Cold torch and hot torch

A hot flare refers to one that is ignited, while a cold flare refers to one that is discharged directly without being ignited

I use that term too; a hot flare is one that burns into the air, while a cold flare is one that releases gases at a higher altitude.

In ammonia synthesis plants, the so-called cold flare generally refers to the safe venting of the synthesis refrigeration system. Because ammonia is at -33°C at standard pressure. There is also the vent from low-temperature methanol washing, and the temperature there is very low as well. The flare gas from these release points is to be sent to the flare for combustion. It’s just that the temperature of the medium is very low. A thermal torch, on the other hand, refers to a torch gas that consists of other media other than those at low temperatures. Let’s all discuss this together.

Cold and hot torches are commonly encountered in the ethylene industry. Due to the complexity of the flare emission systems in ethylene plants, these systems are generally designed separately as wet flare systems, dry flare systems, hot flare systems, and liquid emission systems (cold flare systems), depending on the state of the materials. The hot flare system is used to collect the superheated (around 120 degrees) and high-pressure dry gas discharged from the outlets of the propylene and ethylene compressors. The cold flare emission system is used for the discharge of cold liquids that are partially dry at low temperatures. The liquid that has been discharged vaporizes upon heating in the evaporator and then returns to the dry flare system. Generally, cold and hot torches are defined based on the temperature and state of the material being discharged. For more details, please refer to \"Ethylene Industry and Technology\" published by Sinopec Press

Cold torches tend to crystallize and get clogged. To prevent crystallization, they can be heated with steam.

2.4.3 Flare system of the ethylene plant: The materials discharged from the plant are sent to the following four main pipelines: a) The dry flare main pipeline collects the water-free, cold hydrocarbons from the ethylene plant； b) The wet flare header collects the water-containing, hot hydrocarbons from the ethylene plant ； c) The hot flare header collects water-free, hot hydrocarbons from the ethylene plant ； d) Liquid discharge main: Collects the low-temperature liquids from the low-temperature and cryogenic sections of the ethylene plant. The gas from the wet flare header enters the wet flare separation tank, where the hydrocarbons entrained in the gas are separated and condensed. The gas emerging from the upper part of the tank goes into the main flare header, while the liquid at the bottom is pumped to the quench tower. The gas from the dry flare main pipe enters the dry flare separation tank; after the liquid is separated in this tank, it flows into the main flare main pipe. The material coming from the liquid waste discharge system also enters the dry flare separation tank after being evaporated. The hot flare header is connected directly to the main flare header. The liquid from the liquid discharge main is discharged into the dry flare separation tank. The combined flare gas flows through the main flare pipe to the flare stack, with a molecular seal installed at the top of the flare stack. The emitted hydrocarbons are fully burned in the flare tip (i.e., the combustion burner).

One is direct combustion, and the other is direct emission. . .