مطالعه آزمايشگاهي به‌منظور بررسي عملكرد دستگاه HI-Flow Sampler و شناسايي عوامل مؤثر بر نشت گاز متان از تجهيزات توزيع گاز طبيعي

Experimental Research for Assessing the Hi-Flow Sampler and Effective Parameters on Fugitive Methane Emissions for Natural Gas Distribution System

انتشار متان از تأسيسات زنجيره تأمين گاز طبيعي، يكي از منابع اصلي انتشار گازهاي گلخانه‌اي در جو مي‌باشد كه مي‌بايست براي دستيابي به پتانسيل كاهش انتشار، ارزيابي و پايش شود. اندازه‌گيري ميزان انتشار در محل مصرف از سه منظر زيست‌محيطي، اقتصادي و ايمني حائز اهميت است، لذا مطالعات زيادي در خصوص برآورد يا اندازه‌گيري موجودي انتشار در حال انجام است. يكي از روش‌هاي مرسوم در اندازه‌گيري نشر متان روش اندازه‌گيري جريان بالا مي‌باشد كه دستگاه Hi-Flow Sampler شناخته‌شده‌ترين دستگاه در اين زمينه مي‌باشد.در اين مطالعه نتايج اندازه‌گيري دستگاه Hi-Flow Sampler در قياس با يك دبي سنج ديجيتال استاندارد، قرارگرفته شده در يك بستر آزمون، منطبق با شرايط يك علمك گاز طبيعي ارزيابي شده است. سپس خطاي اندازه‌گيري براي كنتور در مقايسه با دبي سنج‌هاي ديجيتال گاز ارائه شده است. در انتها به مطالعه تأثير پارامترهاي مؤثر نظير افزايش فشار گاز بر ميزان نشتي قبل از رگولاتور پرداخته و تأثير افزايش ميزان مصرف برافزايش يا كاهش ميزان نشتي در مصارف كم و زياد بررسي شده است.

Methane is the main component of natural gas and it is an extremely effective Green House Gas, much more than carbon dioxide. Fugitive methane emission from the distribution facilities, is one of the sources of emissions in the urban environment which could be evaluated and monitored for achieving emission reduction potential. by the way, the emission rate from the end-user side of the distribution network should be considered for both, safety and environmental effects. The first step for evaluating the emissions is measuring and studying the fugitive emission potential. The BACHARACH hi-flow sampler (BHFS) is one of the tools approved for measuring methane emissions by the U.S. Environmental Protection Agency (EPA). BHFS is the only commercially available hi-flow instrument, and it is also used throughout the NG supply chain for directed inspection and maintenance, emission factor development, and greenhouse gas reduction programs. This study, first, focused on assessing the measuring results for the BHFS device and comparing them with a standard digital flow meter in a real-condition simulated metering set for the natural gas distribution unit. during the experiment procedures, the results indicated that the measuring accuracy for the BHFS is reasonable except when the leakage rates are lower than 136 sccm. The second experiment investigated Measurement Error for Metering Set in comparison with Digital Gas Flow Meters which represented reasonable error rates for low flows and relatively high error rates for higher gas flow rates in such facilities. The next experiment showed the effect of increasing the gas pressure on the leakage rate before the regulating device for the consumer side in the distribution network, which leads to increasing the leakage rate during increasing the network pressure. The fourth experiment discussed considering the specific leakage rate after the regulating device (under 0.9 bar) was affected by the gas consumption on the consumer side in low gas flow rates, which showed increasing the leakage rate while the gas consumption was increasing on the consumer side. Finally, the effect of increasing the consumption rate on the constant leakage rate, after the regulating device at a higher gas flow rate was examined, the result was that during the increase in the consumption rate, the leakage rate will increase.