燕山石化公司30×10⁴t/a乙烯装置1994年完成第一次扩能至45×10⁴t/a的改造后，仍存在原料灵活性差、能耗高、与同期建设的乙烯装置比规模偏小等问题。以全面提高技术水平、降低能耗、增加原料灵活性、尽可能扩大生产能力为目标，充分考虑方案的可实施性、实施时的安全性、实施后的可操作性及方案的先进性和经济性，对装置技术改造的方案进行了比选研究。经改造，实现了生产能力扩大到66×10⁴t/a的目标，实际可达71×10⁴t/a，装置能耗明显下降，石脑油、轻柴油、重柴油、加氢裂化尾油均可作为乙烯原料。在世界上，首次在乙烯装置中采用混合冷剂制冷技术和碳三催化精馏加氢技术并获得成功，对世界乙烯工业技术进步有推动作用。

Yanshan Petrochemical Company after having expanded its 300 kt/a steam cracking unit to 450kt/k in 1994 is still experiencing such problems as low feedstock flexibility, high energy consumption and smaller scale as compared to other ethylene units constructed in the same time. In order to fully improve technical capability of steam crackers, reduce energy consumption, improve feedstock flexibility and increase production capacity, a lot of technical revamp cases on steam cracking were studied and compared with attention focused on the feasibility, safety, operability of the related revamp cases, as well as the advanced nature and economical features of the cases studied. As regards the pyrolysis-quench-compression system, the steam crackers will be retrofitted on the site with the pyrolysis gasoline fractionation tower, quench water tower, pyrolysis gas compressor and steam turbine replaced by new ones, respectively. The separation system will adopt a low-pressure methane removal technology with the demathanizer tower replaced, coupled with the C₃ catalytic rectification/hydrogenation technology, while the high-pressure depentanizer will be replaced with the addition of a propylene rectification tower. The fractionation flow sheet and equipment will be adjusted with the addition of a propylene compressor and compressor for binary mixture of methane-ethylene cooling agents. This revamp has expanded the ethylene capacity to the target of 660 kt/a with the actual capacity reaching 710 kt/a. This revamp project has remarkably reduced the energy consumption, which is capable of using naphtha, light diesel fuel, heavy diesel fuel and the hydrocracked tail oil as the steam cracking feedstock. This project is the first to apply refrigeration by means of a mixed ccx)ling agent and has succeeded in using C₃ catalytic rectification/ hydrogenation technology, which has given an impetus to the progress of steam cracking industry in the world.