RU2058366C1 - Method for production of petroleum coke - Google Patents

Abstract

FIELD: petroleum refining and petrochemical industries. SUBSTANCE: method for production of petroleum coke includes heating of initial stock, its supply to lower part of the main rectifying tower; production of secondary stock by mixing reaction products with initial stock in the lower part of tower; separation of remaining reaction products; heating of the secondary stock up to coking temperature and its supply to the preliminarily heated reactor; coking and filling of reactor with coke; steaming, cooling and unloading of produced coke. Reaction products discharged from the reactor in carrying out the stages of reactor heating and steaming of obtained coke and withdrawal to separate tower and separated into liquid and vapor phases. Vapor phase is supplied for separation into the main rectifying tower. Liquid phase is withdrawn from the system. EFFECT: higher efficiency. 1 dwg, 1 tbl

Description

 The invention relates to methods for producing petroleum coke and can be used in the oil refining, petrochemical industry.

 Known methods for producing petroleum coke, of which the most common and industrially developed is the process of delayed coking.

In the method [1], preheated oil residues can withstand 3-30 minutes with the separation of light fractions, boiling up to 400 ^about C. This technique allows you to increase the coking ability of the feedstock, which leads to an increase in plant performance. However, the increased coking ability and aging of petroleum feedstock increase the coking of equipment, the contamination of products, especially liquid ones, with coke breeze, and increase the downtime for cleaning the coils from carbon deposits.

To improve the quality of coke produced in the known method the mixture is subjected to delayed coking of petroleum distillate cracking residue and solvent-refined oil extract fraction boiling above 420 ^C. Coke improved structures obtained from a mixture of petroleum residues and aromatic coal tar.

A known method of continuous coking [2] in which to obtain high-quality coke using a mixture of distillate cracked residue and a fraction of thermal cracking, boiling above 400-420 ^about With that allows you to increase the yield of coke by 2 wt. (12.5% versus 10.5% without the addition of thermocracking fraction).

 To improve the quality of the target coke in the known method, delayed coking of flavored raw materials is carried out in a stream of nitrogen, which is fed into the drum over the past 8 hours. However, the yield of coke is significantly reduced (26.6% versus 57.5% without nitrogen).

A known method of producing petroleum coke [3] by thermal cracking of a wide variety of feedstock (decanted oil, thermal resin, pyrolysis ethylene resin, coal tar). The process involves several steps, including pre-processing of the raw material (temperature 230-315 ^{° C,} during 5-120 min). To reduce coke formation in furnaces during preliminary heating, 50-100 ppm of sulfur is introduced into the raw materials. The method is associated with the complexity of operational operations, multi-stage.

 Known methods have one common drawback: technological issues cannot be resolved to improve the operation of the apparatus, their minimal coking at the stages preceding the formation of the “target” coke, and the preservation of a sufficiently long run between stops to clean up “unwanted” coke deposited on the walls of equipment, apparatus, coils stoves.

One of the known solutions aimed at improving the operation of delayed coking plants is the method [4] in which the primary raw material is not fed to the distillation column for mixing with the raw material, but enters the separator column, where the associates present in the raw material are separated. However, when the process is designed without recirculation of heavy gas oil fractions, the quality and structure of the target coke deteriorate, since the raw materials are depleted in secondary flavored fractions, which are most desirable when producing petroleum coke. Furthermore, in the process of heat transfer conditions deteriorate, as the heating source (primary) heavy oil feedstock greatly simplified if it is fed to the distillation column and mix with the reaction products output from the reaction zone at a temperature ^of 420-500 C; the distillation of light fractions from raw materials is complicated, and their increased content in primary raw materials leads to an increase in the porosity of the target coke and a decrease in its mechanical strength. During partial recirculation and supply of the lower product to the separator column according to the method [4], the secondary raw material entering the reaction coils of the furnaces and then coking into the chambers contains a significant amount of mechanical impurities, which causes the equipment to jiggle, especially intense when coke particles get from the coking reactor at the stages of its steaming and heating with reaction products.

The closest in technical essence and the achieved effect to the invention is a method for producing petroleum coke by delayed coking of heavy petroleum feed, which is the simplest and most industrially mastered [5]
This method is as follows.

 Preheated raw materials (primary raw materials) enter the lower part of the distillation column, where they are mixed with products removed from the reactor at all stages of its operation, including heating, filling with coke and subsequent poultice. Due to the contact of the primary raw material with the reaction products, the light fractions are distilled off, enriched with recycled fractions and the accumulation of coke-forming components. A mixture of the feedstock (primary) feedstock with recycle (secondary feedstock) from the bottom of the distillation column is fed to a heating furnace and then to one of the reactors for the coking process and the isolation of reaction products.

 Reactors for coking, which receives the secondary raw materials, work alternately as follows. Heated raw materials are first supplied from the bottom to one of the reactors using a distributor. The process of delayed coking is continuous in the supply of raw materials, the withdrawal of gaseous and liquid products and periodic in the unloading of coke from the reactor. Gaseous and liquid products are removed from the top of the reactor and sent to a distillation column for separation into gas, gasoline fractions, gas oil and to obtain secondary raw materials. After filling the reactor with coke, it is disconnected from the feed stream, which is switched to the next prepared reactor, continuing the coking process in it in a similar way. The first reactor filled with coke is steamed to recover distillate oil fractions from coke. During steaming, along with the distillate fractions, a partial removal of fines from coke occurs, which, together with liquid products and steam, is carried out into the distillation column. This is an undesirable phenomenon, since coke breeze then enters with the secondary raw materials into pipelines, furnace coils and helps accelerate the coking of equipment and reduce overhaul runs. In addition, particles of coke pollute liquid products, such as gas oil, which is removed from the installation in the form of associated target products, increasing the content of mechanical impurities in it. Therefore, further use of the gas oil fraction is possible only after removal of mechanical impurities from it.

 After the steaming step, the coke is cooled with water and discharged, and the reactor is prepared for operation for a new coking cycle. The main stage of preparation of the reactor is its heating, which is carried out first by water vapor, and then by the vapor of the reaction products from the working reactor. At this stage, as well as during steaming, solid coke particles remaining on the walls of the reactor enter the column. To eliminate this, a mesh filter is installed at the outlet of the reactor. However, small dusty particles are not retained by the grid and are introduced into the column with all the undesirable consequences described above. With a decrease in the size of the through-holes, the resistance sharply increases, the pressure in the reactor increases, and the filter quickly fails. In this regard, the maintenance of the installation is complicated, the costs of its operation are increased, the downtime of the installation increases, the productivity decreases, the work becomes unstable, which generally reduces the efficiency of the process of producing petroleum coke by delayed coking.

 The aim of the invention is to increase the operational efficiency of a delayed coking unit, increase turnaround times, improve the quality of coking raw materials by reducing the mechanical impurities in it and making the fractional composition heavier.

 This goal is achieved in that the reaction products discharged from the reactor during the stages of heating the reactor and steaming the obtained coke are separated from the general stream and taken into a separate column, where they are subjected to separation into liquid and vapor phases, and the vapor phase is fed to separation in the main distillation the column, and the liquid phase is removed from the system.

 Distinctive features of the invention is that the products removed from the reactor during the stages of heating the reactor and steaming the obtained coke are taken into a separate column and subjected to separation into a liquid and vapor phases, the vapor phase being fed to the separation in the main distillation column, and the liquid phase output from the system.

 Such techniques can eliminate the ingress of mechanical impurities down the column with the reaction stream and their accumulation in secondary raw materials. As a result, the causes of coking of the bottom of the distillation column, hot feed pumps, furnace coils are eliminated.

 Distinctive features of the proposed method are significant and the use of new technical solutions represented by these signs was not previously known. The unexpected effect revealed in the invention was manifested in a sharp increase in the duration of the overhaul (continuous) operation of the installation, increasing the stability of its operation, reducing the content of mechanical impurities and making secondary coking raw materials heavier.

PRI me R 1. (see drawing). The feedstock (Feed I) tar (the residue of vacuum distillation of the mixture and the West Siberian petroleum Volga) with a density of 0.983 g / cm ³ at ²⁰ ° C, Conradson carbon residue of 10.2 wt. kinematic viscosity at ¹⁰⁰ ° C 202 mm ² / s is heated in a convection portion of the furnace 1 to a temperature of 380-400 ^{° C} and fed down the distillation column 2 for mixing with the reaction products (stream II), output from the reactor 3 in the coking stage, ie. e. filling the reactor with coke. The reaction products in the column are separated into gas (stream III), gasoline (stream IU), gas oil (stream Y) and recycle fractions directly mixed with the feedstock in column 2. The resulting "secondary" coking feed (stream UI) has a content mechanical impurities 0.02 wt. The beginning of the boiling of secondary raw materials is 290 ^о С, up to 400 ^о С boils 18,0 vol. This raw material enters the reaction part of furnace 1, in which it is heated to a temperature of 495-500 ^о С, and then it is fed to coking in the reactor 3 ^I through the flow distributor of the four-way valve 4. After filling the reactor 3 ^{I with} coke, it is turned off and the stream of secondary raw materials The UI begins to be fed through the distributor 4 to the second reactor 3 ^II , where coking and filling of the second reactor with coke proceeds. In the first reactor 3 ^I , a steaming step for the obtained coke is started. The distillate fractions stripped from coke (stream UII) are removed from the first reactor 3 ^I separately from the reaction products (stream II) discharged from reactor 3 ^II , in which the coking stage is carried out and filled with coke. The isolated products (stream UII) are subjected to separation into liquid and vapor phases in a separate separator column 5, the vapor phase (CS stream) being fed to distillation column 2 for separation without mixing with the original tar (stream I), and the liquid phase (stream IX ) output from the bottom of the column 5 from the installation.

After the coke steaming stage in the first reactor 3 ^I, it is cooled and discharged, and the reactor 3 ^{I is} subjected to a heating step, first supplying water vapor (bp) and then part of the reaction products (stream X) from the second reactor 3 ^II . The stream leaving the first reactor at the heating stage (stream UII) is not mixed with the main product stream of the second reactor (stream II), but separately fed to the same column 5, in which the products of the coke steaming stage were separated, and subjected to separation as described for this stage. The duration of the coke storage stage is 24 hours. The same time is necessary for preparing the reactor for the next cycle of operation, namely for the stage of steaming, cooling, unloading coke, and heating the reactor. Therefore, after the preparation of the first reactor, as described above, the stream of secondary raw materials is switched back to the first reactor, starting the coking and coke accumulation stages in it, and the second reactor is turned off for preparatory operations.

 The overhaul mileage of the installation is 140 days of continuous operation.

EXAMPLE Example 2 The process is carried out according to Example 1 but as starting materials coker distillate used cracked residue from a mixture of oils as in Example 1. Density of cracking residue of 1.028 g / cm ³ at ²⁰ ° C, coking 11 5 wt. kinematic viscosity at 100 ^о С 20.5 mm ² / s, correlation index 108 c.u.

There are no mechanical impurities in the secondary raw materials obtained without feeding to the mixture products removed from the reactor during the stages of heating the reactor and steaming the resulting coke, which are separated from the main stream (less than 0.005 wt.). The beginning of the boiling of secondary raw materials 300 ^о С, up to 400 ^о С boils 16,0 vol. The duration of the installation between repairs is 180 days.

 PRI me R 3. The process is carried out according to the known method [5] As a raw material using tar as in example 1. The indicators are shown in the table.

As can be seen from the table, the proposed method allows, in comparison with the known:
1. To reduce the content of mechanical impurities in the coking feed from no to 0.02 wt. due to the exclusion of coke particles discharged from the reactor at the stages of heating and steaming of coke.

2. weighing secondary raw materials and to reduce the content of light fractions boiling up to 400 ^{° C} at 7-9% by feeding the vapor phase from separator column to a distillation column without mixing with the feedstock.

 3. To increase the duration of the installation between repairs by 1.5-2 times by reducing the downtime for repairs to clean equipment from unwanted carbon deposits (furnace coils, bottom of the distillation column, raw materials pumps, pipelines).

 4. Stabilize the operation of the installation and facilitate its maintenance.

 Thus, in general, the efficiency of delayed coking plants is significantly increased, and technical and economic indicators are improving.

Claims (1)

 METHOD FOR PRODUCING OIL COKE by delayed coking, including heating the feedstock, feeding it to the bottom of the main distillation column, obtaining secondary feedstock by mixing the reaction products with the feedstock at the bottom of the column, separating the remaining reaction products, heating the secondary feedstock to the coking temperature, feeding it to previously preheated reactor, coking and filling the reactor with coke, steaming, cooling and unloading the obtained coke, characterized in that the reaction products removed from the reactor When carrying out the stages of its heating and steaming of the obtained coke, the ora are taken into a separate column and subjected to separation into a liquid and vapor phases, the vapor phase being fed to the separation into the main distillation column, and the liquid phase is removed from the system.

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