diffusion model. The authors did not observe any changes of the sorption parameters of hard coal during consecutive cycles of methane saturation

Laboratory Studies on Permeability of Coals Using Briquettes: Understanding Underground Storage of CO2

The work presents the laboratory studies on permeability of two bituminous coal briquettes under confining pressure conditions. The research was carried out in order to assess the possibility of using bituminous coal as a sorbent for CO2 storage in underground seams. Coal permeability tests were carried out on an original apparatus for testing seepage processes under isobaric conditions on samples subjected to confining pressure. In order to determine the impact of the load on the coal briquettes’ permeability, the tests were carried out at four confining pressures: 1.5, 10, 20 and 30 MPa. The obtained results showed that the coal permeability decreases with an increase in confining pressure. At depths below 250 m, the coal can be a rock poorly permeable to CO2, and under such conditions, the applicability of technologies related to the underground storage of CO2 to coal seams is limited or even impossible

New Instruments and Methods for Analysing the Coal-Methane System

The authors of the present paper designed and constructed a prototype of an instrument which enables fully automated determination of the desorbable methane content and effective diffusion coefficient in underground conditions. Due to microprocessor analysis of the recorded data and the application of the mathematical model of the diffusion process, it is possible to automatically determine the amount of methane whose release from a coal sample occurred before the sample was placed within a measuring instrument. It is also possible to carry out follow-up extrapolation of the recorded data so the time duration needed to determine reliable results can be reduced. The instrument was tested and optimized, and a number of copies sufficient for performing underground tests were constructed. The concept of the instrument represents a totally new approach to the observation of gas release from a coal sample. Instead of short-period measurements, virtually the whole process of methane release from coal is registered and analysed. This is possibly due to the use of a grain fraction lower than one mm which is presently applied for the sake of evaluating the methane- bearing capacity and desorption intensity

COVID-19 Pneumonia on Post-Operative Day 2 after Esophagectomy: Performing Esophago-Gastric Junction Cancer Surgery during the SARS-Cov-2 Second Wave

The coronavirus disease 2019 (COVID-19) pandemic has had a substantial impact on the provision of medical healthcare. Due to an increased risk of severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2) transmission, elective surgical treatment has been suspended in many centers. The effects of COVID-19 in the early post-operative period after esophagectomy remains unknown. In this report, we present three cases of patients diagnosed with esophago-gastric junction cancer who were scheduled for elective esophagectomy with a curative intention during second wave of COVID-19 pandemic in a single high-volume tertiary center. Despite all available safety measures, one of the patients developed COVID-19 pneumonia on post-operative day two, leading to an impaired respiratory function and increased pleural fluid collection from the chest tube, resulting in a prolonged time of hospital stay. Finding a good balance between the COVID-19-related perioperative risks and consequences of delaying surgical treatment in patients diagnosed with esophago-gastric cancer is a challenge. In order to achieve the best possible outcome, care must be taken to ensure availability of necessary treatment options and to reduce the risk of SARS-Cov-2 transmission perioperatively

Methane Emission during Gas and Rock Outburst on the Basis of the Unipore Model

The goal of this paper is to analyze the phenomenon of gas emission during a methane and coal outburst based on the unipore Crank diffusion model for spherical grains and plane sheets. Two occurrences in the Upper Silesian Coal Basin were analyzed: an outburst in a Zofiówka coal mine in 2005 and an outburst in a Budryk coal mine in 2012. Those two outbursts differed considerably. The first one was connected with an unidentified tectonic disturbance in the form of a triple, interlocking fault, and the other one is an example of an outburst in an area free from tectonic disturbances. The model analysis required laboratory tests in order to determine the sorption properties of coals from post-outburst masses. Sorption isotherms and the values of the effective diffusion coefficient were specified. The post-outburst masses were subjected to sieve analysis and the grain composition curves were plotted. The researchers also used the measurement data provided by proper mine services, such as the methane content, the volume of post-outburst masses, and the time courses of CH4 concentration changes in excavations. They were recorded by methane measurement systems in the mines