Secondary Vapor Recovery System

2013-08-30 09:06:00

1. Overview of oil and gas recovery system
Application at refueling vapor recovery system is generally divided into two phases of oil and gas recovery. The first phase refers to the use of oil and gas recovery sealed when unloading tanker offloading, reducing oil spilling to the outside world. The basic principle is: a certain number of oil tanker unloading, would need roughly equal suction gas qi, and underground tanks at service stations and also due to the injection of oil discharged out a considerable amount of oil, this oil through catheter re-transferred back to the tanker, complete the process of unloading the oil and gas cycle, the process shown in Figure 1. Recovered within the oil and gas tanker, the tanker can be brought back to the depot, and then by condensation, adsorption or disposal of burning and other means.The second stage refers to the recovery of oil and gas vehicle refueling , refueling guns on the use of a special device , the oil that would otherwise be spilling from the car in the air and gas , after refueling guns, suction motor , back to the income tanks . Now widely used non-combustion system works, is to save the full recovery of oil and gas pressure in the tank , no emissions. To achieve this effect, the mutual exchange ratio of gasoline and oil demand is close to l than l. In theory, that is, when refueling, every hair lL oil tank level drops space generated by the oil and gas recovery while recovering gun 1L equivalent volume of oil and gas, returned to fill the space inside the tank pressure reaches equilibrium . Saturated hydrocarbon recovery supplement can also reduce the volatilization into the tank of gasoline in the tank . Currently recycling equipment commonly used at home and abroad for the vacuum -assisted vapor recovery system . Working principle of vacuum -assisted vapor recovery systems is the use of additional auxiliary power ( vacuum motor ) produces about 35 to 40 inches of water or 65 to 75 inches of water in the refueling operation (8.7 ~ 10.0KPa or l6.2 ~ 18 .7 KPa) central vacuum pressure through the recovery pipe , gun recovered oil and gas recovery . When the pressure in the tank is too large , the vacuum pressure of the cap on the tank vent is opened automatically by the pressure of the exhaust gas through the discharge port .
2. Introduction of Oil and gas recovery system equipment
2.1 Vaccum Pump
The so-called oil and gas recovery, in fact, is the use of a vacuum pump operation originally spilling out oil and gas sucked back into the tank. Therefore, the vacuum pump is the core of the entire oil and gas recovery system. According to its different forms, can be divided into lessons learned vacuum pumps and vacuum pumps scattered tanker, but also further divided into electric and non-electric. Among them, the central vacuum pump to draw the most widely used. Central vacuum pump to draw a simple structure, easy to install, usually in conjunction with a submersible pump installation phase and into the hole on the cover (see Figure 2), no power supply, the oil produced by the operation of the power when driven submersible pump injectors and their vacuum suction and recovery of oil and gas through pipelines to the oil and gas tanker absorbed back tank.
2.2  Vapor Recovery System Monitor
In order to effectively monitor the vapor recovery system to ensure that it is functioning properly, oil and gas recovery systems typically require the installation of a vapor recovery system at the petrol station surveillance monitor room. The monitoring system is divided into two parts, the vacuum pump is a front monitor, within the section of the oil tank and the pressure monitoring line. If the system is not enough or vacuum suction out excess oil tank emissions, the warning light will light up the monitor and recorded, petrol station staff can be printed according to the daily record, determine whether recovery system functioning properly. If normal, the need for further examination of the system, identify the cause of the malfunction, troubleshooting.
2.3 For oil and gas recovery Nozzle
To realize the need to use oil and gas recovery capabilities, refueling operations for oil and gas recovery when the nozzle, the basic function of this oil is generally automatic nozzle with the same nozzle oil, with three sections of the speed of adjustment of oil, gas filled pores to tip back, automatic off, the other in the back after eight holes with a circle and gas recovery larvae L, L will pump oil from these larvae suck back tank. Automatic oil nozzle and general different, but also the largest oil nozzle advantages: whether full or slow refueling refueling refueling and suction can be adjusted ratio of close to l: l. This advantage is very important, it ensures that every hair lL lL volume of oil equivalent of recoverable oil and gas, to ensure the successful completion of the second phase of oil and gas recovery.
2.4 Other special items vapor recovery
(1) hose from the device. Designed to withstand 100 ~ 200kg pull Jibei divided into two parts to avoid damage to the tanker. When the device is pulled out, while oil and gas passage is sealed, eliminating oil spray, raise petrol station staff and customer safety.
(2) oil and gas recovery quick connector. This connector is used only for the first phase of oil and gas recovery systems, set back to the gas pipeline and the vent line quick connector open on one. When unloading, when the oil return pipe connected to the car, automatically open the top back to the trachea. After unloading operation is completed, when the oil tanker back to the trachea removed, automatically shut down once the recovery line, you can avoid unloading oil leakage.
(3) coaxial hose. It is a special oil vapor recovery hose special gun, using the casing structure, the middle is the oil and gas recovery tube, the outer ring is the pipeline.
(4) oil and gas separation adapter. Through the joint oil and gas together can access a dedicated gun oil and gas recovery.
(5) float valve. When you install it on a manhole cover, vent line connection when unloading the oil level reaches the float valve position, the float valve inside the float will float to stop the oil flow into the vent line.
3. Installation of vapor recovery system equipment
When gas stations equipped with vapor recovery systems during pipeline installation , in addition to the normal laying oil pipelines , but also additional charge of oil and gas recovery . Additional charge of oil and gas recovery generally take two approaches , one more than sharing a pump head of oil and gas recovery , and second, each with each pump head of an independent oil and gas recovery . The second method is slightly higher costs , but the effect is relatively better recovery . When using the first method , each gun oil vapor recovery return legs are in charge and the only oil and gas recovery phase, while the second method , different oil and gas oil gun with the corresponding return legs only oil Head of oil and gas recovery phase . But no matter what method , laying pipelines and gas recovery , the recovery of oil and gas pipelines should ensure that there is a certain inclination slope and aspect tank , so that the inner tube down the river back into the product oil to tanks, if the pipeline is not inclined slope , the inner tube of oil and gas excessive condensation oil recovery , it will produce pipeline fluid resistance , oil and gas can not be passed, oil and gas recovery function will fail . Further , in order to provide maximum space inside the tank to store the recovered gas , the exhaust duct may be communicated to all the gasoline type tanks.
Refueling tanker with ordinary functions in the oil and gas recovery installation is the same, only the corresponding increase in oil and gas recovery pipe recovery, and through the oil separator adapters can access the oil and gas together a dedicated oil and gas recovery the oil gun, oil and gas recovery systems at gas station surveillance monitors installed indoors, connect the cable with two monitors installed in the vacuum line to the vacuum switch, and the other is connected to the exhaust vent line on the monitor switch with two control cables.
4. Vapor recovery system performance testing
After installation of vapor recovery system is completed, in order to ensure the normal operation of the system , the system can perform the following three tests .
( 1 ) System pressure loss leak test. This test aims to test the entire oil and gas recovery system , refueling guns recovered from oil and gas pipelines to oil and gas recovery pipeline to storage tanks and finally to cap the entire oil and gas recovery vacuum pressure piping for leaks circumstances , to ensure that the entire recovery system not because of leak the loss of function of the recovery of oil and gas and pollute the environment. Criteria based on standard methods for CTP 201.3 American Resources Committee , first ascertain the exact volume of the underground storage tank (L), read out the amount of oil in the tank by tank level gauge on the retranslation of oil and gas space , oil and gas space must be more than 25% of the cans 2000L or before pressure leak test. The pressure leak test instrument connected to one end of the recovery of oil and gas pipes, and the other end connected to the nitrogen bottle tee . Nitrogen bottle is opened until the system pressure up to two inches of water column 498Pa and maintain stable , nitrogen bottle closed , press the start time code table , the system records the change in pressure per minute , calculated 5rain pressure reducing test case , according to CARB ( U.S. provisions resources Committee) , the oil and gas space and the pressure readings to determine whether compliance with the standard , if the final pressure is below the allowable range ( ie, the pressure drop is too large ) , which means that the recovery of oil and gas pipeline presents no closed form state technical assistance should be leak check all fittings and vapor recovery system vent position , locate the leak repaired , and repeat the test .
( 2 ) oil and gas recovery tube fluid resistance test , the test should be carried out simultaneously with the construction of the trachea , the method is to inject a certain amount of liquid from the back of the tanker at the bottom of the trachea , opening at the other end of the recovery tank people in the pipeline , container to catch the liquid , and injection quantity is relatively similar, to determine whether the trachea will form liquid resistance . If too much liquid residue in the injection pipe , the return pipe at the bottom of the tanker , the trachea is detected by the air pressure back pressure , the back pressure can be determined if there was resistance exists. You should check the pipe slope is correct, whether the line is not straight bump , after correcting for testing , until the elimination of hydraulic resistance . If there is liquid in the airway resistance , residual liquid left in the pipeline can not be returned to the tank , clogging the pipeline will cause oil and gas recovery system functions so bad , the consequences will result : unable to achieve 95% recovery ; pump kept idle , unable to oil and gas transported back into the tank , causing the pump rotor and blade damage .
( 3 ) the ratio of the vapor recovery system test . Ie the ratio of the exhaust gas recovery ratio and the amount of fuel . The detection is based on the standard American Resources Committee , refueling gun oil recovery test, the use of micro pressure measurement and gas pressure measured oil gun , then after the oil extraction rate and the amount of fuel in terms of the ratio . Depending on the vendor's products , the ratio of the amount of fuel exhaust and certain qualified range detection, the excess or deficiency is unqualified. Eligibility criteria HEALY600 oil gun is 1.0 to 1.2.
5. Application effects of oil and gas recovery system
At refueling vapor recovery system application and promotion of technology, not only can reduce oil and gas consumption, reduce environmental pollution, and improve the safety of the gas station itself , has obvious environmental and ecological benefits, economic and social benefits.
Gas oil vapor is toxic hydrocarbons relative density than air and floating on the surface , thereby increasing the impact and the surrounding environment. Measured data show : Automotive fuel tank and gas concentration mouth is 1050g per cubic emissions , the concentration of the gas station near the oil and gas space is 2.9g/m3. If a man is in this environment of long-term work and life , health will be affected. The installation of oil and gas recovery system , in the process of unloading operations , the oil vapor produced in the first stage of oil and gas recovery directly complement the back tanker unloading site no oil , greatly improving the unloading operations the surrounding environment. When refueling operations , the original four flowing through the second phase of oil and gas recovery, is reabsorbed back into the underground storage tanks , fuel oil spot also smell the odor , to provide customers with a safe and comfortable plus oil environment.
In terms of oil consumption , some gas stations and gas oil vapor recovery system loss of only a few installed. When unloading operations, oil vapor produced by big breath no longer discharged into the atmosphere , but directly into the tanker which has nearly saturated steam into the oil tank , gas-liquid two-phase has basically reached the equilibrium level no longer generate new oil vapor , greatly reducing the oil to evaporate. According to information on Japan 's Energy Office , the general average gasoline closed unloading process loss coefficient of 860g/m3, and gas stations with vapor recovery function is sealed unloading , oil loss coefficient measured only 45g/m3. By a moderate annual operating petrol stations 5000t estimated annual fuel 5.6t. The same principle , when refueling, original oil vapors flowing around being sucked back into the underground tank , tank level drops supplementary space generated , gas-liquid two-phase re- balance, the level does not generate a new oil vapor , greatly reduces the evaporation of underground oil tanks . According to the measured data: from the tank when refueling discharged oil and gas is approximately 1.1 times the volume issued . Also according to a moderate estimate 5000t petrol stations in operation , the annual loss of oil vapor emissions l1.3t. Automobile exhaust and fuel tank filler.