Cracking furnace continuous bow control system and method

Abstract

The present application provides a cracking furnace continuous control system, comprising: one or more branch hydrocarbon feed flow control modules FB i configured to control branch hydrocarbon feed flow FSV i ; one or more branch outlet temperature control modules TB i configured to control the amount of change TC i in branch hydrocarbon feed flow; a fuel gas flow control module FB G for controlling incoming fuel gas flow FC G ; and a cracking furnace outlet COT temperature control module T COT comprising a cascade control loop with the fuel gas flow control module FB G . The present application also relates to a cracking furnace continuous control method, which effectively reduces the fluctuation of branch temperature during the operation and load adjustment process of the cracking furnace, and improves the stability of the overall operation of the cracking furnace.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of petrochemical industry, and particularly relates to a cracking furnace continuous arrow control system and method. BACKGROUND

[0002] The cracking furnace is a core equipment of an ethylene, propylene and other byproduct production device. After preheating, cracking raw materials are often divided into multiple branches to enter the cracking furnace. At present, the cracking furnace process is complex, and is easy to coke. When the operating temperature is high (above 820 DEG C), the product is nonlinearly distributed. In addition, the ethylene production device often needs to increase or decrease the load. During the process of increasing or decreasing the load, the change of the cracking raw material feed quantity directly affects the stable operation of the COT temperature and the branch temperature.

[0003] Therefore, the present application proposes a brand-new concept of a cracking furnace branch balancing system and method, which is called a cracking furnace continuous arrow control system and method. The continuous arrow control idea comes from a weapon that can simultaneously launch multiple arrows, which was made by Zhuge Liang during the Three Kingdoms Period. In the ethylene production device, in order to reduce the furnace tube pressure drop and save energy, and to make the raw materials evenly heated, after preheating, the cracking raw materials are often divided into multiple branches to enter the cracking furnace. The present application introduces the idea of the continuous arrow that simultaneously launches multiple arrows into the control scheme of the cracking furnace, and establishes a cracking furnace continuous arrow control system.

[0004] When the load remains unchanged, based on the principle of heat transfer, the temperature of each branch is taken as a measurement value, and the COT temperature is taken as a set value. A branch temperature controller is established. The output of the branch temperature controller is taken as the raw material flow adjustment quantity required by the branch. Under the condition of ensuring that the load remains unchanged, the cracking furnace flow of each branch is redistributed. The feed quantity of the branch with high branch temperature is increased, and the feed quantity of the branch with low branch temperature is reduced, so as to ensure that the outlet temperatures of the branches are as close as possible.

[0005] When the load of the cracking furnace changes, the continuous arrow control is simultaneously performed on each branch to adjust the feed quantity, so as to realize the adjustment of the load under the premise of ensuring that the flow of each branch is balanced. SUMMARY

[0006] In view of the technical problems in the prior art, the present application discloses a cracking furnace continuous arrow control system, which comprises: one or more branch hydrocarbon feed flow control modules FB i configured to control the branch hydrocarbon feed flow FSV i ; one or more branch outlet temperature control modules TB i configured to control the change quantity TC i of the branch hydrocarbon feed flow; a fuel gas flow control module FB G for controlling the entering fuel gas flow FC G ; and a COT temperature control module T COT which is connected with the fuel gas flow control module FBG The composition cascade control loop.

[0007] Further, the control system of the multi-ram, wherein the one or more branch outlet temperature control module TB i Corresponding to include one or more branch outlet temperature T OUTi .

[0008] Further, the control system of the multi-ram, further comprising a calculation module, configured to calculate one or more branch feed adjustment amount increment and STC HPD And STC HPR , wherein the increment and Wherein the decrement and

[0009] Further, the control system of the multi-ram, further comprising the limit value of each branch adjustment amount STC DRE , wherein STC DRE = min(STC HPD , abs(STC HPR )); the increment and STC HPD Further comprising an increment coefficient C HPD , wherein C HPD = STC DRE / STC HPD ; the decrement and STC HPR Further comprising a decrement coefficient C HPR , wherein C HPR = STC DRE / STC HPR .

[0010] Further, the control system of the multi-ram, wherein the limit value of each branch adjustment amount STC DRE Single maximum increment or maximum decrement is DSV; wherein, further comprising single maximum adjustment increment or maximum adjustment decrement DF BL And single adjustment coefficient C BL ; DF BL = min(STC DRE , DSV), C BL = DF BL / STC DRE ; wherein, further comprising the single adjustment amount DSV i , The branch hydrocarbon feed flow FSV i = FSV i + DSV i .

[0011] Further, the continuous control system of the cracking furnace further comprises a total load setting value QSV of the cracking furnace, QSV=QSV0+DQSV*t, wherein QSV0 is an initial setting value of the cracking furnace load, DQSV is a load adjustment rate of the cracking furnace, and t is a load adjustment time.

[0012] Further, the continuous control system of the cracking furnace, the COT control module T COT has a temperature control range of 700-900℃.

[0013] The application discloses a continuous control method of a cracking furnace, which comprises the following steps: controlling a branch hydrocarbon feed flow FSV i ; controlling a change amount TC i of the branch hydrocarbon feed flow; controlling a fuel gas flow FC G ; and forming a cascade control loop.

[0014] Further, the continuous control method of the cracking furnace further comprises one or more branch feed adjustment amount increments and STC HPD and decrements and STC HPR , wherein the increments and the decrements and

[0015] Further, the continuous control method of the cracking furnace further comprises a limit value STC DRE of each branch adjustment amount, wherein STC DRE = min(STC HPD , abs(STC HPR )); the increments and STC HPD further comprise an increment coefficient C HPD , wherein C HPD = STC DRE / STC HPD ; and the decrements and STC HPR further comprise a decrement coefficient C HPR , wherein C HPR = STC DRE / STC HPR . BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the specific embodiments of the application or the technical solutions in the prior art, the drawings needed in the following description of the specific embodiments or the prior art will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort.

[0017] Figure 1Figure 1 is a schematic diagram of a control system for a cracker furnace according to one embodiment of the present application;

[0018] Figure 2 Figure 2 is a schematic diagram of a control module for a cracker furnace according to one embodiment of the present application;

[0019] Figure 3 Figure 3 is a schematic diagram of a control system for an ethylene cracker furnace according to another embodiment of the present application;

[0020] Figure 4 Figure 4 is a schematic diagram of a control module for an ethylene cracker furnace according to one embodiment of the present application; Figure 3 Figure 5 is a plot of a pre-implementation temperature and flow rate operating curve for an ethylene cracker furnace according to one embodiment of the present application;

[0021] Figure 5 Figure 6 is a plot of a post-implementation temperature and flow rate operating curve for an ethylene cracker furnace according to one embodiment of the present application; Figure 3

[0022] Figure 6 Figure 7 is a flow chart of a method for controlling a cracker furnace according to one embodiment of the present application.

[0023] Reference numerals:

[0024] 101 - cracker furnace; 102 - cracker control module;

[0025] 103 - first branch hydrocarbon feed flow; 103' - i-th branch hydrocarbon feed flow;

[0026] 104 - first branch hydrocarbon feed flow control module; 104' - i-th branch hydrocarbon feed flow control module;

[0027] 105 - first branch outlet temperature control module; 105' - i-th branch outlet temperature control module;

[0028] 106 - first branch outlet temperature; 106' - i-th branch outlet temperature;

[0029] 107 - COT temperature control module; 108 - fuel gas flow;

[0030] 109 - fuel gas flow control module; 201 - cracker control;

[0031] 301 - ethylene cracker furnace; 302 - first branch flow controller;

[0032] 303 - second branch flow controller; 304 - third branch flow controller;

[0033] 305 - fourth branch flow controller; 312 - first branch outlet temperature controller;

[0034] ​313 - second branch outlet temperature controller; 314 - third branch outlet temperature controller;

[0035] 315 - fourth branch outlet temperature controller; 306 - COT temperature controller;

[0036] 307 - fuel gas flow controller; 308 - fuel gas flow. DETAILED DESCRIPTION

[0037] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0038] In the following detailed description, reference will be made to the accompanying drawings, which form a part of this description. In the drawings, similar symbols

[0039] The technical solutions of the present application will be further described below through a specific embodiment. It should be understood by those skilled in the art that the following description is only for the convenience of understanding the technical solutions of the present application and should not be used to limit the protection scope of the present application.

[0040] Figure 1 The structure diagram of the furnace cluster control system according to one embodiment of the present application is shown in the figure. As shown in the figure, the feed flow of the cracking furnace has n groups, and the cracking furnace 101 cluster control system includes a cluster control module 102, a first branch hydrocarbon feed flow 103, an i-th branch hydrocarbon feed flow 103', a first branch hydrocarbon feed flow control module 104, an i-th branch hydrocarbon feed flow control module 104', a first branch outlet temperature control module 105, an i-th branch outlet temperature control module 105', a first branch outlet temperature 106, an i-th branch outlet temperature 106', a COT temperature control module 107, a fuel gas flow control module 108, and a fuel gas flow 109. In the embodiment shown in the figure, the first branch hydrocarbon feed flow control module 104 and the i-th branch hydrocarbon feed flow control module 104' are one or more branch hydrocarbon feed flow control modules FB i configured to control the corresponding branch hydrocarbon feed flow FSVi That is, the first branch hydrocarbon feed flow rate 103 and the i-th branch hydrocarbon feed flow rate 103 ′.

[0041] The input of the COT temperature control module is connected to a COT temperature measuring instrument, the input of the feed flow control module is connected to a flow measuring instrument, and the output is sent to a branch flow regulating valve. The input of the fuel gas flow control module is connected to a fuel gas flow measuring instrument, and the output is sent to a fuel gas flow regulating valve. The temperature control module to which the present invention relates can have a temperature measuring instrument, wherein the temperature measuring instrument has two types: contact type and non-contact type, including but not limited to electric thermal resistors, electric thermocouples, etc. It should be understood by those skilled in the art that the above are only a few types of temperature control modules. Existing replaceable existing temperature control modules in this field can also be applied here.

[0042] The flow control module of the present invention may optionally utilize a flow measuring instrument, including but not limited to a differential pressure flowmeter, a rotameter, an electromagnetic flowmeter, and the like. Those skilled in the art will appreciate that the above are merely a few types of flow control modules. Existing interchangeable flow control modules available in the art may also be used herein.

[0043] like Figure 1 As shown, the cracking furnace 101 crossbow control system of one embodiment of the present invention includes a first branch outlet temperature control module 105 and an i-th branch outlet temperature control module 105', which are one or more branch outlet temperature control modules TB i , configured to control the change in branch hydrocarbon feed flow TC i Cracking furnace 101 fuel gas flow control module FB G 108, used to control the fuel gas flow FC entering the cracking furnace 101 G 109. Cracking furnace 101COT temperature control module T COT 107, which is connected to the fuel gas flow control module FB of the cracking furnace 101 G 108 forms a cascade control loop. Through the fuel gas flow control module FB G 108 Adjust fuel gas flow FC G 109 is used to adjust the COT temperature.

[0044] like Figure 1 As shown, 105, 105' or more branch outlet temperature control modules TB i Corresponding to one or more branch outlet temperatures T including 106, 106' OUTiThe adjustment method of the continuous multiple-bolt control is to increase the feed flow of the branch with high temperature, and to decrease the feed flow of the branch with low temperature. For a single branch, if the outlet temperature of the branch is higher than the COT, the heat absorbed by the branch cannot be adjusted, and the increased heat needs to be shared by increasing the branch flow to reduce the outlet temperature to approach the COT. According to the heat conservation principle and the heat transfer rate equation, the following expression is obtained:

[0045] Q = Cp x FSV i x (T OUTi -T COT ) = Cp x TC i x (T COT -T INi ) (1)

[0046]

[0047] In the formula, TCi is the change amount of the branch hydrocarbon feed flow of the i-th branch to be adjusted, FSVi is the branch hydrocarbon feed flow 103', Q represents the heat transferred before and after adjustment, T INi is the inlet temperature of the i-th branch of the cracking furnace, T OUTi is the outlet temperature 106' of the i-th branch of the cracking furnace, and T COT is the COT temperature 107 of the cracking furnace.

[0048] The continuous multiple-bolt control system of the present application further comprises a calculation module for calculating the sum of increments and the sum of decrements of the feed adjustment amounts of one or more branches, and the following expression is obtained:

[0049]

[0050]

[0051] In the formula, STC HPD represents the sum of increments of the branch feed adjustment amounts, and STC HPR represents the sum of decrements of the branch feed adjustment amounts.

[0052] According to the feed amount, the limit value of the adjustment amount of each branch and the increment coefficient of the sum of increments of STC HPD and the decrement coefficient of the sum of decrements of STC HPR can be further calculated, and the details are as follows:

[0053] STC DRE = min (STC HPD , abs (STC HPR )) (5)

[0054] C HPD = STC DRE / STC HPD(6)

[0055] C HPR =STC DRE / STC HPR (7)

[0056] STC DRE To allow the limit of each branch adjustment, C HPD is the branch increment coefficient, C HPR is the branch reduction coefficient.

[0057] The limit value STC of each branch adjustment amount in the crossbow control system is set DRE The maximum single increment or decrement is DSV, and the distribution relationship is as follows:

[0058] DF BL =min(STC DRE ,DSV) (8)

[0059] C BL =DF BL / STC DRE (9)

[0060] Where DF BL C is the maximum single adjustment increment or maximum adjustment decrement, BL The single adjustment coefficient. The single adjustment amount DFSV of each branch feed i for:

[0061]

[0062] Finally, the adjusted branch hydrocarbon feed flow FSV of each branch i 103' is:

[0063] FSV i =FSV i +DFSV i (11)

[0064] When the overall load of the cracking furnace changes, assuming that the total load setting value of the cracking furnace is QSV=QSV0+ΔQSV·t, the hydrocarbon feed flow rate of each branch FSV i The calculation formula for 103' is:

[0065]

[0066] According to one embodiment of the present invention, the cracking furnace COT control module T COT The temperature control range of 107 is 700℃-900℃.

[0067] Figure 2Figure 1 is a structure diagram of a control operation module for a cracking furnace according to an embodiment of the present application. As shown in the figure, the cracking furnace cluster control 201 is used to read the cracking furnace branch inlet temperature T INi , outlet temperature T OUTi , and branch feed flow FV i , the maximum single increment or decrement of each branch adjustment flow DSV, the initial setting value of the cracking furnace load QSV0, the cracking furnace load adjustment rate AQSV, and the load adjustment time t.

[0068] As shown in the figure, the maximum single increment of the branch adjustment flow DSV HPD and the maximum single decrement of the branch adjustment flow DSV HPR are set. Figure 1 Figure 2 According to the cracking furnace cluster control principle, the cluster control module 102 is developed on the DCS and is downloaded and debugged in the control system. The cluster control module calculates the adjustment flow DSV i of each branch. Finally, the initial setting value of the cracking furnace load QSV0, the cracking furnace load adjustment rate AQSV, and the load adjustment time t are read, and the setting value FSV i of the branch flow controller is calculated according to the cluster control module 102.

[0069] The cracking furnace cluster control method according to the present application has the following advantages compared with the conventional control method. In view of the deviation of the branch outlet temperature during the normal operation and load adjustment of the cracking furnace, the cluster control method is proposed based on the principle of heat balance, which maintains the heat balance before and after adjustment, adjusts the feed flow of each branch, reduces the temperature fluctuation of the branch, effectively reduces the temperature fluctuation of the branch during the operation and load adjustment of the cracking furnace, and improves the stability of the overall operation of the cracking furnace.

[0070] Figure 3 Figure 2 is a structure diagram of an ethylene cracking furnace cluster control system according to another embodiment of the present application. As shown in the figure, the ethylene cracking furnace 301 has four branch feeds. The first branch flow controller 302, the second branch flow controller 303, the third branch flow controller 304, and the fourth branch flow controller 305 are used to control the branch hydrocarbon feed flow FSV i . The first branch outlet temperature controller 312, the second branch outlet temperature controller 313, the third branch outlet temperature controller 314, and the fourth branch outlet temperature controller 315 are used to control the branch outlet temperature T OUTi . The furnace COT temperature 306 is T COT . The fuel gas flow controller 307 FB G is configured to control the fuel gas flow 308 FC G . ​

[0071] Figure 4 According to the present invention Figure 3 The temperature and flow rate operation curve diagram of the ethylene cracking furnace before the crossbow control is implemented in the embodiment, Figure 5 According to the present invention Figure 3 The temperature and flow rate operation curve diagram of the ethylene cracking furnace after the crossbow control is implemented in the embodiment.

[0072] like Figure 3 、 Figure 4 、 Figure 5 The furnace inlet feed is respectively equipped with FIC101, FIC201, FIC301 and FIC401, representing the first branch flow controller 302, the second branch flow controller 303, the third branch flow controller 304 and the fourth branch flow controller 305; TIC101, TIC201, TIC301 and TIC401 represent the first branch outlet temperature controller 312, the second branch outlet temperature controller 313, the third branch outlet temperature controller 314 and the fourth branch outlet temperature controller 315; TIC001 represents the furnace COT temperature controller 306; and FIC001 represents the fuel gas flow controller 307. Due to the uneven distribution of combustion temperature in the cracking furnace, there are differences in branch temperatures. To this end, a cracking furnace crossbow control module was developed. The maximum adjustment increase / decrease per minute of a single branch was set to 0.1 tons. After running for 100 minutes, the load was reduced by 4 tons. After running for 200 minutes, the load was increased by another 4 tons. The module was downloaded and implemented in the DCS system to achieve the purpose of reducing branch temperature differences.

[0073] like Figure 4 and Figure 5 As shown in the figure, before the implementation of the crossbow control system, the COT temperature and the four branch feeds fluctuated within a small range around the set values. When the cracking furnace load decreased or increased, the COT temperature and the four branch temperatures also fluctuated. After the crossbow control system was implemented, the COT temperature and the four branch temperature curves remained stable under normal operating conditions and when the cracking furnace load decreased or increased. Branch feed fluctuations also decreased, which promoted the overall stable operation of the cracking furnace.

[0074] Figure 6 The figure is a flow chart of a cracking furnace crossbow control method according to one embodiment of the present invention.

[0075] In step 610, the branch hydrocarbon feed flow rate is controlled. As previously mentioned, according to an embodiment of the present invention, one or more branch hydrocarbon feed flow rate control modules are used to achieve controllability of the flow rate.

[0076] In step 620, the change in branch hydrocarbon feed flow rate is controlled by quantifying the branch hydrocarbon feed flow temperature data through one or more branch outlet temperature control modules.

[0077] In step 630, the fuel gas flow rate is controlled. As described above, the fuel gas flow rate is controlled by the fuel gas flow rate control module.

[0078] In step 640, a cascade control loop is formed. The cascade control loop can be formed by the COT temperature control module and the fuel gas flow rate control module.

[0079] The above embodiments are only for illustrating the present application, and are not intended to limit the present application. Those skilled in the art can make various changes and modifications without departing from the scope of the present application. Therefore, all equivalent technical solutions should belong to the scope of the present application.

Claims

1. A cracker furnace train control system comprising: one or more branch hydrocarbon feed flow control modules configured to control branch hydrocarbon feed flow ; one or more branch outlet temperature control modules configured to control the amount of change in the branch hydrocarbon feed flow rate, the one or more branch outlet temperature control modules further comprising one or more branch outlet temperatures ; Fuel gas flow control module for controlling the incoming fuel gas flow ; a COT temperature control module, which forms a cascade control loop with the fuel gas flow control module to adjust the COT temperature by adjusting the fuel gas flow ; a calculation module to calculate one or more of a branch feed adjustment amount increment and a reduction amount and , increment and decrement and ; wherein the cracking furnace feed flow has n groups; TC i the change in the branch hydrocarbon feed flow needed to adjust the ith branch, ; wherein Tin is the inlet temperature of the i-th branch of the cracking furnace; By , , and the preset condition, the single adjustment amount of the branch feed amount is calculated, and then the adjusted of each branch is obtained; The method comprises the following steps: , , and preset conditions, the single adjustment amount of the branch feed amount is calculated, and then the adjusted of each branch is obtained. Calculating the limit value of each branch adjustment amount To: ; increment coefficient is: ; decrement coefficient is: ; Limit value of each branch adjustment amount Single maximum increment or maximum decrement is ; Single maximum adjustment increment or maximum adjustment decrement And single adjustment coefficient The formula is as follows; , ; Single adjustment amount of branch feed amount is: ; the branch hydrocarbon feed flow rate .

2. The split furnace multi-shot control system of claim 1, wherein, The temperature control range of the COT temperature control module is 700-900°C.

3. The split furnace multi-shot control system of claim 1, wherein, Cracking furnace total load setpoint is: ； wherein, is the initial set value of the cracking furnace load, is the cracking furnace load adjustment rate, is the time of load adjustment.

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