A process for hemicelluloses fractionation and purification from wheat straw and bran has been investigated and technical considerations (yields, purity) have been coupled to environmental characterizations (water consumption, carbon dioxide emissions) in order to develop an environment-friendly process. Extraction by twin-screw extrusion gave a yield in arabinoxylans equal to 8.5% (weight of (arabinose + xylose) in the extract after fractionation/dry weight of the destarched bran). The extraction of 86 kg of straw and bran (with a ratio 6.2:1) with 5.8 kg of NaOH in pellet form resulted in the production of a complex extract containing 1.0 kg of arabinoxylan polymer, which required concentration and purification steps. Evaporation (EV) followed by ethanol precipitation (P) and freeze-drying (FD), gave a yield in hemicellulosic powder of 36.5% (dry weight of powder/dry weight of extract after liquid/solid separation) with a total sugar content equal to 48.4% but also used a large amount of ethanol. The other studied purification process was based on a combination of ultrafiltration (UF), anion exchange chromatography (CHR) and spray-drying (SD). It gave a yield in hemicellulosic powders of 24.6% and a total sugar content equal to 28.7%. The technical performances of the second process appear to be less attractive but with a lower energetic and ethanol consumption. Thus secondly the environmental impacts (water consumption and CO emission) of the ultrafiltration step were quantified. Life Cycle Assessment data (Ecoinvent) were used to convert materials used for the infrastructure and energy consumed during functioning into carbon dioxide emissions and water consumptions. Results have shown that environmental impacts due to the operating conditions are higher than those relative to raw material involved in the installation. The study showed that this kind of approach allows the determination of optimum conditions for the ultrafiltration step.
Former integrated urban energy assessments and optimisation have modelled domestic hot water (DHW) demand as a single stream, as space heating, currently, is the main energy demand in buildings and a detailed DHW modelling was therefore not required. However, the characterisation of energy saving measures (e.g. grey water heat recovery) and the selection of optimal heating utility in buildings with low temperature space heating would benefit from a differentiation of the various DHW end-uses at urban scale (building blocks, streets, districts, city). To this end, a new method characterising the main DHW appliances in households, hotels and nursing homes at urban level, is proposed. A review of European publications characterising water uses is conducted and utility load and energy consumption equations are developed. A specific model for district heating heat exchangers without thermal storage for integrated urban energy optimisation is proposed. The DHW-related energy consumption results are confirmed by literature values in a real urban case-study. Showering represents more than 80% of the DHW energy demand, and more than 97% of the total DHW heat use is required up to 40 °C. The proposed method contributes to urban energy assessments and optimisation by improving the level of detail of the outcomes and by strengthening their integrated approach.
Residential domestic hot water energy consumption represented 16% of the EU household heating demand in 2013. With the improvement of the building insulation envelope, domestic hot water contribution to energy consumption is expected to increase significantly, with values between 20% and 32% in single family buildings, and between 35% to almost 50% in multifamily buildings. This energy, currently lost to the environment, can be recovered by waste water heat recovery systems inside buildings (in-building solutions). While most publications in this field focus on shower heat recovery and on waste water as heat source for heat pumps, the detailed impact of waste water heat recovery at a city scale by aggregating building data has not been addressed yet. Furthermore, waste water heat recovery potential and relevance was not yet quantified as a function of the specific inhabitant and household numbers, end-use occurrence, and building type and age. A method to quantify the building-specific energy cost and energy saving potentials, based on pinch analysis, at the urban scale of in-building waste water heat recovery systems is therefore proposed. A complementary method to spatially allocate and characterise grey water streams as to thermal load and temperature levels in function of the building specificities is also developed. These methods are applied in two case studies, first as retrofitting solution in a city in Luxembourg and, second, as optimisation measure for high efficiency residential buildings. Grey water heat recovery would reduce the residential fuel consumption of the city by 6.3%. An integrated approach combining grey water heat recovery for hot water preheating and a heat pump yields up to 28% and 41% electricity savings for passive single family houses and multifamily buildings, respectively. With the detailed characterisation of various grey water streams as a function of inhabitant number and end-use occurrence, the quantification of the energy savings and costs through heat recovery is improved. The outcomes of urban energy and cost assessments concerning grey water heat recovery are more specific, as the results at building level are aggregated to the considered geographical scope. The proposed method therefore complements current urban energy and cost assessments with the detailed integration of in-building grey water heat recovery systems.
CFD modeling of pretreatment reactors at very high lignocellulose solids content requires the characterization of rheological properties of this specific system. In this study, the non-Newtonian rheological properties of the corn stover–water mixture at high solid loading up to 50% with helical ribbon agitation were characterized. The rheological model was developed by introducing the power law model and measuring the torque values of the mixing system in a small reactor (5 L), and then applied to the larger reactors (50 L and 500 L). The CFD model was developed based on the determined rheological properties. The fluid dynamics experiments in three reactors with different scales were used for validation of the rheological model. The calculated power consumption and mixing efficiency by CFD modeling were in good agreements with the experimental results. This study provided a practical method for the rheology characterization and CFD model at high solids loading. The CFD model could be applied to the design and structure analysis of pretreatment reactors in lignocellulose biorefining processes.
Wastewater produced from all the domestic uses of water sans toilet flushing is known as greywater. It is often the major component in the domestic wastewater but has fewer pollutant load. Recycling and reuse of treated greywater for non-potable purposes may significantly reduce the stress on the fresh water requirement. This article presents the result of a study undertaken for characterization as well as laboratory-based investigation for treatment of greywater generated from an Indian single household. The greywater constituted at least 80% of the total wastewater with maximum contribution (44%) from the kitchen. The treatment studies, undertaken in an electrochemical reactor where the voltage and current were varied for sacrificial aluminum anodes, revealed that about 70% of the total COD and more than 99.9% pathogens could be removed with an energy consumption of 0.3 kW h/m of wastewater. COD removal reached a maximum of 70%, irrespective of the applied voltage and current density, at an aluminum release from the anode at a rate of 15 mg/L as aluminum. The electrochemical reactor aluminum electrodes, operated with maximum potential difference of 12 V, showed potential for scale-up for real-life use in households for removal of pathogens, turbidity and COD contents of greywater.
We introduce an integrated model for characterization of spatiotemporal building energy consumption patterns in neighborhoods and city districts. The model addresses the need for a comprehensive method to identify present and potential states of building energy consumption in the context of urban transformation. The focus lies on determining the spatiotemporal variability of energy services in both standing and future buildings in the residential, commercial and industrial sectors. This detailed characterization facilitates the assessment of potential energy efficiency measures at the neighborhood and city district scales. In a novel approach we integrated existing methods in urban and energy planning domains such as spatial analysis, dynamic building energy modeling and energy mapping to provide a comprehensive, multi-scale and multi-dimensional model of analysis. The model is part of a geographic information system (GIS), which serves as a platform for the allocation and future dissemination of spatiotemporal data. The model is validated against measured data and a peer model for a city district in Switzerland. In this context, we present practical applications in the analysis of energy efficiency measures in buildings and urban zoning. We furthermore discuss potential applications in educational, urban and energy planning practices.
Four types of bipolar membranes (BMs) with different structural properties were subjected to various electrochemical methods including current-voltage curve, (CVC) chronopotentiometry, and impedance spectroscopy, to be characterized in terms of selectivity, energy consumption and the water splitting capability. Then the bipolar membranes were used in two kinds of electrodialysis modules, lab scale and pilot unit, for acid and base production. The produced acid and base were analyzed to calculate the product purity, energy consumption and current efficiency of each bipolar membrane electrodialysis (BMED). The results obtained with electrodialysis coincided with those of electrochemical methods, indicating that even though the electrochemical methods are rather fast and easy to perform, they are quite reliable. Furthermore the impact of structural properties of each BM on its efficiency was investigated. It was figured out that the reinforcing of a heterogeneous BM improves its properties while the increase in the ion exchange resin content on each layer of the heterogeneous BMs was not resulted in any significant enhancement of BM properties. The investigated homogenous membrane showed higher selectivity and less energy consumption compared to the heterogeneous BMs.
Deadlegs are the pipe sections used for specific services in production and transportation of oil and gas, and they often encounter hydrate management challenges. Despite stagnant fluids in deadlegs, warm water vapor readily condenses on the cold pipe wall, resulting in a risk of hydrate blockages by deposition. Proper management of hydrates in deadlegs is therefore required for economic and safety reasons. Here, we discuss the development of an 1-in. vertical pipe system that is designed to study hydrate deposition from water saturated gas. From a series of hydrate formation and dissociation, the hydrate deposits are characterized to obtain gas/water consumption, thickness/volume hydrate deposit distribution, hydrate morphology, and hydrate porosity and wetness. These characteristic properties are correlated with the header temperature and the time duration for hydrate deposition. Qualitative and quantitative information obtained from the present study contribute to our understandings of hydrate deposition and give insight into establishing management strategies to avoid or minimize the risk of hydrate deposition in deadlegs in oil and gas production and transportation systems.
Recently, fabrication of membranes with low energy consumption has gained much attention of research. The aim of the current work was to design a new low-pressure and efficient multi-poly (piperazine-amide) thin layer which each layer formed alternatively upon a polyester nonwoven backing without using a polymeric support (unlike usual thin film membranes which use an ultrafiltration support). A desired rejection toward CuSO and Congo red day was obtained about 80 and 97%, respectively. Estimated pore size of the membranes (using molecular weight cut off test) showed the values from 150 to 325 Da.
Adhesive bonding techniques have been widely used in many industrial fields, such as aerospace, vehicle and civil engineering, etc., while the bonded structures are designed to perform satisfactorily under complex service conditions. This paper presented an experimental insight into the moisture diffusion process in Araldite 2015 adhesive considering the effect of post-curing process under elevated temperature. Polytetrafluoroethylene mould was adopted for the curing process of dumbbell adhesive specimens and both distilled and salt water were introduced to simulate a severe immersion environment. Quasi-static testing was conducted on both unaged and aged bulk adhesive after certain period of immersion to reveal the mechanical properties variation. Measurements on specimen weight and thickness were performed with different time intervals during the immersion process. It is shown that the strengths of bulk adhesive were significantly degraded due to the presence of water in both immersion conditions, where higher moisture content led to greater strength degradation regardless of the curing and ageing conditions applied. In addition, distilled water environment led to notably higher saturation content and hygroscopic swelling compared to salt water. However, the rates of water diffusion and hygroscopic swelling processes in salt water were detected to be far above the ones in distilled water. It is worth noting that slight increase was observed in moisture saturation content and swelling expansion for post-cured adhesive, while the coefficients of hygroscopic swelling showed no difference for all sample groups studied. Scanning Electron Microscopy observation further revealed the transition in microscopic topography from unaged to saturated samples.