Issue 12/2023 (December)

In the present study, the L485ME low-alloy steel grade, widely used in the last few decades in the natural gas transmission pipelines, subjected to hydrogen was investigated with respect to material degradation. A fracture toughness parameter such as the calculated conditional stress intensity factor was compared to the threshold stress intensity factor for the plane strain hydrogen-assisted cracking derived from the experimental data. Based on macroscopic and microscopic evaluation and measurements,the hydrogen-assisted crack size propagation in steel specimens was compared to the subcritical crack growth. The hydrogen content in the tube wall for the base metal and heat-affected zone was estimated, whereas the pressure and temperature conditions in the pipeline were calculated from a non-isothermal transient gas flow model. The results were used to estimate the fracture toughness of the pipe wall material exposed to the hydrogen-blended natural gas.

The paper analyzes the impact of the proportion of hydrogen in the high-methane gas (group E) pipeline on the design of a building’s gas system. Particular attention was paid to the measures taken regarding the permissible values of added hydrogen. The physical and chemical properties of the natural gas-hydrogen mixture were characterized, leading to the determination of an appropriate calculation methodology. Pressure loss calculations were carried out for natural gas and its mixture with hydrogen. It was confirmed that the 20% share of hydrogen does not significantly affect the operation of the building’s gas system. The occurrence of exceedances of selected physical quantities leading to the necessity of replacing gas meters and gas pressure regulators was demonstrated.

The article discusses the technological aspects of hydrogen production from natural gas (methane). There are various technologies available for this purpose, each with its own advantages and limitations. The focus of the article is on technologies related to hydrogen production from natural gas. Three of these technologies were analyzed in the article: Steam Methane Reforming(SMR), Partial Oxidation (POX), and Autothermal Reforming (ATR). Each of these methods has its distinctive features and applications.

The paper analyzes the effect of changing indoor temperature on energy and natural gas consumption, in a typical single-family building for different energy standards between 1964 and 2021. Indoor air temperature reductions from 20°C to 18°C and 16°C and increases to 22°C were analyzed. The analyses were carried out for five building locations (Koszalin, Wroclaw, Warsaw, Bialystok and Suwalki) in different climatic zones of Poland for the cold period. For the analyses, the monthly and hourly methods of calculating energy demand for heating according to PN-EN ISO 13790 were used and compared, taking into account Polish regulations on the energy performance of buildings. The effect of the type of gas heat source on gas savings was presented.It has been shown that, depending on the energy standard of the building and its location, the change in energy demand for heating can range from 5.4%/°C to 19.9%/°C, where a 1 or 2°C decrease can be compensated by wearing additional clothing.

Membrane technology in wastewater treatment is considered the best method available. However, the high efficiency of wastewater treatment results in increased contaminants in sewage sludge, a byproduct of wastewater treatment processes. Sewage sludge with have soil-forming and fertilizing properties. The best method of managing sludge is to use it as fertilizer. However, the main criterion for the possibility of using them as fertilizers is determined by the content of heavy metals and parasite eggs.This study compared the heavy metal content of sludge from three different wastewater treatment plants before and after upgrading to MBR technology. A speciation analysis of the metals was performed, and risk indicators were calculated to estimatethe actual risk of contamination from the use of sewage sludge as fertilizers. The main research problem of the paper is to answer the question: whether the elevated heavy metal content of sludge from MBR treatment plants can indeed cause a risk of environmental contamination.

This paper presents results of research on changes in morphological parameters and fractal dimensions of Monoraphidium contortum and Microcystis aeruginosa cell aggregates obtained from coagulation using FeCl3. The study used Morphologi G3 as microscopic image analyzer. Based on the microscopic image analysis, the aggregates specific morphological parameters were determined: equivalent diameter (de), „elongation”, „solidity” and aggregate fractal dimensions – D1 and D2. It was found that, size of phytoplankton cell aggregates was subordinated to log-normal distribution. The analysis of changes in aggregate size distribution indicated that along with the increase of coagulant doses (Dc) and flocculation time (tf), their mean equivalent diameter increased. The average diameter of aggregates, on the other hand, decreased with increasing velocity gradient (G). Along with the increase in the amount of energy introduced into the system during mixing (G), a tendency to elongate cell aggregates and reduce their solidity was observed. The morphological characteristics of phytoplankton aggregates based on morphological parameters and fractal geometry allowed to observe a significant relationship between D2 and „solidity”. An increase in the morphological parameter in the form of „solidity” was associated with an increase in the value of the second fractal dimension. Aggregate size evolution, at a constant velocity gradient, occurred in three stages: aggregate growth (I), aggregate break-up (II) and steady state (III). The size and spatial structure of aggregates influenced sedimentation properties of flocs. The reduction of the mean equivalent diameter and solidity of aggregates resulted in a slower sedimentation rate of aggregates.