Abstract:

Flare emissions during the start-up and shutdown process of an ethylene plant are the key to its cost. Meanwhile, flare emissions will affect the environment. With the improvement of environmental protection requirements, how to reduce the start-up cost and flare emissions has become the focus of enterprises. This paper introduces the nitrogen pre-cooling of the ethylene plant at PetroChina Dushanzi Petrochemical Company. Nitrogen circulation was carried out by cracking gas compressor for the pre-cooling of heat exchangers in low temperature zone system prior to the formal feeding, and the minimum temperature of the heat exchangers in low temperature zone system was reduced to -120 ℃ . In addition, corresponding technical transformation was carried out for the specific process, the cold separation zone after pre-cooling was pre-charged to the feed pressure, and the hot separation zone was pre-charged and filled with corresponding liquid. Once the feed was in, on-spec overhead and bottom products could be produced, so as to reduce the flare emissions during the start-up and shutdown process and achieve the goal of no gas, no oil, no noise and no dust during the start-up and shutdown process.

Key words: ethylene plant, nitrogen pre-cooling, low emission, technical measures