大口径、高压力输气管道放空系统泄放后果分析及改进建议

大口径、高压力输气管道在提高天然气管输能力的同时，也对管道放空系统的设计、建设和应用提出了更高的要求。为了探究大口径、高压力输气管道放空后果与管道直径和压力的关系，以长距离输气管道放空系统的设计和建设标准规范为基础，采用TGNET、PHAST、FLARENET等多种仿真软件，对不同直径和压力等级的输气管道进行了放空量、泄放速率、马赫数和安全热辐射半径等放空参数的仿真分析。结果表明：①随着输气管道直径和压力等级的提高，现有规范下截断阀室分割的管段容积显著增加，管段内需要放空的天然气量呈指数级增加；②随着管道规格的升级，放空系统的泄放速率和放空管口流速也呈指数级增加，对应的马赫数、噪声、热辐射安全半径等放空参数均显著提高，天然气安全扩散半径也受到影响，对放空过程人员和环境的威胁显著增加。为了应对大口径、高压力输气管道放空造成的威胁，降低放空系统对人员和环境的不利影响，提出了以下建议：①缩短高规格管道在各类地区的阀室间距以减少放空总量；②增加阀室放空管数量；③延长允许放空时间，减小放空立管的泄放速率。

Discharge effect analysis and improvement of the venting system of large diameter and high pressure gas line pipes

Large diameter and high pressure gas pipes can increase the pipeline transportation capacity of natural gas, but they have higher requirements for the design, construction and operation of pipe venting systems. To explore the relationship between their venting effect and their diameter and pressure, the venting parameters (e.g. vent volume, discharge rate, Mach number and safe thermal radiation radius) of gas pipes of different diameters and pressure ratings were simulated and analyzed using multiple simulation softwares (such as TGNET, PHAST and FLARENET) based on the design and construction standards on venting systems of long distance gas line pipes. And the following research results were obtained. First, with the increase of the diameter and pressure rating of gas pipes, the volume of the section cut by the block valve chamber increases significantly under existing specification, so the amount of natural gas to be released increases exponentially. Second, with the upgrading of pipe size, the discharge rate of the venting system and the flow rate at the nozzle of vent pipes also increase exponentially, and the corresponding venting parameters (e.g. Mach number, noise and safe thermal radiation radius) also rise significantly. Besides, the safe gas diffusion radius is also impacted, and the threat to people and environment in the process of venting is intensified greatly. To cope with the threat caused by the vent of large diameter and high pressure gas pipes and alleviate the adverse impact of venting systems on people and environment, we made the following three suggestions: to shorten the distance of high grade pipes between adjacent valve chambers in various areas so as to reduce the total venting amount; to increase the number of vent pipes in valve chambers; and to extend the allowable venting period so as to decrease the discharge rate of vent risers.