Minimum Energy Requirements Research Articles

Development of a Hammer Mill with Double Sieving Screens

A hammer mill with double sieving device was designed and fabricated from locally available materials for grinding grains and other agricultural products. The conceptual design was based on the principle of design by analysis. The test carried out on the machine showed that the crushing capacity of the machine is 51.5 Kh/hr. The moisture content, machine speed and the interaction between them had significant effect on the milling power and specific energy requirement at 5 % level of significance. Milling power and specific energy requirement of the machine increased with increase in moisture content. The maximum crushing efficiency of 79.3 %, minimum milling power and specific energy requirement of 0.09 Kw and 3.04 Kwh/mg respectively were obtained at moisture content of 8 % (wb) and machine speed of 2000 rpm. Regression models that could be used to express the relationship existing between the hammer mill performance indices, product moisture content and machine speed were established. The machine has dual purpose for either electric motor or petrol engine.

Development of a Hammer Mill with Double Sieving Screens

A hammer mill with double sieving device was designed and fabricated from locally available materials for grinding grains and other agricultural products. The conceptual design was based on the principle of design by analysis. The test carried out on the machine showed that the crushing capacity of the machine is 51.5 Kh/hr. The moisture content, machine speed and the interaction between them had significant effect on the milling power and specific energy requirement at 5 % level of significance. Milling power and specific energy requirement of the machine increased with increase in moisture content. The maximum crushing efficiency of 79.3 %, minimum milling power and specific energy requirement of 0.09 Kw and 3.04 Kwh/mg respectively were obtained at moisture content of 8 % (wb) and machine speed of 2000 rpm. Regression models that could be used to express the relationship existing between the hammer mill performance indices, product moisture content and machine speed were established. The machine has dual purpose for either electric motor or petrol engine.

Insights from Mathematical Modelling into Process Control of Oxygen Transfer in Batch Stirred Tank Bioreactors for Reducing Energy Requirement

Significant energy savings can be made in aerobic stirred tank batch bioreactors by the manipulation of agitator power (Pag) and air flowrate per unit working volume (vvm). Control is often implemented to maintain the oxygen concentration in the bioreaction liquid (COL) at a constant value. This work used model simulations to show that controlling the Pag and vvm continuously over time, such that it is operated at or near the impeller flooding constraint results in the minimum energy requirement for oxygen transfer (strategy Cmin); however, this might prove impractical to control and operate in practice. As an alternative, the work shows that dividing the bioreaction time into a small number of constant Pag time segments (5–10), where a PID controller is used to control vvm to maintain COL constant in each segment, can achieve much of the energy saving that is associated with Cmin. During each time segment, vvm is increased and a sudden decrease in COL is used to detect the onset of flooding, after which there is a step increase in Pag. This sequence of Pag step increases continues until the bioreaction is completed. This practical control approach was shown to save most of the energy that is associated with Cmin.

Determining the minimum energy requirement of an LNG process: New insights into the impact of the vapour liquid equilibrium

The paper provides a detailed first principles analysis of a process of liquefaction of natural gas in which the refrigeration compressors are driven by electric motors. The aim is to determine and understand the impact of the operation of the refrigeration cycles on the power consumption of the process. This study gives insights into the relationship between the discharge pressure of the compressors and the thermodynamic performance of the refrigeration cycles. By doing this, the findings of this research highlight the importance of the vapour liquid equilibrium. The results show that, for a given production rate, there is a minimum in the power consumption when the discharge pressures are close to the refrigerant saturation points. The paper provides a discussion and analysis of the advantages and disadvantages of operating at such points.

Novel Amine-Functionalized Magnesium Oxide Adsorbents for CO2 Capture at Ambient Conditions

• MgO was synthesized using three facile methods • MgO was functionalized with different amines (APTES, DETA and PEI) • APTES-MgO and DETA-MgO adsorbed more than 2 and 1.5 times CO 2 relative to bare MgO • APTES-MgO preserved its full adsorption capacity even after 6 regeneration cycles • Regeneration is carried out using N 2 under mild conditions (30 min, 120 °C, 1 atm) In this study, we synthesized novel magnesium oxide-based adsorbents and utilized them for CO 2 capture at ambient conditions (1 atm, 30 °C). Magnesium oxide (MgO) was synthesized using a facile sol-gel technique starting from magnesium nitrate and ammonium hydroxide, sodium hydroxide or oxalic acid. MgO adsorbent synthesized in the presence of ammonium hydroxide (labeled as MgO-A) showed the highest surface area (350 m 2 /g), which has been correlated with the highest CO 2 adsorption capacity (30 mg/g) relative to those synthesized in the presence of sodium hydroxide (MgO-N) or oxalic acid (MgO-O). The characterization of the MgO samples (MgO-A, MgO-N and MgO-O) using XRD, FTIR, SEM, BET, and elemental analysis revealed that the synthesis route has a significant impact not only on surface area but also on the crystallinity, morphology, and textural properties (surface area, porosity and pore size distribution) of these MgO adsorbents. Nonetheless, the key novelty of the work reported herein is the functionalization of MgO with 3-aminopropyl-triethoxysilane (APTES), diethylenetriamine (DETA) and polyethylenimine (PEI) and their utilization for CO 2 capture at ambient conditions. The functionalization of MgO-A with the three amines significantly altered its characteristics (i.e., crystallinity, morphology, and textural properties). More importantly, the functionalization of MgO-A with APTES and DETA resulted in an increase in CO 2 adsorption from 30 (in the case of the unmodified MgO-A) to 65 and 47.6 mg/g, respectively. These values correspond, respectively, to 0.81 and 1.13 mol CO 2 captured/mol amine loaded on MgO-A. However, the functionalization of MgO-A with the polymeric amine (PEI) caused a significant reduction in the adsorbent surface area, leading to a decrease in CO 2 adsorption. Regeneration studies (using APTES-MgO-A as an example) demonstrated that contacting the spent adsorbent with N 2 gas at 120 °C for a short time can fully restore its original adsorption capacity, suggesting the potential commercial use of APTES-MgO-A for CO 2 capture with a minimal energy requirement.

Thermodynamic modelling of synthetic communities predicts minimum free energy requirements for sulfate reduction and methanogenesis.

Microbial communities are complex dynamical systems harbouring many species interacting together to implement higher-level functions. Among these higher-level functions, conversion of organic matter into simpler building blocks by microbial communities underpins biogeochemical cycles and animal and plant nutrition, and is exploited in biotechnology. A prerequisite to predicting the dynamics and stability of community-mediated metabolic conversions is the development and calibration of appropriate mathematical models. Here, we present a generic, extendable thermodynamic model for community dynamics and calibrate a key parameter of this thermodynamic model, the minimum energy requirement associated with growth-supporting metabolic pathways, using experimental population dynamics data from synthetic communities composed of a sulfate reducer and two methanogens. Our findings show that accounting for thermodynamics is necessary in capturing the experimental population dynamics of these synthetic communities that feature relevant species using low energy growth pathways. Furthermore, they provide the first estimates for minimum energy requirements of methanogenesis (in the range of −30 kJ mol−1) and elaborate on previous estimates of lactate fermentation by sulfate reducers (in the range of −30 to −17 kJ mol−1 depending on the culture conditions). The open-source nature of the developed model and demonstration of its use for estimating a key thermodynamic parameter should facilitate further thermodynamic modelling of microbial communities.

Insights into Potent Therapeutical Antileukemic Agent L-glutaminase Enzyme Under Solid-state Fermentation: A Review.

To review the applications and production studies of reported antileukemic drug L-glutaminase under Solid-state Fermentation (SSF). An amidohydrolase that gained economic importance because of its wide range of applications in the pharmaceutical industry, as well as the food industry, is L-glutaminase. The medical applications utilized it as an anti-tumor agent as well as an antiretroviral agent. L-glutaminase is employed in the food industry as an acrylamide degradation agent, as a flavor enhancer and for the synthesis of theanine. Another application includes its use in hybridoma technology as a biosensing agent. Because of its diverse applications, scientists are now focusing on enhancing the production and optimization of L-glutaminase from various sources by both Solid-state Fermentation (SSF) and submerged fermentation studies. Of both types of fermentation processes, SSF has gained importance because of its minimal cost and energy requirement. L-glutaminase can be produced by SSF from both bacteria and fungi. Single-factor studies, as well as multi-level optimization studies, were employed to enhance L-glutaminase production. It was concluded that L-glutaminase activity achieved by SSF was 1690 U/g using wheat bran and Bengal gram husk by applying feed-forward artificial neural network and genetic algorithm. The highest L-glutaminase activity achieved under SSF was 3300 U/gds from Bacillus sp., by mixture design. Purification and kinetics studies were also reported to find the molecular weight as well as the stability of L-glutaminase. The current review is focused on the production of L-glutaminase by SSF from both bacteria and fungi. It was concluded from reported literature that optimization studies enhanced L-glutaminase production. Researchers have also confirmed antileukemic and anti-tumor properties of the purified L-glutaminase on various cell lines.

Comparative Performance of Recent Advanced Optimization Algorithms for Minimum Energy Requirement Solutions in Water Pump Switching Network

The present work explores the qualitative and quantitative comparative analysis of nine recently developed meta-heuristic algorithms for the optimization of water pump switching problem. Heat transfer search algorithm, Water wave optimization, Ant lion optimizer, Symbiotic organisms search algorithm, Artificial Bee Colony algorithm, Cuckoo search algorithm, Passing vehicle search, Biogeography based optimization, and Sine–cosine algorithm are considered in the present work. A statistical analysis of the results are carried out to identify the statistical significant between the results of comparative algorithms. The effect of various constraint handling techniques on the performance of the algorithms are also identify and presented. A set of the alternative solutions for the minimum energy requirement are obtained for the best algorithm and presented. The solutions for the different number of pump in operation for best performing algorithm are also obtained and presented. Finally, the convergence of the considered algorithm in obtaining the minimum energy solutions are presented and discussed.

A Novel Approach to Minimize Energy Requirements and Maximize Biomass Utilization of the Sugarcane Harvesting System in Sri Lanka

Sugarcane harvesting requires a significant amount of energy and time to manage dry leaves after the harvesting process. Therefore, the objective of this study was to minimize the energy requirement to process the cane and dry leaves’ harvesting (CDLH) for sugarcane while, at the same time, maximizing sugar production from cane and energy from dry leaves in Sri Lanka. The CDLH was conceptualized using a novel approach to optimize sugarcane harvesting to maximize biomass supply for energy production while reducing supply chain sugar-loss. The CDLH was investigated for manual harvesting capacity, energy consumption, sugar loss, and biomass energy potential. It was observed that CDLH consumed higher energy compared to the present practices of harvesting. However, the energy used for fieldwork was reduced because of the shifting of cane chopping and cleaning from the field to the factory. Low bulk density of the harvested cane of the CDLH system had a higher energy requirement in transportation. Comparatively, CDLH showed higher biomass energy potential and less sugar loss. High energy potential increases the energy potential to consumption ratio compared to the existing method. Therefore, the theoretical evaluation showed that the CDLH system can produce more than 20 kg of sugar and 879 MJ of electricity when processing 1 t of sugarcane.

Hybridized Intelligent Home Renewable Energy Management System for Smart Grids

The incorporation of renewable energies and power storage at distribution facilities are one of the important features in the smart grid. In this paper, a hybridized intelligent home renewable energy management system (HIHREM) that combines solar energy and energy storage services with the smart home is planned based on the demand response and time of consumption pricing is applied to programs that offer discounts to consumers that reduce their energy consumption during high demand periods. The system is designed and handled with minimal energy requirements at home through installation of renewable energy, preparation, and arrangement of power stream during peak and off-peak periods. The best energy utilization of residential buildings with various overlapping purposes is one of the most difficult issues correlated with the implementation of intelligent micro-network systems. A major component of the smart grid, the domestic energy control system (HIHREM) provides many benefits, such as power bill reductions, reduction in wind generation, and demand compliance. This showed that the proposed energy scheduling method minimizes the energy consumption by 48% and maximizes the renewable energy consumed at the rate 65% of the total energy generated. A new model for smart homes with renewable energies is introduced in this report. The proposed HIHREM method achieves high performance and reduces cost-utility.

Flow sculpting enabled anaerobic digester for energy recovery from low-solid content waste

Traditionally, energy recovery from low-solid-content wastes occurs in Continuously Stirred Tank Reactors, whereas Plug Flow Reactors (PFR) are used to treat high-solid-content wastes. In comparison, this study uses a special configuration of anaerobic PFR (AnPFR), consisting of a coiled tubular structure, for energy recovery from a mixture of Food Waste and Wastewater, fed at a loading rate of 3 gVS.L−1.d−1 and a solids content of 2.5%. The AnPFR was upgraded into a Flow Sculpting enabled Anaerobic Digester (FSAD), an innovative plug flow design relying on flow sculpting via a sequence of pillars to provide passive mixing. The purpose of the FSAD design is to optimize operational performance while maintaining minimum mixing energy requirements. Computational fluid dynamics simulations revealed that pillars induce local vorticity in the fluid and contribute to the inertial deformation of the flow to enhance mixing. Coherently, experimental results proved that upgrading the AnPFR to FSAD resulted in a better stability (VFA dropped from 4433 to 2034 mg L−1) and a higher efficiency (removal efficiencies of COD and volatile solids increased from 75% to 77%–88% and 91%, respectively). Equally important, the methane yield, indicative of energy generation potential, increased from 181 L kg VSfed−1 to 291 L kg VSfed−1.

Nature inspired evolutionary approaches for robot navigation: Survey

Autonomous robot navigation (ARN) requires intelligent systems equipped with human capabilities to achieve controlled motion among flats, ridgesor obstacles while avoiding collision in known or partially unknown environment with safety of equipment and manpower involved. Its objective is to generate optimal collision free path from initial to target location within minimal time and energy requirement. There are various navigational approaches (classical, heuristics, hybrid or nature inspired) and its choice depends on type of environment (static or dynamic) and application area. Nature inspired evolutionary (NIE) approaches is an emerging paradigm to develop robust and dynamic problems to address non-linear or multi-objective problemsin dynamic environment. This work is an attempt to review recently developed NIE approaches based on different biological groups for application in field of robot path planning (RPP).

Techno-economic analysis to identify key innovations required for electrochemical oxidation as point-of-use treatment systems

Electrocatalytic-driven processes show promise for water purification, including abating persistent organic pollutants via advanced oxidation processes. Since the early 90s, thousands of research articles have systematically explored degradation of organic pollutants in batch systems and synthetic waters. Despite these research efforts, commercial treatment units for water treatment in the field are barely reported. Translation of scientific and technological advances into the market place requires identification of niche applications. Here we consider point-of-use devices. Techno-economic analysis (TEA) of electrochemical oxidation was benchmarked against commercially-available competition in the water purification sector, specifically carbon block adsorption devices. Results identified electrode material as one of the driving capital costs. Decreasing boron-doped diamond cost by ten-fold or exploring alternative emergent materials such as Ti4O7 can enhance competitiveness of electrochemical devices in the market. Meanwhile, the first-order rate constant was identified as one of the most relevant parameters because it affects operational expenses. Strategies to enhance target pollutant selectivity in real water matrices is a research need to ensure efficient water purification with minimum electrical energy requirements. TEA showed a promising scenario for electrocatalytic devices to overcome commercially-available technologies. This initial TEA identified key challenges and research needs to overcome cost limitations and to beat traditional systems in reliability in the road map towards market implementation.

Overheating risk of a typical Norwegian residential building retrofitted to higher energy standards under future climate conditions

Heat waves had attacked Norway in 2018 and 2019. Residents in Norway experienced a very uncomfortable indoor environment in the summer of 2018 and 2019. Few publications on the overheating risk of a typical Norwegian residential building under future climate change conditions were found. The typical Norwegian residential building retrofitted according to the minimum Norwegian energy requirements in the Norwegian Building Act of 2010 (Pbl2010/TEK17) and the international EnerPHit Standard was modelled in this study. Overheating risk of the typical residential building was simulated by Energy Plus engine via Ladybug and Honeybee plugins based on the Grasshopper. Overheating hours of the studied rooms under present-day, the 2050s and the 2080s weather conditions were shown. Too good airtightness does increase the overheating risk of the building when retrofitted to higher energy standards. It was found in this study that better insulation does reduce the overheating hours of the bedrooms slightly. This may be caused by low g-value of the windows based on recommendation according to the EnerPHit Standard. Overheating should be paid more attention in term of the expected future climate conditions. These results can provide some references to the buildings retrofitted to high-performance buildings.

Utilizing the Combined Power of Theory and Experiment to Understand Molecular Structure – Solid-State and Gas-Phase Investigation of Morpholine Borane

The molecular structure of morpholine borane complex has been studied in the solid state and gas phase using single-crystal X-ray diffraction, gas electron diffraction, and computational methods. Despite both the solid-state and gas-phase structures adopting the same conformation, a definite decrease in the B–N bond length of the solid-state structure was observed. Other structural variations in the different phases are presented and discussed. To explore the hydrogen storage potential of morpholine borane, the potential energy surface for the uncatalyzed and BH3-catalyzed pathways, as well as the thermochemistry for the hydrogen release reaction, were investigated using accurate quantum chemical methods. It was observed that both the catalyzed and uncatalyzed dehydrogenation pathways are favourable, with a barrier lower than the B–N bond dissociation energy, thus indicating a strong propensity for the complex to release a hydrogen molecule rather than dissociate along the B–N bond axis. A minimal energy requirement for the dehydrogenation reaction has been shown. The reaction is close to thermoneutral as demonstrated by the calculated dehydrogenation reaction energies, thus implying that this complex could demonstrate potential for future on-board hydrogen generation.

Mechanical Behavior of Apricot and Cherry Pits under Compression Loading

This study was conducted to investigate the mechanical behavior of apricot and cherry pits under compression loading along the three axial dimensions of the pits. The mechanical behavior was expressed in terms of force required to rupture of the pit, deformation at rupture point, deformation ratio (strain), energy absorbed and toughness. Also; masses and geometrical properties (axial dimensions, geometric mean diameter, sphericity and volume) of these pits were determined. These properties are necessary to design of cracking machines and knowledge amount of force and energy requirements for cracking operation. All experiments were carried out at moisture content of 9.81 and 12.92 %, (d.b.) for apricot and cherry pits, resp. The results showed that; the highest values of rupture force, deformation and energy required to crack the apricot pit were at loading position through the length axis, while; the lowest values were through the width axis, whereas; the highest values of rupture force, deformation and energy required to crack the cherry pit were at loading position through the thickness axis, while; the lowest values were through the width axis. In conclusion; the results obtained of the mechanical behavior of apricot and cherry pits indicated that; the compression through the width axis can be recommended for cracking process with minimum force and energy requirements.

Total Site Heat Integration Considering Optimum Pressure Drops

In this study, a new methodology is developed for Total Site Minimum Energy Requirement (MER) targeting, in which optimum stream pressure drops ((Ps) are considered for each individual process. To validate the accuracy of the methodology, two Total Site (TS) systems comprising processes A and B and processes C and D are selected and evaluated using two different approaches; I) considering streams’ assumed heat transfer coefficient (conventional method) and II) considering streams’ allowable (Ps. In the second approach, the possibility of pumps/compressors replacement is first investigated for each individual process, through exploring a 3-way trade-off between energy consumption, area requirement and hydraulic system. The resulting data are then used to construct a Total Site profiles (TSPs) for MER targeting. These profiles depict that the hot and cold utility values, when (Ps are optimized, are much less than those obtained in conventional method using assumed coefficients. Moreover, the TS energy targets that are estimated in this method are more realistic and compatible with the results of detailed design stage.

Simulation and Optimization of a Multitubular Reactor Train for Acrylic Acid Production

Acrylic acid is a major chemical intermediate used in the production of acrylate esters. The most popular route for the manufacture of ester grade acrylic acid is via propylene oxidation. In a typical process, chemical grade propylene is contacted with steam and air in a catalytic reactor train to produce the target compound with carbon dioxide and acetic acid as the major byproducts. Various catalytic systems exist, offering both high selectivity and conversion, and operation can be based on different reactor types and configurations. The highly exothermic nature of the reactions necessitates efficient removal of the reaction heat. In this work the rigorous simulation and optimization of a two-step multitubular oxidation reactor system for the production of acrylic acid was undertaken on the ASPEN Plus platform, with particular emphasis on minimizing energy requirements. In developing the model, several critical parameters were identified for proper representation of the reaction system in the sequential simulation platform. These included adjustments to the properties of molten salt thermal fluids for accurate determination of flow characteristics on the shell side, comprehensive and interactively coupled calculation of the overall heat transfer coefficient and the use of inert pre-heating and oxidation pre-heating zones at the front end on the propylene oxidation reactor tubes. The resultant model was successfully used to optimize for acrylic acid production with minimum energy input, demonstrating the applicability of digital twins for process analysis.

On the economic optimisation of ethanol production using corn stover feedstock: A new kinetic model, a green recovery system and a de-acetylation step

This paper considers the economic assessment and optimisation of a bioethanol production process using corn stover (CS) as the feedstock. This includes a comparison between the use of batch and fed-batch reactors with and without deacetylation. As a basis of the study, a kinetic model describing the co-fermentation of substrates producing ethanol using Zymomonas mobilis is proposed. The model extends work available in the literature to include acetate inhibition. The reported optimisation studies include realistic variations in feedstock quality, deacetylation, a mechanical pre-treatment stage and a green recovery system: extractive distillation with vapour compression. Results indicate that the use of fed-batch reactors using a deacetylation stage achieves an ethanol yield of between 267 and 334 L/ton dry basis of CS and economic potential of between 0.4 and 5.5 MM USD/year higher than the use of batch reactors. This also has the lowest energy requirements in the product recovery stage (3.2–3.4 MJ-fuel/kg-ethanol or 1.6–1.8 MJ/kg-ethanol). Omitting de-acetylation prior to hydrolysis/co-fermentation increases the minimum ethanol selling price and energy requirements by ~3–14% and ~8–30%, respectively.

Combined exergy analysis, energy integration and optimization of syngas and ammonia production plants: A cogeneration and syngas purification perspective

Abstract Modern ammonia production plants are equipped with efficient energy integration networks able to recover an important fraction of the waste heat exergy available throughout the chemical system. However, in order to drive the endothermic reforming reactions at high temperature, as well as the syngas purification and compression processes, additional energy must be supplied by costly non-renewable resources. Moreover, the choice of the carbon capture unit, based on either physical or chemical absorption systems, drastically affects the way in which the waste heat recovery must be performed, and whether one or more energy technologies should or not be integrated (e.g. heat pump). Meanwhile, the selection among various energy resources, e.g. the import of electricity over the autonomous combined heat and power production (CHP), strongly depends on the ratio between the prices of electricity and fuels consumed, as well as on the extent of the energy integration. Accordingly, a simple trial and error approach falls short in efficiently determining the most suitable operating conditions that enable the production plant to run under the minimum operating cost. Thus, by using a systematic methodology, the most suitable utility systems (cooling, refrigeration, and cogeneration) that satisfy the minimum energy requirement (MER) with the lowest energy consumption and operating cost, are selected. Consequently, the conventional plant efficiency is increased about 10% by using a mixed operating mode or autonomous operating mode with combined cycle. Furthermore, reduced cooling (23%) and heating (51%) requirements are expected when physical solvents are used. The lowest exergy consumption corresponds to mixed operating mode by using a physical absorption unit (27.76 GJ/tNH3). Finally, it is found that exergy efficiency drops 24% when the irreversibility in the upstream steps of feedstock obtainment are considered.