Influenced factors and attainment rates of vapor recovery system for service stations in Beijing

The vapor emission control of citywide service stations in Beijing has completed in 2008. 40 service stations have been tested according to China national standards between year 2008 to 2010, and 5 service stations have been tested in 2010 time after time. The result shows that in 2008 the acceptance test attainment rates of air tightness, dynamic back pressure, and air to liquid volume ratio (A/L) of vapor recovery system were 65.0%, 95.3% and 81.5%, which is better than the initial control level of Germany and America. The air tightness failure is due to the leakage of manhole covers, gauge hatches, P/V valves of underground tanks, etc. The dynamic back pressure failure is due to small diameter and inadequate slope of the vapor pipelines, etc. The A/L is failed because the vacuum pump failure, A/L control valve off, etc. The annual test attainment rates of air tightness, dynamic back pressure, and A/L of vapor recovery system raised to 82.5%, 85.0% and 84.8% in 2009, which is about the same in 2010. It also indicates that the attainment rate of distributed vapor recovery system is slightly higher than centralized system. The attainment rate of A/L is positively correlated with dynamic back pressure (R²=0.26), and is negative correlated with the average gasoline amount dispersed by all fueling nozzles of each station (R²=0.04). The exceeded A/L value rate of fueling nozzles, which is about 50% non-attainment of A/L, is less than 10%. Four times of test in every half year can raise the attainment rates of these three indicators of vapor recovery system from 65% to 90%. On-line monitoring systems were suggested to install in designated service stations according to GB 20592 as early as possible.