On the development of compressors in the 21st century

In the 21st century, centrifugal compressors, reciprocating compressors, and screw compressors are the three mainstream compressors used in the chemical process and gas power fields. Centrifugal compressors dominate the development of centrifugal compressors: the large-scale industrial enterprises. Large chemical companies such as 300,000 tons of synthetic ammonia, 500,000 tons of urea, and 300,000 tons of polyethylene have shown great economic efficiency in the operation of the century, and the demand for large-scale air separation plants is also increasing. In such large enterprises, reciprocating The compressor is no longer competent

   At present, the largest single reciprocating compressor for synthetic ammonia has an annual output of 50,000 tons. It has a huge volume and a considerable area. Therefore, it is required to replace it with a centrifugal compressor.

   Clean gas requirements. The gas compressed by the centrifugal compressor will not be contaminated by lubricating oil, while the heat transfer performance of the intercooler is improved, and the oil separation device can be omitted. Reliability requirements. Correctly designed and manufactured centrifugal compressors are highly reliable, and generally only need to be operated individually. However, reciprocating compressors cannot currently be used without backup, because during normal operation, the valve, piston and packing are replaced It is difficult to complete. It can be directly driven by industrial steam turbines to make energy utilization more perfect.

  Practical factors for centrifugal compressors: the practical use of flow field calculations such as ternary flow theory. The application of ternary flow theory can correctly design the flow field and volute flow path of the centrifugal compressor, which greatly improves the performance of the centrifugal compressor. In recent years, the rapid development of computers and the compilation of various mature software have changed this calculation. It's very convenient. The improvement of physical data. The mastery of the properties of the compressed gas and the improvement of the research on the thermodynamic process of various actual gases have deepened the compressor design and researchers' understanding of the energy transformation of the gas compression process, and improved the correctness and accuracy of the calculation. Application of precision processing equipment such as five-axis CNC milling machines. Perfect design without machining means is also in vain. The CNC machining equipment developed since the 1960s can well meet the requirements of space precision machining, which plays an important role in the development of centrifugal compressors and other machines with complex machining surfaces. The driving effect of

  The improvement of technological process. The application of centrifugal compressors in the high-pressure range is still quite difficult. In order to adapt to the working characteristics of centrifugal compressors, various processes requiring high-pressure are gradually improved and completed under low-pressure. For example, the synthetic pressure of the reciprocating compressor used in the synthetic ammonia process is 32 MPa, while the synthetic pressure of the centrifugal compressor is 15 MPa.

   Centrifugal compressor flow and pressure: According to the nature of the gas, the current high-pressure centrifugal compressor has a pressure of 15-25 MPa, and some documents have reported that it has reached 70 MPa in oil fields. The smallest aerodynamic centrifugal compressor is 10m3/min. The reciprocating compressor is still an important equipment in the process. There is a necessity for the reciprocating compressor: After experiencing the glory of the late 19th century to the middle of the 20th century, the reciprocating compressor has gradually been replaced by centrifugal compressors in some fields, but there are three Factors make it appear to be still very alive. There are many types and specifications. From the perspective of air volume and pressure, there are many types of reciprocating compressors, and they have an extremely wide range of applications. Some products can only be produced on a small and medium scale and require higher pressure. It can only be produced by reciprocating compressors. To be done.

   The need for low-density gas compression. It is relatively difficult to compress low-density gases such as hydrogen and methane with centrifugal compressors, while reciprocating compressors do not have this limitation. The continuous improvement of the reciprocating compressor itself. After more than a hundred years of hard work, the research and manufacture of reciprocating compressors have been quite perfect, such as the mathematical simulation of the working process in the cylinder and the valve, the mathematical simulation of the pressure pulsation of the piping system and the vibration of the pipeline, and the finite element of the structural strength of the parts. Analysis shows that machining centers are commonly used in manufacturing to ensure high parts shape and dimensional accuracy. The reliability and life of reciprocating compressors have been greatly improved. In some process systems, stand-alone operation can be achieved without the need for standby machines; even the most problematic valve has greatly improved its reliability. For clean gas, low pressure level It has reached more than 8000 hours, and it can reach 4000-6000 hours for medium and high pressure. In terms of thermal efficiency, reciprocating compressors are in a leading position among many models.

   Application of new materials. The development of material science also provides convenience for reciprocating compressors. Now the oil-free cylinder lubrication is easier to achieve below 15MPa. The flow coefficient and flow area of ​

​the valve made of PEEK (polyether ether ketone) have been greatly improved. This reduces the power consumption of the compressor, and at the same time, the impact noise of non-metallic valves is also lower than that of metallic valves. Therefore, modern reciprocating compressors are no longer an annoying mechanical product.

   Screw compressor The basis for the progress of screw compressors: the application of oil injection technology in the working chamber. The use of oil injection technology in the working cavity can internally cool the compression process, the single-stage pressure ratio can reach 8-10, and the exhaust temperature is lower (not exceeding 150 ℃); and the male and female screws can be driven by self-engaging, The structure is greatly simplified; at the same time, the sealing effect of the lubricating oil sprayed into the working cavity reduces the processing accuracy requirements of the screw. In-depth study of screw profile. In view of the sealing line leakage problem that seriously affects the performance of the screw compressor, some advanced profiles have been manufactured to make the length of the longitudinal contact line of the screw compressor, the leakage triangle and the closed volume at the end of compression be in the optimal situation, thereby making the compression process The leakage is greatly reduced. The precision screw special milling machine and grinder were successfully developed. The emergence of these production equipment not only greatly improves the accuracy of the screw profile processing, but also greatly improves the production efficiency.

   Noise reduction. The realization of hood-type noise reduction turned the screw compressor, which was originally noisier than the reciprocating compressor, into a low-noise compressor. Therefore, the power air compressor with a driving power of 7-250kW at 3~100m3/min Among air-conditioning and refrigeration compressors, and other gas compressors in the corresponding range, the screw type occupies a dominant position. However, the pressure of the screw compressor is generally lower than 4MPa or the pressure ratio is lower than 10, that is, its working range is not as wide as the centrifugal and reciprocating types.

   After the 1950s, the screw compressor has been developed rapidly, and it will replace the reciprocating compressor in a large range now and in the foreseeable future.