High-pressure ethanol oxidation and its interaction with NO

Ethanol has become a promising biofuel, widely used as a renewable fuel and gasoline additive. Describing the oxidation kinetics of ethanol with high accuracy is required for the development of future efficient combustion devices with lower pollutant emissions. The oxidation process of ethanol, from reducing to oxidizing conditions, and its pressure dependence (20, 40 and 60 bar) has been analyzed in the 500–1100 K temperature range, in a tubular flow reactor under well controlled conditions. The effect of the presence of NO has been also investigated. The experimental results have been interpreted in terms of a detailed chemical kinetic mechanism with the GADM mechanism (Glarborg P, Alzueta MU, Dam-Johansen K and Miller JA, 1998) as a base mechanism but updated, validated, extended by our research group with reactions added from the ethanol oxidation mechanism of Alzueta and Hernández (Alzueta MU and Hernández JM, 2002), and revised according to the present high-pressure conditions and the presence of NO. The final mechanism is able to reproduce the experimental trends observed on the reactants consumption and main products formation during the ethanol oxidation under the conditions studied in this work. The results show that the oxygen availability in the reactant mixture has an almost imperceptible effect on the temperature for the onset of ethanol consumption at a constant pressure, but this consumption is faster for the highest value of air excess ratio (¿) analyzed. Moreover, as the pressure becomes higher, the oxidation of ethanol starts at lower temperatures. The presence of NO promotes ethanol oxidation, due to the increased relevance of the interactions of CH3 radicals and NO2 (from the conversion of NO to NO2 at high pressures and in presence of O2) and the increased concentration of OH radicals from the interaction of NO2 and water

Implementation of PEF treatment at real-scale tomatoes processing considering LCA methodology as an innovation strategy in the agri-food sector

In Europe, science and innovation are boosting the agri-food sector and, in parallel, are helping to decrease greenhouse gas emissions (GHG) and European dependency on non-renewable resources. Currently, it is well-known that this sector contributes to the consumption of energy and material resources, causing significant environmental impacts that require a complex and comprehensive environmental evaluation in order to manage them effectively. This becomes even more complicated when new technologies are reaching the level of technological maturity needed to be installed in the production lines. To address this scientific challenge, the life cycle assessment (LCA) has been used in this paper to evaluate the potential of pulsed electric fields (PEF) technology at an industrial scale to facilitate the steam peeling of tomato fruits. Considering the thermo-physical peeling stage, the LCA has shown that PEF technology is environmentally friendly, because when PEF technology is applied, all the considered environmental indicators improve between 17% and 20%

Multicriteria analysis for retrofitting of natural gas melting and heating furnaces for sustainable manufacturing and industry 4.0

Different retrofitting measures can be implemented at different levels of the industrial furnace, such as refractory layers, energy recovery solutions, new burners and fuel types, and monitoring and control systems. However, there is a high level of uncertainty about the possible implications of integrating new technologies, not only in the furnace but also on the upstream and downstream processes. In this regard, there is a lack of holistic approaches to design the optimal system configurations under a multicriteria perspective, especially when innovative technologies and multi-sectorial processes are involved. The present work proposes a holistic approach to natural gas melting and heating furnaces in energy-intensive industries. A multicriteria analysis, based on criteria and subcriteria, is applied to select the most profitable retrofitting solution using the analytic hierarchy process and stakeholder expertise. The methodology is based on technical indicators, i.e., life cycle assessment, life cycle cost, and thermoeconomic analysis, for evaluating the current state of existing natural gas furnaces. Once the current state is characterized, the methodology determines the potential of efficiency improvement, environmental impact reduction, and cost-savings caused mainly by the implementation of new retrofitting solutions including new refractories, new burner concepts (co-firing), and innovative energy recovery solutions based on phase change materials. Therefore, this methodology can be considered as the first stage that guarantees technical, environmental, and economic feasibility in evaluating the effects of new technologies on the overall system performance

The inhibiting effect of NO addition on dimethyl ether high-pressure oxidation

The high-pressure dimethyl ether (DME, CH3OCH3) oxidation has been investigated in a plug flow reactor in the 450–1050 K temperature range. Different pressures (20, 40 and 60 bar), air excess ratios (¿ = 0.7, 1 and 35), and the absence/presence of NO have been tested, for the first time under these conditions. An early reactivity of DME and a negative temperature coefficient (NTC) zone have been observed under the studied conditions, although under very oxidizing conditions (¿ = 35), NTC zone is almost imperceptible because DME is completely consumed at lower temperatures. A chemical kinetic mechanism has been used to describe the DME high-pressure oxidation, with a good agreement with the experimental trends observed. In general, modeling calculations with the present mechanism have been successfully compared with experimental data from literature. The presence of NO has an inhibiting effect on DME high-pressure consumption at low-temperatures because of: (i) the competition between CH3OCH2+O2¿CH3OCH2O2 and CH3OCH2+NO2¿CH3OCH2O+NO reactions, and (ii) the participation of NO in CH3OCH2O2+NO¿CH3OCH2O+NO2 reaction, preventing CH3OCH2O2 radicals continue reacting through a complex mechanism, which includes a second O2 addition and several isomerizations and decompositions, during which highly reactive OH radicals are generated. Consequently, NO and NO2 are interchanged in a cycle but never consumed