This article explores the theory and practices of key factor evaluation that serves technology planning and decision-making. Through case analysis, it explores the evaluation methods of factors that affect technology planning and decision-making in engineering companies in the petrochemical industry, analyzes the key steps in the construction process including factor selection, weight allocation, quantification methods and evaluation models, and adopts the methods of factor analysis and analytic hierarchy process to conduct key factor evaluation. The research results show that a scientifically reasonable key factor evaluation system can effectively promote the achievement of organizational goals. This factor evaluation system plays a positive role in improving planning level, optimizing decision support and other aspects. Finally, the shortcomings of the current research are summarized, and some suggestions are provided for future research directions.

Chemical cleaning is required for the shutdown treatment of ethylene plant during overhaul due to the process complexity in quench zone. This article comprehensively describes the traditional chemical cleaning scheme for shutdown treatment in quench zone during the overhaul of ethylene plant, analyzes the shortcomings of the traditional chemical cleaning scheme, and proposes some optimization and improvement plans. At the same time, further optimization suggestions are proposed for the optimized and improved implementation plan.

The comparison of design parameters, operating parameters, instrument online analysis and offline sample analysis of ethylene plant shows that there are deviations in product indexes during production and there is still room for optimization and improvement of product yield and output. The TRIZ theory was applied to propose innovative solutions to existing problems, and Aspen digital software was used to build analog processes and comprehensive management software (reactor operation information monitoring). The operation law of rectification tower system and acetylene hydrogenation reactor was studied. The optimal control of process parameters was operated and controlled by APC control technology. The existing resources of ethylene plant were used to increase the yield of target products, laying a solid foundation for the long-term, full-load and optimal operation of the rectification system of ethylene plant.

MTBE/butene-1 plant uses three-stage fixed beds and catalytic distillation technology to produce MTBE products, and butene-1 is produced by ultra-precision distillation technology. Corrosion leakage repeatedly occurred in the methanol recovery system since the plant was put into operation, seriously affecting the long-term operation of the plant. At the same time, the corrosion-induced rust residue entered the methanol extraction tower with the extraction water, causing increased tower pressure difference and poorer water washing effect. By taking measures such as strictly controlling the quality of raw materials, installing acid removal device in the methanol recovery system, injecting alkali for neutralization, and upgrading the material of equipment and pipelines, the corrosion leakage problem was solved.

Steel structure pipe racks, characterized by their large volume and lengths often spanning several kilometers, account for a significant proportion of the steel consumption in petrochemical projects. Therefore, optimizing the layout of pipe racks to save steel is of great significance. In terms of design, the span of pipe racks is usually determined by the piping layout of upstream disciplines. However, the structural discipline can collaborate with upstream disciplines in the early stages to determine the scheme and optimize the design by controlling the bay spacings of pipe racks. This paper proposes a universal method that can represent the entire project's steel consumption for pipe racks. By analyzing and comparing the steel consumption of representative double-span steel structure pipe racks with bay spacings of 6 meters and 9 meters, it is concluded that the pipe rack with a 6-meter bay spacing is more economical and represents an optimized design.

In butadiene extraction units by acetonitrile process, acetonitrile solvent needs to be continuously regenerated to maintain its quality. Solvent regeneration is limited for the existing process, and large amounts of impurities cannot be removed effectively. A solvent regeneration technology is developed. Without changing the existing process, the impurities such as alcohols, ketones and butadiene polymer can be removed to obtain a solvent with an acetonitrile content of 94.6％ (mass fraction), thus solving the problem of limited solvent regeneration, improving the solvent quality and prolonging the production cycle of the unit. Pro II software is used to simulate the regeneration process and determine the main process parameters of distillation tower. Less than 1％ acetonitrile is lost in this unit, and the comprehensive energy consumption per ton of acetonitrile product is 76.25 kg.

During the operation of a 220 kt/a ethylene plant, its quench system encountered some problems including the easy emulsification of quench water, the difficulty in controlling quench oil viscosity, the serious coking in heat exchanger, and the severe corrosion of the heat exchanger and its pipelines. These problems shortened the operation cycle of the quench system and increased the energy consumption of the plant. By taking some optimization operation measures, the long-term operation of the quench system is achieved.

In this paper, the causes of the leakage of circulating water line of the second water cooler in the methanol unit of PetroChina Dushanzi Petrochemical Company are analyzed and investigated, and some solutions are developed. By positioning the nozzle of condensate pipe deep into the circulating water pipe and turning the elbow to make the direction of process condensate consistent with that of circulating water, the erosion problem is completely solved.

 In order to effectively deal with heavy pollution weather, scientifically reduce the discharge of pollutants and continuously improve the ambient air quality, the feasibility of directly delivering hydrogenated gasoline to PX unit instead of sending it to tank farm has been analyzed. The risk of the direct delivery process has been assessed, and the risk identification indicators and risk control measures have been summarized. Relevant process parameters have been optimized based on the actual production. After the direct delivery process is put into use, the VOCs values detected at each detection site are significantly reduced. The leakage of light components and the total emission of air pollutants are significantly decreased. These results show that the new direct delivery process can effectively avoids the emission of non-methane total hydrocarbon to the environment, which are caused by the leakage of hydrogenated gasoline from large and small breathing valves of tank T-0003A/B or the safety accessories. The direct delivery process is expected to be an effective new measure for preventing and controlling heavy pollution weather, and play a positive and effective role in promoting the fine control of heavy pollution weather and establishing a proactive, harmonious and effective air pollution emergency system.

Waste heat boiler is one of the critical equipment in ethylene plant. Its leakage failure will lead to the emergency shutdown of cracking furnace and affect the stable operation of ethylene plant. There are multiple mechanisms contributing to the leakage failure of waste heat boiler. This paper analyzes the causes of the failure of waste heat boiler through methods such as metallographic testing and phase analysis, and discusses the solutions to the leakage failure of waste heat boiler in ethylene plant, so as to extend the service life of waste heat boiler, enhance its operation reliability and ensure the long-term stable operation of ethylene plant.

As the pipes connecting steam drum and quench heat exchanger, risers and downcomers are an important part of the quench system for ethylene cracking furnace. In order to ensure the safe, stable and long-term operation of ethylene plant and the reliable use of quench system, it is necessary to carry out a reasonable design and stress analysis of the risers and downcomers. This article introduces the stress analysis process of risers and downcomers, and summarizes the problems and solutions encountered during stress analysis based on the specific example of a project.

 A new aluminum-containing superalloy furnace tube NH1949 was adopted for the cracking furnace F-0401 in the ethylene cracking unit of a petrochemical company, and the average operating cycle of the cracking furnace was extended from 55 days to more than 100 days. After seven operating cycles, the coking speed of furnace tube was accelerated, and the operating cycle was reduced to less than 40 days. The cause may be that the Al₂O₃ membrane on the inner wall of furnace tube peels off to some extent during cyclic use. Practices show that the operating cycle of cracking furnace can be restored to an average of 80 days by passivation of the furnace tube.

The cracking gas dryer of a 700 kt/a ethylene plant used 4.0 MPaG steam to heat the methane for dryer regeneration. During the operation of the vapor phase dryer, the excessive water content at the outlet of dryer led to production capacity constraints and the emergency shutdown of the plant. By analyzing the reasons for the excessive water content of the dryer, leaks in the heater were eliminated. The blockage locations were determined base on the change in pressure difference across equipment during operation. The ice build-up in equipment and pipelines was eliminated by taking some measures to defrost the cryogenic equipment frozen and blocked, and normal production was resumed.