高压天然气含油检测及在除油效果评价中的应用

目的为高压天然气中含油量检测提供方法。方法将取样装置安装在管道中部,在管道上通过一级减压阀将进气压力减压至2 MPa,再通过二级减压阀减压至0.3～0.4 MPa。通过流量计控制流速为18～20 L/min,取样时间为30～50 min。当气体通过取样装置时,气体中的油分截留于取样滤膜上,从而进行取样。将取样滤膜取出,放入萃取烧杯中,使萃取剂充分萃取油分。将萃取后的溶液倒入比色皿中,将比色皿置于油分浓度分析仪,测出气体含油量。结果通过除油器后的压缩天然气含油量较高,体积分数最小值为7.7×10~(-6),最高值为12.1×10~(-6),远超除油器技术协议规定的4×10~(-6)。检测结果表明,除油器出口端含油量超过设计指标2～3倍,除油效果较差。结论提出了减压取样、萃取检测的方法,并通过现场试验验证了该方法可以准确测定高压天然气的含油量。将油量检测方法用于除油效果评估,现场试验验证该检测方法可行。

Detection and Removal Efficiency of Oil in High-pressure Natural Gas

Objective To provide method for detecting oil content in high pressure natural gas. Methods The sampling device was installed in the middle of the pipeline. The inlet pressure of the pipeline was reduced to 2 MPa with a level-1 pressure relief valve, and then to 0.3 - 0.4 MPa with a level-2 pressure relief valve. The flow rate was controlled at 18-20 L/min with a flow meter. The sampling time was 30-50 min. When the gas passed through the sampling device, oil in the gas was trapped in the sampling filter membrane for sampling. The sampled filter membrane was removed and then put into an extraction beaker, to fully extract the oil. The extracted solution was poured into a cuvette which was placed on an oil content analyzer to measure the oil content of gas. Results The oil content of the compressed natural gas passed through the degreaser was high. The minimum volume fraction was 7.7×10-6, the maximum of it was 12.1×10-6, far in excess of 4×10-6 which was specified in the degreaser technology agreement. Test results showed that the oil content at the degreaser outlet was 2-3 times more than design index. The degreasing effect was poorer. Conclusion Methods for decompression sampling, extraction and detection are proposed. The field test shows that this method can accurately measure the oil content of high pressure gas. Field tests verify that it is feasible to use the oil detection method in degreasing effect assessment.