Affect health

Anesthesia on the central nervous system/stimulation on the skin and mucous membranes/fat-removing effects, causing disorders of intracellular lipid balance, causing dermatitis and eczema/long-term exposure to benzene vapor can induce symptoms such as leukemia, chromosomal abnormalities and abnormal hematopoietic functions.

Waste energy

The gasoline loss is estimated according to category A areas, excluding the loading and transportation losses of oil tankers (all according to railway tank cars and automobile tank cars), and excluding transfer losses and barrel filling losses. Oil storage tanks are all counted as floating roof tanks, and gas station storage tanks are all counted as concealed tanks; once railway loading, railway transportation (<500km) once, railway unloading once (floating roof tank), floating roof tank storage, automobile tanker One loading, one transportation by tanker road (<50km), one unloading at a tanker gas station, storage of oil tanks at a gas station, and a retail fuel dispenser. The estimated total loss is: railway tank car loading loss rate + railway transportation loss rate + railway unloading loss rate (floating roof tank) + floating roof tank storage loss rate + automobile tank car loading loss rate + automobile tank car transportation loss rate + automobile tank unloading rate Loss rate (other tanks) + storage loss rate of gas station storage tanks + retail loss rate (fuel dispensers) = 0.17% + 0.16% + 0.01% + 0.01% + 0.10% + 0.01% + 0.23% + 0.01% + 0.29% = 0.99% ≈ 1%

Polluted environment

Pollution to the atmospheric environment (urban photochemical smog)/pollution to underground soil and water sources.

Affect oil quality

Take gasoline as an example. With the evaporation of light components, the initial boiling point and 10% point of gasoline increase, the vapor pressure decreases, and the starting performance deteriorates; the octane number decreases, and the evaporation temperature also rises. When gasoline burns in the engine The anti-knock performance deteriorates, accelerates gasoline oxidation, and increases gasoline gum; when the evaporative loss rate of aviation gasoline reaches 1.2%, the initial boiling point increases by 3°C, the vapor pressure decreases by 20%, and the octane number decreases by 0.5 units.

Affect safety in production

Gasoline and other light oils have the characteristics of being volatile, flammable, leaking, and easy to accumulate static charges. They are extremely prone to explosion or fire accidents, causing significant loss of life and property.

· Adsorption method

Technical Principle：

The adsorption process refers to the process in which the porous solid adsorbent is in contact with the fluid phase (liquid or gas), and single or multiple solutes in the fluid phase are selectively transferred to the surface of the porous solid particles and accumulated on the surface of the porous solid adsorbent. The similar reverse operation is called the desorption process, which can selectively remove various solutes that have been adsorbed on the surface of the porous solid adsorbent.

The principle of oil-gas recovery by adsorption method is to use the difference in the binding force between the components in the oil-gas-air mixed gas and the adsorbent to separate the air components that are difficult to adsorb from the oil and gas components that are easy to adsorb, and then the adsorbent The method of recovering the desorbed oil and gas. At present, the commonly used adsorbents are activated carbon and resin.

Process flow：

The WLDBVR-AD series of adsorption vapor recovery equipment developed by Viland is composed of two alternate adsorption and desorption adsorption tanks, and adopts a pressure swing adsorption process. The regeneration of activated carbon is accomplished through a decompression process provided by a vacuum pump. During the regeneration process, the oil and gas desorbed from the activated carbon bed is first compressed in the vacuum pump, and then enters the heat exchanger. After the temperature is lowered by the heat exchanger, the oil and gas are condensed into liquid and enter the intermediate oil and gas separation tank for recovery.

Major equipment：

The main configuration of the device: adsorption tank, vacuum pump, heat exchanger, oil and gas separation tank, liquid return pump, electrical and control system, etc.

Technical characteristics：

Advantages: It can well control the exhaust gas emission concentration.

Shortcoming:

1) The adsorption heat effect of activated carbon will bring safety hazards;

2) When the adsorbent (activated carbon) directly adsorbs high-concentration oil and gas, the adsorbent (activated carbon) has a large load and a large amount, resulting in a huge volume of the adsorption tank;

3) The process of desorption of oil and gas requires a secondary process.

Application field：

Adsorption and separation of low-concentration organic matter.

 

· Condensation method

Technical Principle：

Condensation oil and gas recovery technology uses the property of oil and gas components (different hydrocarbon substances) to have different saturated vapor pressures at different temperatures and pressures, and reduces the system temperature or increases the system pressure to condense and separate the hydrocarbon components. come out.

During the condensation process, the condensed substance only undergoes physical changes while the chemical properties remain unchanged. Therefore, it can be seen intuitively and can be directly recycled, eliminating the need for secondary processing. The condensation method can theoretically achieve a high degree of purification, but the operating cost is too high when the hazardous substances are required to be controlled to the order of 10-6 (volume fraction).

Process flow：

The condensing temperature of the WLDBVR-CD series condensing method oil and gas recovery device is realized in the steps of pre-cooling, first-stage refrigeration, and second-stage refrigeration according to different oil and gas components and recovery requirements. The main parameter that affects the oil and gas recovery rate is the condensation temperature, and it is determined that the oil and gas recovery rate can reach more than 95% specified by the state when the condensation temperature drops below -80 ℃ (for specific projects, according to the composition of the oil and gas, the requirements for the recovery rate, Factors such as exhaust gas concentration limit comprehensively determine the minimum cooling temperature of oil and gas). If the device is designed for one-step refrigeration, and the oil and gas are directly reduced from 20°C to -80°C, the compressor refrigeration pressure difference is too large, and the requirements on the compressor are very high, and the total energy consumption of the condensing device will also be very high. Therefore, it is advisable to design a three-stage refrigeration process: the first stage is pre-cooling, and the condensation temperature is designed to be 4°C. The purpose is to condense the water vapor in the oil and gas, so as to standardize the state of the oil and gas entering the low-temperature condenser (consistent). Reduce the operating energy consumption of the recovery device. At this time, a small part of the hydrocarbon components with a large number of carbon atoms will also be condensed; the third stage condensation temperature is designed to -80 ℃ to ensure an oil and gas recovery rate of more than 95%; in addition, the design Add the second stage condensing temperature to control the total energy consumption of the condensing device to the lowest level.

Major equipment：

The main configuration of the device: pre-cooler, condenser, mechanical refrigeration device, oil and gas separator, etc.

Technical characteristics：

Advantage：

1) Condensation method The vapor recovery method can be directly condensed under normal pressure, and is not affected by external temperature and pressure, and is not affected by the gas-liquid ratio. The recovery effect is stable, especially suitable for high temperature, high humidity, and high concentration occasions;

2) The working temperature is lower than the flash point of each component of the oil and gas, and the safety is good;

3) The process flow is short and the process is simple. The oil and gas can be condensed into liquid when the oil and gas are connected to the entrance of the equipment. No other intermediate steps are required, which is easy to operate and maintain; and the operation flexibility is large;

4) Small footprint;

5) There is no secondary pollution, and the recovered materials can be sold or used directly.

Shortcoming:

When the hazardous substances are required to be controlled to the order of 10-6 (volume fraction), extremely low cooling temperature is required, and the operating cost is too high.

Scope of application：

Almost all single materials of VOCs gas, and mixed materials that do not react with each other at low temperatures.

 

· Absorption method

Technical Principle：

Absorption is a process of separating the gas mixture according to the different physical solubility or chemical reactivity of the components of the mixed gas in the same liquid solvent. The absorption operation is essentially the mass transfer process of the mixed gas components from the gas phase to the liquid phase. The liquid solvent used is called the absorbent, the component in the mixed gas that can be significantly dissolved in the liquid solvent is called the solute, the almost insoluble component is called the inert component or inert gas, and the solution obtained after absorption is called the absorbent. The remaining gas after absorption is called absorption tail gas or purge gas.

Process flow：

The absorbent used in the WLDBVR-AB series absorption method oil and gas recovery device is based on the actual situation of the project implementation site, and the materials are taken on-site to minimize absorbent consumption and regeneration costs. The following briefly introduces the technology with gasoline as the absorbent. The oil and gas are sent to the bottom of the gasoline absorption tower through the gas collecting pipe. The oil and gas rise through the packing layer and fully countercurrently contact the gasoline from the top of the tower for mass transfer. Most of the hydrocarbons above C3 are absorbed by the gasoline; Emission, the content of oil and gas discharged into the air ≤ 4% (volume fraction). The rich light diesel oil that has absorbed the oil and gas is collected into the rich oil tank at the bottom of the tower, and is finally sent to the oil depot or refining unit.

Major equipment：

According to different designs, the main equipment for oil and gas recovery by absorption method includes absorption tower, desorption tower, lean oil/rich oil/absorbent transfer pump, lean oil/rich oil/absorbent storage tank, desorption equipment (such as vacuum pump), etc.

Technical characteristics：

advantage：

1) The process flow is simple and easy to realize;

2) The absorbent can be selected on-site according to the actual situation of the project (such as lean oil), and the recovered oil and gas can be directly sent to the device for use (such as rich oil);

3) The device occupies a small area and is easy to operate.

Shortcoming：

1) Low oil and gas recovery rate;

2) High exhaust gas emission concentration;

3) Sometimes the desorption process is more complicated.

Scope of application：

Oil depots, refineries and other places where it is convenient to obtain materials for lean oil and where emission indicators are not high.

 

· Membrane separation

Technical Principle：

The gas permeable membrane is a phenomenon in which the membrane is in contact with the raw material gas, and gas molecules permeate the membrane driven by the pressure difference between the two sides of the membrane. The membrane oil and gas recovery device is a measure to recover the oil and gas generated in the process of receiving and sending oil by using the membrane separation method. Its principle is based on the permeability of the membrane to the gas, and the components in the mixed gas under a certain pressure are used in the membrane. With different penetration rates to achieve separation.

Compared with the absorption, adsorption, and condensation method of oil and gas recovery, membrane separation gas mixture is a simpler and more effective technology. Especially with the continuous development of many excellent polymer membranes and inorganic membranes, membrane gas separation has become More effective and economical new separation technology.

Process flow：

The application of membrane separation technology requires different process design in different occasions. The membrane separation organic vapor recovery system is mainly composed of a membrane separation system and an organic vapor recovery system. When the concentration of the complex raw material gas or the exhaust gas after membrane separation is very low, a post-treatment system, such as an adsorption process or a catalytic combustion process, is added. .

Major equipment：

Various membrane separation devices mainly include membrane modules, pump units (compressor units, vacuum pump units), filters, valves, instruments and pipelines, etc. In the specific application of gas membrane separation, it must be assembled into various membrane modules. The membrane module is a device that assembles the membrane in a basic unit device in some form, and then realizes the separation of the components in the mixture under the external driving force. Membrane modules are also called membrane separators. In an industrial device for membrane separation, according to production needs, several or even hundreds of membrane modules can be installed.

There are three main types of polymer membrane modules used for gas separation: flat, tubular and hollow fiber types. Weilunde can use the organic vapor recovery special membrane modules of the German GKSS Research Center, the American MTR Company and the Japanese Nitto Company to carry out the system integration design according to the specific needs of users.

Technical characteristics：

Advantage：

1) In most membrane separation processes, the components do not undergo phase change, and the energy consumption is low;

2) The membrane separation process is carried out at room temperature;

3) Separate azeotropes and components with similar boiling points;

4) With pressure difference as the driving force, the device is simple and easy to operate.

Shortcoming：

1) Membrane modules are not yet domestically produced, their prices are high, and their service life is low, resulting in high operating costs;

2) The membrane separation process is only a concentrated process and cannot completely separate the oil and gas from the air.

Scope of application：

In the actual use process, the membrane separation process is integrated and coupled with condensation, adsorption, absorption and other processes to form a more effective technology and economy.