Heavy oil heating furnace and decoking method thereof

Abstract

The invention relates to the technical field of petrochemical engineering, and particularly discloses a heavy oil heating furnace and a decoking method thereof.The heavy oil heating furnace comprises a furnace body, a first radiation chamber and a second radiation chamber are arranged in the furnace body, a first branch furnace tube, a second branch furnace tube and a first radiation combustor are arranged in the first radiation chamber, and a converging radiation furnace tube is arranged in the second radiation chamber; the converging radiation furnace tube is heated by flue gas in the first radiation chamber or is heated by arranging a second radiation burner in the second radiation chamber; the outlet ends of the first branch furnace tube and the second branch furnace tube are converged and connected with the inlet end of the converging radiation furnace tube, and the sum of the inner diameter sectional areas of the first branch furnace tube and the second branch furnace tube is larger than the inner diameter sectional area of the converging radiation furnace tube. The first branch furnace tube, the second branch furnace tube and the convergence radiation furnace tube are each provided with a set of injection ports arranged at intervals, the injection ports are connected with injection pipelines, the coking area can be reduced, the coking rate can be reduced, and the purpose of prolonging the maintenance period of the heating furnace is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of petrochemical engineering, and in particular to a heavy oil heating furnace and a decoking method thereof. Background Art

[0002] As the trend of heavier and inferior crude oil in the world intensifies, efficient utilization of heavy oil resources is an important issue facing the petrochemical industry. When the process requires a temperature above 350°C during heavy oil processing, a tubular heating furnace is usually required for heating. When the heavy oil is heated in the heating furnace tube, the condensation reaction will cause coking on the inner wall of the furnace tube, resulting in an increase in the temperature of the outer wall of the furnace tube. When the furnace tube temperature exceeds the allowable operating temperature, the furnace must be shut down for coking.

[0003] In addition, as the equipment becomes larger, large heavy oil heating furnaces adopt a symmetrical structural unit with multiple parallel feeding and discharging methods. For example, visbreaking heating furnaces, delayed coking heating furnaces, and vacuum deep drawing heating furnaces all have the above characteristics.

[0004] The current method of decoking heavy oil heating furnaces has serious pollution, high energy consumption costs, and long decoking cycles, which are important factors affecting its production capacity utilization rate and operating costs.

[0005] Therefore, developing a heavy oil heating furnace that reduces the amount of coking, as well as an environmentally friendly, efficient, and low-cost decoking method are key technical issues that need to be solved in the heavy oil processing process. Summary of the invention

[0006] The purpose of the present invention is to provide a heavy oil heating furnace and a decoking method thereof in view of the defects in the prior art.

[0007] The technical solution of the present invention is: a heavy oil heating furnace, comprising a furnace body, wherein a first radiation chamber and a second radiation chamber are arranged in the furnace body, wherein a first branch furnace pipe, a second branch furnace pipe and a first radiation burner are arranged in the first radiation chamber, and a converging radiation furnace pipe is arranged in the second radiation chamber, wherein the converging radiation furnace pipe is heated by the flue gas in the first radiation chamber or by arranging a second radiation burner in the second radiation chamber; The outlet ends of the first branch furnace tube and the second branch furnace tube are connected to the inlet end of the merged radiation furnace tube, and the sum of the inner diameter cross-sectional areas of the first branch furnace tube and the second branch furnace tube is greater than the inner diameter cross-sectional area of ​​the merged radiation furnace tube.

[0008] The first branch furnace tube, the second branch furnace tube and the combined radiation furnace tube are each provided with a group of injection ports arranged at intervals, and the injection ports are connected to the injection pipeline.

[0009] Preferably, a convection chamber is provided on the top of the furnace body, the first radiation chamber and the second radiation chamber are connected to the convection chamber, and a group of convection furnace tubes connected to the inlet ends of the first branch furnace tube and the second branch furnace tube are respectively provided in the convection chamber.

[0010] Preferably, the first branch furnace tube, the second branch furnace tube and the combined radiation furnace tube are all continuous S-shaped reciprocating folding structures, and the injection port is arranged at the bending position of the S-shaped reciprocating folding structure.

[0011] Preferably, the first radiation chamber is divided into a first furnace bin and a second furnace bin, the first branch furnace pipe is located in the first furnace bin, and the second branch furnace pipe is located in the second furnace bin.

[0012] Preferably, the first radiation chamber and the second radiation chamber are arranged left to right, and the first furnace bin and the second furnace bin are arranged up and down and are connected.

[0013] Preferably, the longitudinal sections of the first furnace bin and the second furnace bin are both in a regular trapezoidal structure, and the longitudinal section of the second radiation chamber is in an inverted trapezoidal structure.

[0014] Preferably, the second radiation chamber and the first radiation chamber are arranged up and down, the first furnace bin and the second furnace bin are arranged left and right, and the tops of the first furnace bin and the second furnace bin are both connected to the bottom of the second radiation chamber.

[0015] Preferably, the longitudinal sections of the first furnace bin and the second furnace bin are both in a regular trapezoidal structure.

[0016] A decoking method for a heavy oil heating furnace, comprising the above-mentioned heavy oil heating furnace, the decoking method comprising the following steps: First, stop feeding the heavy oil heating furnace with oil, then introduce steam from the injection port to purge, use steam to replace the oil in the first branch furnace tube, the second branch furnace tube and the converging radiation furnace tube, continue steam purge, raise the steam temperature at the converging radiation furnace tube outlet to 650-700℃, and keep the temperature constant for more than 30 minutes; Next, by controlling the flow rate of injected steam, the temperature of the combined radiation furnace tube is repeatedly raised and lowered, so that most of the coke layer in the combined radiation furnace tube is peeled off; Finally, the amount of steam injected into the first branch furnace tube and the second branch furnace tube is maintained unchanged, and the steam injected into the converging radiation furnace tube is switched to a mixed liquid of deoxygenated water and hydrogen peroxide; The outlet temperature of the combined furnace tube is maintained at 490~500℃, so that the deoxygenated water can be quickly vaporized in the combined furnace tube. The large temperature gradient and expansion impact force generated by vaporization are used to clean the residual coke layer on the inner wall of the furnace tube and blow it out with steam.

[0017] Compared with the prior art, the present invention has the following advantages: The present invention distributes the heating temperature zones by setting up the heating furnaces of the first radiation chamber and the second radiation chamber. The first radiation chamber adopts a higher heat load to heat the low-temperature heavy oil, so that the temperature in the first branch furnace tube and the second branch furnace tube is maintained below the coking temperature, thereby avoiding coking in the first branch furnace tube and the second branch furnace tube. The second radiation chamber adopts a lower heat load to heat the high-temperature heavy oil, thereby reducing the thermal strength of the furnace tube, thereby delaying the coking rate of the high-temperature furnace tube, thereby achieving the purpose of extending the maintenance period of the heating furnace.

[0018] The present invention improves the branch parallel feeding and discharging method of the prior art into a branch feeding combined discharging method, thereby increasing the flow velocity in the combined radiation furnace tube, and delaying the coking rate of the combined radiation furnace tube by increasing the flow velocity inside this section of high-temperature and easily coked furnace tube, thereby achieving the purpose of extending the operation cycle of the heating furnace. In addition, since heavy oil will only coke at the outlet end of the furnace tube, a branch feeding combined discharging structure is adopted, which reduces the number of outlets and thus also reduces the area of ​​the coking region.

[0019] The first radiation chamber of the present invention adopts a furnace with a regular trapezoidal cross-section structure, which can increase the flue gas reflux and enhance heat transfer; the second radiation chamber uses a furnace with an inverted trapezoidal cross-section structure to weaken the flue gas reflux and reduce the thermal strength of the furnace tube, thereby delaying the coking rate of the furnace tube in the high-temperature section and achieving the purpose of extending the operation cycle of the heating furnace. In addition, the furnace tubes in the first radiation chamber and the second radiation chamber can be temperature-controlled independently in sections, which significantly improves the flexibility of the temperature control operation of the heating furnace.

[0020] The present invention improves the branch parallel feeding and discharging method of the prior art into a branch feeding combined discharging method, and can also reduce the total steam injection consumption of the furnace tube during coke cleaning, thereby achieving the goal of energy saving and emission reduction compared with the prior art.

[0021] During the decoking process of the present invention, high-temperature steam is combined with deoxygenated water and hydrogen peroxide injected into the combined radiation furnace tube, the hydrogen peroxide is rapidly vaporized in the combined radiation furnace tube, and the strong oxidation effect at high temperature oxidizes the coke remaining on the surface of the furnace tube into a loose coke layer, while the large temperature gradient and expansion impact force generated by the rapid vaporization of the deoxygenated water when heated are utilized to improve the decoking effect of the furnace tube, thereby achieving the beneficial effects of improving the decoking effect and reducing the energy consumption in the decoking process. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic structural diagram of the horizontal arrangement of the first radiation chamber and the second radiation chamber of the present invention; Figure 2 It is a schematic structural diagram of the longitudinal arrangement of the first radiation chamber and the second radiation chamber of the present invention; In the figure: 1, furnace body, 2, convection chamber, 3, convection furnace tube, 4, first branch furnace tube, 5, first furnace bin, 6, second furnace bin, 7, first radiation chamber, 8, second branch furnace tube, 9, first radiation burner, 10, second radiation burner, 11, second radiation chamber, 12, convergent radiation furnace tube. DETAILED DESCRIPTION

[0023] The present invention is further described below with reference to the accompanying drawings and embodiments. Example 1

[0024] like Figure 1 and Figure 2 A heavy oil heating furnace comprises a furnace body 1, in which a first radiation chamber 7 and a second radiation chamber 11 are arranged.

[0025] Among them, the first radiation chamber 7 is divided into a first furnace bin 5 and a second furnace bin 6. The first furnace bin 5 is provided with a first branch furnace pipe 4, and the second furnace bin 6 is provided with a second branch furnace pipe 8. The first radiation chamber 7 is also provided with a first radiation burner 9 for heating the first branch furnace pipe 4 and the second branch furnace pipe 8.

[0026] A combined radiation furnace tube 12 is provided in the second radiation chamber 11 . The combined radiation furnace tube 12 is heated by the flue gas of the first radiation chamber 7 , or by arranging a second radiation burner 10 in the second radiation chamber 11 to heat the combined radiation furnace tube 12 .

[0027] The outlet ends of the first branch furnace tube 4 and the second branch furnace tube 8 are connected to the inlet end of the merging radiation furnace tube 12, and the sum of the inner diameter cross-sectional areas of the first branch furnace tube 4 and the second branch furnace tube 8 is larger than the cross-sectional area of ​​the merging radiation furnace tube 12.

[0028] A group of injection ports arranged at intervals are provided on the first branch furnace tube 4, the second branch furnace tube 8 and the converging radiation furnace tube 12, and the injection ports are connected to the injection pipelines. The first branch furnace tube 4, the second branch furnace tube 8 and the converging radiation furnace tube 12 are all continuous S-shaped reciprocating fold structures, and the injection points are arranged at the bends of the S-shaped reciprocating fold structures.

[0029] When in use, the heavy oil enters from the inlet of the first branch furnace tube 4 and the second branch furnace tube 8, and is heated by the first radiation burner 9. The first radiation chamber 7 uses a relatively high heat load to heat the low-temperature heavy oil, so that the heating temperature of the heavy oil is lower than the temperature at which coking can be formed, thereby avoiding the formation of coking in the first branch furnace tube 4 and the second branch furnace tube 8. After the heavy oil is heated once by the first branch furnace tube 4 and the second branch furnace tube 8, it converges and enters the convergent radiation furnace tube 12, and then the second radiation burner 10 heats it again, and heats it to the temperature required by the process before discharging the convergent radiation furnace tube 12. In the second radiation chamber 11, a lower heat load is used to heat the high-temperature section heavy oil, reducing the thermal intensity of the furnace tube, thereby delaying the coking rate of the high-temperature section furnace tube, and achieving the purpose of extending the maintenance cycle of the heating furnace.

[0030] The present invention improves the branch parallel feeding and discharging method of the prior art into a branch feeding combined discharging method, thereby increasing the flow rate in the combined radiation furnace tube 12, and delaying the coking rate of the combined radiation furnace tube 12 by increasing the flow rate inside this section of high-temperature and easily coked furnace tube, thereby achieving the purpose of extending the operation cycle of the heating furnace. In addition, since heavy oil will only coke at the outlet end of the furnace tube, a branch feeding combined discharging structure is adopted to reduce the number of outlets, thereby also reducing the area of ​​the coking area.

[0031] In addition, the present invention improves the branched parallel feeding and discharging method of the prior art into a branched feeding combined discharging method, and can also reduce the total steam injection consumption of the furnace tube during coke cleaning, thereby achieving the goal of energy conservation and emission reduction compared with the prior art. Example 2

[0032] This embodiment is further optimized on the basis of the above embodiment, specifically: like Figure 1 and Figure 2 A convection chamber 2 is provided on the top of the furnace body 1, and the first radiation chamber 7 and the second radiation chamber 11 are connected to the convection chamber 2. The smoke from the first radiation chamber 7 and the second radiation chamber 11 passes through the convection chamber 2 and then is discharged from the furnace body 1.

[0033] A group of convection furnace tubes 3 are provided in the convection chamber 2 and are connected to the inlet ends of the first branch furnace tube 4 and the second branch furnace tube 8 respectively.

[0034] When the heavy oil heating furnace is fed, the heavy oil first passes through the convection furnace tube 3. At this time, the flue gas from the first radiation chamber 7 and the second radiation chamber 11 can be used to preheat the heavy oil, and the waste heat of the flue gas can be recycled to further reduce production energy consumption. Example 3

[0035] This embodiment classifies the layout of the first radiation chamber 7 and the second radiation chamber 11 on the basis of the above embodiment, and specifically divides them into two types: like Figure 1 The first layout is: the first radiation chamber 7 and the second radiation chamber 11 are arranged left and right, and the first furnace bin 5 and the second furnace bin 6 are arranged up and down and connected.

[0036] The longitudinal sections of the first furnace bin 5 and the second furnace bin 6 are both in a regular trapezoidal structure, and the longitudinal section of the second radiation chamber 11 is in an inverted trapezoidal structure.

[0037] This structure requires that a second radiation heater be installed in the second radiation chamber 11 to heat the combined furnace tube.

[0038] like Figure 2 The second layout is that the second radiation chamber 11 and the first radiation chamber 7 are arranged up and down, the first furnace bin 5 and the second furnace bin 6 are arranged left and right, and the tops of the first furnace bin 5 and the second furnace bin 6 are connected to the bottom of the second radiation chamber 11.

[0039] The longitudinal sections of the first furnace bin 5 and the second furnace bin 6 are both in the shape of a regular trapezoid.

[0040] This structure does not require the installation of a second radiation heater in the second radiation chamber 11 to heat the combined radiation furnace tube 12 . The combined radiation furnace tube 12 is heated by the flue gas from the first radiation chamber 7 .

[0041] In this embodiment, the first radiation chamber 7 adopts a furnace with a regular trapezoidal cross-section structure, which can increase the flue gas reflux and enhance heat transfer; the second radiation chamber 11 uses a furnace with an inverted trapezoidal cross-section structure to weaken the flue gas reflux and reduce the thermal strength of the furnace tube, thereby delaying the coking rate of the high-temperature section furnace tube and achieving the purpose of extending the operation cycle of the heating furnace.

[0042] In addition, the furnace tubes in the first radiation chamber 7 and the second radiation chamber 11 can be temperature-controlled in sections independently, which significantly improves the flexibility of the temperature control operation of the heating furnace. Example 4

[0043] A decoking method for a heavy oil heating furnace, comprising a heavy oil heating furnace in any one of the above embodiments, wherein the decoking method comprises the following steps: First, the oil feed of the heavy oil heating furnace is stopped, and then steam is introduced from the injection port for purging, and the steam is used to replace the oil in the first branch furnace tube 4, the second branch furnace tube 8 and the converging radiation furnace tube 12; Continue steam purging to raise the steam temperature at the outlet of the combined radiation furnace tube 12 to 650-700°C and keep the temperature constant for more than 30 minutes; Next, the temperature of the combined radiant furnace tube 12 is adjusted by controlling the injected steam flow rate; Rapidly cool the outlet steam of the combined radiation furnace tube 12 to 300-400°C and keep it at a constant temperature for more than 30 minutes, then rapidly heat it to 650-700°C and keep it at a constant temperature for more than 30 minutes, repeatedly heat and cool the combined radiation furnace tube 12 to complete the stripping of most of the coke layer in the furnace tube; Finally, the amount of steam injected into the first branch furnace tube 4 and the second branch furnace tube 8 is maintained unchanged, and the steam injected into the converging radiation furnace tube 12 is switched to a mixture of deoxygenated water and hydrogen peroxide, and the concentration of hydrogen peroxide is 0.1-1% of the mixture.

[0044] Hydrogen peroxide has a strong oxidizing effect on coke, making it loose and easy to fall off. The outlet temperature of the combined furnace tube is maintained at 490~500℃, so that the deoxygenated water can be quickly vaporized in the combined furnace tube. The large temperature gradient and expansion impact force generated by vaporization can be used to clean the residual coke layer on the inner wall of the furnace tube.

[0045] Maintain for more than 1 hour, until the difference between the highest furnace tube wall temperature and the outlet steam temperature of the combined radiation furnace tube 12 is less than 3~5℃, and it can be determined that the decoking is completed.

[0046] During decoking in the present embodiment, high-temperature steam is combined with deoxygenated water injected into the converging radiation furnace tube 12 to cause the deoxygenated water to vaporize rapidly in the converging radiation furnace tube 12. The strong oxidation effect at high temperature oxidizes the coke remaining on the surface of the furnace tube into a loose coke layer. At the same time, the large temperature gradient and expansion impact force generated by the vaporization of deoxygenated water are utilized to improve the decoking effect of the furnace tube, thereby achieving the beneficial effects of improving the decoking effect and reducing the energy consumption of the decoking process.

[0047] Comparative Example Conventional heating furnaces are used for production and decoking operations.

[0048] The existing heating furnace radiation chamber is a square box furnace, the radiation furnace tubes are arranged horizontally from top to bottom in the furnace, and a vertical burner is set at the bottom of the radiation chamber. The total heat load of the heating furnace is 14.58MW, the length of the radiation furnace tube is 17.5m, and the heat transfer area of ​​the radiation furnace tube is 460m 2 , the inner diameter of the furnace tube is 107mm.

[0049] The properties of the heavy oil feed of the heating furnace are shown in Table 1 below. The heavy oil enters the inlet of the existing radiation furnace tube in two ways, and after being heated to the temperature required by the process, it flows out from the outlet of the existing radiation furnace tube in two ways.

[0050] .

[0051] The existing burner provides the heat required for heating oil products during normal production and heating the temperature during the online decoking process. The existing heavy oil heating furnace adopts parallel feeding and discharging. During normal production, the feeding amount of each channel is 30t / h, and the total feeding amount is 60t / h; The heating furnace has an operating cycle of 3 months. The maximum wall temperature of the furnace tube reaches 630℃, and decoking is required. During online decoking, deoxygenated water is injected from the branch inlet furnace tube. The deoxygenated water injection rate for each feed is 5t / h, and the total injection rate for the two furnace tubes is 10t / h. The total online decoking time is 24h.

[0052] Experimental Example 1 like Figure 1 As shown, in this embodiment, the heating furnace adopts the first layout mode, wherein the bottom angle of each regular trapezoidal structure in the first radiation chamber 7 is set to 60°, and the bottom angle of each inverted trapezoidal structure in the second radiation chamber 11 is 100°; The same heavy oil is used in Experimental Example 1 and the comparative example. The total feed rate of the first branch furnace tube 4 and the second branch furnace tube 8 in Experimental Example 1 is 60 t / h, and the total heat transfer area of ​​each furnace tube is the same as that of the furnace tube in Comparative Example 1.

[0053] In this embodiment, the first radiation chamber 7 and the second radiation chamber 11 can independently control the heating load in sections. The combustion heat load of the first radiation chamber 7 accounts for 60% of the total combustion heat load of the whole furnace, and the combustion heat load of the second radiation chamber 11 accounts for 40% of the total combustion heat load. At the same time, the first radiation chamber 7 adopts a double trapezoidal cross-section furnace to further enhance the heat transfer of the low-temperature section furnace tube, and the second radiation chamber 11 adopts an inverted trapezoidal cross-section furnace to reduce the thermal strength of the furnace tube, thereby delaying the coking of the furnace tube and extending the operation cycle.

[0054] During decoking, the steam injection amount required for the first branch furnace tube 4 and the second branch furnace tube 8 is 1.5t / h×2=3t / h, and the steam injection amount required for the merging branch furnace tube is 1t / h, maintained for 12h, and a mixture of hydrogen peroxide and deoxygenated water is injected at 1t / h, the concentration of hydrogen peroxide is 0.5% of the mixture, and the total online decoking time is 24h.

[0055] Compared with the control example, when the heating furnace in this experimental example uses heavy oil, the operation cycle can be extended to 4 months, and the maximum wall temperature of the furnace tube reaches 630°C, requiring decoking.

[0056] During online coke cleaning, the total amount of steam, deoxygenated water and hydrogen peroxide injected into the furnace tube is reduced from 10t / h to 4t / h, and at the same time, the adverse effect of large amount of steam injection during online coke cleaning on subsequent coke tower operation is reduced.

[0057] Experimental Example 2 like Figure 2 As shown, in this experimental example, the layout of the first radiation chamber 7 and the second radiation chamber 11 adopts the second layout, wherein the bottom angle of the furnace chamber of each regular trapezoidal structure in the first radiation chamber 7 is set to 65°, and the second radiation chamber 11 adopts a rectangular cross-section furnace.

[0058] In this experimental example 2, the total feed rate of the first branch furnace tube 4 and the second branch furnace tube 8 is 60 t / h, and the total heat transfer area of ​​each furnace tube is the same as the heat transfer area of ​​the furnace tube in the comparative example.

[0059] In this experimental example 2, by setting the first radiation chamber 7 and the second radiation chamber 11, the heating load can be controlled in sections and independently. The combustion heat load of the first radiation chamber 7 accounts for 100% of the total combustion heat load of the whole furnace. The second radiation chamber 11 uses the high-temperature flue gas from the first radiation chamber 7 to heat the furnace tube. The outlet flue gas temperature of the first radiation chamber 7 is not less than 800°C. At the same time, the first radiation chamber 7 adopts a regular trapezoidal cross-section furnace to further enhance the heat transfer of the low-temperature section furnace tube. The second radiation chamber 11 does not receive direct radiation from the flame, but mainly relies on high-temperature radiation of flue gas and convection heat transfer, which effectively reduces the thermal intensity of the furnace tube, thereby delaying the coking of the furnace tube and extending the operating cycle.

[0060] During decoking, the steam injection amount required for the first branch furnace tube 4 and the second branch furnace tube 8 is 2t / h×2=4t / h, and the steam injection amount required for the merging branch furnace tube is 1t / h, maintained for 6h, and a mixture of hydrogen peroxide and deoxygenated water is injected at 1t / h, the concentration of hydrogen peroxide is 0.5% of the mixture, and the total online decoking time is 24h.

[0061] Compared with the comparative example, the operation period of the heating furnace in Experimental Example 2 can be extended to 5 months, and the maximum wall temperature of the furnace tube reaches 630°C, requiring decoking.

[0062] During coke cleaning, the total amount of steam injected into the furnace tube, deoxygenated water and hydrogen peroxide is reduced from 10t / h to 5t / h, and at the same time, the adverse effect of large amount of steam injection during online coke cleaning on subsequent coke tower operation is reduced.

[0063] Benefit calculation: The energy consumption of the heating furnace decoking process mainly includes two parts: heating furnace fuel consumption and medium-pressure steam consumption. The calculation results of the decoking energy consumption costs of the experimental example and the comparative example are shown in Table 2:

[0064] (1) The difference in benefits between Experimental Example 1 and Comparative Example 1: The heating furnace fuel uses refinery dry gas, the fuel cost is 3,500 yuan / ton, and the price of medium-pressure steam is 250 yuan / ton.

[0065] According to the heating furnace thermal efficiency of 93%, the total fuel consumption of comparative example 1 for heating 10t / h×24h=240t of deoxygenated water is 21t, and the total energy consumption for decoking is 73,500 yuan / time; Experimental Example 1 The total fuel consumption for heating 1t / h×12h=12t of deoxygenated water is 2t, the medium-pressure steam consumption is 4t / h×24h=96t, and the total energy cost for decoking is 31,000 yuan per time.

[0066] A heavy oil processing unit with an annual capacity of 1 million tons requires two heating furnaces. The number of decoking operations is reduced from 4 to 3 times per year. The comparison ratio of Experimental Example 1 can save (7.35*4-3.10*3)*2=402,000 yuan per year in decoking costs.

[0067] (2) The difference in benefits between Experimental Example 2 and the comparative example: In Experimental Example 2, the total fuel consumption for heating 1t / h×12h=12t of deoxygenated water is 2t, the medium-pressure steam consumption is 5t / h×24h=120t, and the total energy cost for decoking is 37,000 yuan per time.

[0068] A heavy oil processing unit with an annual capacity of 1 million tons requires two heating furnaces. The number of decoking times per year is reduced from 4 times to 2.5 times. Therefore, compared with Example 1, Experimental Example 2 can save (7.35*4-3.70*2.5)*2=400,500 yuan / year in decoking costs.

[0069] The present invention is not limited to the above-mentioned embodiments. Various changes can be made within the knowledge scope of those skilled in the art without departing from the spirit of the present invention. The changed contents still fall within the protection scope of the present invention.

Claims

1. A heavy oil heating furnace, comprising a furnace body, characterized in that: The furnace body is provided with a first radiation chamber and a second radiation chamber, the first radiation chamber is provided with a first branch furnace pipe, a second branch furnace pipe and a first radiation burner, the second radiation chamber is provided with a convergent radiation furnace pipe, the convergent radiation furnace pipe is heated by the flue gas of the first radiation chamber, or by arranging a second radiation burner in the second radiation chamber; The outlet ends of the first branch furnace tube and the second branch furnace tube are connected to the inlet end of the combined radiation furnace tube, and the sum of the inner diameter cross-sectional areas of the first branch furnace tube and the second branch furnace tube is greater than the inner diameter cross-sectional area of ​​the combined radiation furnace tube; The first branch furnace tube, the second branch furnace tube and the combined radiation furnace tube are each provided with a group of injection ports arranged at intervals, and the injection ports are connected to the injection pipeline.

2. A heavy oil heating furnace according to claim 1, characterized in that: A convection chamber is provided on the top of the furnace body, the first radiation chamber and the second radiation chamber are connected to the convection chamber, and a group of convection furnace tubes connected to the inlet ends of the first branch furnace tube and the second branch furnace tube are provided in the convection chamber.

3. A heavy oil heating furnace according to claim 1, characterized in that: The first branch furnace tube, the second branch furnace tube and the combined radiation furnace tube are all continuous S-shaped reciprocating folding structures, and the injection port is arranged at the bending position of the S-shaped reciprocating folding structure.

4. A heavy oil heating furnace according to claim 1, characterized in that: The first radiation chamber is divided into a first furnace bin and a second furnace bin, the first branch furnace pipe is located in the first furnace bin, and the second branch furnace pipe is located in the second furnace bin.

5. A heavy oil heating furnace according to claim 4, characterized in that: The first radiation chamber and the second radiation chamber are arranged left and right, and the first furnace bin and the second furnace bin are arranged up and down and are connected.

6. A heavy oil heating furnace according to claim 5, characterized in that: The longitudinal sections of the first furnace bin and the second furnace bin are both in a regular trapezoidal structure, and the longitudinal section of the second radiation chamber is in an inverted trapezoidal structure.

7. A heavy oil heating furnace according to claim 4, characterized in that: The second radiation chamber and the first radiation chamber are arranged up and down, the first furnace bin and the second furnace bin are arranged left and right, and the tops of the first furnace bin and the second furnace bin are both connected to the bottom of the second radiation chamber.

8. A heavy oil heating furnace according to claim 7, characterized in that: The longitudinal sections of the first furnace bin and the second furnace bin are both in a regular trapezoidal structure.

9. A method for decoking a heavy oil heating furnace, characterized in that: A heavy oil heating furnace according to any one of claims 1 to 8, wherein the decoking method comprises the following steps: First, stop feeding the heavy oil heating furnace with oil, then introduce steam from the injection port to purge, use steam to replace the oil in the first branch furnace tube, the second branch furnace tube and the converging radiation furnace tube, continue steam purge, raise the steam temperature at the converging radiation furnace tube outlet to 650-700℃, and keep the temperature constant for more than 30 minutes; Next, by controlling the flow rate of injected steam, the temperature of the combined radiation furnace tube is repeatedly raised and lowered, so that most of the coke layer in the combined radiation furnace tube is peeled off; Finally, the amount of steam injected into the first branch furnace tube and the second branch furnace tube is maintained unchanged, and the steam injected into the converging radiation furnace tube is switched to a mixed liquid of deoxygenated water and hydrogen peroxide; The outlet temperature of the combined furnace tube is maintained at 490~500℃, so that the deoxygenated water can be quickly vaporized in the combined furnace tube. The large temperature gradient and expansion impact force generated by vaporization are used to clean the residual coke layer on the inner wall of the furnace tube and blow it out with steam.

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