Some standard content:
Flare system settings
HG/T20570.12—95
Compiled by: China Huanqiu Chemical Engineering Corporation Approved by: Ministry of Chemical Industry
Implementation date: September 1, 1996 Compiled by:
Yao Guihua, China Huanqiu Chemical Engineering Corporation
Auditor:
Feng Shuyuan, Gong Renwei, Process System Design Technology Center of Ministry of Chemical Industry 1 Scope of application and classification
1.0.1 This regulation applies to the design of flare systems for handling large amounts of flammable, toxic and corrosive gases discharged from petrochemical plants and refineries when accidents occur or during normal production. 1.0.2 The flare system usually consists of four parts: flare gas separation tank, flare gas sealing tank, flare smoke brine and flare pipeline.
1.0.3 The flare type can be divided into high-altitude flare and ground flare. The high altitude flare is composed of smoke (including guy wire support and free support), torch head, pilot light, auxiliary fuel system, igniter and other auxiliary equipment. 1.0.4 Ground flares cannot be used to burn toxic substances. The minimum radius of the barrier-free zone around the ground flare is 76m to 152m, and a fence should be set up to ensure safety. 399
2 Design of flare system
2.0.1 Design principles of flare system
Different flare systems are used for different treatment media and different working conditions. The gases discharged during start-up, normal operation, parking and accidents must be sent to the flare for treatment. 2.0.1.1 The processing capacity of the flare system is designed based on the maximum emission in various situations, and at the same time, the system must operate well within a wide flow range. The flare system itself must ensure the safe operation of the production equipment, and should consider the impact on the environment, eliminate and minimize pollution to the atmosphere, noise, etc. (1) When two flares are arranged together, the distance between the flares should be such that the radiant heat generated by one flare burning at maximum power does not affect the maintenance of the other flare. (2) The air defense signs and lighting protection of the flares shall comply with relevant regulations. 2.0.1.2 The discharge system pipelines of the safety valve and control valve (1) The discharge system of the safety valve and control valve shall be designed in accordance with relevant regulations. If the discharge system is connected to the flare system, the material of the pipeline shall not be lower than carbon steel. Stress analysis and calculation shall be performed for the parts that may produce low and high temperatures, and appropriate materials shall be selected and processed accordingly. (2) The discharge pipeline is preferably connected to the flare system main pipe from above, and there should be an inclination angle with the main pipe to avoid dead corners for exhaust and drainage.
2.0.1.3 Flare main pipe
(1) The exhaust gas is divided into the following four situations according to the medium state: hot gas (t≥0℃, with or without water): a.
c. Cold gas (t<0℃);
c. Both cold gas and hot gas, but without water; d. Liquid discharge system.
In any of the four states of the exhaust gas medium, a main pipe is set up. If it is a combination of the above situations, the dry flare system and the wet flare system should be set up separately. When the mixing of two streams may produce solids or cause dangerous physical or chemical changes, the two streams of materials should be separated. If the size of the pipeline is greatly increased or the material of the pipeline is upgraded due to the mixing of the two streams of materials, the two streams of materials should also be separated. Generally, the discharged liquid is separated from the discharged gas. For the streams containing liquid, separation facilities and a separate liquid phase system should be set up. (2) There should be a certain slope from the flare main pipe to the separator to facilitate drainage. The slope towards the separator should not be less than 0.2%. For drainage dead corners, drainage ports should be set and the discharged liquid should be recovered and stored. (3) The impact of temperature on the pipeline should be considered, and temperature-compensated expansion joints should be set. Generally, annular ones are used, and corrugated expansion joints are used in special cases. If the main pipe is connected to the main pipe or the main pipe is connected to the branch pipe, the material of the joint should be the higher of the two materials, and its length should be at least 5m upstream of the joint. (4) In order to avoid internal explosion or other unsafe factors in the flare system, a fixed purge facility is installed at the farthest upstream end of the flare gas main pipe. The purge facility includes a flow meter, a check valve and a manual regulating valve. All flare main pipes should be equipped with a hose interface for nitrogen purge. The commonly used purge gas is preferably a combustible gas (such as fuel gas), but for low-temperature pipelines, the purge gas should not be partially or completely condensed at the lowest temperature. Nitrogen purge is generally used for this purpose, and the purge gas velocity is 0.03m/s in the maximum flare main pipe. If the flare system is equipped with a water (liquid) seal, the purge gas velocity upstream of the water seal is 0.01m/s. For low flares and hydrogen-rich exhaust gases, the purge gas velocity should be increased. If there is no water seal, the purge gas should preferably be the heaviest gas available as the purge gas, and a low flow alarm and a low pressure alarm indicating the vacuum degree should be installed to prevent air from flowing back into the flare system. 2.0.1.4 Flare gas separation tank
(1) Each flare exhaust gas main pipe should be equipped with a separation tank to separate liquid droplets entrained in the gas or the liquid phase in the two-phase flow that may occur. To prevent the generation of "fire rain", the separation capacity of the separation tank is to separate at least 400um droplets, preferably 150um droplets, to minimize droplet entrainment. The diameter of the separation tank is generally 1/2 to 1/3 of its length and 3 to 4.5 times the size of the flare main pipe. (2) The size of the separation tank is calculated based on the maximum discharge volume in the discharge flow, storing 10 to 30 minutes of discharge volume, generally 20 minutes.
(3) If a separate liquid phase collection system has been set up, or there will not be a large amount of two-phase flow discharged in an emergency with maximum flare load, the discharge flow can be allowed to bypass the separation tank and only a liquid collection pipe connected to the liquid collection system can be set up. (4) The liquid collection system must be equipped with a liquid discharge pump, which is generally centrifugal and connected to the accident power supply. No backup pump is set up. The capacity of the selected pump should be estimated to account for the amount of liquid carried during the accident, and the liquid in the separation tank can be discharged in about half an hour. The pump head is calculated based on the liquid with the smallest weight in the discharged liquid, and the motor power is calculated based on the liquid with the largest weight in the discharged liquid.
2.0.2 Flare calculation
The calculation of the torch includes the diameter of the smoke and the height of the smoke window. The torch head is designed by the manufacturer. The geometric parameter diagram of the torch is shown in Figure 2.0.2-1.
Flame smoke window diameter
Lateral offset of flame
Radius of barrier-free area
Figure 2.0.2-1 Geometric parameter diagram of the torch
In the figure: d:—Flame smoke diameter (inner diameter); R—distance; AX—Lateral offset of flame, AY-
—Radius of barrier-free area, D-
—Distance from the center of the flame to the ground boundary
—Longitudinal offset of flame, X.—Lateral distance from the center of the flame to the center of the torch head; Y. =The longitudinal distance from the center of the flame to the top of the flare head; H-the height of the flare halide; 1-the distance from the center of the flame to the ground; R-the horizontal distance from the center of the flame to the boundary of the ground. 402
-flame length; H-flame
: 2.0.2.1 Simple approximate calculation method
(1) Calculation of the diameter of the flare smoke window
The diameter of the flare smoke depends on the velocity of the fluid in the smoke, and the selection of this velocity is based on the allowable pressure drop. Generally, when determining the size of the flare halide, the following considerations can be made: During normal discharge, the gas flow rate at the outlet should be less than 0.2 Mach number times the speed of sound, and during accident or emergency discharge, its flow rate should be less than 0.5 Mach number times the speed of sound. At this time, the burner pressure drops to 0.01-0.05MPa, the water seal pressure drops to 0.005-0.015MPa, and the flare main pressure drops to 0.01-0.05MPa. Finally, the relationship between the total pressure drop of the flare system and the back pressure of the safety valve must be checked. The diameter of the flare smoke window should not be less than the diameter of the flare system main pipe to avoid the formation of "fire rain" due to the entrainment of liquid droplets in the exhaust gas.
The formula for calculating the diameter of the flare smoke stack is derived as follows: W
Mach=11.61x10-2
From formula (2.0.2-1), we can get:
d;=[11.61×10-2W,
P,·Mach
dj-inner diameter of the top of the flare smoke stack, m,
-flare gas emission flow rate, kg/s
Pj-pressure of the flare gas inside the top of the flare, Pa; Mach-, Mach number, the ratio of the flare gas flow rate to the sound speed of the fluid, dimensionless; M the average molecular weight of the flare gas;
T, flare gas temperature, K,
Adiabatic index of the flare gas, =C,/C.。
（2）Calculation of flare smoke window height
Calculation of flame length
(2.0.2-1)
(2.0.2-2)
The flame length is related to the heat released by the flare gas combustion. The correlation diagram between the flame length (I) and the heat released by the flare gas (Q) is shown in Figure 2.0.2-2.
Fuel gas (508.mm smoke halogen)
Algerian gas well
<Catalytic reforming storage ring gas (p610mm smoke window) outlet catalytic reforming reactor outflow gas (d610mm smoke window) ◆ Dehydrogenation charge (g305mm smoke window)
× oxygen (g787mm smoke halogen)
* hydrogen 62mm smoke window)
Heat released by flare gas (Q)W
Figure 2.0.2-2 Relationship between flame length and heat released b. Calculation of flame inclination caused by wind
（a）The calculation of volume flow rate is shown in formula (2.0.2-3) V=W(2.4)()
-volume flow rate, m\/s
-flare gas temperature.K
(6) Calculation of flame tilt caused by wind 1010
The velocity of flare gas at the flare smoke window outlet (U) is calculated by formula (2.0.2-4): Uj-
(2.0.2-3)
(2.0.2-4)
The velocity of flare gas at the flare smoke window outlet (U) is known, then its ratio to wind speed (Ux) is Ux/U. From Figure 2.0.2-3, we can find (△X/) and (△Y/1), and then calculate the horizontal deviation (AX) and longitudinal deviation (△Y) of the flame. The correlation diagram of flame deviation and Ux/U is shown in Figure 2.0.2-3. The selection of wind speed (U) is based on local meteorological conditions, taking the annual average maximum wind speed. The wind speed at different heights is calculated based on the wind speed and the coefficient of wind speed variation with height (K,). The value of the wind speed height variation coefficient (K,) is shown in Table 2.0.6-1.
Geometric shape of the flame in still air and crosswind 0.5
Comparison (number)
Figure 2.0.2-3
Correlation diagram of flare offset and wind speed (dimensionless) Calculation of flare smoke window height
It can be seen from Figure 2.0.2-1 that there is the following relationship between H', H, R', R, AX, AY and D: H'=H+number AY
R'R—
DR2+H?
The above formula can be rearranged to obtain:
De-(R-),_ 4Y
When △X, AY, D, and R are known, the flare smoke height (H) can be calculated. (3) Summary of simple approximate calculation method
a. The required basic data are as follows:
W--flare gas emission, kg/s;
P--flare gas pressure inside the flare smoke diagram, kPa1.2
(2.0.2-5)
(2.0.2-6)
(2.0.2-7)
(2.0.2-8)
Mach number, dimensionless;
M—average molecular weight of flare gas
T—flare gas temperature, K;
k—insulation index of flare gas, k,=C,/C, R—radius of barrier-free area, m;
hj flare gas lower heating value, kJ/kg
U—design wind speed, m/s,
F—heat radiation factor;
K*maximum allowable heat radiation intensity, kW/m2
heat radiation intensity transfer factor.
b. Calculation contents:
Flare smoke diameter: di-[11.61×10-Flare gas heat release: Q=h·W
Distance from the flame center to the ground boundary: D
Ratio of wind speed to flare gas speed: Ux/U;
From Figure 2.0.2-3, we can find 4X, 4Y
Flare smoke height, HD2(R
P·Maeh
AX)27%
2.0.2.2 Brutuski and Sommer’s approximate calculation method (1) Calculation of flare smoke diameter
The calculation method of the flare smoke window diameter is the same as the simple approximate calculation method, see 2.0.2.1 (1) provisions. (2) Calculation of the flare smoke window height
Q. Determination of the flame center and calculation of the flame offset. The speed of sound C=91.2()og
The flare smoke outlet velocity (U) is
U,-Machx speed of sound
For flare gas, the lower explosion limit parameter (C) is Ch
①Brzustowski, that is, Sommer. 406
(2. 0. 2—9)
(2.0.210)
(2.0.2—11)
C—lower explosion limit of flare gas in air, volume%; Mx—average molecular weight of air, taken as 29; Ux—wind speed, m/s
The lower explosion limit of flare gas (mixed gas) in air (C), its value is calculated according to the following formula: 100
Cr—lower explosion limit of each component of flare gas, volume% Y—molecular fraction of each component of flare gas.
The wind thrust and jet thrust (d, R) values are calculated as follows: (TMiyo.5
djR=d,(
Tair temperature, K;
d;flare smoke diameter, m.
(2.0.2—12)
(2.0.2-13)
Given the C, d, R values, the flame transverse offset (Xc) value and longitudinal offset (Yc) value can be obtained from 2.0.2-4 and Figure 2.0.2-5.
Xe180.0 .01
Figure 2.0.2-4
Flare gas explosion lower limit parameter (Cr)
Flame transverse offset (Xc) and d, R, C. Correlation diagram 5.0
Flare gas explosion lower limit parameter (C)
Figure 2.0.2-5 Flame longitudinal offset (Y) and d, R, C Calculation of the distance from the flame center to the ground boundary b.
N4 yuan K
Calculation of the height of the flare smoke window
(2.0.2--14)
From Figure 2 .0.2-1 It can be seen that there is the following relationship between H', H, R, R, Xc, Yc and D H'-H+Yc
R'-R-Xc
DR'2+H2
From the above three equations, we can get:
HD2-(RX)2-Y
Given D, R, Xc and Yc, the height of the flare smoke window (H) can be calculated. (2.0.2—15)
(2.0.2—16)
(2.0.2—17)
(2.0. 2—18)
The height (H) of the flare smoke stack is related to the selected calculation standard. When the radiation intensity (K) is the maximum allowable thermal radiation intensity, H) is the lowest limit height of the flare smoke stack. The K value is selected according to the specific conditions of the project. (3) The approximate calculation method of Brutuski and Sommer is summarized as follows:
W, flare gas flow rate, kg/s;
M—average molecular weight of flare gas;
average molecular weight of air;
—average wind speed, m/s;From 2-1, we can see that there is the following relationship between H', H, R', R, AX, AY and D: H'=H+AYbZxz.net
R'R—
DR2+H?
From the above formula, we can get:
De-(R-),_ 4Y
When △X, AY, D and R are known, the flare smoke height (H) can be calculated. (3) Summary of simple approximate calculation method
a. The required basic data are as follows:
W--flare gas emission, kg/s;
P--flare gas pressure inside the flare smoke diagram, kPa1.2
(2.0.2-5)
(2.0.2-6)
(2.0.2-7)
(2.0.2-8)
Mach number, dimensionless;
M—average molecular weight of flare gas
T—flare gas temperature, K;
k—insulation index of flare gas, k,=C,/C, R—radius of barrier-free area, m;
hj flare gas lower heating value, kJ/kg
U—design wind speed, m/s,
F—heat radiation factor;
K*maximum allowable heat radiation intensity, kW/m2
heat radiation intensity transfer factor.
b. Calculation contents:
Flare smoke diameter: di-[11.61×10-Flare gas heat release: Q=h·W
Distance from the flame center to the ground boundary: D
Ratio of wind speed to flare gas speed: Ux/U;
From Figure 2.0.2-3, we can find 4X, 4Y
Flare smoke height, HD2(R
P·Maeh
AX)27%
2.0.2.2 Brutuski and Sommer’s approximate calculation method (1) Calculation of flare smoke diameter
The calculation method of the flare smoke window diameter is the same as the simple approximate calculation method, see 2.0.2.1 (1) provisions. (2) Calculation of the flare smoke window height
Q. Determination of the flame center and calculation of the flame offset. The speed of sound C=91.2()og
The flare smoke outlet velocity (U) is
U,-Machx speed of sound
For flare gas, the lower explosion limit parameter (C) is Ch
①Brzustowski, that is, Sommer. 406
(2. 0. 2—9)
(2.0.210)
(2.0.2—11)
C—lower explosion limit of flare gas in air, volume%; Mx—average molecular weight of air, taken as 29; Ux—wind speed, m/s
The lower explosion limit of flare gas (mixed gas) in air (C), its value is calculated according to the following formula: 100
Cr—lower explosion limit of each component of flare gas, volume% Y—molecular fraction of each component of flare gas.
The wind thrust and jet thrust (d, R) values are calculated as follows: (TMiyo.5
djR=d,(
Tair temperature, K;
d;flare smoke diameter, m.
(2.0.2—12)
(2.0.2-13)
Given the C, d, R values, the flame transverse offset (Xc) value and longitudinal offset (Yc) value can be obtained from 2.0.2-4 and Figure 2.0.2-5.
Xe180.0 .01
Figure 2.0.2-4
Flare gas explosion lower limit parameter (Cr)
Flame transverse offset (Xc) and d, R, C. Correlation diagram 5.0
Flare gas explosion lower limit parameter (C)
Figure 2.0.2-5 Flame longitudinal offset (Y) and d, R, C Calculation of the distance from the flame center to the ground boundary b.
N4 yuan K
Calculation of the height of the flare smoke window
(2.0.2--14)
From Figure 2 .0.2-1 It can be seen that there is the following relationship between H', H, R, R, Xc, Yc and D H'-H+Yc
R'-R-Xc
DR'2+H2
From the above three equations, we can get:
HD2-(RX)2-Y
Given D, R, Xc and Yc, the height of the flare smoke window (H) can be calculated. (2.0.2—15)
(2.0.2—16)
(2.0.2—17)
(2.0. 2—18)
The height (H) of the flare smoke stack is related to the selected calculation standard. When the radiation intensity (K) is the maximum allowable thermal radiation intensity, H) is the lowest limit height of the flare smoke stack. The K value is selected according to the specific conditions of the project. (3) The approximate calculation method of Brutuski and Sommer is summarized as follows:
W, flare gas flow rate, kg/s;
M—average molecular weight of flare gas;
average molecular weight of air;
—average wind speed, m/s;From 2-1, we can see that there is the following relationship between H', H, R', R, AX, AY and D: H'=H+AY
R'R—
DR2+H?
From the above formula, we can get:
De-(R-),_ 4Y
When △X, AY, D and R are known, the flare smoke height (H) can be calculated. (3) Summary of simple approximate calculation method
a. The required basic data are as follows:
W--flare gas emission, kg/s;
P--flare gas pressure inside the flare smoke diagram, kPa1.2
(2.0.2-5)
(2.0.2-6)
(2.0.2-7)
(2.0.2-8)
Mach number, dimensionless;
M—average molecular weight of flare gas
T—flare gas temperature, K;
k—insulation index of flare gas, k,=C,/C, R—radius of barrier-free area, m;
hj flare gas lower heating value, kJ/kg
U—design wind speed, m/s,
F—heat radiation factor;
K*maximum allowable heat radiation intensity, kW/m2
heat radiation intensity transfer factor.
b. Calculation contents:
Flare smoke diameter: di-[11.61×10-Flare gas heat release: Q=h·W
Distance from the flame center to the ground boundary: D
Ratio of wind speed to flare gas speed: Ux/U;
From Figure 2.0.2-3, we can find 4X, 4Y
Flare smoke height, HD2(R
P·Maeh
AX)27%
2.0.2.2 Brutuski and Sommer’s approximate calculation method (1) Calculation of flare smoke diameter
The calculation method of the flare smoke window diameter is the same as the simple approximate calculation method, see 2.0.2.1 (1) provisions. (2) Calculation of the flare smoke window height
Q. Determination of the flame center and calculation of the flame offset. The speed of sound C=91.2()og
The flare smoke outlet velocity (U) is
U,-Machx speed of sound
For flare gas, the lower explosion limit parameter (C) is Ch
①Brzustowski, that is, Sommer. 406
(2. 0. 2—9)
(2.0.210)
(2.0.2—11)
C—lower explosion limit of flare gas in air, volume%; Mx—average molecular weight of air, taken as 29; Ux—wind speed, m/s
The lower explosion limit of flare gas (mixed gas) in air (C), its value is calculated according to the following formula: 100
Cr—lower explosion limit of each component of flare gas, volume% Y—molecular fraction of each component of flare gas.
The wind thrust and jet thrust (d, R) values are calculated as follows: (TMiyo.5
djR=d,(
Tair temperature, K;
d;flare smoke diameter, m.
(2.0.2—12)
(2.0.2-13)
Given the values of C, d, and R, the values of the flame transverse offset (Xc) and longitudinal offset (Yc) can be obtained from 2.0.2-4 and Figure 2.0.2-5.
Xe180.0 .01
Figure 2.0.2-4
Flare gas explosion lower limit parameter (Cr)
Flame transverse offset (Xc) and d, R, C. Correlation diagram 5.0
Flare gas explosion lower limit parameter (C)
Figure 2.0.2-5 Flame longitudinal offset (Y) and d, R, C Calculation of the distance from the flame center to the ground boundary b.
N4 yuan K
Calculation of the height of the flare smoke window
(2.0.2--14)
From Figure 2 .0.2-1 It can be seen that there is the following relationship between H', H, R, R, Xc, Yc and D H'-H+Yc
R'-R-Xc
DR'2+H2
From the above three equations, we can get:
HD2-(RX)2-Y
Given D, R, Xc and Yc, the height of the flare smoke window (H) can be calculated. (2.0.2—15)
(2.0.2—16)
(2.0.2—17)
(2.0. 2—18)
The height (H) of the flare smoke stack is related to the selected calculation standard. When the radiation intensity (K) is the maximum allowable thermal radiation intensity, H) is the lowest limit height of the flare smoke stack. The K value is selected according to the specific conditions of the project. (3) The approximate calculation method of Brutuski and Sommer is summarized as follows:
W, flare gas flow rate, kg/s;
M—average molecular weight of flare gas;
average molecular weight of air;
—average wind speed, m/s;0
Lower explosion limit parameter of flare gas (C)
Figure 2.0.2-5 Correlation diagram of flame longitudinal offset (Y) and d, R, C Calculation of the distance from the center of the flame to the ground boundary b.
N4 yuan K
Calculation of the height of the flare smoke window
(2.0.2--14)
It can be seen from Figure 2.0.2-1 that there is the following relationship between H', H, R, R, Xc, Yc and D H'-H+Yc
R'-R-Xc
DR'2+H2
From the above three formulas, we can get:
HD2-(RX)2-Y
Given D, R, Xc and Yc, the height of the flare smoke window (H) can be calculated. (2.0.2—15)
(2.0.2—16)
(2.0.2—17)
(2.0.2—18)
The height (H) of the flare smoke stack is related to the selected calculation standard. When the radiation intensity (K) is the maximum allowable thermal radiation intensity, H) is the lowest limit height of the flare smoke stack. The K value is selected according to the specific conditions of the project. (3) The approximate calculation method of Brutuski and Sommer is summarized as a. The basic data required for the calculation are as follows:
W, flare gas flow rate, kg/s;
M—average molecular weight of flare gas;
average molecular weight of air;
—average wind speed, m/s;0
Lower explosion limit parameter of flare gas (C)
Figure 2.0.2-5 Correlation diagram of flame longitudinal offset (Y) and d, R, C Calculation of the distance from the center of the flame to the ground boundary b.
N4 yuan K
Calculation of the height of the flare smoke window
(2.0.2--14)
It can be seen from Figure 2.0.2-1 that there is the following relationship between H', H, R, R, Xc, Yc and D H'-H+Yc
R'-R-Xc
DR'2+H2
From the above three formulas, we can get:
HD2-(RX)2-Y
Given D, R, Xc and Yc, the height of the flare smoke window (H) can be calculated. (2.0.2—15)
(2.0.2—16)
(2.0.2—17)
(2.0.2—18)
The height (H) of the flare smoke stack is related to the selected calculation standard. When the radiation intensity (K) is the maximum allowable thermal radiation intensity, H) is the lowest limit height of the flare smoke stack. The K value is selected according to the specific conditions of the project. (3) The approximate calculation method of Brutuski and Sommer is summarized as a. The basic data required for the calculation are as follows:
W, flare gas flow rate, kg/s;
M—average molecular weight of flare gas;
average molecular weight of air;
—average wind speed, m/s;
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