What is the Cooling Principle of Gas Collector Mains?
Release date:
Nov 09,2021
The cooling of coke oven gas inside bridge pipes and gas collector mains is realized by intensive spraying of circulating ammonia water through spray nozzles at a gauge pressure of 1.5 to 2.0 kgf/cm². When the fine mist of ammonia water makes full contact with high-temperature, low-humidity coke oven gas, the gas releases a large amount of sensible heat, triggering massive evaporation of ammonia water and rapid heat and mass transfer processes.
The cooling of coke oven gas inside bridge pipes and gas collector mains is realized by intensive spraying of circulating ammonia water through spray nozzles at a gauge pressure of 1.5 to 2.0 kgf/cm². When the fine mist of ammonia water makes full contact with high-temperature, low-humidity coke oven gas, the gas releases a large amount of sensible heat, triggering massive evaporation of ammonia water and rapid heat and mass transfer processes.
The heat transfer process depends on the temperature difference between coke oven gas and ammonia water. Since the temperature of coke oven gas is higher than that of circulating ammonia water, heat transfers from the gas to the ammonia water, thus cooling the gas.
The driving force of the mass transfer process is the partial pressure difference of water vapor between the surface of circulating ammonia water and the coke oven gas. The partial pressure of water vapor above the ammonia liquid surface is higher than that in the gas, so part of the ammonia water evaporates. Meanwhile, the gas temperature drops sharply to provide the latent heat required for ammonia water evaporation.
Most of the heat released by coke oven gas during cooling in the collector main is consumed for ammonia water evaporation (approximately 75%–80%). The remaining heat is used to heat up the ammonia water (about 10%–15%) and accounts for heat dissipation loss of the gas collector main (around 10%).
Through the above cooling process, the gas temperature drops from 650–700 °C to 82–86 °C, and roughly 60% of tar vapor condenses simultaneously. In actual production, the cooled gas temperature is kept 1–3 °C above its final dew point temperature.
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