RU2448145C1 - Method for slow coking - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: starting material is heated in a heat exchanger 1 to 230-270°C and then to 350-430°C in a furnace 2. The hot material is fed into the bottom part of an evaporator 3 and mixed with a recirculator - heavy coker gasoil to form secondary material which is heated to reaction temperature 460-510°C in a heating-reaction furnace 5, followed by coking in one of the alternately working coking chambers 6. The formed distilled products from chambers 6 are fed for fractionation into the bottom part of a fractionation column 4 to obtain gas, gasoline, light gasoil, heavy gasoil and still residue which is fed for mixing with hot secondary material before being fed into the coking chamber 6. The quality and amount of the still residue and heavy coker gasoil is regulated by varying the temperature at the first tray in the bottom part of the fractionation column 4 by feeding heavy coker gasoil as circulating reflux.

EFFECT: longer time between repairs on the equipment and output of distilled products for producing engine fuel.

1 dwg, 3 tbl

Description

The invention relates to the field of oil refining, in particular to the production of petroleum coke by delayed coking.

There is a method of delayed coking, in accordance with which the source (primary) raw material is heated in a furnace and fed to the lower part of the distillation column, where it is in contact with the coking products coming in the vapor phase from the coking chambers. As a result of the contact of liquid raw materials with vapors, part of the highest boiling fractions of coking products condenses, forming recycle, which is mixed with primary raw materials to form secondary raw materials, which, after heating in the furnace, are fed into one of the coke ovens alternately working. In order to control the value of the recirculation coefficient, the primary raw material can be fed into the distillation column through several inlets. If the primary raw material is fed through the upper input, the maximum recycling coefficient. If the primary raw material is fed through the lower input, i.e. below the input of the vapor of the reaction products from the coke oven chambers, the recirculation coefficient is minimal. Another option for regulating the recirculation coefficient by this technology is to organize the supply of heavy gas oil to the first sieve plate in the lower part of the distillation column [Valyavin GG, Yezhov BM, Salyakhov OM Operating experience of technological equipment and measures to increase the time between overhaul runs of delayed coking plants. Thematic review. M., TSNIITE Neftekhim, 1979, p.30-33].

The disadvantage of this technology is the high recirculation coefficient, which causes high energy costs for heating, cooling and pumping a large number of recycle fractions, which slightly affect the coking process. In addition, a high recirculation coefficient reduces the productivity of the plant for fresh (primary) raw materials. And, most importantly, in the vapors of the reaction products coming from the coke oven chambers to the distillation column, coke particles can be contained, which, falling into the reaction furnace with secondary raw materials, cause erosion wear of the chimneys, their coking, and, as a consequence, low turnaround mileage of the installation.

Closest to the claimed object is a method of producing petroleum coke by delayed coking, including heating the feedstock to 300-350 ° C, separating it into light fractions and a heavy residue in an evaporator equipped with contact devices, fractionation of light fractions in a distillation column together with distillation coking products , feeding the bottom residue obtained in the distillation column as a recirculate to the evaporator for mixing with the heavy residue to form secondary raw materials, coke the preheated secondary raw materials obtained in the evaporator with the formation of coke in the coking chambers and distillate products fed to the distillation column. The quantity and quality of the bottom residue involved as recirculate in the feedstock is controlled by the dosed supply of cooling gas oil to the mass transfer devices in the lower part of the distillation column (Pat. RF No. 2209826, class СВВ 55/00, published on 08/10/2003).

The disadvantage of this method is the low yield of distillates, the receipt of which is the main goal of the process of delayed coking, which are used as components of motor fuels.

In addition, this method determines the low turnaround time of the delayed coking unit due to the fact that the use of the bottom residue of a distillation column containing coke particles taken from the coking chambers together with distillate coking products as a recirculate causes erosion wear and coking of the chimneys of reaction-heating furnaces .

The invention is aimed at increasing the yield of distillates with a simultaneous increase in the overhaul mileage of a delayed coking unit.

This is achieved by the fact that in the method of delayed coking, including heating the feedstock to a temperature of 250-430 ° C, feeding the heated feedstock to the evaporator for mixing with the recirculate to form secondary feedstock, heating the secondary feedstock to a reaction temperature of 460-510 ° C followed by coking in a coking chamber, fractionation of light fractions in a distillation column to produce gas, gasoline, light gas oil, heavy gas oil and bottoms, according to the invention, heated secondary cheese is fed to the coking chamber e mixed with the bottoms, the quality and quantity of the bottoms and heavy coker gas oil is controlled by changing the temperature of the first plate in the bottom of distillation column by feeding it as a pumparound heavy coker gas oil, and is used as recirculate heavy coker gas oil.

Involving the distillation column bottoms in the coking process by feeding it directly to the coking chamber and supplying heavy gas oil to the evaporator as recirculate will make it possible to increase the yield of distillates (gasoline and light gas oil) - components of motor fuels. The use of heavy coking gas oil as a recycle, in which there are no carbide particles, will reduce the coking rate of the reaction furnace, as well as reduce the erosive wear of the coils of furnaces and pumps, which will increase the turnaround time of the delayed coking unit.

The ability to control the quality and quantity of bottoms and heavy gas oil will optimize the material balance of the plant for the output of distillates.

The drawing shows a schematic diagram of an installation for implementing the proposed method of delayed coking.

The installation comprises a heat exchanger 1, a heating and reaction furnace 2, an evaporator 3 with mass transfer devices, a distillation column 4, a heating and reaction furnace 5, coking chambers 6. The proposed method is as follows.

The feedstock is heated in the heat exchanger 1 with the heat of the waste product streams to a temperature of 230-270 ° C, then in the furnace 2 to a temperature of 350-430 ° C and served in the lower part of the evaporator 3, equipped with mass transfer devices. In the upper part of the evaporator 3, a heavy coking gas oil from the distillation column 4 in a strictly standardized quantity and, as is known from the prior art, from 2 to 100% or more to the feedstock is fed as a recirculate to the first plate. Secondary raw materials - a mixture of primary raw materials with recycle - are removed from the bottom of the evaporator 3, heated in a heating and reaction furnace 5 to a temperature of 460-510 ° C and served in one of the alternating coking chambers 6 to produce coke. The resulting distillate coking products from the coking chamber 6 through a helmet tube enter the lower part of the distillation column 4 for fractionation. At the top of distillation column 4, hydrocarbon gas and coking gasoline are discharged.

From the bottom of the distillation column 4, bottoms are removed, which is either fed into the coking chambers 6 in a mixture with secondary raw materials preheated in the furnace 5, or removed as a finished product.

In the form of side straps from the distillation column 4, light and heavy coking gas oils are withdrawn. The main part of heavy gas oil is withdrawn in the form of a finished product, and part of it is fed into the slurry pipeline as a cooler to cool the coking products, prevent coking of the helmet lines and reduce the temperature of the bottom residue at the bottom of the distillation column 4. On the first plate of the lower part of the distillation column 4 as a wash liquid to maintain the temperature in the lower part of the column 4 and on the plate in order to regulate the quality of heavy coking gas oil and bottoms is organized and and chilled or hot coker heavy gas oil output from the battery 4 fractionator.

Regulation of the quality and quantity of heavy gas oil and bottoms is carried out as follows:

If it is necessary to increase the yield of heavy coking gas oil with an increase in its fractional composition at the end boiling point, the circulation irrigation feed to the first plate in the lower part of the distillation column 4 is reduced, as a result of which the temperature on the plate rises. At the same time, there is a decrease in the yield of bottom residue, discharged from below the distillation column 4, and its fractional composition becomes heavier (the content of low boiling fractions decreases in it).

On the contrary, if necessary, reduce the yield of heavy gas oil and facilitate its fractional composition according to its end boiling point, increase the supply of circulating irrigation to the first plate of the lower part of distillation column 4, as a result of which the temperature on the plate decreases. At the same time, due to a decrease in temperature on the plate, part of the low-boiling fractions condenses and is involved in the still bottom, which increases its yield and facilitates the fractional composition.

The method is illustrated by the following examples.

Example 1 (by the prototype method).

At an industrial delayed coking unit with a feedstock capacity of 1.2 million tons / year, West Siberian oil tar was coked.

The feedstock - the tar of West Siberian oil (the quality is given in Table 1) - is heated in heat exchangers to a temperature of 260 ° C, then in a furnace to a temperature of 385 ° C and fed to the lower part of the evaporator, bottoms are recycled as a recirculate on the first evaporator plate. the residue from the bottom of the distillation column in the amount of 10% of the feedstock. The secondary raw materials obtained in the evaporator (a mixture of tar and bottom residue) are heated in a furnace to a temperature of 495 ° C and sent to one of the alternately working coking chambers for the formation of coke.

The distillate coking products from the coke oven chambers are sent to a distillation column for fractionation to produce gas, gasoline, light and heavy gas oils. The material balance of coking is given in table.2. As a result of coking, 141.6 thousand tons / g of gasoline and 272.4 thousand tons / g of light coking gas oil, components of the feedstock for the production of motor fuels, were obtained. The overhaul run of the coke production plant was 180 days.

Example 2 (by the proposed method).

Analogously to example 1, the tar was subjected to coking West Siberian oil. However, in this case, heavy coking gas oil was used as recirculate, obtained in the distillation column as a side stream and fed to the evaporator on the first plate in the amount of 10% of the feedstock. And the bottom residue in an amount of 5% from the bottom of the distillation column with a temperature of 380 ° C was mixed with secondary raw materials heated in an oven to a temperature of 500 ° C and sent to the coking chamber. To ensure the amount of bottom residue of 5% distillation column removed from the bottom of the distillation column, the temperature was controlled on the first plate in the lower part of the distillation column at 380 ° С by supplying cooled heavy gas oil to it.

As a result of coking, 157.2 thousand tons / g of gasoline and 288 thousand tons / g of light gas oil were obtained. The quality of heavy gas oil and bottoms is shown in table.3. The overhaul run of the coke production plant was 340 days.

Example 3 (by the proposed method).

Analogously to example 1, the tar of West Siberian oil was coked. In this case, heavy coking gas oil was fed to the evaporator for recycling in an amount of 20% for raw materials. By supplying chilled heavy coking gas oil to the first plate at the bottom of the distillation column as a circulating irrigation, the temperature on the plate was reduced to 365 ° C. As a result, the yield of bottoms residue increased to 10% for raw materials, which were mixed with secondary raw materials with a temperature of 365 ° C and sent for coking in chambers.

As a result of coking, 168 thousand tons / g of gasoline and 298.8 thousand tons / g of light gas oil were obtained. The quality of heavy coking gas oil and bottoms is shown in Table 3. The overhaul run of the coke production plant was 340 days.

Thus, the implementation of this technology for the production of petroleum coke by delayed coking will allow eliminating the probability of coke particles present in the distillate from coke oven chambers entering reactive heating furnaces by supplying bottoms directly to the coking chambers and, as a result, to prevent erosion of chimneys and their premature coking and, thereby, increase the turnaround mileage of the installation.

The supply of bottom residue for coking mixed with secondary raw materials will increase the yield of coking distillates by ~ 50 thousand tons / year.

Arranging the supply of heavy gas oil from the distillation column battery to the first plate at the bottom of the distillation column as circulation irrigation by changing the temperature on it will simultaneously control both the quality and quantity of both heavy coking gas oil and bottoms.

The ability to control the quantity and quality of the bottom residue, if its quality characteristics are met by the regulatory requirements, will make it possible to additionally obtain distillate fractions as raw materials for catalytic cracking or hydrocracking units.

Table 1
Quality of coking feedstock (tar of West Siberian oil) Indicators The value of indicators 1. Density, ρ ₄ ²⁰ 0.9880 2. Coking ability, wt.% 15.9 3. The kinematic viscosity, cSt at 80 ° C 2164 100 ° C 633 4. Content of elements - S _total, wt.% 2,33 - V, ppm 140 - Ni, ppm 23 ITK overclocking No. Fraction, ° С The density of narrow fractions ρ ₄ ²⁰ The content of fractions, wt.% one 360-380 0.9200 0.27 2 380-400 0.9243 0.27 3 400-420 0.9343 0.24 four 420-440 0.9432 0.24 5 440-460 0.9514 0.54 6 460-480 0.9601 1.39 7 480-500 0.9721 4.18 8 > 500 1,0027 92.88 Total 100.00

table 2
Material balance of coking Name Product yield According to the prototype Example 1 According to the proposed method Example 2 Example 3 wt.% thousand t / g wt.% thousand t / g wt.% thousand t / g Taken: raw 100.0 1200 10.0 1200 100.0 1200 Received: 1. hydrocarbon gas 8.2 98.4 8.5 102 8.9 106.8 2. gasoline (fr.nk-180 ° С) 11.8 141.6 13.1 157.2 14.0 168 3. light gas oil (fr. 180-350 ° С) 22.7 272.4 24.0 288 24.9 298 4. heavy gas oil (fr.> 350 ° C) 29.5 354 26,4 316.8 23.9 286.8 5. coke 27.8 333.6 28.0 336 28.3 339.6 Total 100.0 1200 100.0 1200 100.0 1200 Duration of installation overhaul, days 180 340 340 Recycle VAT residue heavy gas oil heavy gas oil The amount of recycle,% of raw materials 10 10 twenty The amount of VAT residue for coking,% of raw materials 10 5 10 The temperature on the first plate of the bottom of the distillation column, ° C 380 380 365

Table 3
Quality of distillation column heavy products The name of indicators Prototype method The proposed method Example 1 Example 2 Example 3 heavy vat heavy vat heavy vat gas oil balance gas oil balance gas oil balance Density ρ ₄ ²⁰ 0.9528 0.9832 0.9438 0,9973 0.9382 0.9789 Coking ability, wt.% 0.85 5,0 0.57 6.3 0.32 4.1 The content of carbides, wt.% - 1.4 - 1.9 - 0.4 Fractional composition: yield of fractions, wt.% NK-300 ° C 4.1 1,6 5.5 2.0 7.3 4.6 300-400 ° C 40.7 15.1 44.7 19.0 50,4 35.1 400-500 ° C 53.6 64.3 49.2 55.0 42.3 50.3 Above 500 ° C 1,6 19.0 0.6 24 - 10.0

Claims (1)

The method of delayed coking, including heating the feedstock to a temperature of 250-430 ° C, supplying heated feedstock to the evaporator for mixing with the recirculate to form secondary feedstock, heating the secondary feedstock to a temperature of 460-510 ° C followed by coking in the coking chamber, fractionation of the lungs fractions in a distillation column to produce gas, gasoline, light gas oil, heavy gas oil and bottoms, characterized in that before being fed into the coking chamber, the heated secondary raw materials are mixed with bottoms, The quality and quantity of the bottom residue and heavy coking gas oil are controlled by changing the temperature on the first plate at the bottom of the distillation column by supplying heavy coking gas oil as circulating irrigation, and using heavy coking gas oil as a recirculate.