Abstract: Aiming at the problem of unbalanced outlet temperature of each group of furnace tubes during the start-up, normal operation and load adjustment of ethylene plant cracking furnace, taking the cracking furnace of ethane to ethylene as the research object, the control method of branch temperature and load of the pyrolysis furnace based on heat balance was put forward. In view of the structural characteristics of multi-branch furnace tubes, it was necessary to keep the heat balance before and after the branch flow adjustment to eliminate the temperature deviation of the cracking furnace branch and stabilize the pyrolysis furnace outlet temperature (COT). At the same time, load control was added to coordinate the flow distribution of each branch to eliminate the influence of load changes on temperature. On this basis, the branch temperature and load controller was designed and developed on the distributed control system (DCS) and applied to five cracking furnaces of 0.60 Mt/a ethane to ethylene plant of a petrochemical company. The results showed that the controller could accurately control the COT within ±0.5 ℃, and the fluctuation range of branch temperature difference was within 1 ℃ without the influence of load adjustment, which reduced the loss of starting materials and ensured the smooth operation of the cracking furnace.

Key words: ethylene, cracking furnace, temperature equalization, load, control