Jorge Arroyo

The high levels of greenhouse gas emissions from energy-intensive industries have created an urgent need for decarbonization. As major sources of pollution, industries are increasingly being forced to reconsider the fuels they use in their processes. Interest in hydrogen combustion, particularly in high-temperature applications, has grown due to its physical properties and the absence of carbon dioxide emissions. Despite its potential, hydrogen combustion presents technical challenges, such as flame stability, burner adjustment requirements, control of nitrogen oxides (NO_x) emissions and material compatibility. This review examines the use of hydrogen as a fuel in industrial furnaces along three complementary axes. First, it analyzes combustion fundamentals, blending limits and mitigation strategies, including oxy-fuel and MILD combustion, and assesses their deployment maturity across the steel, cement, glass, ceramics, and refining and chemicals sectors, together with economic and regulatory constraints. Second, it reviews advances in Computational Fluid Dynamics (CFD) modeling of hydrogen flames, addressing turbulence-chemistry interaction, reaction kinetics, radiative heat transfer, NO_x formation and model validation. Third, it surveys camera-based diagnostics combined with Artificial Intelligence and computer vision for flame monitoring and combustion optimization. By synthesizing recent literature, the review identifies the principal knowledge gaps, notably standardized CFD validation datasets and robust monitoring under industrial conditions, providing a critical reference for researchers and industry.

Construction sites present intrinsically hazardous conditions characterized by dynamic and complex operational environments which persistently contribute to elevated rates of occupational injuries. While conventional safety management emphasizes controls during the execution phase, addressing safety considerations during the earliest phases of a project is more effective. In this work, a Nonlinear Multifactor Safety Index (NMF-SI) is developed to quantify activity-level occupational risk for use in project planning. The index synthesizes multiple risk factors, including accident probability, task severity, exposure duration, workforce size, and contextual variables, such as weekday effects, and site conditions, like waste accumulation. Additionally, it incorporates a structured questionnaire to capture the implementation of safety measures on site. Its nonlinear formulation reflects interactions among factors, penalizes temporal clustering of high-risk tasks, and prioritizes temporal distribution and proactive planning. To produce risk-aware schedules, a hybrid optimization framework that couples a tree-based constructive heuristic with the marine predators algorithm is introduced, maximizing NMF-SI subject to project-duration, precedence, and resource constraints. In simulation, the optimized schedules achieve higher NMF-SI values and a smoother risk profile over time than baseline plans. These results translate into a quantitative, data-driven contribution to safety by design, offering a practical decision-support tool for intelligent, risk-aware construction scheduling.

The use of residual gases from steel production processes as fuel for steel treatment furnaces has attracted great interest as a method for reducing fossil fuel consumption and the steel footprint. However, these gases often have a low calorific value, and a direct substitution can lead to low temperatures or combustion instability issues. CFD simulations of the combustion of these gases can help steel producers forecast the results of the substitution before real testing and implementation. In this study, a CFD model of an industrial experimental furnace in the steel sector is developed and validated. The results are calculated using the combustion, radiation, and heat transfer models included in the software Ansys Fluent. The validation of the simulated results is performed with data acquired from experimental tests under the same simulated conditions at three air-to-fuel equivalence ratios, which vary from an excess of 0% to an excess of 5% oxygen at the outlet. The model is adjusted to the results, capturing the trends of the measured physical variables and pollutant concentrations. In the case of the combustion temperature, the differences between the simulated and measured values vary from 0.03% to 6.9. Based on the simulation results, the use of blast furnace gas as fuel produces temperatures inside the chamber between 1004 °C and 1075 °C and high stream velocities because of the high flow needed to keep the power constant. Flames exhibit straight movements since the high flows absorb the effect of the swirling flames. The addition of natural gases increases the combustion temperature up to 1211 °C and reduces the flow and length of the flames. Finally, temperatures up to 1298 °C and shorter flames are reached with natural gas enriched with a stream of oxygen, but in this case, NOx emissions need to be controlled.

The use of blast furnace gas (BFG) as a fuel provides an alternative for waste stream valorization in the steel industry, enhancing the sustainability and decarbonization of its processes. Nevertheless, the implementation of this solution on an industrial scale requires a continuous control of the combustion due to the low calorific value of BFG. This work analyzes the combustion behavior and monitoring of BFG/CH4 blends in a laboratory premixed fuel burner. We evaluate several stable combustion conditions by burning different BFG/CH4 mixtures at a constant power rate over a wide range of air/fuel equivalence ratios. In addition, relevant image features and chemiluminescence emission spectra have been extracted from flames, using advanced optical devices. BFG combustion causes an increase in CO(2 )and CO emissions, since those fuels are the main fuel components of the mixture. On the other hand, NOx emissions decreased because of the low temperature of combustion of the BFG and its mixtures. Chemiluminescence shows that, in the case of CH4 combustion, peaks associated with hydrocarbons are present, while during the substitution of CH4 by BFG those peaks are attenuated. Image flame features extracted from both ultraviolet and visible bandwidths show a correlation with the fuel blend and air/fuel equivalence ratio. In the end, methodologies developed in this work have been proven to be valuable alternatives with a high potential for the monitoring and control of BFG cofiring for the steel industry.