Understanding and modeling of coal pyrolysis assume particular importance, since it is the first step of combustion and gasification processes. The complex reactions occurring during pyrolysis lead ...to difficulties in the process modeling. The aim of this work is to find a global kinetic model that well represents the pyrolysis of two different coals with opposite rank, a sub-bituminous and an anthracite coal, in order to carry out the kinetic parameters of the process. The Distributed Activation Energy Model (DAEM) was used to fit experimental data obtained with a thermogravimetric analysis. The model assumes that a series of first order parallel reactions occurs sharing the same pre-exponential factor, k 0, and having a continuous distribution of the activation energy. One of the limits of the standard Gaussian DAEM is that with this model is not possible to distinguish the primary from the secondary pyrolysis. A two Gaussians DAEM was developed considering that two classes of reactions take place having the same k 0 and different distribution of activation energy. Since in the model k 0 is highly correlated with the mean activation energies, it was fixed at characteristic values taken from literature.
Petroleum products account for the 32.3% of worldwide primary energy. There are more than 100 oil refineries in Europe that directly employ 119,000 people with a turnover of EUR 600 billion and ...around 1.2% to the total value added in manufacturing. Therefore, the petroleum refining sector is very important in the European economy, and its decarbonization is crucial in the energy transition. Refineries present a high degree of complexity and integration, and the continuous increase of their energy efficiency is a key topic for the sector. In this work an analysis of the energy efficiency in ten Italian refineries based on mandatory energy audits and public data is presented. The primary (0.0963 ± 0.0341 toe/t), thermal (3421.71 ± 1316.84 MJ/t), and electrical (68.20 ± 19.34 kWh/t) specific energy consumptions have been evaluated. Some insights about the impact of refined products mix (mainly driven by production of diesel fuel) and Nelson Complexity Index in energy consumption are presented. Lastly, an overview of energy performance improvement actions (EPIAs) information extracted from energy audits is presented. This work presents a first step for the benchmark of Italian refineries that should be subsequently improved.
The lime industry is a highly energy intensive industry, with a huge presence worldwide. To reduce both production costs and pollutants emissions, some lime production plants are introducing more ...environmentally-friendly energy sources, such as local agro-industry residues. In this paper, a numerical tool is presented, which simulates a large-scale Parallel Flow Regenerative (PFR) kiln that currently uses coke as main fuel. The developed tool aims at investigating the combustion process under conditions of co-firing of coke and biomass and to assist the plant operators in the optimization of such operating conditions. To achieve this goal, a two-way coupling Euler–Lagrange approach is used to model the dynamics of the particulate phase and their interaction with the gas phase. Pyrolysis, volatiles oxidation and char oxidation are modelled by kinetics/diffusion-limited model (for heterogeneous reactions) and mixture fraction approach (for homogeneous reactions). Moreover, two methods are investigated for representing the limestone bed: a porous medium (PM) approach and a “solid blocks” (BM) tridimensional mesh. Comparison of the results for the case of 100% coke showed that the ideal “blocks” method is more accurate as it adequately simulates the scattering of fuel particles through the PFR kiln anchor, which is limited with the PM approach. Moreover, the temperature profile, maximum and minimum temperatures, as well as CO
2
and O
2
concentrations at outlet, are comprised in the expected range for this technology, according to available literature. Finally, the predicted results of a co-firing case with 60% biomass (in mass) were validated with measurements in an industrial facility, with production capacity of 440 calcium oxide tons per day. The results suggest that the model is fairly accurate to predict gas temperature, as well as O
2
and NO
X
concentrations at the kiln outlet. Although some improvements are recommended to refine the CFD predictions, these promising results and the high computational efficiency laid the foundation for future modelling of co-firing of coke and biomass, as well as the modelling of the lime calcination process. It also paves the way for facilitating the reduction of pollutant emissions thus contributing to a more sustainable lime production.
Graphical Abstract
In this work, a novel methodology to assess energy performance indicators of productive and economic sectors trough the analysis of the Italian mandatory energy audits database is presented. The ...updating of sectoral reference energy performance indicators is fundamental for both companies and policy makers—for the formers to evaluate and compare their energy performance with competitors in order to achieve improvements and for the latter to effectively monitor the impact of energy policies. This methodology could be potentially applied to all production sectors, providing key information needed to characterize various production processes from an energy point of view. Awareness of energy efficiency and sectorial benchmarking represent the first necessary steps for companies moving towards energy transition. This paper provides details of the statistical method developed and its application to the NACE 23 division “Manufacturing of other non-metallic mineral products”, with a focus on the cement industry. For this sector, results are presented in terms of specific indicators based on energy source. General results, methodological insights, and validation of the proposed case study are discussed.
In this work, a CFD numerical study of co-firing coal and
cynara in a 350 MWe utility boiler is presented. The most influent operational factors related to the biomass feeding conditions such as ...biomass mean particle size, level of substitution of coal by biomass and feeding location in the furnace, are analyzed, determining their influence in the combustion process. Validation of the simulations is performed using measurements gathered at the plant. Results from the study show interesting conclusions for their implementation in the power plant, suggesting recommendable limits in the maximum biomass substitution level and particle size in order to keep a reasonable boiler efficiency, and pointing out the outstanding influence of the biomass injection location discussing thermal and fluid-dynamic implications and the possibility of introducing retrofitted or specific biomass burners.
Cities are the engine of human development, and increasing urban sustainability is crucial to ensure human prosperity. The development of smart cities generally increases the sustainability of the ...cities. However, technical and environmental aspects are generally developed in smart cities neglecting socio-economic dimensions. The urban resilience concept includes the complex interactions of environmental, economic, and societal pillars. In this context, the emerging maker movement proposes an economic paradigm shift, with the interaction of humans and technology at the center of urban evolution. This paper proposes a multi-criteria methodology to define and assess the main characteristics of the resilient approach of the projects involving maker practices applied to urban development. The proposed methodology is based on the application of computer-assisted qualitative text analysis and a subsequent classification according to 12 indicators (community and urban efficiency, co-creation and professional, making sense and problem-solving, network and site-specific, implementation and optimization, sustainability-oriented and market-oriented) that define different dimensions of a bottom-up project’s resilient approach in three main key principles: inclusiveness, complexity, and durability. The method has been tested in 94 EU-funded projects. This analysis reveals the evolution and orientation of EU-funded projects from economic, technical, and social perspectives. Specifically, the patterns of remediation of non-participatory practices, the weak presence of open innovation initiatives, and the development of activities focusing on co-creation as a participatory tool. The applied methodology could be subsequently implemented at different scales and integrated with LCA in order to evaluate the sustainability of bottom-up projects toward urban development.
Sorption-Enhanced Steam Methane Reforming (SE-SMR) is a promising technology for effective production of hydrogen with simultaneous CO2 capture from conventional fuels (e.g. methane, coal) and ...alternative fuels (e.g. biomass). SE-SMR combines steam methane reforming reaction and water-gas shift conversion reaction with a high temperature CO2 sorption system using a mixture of solid catalyst and sorbent. In this work, a methodology that combines Taguchi robust Design of Experiments (DoE) with previously validated CFD simulations 19 is presented. The main objective is to carry on a multi-criteria analysis of the effect of different sorbents and pretreatments and operation parameters in the response of the 500 kWth bubbling fluidized bed (BFB) reactor installed in the ZECOMIX (Zero Emissions of CarbOn with MIXed technologies) research infrastructure of ENEA. The effect of different sorbents (i.e. naturally occurring dolomite and synthetic CaO-Ca12Al14O33) and pretreatment seems to be negligible at high scales compared with heat and mass transfer mechanisms. Other parameters (i.e. temperature, pressure, particle diameter, gas velocity, bed height, presence of catalyst and sorbent, treatment of sorbent, syngas composition) have been also evaluated. The present methodology can be a useful approach for a preliminary design and optimization of a full-scale SE-SMR reactors.
•A CFD-Taguchi DoE has been applied to evaluate SE-SMR reaction in BFB reactor under industrially relevant conditions.•The effect of sorbent type in the performance of BFB reactor is negligible.•The effect of other operational conditions has been evaluated.•The proposed method can be used confidently for the design and optimization of full-scale SE-SMR reactors.
Sorption-Enhanced Steam Methane Reforming (SE-SMR) represents a novel and energy-efficient hydrogen production route with in situ CO2 capture. A comprehensive Eulerian-Eulerian CFD model of SE-SMR in ...a bubbling fluidized bed reactor, that uses dolomite and other solid sorbents as CO2 acceptors, has been developed. Kinetic models for steam methane reforming and CO2 capture have been implemented. In addition, a new particle drag model has been derived from customary formulas in order to reduce the computational cost. Two different scales have been studied: laboratory and semi-industrial. Results of the computation are in good agreement with literature data at both scales (SMR H2=76–78% vs. SE-SMR H2=90–96% dry basis mole fraction). Numerical simulations demonstrate that CO2 capture is the kinetic limiting step of the SE-SMR mechanism, as compared to steam methane reforming. Temperature is shown to be the key parameter of the SE-SMR chemical process at large scales, and an optimal T=625°C is estimated. Additionally, compared with the classical approaches, the new drag model provides seemingly realistic predictions within the multiple bubble regime, at a low computational cost and using a coarse grid. This represents a further advance for the scaling-up of the reactor to industrial sizes based on numerical simulation.
•A novel drag model for computationally efficient simulations at industrial-scale has been developed.•CO2 capture reaction is the kinetic limiting step of the SE-SMR process compared to SMR.•Temperature is the key parameter in the SE-SMR chemical process at large scale.•Classic drag models provide single bubble regime simulations in coarse CFD simulations.•Novel drag model reproduces a realistic multi-bubble regime in scaled-up CFD simulations.
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•We developed a novel pre-treatment to improve dolomite CO2 capture performance.•The pre-treatment was tested under different operational conditions.•We examine the effect of ...combining different pre-treatments in the sorbent.•An indirect model to characterize textural properties of the sorbent was developed.•Triggered calcination improves carrying capacity and shows promising integration potential.
The high-temperature, solid chemical looping for CO2 capture is a promising technology to mitigate greenhouse gases emission. The choice of a high-performance sorbent is a fundamental need to improve the CO2 uptake in solid regeneration systems. Calcium-based sorbents have demonstrated a good compromise between cost, performance and environmental impact. In particular, calcined dolomite is selected as CO2-acceptor in pre-combustion processes due to its good experimental capacity for CO2 uptake. Moreover, among the solid acceptors investigated in scientific literature, naturally occurring sorbents (e.g. calcite and dolomite) are not considered as potentially hazardous substances, as they are not toxic either to the environment or to humans. This work presents the effect on CO2 carrying capacity of different compositions of the calcination atmosphere, from 100% N2 to 50/50% CO2–N2, as well as a novel pre-treatment (here called triggered calcination) by means of half-calcination in CO2 with subsequent flash N2 calcination. This new decomposition method improves CO2 capture up to 24% in prolonged carbonation/calcination cycling (over 150 cycles). Other factors have been studied such as heating rate, CO2 concentration and carbonation time, as well as other pre-treatments. Increased and sustained rates of CO2 uptake can be explained as a result of changes in the internal structure of sorbent particles. In order to explain them, a study of the surface area has been carried out by means of an indirect method based on TGA experiments.
Millions of tonnes of coal mine waste residues are piled up in dumping sites, causing serious environmental problems. Co-combustion in fluidized bed facilities is the most widespread alternative for ...the energy utilization of these by-products. However, no experiences have been so far reported of coal mine waste residues co-firing under pulverized fuel combustion technology. This work proves the technical feasibility of co-firing coal with up to 20% coal mine waste residues and investigates the impacts of transferring this co-firing alternative into a commercial unit. Experimental co-firing tests of coal mine waste residues were conducted on a 500 kWth pulverized fuel pilot plant. Regulated emissions (CO, CO2, SO2 and NOx) and visible flame radiation were monitored, obtaining regular and stable flicker and acceptable emissions levels for CO (200 mg/m3N) and NOx (700–800 mg/m3N). Finally, the impact analysis of co-firing coal mine waste residues in a full-scale pulverized fuel plant was performed by simulating the power cycle and combustion process in a 160 MWe pulverized coal combustion unit. Simulation results show the viability of this alternative in terms of plant efficiency, increase in power consumptions of auxiliary equipment and pollutant emissions for co-firing ratios under 10% in energy basis.
•Experimental co-firing tests of CMWR and coal were conducted in a PCC pilot plant.•Lower combustion efficiency but stable conditions as CMWR share increases.•An impact analysis of co-firing CMWR in a full scale PCC plant was performed.•Plant efficiency reduction and emissions levels for CMWR co-firing are acceptable.
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