JPH10176170A - Method and apparatus for evaluating heating furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a technique of evaluating a heating furnace having a reaction tube in the inside promptly and easily without requiring many man-hours. SOLUTION: In practicing a method for evaluating a heating furnace having a reaction tube through the inside of which the fluid to be heated flows in the furnace, the reaction tube is regarded as a combination of straight tubes, the transfer of heat from the furnace to the tube is considered as that performed by the heat radiation from a heat radiation wall to the straight tube, and the state of the fluid in the straight tube is determined from the relationships between the heat radiation from the heat radiation wall to the surface of the straight tube, the heat conduction from the surface of the straight tube to the inside surface of the tube and the heat transfer from the inside surface of the tube to the fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for evaluating a heating furnace provided with a reaction tube in which a fluid to be heated flows.

[0002]

2. Description of the Related Art An example of such a heating furnace is shown in FIG.
There is a pyrolysis furnace for ethylene production as shown in FIG. In a pyrolysis furnace for producing ethylene, a mixed fluid containing hydrocarbons (naphtha, natural gas, ethane, etc.) is supplied into a reaction tube provided in the furnace, and the mixed fluid flowing in the reaction tube is supplied to the outside of the tube. To cause a thermal decomposition reaction to obtain an olefin such as ethylene or propylene as a product. Conventionally, when such a heating furnace is evaluated, the shape of the furnace and the shape of the reaction tube disposed through the furnace are accurately determined (if the reaction tube has a bent portion, the bent portion is directly modeled. If the reaction tube has a confluence, the confluence is modeled as it is) and a model was created and evaluated using this model. Here, the so-called combustion heat transfer simulation is used for the heat transfer from the combustion part to the reaction tube in the furnace, and the so-called decomposition reaction simulation for the reaction tube is used for the reaction tube and the fluid in the reaction tube. Was.

[0003]

However, the above prior art requires a model that accurately represents the furnace structure (shape and arrangement of furnace walls, reaction tubes, etc.).
Before the thermo-fluid analysis was performed, a model had to be created, which required a huge amount of work. As a result, there is a problem that it is difficult to quickly respond to a change in the shape of the reaction tube and a change in the conditions required for the design of the heating furnace. Further, in the combustion heat transfer simulation, it is relatively difficult to evaluate the output result. Accordingly, an object of the present invention is to provide a heating furnace evaluation technique that can quickly and easily evaluate a heating furnace having a reaction tube therein without requiring an excessive number of steps.

[0004]

Means for solving the problems The means for evaluating the heating furnace according to the present invention for achieving this object are as follows. That is, as described in claim 1, a method for evaluating a heating furnace having a reaction tube in which a fluid to be heated flows inside the furnace, wherein the reaction tube is regarded as a combination of straight tubes, Transfer of heat from the furnace to the reaction tube is considered to be due to heat radiation from the heat radiating wall to the straight tube, and the state of the fluid in the straight tube is defined between the heat radiating wall and the surface of the straight tube. The heat radiation is transmitted and received between the straight pipe surface and the inner surface of the straight pipe, and the heat transfer between the fluid and the fluid is performed between the straight pipe inner surface and the fluid. In adopting this method, two major modelings are performed. That is, (1) regards the heat transfer of combustion in the furnace as being due to heat radiation from the heat radiation wall, and (2) regards the reaction tube as a combination of straight tubes corresponding to the structure. . When adopting such an evaluation method, a case corresponding to a furnace wall composed of a heat radiation wall is imagined,
Transfer of heat to the reaction tube surface is performed only by heat radiation. Further, regarding the reaction tube and the fluid inside the reaction tube,
By taking into account so-called heat transfer and heat transfer, the physical state of the fluid inside the reaction tube is obtained. Further, a general reaction tube is usually composed of a straight tube corresponding portion, a bent tube portion connecting these straight tube corresponding portions, and a merging portion.
In addition, in consideration of the pressure loss in the fluid, it can be considered that the straight pipe extends, and conversely, it can be considered that the pressure loss is larger at this portion than in the case of the straight pipe. On the other hand, as for the junction, if the condition for maintaining the mass flow rate of the fluid at this portion is satisfied, there is no large difference in the result. Therefore, even if the heating furnace including the reaction tube is regarded as a combination of straight tubes that satisfies the above-described conditions, and is regarded as a heat system including heat radiating walls disposed around the straight tube, it is relatively difficult at present. Suitable simulation (evaluation) can be performed. In this case, since the model to be considered can be a very simple combination of a system having a straight pipe and a heat radiation wall, it is possible to quickly perform the pretreatment which has conventionally been a problem. As a result, an analysis / evaluation method capable of easily and quickly evaluating the heating furnace was obtained. Further, in this case, the simulation conditions are changed quickly, and the examination and evaluation can be performed quickly under various conditions, so that a reasonable evaluation can be easily achieved.

An apparatus using the above-described method for evaluating a heating furnace has the following configuration as described in claim 2. That is, an evaluation apparatus for a heating furnace including a reaction tube in which a fluid to be heated flows inside, which includes a housing having an inner wall that can be regarded as a heat radiating wall, and a straight tube that penetrates the housing. And the state of the fluid in the straight pipe is transmitted and received between the heat radiating wall and the straight pipe surface and between the straight pipe surface and the straight pipe inner surface. A heat-fluid analyzing means for determining based on the relationship between heat transfer and heat transfer between the inner surface of the straight tube and the fluid, and combining the reaction tube with the straight tube based on the input structure of the reaction tube; In addition to the straight pipe modeling conditions required when deeming that the model is integrated, an evaluation object integrated model generating means for generating an evaluation object integrated model configured as a combination of the basic models corresponding to the heating furnace is provided. The heat radiation input A central processing unit that determines the physical state of the fluid in the straight pipe by adapting the thermo-fluid analysis unit to the integrated model to be evaluated based on the initial condition and the boundary condition of the fluid in the straight pipe and the straight pipe; Be prepared. This evaluation device uses the evaluation method of the present invention described above, and includes a housing having an inner wall that can be regarded as a heat radiation wall, a basic model including a straight pipe penetrating the housing, The model is provided with a thermo-fluid analysis means capable of performing a thermo-fluid analysis of the physical state of the fluid in the straight pipe for the model. With this structure, for example, when targeting a simple basic model as shown in FIG. 5, if the initial conditions and boundary conditions are set for the heat radiating wall, the straight pipe, and the fluid in the straight pipe, the The physical state of the fluid can be determined. As described above, in the present application, a reaction tube to be evaluated is regarded as a combination of straight tubes. For example,
When a reaction tube having a structure as shown in FIG. 4 is targeted, as a whole furnace, as shown in FIG. 6, the system is regarded as a combination of a basic model. In such a modeling operation, predetermined conditions are required in order to regard the reaction tube as a combination of straight tubes. That is, a portion of the reaction tube having a straight tube shape is modeled as it is, and a curved tube portion is modeled as a straight tube taking this condition into account. Further, when a plurality of pipes are joined, conditioning is performed so as to satisfy the joining condition. An evaluation object integrated model to which such processing conditions are added is generated by an evaluation object integrated model generation unit. This model is a model as shown in FIG. 6, and is a model that substantially defines basic models and conditions for exchanging data between these basic models. Such an integrated model to be evaluated can perform the entire process in the same manner as applying the above-described thermo-fluid analysis means to each basic model, and as a result, the evaluation results (simulation) suitable for the structure of the reaction tube Result) can be obtained. This function is performed by the central processing means. As a result, in this device,
The method of the present application can be appropriately performed.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the evaluation device 1 of the present application. The evaluation device of the present application includes a so-called computer and software stored in the computer. The computer includes an input / output device 4 including a keyboard 2, a display device 3, etc., a central processing unit 5 for actually performing operations in the computer, and a storage device 6 including a semiconductor memory, a magnetic disk, and the like.
Analysis software and the like are stored in the storage device 6. Apparatus 1
Is provided with a thermo-fluid analysis means 7 which is software for thermo-fluid analysis required for evaluation. In executing the simulation, the software calculates a physical quantity stored in a memory associated with each part of the physical system to be evaluated based on initial conditions and boundary conditions of the physical system to be evaluated which are separately input. By solving so as to satisfy the equation system governing this software, a convergence solution can be obtained and an analysis result of the system can be obtained. In solving this equation system, a so-called finite element method or the like is used.

Next, the configuration of the basic model 8 used in the present application will be described. FIG. 5 shows the configuration of the basic model 8. The basic model 8 has a configuration in which a single straight pipe 11 penetrates a housing 10 in which a heat radiation wall 9 surrounds four sides. In the thermal fluid analysis of the basic model 8, heat is transferred by heat radiation from the heat radiating wall 9 surrounding the straight pipe 11 to the straight pipe surface 11a, and heat is transferred by heat conduction from the straight pipe surface 11a to the straight pipe inner surface 11b. Transfer and heat analysis from the straight pipe inner surface 11b to the moving fluid in the straight pipe and fluid analysis are performed. In such a simulation, it is naturally possible to arbitrarily set conditions such as heat radiation, heat conduction, and heat transfer, as well as boundary conditions and the like, which are conditions in the simulation.

To enable the above analysis, FIG.
As shown in (1), the apparatus 1 stores a thermo-fluid analyzing means 7 which is simulation software. Naturally, this means includes heat radiation analysis means 7a, heat conduction analysis means 7b,
Heat transfer fluid analysis means 7c is included. The heat radiation analyzing means 7a is arranged so that the heat radiating wall 9 surrounding the straight pipe 11 is connected to the straight pipe surface 11a.
A simulation of the transfer of heat by heat radiation to the pipe is performed, the heat conduction analysis means 7b analyzes the transfer of heat by heat conduction from the straight pipe surface 11a to the straight pipe inner face 11b, and further, the heat transfer fluid analysis means 7c. The transfer of heat from the straight pipe inner surface 11b to the moving fluid in the straight pipe and the flow analysis of the fluid itself are performed. Here, the thermal radiation analysis means 7a
Is a general heat radiation equation as its basic equation, and the heat conduction analysis means 7b similarly uses the heat conduction equation as a main basic equation. Further, the heat transfer fluid analysis means 7c uses a Navier-Stokes equation in consideration of energy dissipation accompanying the generation of turbulence as a main basic equation. Therefore, according to this configuration, if the physical state of the heat radiation wall 9 and the physical state of the inlet 12 and the outlet 13 of the straight pipe 11 are set as boundary conditions and the like,
The state of the fluid in the straight pipe can be obtained.

The above is the basic configuration of the evaluation apparatus 1 of the present application. When an actual evaluation of the thermal cracking furnace 14 as shown in FIG. 3 is to be performed, a reaction tube 15 provided in the cracking furnace 14 is required. Is not a simple straight pipe, but, for example, a bent pipe section 16 is provided in the reaction tube 15 and a confluent section 17 is provided. The apparatus 1 of the present application is configured to cope with such a situation. That is, in order to model the actual reaction tube 15 of the thermal decomposition furnace 14 as the straight tube 11 described above, the straight tube modeling condition generating means 18 shown in FIG. 1 is provided. The straight pipe modeling condition generating means 18 generates conditions necessary for simulation when the reaction tube 15 to be actually studied is regarded as a straight pipe. The simplified analysis target example shown in FIG. 4A will be described below. As an example of such a condition, in the case where the evaluation object includes the bent pipe portion 16, in order to represent the presence of the bent pipe portion 16 with the straight pipe 11, a model position corresponding to the bent pipe portion 16 is placed. Conditions for changing the simulation calculation of a certain bent pipe portion corresponding portion 16m (see FIG. 4) (for example, conditions such that the pipeline is regarded as being extended due to the presence of the bent portion and the rate of energy loss is increased). Generate automatically. Here, this condition is referred to as a bent tube portion corresponding condition. Further, when the junction 17 is present, the relationship between the physical quantities satisfies the condition of a constant mass flow rate between lattice points sandwiching the straight pipe corresponding to the junction 17 (the straight pipe junction corresponding to 17 m). As described above, the conditions that the physical quantity relationship between the lattices should satisfy are automatically generated. Here, this condition is called a connection condition. As an example of such connection conditions, when two pipes are merged into one pipe, and the route between the pipe diameters is twice the route before and after the merge, the connection condition is that the flow velocity changes. Make it not exist. On the other hand, if the pipe diameter is the upstream pipe diameter D _{1 and the} downstream pipe diameter D ₂ , the flow velocity before the merge is V _1, and the flow velocity after the merge is V ₂ = 2 (D ₁ /
D ₂ ) ² V ₁ . Such connection conditions are:
This is to be satisfied at a distance of 17 m between lattice points located at a position corresponding to the junction 17. In the apparatus 1, the conditions set by the straight pipe modeling condition generating means 18 are taken into consideration so as to satisfy the relationship between the straight pipe 11 and the physical quantity of each grid set for the fluid existing in the straight pipe. Then, simulate. Therefore, in the apparatus of the present invention, an analysis suitable for the actual reaction tube 15 can be performed while using the basic model 8.

The straight pipe modeling condition generating means 1 will now be described.
The execution program is generated such that the above-described bent pipe section corresponding conditions, connection conditions, and the like generated by step 8 are satisfied by the straight pipe bent pipe section corresponding section 16m and the straight pipe merging section corresponding section 17m. . It is the role of the evaluation object integrated model generation means 19 to perform such a built-in operation.
For example, with regard to the condition corresponding to the bent pipe portion, the calculation condition is changed so that the energy loss at this portion increases when adapting the heat transfer fluid analysis means. Further, with respect to the junction 17, a formula for connecting physical quantities between lattices is added so that each physical quantity has a constant mass flow rate between the lattices sandwiching the junction 17. The evaluation target integrated model generation means 19 automatically generates an execution program (referred to as an evaluation target integrated model) in consideration of such conditions. FIG. 6 is a conceptual diagram corresponding to the structure of FIG. 4 of such an evaluation object integrated model.
It was shown to. It can be seen that this model is configured with three straight tubes. Before and after the merging, the physical quantity of each lattice is transferred so as to satisfy the merging connection condition.

On the other hand, the central processing means 20 in the central processing unit 5 analyzes the generated integrated model for the evaluation object corresponding to the evaluation object based on the initial condition and the boundary condition inputted from the input / output device 4. To obtain a converged solution. In this processing, the central processing means 20 appropriately uses the previously described thermal fluid analysis means 7. Further, the central processing means 20 can output the obtained result to the input / output device 4 and display it as appropriate.

The above is the configuration of the evaluation apparatus 1 of the present application. An example in which the evaluation apparatus 1 is used to evaluate the pyrolysis furnace 14 will be described with reference to FIGS. 2 and 4 (a). This will be described below. Here, (a) schematically shows the actual configuration of the reaction tube 15 to be evaluated.
(B) shows a state where this is represented as the straight pipe 11. FIG. 2 shows a flow of operation steps. In the operation, the operator firstly inputs the conditions including the shape of the reaction tube 15 and the like into the input / output device 4 while referring to the drawing (FIG. 4A) of the pyrolysis furnace 14 which is an example of the heating furnace to be evaluated. Enter more. In this case, the straight tube portion 15
a, identification information of the bent pipe section 16 and the merging section 17 and the like, as well as information such as merging conditions (which pipes merge with which pipes) are also input (step 1). The information on the reaction tube 15 input in this way is passed to the straight tube modeling condition generating means 18, and the straight tube portion 15 a is not changed, and the bent tube portion 16 is not changed. For the merging section 17, the merging connection conditions described above are generated in association with the corresponding positions between the lattices (step 2). Then, by the operation of the evaluation object integrated model generating means 19 described above, an evaluation object integrated model taking into account the above-mentioned curved tube portion corresponding condition and connection condition is constructed (steps 3 and 4).

[0013] On the other hand, in accordance with the operating conditions of the pyrolysis furnace 14, the operator must satisfy the conditions that the heat radiating wall 9 should satisfy.
Initial conditions and boundary conditions of the straight pipe 11, its inlet 12, and outlet 13 are input (step 5).

After this operation, the evaluation device 1 executes a thermo-fluid analysis on the integrated model to be evaluated in accordance with the instruction of the operator (step 6) and outputs the analysis result (step 7). Thus, the simulation of the pyrolysis furnace can be completed.

[Other Embodiments] In the above-described embodiment, the straight pipe modeling conditions are automatically generated. However, when a simple analysis is performed, such straight pipe modeling conditions are not used. Alternatively, the input may be made from the input / output device 4 side by an operator.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a configuration of a heating furnace evaluation apparatus of the present application.

FIG. 2 is a diagram showing a procedure of heating evaluation.

FIG. 3 is a diagram showing an actual configuration example of a thermal decomposition furnace to be evaluated.

FIG. 4 is a conceptual diagram of modeling a reaction tube.

FIG. 5 is a conceptual configuration diagram of a basic model.

FIG. 6 is an explanatory diagram of an integrated model corresponding to FIG.

[Explanation of symbols]

 5 Central Processing Unit 7 Thermal Fluid Analysis Means 7a Heat Radiation Analysis Means 7b Heat Conduction Analysis Means 7c Heat Transfer Fluid Analysis Means 9 Heat Radiation Wall 11 Straight Pipe 16 Bent Pipe 17 Confluence 18 Straight Pipe Modeling Condition Generation Means 19 Evaluation Target Integrated model generation means

Claims (2)

[Claims] 1. A method for evaluating a heating furnace including a reaction tube in which a reaction object fluid flows inside, wherein the reaction tube is regarded as a combination of straight tubes, and heat from the furnace to the reaction tube is provided. Is considered to be due to heat radiation from the heat radiating wall to the straight pipe, and the state of the fluid in the straight pipe is transferred between the heat radiating wall and the surface of the straight pipe. A method for evaluating a heating furnace, which is obtained based on a relationship between heat transfer between a surface and an inner surface of a straight pipe and heat transfer between the inner surface of the straight pipe and the fluid. 2. An evaluation apparatus for a heating furnace having a reaction tube in which a fluid to be heated flows inside the furnace, comprising: a housing having an inner wall which can be regarded as a heat radiation wall; A basic model having a pipe is provided, and the state of the fluid in the straight pipe is transferred between the heat radiating wall and the straight pipe surface by heat radiation transfer between the straight pipe surface and the straight pipe inner surface. Thermofluid analyzing means for obtaining the heat transfer and the heat transfer between the inner surface of the straight pipe and the fluid. In addition to the straight pipe modeling condition required when considering a combination of pipes, an evaluation target integrated model generation that generates an evaluation target integrated model configured as a combination of the basic models in accordance with the heating furnace With means, input The heat radiation wall, the straight pipe, and the central condition for determining the physical state of the fluid in the straight pipe by applying the thermo-fluid analysis means to the integrated model to be evaluated based on the initial conditions and boundary conditions of the fluid in the straight pipe. Heating furnace evaluation device provided with processing means.