HG/T 20541-1992 Chemical Industrial Furnace Structural Design Specifications
Some standard content:
Industry Standard of the People's Republic of China
Regulations on Structural Design of Chemical Industrial Furnaces
HG20541-92
Editor: Industrial Furnace Design Technology Center of the Ministry of Chemical IndustryApproval Department: Ministry of Chemical Industry
Implementation Date: July 1, 1993
Engineering Construction Standard Editing Center of the Ministry of Chemical Industry
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oio.comFree download of various standard industry resources1 General Principles
2 Furnace Structure and Design Principles
2.1 Characteristics of Common Furnace Types and Their Selection
2.2 General Principles of Tube Furnace Design
2.3 Main Structure and Dimensions of Tube Furnace Principles of determination Furnace structure design
3.1 Furnace shell design
3.2 Furnace lining design
Burner design
4.1 Fuel and type selection of burner
4.2 Burner design calculation principles
4.3° Design and calculation of liquid fuel burner 4.4 Design and calculation of gas fuel burner 4.5 Oil-gas combined burner
4.6 Structural design of burner
4.7 Calculation formulas and examples of several burners 5 Pipe rack and tube sheet design.
5.1 Setting and selection requirements of pipe rack and tube sheet 5.2 Spring hanger…
5.3 Pipe rack, tube sheet, Guide frame and its accessories 5.4 Calculation of pipe rack strength
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Design of flue, smokestack, regulating baffle and ventilation equipment 6
6.1 Design of flue
6.2 Design of smoke diagram
6.3 Design of regulating baffle
6.4 Design of ventilation equipment
6.5 Materials
6.6 Design and calculation of flue and smoke window
6.7 Calculation of ventilation equipment
Setting and selection of accessories and components
7.1 Observation hole
7.2 Explosion-proof door
7.3 Manhole
7.4 Soot blower and soot blower
7. 5 Ash door (or cleaning hole)
7.6 Platform and ladder
Test and safety interface setting design
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Temperature measurement interface
8.2 Pressure measurement interface
Extinguishing steam interface
8.4 Flue gas sampling interface
Appendix A Furnace lining node diagram
A.1 Brick lining
A.2 Refractory castable lining
Refractory fiber lining
Appendix B Calculation of low-pressure oil burner
B.1 Symbol explanation
B.2 Calculation formula
B.3 Calculation example
Appendix C
Calculation of high-pressure oil burner
Symbol explanation
C.2 Calculation formula·
Calculation example…
Appendix D
Calculation symbols for medium and high pressure diffusion gas burners
Calculation of cross-sectional area of nozzle (fire hole) of medium and high pressure diffusion gas burners D.2
D.3 Calculation of nozzle (fire hole) diameter of medium and high pressure diffusion gas burners Appendix E Structural types of pipe racks, tube sheets and guide racks E.1
Vertical pipe racks
Horizontal pipe racks
Guide racks
Appendix F
Calculation of flue thermal expansion and its compensation
F.1 Explanation of symbols
F.2 Treatment of flue thermal expansion
F.3 Setting of compensators
F.4 Maximum value of each stage of corrugated and drum compensators Calculation of compression (or stretching) amount F.5 Calculation of rebound force when compensator is compressed (or stretched) F.6 Pre-stretching (pre-compression) amount of compensator
F.7 Calculation of thrust of sleeve-type compensator on fixed support Appendix G Calculation of smokestack height...
G.1 Explanation of symbols:
G.2 Calculation of smoke and sulfur dioxide emissions
G.3 Calculation of the relationship between smoke diagram height and suction force
G.4 Calculation of temperature drop of flue gas in flue and smokestack
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1.0.1 Purpose
This regulation specifies the furnace structure and design principles in the design of chemical industrial furnaces; specifies the requirements for the furnace body structure design and the design, installation and selection of the main auxiliary devices on the furnace. 1.0.2 Scope of Application
These regulations apply to the design of tubular furnaces in chemical and petrochemical plants; to the design of cylindrical furnaces and box furnaces that are directly heated, roasted, calcined and gasified by flames during chemical production; and also to the design of burners; pipe racks and tube sheets; flues, smoke windows, regulating baffles and ventilation equipment; accessories and component settings, selection design; testing and safety interface settings design. These regulations do not apply to the design of injectors and mixers for non-fuel combustion such as heavy oil gasification nozzles. These regulations do not apply to the design of pipe racks used for engineering pipelines. These regulations do not apply to the design of truss-type high smokestacks and smoke windows with pull ropes. 1.0.3 Reference standards
GB150 "Steel Pressure Vessels"
GBJ4 "Trial Standard for Industrial "Three Wastes" Emission" GBJ9 "Building Structure Load Code"
GBJ11 "Building Seismic Design Code"
GBJ17 "Steel Structure Design Code"
TJ36 "Industrial Enterprise Design Hygiene Standard" JB1121 "Corrugated Expansion Joint"
JB2654 "Constant Spring Hanger"
JBJ6 "Factory Power Design Technical Code" HGJ40 "Design and Selection Regulations for Refractory and Insulation Materials for Chemical Industrial Furnaces" HGJ41 "Design and Selection Regulations for Metal Materials for Chemical Industrial Furnaces" HGJ227 "Construction and Acceptance Specifications for Masonry Engineering of Chemical Furnaces" HG20545 "Technical Conditions for Manufacturing Pressure Components of Chemical Industrial Furnaces" HG20544 "Technical Conditions for Structural Installation of Chemical Industrial Furnaces" Standard Photo Network w
2 Furnace Structure and Design Principles
Common Furnace Type Characteristics and Selection
Tube furnaces are generally composed of radiation chambers, convection chambers, waste heat recovery devices, fuel combustion devices and ventilation devices. Furnace types should be classified by the shape of the mold, the shape of the radiation tubes and the arrangement of the burners. According to the shape of the furnace structure, it can be divided into two categories: cylindrical furnaces and box furnaces. According to the shape of the radiation tubes, it can be divided into vertical, horizontal and coil furnaces. According to the arrangement of the burners, it can be divided into top-burning, bottom-burning and side-burning furnaces. To meet various process requirements, pure radiation or pure convection furnaces can be used. 2.1.1 Cylindrical furnace
Cylindrical furnace has the characteristics of simple and compact structure, convenient hanging and supporting of furnace tubes (especially vertical tubes), small amount of high-alloy heat-resistant steel, relatively low cost, easy to handle thermal expansion, small footprint and convenient maintenance. Commonly used cylindrical furnaces are: pure radiation vertical cylindrical furnace and radiation-convection vertical cylindrical furnace. 2.1.1.1 Pure radiation vertical cylindrical furnace
Pure radiation vertical cylindrical furnace is divided into vertical tube type and coil type, as shown in Figure 2.1.1.1-1 and Figure 2.1.1.1-2. It does not have a convection chamber, the exhaust temperature is high, the thermal efficiency is low, but the structure is the simplest. The coil furnace has the characteristics of small resistance drop and complete emptying of the pipe system. Radiant tube
burner
Figure 2.1.1.1-1 Pure radiation vertical tube cylindrical furnace 2.1.1.2 Radiation-convection vertical cylindrical furnace Radiant tube
burner
Figure 2.1.1.1-2 Pure radiation coil cylindrical furnace This furnace type is the most commonly used furnace type. Generally, the radiation tube is a vertical tube and the convection tube is a horizontal tube, as shown in Figure 2.1.1.2-1. There are also furnace types in which the radiation tube is a coil and the convection tube is a horizontal tube or a coil, as shown in Figure 2.1.1.2-2. It is equipped with a convection chamber, and its thermal efficiency is higher than that of a pure radiation furnace. If necessary, finned tubes or nail-head tubes can be used to enhance convection heat transfer. Generally, the convection chamber is located above the radiation chamber, and the convection heat transfer area should not be arranged too much. 2
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For furnaces with large convection loads, the arrangement of the radiation tubes and the arrangement of the burners should be adjusted so that the furnace tubes can obtain double-sided radiation to improve the thermal intensity of the furnace tubes.
The pipe system resistance of the vertical tube furnace is large, and it is difficult to empty it. It is inconvenient to clean the coke mechanically. When there is two-phase flow and the material mass flow rate is small, unstable flow is prone to occur in the vertical riser. Convection tube
Radiation tube
Burners
Figure 2.1.1.2-1 Radiation-convection vertical tube cylindrical furnace Convection tube
Radiation tube
Burners
Figure 2.1.1.2-2 Radiation-convection coil cylindrical furnace 2.1.1.3 Radiation-convection coil cylindrical furnace Figure 2.1.1.3 shows a vertical radiation-convection coil cylindrical furnace, which can also be designed as a horizontal type. It is characterized by small size and compact structure, that is, the convection coil is arranged by using the annular gap between the closely packed radiation coil and the furnace body. An air jacket can be set outside the shell to preheat the combustion air and improve the thermal efficiency of the furnace. Convection tube
Radiation tube
Burner
Figure 2.1.1.3 Radiation-convection type coil cylindrical furnace 3
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2.1.2 Box furnace
Box furnace covers a wide range. Its common characteristics are that the arrangement of radiation furnace tubes, burners and convection chambers is relatively flexible. The structure is generally more complicated than that of cylindrical furnaces and the cost is higher.
Common box furnaces include: horizontal tube vertical furnace, vertical tube vertical furnace, radiation wall furnace, ladder furnace and top-fired vertical tube box furnace. 2.1.2.1 Horizontal tube vertical furnace
The structural diagram is shown in Figure 2.1.2.1. Generally, the top of the radiation chamber is inclined, the convection chamber is the same length as the radiation chamber, the furnace tube is arranged horizontally along the wall, the material flow state in the tube is stable, the coke cleaning is convenient, and the convection chamber is relatively easy to arrange. However, the support of the horizontal furnace tube consumes a large amount of high-alloy heat-resistant steel, which is expensive; because space must be reserved for pulling out the furnace tube, it occupies a large area; when the heated materials enter the furnace in multiple ways, the heat distribution of each way is not easy to be uniform.
2.1.2.2 Vertical tube vertical furnace
The structural diagram is shown in Figure 2.1.2.2. The top of the radiation chamber is flat, and the radiation tubes are arranged along the wall. This type of furnace has the advantages of both vertical tube furnaces and the advantages of convenient arrangement of the convection chamber of general vertical furnaces, which is conducive to improving the thermal efficiency of the furnace. The support and suspension of the radiation furnace tube are generally set outside the furnace roof, and the consumption of high-alloy heat-resistant steel is small. However, because the furnace tube is radiated on one side, the surface heat intensity is low, the furnace tube is difficult to empty and purge, and the furnace steel structure is relatively complex. Convection tube
Radiant tube
Burners
Figure 2.1.2.1 Horizontal tube vertical furnace
2.1.2.3 Radiant wall furnace
Convection tube
Radiant tube
Burners
Figure 2.1.2.2 Vertical tube vertical furnace
Figure 2.1.2.3-1 shows a single-row tube double-sided radiant furnace, and Figure 2.1.2.3-2 shows a double-row tube double-sided radiant furnace. The main feature of the radiant wall furnace is that the burner is located on the side wall of the furnace wall (side-burning type), and is heated by a flameless burner or a wall-flame burner using gas fuel, so that the entire side wall reaches a high temperature, forming a radiant wall, which promotes uniform distribution of heat intensity in the length and circumference of the furnace tube, and can be adjusted in different zones, greatly improving the heat intensity of the furnace tube, and has a compact structure. Several burners (bottom-burning type) can also be set at the bottom of the furnace, which can not only improve the thermal strength of the lower furnace tube, but also burn some liquid fuel. The disadvantage of this type of furnace is that it is limited by the type of fuel and has a large number of burners, which brings certain troubles to the operation. 4
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Radiation tube
Burners
Figure 2.1.2.3-1 Radiant wall furnace (single-row tube) Radiation
Burners
Convection tube
Figure 2.1.2.3-2 Radiant wall furnace (double-row tube) Figure 2.1.2.3-3 shows a combined furnace of radiant wall and bottom burning. The bottom burner can burn gas or oil, the side wall is a radiant wall, and the furnace tube is double-sided radiation. The furnaces shown in Figures 2.1.2.3-2 and 2.1.2.3-3 are prone to bending and deformation due to uneven heating on both sides of the furnace tubes.
Convection tube
Radiation tube
Burners
Radiation wall and bottom burning combined furnace
Figure 2.1.2.33
Step furnace
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Figure 2.1.2.4 shows a positive step furnace (and an inverted step furnace). Its radiation chamber side wall is inclined, and the inclined surface is heated by a flat long flame burner to form a high-temperature radiation wall, which can burn liquid fuel. The upper and lower parts of the furnace can be adjusted in sections to make the heat intensity of the furnace tube reasonably distributed along the length of the furnace tube: the furnace tube radiates on both sides, with high heat intensity: the number of burners is small, and the operation is convenient, but the structure is relatively complex. Convection tube
Radiant tube
Burners
Figure 2.1.2.4 Ladder furnace
2.1.2.5 Top-fired vertical tube box furnace
The structural diagram is shown in Figure 2.1.2.5. This is a type of converter. It has multiple downward-burning burners (top-fired) installed between every two rows of vertical tubes and between the tube rows and the side walls. Its temperature distribution can meet the requirements of the conversion process and has high thermal intensity. The convection chamber is arranged on the ground, which is convenient for installation and maintenance. 2.1.3 Selection of furnace type Radiant tube Convection tube Figure 2.1.2.5 Top-fired vertical tube box furnace Standard exchange search network Free download of various standard industry information Burner The factors that should be considered in the selection of furnace type include: the process conditions adopted, the size of the heat load, the required thermal efficiency of the furnace, the nature of the heated material, the type of fuel, the size of the floor space, etc. The furnace type determined based on technical and economic comparison should meet the following requirements: meet the process conditions, simple structure, low one-time investment, stable and reliable operation, low operating cost and convenient maintenance. 2.1.3.1 For furnaces with an effective heat load of less than 4.2×10°MJ/h or a large effective heat load, which are only used for a short period of time when starting up and heating up, a pure radiation type furnace can be selected.
2.1.3.2 For heating furnaces with effective heat load of 4.2×10°～21×10°MJ/h, vertical tube type or coil type radiation-convection cylindrical furnaces should be preferred.
2.1.3.3 For heating furnaces with effective heat load of 21×103～63X10°MJ/h, technical and economic comparison should be made, and radiation-convection cylindrical furnaces can be preferred.
2.1.3.4 For heating furnaces with effective heat load greater than 63×10°MJ/h, cylindrical furnaces with middle row of pipes in the furnace, vertical furnaces or other furnace types can be selected.
2.1.3.5 In the case where the material in the pipe is easy to coke or block, the pipe system is required to be completely emptied, or in the case of two-phase flow and the mass flow rate of the material is small, horizontal tube vertical furnaces should be used. 2.1.3.6 Where the temperature of the material in the tube is not high, but there are strict restrictions on the temperature of the tube wall, a pure convection furnace should be selected. 2.1.3.7 For special tubular furnaces with chemical reactions such as cracking furnaces and converters, the furnace type should be determined according to the process requirements, fuel type and characteristics.
2.2 General principles for tubular furnace design
2.2.1 General principles for overall design of tubular furnaces
2.2.1.1 The radiation chamber of the tubular furnace must have sufficient furnace space to allow the fuel to burn fully, and the radiation heat transfer surface and burner should be arranged reasonably so that the flame of the fuel combustion does not reach the furnace tube. 2.2.1, 2 The convection chamber of the tubular furnace should be simple and compact in structure and easy to maintain. The determination of the flue gas flow section should have a good heat transfer effect and appropriate flue gas resistance.
2.2.1.3 When there are many furnaces and the heat load is small, if they are arranged in a centralized manner, a convection chamber, smoke window and draft device shared by multiple furnaces can be configured when operation and maintenance permit. 2.2.1.4 When the convection chamber structure is relatively large, the convection chamber can be placed on the ground under the condition that the structure is easy to handle, install and repair.
2.2.1.5 To improve the thermal efficiency of the tubular furnace, the heat transfer area of the convection chamber should be increased first, the convection heat transfer should be strengthened, and the low-temperature process medium should be preheated to reduce the exhaust gas temperature. Secondly, the waste heat of the flue gas should be recovered by adding an air preheater or a waste heat boiler (the investment recovery period of the waste heat utilization system should not exceed three years), and the best solution should be selected after comparison. 2.2.1.6 One furnace is used to heat multiple process materials for control and regulation. The overall design of the furnace can ensure the heating of multiple materials and can be controlled separately without affecting each other, or only one main process material needs to be strictly controlled. In this case, the combined heating of multiple materials in one furnace can be adopted. 2.2.1.7 When the material flow is large, the mass flow rate is too large, and the resistance drop exceeds the allowable range, it should be divided into two or more routes, but the number of routes should be as small as possible, and the distribution of each route should be uniform. In situations where the distribution of each route is required to be strict, a flow regulating device should be installed. In terms of structure, the configuration of the inlet and outlet should be as concentrated as possible to facilitate piping. 2.2.1.8 The thermal expansion of the furnace body, furnace wall, furnace tube, tube plate and other components should be fully considered. For a tubular heating furnace using steam-air charring, the thermal expansion of the furnace tube should be considered according to the wall temperature during charring. 2.2.1.9 The suction force of the smoke window or induced draft fan shall not only overcome all resistances of the flue gas system, but also maintain a negative pressure of 7
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2.2.2 Process conditions to be met in the design of tubular furnaces 2.2.2.1 Composition, density, specific heat, viscosity, flow rate of the heated material, as well as phase changes and reactions in the tube. 2.2.2.2 Reaction residence time requirements of the heated material. 2.2.2.3 Inlet and outlet temperatures, effective heat load, operating pressure and allowable pressure drop of the heated material. 2.2.2.4 Type, composition, density, viscosity, temperature and pressure of the fuel. 2.2.2.5 Type, temperature and pressure of the atomizer of the fuel oil. 2.2.2.6 Basic wind pressure at a height of 10m in the plant construction area, earthquake fortification intensity, soil type, snow load, temperature and air pressure in the plant area.
2.2.2.7 Requirements for noise and pollution control. 2.2.3 Main design parameters of tube furnaces
2.2.3.1 Design heat load: Generally, 1.15 times the calculated effective heat load is taken. The design should allow operation at 60% load.
2.2.3.2 Burner design capacity: Generally, 1.25 times the calculated capacity is taken, at least 1.1 times. 2.2.3.3 Furnace thermal efficiency: The thermal efficiency of tube furnaces (excluding pure radiation type) should generally not be lower than the following values: when the heat load is ≤4.2×10°MJ/h, n≥65%; when the heat load is 4.2×10°～21×10°MJ/h, n≥75%; when the heat load is 21×103～63×103MJ/h, n≥80%; when the heat load is >63×10°MJ/h, m≥85%. 2.2.3.4 Material mass flow rate in the tube: It should be appropriately higher within the allowable range of pressure drop, and this should be used to determine the reasonable furnace tube diameter and number of tubes.
2.2.3.5 Thermal strength of furnace tube (abbreviated as thermal strength): The ratio of the heat absorbed by the material in the tube of a furnace or a region of the furnace (radiation chamber or convection chamber) to the heat transfer area. Its size directly affects the size of the furnace, the operating cycle and various consumption indicators.
The thermal strength of the furnace tube is limited by factors such as process conditions, material properties, furnace tube material, arrangement method and furnace thermal characteristics. The selection should be determined by the following factors:
(1) In the case where the heated material is easy to coke or the heat release coefficient in the tube is small, the thermal strength of the furnace tube should not be high. (2) When the temperature and pressure of the heated material are high, the thermal strength of the furnace tube should not be too high due to the limitations of the allowable temperature and high temperature strength of the tube material.
(3) The maximum temperature of the heated material should be a factor in controlling the thermal strength of the furnace tube. (4) In order to shorten the residence time of materials in the tube and reduce the possibility of coking, water or steam injection should be used to increase the flow rate in the tube, thereby improving the thermal strength of the furnace tube, if the process operation permits. (5) When the thermal strength of the furnace tube is not improved much, and the increase in the tube wall temperature requires the upgrade of the furnace tube material, the thermal strength of the furnace tube can be appropriately reduced.
(6) The thermal strength of the furnace tube can generally be selected based on experience, and finally determined by calculating the maximum temperature of the tube wall. 2.2.3.6 Expanding the surface area
In order to increase the external heat release coefficient of the convection tube, strengthen the convection heat transfer, improve the thermal efficiency of the furnace and reduce the height of the convection chamber, when the difference between the internal and external heat release coefficients of the convection tube is large, the surface area can be expanded (fin tube or nail head tube). When the enlarged surface area is adopted, the following requirements shall be met: 8
Standard fee search network w.bzsosd:.com (1) When the fuel of the furnace is gas, light oil or a mixture of light oil and gas with gas as the main fuel, the convection tube shall adopt fin tubes and nail head tubes; when the fuel of the furnace is heavy oil or a mixture of heavy oil and gas with heavy oil as the main fuel, the convection tube shall adopt nail head tubes. The dimensions of the fins and nail heads used are: the fin height is not more than 25mm, and the spacing is not less than 8mm; the nail head height is not more than 25mm, and the spacing is not less than 16mm.
(2) When the temperature of the material in the tube is low and there is a tendency for condensation to occur on the tube wall, it is not advisable to adopt the enlarged surface area to prevent the soot from adhering to the tube wall and being difficult to remove.
(3) In order to keep the outer wall of the enlarged surface area tube clean regularly, an effective soot blower device shall be set according to the specific use conditions. When the fuel is gas, it is not advisable to install a soot blower. (4) Materials of fins and nail heads: When the operating temperature is less than 450℃, carbon steel is used; when the operating temperature is 450620℃, 1Cr13 steel is used; when the operating temperature is greater than 620℃, 18-8 stainless steel is used. (5) The commonly used dimensions (mm) of fin nail heads are as follows: Fin thickness
Fin height
Fin spacing
Nail head diameterwwW.bzxz.Net
Nail head height
Nail head spacing
2.2.3.7 Heat dissipation loss of tubular furnace
The heat dissipation loss of tubular furnace should be determined by calculation based on the outer wall temperature of the radiation chamber and convection chamber and the environmental conditions. In the heat balance calculation, empirical data can generally be used. The heat dissipation loss of tubular furnace without waste heat recovery system should not exceed 3% of the total calorific value of fuel; the heat dissipation loss of tubular furnace with waste heat recovery system should not exceed 4%.
For large furnaces, the heat loss can be lower, and for small furnaces, it can be higher; for furnaces with furnace tubes laid along the wall, the heat loss can be lower, and vice versa, it can be higher.
2.3 Principles for determining the main structure and size of tubular furnaces 2.3.1 Furnace tube system
2.3.1.1 The design pressure and design temperature of the furnace tube should be determined according to its working pressure, calculated wall temperature, and reference to relevant regulations. 2.3.1.2 The common specifications of furnace tube diameter (outer diameter) are: d=60,89,102,114,127,152,180,219mm. The following specifications can also be used: d=32,38,51,57,76,108,133,159mm. 2.3.1.3 Length of radiation furnace tube
Vertical tube vertical furnace, vertical tube box furnace: generally less than 9000~10000mm. Vertical tube type circular furnace: generally less than 15000~18000mm. Horizontal tube bottom-fired or side-fired furnace: generally less than 24000mm. Radiant furnace tubes should be manufactured in whole pieces. If the designed tube length exceeds the supplied length, the splicing of the furnace tubes should comply with the provisions of HG20545 "Technical Conditions for Manufacturing Pressure-Bearing Components of Chemical Industrial Furnaces". 2.3.1.4 The selection of furnace tube material should be determined by the temperature of the tube wall, the corrosion conditions inside and outside the tube, and economic rationality. Furnace tubes in different parts should use different materials according to specific conditions. The selection of materials should comply with the provisions of HGJ41 "Design and Selection Regulations for Metal Materials for Chemical Industrial Furnaces". 2.3.1.5 The center distance of the furnace tube should be 2d (d is the outer diameter of the furnace tube). When used with standard elbows and elbows, it should be based on the standard elbows and 9
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2.2.3.2 Burner design capacity: generally take 1.25 times the calculated capacity, at least 1.1 times. 2.2.3.3 Furnace thermal efficiency: The thermal efficiency of a tubular furnace (excluding pure radiation type) should generally not be lower than the following values: when the heat load is ≤4.2×10°MJ/h, n≥65%; when the heat load is 4.2×10°～21×10°MJ/h, n≥75%; when the heat load is 21×103～63×103MJ/h, n≥80%; when the heat load is >63×10°MJ/h, m≥85%. 2.2.3.4 Mass flow rate of materials in the tube: It should be appropriately taken as a higher value within the allowable range of pressure drop, and the reasonable furnace tube diameter and number of tubes should be determined accordingly.
2.2.3.5 Thermal strength of furnace tube (abbreviated as thermal strength): the ratio of the heat absorbed by the material in the tube of a furnace or a region of the furnace (radiation chamber or convection chamber) to the heat transfer area. Its size directly affects the size of the furnace, the operating cycle and various consumption indicators.
The thermal strength of furnace tube is limited by factors such as process conditions, material properties, furnace tube material, arrangement method and furnace thermal characteristics. The selection should be determined by the following factors:
(1) When the heated material is easy to coke or the heat release coefficient in the tube is small, the thermal strength of the furnace tube should not be too high. (2) When the temperature and pressure of the heated material are high, the thermal strength of the furnace tube should not be too high due to the limitations of the allowable temperature and high temperature strength of the tube material.
(3) The maximum temperature of the heated material should be a factor in controlling the thermal strength of the furnace tube. (4) In order to shorten the residence time of materials in the tube and reduce the possibility of coking, water or steam injection should be used to increase the flow rate in the tube, thereby improving the thermal strength of the furnace tube, if the process operation permits. (5) When the thermal strength of the furnace tube is not improved much, and the increase in the tube wall temperature requires the upgrade of the furnace tube material, the thermal strength of the furnace tube can be appropriately reduced.
(6) The thermal strength of the furnace tube can generally be selected based on experience, and finally determined by calculating the maximum temperature of the tube wall. 2.2.3.6 Expanding the surface area
In order to increase the external heat release coefficient of the convection tube, strengthen the convection heat transfer, improve the thermal efficiency of the furnace and reduce the height of the convection chamber, when the difference between the internal and external heat release coefficients of the convection tube is large, the surface area can be expanded (fin tube or nail head tube). When the enlarged surface area is adopted, the following requirements shall be met: 8
Standard fee search network w.bzsosd:.com (1) When the fuel of the furnace is gas, light oil or a mixture of light oil and gas with gas as the main fuel, the convection tube shall adopt fin tubes and nail head tubes; when the fuel of the furnace is heavy oil or a mixture of heavy oil and gas with heavy oil as the main fuel, the convection tube shall adopt nail head tubes. The dimensions of the fins and nail heads used are: the fin height is not more than 25mm, and the spacing is not less than 8mm; the nail head height is not more than 25mm, and the spacing is not less than 16mm.
(2) When the temperature of the material in the tube is low and there is a tendency for condensation to occur on the tube wall, it is not advisable to adopt the enlarged surface area to prevent the soot from adhering to the tube wall and being difficult to remove.
(3) In order to keep the outer wall of the enlarged surface area tube clean regularly, an effective soot blower device shall be set according to the specific use conditions. When the fuel is gas, it is not advisable to install a soot blower. (4) Fin and nail head materials: When the operating temperature is less than 450℃, carbon steel is used; when it is 450620℃, 1Cr13 steel is used; when it is greater than 620℃, 18-8 stainless steel is used. (5) The commonly used dimensions (mm) of fin nail heads are as follows: Fin thickness
Fin height
Fin spacing
Nail head diameter
Nail head height
Nail head spacing
2.2.3.7 Tubular furnace heat loss
The heat loss of a tubular furnace should be determined by calculation based on the outer wall temperature of the radiation chamber and convection chamber and the environmental conditions. In the heat balance calculation, empirical data can generally be used. The heat loss of a tubular furnace without a waste heat recovery system should not exceed 3% of the total calorific value of the fuel; the heat loss of a tubular furnace with a waste heat recovery system should not exceed 4%.
For large furnaces, the heat loss can be lower, and for small furnaces, it can be higher; for furnaces with furnace tubes laid along the wall, the heat loss can be lower, and vice versa, it can be higher.
2.3 Principles for determining the main structure and size of tubular furnaces 2.3.1 Furnace tube system
2.3.1.1 The design pressure and design temperature of the furnace tube should be determined according to its working pressure, calculated wall temperature, and reference to relevant regulations. 2.3.1.2 The common specifications of furnace tube diameter (outer diameter) are: d=60,89,102,114,127,152,180,219mm. The following specifications can also be used: d=32,38,51,57,76,108,133,159mm. 2.3.1.3 Length of radiation furnace tube
Vertical tube vertical furnace, vertical tube box furnace: generally less than 9000~10000mm. Vertical tube type circular furnace: generally less than 15000~18000mm. Horizontal tube bottom-fired or side-fired furnace: generally less than 24000mm. Radiant furnace tubes should be manufactured in whole pieces. If the designed tube length exceeds the supplied length, the splicing of the furnace tubes should comply with the provisions of HG20545 "Technical Conditions for Manufacturing Pressure-Bearing Components of Chemical Industrial Furnaces". 2.3.1.4 The selection of furnace tube material should be determined by the temperature of the tube wall, the corrosion conditions inside and outside the tube, and economic rationality. Furnace tubes in different parts should use different materials according to specific conditions. The selection of materials should comply with the provisions of HGJ41 "Design and Selection Regulations for Metal Materials for Chemical Industrial Furnaces". 2.3.1.5 The center distance of the furnace tube should be 2d (d is the outer diameter of the furnace tube). When used with standard elbows and elbows, it should be based on the standard elbows and 9
Standard Find Fee Network w.bzsoe.com15 times the calculated effective heat load, the design should consider allowing operation at 60% load.
2.2.3.2 Burner design capacity: generally take 1.25 times the calculated capacity, at least 1.1 times. 2.2.3.3 Furnace thermal efficiency: The thermal efficiency of a tubular furnace (excluding pure radiation type) should generally not be lower than the following values: when the heat load is ≤4.2×10°MJ/h, n≥65%; when the heat load is 4.2×10°～21×10°MJ/h, n≥75%; when the heat load is 21×103～63×103MJ/h, n≥80%; when the heat load is >63×10°MJ/h, m≥85%. 2.2.3.4 Material mass flow rate in the tube: It should be appropriately taken as a higher value within the allowable range of pressure drop, and the reasonable furnace tube diameter and number of pipelines should be determined accordingly.
2.2.3.5 Thermal strength of furnace tube (abbreviated as thermal strength): the ratio of the heat absorbed by the material in the tube of a furnace or a region of the furnace (radiation chamber or convection chamber) to the heat transfer area. Its size directly affects the size of the furnace, the operating cycle and various consumption indicators.
The thermal strength of furnace tube is limited by factors such as process conditions, material properties, furnace tube material, arrangement method and furnace thermal characteristics. The selection should be determined by the following factors:
(1) When the heated material is easy to coke or the heat release coefficient in the tube is small, the thermal strength of the furnace tube should not be too high. (2) When the temperature and pressure of the heated material are high, the thermal strength of the furnace tube should not be too high due to the limitations of the allowable temperature and high temperature strength of the tube material.
(3) The maximum temperature of the heated material should be a factor in controlling the thermal strength of the furnace tube. (4) In order to shorten the residence time of materials in the tube and reduce the possibility of coking, water or steam injection should be used to increase the flow rate in the tube, thereby improving the thermal strength of the furnace tube, if the process operation permits. (5) When the thermal strength of the furnace tube is not improved much, and the increase in the tube wall temperature requires the upgrade of the furnace tube material, the thermal strength of the furnace tube can be appropriately reduced.
(6) The thermal strength of the furnace tube can generally be selected based on experience, and finally determined by calculating the maximum temperature of the tube wall. 2.2.3.6 Expanding the surface area
In order to increase the external heat release coefficient of the convection tube, strengthen the convection heat transfer, improve the thermal efficiency of the furnace and reduce the height of the convection chamber, when the difference between the internal and external heat release coefficients of the convection tube is large, the surface area can be expanded (fin tube or nail head tube). When the enlarged surface area is adopted, the following requirements shall be met: 8
Standard fee search network w.bzsosd:.com (1) When the fuel of the furnace is gas, light oil or a mixture of light oil and gas with gas as the main fuel, the convection tube shall adopt fin tubes and nail head tubes; when the fuel of the furnace is heavy oil or a mixture of heavy oil and gas with heavy oil as the main fuel, the convection tube shall adopt nail head tubes. The dimensions of the fins and nail heads used are: the fin height is not more than 25mm, and the spacing is not less than 8mm; the nail head height is not more than 25mm, and the spacing is not less than 16mm.
(2) When the temperature of the material in the tube is low and there is a tendency for condensation to occur on the tube wall, it is not advisable to adopt the enlarged surface area to prevent the soot from adhering to the tube wall and being difficult to remove.
(3) In order to keep the outer wall of the enlarged surface area tube clean regularly, an effective soot blower device shall be set according to the specific use conditions. When the fuel is gas, it is not advisable to install a soot blower. (4) Materials of fins and nail heads: When the operating temperature is less than 450℃, carbon steel is used; when the operating temperature is 450620℃, 1Cr13 steel is used; when the operating temperature is greater than 620℃, 18-8 stainless steel is used. (5) The commonly used dimensions (mm) of fin nail heads are as follows: Fin thickness
Fin height
Fin spacing
Nail head diameter
Nail head height
Nail head spacing
2.2.3.7 Heat dissipation loss of tubular furnace
The heat dissipation loss of tubular furnace should be determined by calculation based on the outer wall temperature of the radiation chamber and convection chamber and the environmental conditions. In the heat balance calculation, empirical data can generally be used. The heat dissipation loss of tubular furnace without waste heat recovery system should not exceed 3% of the total calorific value of fuel; the heat dissipation loss of tubular furnace with waste heat recovery system should not exceed 4%.
For large furnaces, the heat loss can be lower, and for small furnaces, it can be higher; for furnaces with furnace tubes laid along the wall, the heat loss can be lower, and vice versa, it can be higher.
2.3 Principles for determining the main structure and size of tubular furnaces 2.3.1 Furnace tube system
2.3.1.1 The design pressure and design temperature of the furnace tube should be determined according to its working pressure, calculated wall temperature, and reference to relevant regulations. 2.3.1.2 The common specifications of furnace tube diameter (outer diameter) are: d=60,89,102,114,127,152,180,219mm. The following specifications can also be used: d=32,38,51,57,76,108,133,159mm. 2.3.1.3 Length of radiation furnace tube
Vertical tube vertical furnace, vertical tube box furnace: generally less than 9000~10000mm. Vertical tube type circular furnace: generally less than 15000~18000mm. Horizontal tube bottom-fired or side-fired furnace: generally less than 24000mm. Radiant furnace tubes should be manufactured in whole pieces. If the designed tube length exceeds the supplied length, the splicing of the furnace tubes should comply with the provisions of HG20545 "Technical Conditions for Manufacturing Pressure-Bearing Components of Chemical Industrial Furnaces". 2.3.1.4 The selection of furnace tube material should be determined by the temperature of the tube wall, the corrosion conditions inside and outside the tube, and economic rationality. Furnace tubes in different parts should use different materials according to specific conditions. The selection of materials should comply with the provisions of HGJ41 "Design and Selection Regulations for Metal Materials for Chemical Industrial Furnaces". 2.3.1.5 The center distance of the furnace tube should be 2d (d is the outer diameter of the furnace tube). When used with standard elbows and elbows, it should be based on standard elbows and 9
Standard Find Fee Network w.bzsoe.comcom (1) When the furnace fuel is gas, light oil or a mixture of light oil and gas with gas as the main fuel, the convection tube should use fin tubes and nail head tubes; when the furnace fuel is heavy oil or a mixture of heavy oil and gas with heavy oil as the main fuel, the convection tube should use nail head tubes. The dimensions of the fins and nail heads used are: the fin height is not more than 25mm, and the spacing is not less than 8mm; the nail head height is not more than 25mm, and the spacing is not less than 16mm.
(2) When the temperature of the material in the tube is low and there is a tendency for condensation to occur on the tube wall, it is not advisable to use an enlarged surface area to prevent the soot from adhering to the tube wall and being difficult to remove.
(3) In order to keep the outer wall of the tube with an enlarged surface area clean at all times, an effective soot blower device should be set according to the specific use conditions. When gas fuel is used, a soot blower should not be installed. (4) Fin and nail head materials: When the operating temperature is less than 450℃, carbon steel is used; when it is 450620℃, 1Cr13 steel is used; when it is greater than 620℃, 18-8 stainless steel is used. (5) The commonly used dimensions (mm) of fin nail heads are as follows: Fin thickness
Fin height
Fin spacing
Nail head diameter
Nail head height
Nail head spacing
2.2.3.7 Tubular furnace heat loss
The heat loss of a tubular furnace should be determined by calculation based on the outer wall temperature of the radiation chamber and convection chamber and the environmental conditions. In the heat balance calculation, empirical data can generally be used. The heat loss of a tubular furnace without a waste heat recovery system should not exceed 3% of the total calorific value of the fuel; the heat loss of a tubular furnace with a waste heat recovery system should not exceed 4%.
For large furnaces, the heat loss can be lower, and for small furnaces, it can be higher; for furnaces with furnace tubes laid along the wall, the heat loss can be lower, and vice versa, it can be higher.
2.3 Principles for determining the main structure and size of tubular furnaces 2.3.1 Furnace tube system
2.3.1.1 The design pressure and design temperature of the furnace tube should be determined according to its working pressure, calculated wall temperature, and reference to relevant regulations. 2.3.1.2 The common specifications of furnace tube diameter (outer diameter) are: d=60,89,102,114,127,152,180,219mm. The following specifications can also be used: d=32,38,51,57,76,108,133,159mm. 2.3.1.3 Length of radiation furnace tube
Vertical tube vertical furnace, vertical tube box furnace: generally less than 9000~10000mm. Vertical tube type circular furnace: generally less than 15000~18000mm. Horizontal tube bottom-fired or side-fired furnace: generally less than 24000mm. Radiant furnace tubes should be manufactured in whole pieces. If the designed tube length exceeds the supplied length, the splicing of the furnace tubes should comply with the provisions of HG20545 "Technical Conditions for Manufacturing Pressure-Bearing Components of Chemical Industrial Furnaces". 2.3.1.4 The selection of furnace tube material should be determined by the temperature of the tube wall, the corrosion conditions inside and outside the tube, and economic rationality. Furnace tubes in different parts should use different materials according to specific conditions. The selection of materials should comply with the provisions of HGJ41 "Design and Selection Regulations for Metal Materials for Chemical Industrial Furnaces". 2.3.1.5 The center distance of the furnace tube should be 2d (d is the outer diameter of the furnace tube). When used with standard elbows and elbows, it should be based on the standard elbows and 9
Standard Find Fee Network w.bzsoe.comcom（1）When the furnace fuel is gas, light oil or a mixture of light oil and gas with gas as the main fuel, the convection tube should use fin tubes and nail head tubes; when the furnace fuel is heavy oil or a mixture of heavy oil and gas with heavy oil as the main fuel, the convection tube should use nail head tubes. The dimensions of the fins and nail heads used are: the fin height is not more than 25mm, and the spacing is not less than 8mm; the nail head height is not more than 25mm, and the spacing is not less than 16mm.
（2）When the temperature of the material in the tube is low and there is a tendency for condensation to occur on the tube wall, it is not advisable to use an enlarged surface area to prevent the soot from adhering to the tube wall and being difficult to remove.
（3）In order to keep the outer wall of the enlarged surface area tube clean regularly, an effective soot blower device should be set according to the specific use conditions. When gas fuel is used, a soot blower should not be installed. (4) Fin and nail head materials: When the operating temperature is less than 450℃, carbon steel is used; when it is 450620℃, 1Cr13 steel is used; when it is greater than 620℃, 18-8 stainless steel is used. (5) The commonly used dimensions (mm) of fin nail heads are as follows: Fin thickness
Fin height
Fin spacing
Nail head diameter
Nail head height
Nail head spacing
2.2.3.7 Tubular furnace heat loss
The heat loss of a tubular furnace should be determined by calculation based on the outer wall temperature of the radiation chamber and convection chamber and the environmental conditions. In the heat balance calculation, empirical data can generally be used. The heat loss of a tubular furnace without a waste heat recovery system should not exceed 3% of the total calorific value of the fuel; the heat loss of a tubular furnace with a waste heat recovery system should not exceed 4%.
For large furnaces, the heat loss can be lower, and for small furnaces, it can be higher; for furnaces with furnace tubes laid along the wall, the heat loss can be lower, and vice versa, it can be higher.
2.3 Principles for determining the main structure and size of tubular furnaces 2.3.1 Furnace tube system
2.3.1.1 The design pressure and design temperature of the furnace tube should be determined according to its working pressure, calculated wall temperature, and reference to relevant regulations. 2.3.1.2 The common specifications of furnace tube diameter (outer diameter) are: d=60,89,102,114,127,152,180,219mm. The following specifications can also be used: d=32,38,51,57,76,108,133,159mm. 2.3.1.3 Length of radiation furnace tube
Vertical tube vertical furnace, vertical tube box furnace: generally less than 9000~10000mm. Vertical tube type circular furnace: generally less than 15000~18000mm. Horizontal tube bottom-fired or side-fired furnace: generally less than 24000mm. Radiant furnace tubes should be manufactured in whole pieces. If the designed tube length exceeds the supplied length, the splicing of the furnace tubes should comply with the provisions of HG20545 "Technical Conditions for Manufacturing Pressure-Bearing Components of Chemical Industrial Furnaces". 2.3.1.4 The selection of furnace tube material should be determined by the temperature of the tube wall, the corrosion conditions inside and outside the tube, and economic rationality. Furnace tubes in different parts should use different materials according to specific conditions. The selection of materials should comply with the provisions of HGJ41 "Design and Selection Regulations for Metal Materials for Chemical Industrial Furnaces". 2.3.1.5 The center distance of the furnace tube should be 2d (d is the outer diameter of the furnace tube). When used with standard elbows and elbows, it should be based on the standard elbows and 9
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