【作者】 郑阳光；

【导师】 喻健良；

【作者基本信息】 大连理工大学 ， 化工过程机械， 2017， 硕士

【摘要】 高压管道作为碳捕集和封存技术链的中间环节,在输运过程中容易发生泄漏,其安全问题备受关注。当长输CO₂管道发生泄漏时,在泄漏口处会形成高速射流,并生成大量干冰颗粒,在CO₂扩散和干冰升华过程中形成的高浓度CO₂危及附近居民健康和设备安全。然而,目前还没有较为符合的理论模型能够准确而又完整的描述高压CO₂泄漏扩散特性,相关工业规模实验亦未曾大量开展。针对如今研究现状,本文将工业规模和小规模CO₂泄漏扩散实验相结合,辅之以数值模拟研究和理论分析,探索高压CO₂泄漏扩散规律。本文主要内容和结论如下:（1）设计并建立了小规模和工业规模CO₂泄漏扩散实验装置,并基于此装置开展了多种泄漏孔径、不同相态CO₂的泄漏实验。分析了泄漏孔径和相态对泄漏过程中泄漏口处温度、射流云演变、干冰层生成与消失以及扩散区域远场温度与浓度变化规律及其影响。（2）开展了小规模CO₂泄漏扩散实验。研究结果表明:同种相态,泄漏孔径越大,泄漏口处温降幅度越大;同种泄漏孔径,超临界相实验较气相温降幅度更大。随着泄漏孔径的增大,筒鼓形盘最大直径逐渐增大,但增大幅度逐渐变缓,最大约150 mm,而膨胀角变化的幅度并不是很明显。气相实验泄漏孔径小于1.6 mm时,没有干冰颗粒生成,孔径大于5.4 mm时未能有稳定的干冰层生成;超临界实验中,泄漏孔径为1.6 mm时有稳定的干冰层,孔径大于5.4 mm时,干冰颗粒无法持续积累形成稳定的干冰层。（3）开展了工业规模CO₂泄漏扩散实验。研究结果表明:射流云的演变可以分为三个阶段;射流云扩散时携带的干冰颗粒和凝结的水雾,随高速气流运动至远场区域,近场产生的干冰颗粒在降至地面前全部升华,未形成干冰床。泄漏后,扩散区域温度均快速减小,后上升至环境温度;扩散区域浓度先快速增大至极值,后慢慢下降至与环境相同;密相泄漏实验低温区域、危险区域面积更大,持续时间更长。泄漏孔径为50 mm时,密相、超临界和气相实验在轴线上危险区域长度估计为45 m、35 m和25 m。（4）以实际管道泄漏为基础建立气相CO₂泄漏扩散的数值模型。研究表明:扩散区域速度场整体呈现为一个不规则的椭圆形。距离泄漏口越近,速度梯度越大。泄漏压力相同时,CO₂的水平扩散范围增大趋势随着孔径的增加而增加,而垂直扩散范围与孔径呈线性增加趋势;泄漏孔径相同时,水平扩散距离和垂直扩散距离与压力均呈现线性增加的趋势。随着扩散距离的增加,轴线温度迅速下降。泄漏压力和泄漏孔径均对温降幅度、低温范围有促进作用。（5）对本文扩散模型在超临界、密相CO₂泄漏扩散的适用性进行了工程评估。发现该模型适合于模拟超临界CO₂浓度场,而模拟密相CO₂泄漏时预测浓度低于实验浓度约5%;模拟超临界和密相CO₂扩散区域温度分布时,预测值高于实验值10²0℃。更多还原

【Abstract】 As the intermediate link of the carbon capture and storage technology,the high pressure pipeline exist a high risk of CO₂ leakage during the transportation process.When a long-distance CO₂ pipeline leaks,a high-speed jet is formed,resulting in a large amount of dry ice particles.The high concentrations of CO₂ formed during CO₂ diffusion and dry ice sublimation endanger the health of nearby residents and the safety of equipment.However,there isn’t a theoretical model to describe the high-pressure CO₂ leakage and diffusion characteristics accurately and completely.The relevant industrial scale experiments have not been carried out.In view of the present research situation,based on the industrial scale and the small-scale CO₂ release experiments,numerical simulation and theoretical analysis,the law of diffusion during high-pressure CO₂ leakage was studied.The main contents and conclusions of this paper are as follows:（1）A small scale and an industrial scale CO₂ release experiment device were designed.Based on these devices,the release experiments with different orifices and different phases have been carried out.The temperature developmentnear the leakage,the evolution of the jet cloud,the generation and disappearance of the dry ice and the change of the far-field temperature and concentration in the diffusion area were analyzed.（2）Small-scale CO₂ release experiments were carried out.The results show that: Under the same initial phase,the temperature drop amplitude near the orifice became greater as the release orifice size increased.Under the same orifice,the temperature drop amplitude near the orifice during the supercritical CO₂ release was larger than that during the gaseous CO₂ release.In the case of gas phase test,when the orifice size was less than 1.6 mm,the dry ice particles wasn’t formed.When the orifice size was larger than 5.4 mm,the stable dry ice wasn’t formed.The dry ice particles were generatedin all supercritical experiments.When the orifice size was 1.6 mm,there was a stable dry ice bank.When the orifice size was larger than 5.4 mm,the dry ice particles accumulated didn’t form a stable dry ice bank.（3）Industrial scale CO₂ release experiments were carried out.The results show that: After the release,the evolution of jet cloud can be divided into three stages.The jet cloud entraining the dry ice particles and condensing water rapidly expanded in the rapid expansion stage and the dry ice particles have been sublimated before falling to the ground and did not form a ice bed.At the moment of the rupture,the temperature in the discharge area dropped rapidly and then increased slowly,while the CO₂ concentrations increased quickly and then decreased.The low temperature region and the dangerous area of dense phase test were larger than that of gas phase test.When the release orifice was 50 mm,the critical region length of dense phase,supercritical phase and gas phase were estimated to be 45 m,35 m and 25 m.（4）Based on the actual pipeline leakage,a numerical model for predicting gas phase CO₂ leakage behaviourwas established.The research showed that: The velocity field in the diffusion region appeared as an irregular ellipse.The velocity gradient became larger with increasing distance from the orifice.Under the same initial pressure,the horizontal diffusion range of CO₂ increased as the orifice size increased,while the vertical diffusion range increased linearly as the orifice size increased.Under the same orifice size,the horizontal and vertical diffusion distance increased linearly as the initial pressure increased.As the diffusion distance increased,the axis temperature dropped rapidly.The leakage pressure and the orifice size had a significant influence on the temperature drop amplitude and the low temperature range in the discharge area.（5）In this paper,the applicability of the diffusion model for predicting supercritical and dense phase CO₂ leakage behaviour was evaluated.The model was suitable for the simulation of the CO₂ concentration field during the supercritical CO₂ leakage.The simulation value of the CO₂ concentration during the dense phase CO₂ leakage was lower than the experimental value of the CO₂ concentration about 5%.The simulation values of the CO₂ temperature in the supercritical and dense phase CO₂ tests were higher than the experimental value about 10²0℃.更多还原