Method for decoking a steam cracking furnace

Abstract

The present application relates to a method for decoking a steam cracking furnace. The method for decoking a steam cracking furnace of the present application comprises the following steps: 1) subjecting a heavy hydrocarbon to gas-liquid separation in a gas-liquid separation device to obtain a gas phase material and a liquid phase material, and depositing residues on the inner wall of the gas-liquid separation device, 2) feeding the gas phase material into a radiant section tube of a steam cracking furnace for pyrolysis to produce pyrolysis products containing ethylene and depositing coke on the inner wall of the radiant section tube; 3) feeding air and / or steam through the radiant section tube to remove at least a portion of the coke to obtain a decoking tail gas, 4) subjecting the decoking tail gas to combustion treatment by entering the furnace chamber via at least one burner arranged in the furnace chamber of the steam cracking furnace. The present application can effectively solve the problem of decoking the gas-liquid separation device of the heavy hydrocarbon cracking furnace.

Description

Technical Field

[0001] This invention relates to the field of steam pyrolysis technology. More specifically, this invention relates to a coking method for a steam pyrolysis furnace. Background Technology

[0002] With economic development, the demand for hydrocarbon chemical raw materials is increasing daily, and ethylene, as an important chemical raw material, is seeing its application market continuously expand. Hydrocarbon cracking to produce ethylene is currently the mainstream process for ethylene production in the market.

[0003] During the operation of a cracking furnace, when hydrocarbons undergo high-temperature thermal cracking, catalytic coking, free radical coking, and condensation coking occur on the inner surface of the furnace tubes in the radiant section. Secondary reaction coking and condensation coking occur on the inner surface of the quench heat exchanger. The resulting coke adheres to the inner walls of the radiant section furnace tubes and the quench heat exchanger, increasing thermal resistance and raising the wall temperature of the radiant section furnace tubes and the outlet temperature of the cracked gas from the quench heat exchanger. Therefore, to prevent overheating, it is necessary to periodically burn off the coke generated in the radiant section furnace tubes. The burn-off gas produced includes carbon oxides, water vapor, and residual coke particles. The temperature of the burn-off gas from the cracking furnace is relatively high, generally in the range of 200-500℃.

[0004] For cracking furnaces containing high-boiling-point heavy hydrocarbon feedstocks, the currently disclosed method is to first preheat the feedstock, then separate the unsuitable materials for cracking using a gas-liquid separation device, and send the suitable materials to the cracking furnace for cracking. During this process, the gas-liquid separation system is also prone to generating residual oil and coke, causing significant pressure drop resistance and affecting the normal operation of the cracking furnace.

[0005] Currently, there are two main publicly disclosed destinations for the coking exhaust gas from conventional feedstock pyrolysis furnaces: Option 1 involves separating the coking particles in a coking cleaning tank before venting it into the atmosphere; Option 2 involves returning it to a separately located coking port at the bottom of the furnace for combustion. Figure 1 As shown. The inventors of this invention discovered that Scheme 1, relying solely on simple physical separation, is insufficient to meet environmental protection requirements. The inventors also discovered that Scheme 2 suffers from incomplete combustion of coke particles in the furnace due to insufficient combustion of the coking gas, leading to accumulation at the furnace bottom. Some coke particles are carried into the convection section, causing ash accumulation and impairing heat transfer. Furthermore, due to the limited space at the furnace bottom, the newly added coking ports can only be located between the burner and the furnace tubes, resulting in the impact of backflow steam on the radiant furnace tubes, such as scouring and damage from water carried by the backflow steam. Additionally, the large diameter of the branch pipelines makes the arrangement of the backflow coking pipelines difficult. Existing technologies suffer from a limited number of backflow coking gas ports, uneven furnace temperature, and poor coking effect.

[0006] CN102227488B discloses a method for removing coke from a gas-liquid separation device for heavy hydrocarbon feedstock cracking furnaces. The method involves passing a mixture of steam and air into the gas-liquid separation device for combustion, and then returning the coke residue after combustion to the furnace through a decoking circulation pipe between the burners of the cracking furnace. Summary of the Invention

[0007] The purpose of this invention is to propose a new comprehensive treatment system and method for coke tail gas from a wide-range heavy hydrocarbon cracking furnace, taking into account the characteristics of cracking and coking in the furnace.

[0008] According to a first aspect of the present invention, a method for coking in a steam cracking furnace is provided, comprising the following steps: 1) performing gas-liquid separation of heavy hydrocarbons in a gas-liquid separation device to obtain gaseous and liquid phase materials, and depositing residue on the inner wall of the gas-liquid separation device; 2) conveying the gaseous material to the radiant section furnace tube of the steam cracking furnace for pyrolysis to produce pyrolysis products containing ethylene and depositing coke on the inner wall of the radiant section furnace tube; 3) conveying air and / or steam through the radiant section furnace tube to remove at least a portion of the coke, obtaining coking tail gas; 4) allowing the coking tail gas to enter the furnace via at least one burner disposed in the furnace of the steam cracking furnace for combustion treatment.

[0009] According to a preferred embodiment of the present invention, the coking method further includes the following steps: A) passing steam through the gas-liquid separation device to remove at least a portion of the residue and obtain mixed steam; B) passing the mixed steam through the radiant section furnace tube to remove at least a portion of the coke and obtain the coking tail gas.

[0010] Technical effect

[0011] 1. The inventors of this invention discovered that the coke produced in the furnace tubes during the operation of a heavy hydrocarbon cracking furnace is more porous than that produced from conventional gas or light liquid feedstocks. Therefore, when the coke particles return to the furnace with the coking gas, they do not need to return through a large coking port. Instead, they can return to the burner through a specially designed coking nozzle. The porous texture of the coke particles makes it less likely to cause burner blockage. This returns the coke to the burner, thus solving the problem of the separate airflow impact on the furnace thermal field, burner combustion, and negative pressure fluctuations in the existing cracking furnace coking gas return operation. This reduces the fluctuations in the operating conditions and makes the coking gas distribution in the furnace more uniform, resulting in a significant improvement in the furnace temperature distribution. This ensures that the heating conditions of different groups of radiant furnace tubes in the furnace are consistent, and the coking effect in the furnace tubes is greatly improved.

[0012] 2. This invention addresses the unique gas-liquid separation device in the heavy hydrocarbon cracking furnace process. Before coking, the cracking furnace and the gas-liquid separation device are purged with steam. Before the coking operation, the steam carries the residual hydrocarbons evaporated from the gas-liquid separator into the furnace tubes of the radiant section. The volatile hydrocarbons contained in the mixed steam help to loosen and remove the coke on the furnace tubes, thereby improving the coke removal effect in the furnace tubes during coking.

[0013] 3. The system of this invention can effectively solve the coking problem in the gas-liquid separation unit of a heavy hydrocarbon cracking furnace, and avoid the safety risks of direct contact between coking air and hydrocarbons, preventing equipment damage. Moreover, the system is simple to switch over, does not require emptying the gas-liquid separation system, reduces the workload of operation, and avoids safety hazards caused by misoperation.

[0014] 4. By introducing the charred exhaust gas into the burner, the present invention can reduce the flame temperature of combustion and reduce the oxygen concentration, thereby effectively reducing the amount of NOx generated during combustion.

[0015] 5. Because the number of branch lines of the return furnace pipeline is the same as that of the burners, and the branch lines are connected to the dedicated nozzles for coking exhaust gas installed in the burners, this invention, compared to the prior art (Scheme 2) which sets a separate coking port at the bottom of the furnace, has smaller branch lines of the return furnace pipeline, occupies less space, solves the problem of difficult arrangement of the return furnace coking port and pipeline, and avoids scouring of the furnace tube or damage to the furnace tube due to water carried by the return furnace steam because the coking port is far away from the furnace tube.

[0016] 6. When the coking gas passes through the burner, the limited size of the coking gas nozzle has a certain throttling effect, which can reduce the uneven flow / velocity of each coking port caused by uneven pipeline distribution. This avoids the coking gas returning to the furnace from being cross-contaminated with high-temperature flue gas in local spaces / pipelines due to uneven pressure in the furnace, which could cause pipeline overheating, combustion disorder, etc.

[0017] 7. It offers better combustion of particulate matter in coke oven gas, reducing the requirements for the coke oven. Currently, coke ovens are required to achieve particulate matter levels of 20 mg / Nm³. 3 Emission requirements are quite difficult to meet. The main function of the coke oven is to separate larger particulate matter into cyclones. If it is directly returned to the furnace, for example, 50 mg / Nm³, the emissions will be significantly higher. 3 Because particulate matter does not directly contact the combustion flame inside the furnace, combustion is inefficient, leading to excessive particulate matter levels at the pyrolysis furnace chimney outlet (ultimately exceeding 20 mg / Nm³). 3 The burner can improve the burning effect of particulate matter, which can reduce the requirements of the burning tank and prevent unburned particles from being carried to the convection section, causing ash accumulation on the fins or remaining at the bottom of the furnace, thus affecting the flue gas circulation.

[0018] 8. For wide-range crude oil cracking, the coke formed by the cracking reaction has different characteristics than that formed by conventional feedstock (ethane, LPG, NAP, etc.) cracking. Crude oil light components have a wider distillation range, resulting in coke particles with larger diameters, greater looseness, and lower hardness. Larger particles benefit from better cyclone separation in the coke removal tank, where most are captured, preventing them from returning to the burner and clogging the burner nozzles and the coke burner nozzles in the furnace. In contrast, coke particles from conventional feedstock cracking are smaller, resulting in poor separation in the coke removal tank. Many small coke particles return to the furnace with the coke combustion gas and cannot be directly introduced into the burner, clogging the burner nozzles and the coke combustion gas nozzles. This invention proposes a new approach based on the characteristics of coke produced by direct crude oil cracking and the characteristics of coke particles returning to the furnace, which can improve the coke combustion effect. Attached Figure Description

[0019] Figure 1 The diagram shows an overall schematic of the return furnace bottom with a separate coking port as described in Scheme 2 in the background section of this invention.

[0020] Figure 2 A detailed schematic diagram of the return furnace bottom separately set with a coking port is shown in Scheme 2 mentioned in the background art of the present invention.

[0021] Figure 3 A schematic diagram of the subsequent connection structure of the coke tail gas pipeline of a comprehensive treatment system for coke tail gas from a heavy hydrocarbon cracking furnace according to the present invention is shown.

[0022] Figure 4 A schematic diagram of the subsequent connection structure of the coke tail gas pipeline of a comprehensive treatment system for coke tail gas from a heavy hydrocarbon cracking furnace according to the present invention is shown.

[0023] Figure 5 A top view of the subsequent connection structure of the coke tail gas pipeline of a comprehensive treatment system for coke tail gas from a heavy hydrocarbon cracking furnace according to the present invention is shown.

[0024] Figure 6 A schematic diagram of the burner of a comprehensive treatment system for coke tail gas from a heavy hydrocarbon cracking furnace provided by the present invention is shown.

[0025] Figure 7 A schematic diagram of a comprehensive treatment system for coke tail gas from a heavy hydrocarbon cracking furnace provided by the present invention is shown.

[0026] The annotations in the attached figures are explained as follows:

[0027] 1-Coking exhaust gas pipeline, 2-Coking removal tank, 3-Main pipeline, 4.1-Bottom burner,

[0028] 4.2-Side wall burner, 5-Furnace chamber of pyrolysis furnace radiant section, 6-Branch pipeline, 7-Coking port of return furnace;

[0029] 8-Quick cooling heat exchanger, 10-Upper heavy hydrocarbon preheating section, 11-Primary dilution steam superheating section, 12-Secondary dilution steam superheating section, 13-Lower superheating section, 14-Gas-liquid separation device, 15-Pyrolysis furnace radiation section;

[0030] 16-Heavy hydrocarbon feed line, 17-Air feed line, A-First valve, B-Second valve, 18-Inlet of gas-liquid separator, 19-Gas phase outlet of gas-liquid separator, 20-Liquid phase outlet of gas-liquid separator, 21-Primary dilution steam feed line, 22-Secondary dilution steam feed line, 23-Coking tail gas, 24-Cracked gas. Detailed Implementation

[0031] The specific embodiments of the present invention will be described in detail below. However, it should be noted that the scope of protection of the present invention is not limited to these specific embodiments, but is determined by the claims in the appendix.

[0032] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0033] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application’s filing, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0034] In the context of this invention, all numerical values ​​of parameters (e.g., quantity or condition) should be understood to be modified by the term “about” in all cases, regardless of whether “about” actually appears before the numerical value.

[0035] In the context of this invention, "substantially" means that deviations that are acceptable or reasonable to those skilled in the art are permitted, such as deviations within ±2%, ±1%, ±0.5%, or ±0.1%.

[0036] In the context of this invention, terms such as "primary dilution steam" and "secondary dilution steam" are used only to distinguish the steam introduced in different steps and do not contain any actual meaning such as the properties of the steam itself.

[0037] In the context of this invention, unless otherwise specified, the various devices used in this invention may use structures conventionally chosen in the art, and there are no particular limitations.

[0038] In the context of this invention, heavy hydrocarbons refer to a wide-range mixture of hydrocarbons with a final boiling point generally above 540°C, for example, an initial boiling point of 15°C and a final boiling point of around 750°C. Specifically, the heavy hydrocarbons can be selected from one or more of the following raw materials: paraffinic crude oil, intermediate-based crude oil, naphthenic crude oil, condensate, and refined products. Here, refined products can be exemplified by gasoline, kerosene, diesel, tail oil, fuel oil, and reformate produced by refineries through atmospheric and vacuum distillation, reforming, catalytic cracking, and coking units.

[0039] In the context of this invention, the method for measuring the initial boiling point, final boiling point, and boiling range is atmospheric and vacuum distillation of crude oil, wherein the atmospheric distillation analysis method adopts ASTM D-2892, and the vacuum distillation analysis method adopts ASTM D-5236.

[0040] In the context of this invention, AP I refers to the specific gravity index, and its analysis method adopts ASTM D-2320.

[0041] In the context of this invention, the method for measuring the solid particle content is the light scattering method.

[0042] In the context of this invention, the average particle size is measured by laser scattering.

[0043] In the context of this invention, vaporization rate refers to the mass percentage of gaseous material (excluding steam) to the total feed volume (excluding steam).

[0044] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this instruction manual are based on weight, and the pressure is gauge pressure.

[0045] In the context of this invention, any two or more embodiments or aspects of this invention can be arbitrarily combined, and the resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of this invention.

[0046] According to one embodiment of the present invention, a coking method for a steam pyrolysis furnace is provided.

[0047] During the operation of the cracking furnace, when hydrocarbons undergo high-temperature thermal cracking, catalytic coking, free radical coking, and condensation coking occur on the inner surface of the furnace tubes in the radiant section of the cracking furnace. Secondary reaction coking and condensation coking occur on the inner surface of the quench heat exchanger. The resulting coke adheres to the inner walls of the radiant section furnace tubes and the quench heat exchanger. The coke buildup increases the thermal resistance, causing the wall temperature of the radiant section furnace tubes to rise and the temperature of the cracked gas at the outlet of the quench heat exchanger to rise. Therefore, to avoid overheating, it is necessary to periodically burn off the coke generated in the radiant section furnace tubes and other parts.

[0048] According to one embodiment of the present invention, the coking method includes step 1): separating heavy hydrocarbons into gas and liquid phases in a gas-liquid separator to obtain gaseous and liquid phase materials, and depositing residue on the inner wall of the gas-liquid separator. The inventors of the present invention have discovered that the main component of the residue is carbon, including coke and volatile hydrocarbons. The coke has a low hydrogen content and also contains small amounts of sulfur, nitrogen, and inorganic salts. Microscopically, the coke is composed of countless tiny spherical particles of different diameters. Due to the large flow area of ​​the gas-liquid separator, some residual volatile hydrocarbons in the gas-liquid separator are swept to the radiant furnace tubes by steam. The volatile hydrocarbons introduced by the gas-liquid separator loosen and dissolve the coke layer deposited on the furnace tubes, which facilitates subsequent coking and coke removal in the furnace tubes.

[0049] According to one embodiment of the present invention, the final boiling point temperature of the heavy hydrocarbon is 540°C or higher (preferably an initial boiling point temperature of 15°C and a final boiling point temperature of 750°C or higher). Preferably, the API value of the heavy hydrocarbon is not less than 32 (preferably 38 or higher). As an example, the heavy hydrocarbon is selected from at least one of paraffinic crude oil, intermediate-based crude oil, naphthenic crude oil, condensate, and refined products.

[0050] According to one embodiment of the invention, the heavy hydrocarbons are heated to a temperature of 100-400°C (preferably 200-370°C) before the gas-liquid separation. According to the invention, the heating can be carried out in any manner conventionally known in the art, but is generally achieved in the convection section of a cracking furnace.

[0051] According to one embodiment of the present invention, the gas-liquid separation device is not particularly limited and can be any type of gas-liquid separation device conventionally known in the art. Furthermore, the present invention does not particularly limit the operating conditions of the gas-liquid separation, but as an example, the operating temperature is generally 260-360°C, the operating pressure is generally 0.2-0.7 MPaG, and the vaporization rate is generally 50-80%.

[0052] According to one embodiment of the present invention, the coking method includes step 2): conveying the gaseous material to the radiant section of the steam cracking furnace tube for pyrolysis to produce pyrolysis products containing ethylene and depositing coke on the inner wall of the radiant section of the furnace tube. The inventors of this invention have discovered that catalytic coking on the furnace tube forms filamentous coke, while free radical coking or gas-phase coking forms tar droplets or coke particles that uniformly adhere to the surface of the furnace tube, eventually forming a stable coking layer, which thickens with increasing operating time. Coking increases the thermal resistance of the furnace tube wall, reduces the heat transfer coefficient, leads to an increase in the temperature of the outer wall of the furnace tube, and causes localized overheating, which shortens the service life of the furnace tube.

[0053] According to the present invention, there are no limitations on the specific structure of the pyrolysis furnace and the radiant section furnace tube, or on the operating conditions of the pyrolysis; conventional content in the field of steam pyrolysis technology can be directly applied. For example, the operating temperature of the pyrolysis is generally 800-900℃, and the operating pressure is generally 0.06-0.15 MPaG.

[0054] According to one embodiment of the present invention, the coking method includes step 3): passing air and / or steam through the radiant furnace tubes to remove at least a portion of the coke (referred to as coking scheme one), thereby obtaining coking exhaust gas. Here, the air and steam can be used separately or in combination. When used in combination, the ratio of air to steam can be selected within a range conventionally known in the art, and is not particularly limited.

[0055] According to one embodiment of the invention, the pyrolysis products are cooled, preferably to 400-600°C via a quench heat exchanger. According to the invention, since the pyrolysis products are transported through the quench heat exchanger, coke deposition also occurs in the quench heat exchanger. Therefore, the coking method of the invention also includes a coking process in the quench heat exchanger, for example, by step 3), sequentially supplying air and / or steam through the radiant furnace tubes and the quench heat exchanger to remove at least a portion of the coke (referred to as coking scheme two), thereby obtaining the coking exhaust gas.

[0056] According to one embodiment of the present invention, in step 3), for the purpose of coking, the temperature of the air is 500-650°C, the pressure is 0.2-0.4 MPaG, and the inlet linear velocity is 30-80 m / s. Additionally, for the purpose of coking, the temperature of the steam is 500-650°C, the pressure is 0.2-0.4 MPaG, and the inlet linear velocity is 30-80 m / s. According to the present invention, the air and steam can achieve these operating conditions by any means conventionally known in the art, such as heating to the required temperature, particularly through the convection section of the pyrolysis furnace or a separately installed preheater, without particular limitation. Furthermore, the inlet linear velocity refers to the linear velocity of the air or steam at the inlet of the radiant section furnace tube. The inventors of the present invention have found that if the temperature of the air or steam is too low, the starting temperature of the coking reaction will not be reached, the coking effect will not be achieved, the coking time will be prolonged, and more fuel will be consumed. Conversely, if the temperature of the air or steam is too high, it can easily lead to localized hot spots, causing overheating and damage to the furnace tube. The inventors of this invention have also discovered that if the inlet linear velocity of the air or steam is too low, the distribution of air or steam in different groups of furnace tubes will be uneven, resulting in temperature deviations between furnace tubes and causing some furnace tubes to overheat. If the inlet linear velocity of the air or steam is too high, the pressure drop inside the furnace tubes will be too large, significantly increasing the overall operating cost of the system and also causing flow deviation in the furnace tubes.

[0057] According to one embodiment of the present invention, before step 3) begins, the feeding of the gaseous material to the radiant section furnace tube is stopped, i.e., the operation of step 2) is stopped. Therefore, according to this embodiment of the present invention, pyrolysis and coking are two independent steps, not performed simultaneously.

[0058] According to one embodiment of the present invention, the coking method further includes step A): passing steam through the gas-liquid separator to remove at least a portion of the residue, thereby obtaining mixed steam. The inventors of the present invention have discovered that if air is supplied to the gas-liquid separator, the air will react with residual hydrocarbons within the separator in a deflagration, posing a safety hazard. The inventors of the present invention have also discovered that by supplying steam to the gas-liquid separator, the purging effect of the steam causes at least a portion of the residue (mainly volatile hydrocarbons) to vaporize and be entrained by the steam, forming a mixture of the steam and the volatile hydrocarbons, i.e., the mixed steam.

[0059] According to one embodiment of the present invention, the temperature of the steam is 500-650°C, the pressure is 0.2-0.4 MPaG, and the inlet linear velocity is 30-80 m / s. Here, the inlet linear velocity refers to the linear velocity of the steam at the steam inlet of the gas-liquid separator. The inventors of the present invention have found that if the steam temperature is too low, the steam purging effect deteriorates, increasing the purging time and operating costs. Conversely, if the steam temperature is too high, it leads to localized overheating of the equipment, posing a safety hazard. The inventors of the present invention have also found that if the inlet linear velocity of the steam is too low, the purging effect deteriorates, failing to effectively remove residual oil from the pipelines before and after the gas-liquid separator. Conversely, if the inlet linear velocity of the steam is too high, the system pressure drop is excessive, increasing operating costs, and the excessively high flow rate can cause pipeline vibration, easily leading to safety hazards.

[0060] According to one embodiment of the present invention, the temperature of the mixed steam is 250-400°C, the pressure is 0.2-0.4 MPaG, and the outlet linear velocity is 25-40 m / s. Here, the outlet linear velocity refers to the linear velocity of the mixed steam leaving the gas-liquid separator or the linear velocity of the mixed steam at the inlet of the radiant furnace tube. The inventors of the present invention have found that if the temperature of the mixed steam is too low, the temperature of the mixed steam entering the radiant section will be low, affecting the coking effect of the furnace tube; while if the temperature of the mixed steam is too high, it can easily cause overheating of pipelines or equipment. The inventors of the present invention have also found that if the outlet linear velocity of the mixed steam is too low, it affects the uniformity of the mixed steam distribution within the furnace tube; while if the outlet linear velocity of the mixed steam is too high, it will cause excessive system pressure drop, increasing operating costs.

[0061] According to one embodiment of the present invention, the coking method further includes step B): conveying the mixed steam through the radiant furnace tubes to remove at least a portion of the coke (referred to as coking scheme three), thereby obtaining coking tail gas. As mentioned above, the inventors of the present invention have discovered that, since the mixed steam contains volatile hydrocarbons, which include some hydrocarbons with a final boiling point above 540°C and residues remaining on the gas-liquid separator, the main component of the residues is carbon, including coke and volatile hydrocarbons. The coke has a low hydrogen content and also contains small amounts of sulfur, nitrogen, and inorganic salts. Microscopically, the coke is composed of countless tiny spherical particles of different diameters. Due to the large flow area of ​​the gas-liquid separator itself, some of the residual volatile hydrocarbons in the gas-liquid separator will be swept to the radiant furnace tubes along with the steam. The volatile hydrocarbons introduced by the gas-liquid separator cause the coke layer deposited on the furnace tubes to loosen and dissolve, which helps in the subsequent coking and coke removal in the furnace tubes.

[0062] According to one embodiment of the present invention, before step A) begins, the supply of the heavy hydrocarbons to the gas-liquid separation device is stopped, i.e., the operation of step 1) is stopped. Therefore, according to this embodiment of the present invention, gas-liquid separation and coking are two independent steps, not performed simultaneously.

[0063] According to one embodiment of the present invention, after step B) is completed, step 3) begins, that is, the mixed steam is first conveyed through the radiant section furnace tubes to remove at least a portion of the coke (referred to as coking scheme four) to obtain coking tail gas, and then air or a mixture of steam and air is conveyed through the radiant section furnace tubes to remove at least a portion of the coke to obtain coking tail gas. The inventors of the present invention have discovered that, in order to effectively prevent air from entering the gas-liquid separator, steps B) and 3) cannot be performed simultaneously, but must be performed sequentially. Steam purging must be performed first to clean the residual hydrocarbons in the convection section furnace tubes and pipelines, and the gas-liquid separator must be disconnected from the system before air is introduced; otherwise, air encountering residual hydrocarbons that have not been purged from the pipelines will cause deflagration, posing a safety hazard.

[0064] According to one embodiment of the present invention, the coking method includes step 4): allowing the coking exhaust gas to enter the furnace via at least one burner (referred to as a coking burner) disposed within the furnace of the steam cracking furnace for combustion treatment. In the context of this invention, any exhaust gas obtained from coking is collectively referred to as coking exhaust gas, without distinguishing between specific coking methods.

[0065] According to one embodiment of the present invention, there are no particular limitations on the operating conditions of the combustion treatment, and conventionally known content in the art can be directly applied. However, as an example, the operating temperature between the coke gas return burners is 300-400°C and the operating pressure is 0.01-0.1 MPaG.

[0066] According to one embodiment of the present invention, the structure of the coking burner is not particularly limited, as long as it has a coking exhaust gas passage through which the coking exhaust gas enters the furnace. Preferably, the coking burner includes a central channel and one or more annular channels arranged around the central channel. More preferably, from the perspective of effectively preventing channel blockage and ensuring complete combustion, the central channel is the coking exhaust gas passage, the annular channel arranged immediately outside the central channel is the air passage, and the annular channel arranged immediately outside the air passage is the fuel passage. The inventors of the present invention have found that a burner with this specific structure is particularly suitable for use as the coking burner of the present invention.

[0067] According to one embodiment of the present invention, in step 4), the coking exhaust gas is transported through a main coking exhaust gas pipeline, and then through multiple branch pipelines provided on the main coking exhaust gas pipeline to the coking burner. Generally, the number of branch pipelines is the same as the number of coking burners, thereby ensuring that one branch pipeline corresponds to one coking burner. According to the present invention, depending on the specific coking scheme, the main coking exhaust gas pipeline can be connected to the outlet of the radiant section furnace tube or the outlet of the quench heat exchanger, without particular limitation.

[0068] According to one embodiment of the invention, in step 4), the coking burner is arranged at the bottom and / or sidewall of the furnace, preferably simultaneously at the bottom and sidewall of the furnace. Furthermore, according to the invention, there is no particular limitation on the number of the coking burners, but it is generally 20-100% of the total number of all burners arranged in the furnace, preferably 50-100% or 100%.

[0069] According to one embodiment of the invention, the coking exhaust gas supplied to the coking burner located at the bottom of the furnace accounts for 50-100 wt% (preferably 65-85 wt%) of the total mass of the coking exhaust gas, and the coking exhaust gas supplied to the coking burners located on the sidewalls of the furnace accounts for 0-50 wt% (preferably 15-35 wt%) of the total mass of the coking exhaust gas. The inventors of the invention have found that the load on the sidewall burners typically accounts for 10%-30% of the total combustion load, therefore the amount of coking exhaust gas entering the sidewall burners is comparable to this load.

[0070] According to one embodiment of the present invention, in step 4), the total mass flow rate of the coking exhaust gas is 40t / hr-120t / h. In this case, the inner diameter of the main coking exhaust gas pipeline is generally 250-800mm.

[0071] According to one embodiment of the present invention, in step 4), at least a portion of solid particles are separated from the coking exhaust gas to obtain purified exhaust gas, which is then introduced into the furnace via the at least one coking burner for combustion treatment. According to the present invention, the separation can be performed using any gas-solid separation method conventionally known in the art, without particular limitation. As an example, the separation is carried out in a coking cleaning tank (preferably a cyclone-type coking cleaning tank). In this case, the main coking exhaust gas pipeline can be connected to the outlet of the coking cleaning tank.

[0072] According to one embodiment of the present invention, the gas-solid separation process ensures that the particulate matter content of the purified exhaust gas is less than 50 mg / Nm³. 3 Preferably less than 20 mg / Nm 3The total weight of the purified exhaust gas is 100 wt%. Preferably, the average particle size of the solid particles contained in the purified exhaust gas is 1 μm-20 mm (preferably less than 10 mm). The inventors of this invention have discovered that this invention has a better combustion effect on particles in coking gas and can reduce the requirements for coking canisters. Currently, coking canisters need to achieve a particulate matter concentration of 20 mg / Nm³. 3 Emission requirements are quite difficult to meet. The main function of the coke oven is to separate larger particulate matter into cyclones. If it is directly returned to the furnace, for example, 50 mg / Nm³, the emissions will be significantly higher. 3 Because particulate matter does not directly contact the combustion flame inside the furnace, combustion is inefficient, leading to excessive particulate matter levels at the pyrolysis furnace chimney outlet (ultimately exceeding 20 mg / Nm³). 3 The burner can improve the burning effect of particulate matter, which can reduce the requirements of the burning tank and prevent unburned particles from being carried to the convection section, causing ash accumulation on the fins or remaining at the bottom of the furnace, thus affecting the flue gas circulation.

[0073] The present invention will be described in more detail below using the integrated treatment system for coke tail gas from a heavy hydrocarbon cracking furnace as an example, but the present invention is not limited thereto.

[0074] According to one embodiment of the present invention, the integrated treatment system for coke tail gas from a heavy hydrocarbon cracking furnace includes a cracking furnace convection section, a gas-liquid separation device, a first valve, a second valve, a cracking furnace radiant section, a burner, a quench heat exchanger, a coke tail gas pipeline, a return furnace pipeline, and optionally a coke cleaning tank.

[0075] According to one embodiment of the present invention, the convection section of the pyrolysis furnace includes at least an upper heavy hydrocarbon preheating section, a dilution steam superheating section, and a lower superheating section; the inlet of the upper heavy hydrocarbon preheating section is connected to a heavy hydrocarbon feed pipeline; the inlet of the dilution steam superheating section is connected to a dilution steam feed pipeline, and optionally to an air feed pipeline; the outlet of the dilution steam superheating section is respectively connected to a first valve and a second valve; the first valve is connected to the inlet of the lower superheating section in sequence through the inlet of the gas-liquid separator and the gas phase outlet of the gas-liquid separator; the second valve is directly connected to the inlet of the lower superheating section.

[0076] According to one embodiment of the present invention, the outlet of the lower superheated section is sequentially connected to the coking gas inlet at one end of the coking gas pipeline via the pyrolysis furnace radiant section, the quench heat exchanger, and the coking gas inlet.

[0077] According to one embodiment of the present invention, the other end of the coking exhaust gas pipeline, the return furnace pipeline, and the burner through which the coking exhaust gas is introduced are connected in sequence; or, the other end of the coking exhaust gas pipeline, the coking cleaning tank, the return furnace pipeline, and the burner through which the coking exhaust gas is introduced are connected in sequence.

[0078] According to one embodiment of the present invention, there are multiple burners arranged at the bottom and / or sidewalls of the furnace chamber in the radiant section of the pyrolysis furnace.

[0079] According to one embodiment of the present invention, preferably, the dilution steam superheating section includes a primary dilution steam superheating section and a secondary dilution steam superheating section; the inlet of the primary dilution steam superheating section is connected to a primary dilution steam feed line, and optionally to an air feed line; the inlet of the secondary dilution steam superheating section is connected to a secondary dilution steam feed line.

[0080] According to one embodiment of the present invention, the outlet of the primary dilution steam superheating section is connected to the first valve and the second valve respectively.

[0081] According to one embodiment of the present invention, the outlet of the secondary dilution steam superheating section is connected to the first valve and the second valve respectively.

[0082] According to one embodiment of the present invention, the liquid phase outlet of the gas-liquid separation device is connected to the outside.

[0083] According to one embodiment of the present invention, the return furnace pipeline includes multiple main pipelines, and each main pipeline is divided into multiple branch pipelines.

[0084] According to one embodiment of the present invention, each burner that receives coke exhaust gas is connected to a branch pipeline, and the branch pipeline is connected to the main pipeline.

[0085] According to one embodiment of the present invention, the coke removal tank is a cyclone-type coke removal tank.

[0086] According to one embodiment of the present invention, each burner that supplies coke exhaust gas is provided with a plurality of nozzles, wherein at least one nozzle is connected only to the branch line.

[0087] According to one embodiment of the present invention, the number of burners that introduce coke exhaust gas accounts for 20-100% of the total number of burners in the system, preferably 50-100%.

[0088] According to one embodiment of the present invention, a burner for introducing coke exhaust gas is arranged at the bottom and / or sidewall of the radiant section of the pyrolysis furnace.

[0089] The comprehensive treatment method for coke tail gas from a heavy hydrocarbon cracking furnace according to the present invention, using the aforementioned system, includes the following steps:

[0090] S1: Steam is fed into the convection section of the pyrolysis furnace for heating, and the resulting heated steam is then fed into the gas-liquid separator through the first valve. The heated steam mixes with the residual hydrocarbons within the gas-liquid separator, and the resulting mixture is fed into the inlet of the lower superheated section through the gas phase outlet of the gas-liquid separator; or...

[0091] Steam and optionally air are fed into the convection section of the pyrolysis furnace for heating, and heated gas is fed into the inlet of the lower superheated section through the second valve;

[0092] S2: The mixture or heating gas is sequentially heated in the lower superheating section and coked in the radiant section of the pyrolysis furnace to obtain coking tail gas;

[0093] S3: The coking exhaust gas is sequentially fed through the quench heat exchanger, the coking exhaust gas pipeline, and the return furnace pipeline into the burners located at the bottom and / or sidewalls of the furnace in the radiant section of the pyrolysis furnace for combustion treatment; or,

[0094] The coking exhaust gas is sent to the coking tank for treatment through the quench heat exchanger and the coking exhaust gas pipeline, and then sent from the coking tank to the burner located at the bottom and / or side wall of the furnace in the radiant section of the pyrolysis furnace for combustion treatment through the return furnace pipeline.

[0095] According to one embodiment of the present invention, the residual hydrocarbon is residual oil and coke produced by gas-liquid separation of the heavy hydrocarbon.

[0096] According to one embodiment of the present invention, the final boiling point of the heavy hydrocarbon is above 540°C.

[0097] According to one embodiment of the present invention, the steam includes steam fed from the primary dilution steam superheater section and / or steam fed from the secondary dilution steam superheater section.

[0098] According to one embodiment of the present invention, the coking exhaust gas includes at least one of steam, carbon oxides, air and coke powder.

[0099] According to one embodiment of the present invention, the gas flow rate in the return furnace pipeline is 120-2500 kg / h, preferably 300-1000 kg / h.

[0100] According to one embodiment of the present invention, the mass flow rate of the coking exhaust gas fed into the burners located at the bottom of the furnace in the radiant section of the pyrolysis furnace is 50-100% of the total mass flow rate of the coking exhaust gas, preferably 65%-85%; the mass flow rate of the coking exhaust gas fed into the burners located on the side walls of the furnace in the radiant section of the pyrolysis furnace is 0-50% of the total mass flow rate of the coking exhaust gas, preferably 15%-35%. In this invention, as a preferred embodiment, the gas flow rate in the branch lines connected to each bottom burner is the same; the gas flow rate in the branch lines connected to each side wall burner is the same.

[0101] The present invention will be further described below with reference to the accompanying drawings, but the present invention is not limited thereto.

[0102] The integrated treatment system for pyrolysis furnace coke tail gas according to the present invention, such as Figure 3 As shown. The system includes a coke burner tail gas pipeline 1, a return furnace pipeline, burners, a radiant section furnace 5 of the pyrolysis furnace, and a coke cleaning tank 2; the radiant section furnace 5 of the pyrolysis furnace is a bottom + sidewall combined heating system; one end of the coke burner tail gas pipeline 1 is the inlet of the coke burner tail gas; the other end of the coke burner tail gas pipeline 1, the coke cleaning tank 2, the return furnace pipeline, and the burners that supply the coke burner tail gas are connected in sequence; there are multiple burners that supply the coke burner tail gas. The return furnace pipeline includes multiple main pipelines 3, each main pipeline 3 is divided into multiple branch pipelines 6; each burner that supplies the coke burner tail gas is connected to a corresponding branch pipeline 6, and is connected to the main pipeline 3 through the branch pipeline 6. Each burner that supplies the coke burner tail gas is equipped with multiple nozzles, such as... Figure 6 As shown, one of the nozzles is connected only to the branch pipeline 6. The coke cleaning tank 2 is a cyclone type coke cleaning tank.

[0103] According to the present invention, the comprehensive treatment method of coking tail gas from pyrolysis furnace using the above-described system includes the following steps: the coking tail gas generated by coking in the pyrolysis furnace is sent to the coking tail gas pipeline 1 into the coking cleaning tank 2 for preliminary separation treatment, and then sent from the coking cleaning tank 2 into the burners located at the bottom and side walls of the furnace 5 in the radiant section of the pyrolysis furnace for combustion treatment via the return furnace pipeline.

[0104] Another integrated treatment system for coke exhaust gas from a pyrolysis furnace according to the present invention, such as Figure 4 , 5As shown, the system includes a coke exhaust gas pipeline 1, a return furnace pipeline, burners, and a radiant section furnace 5 of the pyrolysis furnace; the radiant section furnace 5 of the pyrolysis furnace is the entire bottom heating system; one end of the coke exhaust gas pipeline 1 is the inlet for the coke exhaust gas; the other end of the coke exhaust gas pipeline 1, the return furnace pipeline, and the burners that supply the coke exhaust gas are connected in sequence; there are multiple burners that supply the coke exhaust gas. The return furnace pipeline includes multiple main pipelines 3, each main pipeline 3 is divided into multiple branch pipelines 6; each burner is connected to a corresponding branch pipeline 6, and is connected to the main pipeline 3 through the branch pipeline 6. Each burner that supplies the coke exhaust gas is equipped with multiple nozzles, such as... Figure 6 As shown, one of the nozzles is connected only to the branch line 6.

[0105] According to the present invention, the comprehensive treatment method of coking tail gas from pyrolysis furnace using the above system includes the following steps: the coking tail gas generated by coking in the pyrolysis furnace is sequentially sent to the burner 4.1 at the bottom of the furnace 5 in the radiant section of the pyrolysis furnace through the coking tail gas pipeline 1 and the return furnace pipeline for combustion treatment.

[0106] Example

[0107] The present invention will be further described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0108] All raw materials used in the examples and comparative examples were obtained through commercial purchases.

[0109] The comparative indicators in the examples and comparative examples are the coking time, particulate matter emission concentration in flue gas, NOx emission index in flue gas, deviation of furnace tube outlet temperature (COT) during coking, annual online operation time of the pyrolysis furnace, equipment maintenance cost, and economic loss cost.

[0110] The coking time refers to the total time from the start to the end of a single coking operation in the pyrolysis furnace.

[0111] The NOx emission index in the flue gas is measured using a chemiluminescence online monitoring method.

[0112] The coking tube COT deviation during coking refers to the absolute value of the deviation of the outlet temperature of the radiant section furnace tube, which is detected by a furnace tube surface thermometer.

[0113] The total online operating time of the pyrolysis furnace throughout the year refers to the total time the pyrolysis furnace is in operation during the feeding period.

[0114] The equipment maintenance cost is based on the one-time replacement purchase cost of the equipment.

[0115] The economic loss fee is calculated based on the average market price of high value-added products over the past three years.

[0116] Example 1

[0117] Heavy hydrocarbons are used as feedstock for steam cracking in the cracking furnace. The heavy hydrocarbons are a wide-range crude oil, specifically a low-sulfur paraffin-based crude oil with an API value of 44. The initial boiling point of the heavy hydrocarbons is 15°C, and the final boiling point is 800°C.

[0118] like Figure 7 As shown, the system includes a cracking furnace, a gas-liquid separation device (14), a coke cleaning tank (2), and a quench heat exchanger (8). The cracking furnace includes a heavy hydrocarbon preheating section (10), an upper mixing superheating section (11), a dilution steam superheating section (12), a lower mixing superheating section (13), a radiant section furnace tube (15), a primary dilution steam feed line (21), a secondary dilution steam feed line (22), and an air feed line (17).

[0119] In the cracking furnace operation mode, the heavy hydrocarbon first enters the upper heavy hydrocarbon preheating section (10) of the cracking furnace for preheating, and the feed rate of the heavy hydrocarbon is 100 t / h. The temperature of the preheated heavy hydrocarbon is 180℃, and the primary dilution steam is mixed with the heated heavy hydrocarbon through pipeline (21) to obtain mixed hydrocarbon. The flow rate of the primary steam is 20 t / h, the temperature is 200℃, and the temperature of the mixed hydrocarbon is 190℃.

[0120] The mixed hydrocarbons are further preheated in the mixing superheater (11) to a temperature of 250°C. Secondary dilution steam is sent via pipeline (22) to the dilution steam superheater (12) for superheating. The flow rate of the secondary dilution steam is 40 t / h. After being superheated to 500°C, it is mixed with the preheated mixed hydrocarbons to obtain the feed for the gas-liquid separator. The feed temperature of the gas-liquid separator is 320°C. The feed consisting of hydrocarbons and steam is in a two-phase flow form. Gas-liquid separation is performed in the gas-liquid separator to obtain gaseous and liquid phase materials. The operating temperature of the gas-liquid separator is 320°C, the operating pressure is 0.33 MPaG, and the gasification rate is 75% Wt. The gaseous material is then transported to the radiant section of the steam cracking furnace for pyrolysis to produce pyrolysis products containing ethylene and deposit coke on the inner wall of the radiant section furnace tubes. The operating temperature of the pyrolysis is 820°C, and the operating pressure at the outlet of the radiant section furnace tubes is 0.1 MPaG. In this embodiment, the pyrolysis products are cooled in a subsequent quenching system, reaching 420°C at the beginning of the cracking furnace operation and 600°C at the end of the cracking furnace operation before shutdown and coking.

[0121] Because the pyrolysis furnace produces coke in the radiant section furnace tubes and quench heat exchanger during the above-mentioned operation, a coke removal and burning operation is required. In this embodiment, a hot standby preparation mode is performed before burning coke. First, coke is removed, and the dilution steam process is the same as the pyrolysis furnace operation mode, except that the primary dilution steam flow rate is increased to 25 t / h and the secondary dilution steam flow rate is increased to 45 t / h. The primary steam and secondary dilution steam are heated separately in the convection section and then mixed to obtain the feed steam for the gas-liquid separator. The gas-liquid separator removes at least a portion of the residue. The temperature of the primary steam after the secondary steam is superheated is 500°C, and the pressure of the primary dilution steam is 0.25 MPaG with an inlet linear velocity of 40 m / s. The temperature of the mixed steam is 320°C, the pressure is 0.23 MPaG, and the outlet linear velocity is 40 m / s. Some of the residual volatile hydrocarbons in the gas-liquid separator are purged to the radiant section furnace tubes with the steam.

[0122] Steam containing volatile hydrocarbons is further heated in the radiant furnace tubes and used to purge the tubes. At high temperatures, the hydrocarbon-containing steam has a certain dissolving and loosening effect on the coke layer inside the furnace tubes. The outlet temperature of the furnace tubes is approximately 800℃. The purging steam is cooled by a quench heat exchanger and then... Figure 7 The cracked gas main valve TLV and cracked gas pipeline shown are sent to the downstream separation system. After a certain period of purging, it is opened. Figure 7 Valve B shown is closed. Figure 7 Valve A, as shown, isolates the gas-liquid separator system from the pyrolysis furnace system. Simultaneously, it closes the pyrolysis gas main valve (TLV) and opens the coking gas main valve (DV). At this time, the pyrolysis furnace enters the coking mode. As previously described, the pyrolysis furnace quench heat exchanger is connected to the coking gas inlet at one end of the coking gas pipeline, and the other end of the coking gas is connected to a cyclone-type coking tank. The gas then returns to the burner via the return coking gas pipeline.

[0123] When the pyrolysis furnace is in coking mode, coking exhaust gas is obtained by passing air or a mixture of steam and air through the radiant section furnace tubes to remove at least a portion of the coke.

[0124] In this embodiment, the air, after being finally heated in the convection section of the pyrolysis furnace, has a temperature of 550°C, a pressure of 0.22 MPaG, and an inlet linear velocity of 50 m / s. Additionally, for the purpose of coking, the steam, after being finally heated in the convection section of the pyrolysis furnace, has a temperature of 550°C, a pressure of 0.22 MPaG, and an inlet linear velocity of 50 m / s.

[0125] Bottom and sidewall burners are installed inside the furnace of the steam cracking furnace, with a total of 48 bottom burners and 96 sidewall burners. 36 of the bottom burners are designated as bottom coking burners, and 72 of the sidewall burners are designated as sidewall coking burners. Coking exhaust gas is fed into the bottom and sidewall coking burners in the furnace via a coking pipeline for combustion. The operating temperature between the coking gas return burners is 380°C, and the operating pressure is 0.02 MPaG.

[0126] In this embodiment, the coking burner includes a central channel and one or more annular channels surrounding the central channel. The central channel is a coking exhaust gas passage, the annular channels immediately outside the central channel are air passages, and the annular channels immediately outside the air passages are fuel passages.

[0127] The coking exhaust gas is transported through a main coking exhaust gas pipeline, and then through multiple branch pipelines located on the main coking exhaust gas pipeline to the coking burners. The coking burners are arranged at the bottom and side walls of the furnace. The number of coking burners accounts for 100% of the total number of burners installed in the furnace.

[0128] In this embodiment, the coking exhaust gas supplied to the coking burner located at the bottom of the furnace accounts for 75 wt% of the total mass of the coking exhaust gas, and the coking exhaust gas supplied to the coking burners located on the side wall of the furnace accounts for 25 wt% of the total mass of the coking exhaust gas. The total mass flow rate of the coking exhaust gas is 60 t / h. At this time, the inner diameter of the coking exhaust gas main pipeline is generally 450 mm. At least a portion of solid particles are separated from the coking exhaust gas to obtain purified exhaust gas, which is then fed into the furnace via the at least one coking burner for combustion treatment. The separation is carried out in a cyclone-type coking cleaning tank. At this time, the coking exhaust gas main pipeline is connected to the outlet of the coking cleaning tank.

[0129] In this embodiment, the gas-solid separation achieves a particulate matter content of 30 mg / Nm³ in the purified exhaust gas. 3 The total weight of the purified exhaust gas is 100 wt%. The solid particles contained in the purified exhaust gas have an average particle size of 1 μm-10 mm.

[0130] The technical effects described in this embodiment are detailed in Tables 1-3.

[0131] Example 2

[0132] Similar to Example 1, except that the heavy hydrocarbon is paraffin-based crude oil with a final boiling point of 800°C, an initial boiling point of 20°C, and an API value of 39.

[0133] According to Embodiment 2, most of the effects of Embodiment 1 can still be achieved. However, due to the increased density of heavy hydrocarbons, the cracking furnace is more prone to producing more coke in the convection section, radiation section, and quench heat exchanger. Therefore, the operating cycle of the cracking furnace will be shortened, the purging time before coking will be longer, and the coking time will also be longer. Compared with Embodiment 1, the improvement in coking effect is slightly reduced. The detailed technical effects of this embodiment are shown in Tables 1-3.

[0134] Example 3

[0135] Similar to Example 1, except that the heavy hydrocarbons are heated to 350°C before being processed by the gas-liquid separation device.

[0136] The technical effects of this embodiment are detailed in Tables 1-3.

[0137] Example 4

[0138] Similar to Example 1, except that the gas-liquid separation device operates at a temperature of 370°C, an operating pressure of 0.25 MPaG, and a vaporization rate of 80% Wt.

[0139] According to Embodiment 4, most of the effects of Embodiment 1 can still be achieved. However, due to the higher operating temperature and higher gasification rate of the gas-liquid separation device, some colloids are entrained in the gaseous material, accelerating coking in the radiation section, shortening the operating cycle of the pyrolysis furnace, and slightly increasing purging and coking. The technical effects of this embodiment are detailed in Tables 1-3.

[0140] Example 5

[0141] The difference from Example 1 is that the operating temperature of the pyrolysis of the radiant section furnace tube is 820℃, and the operating pressure at the outlet of the radiant section furnace tube is 0.1 MPaG. The detailed technical effects of this example are shown in Tables 1-3.

[0142] Example 6

[0143] Similar to Example 1, the difference is that the air, after being heated in the convection section of the pyrolysis furnace or by an external heater, has a temperature of 550°C, a pressure of 0.3 MPaG, and an inlet linear velocity of 15 m / s; the steam, after being heated in the convection section of the pyrolysis furnace or by an external heater, also has a temperature of 550°C, a pressure of 0.3 MPaG, and an inlet linear velocity of 15 m / s. The detailed technical effects of this embodiment are shown in Tables 1-3.

[0144] Example 7

[0145] Similar to Example 1, the difference is that the operating temperature of the coke gas requiring combustion treatment before return is 350°C, and the operating pressure is 0.05 MPaG. The detailed technical effects of this example are shown in Tables 1-3.

[0146] Example 8

[0147] Similar to Embodiment 1, the difference is that the char-burning burner includes a central channel and one or more annular channels surrounding the central channel. The technical effects of this embodiment are detailed in Tables 1-3.

[0148] Example 9

[0149] Similar to Embodiment 1, the difference is that the burners are evenly arranged at the bottom of the pyrolysis furnace, and each burner is equipped with a central channel for receiving the coke exhaust gas returning to the furnace. An annular channel immediately outside the central channel is an air channel, and an annular channel immediately outside the air channel is a fuel gas channel. The detailed technical effects of this embodiment are shown in Tables 1-3.

[0150] Example 10

[0151] Similar to Example 1, the difference is that the coking exhaust gas is transported through a main coking exhaust gas pipeline, and then through multiple branch pipelines installed on the main coking exhaust gas pipeline to the coking burner. The number of branch pipelines is the same as the number of burners. The detailed technical effects of this embodiment are shown in Tables 1-3.

[0152] Example 11

[0153] Similar to Example 1, the difference is that the coking burners are arranged at the bottom and side walls of the furnace, and the number of coking burners is 80% of the total number of all burners (including bottom and side wall burners). The technical effects of this embodiment are detailed in Tables 1-3.

[0154] Example 12

[0155] Similar to Example 1, the difference is that the coking exhaust gas supplied to the coking burner located at the bottom of the furnace accounts for 80 wt% of the total mass of the coking exhaust gas, and the coking exhaust gas supplied to the coking burner located on the side wall of the furnace accounts for 20 wt% of the total mass of the coking exhaust gas. The technical effects of this embodiment are detailed in Tables 1-3.

[0156] Example 13

[0157] Similar to Example 1, except that the mass flow rate of the coking exhaust gas entering a single unit is 1000 kg / h. The detailed technical effects of this example are shown in Tables 1-3.

[0158] Example 14

[0159] Similar to Example 1, the difference is that at least a portion of the solid particles in the coking gas are separated in the coking tank to obtain purified exhaust gas. This purified exhaust gas is then fed into the furnace via 36 bottom coking burners and 18 sidewall burners for combustion treatment. The detailed technical effects of this embodiment are shown in Tables 1-3.

[0160] Example 15

[0161] Similar to Example 1, the difference is that the separation is carried out in a coke removal tank, which is a cyclone-type coke removal tank. The detailed technical effects of this example are shown in Tables 1-3.

[0162] Example 16

[0163] Similar to Example 1, except that the particulate matter content of the purified exhaust gas is 20 mg / Nm3, calculated based on a total weight of 100 wt% of the purified exhaust gas. The detailed technical effects of this example are shown in Tables 1-3.

[0164] Example 17

[0165] Similar to Example 1, except that the average particle size of the solid particles contained in the purified exhaust gas is 1μm-15mm. The detailed technical effects of this example are shown in Tables 1-3.

[0166] Example 18

[0167] Similar to Example 1, except that in step A), the temperature of the steam is 480°C, the pressure is 0.3 MPaG, and the inlet linear velocity is 30 m / s.

[0168] The technical effects of this embodiment are detailed in Tables 1-3.

[0169] Example 19

[0170] Similar to Example 1, except that in step A), the temperature of the mixed steam is 320°C, the pressure is 0.28 MPaG, and the outlet linear velocity is 40 m / s.

[0171] The technical effects of this embodiment are detailed in Tables 1-3.

[0172] Example 20

[0173] Similar to Example 1, except that before step 3) begins, the gaseous material is stopped from being transported to the radiant section furnace tube.

[0174] The technical effects of this embodiment are detailed in Tables 1-3.

[0175] Example 21

[0176] Similar to Example 1, except that the heavy hydrocarbon is stopped from being transported to the gas-liquid separator before step A) begins.

[0177] The technical effects of this embodiment are detailed in Tables 1-3.

[0178] Example 22

[0179] Similar to Example 1, except that step 3 begins after step B).

[0180] The technical effects of this embodiment are detailed in Tables 1-3.

[0181] Example 23

[0182] Similar to Example 1, the difference is that the API value of the heavy hydrocarbon is 35. Due to the excessive weight of the crude oil, the risk of coking in the convection and radiation sections increases, resulting in more coke being produced during operation, a shorter operating cycle, a longer coking time, a larger amount of coke, and a greater risk of burner blockage during coking in the furnace, as well as a greater impact on the thermal field within the furnace. The detailed technical effects of this example are shown in Tables 1-3.

[0183] Example 24

[0184] Similar to Example 1, the difference is that the air, after being heated to 500°C in the convection section of the pyrolysis furnace or by an external heater, and the steam, after being heated to 500°C in the convection section of the pyrolysis furnace or by an external heater, are both at a lower initial temperature. The lower initial temperature of the air and steam entering the radiant section furnace tubes increases the burner load, and the reduced reaction rate of the air and steam in the initial stage within the furnace tubes decreases, thus reducing the decoking effect of the radiant section furnace tubes in the initial stage. The detailed technical effects of this embodiment are shown in Tables 1-3.

[0185] Example 25

[0186] Similar to Embodiment 1, the difference is that the coking burners are arranged at the bottom and / or sidewalls of the furnace, and their number accounts for 40% of the total number of burners in the furnace. The smaller number of burners results in a higher flow rate of coking gas in each burner, easily causing the airflow to jet outwards from the center of the burner. Since the coking gas contains a large amount of steam and inert gases, it can easily cause the burner nozzles to extinguish. The airflow can also impact the furnace lining and furnace tubes, causing equipment damage. Furthermore, the smaller number of coking burners leads to greater unevenness or deviation in the flow rate distribution of coking gas in each burner, thus affecting the uniformity of the thermal field throughout the furnace. The detailed technical effects of this embodiment are shown in Tables 1-3.

[0187] Example 26

[0188] Similar to Example 1, the difference is that the particulate matter content of the purified exhaust gas is 40 mg / Nm3, calculated as 100 wt% of the total weight of the purified exhaust gas. Because the purified exhaust gas was not well separated in the cyclone separator, the particulate matter content in the coking exhaust gas introduced into the coking burner is relatively high. Since the fuel gas nozzles generally have small orifice diameters, this easily causes clogging of other fuel gas nozzles in the burner. In this example, more than 20% of the burner nozzles were clogged. The detailed technical effects of this example are shown in Tables 1-3.

[0189] Example 27

[0190] Similar to Example 1, the difference is that the particulate matter content of the purified exhaust gas is 100 mg / Nm3, calculated as 100 wt% of the total weight of the purified exhaust gas. Because the purified exhaust gas was not well separated in the cyclone separator, the particulate matter content in the coking exhaust gas introduced into the coking burner is relatively high, approximately 100 mg / Nm3. Since the fuel gas nozzles generally have a small orifice diameter of 2-5 mm, this easily causes blockage of the burner fuel gas nozzles, resulting in sintering damage to the burner nozzles and uneven or insufficient heating in the furnace. In this example, more than 30% of the burner nozzles were sintered and damaged. The detailed technical effects of this example are shown in Tables 1-3.

[0191] Example 28

[0192] Similar to Example 1, the difference is that the coking gas is emitted through an annular channel instead of an upward channel from the center of the burner. This results in the coking gas being too close to the fuel injector, easily causing the fuel gas nozzle to extinguish. Simultaneously, it does not effectively reduce the flame center temperature, thus having little effect on NOx reduction. The detailed technical effects of this example are shown in Tables 1-3.

[0193] Example 29

[0194] Similar to Example 1, the difference is that the coking gas in the sidewall coking burner accounts for 70 wt% of the total coking gas mass. The uneven distribution of coking gas between the bottom and sidewall burners results in too low a coking gas volume in the bottom burner and too high a volume in the sidewall burners. Typically, the heat load of a single sidewall burner in a pyrolysis furnace is much lower than that of the bottom burner, thus the throughput of the bottom burner is much greater than that of the sidewall burner. The uneven distribution leads to a risk of flameout in the sidewall burners, and the particles in the coking gas cannot achieve good combustion in the sidewall burners. The detailed technical effects of this example are shown in Tables 1-3.

[0195] Example 30

[0196] Similar to Example 1, the difference is that the coking process does not first pass through a gas-liquid separator to obtain mixed steam, so it cannot bring particle impact to the coke layer already present in the furnace tube. The technical effects of this example are detailed in Tables 1-3.

[0197] Example 31

[0198] Similar to Example 1, the difference is that the temperature of the air after being heated to 350°C in the convection section of the pyrolysis furnace or by an external heater, and the temperature of the steam after being heated to 350°C in the convection section of the pyrolysis furnace or by an external heater, are both 350°C. The initial temperature of the air and steam entering the radiant section furnace tubes is too low, significantly increasing the burner load. Furthermore, the reaction rate of the air and steam in the initial stage within the furnace tubes is reduced, greatly diminishing the decoking effect in the front section of the radiant section furnace tubes. The increased coking time leads to increased utility consumption. The detailed technical effects of this embodiment are shown in Tables 1-3.

[0199] Example 32

[0200] Similar to Example 1, the difference is that the steam inlet linear velocity is 90 m / s. Due to the excessively high linear velocity of the steam before it enters the radiant section furnace tubes, the pipeline before entering the tubes vibrates, causing excessive system pressure drop and increased consumption. Under long-term vibration, the pipeline is prone to stress tearing, leading to equipment damage. The detailed technical effects of this example are shown in Tables 1-3.

[0201] Example 33

[0202] Similar to Example 1, the difference is that the steam inlet linear velocity is 15 m / s. Because the steam linear velocity before entering the radiant section furnace tubes is too low, the venturi does not throttle, resulting in uneven fluid distribution within the furnace tubes and causing localized overheating. This necessitates reducing the load and operating temperature of the pyrolysis furnace, thus prolonging the coking operation time. The detailed technical effects of this example are shown in Tables 1-3.

[0203] Example 34

[0204] Similar to Example 1, the difference is that only all 48 bottom burners are used as scorch burners. The detailed technical effects of this example are shown in Tables 1-3.

[0205] Example 35

[0206] Similar to Example 1, except that all 96 sidewall burners are used as scorch burners. The detailed technical effects of this example are shown in Tables 1-3.

[0207] Example 36

[0208] Similar to Example 1, except that the heavy hydrocarbons are heated to 150°C before the gas-liquid separation. The technical effects of this example are detailed in Tables 1-3.

[0209] Comparative Example 1

[0210] Similar to Example 1, except that ethane is used as the steam cracking feedstock. The detailed technical effects of this example are shown in Tables 1-3.

[0211] Comparative Example 2

[0212] Similar to Example 1, except that naphtha is used as the steam cracking feedstock. The detailed technical effects of this example are shown in Tables 1-3.

[0213] Comparative Example 3

[0214] Similar to Example 1, the difference lies in the conventional method of returning the material to the furnace, i.e., only returning it to the furnace through the coking port between the burners. The technical effects of this example are detailed in Tables 1-3.

[0215] As shown in Tables 1-3, a comparison of the data from Examples 1-35 (especially Examples 1-22) with Comparative Examples 1-3 shows that the coking method using heavy hydrocarbons mentioned in this invention can reduce the coking time by an average of about 20%, reduce the particulate matter concentration in flue gas by about 30%, reduce NOx emissions in flue gas by about 30%, reduce the COT deviation during coking by more than 10°C, and save economic losses of more than 5 million yuan.

[0216]

[0217]

[0218]

Claims

1. A method for burning coke in a steam pyrolysis furnace, comprising the following steps: 1) Heavy hydrocarbons are subjected to gas-liquid separation in a gas-liquid separation device to obtain gaseous and liquid phase materials, and residue is deposited on the inner wall of the gas-liquid separation device. 2) The gaseous material is fed into the radiant section of the steam cracking furnace for pyrolysis to produce pyrolysis products containing ethylene and to deposit coke on the inner wall of the radiant section of the furnace. 3) Air and / or steam are passed through the radiant furnace tubes to remove at least a portion of the coke, yielding coke exhaust gas. 4) The coking exhaust gas is fed into the furnace of the steam pyrolysis furnace via at least one coking burner installed inside the furnace for combustion treatment. The charring method further includes the following steps: A) Passing steam through the gas-liquid separator to remove at least a portion of the residue, obtaining mixed steam. B) The mixed steam is conveyed through the radiant section furnace tube to remove at least a portion of the coke, thereby obtaining the coking tail gas.

2. The method of claim 1, wherein in step 1), the final boiling point temperature of the heavy hydrocarbon is above 540°C, and / or the API gravity of the heavy hydrocarbon is not less than 32, and / or the heavy hydrocarbon is selected from at least one of paraffinic crude oil, intermediate-based crude oil, naphthenic crude oil and condensate.

3. The method of claim 1, wherein in step 1), the initial boiling point temperature of the heavy hydrocarbon is 15°C and the final boiling point temperature is above 750°C, and / or, the API degree of the heavy hydrocarbon is above 38.

4. The method of claim 1, wherein in step 1), the heavy hydrocarbon is heated to a temperature of 100-400°C before the gas-liquid separation is performed.

5. The method of claim 1, wherein in step 1), the heavy hydrocarbon is heated to a temperature of 200-370°C before the gas-liquid separation is performed.

6. The method of claim 1, wherein in step 1), the operating temperature of the gas-liquid separation is 260-360°C, the operating pressure is 0.2-0.7 MPaG, and the gasification rate is 50-80 wt%.

7. The method of claim 1, wherein in step 2), the pyrolysis operating temperature is 800-900℃ and the operating pressure is 0.05-0.15 MPaG.

8. The method of claim 1, wherein the pyrolysis products are cooled to 400-600°C via a quench heat exchanger.

9. The method of claim 1, wherein in step 3), the temperature of the air is 500-650°C, the pressure is 0.2-0.4 MPaG, and the inlet linear velocity is 30-80 m / s, and the temperature of the steam is 500-650°C, the pressure is 0.2-0.4 MPaG, and the inlet linear velocity is 30-80 m / s.

10. The method of claim 1, wherein in step 4), the operating temperature of the combustion treatment is 300-400°C and the operating pressure is 0.05-0.1 MPaG.

11. The method of claim 1, wherein in step 4), the coking burner includes a central channel and one or more annular channels arranged around the central channel.

12. The method of claim 11, wherein the central channel is a coking exhaust gas channel, the annular channel disposed immediately outside the central channel is an air channel, and the annular channel disposed immediately outside the air channel is a fuel channel.

13. The method of claim 1, wherein in step 4), the coking exhaust gas is transported through a coking exhaust gas main pipeline and then through multiple branch pipelines provided on the coking exhaust gas main pipeline to the coking burner.

14. The method of claim 1, wherein in step 4), the coking burners are arranged at the bottom and / or sidewalls of the furnace, and their number is 20-100% of the total number of all burners provided in the furnace.

15. The method of claim 1, wherein in step 4), the number of coke burners is 50-100% of the total number of all burners provided in the furnace.

16. The method of claim 14, wherein the coking exhaust gas supplied to the coking burner disposed at the bottom of the furnace accounts for 50-100 wt% of the total mass of the coking exhaust gas, and the coking exhaust gas supplied to the coking burner disposed on the side wall of the furnace accounts for 0-50 wt% of the total mass of the coking exhaust gas.

17. The method of claim 14, wherein the coking exhaust gas supplied to the coking burner disposed at the bottom of the furnace accounts for 65-85 wt% of the total mass of the coking exhaust gas, and the coking exhaust gas supplied to the coking burner disposed on the side wall of the furnace accounts for 15-35 wt% of the total mass of the coking exhaust gas.

18. The method of claim 1, wherein in step 4), the total mass flow rate of the coking exhaust gas is 40-120 t / h.

19. The method of claim 1, wherein in step 4), at least a portion of solid particles are separated from the coking exhaust gas to obtain purified exhaust gas, and then the purified exhaust gas is introduced into the furnace via the at least one coking burner for the combustion treatment.

20. The method of claim 19, wherein the separation in step 4) is carried out in a cyclone descaling tank.

21. The method of claim 19, wherein the particulate matter content of the purified exhaust gas is less than 50 mg / Nm³. 3 The total weight of the purified exhaust gas is 100wt%.

22. The method of claim 19, wherein the particulate matter content of the purified exhaust gas is less than 20 mg / Nm³. 3 The total weight of the purified exhaust gas is 100wt%.

23. The method of claim 19, wherein the particle size range of the solid particles contained in the purified exhaust gas is 1 μm-20 mm.

24. The method of claim 19, wherein the particle size range of the solid particles contained in the purified exhaust gas is 1 μm-10 mm.

25. The method of claim 1, wherein in step A), the temperature of the vapor conveyed through the gas-liquid separation device to remove at least a portion of the residue is 400-500°C, the pressure is 0.2-0.7 MPaG, and the inlet linear velocity is 20-50 m / s.

26. The method of claim 1, wherein in step A), the temperature of the mixed steam is 250-400°C, the pressure is 0.2-0.4 MPaG, and the outlet linear velocity is 25-40 m / s.

27. The method of claim 1, wherein before step 3) begins, the delivery of the gaseous material to the radiant section furnace tube is stopped.

28. The method of claim 1, wherein before step A) begins, the supply of the heavy hydrocarbon to the gas-liquid separator is stopped.

29. The method of claim 1, wherein step 3 begins after step B) is completed.

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