Design Of Recovery Systems Research Articles

Design of energy recovery systems: thermoelectric combi boiler generator and power analysis

Gas-fired combi boilers are commonly used to meet the need for heating and general-purpose hot water in developing countries. In this study, a thermoelectric combi boiler generator (TECBG) was developed. When the boiler is operated, cold water flows through the cold surface of TECBG and enters the boiler. In the same way, it is used by flows through the hot surface of TECBG in heated water. Thus, temperature difference occurrs between the surfaces of TECBG. The temperature difference is converted into electrical energy by Seebeck effect. The proposed system was implemented on a domestic combi boiler. The maximum temperature difference between the designed system and the TECBG surfaces was recorded as 48 °C. 12V9AH battery was used to charge through a DC-DC charge regulator. About 14.28 Wh power was generated by the TECBG when the temperature difference of the TECBG, current, and voltage were 48 °C, 1.18 A, and 13.8 V, respectively. The electrical energy consumed by the combi boiler was measured as 115 Wh. Although the obtained energy is not quite high, it is an important gain in terms of energy efficiency because according to data recorded in Turkey, there are 15 million combi boiler users. Assuming that a single heating boiler runs for 4 h, it is possible to produce 306.6 GWh/year, derived from 14.28 Wh × 4 h × 365 days × 15,000,000 heating boiler. The proposed system provides significant advantages and thus can decrease power consumption.

Comparison of direct and indirect contact heat exchange to improve recovery of bio-oil

This study investigates whether the rate of cooling of pyrolysis vapors affects the composition of the resulting bio-oil. Pure cellulose was pyrolyzed in a laboratory-scale fluidized bed reactor at 500 °C and the bio-oil collected in either an indirect contact heat exchange (conventional water-cooled condenser system) or a direct contact heat exchange (liquid quench) system developed in our laboratory. The liquid quench system was estimated to achieve a seven-fold increase in cooling rate compared to the water-cooled condensers. Direct contact cooling in the quench system also eliminated temperature gradients experienced by films of bio-oil running down the walls of the water-cooled condensers. The combination of these two factors helped reduce secondary decomposition of primary pyrolysis products, especially anhydrosugars such as levoglucosan. The quench system increased the yield of levoglucosan by over 20% while minimally effecting yield of other compounds.The concept of direct contact cooling was applied to a pilot-scale, lignocellulosic biomass pyrolysis plant using water as a more practical quench media than liquid nitrogen. As with the liquid nitrogen quench, the water flashed to gas while the heavy ends of the bio-oil condensed to liquid. The quench vessel was operated above the dew point of the water to assure that it left the vessel as gas along with produced water and light ends of bio-oil, which were recovered in a condenser as an aqueous phase. In pyrolysis experiments with red oak, the quench vessel increased the yield of heavy ends by 15% compared to conventional condensers. These results encourage the design of bio-oil recovery systems that can rapidly quench products to achieve high yields and improve the quality of bio-oil.

Entropy generation analysis of sequential Anaerobic Digester Ion-Exchange technology for Phosphorus extraction from waste

Phosphorus (P) recovery from waste is a crucial sustainability challenge both for meeting the growing food demand and maintaining water quality effected by P run-off. Several new technologies are under development to address this issue, however each technology presents a trade-off in terms of cost vs benefits. Energy consumption forms one such critical trade-off as energy intensive technologies can lead to unintended consequences. However, the energy assessment of waste treatment and nutrient recovery systems are limited in literature and mostly focused on empirical analysis. This limits the design optimization of these systems for improving energy utilization. In this work, this critical gap of rigorous energy assessment of waste recovery technologies has been addressed by proposing the method of entropy generation analysis (EGA) as a tool for evaluating the design of waste recovery systems in order to improve energy utilization. To demonstrate the method of EGA for waste recovery technologies, the method was applied on a sequential Anaerobic Digester (AD)-Ion Exchange (IE) based side stream process used for extraction of P from waste water system which is the first step in recovery of nutrient from waste. EGA was performed by assuming a black box model for the technology and thermodynamic parameters were calculated using mechanism based approach by considering biochemical reactions in AD, stream flow analysis in ASPEN PLUS and batch IE experiments. The study successfully shows how to account for entropy generation in processes like AD and IE using mechanisms that result in entropy generation leading to energy losses. Results from the study indicate that the entropy generated from the heat exchange system to maintain the operating temperature for AD and IE was leading cause of entropy generation which provides guidance for targeting design improvements to design cleaner technologies in future. Such insights about mechanism behind energy losses is not feasible using widely used energy analysis methods and the method of total exergy destruction analysis which combines the total losses for a subsystem but does not elucidate exact causes of losses, thus EGA provides a distinct advantage for guiding the design of technologies to minimize energy losses.

A Finite Volume Analysis of Thermoelectric Generators

ABSTRACTThe electric power produced by a thermoelectric generator (TEG) is strongly influenced by the applied heat sink. While a TEG is aimed at harvesting waste heat, the optimization of the efficiency of the heat sink is a key task for the design of waste heat recovery systems implementing TEG. A TEG model is proposed and implemented in an open source toolbox for field operation and manipulation (OpenFOAM) for the purpose of performing optimizations of the heat sink, using a commercially available TEG as basis. This model includes the multi-physics thermoelectric coupled effects. Conservation principles of energy and current are considered simultaneously. This includes the thermal and electric conduction, Seebeck effect, Peltier effect, Thomson effect, and Joule heating. Particular attention is given to a proper modeling of the boundary conditions. The thermoelectric model is implemented in such a way that it can readily be combined with other physical models in OpenFOAM. The model is validated by comparing the predictions to analytical results, measurements as well as the simulation data of other authors.

Model-based assessment of energy-efficiency, dependability, and cost-effectiveness of waste heat recovery systems onboard ship

Technological systems are not merely designed with a narrow function in mind. Good designs typically aim at reducing operational costs, e.g. through achieving high energy efficiency and improved dependability (i.e. reliability, availability and maintainability). When there is a choice of alternative design options that perform the same function, it makes sense to compare alternatives so that the variant that minimises operational costs can be selected. In this paper, we examine this issue in the context of the design of Waste Heat Recovery Systems (WHRS) for main engines of large commercial freight vessels. We propose a method that can predict the operational cost of a WHRS via thermodynamic analysis which shows costs related to energy utilisation, and dependability analysis which shows costs related to system unavailability and repair. Our approach builds on recent advances in thermodynamic simulation and compositional dependability analysis techniques. It is a model-based approach, and allows reuse of component libraries, and a high degree of automation which simplify application of the method. Our case study shows that alternative designs can be explored in fast iterations of this method, and that this facilitates the evidence-based selection of a design that minimises operational costs.

Implementing energy efficiency measures in industrial clusters - A design approach for site-wide heat recovery systems

Heat integration between chemical production facilities in an industrial cluster provides significant cost savings opportunities. While single chemical processes are often well integrated, site-wide heat integration based on Total Site Analysis (TSA) tools often identifies opportunities to further increase energy efficiency. However, further development of the TSA methodology is required to improve its applicability for identifying practical heat integration measures and providing key information for investment decision makers. The design of common site-wide heat recovery systems in an industrial cluster is a complex task in which a large number of aspects other than thermal process and utility flows must be considered. This paper presents a procedure for identifying site-wide heat recovery measures based on TSA. The proposed approach is illustrated for a chemical cluster located on the West Coast of Sweden, showing feasible site-wide heat recovery systems achieving up to 42 % of the maximum total site heat recovery target of 129 MW. A number of systems are suggested ranging from low complexity achieving a minor share of the heat recovery potential to complex, strongly interdependent systems demanding large investments and a high level of collaboration. Estimated pay-back periods for the proposed systems range from 3.2 to 4.2 years, while up to approx. 12 % of the cluster's CO2 emissions can be avoided.

Optimization design of heat recovery systems on rotary kilns using genetic algorithms

Heat loss from rotary kilns accounts for certain amounts of the total energy consumption in chemical and metallurgical industries. To reduce the heat loss, a parallel and a series-parallel heat recovery systems with nine heat recovery exchangers are proposed to preheat the cold water in this paper. Experimental measurements are carried out to determine the heat transfer coefficient equations of each heat recovery exchanger. Then, the heat recovery systems are analyzed to deduce the mathematic relation between the design parameters and the system requirements, i.e. the temperatures and heat transfer rates of the nine heat recovery exchangers. The total heat transfer area, the total power consumption and the entropy generation due to heat transfer and fluid flow are set as the objective functions in four multi-objective optimization (MOO) cases. With the aid of the genetic algorithm in the Matlab 2015, the optimized operational and structural parameters are obtained. Finally, the MOO results are compared with that of the single objective optimization (SOO) method and the original values. The optimization results show that the MOO method are more suitable for the operational parameters design of the heat recovery systems compared with the SOO method. The required total heat transfer area and the total power consumption are decreased by at least 12.1% and 13.7%, respectively. Besides, as the entropy generation due to heat transfer and fluid flow decrease in the MOO cases, the corresponding heat transfer area and power consumption of the heat recovery system decrease, respectively.

A practical multi-objective design approach for optimum exhaust heat recovery from hybrid stand-alone PV-diesel power systems

Integration of solar power and diesel generators (DGs) together with battery storage has proven to be an efficient choice for stand-alone power systems (SAPS). For higher energy efficiency, heat recovery from exhaust gas of the DG can also be employed to supply all or a portion of the thermal energy demand. Although the design of such heat recovery systems (HRSs) has been studied, the effect of solar power integration has not been taken into account. In this paper, a new approach for practical design of these systems based on varying engine loads is presented. Fast and elitist non-dominated sorting genetic algorithm (NSGA-II) equipped with a novel local search was used for the design process, considering conflicting objectives of annual energy recovery and total cost of the system, and six design variables. An integrated power system, designed for a remote SAPS, was used to evaluate the design approach. The optimum power supply system was first designed using the commercial software Hybrid Optimization of Multiple Energy Resources (HOMER), based on power demand and global solar energy in the region. Heat recovery design was based on the outcome of HOMER for DG hourly load, considering different power scenarios. The proposed approach improves the annual heat recovery of the PV/DG/battery system by 4%, PV/battery by 1.7%, and stand-alone DG by 1.8% when compared with a conventional design based on nominal DG load. The results prove that the proposed approach is effective and that load calculations should be taken into account prior to designing HRSs for SAPS.

Understanding Ammonium Transport in Bioelectrochemical Systems towards its Recovery.

We report an integrated experimental and simulation study of ammonia recovery using microbial electrolysis cells (MECs). The transport of various species during the batch-mode operation of an MEC was examined experimentally and the results were used to validate the mathematical model for such an operation. It was found that, while the generated electrical current through the system tends to acidify (or basify) the anolyte (or catholyte), their effects are buffered by a cascade of chemical groups such as the NH3/NH4+ group, leading to relatively stable pH values in both anolyte and catholyte. The transport of NH4+ ions accounts for ~90% of the total current, thus quantitatively confirming that the NH4+ ions serve as effective proton shuttles during MEC operations. Analysis further indicated that, because of the Donnan equilibrium at cation exchange membrane-anolyte/catholyte interfaces, the Na+ ion in the anolyte actually facilitates the transport of NH4+ ions during the early stage of a batch cycle and they compete with the NH4+ ions weakly at later time. These insights, along with a new and simple method for predicting the strength of ammonia diffusion from the catholyte toward the anolyte, will help effective design and operation of bioeletrochemical system-based ammonia recovery systems.

A new correlation for predicting the minimum miscibility pressure regarding the enhanced oil recovery processes in the petroleum industry

ABSTRACTMiscible gas injection is a promising technique to enhance the oil recovery from petroleum reservoirs. Natural gas is usually injected because of consistency between the gas and reservoir fluid composition and accessibility of the injected fluid. In this work a new correlation is presented for accurate prediction of the required minimum miscibility pressure (MMP) for multicontact miscible displacement of reservoir petroleum by hydrocarbon gas injection. Accurate estimation of the MMP is required for optimal design of recovery systems and optimization of the production economics. It is shown that the presented correlation is very accurate and reliable for predicting the MMP over wide ranges of oil and gas compositions. Comparison of the suggested correlation with the most important existing correlations shows that the presented correlation outperforms the other alternatives both in accuracy and generality.

Hydrogen Production in the Anaerobic Treatment of Domestic-Grade Synthetic Wastewater

The aim of this study was to evaluate the potential of domestic wastewater for anaerobic hydrogen production. High-strength and ordinary-strength organic loadings of synthetic wastewater, i.e., real-time domestic wastewater with and without a mixture of food waste, were tested. During operation at a high strength loading, the initial pH was maintained at 7 and then gradually decreased, and a pH of 5–5.5 was observed as the best experimental condition. A pH of 5–5.5 was controlled during the operation at an ordinary-strength loading. Maximum hydrogen yields of 1.125 mol H2/mol glucose and 1.01 mol H2/mol glucose were observed during operation at high (48 g COD/L·day) and ordinary (3 g COD/L·day) strength loadings in terms of chemical oxygen demand (COD), respectively, with hydrogen contents of 42%–53%. The operating environment of the hydrogen production system was found to be very crucial because the metabolic pathway of the microorganism and production of intermediates were found to be dynamic with the controlled environment. Smaller COD removals of 30% and 26% were observed in high-strength and ordinarystrength loadings, respectively. Organic mass balance in terms of COD described the distribution of organics in the system via reactor byproducts. The findings of this study can be applied during the design of onsite domestic wastewater and energy recovery systems.

Cost Scaling of a Real-World Exhaust Waste Heat Recovery Thermoelectric Generator: A Deeper Dive

Cost is equally important to power density or efficiency for the adoption of waste heat recovery thermoelectric generators (TEG) in many transportation and industrial energy recovery applications. In many cases, the system design that minimizes cost (e.g., the $/W value) can be very different than the design that maximizes the system’s efficiency or power density, and it is important to understand the relationship between those designs to optimize TEG performance-cost compromises. Expanding on recent cost analysis work and using more detailed system modeling, an enhanced cost scaling analysis of a waste heat recovery TEG with more detailed, coupled treatment of the heat exchangers has been performed. In this analysis, the effect of the heat lost to the environment and updated relationships between the hot-side and cold-side conductances that maximize power output are considered. This coupled thermal and thermoelectric (TE) treatment of the exhaust waste heat recovery TEG yields modified cost scaling and design optimization equations, which are now strongly dependent on the heat leakage fraction, exhaust mass flow rate, and heat exchanger effectiveness. This work shows that heat exchanger costs most often dominate the overall TE system costs, that it is extremely difficult to escape this regime, and in order to achieve TE system costs of $1/W it is necessary to achieve heat exchanger costs of $1/(W/K). Minimum TE system costs per watt generally coincide with maximum power points, but preferred TE design regimes are identified where there is little cost penalty for moving into regions of higher efficiency and slightly lower power outputs. These regimes are closely tied to previously identified low cost design regimes. This work shows that the optimum fill factor Fopt minimizing system costs decreases as heat losses increase, and increases as exhaust mass flow rate and heat exchanger effectiveness increase. These findings have profound implications on the design and operation of various TE waste heat recovery systems. This work highlights the importance of heat exchanger costs on the overall TEG system costs, quantifies the possible TEG performance-cost domain space based on heat exchanger effects, and provides a focus for future system research and development efforts.

Closed-loop fertility cycle: Realizing sustainability in sanitation and agricultural production through the design and implementation of nutrient recovery systems for human urine

As a solution to the drawbacks of modern sanitation systems and to shift towards a recycling society, source separation of human wastes coupled with resource recovery could be seen as a potential solution. In this research, microwave activated coconut shells were utilized to recover urea from human urine. Batch adsorption studies were carried out to determine the effect of initial concentration, adsorption temperature, microwave output power and irradiation time on the urea uptake capacity of the tailored activated carbon. The shells pretreated with microwave irradiation of 360 W, for 15 min (MACCS-360W-15) shown to be promising adsorbents with BET surface area >1000 m2 g−1. The sorption data were tested against different isotherm models and found to closely follow Langmuir isotherm with a maximum monolayer sorption capacity of 312 mg g−1. Kinetic data over temperature range of 30–60 °C was found to closely follow pseudo-first-order at all adsorbate concentrations. Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) indicated the spontaneity and physical nature of the sorption; sorption experiments indicated a urea recovery of ∼95% from urine. Finally, the application of urea adsorbed carbon as a soil conditioner in field trials resulted in significant improvement in the number of seed germination and plant biomass (132%) with a substantial increase in the soil nitrogen and cation exchange capacity. Results also indicated that nearly all the urea was desorbed within the soil during irrigation becoming readily available to the plants. This study demonstrates a closed-loop sanitation cycle that channels nutrients from human beings back to agricultural fields.

Accurate Prediction of Two-Phase Behavior of the Mixtures of Carbon Dioxide and Different Perfluoroalkane Compounds: Comparison of the Presented Neuro-Fuzzy Model with Advanced Soft-SAFT Molecular Model

An advanced adaptive neuro-fuzzy inference system (ANFIS) has been proposed for accurate prediction of the two-phase behavior of CO2/perfluoroalkane mixtures regarding the design of CO2 sequestration and recovery systems. The most important fluoroalkane solvents such as linear (perfluoro-n-octane), cyclic (perfluorodecalin and perfluoromethylcyclohexane), and aromatic compounds (perfluorobenzene and perfluorotoluene) are considered in this study. The proposed ANFIS model can be used for accurate predictions of CO2/perfluoroalkane phase behavior over wide ranges of temperatures and pressures and is a useful tool for the design of environmental friendly CO2 recovery processes. The proposed neuro-fuzzy model outperforms the soft-SAFT (Statistical Associating Fluid Theory) and polar soft-SAFT molecular models both in accuracy and in generality.

Isobaric Heat Capacity of Boric Acid Solution

The isobaric heat capacities of boric acid solution are crucial for the design of boron recovery systems in nuclear power plants. In this work, the isobaric heat capacities of boric acid solution containing 0.648 mol/kg and 3.700 mol/kg 10B from T/K = (303.16 to 394.25) and up to 5.11 MPa are measured with a flow calorimeter. The expanded uncertainties in temperature, pressure, and isobaric heat capacity were ± 0.02 K, ± 3.20 kPa, and ± 0.0098, respectively. The isobaric heat capacity of boric acid solution decreases when the 10B concentration and pressure increase, and increases as the temperature increases. A correlation equation is presented for the isobaric heat capacities of boric acid solution, the absolute relative deviation between the correlation and experiment is less than 0.6 %.

Geophysical and Hydrochemical Identification of Flow Paths with Implications for Water Quality at an ARR Site

AbstractTwo key challenges regarding the design and operation of aquifer recharge and recovery (ARR) systems are evaluating aquifer heterogeneity and understanding hydrochemical interactions. Uncertainty in this respect can impact the volume of recoverable water and the improvement in water quality. The objective of this research is to leverage the advantages of geophysical measurements and hydrochemical sampling to reveal the properties of an ARR site to inform current ARR system operations and future design decisions. Electrical resistivity tomography was used to image the subsurface below two key infiltration/extraction areas of an ARR site in Colorado, USA. Hydrochemical measurements on transects intersecting the geophysical measurements resolved bulk parameters (i.e., total organic carbon, nitrate, and major cations and anions) and trace organic chemicals (e.g., pharmaceuticals, personal care products). Conservative tracers were also used to estimate degrees of mixing and water travel times and to better assess the performance of the ARR site regarding water quality changes and water recovery. The electrical resistivity measurements suggest that certain areas of the infiltration basins have hydraulic connections to the extraction wells through preferential flow paths, compared with other infiltration basins that are separated by fine‐grained materials from their respective extraction wells. The hydrochemical results indicate that consistent improvements in water quality can be achieved in these preferential flow paths within relatively short travel times (<5 d) at this ARR site.

Intelligent design of waste heat recovery systems using thermoelectric generators and optimization tools

Optimal design of thermal systems that effectively use energy resources is one of the foremost challenges that researchers almost confront. Until now, several researches have been made to enhance the performance of major thermal systems. In this investigation, the authors try to make a conceptual design to maximize the electricity demand of Damavand power plant as the biggest thermal system in Middle East sited in Iran. The idea of designing is laid behind applying a number of thermoelectric modules within the condenser in order to recover the waste heat of the thermal systems. Besides, the authors have developed some intelligent tools to elaborate on the performance of their proposed model. Firstly, an artificial neural network has been utilized to estimate the potential power generation of the thermoelectric modules. At the second step, computational fluid dynamic solver, FLUENT is used to determine the variation of the temperature through the length of the thermoelectric module assembly. Based on the gained results, an intelligent multi-objective optimization algorithm called Pareto based mutable smart bee is developed to optimize the properties of the thermoelectric component.

Heat Recovery from Urban Wastewater: Analysis of the Variability of Flow Rate and Temperature in the Sewer of Bologna, Italy

Domestic wastewater were characterize by higher temperature because inside the buildings 60% of the water was heated by showers, tubs, sinks, dishwashers and clothes washers. This heat, nowadays lost into the sewer system, could be make the wastewater a carrier of heat. This heat can be reused, for the production of clean and regenerable thermal energy, through heat exchangers and heat pumps, for the conditioning and heating of buildings. There are several options to recover this heat embedded in the wastewater: within houses (small scale applications), from the sewer (medium scale applications), or at wastewater treatment plants (large scale applications). In this paper results of a monitoring period of six months in the sewer system of Bologna (Italy) have showed the variability of wastewater flow rate and temperature and their daily trend. The trend of the flow (ratio between the hourly flow and the medium daily flow) for the generic day is linked with the population, with coefficients that are in the range of 0.25 - 1.50 with peak values ranging between 1.30 and 1.50; the trend of the sewage temperature for the generic day has coefficients in a range between 0.90 and 1.05, and it is independent by the population. The amount of thermal energy that can be obtained from wastewater and the optimally design of heat recovery systems depend on knowledge of the flow rate and wastewater temperature. This study can be useful to map the potential thermal energy of sewage systems and to design the heat recovery systems.

Heat recovery from urban wastewater: Analysis of the variability of flow rate and temperature

Heating, cooling and domestic hot water supply represent the biggest share of energy demands in residential buildings. Usually for these demands fossil fuels are used, however in the last years international energy policies recommended the use of less valuable energy. This paper investigated the possibility to use sewer water as alternative source of heat. Wastewater deriving from buildings is characterized by higher temperature than clean water because inside the buildings 60% of water is heated. The amount of energy that can be obtained from wastewater and the optimal design of heat recovery systems depend on knowledge of the flow rate and the temperature. In this paper the sewer system in Bologna (Italy) is taken as case study. Results of a monitoring period have showed the variability of wastewater flow rate and temperature and their correlation. Data analysis allowed to identify the daily trend for the wastewater flow, whose coefficients in relation to the average flow (where average flow=1) vary between 0.25 and 1.50, and for the wastewater temperature in which the coefficients ranging from 0.90 to 1.05. This study can be useful to map the potential thermal energy of sewage systems and to design of heat recovery system.

Design and analysis of Kinetic Energy Recovery Systems in Bicycles

Design and analysis of Kinetic Energy Recovery Systems in Bicycles