LNG Liquefaction Plant Research Articles

Thermodynamic Analysis and Optimization of the C3/MRC Liquefaction Process

In the natural gas liquefaction process, the mixed refrigerant natural gas liquefaction process is widely used in LNG liquefaction plants because of its advantages of low energy consumption. This paper focuses on the influences of important parameters in the C3/MRC liquefaction process, that is, the comparison between propane precooling temperature and the number of moles of methane in mixed refrigerant, power consumption and loss. In addition, the total process was optimized with the optimizer and manual adjustment in HYSYS software to minimize the total power consumption. The results show that with increasing propane precooling temperature, the propane flow rate is almost unchanged, while the mixed refrigerant flow rate decreases significantly, and the loss of the heat exchanger increases significantly. The power consumption of the propane precooling cycle and hybrid refrigeration cycle increases with increasing methane content in the refrigerant, so the power consumption of the whole process increases accordingly. The effect of the methane content in the mixed refrigerant on the process evaluation index is more significant than that of the propane precooling temperature.

Turbo-Expander Generators for Supplemental Power Generation in LNG Liquefaction Plants

Incentives to increase efficiency and reduce CO2 emissions have led to the development of many plant process designs incorporating turbo-expanders. Turbo-expanders provide the most efficient solution when it is required to reduce the pressure of a fluid stream. By expanding high pressure fluid, energy in the high-pressure fluid entering the turbo-expander can be efficiently used for electrical power generation. The energy recovered from the expansion is supplementary, thereby improving the thermal efficiency of the plant without leaving any noticeable trace of greenhouse gas emissions. This article focuses on both mechanical and electrical considerations for the implementation of turbo-expander generators. In an example of LNG liquefaction plant, the article discusses the plant thermal efficiency, turbo-expander performance curve, generator sizing, and the choice between the induction and the synchronous generator. The impact on the plant real and reactive power balance and the system stability is shown in an example. Furthermore, this article evaluates the options for the turbo-expander generator tie-in points within the electrical system.

Large Synchronous Motors as Drivers for Centrifugal Compressors in LNG Liquefaction Plants

Centrifugal compressors are major components in LNG liquefaction plants. Design considerations for optimal selection and proper sizing of compressor drivers include large starting torque requirements to enable compressor start from settle-out conditions and to prevent flaring the gas. Start-up capabilities of the motor driver can significantly impact the reliability and operability of the compressor train. The article reviews the requirements of API 617 and API 546, and addresses a number of important design and sizing criteria used to properly match the large centrifugal compressor and its synchronous motor driver. In the effort to optimize plant design and maintain the performance requirements, the article discusses optimization options, such as direct on line starting method to explore the motor rating limits, and the use of synchronous motors for power factor correction to eliminate or reduce the need for reactive power compensation by capacitor banks. This article presents a novel approach to show constant reactive power lines on traditional V curves. It also complements capability curves of synchronous motors with lines of constant efficiency.

Research on the construction of a natural gas price index in China

A natural gas price index (NGPI) can be used by stakeholders to comprehensively evaluate the natural gas market. At present, there is no NGPI to measure the volatility of China's entire natural gas market. As a result, when studying the status and trend of natural gas industry, Chinese researchers can reference only the NGPIs compiled by international companies such as Platts and Argus. Therefore, based on the development status of its natural gas industry, this study builds an NGPI for China. The NGPI designed here mainly includes an LNG cost, insurance, and freight (CIF) index, inter-provincial gate station price index, LNG liquefaction plant price index, and unconventional gas price index. The inter-provincial gate station price index consists of residential pipeline gas price index and industrial pipeline gas price index. The unconventional gas price index comprises direct-supply gas price index, shale gas price index, coal gas price index, coalbed methane price index, and tight gas price index. The index design method in this study provides a useful reference for the construction of NGPIs for China in the future.

Opportunities and Challenges for the Industrial Titanium Market

The industrial titanium market is the second largest segment of the titanium industry and currently comprises less than 20 % of the overall titanium market. In spite of a more than 50 year history of successful application in corrosive environments myths about availability, fabrication, pricing and corrosion resistance are still part of the conversation and culture with many potential customers. The author will discuss these issues and present comparisons with other common materials of construction to demonstrate the business case for titanium. With seawater/brackish water being the most common corrosive environment where titanium is applied examples of current applications will be presented. By highlighting the characteristics of titanium that led to the material choice in these examples potential new applications can be identified. These examples will come from application on offshore platforms, LNG liquefaction plants, power generation, desalination and petroleum refining operations. Against the backdrop of the application analysis the author will also explore regulatory, market influences and new technology impacting the industrial titanium market segment. Drawing on statistics from the Titanium Association and other resources a projection for industrial growth will be presented for the next decade.

Malaysia’s Petronas is Looking Near and Far for Gas and Oil

Petronas is looking within its home country, around Southeast Asia, and to the Americas in an effort to maintain its forecast average yearly production of 1.7 million BOE/D over the next 5 years. It is also exploring new partnerships with other global operators that offer regional and technical expertise. The integrated company, whose upstream portfolio consists primarily of natural gas, wants to both accelerate its exploitation of the hydrocarbon and add more oil to the mix. Back home, Petronas—the world’s third-largest LNG seller—continues to target domestic gas to leverage its control of the gas value chain all the way to its petrochemical and LNG liquefaction plants. The company’s LNG facilities include its 30-million tonnes/annum (mtpa) complex in Sarawak, and the world’s first floating LNG facility, the 1.2-mtpa PFLNG Satu. A second floating LNG facility is expected to be ready for sail away by 2020. Petronas is taking advantage of a growing Southeast Asia gas market, counting Japan, Korea, Taiwan, “and increasingly China” as major LNG customers, said Adif Zulkifli, Petronas executive vice president and chief executive officer of gas and new energy, on the sidelines of a recent SPE forum in Kuala Lumpur. Adif said one of Petronas’ primary goals is to turn Malaysia’s large inventory of contingent resources into proved reserves. The company has worked “to intensify exploration activities in Malaysia,” and it is seeking to bring more partners into the fold: The country recently revised terms in its deepwater production-sharing contracts to attract more international participation. “We are quite progressive in terms of attracting investment, and that has brought in some new plays into the space,” he said. Adif believes “there is much potential within the deep waters of Sabah that is still left untapped and remains very attractive to investors.” Last year, the Total-operated Tepat-1 well in deepwater Sabah tested a frontier Miocene carbonate buildup “and is believed to have found oil and gas, though commerciality is uncertain and the results are being kept very tight,” according to a report from research consultancy Westwood Global Energy. “Tepat demonstrates that explorers are still testing new plays in the region and that a breakthrough could yet happen.” Elsewhere in Southeast Asia, said Adif, the company hopes to soon monetize its operated deepwater Kelidang cluster project off Brunei, continue exploratory work on the recent onshore Sakakemang discovery in Indonesia, and improve recovery from its Yetagun block off Myanmar. Petronas farmed in to the Sakakemang block in January, a month before operator Repsol announced the discovery, which comes with a preliminary estimate of 2 Tcf in recoverable resources. Petronas also intends to explore the deepwater Moat-tama Basin off Myanmar and frontier areas off East Indonesia, he added.

Integration of fault tree and importance measure for toxic prevention barrier

This paper discusses the procedure of integrating importance measures into fault tree analysis. Importance measures (IM) are analytical tools developed to quantitatively appraise the contribution of a plant component towards the overall risk. As part of safety assessment, this method can be used to rank and identify the root cause of undesired events. The critical component is usually prioritised in order to improve the reliability of the system. Fussell-Vesely (FV) importance measure is one of the most commonly used IM. This method is applied to a case study involving typical toxic prevention barriers based on an LNG liquefaction plant. This paper also includes event ranking using other IM.

Self-optimizing control of an LNG liquefaction plant

In this paper we apply self-optimizing control (SOC) to a cascaded LNG liquefaction plant. We first introduce the model, and then define the operational objective, which is to achieve minimal energy consumption while satisfying operational constraints. Four control structures are compared; a “standard” temperature control structure, an SOC structure with two plant measurements, an SOC structure that uses a combination of plant measurements as controlled variable, and an SOC structure where we also include measurements of disturbances in addition to the plant measurements. We find that the SOC structures significantly reduce the average steady-state loss when the operating conditions change. We furthermore find that using more plant measurements in the SOC structure results in lowered losses. In particular, for the disturbances considered, the steady-state loss becomes acceptably low, such that there is no need for a supervisory real-time optimization layer. Finally, it has been found that including disturbance measurements results in somewhat reduced losses, although the improvement was insignificant for the studied case. The effectiveness of the SOC framework is shown by closed-loop step responses to selected disturbances.

A Study on the Vibration Analysis of Impeller and Shaft in Cryogenic Submerged Pump

In this research, reverse engineering was applied to the product manufactured by “Vanzetti” from Italy to develop a localized cryogenic submerged pump used in small-scale LNG liquefaction plants. The results of modal analysis of the impeller and shaft confirmed that the resonance frequency of the impeller and shaft played an important role in the rotor. Modal analysis of the rotor confirmed that the forcing frequency had no influence on the resonance phenomenon.

Effects of varying the ambient temperature on the performance of a single mixed refrigerant liquefaction process

This paper presents the optimal design and operational solutions for a single mixed refrigerant liquefaction process under varying ambient temperatures. Given that the ambient temperature can affect the performance of air coolers and gas turbines, the correlation between changes in the ambient temperature and the performance of a single mixed refrigerant liquefaction process should be investigated. A simulation model and a mathematical model were devised and linked to find the optimal design and operational solutions for a single mixed refrigerant liquefaction process, and the particle swarm optimization method was adopted for used with the mathematical model. The results of this study can provide insight about taking advantage of low ambient temperatures for process engineers associated with LNG liquefaction plants.

MODELING THE IMPACT OF NATURAL AND SECURITY HAZARDS IN AN LNG PROCESSING FACILITITY

Development of accident models based on cause and effect relationships facilitates the formulation of accident prevention and mitigation plans in the Chemical Process Industries (CPIs). In this paper, failures of accident prevention barriers triggered by man-made and natural hazards are causally modeled using Fault Trees (FTs) models. Additionally, updated technique of FTs basic and top events failure probabilities was applied using Hierarchy Bayesian Approach (HBA) based on basic events precursor data. This updated methodology overcomes the uncertainty limitation in the determination of FTs reliability data, as well as converge them into their accurate values. Moreover, it provides valuable information supporting risk based decision. The methodology was applied to LNG pipeline and liquefaction plant Dispersion Prevention Barrier (DPB). The result shows the capability of the methodology to model natural and security hazards (NE&ISHs) in both qualitative and quantitative manners, as well as, to update FT events failure probabilities through the use of the precursor data to the HBA. Outcomes demonstrate that the average posterior failure probability of DPB of that particular case study increased from 0.0613 to 0.204232 which represents a 3.33 times increment compared with the prior.

천연가스 액화공정의 C3MR 냉동사이클의 공정모사와 최적화에 관한 연구

Abstract - The LNG liquefaction plant which have a higher value-added business in the LNG value chain takes about 35% of total cost. Liquefaction process is core technology of liquefaction plant. Almost all of cost which was consumed from the liquefaction plant, using for operation energy of liquefaction process. The cost can be reduced by increasing efficiency of liquefaction cycle. C3MR(propane pre-cooled, mixed refrigerant cycle) which liquefies NG using propane and MR cycle has the high efficiency, so C3MR is mostly used lique-faction process in LNG industry. In this study, process simulation and analysis were performed for C3MR process. C3MR process variables were found through this simulation and analysis, and then the process opti-mization was performed. It is considered that the results of process analysis, process variables and process opti-mization study can be utilized to develope new liquefaction process.Key words : natural gas liquefaction, C3MR, simulation, optimization 1)

Hydrodynamics of an FLNG system in tandem offloading operation

Floating liquefied natural gas (FLNG) is a new type of offshore platform that consists of a ship-type floating production storage and offloading (FPSO) hull equipped with LNG storage tanks and liquefaction plants. In LNG offloading operation, tandem configuration where LNG carrier connects to the stern of an FLNG, shows its prospects. In this study, the hydrodynamic characteristics of a single point turret-moored FLNG system in tandem offloading operation are investigated by using a time-domain coupled dynamic analysis program and a set of comparative model tests. The numerical simulation model features well the hydrodynamic performance of the coupled system obtained from the experiments. The influence of distance between the two vessels on their hydrodynamic performance has been investigated. Furthermore, two different ways of connecting FLNG vessel and LNG carrier have also been comparatively studied. The numerical results show that there is significant difference at the hydrodynamic performance in the two ways of tandem offloading operations, which means that the connection between FLNG vessel and LNG carrier plays an important role. The outcome of this study would offer better understanding on the hydrodynamics of multi-bodies, which can further lead to more practical applications for the design and operation of FLNG.

Optimization of Coalbed Methane Liquefaction Process Adopting Mixed Refrigerant Cycle with Propane Pre-cooling

Coalbed methane (CBM) is an important energy resource in the world, and to recover this important energy, liquefaction is a good option. Different from ordinary natural gas, CBM usually consists of a lot of nitrogen, which cannot be removed by the ordinary purification technology of LNG. One way of separating nitrogen from CBM is by distillation after liquefaction. In this way, nitrogen is liquefied together with methane, so the liquefaction process and its system performance may be different from that of the ordinary natural gas and will change along with the nitrogen content of CBM feed gas. The liquefaction process adopting a mixed refrigerant cycle with propane pre-cooling is discussed in this paper, which is widely used in LNG liquefaction plants. Taking the unit product liquefaction power consumption as the major index for analysis, the optimum parameters of the liquefaction processes at different nitrogen content of CBM feed gas are worked out, and the corresponding system performance is obtained and compared.

Liquid expanders in LNG liquefaction plants

Ebara International Corporation has successfully introduced a new product that enables the process efficiency of liquefaction plants to be increased by between 3% and 5%. The first machines have already been introduced at the Oman LNG Liquefaction Plant at Qalhat, Oman.