Several questions regarding the torch system
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I have a few small questions regarding torches for those who are more experienced: 1. In the calculations related to torches, the thermal emissivity is usually set to 0.2 – where does this value of 0.2 come from? 2. What does the maximum heat reception point of the flame refer to, and what is its relationship with the intensity of thermal radiation? 3. In the method for calculating the maximum average wind speed at the outlet of the torch tip, GB 3840-91 specifies the calculation based on the annual average wind speed over 5 years, rather than the maximum average wind speed; there is a contradiction in this regard. 4. In the calculation of the maximum average wind speed at the torch outlet, there is a wind speed at the torch outlet itself. But the height of the torch has not been calculated yet; how can we know the height at which the torch outlet is located? Is it necessary to estimate first and then verify? 5. Additionally, the allowable linear velocity of the gas, within the range of 0.2–0.5 Mach, is too wide, making it difficult to control. I’m not sure if everyone has encountered and solved these issues when calculating the torch. . . I hope to discuss this with everyone! ! 1 Thank you for your support! ! !
1. The theoretical value of the thermal emissivity can reach 0.35, but the actual values measured on site are much lower than this theoretical value. The injection of steam **reduces the thermal emissivity; foreign studies have shown that without steam for smoke suppression, the thermal emissivity is 0.15. Moreover, the thermal emissivity varies depending on the type of gas. To simplify calculations, a value of 0.2 is used, which can be considered empirical data. 2. As the flame changes, the maximum heat affected zone also changes. The calculation formulas assume that the flame center is at the midpoint of the flame axis, and that all the heat is released from the center of the flame. 3. There’s no contradiction. The maximum average wind speed at the outlet of the torch head needs to be calculated, with the calculation method referred to in GB 3840-91. 4. The wind speed at the location of the torch varies with altitude, and this change in altitude is quite significant; however, the height of the torch is limited – currently, it’s at most 150 meters. The person asking should look up some information on this topic. 5. Refer to Article 1 in Appendix D of SH3009-2001.
For a value of F equal to 0.2, it indicates doubt; according to the examples in API521, Pages 153 and 162, the value of F is 0.3 in both cases； According to the theoretical formula, e = 0.048M*0.5; at t=1, the calculated value of F is greater than 0.2 ； There are no actual data providing empirical values; I wonder where the value F=0.2 comes from. I hope experts can point this out.
F=0.2 is a value determined by foreigners through experiments and experience, and can be used for preliminary design. F=0.048×(M)^0.5 is also merely an empirical formula derived from experiments on single alkanes such as C1, C2, C3, etc. It is higher than the actual value. When designing, the lower heating value of the flare gas also needs to be taken into account; generally, when it is below 8000 KCAL/NH3, F
To the experts upstairs, I hope there will be a chance to exchange ideas and learn from each other. My QQ is 379878468
F=0.2 is a value determined by foreigners through experiments; in fact, it may be even lower than 0.2, and it can be used for preliminary design in the chemical industry. But on offshore oil platforms, the value of F is generally 0.3, as the gases emitted are mainly hydrocarbons!