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There are several well-known and widely used industrial cleaning methods in the market today. One of them is dry ice blasting. In this method, moisture-free air is compressed, mixed with solid CO2 particles, and blasted though a nozzle; in the process, the gas expands, propelling its velocity. The high-speed, two-phase flow cleans by supercooling and crushing particles on the surface, causing dry ice sublimation. As the nozzle is a crucial component of the system, the authors conducted a numerical analysis of the geometry of the proposed convergent-divergent nozzle. A mathematical model of the supersonic, two-phase flow was developed and implemented in commercial Computational Fluid Dynamics (CFD) code. Various operating parameters, such as inlet pressure and dry ice mass flow, were taken into consideration.

The study objective was to adjust the hydrodynamic disintegrator dedicated to sewage sludge pre-treatment (HDS) to work with agricultural substrate. This involved the development and implementation of a mathematical model of flow via the device’s domain. An innovative disintegrator (HAD—hydrodynamic disintegrator for agriculture) was designed, built, and tested based on the obtained results. The main improvements to the HDS include the implementation of shredding knives in order to overcome clogging by crushed substrate, and the application of ribs in the recirculation zone, contributing to the development of an additional structure damage zone. The challenge of this study was also to determine the operating parameters of the HDA that would provide for an increase in methane production with positive energy balance. The testing procedures, for which maize silage was selected, involved batch disintegration tests and biochemical methane potential tests. No clogging of rotor or spontaneous shutting off of the device, in other words, problems that had occurred in the HDS, were observed. The applied pre-treatment method permitted an increase in the methane potential of maize silage by 34.4%, 27.0%, and 21.6%, respectively for samples disintegrated at energy densities of 10 kJ/L, 20 kJ/L, and 35 kJ/L with net energy profit.

Non-Newtonian fluids are commonly used in a wide range of industries; one example are in biogas power plants. Proper measurements and modeling of such fluids can be crucial from the design and operations point of view. Results presented in this study covered seven samples from three plants (a sewage sludge treatment plant, utilization biogas station and a biogas plant in a sugar factory), including mechanically thickened excessive activated sludge (MTEAS), sugar beet pulp (SBP), liquid fruit and vegetable waste (FVW), beet roots (BR) and corn waste (CW); their mixtures were prepared as in a real plant. The total solid content remained below 6.8% for all samples. The apparent viscosity (15 RPM) did not exceed 10 Pas in any sample. A correlation analysis for solvent type influence on the viscosity was carried out. The obtained results were analyzed, and the Herschel–Bulkley rheological model was selected for the fluid description. Then, the Moullinex method was applied to determine the H–B model parameters. The obtained results may contribute to the proper design and operation of various biogas power plants, in which viscosity seems to be one of the crucial flow parameters that influences the device types used, as well as energy consumption.

The objective of this work was to present an overview of abrasive technologies with solid carbon dioxide as a blasting medium. These methods can be successfully used for the removal of a wide range of types of industrial pollution. The article covers literature reports in the field of the examined cleaning mechanisms and manufacturing process of dry ice, focusing on the structure and size of the product. Having the correct understanding of these processes is crucial for further technological development. Then various configurations of the dry-ice-blasting and snow-blasting systems are presented, including a range of typical parameters met in the literature and in industrial applications. Because the nozzle can be treated as a key part of the system, typical examples of nozzles are described. Special attention is paid to the usability of each type. This study also covers the actual scope of applications for the described systems, especially in industry and science.

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