Liquefaction Process Research Articles

Exergy and exergoeconomic analysis of a hybrid airborne wind and solar energy system for power, liquid nitrogen and carbon dioxide production

Airborne wind energy (AWE) systems have emerged as cost-effective and sustainable solutions that have not yet been coupled with solar technologies and integrated power plants to produce energy and on-demand substances. This study proposes an integrated system driven by an innovative AWE and photovoltaic (PV) hybrid system. This combination can harness stronger and more stable wind energy while decreasing system costs and power intermittency. The proposed system combines seven subsystems, including AWE, PV, air separation unit, oxyfuel power plant, absorption refrigeration, a nitrogen liquefaction process, and Organic Rankine Cycle (ORC) to simultaneously generate power, liquid nitrogen, and liquid carbon dioxide. The hybrid AWE-PV system can generate 10.8 MW power to initiate the system to produce 55 MW power, 127.2 m3/h liquid nitrogen, and 98.4 m3/h liquid carbon dioxide. The exergy analysis has been conducted, showing maximum exergy destruction in heat exchangers, and the total exergy efficiency of the integrated structure reaches 90.21 %. The exergoeconomic analysis illustrates that the maximum capital cost occurs in compressors and turbines with a percentage of 51 % (∼4600 $/h) and 26 % (∼2400 $/h), respectively. This first demonstration of implementing hybrid AWE-PV renewable energy sources in an integrated structure can open new perspectives and avenues toward using AWE and its combination with other renewable energy sources in the future.

Alkaline membrane-free water electrolyser for liquid hydrogen production

Transporting hydrogen in liquid state holds promise as a cost-effective solution for long-distance and large-scale distribution. This paper investigates the feasibility of the application of a membrane-free water electrolyser for liquid hydrogen production. Both conventional alkaline and membrane-free water electrolysers are considered for hydrogen production. The hydrogen produced by these electrolysers are used as the feedstock for subsequent purification and liquefaction processes. Aspen HYSYS is used for systematic investigation of the impact of electrolyser operating conditions and hydrogen purity on the total power consumption for liquid hydrogen production. The findings reveal that, if the safety concerns of the membrane-free water electrolysers can be addressed, they can offer an energy-efficient alternative to alkaline water electrolysers, potentially reducing power consumption by approximately 4 %–10 %.

Hydrogen liquefaction process using carbon dioxide as a pre-coolant for carbon capture and utilization

With the increasing demand for hydrogen (H2), producing liquefied H2 with a high energy density (10.1 MJ/L) has become essential. Research on the H2 liquefaction process, specifically, the effects of various refrigerants and cooling cycles has been conducted. Yet, large-scale use of carbon dioxide (CO2) in H2 liquefaction hasn't been achieved. In this study, a cooling cycle that uses captured CO2 as a refrigerant in large quantities was selected for a 100 tpd H2 liquefaction process. Optimization minimized the specific energy consumption (SEC), leading to SEC of 7.3 kWh/kgLH2, a coefficient of performance of 0.17, a figure of merit of 0.33, a specific exergy efficiency (SEE) of 33 %, and an overall exergy efficiency of 82.2 %. Performance indicators were compared with other processes, showing that the SEC and SEE were improved by 43 % and 50 % compared to commercial processes and by 4 % and 6 % compared to previous studies using CO2. This study used 5.7 times more CO2 at the same capacity, utilizing 47.8 Mt of CO2, representing 14 % of the CO2 utilization amount of the total carbon capture and utilization (CCU) project. Thus, the results should facilitate the development of hydrogen liquefaction processes for use in CCU applications in the future.

Two-stage hydrothermal liquefaction of Spirulina: Experimental observations, energy analysis and techno-economic assessment

The intensification of environmental pollution and significant consumption of fossil fuels has led to widespread attention on developing renewable resources. As a carbon-containing renewable energy source, Spirulina is characterized by its fast growth cycle and wide distribution. Currently, one of the research hotspots is the conversion of Spirulina into bio-oil through hydrothermal liquefaction. However, studies on the two-stage hydrothermal liquefaction of Spirulina predominantly concentrate on the product yield or composition. There is relatively little research on thermodynamic (energy) analysis and techno-economic assessment during the reaction process. The main bio-oil components from two-stage hydrothermal liquefaction of Spirulina are ketones and acids with 44.9 % and 34.1 %, respectively. Compared to no-catalysis, two-stage hydrothermal liquefaction of Spirulina over HZSM-5, alkili-modified HZSM-5, and Ni@alkali-modified HZSM-5 increase the relative content of hydrocarbons to 6.6 %, 32.9 % and 48.1 %, respectively. Energy analysis and techno-economic assessment are conducted with Aspen Plus simulation, revealing a exergy efficiency of 56.4 % for the catalytic two-stage hydrothermal liquefaction of Spirulina compared with 43.6 % over no-catalyst. The primary losses occur in the first stage of the reaction process (248.6 kW) and the cooling process (10.7 kW) for catalytic two-stage hydrothermal liquefaction of Spirulina. The hourly price of producing 1 kg bio-oil with a catalyst is $3.67, while without a catalyst, it is $4.54 kg−1; obtaining a unit of chemical exergy costs $0.14×10−3 kJ−1 through catalysis. Moreover, the fluctuations in the prices of sulfuric acid and catalysts are most sensitive to the cost price of bio-oil with or without catalysts in the two-stage hydrothermal liquefaction process, with the values being 10.06 % and 8.10 %. This study has important significance for efficient transformation and energy utilization of Spirulina.

Injecting Sustainability into Epoxy-Based Composite Materials by Using Bio-Binder from Hydrothermal Liquefaction Processing of Microalgae.

We report a transformative epoxy system with a microalgae-derived bio-binder from hydrothermal liquefaction processing (HTL). The obtained bio-binder not only served as a curing agent for conventional epoxy resin (e.g., EPON 862), but also acted as a modifying agent to enhance the thermal and mechanical properties of the conventional epoxy resin. This game-changing epoxy/bio-binder system outperformed the conventional epoxy/hardener system in thermal stability and mechanical properties. Compared to the commercial EPON 862/EPIKURE W epoxy product, our epoxy/bio-binder system (35 wt.% bio-binder addition with respect to the epoxy) increased the temperature of 60% weight loss from 394 °C to 428 °C and the temperature of maximum decomposition rate from 382 °C to 413 °C, while the tensile, flexural, and impact performance of the cured epoxy improved in all cases by up to 64%. Our research could significantly impact the USD 38.2 billion global market of the epoxy-related industry by not only providing better thermal and mechanical performance of epoxy-based composite materials, but also simultaneously reducing the carbon footprint from the epoxy industry and relieving waste epoxy pollution.

Optimization and analysis of a novel hydrogen liquefaction coupled system with dual path hydrogen refrigeration cycle and the closed nitrogen cycle pre-cooling

The high cost and inefficiency of the hydrogen liquefaction process have impeded the growth of the liquid hydrogen industry. Through the analysis of existing hydrogen liquefaction systems, a novel compact hydrogen liquefaction system that can reduce energy consumption is developed. The system comprises a closed cycle of nitrogen pre-cooling process and dual hydrogen refrigeration cycle cryo-cooling process that are integrated to form and create the coupled system. To evaluate the performance of the proposed hydrogen liquefaction system, an independent system is additionally constructed for comparative analysis, which separates the pre-cooling process and cryo-cooling process. The parameters are optimized using a genetic algorithm for both independent and coupled systems. The results show that the specific energy consumption, coefficient of performance and exergy efficiency of the coupled system are 11.41 kWh/kgLH2, 0.12 and 26.1%, respectively. Furthermore, the coupled system demonstrates significant performance, where the useful and recoverable exergy of the coupled system surpasses that of the independent system. The coupled system's exergy destruction and total UA values decrease by 7.25% and 40.93%, respectively. Moreover, the economic evaluation shows that the total annual cost of the coupled system is $6.22 million per year. The total system cost is sensitive to the electricity price, and the operating expenditure as a percentage of total annualized cost increases from 16% to 53% when the operating electricity price increases from $0.01 to $0.06. This study aims to support the practical development of future hydrogen liquefaction systems by optimizing the cooling system structure.

Study on Fast Liquefaction and Characterization of Produced Polyurethane Foam Materials from Moso Bamboo.

Although bamboo is widely distributed in Japan, its applications are very limited due to its poor combustion efficiency for fuel. In recent years, the expansion of abandoned bamboo forests has become a social issue. In this research, the possibility of a liquefaction process with fast and efficient liquefaction conditions using moso bamboo as raw material was examined. Adding 20 wt% ethylene carbonates to the conventional polyethylene glycol/glycerol mixed solvent system, the liquefaction time was successfully shortened from 120 to 60 min. At the same time, the amount of sulfuric acid used as a catalyst was reduced from 3 wt% to 2 wt%. Furthermore, polyurethane foam was prepared from the liquefied product under these conditions, and its physical properties were evaluated. In addition, the filler effects of rice husk biochar and moso bamboo fine meals for the polyurethane foams were characterized by using scanning electron microscopy (SEM) and thermogravimetry and differential thermal analysis (TG-DTA), and the water absorption and physical density were measured. As a result, the water absorption rate of bamboo fine meal-added foam and the thermal stability of rice husk biochar-added foam were improved. These results suggested that moso bamboo meals were made more hydrophilic, and the carbon content of rice husk biochar was increased.

Operation optimization of propane pre-cooled mixed refrigerant LNG Process: A novel integration of knowledge-based and constrained Bayesian optimization approaches

Liquefied natural gas (LNG) technology, particularly the propane precooled mixed refrigerant (C3MR) process, has demonstrated efficiency and emerged as a distinctive dual-refrigerant technology widely used in LNG production. However, the liquefaction process is the highest energy-intensive stage within its supply chain as it consumes about 8 % of the LNG energy content. Thus, for the first time, this study proposes systematic knowledge-based and constrained Bayesian optimization approaches to identify the optimal operation of the C3MR process. These approaches optimize both the operational parameters (pressures and flow rates) and the composition of the mixed refrigerant with practical equipment specifications and rigorous constraints. The results show that the specific energy consumption (SEC) is reduced to 0.264 kWh/kgLNG, which is 14.6 %, and 26 % lower than the basic C3MR process (unoptimized case) and typical industrial C3MR processes, respectively. In addition, the optimized SEC in this study is 14.5 % to 38.6 % lower than those reported in the literature. At large-scale LNG production (10,000 tons per day), the reduction in the SEC is translated into an 18 MW decrease in compression power, saving approximately 4.7 million $ per year for each C3MR train. Moreover, the coefficient of performance (COP) of the C3MR process was improved by about 15 %, and the CO2 emissions were reduced by 17 % (7 tons per year) compared to the basic C3MR process, indicating potential advancements in large-scale LNG liquefaction processes.

Integration of the single-effect mixed refrigerant cycle with liquified air energy storage and cold energy of LNG regasification: Energy, exergy, and efficiency prospectives

The escalating global energy demand has prompted increased focus on the industry of liquefied natural gas (LNG), emphasizing the need for optimizing liquefaction processes to minimize capital costs. Thus, the integration between liquified natural gas LNG regasification and liquid air energy storage (LAES) to produce electricity and utilize the cold energy of LNG regasification has several interests to maximize the benefits of the process to generate power and face the challenges such as energy saving and reducing the total operations costs … etc. Fortunately, this study introduces a novel approach that combines a single-effect mixed refrigerant (SMR) cycle with air liquefaction, incorporating regenerative Rankine cycles for enhanced efficiency. The effectiveness of the LNG-SMR-LAES process was evaluated using comprehensive energy, exergy, and economic analyses to ascertain its viability. The results showed a notable improvement in the overall net power energy by 6 % and an increase in exergy efficiency by 11.7 % compared to the base case. Energy savings of 31.6 % (470.10 kW) contributed to the process's environmental and economic feasibility. The net present value was estimated at 11,230.4 US dollars, affirming the industrial-feasible design and economic viability of the LNG-SMR-LAES process.

Liquefaction pathway of corn stalk cellulose in the presence of polyhydric alcohols under acid catalysis

In this paper, the experiment of cellulose from corn stalk using 1, 2-propylene glycol (PG) and diethylene glycol (DEG) liquefaction catalyzed by phosphoric acid at atmosphere pressure was carried out. The effect of reaction time on the structural changes of cellulose in the liquefaction process of polyhydric alcohols was investigated, aiming at understanding the mechanism of cellulose liquefaction reaction under the action of acid catalyzed polyhydric alcohols. It was found that the liquefaction yield increased first and then decreased with the extension of reaction time, and reached the highest at 150 min (99.34 %). In the phase of increasing liquefaction yield, cellulose was degraded and translated into glucose, which was then converted into plenty of glycosides with PG/DEG. These glycosides were further converted into low molecular weight (LMW) substances such as hydrocarbons, acids, alcohols, esters, ketones, and ethers. At this time, the biofuel contained 70 %–85 % compounds with carbon number less than 25 and 5 %–10 % compounds with carbon number more than 25. As the prolongation of reaction time (after 150 min), quantities of unstable free radicals formed by cellulose degradation could combine with each other or with hydrogen atoms provided by PG/DEG to produce relatively stable macromolecular substances. That is, the polydispersity (Mw/Mn, abbreviated Ð = 1.28) of the generated biofuel at this stage no longer decreased. However, liquefaction residue produced at 240 min had changed essentially, which was completely different from the liquefaction residue produced in the early stage of liquefaction. In conclusion, this paper revealed the partial reaction process of cellulose by studying the structural changes in the liquefaction process of polyhydric alcohols, which laid a theoretical foundation for exploring the liquefaction mechanism of cellulose.

4E analysis for a novel cryogenic hydrogen liquefaction process using various refrigerants: Energy, exergy, economic, and environment

Hydrogen liquefaction process (HLP) is a principal technology to overcome energy storage and transportation problems and to meet the demand for an eco-friendly energy source. This study proposes three conceptual designs of HLPs with various refrigerant cycles. The specific energy consumption (SEC) of HLP could be reduced by various refrigerants. Three different refrigerants (liquid air (LA)), liquified natural gas (LNG), and mixed refrigerants (MR)) were compared to the conventional LN2-based HLP to verify 4E (efficiency, exergy, economics, and environmental) of each process based on their thermodynamic properties. From the results, we found that the process performance, economics, and environmental effects of the LNG-based hydrogen liquefaction process (LNG-HLP) were the best. In particular, the LNG-HLP, which uses the cold energy of LNG, required less refrigerant than LN2, thereby reducing the energy consumed by major compressors. It had an SEC of 11.04 KWh/kg-LH2 and capital, operating cost, and CO2 emissions of the LNG-HLP process were considerably lower by 5.5 %, 6.2 %, and 12.2 % (unit kg CO2eq/kg LH2), respectively, compared to the conventional process. To propose better economic or environmental scenarios to stakeholders and governments, in this study, the HLP and hydrogen production processes were expanded to include CO2 emission calculation and carried out analysis for levelized cost of hydrogen contribution rate to electricity production types by country.

Review on Absorption Refrigeration Technology and Its Potential in Energy-Saving and Carbon Emission Reduction in Natural Gas and Hydrogen Liquefaction

With the requirement of energy decarbonization, natural gas (NG) and hydrogen (H2) become increasingly important in the world’s energy landscape. The liquefaction of NG and H2 significantly increases energy density, facilitating large-scale storage and long-distance transport. However, conventional liquefaction processes mainly adopt electricity-driven compression refrigeration technology, which generally results in high energy consumption and carbon dioxide emissions. Absorption refrigeration technology (ART) presents a promising avenue for enhancing energy efficiency and reducing emissions in both NG and H2 liquefaction processes. Its ability to utilize industrial waste heat and renewable thermal energy sources over a large temperature range makes it particularly attractive for sustainable energy practices. This review comprehensively analyzes the progress of ART in terms of working pairs, cycle configurations, and heat and mass transfer in main components. To operate under different driven heat sources and refrigeration temperatures, working pairs exhibit a diversified development trend. The environment-friendly and high-efficiency working pairs, in which ionic liquids and deep eutectic solvents are new absorbents, exhibit promising development potential. Through the coupling of heat and mass transfer within the cycle or the addition of sub-components, cycle configurations with higher energy efficiency and a wider range of operational conditions are greatly focused. Additives, ultrasonic oscillations, and mechanical treatment of heat exchanger surfaces efficiently enhance heat and mass transfer in the absorbers and generators of ART. Notably, nanoparticle additives and ultrasonic oscillations demonstrate a synergistic enhancement effect, which could significantly improve the energy efficiency of ART. For the conventional NG and H2 liquefaction processes, the energy-saving and carbon emission reduction potential of ART is analyzed from the perspectives of specific power consumption (SPC) and carbon dioxide emissions (CEs). The results show that ART integrated into the liquefaction processes could reduce the SPC and CE by 10~38% and 10~36% for NG liquefaction processes, and 2~24% and 5~24% for H2 liquefaction processes. ART, which can achieve lower precooling temperatures and higher energy efficiency, shows more attractive perspectives in low carbon emissions of NG and H2 liquefaction.

An in-depth study of the oxidative liquefaction process for polymeric waste reduction and chemical production from wind turbine blades and personal protective equipment used in the medical field

An in-depth study of the oxidative liquefaction process has been provided to degrade the polymeric waste from personal protective equipment (PPEs) and wind turbine blades (WTBs). Thermogravimetric investigations demonstrate that WTBs have three prominent peaks throughout the degradation, whereas PPEs display solitary peak features. Experiments are carried out employing specific experimental design approaches, namely the Central Composite Face-Centered Plan (CCF) for WTBs and the Central Composition Design with Fractional Factorial Design for PPEs in a batch-type reactor at temperature ranges of 250–350 °C, pressures of 20–40 bar, residence times of 30–90 min, H2O2 concentrations of 15–45 %, and waste/liquid ratios of 5–25 % for WTBs. These values were 200–300 °C, 30 bar, 45 min, 30–60 % and 5–7 % for PPE. A detailed comparison has been provided in the context of total polymer degradation (TPD) for PPE and WTBs. Liquid products from both types of wastes after the oxidative liquefaction process are subjected to gas chromatography with flame ionization detection (GC-FID) to identify the existence of oxygenated chemical compounds (OCCs). For WTBs, TPD was 20–49 % and this value was 55–96 % for PPE while the OCC yield for WTBs (36.31 g/kg - 210.59 g/kg) and PPEs (39.93 g/kg - 212.66 g/kg) was also calculated. Detailed optimization of experimental plans was carried out by performing the analysis of variance (ANOVA) and optimization goals were maximum TPD and OCCs yields against the minimum energy consumption, though a considerable amount of complex polymer waste can be reduced and high concentrations of OCC can be achieved, which could be applied for commercial and environmental benefits.

Comparative energy and exergy analysis of ortho-para hydrogen and non-ortho-para hydrogen conversion in hydrogen liquefaction

This study reports the comparative energy and exergy analysis of ortho-para hydrogen and non-ortho-para hydrogen conversion in hydrogen liquefaction process. Two cases were simulated, case A – hydrogen liquefaction with ortho-parahydrogen conversion and case B – hydrogen liquefaction without ortho-parahydrogen conversion. This is the first study that presents a comparative energy and exergy analysis between such two cases. In this research, a hydrogen liquefaction process was designed adopting cascaded five-stage Brayton refrigeration cycle. The process was simulated in Aspen PLUS. The process used a mixed refrigerant (of liquefied natural gas) refrigeration cycle to precool the gaseous hydrogen feed from 26 °C temperature to −192 °C temperature, and mixed refrigerant (of nelium) was subsequently used to further deep-cool the the hydrogen stream from −192 °C temperature to −245.99 °C temperature in the cryogenic section of the process. Liquefaction was achieved by expanding the hydrogen through Joule-Thomson valve at −248.37 °C and 1 bar. The simulated results of the two cases showed the specific energy consumption of case A to be 8.45 kWhr/kgLH, and that of case B to be 15.65 kWhr/kgLH respectively. The results also indicated a total exergy efficiency of 92.42% in case A and 87.18% in case B. The research results showed that the hydrogen liquefaction designed with configuration of ortho-parahydrogen conversion has better performance indicators than the liquefaction without ortho-parahydrogen conversion. Therefore, hydrogen liquefaction with ortho-parahydrogen conversion can be considered in the design and development of new hydrogen liquefaction plants. Process optimization is recommended to further enhance the specific energy consumption and exergy efficiency of both processes.

Arboform – a liquid wood technology: future of bioplastics: A review

Arboform, also known as "liquid wood," represents an innovative and sustainable approach in material science. It is an overview of Arboform technology, its manufacturing process, properties, applications, and environmental implications. Arboform is derived from lignin, a natural polymer abundant in wood, and is produced through a patented liquefaction process that transforms lignin into a moldable thermoplastic material. Unlike plastics, it offers several advantages, including biodegradability, low carbon footprint, and renewable sourcing. Its unique composition endows Arboform with desirable mechanical properties, such as high tensile strength, low thermal expansion, and excellent dimensional stability. Its versatility lends to a wide range of applications and its biocompatibility and non-toxic nature make it suitable for use in food packaging and medical devices, addressing growing concerns over plastic pollution and human health impacts. Despite its promising attributes, challenges remain in scaling up production, optimizing material properties, and ensuring cost competitiveness with conventional plastics. Nevertheless, Arboform represents a promising avenue for transitioning towards a more sustainable and circular economy, offering a renewable alternative to petroleum-based plastics and contributing to the mitigation of environmental degradation associated with conventional plastic production and disposal. It encompasses the potential of Arboform technology in advancing sustainable development goals and fostering innovation in material science towards a more resilient and eco-friendly future.

The technical, economic, and environmental assessment of solvothermal liquefaction processes: An experimental and simulation study on the influence of solvent reichardt parameter

This study explored solvothermal liquefaction (STL) as a viable method for repurposing food waste (FW). Various solvents with different Reichardt parameters were used to facilitate liquefaction, and their impacts on biocrude yields were analyzed. Notably, among the solvents investigated, water and ethanol yielded the highest biocrude yields of 24.7 wt% and 23.6 wt%, respectively. Synergistic effects from combining these solvents were also observed, resulting in enhanced biocrude yields. The STL process was simulated using ASPEN Plus to evaluate its economic feasibility, including sensitivity analysis on input data. Additionally, a negative non-linear correlation was found between net greenhouse emissions and processing capacity. The study determined that the environmental performance of STL becomes less competitive compared to FW landfilling when process capacity falls below a minimum level. Overall, these findings highlight the potential of STL technology for FW management, offering both economic and environmental benefits.

Helium screw compressor for 5tpd large-scale hydrogen liquefier

Liquid hydrogen has promising applications in various industries. As an important heart role, compressors are essential for efficient hydrogen liquefaction. This study introduced a novel profile screw compressor employed in large-scale hydrogen liquefaction processes. The development addressed the challenges associated with large-scale rotors, high pressure differences, and demanding capacity or torque requirements. By utilizing a 5/7-lobe combination of male to female rotors, this technology effectively tackled issues related to rotor dynamics, such as heavy-load rotor stiffness and dynamic balance. The profile design followed hydrodynamics principles, reducing viscosity loss and oil–gas flow loss at high speeds, large flow rates, and significant pressure differences. The profile curve’s curvature and geometric configuration were tailored to the specific pressure state during compression. In high-pressure areas, the profile remained relatively flat to maintain machining accuracy. While in low-pressure areas, the curvature was increased, and the meshing clearance was reduced to minimize helium leakage. Experimental tests conducted under conditions similar to actual hydrogen liquefaction processes have successfully validated the theoretical profile design and the newly developed multi-point oil injection cooling technologies. These advancements have led to an impressive isothermal efficiency of 58.1 % for the entire screw set. Furthermore, the stability and reliability of the compressor were verified through noise and vibration signal testing. The results demonstrated that the compressor operated with noise levels below 96 dB (A) and vibration levels below 7 mm/s, further ensured its suitability for large-scale cryogenic applications. These compressors have successfully run stably on the 5.17 tpd (ton per day) hydrogen liquefier. Overall, this research would significantly contribute to the advancement of screw compressors and large-scale cryogenic technology.

Surrogate-assisted constrained hybrid particle swarm optimization algorithm for propane pre-cooled mixed refrigerant LNG process optimization

The propane pre-cooled mixed refrigerant (C3MR) process is one of the most widely used and efficient natural gas liquefaction processes. However, optimization of this process involves various design and operational constraints, complex thermodynamics, and hence nonconvex in nature. Therefore, it's computationally expensive, often involving trial and error approaches. Existing optimization algorithms often possess flaws such as insufficient accuracy and premature convergence, leading to suboptimal solutions that may violate essential process constraints. This article proposes a novel method to optimize the C3MR process that handles the computational complexity, meets the constraints, and achieves feasible solutions quickly. The proposed method includes modified feasibility-based constraint handling and radial basis function network-assisted surrogate modeling and optimization, where the power consumption is optimized using a hybrid of the particle swarm optimization (PSO) and social learning PSO algorithm. The proposed algorithm achieves the optimum power consumption (121109.31 kW), which is 21.5 % less than the base case (154200 kW). The optimization results are compared with similar optimization algorithms, where the proposed algorithm outperformed the other algorithm regarding optimal solution, convergence, and speed. The results from this study are compared to previous studies from the literature, which validate the accuracy and applicability of the proposed method.

Unlocking the potential of cryogenic biogas upgrading technologies integrated with bio-LNG production: A comparative assessment

Biogas has gained increasing consideration as a competitive, environmentally benign, and sustainable alternative to fossil fuels. These benefits of biogas necessitate the need for intercontinental transportation, which is challenging because of its low energy density. Liquefaction is a viable approach to increase energy density, but this approach is energy and cost-intensive and requires high purity of biomethane. Cryogenic biogas upgrading integrated with the biomethane liquefaction (or bio-LNG) process is an efficient technique to meet these challenges due to its dual benefits: separation with high purity/recovery and precooling of biomethane. This study evaluates different cryogenic technologies (distillation, controlled freeze zone (CFZ), and anti-sublimation) and their integration potential with the bio-LNG production process from a technical and economic perspective. This type of comparative assessment is not found in the open literature. In addition, the CFZ process has not been investigated previously for biogas upgrading. The processes are designed and simulated in Aspen Hysys v14. Among all these processes, the CFZ performs better due to its single-column operation, which reduces cost and energy requirements. The results reveal that the CFZ process is an efficient and economical integrated process, boasting high exergy efficiency (40%), competitive energy consumption (0.30 kWh/kg), and a low production cost (6.3 $/MMBtu). This study can help process engineers design an improved biogas supply chain in terms of cost and energy.

Pyrolysis pretreatment and low-temperature liquefaction: Developing rice straw biochar-based clean liquid biofuel

To overcome the challenges of high oxygen content and low energy density in converting biomass into liquid biofuels, this study proposes an efficient and eco-friendly method: first pyrolyzing rice straw biomass, then converting it into liquid biofuel. It was found that: (1) Characterizing the elemental composition, higher heating value (HHV), thermogravimetric properties, and functional groups of rice straw-biochar-liquid fuel (RS-C-LF), along with analyzing the mass and energy balance of the liquefaction process, revealed that 150 °C was the optimal low liquefaction temperature. (2) The HHV, O and S content, mass and energy yield of RS-C-LF150 were significantly enhanced compared to direct biomass-to-liquids and met the biodiesel standard, with values of 42.16 MJ/kg, 0.82 %, 0 %, 67.49 %, and 69.42 %, respectively. (3) The feasibility and commercial potential of this research was further demonstrated through economic and SWOT analysis of this study liquid biofuel (the total production expenditure is only $171.29/bbl), and the design of the zero-waste and self-circulating preparation system.