During the 13^th Five-Year Plan period, private enterprises have sprung up in the construction of ethylene projects, and the survival and development of large-scale state-owned petrochemical enterprises were facing great challenges. In order to cope with this challenge and continue to maintain the market share and discourse power of large-scale state-owned petrochemical enterprises in the domestic petrochemical market, large-scale state-owned petrochemical enterprises actively studied the expansion planning of existing Petrochemical bases at the beginning of the 14^th Five-Year Plan. Taking the phase II planning scheme of a petrochemical base as an example, this paper discusses and analyzes the product scheme of a newly built phase II ethylene project of a state-owned petrochemical enterprise.

This paper mainly introduces the causes and treatment methods of boil off gas (BOG) during the low temperature storage and transportation of liquefied ethane, and proposes a process optimization scheme to solve the problems of high energy consumption of BOG re-liquefaction process and high percentage of gas phase in the fluid returned to storage tank after liquefaction. HYSYS simulation software is used to simulate and analyze the process flow of liquefied ethane BOG re-liquefaction before and after optimization. The results show that the optimized re-liquefaction process can improve the energy efficiency by 10% and reduce the percentage of gas phase in the fluid returned to storage tank after liquefaction by 50%.

Based on cracking feedstock processing load, the 1,000 kt/a ethylene plant at PetroChina Dushanzi Petrochemical Company installs one more gas cracking furnace to further enhance the plant capacity and operational flexibility, so as to meet the goal of maximizing the processing of light feedstock and maintain the advanced economic indicators. After transformation, the plant can adapt to both heavy and light cracking feedstock.

In this paper, two design schemes of quench system are simulated under different light cracking raw material to estimate the energy consumption. Based on the estimation results and the actual operation conditions, the energy consumption differences between the two schemes under different raw materials are compared. The design schemes of quench system in ethylene plant with light raw material are investigated from the viewpoint of energy consumption, providing reference for the selection of quench system design scheme for ethylene plant with light raw material.

The operation status of high temperature methanation catalyst and low temperature methanation catalyst are compared. Both of them can ensure a 100% qualification rate of methanated hydrogen product, but low temperature methanation catalyst can save 3,392 tons of super high pressure steam each year. Lower steam temperature, pressure and reaction temperature are favorable for the stable and safe operation of ethylene plant, and the 2,000～8,000 h^-1 space velocity and high temperature resistant properties of low temperature methanation catalyst contribute to greater operational flexibility.

Prefractionation system of pygas hydrogenation plant mainly includes depentanizer and deoctanizer systems. Some problems are often encountered under abnormal conditions, such as the overhigh C₄ light hydrocarbon content of the feedstock of crude pyags during start-up or in summer, the decomposition of DCPD in deoctanizer bottom at higher temperatures, and the polymerizaiton coking and blockage of easily-polymerized components at higher temperatures. These problems will cause operation fluctuation of the towers, affect product quality, and even lead to overpressure or affect the long-term operation of the towers. The depentanizer and octanizer under abnormal conditions are simulated and calculated respectively. Analysis is carried out combined with the actual production and the simulation results. The design of depentanizer and octanizer is optimized respectively according to the analysis results.

The separation of methane in high pressure demethanation system is discussed in this paper. Based on the analysis of the trend of methane in demethanation system, the influence of the feed temperature of C₂ condensing fractionator on the refrigerant load of ethylene is discussed. By adding liquid phase methane from the – 140℃methane/hydrogen separation drum to the reflux drum of demethanizer, the ethylene loss and the refrigerant consumption of ethylene can be reduced. Finally, the comprehensive analysis of the feed temperature of C₂ condensing fractionator and the bypass line flow rate is carried out, and the local optimal solutions are obtained.

Twisted tube has been widely used in radiation tubes of ethylene cracking furnace. By introducing several casting technologies for twisted tubes, this paper analyzes the non-destructive testing and mechanical properties of twisted tube for different casting technologies, so as to illustrate the advantages and disadvantages of different casting technologies.

In this paper, the problems in cracking furnace after low NO_X burner modification are analyzed and studied. The single burner CFD numerical simulation of cracking furnace is carried out. Through the analysis of temperature field, velocity field and concentration field, the technical bottlenecks that affect the distribution of furnace temperature field, furnace pressure control and NOx emissions are found out. Some suggestions are put forward for the improvement of burner structure.

After seven months of operation since the overhaul of cracking gas compressor in the 200 kt/a ethylene plant at PetroChina Liaoyang Petrochemical Company, the loss of lube oil increased significantly. It was judged that the leakage failure of the four-stage mechanical seal of the compressor high pressure cylinder was the cause. To solve this problem, the engineering and technical staff analyzed the problem from the perspective of equipment manufacturing and maintenance quality, process operation stability and production fluctuations, identified the fundamental reasons for the mechanical seal failure, and proposed some improvement measures to ensure the stable, safe and long-term operation of the compressor.

This paper briefly introduces the abnormal exhaust pressure problem of steam turbine, analyzes the reasons for the problem and puts forward some corresponding measures to solve the hidden problem caused by the unstable exhaust pressure of turbine to the normal operation of the plant during operation. The problems of air on the water side of condenser, corrugated pipe rupture and seal steam pipe breakage are introduced. By adopting correct treatment methods, the stability of exhaust pressure can be ensured, thus ensuring the stable operation of the ethylene plant.

During the operation of cracking gas compressor in an ethylene plant, the actual speed cannot reach the set value and the pressure difference between sections is rising. The causes of the problems are analyzed, and the operation cycle of the compressor are prolonged by adjusting the suction load of each section of compressor and adding wash oil injection points at the inlet feed pipe on process side of compressor inter-section cooler for wash oil injection.

When the ethylene plant was shut down for overhaul, as the cracking furnaces were shut down one by one, methane from other units and nitrogen from battery limit were gradually introduced into cracking gas compressor. After transiting to full-nitrogen operation, long-period stable operation was maintained through adjustment, so as to effectively recover the materials in the system, reduce the loss and improve the economic benefit, thus achieving environmental friendly shutdown.

The cyrogenic separation process of ethylene plant requires the refrigeration system to provide cold energy at different temperature levels, and the low temperature LNG releases large amounts of cold energy during heating and vaporization. This paper studies the cold energy integration of LNG terminal and ethylene plant. It is proposed to use the cold medium carrying LNG cold energy to replace the ethlyene and propylene refrigerants in ethylene plant, so as to reduce the compressor power and reduce the energy consumption of ethylene plant. In a 1,200 kt/a ethlyene plant, -80℃ cold medium is used to replace part of the ethlyene and propylene refrigerants, and the cold medium consumption is about 800 t/h. Compared to the ethlyene plant of the same capacity, the power of propylene refrigeration compressor is reduced by 11,600 kW and the power of ethylene refrigeration compressor is reduced by 1,500 kW, therefore the unit energy comsumption of ethylene plant is reduced by 25 kg EO/t ethylene.

The energy for the 220 kt/a ethylene plant in Dushanzi consists of fuel gas, fresh water, desalted water, circulating water, electricity consumption, high pressure steam, medium pressure steam, low pressure steam, nitrogen, plant air and instrument air. By changing the processing mode of raw materials, adopting advanced management experience, strengthening process management, providing special care for key equipment, optimizing key operating parameters and breaking down the energy consumption index into months, the ethylene plant can improve the output of target products, reduce energy consumption and ensure that the annual energy consumption meet the standard.