Cycle Gas Research Articles

Study on the role of the reaction time in the upcycling of HDPE by co-hydrocracking it with VGO

Pursuing the aim of improving the current waste plastics management strategy, we have investigated the co-hydrocracking of high-density polyethylene (HDPE) with vacuum gasoil (VGO) over a PtPd/HY catalyst for converting this blend into high-quality fuels. In particular, the work was focused on assessing the effects of the reaction time on the product yields and on the composition of the gas, naphtha and light cycle oil (LCO) fractions, which was determined by chromatographic means. The experimental runs were carried out in a 100 mL semi continuous stirred tank reactor varying the reaction time between 15 and 120 min and maintaining constant the rest of the variables at 420 °C (temperature reached using an electrical heating jacket and following a 5 °C min−1 heating ramp), 80 bar and a catalyst to oil mass ratio of 0.075 gcat goil−1. The results shown that at 120 min a naphtha fraction rich in 1-ring aromatics and with a RON value of 92.5 was obtained, while the LCO fraction was mainly iso-paraffinic with a cetane index of 43.8. Hence, these fractions could be used in the corresponding blending stages of commercial gasoline and diesel. Furthermore, the coke deposited on the catalyst was analyzed by means of TPO, obtaining that it was mainly formed at short contact times (< 15 min) and that its nature evolved with contact time being less condensed at long contact times.

Shaken, but not expelled: Gentle baryonic feedback from nearby starburst dwarf galaxies

Baryonic feedback is expected to play a key role in regulating the star formation of low-mass galaxies by producing galaxy-scale winds associated with mass-loading factors of β ∼ 1 − 50. We test this prediction using a sample of 19 nearby systems with stellar masses of 107 &lt; M⋆/M⊙ &lt; 1010, mostly lying above the main sequence of star-forming galaxies. We used MUSE at VLT optical integral field spectroscopy to study the warm ionised gas kinematics of these galaxies via a detailed modelling of their Hα emission line. The ionised gas is characterised by irregular velocity fields, indicating the presence of non-circular motions of a few tens of km s−1 within galaxy discs, but with intrinsic velocity dispersion of 40 − 60 km s−1 that are only marginally larger than those measured in main-sequence galaxies. Galactic winds, defined as gas at velocities larger than the galaxy escape speed, encompass only a few percent of the observed fluxes. Mass outflow rates and loading factors are strongly dependent on M⋆, the star formation rate (SFR), SFR surface density, and specific SFR (sSFR). For M⋆ of 108 M⊙ we find β ≃ 0.02, which is more than two orders of magnitude smaller than the values predicted by theoretical models of galaxy evolution. In our galaxy sample, baryonic feedback stimulates a gentle gas cycle rather than causing a large-scale blow-out.

Environmental Impact Assessment from the Emission of Combined Natural Gas Cycle Power Plant

Environmental Impact Assessment from the Emission of Combined Natural Gas Cycle Power Plant

Characteristics of the nitrogen gas cycle for small scale LNG production

Characteristics of the nitrogen gas cycle for small scale LNG production

Natural gas‐fueled multigeneration for reducing environmental effects of brine and increasing product diversity: Thermodynamic and economic analyses

AbstractWater scarcity threatens human life and it is likely to be a main concern in the next century. In this work, a novel multigeneration system (MGS) is introduced and assessed with energy, exergy, and economic analyses. This MGS includes a gas cycle, multieffect distillation, an absorption refrigeration cycle, a heat recovery steam generator, and electrodialysis. Electrodialysis is integrated into this configuration to produce sodium hydroxide and hydrogen chloride from brine to prevent its release to the environment with harmful impacts. The other products are electricity, cooling, and demineralized water. For the evaluation of the proposed system, one computer code is provided in engineering equation solver software. For physical properties calculation, the library of this software is used. The MGS produces 614.7 GWh of electrical energy, 87.44 GWh of cooling, 12.47 million m3 of demineralized water, and 0.092 and 0.084 billion kg of sodium hydroxide and hydrogen chloride over a year. Energy and exergy evaluations demonstrate that the MGS energy and exergy efficiencies are 31.3% and 18.7%, respectively. The highest and lowest value of exergy destruction rate is associated with the combustion chamber and pump, respectively. The economic evaluation indicates that the net present value of this proposed system is 3.8 billion US$, while the internal rate of return and payback period, respectively, are 0.49 and 2.1 years.

New optimal scheme for the poly-generation system, integrated with ORC and hydrogen production units, using technical, emergy, and thermo-risk analyses-case study for qeshm power and water co-generation plant

The diversity of energy demand in terms of products has led to the upgrading the power plants into multi-generation systems. The Qeshm freshwater and power plant located in Qeshm Island, Iran, has been investigated. The existing plant was integrated with an absorption chiller, solar thermal collector, and RO desalination unit in the previous study. This study has proposed and evaluated a new configuration for this plant. This new scheme consists of power, heating, cooling, freshwater, and hydrogen production units. A PEM electrolyzer and an organic Rankine cycle have been integrated into the previously proposed system to generate hydrogen and more power. In order to evaluate the proposals for the Qeshm freshwater and power plant, the energy, exergy, exergo-economic, exergo-environmental, emergo-economic, emergo-environmental, and exergo-risk (7E) analyses have been performed on the new integrated system. Furthermore, a multi-objective optimization process has been conducted on the proposed system using the multi-objective particle swarm optimization (MOPSO) algorithm to obtain the optimal scheme of the proposed configuration. The results of the thermo-risk analysis indicate that the most hazardous unit of the system is the gas cycle section, with a 91.21% share of the total rate of risk in the site, which equals 11.705 × 10 - 6 i n j u r e d / y e a r . By comparing the results of the previous work and the new proposed integrated plant, the new system’s poly-generation efficiency and net power output have been enhanced by 5.523% and 7.945%, respectively. The new integrated plant can produce two new hydrogen and oxygen products in 0.003 and 0.21 kg/s, respectively. Also, the cost of power produced by the system has been raised only by 0.393 $/MWh or 0.91%, while its environmental impact has been decreased by 0.702 pts/MWh or 3.98%. The total rate of risk of the system will increase due to adding ORC and PEMEC units to the cycle, which is from 10.129 to 11.105 × 10 - 6 i n j u r e d / y e a r . But, from the thermo-risk point of view, the total specific risk of the plant’s products has been reduced from 37.820 to 37.486 × 10 - 8 i n j u r e d / ( y e a r . M W ) . Furthermore, the optimization process results show that implementing the optimization process has improved the objective functions of the proposed integrated plant from technical, monetary, ecological, and risk points of view.

A new solar, natural gas, and biomass-driven polygeneration cycle to produce electrical power and hydrogen fuel; thermoeconomic and prediction approaches

Nowadays, due to the limitations of fossil fuels utilization, renewable energies-driven polygeneration systems (PGSs) are becoming popular. In this article, the simulation and conceptual design of a PGS based on biomass and natural gas fuels to produce products such as electricity, hydrogen fuel, hot water (HW) and chilled water (CHW) is presented and discussed. The introduced PGS is integrated with units and cycles such as water electrolysis (based on polymer electrolyte membrane (PEM) electrolyzer), a ground source heat pump (based on geothermal well), and an absorption chiller. Additionally, in order to supply a fraction of the heat required for the cycle, a solar thermal unit (based on parabolic trough solar collectors, PTSCs) has been embedded. The proposed PGS is evaluated and analyzed from thermodynamic and exergoeconomic points of view. Moreover, as an innovative approach, a prediction on machine learning (ML) model is developed to predict and evaluate hydrogen production rate through biomass gasification. Besides, a state-of-art structure and configuration is considered for the proposed PGS, which had not been reported in the literature. The outcomes indicated that the considered PGS is capable of generating nearly 3.71 MW of electricity, 11.42 kg/h of hydrogen fuel, 5.7 kg/h of oxygen gas, 5.9 MW of CHW, and 2.95 MW of HW. In such a context, the energy and exergy efficiencies of PGS are yielded 74.2 % and 32.3 %, respectively. It is estimated that the implementation of such a system will require an investment cost of almost $ 3.9 million. It was also found that the HW unit exergy cost is approximately 37.8 % higher than that of CHW. Besides, the unit exergy cost of hydrogen fuel is almost 4.4-fold higher than that of electricity. In addition, a detailed parametric research is conducted to analyses the influence of the costing metrics on the PGS behavior under consideration. Finally, the results demonstrated that ML model had acceptable accuracy and could predict the hydrogen production rate through biomass gasification.

Optimal design of a novel hybrid solar tower‐gas turbine combined cycle with proton exchange membrane polygeneration system: Application of machine learning

AbstractAn innovative polygeneration system is proposed to generate power, heat, hydrogen, and oxygen simultaneously. The system integrates a solar central tower system and the heliostat field, a gas turbine cycle, a supercritical carbon dioxide cycle, an Organic Rankine Cycle with a cyclopentane working fluid, and a Rankine steam cycle, and a Proton Exchange Membrane electrolyzer. In this study, to reduce the gas cycle fuel consumption, the solar tower system is integrated with the gas cycle. In the studied system, a Supercritical Carbon Dioxide cycle and an Organic Rankine Cycle have been used to heat recovery of the exhaust gases of the gas turbine. In addition, Energy, Exergy, Exergoeconomic, Exergoenvironmental, Emergoeconomic, and Emergoenvironmental analyses have been performed for this system hour by hour. A computer code was developed in MATLAB for these analyses, and the results are validated by simulation in Thermoflex software and primary references with high accuracy. A systematic approach based on thermodynamic analysis and a combination of Genetic Programming and Artificial Neural Networks is proposed for optimal design. Multi‐Objective Genetic Optimization has been employed to find optimum design parameters. Due to the reduction of computation time of optimization, the integration of Genetic Programming and Artificial Neural networks have been employed to generate correlations for objective functions based on the decision variables. By adding the solar system, the mass flow rate of natural gas consumption in the gas cycle decreases by about 9% and reaches 1.53 kg/s. Utilizing solar energy and the Rankine steam cycle, the production capacity of the considered cycle increases from 43 to 66 MW. Also, the performance analysis of the Proton Exchange Membrane electrolyzer and the primary cycle shows that this equipment can produce 0.01 g/s of hydrogen from 5 g/s of water entering the equipment per second by consuming 2.33 kW of power. The results show that when the decision variables are considered at the optimal performance point, the exergy efficiency, the total cost, the rate of destruction related to environmental impacts, cost based on emergy, and the rate of destruction environmental effects based on energy improve. The highest percentage of improvement among the objective functions compared to the initial state is related to the exergy efficiency with 46%, and then the environmental impact rate based on emergy with an improvement of 36%.

Experimental simulations of methane-oriented underground coal gasification using hydrogen - The effect of coal rank and gasification pressure on the hydrogasification process

This paper presents a series of surface experimental simulations of methane-oriented underground coal gasification using hydrogen as gasification medium. The main aim of the experiments conducted was to evaluate the feasibility of methane-rich gas production through the in situ coal hydrogasification process. Two multi-day trials were carried out using large scale gasification facilities designed for ex situ experimental simulations of the underground coal gasification (UCG) process. Two different coals were investigated: the “Six Feet” semi-anthracite (Wales) and the “Wesoła" hard coal (Poland). The coal samples were extracted directly from the respective coal seams in the form of large blocks. The gasification tests were conducted in the artificial coal seams (0.41 × 0.41 × 3.05 m) under two distinct pressure regimes - 20 and 40 bar. The series of experiments conducted demonstrated that the physicochemical properties of coal (coal rank) considerably affect the hydrogasification process. For both gasification pressures applied, gas from “Six Feet” semi-anthracite was characterized by a higher content of methane. The average CH4 concentration for “Six Feet” experiment during the H2 stage was 24.12% at 20 bar and 27.03% at 40 bar. During the hydrogasification of “Wesoła" coal, CH4 concentration was 19.28% and 21.71% at 20 and 40 bar, respectively. The process was characterized by high stability and reproducibility of conditions favorable for methane formation in the whole sequence of gasification cycles. Although the feasibility of methane-rich gas production by underground hydrogasification was initially demonstrated, further techno-economic studies are necessary to assess the economic feasibility of methane production using this process.

Evaluation and optimization of a new energy cycle based on geothermal wells, liquefied natural gas and solar thermal energy

Today, due to the increase in environmental crises and the challenges facing fossil energies, it seems necessary to exploit and use renewables. Solar and geothermal energies can be integrated as a clean and promising energy production system to produce different forms of useful energy. The existing geothermal wells in Sabalan power plant provide different thermodynamic characteristics. In this regard, this paper develops the thermodynamic-conceptual design and optimization of a new energy cycle based on Sabalan geothermal wells. The considered energy process is based on two flash cycles (FCs), and two bottoming cycles (a Kalina cycle (KC) and a CO2-based Transcritical Rankine cycle (CTRC)). KC and CTRC can increase the level of power generation. Besides that, in the planned energy process, heat exchangers are employed in order to reduce energetic and exergetic losses to transfer thermal energy to a liquefied natural gas cycle (LNGC). LNGC can improve the electrical energy production level. Further, it can supply natural gas (NG) to consumers in the suburbs of the power plant. Additionally, a solar energy system based on parabolic trough solar collectors (PTSCs) has been embedded in order to produce a part of the thermal energy of the energy process. In order to achieve optimal results, the genetic algorithm has been applied to optimize the energetic and exergetic performance of the considered energy process. Based on the research outcomes, the total electricity output of the designed energy process is approximately equal to 26.1 MW. Energy efficiency of almost 24.9% and exergy efficiency of nearly 53.4% are calculated for the energy cycle. Furthermore, the total exergy destroyed through the energy process is approximately 29.5 MW. Under the optimization results, the rates of energy efficiency improvement and exergy destruction reduction for mode A (with NG production) are 17.9% and 3.53%, respectively. Besides, for mode B (without NG production) the rates of energy efficiency reduction and exergy efficiency improvement are 31.7% and 22.1%, respectively. Finally, it was found that, on average, almost 112 collectors are required to supply heat based on the assumption of using solar energy.

Study on nitrogen plasma gasification for small scale waste processing

High temperature thermal plasma gasification can treat non-homogeneous waste at increased conversion efficiency, compared to conventional gasification. A novel nitrogen plasma technology demonstration system is presented. The system can convert 20 kg/h of biomass to synthesis gas and is constructed inside a shipping container, which makes it mobile and suitable for application in remote rural areas of developing countries. An Aspen Plus model of the plasma gasification reactor was developed to enable energy and exergy analysis. The model gave good predictions of the real synthesis gas composition obtained during experimental runs. Simple gas and steam power cycles were also modelled to assess the feasibility of the system producing its own power. Based on typical composition of wood, it was found that the plasma torch power requirement is 20.7 kW. This amount of power can be generated using an open gas turbine cycle with compressor pressure ratio of 5 and turbine inlet temperature of 1007 °C. For a combined cycle case, using steam at 8 bar and 400 °C in a steam cycle, 14.6 kW of excess power becomes available. Alternatively, 68 kg/h of steam can be delivered, in addition to satisfying the torch requirement.

Machine learning-based metaheuristic optimization of an integrated biomass gasification cycle for fuel and cooling production

Nowadays, Combined cycles have attracted much attention for improving the efficiency of the thermodynamic cycles. In these systems, the main idea is to optimally use the waste energy from the power cycle, to run the cooling, heating, and storage cycles of hydrogen and biofuel-based ammonia. In this research study, an innovative integrated biomass gasification energy system for ammonia production is used alongside hydrogen storage. In addition, gasification is used to produce the required fuel for power generation. The gasification intake air is preheated with solar panels and then enters the gasification unit. The cooling water passing through this stage is heated up to the temperature of the electrolysis and then gets decomposed. The produced hydrogen fuel is used and stored for ammonia fuel production. The power cycle consists of a gas turbine system alongside a Rankin cycle, and then the exhaust gas is guided towards the cooling cycle of a double-effect absorption chiller. The results show that this system can generate power up to 7 megawatts with an exergy efficiency of 66%. Furthermore, ammonia production and hydrogen storage rates are 0.38 and 0.101 kg per second, respectively. Genetic algorithm optimization along with machine learning methods is used to achieve the optimization points of this cycle. At the optimized point, this cycle can produce 0.5347 kg per second of ammonia with an exergy efficiency of nearly 64%.

Waste heat recovery of an UAV propulsion system based on PEM fuel cell by a novel transcritical CO2 - LNG hybrid cycle; thermodynamic and multiple linear regression analyses

ABSTRACT In this work, the performance of a proposed hybrid system consisting of a transcritical carbon dioxide-natural gas cycle for recovery of waste heat produced in a proton exchange membrane fuel cell has been evaluated. The effects of different parameters on proposed cycle performance have been investigated thermodynamically. This hybrid system can convert fuel cell’s released heat to electricity, augment production power, convert natural gas from the liquid phase to gas, and appropriate use of heat energy from consumed water. Results show that increasing the cell’s power by about 52% leads to a growth in overall efficiency of transcritical power cycle. Also, in a constant fuel cell power, the higher carbon dioxide mass flow rate tends to lower carbon dioxide turbine output power, and consequently, the efficiency of transcritical power cycle decreases. Changes in waste heat recovery efficiency among models with different values of CO2 mass flow rate increases very slightly as fuel cell power augments. For instance, at lowest examined fuel cell power (790 kW), growth in CO2 mass flow rate by about 26% causes a decline in cycle efficiency by about 6.35%. By increasing fuel cell thermal efficiency by 30%, improvement in overall cycle efficiency rises significantly by about 109.92%. On the other hand, augmentation in fuel cell thermal efficiency by about 30% leads to a very slight growth in improvement of the waste heat recovery efficiency by about 2.67%. Moreover, by increasing adiabatic efficiency of turbines by about 21.43%, improvement in waste heat recovery efficiency declines by about 10.75%. Increasing carbon dioxide turbine’s inlet temperature and reducing carbon dioxide mass flow rate have beneficial effects on efficiency of carbon dioxide transcritical power cycle. Eventually, two high-accuracy models have been presented for output power and efficiency of proposed hybrid cycle using multiple linear regression.

Pilot test of low-rank coal pyrolysis coupled with gasification to hydrogen-rich gas for direct reduced iron: Process modeling, simulation and thermodynamic analysis

A Coal-Coke-Hydrogen-Iron (CCHI) system, low-rank coal pyrolysis coupled with gasification based on pilot test to hydrogen-rich gas for direct reduced iron (DRI), was proposed. The new process creatively proposes to blend the pyrolysis gas produced by pyrolysis of non-coking coal with the gasification gas produced by gasified coke to obtain the reducing gas that can meet the requirements of the DRI technology, addressing the problems of overcapacity in the coking industry and high carbon emissions in the steel industry. A strategy of partial cycle of top gas (rich in H2 and CO) from the shaft furnace is adopted to improve gas utilization and reduce carbon emissions, which is named as CCHI system with top gas cycle (CCHI-WTC) system. The key operation parameters and conditions such as steam/coke ratio, oxygen/coke ratio, reforming ratio and circulation ratio are optimized at 0.98, 0.43, 1.00 and 12.33 %, under which the energy consumption per unit product, exergy loss per unit product and greenhouse gas unit product emission of CCHI-WTC system can reach 15.13 GJ/t, 7.85 GJ/t and 761.50 kg/t, being reduced by 24.16 %, 20.14 % and 50.01 % compared to the traditional Coking-Blast furnace ironmaking process, respectively. This work provides a new low-rank coal application approach and breaks down the industry barriers of coal chemical industry and metallurgy.

PRE-CLASS TUTORIAL (PCT): LEARNING STRATEGIES TO IMPROVE STUDENTS' UNDERSTANDING OF THE P–V–T DIAGRAM ON THERMODYNAMICS

This research was motivated by students' difficulties drawing and interpreting P-V-T diagrams to describe thermal processes and the ideal gas cycle. The method used in this study is a quasi-experimental method by comparing the results of the students' pre-test and post-test. This research was conducted on 21 students in one of the public schools in Pandeglang, Banten. Based on the study's results, PCT improved students' understanding of drawing and interpreting P-V-T diagrams to describe thermal processes and the ideal gas cycle. Several conceptual difficulties founded during the research. First, the most difficult in P-V, P-T, and V-T diagrams, respectively, is to draw the adiabatic process. Second, the percentage of students who answered the P-V diagram correctly was higher than those who answered the P-T and V-T diagrams. Third, students were more interested in and understood processes with unique characteristics such as isobaric, which means constant pressure; isochoric, which means constant volume and isothermal, which means constant temperature.

Brazilian integrated oilpalm-sugarcane biorefinery: An energetic, exergetic, economic, and environmental (4E) assessment

Given the imminent energy transition towards more sustainable and renewable energy systems, bioenergy represents an indispensable short and medium-term alternative. However, a key factor for developing the global bioindustry is establishing and consolidating integrated multi-product systems capable of efficiently and sustainably converting some organic materials into biofuels, bioelectricity, and other affordable bioproducts. Under this horizon, this work aims to evaluate and compare, through the thermodynamics precepts (1st and 2nd law), fixed capital investment, and life cycle analysis, different integrated bioenergetic complexes in which lignocellulosic material from oil palm and sugarcane cultures are processed simultaneously. These systems were structured for the Brazilian scenario, a country with a prominent role in bioenergy conversion, given its recognized soil and climate potential, large territory, and expertise in the bioenergy field. Consequently, this work presents a study of three scenarios: the first (CI), conventional palm oil biodiesel and sugarcane ethanol system; the second (CII) oilpalm–sugarcane biorefinery annexed to a lignocellulosic biomethanol plant; and the third (CIII) which is an extension of the second, but in this one, the concepts of advanced gas turbine integrated biomass gasification (BIG-GTCC) cycles are inserted. In this sense, a systematic analysis methodology is developed and implemented, which allows characterizing and measuring the energy, exergy, and environmental aspects related to the lignocellulosic material energy conversion, providing indicators that enable and facilitate the evaluation and selection of technologies that contribute to global energy decarbonization. The results obtained from the thermodynamic evaluation expose the advantage of getting a more prominent energy portfolio from various raw materials, with CIII standing out before the other scenarios, with superior performance in Global plant efficiency (53.4 %), Surplus Electricity Index (86.6 kWh tonMP−1), and Global plant exergy efficiency (62.7 %), associated with BIG-GTCC integrating, verifying how attractive it is for agribusinesses. From an economic point of view, integration is not feasible; however, it could be significantly improved through fiscal incentives founded on fossil energy use reduction, enhanced conversion yielding, and improvements in conversion technologies. On the other hand, the LCA results showed the potential environmental benefits associated with the fossil diesel partial substitution by biodiesel (considering methanol derived from lignocellulosic material), both in sugarcane and palm culture, enabling the fossil energy consumption reduction by 79.6 % (sugarcane) and 69.2 % (palm) by the methyl route. Consequently, Fossil Energy Ratio (FER) increases to 9 energy units and Life Cycle Energy Efficiency (LCEE) up to 52.6 % are achieved in the oilpalm–sugarcane biorefinery.

Evaluation of Korean Firefighters’ Fitness Using Candidate Physical Ability Test: Pilot Study

OBJECTIVES The Candidate Physical Ability Capability Test (CPAT) is a complex performance test to assess whether firefighters have sufficient ability to meet the physical demands of firefighting, and is widely used in many countries, especially in North America. In South Korea, however, simple basic physical fitness assessments are still used for firefighters’ fitness evaluation. Here, we report the physical fitness of Korean firefighters using the CPAT for the first time in Korea.METHODS Eighteen male Korean firefighters aged between 20 to 30 years participated in this study. All subjects were measured for maximum oxygen consumption (VO2max) by using gas analyzer and cycle ergometer before CPAT. On a separate day, each subject performed CPAT with the best effort. Each subject’s oxygen consumption (VO₂), heart rate (HR) and completion time were measured during the CPAT. The results of CPAT were analyzed based on VO2max and HRmax and compared to the those of previous study from North American firefighter candidates.RESULTS VO2max was significantly (p&lt; .001) lower and HRmax was significantly (p&lt; .05) higher in Korean firefighters (45.4±4.6 ml/kg/min and 194.2±2.1 beat/min) than American firefighter candidates (53.0±7.4 ml/kg/min and 188.0±8.0 beat/min). During CPAT, Korean firefighters showed 69.4±15.8 %VO2max and 87.6±7.8 %HRmax and American firefighter candidates had 73.1±8.0 %VO2max and 90.1±5.3 %HRmax, but these were not statistically significant. However, the completed time of CPAT was significantly slower in Korean firefighters than American firefighter candidates (726.8±84.6 sec vs. 512.0±51.0 sec, p&lt;.001).CONCLUSIONS Korean firefighters have lower cardiorespiratory endurance capacity and CPAT performance than American firefighter candidates. In addition, Korean firefighters did not complete the CPAT within the pass time limit. It suggests that Korean firefighters need to improve more physical ability for physical demands of firefighting.

The switching behavior of CO2/N2 responsive emulsion systems formed by an amine functionalized quaternary ammonium surfactant

Stimulus-responsive surfactants (N+–Cn-N,n = 14 or 16) can stabilize conventional emulsions, Pickering emulsions and oil-in-dispersion emulsions in the presence of oppositely and similarly charged nanoparticles. Rapid demulsification can be successfully achieved by bubbling CO2. In the presence of CO2, N+–Cn-N becomes a hydrophilic Bola-type surfactant, N+–Cn-NH+, and is an inferior emulsifier either when used alone or together with charged nanoparticles, resulting in demulsification. In addition, nearly all N+–Cn-NH+ molecules are present in the aqueous phase after demulsification without contaminating the oil phase. The aqueous phase can be recycled and used again for further emulsification of oils. Compared with the pH responsive systems, there is no accumulation of salt after the gas cycles, and more cycles can be performed. This protocol is a green process and leads to preparation of various temporarily stable emulsions used in oil emulsion transportation, emulsion polymerization, industrial catalysis, nanomaterial synthesis and other fields.

Techno–Economic and Risk Evaluation of Combined Cycle Propulsion Systems in Large Container Ships

Owing to the stringent regulations on pollutant emissions that are imposed by the International Maritime Organization and increasing fuel prices, there has been significant research on developing cleaner fuels and novel propulsion systems. This study presents a techno-economical and risk assessment method for evaluating alternative propulsion technologies and cleaner fuels as substitutes for heavy fuel oil and two-stroke diesel engines in marine transportation. This analysis was carried out for two different journeys. Accordingly, we evaluated the economic benefits of using an enhanced intercooler/reheat combined gas and steam cycle or simple and intercooler/reheat combined gas and steam cycles that were fueled by marine diesel oil or liquified natural gas instead of a two-stroke diesel engine that was fueled by MDO as the propulsion system in a large container ship, considering different shipping routes. The results highlighted the advantages of implementing the simple, intercooler/reheat, and enhanced combined gas and steam cycles as propulsion systems. A sensitivity analysis was performed to investigate the effects of the fuel cost, capital cost, and hull fouling resistance on the economic analysis. For the routes that were considered herein, compared to a two-stroke diesel engine that was fueled by MDO, the simple, intercooler/reheat, and enhanced gas and steam combined cycles that were fueled by LNG increased the net present value by 78.3%, 78.5%, and 76.4%, respectively, and reduced the payback period by 38.8%, 38.9%, and 35%, respectively. Furthermore, the fuel and capital costs had a significant influence on the overall economic profit.

Effect of Miller cycle and exhaust gas recirculation on combustion characteristics of a gasoline direct-injection engine

ABSTRACT A numerical method is used to investigate the effect of variation Miller cycle and Exhaust gas recirculation (EGR) on fuel economy and combustion characteristics of a turbocharged gasoline direct-injection (GDI) engine, in which one-dimensional (1D) and three-dimensional (3D) model are established in GT-Power and CONVERGE software, respectively. The simulation values of the model are validated well with experimental results at part load and full load conditions. The results demonstrate that fuel economy is improved with Miller degree increasing at 50% loads because of the reduction of pumping loss. Further studies have shown that, especially at ±58°CA Miller degrees, early intake valve closure (EIVC) has a better performance than late intake valve closure (LIVC) on fuel economy. In addition, EGR can further decrease fuel consumption based on miller cycle because of further decline for pumping loss and combustion phase optimization. Meanwhile, LIVC can match wider EGR rates than EIVC in terms of good fuel economy. Compared to the baseline scheme, the brake specific fuel consumption is reduced by 4.3% with LIVC58 + 7% EGR. And combustion process of the LIVC58 + 7% EGR also gets optimized which result in lower maximum in-cylinder temperature due to the advance of CA50 and delay of combustion duration.