As we all know, because the water ring vacuum pump and the water ring compressor have the characteristics of simple structure, convenient use and maintenance, they have been widely used in all walks of life. Especially with the characteristics of isothermal compression, it is easy to suck and compress flammable and explosive gases. Here are some rough ideas about their development.
1. Large-scale development Due to the development of industries such as coal mines, chemical industry, pharmaceuticals, and papermaking, the requirements for water ring vacuum pumps have been increasingly developed toward large-scale. Before 2000, China was able to produce only 3-4 water ring vacuum pumps with a pumping capacity of 100m3/min or more, and the annual output of the country was only a few dozen. Only three years later, in 2003, there were more than 10 manufacturers of large pumps capable of producing more than 100m3/min in the country (of which only 7-8 were in Zibo area). According to incomplete statistics, the country’s largest pump With a production capacity of several hundred units or more, these products are mainly used for:
(1) Coal mine industry As the country has strengthened the safety requirements for coal mines, the use of water ring vacuum pumps, especially large-scale water ring vacuum pumps, to remove gas has become a necessary safety requirement for the coal industry, for example, a coal mine bureau in Shaanxi last year ordered many An extremely large-scale water ring vacuum pump with a pumping capacity of 400m3/min is used to remove gas, and some large coal mines use a large pump of 100m3/min or more to reach 7-8 units. As the country further strengthens the safety work, large-scale and extra-large water ring vacuum pumps will be increasingly used in coal mine systems.
In addition, due to the rapid increase in coal production, the vacuum filter used for coal washing and coal dressing has also grown to large scale. In the 1980s, most of them were SZ-4 water ring vacuum pumps with a suction capacity of 27m3/min. It was also larger at the time. In recent years, coal mine filter units have been equipped with large-scale water ring vacuum pumps with an air volume of 80--150 m3/min, and some have reached 200m3/min or more, and there is a tendency for air volume to continue to increase.
(2) Chemical industry a) Chlor-alkali industry In recent years, China has launched many large-scale capital construction and technological transformation projects. The actual children of these projects all require large amounts of PVC materials, especially the prosperity of real estate, which further promotes the development of polychlorinated compounds. According to statistics from the chlor-alkali industry, China produced 4.1 million tons of polyvinyl chloride last year, and imported 200 tons of it. According to the forecast of the industry, the national demand in 2005 will reach 8 million tons, and by 2010 it will reach 15 million tons. It is precisely because of the rapid increase in demand that the enterprises in the chlor-alkali industry in China will increase their production capacity and expand production. In one or two years, many new businesses were introduced. The development of chlor-alkali enterprises must be matched with water-salinity pumps and water-ring compressors. The water ring vacuum pumps and water-ring compressors used to extract and compress acetylene and hydrogen have only reached 30m3/min in the past, but now they produce 100,000 tons per year. Companies that use caustic soda and 100,000 tons of polyvinyl chloride need more than 70m3/min of water ring vacuum pumps and water ring compressors.
What needs special introduction here is that it is precisely because of the development of this industry that it has promoted and accelerated the development and production of higher I water and water ring compressors.
For a long time, China's water ring compressor is generally when the suction pressure is 1 atmosphere or slightly lower than the helium pressure, the exclusion pressure is O. 1 MPa, ie a compression ratio of 2, individual companies have produced water-ring compressors with pressures of up to 25 MPaG, and only 1 to 2 sizes. In order to adapt to the production of PVC, the former State Council’s major equipment office proposed the recycling of vinyl chloride recycling water ring compressors in the “Eighth Five-Year” major technological equipment research project—the annual production of 4 tons of low-polymerization PVC plant equipment. Research and development issues, this water-ring compressor for vinyl chloride monomer recovery requires a discharge pressure of O.55-0.6 MPaG and a displacement of 700 m3/ when the suction pressure is normal or slightly negative. Min. After several years of hard work, our company passed the technical appraisal organized by the former State Ministry of Machinery in December 1996, and the guest technology technology has reached the requirements for research. Based on this product, our company has also developed a series of products with a displacement of 90m3/min to 2000m. /h. Because this equipment is one of the key equipments in the PVC industry, in the situation of PVC products in China in recent years, this water ring compressor has been popularized and applied, completely replacing imports.
b) Fertilizer industry Fertilizer industry, especially the production of phosphate fertilizer is also a key support industry in China's macroeconomic regulation and control. As new projects and old enterprises are technologically advanced at or above the scale, large-scale and extra-large water ring vacuum pumps are This has also been applied, such as a phosphate fertilizer company in Yunnan, a new transformation of the additional pumping volume of 300m3/min three super-large water ring pump.
In addition, there are many phosphate fertilizer companies that require greater pumping capacity when the pressure is 80-lOOhPa absolute. Therefore, two-stage water ring vacuum pumps and two-stage water ring vacuum pumps with atmospheric ejectors are used here. Under these operating conditions, they have unique advantages. Many chemical fertilizer companies have eliminated reciprocating vacuum pumps with high vibration and noise and high vacuum levels. They have replaced them with two-stage water ring vacuum pumps and received good results. Two levels of water rings can be said. Vacuum pumps will become more and more widely used in this industry.
c) Papermaking industry At the end of the last century and at the beginning of this century, China’s national debt was invested in the papermaking industry and it occupied a relatively large proportion. Paper mills across the country rushed to reform the level and scale, which greatly stimulated the development and production of large-scale water ring vacuum pumps. A paper mill in northeast China once reconstructed six super-sized water ring vacuum pumps (the largest size water ring vacuum pump currently produced in China) with a pumping capacity of 400 IIl3/min, and a total distribution power of 400 kW. It can be said that 50% of the large-scale water ring vacuum pumps with pumping volumes above 100m3/min have been used in the papermaking industry in recent years, and this trend is increasing.
d) The pharmaceutical industry's vacuum concentration, dehydration, drying, and distillation are the major technological processes of pharmaceutical companies. The technological transformation of pharmaceutical companies is also on the same level and on the scale. This is even more apparent in some large pharmaceutical companies. In the past, most of them used small pumps of 10m3/min or less. Now, in the bids for these companies, medium and large pumps with pumping volumes of 20m3/min or more account for the majority. In addition, many plants in the pharmaceutical industry have used two-stage water ring vacuum pumps with pumping volumes of 6-12 m3/min in the past, but now they all have 20-30m3/min two-stage water ring vacuum pumps, and some have reached 60m3/min. For example, in a joint venture pharmaceutical factory in Sichuan last year, a bid to buy 10 pumps with an air pump volume of 60m3/min was completed.
In addition to the above industries, the vacuum systems in the food, beer, and metallurgy, power generation, petrochemical, building materials, and other industries of the light industry are all developing toward large scales. For example, an aluminum plant in Shandong has long used multiple water rings with an air volume of 85m3/min. The vacuum pump, and last year's technical renovation project equipment bidding required water ring vacuum pumping volume to reach 140m3/min.
2. Completeness It should be said that before 2000, almost all manufacturers of water ring vacuum pumps in China were based on sales of single pumps, and very few users had set complete sets of equipment. In the past two years, the technical transformation projects in the chemical and pharmaceutical industries have been completed. In equipment bidding, the proportion of complete sets of equipment is increasing. Generally, it is required to install separators, coolers (heat exchangers), fluid replacement pumps, valves, meters, fittings, and control devices to form a closed cycle and require The OCS system is connected to perform on-line control of liquid level, pressure, and force. The requirements for such mechatronics complete sets of equipment are becoming more common in many industries. Higher vacuum also requires larger pumping volumes.
Many vacuum distillation, concentration, dehydration, drying in the chemical and pharmaceutical industries, and the extraction of exhaust gas from power plants require a large amount of suction between suction pressures of 3--8 kPa. A single-stage water ring vacuum pump is pumped in this interval. The gas capacity is quite weak, and the two-stage water ring vacuum pump and the two-stage water ring vacuum pump with an atmospheric ejector are characterized by a large amount of inhalation in this interval. Before 2000, the demand for two-stage pumps was mostly It is less than 15m3/min, but it is now 40-50m3/min. In addition, it should also be pointed out that when a single-stage water ring vacuum pump has an atmospheric ejector, if the design is reasonable, there will still be a large amount of suction at the suction pressure of 4--5 kPa, which greatly expands the single-stage water ring vacuum pump. The scope of use, such as an aircraft research institute in China, uses more than one such pump.
In summary, it can be seen that the water ring vacuum pump and the water ring compressor have been widely used in various industries as basic rough low vacuum obtaining equipment. It can also be said that the rapid development of various industries in the national economy has promoted the water ring vacuum pump and Water ring compressor development and production. Therefore, in order to better adapt to the development of various industries, the following rough points are put forward for the research and development of the pump.
(1) Improve the MTBF of the whole machine with feasibility design and high performance seals
The operating reliability of the water ring vacuum pump and the water ring compressor, that is, the average failure-free operation period, should be said to be higher compared with other rough low vacuum obtaining equipment, and the average failure-free operation period can reach more than 10,000 hours. However, with the improvement of technical progress in various industries and the improvement of the reliability requirements of the entire vacuum system, the reliability requirements thereof are correspondingly higher. In particular, under the conditions of strict safety requirements for chemical and coal mining gas, the pump will continue to operate for a long period of time, and the international advanced level can reach tens of thousands of hours. Therefore, the design conditions of water ring vacuum pumps and water ring compressors, the limitations of manufacturing conditions, and the quality of seals (especially mechanical seals) must be further improved in order to improve the reliability of the complete machine. The work is further strengthened.
(2) Optimize the design method, strive to increase the efficiency of the pump, reduce the energy consumption The water ring vacuum pump and the water ring compressor are products with high energy consumption and low efficiency. This is a recognized fact. Small pumps are generally 30-35%. Large pumps reach 40% or slightly higher. This low efficiency is incompatible with the state's requirements for electromechanical products and the current state of energy shortages in China. Therefore, an optimization design method should be used as soon as possible to establish a mathematical model for the geometric parameters of the most critical impeller affecting the efficiency of the pump and the starting position and area of the suction/exhaust holes, etc., to optimize the design, to select the combination scheme for each parameter, and to use the vapor and liquid. The theory and calculation formulae of the two-phase flow are designed to minimize the eddy current loss of the water ring and achieve the purpose of improving efficiency. Therefore, the design and development of water efficient energy-efficient water ring vacuum pumps and compressors as soon as possible to eliminate obsolete products with high energy consumption and low efficiency is an important task in the design, development, and production of water ring vacuum pumps.
(3) Increasing the amount of gas at operating point with atmospheric ejectors Whether a single-stage water ring vacuum pump or a two-stage water ring vacuum pump with an atmospheric ejector is used abroad to increase the amount of exhaust gas under lower suction pressure is still more . From the technical data of advanced technology companies abroad, we can see that when a single-stage water ring vacuum pump has an atmospheric ejector, the suction pressure is 5 kPa, and the pumping rate can reach the pump without atmospheric injection. The suction rate at 400hPa (65-70% of the commonly used single-stage water ring vacuum pump common point), two-stage water ring vacuum pump with one-stage atmospheric ejector, suction at a suction pressure of 1.5kPa points The rate is up to 70-75% of the pumping rate of the pump without an atmospheric ejector at a suction pressure of 8 kPa (usual operating point for a two-stage water ring vacuum pump), which greatly expands the water ring vacuum pump. The scope of application, that is, to meet the chemical, pharmaceutical, light industry, instrumentation, metallurgy, power generation and other industries require suction pressure of 1.5--5kPa point of the large pumping rate of the process conditions. However, at present, the domestic one is that the application of a water ring type vacuum pump with an atmospheric ejector is not wide enough; second, the pumping rate at a point of 1.5--5 kPa is relatively small, and there is a certain gap between the technical level of foreign advanced manufacturers. To further promote the application, the design of the improved atmospheric ejector and the ratio of the water ring vacuum pump should be studied. Since the air flow is in the tapered section of the nozzle of the atmospheric ejector (Laval nozzle) and the diffuser, the flow is supersonic air flow. , and the momentum exchange in the mixing process of the atmosphere and the extracted gas is complex. It cannot be completely designed by theoretical calculation methods. It is necessary to carry out many tests, but from the perspective of expanding the application of the water ring vacuum pump and improving its efficiency. The starting point should be to strengthen experimental research and strive to increase its pumping efficiency.
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