Results 1 - 10 of 125
Results 1 - 10 of 125. Search took: 0.019 seconds
|Sort by: date | relevance|
[en] Epoxidized fatty acid methyl ester (EFAME) is a renewable and biodegradable plasticizer that can be produced from various vegetable oils and even waste oils. In this work, refined soybean oil (RSO) was first converted to fatty acid methyl ester (FAME) by enzymatic transesterification, followed by epoxidation with performic acid in situ generated via auto-catalyzed reaction of formic acid with hydrogen peroxide. Effects of several factors on epoxidation of RSO FAME were investigated, and the conditions were optimized by response surface methodology. Impacts of several potential impurities on epoxidation were further investigated. It was found that the effects of triglyceride (RSO), glycerol and free fatty acid could be negligible. However, mineral acid such as sulfuric acid could significantly improve the rate of epoxidation, but the cleavage of epoxy group was also strengthened, resulting in lower epoxy value of the EFAME product. Surfactants showed significant negative effects on epoxidation. The feasibility of producing EFAME from waste cooking oil was further investigated. Compared with RSO, waste oil needed a second-stage epoxidation to epoxidize most of the double bonds, but obtained poorer epoxy value with lower degree and selectivity of epoxidation and EFAME yield.
[en] Chemical and biological pretreatments (with NaOH, HCl, CO(NH2)2 and cellulase) were used to pretreat rice straw at ambient temperature (about 20 °C) to improve its biodegradability and increase anaerobic biogas production. The NaOH and CO(NH2)2 pretreatments reduced the percentage contents of hemicellulose and lignin. The HCl pretreatment mainly dissolved the hemicellulose and resulted in decreases of 12.5–7.1% of the hemicellulose. The percentage content of cellulose showed a dramatic decrease, from 38.3 to 10.9%, after the cellulase pretreatment. Compared with untreated rice straw substrate, the total biogas yield ratios were 3.38–5.91, 1.63–2.99, 1.93–5.22 and 3.62–6.45, with a hydraulic retention time of 30 days, under NaOH, HCl, CO(NH2)2 and cellulose pretreatments, respectively. The highest yields of biogas and methane were obtained from 40 U/g total solids (TS) cellulase-pretreated rice straw (20.433 and 9.918 L respectively). Biogas production yields of volatile solids (VS) were 123.7, 273.8, 318.5, 353.5 mL/g for control, 6% CO(NH2)2-, NaOH- and 40 U/g TS cellulase-pretreated rice straw substrate, respectively. Compared to untreated rice straw substreates, cumulative biogas production yields increased 16–103, 25–122% for NaoH- and cellulase-pretreated rice straw substrate, respectively. The results suggested that the highest removal efficiencies of TS and VS were obtained from 6% NaOH-pretreated (53.80 and 36.80%), 6% CO(NH2)2-pretreated (54.90 and 36.10%) and 40 U/g TS cellulase-pretreated (51.30 and 37.30%) rice straw substrate. In short, NaOH, HCl, CO(NH2)2 and cellulase pretreatment was suitable to enhance the biogas production. However, to choose the optimal treatment, the energy requirements relative to the energy gain as extra biogas production have to be taken into account, as well as the costs of chemicals or enzymes.
[en] Extracellular polymeric substance (EPS), a high molecular weight biological polymer that can bind to a large amount of organic matter and moisture, plays a vital role in the process of sludge formation and structural stability, affecting sedimentation and dewatering performance of sludge. The aim of this study was to observe the changes in the key components of EPS extracted from mechanical dewatered sludge before and after enzyme and thermal pressure treatment. The results showed that the soluble protein content increased by 160 and 110% and the polysaccharide content increased by 180 and 200% after adding 0.03 g/g TSS neutral protease and alpha-amylase, respectively. The effect of compound enzyme treatment was better than that of single enzyme treatment. Furthermore, three-dimensional fluorescence spectroscopy indicated the presence of tryptophan and aromatic-like proteins, and Fourier transform infrared spectroscopy showed that the types of functional groups exhibited a sharp decrease in the loosely bound-EPS layer after thermal pressure treatment.
[en] Algae are considered as a good substrate for bioethanol production. This study was carried out to evaluate the potential chemical and biological hydrolysis of the macrogreen alga Ulva fasciata and the microgreen alga Chlorella vulgaris to pretreatment of cell wall and sugar production. Different concentrations of reduced sugar extracted from U. faciata was studied to obtain the maximum amount of bioethanol. Saccharomyces cerevisiae SH02, Pseudomonas sp. SH03, were used to determine the best microorganisms that affect in fermentation process and hence the production of bioethanol. U. fasciata contains maximum amount of sugar. Chemical hydrolysis is the best methods for pretreatment of algae. S. cerevisiae SH02 was the best microorganisms for fermentation process with sugar obtained from U. faciata by chemical hydrolysis. The highest ethanol production by S. cerevisiae SH02 was 40% with 5% sugar concentration that produced by acid hydrolysis and with increasing sugar ratio ethanol production decrease. The highest ethanol yield with Pseudomonas sp. SH03 was 22% obtained by fermentation of 5% algal sugar.
[en] A sustainable development of Concentrating Solar Power plants can be really undertaken by using locally made components and low cost eco-materials. This study is focused on the use of coal bottom ash from Niger coal power plant and slaked lime from Burkina Faso acetylene production as industrial wastes, as well as laterite and clay from Burkina Faso as natural stones for the elaboration of thermal storage materials. The various materials have been used directly or combined together to obtain a suitable mixture. In order to determine the effect of heat treatment on the materials obtained, their structural organisation, microstructure, chemical composition and thermal behaviours were investigated. The results showed that after heat treatment of the laterite, the iron-spinel phase with inclusion of repetitive dendrites of the magnetite phase was obtained. The bottom ashes have highlighted the possibility to elaborate mullite refractory ceramic after heat treatment. The results also showed that anorthite ceramic can be synthesized from the mixtures of bottom ash with slaked lime and laterite. The obtained materials showed good thermal behaviour. Therefore, the main benefits of these materials are their sustainable character, wide availability, relevance to thermal energy storage applications up to 900 °C, and absence of use conflict.
[en] Raw materials of mineral industries are mainly in the form of ore, which generate fine mineral particles during the extraction, comminution and transport which are primarily regarded as non-recyclable waste. The aim of this paper is to develop and characterize materials using recycled fine particles of bauxite sintered at high temperature at a laboratory scale for the calcium aluminate industry. To use these recycled materials as raw materials, the physico-chemical transformations during high-temperature processing are described. Phase transformations as a function of temperature were determined by XRD, and optical and electronic microscopies were utilized to observe microstructures. Materials with different particle size distributions showed different chemical reactivity as a function of particle size. The optimization of particle size distribution makes it possible to substitute synthetic bricks for bauxite ore using recycled fine particles of bauxite.
PurposeTo achieve the optimization of the solid-state fermentation (SSF) processes where agro-industrial wastes are used, a better understanding of biological aspects (mathematical modeling) are needed, due the heterogeneity of these materials. The purpose of this study was to compare the effect of the bioreactor arrangement (Tray and Column) in the synthesis of xylanase by Rhizomucor pusillus strain in SSF process.
MethodsFermentation process was realized in both, tray and column bioreactors, using corn-cob (CC) as a carrier-substrate. Tray bioreactor and packed-bed bioreactor, containing fungal spores, 3 g of CC as substrate and support, and 8 mL of minimum Czapek-Dox culture medium; were incubated at 50 °C for 5 days. Maximal specific growth rate (μmax), maximal biomass level (Xmax), product/biomass yield (α) and secondary coefficient of product formation or destruction (β) were estimated by mathematical models.
ResultsHigh value of xylanase enzyme activity (587.6 U/gds) was found in the column bioreactor. The logistic equation for cell growth and Luedeking-Piret equation for xylanase production could satisfactorily simulate the bioreactors’ kinetics data.
ConclusionsThe production of xylanase by Rhizomucor pusillus SOC-4A is affected by the type of bioreactor. Data showed that the most efficient bioreactor in production of the xylanase enzyme is the column bioreactor.
[en] This study presented a techno-economic evaluation of the thermal conversion of sludge and digestate integrated with anaerobic digestion (AD) as a means of waste volume reduction, carbon emissions mitigation and energy recovery in wastewater treatment plants. The study was supported by empirical data and thermodynamic modelling of processes involved in sludge conversion. A gasification plant (6 MWel) with combustion engines produced sufficient power for treating wastewater (1.6 Mp.e.) and 130 tpd dry sludge. The integration of AD with gasification increased total energy coverage by up to 46%. Treatment costs between €132 and 210 dry t−1 were achieved and the associated levelised costs of electricity (23–85c kWh−1) were within the cost range known for biomass digestion and other CHP technologies. Biomass and waste co-processing was evaluated in order to avoid heat and electricity deficits due to variations in sludge availability and properties, showing potential for reducing carbon footprint and associated electricity costs.
[en] Raw biomass resources and many wastes are composed of poor-LHV organic matter (LHV <20 MJ/kg). Their use as renewable fuels for heat or power generation is challenging, particularly when they are in solid form. Indeed, their combustion in air is critical and it is not possible to build autonomous burners independently of external conditions without assistance. Three main options are currently studied: (i) the co-combustion, in which the poor-LHV fuel flame is supported thanks to an additional rich fuel, (ii) the oxy-combustion (iii) the electro-combustion, consisting in the generation of thermal plasma for activating and assisting the combustion. This last option is highly interesting because it only requires electricity (having low carbon content if renewable electricity). Depending on the nature of the feedstock, the electric power of the plasma does not exceed 1–5% of the flame power. Most plasma electro-burners technologies today on the market use DC plasma torches. These technologies suffer from many drawbacks among which: limited electrodes lifetime, poor reliability, important water cooling needs, need of AC/DC transformers, etc. leading to high CAPEX and OPEX. With the objective to go over these limits and reduce OPEX and CAPEX while increasing reliability, the Center PERSEE MINES-ParisTech has been working in the development of an original three-phase AC plasma technology to be integrated in a plasma electro-burner. This paper presents the main achievements on the plasma technology with a special focus on the limitation of electrodes erosion thanks to an active thermochemical gas sheathing.
[en] This paper presents an experimental and thermodynamic contribution about the role of inorganics in ash-bed material interactions during thermal conversion of miscanthus in fluidized bed. The objectives are (1) to describe the transformation of inorganics at high temperature, (2) to reveal their role in the agglomeration and (3) to provide recommendations for miscanthus gasification in fluidized bed. The main ash forming elements in miscanthus are K, Si, Ca, Mg, P, S and Cl. The ashes are composed of silica, carbonates and salts. The carbonates and salts decompose and volatilise at 700 °C. At elevated temperature, the dominant solid phases are Ca and Mg silicates. The liquid phase is composed of SiO2, K2O, CaO, MgO regardless of the atmosphere. The accuracy of thermodynamic prediction tool is evaluated with the experimental results. The ash-bed interactions show that the wetting of bed material by molten ashes is one of the key parameters of the agglomeration. The adhesion of particles increases in the order of silica sand, olivine, calcined olivine. There is no significant difference in the agglomeration mechanism in oxidizing or reductive atmosphere. However, in reductive atmosphere, two immiscible liquid phases can occur. The parametric investigation shows that the operating temperature has a significant effect on the agglomeration ratio and the addition of kaolin or dolomite is the most effective tool to reduce agglomeration risks.