In view of the high propylene content of overhead stream and the over high ethane in tower bottoms of deethanizer in the No.2 ethylene plant in Dushanzi, this paper analyzes the design data and operation data of deethanizer feed, tower bottom product and front-end predistillation system, and concludes that the high temperature of feed in the No.2 predistillation tower is the cause of the high overhead temperature and high propylene loss of deethanizer. Through technical transformation, by-pass regulation is installed, the quantity and temperature of the feed to deethanizer are reduced, the distillation effect of deethanizer is improved, and the loss of overhead C₃ and the loss of C₂ in tower bottoms are reduced.

Through the analysis on the material balance, steam/water balance and environmental pollution data in the No.2 Workshop of the Ethylene Plant in Dushanzi, it is concluded that the causes of high material consumption, high energy consumption and high pollution of ethylene plant include the high temperature emission of flue gas from cracking furnace, the coking gas from coke oven, the discharge of breathing valves in doom roof tank area, and the discharge of water system, oil system and caustic system. Corresponding measures are taken to prevent and reduce the production of pollutants.

As the feedstock to the 220 kt/a ethylene plant at PetroChina Dushanzi Petrochemical Company becomes lighter, the cracking gas components becomes lighter, and some problems such as high suction pressure and low discharge pressure gradually emerged in the cracking gas compressor. As a result, the ethylene yield and the output cannot meet the requirements at the same time. This paper introduces the analysis and investigation process of the influence of lighter cracking gas components on cracking gas compressor, and puts forward some optimization measures and suggestions.

This paper introduces the common structure of radiant section lining in cracking furnace in ethylene plant, the selection principle of heat insulation refractory material and the matters needing attention during the installation and construction of radiant section lining, and analyzes the reasons for the failure of radiant section lining，so as to improve the design scheme, minimize the premature damage of radiant section lining caused by design reasons and construction quality, improve the thermal efficiency of cracking furnace and prolong the service life of radiation section lining in cracking furnace.

Oil circuit system is an important part of the compressor in ethylene plant, and the stable operation of oil circuit system directly affects the stable operation of ethylene plant. The reliability of oil circuit system can be improved from the aspects of preparation before commissioning, commissioning, routine operation and maintenance and design improvement. Strengthening the management on switching of oil coolers, oil filters and oil pumps, setting up a special maintenance team for critical compressor unit to ensure the daily maintenance, carrying out monthly sample analysis, checking the accumulator of oil circuit system on a regular basis (once every six months), following up the oil sample results, strengthening the inspection of oil circuit system and strengthening the maintenance of oil pump can ensure the stable operation of the oil circuit, thus ensuring the long period operation of ethylene plant.

With the development of refining and petrochemical integration, ethylene plant is developing towards long term and high load operation, and the problems of compressor scaling and heat exchanger blockage becomes more prominent due to the lighter cracking feedstock. The effective control of compressor scaling and heat exchanger blockage is one of the key points to achieve the long-term operation of ethylene plant. The ethylene plant in Sichuan was restarted up after overhaul in June 2018, and the interstage heat exchanger in cracking gas compressor was blocked only one year later, seriously affecting the long-term operation of the ethylene plant. Based on cause analysis, some measures were taken including adding interstage dispersant, changing the composition of wash oil and installing the wash oil injection line of heat exchanger to achieve the expected effect, and the loss caused by the 10-day unplanned shutdown of ethylene plant each time was avoided.