A swirling burner with a variable inner secondary air (ISA) flaring angle β is proposed and a laboratory scale opposed-firing furnace is built. Temperature distribution and NOx emission are designedly measured. The combustion characteristics affected by variable β are experimentally evaluated from ignition and burnout data. Meanwhile, NOx reduction by the variable β is analyzed through emissions measurements. Different inner/outer primary coal-air concentration ratios γ, thermal loads and coal types are considered in this study. Results indicate that β variation provides a new approach to promote ignition and burnout, as well as NOx emission reduction under conditions of fuel rich/lean combustion and load variation. The recommended β of a swirling burner under different conditions is not always constant. The optimal βopt of the swirling burner under all conditions for different burning performance are summarized in the form of curves, which could provide reference for exquisite combust... [more]

Autoignition of an ethanol-based gel droplet was experimentally investigated by adding 10 wt % of methylcellulose as gellant to liquid ethanol. Experimental studies of the ignition behavior of the gel droplet were found to be quite rare. The initial droplet diameter was 1.17 ± 0.23 mm. The gel droplet was suspended on a K-type thermocouple and its evaporation, ignition and combustion characteristics were evaluated and compared with pure ethanol at an ambient temperature of 600, 700, and 800 °C under atmospheric pressure conditions. The gel droplet exhibited swelling and vapor jetting phenomena. Before ignition, a linear decrease in droplet diameter followed by a sudden increase was repeatedly observed, which was caused by evaporation and swelling processes, respectively. Major droplet swelling was detected just before the onset of ignition at all temperatures. But no further swelling was detected after ignition. For the gel droplet, the ignition delay accounted for 93% of the droplet l... [more]

The volatilization characteristics and occurrence forms of V and Ni in petroleum coke (petcoke) were investigated during steam (H₂O) and carbon dioxide (CO₂) gasification on a fixed bed reactor at 800⁻1100 °C. The Tessier sequential chemical extraction procedure was employed to determine the different forms of V and Ni. The results showed their volatilities were not dependent on the gasification atmosphere, but rather relied mainly on the reaction temperature. The CO₂ atmosphere accelerated the conversion of organic-bound nickel to residual form at low temperature and promoted Fe-Mn oxides formation at high temperature. However, the H₂O atmosphere was conducive to form vanadium bound to Fe-Mn oxides and promoted the decomposition of residual forms. In addition, the thermodynamic equilibrium calculations showed the volatilization of Ni mainly released Ni₃S₂ between 800⁻1100 °C. The H₂O atmosphere was favorable to generate the more stable NixSy compound, thereby suppressing the volatiliz... [more]

This paper evaluated the effectiveness of nitric acid pretreatment on the hydrolysis and subsequent fermentation of Jerusalem artichoke stalks (JAS). Jerusalem artichoke is considered a potential candidate for producing bioethanol due to its low soil and climate requirements, and high biomass yield. However, its stalks have a complexed lignocellulosic structure, so appropriate pretreatment is necessary prior to enzymatic hydrolysis, to enhance the amount of sugar that can be obtained. Nitric acid is a promising catalyst for the pretreatment of lignocellulosic biomass due to the high efficiency with which it removes hemicelluloses. Nitric acid was found to be the most effective catalyst of JAS biomass. A higher concentration of glucose and ethanol was achieved after hydrolysis and fermentation of 5% (w/v) HNO₃-pretreated JAS, leading to 38.5 g/L of glucose after saccharification, which corresponds to 89% of theoretical enzymatic hydrolysis yield, and 9.5 g/L of ethanol. However, after f... [more]

Thermogravimetric analysis was employed to investigate the combustion characteristics of flax shives, beech wood, hemicellulose, cellulose, lignin, and their chars. The chars were prepared from raw materials in a fixed-bed reactor at 850 °C. In this study, the thermal behavior based on characteristic temperatures (ignition, maximum, and final temperatures), burnout time and maximum rate was investigated. The kinetic parameters for the combustion of different materials were determined based on the Coats-Redfern approach. The results of our study revealed that the combustion of pure pseudo-components behaved differently from that of biomass. Indeed, principal component analysis showed that the thermal behavior of both biomasses was generally similar to that of pure hemicellulose. However, pure cellulose and lignin showed different behaviors compared to flax shives, beech wood, and hemicellulose. Hemicellulose and cellulose chars had almost the same behaviors, while being different from b... [more]

Absorption systems are a sustainable solution as solar driven air conditioning devices in places with warm climatic conditions, however, the reliability of these systems must be improved. The absorbing component has a significant effect on the cycle performance, as this process is complex and needs efficient heat exchangers. This paper presents an experimental study of a bubble mode absorption in a plate heat exchanger (PHE)-type absorber with NH₃-LiNO₃ using a vapor distributor in order to increase the mass transfer at solar cooling operating conditions. The vapor distributor had a diameter of 0.005 m with five perforations distributed uniformly along the tube. Experiments were carried out using a corrugated plate heat exchanger model NB51, with three channels, where the ammonia vapor was injected in a bubble mode into the solution in the central channel. The range of solution concentrations and mass flow rates of the dilute solution were from 35 to 50% weight and 11.69 to 35.46 × 10−... [more]

The sustainability of petroleum-based fuel supply has gained broad attention from the global community due to the increase of usage in various sectors, depletion of petroleum resources, and uncertain around crude oil market prices. Additionally, environmental problems have also arisen from the increasing emissions of harmful pollutants and greenhouse gases. Therefore, the use of clean energy sources including biodiesel is crucial. Biodiesel is mainly produced from unlimited natural resources through a transesterification process. It presents various advantages over petro-diesel; for instance, it is non-toxic, biodegradable, and contains less air pollutant per net energy produced with low sulphur and aromatic content, apart from being safe. Considering the importance of this topic, this paper focuses on the use of palm oil, its by-products, and mill effluent for biodiesel production. Palm oil is known as an excellent raw material because biodiesel has similar properties to the regular p... [more]

A study was conducted to investigate the parameter that has influence on steam gasification kinetics between the biomass type and char preparation. Thermogravimetric analysis (TGA) was carried out on steam gasification of seven biomass samples as well as chars from three of these samples. Chars were prepared using three different sets of low heating rate (LHR) pyrolysis conditions including temperature and biomass bed geometry. It was shown by a characteristic time analysis that these pyrolysis conditions were not associated with a chemical regime in a large amount of devices. However, it has been shown experimentally that conditions used to prepare the char had a much lower influence on steam gasification kinetics than the biomass type.

Nejayote (corn step liquor) production in Mexico is approximately 1.4 × 1010 m³ per year and anaerobic digestion is an effective process to transform this waste into green energy. The biochemical methane potential (BMP) test is one of the most important tests for evaluating the biodegradability and methane production capacity of any organic waste. Previous research confirms that the addition of conductive materials significantly enhances the methane production yield. This study concludes that the addition of granular activated carbon (GAC) increases methane yield by 34% in the first instance. Furthermore, results show that methane production is increased by 54% when a GAC biofilm is developed 10 days before undertaking the BMP test. In addition, the electroactive population was 30% higher when attached to the GAC than in control reactors. Moreover, results show that electroactive communities attached to the GAC increased by 38% when a GAC biofilm is developed 10 days before undertaking... [more]

As the pretreatment process is the most expensive and energy-consuming step in the overall second generation bioethanol production process, it is vital that it is studied and optimized in order to be able to develop the most efficient production process. The aim of this paper was to investigate chemical and physical changes in biomass during the process of applying the explosive decompression pretreatment method using two different gases—N₂ and synthetic flue gas. The explosive decompression method is economically and environmentally attractive since no chemicals are used—rather it is pressure that is applied—and water is used to break down the biomass structure. Both pre-treatment methods were used at different temperatures. To be able to compare the effects of the pretreatment, samples from different process steps were gathered together and analysed. The results were used to assess the efficiency of the pretreatment, the chemical and physical changes in the biomass and, finally, the... [more]

This article aims to study the codigestion of food waste (FW) and three different lignocellulosic wastes (LW) (Corn stover (CS), Prairie cordgrass (PCG), and Unbleached paper (UBP)) for thermophilic anaerobic digestion to overcome the limitations of digesting food waste alone (volatile fatty acids accumulation and low C:N ratio). Using an enriched thermophilic methanogenic consortium, all the food and lignocellulosic waste mixtures showed positive synergistic effects of codigestion. After 30 days of incubation at 60 °C (100 rpm), the highest methane yield of 305.45 L·kg−1 volatile solids (VS) was achieved with a combination of FW-PCG-CS followed by 279.31 L·kg−1 VS with a mixture of FW-PCG. The corresponding volatile solids reduction for these two co-digestion mixtures was 68% and 58%, respectively. This study demonstrated a reduced hydraulic retention time for methane production using FW and LW.

The aim of this study is to investigate the spray characteristics of diesel and gasoline under various ambient conditions. Ambient conditions were simulated, ranging from atmospheric conditions to high pressure and temperature conditions such as those inside a combustion chamber of an internal combustion engine. Spray tip penetration and spray cross-sectional area were calculated in liquid and vapor spray development. In addition, initial spray development and end of injection near nozzle were visualized microscopically, to study spray atomization characteristics. Three injection pressures of 50 MPa, 100 MPa, and 150 MPa were tested. The ambient temperature was varied from 300 K to 950 K, and the ambient density was maintained between 1 kg/m³ and 20 kg/m³. Gasoline and diesel exhibited similar liquid penetration and spray cross-sectional area at every ambient density condition under non-evaporation. As the ambient temperature increased, liquid penetration length and spray area of both... [more]

One of the bottlenecks hindering the usage of polymer electrolyte membrane fuel cell technology in automotive applications is the highly load-sensitive degradation of the cell components. The cell failure cases reported in the literature show localized cell component degradation, mainly caused by flow-field dependent non-uniform distribution of reactants. The existing methodologies for diagnostics of localized cell failure are either invasive or require sophisticated and expensive apparatus. In this study, with the help of a multiscale simulation framework, a single polymer electrolyte membrane fuel cell (PEMFC) model is exposed to a standardized drive cycle provided by a system model of a fuel cell car. A 2D multiphysics model of the PEMFC is used to investigate catalyst degradation due to spatio-temporal variations in the fuel cell state variables under the highly transient load cycles. A three-step (extraction, oxidation, and dissolution) model of platinum loss in the cathode cataly... [more]

This paper addresses the issues related to the rapid production of hydrogen from methane steam reforming by means of process intensification. Methane steam reforming coupled with catalytic combustion in thermally integrated microchannel reactors for the production of hydrogen was investigated numerically. The effect of the catalyst, flow arrangement, and reactor dimension was assessed to optimize the design of the system. The thermal interaction between reforming and combustion was investigated for the purpose of the rapid production of hydrogen. The importance of thermal management was discussed in detail, and a theoretical analysis was made on the transport phenomena during each of the reforming and combustion processes. The results indicated that the design of a thermally integrated system operated at millisecond contact times is feasible. The design benefits from the miniaturization of the reactors, but the improvement in catalyst performance is also required to ensure the rapid pr... [more]

Hydrothermal carbonization (HTC) is a useful method to convert wet biomass to value-added products. Fruit waste generated in juice industries is a huge source of moist feedstock for such conversion to produce hydrochar. This paper deals with four types of fruit wastes as feedstocks for HTC; namely, rotten apple (RA), apple chip pomace (ACP), apple juice pomace (AJP), and grape pomace (GP). The operating conditions for HTC processing were 190 °C, 225 °C, and 260 °C for 15 min. For all samples, higher heating value and fixed carbon increased, while volatile matter and oxygen content decreased after HTC. Except for ACP, the ash content of all samples increased after 225 °C. For RA, AJP, and GP, the possible explanation for increased ash content above 225 °C is that the hydrochar increases in porosity after 230 °C. It was observed that an increase in HTC temperature resulted in an increase in the mass yield for RA and GP, which is in contrast with increasing HTC temperature for lignocellul... [more]

This article presents gas hydrate experimental measurements for mixtures containing methane (CH₄), carbon dioxide (CO₂) and nitrogen (N₂) with the aim to better understand the impact of water (H₂O) on the phase equilibrium. Some of these phase equilibrium experiments were carried out with a very high water-to-gas ratio that shifts the gas hydrate dissociation points to higher pressures. This is due to the significantly different solubilities of the different guest molecules in liquid H₂O. A second experiment focused on CH₄-CO₂ exchange between the hydrate and the vapor phases at moderate pressures. The results show a high retention of CO₂ in the gas hydrate phase with small pressure variations within the first hours. However, for our system containing 10.2 g of H₂O full conversion of the CH₄ hydrate grains to CO₂ hydrate is estimated to require 40 days. This delay is attributed to the shrinking core effect, where initially an outer layer of CO₂-rich hydrate is formed that effectively s... [more]

A considerable proportion (about 64%) of biomass energy is produced from woody biomass (wood and its wastes). However, waste wood (WW) is very often contaminated with metal(loid) elements at concentrations leading to toxicity emissions and damages to facilities during thermal conversion. Therefore, procedures for preventing and/or alleviating the negative impacts of these elements require further development, particularly by providing informative and supportive information regarding the phase transformations of the metal(loid)s during thermal conversion processes. Although it is well known that phase transformation depends on different factors such as elements’ vaporization characteristics, operational conditions, and process configuration; however, the influences of reaction atmosphere composition in terms of interactions and interferences are rarely addressed. In response, since Cu, Cr, and As (CCA-elements) are the most regulated elements in woody biomass, this paper aims to explore... [more]

Combustion tests and gaseous emissions of olive mill solid wastes pellets (olive pomace (OP), and olive pits (OPi)) were carried out in an updraft counter-current fixed bed reactor. Along the combustion chamber axis and under a constant primary air flow rate, the bed temperatures and the mass loss rate were measured as functions of time. Moreover, the gas mixture components such as O₂, organic carbon (Corg), CO, CO₂, H₂O, H₂, SO₂, and NOx (NO + NO₂) were analyzed and measured. The reaction front positions were determined as well as the ignition rate and the reaction front velocity. We have found that the exhaust gases are emitted in acceptable concentrations compared to the combustion of standard wood pellets reported in the literature (EN 303-5). It is shown that the bed temperature increased from the ambient value to a maximum value ranging from 750 to 1000 °C as previously reported in the literature. The results demonstrate the promise of using olive mill solid waste pellets as an a... [more]

We wish to correct Table 5 of the published paper in Processes [1].[...]

This paper presents an experimental study of the self-initiation reaction of n-butyl acrylate (n-BA) in free-radical polymerization. For the first time, the frequency factor and activation energy of the monomer self-initiation reaction are estimated from measurements of n-BA conversion in free-radical homo-polymerization initiated only by the monomer. The estimation was carried out using a macroscopic mechanistic mathematical model of the reactor. In addition to already-known reactions that contribute to the polymerization, the model considers a n-BA self-initiation reaction mechanism that is based on our previous electronic-level first-principles theoretical study of the self-initiation reaction. Reaction rate equations are derived using the method of moments. The reaction-rate parameter estimates obtained from conversion measurements agree well with estimates obtained via our purely-theoretical quantum chemical calculations.