Supply chain analysis and upgrading of liquefied natural gas (LNG) to meet Finnish gas market specifications

Liquefied natural gas (LNG) presents clean, cost-effective solution for transportation/ shipping of natural gas from remote reservoirs to consumer market. Until recently, the limits of natural gas properties, acceptable to LNG importers, had been lenient, as it was generally used for power production. However, new markets, as they use LNG to supplement their current supplies, demand an LNG with characteristics/ quality compatible to their existing pipeline grid and clientele specifications. This raises natural gas harmonization, interoperability and interchangeability issues in potential LNG importers, such as Finland which is wholly reliant on single natural gas source from Russia. Rising environmental concerns, stiffening emission regulations and energy security drive Finland to import LNG. This thesis is aimed at identifying the world LNG sources suitable for import to Finnish market based on specifications required by natural gas applications in Finland. The thesis also studies the LNG value chain in general and the LNG quality modification at import terminal/ regasification plant. Production, liquefaction, storage, transportation, and regasification are core components of LNG value chain besides numerous minor constituents including LNG liquid fuel engines. Finnish natural gas market is divided into broad segments of traffic, off-grid industry and existing gas grid users. Specification-data of all three designated sectors was collected from the manufacturers and industry. By considering three interchangeability parameters of natural gas: methane number, Wobbe index (lower), and lower heating value, this data was mapped on charts to determine the requirement of each sector and finally the common demand band (common window) of all the sectors. Similarly, the data of 27 available LNG sources and 3 European LNG re-export terminals was gathered and graphically analyzed. A preliminary simulation of 3 alternative processes, by means of Aspen HYSYS software, and their subsequent comparison resulted in selection of LPG Extraction as the most feasible LNG de-richment technique employed at a receiving terminal LNG re-vapourization plant. As per the current Finnish market requirement and grid conditions, out of 27 global LNG sources, the number of feasible sources remains 3; however, it could be increased to 7 by compromising land traffic sector methane number demand, and to 11 if the upper bounds for heating value are relaxed up to +3%. LNG from rest of the producers can be viable with additional processing at the targeted market in Finland

Modelling the weathering process of stored liquefied natural gas (LNG)

Weathering occurs in stored liquefied natural gas (LNG) due to the removal of the boil-off gas (BOG) from the LNG container and results in the remaining LNG being richer in heavier components. A model has been developed to predict stored LNG weathering in containment tanks, typically used in regasification. The model integrates a vapour-liquid equilibrium model, and a realistic heat transfer model. It provides a number of advances on previously developed models: (i) heat ingress is calculated based on outside temperature and LNG composition, allowing for daily/seasonal variations; (ii) boil-off-ratio is not an input; (iii) LNG density is estimated using an experimentally based correlation. The model was validated using real industry data and the agreement obtained in predicting overall composition, density and amount vaporized was within industry requirements. Two modelling approaches have been developed: (i) assuming thermodynamic equilibrium between vapour and liquid; and (ii) assuming heat exchange between the two phases. Both models were run in a predictive mode to assess the BOG under different scenarios. One of the main results of this work is that the BOG generation is 25% less when considering the non-equilibrium approach, which will have a significant impact on industry where simple equilibrium models are used. In the initial stages of weathering nitrogen content of LNG has a marked effect on BOG generation. Even 0.5% mol of nitrogen leads to nearly 7% BOG decrease, making the initial BOG unmarketable. That is a result of preferential evaporation of nitrogen and increase in the direct differential molar latent heat. In the final stages of weathering the heavier hydrocarbons govern the BOG dynamics, which becomes a strong function of initial composition and the LNG remaining in the tank.Open Acces

Management of Emissions at Abu Dhabi Gas Liquefaction Company

Gas industries in the United Arab Emirates are vastly growing in order to mainly cope with the increasing demand for energy productions as well as for the wise utilization of gas associate with the crude oil. Environmental problems coupled with gas employment necessitates the development of a management techniques that can lead to better control of emissions from gas processing companies since some of these emissions are unavoidable for safety reasons. This study suggests a framework to be used to control emissions from Abu Dhabi Gas Liquefaction Company (ADGAS) in Das Island, which represents a typical major gas processing company in the region, through investigations of the impact of introducing a modification scheme, within the unit processes, on the quality of the surrounding atmosphere. A baseline study for current emissions and ground level concentrations of four pollutants (sulphur dioxide, nitrogen oxides, carbon monoxide and particulates) was established. A computer model was then used to simulate the proposed modifications in order to reduce ground level concentrations that exceed regulatory standards. Two main approaches were considered to minimize ground level concentrations. First, reducing flow of gas into the flares by adding compressors to recover any excess gas from going into the flares during operations. Second, upgrading sulphur recovery units to a higher efficiency and some other reduction can also be accomplished through sweetening of fuel gas directed to utilities. The study concluded that the rates of emitted gas at ADGAS Liquefied Natural Gas Plant are exceeding the exposure limits under all emergency and current normal operation conditions. Gas turbines and boilers were proved to be the major sources for nitrogen oxides and carbon monoxide, while both sulphur recovery units and gas turbines are contributing to the emission of sulphur dioxide. In the meantime, upgrading of the sulphur recovery units to 97.5% resulted in 30% decrease in sulphur dioxide concentration. A significant decrease in nitrogen oxides and carbon monoxide as well as particulate concentrations resulted from adding a third boil-off-gas compressor

동적 시뮬레이션을 활용한 LNG-FSRU 탑사이드 공정의 설계 및 운전에 대한 연구

학위논문 (박사)-- 서울대학교 대학원 : 화학생물공학부, 2015. 2. 한종훈.최근 증가하는 천연가스의 수요에 맞춰 액화 천연가스(LNG) 공급 시설의 수요가 높아지고 있으며 특히 기존의 육상 공급 시설보다 공사기간, 비용 측면에서 유리한 해상 부유식 저장 및 기화 설비(FSRU)에 대한 관심이 확대되고 있다. LNG-FSRU는 그 설계 방법이 육상 천연가스 터미널이나 천연가스 수송선의 경우와 유사하지만 기존 공정 설계에서 다루지 않던 해양 상황을 설계에 반영하여야 한다. 또한 LNG-FSRU의 공정 및 운전 절차의 설계와 안전한 운전을 위해서는 높은 정확성을 가진 동적 시뮬레이션 모델이 필요할 뿐만 아니라 충분한 수와 종류의 센서 설치가 요구된다. 이 논문은 동적 시뮬레이션을 활용한 LNG-FSRU의 탑사이드 공정의 설계와 운전에 대한 연구를 다루었다. 먼저 공정 시뮬레이션을 통해 LNG-FSRU의 공정에 대한 해양 환경의 영향에 대해 연구하였으며 또한 LNG-FSRU의 공정 및 운전 절차 설계를 위한 정확한 동적 시뮬레이션 모델, 그 중에서도 공정의 핵심이 되는 재액화기에 대한 상세 모사를 수행하였다. 아울러 LNG-FSRU 배관 내의 작업자가 알고 싶은 어떤 지점에 대해서도 값을 예측할 수 있는 변수 자동 예측 기법을 제안하였다. 이 논문은 세 개의 주요한 부분으로 구성된다. 첫째, 해양 환경이 공정에 영향을 미칠 수 있는 요인을 유동현상의 장치 내 유입, 플랜트 설치 가능 영역 제한, 그리고 장치 무게에 대한 고려 세 가지로 구분하여 각각의 요인들이 공정 설계에 얼마나 영향을 미치는 지를 분석하였다. 그리고 이 결과를 토대로 LNG-FSRU 탑사이드의 최적 공정 설계를 수행하였다. 둘째, 설계한 LNG-FSRU의 공정을 바탕으로 동적 시뮬레이션을 수행하였다. 특히 LNG-FSRU 공정 내에서 가장 모사가 난해한 증발가스 재액화기에 대한 상세 모사를 수행하여 기존 시뮬레이션 사례보다 높은 정확도로 재액화기의 운전을 모사하였다. 마지막으로 LNG-FSRU의 배관을 대상으로 센서가 없는 어느 지점을 선택하더라도 해당 지점의 공정 변수를 자동화된 시뮬레이션을 통해 가장 빠르게 예측할 수 있는 방법론을 개발하였다. 개발된 방법론을 통하여 변수 예측에 걸리는 시간을 기존보다 1/10 이하로 줄일 수 있었다.Abstract Contents List of Figures List of Tables Chapter 1 : Introduction 1.1. Research motivation 1.2. Research objectives 1.3. Outline of the thesis Chapter 2 : Topside process design of LNG-FSRU 2.1. Introduction 2.2. Theoretical backgrounds 2.2.1. LNG-FSRU 2.2.2. Traditional process design procedures 2.2.3. Process design for offshore plant topside 2.3. Basis of design for LNG-FSRU 2.3.1. Design specification 2.3.2. Target specification 2.4. LNG-FSRU Topside process design 2.4.1. Basic process scheme 2.4.2. Detailed design of topside process 2.4.3. Vaporizator selection 2.4.4. Heat and material balance sheet 2.5. Result and discussion Chapter 3 : Dynamic Simulation of LNG-FSRU topside process 3.1. Introduction 3.2. Theoretical backgrounds 3.2.1. BOG Recondenser 3.2.2. Prior researches about recondenser modeling 3.3. Proposed modeling methodology 3.3.1. General dynamic simulation of a BOG recondenser 3.3.2. Building the flash ratio function 3.4. Case study : Data preprocessing 3.4.1. Noise filtering 3.4.2. Raw data selection 3.5. Case study : Advanced dynamic modeling for BOG recondenser 3.5.1. Model building 3.5.2. Model validation 3.5.3. HYSYS non-equilibrium solving method 3.6. Result and discussion Chapter 4 : Automatic simulation-based soft sensor generation for LNG-FSRU 4.1. Introduction 4.2. LNG terminal 4.3. Methodology 4.3.1. Quantization of target location information 4.3.2. Model boundary selection 4.3.3. Degree of freedom calculation for the LNG pipeline 4.3.4. Simulation of the target model with minimizing error 4.4. Case study 4.4.1. Case study 1 4.4.2. Case study 2 4.5. Result and discussion Chapter 5 : Conclusion and Future Works 5.1. Conclusion 5.2. Future worksDocto