Furnaces section of hydrocarbon feedstock pyrolysis plant

Abstract

The invention is directed to chemical processing of light paraffins. The furnace unit of the hydrocarbon feedstock pyrolysis plant comprises a unified frame of the furnaces group of the pyrolysis plant, having a 3D-arched shape, indirect quenching exchangers, secured on the back end wall of the pyrolysis plant with an inlet nozzle opposite to the pyrolysis plant furnace outlet of the last reaction tube of pyrolysis coil, and the inner loop of the frame of pyrolysis unit furnaces group which is the same distance away from the casing of the pyrogas direct oil quenching column. Each furnace is individually connected with the pyrogas direct oil quenching column using its own transfer line. The circulating oil flow is supplied separately into each transfer line. The pyrogas and circulation oil are supplied into each transfer line by an injector device. An increase in the output of the pyrolysis plant for the processed raw materials along with an increase in the yield of target olefins to optimal parameters, optimal performance of each furnaces section of hydrocarbon feedstock pyrolysis plant and the furnace unit in whole, are provided.

Description

[0001] FURNACES SECTION OF HYDROCARBON FEEDSTOCK

[0002] PYROLYSIS PLANT

[0003] TECHNICAL FIELD OF THE INVENTION

[0004] The furnaces section of hydrocarbon feedstock pyrolysis plant is intended for chemical conversion of light paraffins into olefines and may be used in petrochemical and gas-chemical industries.

[0005] Pyrolysis of gaseous and light liquid paraffins provides thermal splitting and dehydrogenation of paraffins with the purpose of producing various olefines (ethylene, propylene, butene, etc.) which are the basic feedstock for the developing petrochemical and gas-chemical industries. Streamlined organic synthesis of basic olefines produces polymers, rubber, alcohols, organic acids, and a wide range of other products.

[0006] Any hydrocarbon pyrolysis plant includes two zones: the feedstock conversion zone and the reaction products splitting zone.

[0007] The reaction products splitting zone is based on mass transfer processes realized mainly in rectification columns with associated heat exchanger and pumping equipment. In line with the tendency for increasing the output of the refining and petrochemical processes, the equipment at the facilities under construction is constantly being expanded into larger units, while the process flow and the equipment quantity barely changes. For instance, the ethylene output of pyrolysis plants has grown from 60 to 450 KTPA. Process conditions of the equipment operation is determined by composition of the reaction mixture fed from the chemical conversion zone.

[0008] However, the case is different with the equipment in the feedstock conversion zone of the tube furnace of a pyrolysis plant. Pyrolysis takes place in the tube coil of the pyrolysis plant furnace, with first heating the feedstock mixed with water steam to 600-650 °C, then evaporating (if necessary), and then additional heating of the steam and gas mixture and completing the chemical process at 840-870 °C. Specific features of the pyrolysis process include high temperature and low pressure that provide for subsequent transfer of reaction products throughout other equipment. In order to reduce the partial pressure of hydrocarbons, which drops below 0.1 MPa, large quantities of water steam are introduced to the hydrocarbon flow. Due to the combination of high temperature and low pressure, the output of pyrolysis plants has barely changed over the last 15 years, remaining at 10-15 TPH of converted feedstock. Any potential increase of the output is inhibited by the fact that greater feedstock amount will require a longer coil, which results in unacceptable pressure increase in the pyrolysis coil. In view of the above, modernization applies mainly to the design of coil, furnace heat input systems, and the produced pyrogas quenching systems at the furnace outlet in order to cause an abrupt decrease of temperature of pyrogas (and, consequently, the speed of reactions in the pyrogas, primarily the polymerization reactions) of the produced olefines that results in lower output of the target products.

[0009] BACKGROUND

[0010] There is a process fluid heater that has a radiation chamber with multiple double-pass tube sections, which have at least one inlet branch, enabling the fluid flow and connected with at least one outlet branch, and a bent tubular element, which connects the inlet branch with the outlet branch and enables the fluid flow between the inlet branch and the outlet branch; where every tube section has inner fins, a device for process fluid feeding into the inlet branch, a device for infrared radiation treatment of the outside surface of the double-pass tube sections for their heating, an outlet device for cooling and accumulation of process fluid coming from the outlet branch (invention patent RU 2211854, IPC C10G 9 / 20, F28D 7 / 06, filed on June 9, 1998, published on September 10, 2003). Deficiencies of this invention are as follows:

[0011] • multiple tube sections installed in the same radiation chamber, in particular those four shown in the description, complicates the maintenance of process conditions in terms of heat supply, as it is practically impossible to provide the same flows of feedstock and water steam in all the sections and of fuel in all the burners of the same chamber, while any deviation of these parameters from the required value will result in a change of the necessary pyrogas residence time in the reaction zones of the sections and in a decrease of the reaction target products (olefines) output, since the formation of olefines during the reaction time (0.2 s to 0.6-0.8 s) changes from zero to its maximum value of 28-35 % and then starts to decrease due to intensification of secondary reactions of polymerization of the produced olefines;

[0012] • the inner fins of the radiation chamber significantly increase the cost of the pyrolysis plant furnace as a whole, while it is problematic to fabricate shaped fins in contact with adjacent fins: they are usually made by internal spiral cutting of grooves with a 1.6—50 mm pitch, the height of fins being only about 0.4 mm; moreover, the doubled heat emission caused by finning is accompanied by a five times greater pressure loss when the stream flows inside the tube (Skrypnik A. N. Gidravlicheskoye soprotivleniye i teplootdacha trub c vnutrennim spiralnym orebreniyem pri odnofaznom techeniyi teplonositelya: diss. k. t. n. [Flow friction and heat emission of tubes with inner spiral fins with single-phase flow of heat carrier: dissertation of Candidate of Sciences] 01.04.14 -Kazan, 2020. - 196 p.), the pressure drop increase causes an increase of absolute pressure in the coil in the reaction zone of the section, which will reduce the output of olefines and accelerate the secondary reactions according to Le Chatelier’s principle;

[0013] • the inner fins of the radiation chamber in the radiation chamber cause coking in fin grooves (4 mm) during pyrolysis of hydrocarbons due to a decreased flow speed in the grooves and a lower heat emission factor.

[0014] There is a method of alkane pyrolysis that includes feeding a flow of gaseous C2-C4 alkanes into the pyrolysis tube, external heating of the tube with heating of the alkane flow by the tube walls, input of one or more radiation emission beams with restricted cross section in the alkane flow, with additional feeding of hydrocarbons with one or more double -C-C- linkage and / or CO2 into the reaction mixture; alkane pressure range is between 0.1 and 10 atm at laser emission power density in the reaction medium above 10 W / cm2, temperature of the reaction medium at the tube walls does not exceed 900 °C; distance between the laser emission beam boundary and the tube wall is within 0.1-10 cm; and that is implemented with a device that includes but is not limited to: heating chamber (1) with pyrolysis tube made of steel (2); laser emitter (3); optical laser emission former (4); at least one optical window for emission input with optical window isolation system; nozzles for pyrolysis feedstock input (6) and output (7); nozzle for shielding gas feeding of optical window (8); gas flows mixing orifice (9); out-of-fumace chamber of laser emission input with heat insulation (10). The pyrolysis tube has the zone of laser emission absorption by feedstock (11) (invention patent RU 2593371, IPC C10G 15 / 08, C07C 5 / 327, C07C 11 / 04, C07C 11 / 06, C07C 11 / 08, filed on August 28, 2015, published on August 10, 2016). The invention may be used only in laboratory environment due to a number of deficiencies related to its potential use in an industrial pyrolysis furnace, which are as follows:

[0015] • the required additional feeding of hydrocarbons with one or more double -C=C- linkage and / or CO2 into the feedstock entails equipment-specific complications of both the feedstock preparation and the reaction product splitting unit downstream the furnaces section of hydrocarbon feedstock pyrolysis plant;

[0016] • the laser can not provide the input of energy necessary for the pyrolysis process: with heat density of the surface of radiant tubes being 40 kW / m2at tube diameter of 0.1 m and length of 15 m, the required heat supply per tube is 188 kW / h; the laser beam with diameter of 0.1 m and specific power of 20 W / cm2 shall have the power of 157 TW; the All-Russian Scientific Research Institute of Experimental Physics has such a single research laser ISKRA-5 with power of 100 TW at pulse energy of 30000 J and pulse duration of 3* 105 fs;

[0017] • the suggested laser emission input in the reaction tube of the pyrolysis coil (2) can not be implemented on the tube endface in industrial equipment, from the technical viewpoint and, if implemented on the side face, will not provide an intensifying effect on the pyrolysis process, since the laser beam will only impact the reaction flow at right angle to the tube axis for a medium over 10 W / cm2, tube diameter of (0.1-0.2 m);

[0018] • from the structural viewpoint, an industrial pyrolysis furnace can not provide a distance between the lase emission beam boundary and the tube wall within the range of 0.1-10 cm. There is a gas-chemical ethylene and propylene production process that uses hydrocarbon feedstock in gaseous and / or liquid phase and includes the following units with feedforward and backward connections, pipelines in particular:

[0019] (1) feedstock treatment unit that provides for removal of unwanted impurities and generation of a treated feed flow and that comprises:

[0020] (a) stage of mechanical particles removal by filtration;

[0021] (b) stage of carbon dioxide and sulfur compound impurities removal by absorption and / or adsorption;

[0022] (c) stage of methanol removal by absorption and / or adsorption and / or water flushing;

[0023] (2) mixing unit that provides for combining the treated feed flow with water steam and recycled pyrolysis products recovered in thermal splitting unit (3) and recovered in gas separation unit (8) as the ethane fraction of stage (c), and / or the propane fraction of stage (g), and / or C3+ fraction of stage (c), and / or C4+ fraction of stage (f), and / or recycled C4- fraction of stage (b) of metathesis unit (9) with recovery of the pyrolysis process feedstock;

[0024] (3) thermal splitting unit that provides for alternation of the stage of pyrolysis proper of the pyrolysis feedstock in the heating coils of the reaction furnaces and the stage of steam decoking with coke particles catching by cyclones and / or water flushing with simultaneous generation of water steam at both stages, to be returned into mixing unit (2), and overheating of said steam with the heat of flue gases of the reaction furnace;

[0025] (4) primary fractionation and water flushing unit, comprising:

[0026] (a) primary fractionation stage that provides for pyrogas quenching by recycling the quenching oil with output of pyrolysis tar, tar water, and pyrolysis gasoline, using circulation and / or live reflux, and / or with generation of water steam in waste heat recovery unit;

[0027] (b) pyrogas water flushing stage with output of pyrolysis tar, tar water, and pyrolysis gasoline, using circulation and / or live reflux, and / or with generation of water steam in waste heat recovery unit; (5) compression unit that provides pyrogas compression to 3.0— 4.0 MPa in a four or five stage compressor, which is driven by high-pressure water steam supplied from thermal splitting unit (3) and / or from the outside; with separation of the water condensed during compression from pyrogas between the compressor stages in water-removing separators with a possibility of said water return to stage (b) of primary fractionation and water flushing unit (4); the hydrocarbons condensed during compression are separated from pyrogas between the compressor stages in water-removing separators and are sent to stage (f) of gas separation unit (8), to pyrolysis gasoline fractionation column, and / or to stage (c) of gas separation unit (8) in pyrogas deethanization column, and / or to stage (d) of gas separation unit to depropanization column; the pyrogas is sent to alkali purification unit (6) before the last compression stage and to dehydration unit (7) after the last compression stage;

[0028] (6) alkali purification unit that provides removal of impurities, including carbon dioxide and hydrogen sulfide, from pyrogas, and that comprises:

[0029] (a) pyrogas purification stage in one or more sections by washing the pyrogas with circulating alkali solution, using fresh alkali solution makeup and spent alkali solution removal;

[0030] (b) stage of pyrogas water flushing to remove alkali and salts, with pyrogas return to the last compression stage in compression unit (5);

[0031] (c) stage of spent alkali solution treatment before feeding it to purification facilities by preliminary oxidation of sulfides to obtain thiosulphates and / or sulphates or by neutralization of alkali using sulphuric acid, with subsequent sour gas stripping;

[0032] (7) dehydration unit that provides for water steam removal from compressed pyrogas using adsorbents to the depth that prevents hydrate formation in gas separation unit (8), with or without pyrogas pre-dehydration cooling to the temperature that is not lower than hydrate formation temperature, with subsequent adsorbent regeneration using hot dehydrated gas: methane fraction from the outside, or ethane feed fraction, or methane-hydrogen fraction that is coming from stage (a) of gas separation unit (8), or recycled ethane fraction coming from stage (e) of gas separation unit (8);

[0033] (8) gas separation unit that provides for removal of necessary components from dehydrated compressed pyrogas and that comprises the following stages:

[0034] (a) stage of demethanization of pyrogas coming from dehydration unit (7), or stage (h) of gas separation unit (8), or C2— fraction of stage (c) or (h) of gas separation unit (8), with or without simultaneous generation of hydrogen-containing gas, or demethanization of C3- fraction coming from stage (d) of gas separation unit (8) that provides for sequential cooling of pyrogas or C3- fraction with coolants or cool process streams of other stages of gas separation unit (8), isentropic expanding and cooling of pyrogas or C3- fraction in one, two, or three expansion turbines, separation, and subsequent stripping of methane-hydrogen fraction and / or hydrogencontaining gas stream in gas phase from the coolest separator, and / or rectification column zone, and / or rectification columns system, and separation of C2+ fraction fed to stage (c), (e), or (h) of gas separation unit (8), or combination of separation and hydrogenation processes in stages (a), and / or (c), and / or (d), and / or (i) of gas separation unit (8) in presence of hydrogen with relevant conversion of acetylene and diene hydrocarbons of pyrogas in a rectification column or a system of rectification columns with a catalyst integrated inside the rectification column;

[0035] (b) stage of hydrogen-containing gas treatment against hydrocarbons, and / or carbon dioxide, and / or carbon oxide, and / or nitrogen, and / or oxygen in adsorbers by varying pressure and / or varying temperature method and / or in diaphragm equipment with subsequent use of treated hydrogen-containing gas as a process agent;

[0036] (c) stage of deethanization of C2+ fraction produced at stage (a) of gas separation unit (8), or deethanization of pyrogas coming from dehydration unit (7), or deethanization of C3- fraction produced at stage (d) of gas separation unit (8) that provides for stream separation in a rectification column or a system of rectification columns into ethane-ethylene fraction, or C2— fraction and C3+ fraction, or propanepropylene fraction, or a combination of pyrogas, or C2+ fraction, or C3- fraction separation and hydrogenation processes in hydrogen presence with relevant conversion of acetylene and diene hydrocarbons of pyrogas in a rectification column or a system of rectification columns with a catalyst integrated inside the rectification column; C3+ fraction is sent for separation to stage (d) or (f) of gas separation unit (8) or as a recycled stream to mixing unit (2); propane-propylene fraction is sent to stage (g) or (h) of gas separation unit (8) or as a recycled stream in mixing unit (2);

[0037] (d) stage of depropanization of pyrogas coming from dehydration unit (7) or stage (h) of gas separation unit (8), or depropanization of C3+ fraction coming from stage (c) or (h) of gas separation unit (8) that provides for pyrogas of C3+ fraction separation in a rectification column or a system of rectification columns into propane-propylene fraction, or C3- fraction and C4+ fraction, or a combination of pyrogas or C3+ separation and hydrogenation processes in hydrogen presence with relevant conversion of acetylene and diene hydrocarbons of pyrogas or C3+ fraction in a rectification column or a system of rectification columns with a catalyst integrated inside the rectification column; C3- fraction is sent to stage (a), (c) or (h) of gas separation unit (8); propane-propylene fraction is sent to stage (g) of gas separation unit (8);

[0038] (e) stage of separation of ethane-ethylene fraction produced at stage (a), (c), or (d) of gas separation unit (8) that provides for its separation in a rectification column or a system of rectification columns into high-purity ethylene and ethane, sent by recycled stream into mixing unit (2), or a combination of ethane-ethylene fraction separation and hydrogenation processes in hydrogen presence with relevant conversion of acetylene hydrocarbons of ethane-ethylene fraction in a rectification column or a system of rectification columns with a catalyst integrated inside the rectification column;

[0039] (f) stage of separation of C3+ fraction produced at deethanization stage (c) of gas separation unit (8) that provides for its separation in a rectification column or a system of rectification columns into propane-propylene fraction and C4+ fraction, or propane-propylene and butane-butene fractions, and C5+ fraction, with flow cooling by coolants or cool streams of stage (a) and / or (c) of gas separation unit (8); propane-propylene fraction is sent to stage (g) of gas separation unit (8); C4+ fraction is removed as commercial product or sent with recycled flow into mixing unit (2); C4 fraction is removed as commercial product or sent to stage (a) of metathesis unit (9) or recycled flow into mixing unit (2); fraction C5+ is used as a gasoline component and is discharged to the outside;

[0040] (g) stage of separation of propane -propylene fraction produced at stage (c), (d) or (h) of gas separation unit (8) that provides for its separation in a rectification column or a system of rectification columns into pure propylene and propane sent with recycled flow into mixing unit (2) or removed as commercial product, or a combination of propane-propylene fraction hydrogenation and separation processes with its pre-hydrogenation in hydrogen presence, with associated conversion of methylacetylene and propadiene in gaseous or liquid phase on catalysts with subsequent separation of produced hydrogenate in a rectification column or a system of rectification columns;

[0041] (h) stage of hydrogenation of pyrogas coming from dehydration unit (7), or hydrogenation of ethane-ethylene fraction coming from stage (e) of gas separation unit (8), or hydrogenation of C2- coming from stage (c) of gas separation unit (8), or hydrogenation of propane-propylene fraction coming from stage (g) of gas separation unit (8), or hydrogenation of C3- fraction coming from stage (d) of gas separation unit (8), of hydrogenation of C4+ fraction coming from stage (f) of gas separation unit (8) that provides for conversion of acetylene and / or diene components into relevant alkene compounds in a hydrogenation reactor on a catalyst in hydrogen presence in one or several stages with intermediate cooling; then, depending on the hydrocarbon feedstock and the output products, the reaction products are sent to stage (a), (c), (d), (e), (f) or (g) of gas separation unit (8);

[0042] (i) stage of separation of C4+ fraction coming from stage (d) of gas separation unit (8) that provides for its separation in a rectification column or a system of rectification columns into butane-butene fraction and C5+ fraction with flow cooling by coolants or cool streams of stage (a) and / or (c) of gas separation unit (8); butanebutene fraction is removed as commercial product or sent to stage (a) of metathesis unit (9) or by recycled flow into mixing unit (2); fraction C5+ is removed as a gasoline component;

[0043] (9) metathesis unit comprising:

[0044] (a) metathesis stage that provides for the reaction between C4- fraction, which comes from stage (f) of gas separation unit (8) and contains 1 -butene- 1 and 2-butene, and ethylene, which comes from stage (e) of gas separation unit (8), with generation of propylene and isomerization of 1 -butene into 2-butene;

[0045] (b) stage of separation of metathesis products coming from stage (a) of metathesis unit (9) in a system of rectification columns with generation of commercial products: pure propylene, or propylene and isobutane, or propylene, isobutane and isobutene - and unreacted components of C4- fraction that return to stage (g) of gas separation unit (8) or to mixing unit (2) as recycle.

[0046] In this case all kinds of hydrocarbon feedstock are processed in unified process lines that are adapted into individual process lines for specific kind of hydrocarbon feedstock according to its pyrolitic properties by means of bypassing the non-specific units and / or stages (invention patent RU 2670433, IPC C07C 11 / 04, C07C 11 / 06, C07C 2 / 76, C07C 4 / 04, C07C 7 / 00, filed on December 29, 2017, published on October 23, 2017). This invention has a deficiency represented by the fact that with a number of unified process lines, when individual thermal splitting units (3) are preserved to ensure the specific processing conditions, the downstream equipment has not undergone any expansion, which would have helped reduce the number of equipment units and simplified the control over the gas -chemical production facility as a whole.

[0047] There is a method of pyrogas purification by quenching it in a transfer line exchanger with its subsequent direct contact with circulating quenching oil in oil quenching units; this method is characterized by the quenching oil composition including high-boiling sulfur compounds with boiling point over 180 °C at 0.1- 2.5 wt % on sulfur basis, and by using diesel fuel or gasoil with boiling point of 190- 500 °C as the quenching oil (invention patent RU 2739027, IPC C10G 9 / 00, filed on March 19, 2020, published on December 21, 2020). Deficiencies of this invention are as follows:

[0048] • quality pyrogas stripping of resins and coke particles is not guaranteed with direct contact of pyrogas with circulating quenching oil in equipment 2 without any additional devices which intensify the purification process in the equipment;

[0049] • presense of sulfur compounds in the circulating quenching oil that result in corrosion of the equipment.

[0050] There is a method of cooling and preparing for compression and gas separation of hydrocarbon feedstock pyrolysis products, including sequential cooling in transfer line exchangers, in primary fractionation column and in water flushing column with the supply of the bottom product of the primary fractionation column for pyrogas cooling by direct contact and as reflux to the middle part of the primary fractionation column and the hydrocarbon bed of the bottom product of the water flushing column as a reflux for the overhead part of the primary fractionation column, as well as by maintaining the temperature at the outlet of the primary fractionation column not higher than 100 °C, characterized by the fact that when the hydrocarbon pyrolysis feedstock is liquefied hydrocarbons or a mixture of liquefied hydrocarbons and liquid hydrocarbon feedstock, the share of which is less than 50 wt %, or a mixture of liquefied hydrocarbons with ethane fraction, the share of which is less than 60 wt %, the hydrocarbon fraction that boils off in the temperature range of 160-380 °C is added to the primary fractionation column bottom product stream, which is supplied for cooling by direct contact and in the form of reflux into the middle part of the primary fractionation column, and the hydrocarbon fraction that boils off in the temperature range of 35-190 °C is added for reflux of the overhead part of the primary fractionation column, from the compression and gas separation unit (invention patent RU 2215774, IPC C10G 9 / 00, filed on October 1, 2002, published on November 10, 2003). This invention has a deficiency of high flow friction at the pyrogas direct oil quenching stage, as downstream the transfer line exchanger the pyrogas sequentially passes through the primary fractionation column and the water flushing column; when each of these columns has only 10 bubble cap trays, the hydraulic resistance of only two columns will be 0.02 MPa, without taking into account the pressure losses in the tubes of the columns (the pyrogas pressure at the furnace outlet should approach 0.1 MPa with a minimum excess for the passage of pyrogas through the direct quenching stage), which indirectly significantly increases the pressure in the reaction coil of the pyrolysis furnace, negatively affects the chemistry of the pyrolysis process, and reduces the output of target olefins.

[0051] There is a method for step-by-step cooling and purification of pyrogas by quenching it in transfer line exchanger, followed by its cooling and purification by direct contact with circulating quenching oil in oil quenching equipment while maintaining the concentration of resins in the circulating quenching oil at the set level due to its purification in a separator, which is characterized by oil quenching stage, which is divided into two steps, and the deresination and decoking of the circulating oil by separating the contaminated oil from the gas-and-oil stream after the first oil quenching step (invention patent RU 2172763, IPC C10G 9 / 00, filed on July 21, 2000, published on August 27, 2001). Deficiencies of this invention are as follows:

[0052] • high flow friction of the pyrogas direct oil quenching stage, as the pyrogas sequentially passes through first-step quenching unit MZ-1 (a hollow unit with nozzles for oil injection), separator SM, second-step quenching unit MZ-2 (same design as MZ-1) and column K-l, which indirectly increases the pressure in the reaction coil of the pyrolysis furnace, which negatively affects the chemistry of the pyrolysis process, and reduces the output of target olefins;

[0053] • oil injection through nozzles into the pyrogas flow does not provide for high- quality deresination and decoking of pyrogas, creating a need for an additional quenching unit that increases flow friction of the direct quenching unit.

[0054] A common deficiency of all modem hydrocarbon pyrolysis plants is that, due to the low output capacity of pyrolysis furnaces dictated by the specifics of the pyrolysis process, one pyrolysis plant has several pyrolysis furnaces, installed in a row, the majority of which use low-octane gasoline as feedstock and the minority use light gaseous alkanes. For example, a pyrolysis plant considered as a prototype has 9 out of 10 pyrolysis furnaces that are tubular furnaces in parallel gasoline - processing operation, and one furnace that processes the ethane-propane fraction (Akhmetov S.A., Serikov T.P., Kuzeev I.R., Bayazitov M.I. Tekhnologiya i oborudovaniye protsessov pererabotki nefti i gaza [Technology and equipment of oil and gas processing]. - St. Petersburg: Nedra Publ., 2006. - p. 872). Many pyrolysis furnaces within a petroleum products pyrolysis plant cause its division into two sections with fundamentally different equipment configurations. The first section is the pyrolysis furnaces section with a large quantity of the same type of equipment, i. e. linearly placed pyrolysis furnaces with transfer line exchangers that form multiple pyrogas flows, which are then deresinated and decoked in a common column for direct oil quenching of pyrogas. The second section is for compressing and separating pyrogas into individual components and groups of components (ethylene, propylene, unreacted feedstock, reaction byproducts), consisting of multiple densely-placed equipment units of various kinds.

[0055] The result of the linear arrangement of pyrolysis furnaces is that the head loss in the pyrolysis gas flow moving along transfer lines from the transfer line exchangers of the pyrolysis furnaces to the pyrogas direct oil quenching column will look different for different furnaces, which makes the parameters of pyrolysis furnaces deviate from their optimal operating process values with negative end results. Any differences in pressure losses in the transfer lines of the pyrolysis furnace section can be compensated in two ways:

[0056] • by increasing the pressure of feedstock at the furnace inlet, however, this raises the pressure in the reaction zone, which reduces the output of target olefines due to the intensification of secondary reactions of olefin polymerization;

[0057] • by reducing the supply of feedstock, which leads to increased residence time of pyrogas in the reaction zone and to decreased output of target olefines.

[0058] SUMMARY OF THE INVENTION

[0059] The invention development process had the objective of developing a furnaces section of the hydrocarbon feedstock pyrolysis plant that would increase the output capacity of the pyrolysis plant on processed feedstock basis with a simultaneous increase of the output of target olefines to the optimal parameters due to design solutions of the section.

[0060] This objective is fulfilled by the furnaces section of the hydrocarbon feedstock pyrolysis plant that comprises the following stages: a) stage of pyrolysis of feedstock of various compositions, including a furnaces group of gaseous, and / or mixed, and / or liquid feedstock pyrolysis plant, with each furnace installed on the same frame for the entire stage, each of the pyrolysis plant furnaces comprising a radiant section, which includes pyrolysis coils and fuel burning nozzles, and a convection section, which includes feedstock heating coils and water steam generation coils; lines for pyrogas transfer to the pyrogas direct oil quenching column that include transfer line exchangers for indirect pyrogas quenching, pyrogas streams, circulating and fresh quenching oil supply streams, and an assembly for circulating quenching oil introduction into the pyrogas stream; b) pyrogas direct oil quenching stage that includes a pyrogas direct oil quenching column fitted with nozzles that introduce pyrogas, which is pre-mixed with circulating oil, and that are arranged on the line that transfers pyrogas from the pyrolysis stage to the pyrogas direct oil quenching column; outlet nozzles for mixed stream of liquid pyrolysis products with oil; outlet nozzles for pyrogas; pumps; characterized by the fact that the unified frame of the furnaces group of the pyrolysis plant has a 3D-arched shape; the inlet tube of the vertical radiant pyrolysis coil of each furnace of the pyrolysis plant faces the front end wall of the pyrolysis plant furnace, and the outlet tube faces the back end wall of the pyrolysis plant; the indirect quenching transfer line exchangers are secured on the back end wall of the pyrolysis plant with an inlet nozzle opposite to the pyrolysis plant furnace outlet of the last reaction tube of pyrolysis coil; the inner loop of the frame of pyrolysis unit furnaces group is the same distance away from the casing of the pyrogas direct oil quenching column; each furnace of the pyrolysis plant has a flue gas dispersion tube and is individually connected with the pyrogas direct oil quenching column using its own transfer line, which expansion joints configuration and length are the same relative to the transfer lines of other furnaces of the pyrolysis unit; and the circulating oil flow is supplied separately into each transfer line; pyrogas and circulation oil are supplied into each transfer line by an injector device where pyrogas injection at oil overpressure of 3.0-16.0 MPa reduces the pressure in pyrolysis zone of the radiant section coil by 0.01-0.05 MPa, and the pyrogas and circulating oil input nozzles are arranged along the perimeter of the pyrogas direct oil quenching column in a way that ensures the same transfer line length from all the pyrolysis plant furnaces to the pyrogas direct oil quenching column.

[0061] Such a design solution for the furnace section of pyrolysis plant makes it possible to arrange the pyrolysis plant furnaces in such a way that the movement route of the heated and chemically converted feedstock from the point of feedstock input into the pyrolysis plant furnace and then through the tube coil and the indirect quenching transfer line exchanger to the point of pyrolysis gas entry into the pyrogas direct oil quenching column is the same in length for all pyrolysis plant furnaces, which allows them to operate with optimal parameters, ensuring the production of extra olefines. In addition, injector mixing of cooled pyrogas with circulating oil makes it possible to reduce the pressure in the reaction zone and shift the position of extreme olefine output towards a shorter residence time of pyrogas in the reaction zone, and thereby increase the output capacity of the pyrolysis plant.

[0062] It is recommended to make the unified frame of the furnaces group for pyrolysis plant in the 3D-arch shape represented by a partial circle, semi-circle or quarter-circle (circle arches of 180°, 120°, 90°, and 360°), since in this case, when the pyrogas direct oil quenching column is in the center of the arch, the length of the transfer lines of all pyrolysis plant furnaces will be the same, which makes it possible to implement the same process conditions for all furnaces of the pyrolysis plant.

[0063] Whenever during reconstruction of a pyrolysis plant any outdated equipment is replaced with modernized equipment (for example), it is possible (if necessary) to depart from the dimensions that are universal for the pyrolysis plant furnaces group and / or the configuration of transfer lines and / or injectors, with consideration of the differences in technology, output capacity and designs of the pyrolysis plant furnaces operating on different feedstock types.

[0064] The pyrolysis plant furnace casings are designed to be either conventionally rectangular or trapezoidal in shape, with the back end wall of the pyrolysis plant furnace being narrower than the front end wall, which leads to a slight narrowing of the pyrolysis plant furnace casing in the reaction zone and intensification of the heat supply to pyrogas in this zone due to bringing the radiating wall of the radiant section closer to the surface of the coil tubes, since during pyrolysis of hydrocarbons there is such an intense absorption of energy spent on breaking the C-C bonds that it is even possible to reduce the pyrogas temperature, which reduces the rate of pyrolysis reactions.

[0065] It is useful to make the connection of the transfer lines with the pyrogas direct oil quenching column in sequence along the perimeter of the casing and at an angle to form a multi-point tangential input of the gas-liquid mixture flows and separation of the liquid phase from the pyrogas, forming in the casing of the pyrogas direct oil quenching column a swirling flow of gas-and-liquid mixture, which is easily separated into pyrogas and oil under the impact of the created centrifugal force.

[0066] It is practical to provide collection of flue gases from all furnaces of the pyrolysis plant, to be sent into dispersion stack and / or sent to carbon dioxide recovery from flue gases, with a single gas duct header that has the same shape as the outline arch of the pyrolysis unit furnaces group, which allows the entire furnaces section of a pyrolysis plant to have one dispersion stack, whereas usually each pyrolysis plant furnace or a pair of pyrolysis plant furnaces has its own dispersion pipe and simplifies the flue gases collection system for further extraction of carbon dioxide from them.

[0067] It is recommended to place the flue gas dispersion stack in the center of the outline arch of the pyrolysis unit furnaces group, introducing flue gases from two sides via symmetrical gas duct headers, which reduces pressure losses due to friction of flue gases in the flue stack, improves draft in the pyrolysis plant furnaces or allows to reduce the height of the dispersion stack. It is also recommended to install PETON cross-flow contactors in the direct pyrogas oil quenching column, which under otherwise equal conditions have lower flow friction compared to other contactors, which makes it possible to indirectly reduce the pressure in the reaction zone, which helps to increase the output of target olefines according to Le Chatelier’s principle.

[0068] LIST OF THE DRAWINGS

[0069] Implementation of this invention that consists in the pyrolysis plant furnaces section is illustrated by figures 1 through 5 which show the basic circuits of the pyrolysis plant furnaces section with the following part reference numbers:

[0070] 1-23 show the flows;

[0071] 101-110 show the pyrolysis plant furnace;

[0072] 111 shows the radiant section;

[0073] 112 shows the convection section;

[0074] 113, 119-124 show the flue stack;

[0075] 114 shows the indirect quenching transfer line exchanger;

[0076] 115, 125-130 show the injector device;

[0077] 116, 131-132 show the pyrogas direct oil quenching column;

[0078] 117 shows the pump;

[0079] 118 shows the cooler.

[0080] BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 shows a schematic diagram of the pyrolysis plant furnaces section with flows of feedstock and target products. Pyrolysis plant furnace 101, which is part of the pyrolysis plant furnaces section, arranged within the unified frame of the stage, receives gas, and / or mixed, and / or liquid feedstock in flow 1 which may differ in composition for different pyrolysis plant furnaces 101-110 of the pyrolysis plant furnaces section (items 102-110 are shown in Fig. 2—4). Each of pyrolysis plant furnaces 101-110 comprises a radiant part 111, including pyrolysis coils and nozzles for combustion of the fuel supplied in flow 15, and a convection part 112, including feedstock heating coils 1 and water steam generation coils (not shown in the figure). Flue gases are generated in radiant section 111 from combustion of fuel 15, pass through convection section 112 and are discharged through flue stack 113 with flow 14 for further purification and disposal. Thus, for feeding to the dispersion stack and / or for feeding to the flue gas carbon dioxide extraction unit, the flue gases come from the entire furnaces section of the pyrolysis plant, and may also be collected in a single gas duct header (not shown in the diagram), the shape of which is similar to the shape of the outline arch of the furnaces group of the pyrolysis unit. In any of the embodiments of the invention, the flue gas dispersion stack is placed in the center of the outline arch of the pyrolysis plant furnaces group, introducing flue gases from two sides via symmetrical gas duct headers. The lines of pyrogas transfer from pyrolysis plant furnace 101 to pyrogas direct oil quenching column 116 include transfer line exchangers for indirect pyrogas quenching 114, where the pyrogas is supplied with flow 2 for instantaneous water cooling, which is supplied with flow 9 circulating through the intertube space and transformed by quenching into steam, which is discharged with flow 10. The pyrogas which is partially cooled by flow 3 enters injector 115, which injects circulating quenching oil in flow 7 and fresh quenching oil in flow 8 into the pyrogas flow so that the injection of pyrogas at increased oil pressure of 3.0 to 16.0 MPa reduces the pressure in the pyrolysis zone in the radiant section coil by 0.01-0.05 MPa. The mixed and cooled pyrogas with quenching oil is supplied in flow 4 to pyrogas direct oil quenching column 116. Pyrogas direct oil quenching column 116 is equipped with inlet nozzles for pyrogas, pre -mixed with circulating oil in flow 4, located on the transfer line of pyrogas from the pyrolysis stage to pyrogas direct oil quenching column 116; the outlet nozzles for mixed liquid pyrolysis products with oil in flow 6 and the output nozzles for pyrogas in flow 5 send the products for further separation (the nozzles are not shown in the figure for simplicity). PETON cross-flow contactors are installed in pyrogas direct oil quenching column 116. Mixed liquid flow 6, consisting of liquid pyrolysis products carried away together with quenching oil, is discharged from the bottom of pyrogas direct oil quenching column 116. This flow is sent by pump 117 to cooler 118, where it is cooled by water entering in flow 11, circulating through the intertube space and leaving as steam condensate in flow 12, and returned back to the process as a flow of circulating quenching oil with flow 7. The cooled pyrogas is sent in flow 5 from the overhead of pyrogas direct oil quenching column 116 to the stage of primary fractionation and further separation of commercial products (not shown in the figure). In this case, in order to reduce the share of liquid components carried away with pyrogas flow 5 from pyrogas direct oil quenching column 116, the quenching oil is provided by the flow 13 for overhead reflux of pyrogas direct oil quenching column 116.

[0082] Figure 2 shows how the main equipment of the furnaces section of the pyrolysis plant are interconnected and shows the mixing system for circulating oil and pyrogas. Figure 2 shows the unified frame of a group of pyrolysis plant furnaces operating on fuel supplied by flow 15, designed in the form of a 3D arch and comprising seven pyrolysis plant furnaces 101-107 equipped with flue stacks 113, 119-124. The casing design of the pyrolysis plant furnaces is rectangular and / or trapezoidal in shape; the inlet tube of the vertical radiant pyrolysis coil of each furnace of the pyrolysis plant faces the front end wall of the pyrolysis plant furnace, and the outlet tube faces the back end wall of the pyrolysis plant; indirect quenching transfer line exchangers 114 are secured on the back end wall of the pyrolysis plant with an inlet nozzle opposite to the pyrolysis plant furnace outlet of the last reaction tube of pyrolysis coil (not shown in the figure). The inner outline of the frame of the group of pyrolysis plant furnaces 101-107 is the same distance away from the casing of pyrogas direct oil quenching column 116, and each pyrolysis plant furnace 101— 107 is separately connected to pyrogas direct oil quenching column 116 by its own transfer line, which length and configuration of the expansion joints are the same as those of the transfer lines of other pyrolysis plant furnaces.

[0083] Circulating oil and pyrogas are supplied from the pyrolysis furnaces separately to each transfer line by means of an injector. For each transfer line from pyrolysis unit furnaces 101-107 to pyrogas direct oil quenching column 116, respective injectors 115, 125-130 are shown, with each injector receiving circulating oil flow 7, which is mixed with fresh quenching oil in flow 8 and pyrogas from the pyrolysis furnaces. Nozzles that introduce the mixture of pyrogas and circulating oil in flows 4, 16-21, respectively, are arranged along the perimeter of the pyrogas direct quenching oil column 116 so as to provide the same length of transfer line from all the pyrolysis plant furnaces 101-107 to the pyrogas direct oil quenching column 116. In this case, the transfer lines and the pyrogas direct oil quenching column casing 116 are connected in sequence along the casing perimeter and at an angle to form a multi-point tangential inlet of gas-liquid mix streams and to separate the liquid phase from pyrogas. Liquid pyrolysis products together with quenching oil and flow 6 coming from the bottom of pyrogas direct oil quenching column 116 are fed to cooler 118 by pump 117, after which they are returned as circulating quenching oil in flow 7, also replenished with fresh quenching oil by flow 8. Part of the circulating quenching oil is also supplied by flow 13 for reflux to the overhead of the pyrogas direct oil quenching column 116. The cooled pyrogas is sent in flow 5 from the overhead of pyrogas direct oil quenching column 116 to the stage of primary fractionation and further separation of commercial products.

[0084] Figure 3 shows a fragment of the layout of the linear arrangement of pyrolysis plant furnaces used for the calculation analysis of the prototype in Example 1, comprising pyrolysis plant furnaces 101-105 and 110 within the pyrolysis plant furnaces section and arranged linearly within the unified frame of the pyrolysis plant furnaces section, and connected with pyrogas transfer lines 4, 16-19 and 24 respectively from pyrolysis plant furnaces 101-105 and 110 to pyrogas direct oil quenching column 116. Linear arrangement of the pyrolysis plant furnaces is characterized by different lengths of transfer lines from pyrolysis plant furnaces 101-105, 110 to pyrogas direct oil quenching column 116.

[0085] Figure 4 shows options of the schematic diagram of the layout of the pyrolysis plant furnaces section according to this invention in a 3D-arch shape in the form of an incomplete circle, a semi-circle or a quarter-circle (circle arches of 180° (a), 120° (b), 90° (c) and 360° (d)). Picture (a) of Figure 4 shows the unified frame of a group of pyrolysis plant furnaces with a 180° circular arch shape and comprising nine pyrolysis plant furnaces 101-109 connected by pyrogas transfer lines 4 and 16- 23 respectively from pyrolysis unit furnaces 101-109 to pyrogas direct oil quenching column 116. Picture (b) of Figure 4 shows the unified frame of a group of pyrolysis plant furnaces with a 120° circular arch shape and comprising seven pyrolysis plant furnaces 101-107 connected by pyrogas transfer lines 4 and 16-21 respectively from pyrolysis unit furnaces 101-107 to pyrogas direct oil quenching column 116. Picture (c) of Figure 4 shows the unified frame of a group of pyrolysis plant furnaces with a 90° circular arch shape and comprising five pyrolysis plant furnaces 101-105 connected by pyrogas transfer lines 4 and 16-19 respectively from pyrolysis unit furnaces 101-105 to pyrogas direct oil quenching column 116. Picture (d) of Figure 4 shows the unified frame of a group of pyrolysis plant furnaces with a 360° circular arch shape and comprising nine pyrolysis plant furnaces 101-109 connected by pyrogas transfer lines 4 and 16-23 respectively from pyrolysis unit furnaces 101- 109 to pyrogas direct oil quenching column 116. Basic layouts of the pyrolysis plant furnaces section shown in Figure 4 are not the only possible options and may include any number of pyrolysis plant furnaces.

[0086] Figure 5 shows the basic layout options of the pyrolysis furnace plant according to this invention in the form of one large-diameter circle (a) and two smalldiameter circles (b) for the calculation analysis in Examples 2 and 3. If necessary, it is possible to depart from the dimensions that are universal for the pyrolysis plant furnaces group and / or the configuration of transfer lines and / or injectors, in particular, with different layouts of the pyrolysis plant furnaces section. Picture (a) of Figure 5 shows the unified frame of a group of pyrolysis plant furnaces with the shape of a 360° large-diameter circle and comprising ten pyrolysis plant furnaces 101-110 connected by pyrogas transfer lines to pyrogas direct oil quenching column 116. Such an arrangement of the pyrolysis unit furnaces with direct oil quenching pyrogas column 116 in the center requires a large production site, as there will be a lot of empty space in the area around pyrogas direct oil quenching column 116. Picture (b) of Figure 5 shows two groups of pyrolysis plant furnaces, each having a unified 360° circle-shaped frame of smaller diameter. In this case, the first group of five pyrolysis plant furnaces 101 - 105 is connected by pyrogas transfer lines to pyrogas direct oil quenching column 131, and the second group of five pyrolysis plant furnaces 106-110 is connected by pyrogas transfer lines to pyrogas direct oil quenching column 132. Such an arrangement of pyrolysis plant furnaces allows for a more practical use of production site space and takes into account the differences in technology, output capacity and design of pyrolysis plant furnaces operating on different types of feedstock.

[0087] Example 1. A design calculation of the furnaces section for a hydrocarbon pyrolysis plant was carried out according to a prototype with linear arrangement of 10 pyrolysis plant furnaces (nine furnaces for gasoline fraction pyrolysis plant, one furnace for ethane-propane fraction pyrolysis plant) that vertical tubular furnace units. The pyrolysis plant furnace casing consists of metal structures of various profiles, ensuring the strength of the equipment, insulation, piping and fittings installed on it, and has the following overall dimensions: width: 16,110 mm, length: 11,190 mm, height: 23,600 mm. The pyrolysis plant furnaces are arranged in frontal, linear, symmetrical manner relative to the center line of the hydrocarbon pyrolysis plant footprint at a distance of 5 m from each other (Figure 3).

[0088] Output capacity of the pyrolysis plant is 20 TPH on feedstock basis. Number of tubes in the pyrolysis plant furnace coil: 54 pcs., tube length: 10 m, total coil length Lcoii-540 m. Optimal operating parameters of the pyrolysis plant furnace are as follows: ratio of water vapor to feedstock is 0.6:1, pressure and temperature of feedstock at the pyrolysis plant furnace inlet and of pyrogas at the pyrolysis plant furnace outlet are 0.4 and 0.2 MPa and 120 and 820 °C respectively, pyrogas residence time is 2 s in the heating zone and 0.6 s in the reaction zone. The total output of olefines (ethylene and propylene) is 42%. The circulating oil is injected into the pyrogas in the transfer line through a nozzle. The optimal mode of the pyrolysis plant furnace, which is the closest in the row of pyrolysis plant furnaces to the symmetry axis of the pyrolysis plant, corresponds to the 0.03 MPa head loss in the transfer line with the length Ln= 15.2 m from the indirect quenching transfer line exchanger to the pyrogas direct oil quenching column. The length of the transfer line from the second, third, fourth and fifth furnace of the pyrolysis plant relative to the axis of symmetry of the pyrolysis plant is LT2=33.0 m, LT3=52.5 m, LT4=72.0 m, LT5=92.0 m, respectively. For the operation case of the system with five pyrolysis furnaces at a pressure drop in the system of 0.23 MPa the first furnace of the pyrolysis plant, with the system length of 555.2 m and the conditional flow rate in the tubes Wi, operates in the optimal mode, while in order to maintain the hydrodynamic conditions and the olefine output of 42% in the remaining four furnaces of the pyrolysis plant it is necessary to reduce the output capacity of these four furnaces of the pyrolysis plant to the value Z in relation to the first furnace of the pyrolysis plant by reducing the flow rate in the i-th furnace Wi according to the equation:

[0089] Refer to Table 1 for summarized results of pyrolysis process calculations of the pyrolysis plant furnaces from the first one to the fifth one (furnaces 101 through 105 in figure 3) relative to the symmetry axis of the pyrolysis plant.

[0090] Calculations have shown that with optimal operation of 10 pyrolysis plant furnaces with total output capacity of 200 TPH on feedstock basis it is possible to produce 84 TPH of olefines, however, in case of linear generation structure for maintenance of optimal operating conditions of the pyrolysis plant furnaces, the plant output needs to be reduced from 200 to 193.6 TPH with reduction of olefine production to 81.3 TPH. Thus, due to the linear layout of the pyrolysis plant furnaces section, 2.7 TPH or 21,600 TPA of olefinic hydrocarbons are underproduced by the plant, i.e. the lost profit at the average cost of olefines being 40,000 rubles per ton is 864 million rubles per annum for one pyrolysis plant.

[0091] Example 2. In accordance with this invention, a design calculation is provided for the furnaces section of a hydrocarbon feedstock pyrolysis plant with non-linear arrangement of 10 pyrolysis plant furnaces similar to Example 1. Since in Example 1 the distance between pyrolysis plant furnace 101 and the pyrogas direct oil quenching column is 15.2 m, and the length of the linear set of 5 pyrolysis plant furnaces is 102 m, the option of placing 10 pyrolysis plant furnaces in two zones is considered, each of which has the shape of an incomplete circle with a diameter of 33.4 m (taking into account the placement of the pyrogas direct oil quenching column with a diameter of 3 m in the center of the circle) with a 104.8 m long arch where five pyrolysis plant furnaces are placed, with the rest of the equipment of the product separation zone placed outside the areas of pyrolysis plant furnaces section (Figure 5). Since the thermal and hydrodynamic conditions of all five columns of pyrogas direct oil quenching are the same due to the same length of transfer lines equal to 15.2 m, all five pyrolysis plant furnaces of both the first and the second zone function in their optimal mode, processing in total 200 TPH of hydrocarbon feedstock, producing 84 TPH of olefines (100% of the potential). In comparison with the prototype, this allows to produce additional 21 ,600 TPA of olefines that are prices at 864 million rubles per year for one pyrolysis plant.

[0092] Example 3. In the conditions of Example 2, instead of circulating oil input into the pyrogas in the transfer line through a nozzle, the input of circulating oil into the transfer line by means of an injector is considered, where the pyrogas is injected with oil at increased oil pressure, which makes it possible to reduce the pressure in the pyrolysis zone in the radiant section coil by 0.02 MPa, reducing the reaction time from 0.6 s to 0.5 s, and reducing the total product residence time in the furnace of the pyrolysis unit from 2.6 to 2.5 s, i.e. by 3.84%, which makes it possible to maintain the output capacity of the pyrolysis plant at the level of 200 TPH or, if the length of the pyrolysis plant furnace tube coil is maintained, to increase the output capacity of the pyrolysis plant by 3.84%, bringing it to 207.68 TPS and producing extra 3.22 TPH of olefines. Taking into account the advantage of this invention as illustrated by Example 2, compared to the prototype, the pyrolysis plant can produce extra 5.92 TPH of olefines or 47,360 TPA that are price at 1.89 billion rubles per year.

[0093] Thus, the invention will increase the output capacity of the pyrolysis plant on processed feedstock basis and, at the same time, will increase the output of target olefines to the optimal parameter values, while the design solutions and the layout of the unit will provide for optimal operation of every furnace within the hydrocarbon pyrolysis plant and the pyrolysis plant furnaces section as a whole.

Claims

CLAIMS OF THE INVENTION1 The furnaces section of hydrocarbon feedstock pyrolysis plant that comprises the following stages: a) stage of pyrolysis of feedstock of various compositions, including a furnaces group of gaseous, and / or mixed, and / or liquid feedstock pyrolysis plant, with each furnace installed on the same frame for the entire stage, each of the pyrolysis plant furnaces comprising a radiant section, which includes pyrolysis coils and fuel burning nozzles, and a convection section, which includes feedstock heating coils and water steam generation coils; lines for pyrogas transfer to the pyrogas direct oil quenching column that include transfer line exchangers for indirect pyrogas quenching, pyrogas streams, circulating and fresh quenching oil supply streams, and an assembly for circulating quenching oil introduction into the pyrogas stream; b) pyrogas direct oil quenching stage that includes a pyrogas direct oil quenching column fitted with nozzles that introduce pyrogas, which is pre-mixed with circulating oil, and that are arranged on the line that transfers pyrogas from the pyrolysis stage to the pyrogas direct oil quenching column; outlet nozzles for mixed stream of liquid pyrolysis products with oil; outlet nozzles for pyrogas; pumps; characterized by the fact that the unified frame of the furnaces group of the pyrolysis plant has a 3D-arched shape; the inlet tube of the vertical radiant pyrolysis coil of each furnace of the pyrolysis plant faces the front end wall of the pyrolysis plant furnace, and the outlet tube faces the back end wall of the pyrolysis plant; the indirect quenching transfer line exchangers are secured on the back end wall of the pyrolysis plant with an inlet nozzle opposite to the pyrolysis plant furnace outlet of the last reaction tube of pyrolysis coil; the inner loop of the frame of pyrolysis unit furnaces group is the same distance away from the casing of the pyrogas direct oil quenching column; each furnace of the pyrolysis plant has a flue gas dispersion tube and is individually connected with the pyrogas direct oil quenching column using its own transfer line, which expansion joints configuration and length are the same relative to the transfer lines of other furnaces of the pyrolysis unit; and the circulating oil flow is supplied separately into each transfer line; pyrogas and circulation oil aresupplied into each transfer line by an injector device where pyrogas injection at oil overpressure of 3.0-16.0 MPa reduces the pressure in pyrolysis zone of the radiant section coil by 0.01-0.05 MPa, and the pyrogas and circulating oil input nozzles are arranged along the perimeter of the pyrogas direct oil quenching column in a way that ensures the same transfer line length from all the pyrolysis plant furnaces to the pyrogas direct oil quenching column.2 The furnaces section according to claim 1 wherein the unified frame of the pyrolysis plant furnaces group has a 3D-arched shape of an incomplete circle, a semi-circle, or a quarter-circle.3 The furnaces section according to claim 1 wherein the casings of pyrolysis plant furnaces have a rectangular and / or trapezoidal shape.4 The furnaces section according to claim 1 wherein the transfer lines and the pyrogas direct oil quenching column casing are connected in sequence along the casing perimeter and at an angle to form a multi-point tangential inlet of gas-liquid mix streams and to separate the liquid phase from pyrogas.5 The furnaces section according to claim 1 wherein collection of flue gases from all furnaces of the pyrolysis plant, to be sent into dispersion stack and / or sent to carbon dioxide recovery from flue gases, is implemented with a single gas duct header that has the same shape as the outline arch of the pyrolysis unit furnaces group.6 The furnaces section according to claim 1 and 5 wherein the flue gas dispersion stack is placed in the center of the outline arch of the pyrolysis unit furnaces group, introducing flue gases from two sides via symmetrical gas duct headers.7 The furnaces section according to claim 1 wherein the pyrogas direct oil quenching column has PETON cross-flow contactors.

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