CN107974270B - Cracking furnace - Google Patents
Cracking furnace Download PDFInfo
- Publication number
- CN107974270B CN107974270B CN201610938106.5A CN201610938106A CN107974270B CN 107974270 B CN107974270 B CN 107974270B CN 201610938106 A CN201610938106 A CN 201610938106A CN 107974270 B CN107974270 B CN 107974270B
- Authority
- CN
- China
- Prior art keywords
- furnace
- tube
- radiation
- tubes
- cracking
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- 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
Abstract
The invention discloses a cracking furnace, wherein the cracking furnace comprises: convection current section, with the radiant section of convection current section intercommunication, quench boiler and steam pocket, wherein: the convection section is internally provided with a convection tube bundle communicated with a feed inlet of the cracking furnace, the steam pocket is arranged at the top of the convection section, the top of the cracking furnace is provided with a fan communicated with the cracking furnace, the radiation section is internally provided with a plurality of groups of radiation tube bundles, the radiation tube bundles comprise a plurality of radiation furnace tubes, the plurality of radiation furnace tubes are arranged at intervals along the periphery of the radiation tube bundles, the radiation furnace tubes are communicated with the convection tube bundle, the bottom of the hearth and the side wall of the hearth of the radiation section are respectively provided with a plurality of burners, and the outlet ends of the radiation furnace. The cracking furnace improves the arrangement mode of the radiation furnace tubes, can reduce the arrangement difficulty of the radiation furnace tubes, can ensure that each group of radiation furnace tubes in the cracking furnace have the same reaction condition as far as possible, and has the advantage of small occupied area of the cracking furnace with unit production capacity.
Description
Technical Field
The invention relates to the technical field of tubular furnace petroleum hydrocarbon steam cracking, in particular to a cracking furnace adopting an oxygen-enriched combustion system.
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.
Currently, most of research on cracking furnaces focuses on how to arrange furnace tubes in a 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 within 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.
From the standpoint of the heat transfer of the furnace, fuel gas (primarily methane and hydrogen) is combusted to provide heat within the furnace chamber of the furnace, which is transferred into the furnace tubes by both radiant and convective heat transfer. Cracking furnaces typically employ mixed combustion of fuel gas and air to provide the heat required for the cracking reaction. Traditional pyrolysis furnace generally adopts the air as combustion-supporting gas, and in the combustion process, the burning rate of fuel gas is slower, and burning flame is longer, and in pyrolysis furnace's direction of height, furnace temperature is the curve and distributes, and is few in furnace bottom heat supply, and furnace middle part is then heat supply most, and furnace upper portion heat supply begins to reduce. For a cracking furnace with a multi-pass furnace tube, because the residence time is long, the contradiction between the heat supply of a hearth and the heat absorption of the furnace tube is not outstanding, and for a single-pass furnace tube, the contradiction is highlighted, the material is continuously and rapidly heated at the inlet end of the furnace tube, a large amount of heat is continuously provided, but the heat supply at the bottom of the traditional combustion system is less; at the outlet end of the furnace tube, the coking rate of the materials is increased sharply, secondary reaction needs to be controlled, and the heat supply at the middle upper part of the traditional combustion system is maximized. That is, there is a matching problem between the combustion system and the once-through furnace tubes.
From the view point of the furnace chamber of the cracking furnace, the heat required by the reaction of the furnace tube of the cracking furnace is provided by the furnace chamber, fuel gas (mainly methane and hydrogen) is combusted to provide heat in the furnace chamber of the cracking furnace, and the heat enters the furnace tube through radiation heat transfer and convection heat transfer, wherein the radiation heat transfer is the main heat transfer mode and accounts for more than 85 percent of the total heat transfer. The radiation heat transfer of the hearth of the cracking furnace is influenced by various complex factors, such as the structure and the size of the hearth, the type and the heat supply mode of fuel, the type of a burner and the like. At present, the traditional cracking furnace adopts ceramic fiber or refractory bricks as the furnace wall of the cracking furnace, the reaction materials in the radiation furnace tube of the cracking furnace are heated by utilizing the high-temperature flue gas combusted by fuel gas and the radiation heat transfer of the furnace wall, the furnace wall of the cracking furnace adopts a flat furnace wall structure, and the radiation of the furnace wall of the cracking furnace is the same for the inlet part and the outlet part of the furnace tube from the radiation heat transfer angle.
The heat transfer process of the hearth of the cracking furnace at present has the following two problems, namely, the heat transfer area of the hearth of the cracking furnace is insufficient, and the heat transfer process of the hearth of the cracking furnace is mainly radiation heat transfer; secondly, the radiant heat transfer of the furnace wall of the cracking furnace has no difference for the furnace tube rows, namely the furnace wall of the cracking furnace has consistent heat transfer area for the inlet tube row or the outlet tube row, and is also the same for a region with large heat flux and a region with small heat flux, which can cause the local heating of the cracking furnace to be uneven, thereby causing the local temperature of the furnace tube to be overhigh and reducing the operation period of the cracking furnace.
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, which is simple in structure, realizes reduction of the floor area of the cracking furnace in unit production capacity and the difficulty of arrangement of radiation furnace tubes by improving the arrangement mode of the radiation furnace tubes, and enables each group of furnace tubes to keep the same configuration, thereby ensuring that each group of furnace tubes in the cracking furnace have the same reaction conditions 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 inner surface of the furnace wall of the radiant section is corrugated or provided with protrusions.
The cracking furnace as described above, wherein the burner uses oxygen-enriched air as combustion-supporting gas.
The cracking furnace as described above, wherein the volume fraction of oxygen in the oxygen-enriched air is 22% -60%
The cracking furnace is characterized in that the cross sections of the plurality of groups of radiation tube bundles are circular or elliptical, and the radiation 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 spacing between two adjacent single-pass furnace tubes to the inner diameter of the single-pass furnace tubes is 1.2-3.0.
The cracking furnace as described above, wherein the multi-pass furnace tube is a two-pass furnace tube, the two-pass furnace tube includes an outlet tube and at least one inlet tube, an inlet end of the inlet tube is communicated with the convection tube bundle, an outlet end of the inlet tube is communicated with an inlet end of the outlet tube, and an outlet end of the outlet tube is communicated with the quenching 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 cracking furnace has a simple structure, the arrangement mode of the radiation furnace tubes is improved, the arrangement difficulty of the radiation furnace tubes can be reduced, each group of radiation furnace tubes in the cracking furnace can be ensured to have the same reaction condition as far as possible, the cracking furnace is favorable for cracking reaction to have the same reaction condition, and the cracking furnace with unit production capacity has the advantage of small occupied area.
Furthermore, the cracking furnace improves the inner surface of the furnace wall of the radiation section, can increase the heat transfer area of the hearth, strengthens the heat transfer process of the cracking furnace, and also effectively prolongs the operation period of the cracking furnace.
Furthermore, the cracking furnace adopts an oxygen-enriched combustion system, so that the emission of smoke gas can be reduced, and the consumption of fuel can be reduced.
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 of the present invention;
FIG. 2 is a top view of a cracking furnace having a type 1-1 two-pass furnace tube according to the present invention;
FIG. 3 is a top view of a cracking furnace having 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 four radiant tube bundle cracking furnace of the present invention;
FIG. 7 is a top plan view of a cracking furnace with elliptical radiant tube bundles according to the present invention;
FIG. 8 is a top view of a conventional furnace tube arrangement cracking furnace;
fig. 9 is a schematic structural view of the furnace wall projection of the present invention.
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.
FIGS. 1 to 9 are respectively a schematic structural diagram of the cracking furnace of the present invention, a top view of a 1-1 type two-pass furnace tube cracking furnace, a top view of a 2-1 type two-pass furnace tube cracking furnace, a top view of a single-pass furnace tube cracking furnace, a top view of two radiant tube bundle cracking furnaces, a top view of four radiant tube bundle cracking furnaces, a top view of an elliptical radiant tube bundle cracking furnace, and a top view of a conventional furnace tube arrangement cracking furnace; the structure of the furnace wall bulge is shown schematically.
As shown in fig. 1, 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 groups 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 51 are arranged at the center of each radiation tube bundle 21, and the bottom burners 51 are also the burners 5 arranged on the bottom of the furnace and located at the center of the radiation tube bundle 21.
Further, the inner surface of the furnace wall 6 of the invention adopts the special-shaped furnace wall structure 61, thereby increasing the radiation heat transfer area of the hearth and strengthening the heat transfer process of the cracking furnace, in particular, the special-shaped furnace wall structure 61 is in a corrugated surface shape or is provided with bulges (or becomes a bulge gallery structure) and the like, in the invention, the direction of the special-shaped furnace wall structure 61 is consistent with the direction of the flue gas of the radiation section 2 in the cracking furnace, thereby reducing the increase of the flue gas pressure drop caused by the special-shaped furnace wall structure 61.
In the present invention, the arrangement of the special-shaped furnace wall structure 61 in the cracking furnace is arranged according to the principle that the cracking furnace has more radiant heat transfer and transfers the heat to the inlet part of the radiant furnace tubes 22 of the cracking furnace. Namely, the furnace wall 6 with the same height as the outlet part of the radiation furnace tube 22 of the cracking furnace is completely or partially provided with the special-shaped furnace wall structure 61, the radiation surface of the part of the furnace wall 6 faces the inlet part of the radiation furnace tube 22 of the cracking furnace, the cracking reaction of the cracking raw material at the inlet is accelerated, and the heat intensity of the outlet part of the furnace tube of the cracking furnace is reduced, so that the highest tube wall temperature of the radiation furnace tube of the cracking furnace is reduced, namely, the local heating unevenness of the cracking furnace is avoided, and the local temperature of the furnace tube is overhigh, thereby being beneficial to the long-period operation of the cracking furnace.
Further, the radiation area increasing rate is defined as the ratio of the actual surface area of the profiled furnace wall structure 61 to the vertical projected area (i.e. when the furnace wall is flat). In the invention, the radiation area increasing rate of the special-shaped furnace wall structure 61 is 1.05-1.4, and preferably, the radiation area increasing rate of the special-shaped furnace wall structure 61 is 1.1-1.3.
In one embodiment, the ratio of the area of the special-shaped furnace wall structure 61 to the total furnace wall area of the radiation section is 10-80%, preferably 30-60%.
In general, the special-shaped furnace wall structure 61 is not used in the flame height range of the cracking furnace burner 5, because the combustion condition of the flame of the cracking furnace burner 5 is related to the mixing condition of the fuel gas and the air, and if the special-shaped furnace wall structure 61 is used in the flame height range, the mixing of the fuel gas and the air is influenced, so that the normal shape of the flame is influenced, and the heat flux distribution of a combustion system is changed, and the operation of the cracking furnace is influenced.
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 8 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 furnace tube spacing to the furnace tube diameter is as follows: 1.6-3.0, where the furnace tube includes an inlet tube 9 and an outlet tube 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, and the side wall burner is the burner 5 at the side wall of the furnace, 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 cracking reaction.
In the invention, a combustion system of a cracking furnace adopts methane or a methane-hydrogen mixture as fuel, and oxygen-enriched air as combustion-supporting gas, specifically, in the embodiment, the oxygen-enriched air has a concentration of 25-40% (volume fraction), preferably 27-33% (volume fraction), wherein the oxygen-enriched air is obtained by a pressure swing adsorption or membrane permeation method. Thereby the following advantages are realized: has the advantages that: firstly, because the radiation heat transfer is the main mode of pyrolysis furnace heat transfer, according to the characteristics of gas radiation, only the triatomic gas and polyatomic gas have the radiation ability, and the diatomic gas has almost no radiation ability, and under the combustion-supporting condition of conventional air, the proportion of nitrogen gas without radiation ability is very high, and the blackness of flue gas is very low, has influenced the radiation heat transfer process of flue gas to the boiler tube bank. Oxygen-enriched air is adopted for combustion supporting, and the nitrogen content is low, so that the air quantity and the flue gas quantity are both obviously reduced, the flame temperature and the blackness are obviously improved along with the increase of the oxygen proportion in the combustion air, the flame radiation intensity is further improved, and the radiation heat transfer is enhanced; secondly, oxygen-enriched air is adopted for supporting combustion, the flame of combustion is shortened, the combustion intensity is improved, the combustion speed is accelerated, the complete combustion reaction is facilitated, the use efficiency of fuel is improved, and the thermal efficiency of the cracking furnace is further improved; and thirdly, oxygen-enriched air is adopted for combustion supporting, so that the excess air coefficient can be properly reduced, the smoke exhaust volume is reduced, the smoke quantity after combustion is reduced, the smoke exhaust loss is further reduced, and the energy conservation of the cracking furnace is promoted.
Further, the radiant furnace tubes 22 of the radiant section 2 are provided with heat transfer enhancing elements, which may be any known or unknown elements, such as spiral sheet inserts, twisted tape inserts, zigzag inserts, coil core inserts, filament wound porous bodies, spherical matrix inserts, etc., to facilitate heat transfer. 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 improves the arrangement mode of the radiation furnace tubes, can reduce the arrangement difficulty of the radiation furnace tubes, can ensure that each group of radiation furnace tubes in the cracking furnace have the same reaction condition as far as possible, is favorable for cracking reaction to have the same reaction condition, 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:
naphtha at 60 ℃ is gasified and preheated in the convection section 1 and then enters the radiation furnace tube 22 of the radiation section 2 for cracking reaction, the combustion system of the radiation section 2 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 burner 5 uses oxygen-enriched combustion, and the oxygen concentration is 30% (volume fraction). The temperature of naphtha preheated in the convection section 1, namely the crossing temperature (XOT) of the cracking furnace is 590 ℃, the outlet temperature (COT) of the radiation section 2 of the cracking furnace is 830 ℃, the radiation furnace tube 22 of the radiation section 2 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 inlet and an upward outlet. The furnace tubes are arranged in the manner of the radiation furnace tube 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. The cracking furnace wall 6 is the furnace wall 6 shown in fig. 9, the special-shaped furnace wall structure 61 in the hearth is positioned at more than half of the height of the hearth, the radiation surface of the special-shaped furnace wall structure 61 faces the inlet part of the radiation furnace tube, and the radiation heat transfer area is increased by 10% compared with a plane furnace wall through comprehensive calculation.
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) | 6795 | 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 ℃) | 37 | 31 |
| Cracking furnace floor area (100KTA) (m2) | 32 | 63 |
TABLE 2
| Components | mol％ |
| Hydrogen gas | 3.6 |
| Methane | 95.8 |
| Ethane (III) | 0. |
| 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 8. 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. After the special-shaped furnace wall structure 61 is adopted, the radiation heat transfer area of the hearth is increased, and after the oxygen-enriched combustion is adopted, the excess air coefficient is reduced, so that the fuel gas consumption of the cracking furnace is reduced from 7050Nm of the comparative example3The/h is reduced to 6795Nm3The fuel gas is saved by about 3.62 percent, and the heat absorption capacity of the cracking reaction at the inlet end of the furnace tube is increased, so that the heat intensity at the outlet end of the furnace tube is relatively reduced, the temperature of the highest tube wall of the cracking furnace is reduced, and the operation period of the cracking furnace is prolonged. The operation period of the cracking furnace is prolonged from 31 days to 37 days in comparison.
The cracking furnace improves the arrangement mode of the radiation furnace tubes, can reduce the arrangement difficulty of the radiation furnace tubes, can ensure that each group of radiation furnace tubes in the cracking furnace have the same reaction condition as far as possible, is favorable for cracking reaction to have the same reaction condition, and has the advantage of small occupied area of the cracking furnace with unit production capacity.
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 (9)
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 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 inner surface of the furnace wall of the radiation section is of a corrugated curved surface shape or is provided with a raised special-shaped furnace wall structure, the direction of the special-shaped furnace wall structure is consistent with the direction of flue gas of the radiation section in the cracking furnace, the arrangement of the special-shaped furnace wall structure is arranged according to the principle that more radiant heat transfer of the cracking furnace is transferred to the inlet part of the radiation furnace tube of the cracking furnace, the special-shaped furnace wall structure is completely or partially adopted on the furnace wall of the inlet part of the cracking furnace which has the same height with the outlet part of the radiation furnace tube of the cracking furnace, and the radiation surface of the furnace wall of the special-shaped furnace wall structure is completely or partially towards the inlet part of the radiation furnace tube of the cracking furnace.
2. The cracking furnace of claim 1, wherein the burner uses oxygen-enriched air as a combustion-supporting gas.
3. The cracking furnace of claim 2, wherein the oxygen-enriched air has a volume fraction of oxygen of 22% to 60%.
4. The cracking furnace of claim 1, wherein the cross-sections of the plurality of groups of radiant tube bundles are circular or elliptical, and the radiant tubes are single-pass tubes or multi-pass tubes.
5. The cracking furnace of claim 4, 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.
6. The cracking furnace according to claim 4 or 5, 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.
7. The pyrolysis furnace of claim 4, 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 being in communication with the convection tube bundle, an outlet end of the inlet tube being in communication with an inlet end of the outlet tube, and an outlet end of the outlet tube being in communication with the quench boiler.
8. The cracking furnace of claim 7, wherein the ratio of the inner diameter of the outlet pipe to the diameter of the inlet pipe is 1-1.4.
9. The cracking furnace of claim 7 or 8, 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.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201610938106.5A CN107974270B (en) | 2016-10-25 | 2016-10-25 | Cracking furnace |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201610938106.5A CN107974270B (en) | 2016-10-25 | 2016-10-25 | Cracking furnace |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN107974270A CN107974270A (en) | 2018-05-01 |
| CN107974270B true CN107974270B (en) | 2020-02-18 |
Family
ID=62004944
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201610938106.5A Active CN107974270B (en) | 2016-10-25 | 2016-10-25 | Cracking furnace |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN107974270B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107974268B (en) * | 2016-10-25 | 2020-07-24 | 中国石油化工股份有限公司 | Cracking furnace |
| CN107974269B (en) * | 2016-10-25 | 2020-07-21 | 中国石油化工股份有限公司 | Cracking furnace |
| CN111019688B (en) * | 2018-10-10 | 2022-03-15 | 中国石油化工股份有限公司 | Low-carbon olefin cracking equipment and cracking method |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2876613Y (en) * | 2005-06-29 | 2007-03-07 | 中国石油天然气华东勘察设计研究院 | Intermediate furnace tubeseat hanging combination structure for cylinder pipe type heating furnace |
| CN102234521A (en) * | 2010-04-30 | 2011-11-09 | 中国石油化工集团公司 | Cracking furnace for cracking of hydrocarbons to ethylene |
| CN202041079U (en) * | 2011-01-20 | 2011-11-16 | 中国石油天然气华东勘察设计研究院 | Double-cylinder radiation chamber heating furnace |
| CN202595045U (en) * | 2012-05-30 | 2012-12-12 | 张宝祯 | Oil refining furnace with energy-saving and emission-reduction function |
| CN203728775U (en) * | 2013-06-09 | 2014-07-23 | 中国石油化工股份有限公司 | Novel ethylene cracking furnace |
-
2016
- 2016-10-25 CN CN201610938106.5A patent/CN107974270B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2876613Y (en) * | 2005-06-29 | 2007-03-07 | 中国石油天然气华东勘察设计研究院 | Intermediate furnace tubeseat hanging combination structure for cylinder pipe type heating furnace |
| CN102234521A (en) * | 2010-04-30 | 2011-11-09 | 中国石油化工集团公司 | Cracking furnace for cracking of hydrocarbons to ethylene |
| CN202041079U (en) * | 2011-01-20 | 2011-11-16 | 中国石油天然气华东勘察设计研究院 | Double-cylinder radiation chamber heating furnace |
| CN202595045U (en) * | 2012-05-30 | 2012-12-12 | 张宝祯 | Oil refining furnace with energy-saving and emission-reduction function |
| CN203728775U (en) * | 2013-06-09 | 2014-07-23 | 中国石油化工股份有限公司 | Novel ethylene cracking furnace |
Also Published As
| Publication number | Publication date |
|---|---|
| CN107974270A (en) | 2018-05-01 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP4871928B2 (en) | Cracking furnace with more uniform heating | |
| CN101333147B (en) | Ethylene pyrolysis furnace | |
| CN106631660B (en) | Steam cracking method | |
| CN107974270B (en) | Cracking furnace | |
| CN107974271B (en) | Cracking furnace with novel furnace tube arrangement | |
| KR20010012562A (en) | Cracking furnace with radiant heating tubes | |
| CN107974268B (en) | Cracking furnace | |
| JPH0613710B2 (en) | Pyrolysis heater | |
| US6425757B1 (en) | Pyrolysis heater with paired burner zoned firing system | |
| CN107974269B (en) | Cracking furnace | |
| US3667429A (en) | Fired heater | |
| CN106631659B (en) | Steam cracking method | |
| CN111019691B (en) | Low-carbon olefin cracking equipment and cracking method | |
| CN111019688B (en) | Low-carbon olefin cracking equipment and cracking method | |
| CN106631661B (en) | Steam cracking method | |
| CN111019689B (en) | Low-carbon olefin cracking equipment and cracking method | |
| CN111019690B (en) | Low-carbon olefin cracking equipment and cracking method | |
| JPS6338888A (en) | Heat exchanger, method of forming heat exchanger and hydrocarbon decomposing furnace including said heat exchanger | |
| CN106635125B (en) | A kind of steam cracking method | |
| CN212375196U (en) | Ethylene cracking furnace for light raw materials of DU-type furnace tube | |
| CN205473600U (en) | Light raw materials ethylene cracking furnace | |
| CN106635123B (en) | Using the pyrolysis furnace of the multi-way boiler tube of oxygen-enriched combusting | |
| CN106631662A (en) | Steam cracking method | |
| CN117965192A (en) | Cracking process | |
| CN106635126B (en) | A kind of steam cracking method |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |