Analysis of the use of air compressor facilities in the petrochemical industry

1. After more than 30 years of development, HAZOP analysis methods have been widely used in petroleum exploration, refining, chemical, chemical fiber, mining, metallurgy and information science industries, and HAZOP analysis is still relatively rare in domestic air separation plants. The air separation plant of PetroChina Guangxi Petrochemical Company was successfully driven on November 30, 2009. It has been running for more than half a year, and the working conditions are running smoothly. This is also due to the HAZOP analysis of this set of equipment in time during the design phase, from the design source. In order to avoid the hidden dangers of accidents, this article makes a review of the HAZOP analysis conducted by Guangxi Petrochemical Air Separation Unit, hoping to give reference to colleagues.

Second, the device background

The air separation air compressor of Guangxi Petrochemical is a single item of the 10 million t/a refinery project of PetroChina Guangxi Petrochemical. The single item consists of air separation and air pressure, and adopts a joint arrangement. The device supplies low pressure nitrogen, medium pressure nitrogen, instrument air and device air to the entire plant network system. Nitrogen is mainly used for compressor sealing of various process units, polypropylene regeneration, nitrogenation protection during replacement, purging and accidental state of various process equipments; or instrument air is used as the power source for the whole plant control system. The device air is used for the air delivery system of some process devices, the packaging system, and the replacement, purge, etc. during the maintenance or equipment maintenance.

According to the whole plant nitrogen, instrument air and installation air load, the air separation scale is 2×6000m3 /h product nitrogen, the air pressure part is 3×17500m3 /h, and the air separation and air pressure are five raw material compressors. Mutual backup. In addition, in order to ensure the reliability of nitrogen supply to the air separation unit, two sets of 6000m3/h air separation nitrogen production equipment are used at the same time.

1. Air separation air compressor unit HAZOP review background

The HAZOP Review Meeting of the Air Separation Air Compressor Unit was held from January 28, 2008 to February 1, 2008 at Daqing Petrochemical Engineering Company. The chairman of the HAZOP meeting was chaired by Indian craftsman Ajit.Kale. The review team included technical, automation, equipment, safety, production management and other related professionals.

On the basis of in-depth analysis and discussion by the review team members, combined with the process design and operability data, the system process safety analysis of the air separation air compressor process, comprehensively systematically find possible problems in the process and operability, Identify the dangers of the device that can cause major process safety accidents, and conduct a comprehensive analysis of the protective layer, and propose corresponding solutions to ensure the safe and stable operation of the process.

When the conference was available for 40 hours, 11 PID patterns were analyzed and 35 suggestions were generated.

2. Air separation air compressor unit HAZOP review

The review process covers the various units of the air separation air compressor, including the air filtration and compressor system of the air separation unit, the air pre-cooling system, the air purification system, the fractionation tower system, the nitrogen compression system, the liquid nitrogen storage and vaporization system, and the nitrogen storage. And delivery systems, air filtration and compressor systems for air compressors, drying systems, filtration systems, instrument air pressurization and storage systems. During the HAZOP review, a total of 9 nodes were divided according to different systems, and the deviations, causes, consequences and protection measures of the nodes were analyzed in detail.

The combination of the leading words and deviations and possible causes that may be used in the HAZOP analysis, and the process records are analyzed.

3. Air separation air compressor unit HAZOP review conclusion

Among the 35 recommendations made by the HAZOP analysis meeting, there are suggestions on the clarification of the operation plan, suggestions on the written expression of the design documents, and suggestions on the consistency of the design documents and specifications. The more important suggestions are:

1) It is recommended that the design contractor and the compressor supplier confirm that if the compressor inlet control valve is shut down by mistake, the compressor will stop from my protection.

2) The piping system may be vibrated due to the large difference between the compressor outlet pressure and the pipe network system pressure. For example, the reason for the large difference may be the failure of the pressure transmitter. Suppliers are required to provide relevant information to reduce the losses caused by this situation.

3) The liquid nitrogen vaporizer has the possibility of being frozen, and the pump stop chain should be increased. When the water temperature is lower than 10 °C, consider interlocking to stop the pump.

4) The condensate overflow line of the liquid nitrogen vaporizer is connected to the DSW feed line and connected to the drain valve. If the shut-off valve is mishandled, the condensation in the liquid nitrogen vaporizer may not be discharged, resulting in the vaporizer not working properly. The most reliable operating experience is that the overflow line should be connected directly to the floor drain.

5) A low level alarm for condensate should be set on the shell side of the liquid nitrogen vaporizer.

6) It should be ensured that no cold gas will appear in the work area when the nitrogen is released.

7) It is recommended to add 8 word blind plates near the cold box interface during parking to completely isolate.

8) It should be confirmed with the liquid nitrogen vaporizer supplier whether thermal expansion safety valve protection is provided.

9) It is recommended that the design contractor combine all nitrogen venting lines and vent to a safe height through a unified main pipe. According to the requirements of the Ministry of Chemical Industry Standard HG20570.2, 95, the vent should be at least 7.5m above the discharge port. The ground in the radius, the platform of the equipment is more than 2.5m.

Third, the conclusion

Many domestic owners and engineering companies have not paid enough attention to HAZOP because of the consideration of project investment and progress, and the ideological concept. Even if the project already contains HAZOP research report in the foreign basic design package, it is also in the detailed design. The HAZOP results were not incorporated into the design. It is believed that if the design and operation are carried out in accordance with the results of HAZOP, on the one hand, the investment will increase, and on the other hand, it will be difficult to drive or drive at all.

In fact, HAZOP is equivalent to a more systematic and comprehensive analysis of the design review of the design phase and the accident plan of the plant operation, and this consideration is integrated into the device design at the beginning of the project. The concept of “Safety comes from design” is best implemented, and it guarantees the transfer of a safe and qualified device to the owner. It should be said that the current domestic installations rarely do HAZOP research, but with the extensive involvement of foreign technology and international engineering companies, and the convergence of domestic and engineering companies with the international advanced level in terms of concepts and procedures, HAZOP research will be more and more A lot of engineering applications have been applied.

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