1 Overview
In response to the problem of oil and gas generation in the tank area, we have taken some measures to reduce the generation of oil and gas. For example, for oil storage tanks with strong volatility, we use a combination of internal floating roof and nitrogen sealing, and implement lower loading and unloading processes during loading and unloading. These measures have effectively reduced the generation of oil and gas to a certain extent, but they cannot be completely eliminated. Therefore, the recovery of oil and gas has become an important link.
2 Introduction to mainstream oil and gas recovery technologies and analysis of their advantages and disadvantages
At present, the oil and gas recovery methods commonly used in the petrochemical industry include extraction, adsorption, cooling, combustion and membrane decomposition [2] and other technologies.
These technologies are rigorous, stable, rational and official, and are aimed at ensuring the safety, environmental protection and efficient operation of the petrochemical industry.
2.1 Absorption method
We will use the reverse flow method to allow the mixed oil and gas to interact with the absorption liquid sprayed from top to bottom to achieve effective separation of oil and gas from air. In this process, we will use special absorption liquid to capture specific types of hydrocarbons. The gas that is not absorbed will be discharged through fire protection equipment. Then, the absorption liquid will be transferred to the vacuum desorption container for desorption operation, and the collected oil and gas will be further processed into usable oil products.
The advantage of this method is that its production process is simple, easy to understand, and the operating cost is relatively low. However, in order to ensure that the unabsorbed gas meets the emission standards, the temperature required for the absorption process must be maintained at low temperature conditions. Therefore, the process system may need to add a refrigeration system, and low-temperature resistant materials need to be used, and attention should be paid to ice formation. In addition, the consumption of absorbent needs to be continuously replenished, which directly leads to an increase in investment and operating costs. In addition, the recovery volume of this method is relatively low, which generally cannot meet the current national standards.
2.2 Adsorption method
This technology relies on adsorbent materials such as activated carbon, silica gel or activated fiber to distinguish and separate oil and oxygen in the mixed gas. The specific implementation process is as follows: ① When the oil gas passes through these adsorbents, its components are attracted to the surface of the adsorbent; ② We use steam desorption or reduce the pressure to extract the enriched oil gas and transfer them to the oil storage container or take other liquefaction treatment methods; ③ Because the adsorbent has a relatively low absorption capacity for oxygen, the remaining exhaust gas can be released from the exhaust pipe. The above operations must strictly comply with relevant regulations to ensure that the separation task is completed safely and effectively.
However, in some cases, such as a sudden increase in oil and gas concentration, the adsorbent may not be able to quickly adsorb all the oil and gas molecules, resulting in a sharp increase in local temperature. This overheating phenomenon may cause overheating and peroxides to form on the surface of the adsorbent. These substances are highly reactive and easily cause spontaneous combustion.
2.3 Condensation method
When using the condensation method, we use the heat treatment method of refrigeration exchange to remove the energy in the oil and gas, and achieve a seamless transformation from gas to liquid. The key to this method is based on the relationship between the boiling point and pressure of various hydrocarbons in the oil and gas. Lowering the temperature can make some hydrocarbons evaporate to a supersaturated state, thereby producing liquid petroleum products that can be collected.
To achieve this goal, we usually use multi-stage continuous refrigeration to reduce the working temperature of the oil and gas, allowing them to condense into liquid and be used. According to the composition of the mixed gas, the required recovery rate and the final exhaust gas concentration limit value discharged to the atmosphere, we can calculate the minimum temperature that the condensation device system must maintain.
Although the existing refrigeration technology is mature and reliable, which provides a guarantee for the smooth operation of the oil and gas recovery device, the high price of cryogenic materials directly leads to an increase in the overall equipment cost.
2.4 Combustion method
2.4.1 Combustion in heating furnace of the device
The device adopts direct heating furnace combustion, which has a simple and clear principle; it can treat waste gas and waste liquid at the same time; it uses auxiliary fuels such as natural gas and diesel; and the price is relatively low. However, in order to prevent the mixed gas from being within the explosion limit when entering the heating furnace of the device, causing flash explosion or more serious accidents, it is necessary to control the total hydrocarbon content and oxygen content of the mixed gas.
2.4.2 Ultra-low emission combustion
Ultra-low emission combustion (CEB) technology uses a unique metal fiber burner, which has extremely high adaptability when treating oil and gas, and can achieve an oil and gas treatment efficiency of up to 99.9%. This smokeless and flameless combustion method is committed to promoting environmental protection and achieving ultra-low emission goals.
The mixed oil and gas are carefully fed into the combustion device through an efficient fan to ensure that it participates in the combustion process stably and evenly.
At the same time, the supplementary fuel gas for the burner passes through a set of precise pressure reducing devices, which is designed to adjust its pressure to the optimal state before entering the burner to provide continuous energy for the flame. Both gas lines are equipped with automatic shut-off valves and pressure regulating valves. These advanced equipment are like guardians, constantly monitoring and adjusting the flow and pressure of the gas to ensure the smooth progress of the combustion process. When an abnormal situation occurs, the automatic shut-off valve will respond quickly and cut off the gas supply to prevent any potential danger. The combustion air enters the premixer at the bottom of the burner through a fan set at the bottom of the burner. The fan is stable and efficient, which can ensure that the combustion air and fuel gas are fully mixed to form ideal combustion conditions. The mixed gas is further mixed in the premixer to prepare for the subsequent combustion process. When all conditions are in the optimal state, the mixed gas enters the combustion chamber and burns together with the fuel gas. This design ensures efficient use and full combustion of fuel, while reducing the emission of harmful substances and contributing to environmental protection. The exhaust gas produced by combustion is discharged after being treated to meet the standards.
4 Conclusion
From the above explanation, it can be clearly seen that different oil and gas recovery processes have their own unique advantages and disadvantages, and it is impossible to achieve the best effect with a single method. Although the combination of several processes, such as adsorption and condensation, membrane separation and condensation, condensation and CEB, can better play the advantages of each process to a certain extent, it is still impossible to completely overcome their shortcomings.
