This paper introduces the technical characteristics of several main ethylene process compression units, and focuses on the design of circulating water cooler between cracking gas compressor sections and the oil injection and water injection system of the unit and the operation of alkali washing unit and drying unit. Reasonable suggestions are given to deal with the possible out-of-control during the operation of compression system.

The composition and pyrolysis performance of four kinds of feedstock were studied by using analytical instruments and pyrolysis furnace simulation experimental apparatus. Feedstock 1 is hydrocracking tail oil from domestic petrochemical enterprises, feedstock 2 is hydrocracking tail oil containing diesel oil from joint-venture petrochemical enterprises, feedstock 3 is hydrocracking tail oil containing diesel oil from domestic petrochemical enterprises, and feedstock 4 is diesel oil from domestic petrochemical enterprises. The experimental conditions of pyrolysis reaction are as follows: the outlet temperature of pyrolysis furnace is 780～820 ℃, the outlet pressure of pyrolysis furnace is 0.08 MPa, the residence time of pyrolysis furnace is 0.24 s, and the water oil ratio is 0.8. The results showed that the order of the yield of ethylene, propylene and butadiene was as follows: feedstock 1 > feedstock 2 > feedstock 3 > feedstock 4. The order of the economic benefit of the four kinds of feedstock are as follows: feedstock 1 > feedstock 2 > feedstock 3 > feedstock 4. Comprehensive evaluation shows that it is a feasible method to use the mixed feedstock (feedstock 2 and feedstock 3) of hydrocracking tail oil and diesel oil as the cracking feedstock under the conditions of existing industrial plants.

This paper analyzes the estimation method of piping material quantity of overseas megaton ethylene plant in the quotation stage. Based on the data analysis of the piping material take-off of 7 megaton ethylene plants completed, the empirical benchmark quantity of various piping materials in different process units and the empirical ratio of some small-size materials to large-size materials are calculated, which provides a data reference for the estimation of piping material quantity in the quotation of new megaton ethylene plants.

Vinyl acetate is an important industrial organic raw material. There are two main vinyl acetate production processes, i.e. acetylene method and ethylene method. The technological progress in vinyl acetate production process is introduced, including the latest achievements in reaction kinetics study and reaction process, catalyst preparation process and reactor structure optimization. The advantages and disadvantages of the two technological routes are compared in terms of technical difficulty and production cost. The process characteristics of two ethylene methods including Vantage Process and Leap Process and their breakthroughs in catalyst and reactor research and development are mainly introduced. The problems in China’s vinyl acetate industry are analyzed, and the future research and development direction of vinyl acetate process is prospected.

Taking the reconstruction of a 1100 kt/a ethylene plant as an example, the project background of the early removal of low-pressure methane compressor is introduced, the changes in operation parameters of ethylene plant after compressor shutdown is analyzed, and the influence of hydrogen purity reduction on ethylene plant and downstream units is evaluated. The conclusion is that the early shutdown of the low-pressure methane compressor will not lead to load reduction of the ethylene plant or cause the discharge of methane tail gas to the flare. The feasibility demonstration of the scheme provides a reliable technical basis for the owner to formulate the shutdown and reconstruction scheme. At the same time, it provides reference for ethylene plants with low-pressure methane compressor to deal with special conditions such as the unplanned shutdown of compressor unit.

This paper introduces the problems in the use of the original sealing scheme of pyrolysis fuel oil product pump in the 200 kt/a ethylene plant in Tianjin. The rationality of applying several sealing schemes stipulated in API682-2004 in the pyrolysis fuel oil product pump in the 200 kt/a ethylene plant in Tianjin is analyzed through the comparison of the advantages and disadvantages of the sealing schemes. The actual transformation scheme and application effect of the sealing scheme of pyrolysis fuel oil product pump are introduced.

In view of the shortage of ultra-high pressure steam driven by the turbine of cracking gas compressor in the No. 2 ethylene plant in Dushanzi, the ultra-high pressure steam generation system, the ultra-high pressure steam transmission and distribution system and the ultra-high pressure steam users were investigated, and some optimization measures were put forward and implemented during the overhaul in 2019. These measures not only reduced the loss of ultra-high pressure steam and the consumption of medium pressure steam, but also reduced the consumption of fuel gas and improved the thermal efficiency of cracking furnace.

Axial flow pump is the core equipment of ST-Ⅱ polypropylene PDP as a part of loop reactor. As the circulating pump of process fluid, axial flow pump may be operated unstably during actual operation, resulting in the fluctuation of shaft power. To achieve the long-term, safe and stable operation of axial flow pump, it`s important to analyze the internal flow field characteristics and study the internal flow pattern of axial flow pump, mix the process fluid well, obtain uniform distribution of material and temperature and avoid the sedimentation of polymers. Axial flow pump has high requirements for hydraulic performance, so there`s no regulating valve at the suction and discharge of axial flow pump. This paper adopts lifting design method to analyze the axial flow pump with CFD technology, and decreases local vortex motion to avoid the accumulation of process fluid while meeting the hydraulic performance.

The 800 kt/a ethylene plant of PetroChina Sichuan Petrochemical Company is built on the basis of a 10000 kt/a oil refining project, and the patented technology of S & W Company in the United States is adopted. The project makes full use of the advantages of mutual supply of raw materials in the refining and chemical integration enterprise to produce ethylene, propylene, butadiene and other major chemical products by cracking the naphtha and topping oil from primary processing as well as the reformate refined oil, hydrocracking naphtha and liquefied gas from secondary processing. The original design feed includes hydrocracking tail oil, light naphtha, heavy naphtha and light hydrocarbon. Due to the changes in refining load and crude oil, the quality of naphtha, which is the main feed to ethylene plant, gets worse, seriously affecting the ethylene yield of the plant. From the perspective of processing efficiency, the evaluation and optimization of cracking feedstock is of great significance for improving the product yield of the plant.

This paper discusses the problem of excessive axis displacement of intermediate pressure cylinder occurred during the long-term operation of cracking gas compressor in the 640 kt/h ethylene plant at Sinopec Maoming Petrochemical Company. Based on the analysis of possible causes of the axis displacement failure, some measures were taken such as adjusting the process system, optimizing the injection of wash oil, adjusting the lubricating oil system, injecting water into the intermediate pressure cylinder and adding dispersant. These measures reduced the axis displacement to a certain extent, especially when the operating load was reduced, the axis displacement decreased significantly. However, none of these measures could completely solve the problem of excessive axis displacement of intermediate pressure cylinder. By injecting the mixed solution of aviation kerosene and polyethylbenzene as the wash oil, a large amount of fouling substance was dissolved and flushed out, completely solving the problem of excessive axis displacement caused by cylinder fouling.

The lubricating oil system of compressor is an important part of the auxiliary system of centrifugal compressor, and the oil flushing quality of lubricating oil pipeline in the early stage of operation directly affects the long-term operation of the compressor. How to reduce the time of qualified oil flushing under the premise of ensuring oil flushing quality is the target in the early stage of project construction. This paper analyzes the problems in the oil flushing of oil pipeline of cracking gas compressor unit, puts forward some countermeasures, and presents some methods for improving the oil flushing efficiency, so as to reduce the oil flushing time.

The TAE-100A/30 centrifugal compressor of the air compressor station in the Ethylene Plant of PetroChina Dushanzi Petrochemical Company is mainly used to provide coke cleaning air for the old chemical plant area. During operation, the compressor experienced a secondary interlock shutdown and failed to start up again after interlock reset. The causes of the interlock shutdown of the compressor were analyzed, and the primary, secondary and tertiary cylinders of the compressor unit were repaired. The main cause of the failure was the fatigue fracture of impeller during the long-term operation of compressor. Some preventive measures were developed to ensure the long-term operation of the compressor unit.

This paper introduces the anomaly of gradual increase in axial displacement of cracking gas compressor, and provides a detailed analysis of the reasons for the change in axial force of rotor in the medium-pressure cylinder of centrifugal compressor through troubleshooting. By analyzing the causes, it comes to the conclusion that the gradual increase in the axial displacement of rotor in the medium-pressure cylinder is due to the scale formation of stator of the compressor. Through injecting wash oil with higher distillation range into the cylinder of the compressor to wash the flow passage, the scale formation problem of the stator of the compressor is solved, thereby changing the axial force distribution of the rotor and finally removing the risk of gradual increase in axial displacement that may cause equipment failure.

Because cracking gas has complex components and contains olefins, high molecular olefins and sulfides, the heavy components, especially butadiene, will rapidly accelerate the polymerization reaction at high temperature, and the polymerization reaction is very easy to occur, seriously affecting the mechanical performance and efficiency of cracking gas compressor and shortening the operation cycle. In order to reduce the high temperature scaling of compressor impeller, water injection is needed to reduce the temperature. Metering pump, which was designed for water injection, has many defects. After optimization, boiler feed water pump is used to supply water, overcoming the defects of metering pump. Ensuring the continuous and stable operation of water injection system is critical for reducing the outlet temperature of compressor, slowing down the coking rate and prolonging the operation cycle of compressor unit.

This paper introduces the design and manufacturing technology of a new type of COT for radiant coil of cracking furnace, analyzes the causes of erosion and corrosion of COT sleeve of existing cracking furnace, and optimizes the structure design, material selection and manufacturing scheme of COT and base tube. After a series of tests, the stability of cot sleeve for long-term operation of cracking furnace is ensured.

With the improvement of national standards for discharge of pollutants, the 150 mg/Nm³ emission of NOx from the cracking furnace of the ethylene plant in Yangzi cannot meet the requirement of no more than 100 mg/Nm³ stipulated in the new standard. The burner was modified while the process conditions remained the same. To solve the problem of over high NOx emission after modification, some measures such as daily adjustment and optimization, steam injection and valve sealing were taken to meet the NOx emission standard.