CN103814110A - Method for the retarded coking of petroleum residues - Google Patents

Abstract

The invention relates to the oil-refining industry, in particular to the process of delayed coking with the purpose of obtaining oil coke and gas oil fractions. The exploitation of many delayed coking installations, particularly in the reprocessing of oil residues, from which coke with high sulfur content is obtained in the process of coking, is oriented to obtaining the maximum possible quantity of distillated fractions: gasoline, light and heavy coking gas oil. Further on, high quality motor fuels are produced from the obtained distillates by using hydro-catalytic processes - hydraulic cleaning, catalytic cracking, and hydrocracking.

Description

Delayed coking method of residual oil

technical field

The invention relates to petroleum refining, in particular to obtaining petroleum coke and gas oil fractions through a delayed coking process.

Background technique

Development of a variety of delayed coking units, especially for the aftertreatment of residual oil, in which coke with a high sulfur content is obtained, obtaining as many fractions as possible: gasoline, light gas oil and heavy gas oil. In addition, the resulting fractions are subjected to hydrocatalytic processes, namely hydraulic cleaning, catalytic cracking, and hydrocracking to produce high-quality fuels. The coking product thus obtained must meet certain quality requirements. Coked gasoline (the initial boiling point of the fraction is 180°C) is hydraulically cleaned, and then modified to obtain high-octane commercial gasoline. Light coking gas oil (initial boiling point at 180-350°C) is hydraulically washed to obtain diesel oil. This is why it is necessary to take into account the end boiling point of light gas oils, where a high content of high boiling point components contributes to carburization of hydraulic cleaning catalysts and pressure regeneration of coked heavy gas oils (boiling point greater than 350°C). Hydraulic cleaning during the coking process of sulfur raw materials, high-octane gasoline through catalytic cracking, and diesel through hydrocracking. This is why there are strict requirements on the final boiling point of heavy gas oil, because the high boiling point fraction in it determines the high coking property and also leads to premature carburization of the catalyst used. The bubble point temperature of heavy gas oil needs to be taken into consideration, firstly, the low boiling point fraction, boiling temperature can reach 350°C, the yield of light gas oil used to produce diesel fuel is reduced, and secondly, these low boiling point fractions are hydrocatalytic process In the ballast, excessive use will reduce the final product yield. For heavy gas oil and bottom liquid, the content of coke particles (also known as oil coke) deposited on the surface of the catalyst during the catalytic process is strictly limited. If the oil coke content is high (eg >0.1%), such products cannot be used for catalytic treatment, only as a component of boiler fuel.

To improve distillate production, delayed cokers are operated with the smallest possible recycle ratio (sometimes even zero) and the lowest possible coker pressure. Delayed coker operation under such technical parameters will obviously help to increase the production of heavy coker gas oil (distillate boiling temperature over 350°C). However, coking properties, as well as the amount of high molecular weight polycyclic aromatic hydrocarbons, resins, bitumen and metal organic compounds also increased with a marked increase in end boiling point temperature. These high molecular weight hydrocarbons contained in heavy coker gas oil fractions lead to rapid deactivation of catalysts used for hydraulic cleaning and hydrocracking.

The process of delayed coking of resid is known, cooling heavy coker gas oil is used to adjust the final boiling point of the coker obtained from the rectification column according to the amount of cold heavy coker gas oil as reflux at the bottom of the column to be achieved temperature to improve its quality [G.M.Sieli, A.Faegh, S.Shimoda, "Fine Tuning of Coking Behavior".-Oil-Gas Technologies Impurities, 2008, Issue 1, pp. 74-77]. As a result, the high boiling fractions contained in the heavy gas oil are condensed to form a recycle, and the fresh feedstock at the bottom of the rectification column is passed (mainly) to the coking chamber furnace as a secondary feedstock. Removal of the highest boiling fractions of the heavy coker gas oil in this way improves its quality and subsequently has a favorable effect on obtaining fuels after catalytic treatment.

An important disadvantage of this method is the fact that when the cold reflux medium enters the bottom (pipeline) of the rectification column, the final boiling point temperature of the heavy coker gas oil is lowered, and the reflux ratio is increased at the same time, resulting in higher energy consumption and reduced raw material The production efficiency and reduce the yield of heavy gas oil. In addition to this, coke particles introduced from the carbonization chamber to the rectification tower, enter the secondary raw material and subsequently enter the furnace causing its carburization.

The residual oil delayed coking process closest to the purpose of the present invention includes heating the feedstock, separating it into light fractions and heavy residues in an evaporator, fractionating the light fractions in a rectification tower and the vapor-liquid products of the coking process, mixing Heavy residue from evaporator with recycle - bottom liquid, rectification column coking preheat mixture. Adjust the quantity and quality of the bottom liquid by changing the amount of cold heavy gas oil as the reflux of the mass exchange device at the bottom of the rectification tower, and the bottom liquid enters the upper part of the evaporator with the mass exchange device (Russian Federation Patent No. 2209826, August 2003 10, classification number C 10 B 55/00).

This method begins with adjusting the mass (relative to density, coking and fractionation components) of the bottoms liquid from the bottom of the rectification column and sent to the evaporator to be mixed with the feedstock as recycle. In this method, the bottom liquid formed in the rectification tower is taken out from the bottom, sent to the evaporator to be mixed with the raw material to form a secondary raw material as a recycle, heated in the coke oven and sent to the carbonization chamber for carbonization. The amount of cold gasoline supplied to the mass exchange device at the bottom of the rectification column, the supply of bottom liquid from the bottom of the rectification tower to the upper part of the evaporator, the amount of steam entering the bottom of the evaporator, leading to the bottom of the evaporator (secondary raw material) Increased residue weight increases coke yield and reduces power consumption.

This method has the disadvantage that in the case of foam transfer from the coking chamber, the liquid at the bottom of the rectification column may contain coke particles deposited on the mass exchange device of the evaporator, impairing the operation of the unit, coke particles in the furnace and the two Mixing of secondary raw materials leads to carburization, thereby reducing the time between required overhauls of the delayed coker. This method cannot control the quantity and quality of light oil obtained from the unit. Variations in the amount of cold oil in this method lead to variations in the recirculation rate.

Contents of the invention

The purpose of the method proposed by the present invention is to increase the overhaul interval of the residual oil delayed coking unit by reducing the carburization of the mass exchange device of the evaporator, to increase the overhaul interval of the reaction furnace coil by eliminating the coke particle component, and to lower the respective independent cycle ratios. Two heavy gas oils are obtained while being able to control the quality of the resulting fractions (light gas oil and two heavy gas oils).

According to the residual oil delayed coking method of the present invention, it includes heating the coking raw material, transporting it to the evaporator and mixing it with the recycle to form a secondary raw material, heating the secondary raw material and transporting it to the carbonization chamber, and discharging the coking product from the carbonization chamber Sent to the rectification column for fractional distillation to obtain gas, gasoline, light coker gas oil, heavy coker gas oil and bottom liquid, the cooled heavy gas oil is sent to the mass exchange device at the lower part of the rectification tower, by providing light gas oil to the bottom of the rectification tower The gas exchange device is realized.

The amount of cooling light gas oil and heavy gas oil supplied varies depending on the quantity and quality of light gas oil, heavy gas oil and bottom liquid to be obtained.

Heavy coker gas oil is used as recycle.

Further, the cooled heavy coker gas oil is used as a reflux medium for adjusting the final boiling point of the heavy gas oil, and the cooled light coker gas oil is used for adjusting the bubble point temperature of the heavy gas oil.

The method of the present invention is implemented as follows. The feedstock is heated in tube furnace 1 and/or in heat exchangers and sent to evaporator 2, the upper part of which receives as recycle heavy coker gas oil from main rectification column 3. The resulting secondary raw material, a mixture of raw material and recycle, is heated in a tube furnace 4 and conveyed to one of the alternately operating carbonization chambers 5 . The distillate formed by coking is transported to the rectification tower 3 through the gas pipeline at the top for fractionation. Gases and unstable gasoline are separated at the top of the distillation column. In order to regulate the quality of gasoline, the unstable gasoline part is conveyed to the first tray with active return medium. The light coker gas oil and the heavy coker gas oil pass through the stripper 6 and are separated and extracted from the main rectification column in the form of side draw. The main part of the heavy gas oil from the strip 6 and cooler 7 is extracted from the plant as a final product, part of which is sent to the overhead gas line as a coolant. The cooled heavy gas oil from the rectification tower 3 liquid reservoir is sent to the first mass exchange device at the bottom of the rectification tower as a flushing liquid, which is used to adjust the final boiling point of the heavy coking gas oil in the rectification tower. The cooled light coked gas oil is sent to the mass exchange device at the upper part of the rectification tower 3 to adjust the bubble point temperature of the heavy gas oil and the final distillation point of the light coked gas oil.

The amount of cooled light and heavy gas oil supplied as reflux medium depends on the desired quantity and quality of light gas oil, heavy gas oil and bottom liquid obtained.

After cooling, the bottom liquid is extracted from the bottom of rectification column 3 as a commercial product.

In this way, the method proposed by the present invention is able to obtain the adjustment of two heavy gas oil fractions at the same time: heavy coker gas oil, used for hydrocracking or hydraulic cleaning and further used for catalytic cracking; bottom liquid, based on Its quality can be used as raw material for hydrogenation catalytic process or as boiler fuel. Thus, the recycling rate does not change.

The increased reflux at the bottom of the rectification column promotes condensation of the highest boiling point fraction of the coked fraction from the coking chamber. Therefore, the end boiling point temperature of heavy gas oil is lowered, and its density, coking and PAH content are reduced. In connection with this, due to the dilution of the heavy gas oil, the functional composition of the bottom liquid extracted from the bottom of the rectification column is reduced, and its density, coking and carbide content are reduced.

Adjustment of the amount of cold light coker oil supplied to the upper mass exchange unit of the rectification column allows adjustment of the bubble point temperature of the heavy coker gas oil and, respectively, the end boiling point of the light oil.

Therefore, the properties of the coker gas oil that are adjusted for supply are not related to changes in the recycle rate, and the amount of recycle fraction entering the coking process is strictly limited by the amount of heavy coker gas oil entering the evaporator.

Description of drawings

The delayed coking device proposed by the present invention for realizing the method of the present invention is shown in FIG. 1 .

The device includes a tube furnace 1 for heating raw materials; an evaporator 2 with a mass exchange device, a rectification tower 3 , a tube furnace 4 , a carbonization chamber 5 , a stripper 6 , and a cooler 7 .

Detailed ways

The method of the invention is illustrated by the following examples.

Example 1 (prototype based)

In industrial units, the coking feedstock, whose characteristics are listed in Table 1. The raw material is heated to 270°C in the heat exchanger and then sent to the bottom of the evaporator. In the upper part of the evaporator, the bottom liquid from the main rectification column is used as a recycle, and its amount is 10% of the raw material amount. The secondary raw material formed in this way in the evaporator is heated to 500°C in the furnace and sent to the carbonization chamber for coking. Coking products in the carbonization chamber enter the lower part of the main rectification tower through the top gas pipeline of the rectification tower. The coking product with the highest boiling point is condensed in the top mass exchange device in the lower part of the rectification tower, and the cold heavy coking gas oil is used as the reflux medium in the lower part, and the dosage is 10% of the raw material. All concentrated high-boiling point coking products (bottom liquid) are sent to the evaporator as a recycle to mix with feedstock, and non-concentrated low-boiling point products are sent to the upper fraction of the rectification column to obtain gas, gasoline, light and heavy coker oil. The overhaul interval is 275 days. The yield and quality of the petroleum fractions obtained during the bedding process and the interval between overhauls are shown in Table 2.

As a result of coking, the yield of heavy gas oil was 28.2%, which has low density and low coking properties, but contains 37% by volume of fractions with boiling points up to 350°C, which is relatively high for light oil produced as diesel fuel feedstock. % (27.1% mass content) has a negative impact.

Embodiment 2 (according to the method proposed by the present invention).

According to the accompanying drawings, the characteristics of coker oil raw materials are shown in Table 1. The feedstock is heated to 270°C in heat exchange and then sent to the evaporator where heavy coker gas oil is provided as recycle in the top tray of the evaporator, which is used in an amount of 10% of the feedstock. The secondary raw material obtained at the bottom of the evaporator is heated to 500°C in the furnace, and then transported to the carbonization chamber for coking. The coked product is sent to the bottom of the rectification column through the upper pipeline. In order to adjust the final boiling point of the heavy coker gas oil separated from the device, the cooled heavy gas oil is provided as the lower reflux medium, and its consumption is 10% of the raw material, which is transported into the first mass exchange device at the bottom of the rectification tower. In order to adjust the bubble point temperature of the heavy coker gas oil located in the mass exchange device at the upper part of the rectification tower, cool light coker gas oil (top reflux medium) is provided in an amount of 20% of the raw material. The yield and quality of the petroleum fractions obtained, as well as the time intervals between overhauls are shown in Table 2.

As can be seen from the table, compared with the prototype of Example 1, the productive rate of heavy gas oil is slightly reduced, but the provision of top reflux medium reduces the content of cuts therein. 20% (mention content)%. This heavy gas oil can be used as a feedstock for fuels obtained by hydrocracking.

In addition, the yield of light gas oil has increased compared to the prototype embodiment.

From the bottom of the rectification tower, the amount of extracted bottom liquid is 7% of the feedstock, which can be used to obtain fuel diesel through hydrocracking, considering that the content of carbonized particles is not significant.

In this way, according to the provided examples, the method of the present invention not only increases the production of light gas oil, but also the total yield of heavy gas oil (heavy coker gas oil and bottom liquid) rises to 30.4% (in the prototype implementation In the example, the yield of heavy gas oil is 28.2%), and the quality is guaranteed.

Embodiment 3 (method proposed according to the present invention)

Under this example, the aim is to increase the yield of heavy gas oil relative to Example 2, wherein the quality of this heavy gas oil can be used as a feedstock for hydrocracking.

To achieve this purpose, similar to Example 2, coking the raw material, but reducing the amount of heavy gas oil entering the mass exchange device at the bottom of the rectification tower as reflux to 5% volume content, and supplying the mass exchange device at the top of the rectification tower The amount of light gas oil is the same as in Example 2.

The coking results are shown in Table 2.

It can be seen from Example 3 that, compared with Example 2, the reduction in the amount of the lower reflux medium (i.e., the reflux medium supplied to the first mass exchange device at the bottom of the rectification column) results in the supplied heavy coking gas being formed from the fraction in Weight gain due to low concentration of the high boiling fraction in the coking distillate: if 10% of the lower reflux medium is supplied, the fraction boiling above 500°C is 10% by volume in the fraction; 5% of the lower reflux is supplied Medium, the content of the fraction with a boiling point higher than 500°C in the fraction is increased to 14% by volume. Meanwhile, according to Example 3, when the amount of the upper reflux medium supplied remains unchanged, the content of heavy gas oil in the fraction with a boiling point as high as 350°C Reduced by 20% to 16%, thereby increasing the yield of heavy coking gas. At the same time, the weight of the liquid at the bottom of the tower increases and the output decreases. The high carbon content (0.12%) in the bottom liquid does not allow its use as a feedstock for the hydrocatalytic process due to possible deactivation of the catalyst. That's why it can be used as a fuel component, or initially blended with heavy coker oil as a cracking feedstock, separated from the side of the rectification column to reduce the concentration of carbon.

Embodiment 4 (according to the method proposed by the present invention)

The purpose is to increase the yield of light gas oil relative to Example 2 while maintaining the quality of heavy gas oil as the raw material for hydrocracking. Coking was carried out in a similar manner to Example 2 using the same feedstock in Examples 1-3. The amount of heavy gas oil added as the reflux medium of the mass exchange unit at the bottom of the rectification column was the same as in Example 2, but the amount of top reflux medium (light gas oil) was 15%.

The coking results are shown in Table 2.

From Table 2, we can see that the yield of light gas oil can be increased by 1.6% (relative to the raw material) by reducing the amount of the top reflux medium, and its weight, density and final distillation point can be improved. At the same time, the yield of heavy gas oil decreased, and naturally, its quality changed: density from 0.9517 g/cm3 to 0.9541 g/cm3, coking property increased from 0.31 to 0.49, fraction content with a boiling point up to 350 ° C from 20% Reduced to 9% (volume content).

In this way, there are two refluxes from Table 2: heavy gas oil at the bottom of the rectifier and light gas oil at the top of the rectifier, adjusted based on the production needs of the yield and quality of the extraction separation from the rectifier . Therefore, when it is necessary to increase the output of heavy coker gas oil, for example, as a raw material for catalytic cracking, while reducing the generation of bottom liquid as fuel, it is necessary to reduce the amount of heavy gas oil bottom reflux medium (Example 2 and 3). Simultaneously, the amount of the heavy gas oil and the bottom liquid extracted from the separation and extraction of the rectification tower changes: the density and coking of the heavy gas oil increase within the limit range satisfying the catalytic cracking feedstock, and the composition of this part becomes heavier (the boiling temperature of the fraction is higher than 500 ℃), the density and coking of the bottom liquid also increase, and its fraction becomes heavier.

On the other hand, when it is necessary to increase the yield of light coker gas oil for the production of diesel oil and reduce the content of fractions with boiling points up to 350°C in heavy coker gas oil (i.e. diesel fraction), it is necessary to reduce the amount of the top reflux medium (Example 2 and 4). The yield of light coker gas oil increased from 29.9% to 31.4%, density also increased, fraction composition, and fraction content boiling up to 350°C in heavy gas oil decreased from 20% to 9%.

In the process of the present invention, compared to the prototype process, the process of the present invention can extend the time required to achieve a resid delayed coker overhaul due to the use of heavy coking gas as recycle and from the bottom of the rectification column. Extraction of the separated bottom liquor, containing coke particles, as a commercial product precludes bottom liquor participation in the coking process and prevents coke particles from entering the mass exchange tray of the evaporator and carburizing in the reactor.

In addition, the delayed coking method disclosed in the present invention can obtain two kinds of heavy coking gas oils, the difference of these two kinds of oils lies in the physical and chemical properties and the specific application fields: the heavy coking gas oil extracted from the side of the rectification tower can be obtained by adding Hydrocracking or refining, followed by catalytic cracking to obtain motor fuel; bottom liquid, based on its quality, can be used as feedstock for hydrocatalytic processes or as a component of boiler fuel.

In addition, the total yield of heavy coking gas oil in the method proposed by the present invention is higher than that of the prototype technical solution. This is because the bottom liquid of the technical scheme of the prototype method is mixed with raw materials in coking to form additional coke, gas and gasoline, while the bottom liquid extracted from the device is extracted as a finished product in the method proposed by the present invention.

In addition, the method disclosed in the present invention enables adjustment of the obtained light gas oil, heavy gas oil and bottoms liquid quantities independently of the recirculation rate, whereas in the prototype method when the mass supplied to the bottom of the rectification column When the amount of cooling oil in the exchange device changes, the recirculation rate also changes.

Table 1: Feedstock characteristics for coking (West-Siberian and Arlansk oil mixtures)

Claims (3)

1. the delayed coking method of Residual oil, comprise the raw material of heating for coking, be delivered to the secondary raw material that vaporizer and recycled matter are mixed to form coking, heating secondary raw material is delivered to coking chamber, from coking chamber, coking product is delivered to rectifying tower fractionation and obtains gas, gasoline, light coker gas oil, heavy coker gas oil and end liquid, cooling heavy gas oil is transported to the mass exchange unit of rectifying tower bottom, it is characterized in that, cooling light gas oil is transported to the gas exchange device of rectifier.

2. according to claim 1 ground method, it is characterized in that the light gas oil of the variation of the cooling light gas oil being loosened and the amount of heavy gas oil based on obtained and quality and the quantity of heavy gas oil and end liquid.

3. method according to claim 1 and 2, is characterized in that, heavy coker gas oil is as recycled matter.

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