Air preheater for bottom burner of ethylene cracking furnace

Abstract

The invention discloses an air preheater for a burner at the bottom of an ethylene cracking furnace, and relates to the field of ethylene cracking, the air preheater comprises an air preheater body and a connecting air duct, the air preheater body comprises a preheater shell, an air inlet and an air outlet are formed in the two ends of the preheater shell respectively, and a heat exchange tube bundle is arranged in the preheater shell; a heat source inlet and a heat source outlet are formed in the preheater shell and connected to the two ends of the heat exchange tube bundle correspondingly. The air outlet is connected to a combustor at the bottom of the cracking furnace through a connecting air duct; one air preheater body is matched with a plurality of cracking furnace bottom combustors. The cracking furnace solves the problem that the bottom space of the cracking furnace is limited, is suitable for limited space, saves occupied area and is high in heat exchange efficiency.

Description

Technical Field

[0001] The invention relates to an air preheater for a bottom burner of an ethylene cracking furnace, and is intended to heat the combustion-supporting air of the bottom burner of the ethylene cracking furnace. Background Art

[0002] The ethylene cracking furnace is a major energy consumer in the ethylene cracking process, accounting for more than 50% of the energy consumption of the entire ethylene plant area. At present, all domestic ethylene plants are conducting research on energy conservation and consumption reduction of ethylene cracking furnaces. In recent years, in the newly built ethylene refining and chemical integration projects, the air preheating energy-saving technology of the bottom burner of the cracking furnace has been adopted. At the inlet of the bottom burner of the cracking furnace, an air preheater is added to use the low-temperature waste heat (circulating quenching water, various condensates, process hot water, etc.) of the device area to preheat the combustion-supporting air entering the burner. On the one hand, it reduces the consumption of fuel gas, reduces carbon dioxide emissions, and improves the overall thermal efficiency of the cracking furnace. On the other hand, it realizes the recovery and utilization of low-temperature waste heat. This technology has achieved good energy-saving and emission reduction effects and is widely used in ethylene cracking furnaces.

[0003] However, some of the early built ethylene cracking furnaces did not consider installing air preheaters at the bottom burners during the initial design. The bottom of the cracking furnace is arranged with various pipelines such as fuel gas pipelines, nitrogen reduction steam pipelines, char gas pipelines, burner adjustment connecting rods, etc. The space conditions at the bottom of the furnace are relatively tight, which brings great difficulties to the installation of air preheaters. Summary of the invention

[0004] The technical problem solved by the present application is: to overcome the deficiencies of the prior art and provide an air preheater for the bottom burner of an ethylene cracking furnace, which solves the problem of tight space at the bottom of the cracking furnace, is suitable for confined spaces, saves space, and has high heat exchange efficiency.

[0005] The technical solutions provided by this application are as follows:

[0006] An air preheater for a bottom burner of an ethylene cracking furnace comprises an air preheater body and a connecting air duct. The air preheater body comprises a preheater shell, two ends of the preheater shell are respectively an air inlet and an air outlet, a heat exchange tube bundle is arranged in the preheater shell, a heat source inlet and a heat source outlet are arranged on the preheater shell, and the heat source inlet and the heat source outlet are respectively connected to the two ends of the heat exchange tube bundle; the air outlet is connected to the bottom burner of the cracking furnace through the connecting air duct; one air preheater body is matched with more than one bottom burner of the cracking furnace.

[0007] The connecting air duct comprises: an air duct inlet, a distribution air duct, an air duct outlet, a pressure detection and an adjusting distributor, the air duct inlet is connected to the air outlet, the air duct outlet is connected to the bottom burner of the cracking furnace, the distribution air duct is between the air duct inlet and the air duct outlet, the number of the air duct inlets is the same as the number of the preheater body, and the number of the air duct outlets is the same as the number of the matching bottom burners of the cracking furnace; a pressure detection is arranged on each air duct outlet, and the pressure detection is used to detect the pressure in the air duct outlet; the adjusting distributor is arranged in the distribution air duct and located between adjacent air duct outlets, and the adjusting distributor is used to adjust the distribution of the heated air so that the pressure of each air duct outlet is consistent.

[0008] The regulating distributor comprises an regulating shaft and an air regulating plate. The regulating shaft passes through the distribution air duct and is rotatably connected to the distribution air duct. The air regulating plate is located in the distribution air duct and is fixedly connected to the regulating shaft.

[0009] A dial is arranged outside the distribution air duct, and a pointer is arranged on the adjustment shaft. The opening of the air regulating plate is determined by the relative position of the pointer and the dial.

[0010] An air distribution plate is arranged at the inlet of the distribution air duct, and the air distribution plate is a porous plate.

[0011] The heat exchange tube bundle comprises a base tube, fins and a spoiler element. The fins are connected to the outer wall of the base tube. A plurality of spoilers are arranged on the inner wall of the base tube. Each spoiler element comprises a plurality of swirl blades so that a swirl is generated after the heat source passes through the heat exchange tube bundle.

[0012] The spoiler elements are arranged at intervals inside the base pipe, and the interval between two adjacent spoiler elements is 0.2-0.6 m.

[0013] An air filter is arranged at the air inlet of the preheater housing, and the air filter is used to filter the air; the preheater housing is provided with a bracket, and the air filter is slidably connected to the bracket so that the air filter can be drawn out.

[0014] A soot blowing device is arranged on the side of the air filter away from the air inlet direction, and the soot blowing device includes a soot blowing interface, a soot blowing collection pipe and a purge nozzle. The soot blowing collection pipes are arranged in multiple rows, and multiple purge nozzles are arranged on each row. The purge nozzles purge the air filter; the soot blowing interface is used to connect the soot blowing collection pipe with the purge medium delivery pipeline.

[0015] The heat source inlet is used for the inflow of the heat source, and the heat source flows out from the heat source outlet through the heat exchange tube bundle. The air inlet is used for the entry of air, and the air flows out from the air outlet after being heated by the heat exchange tube bundle. The flow direction of the heat source and the flow direction of the air are in countercurrent.

[0016] In summary, this application at least includes the following beneficial technical effects:

[0017] The present invention relates to an air preheater for a bottom burner of an ethylene cracking furnace, which adopts a preheater body and matches a plurality of bottom burners of the cracking furnace, and is suitable for the situation where the bottom space of the cracking furnace is tight. The form of the connecting air duct is in accordance with the number of the air preheater body and the matching bottom burners of the cracking furnace, and a distribution air duct is provided to evenly distribute the combustion-supporting air. The heat exchange tube bundle adopts a fin tube type, and the fins are made of materials with high heat exchange coefficients such as aluminum or copper, and have high heat exchange efficiency. Inside the heat exchange tube, a plurality of spoiler elements are arranged at intervals, and the swirl blades on the spoiler elements can make the fluid produce a rotating flow, thereby enhancing the heat exchange effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a front schematic diagram of a "one-to-two" type of air preheater example of the present invention.

[0019] Figure 2 It is a front schematic diagram of a "two to three" type of air preheater example of the present invention.

[0020] Figure 3 It is a side schematic diagram of the air preheater of the present invention.

[0021] Figure 4 It is a schematic diagram of the heat exchange tube bundle and the spoiler element of the present invention.

[0022] Figure 5 It is a schematic diagram of the swirl blade of the present invention.

[0023] Explanation of the accompanying drawings: 1- bracket; 2- air inlet; 3- heat source outlet; 4- preheater shell; 5- heat source inlet; 6- air outlet; 7- air duct inlet; 8- temperature detection; 9- spare damper; 10- air duct outlet; 11- pressure detection; 12- regulating distributor; 13- distribution duct; 14- tube sheet; 15- air distribution plate; 16- soot blowing manifold; 17- soot blowing interface; 18- purge nozzle; 19- air filter; 20- heat exchange tube bundle; 21- spoiler element; 22- fin; 23- base tube; 24- swirl blade. DETAILED DESCRIPTION

[0024] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments disclosed in the present invention will be further described in detail below with reference to the accompanying drawings.

[0025] The present application embodiment discloses an air preheater for a bottom burner of an ethylene cracking furnace, such as Figure 1 and Figure 2 As shown, it includes a preheater body, a connecting air duct, an air filter, a soot blowing device and a bracket.

[0026] The correspondence between the preheater body and the cracking furnace bottom burner is: one air preheater body matches multiple cracking furnace bottom burners; or multiple air preheater bodies match multiple cracking furnace bottom burners, but the number of cracking furnace bottom burners is greater than the number of air preheater bodies.

[0027] like Figure 1 As shown, the air preheater body is used for heat exchange between the heat source and the combustion air, and the air preheater body includes: a preheater shell 4, and a heat exchange tube bundle 20, a heat source inlet 5, a heat source outlet 3, an air inlet 2, an air outlet 6, a soot blowing device, etc., which are arranged in the preheater shell 4. The heat source enters the preheater shell 4 from the heat source inlet 5, heats the air through the heat exchange tube bundle 20, and then flows out of the air preheater through the heat source outlet 3. The combustion air enters from the air inlet 2, flows out from the air outlet 6 after being heated, enters the connecting air duct, and enters the bottom burner of the cracking furnace through the connecting air duct. The flow direction of the heat source and the flow direction of the air are in countercurrent.

[0028] The capacity of the air preheater body is designed to meet the simultaneous operation of multiple cracking furnace bottom burners, such as Figure 1 As shown, generally, one air preheater body is matched with two bottom burners, which is a "one to two" type. Figure 2 As shown in the figure, two air preheater bodies are matched with three bottom burners, i.e., a "two to three" type. The solution of using one air preheater and matching multiple bottom burners takes up less space and can effectively solve the problem of tight space at the bottom of the cracking furnace.

[0029] like Figure 4 The heat exchange tube bundle 20 is in the form of a finned tube, which is composed of a base tube 23, fins 22, and a spoiler element 21. The fin 22 is made of aluminum or copper and has a high heat transfer coefficient to improve the heat exchange efficiency. The base tube 23 is circular or elliptical in shape, and the heat exchange tube bundle 20 is arranged in multiple layers. A plurality of spoilers 21 are arranged inside the heat exchange tube bundle 20, and the interval between two adjacent spoilers 21 is 0.2 to 0.6 m. Each spoiler element includes a plurality of swirl blades 24, which can enhance the heat exchange effect without increasing excessive pressure loss. Figure 5 shown.

[0030] The air filter 19 is made of a 4-10 mesh stainless steel woven mesh to block impurities such as flying catkins and dust in the air to prevent clogging of the heat exchange tube bundle and affecting the normal operation of the preheater. The air filter 19 is located at the air inlet 2 of the preheater body, and the bracket 1 is placed at the bottom of the preheater to support the preheater. On the bracket 1, the air filter 19 is placed on a support pre-welded on the bracket 1, and a handle is provided to pull out the air filter 19 and blow and clean the filter.

[0031] like Figure 3 As shown, the soot blowing device is arranged above the air filter 19, and is composed of a soot blowing interface 17, a soot blowing manifold 16, and a purge nozzle 18. The soot blowing interface 17 is in the form of a flange, connected to the purge medium delivery pipeline, and the soot blowing interface 17 is used to connect the soot blowing manifold 16, so that the purge medium enters the soot blowing manifold 16 through the purge medium delivery pipeline; the soot blowing manifold 16 is arranged in multiple rows, and multiple purge nozzles 18 are arranged on each row, and the purge nozzles 18 purge the air filter 19, and the medium used is compressed air or low-pressure steam.

[0032] The connecting air duct is used to connect the preheater body and the bottom burner of the cracking furnace, and transport the heated combustion-supporting air to the inlet of the bottom burner of the cracking furnace. The connecting air duct is provided with an air duct inlet 7, a distribution air duct 13, an air duct outlet 10, a pressure detection 11, a temperature detection 8, an adjustment distributor 12 and a spare damper 9. The air duct inlet 7 is connected to the air outlet 6 of the preheater body, and the number of air duct inlets 7 is the same as the number of preheater bodies. The air duct outlet 10 is connected to the inlet of the bottom burner of the cracking furnace, and the number of air duct outlets 10 is the same as the number of matching bottom burners of the cracking furnace. Between the air duct inlet 7 and the air duct outlet 10 is a distribution air duct 13, and the distribution air duct 13 is provided with an air distribution plate and an adjustment distributor 12. The air distribution plate is in the form of a porous plate regularly distributed in a certain proportion, located at the inlet of the distribution air duct 13, fixedly connected to the inner wall of the distribution air duct 13, and arranged perpendicular to the flow direction of the combustion-supporting air. The regulating distributor 12 is located between two adjacent air duct outlets 10. The regulating distributor 12 includes an adjusting shaft and an air regulating plate. The adjusting shaft vertically passes through the distribution air duct 13 and is rotatably connected to the distribution air duct 13. The air regulating plate is located in the distribution air duct 13 and is fixedly connected to the adjusting shaft. The adjusting shaft rotates, driving the air regulating plate to rotate, so that the air regulating plate contacts or separates from the inner wall of the distribution air duct to adjust the opening degree of the distribution air duct 13. After the heated combustion-supporting air flowing out of the air outlet 6 enters the distribution air duct 13 from the air duct inlet 7, the distribution amount in the two adjacent air duct outlets 10 can be further adjusted by the air regulating plate. A dial is provided outside the distribution air duct 13, and a pointer is provided on the regulating shaft. The opening degree of the air regulating plate can be determined by the relative position of the pointer and the dial. A pressure detector 11 is provided at each air duct outlet 10, and an adjusting distributor 12 is provided on the distribution air duct 13. The adjusting distributor 12 is adjusted according to the pressure value of the pressure monitoring 11, so that the pressure of each air duct outlet 10 is consistent, thereby achieving uniform distribution of combustion-supporting air and satisfying the uniform air flow of each burner. A temperature detector 8 is provided at each air duct outlet 10, which can directly display the temperature of the preheated air. A spare damper 9 is provided on the connecting air duct. When the air preheater is blocked, the spare damper can be opened to supplement the insufficient air and maintain the burner in normal working condition.

[0033] Figure 1 In the "one to two" type shown, the number of air duct inlet 7 is one, connected to the air outlet 6 of the preheater body, and the number of air duct outlets 10 is two, respectively connected to the inlets of the two cracking furnace bottom burners. Figure 2 In the "two to three" type shown, the number of air duct inlets 7 is two, connected to the air outlet 6 of the preheater body, and the number of air duct outlets 10 is three, respectively connected to the inlets of the bottom burners of the three cracking furnaces.

[0034] Attached Figure 1 , Attachment Figure 2 The present invention has been described with two common types, but these two types are exemplary and only serve as an illustration. On this basis, the present invention can be subjected to a variety of substitutions and improvements, all falling within the scope of protection of the present invention.

[0035] The contents not described in detail in this application specification belong to the common knowledge of those skilled in the art.

[0036] The present application is described in detail above in conjunction with specific implementation methods and exemplary examples, but these descriptions cannot be understood as limiting the present application. Those skilled in the art understand that, without departing from the spirit and scope of the present application, a variety of equivalent replacements, modifications or improvements can be made to the technical solution of the present application and its implementation methods, all of which fall within the scope of the present application. The scope of protection of the present application shall be subject to the attached claims.

Claims

1. An air preheater for a bottom burner of an ethylene cracking furnace, characterized in that: The air preheater comprises an air preheater body and a connecting air duct. The air preheater body comprises a preheater shell (4). The two ends of the preheater shell (4) are respectively an air inlet (2) and an air outlet (6). A heat exchange tube bundle (20) is arranged inside the preheater shell (4). A heat source inlet (5) and a heat source outlet (3) are arranged on the preheater shell (4). The heat source inlet (5) and the heat source outlet (3) are respectively connected to the two ends of the heat exchange tube bundle (20). The air outlet (6) is connected to the bottom burner of the cracking furnace through the connecting air duct. One air preheater body is matched with multiple cracking furnace bottom burners.

2. The air preheater for bottom burner of ethylene cracking furnace according to claim 1, characterized in that: The connecting air duct comprises: an air duct inlet (7), a distribution air duct (13), an air duct outlet (10), a pressure detector (11) and an adjusting distributor (12); the air duct inlet (7) is connected to the air outlet (6); the air duct outlet (10) is connected to the bottom burner of the cracking furnace; the distribution air duct (13) is between the air duct inlet (7) and the air duct outlet (10); the number of the air duct inlets (7) is the same as the number of the preheater body; the number of the air duct outlets (10) is the same as the number of the matching bottom burners of the cracking furnace; each air duct outlet (10) is provided with a pressure detector (11), and the pressure detector (11) is used to detect the pressure in the air duct outlet (10); the adjusting distributor (12) is provided in the distribution air duct (13) and between adjacent air duct outlets (10); the adjusting distributor (12) is used to adjust the distribution of the heated air so that the pressure of each air duct outlet (10) is consistent.

3. The air preheater for bottom burner of ethylene cracking furnace according to claim 2, characterized in that: The regulating distributor (12) comprises an regulating shaft and an air regulating plate. The regulating shaft passes through the distribution air duct (13) and is rotatably connected to the distribution air duct (13). The air regulating plate is located in the distribution air duct (13) and is fixedly connected to the regulating shaft.

4. The air preheater for bottom burner of ethylene cracking furnace according to claim 3, characterized in that: A dial is arranged outside the distribution air duct (13), and a pointer is arranged on the adjustment shaft, and the opening of the air regulating plate is determined by the relative position of the pointer and the dial.

5. The air preheater for bottom burner of ethylene cracking furnace according to claim 2, characterized in that: An air distribution plate is provided at the entrance of the distribution air duct (13), and the air distribution plate is a porous plate.

6. The air preheater for bottom burner of ethylene cracking furnace according to claim 1, characterized in that: The heat exchange tube bundle (20) comprises a base tube (23), fins (22) and a flow-disturbing element (21); the fins (22) are connected to the outer wall of the base tube (23); a plurality of flow-disturbing elements (21) are arranged on the inner wall surface of the base tube (23); each flow-disturbing element (21) comprises a plurality of swirl blades (24) so ​​that a swirl is generated after a heat source passes through the heat exchange tube bundle (20).

7. The air preheater for bottom burner of ethylene cracking furnace according to claim 1, characterized in that: The flow-disrupting elements (21) are arranged at intervals inside the base tube (23), and the interval between two adjacent flow-disrupting elements (21) is 0.2 to 0.6 m.

8. The air preheater for bottom burner of ethylene cracking furnace according to claim 1, characterized in that: An air filter (19) is provided at the air inlet (2) of the preheater housing (4), and the air filter (19) is used to filter the air; the preheater housing (4) is provided with a bracket (1), and the air filter (19) is slidably connected to the bracket (1) so that the air filter (19) can be easily drawn out.

9. The air preheater for bottom burner of ethylene cracking furnace according to claim 1, characterized in that: A soot blowing device is arranged on the side of the air filter (19) facing away from the air inlet direction, and the soot blowing device comprises a soot blowing interface (17), a soot blowing collection pipe (16) and a purge nozzle (18). The soot blowing collection pipe (16) is arranged in multiple rows, and multiple purge nozzles (18) are arranged on each row. The purge nozzles (18) purge the air filter (19); the soot blowing interface (17) is used to connect the soot blowing collection pipe (16) to a purge medium delivery pipeline.

10. The air preheater for bottom burner of ethylene cracking furnace according to claim 1, characterized in that: The heat source inlet (5) is used for the inflow of the heat source, which flows out from the heat source outlet (3) through the heat exchange tube bundle (20); the air inlet (2) is used for the entry of air, which flows out from the air outlet (6) after being heated by the heat exchange tube bundle (20); the flow direction of the heat source and the flow direction of the air are in countercurrent.

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