Method for reducing coking in heavy oil hydrogenation process

Abstract

The invention discloses a method for reducing coking in a heavy oil hydrogenation process. The stability of a heavy oil colloid system is enhanced by doping coal tar into a heavy oil system, so that green coke in the heavy oil hydrogenation process is reduced. The method comprises the following steps: (1) doping a certain proportion of coal tar into heavy oil, and stirring for 1-4 hours in a reaction kettle at a specific temperature; and the two oil products are uniformly mixed. And (2) stopping heating and stirring after the reaction time is up, and rapidly reducing the temperature in the kettle to room temperature in an air cooling manner. And (3) filling a catalyst, respectively purging with N2 and H2 for three times to discharge air and nitrogen in the kettle, then filling H2 to enable the pressure in the kettle to reach 7-11 Mpa, raising the temperature to 350-430 DEG C at a speed of 10 DEG C / min, and reacting for 0.5-4 hours at a constant stirring speed (400 r. Min <-1 >). Heating and stirring are stopped after the reaction time is up, and the temperature in the kettle is rapidly reduced to room temperature in an air cooling manner to terminate the reaction, so that the coking of the heavy oil can be reduced by 50-100%.

Description

Technical Field

[0001] The invention belongs to the field of heavy oil hydrogenation, and in particular relates to a method for reducing coking in the heavy oil hydrogenation process. Background Art

[0002] In recent years, due to the growing demand for more environmentally friendly and lightweight fuels, the shortage of crude oil reserves and the shrinkage of conventional oil, there is an urgent need to develop heavy oil upgrading technology. In the field of oil processing, research focuses on the advancement of refining technology for low-value industrial by-products (such as vacuum residue oil, etc.) and unconventional oils (such as extra heavy oil, oil sands, etc.) that are regarded as alternative energy sources. According to 2020 data, recoverable reserves of heavy oil account for 40% of total oil reserves, while conventional oil accounts for only 30%. In addition, a large amount of difficult-to-process residues will remain in the processing of conventional oil. Most of my country's crude oil is heavy, and the vacuum residue content is generally as high as 40-50%. The composition of heavy oil is also complex, containing a high amount of sulfur, nitrogen, metals and macromolecular asphaltene, which makes the coking rate of heavy oil in the hydrogenation process as high as 20%, seriously reducing the catalytic efficiency of the catalyst and the safety of the device, causing difficulties in the lightening of heavy oil.

[0003] Heavy oil is actually a colloidal system. Asphaltene forms micelle cores, which are peptized by colloids and pentane solubles to form micelles. The molecules (colloids) with larger average relative molecular mass and aromaticity are closer to the core, and the periphery is small molecules with lower aromaticity (aromatic fractions and saturated fractions). This colloidal structure composed of four components (saturated fractions, aromatic fractions, colloids and asphaltene) has a gradual and continuous change in average relative molecular mass and aromaticity. Generally, the higher the content of colloids and aromatic fractions in oil products, the stronger their colloidal stability.

[0004] When heavy oil is hydrogenated to produce light fuel oil, the reaction temperature is high, and the thermal reaction of the heavy oil system is dominant. The cracking and aggregation of asphaltenes and colloids destroy the colloidal system. The asphaltenes associate or condense to form a second liquid phase and gradually evolve from an intermediate phase to coke, causing coking in the reactor. That is, the colloidal dispersed phase asphaltene is the main coking precursor in the hydrogenation process. At the same time, after the coking induction period, the system cokes rapidly, and the colloidal stability decreases and an inflection point appears, which corresponds to the starting point of a large amount of coking. The deposition and flocculation of asphaltene are the result of the heavy oil colloidal structure losing stability under the action of various physical and chemical factors. Therefore, how to effectively adjust the colloidal stability during heavy oil hydrogenation, thereby reducing the coking problem in the heavy oil hydrogenation process, has become one of the key bottlenecks in the utilization of heavy oil resources. Summary of the invention

[0005] The purpose of the present invention is to add coal tar into the heavy oil system to improve the colloid stability of the heavy oil, thereby reducing the amount of coke produced in the hydrogenation of the heavy oil.

[0006] The technical solution adopted by the present invention to solve the above technical problems is as follows: (1) Add a certain proportion of coal tar to heavy oil and stir in the reactor for 1-4 hours at a specific temperature to mix the two oil products evenly. (2) Stop heating and stirring after the reaction time is reached, and use air cooling to quickly reduce the temperature in the reactor to room temperature. (3) Load the catalyst, purge the air and nitrogen in the reactor with N2 and H2 three times respectively, then fill H2 to reach 7-11 MPa in the reactor, raise the temperature to 350-430℃ at 10℃ / min, and react for 0.5-4 hours at a constant stirring speed (400 r·min-1). Stop heating and stirring after the reaction time is reached, and use air cooling to quickly reduce the temperature in the reactor to room temperature to terminate the reaction, which can reduce heavy oil coking by 50-100%.

[0007] The coal tar in step (1) is one of low-temperature coal tar, medium-temperature coal tar, medium-low-temperature coal tar and high-temperature coal tar.

[0008] The blending ratio of the coal tar described in step (1) is 30%-90%.

[0009] Compared with the existing heavy oil hydrogenation technology, the blending of coal tar and heavy oil is a new way to inhibit the coking of heavy oil. Coal tar also exists in a colloidal state. Due to the particularity of its source, the content of colloid and aromatic components in coal tar is much higher than that of heavy oil, and the average molecular weight of coal tar is also much lower than that of heavy oil, resulting in high colloidal stability of coal tar, which can greatly inhibit the coking of coal tar under appropriate catalytic action, or even prevent it from coking. When coal tar and heavy oil are blended, the addition of coal tar will greatly improve the stability of the heavy oil colloidal system, making it difficult for asphaltene in coal tar to deposit and coke. At the same time, the sulfide catalyst particles, micro-sized carbonaceous particles and inorganic minerals in coal tar can provide independent condensation nuclei or growth nuclei for heavy oil macromolecular free radicals, which promotes the dispersion of spherical coke precursors, inhibits the agglomeration of coke precursors, and reduces the formation of coke. DETAILED DESCRIPTION

[0010] The present invention is further illustrated by way of examples below, but they do not constitute any limitation to the present invention. Any limited number of modifications made by anyone within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0011] Implementation Case 1 (1) Add 30% low-temperature coal tar to heavy oil and stir in a reactor at 100°C for 1 h to mix the two oils evenly. (2) Stop heating and stirring after the mixing time is reached, and use air cooling to quickly reduce the temperature in the reactor to room temperature. (3) Load the catalyst, purge the reactor with N2 and H2 three times respectively to expel the air and nitrogen in the reactor, then fill the reactor with H2 to reach 11 Mpa, raise the temperature to 430°C at 10°C / min, and keep stirring at a constant speed (400 r·min-1 ) for 1 h. After the reaction time was reached, the heating and stirring were stopped, and the temperature in the kettle was quickly reduced to room temperature by air cooling to terminate the reaction. The coking of heavy oil decreased by 95%.

[0012] Implementation Case 2 (1) Add 70% of medium-temperature coal tar to heavy oil and stir in a reactor at 120°C for 4 h to mix the two oils evenly. (2) Stop heating and stirring after the mixing time is reached, and use air cooling to quickly reduce the temperature in the reactor to room temperature. (3) Load the catalyst, purge the reactor with N2 and H2 three times respectively to expel the air and nitrogen in the reactor, then fill the reactor with H2 to reach 10 Mpa, raise the temperature to 420°C at 10°C / min, and keep stirring at a constant speed (400 r·min -1 ) for 2 h. After the reaction time was reached, the heating and stirring were stopped, and the temperature in the kettle was quickly reduced to room temperature by air cooling to terminate the reaction. The coking of heavy oil decreased by 90%.

[0013] Implementation Case 3 (1) Add 90% of medium-low temperature coal tar to heavy oil and stir in a reactor at 180°C for 2 h. Mix the two oils evenly. (2) Stop heating and stirring after the mixing time is reached, and use air cooling to quickly reduce the temperature in the reactor to room temperature. (3) Load the catalyst, purge the reactor with N2 and H2 three times respectively to expel the air and nitrogen in the reactor, then fill the reactor with H2 to reach 9 Mpa, raise the temperature to 410°C at 10°C / min, and keep stirring at a constant speed (400 r·min -1 ) for 4 h. After the reaction time was reached, the heating and stirring were stopped, and the temperature in the kettle was quickly reduced to room temperature by air cooling to terminate the reaction. The coking of heavy oil decreased by 60%.

Claims

1. A method for reducing coking during heavy oil hydrogenation, the specific steps of which are: (1) Add a certain proportion of coal tar to heavy oil and stir in the reactor for 1-4 hours at a specific temperature to mix the two oil products evenly. (2) Stop heating and stirring after the reaction time is reached, and use air cooling to quickly reduce the temperature in the reactor to room temperature. (3) Load the catalyst, purge the reactor with N2 and H2 three times respectively to expel the air and nitrogen in the reactor, then fill H2 to reach 7-11Mpa in the reactor, raise the temperature to 350-430℃ at 10℃ / min, and keep stirring at a constant speed (400 r·min -1 ) for 0.5-4 h. After reaching the reaction time, stop heating and stirring, and use air cooling to quickly reduce the temperature in the kettle to room temperature to terminate the reaction, which can reduce heavy oil coking by 50-100%.

2. The method according to claim 1, characterized in that The coal tar described in step (1) is one of low-temperature coal tar, medium-temperature coal tar, medium-low-temperature coal tar and high-temperature coal tar.

3. The method according to claim 1, characterized in that The blending ratio of coal tar in step (1) is 30%-90%.