Abstract:

Three groups of CO₂ pipeline release experiments were performed using an industrial scale (256 m long, 233 mm id) instrumented pipeline with CO₂ pre-discharge phase of gas phase, gas-liquid phase and supercritical phase, respectively. The pressure response and the phase transition were recorded and analyzed in the process of CO₂ pipeline release. The results showed that when the pressure wave front arrived, the pressure fall and stagnation appeared in the process of gaseous CO₂ release. The phase of CO₂ in the pipeline during the gaseous CO₂ release was mainly in gas state, but the temperature at the end pipe decreased sharply, leading to the formation of gas-liquid homogeneous CO₂. The decompression multiple reflection led to multiple pressure fall sharply and rebound in the release of gas-liquid CO₂. Gas-liquid layered CO₂ transformed to gas-liquid homogeneous CO₂ in the phase transition process of gas-liquid CO₂, and then the gas-liquid homogeneous CO₂ at the top of pipeline transformed to the gas CO₂ and consequently the bottom. The pressure fall sharply and rebound appeared near critical region in the release of supercritical CO₂. When the pressure passed through the critical pressure line, the pressure change rate could be stagnation and slow down. The discharge of the supercritical CO₂, gas-liquid homogeneous CO₂ and gas CO₂ appeared in the process of supercritical CO₂ release.

Key words: carbon dioxide, pipeline release, pressure response, phase change, gas-liquid flow

摘要：

基于CO₂相态分别进行了气相、气液两相和超临界状态的3组工业规模CO₂管道(长256 m,内径233 mm)泄放实验,分析了CO₂管道泄放过程中的压力响应和相态转变过程。研究表明:在管道内,气相CO₂泄放开始时压力发生突降,而后压降停滞或减慢;管内相态主要为气态,但管道末端温度大幅下降使该处形成气液均相CO₂。泄放口位于气液界面之上的气液两相CO₂泄放中,减压波多次反射并导致多次压力突降和反弹;管内相态由气液分层向气液均相转变,管道顶部和底部气液均相CO₂先后向气相CO₂转变。超临界CO₂泄放中的压力突降和反弹发生在临界区域附近,且压力穿过临界压力时,压变速率会停滞或减慢;管内相态经历了超临界、气液均相和气相泄放3个过程。

关键词: 二氧化碳, 管道泄放, 压力响应, 相变, 气液两相流