Discussion on the importance and strategy of vapor recovery to storage and transportation safety

1.1 Save resources and improve economic benefits

As the blood of modern industry, the scarcity and non-renewability of vapor resources determine the importance of effective recycling. During the storage and transportation process, the volatilization loss of vapor not only causes direct economic losses, but also indirectly increases the production costs of enterprises. The application of vapor recovery technology can recapture and utilize this part of the resources that should have been lost. Through advanced processes such as closed storage, gas phase balance and condensation recovery, the volatilization loss can be minimized. This not only improves the utilization rate of resources, but also brings considerable economic benefits to enterprises. Taking a large oil depot as an example, the annual processing capacity reaches 1 million tons. After adopting vapor recovery technology, about 1,000 tons of vapor can be recovered each year.

1 Importance of vapor recovery technology application

1.1 Save resources and improve economic benefits

As the blood of modern industry, the scarcity and non-renewability of vapor resources determine the importance of effective recycling. During the storage and transportation process, the volatilization loss of vapor not only causes direct economic losses, but also indirectly increases the production costs of enterprises. The application of vapor recovery technology can recapture and utilize this part of the resources that should have been lost. Through advanced processes such as closed storage, gas phase balance and condensation recovery, the volatilization loss can be minimized. This not only improves the utilization rate of resources, but also brings considerable economic benefits to enterprises. Taking a large oil depot as an example, the annual processing capacity reaches 1 million tons. After adopting vapor recovery technology, about 1,000 tons of vapor can be recovered each year.

According to the current oil price, the annual economic benefits can reach millions of yuan.

In addition, the promotion and application of vapor recovery technology can also promote the development of related industrial chains, such as recovery equipment manufacturing, process optimization and other fields, thereby driving the technological progress and economic growth of the entire industry.

The Ministry of Ecology and Environment issued the "Volatile Organic Unorganized Emission Control Standard" in 2023, which puts forward stricter requirements for vapor recovery in storage tanks and loading and unloading facilities. The new specification clearly stipulates the sealing performance and breathing valve parameters of different types of storage tanks and the vapor recovery efficiency standards during loading and unloading. vapor contain a large amount of volatile organic compounds (VOCs), such as benzene, toluene, xylene, etc. Once these substances enter the atmosphere, they will not only cause the air quality to deteriorate, but also react with nitrogen oxides under sunlight to produce secondary pollutants such as ozone, exacerbating the formation of haze weather. Long-term exposure to this environment will seriously affect the human respiratory system and nervous system. In addition, vapor leakage will also pollute water and soil, destroy the balance of the ecosystem, and endanger the growth of crops and groundwater safety. Therefore, the implementation of vapor recovery is not only a regulatory requirement, but also an inevitable choice to protect the environment and human health. The application of vapor recovery technology can control the emission of pollutants from the source.

The safety of vapor storage and transportation has always been the focus of the industry. Its flammable and explosive characteristics make any small negligence likely to lead to a disaster.

In the process of storage tanks, pipelines and loading and unloading, the volatilization and leakage of vapor will form a combustible mixture in the air, which may cause fire and explosion accidents when encountering open flames or static discharge. It will not only threaten the life safety of on-site workers, but also cause huge property losses and environmental pollution. The application of vapor recovery technology can effectively reduce these safety risks. Through closed transformation and installation of recovery systems, vapor can be controlled in a closed space, greatly reducing the possibility of leakage and diffusion. At the same time, the pressure balance technology in the recovery process can prevent deformation or rupture caused by excessive pressure difference between the inside and outside of the storage tank. Taking the safety transformation of a large oil depot as an example, after the implementation of vapor recovery technology, the concentration of combustible gas in the plant area was reduced by 95%, and the fire and explosion risk index was significantly reduced. In addition, the application of vapor recovery technology can also improve the safety of the working environment, reduce the chances of operators being exposed to harmful gases, and ensure occupational health. From the perspective of risk prevention and control, vapor recovery technology is not only a technical means, but also a manifestation of a safety concept, which is of great significance for building a comprehensive and multi-level safety protection system.

During the oil unloading process, the "big breathing" phenomenon caused by the rising level of the oil tank seriously threatens the safety of storage and transportation, especially in the hot season.

For this reason, enterprises have taken source control measures and installed vapor recovery devices to effectively collect and treat the volatilized vapor during the oil unloading process, which significantly reduces the safety hazards. The "small breathing" problem faced in the oil storage stage should not be ignored. The volatilization of vapor caused by the change of external temperature not only causes resource loss, but also increases safety risks. In this regard, it is necessary to strengthen the sealing and thermal insulation of the oil storage tank to reduce the impact of the external temperature on the vapor in the storage tank. For example, the use of a fully liquid-contacted steel floating plate can significantly reduce the volatilization of vapor. Its design allows the floating plate to always keep in contact with the oil product, minimizing the vapor space. At the same time, the storage tank is transformed into a gas collection device, and the exhaled vapor are uniformly collected and introduced into the recovery device, further improving the safety factor. In addition, the application of nitrogen sealing technology can effectively reduce the volatility of oil products and reduce safety hazards by filling the top space of the storage tank with inert nitrogen. The transportation link is also a key area for the application of vapor recovery technology. Vehicle bumps and temperature changes can easily cause vapor to volatilize. The use of double-layer tank trucks and other transportation tools with excellent sealing properties, and the use of vapor recovery devices during transportation, effectively control the transportation risks. The widespread application of vapor recovery technology has significantly reduced the risk of fire and explosion and reduced vapor pollution.

3.1 Optimization of recovery process

To optimize the vapor recovery process, we should focus on simplifying the process and improving the automation level.

In terms of process simplification, the residence time of vapor in the system can be shortened and the risk of leakage can be reduced by merging unit operations with similar functions, reducing intermediate storage links, optimizing pipeline layout, etc. For example, transforming the traditional multi-stage adsorption-desorption process into an integrated design can significantly reduce potential leakage points such as valves and pipelines.

In terms of automation control, an advanced distributed control system (DCS) is introduced to achieve real-time monitoring and precise adjustment of key parameters such as temperature, pressure, and flow. The use of intelligent sensors and actuators can realize the full automatic operation of the recovery process and reduce human operation errors. In terms of energy consumption control, frequency conversion technology is used to control the speed of high-power equipment such as pumps and compressors, and the operating parameters are flexibly adjusted according to actual working conditions to avoid energy waste caused by equipment running at no load or full load. In recent years, some advanced vapor recovery technologies have gradually been applied. For example, the condensation-adsorption combined process can efficiently recover heavy components at low temperatures, and then recover light components through activated carbon adsorption, with an overall recovery efficiency of more than 99%. In addition, the photocatalytic oxidation method uses photocatalysts such as nano-TiO2 to degrade VOCs under ultraviolet light irradiation, which not only has high recovery efficiency, but also can convert harmful substances into CO2 and H2O. In addition, the waste heat generated during the recovery process can be used in stages, such as using the heat discharged from the condenser to preheat the feed, or using the waste heat from the compressor for adsorbent regeneration, which can further improve the system's energy efficiency.

To optimize the vapor recovery process, we should focus on simplifying the process and improving the automation level.

In terms of process simplification, the residence time of vapor in the system can be shortened and the risk of leakage can be reduced by merging unit operations with similar functions, reducing intermediate storage links, optimizing pipeline layout, etc. For example, transforming the traditional multi-stage adsorption-desorption process into an integrated design can significantly reduce potential leakage points such as valves and pipelines.

In terms of automation control, an advanced distributed control system (DCS) is introduced to achieve real-time monitoring and precise adjustment of key parameters such as temperature, pressure, and flow. The use of intelligent sensors and actuators can realize the full automatic operation of the recovery process and reduce human operation errors. In terms of energy consumption control, frequency conversion technology is used to control the speed of high-power equipment such as pumps and compressors, and the operating parameters are flexibly adjusted according to actual working conditions to avoid energy waste caused by equipment running at no load or full load. In recent years, some advanced vapor recovery technologies have gradually been applied. For example, the condensation-adsorption combined process can efficiently recover heavy components at low temperatures, and then recover light components through activated carbon adsorption, with an overall recovery efficiency of more than 99%. In addition, the photocatalytic oxidation method uses photocatalysts such as nano-TiO2 to degrade VOCs under ultraviolet light irradiation, which not only has high recovery efficiency, but also can convert harmful substances into CO2 and H2O. In addition, the waste heat generated during the recovery process can be used in stages, such as using the heat discharged from the condenser to preheat the feed, or using the waste heat from the compressor for adsorbent regeneration, which can further improve the system's energy efficiency.