Cracking furnace temperature control system, method, cracking furnace, and machine-readable storage medium

Abstract

The embodiment of the present application provides a cracking furnace temperature difference control system, method, cracking furnace and machine readable storage medium, and belongs to the field of chemical production process. The cracking furnace temperature difference control system opens the control valve of the first-stage lance manifold and the second-stage lance manifold under normal operation conditions, controls COT by the control valve of the second-stage lance manifold; opens only the control valve of the first-stage lance manifold under the conditions of coke burning and hot standby, controls COT by the control valve, and calculates the difference between the COT average value of each group of furnace tubes and the COT average value of all furnace tubes, and adjusts the opening of the corresponding TDC control valve according to the difference, so that the COT of each group of furnace tubes is consistent. The cracking furnace temperature difference control system and method provided by the present application are suitable for a wide range of cracking furnace types and are not limited by the feed form of the cracking furnace or the configuration of the side wall burner. The present application can satisfy TDC control under all conditions including normal operation, coke burning and hot standby.

Description

Technical Field

[0001] This invention relates to the field of chemical production processes, and more specifically to a temperature control system, method, pyrolysis furnace, and machine-readable storage medium for a pyrolysis furnace. Background Technology

[0002] In ethylene plant cracking furnaces, TDC (Total Discharge Temperature) refers to the difference between the average outlet temperature of a single furnace tube and the average outlet temperature of all furnace tubes in the same furnace chamber. Depending on the feed method of the cracking furnace, there are currently two main TDC control technologies:

[0003] (1) For traditional pyrolysis furnaces, each group of furnace tubes corresponds to a raw material control valve. The TDC of each group of furnace tubes is adjusted within the allowable range by adjusting the feed rate of each group of furnace tubes. Specifically, the feed rate of each group of raw materials in each pyrolysis furnace (furnace chamber) is cascaded controlled, and the total feed flow controller outputs a set value to each group of raw material feed controllers. In addition, each group of furnace tubes is equipped with a temperature difference controller (TDC). By adding a small positive or negative offset to the set value output by the total feed rate controller of the pyrolysis furnace, the corrected value is used as the final set value of each group of raw material feed controllers. That is, within the allowable range of the temperature deviation of the radiant section outlet of each group, the radiant section outlet temperature (COT) of each group of furnace tubes is kept consistent by adjusting the feed rate of each group.

[0004] (2) For large-group feed pyrolysis furnaces, the number of feedstock groups and the number of pyrolysis gas groups exiting the radiant section are inconsistent. The traditional feedstock quantity control TDC cannot achieve one-to-one adjustment. Therefore, the fuel gas nozzles on the side wall of the pyrolysis furnace are grouped according to the number of pyrolysis gas outlet groups in the radiant section. A control valve is added to the main side combustion pipeline of each group. The TDC of each group automatically controls the opening of this regulating valve. That is, the fuel gas flow rate of each group on the side wall is adjusted through this regulating valve, thereby ensuring that the radiant section outlet temperature (COT) of each group of furnace tubes is consistent.

[0005] In the process of developing this invention, the inventors discovered that the existing technology has a problem with the number of raw material groups and the number of pyrolysis gas groups exiting the radiation section being inconsistent. Traditional methods of controlling the TDC by adjusting the raw material quantity cannot achieve a one-to-one correspondence. Furthermore, this pyrolysis furnace only has bottom burners and no sidewall burners, making it impossible to control the TDC by adjusting the flow rate of each group of sidewall fuel gas. In addition, during coking in the pyrolysis furnace, both the raw material and the sidewall burners are shut off, rendering the above control techniques ineffective for adjusting the TDC; adjustment can only be achieved by adjusting the bottom damper.

[0006] There is a lack of effective technical solutions for TDC control of pure bottom-fired, large-feed pyrolysis furnaces under various operating conditions. Developing a TDC control scheme that is applicable to a wide range of pyrolysis furnace types, covers all operating conditions, and is sensitive and stable is therefore of paramount importance. Summary of the Invention

[0007] The purpose of this invention is to provide a widely applicable temperature difference control system for pyrolysis furnaces, making the pyrolysis furnace unrestricted by the feeding method or the configuration of the sidewall burners. This invention can meet the TDC control requirements for all operating conditions, including normal operation, coking, and hot standby.

[0008] To achieve the above objectives, embodiments of the present invention provide a temperature difference control system for a pyrolysis furnace. This system includes: multiple sets of furnace tubes disposed at the bottom of the furnace chamber of the pyrolysis furnace, each set consisting of multiple furnace tubes, where an oil-gas mixture undergoes a thermal pyrolysis reaction; multiple sets of burners symmetrically arranged corresponding to each set of furnace tubes; multiple sets of primary spray nozzles, each set of burners containing one set of primary spray nozzles, with combustion gas supplied to each set of primary spray nozzles via a primary spray nozzle manifold; and multiple sets of secondary spray nozzles, each set of burners containing one set of secondary spray nozzles, with combustion gas supplied to each set of secondary spray nozzles via a secondary spray nozzle manifold. Within each set of burners, the heat load of the primary spray nozzle is less than that of the secondary spray nozzle. The system includes: a heat load for the spray gun; COT control valves, respectively installed in the primary spray gun main pipe and the secondary spray gun main pipe, for controlling the flow rate of combustion gas in the primary spray gun main pipe and the secondary spray gun main pipe; multiple TDC control valves, installed between the COT control valve in the primary spray gun main pipe and each group of primary spray guns, for controlling the flow rate of fuel gas in each group of primary spray guns; and a controller for performing the following operations: obtaining the average COT value of each group of furnace tubes; obtaining the average COT value of all furnace tubes in the multiple groups of furnace tubes; calculating the difference between the average COT value of each group of furnace tubes and the average COT value of all furnace tubes, and adjusting the opening of the corresponding TDC control valve according to the difference to ensure that the COT values ​​of each group of furnace tubes are consistent.

[0009] Optionally, under normal operating conditions, the COT control valves of the primary spray gun main pipe and the secondary spray gun main pipe are opened; under coking and hot standby conditions, only the COT control valve of the primary spray gun main pipe is opened.

[0010] Optionally, the system includes a selector, through which the controller selects the opening and closing of the corresponding COT control valve under different operating conditions.

[0011] Optionally, the average COT of each group of furnace tubes is calculated using the following formula:

[0012] R t =ΣAi / N, (i=1,2,3...,N),

[0013] Among them, R tLet Ai be the average COT value of the i-th furnace tube in the t-th group, and N be the number of furnace tubes in the t-th group.

[0014] The average COT of all furnace tubes is calculated using the following formula:

[0015] R M =ΣR t / M, (t=1,2,3…,M)

[0016] Among them, R M Rt is the average COT of all furnace tubes, Rt is the average COT of the t-th group of furnace tubes, and M is the total number of furnace tube groups.

[0017] On the other hand, the present invention provides a method for controlling the temperature difference in a pyrolysis furnace, used in a pyrolysis furnace temperature difference control system. The system is characterized by comprising: multiple sets of furnace tubes disposed at the bottom of the furnace chamber of the pyrolysis furnace, each set consisting of multiple furnace tubes, where an oil-gas mixture undergoes a thermal pyrolysis reaction; multiple sets of burners symmetrically arranged corresponding to each set of furnace tubes; multiple sets of primary spray guns, each set of burners containing one set of primary spray guns, with combustion gas supplied to each set of primary spray guns via a primary spray gun manifold; and multiple sets of secondary spray guns, each set of burners containing one set of secondary spray guns, with combustion gas supplied to each set of secondary spray guns via a secondary spray gun manifold, wherein within each set of burners, the primary... The number of spray guns is less than the number of secondary spray guns; COT control valves are respectively installed in the primary spray gun main pipe and the secondary spray gun main pipe, used to control the flow rate of combustion gas in the primary spray gun main pipe and the secondary spray gun main pipe; and multiple TDC control valves are installed between the COT control valve in the primary spray gun main pipe and each group of primary spray guns, used to control the flow rate of fuel gas in each group of primary spray guns; the method includes the following steps: obtaining the average COT value of each group of furnace tubes in multiple groups of furnace tubes; obtaining the average COT value of all furnace tubes in multiple groups of furnace tubes; calculating the difference between the average COT value of each group of furnace tubes in multiple groups of furnace tubes and the average COT value of all furnace tubes; and adjusting the opening of the corresponding TDC control valve according to the difference to make the COT of each group of furnace tubes consistent.

[0018] Optionally, under normal operating conditions, the COT control valves of the primary spray gun main pipe and the secondary spray gun main pipe are opened; under coking and hot standby conditions, only the COT control valve of the primary spray gun main pipe is opened.

[0019] Optionally, the opening and closing of the corresponding COT control valve can be selected via a selector under different operating conditions.

[0020] Optionally, the average COT of each group of furnace tubes is calculated using the following formula:

[0021] R t =ΣAi / N, (i=1,2,3...,N),

[0022] Among them, R t Let Ai be the average COT value of the i-th furnace tube in the t-th group, and N be the number of furnace tubes in the t-th group.

[0023] The average COT of all furnace tubes is calculated using the following formula:

[0024] R M =ΣR t / M, (t=1,2,3…,M)

[0025] Among them, R M Rt is the average COT of all furnace tubes, Rt is the average COT of the t-th group of furnace tubes, and M is the total number of furnace tube groups.

[0026] On the other hand, the present invention provides a pyrolysis furnace, which includes the pyrolysis furnace temperature difference control system of the present invention.

[0027] On the other hand, the present invention provides a machine-readable storage medium storing instructions for causing a machine to execute the pyrolysis furnace temperature difference control method of the present invention.

[0028] This invention employs a novel TDC (Total Temperature Difference) control technology. The primary fuel gas nozzles of the pyrolysis furnace are grouped according to the number of pyrolysis gas outlet groups in the radiant section. A control valve is added to the main primary fuel gas pipeline of each group. The TDC of each group automatically controls the opening of this regulating valve, thereby adjusting the primary fuel gas flow rate of each group and ensuring that the radiant section outlet temperature (COT) of each group of furnace tubes is consistent. The pyrolysis furnace temperature difference control system and method of this invention are applicable to a wide range of pyrolysis furnace types, and are not limited by the feeding method or the configuration of the sidewall burners. This invention can meet the TDC control requirements of the pyrolysis furnace under all operating conditions, including normal operation, coking, and hot standby.

[0029] The pyrolysis furnace temperature difference control system of this invention can effectively control the temperature difference control (TDC) under multiple operating conditions, including pure bottom-firing, large-group-feed pyrolysis furnaces, normal operation, and coking conditions. Compared with traditional pyrolysis furnace TDC temperature difference control schemes, it has the following advantages:

[0030] 1) The method of controlling TDC by adjusting the feed rate of each furnace tube cannot be applied in large-group feed cracking furnaces, and adjusting the feed rate will result in unequal feed rates for each furnace tube, thus leading to unequal coking rates. This invention avoids controlling TDC by the feed rate.

[0031] 2) Not all ethylene cracking furnaces are equipped with side-wall burners, so the method of controlling TDC by adjusting the side-wall fuel gas flow cannot be widely applied. However, ethylene plant cracking furnaces are all equipped with bottom burners, so the technical solution of this invention can be widely promoted and used.

[0032] 3) The scheme of adjusting TDC using all burners corresponding to each group of furnace tubes is prone to causing large fluctuations. In actual operation, it is often necessary to adjust the Kock valve (burner fuel gas root valve) on site in conjunction with this. The technical solution provided by this invention uses a single-stage burner with a lower load as the adjustment means, which provides more precise control of TDC and is less prone to fluctuations.

[0033] 4) The primary burner is used in both normal operation of the pyrolysis furnace and coking and hot standby conditions. Therefore, compared with the method of adjusting TDC using a secondary burner, this invention is more adaptable to various operating conditions.

[0034] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0035] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0036] Figure 1 This is a schematic diagram of a traditional pyrolysis furnace that controls the temperature difference based on the amount of raw material fed into the cascade.

[0037] Figure 2 This is a schematic diagram of a large-group feed pyrolysis furnace based on the temperature difference controlled by the sidewall fuel gas flow rate.

[0038] Figure 3 This is a schematic diagram of the control valve of the pyrolysis furnace temperature difference control system according to an embodiment of the present invention.

[0039] Figure 4 This is a schematic diagram of the furnace tube assembly of the pyrolysis furnace temperature difference control system according to an embodiment of the present invention.

[0040] Figure 5 This is a flowchart of an embodiment of the pyrolysis furnace temperature difference control method of the present invention.

[0041] Explanation of reference numerals in the attached figures

[0042] TY0X011 Average COT of the first group of furnace

[0043] TY0X000A-A Furnace Four Groups Average COT

[0044] TICX000A-A Furnace Main COT Regulator

[0045] TDY0X011 Furnace First Group Average COT and Fourth Group Average COT Deviation Calculation Module

[0046] TDIC0X011 First set of temperature difference regulators in the furnace

[0047] FIC0X011 First set of raw material flow regulators in the furnace

[0048] FY0X000 Sum of the SV values ​​(control system setpoints) of the four sets of raw material flow regulators.

[0049] FIC0X000-A Furnace Raw Material Total Feed Rate Regulator

[0050] FY0X011-A Module for Calculating the Summation of the OP Value (Valve Opening) of the Total Furnace Raw Material Feed Regulator and the OP Value (Valve Opening) of the First Group of Temperature Difference Regulators

[0051] FIC0X011 First set of feed flow regulators in the furnace

[0052] TY09011 Large-scale feed cracking furnace, first group average COT

[0053] The average COT of the six groups of TY09000 large-group feed pyrolysis furnaces

[0054] TIC09000 Large-Group Feed Cracking Furnace Total COT Regulator

[0055] TDY09011 Large-Group Feed Cracking Furnace Average COT Deviation Calculation Module for Group 1 and Group 6

[0056] TDIC09011 Large-scale feeding pyrolysis furnace, first group temperature difference regulator

[0057] PY09180 First Group of Sidewall Fuel Gas Pressure High Selector

[0058] PIC09180 First Group Side Wall Fuel Gas Pressure

[0059] PV09180 First set of sidewall fuel gas pressure control valves

[0060] TY03011 Cracking Furnace Temperature Difference Control System First Group Average COT

[0061] TY03000 pyrolysis furnace temperature difference control system with six average COT groups

[0062] TIC03000 Cracking Furnace Temperature Difference Control System Total COT Regulator

[0063] TDY03011 Cracking Furnace Temperature Difference Control System First Group Average COT and Sixth Group Average COT Deviation Calculation Module

[0064] TDIC03011 Pyrolysis Furnace Temperature Difference Control System First Group of Temperature Difference Regulators

[0065] PY03181 First Group Bottom Stage Fuel Gas Pressure High Selector

[0066] PIC03181 First Group Bottom Stage Fuel Gas Pressure

[0067] PV03181 First group of bottom stage fuel gas pressure control valve

[0068] QIC03081 Total heat load of a single-sided furnace

[0069] HS03081 Selector Controller

[0070] PIC03082 Single-sided furnace primary fuel gas main pressure

[0071] PIC03081 Single-sided furnace secondary fuel gas main pressure

[0072] QY03082 / 03081 Pressure and Calorific Value Selector Controller Detailed Implementation

[0073] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0074] Figure 1 This is a schematic diagram of a traditional pyrolysis furnace based on the cascade control of temperature difference according to the feed rate. It has multiple control valves set according to the number of groups of pyrolysis gas outlets in the radiant section of the pyrolysis furnace. Each control valve is used to control the flow rate of a group of sidewall fuel gas nozzles. Figure 2 This is a schematic diagram of a large-group feed cracking furnace based on the temperature difference control of the sidewall fuel gas flow rate. For example, the single furnace feed of Zhenhai Refining & Chemical's No. 2 ethylene F-009 is divided into four groups, and the cracking gas exiting the radiant section is divided into six groups. The sidewall fuel gas nozzles of the cracking furnace are grouped according to the number of radiant section cracking gas outlet groups. A control valve is added to the sideburn main pipeline of each group. The TDC of each group automatically controls the opening of this regulating valve, that is, the sidewall fuel gas flow rate of each group is adjusted through this regulating valve, thereby ensuring that the radiant section outlet temperature (COT) of each group of furnace tubes is consistent.

[0075] This invention mainly achieves TDC control of large-group feeding, pure bottom-burning pyrolysis furnace under multiple operating conditions such as normal operation and coking through the following technical solutions:

[0076] (1) Bottom burners are installed on both sides of the pyrolysis furnace tubes. Each burner has several spray guns, including a primary spray gun (main burner) and a secondary spray gun (auxiliary burner). During normal operation of the pyrolysis furnace, both primary and secondary spray guns are in use. During coking and hot standby conditions, only the primary spray gun needs to be used to meet the requirements. Each furnace chamber of the pyrolysis furnace has a control valve installed on the fuel gas main of the primary and secondary spray guns. During normal operation, both primary and secondary spray guns are in use. At this time, the selector selects the secondary spray gun with higher heat load to control the pyrolysis furnace COT, while the primary spray gun is controlled by heat load. During coking conditions, the secondary spray gun is deactivated, and the selector selects the primary spray gun to control the pyrolysis furnace COT.

[0077] (2) Each group of furnace tubes in the pyrolysis furnace is equipped with a primary fuel gas path and a control valve. The control valve controls the heat of each group of burners, thereby achieving TDC control. Since the primary spray gun is used under both normal operating conditions and coking conditions, TDC control of the pyrolysis furnace under multiple operating conditions can be achieved.

[0078] Specifically, the pyrolysis furnace temperature difference control system according to an embodiment of the present invention includes: multiple sets of furnace tubes, multiple sets of burners, multiple sets of primary spray guns, multiple sets of secondary spray guns, COT control valves, multiple TDC control valves, and a controller.

[0079] According to an embodiment of the present invention, the pyrolysis furnace temperature difference control system comprises multiple sets of furnace tubes arranged at the bottom of the furnace chamber. Each set of furnace tubes consists of multiple tubes, where the oil-gas mixture undergoes thermal pyrolysis. The multiple sets of furnace tubes are the tubes of the radiant section of the pyrolysis furnace. Each set of furnace tubes may include multiple sub-groups of radiant furnace tubes. After the oil-gas mixture undergoes thermal pyrolysis in a set of furnace tubes, the high-temperature pyrolysis gas exits the radiant section and enters the corresponding quench heat exchanger module. Each furnace tube exiting the radiant section is equipped with a wall-mounted thermocouple. The real-time COT value measured by the thermocouple is transmitted to the DCS system as the input process value for the controller of the pyrolysis furnace outlet temperature (described later).

[0080] According to an embodiment of the present invention, the multiple burners of the pyrolysis furnace temperature difference control system are symmetrically arranged corresponding to each of the multiple furnace tubes. For example, a set of burners is arranged on each of the upper and lower sides of a set of furnace tubes, and each set of burners may contain multiple burners.

[0081] In the pyrolysis furnace temperature difference control system according to an embodiment of the present invention, each of the multiple burners is provided with a set of primary spray guns. The combustion gas is delivered to each of the multiple sets of primary spray guns through the primary spray gun manifold. That is, a set of primary spray guns is evenly distributed in each burner of a set of burners, and its fuel gas quantity is adjusted by the COT control valve and TDC control valve described later, thereby adjusting the corresponding COT.

[0082] In the pyrolysis furnace temperature difference control system according to an embodiment of the present invention, each of the multiple sets of burners is provided with a set of secondary spray guns. Combustion gas is delivered to each of the multiple sets of secondary spray guns through a secondary spray gun manifold. Similarly, a set of secondary spray guns is evenly distributed within each burner of a set of burners, and its fuel gas quantity is adjusted by a COT control valve described later, thereby adjusting the corresponding COT.

[0083] In each burner group, the heat load of the primary spray gun is less than that of the secondary spray gun. The heat loads of the primary and secondary spray guns differ, and the typical ratio of the number of spray guns is 4:6 or 3:7. The heat load of the primary spray gun is sufficient for coking and hot standby conditions. The total load of the primary and secondary spray guns meets the requirements for normal operation. This invention primarily adjusts the COT deviation of the pyrolysis furnace by using the relatively small proportion of the primary spray gun, thus achieving more accurate control.

[0084] Figure 3 This is a schematic diagram of the control valve of the pyrolysis furnace temperature difference control system according to an embodiment of the present invention, as shown below. Figure 3 As shown, COT control valves are respectively installed in the primary and secondary spray gun mains to control the flow rate of combustion gas in the primary and secondary spray gun mains. The average value of the outlet temperatures of all radiant section furnace tubes is the total COT (Coil Outlet Temperature) of the pyrolysis furnace. At this time, the COT control valve controls the flow rate of fuel gas based on the pressure and calorific value of the primary and secondary fuel gas mains. That is, the output of the pyrolysis furnace average outlet temperature regulator is used as the set value of the fuel calorific value regulator to adjust the total calorific value of the burners. The flow rate of fuel gas is calculated with the calorific value of the fuel gas after temperature and pressure compensation. Under normal operating conditions, the fuel gas is controlled by calorific value; under low load, there is low-pressure override protection.

[0085] According to an embodiment of the present invention, a plurality of TDC control valves in the pyrolysis furnace temperature difference control system are disposed between the COT control valve of the primary spray gun main pipe and each group of primary spray guns, for controlling the flow rate of fuel gas in each group of primary spray guns. This configuration effectively solves the problem that, during coking in the pyrolysis furnace, when the raw materials and sidewall burners are closed, traditional technical solutions cannot adjust the TDC and can only adjust it by adjusting the bottom damper. This design allows for wide applicability to pyrolysis furnace types, comprehensive operating conditions, and sensitive and stable adjustment.

[0086] According to an embodiment of the present invention, the controller of the pyrolysis furnace temperature difference control system is configured to perform the following operations: obtain the average COT value of each group of furnace tubes in the plurality of furnace tubes; obtain the average COT value of all furnace tubes in the plurality of furnace tubes; calculate the difference between the average COT value of each group of furnace tubes and the average COT value of all furnace tubes, and adjust the opening degree of the corresponding TDC control valve according to the difference, so that the COT of each group of furnace tubes is consistent.

[0087] Specifically, the average COT of each group of furnace tubes is transmitted to the total COT regulator via the PV value (calorific value) as the real-time total COT value of the cracking furnace. The average COT of each group is transmitted to the corresponding average COT and total COT deviation calculation module, and the difference between the average COT and the total COT is transmitted to the temperature difference regulator of each group. The temperature difference regulator of each group transmits the data to the corresponding group's first-stage fuel gas pressure control valve via the corresponding first-stage fuel gas pressure selector, and adjusts the first-stage fuel gas flow of the corresponding group to eliminate the deviation of COT in each group, so as to ensure that the radiant section outlet temperature (COT) of each group of furnace tubes is consistent.

[0088] In some implementations, under normal operating conditions, the COT control valves of the primary spray gun main pipe and the secondary spray gun main pipe are opened. At this time, the COT control and TDC control are connected in parallel, which effectively avoids the mutual interference between the two control loops before and after the series control in the prior art.

[0089] During coking and hot standby conditions, only the COT control valve of the primary spray gun main pipe is opened. In this case, the COT and TDC controls on the primary spray gun are essentially connected in series, and adjustments before and after will cause some interference. However, during coking and hot standby, the control requirements for these two indicators are reduced, thus remaining within an acceptable range.

[0090] In some embodiments, the system includes a selector, through which the controller selects the opening and closing of the corresponding COT control valve under different operating conditions to automatically control the COT. For example, under normal operating conditions, the selector selects the secondary spray gun with higher heat load to control the pyrolysis furnace COT, while the primary spray gun is controlled by heat load. Here, heat load control is the control of converting fuel gas flow rate into heat load. That is, the COT temperature control first provides a setpoint SP to the calorific value controller, and the actual measured calorific value per unit mass of fuel gas and the total fuel gas volume are used to calculate the current calorific value PV. The difference between PV and SP is used to control the COT control valve.

[0091] Specifically, when the pyrolysis furnace is in normal operation, the selector controller chooses the secondary fuel gas pressure and calorific value high-selection controller to control the pyrolysis furnace COT. After comparing the real-time value of the total pyrolysis furnace COT with the set value, it is transmitted to the bottom secondary fuel gas controller and the secondary fuel gas pressure high-selection controller (selecting the larger signal as the control basis). Then, the bottom secondary fuel gas quantity is adjusted through the secondary nozzle main pipe COT control valve to control the total pyrolysis furnace COT. When the pyrolysis furnace is in the coking state, the secondary burner is shut down. At this time, the selector selects the primary fuel gas pressure and calorific value high-selection controller to control the pyrolysis furnace COT. After comparing the real-time value of the total pyrolysis furnace COT with the set value, it is transmitted to the bottom primary fuel gas controller to adjust the bottom primary fuel gas quantity and control the total pyrolysis furnace COT.

[0092] In some embodiments, the average COT of each group of furnace tubes is calculated using the following formula:

[0093] R t =ΣAi / N, (i=1,2,3...,N),

[0094] Among them, R t Let Ai be the average COT value of the i-th furnace tube in the t-th group, and N be the number of furnace tubes in the t-th group.

[0095] The average COT of all furnace tubes is calculated using the following formula:

[0096] R M =ΣR t / M, (t=1,2,3…,M)

[0097] Among them, R M Rt is the average COT of all furnace tubes, Rt is the average COT of the t-th group of furnace tubes, and M is the total number of furnace tube groups.

[0098] Figure 4 This is a schematic diagram of the furnace tube assembly of the pyrolysis furnace temperature difference control system according to an embodiment of the present invention. The following will use the newly built dual-furnace light oil furnace F-003 in Zhenhai as an example, combined with... Figure 3 and Figure 4 A brief description of the implementation of the temperature difference control system for the cracking furnace of the present invention: In this embodiment, the F-003 has a production capacity of 200,000 tons of ethylene per year. The liquid feedstock from one side of the furnace enters the convection section of the cracking furnace for preheating, vaporization, and superheating via two flow control valves. Then, through a Venturi flow distributor, the oil-gas mixture is evenly distributed to each group of 2-1 type radiant furnace tubes. For example... Figure 4As shown, the F-003 single-sided radiant furnace tubes consist of 6 large groups, each group comprising 12 subgroups of type 2-1 radiant furnace tubes. The oil-gas mixture undergoes thermal cracking within these 6 groups of radiant furnace tubes. The high-temperature cracked gas exiting the radiant section then enters one of 6 linear quench heat exchanger modules. Each furnace tube exiting the radiant section is equipped with a wall-mounted thermocouple. The real-time COT value measured by the thermocouple is transmitted to the DCS system, serving as the input process values ​​TT03011A~L, TT03012A~L, TT03013A~L, TT03014A~L, TT03015A~L, and TT03016A~L for the controller of the cracking furnace outlet temperature. The DCS logic can then calculate the average COT (TY03011~6) for each group.

[0099] The calculation method for the average COT (TY03011~6) of each group is as follows:

[0100] Taking the average COT (TY03011) of the first group as an example:

[0101] TY03011=ΣAi / 12

[0102] Ai = TT03011A ~ L(PV);

[0103] If a single furnace tube with a defective COT value needs to be removed, the formula is as follows:

[0104] TY03011=Σ(Ai*Si) / Σ(Si)

[0105] In the formula:

[0106] Ai = TT03011A ~ L(PV);

[0107] Si = TT03011A ~ L good / bad value status (0 = bad value; 1 = good value).

[0108] After calculating the average COT of the six groups (TY03011~6), the total COT of the cracking furnace (TY03000) is obtained by averaging the values ​​through DCS logic. The calculation formula is as follows:

[0109] TY03000=ΣRt / 6

[0110] Rt = TY03011~6 (average COT for each group);

[0111] like Figure 3As shown, the six average COTTY03000 values ​​are transmitted via PV values ​​to the total COT regulator TIC03000 as the real-time value of the cracking furnace's total COT. When the cracking furnace is in normal operation, the COT of the cracking furnace is controlled by the secondary fuel gas through the selection controller HS03081. After comparing the real-time value of the total COT of the cracking furnace with the set value, it is transmitted to the bottom secondary fuel gas pressure, low calorific value controller QY03081 and the secondary fuel gas pressure (single-sided furnace secondary fuel gas main pipe pressure) PIC03081. After high selection, the bottom secondary fuel gas quantity is adjusted to control the total COT of the cracking furnace.

[0112] When the pyrolysis furnace is in the coking state, the secondary burner is shut down. At this time, the selector selects the primary fuel gas pressure and calorific value high selector controller QY03082 to control the pyrolysis furnace COT. The real-time value of the total COT of the pyrolysis furnace is compared with the set value and then transmitted to the bottom primary fuel gas controller to adjust the total amount of bottom primary fuel gas and control the total COT of the pyrolysis furnace.

[0113] Regardless of whether the pyrolysis furnace is in normal operation or coking state, the six average COTTY03000 values ​​are transmitted separately to the first to sixth average COT and the six average COT deviation calculation module TDY03011-6. The difference between the six average COT values ​​(first to sixth average COTTY03011-6) is transmitted to the first to sixth temperature difference regulators TDIC03011-6. The first to sixth temperature difference regulators TDIC03011-6 transmit the data to the corresponding first-stage fuel gas pressure selector (first to sixth bottom first-stage fuel gas pressure selector PY03181-6) via the corresponding first-stage fuel gas pressure control valve. The first-stage fuel gas quantity of the corresponding group is adjusted to eliminate the deviation of COT in each group of the first to sixth temperature difference regulators TDIC03011-6, ensuring that the radiant section outlet temperature (COT) of each group of furnace tubes is consistent.

[0114] Example 1

[0115] The eight newly built pyrolysis furnaces at Zhenhai 150 ethylene plant were all designed using the novel TDC control technology provided by this invention, which enabled effective TDC control of the pyrolysis furnaces under various operating conditions, including pure bottom burning and large-group feeding, as well as coking conditions.

[0116] Example 2

[0117] A manual adjustment test was conducted on the Zhenhai No. 2 ethylene F-007 cracking furnace. The six primary spray gun Cocker valves corresponding to the second group of furnace tubes in the F-007A furnace were gradually closed by 50% and then manually restored to full opening one by one. This process simulated the new control scheme.

[0118] Based on the actual on-site conditions, the COT of each furnace tube in the second group changed by 3-4℃ / 5min. Because the six Kock valves in each group were manually controlled and not adjusted simultaneously during the experiment, while this invention can automatically and simultaneously adjust the fuel gas volume of a single group, the technology in this invention, i.e., Example 1, will be more sensitive when adjusting the total primary fuel gas volume of each group. For TDC (TDC controlled within a 5℃ deviation) that only requires fine-tuning, this scheme can achieve rapid and precise adjustment.

[0119] This invention provides a method for controlling the temperature difference in a pyrolysis furnace. This method can be applied to any of the pyrolysis furnace temperature difference control systems and pyrolysis furnaces described in this invention. The control method is as follows: Figure 5 As shown, it includes:

[0120] First, obtain the average COT value for each group of furnace tubes in multiple groups;

[0121] Then, obtain the average COT value of all furnace tubes in multiple groups of furnace tubes;

[0122] Next, the difference between the average COT of each group of furnace tubes and the average COT of all furnace tubes is calculated.

[0123] Finally, based on this difference, adjust the opening of the corresponding TDC control valve to ensure that the COT of each group of furnace tubes is consistent.

[0124] In some implementations, under normal operating conditions, the COT control valves of the primary spray gun main pipe and the secondary spray gun main pipe are opened; under coking and hot standby conditions, only the COT control valve of the primary spray gun main pipe is opened.

[0125] In some implementations, the opening and closing of the corresponding COT control valve is selected by a selector under different operating conditions to automatically control the COT.

[0126] In some embodiments, the average COT of each group of furnace tubes is calculated using the following formula:

[0127] R t =ΣAi / N, (i=1,2,3...,N),

[0128] Among them, R t Let Ai be the average COT value of the i-th furnace tube in the t-th group, and N be the number of furnace tubes in the t-th group.

[0129] The average COT of all furnace tubes is calculated using the following formula:

[0130] R M =ΣR t / M, (t=1,2,3…,M)

[0131] Among them, R M Rt is the average COT of all furnace tubes, Rt is the average COT of the t-th group of furnace tubes, and M is the total number of furnace tube groups.

[0132] This invention provides a pyrolysis furnace, including the pyrolysis furnace temperature difference control system of this invention.

[0133] This invention provides a machine-readable storage medium storing program instructions that cause a machine to execute the method for controlling the temperature difference in a pyrolysis furnace according to this invention.

[0134] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0135] The above are merely embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A temperature difference control system for a pyrolysis furnace, characterized in that, include: Multiple sets of furnace tubes are installed at the bottom of the furnace chamber of the pyrolysis furnace. Each set of furnace tubes consists of multiple furnace tubes, where the oil-gas mixture undergoes thermal pyrolysis reaction. Multiple sets of burners are symmetrically arranged corresponding to each set of furnace tubes; Multiple sets of primary spray guns, each set of burners in the multiple sets of burners is equipped with a set of primary spray guns, and the combustion gas is delivered to each set of primary spray guns in the multiple sets of primary spray guns through the primary spray gun manifold. Multiple sets of secondary spray guns are provided. Each set of burners in the multiple sets of burners is equipped with a set of secondary spray guns. Combustion gas is delivered to each set of secondary spray guns in the multiple sets of secondary spray guns through the secondary spray gun manifold. In each set of burners, the heat load of the primary spray gun is less than the heat load of the secondary spray gun. COT control valves are respectively installed in the primary spray gun main pipe and the secondary spray gun main pipe, and are used to control the flow rate of combustion gas in the primary spray gun main pipe and the secondary spray gun main pipe; Multiple TDC control valves are disposed between the COT control valve of the primary spray gun manifold and each group of primary spray guns, for controlling the flow rate of fuel gas in each group of primary spray guns; as well as The controller is used to perform the following operations: Obtain the average COT value for each group of furnace tubes among the multiple groups of furnace tubes; Obtain the average COT value of all furnace tubes in the multiple groups of furnace tubes; The difference between the average COT of each group of furnace tubes and the average COT of all furnace tubes is calculated, and the opening of the corresponding TDC control valve is adjusted according to the difference to make the COT of each group of furnace tubes consistent.

2. The pyrolysis furnace temperature difference control system according to claim 1, characterized in that, Under normal operating conditions, open the COT control valves of the primary spray gun main pipe and the secondary spray gun main pipe; In the coking and hot standby conditions, only the COT control valve of the primary spray gun main pipe is opened.

3. The pyrolysis furnace temperature difference control system according to claim 1, characterized in that, The system includes a selector, through which the controller selects the opening and closing of the corresponding COT control valve under different operating conditions.

4. The pyrolysis furnace temperature difference control system according to any one of claims 1-3, characterized in that, The average COT value for each group of furnace tubes is calculated using the following formula: R t =ΣAi / N,(i=1,2,3…,N), Among them, R t Let Ai be the average COT value of the i-th furnace tube in the t-th group, and N be the number of furnace tubes in the t-th group. The average COT of all furnace tubes is calculated using the following formula: R M =ΣR t / M,(t=1,2,3…,M) Among them, R M Rt is the average COT of all furnace tubes, Rt is the average COT of the t-th group of furnace tubes, and M is the total number of furnace tube groups.

5. A method for controlling the temperature difference in a pyrolysis furnace, used in a pyrolysis furnace temperature difference control system. Its features are, The system includes: Multiple sets of furnace tubes are installed at the bottom of the furnace chamber of the pyrolysis furnace. Each set of furnace tubes consists of multiple furnace tubes, where the oil-gas mixture undergoes thermal pyrolysis reaction. Multiple sets of burners are symmetrically arranged corresponding to each set of furnace tubes; Multiple sets of primary spray guns, each set of burners in the multiple sets of burners is equipped with a set of primary spray guns, and the combustion gas is delivered to each set of primary spray guns in the multiple sets of primary spray guns through the primary spray gun manifold. Multiple sets of secondary spray guns, each set of burners in the multiple sets of burners is provided with a set of secondary spray guns, and the combustion gas is delivered to each set of secondary spray guns in the multiple sets of secondary spray guns through the secondary spray gun manifold. In each set of burners, the number of primary spray guns is less than the number of secondary spray guns. COT control valves, respectively installed in the primary spray gun main pipe and the secondary spray gun main pipe, are used to control the flow rate of combustion gas in the primary spray gun main pipe and the secondary spray gun main pipe; and Multiple TDC control valves are disposed between the COT control valve of the primary spray gun manifold and each group of primary spray guns, for controlling the flow rate of fuel gas in each group of primary spray guns; The method includes the following steps: Obtain the average COT value for each group of furnace tubes from multiple groups; Obtain the average COT value of all furnace tubes in multiple furnace tube groups; Calculate the difference between the average COT of each group of furnace tubes and the average COT of all furnace tubes; and Based on this difference, adjust the opening of the corresponding TDC control valve to ensure that the COT of each group of furnace tubes is consistent.

6. The method for controlling the temperature difference in a pyrolysis furnace according to claim 5, characterized in that, Under normal operating conditions, open the COT control valves of the primary spray gun main pipe and the secondary spray gun main pipe; In the coking and hot standby conditions, only the COT control valve of the primary spray gun main pipe is opened.

7. The method for controlling the temperature difference in a pyrolysis furnace according to claim 5, characterized in that, Under different operating conditions, the selector can be used to select the opening and closing of the corresponding COT control valve.

8. The method for controlling the temperature difference in a pyrolysis furnace according to claim 5, characterized in that, The average COT value for each group of furnace tubes is calculated using the following formula: R t =ΣAi / N,(i=1,2,3…,N), Among them, R t Let Ai be the average COT value of the i-th furnace tube in the t-th group, and N be the number of furnace tubes in the t-th group. The average COT of all furnace tubes is calculated using the following formula: R M =ΣR t / M,(t=1,2,3…,M) Among them, R M Rt is the average COT of all furnace tubes, Rt is the average COT of the t-th group of furnace tubes, and M is the total number of furnace tube groups.

9. A pyrolysis furnace, characterized in that, Includes a pyrolysis furnace temperature difference control system as described in any one of claims 1-4.

10. A machine-readable storage medium storing instructions for causing a machine to perform the pyrolysis furnace temperature difference control method as described in any one of claims 5-8.

Images