1,720,972 research outputs found
Conversion of Sewage Sludge to combined heat and power: Modeling and optimization
No full textCombined Heat and Power (CHP) generation from Sewage Sludge (SS) offers two simultaneous advantages: greenhouse gas emission reduction and increase of renewable energy generation as promoted by the European Union Green Deal 2021. In this work, a numerical model has been developed via Aspen Plus for the evaluation of CHP generation potentiality from SS through gasification integrated with an internal combustion engine system. The model is applied to the case of Italy and eight other European countries for the first time. The gasification model has been developed based on the experimental data on syngas generation from SS in a bench-scale rotary kiln reactor under laboratory conditions available in the literature. Sensitivity analysis revealed optimal operating temperature and equivalence ratios for gasification were 900 °C and 0.2 respectively. The CHP generation potentiality of SS resulted to be 2.73 kWh per kg SS as dry solid.
According to the statistical analysis used in the present study, SS generation will reach 680 kt per year as dry solid by 2030 based on the current sludge generation rate as well as improvement in the wastewater collection and treatment expected for the future in Italy. Within this time, the projected electrical and thermal energy generation rate per year can reach 714 GWh and 1142 GWh respectively. Electrical and thermal energy generation rates from sewage sludge have been estimated for eight EU countries in 2015 and compared with the Italian scenario, founding the highest one in Spain and the lowest in Luxembourg
Combined heat and power production based on sewage sludge gasification: An energy-efficient solution for wastewater treatment plants
No full textThe main operating costs of wastewater treatment plants are related to the energy consumption and the disposal of by-products. Energy recovery from sewage sludge may be a solution to face both these challenges, improving the sustainability of wastewater treatment plants and making them an example of a circular economy. In this work, the energy and economic analysis of an integrated combined heat and power system based on sewage sludge gasification is proposed. The whole process is simulated by using the commercial software Aspen Plus®. A restricted equilibrium model is used to simulate the gasification of sewage sludge in an atmospheric fluidized bed reactor using air as a gasification agent. Syngas produced from gasification is used as a fuel in an internal combustion engine for combined heat and power production. Different solutions are compared: the internal combustion engine is supposed to be fuelled with syngas or with syngas and methane. In line with the pertinent literature on integrated biomass gasification–internal combustion engine systems, the engine is modeled by combining a compressor, a combustor and a turbine to simulate the four thermodynamic steps of an internal combustion engine. Electric and thermal energy produced by the system is used to supply a fraction of the demand for wastewater and sludge treatment. The energy analysis is carried out for a real wastewater treatment plant that serves 1.2 million of population equivalent, located in Southern Italy. The obtained results are used to carry out an energy and economic analysis, which aims at assessing the feasibility and environmental benefits of the proposed system over conventional technologies
Geothermal energy for drying of wastewater sludge and electricity production
No full textWaste treatment and disposal and electric energy production are crucial challenges in geographically disadvantaged
areas, such as small islands, due to limited connection with mainland. Scarce land availability, environmental
restrictions and tourism activity, that often characterize small islands, make difficult to adopt ordinary
technical solutions, increasing these issues. Then, the most common strategy for waste disposal is shipping to
the mainland, whereas electricity generation is based on the importation of fossil fuels for local production.
Both these options make small islands strongly dependent on the mainland, and cause significant energetic, environmental
and economic costs. For these reasons, the use of renewable energy sources for waste treatment
and energy production is particularly attracting in small islands.
In this work, geothermal energy at medium enthalpy is considered to produce heat for thermal drying of
wastewater sludge and to power an Organic Rankine Cycle system for electric energy production. The analysis
is carried out for the case study of a small Italian island.
The geo-fluid, through an air-water heat exchanger, heats fresh air to produce the desiccant current for sludge
drying, which is carried out by using a belt convective dryer, operating in the range of 90.0-180°C. The dryer is
designed to achieve a final solids content of dry sludge higher than 90.0%. A fraction of the desiccant current
exiting the dryer is recirculated in order to reduce thermal energy demand of the dryer and, at the same time, the
flow rate of exhausts to be treated. Before reinjection, the geo-fluid powers a small-scale ORC system, designed
to self-supply the proposed layout, providing electricity for the dryer and the geo-fluid pumps, and to produce
electricity for the wastewater treatment facilities.
An energy analysis of the proposed system is carried out through the software Aspen PLUS, and an economic
and environmental model is developed to assess its profitability. This model estimates the economic and environmental
benefits coming from sludge drying, which significantly decreases the amount of sludge to be transported
and disposed, and from the use of a renewable energy source with respect to conventional fossil fuels,
for sludge treatment and electric energy production
Thermo-economic analysis of a novel cogeneration system for sewage sludge treatment
No full textWastewater treatment plants are high energy-consuming systems, and their electric energy consumption contributes to 25-30% of the total operating costs. A significant part of thermal energy is needed for management of the sludge produced during the process. Sludge drying by Combined Heat and Power (CHP) systems is attractive to obtain substantial economic and energy savings, especially if all the waste heat can be used. Since biogas production, where available, is insufficient for sludge drying, the direct use of the exhaust gases of a CHP system fuelled with syngas derived from sludge gasification and waste vegetable oil, is proposed. The profitability of this system is comparable with that of the systems currently employed in advanced wastewater treatment plants. The economic convenience derives from the reduction of sludge to be disposed and the overall energy saving in the plant. The simple payback of the proposed system, equal to 6.8 years, is only one year higher than that found for of an analogue conventional system, while the Net Present Value is 30% higher than that calculated for a conventional system. In terms of environmental impact, the layout presented is more efficient as biomass-derived fuels are used instead of fossil fuels
Biomass Polygeneration Systems Integrated with Buildings: A Review
No full textBiomass is widely acknowledged as a plentiful and easily accessible source of renewable energy. Unlike many other renewable sources, biomass offers a consistent and predictable power supply without significant concerns about energy and environmental impacts. When used as a fuel in polygeneration systems designed to produce multiple outputs such as electricity, heat, chemicals, and synthetic fuels, biomass greatly enhances overall system efficiency by minimizing energy losses. These systems gain further advantages when integrated in a decentralized manner with energy-intensive applications like buildings. This review article aims to shift the focus of readers from generic biomass-based systems to polygeneration systems tailored for specific applications, such as buildings. The overview will discuss various biomass resources, systematic approaches, technologies, successful case studies, potential benefits, and limitations of such systems integrated into real-life building applications. It also categorizes studies based on different conversion processes such as combustion, gasification, and anaerobic digestion, with combustion-based polygeneration systems being the most prevalent. The review also explores the use of standalone and hybrid biomass-based energy systems. Taking a multidisciplinary approach, the analysis considers energy, exergy, economic, and environmental perspectives. Parameters such as the primary energy savings (PES), exergy efficiency, simple payback (SPB) period, and CO2 emission reductions are commonly used in system analyses. The review underscores how polygeneration systems integrated into the building sector can enhance efficiency, resilience, and environmental sustainability. This synthesis aims to address current gaps, particularly in the domain of polygeneration systems connected with buildings, offering essential insights for researchers and specialists in the field
Effectiveness of flow obstructions in enhancing electro-osmotic flow
Full text linkIn this paper the influence of obstructions on micro-channel electroosmotic flow is investigated for the first time. To carry out such a study, regular obstructions are introduced into micro-channels and flow rates are numerically calculated. The effect of channel width on flow rates is analysed on both free and obstructed channels. The solid material considered for channel walls and obstructions is silicon and the electrolyte is de-ionised water. The parameters studied include channel width, obstruction size and effective porosity of the channel. The effective porosity is varied between 0.4 and 0.8 depending on other chosen parameters. The results clearly demonstrate that, under the analysed conditions, introduction of obstructions into channels wider than100 micro meters enhances the flow rate induced by electro-osmosis
Using flow obstructions in electro-osmotic systems for fluid flow enhancement
No full textA numerical investigation of Electro-Osmotic Flow (EOF) in plain channels and channels with obstructions is presented. The aim of the work is to analyse fluid flow enhancement in EO systems due to flow obstructions. The results show that the introduction of flow obstructions allows to increase the range of channel width in which EOF is effective, and to produce higher fluid flow rates than those corresponding to plain channels. The results also show that beyond a channel width of 100μm, EOF driven systems are possible only if flow obstructions are employed
An integrated system for sewage sludge drying through solar energy and a combined heat and power unit fuelled by biogas
No full textThe main challenges of wastewater treatment plants are high-energy demand and sludge disposal. A hybrid system for sewage sludge drying is proposed in this work to face both these issues. The developed layout is based on the integration of two renewable energy sources, biogas from anaerobic digestion of sludge and solar energy in order to increase sustainability and energy self-sufficiency of the plant. Biogas is used to fuel a combined heat and power system and solar energy is exploited through a parabolic trough collector field. Electrical energy produced by the combined heat and power is used to cover the plant demand, whereas thermal energy coming from the combined heat and power unit and solar field is employed to run an anaerobic digestion process and for thermal drying of the residual sludge. The considered case study is based on data collected for an existing wastewater treatment plant. The proposed system is studied through data obtained from the scientific literature, suppliers of the considered equipment and properly developed sub-models of the various components, to assess its feasibility and the overall energy, environmental and economic performance. The system is dynamically simulated and daily, weekly and yearly results are presented. For the considered desiccant flow temperatures, the solar collector field achieves a thermal efficiency of about 56.0%, while for the combined heat and power unit it is about 44.0%, which is slightly higher than the nominal one, due to the preheating of combined heat and power unit intake air. The integration of solar energy with the combined heat and power system leads to a primary energy saving of about 14.6% with respect to the existing plant, where the sludge is not digested and neither thermally dried. The economic analysis shows that the Simple Pay Back period of the system is less than 3.40 years
Solar-based systems
No full textThis chapter describes solar-based polygeneration systems. After a brief overview of the most used solar technologies, different solar-based polygeneration systems presented in the literature are illustrated. The operation and the methodology used for the analysis of such systems are described. Then, for each example, the plant location, the solar technology used, the produced outputs, and the achieved efficiency are illustrated. This chapter also presents an example of a solar-based polygeneration system, with a detailed description of the system layout and the operation strategy. A dynamic simulation model of such a system is developed to carry out its energy and economic analysis. Finally, daily, weekly, and yearly results carried out with the dynamic simulation are presented
Green Energy Production and Integrated Treatment of Pharmaceutical Wastewater Using MnCo2O4 Electrode Performance in Microbial Fuel Cell
No full textThe wastewater produced by the pharmaceutical industry is highly organic and toxic. Dual-chambered microbial fuel cells (DMFCs) may represent a sustainable solution to process wastewater while simultaneously recovering its energy content. DMFCs are bio-electrochemical devices that employ microorganisms to transform the chemical energy of organic compounds into electrical energy. This study aims to demonstrate the feasibility of a DMFC with a manganese cobalt oxide-coated activated carbon fiber felt (MnCo2O4-ACFF) electrode to treat pharmaceutical industry wastewater (PW) and exploit its energy content. The proposed technology is experimentally investigated considering the effect of the organic load (OL) on the system performance in terms of organic content removal and electricity production. As per the experimental campaign results, the optimum OL for achieving maximum removal efficiencies for total chemical oxygen demand, soluble oxygen demand, and total suspended solids was found to be 2 g COD/L. At this value of OL, the highest current and power densities of 420 mA/m2 and 348 mW/m2 were obtained. Therefore, based on the outcomes of the experimental campaign, the (MnCo2O4-ACFF) electrode DMFC technique was found to be a sustainable and effective process for the treatment and energy recovery from PW
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