Liquefaction Technology Research Articles

A techno-economic assessment of gas-to-liquid and coal-to-liquid plants through the development of scale factors

Fluctuations in conventional crude oil price globally and initiatives towards the phase-out of coal-based power have initiated a focus on alternative sources of liquid fuels from natural gas and coal. Gas-to-liquid (GTL) and coal-to-liquid (CTL) processes are two liquefaction technologies that could be used. There is a limited work on either the development of scale factors to estimate capital costs or on techno-economic assessments of the plants. This study addresses this gap and focusses on western Canada, which has large deposits of coal and natural gas. The capital costs of the plants' key equipment are estimated through the development of cost scale-up factors. The production cost for 50,000 bbl/day of liquid fuels from GTL and CTL plants is estimated through modelling using a bottom-up approach. The developed scale-up factors for the GTL and CTL plants were found to be 0.70 and 0.65, respectively. For both plants, most of the benefits of economies of scale are achieved at a capacity of 20,000 bbl/day. The production costs of the GTL and CTL processes are 44.61 and 57.65 Canadian cents/liter respectively. With carbon capture and sequestration (CCS), the production cost of fuel from the CTL plant is higher than from the GTL plant.

Status of SF 6 separation/refining technology development for electric industry in Korea

Abstract KEPCO (Korea Electric Power Corporation) possesses and regularly maintains SF6 filled power distribution facilities containing SF6 gas from several liters up to several tens of liters. During the replacement of expired facilities, waste SF6 gas is produced. And some facilities are refilled with SF6. Since SF6 is one of the most potent greenhouse gases, KEPCO is developing technologies to recover and separate/refine SF6 from expired power distribution facilities and reuse it to reduce SF6 release and maintenance cost. A hybrid system of liquefaction and PSA (Pressure Swing Adsorption) had been developed, even though its refinement rate was too slow to use practically. The technology developed next was liquefaction technology, which has been under test. Its process is relatively simple and its manufacturing cost is low, but its refinement quality is expected to be low. A cryogenic freezing technology freezes SF6 for refinement. Even though the technology is energy-intensive, it can produce high purity SF6 and can be easily scale up, which make the technology suitable to be commercialized. Currently, this technology is being optimized. The last technology under development is a hydrate technology, which utilized SF6-hydrate formation. Its advantage is less energy-intensive and it is considered to be suitable for refining relatively low quality SF6 (>70%).

Economic analysis on PRICO process for natural gas liquefaction based on TCI criteria

Liquefied Natural Gas has become a global fuel with an annual trade volume growth of more than 7%, an expected growth of 6.7% per year until 2020 and with a current trade volume of over 240 million tons. There were seven main liquefaction technologies in use, the most common one being the PRICO process, also known as Single Mixed Refrigerant (SMR). PRICO LNG process comprises of only single mixed refrigerant and one NG stream, thus makes it the simplest LNG process exists so far. This paper applies economic analysis to a PRICO process to determine the Total Capital Investment (TCI). The analysis in this paper using the results that was obtained from energetic analysis by executed the simulation using DWSIM software. The results obtained after calculated the TCI later is discussed with a few criteria of TCI itself.

Growth and metabolic characteristics of oleaginous microalgal isolates from Nilgiri biosphere Reserve of India

BackgroundRenewable energy for sustainable development is a subject of a worldwide debate since continuous utilization of non-renewable energy sources has a drastic impact on the environment and economy; a search for alternative energy resources is indispensable. Microalgae are promising and potential alternate energy resources for biodiesel production. Thus, our efforts were focused on surveying the natural diversity of microalgae for the production of biodiesel. The present study aimed at identification, isolation, and characterization of oleaginous microalgae from shola forests of Nilgiri Biosphere Reserve (NBR), the biodiversity hot spot of India, where the microalgal diversity has not yet been systematically investigated.ResultsOverall the higher biomass yield, higher lipid accumulation and thermotolerance observed in the isolated microalgal strains have been found to be the desirable traits for the efficient biodiesel production. Species composition and diversity analysis yielded ten potential microalgal isolates belonging to Chlorophyceae and Cyanophyceae classes. The chlorophytes exhibited higher growth rate, maximum biomass yield, and higher lipid accumulation than Cyanophyceae. Among the chlorophytes, the best performing strains were identified and represented by Acutodesmus dissociatus (TGA1), Chlorella sp. (TGA2), Chlamydomonadales sp. (TGA3) and Hindakia tetrachotoma (PGA1). The Chlamydomonadales sp. recorded with the highest growth rate, lipid accumulation and biomass yield of 0.28 ± 0.03 day−1 (μexp), 29.7 ± 0.69% and 134.17 ± 16.87 mg L−1 day−1, respectively. It was also found to grow well at various temperatures, viz., 25 °C, 35 °C, and 45 °C, indicating its suitability for open pond cultivation. The fatty acid methyl ester (FAME) analysis of stationary phase cultures of selected four algal strains by tandem mass spectrograph showed C16:0, C18:1 and C18:3 as dominant fatty acids suitable for biodiesel production. All the three strains except for Hindakia tetrachotoma (PGA1) recorded higher carbohydrate content and were considered as potential feed stocks for biodiesel production through hydrothermal liquefaction technology (HTL).ConclusionsIn conclusion, the present investigation is a first systematic study on the microalgal diversity of soil and water samples from selected sites of NBR. The study resulted in isolation and characterization of ten potent oleaginous microalgae and found four cultures as promising feed stocks for biodiesel production. Of the four microalgae, Chlamydomonadales sp. (TGA3) was found to be significantly thermo-tolerant and can be considered as promising feedstock for biodiesel production.

Optimization to Hydrothermal Liquefaction of Low Lipid Content Microalgae Spirulina sp. Using Response Surface Methodology

The production and nature of the biocrude obtained from Spirulina sp. by hydrothermal liquefaction (HTL) technology is focused in this investigation. Our aim is to evaluate the interaction of different factors on the bio-oil production through HTL using microalgae that contains relatively low lipid content and high protein. Optimization of three key parameters—concentration (mass of algae per mass of solvent), reaction temperature, and holding time—was carried out by response surface methodology (RSM). In this work, we used central composite design to conduct the experiment process. Graphical response surface and contour plots were used to locate the optimum point. The final results showed that the optimum concentration, temperature, and holding time were 10.5%, 357°C, and 37 min, respectively. Under the optimum conditions established, yield of the biocrude (41.6 ± 2.2%) was experimentally obtained using the fresh microalgae. This study showed the potential of bio-oil production of Spirulina sp. by HTL technology, but it still needs more improvement of the biocrude for utilization.

Analysis of distillate product in the direct coal liquefaction of a Chinese bituminous coal

To understand the reaction mechanism of coal liquefaction process and further improve the direct coal liquefaction (DCL) technology, a certain kind of DCL oil, which was prepared from a Chinese bituminous Yulin coal, was first separated into different fractions using improved silica-gel column chromatography (SGCC) coupled with the UV-absorbance detector, and then identified by gas chromatography-mass spectrometer (GC-MS), the comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometer (GC × GC-TOFMS), 1H NMR and FTIR. Around 95% of DCL oil was successfully separated into seven fractions by four mobile phases and analysed. It was found that DCL oil consists of 9.06% of alkanes, 36.32% of hydroaromatics, 17.85% of aromatics, 15.39% of oxygen-containing compounds, 16.21% of nitrogen-containing compounds and 2.33% of polyheteroatomic compounds, respectively. [Received: August 22, 2017; Accepted: March 1, 2018]

Energy efficiency enhancement of a single mixed refrigerant LNG process using a novel hydraulic turbine

The advancement in hydraulic turbine (HT) technology was exploited for energy and cost benefits in natural gas liquefaction. Replacing the conventional Joule–Thompson (JT) valve with HT has the potential to recover the work input. This research investigated the effect of replacing the JT valve with HT in the energy efficiency enhancement of a single mixed refrigerant (SMR) process. To fully take the potential benefit of the HT, the proposed SMR schemes were optimized by using a modified coordinate descent optimization method, which was implemented in Microsoft Visual Studio environment and linked to the rigorous HYSYS® model. The results showed that the required energy of the proposed HT based SMR process could be saved up to 16.5% in comparison with the conventional SMR process using the JT valves. Utilization of the recovered energy into boosting the natural gas feed pressure could further reduce the energy requirement up to 25.7%. Exergy efficiency analysis also showed that whole exergy efficiency of the enhanced SMR process can be increased by about 11% as compared to the base case. The proposed HT based liquefaction technology can be extended to other natural gas liquefaction processes as an attractive option for enhancing the energy efficiency.

Pencairan Batubara Peringkat Rendah Papua Menggunakan Katalis Bijih Besi

Low rank coal utilization often adversely affects the equipment used. Distinct with coal liquefaction technology that prioritizes the use of low rank coal. This condition encourages this research, with the aim of observing the liquid potential of low rank Papuan coal by using iron ore catalysts. Papua low rank coal is liquefied on the autoclave 5 liter with iron ore catalyst and antrasen as solvent. Operating conditions consist of temperature of 400ºC and holding time of 60 minutes. The result of conversion of the three samples without catalyst is only in the range of 65.72-66,45 %, whereas the conversion with iron ore catalysts ranged from 88.63-89.94 % and oil yield between 62.11-63,34%. This result also shows the contribution of iron ore catalyst to increase the conversions that averaged 23.04 %.

Thermodynamic characteristics of a novel wind-solar-liquid air energy storage system

Due to the nature of fluctuation and intermittency, the utilization of wind and solar power will bring a huge impact to the power grid management. Therefore a novel hybrid wind-solar-liquid air energy storage (WS-LAES) system was proposed. In this system, wind and solar power are stored in the form of liquid air by cryogenic liquefaction technology and thermal energy by solar thermal collector, respectively. Owing to the high density of liquid air, the system has a large storage capacity and no geographic constraints. The WS-LAES system can store unstable wind and solar power for a stable output of electric energy and hot water. Moreover, a thermodynamic analysis was carried out to investigate the best system performance. The result shows that the increases of compressor adiabatic efficiency, turbine inlet pressure and inlet temperature all have a beneficial effect.

Bubble growth, departure and rising of ethane at nucleate pool boiling condition

Boiling heat transfer exists in many industrial heat exchangers such as the evaporator of the refrigerator and the air conditioner, the reboiler of the chemical equipment and steam generator of the nuclear reactor. In the process of boiling, bubble movement can speed up the heat transfer between liquid and solid, leading to the improvement in heat transfer efficiency. Traditional refrigerants used in the industrial facilities have serious environmental problems, therefore, new substitutes are needed. Hydrocarbons are good alternatives. Ethane was suggested as one component of a mixed- refrigerant for its zero ozone depletion potential, low global warming potential and high thermodynamic properties. Therefore, it is important to investigate the bubble behavior of ethane in saturated nucleate pool boiling to design and optimize the industrial equipment like evaporator, improve natural gas liquefaction technology, and research characteristics of heat transfer and multiphase flow as well. Although there are a lot of researches on the heat transfer characteristics of pool boiling, the research on the bubble behavior in ethane is still lacking. In this paper, visualization experiments on the pool boiling heat transfer characteristics of ethane were carried out at 0.2 MPa. The heat fluxes varied from 14.65 kW m−2 to 80.79 kW m−2. Boiling occurred on the upward facing side of a smooth vertical copper cylinder with 20 mm diameter, connected to a DC power supply to control the heat flux on the surface. The measured roughness of the surface was 68.1 nm (root mean square average of the height deviations) and 50.7 nm (the arithmetic average of the absolute values of the surface height deviations). Acquisition of the temperature and pressure was accomplished by using a Keithley 2700 and six thermocouples. The experimental apparatus has a steel ruler inside the pool as the reference length to measure the bubble sizes and the maximum uncertainty for length measurement is 0.060 mm. Some conclusions can be drawn. (1) According to the change of diameter with time, the growth process was divided into three stages. The bubble growth process has obvious segmentation characteristics, and piecewise prediction models are recommended. (2) The bubbles in boiling pool exhibit the characteristics of axial symmetry and uneven distribution; the shape of separation of ethane bubbles has ellipsoidal and irregular shapes relative to normal temperature liquids. (3) There were trail changes and additional movements of large bubbles. Compared to normal temperature liquids, the trail changes were relatively simple; and the bubbles are bubbly and slug flow of two flow regimes. (4) System pressure, heating wall properties like surface roughness, liquid properties like contact angle and surface tension have an important influence on bubble behavior. This paper suggests that the heat transfer prediction equation should consider them.

Dynamic simulation of a single nitrogen expansion cycle for natural gas liquefaction under refrigerant inventory operation

Nitrogen (N2) expansion natural gas liquefaction technology is wildly used for liquefied natural gas production due to its unique advantages. However, few works have been reported about the detailed unit operating performance of N2 expansion system under refrigeration inventory operation that is one of the most effective operations for adjusting system refrigeration capacity. In this study, we have comprehensively investigated the dynamic characteristics of a single N2 expander liquefier under inventory operation. Firstly, system model of the liquefier is developed based on rigorous first principles, valid empirical correlations and accurate physical property. Meanwhile, plate-fin heat exchanger model, as a key component, is reasonably and greatly simplified according to symmetric layer arrangements. Using the system model, the transient system behaviors are identified and evaluated. The primary performance parameters of centrifugal compressor train, e.g. efficiency, surge margin and input power, experience the most dramatic changes during the first several seconds after the operation starts. ±6% variations in total nitrogen refrigerant mass result in −4.5 and +5.6°C variations in LNG temperature, +8.7% and −8.4% variations in liquefier input power and maximum −7.8% variation in compressor surge margin, eventually. In general, the liquefier exhibits strong nonlinear behaviors.

Bio-oil production from refinery oily sludge using hydrothermal liquefaction technology

This study investigates direct hydrothermal liquefaction (HTL) of refinery oily-sludge (ROS) to produce bio-oil (BO). Optimum operating conditions of HTL were experimentally determined by response surface methodology (RSM). Experiments were implemented in a tube-bomb reactor at various temperatures (275–350°C), reaction time (30–75min) and ROS content (10–40wt%) in feed. BO yield reached to 45.52wt% on dry ash-free basis at optimum conditions (290°C, 65min and 16wt% of ROS). GC/MS analysis showed that BO mainly contained aliphatic, saturated and unsaturated fatty acids, monoaromatic and polyaromatic compounds. Moreover, it was found that by increasing temperature, small compounds were converted into heavier molecules via repolymerization reactions. With increasing reaction time at low temperatures, the amount of nitrogen-containing compounds increased, emphasizing the undesired effect of very long reaction time. Results also indicated that catalytic upgrading is required for dehydrogenation, oxygen removal and new CH bonds creation.

Fundamentals of Hydrofaction™: Renewable crude oil from woody biomass

As a response to the global requirement for renewable transportation fuels that are economically viable and fungible with existing petroleum infrastructure, Steeper Energy is commercializing its proprietary hydrothermal liquefaction (HTL) technology as a potential path to sustainable lignocellulosic-derived transport fuels. Hydrofaction™ utilizes high-density, supercritical water chemistry at distinctly higher pressures and temperatures than most literature on HTL. The paper presents a direct relation between density and the chemical properties that make near-critical water an appealing HTL reaction medium. Further, the fundamentals of Hydrofaction™ and how these are carefully chosen to favor certain chemical reaction paths are explained, including the use of high-density supercritical water, homogenous alkaline metal catalysts at alkaline conditions and recycling of aqueous and oil products. Steady state operational data from a campaign producing 1 barrel (>150 kg) of oil at a dedicated pilot plant is presented, including closure of mass, energy, and three elemental balances. A detailed oil assay specifying the oil quality as well as mass and energy recoveries from wood to oil of 45.3 wt.% and 85.6%, respectively, reflect that Hydrofaction™ is an energy-efficient technology for sourcing renewable biofuels in tangible volumes.

Roadmap to economically viable hydrogen liquefaction

The distribution of hydrogen in liquid state has several advantages because of its higher volumetric density compared to compressed hydrogen gas. The demand for liquid hydrogen (LH2), particularly driven by clean fuel cell applications, is expected to rise in the near future. Large-scale hydrogen liquefaction plants will play a major role within the hydrogen supply chain. The barriers of built hydrogen liquefiers is the low exergy efficiency and the high specific liquefaction costs. Exergy efficiency improvements, however, are limited by economic viability. The focus of this paper is to present a roadmap for the scale-up of hydrogen liquefaction technology, from state-of-the-art plants to newly developed large-scale liquefaction processes. The work is aimed at reducing the specific liquefaction costs by finding an optimal trade-off between capital costs and operating costs. To this end, two developed hydrogen liquefaction processes were optimized for specific energy consumption and specific liquefaction costs, showing the potential to reduce the specific liquefaction costs by 67% for a 100 tpd LH2 plant compared to a conventional 5 tpd LH2 plant while achieving a specific energy consumption between 5.9 and 6.6 kWh per kg LH2 with technology that is or will be available within 5 years. The results make liquid hydrogen a viable distribution route for hydrogen for mobility.

Application of zeolite adsorption and biological anaerobic digestion technology on hydrothermal liquefaction wastewater

The post-hydrothermal liquefaction wastewater (PHWW) was obtained from a conversion process of Spirulina sp. to bio-crude oil via hydrothermal liquefaction (HTL) technology that was rich in organic matter and toxicant. In this study, zeolite was applied to overcome the inhibitions and improve anaerobic digestion (AD) efficiency. Three zeolite adding ways were evaluated: PHWW pretreated with zeolite for 5 h with/without solid-liquid separation before AD process and zeolite added to PHWW AD process directly, in order to find the most ideal way to add zeolite. Results indicated that zeolite had a positive effect on the AD process of the PHWW. The gas potential of PHWW after adding zeolite, as well as the chemical oxygen demand (COD) removal rate, was much higher than those of its initial state. Especially when the PHWW was pretreated by zeolite for 5 h without separation, the biogas yield increased by 73.96% (6170 μmol/g CODremoved) compared with the initial PHWW (3546.7 μmol/g CODremoved). Keywords: post-hydrothermal liquefaction wastewater, anaerobic digestion, zeolite adsorption, biogas DOI: 10.3965/j.ijabe.20171001.2704 Citation: Li R R, Ran X, Duan N, Zhang Y H, Liu Z D, Lu H F. Application of zeolite adsorption and biological anaerobic digestion technology on hydrothermal liquefaction wastewater. Int J Agric & Biol Eng, 2017; 10(1): 163–168.

Life cycle assessment and nutrient analysis of various processing pathways in algal biofuel production

This study focuses on analyzing nutrient distributions and environmental impacts of nutrient recycling, reusing, and discharging in algal biofuels production. The three biomass conversion pathways compared in this study were: hydrothermal liquefaction technology (HTL), hydrothermal hydrolysis pretreatment +HTL (HTP), and wet lipid extraction (WLE). Carbon, nitrogen, and phosphorous (C, N, P) flows were described in each pathway. A primary cost analysis was conducted to evaluate the economic performance. The LCA results show that the HTP reduced life cycle NOx emissions by 10% from HTL, but increased fossil fuel use, greenhouse gas emissions, and eutrophication potential by 14%, 5%, and 28% respectively. The cost of per gallon biodiesel produced in HTP was less than in HTL. To further reduce emissions, efforts should be focused on improving nutrient uptake rates in algae cultivation, increasing biomass carbon detention in hydrothermal hydrolysis, and/or enhancing biomass conversion rates in the biooil upgrading processes.

Renewable energy technologies: enlargement of biofuels list and co-products from microalgae

Microalgae is a perspective feedstock for producing a wide variety of biofuels and co-products with high added value. An alternative to the traditional technology of biodiesel from algae by the transesterification is the technology of hydrothermal liquefaction (HTL). The article presents the results of promising strains screening and directed cultivation of microalgae for the processing by means of variety of technologies and production of valuable co-products. An algorithm for selecting suitable areas for industrial plantations of algae is presented.

Coupling of high temperature nuclear reactor with chemical plant by means of steam loop with heat pump

High temperature nuclear reactors (HTR) can be used as an excellent, emission-free source of technological heat for various industrial applications. Their outlet helium temperature (700°-900°C) allows not only for heat supply to all processes below 600°C (referred to as “steam class”), but also enables development of clean nuclear-assisted hydrogen production or coal liquefaction technologies with required temperatures up to 900°C (referred to as “chemical class”). This paper presents the results of analyses done for various configurations of the steam transport loop coupled with the high-temperature heat pump designed for “chemical class” applications. The advantages and disadvantages as well as the key issues are discussed in comparison with alternative solutions, trying to answer the question whether the system with the steam loop and the hightemperature heat pump is viable and economically justified.

Process modeling of direct coal-biomass to liquids (CBTL) plants with shale gas utilization and CO2 capture and storage (CCS)

Direct coal liquefaction (DCL) technologies have been commercially demonstrated for producing transportation fuels from non-petroleum sources. However, significant amount of hydrogen is required in the DCL process due to the low H/C ratio in coal. As a result, DCL processes are usually associated with a high level CO2 emission from hydrogen production units. Hence, direct coal biomass to liquids (CBTL) processes with CO2 capture and storage (CCS) and shale gas utilization are proposed in this work as an option for reducing CO2 emission. In this study, the focus is on process simulation and calculation of material and energy balances of novel direct CBTL plants, which can be used as a basis for further studies, such as optimization, techno-economic analysis and life-cycle analysis. In this process, coal with moderate amount of biomass is converted into syncrude through reaction with H-donor solvent and gaseous hydrogen in a catalytic two-stage liquefaction unit. Hydrogen required for the liquefaction and product upgrading unit is produced from the liquefaction residue partial oxidation unit and the shale gas steam reforming unit or from the coal/biomass/residue co-gasification unit. Different CCS technologies are evaluated to achieve 90% overall carbon capture if high extent of CO2 capture is considered. Results of individual plant sections are validated with the existing data, if available. Sensitivity studies have been conducted to analyze the effects of key operating parameters and design parameters, such as the sources of hydrogen, CCS technologies, extent of CCS, and biomass/coal ratio. Key measures studied in this work include the fuel yield, thermal efficiency, CCS penalty and CO2 emission.

Development and industrial tests of the first LNG hydraulic turbine system in China

The cryogenic hydraulic turbine can be used to replace the conventional J–T valve for LNG or mixed refrigerant throttling and depressurization in a natural gas liquefaction plant. This advanced technology is not only to enhance the efficiency of the liquefaction plant, but to usher a new trend in the development of global liquefaction technologies. China has over 136 liquefaction plants, but the cryogenic hydraulic turbines have not been deployed in industrial utilization. In addition, these turbines cannot be manufactured domestically. In this circumstance, through working on the key technologies for LNG hydraulic turbine process & control system development, hydraulic model optimization design, structure design and manufacturing, the first domestic cryogenic hydraulic turbine with a flow rate of 40 m3/h was developed to recover the pressure energy from the LNG of cold box. The turbine was installed in the CNOOC Zhuhai Natural Gas Liquefaction Plant for industrial tests under multiple working conditions, including start-stop, variable flow rates and variable rotation speeds. Test results show that the domestic LNG cryogenic hydraulic turbine has satisfactory mechanical and operational performances at low temperatures as specified in design. In addition, the process & control system and frequency-conversion power-generation system of the turbine system are designed properly to automatically and smoothly replace the existing LNG J–T valve. As a result, the domestic LNG cryogenic hydraulic turbine system can improve LNG production by an average of 2% and generate power of 8.3 kW.