Processes

Efficient atomization of liquid fuels over a broad range of physical properties is important for practical utilization. However, the response of pressure-swirl atomization to substantial variations in liquid viscosity remains insufficiently understood, particularly the transition from a hollow-cone atomization to a degraded atomization regime. A volume-of-fluid numerical method is employed to investigate liquid-film formation and primary breakup in a pressure-swirl nozzle over a range of viscosities and surface tensions of waste-derived pyrolysis oils in this study. The results show that increasing viscosity substantially alters the liquid-film morphology, cone angle, and primary breakup behavior. At high Reynolds numbers, a hollow-cone liquid film develops and undergoes interfacial destabilization and breakup. As the Reynolds number decreases, the hollow-cone morphology is replaced by a spiral-blade morphology. The high-viscosity condition is accompanied by substantially weakened internal swirl and circumferential mixing, allowing the liquid streams originating from individual tangential slots to retain distinct spiral paths. Consequently, centrifugal expansion is suppressed and continuous liquid persists in the central region. These results clarify the flow characteristics associated with the viscosity-dominated transition from hollow-cone to spiral-blade atomization and provide insight into the pressure-swirl atomization of liquids with a broad range of viscosities.

Valorisation of animal-processing co-products through advanced bioprocesses can generate collagen hydrolysates and bioactive peptides, but the scale and accessibility of collagen-bearing feedstocks remain poorly quantified across Europe. This study estimated skin-derived collagen potential across the EU-27 from harmonised Eurostat slaughterhouse data for bovines, pigs, sheep, goats and chickens (2010–2025), using species-specific dressing and skin fractions, low/base/high recovery scenarios, country fixed-effects models, compositional analysis and Monte Carlo uncertainty propagation. Across species-specific available observations in 2025, 40.724 million tonnes of carcass production corresponded to an estimate base-case technical collagen potential of 729.5 kt. A bioprocess-oriented opportunity matrix showed that chicken combined the largest scale (365.1 kt) with high collagen intensity (30.0 kg/t carcass) and a significant positive temporal trend, whereas sheep had the highest intensity (36.2 kg/t) but much smaller scale. The 24-country complete ruminant subset contained 882.6 kt of directly separable hide/skin feedstock and 132.4 kt of collagen potential; France, Germany, Spain, Italy and Ireland accounted for 66.3% of this resource. These estimates represent technical potential under the stated feedstock-capture and recovery assumptions, not economically available collagen resources or realised collagen production, peptide yield or biological activity.

In longwall mining, conventional centralized fluid-supply systems generally operate at a fixed flow rate and therefore cannot respond effectively to the highly time-varying and overlapping demands of multiple hydraulic supports operating in coordination with an automated shearer. This mismatch can cause excessive relief flow, insufficient supply, and substantial pressure fluctuations. To address this problem, this study proposes a surrogate-based fluid supply optimization (SFSO) method in which a continuous supply trajectory is parameterized by a limited number of time–flow control points and reconstructed using a radial basis function model. The control-point parameters are optimized subject to constraints on pump capacity and flow-rate variation, while pressure stability and supply efficiency are considered simultaneously. An AMESim hydraulic system model was validated against measurements obtained from a laboratory hydraulic support platform and was subsequently used to evaluate the proposed method under a predefined multi-support operating sequence. Under 200 independent test scenarios with demand perturbations of up to ±10%, SFSO increased the mean cycle-based volumetric efficiency from 30.16% to 60.10%, representing an increase of 29.94 percentage points. Meanwhile, the mean pressure fluctuation metric J_P decreased from 0.625 MPa² to 0.150 MPa². Under the model, operating sequence, and demand perturbation range considered in this study, these results indicate that the proposed trajectory-surrogate formulation can improve demand supply matching and reduce the pressure fluctuation index relative to the constant-flow reference. Further work is required to evaluate the method under broader sources of uncertainty and in underground field applications.