液化天然气港口转储系统泄漏逸散机理与演变研究

发布时间：2018-06-14 15:47

本文选题：液化天然气 + 转储系统　；参考：《武汉理工大学》2014年博士论文

【摘要】：能源是世界发展的重要资源，环境是人类生存的基本条件，能源与环境问题是当今人类面临的世界性难题，解决该难题，既要开发新型能源，又要保护环境免受污染。LNG是清洁高效的能源，拥有丰富的来源，合理开发和利用LNG是人类解决未来环境与能源问题的重要途径，受到国内外的高度重视。我国是LNG利用大国，大量的LNG通过船舶从国外进口，由港口通过管线转输至储罐进行储存。LNG在转储过程中会面临着火灾、爆炸、热力学毁坏、快速相变、低温破坏、窒息等危害，危害的发生会严重影响生命和财产的安全。文中研究对象为到港LNG船舶、LNG传输管线和LNG储罐所构成的LNG转储系统。鉴于LNG转储系统的危险性，文中在国内外研究成果的基础上，对LNG船舶、储罐、管线的泄漏逸散机理、LNG液池的形成、演变、蒸气云的扩散进行了研究，具体研究内容与结论如下：（1）将液化天然气的港口转运及储存作为一个完整的系统，对船舶在码头装卸区LNG的泄漏原因、初始泄漏率模型、泄漏口的位置及其他影响因素等问题进行了研究。发展了LNG转储系统泄漏逸散的初始泄漏率模型，根据泄漏口与水线面的位置关系，将LNG船舶的泄漏逸散分为水线面以上、水线面和水线面以下三种情况，以一艘双层船壳的薄膜型LNG船舶为实例，对三种情况下的泄漏逸散分别进行了计算和预测。所发展的初始泄漏率模型具有一定的适应性；对于双层船壳的薄膜型LNG船舶，当泄漏口位于水面以下时，无论船舶仅外壳单层穿刺还是外壳和储罐双层穿刺，，最终都会达到一种平衡状态。（2）对LNG罐区和管线的泄漏风险、LNG管线泄漏蒸发率、罐内翻滚现象进行了研究。研究了LNG储罐的翻滚现象，给出了消除分层和翻滚的措施，通过分开储存或内部搅拌充注方式，使LNG储罐内的密度差和温度差减小为零，可以防止LNG分层与翻滚。建立了LNG管线泄漏蒸发率模型，以LNG通过管线转到储罐的过程中管线发生完全破裂为例，对泄漏蒸发率进行了理论预测。研究了在LNG泄漏逸散的过程中能量的传递和不同地面基质的传热，在考虑了不同地面基质的热力学特性后所建立的LNG蒸发率模型能够较好的反应LNG的蒸发。（3）对泄漏中液池的演变过程、演变模型、液池蒸发、热通量变化规律、池火等进行了研究。LNG转储系统出现裂口形成射流，液体射流会分裂成雾状小液滴，小液滴在下落过程中将会部分蒸发或者全部蒸发。当LNG射流量较大时，将会形成液池，当LNG液池的厚度超出维持稳定的最小值时，稳定性将会被打破，LNG液池不断地扩展和蒸发，直至液池的半径达到最大值。随着蒸发率的增加，沸腾气泡的密度也随着增加，当液体和蒸气的相互作用阻止了流体向过热表面的接触导致温度足够高时，核沸腾将会停止，随着过热温度的继续增加，沸腾变得相对稳定，逐渐成为过渡沸腾。当热通量达到最小值时，过渡沸腾转变为薄膜沸腾。泄漏之初液体的沸腾温度几乎没有变化，液池蒸发的后期，蒸气的组分几乎不变，但是液体的沸腾温度剧烈升高。对于大型LNG液池的燃烧，建立了池火的简化模型，能较好的反应火焰的特点和在不同风向时火焰的发展趋势。（4）对LNG泄漏后蒸气云的扩散过程、影响因素、扩散距离模型进行研究。由于风的存在，将使烟羽向下风向扩展。在烟羽和携带的空气之间存在一种平衡，烟羽向下风向扩展，密度快速降低，而其携带的空气将阻止这一现象的快速发生，使扩展以及密度的快速降低得到平衡。在考虑了风速、大气稳定度、地面粗糙度、障碍物以及重气属性等因素后所建立的LNG蒸气云扩散在下风向的最大距离的数学模型具有良好的适用性。（5）对LNG转储系统的事故预防及应急响应措施进行了研究。研究LNG转储系统的泄漏逸散机理的最终目的是要防止LNG转储系统事故的发生，降低由LNG转储过程中的泄漏逸散事故所造成的损失。根据LNG转储系统的泄漏逸散机理，主要从转储系统的安全管理、事故的预防、应急响应措施的制定等三个方面进行了研究。
[Abstract]:Energy is an important resource for the development of the world. The environment is the basic condition for human survival. Energy and environmental problems are the world's difficult problems facing today. To solve this problem, we should develop new energy and protect the environment from pollution.LNG is a clean and efficient energy, have a rich source. The rational development and use of LNG is a human solution. The important way to come to the problem of environment and energy is highly valued at home and abroad. China is a big country in which LNG uses a large country. A large number of LNG are imported by ships from abroad. The storage of.LNG from the port through the pipeline to storage tank will face fire, explosion, thermodynamic destruction, rapid phase change, low temperature damage, asphyxiation and other hazards. It will seriously affect the safety of life and property.
In this paper, the research object is the LNG dump system of port LNG, LNG transmission pipeline and LNG storage tank. In view of the danger of LNG dump system, based on the research results at home and abroad, the leakage and escape mechanism of LNG ships, storage tanks and pipelines, the formation of LNG liquid pool, the evolution of LNG liquid pool and the diffusion of steam clouds are studied. The conclusions are as follows:
(1) take the port transport and storage of liquefied natural gas as a complete system, study the causes of the leakage of LNG, the initial leakage rate model, the location of the leakage and other influencing factors, and develop the initial leakage rate model of the leakage and escape of the LNG dump system, according to the position of the leakage and the water line. The leakage and escaping of the LNG ship is divided into three cases above the waterline surface, the waterline surface and the waterline, and the leakage and escape of the three cases are calculated and predicted with the example of a thin film type LNG ship of a double hull hull. A membrane type LNG ship, when the leakage is below the surface of the water, will eventually reach a state of balance, regardless of the single layer puncture of the shell, or the double layer piercing of the shell and the tank.
(2) the leakage risk of the LNG tank and the pipeline, the evaporation rate of the LNG pipeline and the rolling phenomenon in the tank are studied. The roll phenomenon of the LNG tank is studied. The measures to eliminate the stratification and rolling are given. The density difference and the temperature difference in the LNG storage tank are reduced to zero by the separate storage or internal stirring filling method, which prevents the LNG layer from delamination and turn over. The evaporation rate model of the LNG pipeline leakage was established. The leakage evaporation rate was predicted by the case of complete rupture of the pipeline in the process of transferring LNG through the pipeline to the tank. The transfer of energy in the process of LNG leakage and the heat transfer of different ground substrates were studied, and the thermodynamic properties of different ground substrates were considered. The LNG evaporation rate model can better reflect the evaporation of LNG.
(3) the evolution process of the liquid pool in the leakage, the evolution model, the evaporation of the liquid pool, the law of the change of the heat flux, the pool fire, etc. have been studied to study the formation of the jets in the.LNG dump system. The liquid jet will split into a small fog droplet, and the small droplets will be partially evaporated or all evaporated during the falling process. When the LNG discharge is large, a liquid pool will be formed. When the thickness of the LNG tank exceeds the minimum value for maintaining stability, the stability will be broken and the LNG pool expands and evaporates until the radius of the liquid pool reaches the maximum. As the evaporation rate increases, the density of the boiling bubbles increases as the interaction between the liquid and steam prevents the fluid from contacting the overheated surface. When the heating temperature continues to increase, the boiling will become relatively stable and gradually become a transition boiling. When the heat flux reaches the minimum, the transition boiling is transformed into a film boiling. The boiling temperature of the initial liquid is almost unchanged, and the vapour component is almost invariable in the later period of the liquid pool evaporation, but the liquid is almost unchanged. The boiling temperature rises violently. For the combustion of the large LNG liquid pool, a simplified model of the pool fire is established, which can better reflect the characteristics of the flame and the development trend of the flame at different wind direction.
(4) the diffusion process of the vapor cloud after LNG leakage, the influencing factors and the diffusion distance model are studied. Due to the existence of the wind, the smoke plume will expand downward. There is a balance between the smoke plume and the air carried, the smoke plume expands downward and the density decreases rapidly, and the air carrying the plume will prevent the rapid occurrence of this phenomenon and make the expansion of the phenomenon. The rapid reduction of the density is balanced. The mathematical model of the maximum distance of LNG vapor cloud diffusion in the downward wind direction is well applicable in the consideration of the factors such as wind speed, atmospheric stability, ground roughness, obstacles and heavy gas properties.
(5) the accident prevention and emergency response measures of the LNG dump system are studied. The final purpose of the study of the leakage and escape mechanism of the LNG dump system is to prevent the occurrence of the accident in the LNG dump system and reduce the loss caused by the leakage and escape accident in the LNG dump process. The leakage and escape mechanism of the LNG dump system is mainly from the transfer of the dump system. System safety management, accident prevention, emergency response measures and other three aspects were studied.
【学位授予单位】：武汉理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TE88;U698.5

【参考文献】