Development and application of centrifugal compressor for 10000m3h air separation plant

1 Overview

Kaifeng Air Separation Group Co., Ltd. has been designing and manufacturing centrifugal compressors for more than 30 years since it started manufacturing centrifugal compressors in 1969. In the 1970s, it mainly produced DA200 and DA350 single-shaft centrifugal compressors for 1500m3/h and 3200m3/h air separation plants. In the 1980s, our company's centrifugal compressor production has been greatly developed. In 1981, we successfully developed the first H-type double-shaft centrifugal compressor in China, which was used in 3200m3/h air separation equipment, replacing the original DA350. The single-shaft centrifugal compressor greatly improves the isothermal efficiency. With the development of electronic computers and the application of ternary flow theory in centrifugal compressors, our company has successfully developed 800~1500m3/h air separation equipment and ternary impellers for air power sources in the mid-20th century. The twin-shaft centrifugal compressor.

In the early 1990s, based on market demand and user requirements, our company used the successful experience of designing and manufacturing H-type double-shaft centrifugal compressors and successfully developed H700 centrifugal compressors for 6000m3/h air separation equipment. On this basis, H500 series compressors for 4500m3/h air separation equipment and H800 series compressors with 7000m3/h air separation equipment have been developed to make double-shaft compressors large-scale and serialized. At the same time, using the new technology of ternary flow theory, the original DA200 and DA350 compressors were updated and transformed, and the large-flow ternary impeller rotor was designed, which improved the isothermal efficiency of the original machine and increased the flow rate. The capacity-increasing transformation of the air separation equipment provides a guarantee.

In recent years, with the continuous popularization and development of CAD technology, especially after 1995, through the introduction of advanced turbomachinery CAD/CAM software and five-axis linkage CNC milling machine investment from the United States NREC company, our company's turbomachinery has been greatly improved. The level of design and manufacturing technology. The DAl800-51 type centrifugal compressor developed by our company in 1997 for the 15000m3/h air separation plant of Tianjin Iron Works is the largest single-shaft centrifugal compressor designed and manufactured in China. The machine has high efficiency and stable operation, and has been in continuous operation for five years. So far, our company has designed and produced two series of double-shaft H-type and single-shaft DA-type, dozens of different specifications and more than 100 air and nitrogen centrifugal compressors. The products are distributed all over the country and exported to Indonesia, India, and Vietnam. Waiting for the country. It can provide users with various air and nitrogen centrifugal compressors with a flow range of 3000~120000m3/h and a pressure range of 0.5~3.0MPa.

2 Brief introduction of centrifugal air compressor for 10000m3/h air separation plant At present, there are two types of centrifugal air compressors produced at home and abroad that are used in air separation plants above 6000m3/h, which are biaxial and uniaxial. In the early 1970s, because centrifugal compressors mostly used binary impellers, in order to improve the variable efficiency of the stage, in the small flow range, the biaxial centrifugal compressor has more advantages, so the flow rate is less than 40000m3/h. Double-shaft centrifugal compressors are used, and single-shaft centrifugal compressors are mostly used for flow rates above 40,000m3/h. In the 1990s, due to the adoption of ternary impellers and advanced processing technology, the working range of these two types of centrifugal compressors was expanded. The capacity of the double-shaft MSG series centrifugal compressor of foreign Cooper company can reach 150000m3/h; the maximum flow of the double-shaft VK series centrifugal compressor of Demag company can reach 500000m3/h; the flow range of the SULZER RIK single-shaft centrifugal compressor series is 35000~400000m3/h; and the flow range of RR single-shaft centrifugal compressor series developed by Demag company is 50000~500000m3/h. It can be seen that in the case of large flow, the twin-shaft compressor still has strong competitiveness. Domestically, centrifugal compressors equipped with air separation plants above 6000m3/h are available in dual-shaft and single-shaft types, both of which can meet the needs. The single-shaft centrifugal compressor can be driven by a motor or a steam turbine, which is more suitable for air separation equipment in the chemical industry. Therefore, there is a broader market prospect.

According to the design and manufacturing capacity of our company's turbocompressor and the needs of air separation equipment, we believe that the maximum flow rate of the double-shaft centrifugal compressor is 45000m3/h, and the maximum flow rate of the single-shaft centrifugal compressor is set to 120000m3/h. suitable. According to the requirements of Egang Group, on the basis of data collection, analysis and research on the structural design, material selection, automatic control, installation and maintenance of large-scale centrifugal air compressors at home and abroad, combined with the design and manufacture of centrifugal compressors by our company for many years Based on the mature experience, it is finally determined that the air compressor for 10000m3/h air separation plant adopts single-cylinder, single-suction, double-support, single-shaft four-stage isothermal centrifugal compressor. The machine has four stages of impellers and three intermediate cooling. The first stage is cantilever type, axial air intake, with imported guide vane adjustment, which not only has the advantages of good adjustment performance and high aerodynamic efficiency of the double-shaft compressor, but also has the advantages of high operating reliability of the single-shaft compressor. The situation of the machine is briefly introduced as follows. 2.1 Technical parameters

Model: DA1200—41

Medium: air

Inlet volume flow: 1150m3/min

Inlet pressure: 0.097MPa(A)

Export pressure: 0.60MPa(A)

Import temperature: 35℃

Import relative humidity: 80%

Cold water temperature: ≤33℃

Shaft power: 4453kW

Compressor weight: 14.6t (excluding auxiliary equipment and motors)

External dimensions of the compressor L×b×h: 3000× 2800mm×2000mm

Motor power: 5400kW

2.2 Main composition and structural characteristics

(1) In order to obtain a higher level of efficiency, we counted all four impellers as ternary impellers with good aerodynamic performance, and adopted a vane diffuser.

(2) In order to optimize the local load conditions, the first stage adopts a cantilever structure and a separate volute, so that the single-shaft compressor has the same axial intake inlet guide vane adjustment as the double-shaft compressor, which improves the adjustment performance. Improve the aerodynamic efficiency, which is the biggest technological innovation of this machine.

(3) The casing adopts a horizontal and vertical split structure, which is convenient for processing and manufacturing. The bonding surface is precisely processed to ensure that the high-pressure gas in the casing does not leak. The impeller is welded by stainless steel, and has been subjected to static and dynamic balance and overspeed tests, which has high reliability and safety. The first-stage impeller is connected to the shaft with bolts, which avoids the phenomenon of shaft fracture caused by the large vibration of the rotor impeller in the previous double-shaft H-type compressor. The entire rotor has undergone strict dynamic balance correction to ensure smooth operation.

(4) The supporting bearing is a tilting pad bearing. Five tilting pads are evenly distributed along the circumference and supported on the inner hole of the bearing. The movable pads can adapt to changes in load and swing in the circumferential direction. This kind of bearing has high vibration resistance.

(5) The machine base is an integral frame structure welded by steel plates. The four cat's claws of the machine casing are seated on the machine base. In order to reduce the offset and thermal stress of each axis caused by the thermal expansion of the unit, the machine base Guide keys are installed along the axial and transverse directions to ensure the concentricity between the units under any circumstances.

(6) The compressor and the speed increaser, and the speed increaser and the motor are all connected by a diaphragm coupling. Due to the flexible metal structure of this coupling, it has the advantages of heat resistance, corrosion resistance, no need for lubrication, long service life, absorbing greater shaft deviation, reducing coupling installation accuracy requirements, and mitigating impact. Compared with gear couplings, due to the small additional bending moment to the unit during operation, it has a good protective effect on the shafts at both ends. At the same time, it can reduce shaft vibration and increase the service life of the entire unit.

(7) The speed increaser is a single-stage transmission, and the box body is cast iron. The large and small gears are made of high-quality carburized steel, and have been hobbed, carburized and ground with high machining accuracy. The pinion bearing is a tilting pad bearing, which has low bearing temperature and good vibration resistance. Since the speed increaser is an independent structure, it avoids the influence of the compressor rotor impeller vibration on the gear meshing, and improves the operational reliability.

(8) The unit is equipped with a lubrication system and a cooling system. All oil pipes and intake pipes at all levels are made of stainless steel, and the cooler shell is treated with anti-corrosion on the surface to prevent rust from entering the impeller, affecting dynamic balance, and extending the continuous operation cycle.

(9) In order to ensure the safety of the unit operation and operation and prevent any accidents, safety protection including start-up interlocking conditions, operation safety protection, automatic stop protection, interlocking control, automatic adjustment, and anti-surge device are provided. system. The unit is equipped with an on-line monitoring device for shaft vibration, which can check the running status of the rotor at all times and extend the life of the unit.

(10) This machine is equipped with a soundproof cover, which can reduce the noise by 15 decibels, and the noise outside the soundproof cover is less than 85 decibels.

2.3 The actual operation result of the compressor

The DAl200-41 centrifugal compressor was successfully installed and started up in Egang Group Co., Ltd. in February 2002. The results of mechanical operation and performance test show that the unit runs smoothly and reliably, and the bearing temperature and vibration meet the design requirements. When the inlet temperature is 10℃, the inlet guide vane is 60 degrees, and the outlet pressure is 0.5 MPa (C), the outlet standard flow rate is 66000m3/h; when the inlet guide vane is 90 degrees and the outlet pressure is 0.5 MPa (G), the outlet standard flow rate is 75000m3/h, can fully meet the needs of 10000m3/h air separation equipment. Because this machine has good adjustment performance, if appropriate modification, it is completely possible to be used as a supporting air compressor for 6000~15000m3/h air separation plant.

3 Conclusion

The DAl200-41 centrifugal compressor developed by Kaifeng Air Separation Group Co., Ltd. has advanced structure, superior performance, safe and reliable operation, strong modification ability, and has broad market prospects. However, due to the short delivery time of the machine, some shortcomings and problems will definitely be exposed during use. We will listen carefully to the user’s suggestions for improvement of the product, further improve the design, improve the manufacturing level, and make this large single-axis centrifuge The compressor series are more advanced and reliable, making greater contributions to the development of my country's air separation industry.