Decrease In Specific Energy Consumption Research Articles

Capacitive deionization exploiting La-based LDH composite electrode toward energy efficient and selective removal of phosphate

Capacitive deionization (CDI) is a promising technology for removing phosphate from wastewater. Its practical implementation is however hindered by the constraints on the electrode materials. To boost the adsorption capacity, phosphate selectivity, and cost-effectiveness of the electrode, this study proposed a composite electrode blending Lanthanum-based layered double hydroxide (Ca-La LDH) and activated carbon (AC). It capitalizes on the synergistic effects of electric double layer capacitance (EDLC) of AC and the diffusion-controlled charge storage (pseudocapacitive behavior) of Ca-La LDH. By optimizing the mass ratios of the constituents and the electrode material loading capacities, the composite electrode AC/Ca-La LDH-5020 was developed, which contains 20 mg of 50 wt% Ca-La LDH. This composition achieved a remarkable phosphate adsorption capacity of 34.8 mg P /g and a low energy consumption of 0.0051 kWh/g P in constant voltage (CV) mode. It represented a 241 % increase in adsorption capacity (mg P/g) and 71 % decrease in specific energy consumption (kWh/g P) compared to the electrode made solely of AC. Particularly the moderate inclusion of Lanthanum contributes to its cost-effectiveness. Moreover, further studies extensively examined the impacts of electrical driving force, including applied voltage in constant voltage (CV) mode and applied current in constant current (CC) mode, on the phosphate removal efficiency. The composite electrode remained stable performance with the presence of the high content of coexisting anions (e.g.，Cl−，SO42−, HCO3−, NO3−), obtaining high selectivity coefficient of phosphate over other anions. This study highlighted the practical potential of AC/Ca-La LDH composite electrode for advancing CDI technology for phosphate removal in an efficient, energy-saving and cost-effective manner.

Fouling Reduction and Thermal Efficiency Enhancement in Membrane Distillation Using a Bilayer-Fluorinated Alkyl Silane-Carbon Nanotube Membrane.

In this study, we report the robust hydrophobicity, lower fouling propensity, and high thermal efficiency of the 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FAS)-coated, carbon nanotube-immobilized membrane (CNIM) when applied to desalination via membrane distillation. Referred to as FAS-CNIM, the membrane was developed through a process that combined the drop-casting of nanotubes flowed by a dip coating of the FAS layer. The membranes were tested for porosity, surface morphology, thermal stability, contact angle, and flux. The static contact angle of the FAS-CNIM was 153 ± 1°, and the modified membrane showed enhancement in water flux by 18% compared to the base PTFE membrane. The flux was tested at different operating conditions and the fouling behavior was investigated under extreme conditions using a CaCO3 as well as a mixture of CaCO3 and CaSO4 solution. The FAS-CNIM showed significantly lower fouling than plain PTFE or the CNIM; the relative flux reduction was 34.4% and 37.6% lower than the control for the CaCO3 and CaCO3/CaSO4 mixed salt solution. The FAS-CNIM exhibited a notable decrease in specific energy consumption (SEC). Specifically, the SEC for the FAS-CNIM measured 311 kwh/m3 compared to 330.5 kwh/m3 for the CNIM and 354 kwh/m3 for PTFE using a mixture of CaCO3/CaSO4. This investigation underscores the significant contribution of the carbon nanotubes' (CNTs) intermediate layer in creating a durable superhydrophobic membrane, highlighting the potential of utilizing carbon nanotubes for tailored interface engineering to tackle fouling for salt mixtures. The innovative design of a superhydrophobic membrane has the potential to alleviate wetting issues resulting from low surface energy contaminants present in the feed of membrane distillation processes.

Experimental study on the damage and fracture mechanism of deep coal beds impacted by water jets at different temperatures

The development of abundant deep coalbed methane (CBM) resources has attracted significant attention due to their commercial development potential. However, developing such resources presents many challenges due to their generation in complex geological environments governed by high temperatures and stresses. Thus, this work investigated coal fragmentation using water jets at different reservoir temperatures. The results show that compared with room temperature conditions, under water jet impact, the threshold fracturing pressure of high-temperature coal is lower, the rock-breaking volume is larger, and thermal stress leads to intensified dynamic damage. Indeed, when the temperature exceeds 75.0 °C, the coal undergoes volume fragmentation, and the depth of water jet-breaking coal increases by 81.0 %, while the specific energy consumption decreases by 52.4 %. The threshold fracturing pressure rapidly decreases as temperature increases and stabilizes, presenting an exponential trend. When the temperature exceeds 75.0 °C, the threshold fracturing pressure is maintained at around 10.0 MPa and no longer decreases with the temperature increase. In addition, three-dimensional (3D) damage field analysis highlights that the coal breaking mode shifts from a “water wedge” dominated mode to a “water wedge-thermal fracture” mode as temperature increases. Finally, the dynamic fracturing mechanism of coal under high-temperature conditions of water jet impact has been revealed. The research results of this paper provide a theoretical basis for the hydraulic permeability enhancement design of deep coal seams.

The Effect of Bulk Modification of the MF-4SK Membrane with Phosphorylated Hyper-Branched Dendrimer Bolthorn H20 on the Mechanisms of Electroconvection/Dissociation of Water and Specific Selectivity to Divalent Ions

This study focuses on the modification of ion-exchange membranes by incorporating a phosphorylated dendrimer into sulfonated polytetrafluoroethylene membranes to enhance the specific selectivity between mono-/divalent ions, using the Ca2+/Na+ pair as an example. This research employs mechanical, physicochemical, and electrochemical analyses to explore the effects of P-H20 incorporation on membrane properties. Bulk modification significantly increases membrane selectivity towards calcium ions (the specific permselectivity coefficient rises from 1.5 to 7.2), while maintaining the same level of the limiting current density. Other findings indicate that bulk modification significantly changes the transport-channel structure of the membrane and alters the mechanism of over-limiting mass transfer. The over-limiting current for the pristine membrane is mainly due to non-equilibrium electroconvection, while modified membranes actively participate in the water-splitting reaction, leading to the suppression of the electroconvection. Despite this drawback, the decrease of the over-limiting potential drop results in a decrease in specific energy consumption from 0.11 to 0.07 kWh/mol. In the underlimiting current mode, the specific energy consumption for all studied membranes remains within the same limits of 0.02–0.03 kWh/mol.

Thermodynamic analysis of cold energy recovery from LNG regasification

The LNG market connects numerous export and import markets, and the global LNG trade has been growing steadily. Despite the availability of multiple alternatives, only a small fraction of this global cryogenic potential is currently utilized, and a negligible number of regasification terminals are equipped with cold energy recovery systems. This paper explores various options for recovering cold energy from LNG regasification processes including electricity production, refrigeration, cryogenic separation processes, CO 2 capture and liquefaction. The present study examines the industrial recovery options, proposing both conventional and innovative process schemes and analysing them in terms of their thermodynamic modelling and feasibility. Nine case studies were selected and simulated using Aspen Hysys software, considering material and energy balances. Specific energy consumptions are calculated, and an exergetic comparison methodology is adopted to provide a unified approach capable to embrace heterogeneous systems utilizing mechanical/electrical energy, thermal energy, and “chemical energy”. The temperature profiles are examined, and sensitivity analyses are performed on key parameters. The integration of direct cooling and condensation brings high exergy efficiency of above 40% and economic advantages due to the absence of an external refrigeration cycle. Coupling regasification with CO2 liquefaction reduces specific energy consumption by 53% compared to the conventional process. Similarly, in the case of an ethylene production plant, energy consumption is reduced by 95%. Simulations for electricity generation using an ORC cycle with LNG as the cold source achieve around 25% exergy efficiency, but the LCOE (Levelized Cost of Electricity) is attractive, ranging from 0.07 to 0.09 €/kWh. Integration with an Air Separation Unit (ASU) for cryogenic distillation leads to a 41% decrease in specific energy consumption. Further integration with Allam and cascade ORC cycles has been simulated. Globally, air separation shows exergy efficiencies of 37–38%, which is higher than the average 25% obtained from conventional thermodynamic cycles with low-temperature hot sources. Regarding cryogenic CO2 capture, it exhibits lower specific energy consumption compared to traditional processes. The exergy efficiency is high at 22%, and the LCOP (Levelized Cost of CO2 Production) of 55 €/ton is attractive for carbon capture processes that can be coupled with regasification units and NG utilization (a.e. for hydrogen and electricity production).

Influence of poly(ionic) liquid incorporation within resin wafer electrodeionization for reduced energy consumption in brackish water desalination

Resin Wafer Electrodeionization (RW-EDI) is recognized as a promising technology for energy-efficient desalination of brackish water. However, RW-EDI is limited by energy requirements for the treatment of high-salinity feeds which prevent the large-scale deployment of this technology. Several material factors influence the resulting performance of RW-EDI. Current state-of-the-art wafers rely on a nonconductive polymer binder to ensure mechanical stability of resin wafers. However, a robust ionic polymer could improve resin wafer conductivity and energy efficiency of RW-EDI systems. Herein, this research studied the influence of ionic polymers within RW-EDI resin wafers. Specifically, polymer ionic liquid-based (PIL) ionic polymers were incorporated within ion exchange resin wafer formulations to enhance ion conductivity during RW-EDI operation. Two different resin wafer formulations were developed incorporating phosphonium-based PILs. These new resin wafer formulations were tested in a benchtop RW-EDI system at varied applied voltages. The results demonstrated that PIL loading had a major influence on the mechanical stability and conductive properties of the resin wafer as well as the RW-EDI performance. Resin wafers incorporating PILs exhibited an order of magnitude increase in ion conductivity (2.21 × 10-2 mS/cm) as compared to conventional polyethylene resin wafers (8.64 × 10-3 mS/cm). In the RW-EDI system, a 9.3 % decrease in specific energy consumption was achieved when PIL with 2.5 g loading of phosphonium-based PIL was employed, as compared to conventional polyethylene-based resin wafers. The results indicate that PIL ionic polymers can significantly improve energy efficiency within RW-EDI systems. The results also suggest that future studies should investigate additional ionic polymer materials for additional energy efficiency improvements within RW-EDI systems.

The Effect of RME-1-Butanol Blends on Combustion, Performance and Emission of a Direct Injection Diesel Engine

The main objective of this study was assessment of the performance, emissions and combustion characteristics of a diesel engine using RME–1-butanol blends. In assessing the combustion process, great importance was placed on evaluating the stability of this process. Not only were the typical COVIMEP indicators assessed, but also the non-burnability of the characteristic combustion stages: ignition delay, time of 50% heat release and the end of combustion. The evaluation of the combustion process based on the analysis of heat release. The tests carried out on a 1-cylinder diesel engine operating at a constant load. Research and evaluation of the combustion process of a mixture of RME and 1-butanol carried out for the entire range of shares of both fuels up to 90% of 1-butanol energetic fraction. The participation of butanol in combustion process with RME increased the in-cylinder peak pressure and the heat release rate. With the increase in the share of butanol there was noted a decrease in specific energy consumption and an increase in engine efficiency. The share of butanol improved the combustion stability. There was also an increase in NOx emissions and decrease in CO and soot emissions. The engine can be power by blend up to 80% energy share of butanol.

Modeling and energy analysis of a solar thermal vacuum membrane distillation coupled with a liquid ring vacuum pump

In this paper, a study of the energy performance of a solar powered vacuum membrane distillation coupled with liquid ring vacuum pump was investigated through various energy evaluation criteria. This analysis was investigated for the twelve months of the year. The results showed that the average daily production varied over the months from 598 to 217 kg/day. The average specific energy consumption, the average gained output ratio and the average energy efficiency were between 671 and 699 kWh/m3, 0.93–1.01 and 56.2–59.3% respectively. The maximum productivity and the best energy performance were that of June which is the month corresponding to the most important solar radiation. In addition, it was observed that vacuum liquid ring pump is characterized by a lower electrical energy consumption, which varies during the year between 4.2 and 7.47 kWh/m3. Besides, the effect of the vacuum level applied and liquid ring temperature on the energy performance was examined. Obviously, the results reveal that while increasing the vacuum, the specific energy consumption decreases. Moreover, it has been demonstrated that using an operating liquid at reduced temperatures reduces the flow rate required to ensure total condensation and decreases energy loss and specific energy consumption.

Technical and Economic Assessment for the Promotion of Non- Carbonized Pellets in MSME Sector in Nepal

Pellets are densified biomass fuel compatible for household as well as industrial use. Pellets can be potentially used as an alternative fuel source in many medium, small and micro enterprises (MSME) such as dairy, dyeing, laundry, khoa making, pickle making, yogurt making, soap making enterprises etc. in Nepal. Despite of the presence of large number of such industries and abundant biomass resources, production and application of pellets as a fuel source is almost non-existent in Nepal. Hence, to assess the benefits of using pellets as alternative fuel, an applied research of pellets application was carried out in a dyeing industry. Energy, environment and economic performances of the dyeing industry was compared between the baseline scenario of utilizing sawdust and wood chips mixture in loose form with that of non-carbonized pellets application as an alternative fuel. Results showed decrease in specific energy consumption by 6% on utilizing non-carbonized pellets compared to baseline. In terms of the environmental performance, emission of CO decreased from 100 Mg/L to 10 Mg/L and CO2 emission decreased from 7.5% to 4%. Similarly, suspended particulate matter (SPM) emission decreased from 37.4 mg/Nm3 to 14.8 mg/Nm3 but the negligible increment of NO2 emission was observed. However, emission of SO2 increased significantly from 3.3μgm/m3 to 33.7μgm/m3. High Sulphur content was found in the pellet which could be from the lubrication used in the pellet machine, but this could not be confirmed. The economic analysis revealed that the energy cost was almost twice with pellet application which was mainly because of the higher cost of imported pellets. If the production could be initiated in Nepal, utilizing the abundantly available local biomass resources, the cost could be considerably lowered thus making use of such fuel economically feasible.

Bucket working bodies with conveyor bottom: systematics and design features

Introduction. The creation of new types of bucket working bodies of excavators through synthesizing technical solutions to improve the transporting functions of the bottom is considered. These solutions are based on reducing the resistance and energy consumption under digging-in and scooping due to the transition from sliding friction to rolling friction during the movement of the rock mass along the bottom of the bucket. Materials and Methods. Analysis of the bulk materials handling processes using existing loading appliances identified design flaws that affect the efficiency of their operation. Advanced design diagrams of loading bodies were searched on the basis of the accumulated experience and the study of the morphological features of the existing equipment. Combinatorial analysis of possible combinations of elements with their various qualitative compositions, mutual arrangement, imposed links, and synthesis of new technical solutions for loading and transportation modules are carried out. Results. The results of the morphological synthesis implementation were the systematization and development of designs of bucket working bodies with a bottom in the form of a roller surface and a closed belt, as well as with a conveyor-type drive mechanism. The application of rollers as a supporting surface of a loaded rock mass causes a decrease in friction forces and in the power capacity of the work process. In addition, rotating rollers provide uniform abrasion of the working surface, which increases significantly the time to the equipment breakdown and increases the process efficiency. Working bodies with a drive mechanism make it possible to activate the interaction of the conveyor bottom in the form of a closed belt with the rock mass and, as a result, to accelerate the process of filling the bucket container. Discussion and Conclusions. The bucket working bodies described in the paper compare favorably with existing analogues in that they provide a reduction in the time to digging-in, scooping and unloading, a decrease in specific energy consumption, an increase in bucket filling, which ultimately contributes to an increase in productivity. A slight increase in the structural complexity and cost of the working body causes additional capital costs, which are paid back within two to four months.

Implementing multiple-effect distillation and reverse osmosis thermal coupling to improve desalination process performance in combined water and power plants

Cogeneration has recently been an appropriate engineering approach to supply increasing energy demands. The present study demonstrates a significant influence on increase in productivity and reduction of utility consumption of thermal desalination, considering a novel internally coupled multiple-effect distillation and reverse osmosis desalination process in a cogeneration of water and power plant. The proposed power generation unit, consisting of two SGT600 gas turbines as prime movers, two heat recovery steam generators and one back-pressure steam turbine, has been applied. The objective is to propose a modified multiple-effect distillation process, due to availability of sufficient cooling water, provided by reverse osmosis reject water. The basic configuration comprises a hybrid desalination using a dual purpose condenser, results of which showed a 45% reduction in electrical energy consumption of multiple-effect distillation, accompanying a 67% decrease in intake water cost. In modified configuration, condenser temperature decreases from 48 to 45℃, allowing number of effects to increase from 5 to 7. Therefore, produced water rate and gain output ratio of the modified multiple-effect distillation increase by 30% and 31%, respectively, while specific energy consumption decreases by 6%, causing a two-year reduction in cogeneration of water and power plant pay-back period compared to the basic configuration.

Performance, combustion and emission characteristics of a single cylinder CI engine running on diesel-biodiesel-water emulsion with additive

ABSTRACT The various researches on biodiesel and its blends as a fuel in a CI engine resulted in higher NOx emissions compared to diesel operation. The main objective of this study is to overcome the negative aspect of significant NOx emission than HC and CO emissions in the biodiesel blended fuel by the addition of water. The water emulsion has been used in diesel engine combustion for a long time showed encouraging results, but the point of efficiency and NOx trade-off, which is a highly challenging task for diesel engines. The objective of this study was achieved through the new blend consists of diesel- biodiesel blend (80:20 by volume), water (5% by volume), span-80 surfactant (1% by volume) and Cetane enhancing additive of Di-tertiary butyl peroxide (0.5% by volume). The chosen blend was tried in this study is unexplored. The new blend is designated as B3. Neem oil biodiesel was prepared through transesterification process. This study is to investigate the performance and emission characteristics of a single-cylinder diesel engine running on B3 fuel. The results of B3 fuel were compared with diesel (D), diesel-biodiesel blend (B1) and diesel-biodiesel with water emulsion through surfactant (B2). The conclusion reveals that B3 fuel has shown better performance intern of 17% decrease in specific energy consumption and reduction in HC and CO emissions especially NOx emission was reduced up to 29% and 45% than diesel fuel and B1 fuel respectively.

Experimental studies of the kinetics of infrared drying of spent coffee grounds

The object of research is drying of spent coffee grounds. In modern production, the issues of rational use of energy in all processes of food technology, including drying, are urgently raised. In many food technologies, 2–3 times more energy is used than is physically necessary for the process. This determines the energy intensity of production and the quality of products. Drying processes are among the most energy-intensive, and in many cases the proportion of energy in the cost of production is up to 30 %. When drying of spent coffee grounds, convective dryers are mainly used, the energy consumption of which is 5 MJ/kg of removed moisture and above. Convective drying uses 40 % of the supplied energy to evaporate moisture. Also, a significant drawback of convective dryers is the discharge of waste coolant into the atmosphere, which has a heat content of only 10–15 % less than the hot air supplied to the drying chamber. The paper proposes the use of infrared radiation for drying of spent coffee grounds in periodic and continuous units. This will allow in the future to reduce specific energy consumption. During the study, the influence of the energy supply intensity, temperature, air flow rate, product layer thickness and specific load on the kinetics of periodic infrared drying of spent coffee grounds is determined. The influence of the energy supply intensity, specific load, tape speed, and the number of infrared modules on the kinetics of continuous infrared drying of spent coffee grounds is determined. The results are compared with convective drying in terms of specific energy consumption. A feature of the use of infrared radiation is its high efficiency and high rate of moisture removal from the surface layers of spent coffee grounds, and as a result, an increase in the productivity of the drying method and a decrease in specific energy consumption. The specific energy consumption obtained during operation of infrared drying of spent coffee grounds is 3.2 MJ/kg. This is below existing convection dryers.

Establishing patterns of change in the indicators of using milk processing shops at a community territory

An approach has been proposed to the justification of patterns in the changes of indicators related to using milk processing shops at their various parameters at a community territory, taking into account changes in production conditions. The basis of the approach is a series of experimental studies on components of production conditions, taking into consideration their characteristics in each individual community. The study implied modeling of work at processing shops.It was established that there are two periods of milk processing ‒ intensive one (from day 119 to day 301 within a calendar year) and non-intensive one (from day 1 to day 118 and from day 302 to day 365 within a calendar year) based on forecasting daily volumes of milk supplied for processing from communities' farms over a calendar year. It is necessary to organize operation of shops in two shifts during the intensive period of milk processing, and in one shift during the non-intensive one. It was established that the laws of Weibull distribution describe daily volumes of milk processing. Their statistical characteristics during the intensive and non-intensive periods are: coefficient of variation is 0.65 and 0.62; shape parameter is 1.56 and 1.64, respectively. The confidence interval is within 509...6,995 and 46...634 liters.We carried out a study to justify regularities of change in the indicators of using milk processing shops at their various parameters at a community territory, taking into account changes in production conditions using an example of production conditions in the Brodivsky region of Lviv oblast (Ukraine). It was found that an increase in the productivity of milk processing shops from 0.5 to 20 t/day leads to the proportional decrease in specific energy consumption from 116 to 10 kW/t, specific water consumption from 10 to 0.3 m3/t and the specific demand (Nu) in human labor from 0 to 0.3 people/t in the production of various types of dairy products.We studied changing production conditions and identified trends in changes in the parameters of using milk processing shops at community territories. They underlie the determination of cost indicators. The results of this study will be useful for the identification of a configuration of projects to create milk production shops at a community territory

Performance Assessment of Coal Fired Power Plant Integrated with Calcium Looping CO2 Capture Process

ABSTRACT CaL technology is a promising means for post-combustion CO2 capture in already existing power plants, and heat integration is an effective way to lower the efficiency penalty caused by CO2 capture. Three cases with different heat integration degree were investigated in the manuscript to predict the efficiency penalty and the specific energy consumption for CO2 capture, aiming to find the optimum scheme of integrating capture unit into coal-fired power plant. The sensitivity analysis was also conducted to compare the impacts of key parameters. The simulation results show that the Case 3, which employs a variety of measures to improve the internal heat integration within CaL and reclaims the surplus released heat via an additional steam cycle, has the lowest efficiency penalty, 5.75%. It also indicates that heat integration in Case 3 results in a 14.4% of decrease in coal consumption, a 5.8% of reduction in power consumed by CO2 compression process, a 13.6% of drop in power consumption in ASU, and a 31.5% of decrease in specific energy consumption for CO2 capture. The sensitivity analysis shows that the efficiency penalty may be reduced by 0.011 percentage points for each degree decrease in temperature difference of MH-1. As the compression efficiency increases from 70% to 85%, the efficiency penalty decreases from 6.51% to 5.47%, and the specific energy consumption reduces from 2.21 MJ/kg CO2 to 1.80 MJ/kg CO2. Abbreviations: APH: Air Preheater; ASUL: Air Separation Unit; BFPT: Boiler Feedwater Pump Turbine; CaL: Calcium Looping; CCS: Carbon Capture and Sequestration; CFPP: Coal-Fired Power Plant; GSS: Gas-Solid Separator; HPC: High Pressure Column; HPEC: High Pressure Economizer; HPSH: High Pressure Super-Heater; HPST: High Pressure Steam Turbine; HRSG: Heat Recovery Steam Generator; IPEC: Intermediate Pressure Economizer; IPEV: Intermediate Pressure Evaporator; IPSH: Intermediate Pressure Super-Heater; LPST: Low Pressure Steam Turbine; LHV: Low Heat Value; LPC: Low Pressure Column; LPEC: Low Pressure Economizer; LPEV: Low Pressure Evaporator; ORC: Organic Rankine Cycle; RH: Reheater.

RESEARCH OF WHEAT DRYING IN A MICROWAVE AND COMBINED FILTER-MICROWAVE DRYER

The aim of the conducted study is to determine kinetics of the complex effect of microwave energy supply and filter drying of the process of water release from the wheat layer. There is offered a combination of MW and filter drying. A special feature of this combination must be its more effectiveness and high speed of water elimination from surface layers of wet seeds and, as a result, the productivity increase of the drying way, decrease of specific energy consumption. There was determined the influence of the specific load of the material, radiator power on processes of microwave and filter-microwave drying of wheat seeds. There were compared microwave, filter-microwave and convective drying of seeds by parameters of specific energy consumption, drying speed. The specific energy consumption at microwave drying of seeds was 4 MJ/kg, at filter-microwave drying 3.8 MJ/kg that is lower than existent convective dryers. The speed of microwave drying changes from 0,5 to 3 %/min, filter-microwave – from 0.3 to 0.7 %/min. The speed is at the level of standard convective dryers. The conducted studies allow to recommend a new combined way of FMW drying of seeds with low energy consumption. Revealed features of heating and drying are possible to be used at developing industrial dryers. The base of experimental data is possible to be used for optimizing and determining effective conditions of MW and FMW drying.

Integrated membrane distillation-reverse electrodialysis system for energy-efficient seawater desalination

Although desalination market is today dominated by Seawater Reverse Osmosis (SWRO), important technological issues remain unaddressed, specifically: relatively low water recovery factor (around 50%) and consequent huge amount of brine discharged, and energy consumption (3–5 kWh/m3) still far from the minimum thermodynamic value (∼1 kWh/m3). Herein, the energy performance of an innovative systems combining SWRO, Membrane Distillation (MD) and Reverse Electrodialysis (RED) for simultaneous production of water and energy is investigated. The valorization of hypersaline waste brine by Salinity Gradient Power production via RED and the achievement of high recovery factors (since MD is not limited by osmotic phenomena) represent a step forward to the practical implementation of Zero Liquid Discharge and low-energy desalination. The analysis is supported by lab-scale experimental tests carried out on MD and RED over a broad set of operational conditions. Among the different case studies investigated, exergetic efficiency reached 49% for the best scenario, i.e. MD feed temperature of 60 °C, MD brine concentration of 5 M NaCl, RED power density of 2.2 W/m2MP (MP: membrane pair). Compared to the benchmark flowsheet (only SWRO), up to 23% reduction in electrical energy consumption and 16.6% decrease in specific energy consumption were achieved when including a RED unit. The analysis also indicates that optimization of thermal energy input at the MD stage is critical, although it can potentially be fulfilled by low-grade waste heat or solar-thermal renewable sources. Overall, the proposed integrated system is coherent with the emergent paradigm of Circular Economy and the logic of Process Intensification.

Energy, exergy and economic analyses of two modified and optimized small-scale natural gas liquefaction (LNG) cycles using N2 and N2/CH4 refrigerants with CO2 precooling

Natural gas liquefaction cycles require high amounts of shaft power and any effort for decreasing power consumption of these cycles is a subject of interest. Among natural gas liquefaction cycles, N2 and N2/CH4 cycles with CO2 pre-cooling are attractive due to their simplicity. The novel work here is that two above cycles are first modified. Then by choosing the ratio of power consumption to the liquefied gas molar flow rate (Specific Energy Consumption, SEC) as the objective function and 13 design parameters for N2-CO2 cycle and 12 design parameters for N2/CH4-CO2 cycle, these cycles are optimized. Results of the above procedure showed decrease in both SEC and the total annual cost in comparison with those for similar cycles published in open literature. Two modified and optimized N2-CO2 and N2/CH4-CO2 liquefaction cycles showed 5.25% and 3.62% decrease in specific energy consumption and 9.4% and 16% decrease in exergy destruction respectively. The total cost of two above cycles also decreased for 0.5% and 1.2% respectively.

THE ENERGY EFFICIENCY OF THE HEAT PUMP RECUPERATIVE SYSTEM OF WATER HEATING AND VENTILATION USING THE HEAT OF THE SOIL AND VENTILATION EMISSIONS

The combined heat pump-recuperative scheme of water heating and ventilation using ground heat and ventilation emissions is considered. A thermodynamic analysis of the heat supply scheme was completed. Based on this analysis, the temperature parameters at the nodal points of the system, the unit cost of external energy per unit of heat produced at the entrance to the object of heating and ventilation and the proportion of heat load covered by the soil heat exchanger are determined. The graphical dependences of the efficiency criteria on the quantities that determine the conditions of operation of the circuit are constructed and analysed. A comparison of the obtained energy efficiency criteria with the corresponding values for a traditional heat pump system with the ground heat exchanger was completed. The introduction of the proposed combined scheme increases the air temperature supplied to the heater of the ventilation system. This, in turn, reduces the capacity of the heat exchangers of the ventilation system and improves the conditions of their operation, reducing the risk of icing over ducts. The proposed heat pump scheme leads to a decrease in specific energy consumption per unit of heat to meet the needs of water heating and ventilation of the premises. The energy efficiency of the heat supply system increases with the increase of both the recuperation coefficient of the recuperator and the relative heat consumption for ventilation compared with the heat consumption for heating. Reducing the total energy consumption for the heating and ventilation system results not only in increasing the energy efficiency of the heat supply system, but also leads to a decrease in capital costs for the construction of a heat pump unit (in particular, for the construction of a pre-heavily ground heat exchanger) in proportion to the reduction of its required capacity.

Investigation of the possibility of carbon dioxide reduction by Waelz processing of oxidized zinc-containing material

The results of model studies on the possibility of reducing energy costs and carbon dioxide emissions during the Waelz processing of oxidized zinc-containing material in waelz kilns are presented. The studies were carried out using a specialized software product METSIM widely known in the world practice of metallurgical process and production modeling that allows analyzing the effect of changes in technological modes on the final results of the process. Model calculations showed that the greatest decrease in specific energy consumption and CO 2 emissions is observed when using blast air heated to 200 °C with an increase in its flow rate from 1000 to 7000 n.m 3 /h and concomitant decrease in atmospheric air suction. The estimated reduction in the specific costs of carbon and CO 2 emissions amounted to 30,2—35,5 %, and the total specific cost of energy carriers — 28—32 %. At the same time, blast air heating to 200 °C in the heat exchanger of the recovery boiler does not require additional energy inputs, in contrast to the use of oxygen blast with the cost of electricity for producing oxygen. Intensification of the waelz process using additional oxygen blasting (or air blast enrichment with oxygen) and heated blast air supply with concomitant decrease in air suction into the furnace from the atmosphere leads not only to a decrease in the specific consumption of the carbon energy carrier, but also to an increase in the degree of carbon utilization. The maximum estimated increase in the degree of carbon utilization was 6,2 rel.% — from 60,3 % on cold air blast without oxygen to 66,5 % on an air-oxygen blast (7000 n.m 3 /h of air and 185 n.m 3 /h of oxygen) heated up to 200 °C without atmospheric air. Maintaining optimal oxidation-reduction and thermal modes of the process requires correct regulation of the kiln draft mode taking into account atmospheric air suction in the unloading head of the kiln. Uncoordinated changes in the specific consumptions of charge, carbon, blast air and rarefaction in the dust chamber lead to a concomitant decrease in the extraction of zinc to sublimates and increase in its losses with clinker.