Nowadays, many megaton ethylene plants have been built and put into operation in China. It is crucial to improve the marginal benefits of ethylene plants and win market competitiveness. The calculation of marginal benefits of ethylene plant should take into consideration the raw material input cost, the product revenue and the variable cost, and the variable cost consists of auxiliary material cost and fuel power cost. This article discusses the costs of auxiliary materials, fuel and power. Through methods such as original design, process adjustment and equipment modification, the consumption of catalysts, solvents and additives as well as raw and auxiliary materials can be reduced, and the energy utilization efficiency can be improved. It is expected to save 10% of the comprehensive costs, thereby improving the marginal benefits of ethylene plants.

This article discusses the important significance and core tasks of information management for special equipment. Taking the information management platform for special equipment developed by PetroChina Dushanzi Petrochemical Company as an example, this paper introduces the application of the functions of the platform, such as the overall functional architecture, the module function details, the information interconnection of various equipment management systems within the enterprise, and the business process management, and describes the information management methods for special equipment. Relevant laws and regulations, codes and standards, and enterprise management systems are fully incorporated into the information management platform for special equipment.With the management concepts of data platformization, platform informatization and intelligent information, the special equipment is supervised throughout the entire process. Risks of non-compliance, such as over-service equipment and operation beyond allowable parameters, caused by human error are to be reduced. The effort and time for manual management is to be minimized to improve work efficiency through informatization and intelligence. Finally, by prospecting the development of information technology for special equipment, some ideas are proposed for the development of information technology for special equipment.

The operation difficulty of debutanizer is one of the bottlenecks in the later stage of operation for many ethylene plants. In order to solve this problem, the process technology is transformed to direct the discharge of low-pressure depropanizer to tank farm, the debutanizer is isolated for treatment, and then the off-spec mixed C₄ is recycled to the debutanizer for refining. In this way, the debutanizer can be isolated for treatment without shutting down the ethylene plant, thus ensuring the long-term operation of ethylene plant.

This paper introduces the operation bottlenecks of condensate recovery system in the 220 kt/a ethylene plant of PetroChina Dushanzi Petrochemical Company. Through technical investigation, design optimization and implementation of technical measures, the operation bottlenecks of condensate recovery system are eliminated, the industrial condensate is further recovered and reused, and the goal of green factory without odor is achieved. Through minor modifications in local areas, the operation efficiency of the upstream and downstream units of the ethylene plant is improved, and the production cost is reduced.

In the unit for extracting styrene from cracked C₈ fractions, the decolorization system is very important. After acid washing, alkali washing and water washing, the color index of crude styrene extracted can meet the requirements of relevant national standards. However, strong acids and strong alkalis are highly corrosive to pipelines and equipment due to their strong corrosivity. This article introduces the process flow of extracting styrene from cracked C₈ fractions, briefly discusses the process of styrene decolorization system, analyzes the causes of pipeline and equipment corrosion in the unit, and proposes some corresponding anti-corrosion measures to avoid similar acid and alkali corrosion in the future.

Compared with the direct injection of dilution steam into traditional naphtha cracker, the ethane cracker controls the required dilution ratio by controlling the humidification or saturation of ethane in ethane saturator. The long-term operation of ethane saturator has become a key control point for the long-term operation of ethylene plant. This article explains that the long-term operation of ethane saturator can be ensured by controlling the oil content, COD, pH, iron ion concentration, conductivity and blowdown flow rate of the circulation process water of ethane saturator, continuously monitoring the pressure difference of packing in ethane saturator, and regularly switching the circulation pumps of ethane saturator.

During the start-up of an ethylene plant using propylene heat pump system, the components in the tower were disordered, the reboiler failed, the pressure difference between the reflux tank and the tower was insufficient, and the system heat could not be balanced. The causes of these problems were analyzed, and some improvement measures were put forward correspondingly, so as to ensure the safe and stable operation of the plant.

 The control of water content in the rectification system of butadiene unit is a difficulty in the startup operation of the unit, especially during the start-up of unit after passivation when the time required for water content to reach the standard is long and the startup cost is high. The schemes for water content control, startup drying and startup water content adjustment of the rectification system are optimized. Through the long-term operation practice of the unit, the stable and controllable water content of butadiene product is ensured, and the operational efficiency of the unit is improved.

Solvent pump is one of the key pumps in butadiene extraction unit. Its failure will interrupt solvent delivery and lead to unit shutdown. Therefore, the normal operation of this pump directly influences the smooth production of the unit and downstream units. The status of the pump, such as vibration and temperature, is timely monitored and analyzed using an intelligent status monitoring and analysis platform to check the operation of pump bearings and seals. It is particularly important to use the platform to analyze and judge in advance the early failure of pumps. It is necessary to formulate corresponding maintenance strategies, carry out preventive maintenance to solve the faults in operation, prevent serious damage to pumps, extend the service life of equipment, ensure the safe, stable and long-term operation of the unit, and minimize the impact of equipment on production to achieve the best overall performance.

The bed pressure difference of the cracking gas dryer in a 1.25 Mt/a ethylene plant had gradually increased since the startup of the plant and reached 65 kPa after two and a half years of operation. Some problems emerged, such as the poor heat transfer effect of heat exchanger in regeneration system, the blockage of coalescer in fuel gas system and the blockage of inlet filter in PSA unit. After disassembly, it was found that the blockage was mainly molecular sieve powder with a diameter of about 3 μm. In order to ensure the long cycle operation of the plant, it was decided to carry out online replacement of the agents for the dryer prior to the occurrence of water penetration. This paper mainly introduces the causes of molecular sieve pulverization and the subsequent measures taken.

An ethylene plant expanded its production capacity from 800 kt/a to 1 100 kt/a in 2020. Since the beginning of this operation cycle, the steam turbine of cracking gas compressor, the core equipment in ethylene plant, has successively encountered some problems such as low inlet pressure, low flowrate ratio of extracted steam to condensed steam and increased vibration of the unit during high-load operation, affecting the safe and stable operation of the unit and the whole plant while increasing the energy consumption of the unit. This paper analyzes the reasons for these problems and makes quantitative calculation, identifies the specific reasons, and puts forward relevant suggestions for further transformation and optimization.

Through the analysis of the inter-stage pressure difference and polymers in charge gas compressor of ethylene plant, the problems affecting long-term operation of the charge gas compressor in the No.2 ethylene plant of PetroChina Jilin Petrochemical Company were identified. Hot tapping was carried out for the pipelines of the inter-stage heat exchanger of charge gas compressor, and wash oil injection, dispersant line and nozzles were provided. The inter-stage heat exchanger of the charge gas compressor was cleaned by injecting washing oil and dispersant to reduce the polymers in heat exchanger, reduce the inter-stage pressure difference in charge gas compressor, and prolong the operation cycle of the compressor.

Pyrolysis gas compressor is the most critical and important equipment of ethylene plant. This paper analyzes the causes of the abnormal vibration of high pressure cylinder in pyrolysis gas compressor, and uses status monitoring software and frequency and map analysis to determine that the root cause of vibration is the fluid-induced vibration caused by coking inside the cylinder. By taking some measures such as increasing the frequency of oil injection, extending the oil injection time, and optimizing and adjusting the amount of oil injection in each cylinder, the vibration of the compressor unit is eliminated, thus ensuring the normal and stable operation of the pyrolysis gas compressor.

Cracking furnace is an important equipment in ethylene plant, and cracking gas pipeline, featured by large diameter, high temperature and complex working conditions, is one of the key pipelines in cracking furnace. This article briefly summarizes the cracking gas process. Based on the engineering example of a new ethylene plant, the layout of cracking gas main pipe, branch pipe of each furnace, cracking gas valve, decoking valve and purge pipeline is introduced, and the key design points and principles of cracking gas pipelines, the piping layout and the pipe support design scheme are explained.

Ethylene cracking furnace is a major energy consumer in ethylene plant. By increasing air preheating temperature, the fuel consumption of cracking furnace can be reduced and the thermal efficiency can be improved. However, while reducing fuel consumption, changes in the air preheating temperature also affects the operation of cracking furnace. This article takes the design of a 150 kt/a cracking furnace in an ethylene plant as the example, analyzes and studies the influence of different air preheating temperatures on the main process parameters. The calculation results show that with the increase of air preheating temperature, fuel consumption can be effectively reduced and thermal efficiency can be improved, but at the same time, some problems will emerge such as a decrease in flue gas volume and a reduction in ultra-high pressure steam production. Some relevant suggestions are proposed for the application of air preheating technology in cracking furnaces.