【HaiChuan: Lessons from Other Places】Lanzhou’s use of fossil oil-derived light hydrocarbons for direct supply to ethylene cracking plants serves as a model for transformation through \"de-tanking + direct supply\" approaches

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On August 26, 60 tons of light hydrocarbons produced by the 5.5 million tons per year atmospheric and vacuum distillation unit in Unit 3 of Lanzhou Fossil Oil Refining were sent directly to Unit 2 for ethylene production via the interconnection pipeline for isobutane supply between refining and chemical processing units. The operation was stable and all process parameters were within normal ranges, marking another typical example of Lanzhou Petrochemical’s approach of focusing on both overall strategies and detailed actions to accelerate its strategy of reducing oil production and increasing chemical product output, thereby achieving green transformation and upgrading of the enterprise. In light of its actual production conditions, Lanzhou Petrochemical has stopped using the two small spherical tanks at the gas loading station in the refining area, and instead transports the liquefied gas from Pump Room 71 in Refining Department 3 directly to the loading site outside the plant for shipment. During this process, tank No. 83, which was originally used to receive recovered light hydrocarbons and propane, needs to be converted into a liquid hydrocarbon tank, resulting in an urgent need for a new route for transporting the recovered light hydrocarbons. Therefore, a technical upgrade was developed to transport the light hydrocarbons recovered through atmospheric and vacuum distillation directly to Unit 2 of the ethylene plant via an isobutane interconnection pipeline. Recycled light hydrocarbons and propane are important components as raw materials for ethylene production, and their quality directly affects the yield of ethylene and the production costs. Before the renovation, the light hydrocarbons recovered by the 5.5 million tons per year atmospheric and vacuum distillation unit, along with propane from two gas separation units, were all stored in tank No. 83. The mixing of these two types of materials resulted in low purity and large fluctuations in the propane supplied to the ethylene plant, which in turn affected the long-term stable operation of the ethylene cracking furnace. After the renovation, the recovery of light hydrocarbons and propane is carried out through separate storage and transportation, which not only reduces the number of intermediate storage steps and improves transportation efficiency but also ensures greater stability in the quality of raw materials, fully meeting the high-standard production requirements of ethylene plants. “This breakthrough was made possible by the company’s determination to optimize and adjust its existing production structure. ”He Yucheng, head of the Production Management Team in the Production Operations Department, is full of confidence. Since the project was completed and put into operation on August 6, over 900 tons of recovered light hydrocarbons have been delivered via the interconnection pipelines. This direct supply model overcomes the limitations associated with traditional tank farm intermediation, enabling precise connection between devices; it can be expanded to a network of mutual supply across the entire plant in the future, thus creating a closed-loop system from raw materials to products. It serves as a model for similar enterprises to undertake transformation and upgrading through the elimination of tanks and adoption of direct supply methods. It is understood that the main challenge during this renovation process lies in the process adjustments required during the suspension of light hydrocarbon supply. The 5.5 million tons per year atmospheric and vacuum distillation unit strictly follows the operational plan by adjusting process parameters to reduce the production of light hydrocarbon fractions. At the same time, the project team accelerated the purging and replacement of the new configuration process pipeline; after 24 hours of continuous effort, they finally established a direct supply process.