CN107974269B - Cracking furnace - Google Patents

Cracking furnace Download PDF

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Publication number
CN107974269B
CN107974269B CN201610938057.5A CN201610938057A CN107974269B CN 107974269 B CN107974269 B CN 107974269B CN 201610938057 A CN201610938057 A CN 201610938057A CN 107974269 B CN107974269 B CN 107974269B
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China
Prior art keywords
furnace
tube
radiation
tubes
cracking
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CN107974269A (en
Inventor
张利军
周丛
王国清
杜志国
张永刚
张兆斌
刘俊杰
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Sinopec Beijing Research Institute of Chemical Industry
China Petroleum and Chemical Corp
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Sinopec Beijing Research Institute of Chemical Industry
China Petroleum and Chemical Corp
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    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G9/00—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
    • C10G9/14—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils in pipes or coils with or without auxiliary means, e.g. digesters, soaking drums, expansion means
    • C10G9/18—Apparatus
    • C10G9/20—Tube furnaces
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C4/00—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms
    • C07C4/02—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms by cracking a single hydrocarbon or a mixture of individually defined hydrocarbons or a normally gaseous hydrocarbon fraction
    • C07C4/04—Thermal processes
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
    • C10G2300/10—Feedstock materials
    • C10G2300/1037—Hydrocarbon fractions
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
    • C10G2300/10—Feedstock materials
    • C10G2300/1081—Alkanes
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G2400/00—Products obtained by processes covered by groups C10G9/00 - C10G69/14
    • C10G2400/20—C2-C4 olefins

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Gasification And Melting Of Waste (AREA)
  • Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)

Abstract

The invention discloses a cracking furnace, which comprises: the convection section, with the radiation section, rapid cooling boiler and the steam pocket that the convection section communicates, be equipped with the convection bank that is linked together with the feed inlet of pyrolysis furnace in the convection section, the top of convection section is located to the steam pocket, be equipped with the fan that is linked together with the pyrolysis furnace on the furnace roof of pyrolysis furnace, be equipped with multiunit radiation tube bank in the radiation section, the radiation bank includes many radiation boiler tubes, many radiation boiler tubes set up along the periphery interval of radiation tube bank, radiation boiler tube and convection bank are linked together, the furnace bottom and the furnace lateral wall of radiation section are equipped with a plurality of combustors respectively, the exit end of radiation boiler tube with the rapid cooling boiler is linked together. The cracking furnace has a simple structure, can reduce the arrangement difficulty of the radiation furnace tubes and ensure that each group of radiation furnace tubes in the cracking furnace have the same reaction conditions as far as possible by improving the arrangement mode of the radiation furnace tubes, and has the advantage of small occupied area of the cracking furnace with unit production capacity.

Description

Cracking furnace
Technical Field
The invention relates to the technical field of tubular furnace petroleum hydrocarbon steam cracking, in particular to a cracking furnace.
Background
Low carbon olefins such as ethylene, propylene and butadiene are important basic materials for petrochemical industry. At present, the method for producing low-carbon olefin is mainly a tubular furnace petroleum hydrocarbon steam cracking process. Statistically, about 99% of the world's ethylene, over 50% of the world's propylene, and over 90% of the world's butadiene are produced by this process.
The core equipment of the tubular furnace petroleum hydrocarbon steam cracking process is a tubular cracking furnace (hereinafter referred to as a "cracking furnace"), and when cracking raw materials such as ethane, propane, naphtha and hydrogenated tail oil are heated to high temperature in the cracking furnace, carbon chain breaking chemical reaction can occur to generate target products such as low-carbon olefin, ethylene, propylene, butadiene and the like.
Since the successful development of tubular cracking furnaces in the last 60 th century, in order to reduce construction investment and production cost, patentees of various cracking furnaces have focused research on the large-scale of cracking furnaces, the improvement and improvement of selectivity and product yield of cracking furnaces, the extension of operating cycle of cracking furnaces and the like. In particular, in terms of the enlargement of the cracking furnace, the single cracking furnace has been developed from the first capacity of less than 1 ten thousand tons/year to the capacity of 20 ten thousand tons/year nowadays.
In the continuous large-scale process, the traditional arrangement mode of the cracking furnace tubes cannot reduce the occupied area of unit production capacity, which brings obstacles to large-scale of the cracking furnace.
At present, the research of cracking furnaces mostly focuses on how to arrange furnace tubes in the radiation section of the cracking furnace so as to ensure that more furnace tubes are arranged in a hearth and better obtain radiation heat transfer, so that materials in the furnace tubes can be quickly heated in a very short retention time. However, the arrangement of the tube rows is in a certain plane or two vertically alternating planes, the furnace tubes are still in linear distribution, and the phenomenon of crossed arrangement exists between the inlet furnace tubes and the outlet furnace tubes.
The tube rows of the furnace tubes are arranged in the same plane, for two-pass furnace tubes widely applied to the cracking furnace, inlet tubes and outlet tubes of the two-pass furnace tubes need to be connected, and the arrangement in the same plane can undoubtedly bring the mutual intersection of each group of furnace tubes (consisting of one inlet tube and one outlet tube), so that the lengths or the structures of each group of furnace tubes are inconsistent, a small difference in the structure among the furnace tubes is formed, and the reaction of cracking raw materials in the furnace tubes is further influenced.
In order to solve the above problems, it is necessary to provide a new cracking furnace.
Disclosure of Invention
The invention provides a cracking furnace with simple structure, which reduces the floor area of the cracking furnace with unit production capacity and the difficulty of arrangement of the radiation furnace tubes by improving the arrangement mode of the radiation furnace tubes, and ensures that each group of furnace tubes in the cracking furnace has the same configuration as much as possible.
In order to achieve the above object, the present invention provides a cracking furnace, wherein the cracking furnace comprises: a convection section, a radiant section in communication with the convection section, a quench boiler, and a steam drum, wherein:
a convection tube bundle communicated with a feed inlet of the cracking furnace is arranged in the convection section, the steam pocket is arranged at the top of the convection section, and a fan communicated with the cracking furnace is arranged on the top of the cracking furnace;
a plurality of groups of radiation tube bundles are arranged in the radiation section, each radiation tube bundle comprises a plurality of radiation furnace tubes, the plurality of radiation furnace tubes are arranged at intervals along the periphery of the radiation tube bundle, the radiation furnace tubes are communicated with the convection tube bundle, and the bottom and the side wall of a hearth of the radiation section are respectively provided with a plurality of burners;
the outlet end of the radiation furnace tube is communicated with the quenching boiler.
The cracking furnace as described above, wherein the plurality of radiant tube bundles have a circular or elliptical cross-section.
The cracking furnace as described above, wherein the radiant furnace tubes are single-pass furnace tubes or multi-pass furnace tubes.
The cracking furnace as described above, wherein the single pass furnace tube is a straight tube or the single pass furnace tube is an expanding tube with an inlet end smaller than an outlet end.
The cracking furnace as described above, wherein the ratio of the tube pitch between two adjacent single-pass tubes to the inner diameter of the single-pass tube is 1.2 to 3.0.
The cracking furnace as described above, wherein the multi-pass tube is a two-pass tube, the two-pass tube includes an outlet tube and at least one inlet tube, an inlet end of the inlet tube communicates with the convection tube bundle, an outlet end of the inlet tube communicates with an inlet end of the outlet tube, and an outlet end of the outlet tube communicates with the cold boiler.
The cracking furnace is characterized in that the ratio of the inner diameter of the outlet pipe to the diameter of the inlet pipe is 1-1.4.
The cracking furnace is characterized in that the ratio of the pipe distance between two adjacent outlet pipes to the inner diameter of the outlet pipe is 1.2-5.0, and the ratio of the pipe distance between two adjacent inlet pipes to the inner diameter of the inlet pipe is 1.2-5.0.
The pyrolysis furnace as described above wherein the radiant furnace tubes employ heat transfer elements of the spiral fin insert, twisted ribbon insert, cross zigzag insert, coil core insert, filament wound porous body or spherical matrix insert type.
The cracking furnace is characterized in that the heat supply proportion of the bottom burner accounts for 60-100% of the combustion system.
The cracking furnace has a simple structure, can reduce the arrangement difficulty of the radiation furnace tubes and ensure that each group of the radiation furnace tubes in the cracking furnace have the same reaction conditions as much as possible by improving the arrangement mode of the radiation furnace tubes, is favorable for cracking reactions to have the same reaction conditions, and has the advantage of small occupied area of the cracking furnace with unit production capacity.
Drawings
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. In addition, the shapes, the proportional sizes, and the like of the respective members in the drawings are merely schematic for facilitating the understanding of the present invention, and do not specifically limit the shapes, the proportional sizes, and the like of the respective members of the present invention. Those skilled in the art, having the benefit of the teachings of this invention, may choose from the various possible shapes and proportional sizes to implement the invention as a matter of case.
FIG. 1 is a schematic view of the structure of a cracking furnace according to the present invention;
FIG. 2 is a top view of a cracking furnace with 1-1 type two-pass tubes according to the present invention;
FIG. 3 is a top view of a 2-1 type two-pass furnace tube according to the present invention;
FIG. 4 is a top plan view of a cracking furnace with single pass furnace tubes according to the present invention;
FIG. 5 is a top plan view of a cracking furnace with two radiant tube bundles according to the invention;
FIG. 6 is a top plan view of a three radiant tube bundle cracking furnace of the present invention;
FIG. 7 is a top plan view of a four radiant tube bundle cracking furnace of the present invention;
FIG. 8 is a top plan view of the oval radiant tube bundle cracking furnace of the present invention;
FIG. 9 is a top view of a cracking furnace with conventional furnace tube arrangements.
Detailed Description
The details of the present invention can be more clearly understood in conjunction with the accompanying drawings and the description of the embodiments of the present invention. However, the specific embodiments of the present invention described herein are for the purpose of illustration only and are not to be construed as limiting the invention in any way. Any possible variations of the invention, which may be considered to be within the scope of the invention, will occur to those skilled in the art upon studying the disclosure and the accompanying drawings, and the invention will be further described below.
Fig. 1 to 9 are respectively a schematic structural diagram of a cracking furnace, a top view of a cracking furnace with 1-1 type two-pass furnace tubes, a top view of a cracking furnace with 2-1 type two-pass furnace tubes, a top view of a cracking furnace with one-pass furnace tubes, a top view of a cracking furnace with two radiation tube bundles, a top view of a cracking furnace with three radiation tube bundles, a top view of a cracking furnace with four radiation tube bundles, a top view of a cracking furnace with oval radiation tube bundles, and a top view of a cracking furnace with traditional furnace tube arrangement.
As shown in fig. 1 to 8, the cracking furnace of the present invention comprises: convection section 1, radiant section 2 in communication with convection section 1, quench boiler 3 and steam drum (or referred to as high pressure steam drum, not shown in the figure), wherein: a convection bank (not shown) communicated with a feed inlet of the cracking furnace is arranged in the convection section 1, a steam pocket is arranged at the top of the convection section 1, and a fan 4 communicated with the cracking furnace is arranged on the top of the cracking furnace; be equipped with multiunit radiation tube bank 21 in radiation section 2, radiation tube bank 21 includes many radiation furnace tubes 22, and many radiation furnace tubes 22 set up along radiation tube bank 21's periphery interval, and radiation furnace tube 22 is linked together with this convection bank, and the furnace bottom and the furnace lateral wall of radiation section 2 are equipped with a plurality of combustors 5 respectively (constitute the combustion system of pyrolysis furnace), and the exit end and the rapid cooling boiler 3 of radiation furnace tube 22 are linked together.
Specifically, in the present invention, the radiation tube bundles 21 are arranged in the middle of the furnace, the burners 5 are symmetrically arranged on the bottom of the furnace and the side wall of the furnace around the radiation tube bundles 21, in a specific embodiment, the cross sections of a plurality of radiation tube bundles 21 are circular or elliptical, each group of radiation furnace tubes 22 in the radiation tube bundles 21 are uniformly distributed on the circular or elliptical circumference with the center of the radiation tube bundle 21 as the center, a plurality of bottom burners are arranged at the center of each radiation tube bundle 21, and the bottom burners are also the burners 5 arranged on the bottom of the furnace and located at the center of the radiation tube bundle 21.
Specifically, in the present invention, the radiant tube bundle 21 is composed of 4-20 groups of radiant tubes 22, preferably, the radiant tube bundle 21 is composed of 6-12 groups of radiant tubes 22, and in one embodiment, the distance from the radiant tubes 22 in the radiant tube bundle 21 to the center of the radiant tube bundle 21 is in the range of: 350mm to 1500 mm. Preferably, the range of the distance of the radiant tubes 22 from the center of the radiant tube bundle 21 is: 400mm to 1200 mm.
Further, the radiant furnace 22 is a single-pass furnace or a multi-pass furnace, wherein the definitions of the single-pass furnace and the multi-pass furnace are well known to those skilled in the art and will not be described herein.
In the invention, the one-way furnace tube is a straight tube (namely, a non-reducing tube) or a reducing tube with gradually changed tube diameter from an inlet to an outlet. In this embodiment, the inside diameter of the inlet end pipe orifice of the tapered pipe is smaller than the inside diameter of the outlet end pipe orifice of the tapered pipe, and specifically, in the present invention, the range of the inside diameter of the inlet end pipe orifice of the tapered pipe is as follows: 25mm to 50mm, preferably the internal diameter of the inlet end nozzle is in the range: 35mm to 45 mm; the range of the inner diameter of the outlet end pipe orifice of the tapered pipe is as follows: 35mm to 65mm, the preferred range of the outlet end nozzle inner diameter is: 45mm to 60 mm. Of course, the pipe diameter of the single-pass pipe can be adjusted correspondingly according to the size of the cracking furnace, that is, the pipe diameter of the single-pass pipe can also adopt other sizes, and is not limited specifically here.
Further, in the present invention, when the single-pass furnace tubes are arranged in the radiant tube bundle, the ratio of the furnace tube pitch to the furnace tube diameter is: 1.2-3.0, preferably, when the single-pass furnace tubes are arranged in the radiant tube bundle, the ratio of the furnace tube spacing to the furnace tube diameter is as follows: 1.6-2.2. The inventor finds that the proportion design is more favorable for cracking reaction and simultaneously helps to prolong the operation period of the cracking furnace.
In a specific embodiment, the multi-pass furnace tube is a two-pass furnace tube, the two-pass furnace tube includes an outlet tube 8 and at least one inlet tube 9, an inlet end of the inlet tube 9 is communicated with the convection tube bundle, an outlet end of the inlet tube 9 is communicated with an inlet end of the outlet tube 8, an elbow tube may be used to communicate the outlet end of the inlet tube 9 with the inlet end of the outlet tube 8, or other manners may be used to communicate, which is not limited herein, and the outlet end of the outlet tube 9 is communicated with the quenching boiler 3.
In a specific embodiment, in the two-pass furnace tube, the first pass is a vertical inlet tube 9, and the second pass is a vertical outlet tube 8, so as to form a 1-1 type radiation furnace tube. In another specific embodiment, or the first pass is two parallel vertical inlet pipes 9, the second pass is one vertical outlet pipe 8, both the two parallel vertical inlet pipes 9 are communicated with the vertical outlet pipe 8 to form a 2-1 type radiation furnace tube, of course, in the two-pass furnace tube, the first pass is n (n is a positive integer and is not less than 3) vertical inlet pipes 9, the second pass is one vertical outlet pipe 8, the n vertical inlet pipes 9 are respectively communicated with the vertical outlet pipe 8 to form an n-1 type radiation furnace tube, wherein the number of n is not specifically limited herein.
Furthermore, the ratio of the inner diameter of the outlet pipe of the two-pass furnace tube to the inner diameter of the inlet pipe is 1 to 1.4 (including 1.4), thereby being more beneficial to the cracking reaction.
In one embodiment, the range of the inner diameter of the inlet tube of the two-pass furnace tube is: 25mm to 60 mm. The preferred range of inlet tube internal diameter is: 35mm to 55 mm; the range of the inner diameter of the outlet pipe of the two-stroke furnace pipe is as follows: 45mm to 120 mm. The preferable range of the inner diameter of the nozzle at the outlet end is as follows: 55mm to 95 mm.
Further, when the two-pass furnace tubes are arranged in the radiant tube bundle, the ratio of the furnace tube spacing to the furnace tube diameter is as follows: 1.2-5.0, preferably, when the two-pass furnace tubes are arranged in the radiant tube bundle, the ratio of the distance between the radiant furnace tubes 22 to the diameter of the radiant furnace tubes 22 is as follows: 1.6-3.0, where the radiant furnace tubes 22 include inlet tubes 9 and outlet tubes 8.
Of course, the multi-pass furnace tube can be a three-pass furnace tube, a four-pass furnace tube, a five-pass furnace tube or a multi-pass three-pass furnace tube. The three-pass furnace tube is designed in a manner that an intermediate furnace tube is arranged between an inlet tube 9 and an outlet tube 8 of the two-pass furnace tube, the intermediate furnace tube is parallel to the inlet tube 9 and the outlet tube 8, the intermediate furnace tube communicates the inlet tube 9 and the outlet tube 8, so that the three-pass furnace tube is formed, and the design method of the four-pass furnace tube or more-pass furnace tubes is similar to that of the three-pass furnace tube, and is not described in detail herein.
Further, in the present invention, the combustion system of the cracking furnace is only provided with a bottom burner or consists of a bottom burner and a side wall burner, wherein the bottom burner is the burner 5 at the bottom of the furnace, the side wall burner is the burner 5 at the side wall of the furnace, the combustion system of the cracking furnace uses a mixture including but not limited to methane or methane-hydrogen as fuel and air as combustion-supporting gas, and further, in the present embodiment, the heat supply ratio of the bottom burner is 60% to 100%, preferably 70% to 85%, so as to facilitate the occurrence of the cracking reaction.
Further, the radiant furnace tubes 22 of the radiant section 2 described herein employ heat transfer enhancement elements, which may be any known or unknown elements, such as spiral fin inserts, twisted ribbon inserts, zig-zag inserts, coil core inserts, wound filament porous bodies, spherical matrix inserts, and the like, to facilitate heat transfer, wherein these thereby facilitate the occurrence of cracking reactions within the radiant furnace tubes 22. Different heat transfer enhancing elements can be added to different parts of the furnace tube respectively. Thereby increasing the heat transfer efficiency and facilitating the reduction of the degree of the difference in the cracking reaction conditions within the radiant furnace tubes 22.
The cracking process of the cracking furnace of the invention is as follows: raw materials (such as naphtha) enter a convection tube bundle of a convection section 1 through an inlet of a cracking furnace, the convection tube bundle also comprises a plurality of convection furnace tubes, namely the raw materials enter the convection furnace tubes, the convection furnace tubes are communicated with corresponding radiation furnace tubes, the naphtha enters a radiation furnace tube 22 of a radiation section 2 after being gasified and preheated in the convection section 1 to carry out cracking reaction, a combustion system of the radiation section 2 adopts a mode of combining a bottom burner and a side wall burner, the heat supply ratio of the bottom burner is 80%, a burner 5 adopts oxygen-enriched combustion, the burner burns to generate high-temperature flue gas, the high-temperature flue gas carries out radiation heating on the naphtha in the radiation furnace tube 22, the naphtha is subjected to cracking reaction in the radiation furnace tube 22, the naphtha enters a quenching boiler 3 after the cracking of the radiation furnace tube 22 to be cooled to obtain an intermediate product, and then the intermediate product is separated to finally obtain a low-, wherein, when adopting the one-way boiler tube to radiation boiler tube 22, radiation boiler tube 22 adopts and advances from bottom to top, if radiation boiler tube 22 adopts the two-way boiler tube, radiation boiler tube 22 adopts and advances from top to top, after the combustion gas of radiation section 2 heats the naphtha radiation in radiation boiler tube 22, get into convection section 1, be used for in convection section 1 in the convection section in the naphtha in the convection bank gasify and preheat, in the portion of convection section, the combustion gas temperature reduces, steam condensation, the condensate gets into the high-pressure steam pocket, low temperature flue gas is taken away to fan 4, thereby make high temperature flue gas get into in convection section 1.
The cracking furnace has a simple structure, can reduce the arrangement difficulty of the radiation furnace tubes and ensure that each group of the radiation furnace tubes in the cracking furnace have the same reaction conditions as much as possible by improving the arrangement mode of the radiation furnace tubes, is favorable for cracking reactions to have the same reaction conditions, and has the advantage of small occupied area of the cracking furnace with unit production capacity.
The advantages of the present invention are demonstrated by comparing one of the embodiments with an existing cracking furnace, i.e., the following example one with the comparative example one.
Example one
The cracking furnace shown in FIG. 1 was used to perform the cracking reaction. The specific process comprises the following steps:
the method comprises the following steps of gasifying and preheating 60 ℃ naphtha in a convection section 2, then enabling the naphtha to enter a radiant section furnace pipe 3 for cracking reaction, wherein a combustion system of a radiant section 5 adopts a combination mode of a bottom combustor and a side wall combustor, and the heat supply ratio of the bottom combustor is 80%; the preheating temperature of naphtha in the convection section, namely the crossing temperature (XOT) of the cracking furnace is 590 ℃, the outlet temperature (COT) of the radiation section of the cracking furnace is 830 ℃, the furnace tube 3 of the radiation section adopts a one-way furnace tube, the diameter of the inlet tube of the furnace tube is 41mm, the diameter of the outlet tube of the furnace tube is 53mm, the length of the furnace tube is 12.8m, and the furnace tube adopts a downward feeding mode and an upward discharging mode. The furnace tubes are arranged in a novel manner as shown in fig. 4. Other process parameters of the cracking furnace are shown in table 1, and the composition of the cracking furnace fuel gas is shown in table 2 by analyzing the cracking furnace fuel gas.
TABLE 1
Period of operation Example 1 Comparative example 1
Batch (kg/H) 35000 35000
Amount of dilution steam (kg/H) 17500 17500
Fuel gas amount (Nm)3/h) 7050 7050
XOT(℃) 590 590
COT(℃) 830 830
Radiation section inlet pressure XOP (Mpa, G) 0.0972 0.0972
Radiation section outlet pressure COP (Mpa, G) 0.0783 0.0783
Run cycle (day) (TMT up to 1100 ℃) 33 31
Cracking furnace floor area (100KTA) (m)2) 32 63
TABLE 2
Components mol％
Hydrogen gas 3.6
Methane 95.8
Ethane (III) 0.23
Propane 0.08
Others 0.29
Total up to 100.00
Comparative example 1
The cracking furnace shown in FIG. 1 was used to perform the cracking reaction. The specific process comprises the following steps:
the method comprises the following steps of gasifying and preheating 60 ℃ naphtha in a convection section 2, then enabling the naphtha to enter a radiant section furnace pipe 3 for cracking reaction, wherein a combustion system of a radiant section 5 adopts a combination mode of a bottom combustor and a side wall combustor, and the heat supply ratio of the bottom combustor is 80%; the temperature of naphtha preheated in the convection section, namely the crossing temperature (XOT) of the cracking furnace is 590 ℃, the outlet temperature (COT) of the radiation section of the cracking furnace is 830 ℃, the furnace tube 3 of the radiation section adopts a one-way furnace tube, the diameter of the inlet tube of the furnace tube is 41mm, the diameter of the outlet tube of the furnace tube is 53mm, the length of the furnace tube is 12.8m, the furnace tube adopts a downward feeding and an upward discharging, and the arrangement of the furnace tubes adopts a traditional mode as shown in figure 9. Other process parameters of the cracking furnace are shown in table 1, and the composition of the cracking furnace fuel gas is shown in table 2 by analyzing the cracking furnace fuel gas.
As can be seen from Table 1, with the novel arrangement of the furnace tubes, the floor space of the cracking furnace is 63m from that of the comparative example due to the optimized arrangement of the furnace tubes2Reduced to 32m of the example2(ii) a Meanwhile, due to the optimized arrangement of the furnace tubes, the heat transfer process is more uniform and reasonable, the operation period of the cracking furnace is prolonged from 31 days to 33 days of the comparative example, and the operation period of the cracking furnace is prolonged.
From the comparison, the cracking furnace has a simple structure, the arrangement difficulty of the radiation furnace tubes can be reduced and each group of radiation furnace tubes in the cracking furnace can be ensured to have the same reaction condition as much as possible by improving the arrangement mode of the radiation furnace tubes, so that the cracking furnace is favorable for cracking reaction to have the same reaction condition, and meanwhile, the cracking furnace with unit production capacity has the advantage of small occupied area.
While the invention has been described with reference to a preferred embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In particular, the technical features mentioned in the embodiments can be combined in any way as long as there is no structural conflict. It is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (8)

1. A cracking furnace, characterized in that the cracking furnace comprises: a convection section, a radiant section in communication with the convection section, a quench boiler, and a steam drum, wherein:
a convection tube bundle communicated with a feed inlet of the cracking furnace is arranged in the convection section, the steam pocket is arranged at the top of the convection section, and a fan communicated with the cracking furnace is arranged on the top of the cracking furnace;
a plurality of groups of radiation tube bundles are arranged in the radiation section, each radiation tube bundle comprises a plurality of radiation furnace tubes, the cross section of each radiation tube bundle is circular, the plurality of radiation furnace tubes are arranged at intervals along the periphery of the radiation tube bundle, the radiation furnace tubes are communicated with the convection tube bundle, the bottom and the side wall of a hearth of the radiation section are respectively provided with a plurality of burners, and the burners arranged at the bottom of the hearth are positioned at the center of the radiation tube bundle; the heat supply proportion of the bottom burner accounts for 60-100% of the combustion system;
the outlet end of the radiation furnace tube is communicated with the quenching boiler.
2. The cracking furnace of claim 1, wherein the radiant coils are single pass coils or multi-pass coils.
3. The cracking furnace of claim 2, wherein the single pass furnace tubes are straight tubes or the single pass furnace tubes are diverging tubes with an inlet end smaller than an outlet end.
4. The cracking furnace of claim 2, wherein the ratio of the tube spacing between two adjacent single-pass furnace tubes to the inner diameter of the single-pass furnace tubes is 1.2-3.0.
5. The cracking furnace of claim 2, wherein the multi-pass tubes are two-pass tubes, the two-pass tubes including an outlet tube and at least one inlet tube, an inlet end of the inlet tube communicating with the convection tube bundle, an outlet end of the inlet tube communicating with an inlet end of the outlet tube, and an outlet end of the outlet tube communicating with the quench boiler.
6. The cracking furnace of claim 5, wherein the ratio of the inner diameter of the outlet pipe to the diameter of the inlet pipe is 1-1.4.
7. The cracking furnace of claim 5 or 6, wherein the ratio of the tube distance between two adjacent outlet tubes to the inner diameter of the outlet tube is 1.2-5.0, and the ratio of the tube distance between two adjacent inlet tubes to the inner diameter of the inlet tube is 1.2-5.0.
8. The pyrolysis furnace of any of claims 1 to 6, wherein the radiant furnace tubes employ heat transfer elements in the form of spiral fin inserts, twisted ribbon inserts, cross-zigzag inserts, coil core inserts, filament wound porous bodies, or spherical matrix inserts.
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