From crude oil to petroleum through a variety of processes, different processes will be the same raw material to produce different products.

The basic route from crude oil to petroleum is generally:

(1) The crude oil is first divided into different straight-run distillates according to the boiling point requirements of different products, and then the non-ideal components in these distillates are removed according to the quality standards of the products;

② Through chemical reaction conversion, the required components are generated, and then a series of qualified petroleum products are obtained.

The common processes of petroleum refining include atmospheric and vacuum distillation, catalytic cracking, delayed coking, hydrocracking, solvent deasphalting, hydrofining and catalytic reforming.

(1) Atmospheric and vacuum distillation

1. Raw materials:

Crude oil, etc.

2. Products:

2. Naphtha, crude diesel oil (gas oil), residual oil, asphalt, reduced line.

3. Basic concepts:

Atmospheric and vacuum distillation is a combination of atmospheric distillation and vacuum distillation, basically a physical process: raw oil in the distillation tower is divided into different boiling point range of oil products (called fractions) according to the evaporation capacity, some of these oils are blended, added additives in the form of products, and a considerable part is the raw material of the subsequent processing device.

Atmospheric and vacuum distillation is the first process of oil processing in refineries, called a crude oil processing, including three processes: a. Desalting and dewatering of crude oil; b. Atmospheric distillation; c. Vacuum distillation.

4. Production process:

Crude oil is generally with salt and water, which can lead to the corrosion of the equipment, so the crude oil is first dehydrated and dehydrated before entering the atmospheric and vacuum treatment, usually adding demulsifier and water.

The crude oil is formed into two parts by the flow meter, the heat exchange part and the distilling tower, and one part forms the top oil of the tower, which passes through the cooler and the flow meter, and then enters the tank area. This part is the chemical light oil (the so-called naphtha); One part forms the bottom oil of the tower, and then through the heat exchange part, it enters the atmospheric furnace and the atmospheric tower to form three parts, a part of diesel oil, a part of wax oil and a part of the bottom oil of the tower; The remaining bottom oil is further processed through the decompression furnace and the decompression tower to produce reduced line, wax oil, residual oil and asphalt.

The respective yield: naphtha (light gasoline or chemical light oil) accounts for about 1%, diesel oil accounts for about 20%, wax oil accounts for about 30%, residual oil and asphalt account for about 42%, and the reduction line accounts for about 5%.

The process of atmospheric and vacuum pressure does not produce gasoline products, in which wax oil and residual oil enter the catalytic cracking process to produce gasoline, diesel, kerosene and other refined oil; Naphtha is sold directly to other small enterprises to produce solvent oil or to the next step of deep processing, usually catalytic reforming to produce solvent oil or extract compounds; The reducing line can be used to adjust the lubricating oil directly.

5. Production equipment:

The atmospheric and vacuum pressure unit is a distillation unit for a single processing of crude oil, that is, a processing unit for fractionating crude oil into gasoline, kerosene, diesel oil, wax oil, residual oil and other components. Crude oil distillation generally includes atmospheric distillation and vacuum distillation two parts.

a. Atmospheric distillation tower

The so-called atmospheric distillation of crude oil is the distillation of crude oil under atmospheric pressure (or slightly higher than atmospheric pressure), and the distillation equipment used is called the atmospheric distillation tower of crude oil (or atmospheric tower).

The remaining heavy oil components of atmospheric distillation have large molecular weight, high boiling point, and are easy to decompose at high temperature, so that the distilled product deteriorates and produces coke, destroying normal production. Therefore, in order to extract more light components, the boiling point range of the raw oil being distilled is often reduced by reducing the distillation pressure. This process of distillation under reduced pressure is called vacuum distillation.

b. Vacuum distillation column

Vacuum distillation is a distillation process performed at a negative pressure of less than 100KPa. The core equipment of vacuum distillation is the vacuum tower and its vacuum pumping system.

The vacuum pumping equipment of the decompression tower is commonly used as a steam ejector (also known as a steam ejector pump) or a mechanical vacuum pump. Among them, mechanical vacuum pumps are only used in some dry vacuum distillation towers and small refinery vacuum towers, and steam ejectors are widely used.

(2) Catalytic cracking

General crude oil can be obtained after atmospheric and vacuum distillation of gasoline, kerosene and diesel oil and other light oil products only 10 to 40%, the rest is heavy distillates and residual oil. If more light oils are to be obtained, heavy distillates and residual oils must be reprocessed. Catalytic cracking is a common production process of gasoline and diesel oil, and gasoline and diesel oil are mainly produced by this process. This is also the most important production link of the general petroleum refining and chemical enterprises.

1. Raw materials:

Residual oil and wax oil about 70%, catalytic cracking is generally vacuum distillate oil and coking wax oil as raw materials, but with the increasing weight of crude oil and the increasing demand for light oil, most of the petrochemical enterprises began to add pressure reduction residual oil in the raw material, and even directly to atmospheric residual oil as raw materials for refining.

2. Products:

Gasoline, diesel, oil slurry (heavy distillate), liquid propylene, liquefied gas; Gasoline accounted for 42%, diesel accounted for 21.5%, propylene accounted for 5.8%, liquefied gas accounted for 8%, oil slurry accounted for 12%.

3. Basic concepts:

Catalytic cracking is the main process of processing heavy oil (such as residual oil) into light oil (gasoline, kerosene, diesel) in the presence of catalysts, and is the main secondary processing means in the refining process. It is a chemical processing process.

4. Production process:

The normal slag and wax oil enter the lifting pipe, settler and regenerator through the raw oil buffer tank to form oil and gas and enter the fractionating tower.

A part of the oil and gas enters the crude gasoline tower, the absorption tower, the air compressor enters the condensate tank, and the gasoline is refined after the re-absorption tower, the stabilization tower, and the most, and the gasoline is produced.

Part of the oil and gas enters the diesel stripper through the fractionating column, and then refines the diesel oil to produce diesel oil. A part of the oil and gas enters the slurry circulation through the fractionator, and the slurry is produced at the last minute.

Part of the oil and gas enters the liquid hydrocarbon buffer tank through the fractionation tower, passes through the desulfurization adsorption tank, sand filter tower, water washing tank, sweetening extraction tower, pre-alkali washing tank, amine liquid recovery device, desulfurization extraction tower, buffer tower, and finally enters the liquid hydrocarbon tank to form liquefied gas.

Part of the oil and gas through the liquid hydrocarbon buffer tank into the depropane tower, reflux tower, deethane tower, fine propylene tower, reflux tank, and finally into the propylene zone spherical tank, forming liquid propylene. The liquid propylene is then further processed in the polyacrylic workshop to produce polyacrylic.

5. Production equipment:

a. regenerator

The main function of the regenerator is to burn off the coke on the coke catalyst to restore the activity of the catalyst, while also providing the heat required for cracking. The regenerator is composed of a shell, a cyclone separator, an air distributor, an auxiliary combustion chamber and a heat extractor

b. Riser reactor

Straight tube type: used for high and low parallel anti-reflow system, characterized by direct insertion from the bottom of the settler, simple structure, small pressure drop.

Folding type: mostly used in coaxial reflexive systems.

c. settler

The function of the settler is to separate the reaction oil and gas from the lifting tube and the catalyst. The oil and gas are separated by the cyclone separator and then go through the gas collecting chamber to the fractionation system. The catalyst from the fast separator settles down in the settler by gravity and falls into the gas section.

d. Three engines

Main fan: Supply air to the regenerator for burning.

Air compressor: Used to boost the pressure of the rich gas from the fractionation system, and then sent to the absorption stabilization system.

Booster: Supply the dense phase lifting tube of the type IV reaction regeneration device to regulate the amount of catalyst circulation.

e. three-valve

Single-acting slide valve: In the type IV catalytic cracking unit, it is fully opened during normal operation and closed in emergency cases to cut off the connection between the two units to prevent catalyst backflow; Adjust the amount of two catalyst cycles in a riser catalytic cracking unit.

Double-acting slide valve: installed between the outlet of the regenerator and the vent chimney, regulating the pressure of the regenerator and maintaining the pressure balance of the two units.

Plug valve: Regulating the amount of catalyst circulating in a coaxial catalytic cracking unit.

(3) Delayed coking

Coking (referred to as coking) is a deep thermal cracking process and one of the means of treating residual oil. It is the only process that can produce petroleum coke, which can not be replaced by any other process. In particular, the special demand for high-quality petroleum coke in some industries has made the coking process occupy an important position in the oil refining industry.

1. Raw materials:

Delayed coking is a decarbonization process similar to catalytic cracking to change the hydrocarbon ratio of petroleum. The raw materials for delayed coking can be heavy oil, residual oil or even asphalt, and the quality requirements for raw materials are relatively low. The main conversion processes of residual oil are delayed coking and hydrocracking.

2. Products:

The main products are wax oil, diesel, coke, crude gasoline and some gases, their respective proportions are: wax oil accounted for 23-33%, diesel 22-29%, coke 15-25%, crude gasoline 8-16%, gas 7-10%, oil 1-3%.

3. Basic concepts

Coking is a deep thermal cracking reaction at high temperature (400 ~ 500℃) with hydrogen-poor heavy residual oil (such as vacuum residual oil, cracking residual oil and asphalt, etc.) as raw materials. Through cracking reaction, part of the residual oil is transformed into gas hydrocarbon and light oil products; Due to the condensation reaction, another part of the residual oil is converted to coke. On the one hand, because the raw material is heavy and contains a considerable amount of aromatics, on the other hand, the reaction conditions of coking are more harsh, so the condensation reaction accounts for a large proportion of coke.

4. Production process

The production process of the delayed coking unit is divided into two parts: coking and de-coking, coking is continuous operation, de-coking is gap operation. Since industrial plants generally have two or four coke towers, the entire production process is still a continuous operation.

a. The crude oil is preheated, and the coking raw material (vacuum residue) first enters the raw material buffer tank, and then is pumped into the convection section of the heating furnace to rise to about 340~350 ℃.

b. The preheated crude oil enters the bottom of the fractionating tower and exchanges heat with the oil and gas produced by the coke tower in the fractionating tower (the bottom temperature of the tower does not exceed 400℃).

c. The raw oil and circulating oil are extracted from the bottom of the fractionating column together, pumped into the radiation section of the heating furnace with a hot oil pump, heated to the temperature required for the coking reaction (about 500 ° C), and then entered the coke tower from the lower part through the four-way valve for coking reaction.

d. Raw materials react in the coke tower to produce coke accumulation in the coke tower, oil and gas from the top of the coke tower into the fractionation tower, and raw oil after heat exchange, fractionation to get gas, gasoline, diesel and wax oil. The circulating oil at the bottom of the tower and the raw material are then coked.

5. Production equipment

a. Coke tower

The coke tower is an empty cylinder made of thick boiler steel plate and is the place where the coke reaction is carried out.

b. Hydraulic coke removal equipment

The coke tower is used in rotation, that is, when the coke in one tower coalesces to a certain height, the raw material is switched to another coke tower through a four-way valve. The coke tower where the coke is coalesced is cooled by steam and then hydraulically de-coked.

c. Flameless combustion furnace

The coking heating furnace is the core equipment of the unit. Its function is to heat the residue flowing rapidly in the furnace to a high temperature of about 500℃. Therefore, a high heat transfer rate in the furnace is required to ensure that sufficient heat is provided to the oil in a short time, and a uniform heat field is required to prevent local overheating from causing coking of the furnace tube. For this reason, flameless furnace is usually used for delayed coking.

(4) Hydrocracking

The basic principle of lightweight heavy oil is to change the relative molecular weight and hydrogen-carbon ratio of oil, and the change of relative molecular weight and hydrogen-carbon ratio is often carried out at the same time. There are two ways to change the hydrogen-carbon ratio of oil products, one is decarbonization and the other is hydrogenation.

1. Raw materials:

1. Heavy oil, etc

2. Products:

2. Light oil (gasoline, kerosene, diesel or catalytic cracking, cracking raw materials for olefin)

3. Basic concepts

Hydrocracking belongs to the hydrogenation route of petroleum processing, which is to supplement hydrogen from outside in the presence of catalyst to improve the hydrogen-to-carbon ratio of oil.

Hydrocracking is essentially the organic combination of hydrogenation and catalytic cracking process, on the one hand, it can convert heavy oil products into light oil products such as gasoline, kerosene and diesel through cracking reaction, on the other hand, it can prevent a large amount of coke like catalytic cracking, and can also remove sulfur, chlorine and oxygen compounds in the raw material through hydrogenation, so that the olefin is saturated.

4. Production process

According to the different state of catalyst in the reactor, it can be divided into several types, such as fixed bed, boiling bed and suspended bed.

(1) Fixed bed hydrocracking

The fixed bed means that the granular catalyst is placed in the reactor to form a static catalyst bed. The raw oil and hydrogen enter the reaction system after the reaction conditions are reached by heating and pressure increase, and are first hydrorefined to remove sulfur, nitrogen, oxygen impurities and diolefin, and then hydrocracking. After the reaction product is cooled, separated, depressurized and fractionated, the target product is sent to the device, and the gas with high hydrogen content (80%, 90%) is separated and used as recycled hydrogen.

Unconverted oil (called tail oil) can be partially recycled, fully recycled, or not recycled once.

(2) boiling bed hydrocracking

The boiling bed (also known as expansion bed) process is to drive the movement of the catalyst with a certain particle size by the flow rate of the fluid, forming a three-phase bed of gas, liquid and solid, so that hydrogen, raw oil and catalyst are fully in contact with each other to complete the hydrogenation reaction process.

The boiling bed process can handle raw materials with high metal content and carbon residue value (such as vacuum residue). And can make deep conversion of heavy oil; However, the reaction temperature is relatively high, generally in the range of 400~450℃.

This kind of process is more complex, the domestic has not yet industrialized.

(3) Suspension bed (slurry bed) hydrogenation process

The suspended bed process is a hydrogenation process that has gained renewed attention in order to adapt to very inferior raw materials. Its principle is similar to the boiling bed, its basic process is to pre-mix the fine powder catalyst with the raw material, and then enter the reactor with hydrogen to flow from bottom to bottom, the catalyst is suspended in the liquid phase, and the hydrocracking reaction is carried out, and the catalyst flows from the top of the reactor with the reaction product.

The equipment can process all kinds of heavy crude oil and ordinary crude oil residue, but the equipment investment is large. At present, the process is still in the research and development stage in China.

5. Production equipment

The main equipment of the hydrogenation process production unit is operated under high temperature, high pressure and the presence of hydrogen and hydrogen sulfide, so its design, manufacturing and material selection requirements are very high, and the control of the production operation is also very strict.

The high pressure hydrogenation reactor is the key equipment in the plant, the working condition is harsh, the manufacture is difficult and the price is expensive.

According to whether the medium is in direct contact with the metal wall, it can be divided into cold wall reactor and hot wall reactor. The reactor consists of two parts: a cylinder and an internal structure.

a. Hydrogenation reactor cylinder

The reactor barrel is divided into two types: cold wall barrel and hot wall barrel.

b. Hydrogenation reactor internals

Hydrogenation reaction is operated under high temperature and high pressure and corrosive media (H2, H2S). In addition to preventing hydrogen corrosion and corrosion of other media on the material, the hydrogenation reactor should also ensure that the reactants (oil, gas and hydrogen) are evenly distributed in the reactor to ensure good contact between the reactants and the catalyst; Remove the reaction heat in time to avoid excessive reaction temperature and overheating of catalyst. To ensure the best reaction conditions and extend catalyst life; Under the premise of uniform distribution of reactants, the pressure drop inside the reactor is not too large, so as to reduce the load of the circulating compressor and save energy.

Therefore, the reactor should be equipped with necessary internal components to achieve the uniform distribution of gas and liquid as the main goal. Typical reactor internals include inlet diffuser, gas-liquid distribution tray, descaling basket, catalyst support tray, quench tank and redistribution tray, outlet collector, etc.

(5) solvent deasphalting

Solvent deasphalting is a pretreatment process of inferior residual oil. A deasphalted oil is produced by extraction by removing gum and bitumen from the vacuum residue (sometimes also from the atmospheric residue) of crude oil distillation