No abstract

The use of pyrolysis oil can be seen as an alternative fuel for maritime transport. However, pyrolysis oil from tires must be desulfurized for this. Recently, this can be done by hydrodynamic cavitation. This process does not require oxidation chemicals but only water, a cavitation generator, and a pump to drive it. In the literature, this concept has been successfully tested on model fuels. In this study, the cavitation generator for the desulfurization of waste tire pyrolysis oil was printed from polylactic acid-based on simulations of the optimal design, which allows for much cheaper production and easy replacement in case of wear or testing of alternative designs. After 60 min of treatment at 5 bar inlet pressure, a desulfurization of almost 33% was achieved. Furthermore, an interaction analysis showed that only from a pyrolysis oil content of 5.5 to 6% does hydrodynamic cavitation have an effective effect on desulfurization.

Today, it is very important to select and install the optimal equipment for the treatment of ballast water in existing ships. Increasing cargo volumes demand for a greater number of ships for transportation and expanded navigation geography as well as result in increased amount of discharged ballast water. Consequently, sea water pollution is increasing and invasive microorganisms appear that the existing flora and fauna are unaccustomed to. In order to protect territorial waters from these invasive species, International Maritime Organization (IMO) requirements have been implemented that regulate the quality parameters of discharged ballast water from ships. This problem has become particularly relevant for operational ships, in which ballast water treatment equipment and technical solutions had not been anticipated in the design stage. This article provides a comparative analysis of the treatment equipment of ballast water and the related technical parameters, in order to distinguish the most important equipment criteria. A Carrier, according to its technical characteristics, was analysed together with the water treatment method for operated bulk. An expert evaluation for the characteristics of the technical equipment was established.

Abstract. The paper looks at the impact of the internal welding defects on the strength of joints. The tension tests provided the values of the welded joint strength limits depending on the area of sporadic voids, slag intrusions and the field of discontinuities. Considering the results of the conducted experiments, the mathematical relationships between the strength of the welded joint and defected area were concluded. In presence of all three defects, the distance of the defects from the weld surface was measured. It is deduced that the defects nearer to the surface reduce the strength of the welded joint more than those noticed in deeper layers.

The paper deals with analysis of dynamic stability and behavior of automatic dynamic balance (ADB) by applying theoretical approach. Differential equations of the considered system were established using Lagrange equation. Numerical analysis of the dynamic equations was performed and influence of dynamic viscosity coefficient on self-balancing process was estimated. It is demonstrated that the balancing time decreases in non-linear character. The optimal value of dynamic viscosity for achieving minimal balancing time can be determined for the analyzed system.

This article studies an operational problem arising at a container terminal. Klaipeda city port operations were surveilled up close and relevant remarks were made. The time efficiency of the existing container-lowering procedures using the simulation studies with a test-bed and with a real life crane operation was examined. Statistical analysis of the experimental results has showed that non-automated processes have higher time variance for the lowering process. The operations of quay crane for container handling “ship-to-shore” were analyzed, and lowering procedures time variations were determined. Each container is transported at operators own risk and with pre-defined time efficiency; therefore, it is hard to predict the optimal time for each container handling operation, thus, eventually, additional costs arise. Mathematical model was developed, which described dynamical characteristics of the container movement during lowering procedures. The lowering crane operation was modeled using known dynamic values for each separate case, and the complexity of the problem was proven. The results of modeling and experimental results show that it is possible to achieve optimal values with the existing processes.

The hydrodynamic and thermodynamic processes of geothermal well extraction are investigated and presented in this paper. The paper presents mathematical models for a multi-level centrifugal pump and pipeline system. The mathematical models were used to evaluate gas (nitrogen) emission in water and its effects on hydrodynamic processes. Experimental studies and mathematical modelling showed that the gas content of the fluid increases the pressure and flow pulsations within a centrifugal pump. The variation in the height of the liquid column in extraction has an influence on characteristics of the multistage centrifugal pump used in wells.

Abstract. Growth kinetics, i.e. the relationship between specific growth rate and the concentration of a substrate, is one of the basic tools in the modelling of activated sludge community growth. The above-described conventional growth kinetics derived from single-substrate-controlled laboratory experiments have invariably been used for describing both growth and substrate utilization in wastewater treatment. After technological processes various mineral substances, such as chlorides, get into water bodies. These substances are not removed from wastewater by the biological treatment method. The purpose of this study is to determine the concentrations of chlorides, investigate the influence of enzyme preparations upon wastewater treatment quality during biological process modelling. Kinetics of microbial growth was designed using the model of Monad. To analyse the chloride influence on the biooxidation process a series of laboratory tests was carried out: biochemical oxygen consumption (BOD), activated sludge concentration and other indexes. It is found experimentally that a 400 mg/l concentration of chlorides disarranges the activity of microorganisms and activated sludge is no longer suitable for biological treatment. Also, we investigated the effect of enzyme preparation on effluence on sewage treatment. As chloride concentrations are increased in a tank without an enzyme, bacterial spores contained in the enzyme preparation produce a renewing effect upon active sludge.