Air supply system and air supply method of cracking unit and application

Abstract

The invention relates to the field of air supply of cracking devices, and discloses an air supply system and an air supply method of a cracking unit. The system comprises a forced air supply unit and a centralized heat exchange unit which are arranged at an inlet of a cracking unit in series in the gas flowing direction, and the forced air supply unit is used for sucking gas and forcibly supplying air to the centralized heat exchange unit for centralized heat exchange; and the cracking unit comprises at least one cracking furnace. According to the system, forced air supply and concentrated heat exchange of the cracking unit can be achieved, the temperature of air entering the cracking furnace is increased, equipment investment and fuel gas consumption of the cracking furnace are effectively reduced, and high economic price and social value are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of air supply for a cracking device, and in particular to an air supply system and an air supply method and application of a cracking unit. Background Art

[0002] Cracking refers to the process in which petroleum hydrocarbon raw materials such as liquefied gas, C5, naphtha and cracking tail oil undergo carbon chain scission or dehydrogenation under high temperature conditions to generate olefins and other products. The reaction of hydrocarbon cracking is very complex, including dehydrogenation, chain scission, isomerization, dehydrogenation cyclization, aromatization, dealkylation, polymerization, condensation and coking. The purpose of the cracking reaction is to produce ethylene and propylene, and also to produce high value-added products such as butadiene, hydrogen, aromatics and other by-products such as light cracking fuel oil and cracking fuel oil. The cracking reaction is a strong endothermic reaction with a high reaction temperature. Therefore, a large amount of fuel gas is consumed to provide the required energy for the reaction. In order to ensure the full combustion of the fuel gas in the cracking furnace, a certain amount of air needs to be distributed through the bottom damper. At present, it is generally heated to 60-80℃ through natural ventilation before entering the furnace through a certain heat exchange (generally quenching water). In order to achieve heat exchange, it is necessary to set up multiple sets of air preheaters at the bottom of the cracking furnace, and the equipment investment is relatively high. The high temperature of the ethylene cracking furnace also provides conditions for treating waste gas from other devices.

[0003] As environmental protection indicators for oil refining and chemical plants continue to tighten, unqualified waste gas needs to be treated before it can meet emission standards, and the construction of new treatment facilities will increase equipment investment costs and operating costs. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem that when the cracking unit in the prior art is configured with air, multiple groups of air preheaters need to be configured at the bottom of the cracking furnace, which has high equipment investment and high energy consumption. An air supply system and air supply method for a cracking unit are provided. The system can realize forced air supply and centralized heat exchange, increase the temperature of the gas entering the cracking unit, and effectively reduce equipment investment and fuel gas consumption.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides an air supply system for a cracking unit, wherein the system comprises: a forced air supply unit and a centralized heat exchange unit arranged in series at the inlet of the cracking unit along the flow direction of the air-containing gas, the forced air supply unit being used for inhaling the gas and forcing air to be supplied to the centralized heat exchange unit for centralized heat exchange; the cracking unit comprises at least one cracking furnace arranged in parallel.

[0006] The second aspect of the present invention provides an air supply method for a cracking unit, wherein the method comprises: air-containing gas is sucked in through a forced air supply unit and forcedly supplied to a centralized heat exchange unit for centralized heat exchange, and then distributed into at least two parallel-arranged cracking furnaces in the cracking unit as air distribution for fuel gas.

[0007] The third aspect of the present invention provides the use of the air supply system of the present invention in the cracking of petroleum hydrocarbon raw materials.

[0008] Compared with the prior art, the present invention has at least the following advantages and effects:

[0009] The system of the present invention can realize forced air supply and centralized heat exchange of the cracking unit, increase the temperature of air entering the cracking furnace, effectively reduce the investment in cracking furnace equipment and fuel gas consumption, and has high economic price and social value. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a flow chart of an air supply system of a cracking unit according to a preferred embodiment of the present invention.

[0011] Description of Reference Numerals

[0012] 1 Filter 2 Air compressor

[0013] 3 Air heat exchanger 4 Heat exchanger

[0014] 5 tail gas 6 cracking furnace DETAILED DESCRIPTION

[0015] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0016] In the present invention, pressure refers to gauge pressure; the term "about" means that the numerical value range is within the range of ±5.

[0017] A first aspect of the present invention provides an air supply system for a cracking unit, wherein the system comprises: a forced air supply unit and a centralized heat exchange unit arranged in series at the inlet of the cracking unit along the flow direction of the air-containing gas, the forced air supply unit being used for inhaling the gas and forcing air to be supplied to the centralized heat exchange unit for centralized heat exchange; the cracking unit comprises at least one cracking furnace.

[0018] In order to achieve the requirement of output, there are more than one cracking furnace in a general plant area, and multiple cracking furnaces are often configured to work simultaneously. In the present invention, they are collectively referred to as cracking units. As mentioned above, in order to ensure the full combustion of the cracking furnace fuel gas, it is necessary to set multiple groups of air preheaters in the existing cracking units, and distribute air by natural ventilation, so that the air entering the furnace is heated to 60-80°C through a certain heat exchange (generally quenching water). However, the setting of multiple groups of air preheaters not only has high equipment investment, but also high energy consumption. In the present invention, by setting a forced air supply unit and a centralized heat exchange unit at the entrance of the cracking unit, the gas is forced to be sucked in, concentrated heat exchanged, and sent down to be distributed into the cracking furnace in the cracking unit as the air distribution of fuel gas, wherein, by forced air supply, the gas can be effectively sucked in and sent to the centralized heat exchange unit to better realize centralized heat exchange, and the coordinated effect of the forced air supply unit and the centralized heat exchange unit can not only reduce the investment and energy consumption of the equipment, but also improve the temperature of the gas entering the cracking unit, which can effectively reduce the consumption of fuel gas.

[0019] There are multiple cracking furnaces in a workshop. According to the system of the present invention, the number of cracking furnaces is not particularly limited and can be selected according to the actual output of cracking products. In some embodiments, the cracking unit includes one cracking furnace or at least two cracking furnaces arranged in parallel, preferably 6-12 cracking furnaces arranged in parallel. The above-mentioned embodiment can effectively save equipment investment and reduce energy consumption.

[0020] According to the system of the present invention, in some embodiments, the forced air supply unit includes one air compressor or at least two air compressors arranged in series, such as 1 air compressor, 2, 3 or 4 air compressors arranged in series.

[0021] According to the system of the present invention, in some embodiments, along the gas flow direction, the heat exchange unit is provided with a low-temperature heat exchange subunit and / or a high-temperature heat exchange subunit in series. In the actual use of the system of the present invention, the low-temperature heat exchange subunit and / or the high-temperature heat exchange subunit can be used according to actual needs. By adopting the above-mentioned embodiments, energy consumption can be better reduced, and the consumption of fuel gas can be further reduced.

[0022] After the cracking unit is cracked, cracking gas is generated. In the actual process, the cracking gas will be separated. During the separation, a quenching water system will be configured with a corresponding cracking furnace's own quenching circulation system. The cracking gas after being cold-cut by the quench cooler and the quenching oil system will be further cooled to the inlet temperature required by the compressor. At the same time, the low-temperature energy in the cracking gas is recovered by providing heat to each quenching water user. The circulating quenching water that recovers the heat is circulated back to the quenching water tower as the top reflux. In the present invention, circulating quenching water can be used as a heating medium. According to the system described in the present invention, in some preferred embodiments, the low-temperature heat exchange subunit includes an air heat exchanger or multiple air heat exchangers arranged in series, which are used to use circulating quenching water as a heating medium to perform low-temperature heat exchange with the gas entering the low-temperature heat exchange subunit. The above-mentioned embodiment can better reduce energy consumption and further reduce the consumption of fuel gas. At the same time, it can fully utilize the low-temperature heat of the quenching water to reduce the overall energy consumption.

[0023] According to the system of the present invention, in some preferred embodiments, the high-temperature heat exchange subunit includes one heat exchanger or multiple heat exchangers arranged in series, which are used to use hot water or steam as a heating medium to perform high-temperature heat exchange with the gas entering the high-temperature heat exchange subunit. By adopting the above embodiment, the temperature of the gas entering the cracking furnace can be further increased, and the energy consumption and fuel gas consumption can be effectively reduced.

[0024] As the environmental protection indicators of oil refining and chemical plants are constantly tightened, unqualified tail gas in the plant area needs to be treated before it can be discharged, and the construction of new treatment facilities will increase equipment investment costs and operating costs. According to the system described in the present invention, in some embodiments, the system described in the present invention also includes: tail gas treatment piping connected to the inlet and / or outlet of the forced air supply unit, which is used for tail gas treatment of other devices. The above-mentioned embodiment can achieve the purpose of treating tail gas from other devices, and at the same time can further reduce energy consumption and equipment investment.

[0025] According to the system of the present invention, in some preferred embodiments, the tail gas treatment pipe is connected to the outlet of the forced air supply unit. The above embodiment can reduce the overall energy consumption.

[0026] According to the system of the present invention, in order to reduce solid impurities in the gas entering the cracking furnace, in some embodiments, the system of the present invention further includes: a filtering unit disposed upstream of the forced air supply unit.

[0027] According to the system of the present invention, as long as the purpose of the present invention can be achieved, the specific components of the filtering unit are not particularly limited. In some embodiments, the filtering unit includes one or more filters connected in series.

[0028] According to the system of the present invention, in some embodiments, the system of the present invention further comprises: an air induction unit provided at the outlet of the cracking unit, which is used to provide power for the gas after passing through the centralized heat exchange unit, so that the gas enters the cracking unit as the distribution air of the fuel gas. The above-mentioned embodiment can better reduce energy consumption.

[0029] According to the system of the present invention, in some preferred embodiments, the induced draft units include induced draft fans each disposed at an upper outlet of the cracking furnace.

[0030] In the present invention, each material inlet or material outlet may be directly or cross-connected, and the present invention has no special limitation on this, which will not be elaborated herein.

[0031] In the present invention, there is no special limitation on the structure of the cracking furnace, and a cracking furnace suitable for the art, such as an ethylene cracking furnace, can be selected according to the cracking raw materials.

[0032] The second aspect of the present invention provides an air supply method for a cracking unit, wherein the air supply method is carried out in the system described in the first aspect of the present invention, and the air supply method comprises: air-containing gas is sucked in through a forced air supply unit and forcibly supplied to a centralized heat exchange unit for centralized heat exchange, and then distributed into at least one cracking furnace in the cracking unit as fuel gas distribution air.

[0033] In the present invention, the gas adopts a forced air supply, centralized heat exchange, and upward distribution air supply method, which can increase the temperature of the gas entering the cracking furnace and effectively reduce the equipment investment and fuel gas consumption of the cracking furnace.

[0034] In the present invention, the flow rate of gas and the flow rate of gas distributed into the cracking furnace as the fuel gas can be set as required, and the present invention has special restrictions on this.

[0035] According to the present invention, in some preferred embodiments, the air supply method of the cracking unit includes: the air-containing gas is sucked in and forcedly supplied to the low-temperature heat exchange subunit and the high-temperature heat exchange subunit in the centralized heat exchange unit through an air compressor or multiple air compressors arranged in series in the forced air supply unit for centralized heat exchange, and at the same time, the induced draft fan in the induced draft unit provides power so that the gas after the centralized heat exchange is distributed into at least two parallel-arranged cracking furnaces in the cracking unit as air distribution for fuel gas.

[0036] According to the present invention, the specific use parameters of the induced draft fan can be selected according to needs. In some embodiments, the induced draft volume of the induced draft fan is 100000-1300000Nm 3 / h.

[0037] According to the present invention, in some embodiments, the outlet pressure of the induced draft fan is 20-50 kPa.

[0038] According to the present invention, in some embodiments, the pressure of the gas entering the centralized heat exchange unit is 20-50 kPa. The above-mentioned embodiments can effectively ensure the effect of air distribution and effectively reduce the consumption of fuel gas.

[0039] According to the present invention, in some embodiments, one or more series-connected air heat exchangers in the low-temperature heat exchange subunit use circulating quench water as a heating medium to perform low-temperature heat exchange with the gas entering the low-temperature heat exchange subunit. The above-mentioned embodiment can better reduce the overall energy consumption.

[0040] According to the present invention, in some embodiments, the temperature of the circulating quenching water is 70-90° C., preferably 75-88° C. The above embodiments can better reduce the overall energy consumption.

[0041] During the operation of the plant, the device will generate hot water or balanced low-pressure vent steam. According to the present invention, in some embodiments, one or more heat exchangers arranged in series in the high-temperature heat exchange subunit use hot water or steam as a heating medium to perform high-temperature heat exchange with the gas entering the high-temperature heat exchange subunit to 85-120°C, such as 85°C, 90°C, 95°C, 100°C, 105°C or 120°C. By adopting the above-mentioned embodiment, the heat of the hot water or steam in the plant can be effectively utilized, the temperature of the gas entering the cracking furnace can be further increased, and the energy consumption and fuel gas consumption can be effectively reduced.

[0042] According to the present invention, in some preferred embodiments, steam is used as the heating medium during high temperature heat exchange. The above embodiments can effectively reduce energy consumption and fuel gas consumption.

[0043] According to the present invention, in some preferred embodiments, steam is used as a heating medium to perform high-temperature heat exchange with the gas entering the high-temperature heat exchange subunit to a temperature of 85-120°C.

[0044] According to the present invention, in some embodiments, the air supply method further comprises: the air enters the forced air supply unit after being filtered by the filter unit.

[0045] The cracking unit is generally carried out under catalyst and high temperature conditions during cracking. According to the present invention, the air supply method also includes: the tail gas from other devices enters the inlet of the forced air supply unit through the tail gas treatment pipe and is mixed with the air entering the inlet of the forced air supply unit and then sucked into the forced air supply unit, and / or the tail gas from other devices enters the outlet of the forced air supply unit through the tail gas treatment pipe and is mixed with the air entering the centralized heat exchange unit and then enters the centralized heat exchange unit. By adopting the above-mentioned embodiment, the unqualified tail gas from other devices can be treated by the corresponding tail gas treatment pipe using the high temperature of the cracking furnace and the catalyst in the furnace body, and the unqualified tail gas is used as the air supply for centralized treatment, so that the flue gas meets the emission standards.

[0046] According to the present invention, in some preferred embodiments, the source of the tail gas includes at least one of EVA device silo gas, POE device silo gas, FDPE / LDPE / HDPE device silo gas and PP device silo gas. Using the above embodiment, those skilled in the art know that the tail gas includes nitrogen, oxygen and ethylene, as well as other inevitable impurity gases. In the present invention, through the air supply method of the present invention, the introduction of the tail gas can not only achieve the treatment of the tail gas, but also reduce the consumption of fuel gas.

[0047] According to the present invention, in some embodiments, the ratio of exhaust gas from other devices to air flow entering the forced air supply unit is (0.8-1.5): 1, such as 0.8: 1, 0.9: 1, 1: 1, 1.1: 1, 1.2: 1, 1.3: 1, 1.4: 1 or 1.5: 1. The above embodiments can further reduce energy consumption and equipment investment.

[0048] According to the present invention, in some preferred embodiments, the tail gas enters the inlet of the forced air supply unit through the tail gas treatment pipe and is mixed with the air entering the inlet of the forced air supply unit before being sucked into the forced air supply unit, and / or enters the outlet of the forced air supply unit and is mixed with the air entering the centralized heat exchange unit before entering the centralized heat exchange unit. The aforementioned embodiment can reduce the energy consumption of the compressor while making the reaction more stable, and can effectively reduce energy consumption and fuel gas consumption without affecting the cracking reaction.

[0049] According to the present invention, in some preferred embodiments, the flow ratio of the tail gas entering the inlet of the forced air supply unit to the tail gas entering the outlet of the forced air supply unit is (1.2-2): 1, such as 1.2: 1, 1.4: 1, 1.5: 1, 1.8: 1, 1.9: 1, 2: 1, preferably (1.5-2): 1. The above embodiment can effectively reduce energy consumption and fuel gas consumption without affecting the cracking reaction.

[0050] The third aspect of the present invention provides the use of the air supply system of the present invention in the cracking of petroleum hydrocarbon raw materials.

[0051] In the present invention, the petroleum hydrocarbon raw material is cracked by using the air supply system of the present invention, which can not only solve the energy consumption, but also further reduce the use of fuel gas required for cracking.

[0052] According to the present invention, as long as the purpose of the present invention can be achieved, the specific selection of the petroleum hydrocarbon feedstock is not particularly limited. In some preferred embodiments, the petroleum hydrocarbon feedstock includes one or more of liquefied gas, C5 hydrocarbons, naphtha hydrocracking tail oil and refinery dry gas.

[0053] In the present invention, there is no particular limitation on the cracking method, and a cracking method suitable for the art can be selected according to the cracking raw material, such as cracking to produce ethylene and propylene.

[0054] According to the present invention, Figure 1 As shown, in some preferred embodiments, the system for implementing the air supply method of the cracking unit includes: a filter 1, an air compressor 2, an air heat exchanger 3, a heat exchanger 4, tail gas 5, and a cracking furnace 6.

[0055] Specifically, Figure 1 As shown, take the cracking production of ethylene and propylene as an example:

[0056] The air supply method of the cracking unit includes: air is filtered by a filter 1 and then enters the inlet of an air compressor 2; a part of the tail gas 5 from other devices enters the inlet of the air compressor 2 through a tail gas treatment pipe and is mixed with the air at the inlet of the air compressor 2, then enters the air compressor 2 for compression and then is forcibly supplied to the outlet of the air compressor 2; another part of the tail gas 5 from other devices enters the outlet of the air compressor 2 and is mixed with the mixed gas at the outlet of the air compressor 2, then enters the air heat exchanger 3 for low-temperature heat exchange with circulating quenching water, and then enters the heat exchanger 4 for high-temperature heat exchange with low-pressure vent steam from the plant area after balance; at the same time, two induced draft fans (not shown) provided at the upper outlets of two parallel cracking furnaces provide power, so that the mixed gas after high-temperature heat exchange is distributed as needed to enter the two parallel cracking furnaces 6 for air distribution;

[0057] The cracking method includes: a mixture of dilution steam (water vapor) and petroleum hydrocarbon raw materials is cracked in a cracking furnace in a cracking unit, and the cracked gas obtained after the cracking is entered into a quenching boiler for quenching, the cracked gas is merged at the outlet of the quenching boiler and is mixed with quenching oil in an oil quencher for further cooling, and then sent to a downstream system through a cracked gas main pipe; the flue gas is finally discharged into the atmosphere through an induced draft fan.

[0058] The present invention will be described in detail below through examples. In the following examples: the cracking methods in each example describe the method when a cracking furnace is working, and the cracking methods in other examples are the same as the method when the cracking furnace is working.

[0059] Example 1

[0060] like Figure 1 As shown, take the cracking production of ethylene and propylene as an example:

[0061] The air supply method of the cracking unit includes: air (flow rate is 74785Nm 3 / h) is filtered by filter 1 and enters the inlet of air compressor 2, and a part of tail gas 5 (source is POE device silo gas) (flow rate is 44871Nm 3 / h) enters the inlet of air compressor 2 through the tail gas treatment pipe, mixes with the air in the inlet of air compressor 2, enters air compressor 2 for compression, and then is forced to be sent to the outlet of air compressor 2. The other part of the tail gas 5 from other devices (source is the silo gas of the POE device) (flow rate is 29900Nm 3 / h) enters the outlet of air compressor 2 and mixes with the mixed gas at the outlet of air compressor 2, then enters the air heat exchanger 3 to exchange low-temperature heat with circulating quench water (temperature is 82°C), and then enters the heat exchanger 4 to exchange high-temperature heat with the low-pressure steam from the plant area after equilibrium to about 100°C. At the same time, two induced draft fans (not shown) (pressure of 30KPa and air volume of 120000Nm) are installed at the upper outlets of the two parallel cracking furnaces. 3 / h) to provide power, so that the mixed gas after high-temperature heat exchange is evenly distributed and enters two parallel cracking furnaces 6 (F1010 cracking furnaces with an annual output of 100,000 tons of ethylene) for air distribution;

[0062] The cracking method comprises: a mixture of dilution steam (water vapor) and petroleum hydrocarbon raw materials is cracked in a cracking furnace 6 in a cracking unit, and the cracked gas obtained after the cracking is entered into a quenching boiler for quenching, the cracked gas is merged at the outlet of the quenching boiler and is further cooled by mixing with quenching oil in an oil quencher, and then sent to a downstream system through a cracked gas main pipe; the flue gas is finally discharged into the atmosphere through an induced draft fan;

[0063] Among them, the petroleum hydrocarbon raw material is naphtha, the feed rate is 40000kg / h, the weight ratio of dilution steam to petroleum hydrocarbon raw material is 0.5:1; the inlet temperature of the cracking furnace 6 radiation section tube furnace is 587℃ and the outlet temperature is 838℃; the fuel gas is methane and hydrogen with a gas volume ratio of 19:1.

[0064] The average amount of fuel gas used in a cracking furnace 6 is 7771Nm 3 / h;

[0065] The average total yield of ethylene and propylene in the cracking gas of one cracking furnace 6 is 48.56%;

[0066] The average nitrogen oxide content in the flue gas of a cracking furnace 6 is 58 mg / m3 .

[0067] Example 2

[0068] Take cracking to produce ethylene and propylene as an example:

[0069] The air supply method of the cracking unit includes: air (flow rate is 312210Nm 3 / h) enters the air compressor inlet after being filtered by the filter, and part of the tail gas (source is the silo gas of the FDPE / LDPE / HDPE device) (flow rate is 200700Nm 3 / h) enters the air compressor inlet through the tail gas treatment pipe, mixes with the air in the air compressor inlet, enters the air compressor for compression, and then is forced to be sent to the air compressor outlet. The other part of the tail gas from other devices (source is the silo gas of the FDPE / LDPE / HDPE device) (flow rate is 111500Nm 3 / h) enters the outlet of the air compressor and is mixed with the mixed gas at the outlet of the air compressor. After being forced into the air heat exchanger, it undergoes low-temperature heat exchange with the circulating quench water (temperature is 82°C). After that, it enters the heat exchanger and undergoes high-temperature heat exchange with the balanced low-pressure steam from the plant area to about 100°C. At the same time, eight induced draft fans (pressure of 40KPa and air volume of 127800Nm) are installed at the upper outlets of the eight parallel cracking furnaces. 3 / h) to provide power, so that the mixed gas after high-temperature heat exchange is evenly distributed and enters eight parallel cracking furnaces (F1010 cracking furnaces with an annual output of 100,000 tons of ethylene) for air distribution;

[0070] The cracking method comprises: a mixture of dilution steam (water vapor) and petroleum hydrocarbon raw material is cracked in a cracking furnace in a cracking unit, the cracked gas obtained after the cracking is entered into a quenching boiler for quenching, the cracked gas is merged at the outlet of the quenching boiler and enters an oil quencher to be mixed with quenching oil for further cooling, and then is sent to a downstream system through a cracked gas main pipe, the flue gas generated during the cracking process leaves the radiation section of the cracking furnace and enters the convection section of the cracking furnace for further heat recovery, and finally is discharged to the atmosphere through an induced draft fan;

[0071] Among them, the petroleum hydrocarbon raw material is naphtha, the feed rate is 41000kg / h, the weight ratio of water vapor to petroleum hydrocarbon raw material is 0.5:1; the inlet temperature of the cracking furnace radiation section tube furnace is 605℃ and the outlet temperature is 843℃; the fuel gas is methane and hydrogen with a gas volume ratio of 19:1.

[0072] The average amount of fuel gas used in a cracking furnace is 8044Nm 3 / h;

[0073] The average total yield of ethylene and propylene in the cracking gas from one cracking furnace is 49.04%;

[0074] The average nitrogen oxide content in the flue gas of a cracking furnace is 60 mg / m 3 .

[0075] Example 3

[0076] The method according to Example 2 is different in that:

[0077] The air supply method of the cracking unit includes: air (flow rate is 624420Nm 3 / h) is filtered through a filter and then enters the air compressor inlet. It is then forced into the air heat exchanger to exchange low-temperature heat with circulating quench water (temperature is 82°C), and then enters the heat exchanger to exchange high-temperature heat with balanced low-pressure steam from the plant area to about 100°C. At the same time, eight induced draft fans (pressure of 40KPa and air volume of 127800Nm) are installed at the upper outlets of eight parallel cracking furnaces. 3 / h) to provide power, so that the mixed gas after high-temperature heat exchange is evenly distributed into eight parallel cracking furnaces (F1010 cracking furnaces with an annual output of 100,000 tons of ethylene) for air distribution.

[0078] The average fuel gas consumption in a cracking furnace is 8166Nm 3 / h;

[0079] The average total yield of ethylene and propylene in the cracking gas from a cracking furnace is 48%;

[0080] The average nitrogen oxide content in the flue gas of a cracking furnace is 62 mg / m 3 .

[0081] Comparative Example 1

[0082] The method according to Example 2 is different in that:

[0083] The air supply method of the cracking unit includes: air (flow rate is 312210Nm 3 / h) is filtered through the filter and then enters the tail gas (source is the same as in Example 2, flow rate is 312200Nm 3 / h) enters the filter outlet through the tail gas treatment pipe and mixes with the filtered air, then enters the air heat exchanger in the form of natural ventilation to exchange low-temperature heat with the circulating quench water (temperature is 82°C), and then enters the heat exchanger to exchange high-temperature heat with the balanced low-pressure steam from the plant area to about 100°C. At the same time, eight induced draft fans (pressure of 40KPa and air volume of 127800Nm) installed at the upper outlets of eight parallel cracking furnaces 3 / h) to provide power, so that the mixed gas after high-temperature heat exchange is evenly distributed into eight parallel cracking furnaces (F1010 cracking furnaces with an annual output of 100,000 tons of ethylene) for air distribution.

[0084] The average fuel gas consumption in a cracking furnace is 8335Nm 3 / h;

[0085] The average total yield of ethylene and propylene in the cracking gas from one cracking furnace is 47.8%;

[0086] The average nitrogen oxide content in the flue gas of a cracking furnace is 88 mg / m 3 .

[0087] Comparative Example 2

[0088] The air supply method of the cracking unit includes: air (flow rate is 624410Nm 3 / h) is filtered by the filter and then enters the air heat exchanger by natural ventilation to exchange low-temperature heat with the circulating quench water (temperature is 82°C), and then enters the heat exchanger to exchange high-temperature heat with the low-pressure steam from the plant area after balance to about 100°C. At the same time, eight induced draft fans (pressure of 40KPa and air volume of 127800Nm) installed at the upper outlets of eight parallel cracking furnaces are 3 / h) to provide power, so that the mixed gas after high-temperature heat exchange is evenly distributed into eight parallel cracking furnaces (F1010 cracking furnaces with an annual output of 100,000 tons of ethylene) for air distribution.

[0089] The average fuel gas consumption in a cracking furnace is 8467Nm 3 / h;

[0090] The average total yield of ethylene and propylene in the cracking gas from one cracking furnace is 47.6%;

[0091] The average nitrogen oxide content in the flue gas of a cracking furnace is 68 mg / m 3 .

[0092] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. An air supply system for a cracking unit, characterized in that: The system includes: Along the flow direction of the air-containing gas, a forced air supply unit and a centralized heat exchange unit are arranged in series at the inlet of the cracking unit. The forced air supply unit is used to inhale the gas and force air to the centralized heat exchange unit for centralized heat exchange. The cracking unit includes at least one cracking furnace.

2. The system according to claim 1, wherein: The cracking unit comprises one cracking furnace or at least two cracking furnaces arranged in parallel, preferably 6-12 cracking furnaces arranged in parallel; and / or The forced air supply unit comprises an air compressor or at least two air compressors arranged in series; and / or The heat exchange unit comprises a low-temperature heat exchange subunit and / or a high-temperature heat exchange subunit, and preferably comprises a low-temperature heat exchange subunit and a high-temperature heat exchange subunit arranged in series along the gas flow direction.

3. The system according to claim 2, wherein: The low-temperature heat exchange subunit includes an air heat exchanger or a plurality of air heat exchangers arranged in series, which are used to perform low-temperature heat exchange with the gas entering the low-temperature heat exchange subunit by using circulating quench water as a heating medium; and / or The high-temperature heat exchange subunit includes one heat exchanger or multiple heat exchangers arranged in series, which are used to use hot water or steam as a heating medium to perform high-temperature heat exchange with the gas entering the high-temperature heat exchange subunit.

4. The system according to any one of claims 1 to 3, wherein: The system also includes: an exhaust gas treatment pipe connected to the inlet and / or outlet of the forced air supply unit for exhaust gas treatment of other devices. Preferably, the exhaust gas treatment pipe is connected to the inlet and outlet of the forced air supply unit respectively.

5. The system according to any one of claims 1 to 4, wherein: The system further comprises: a filter unit disposed upstream of the forced air supply unit, preferably the filter unit comprises one or more filters connected in series; and / or The system also includes an induced draft unit disposed at the outlet of the cracking unit, which is used to provide power for the gas after passing through the centralized heat exchange unit so that it enters the cracking unit as a distribution air for the fuel gas. Preferably, the induced draft unit includes induced draft fans each disposed at the upper outlet of the cracking furnace.

6. A method for supplying air to a cracking unit, characterized in that: The air supply method is performed in the system described in any one of claims 1 to 5, and the air supply method comprises: The air-containing gas is sucked in by the forced air supply unit and forced to be supplied to the centralized heat exchange unit for centralized heat exchange, and then distributed to at least one cracking furnace in the cracking unit as the distribution air of the fuel gas.

7. The air supply method according to claim 6, wherein: The method comprises: air-containing gas is sucked in sequentially through an air compressor or a plurality of air compressors arranged in series in a forced air supply unit and forced to be supplied to a low-temperature heat exchange subunit and / or a high-temperature heat exchange subunit in a centralized heat exchange unit for centralized heat exchange, and at the same time, an induced draft fan in an induced draft unit provides power so that the gas after centralized heat exchange is distributed into at least two parallel-arranged cracking furnaces in a cracking unit as air distribution for fuel gas.

8. The air supply method according to claim 7, wherein: The induced air volume of the induced draft fan is 100000-1300000Nm 3 / h; and / or The outlet pressure of the induced draft fan is 20-50 kPa.

9. The air supply method according to any one of claims 6 to 8, wherein: The pressure of the gas entering the centralized heat exchange unit is 20-50 kPa; and / or One or more series-arranged air heat exchangers in the low-temperature heat exchange subunit use circulating quench water as a heating medium to perform low-temperature heat exchange with the gas entering the low-temperature heat exchange subunit, and the temperature of the circulating quench water is preferably 70-90°C, preferably 75-88°C; and / or One or more heat exchangers arranged in series in the high-temperature heat exchange subunit utilize hot water or steam as a heating medium to perform high-temperature heat exchange to 85-120°C with the gas entering the high-temperature heat exchange subunit.

10. The air supply method according to any one of claims 6 to 9, wherein: The air supply method further comprises: the air enters the forced air supply unit after being filtered by the filter unit; and / or The air supply method further includes: exhaust gas from other devices enters the inlet of the forced air supply unit through the exhaust gas treatment pipe, mixes with the air entering the inlet of the forced air supply unit, and then is sucked into the forced air supply unit; and / or exhaust gas from other devices enters the outlet of the forced air supply unit through the exhaust gas treatment pipe, mixes with the air entering the centralized heat exchange unit, and then enters the centralized heat exchange unit; Preferably, the source of the tail gas includes at least one of EVA device silo gas, POE device silo gas, FDPE / LDPE / HDPE device silo gas and PP device silo gas.

11. The air supply method according to claim 10, wherein: The ratio of exhaust gas from other devices to air flow entering the forced air supply unit is (0.8-1.5):1; and / or The exhaust gas passes through the exhaust gas treatment piping: it enters the inlet of the forced air supply unit and is mixed with the air entering the inlet of the forced air supply unit and then is sucked into the forced air supply unit, and / or enters the outlet of the forced air supply unit and is mixed with the gas entering the centralized heat exchange unit and then enters the centralized heat exchange unit. Preferably, the flow ratio of the exhaust gas entering the inlet of the forced air supply unit and the exhaust gas entering the outlet of the forced air supply unit is (1.2-2):

1.

12. Application of the air supply system according to any one of claims 1 to 6 in cracking of petroleum hydrocarbon raw materials; Preferably, the petroleum hydrocarbon feedstock includes one or more of liquefied gas, C5 hydrocarbon, naphtha, hydrocracking tail oil and refinery dry gas.

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